Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

March 17

How often does Sansevieria trifasciata bloom?

How often does Sansevieria trifasciata (snake plant) bloom? My mother has one that is blooming now and she says that it is rare. Bubba73 ^{You talkin' to me?} 01:04, 17 March 2011 (UTC)

When grown as a houseplant, the period between blooms is highly variable, based on sun exposure, and how root-bound it is in its container. I'm sure you could not see a bloom for several years in some cases, especially if starting from a small clone in a large pot. Under 'average' houseplant conditions for a mature individual, expect a bloom every 2-4 years. They are more likely to bloom the more root-bound they are, because this is when they have reached the limit of vegetative growth. Note that it spreads rapidly through clonal growth in its natural environment, so sexual reproduction every year is not critical for long-term population success. Also, as a side note they have nectaries on the base of each flower on the raceme, which each produce a large drop of sweet nectar. Your mother may enjoy trying some; it tastes much like honey :) SemanticMantis (talk) 02:32, 17 March 2011 (UTC)

This one is in a small pot but it gets plenty of sunlight (next to a picture window). Mother says that she has never seen one bloom. She had me take photos to show the women in the beauty shop to prove that it does bloom. Bubba73 ^{You talkin' to me?} 02:58, 17 March 2011 (UTC)

I should have flagged (OR) above, maybe 2-4 years is a bit optimistic, as it is in the same family as the century plant, which is known for its long bloom interval. The bloom definitely feels special when it happens. SemanticMantis (talk) 14:00, 17 March 2011 (UTC)

That helps explain it, thanks. Bubba73 ^{You talkin' to me?} 15:37, 17 March 2011 (UTC)

Scent

I'm a hunter and I know how good an animals sense of smell is. My question is, all else considered, does hair make it easier for an animal to smell you? I heard it helps to vaporize it, which sounds bad, as that odor no doubt travels.

Any help would be appreciated, and if you know of any odor blockers (not stuff that leaves you smelling like perfume, but true blockers) I'd be much obliged. —Preceding unsigned comment added by 148.61.220.214 (talk) 01:08, 17 March 2011 (UTC)

Body odour is increased by the presence of pubic hair. That has even been proposed as the reason we have pubic hair. --Tango (talk) 01:24, 17 March 2011 (UTC)

Maybe for our naked cave-dwelling fore-bearers, but wouldn't the clothing of a hairless human absorb and hold odors just as well as, if not better than, body hair?

I assume he's not talking about shaving his body and then going out into the woods nude. APL (talk) 02:11, 17 March 2011 (UTC)

Here's a blog called ArcheryTalk that discusses this issue from a bowhunter's perspective. The author discusses five main strategies in further detail there:

1. Cleanse – Your body……..
2. Neutralize – Odor causing Bacteria…….
3. Maintain – Clean clothing/footwear…….
4. Mask – We’ll talk about this one……
5. Play the wind – Enough said………

He "neutralizes" by scrubbing down with an antiseptic like Betadine, and claims that a product called 'Bob’s “Skunk Essence”' works as an effective mask for him.

Also, as far as hair-odor-blockers, here's a plug for the product Invisible Hunter Shampoo^tm:

"Sometimes overlooked, human hair carries odors from not only one’s own body but from other environments that one has visited. A good practice of shampooing with Invisible Hunter’s Scent–Removing Shampoo is all you need to eliminate dirt and odors. Invisible Hunter’s Scent-Removing Shampoo will leave your hair clean and soft while providing you the extra scent control the serious hunter seeks."

WikiDao ☯ 04:20, 17 March 2011 (UTC)

Just curious, how do you get rid of the skunk essence smell. Great in the woods, real bad at home! Richard Avery (talk) 12:00, 17 March 2011 (UTC)

Real hard-core hunters wouldn't care about that. Real hard-core hunters are also probably single. (If not, see No true Scotsman) :-) . {The poster previously known as 87.81.230.195} 90.197.66.165 (talk) 01:48, 18 March 2011 (UTC)

Thanks, all. I like your comment though that clothes themselves would be a big issue...Do you know some products specific to cleaning your clothes, but not leaving it smelling like Tide, either? Thanks again. —Preceding unsigned comment added by 148.61.220.214 (talk) 03:25, 18 March 2011 (UTC)

More examples of millisievert doses?

I am skeptical of Sievert#Yearly_Dose_Examples-- for example, how could "some parts of Iran" naturally have half the carcinogenic dose? Can anyone find a good source for this kind of information? Shii (tock) 01:10, 17 March 2011 (UTC)

What you are calling the "carcinogenic dose" is the dose at which the probability of you getting cancer is measurably higher than normal. It isn't much higher, though. It is still an insignificant dose as far as individuals are concerned (other factors, such as diet and lifestyle, affecting cancer cause far more variation from person to person). When you look at a large number of people, it becomes significant, but only just. --Tango (talk) 01:21, 17 March 2011 (UTC)

Seems reasonable to me. Why do you find that so surprising? Dauto (talk) 03:01, 17 March 2011 (UTC)

The figure "Background radiation in parts of Iran, India and Europe: 50 mSv/year" sounds somewhat high to me, even though it comes from a BBC source - a value that high must be very localised. Our article on Ramsar, Mazandaran says "Some areas around Ramsar have the highest level of natural radioactivity in the world, due to the presence of radioactive hot springs ... the medium value in the Ramsar area is 10.2 mSv/year" - although background radiation levels in and around the springs themselves can be much higher. Gandalf61 (talk) 07:12, 17 March 2011 (UTC)

Full meltdown?

According to this, http://www.cnn.com/interactive/2011/03/world/interactive.nuclear.japan/index.html?hpt=C2

Three mile island and Chernobyl were only partial meltdowns. What's a full meltdown? This never happened? I always thought Chernobyl was a full meltdown. How far deep can a meltdown melt through stuff? ScienceApe (talk) 02:50, 17 March 2011 (UTC)

Nuclear meltdown refers to the heating of the Nuclear reactor core to the point where it melts; i.e. turns to a liquid. In a partial meltdown, parts of the core would melt, and other parts would remain intact. In a total meltdown, the entire core would be a pool of liquid at the bottom of the reactor; AFAIK this has never yet happened. In Chernobyl, the problem wasn't no much a meltdown, which is a serious but managable event, it was the excursion (i.e. the fissile material reached criticality) which damaged the containment security in the plant and allowed radioactive material to be sent into the atmosphere. Indeed, our article on the Chernobyl disaster doesn't even mention a meltdown, except briefly in passing. Indeed, an excursion (basically the reactor turns into a bomb) is a far more serious event than a meltdown; once the reactor core exploded, whether or not it melted is somewhat moot. --Jayron32 03:01, 17 March 2011 (UTC)

Side-questions: I'm kind of kidnapping this question, but the questions about nuclear reactors are a hot (sorry for the pun) topic this week. So, here for the questions: (1) if we let it meltdown, wouldn't this bore a hole and let the atomic material slip through this hole, and in the same process, cover it with other molten substances? Sounds pretty optimistic, I know. (2) Have anyone let a small core meltdown to test the question (1)? (worse experiments indeed happened) Quest09 (talk) 18:15, 17 March 2011 (UTC)

1. Probably not. I mean if you put a pile of melted nuclear fuel it might burn down into the earth, but unless the nuclear pile is actually vaporizing everything it touches, how is the dirt and rocks and such going to get out of the hole? Plus all the stuff you are melting is becoming radioactive at the same time. 2. I would really, really hope not. That sounds like a very expensive experiment with potential to cause enormous environmental damage and large negative impacts to human health and for what real purpose? Googlemeister (talk) 19:00, 17 March 2011 (UTC)

See corium. Once the fuel melts, you get a radioactive slag of fuel oxides plus everything else the fuel encounters. If the molten corium encounters water (say, the suppression tank underneath the reactor) you get a steam explosion that spreads a radioactive dust over a huge area. --Carnildo (talk) 23:29, 17 March 2011 (UTC)

Earths axis

Does the 6.5 inch shift in the earths axis from the earthquake create any changes, such as change in seasonal patterns or tides? —Preceding unsigned comment added by 68.36.96.146 (talk) 03:02, 17 March 2011 (UTC)

The circumference of the earth is roughly 40,000,000 meters. 6.5 inches is .1651 meters. .1651/40,000,000 = 0.0000000041275 or 4 parts per billion variation. That's pretty imperceptible. --Jayron32 03:08, 17 March 2011 (UTC)

In a related note, I've been trying to find out which way it's shifted. Here in Connecticut, am I closer or farther from equator? APL (talk) 07:36, 17 March 2011 (UTC)

It means Mrs. Claus is yelling at Santa to get his fat ass off that Nintendo game and go out there and move that pole! Wnt (talk) 17:14, 17 March 2011 (UTC)

Jayron, thanks for enlightening us on the imperceptibility of 6.5 in. in relation to the circumference of the earth. Does someone else care to answer the straightforward question? it obviously is different that before, so what does that difference equate to in more or less sunlight each day for the northern hemisphere? —Preceding unsigned comment added by 165.212.189.187 (talk) 17:28, 17 March 2011 (UTC)

The Earth's axis already shifts seasonally (at a greater magnitude than caused by the Earthquake, I believe), due to the rearrangement of mass caused by the weather (mostly the redistribution of water, I believe). Here are a couple articles on it, though they relate more to the change in day length than the axis shift [1], [2]. As these articles point out, pretty much every earthquake redistributes the mass at least some, but you can also see that the changes are on par with the yearly variation that is experienced anyway, regardless of earthquakes. The answer is definitely "no", this Earthquake will not have a noticable effect on seasonal patterns or tides. Buddy431 (talk) 18:03, 17 March 2011 (UTC)

Addendum: Here's a source that explicitly addresses the axis shift issue: the Earth's axis shifts about 3.3 ft seasonally, about 6 times the shift caused by the quake. Richard Gross, a Geophysicist, says "These changes in Earth's rotation are perfectly natural and happen all the time. People shouldn't worry about them." [3] Straight from the mouth of a real scientist. Buddy431 (talk) 18:07, 17 March 2011 (UTC)

This shift is in addition to the regular shift of the seasons. Who said anything about worrying, what did he say about curiosity, that it killed the cat? That is why this desk exists - to inform and enlighten not easy worrys of. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:24, 17 March 2011 (UTC)

And it's doing a great job - who knew that the Earth's axis moves? Or that there was both an axis and a figure axis to keep track of? Wnt (talk) 23:32, 17 March 2011 (UTC)

Storing electricity via “counterbalance” batteries?

Some time ago, I asked about the viability of using dams to augment sporadic electricity production via windmills and solar panels. The method is used in Sydney. When more than enough power is being produced, the power not needed is used to raise water to storage dams, where it can later be used to create hydroelectric power. This is, in effect, a battery, and I was surprised that it returned about 70% of the power it took to raise the water. Now, there are other ideas for batteries, as not all that many sites have big dams nearby.

My idea is: when the wind is strong and more power than is needed is being produced, why not have the mill raise a heavy weight chained below the vanes? When power is needed later, the weight can be slowly lowered, turning the vanes via gears and generating electricity.

I did read in New Scientist, years ago, in one of their historical featurettes, that in the early 20th Century, there were at least some English farmhouses which had a wind mill such as I have described on their thatched roofs. When the vanes turned, they could raise a weight, enclosed by a cylindrical cage located in the main room. When the wind died down, that weight could be allowed to slowly descend, generating electricity. I can’t find that source now, and I am wondering if someone knows anything about such an ingenious contraption. Myles325a (talk) 03:57, 17 March 2011 (UTC)

The idea's good - but the "engineering details" are hard. Gravitational potential energy is usually approximated as mgh - so pick some reasonable numbers for a mass (let's say, 10 tons), and a tower height (say, 100 meters); how much energy is that going to actually store? About ten megajoules of gravitational potential energy - about 3 kilowatt-hours. And that's a huge weight, and a really tall tower! Now, consider that one single barrel of oil contains (in the form of chemical energy) about one-thousand times as much energy as our massive 10,000kg, 100-meter-tall contraption!

To store a lot of energy in the form of gravitational potential energy, you need a lot of mass - which is why pumped storage hydroelectric is the only practical way to do it. Nimur (talk) 04:29, 17 March 2011 (UTC)

Myles325a's suggestion was used in practice for a couple of centuries in the longcase clock. I agree with Nimur that the attraction of using water is that vast amounts of it are available, and can be pumped into elevated storage. Solid components that could be used for storage of energy are miniscule compared with the mass that is available as water. Dolphin (t) 04:34, 17 March 2011 (UTC)

The use of such dams is not fondly regarded by environmentalists. Realize that such a system creates a large body of water without a shoreline, but just a large muck zone that is irregularly covered by water. Wnt (talk) 04:51, 17 March 2011 (UTC)

A similar system installed on a tidal shoreline can be more than 100% efficient (in effect) if the seawater is pumped up at high tide and used to generate electricity at low tide. On a coast with a big variation in times of high tide (such as the UK) such a system would be economically beneficial, though environmentalists would not be happy (but very few people are happy to have any generation scheme in their back yard!) Dbfirs 13:46, 19 March 2011 (UTC)

Grid energy storage covers almost all options for power storage. Instead of raising a weight with a windmill, pumped storage (already mentioned) and flywheel storage seem more viable. Zunaid 13:18, 21 March 2011 (UTC)

What exactly is the reason for the radioactivity?

I'm a little confused after having read Fukushima I nuclear accidents. If the containment vessels are indeed all intact, what exactly is the source of the radiation that has been detected? Is the problem that water within the containment vessel is being made radioactive as it flashes into steam and gets vented (as an emergency measure) because the pressure within the containment vessel is high enough? Wouldn't this mean the vented steam is riddled with decay products? I'm not very clear on whether this reactor design has water pumped directly at the fuel rods so there's essentially direct contact between the fuel rods and the water that gets flashed into steam and then spins the turbines. On reflection, I suppose it must. Doesn't this mean that these "containment vessels" aren't actually able to be sealed? Comet Tuttle (talk) 06:26, 17 March 2011 (UTC)

The main thing is that spent nuclear fuel is kept in open ponds with very little containment. That's where most of the radiation has come from - there's a lot more to be released from there than from the reactors themselves. This is mostly slovenliness - there are other countries which have moved largely to dry cask storage. It is well known that in any natural disaster (such as a major pestilence or all-out civil war) anywhere in the world, which would cause nuclear reactors to go unattended, eventually the reactor will shut down, the diesel backup will run out, and the spent fuel pools will go Chernobyl at every unattended site. In addition, the containment for #2 is cracked.^[4] Wnt (talk) 06:46, 17 March 2011 (UTC)

I only know of the Pebel bed reactors not using Spent fuel pools for the first few months or years. The heat generated for the first few half lives of the fast decaying isotopes is in an order of magnitude that all other methods are impractical. Most reactors store the spent fuel close to the reactor, this might change after the disaster.--Stone (talk) 07:22, 17 March 2011 (UTC)

I don't think it is "slovenliness" that dictates whether one uses wet storage. For one thing, Japan reprocesses — that usually dictates against dry storage. In any case, you need to store it in wet storage for awhile (at least a year) before you do anything else with it, so the really nasty stuff burns itself out. It's unclear to me how "old" the fuel in the wet storage is (you could calculate it if you knew the time between refuelings and the amount of spent fuel in there). --Mr.98 (talk) 15:01, 17 March 2011 (UTC)

Would someone more reliable than Wnt on physics-related subjects please confirm or deny what (s)he wrote above? Especially the claim that active cooling is the only defense against a Chernobyl-like disaster at any nuclear plant with a spent fuel pool? The article seems to say that this is false, but I don't know what to believe any more. -- BenRG (talk) 08:20, 17 March 2011 (UTC)

Yah I don't think he's right about that. Even if you left the reactor completely alone it wouldn't go Chernobyl. Especially once the control rods are in place a real catastrophe is pretty much impossible - and those rods are designed to fall into place at any disruption. It may melt down, but it will stay inside the containment. And the urnanium in storage can't go Chernobyl either. However it does seem that the containment pools are a weak spot. People paid a ton of attention to reactor design, and it looks like their designs worked. However the pools did not receive as much attention and most of the current problems (fires) are from those. Spent fuel pool#Status implies that someone noticed the problems and new designs are better. I have to assume that the Japanese fuel is not designed this way. Ariel. (talk) 09:03, 17 March 2011 (UTC)

To clarify, I used "go Chernobyl" to mean "produce all kinds of radioactive smoke and fire", not "break the reactor containment". I thought I was being clear there that the radiation would be coming from the pools. Wnt (talk) 10:34, 17 March 2011 (UTC)

Fukushima I nuclear accidents says:

"The nuclear fuel requires 1–3 years of constant active cooling (by flowing water) before the decay heat production gets low enough that effective passive cooling becomes sufficient to avoid excessive heating up to temperatures where the integrity of the fuel is at risk."

"At the time of the earthquake unit 4 had been shut down for maintenance and refueling since 30 November 2010. All fuel rods had been transferred in December 2010 from the reactor to the spent fuel pool on the top floor of the reactor building where they were held in racks containing boron to damp down any nuclear reaction. These recently active fuel rods were hotter and required more cooling than the spent fuel in units 5 and 6."

and mentions speculation "that the Fukushima management could have been engaged in an unsafe industry practice of re-racking spent rods in the pool well beyond its rated capacity, in effect heightening danger of melting and pool boil-off". Gandalf61 (talk) 09:51, 17 March 2011 (UTC)

So, the with problem with the spent fuel pools is that they are not contained . Also the fuel rods are still relatively rich in fissionable fuel and the racks that should hold them upright and provide some necessary separation to prevent criticality coming about, have been subjected to several server shakeings. If some off these racks (and any other safety devices like boron separation sheets) have been badly damaged or collapsed by the quake, then the evacuation of the local population seem like a very sensible step to take. The fuel may not be combustible but it can possible go critical again, given the right circumstances and until they can dump a lot of boric acid into the pool, there may still be enough water to facilitate this.--Aspro (talk) 10:13, 17 March 2011 (UTC)

I suspect, but do not know for sure, that criticality is not the major concern with the spent fuel at this point. I suspect that they would need to really be in a very poor state (e.g. melted sludge) for that to be an issue. The bigger problem is that they are very hot and full of very nasty things, and could catch fire, vent, melt, etc. --Mr.98 (talk) 15:31, 17 March 2011 (UTC)

Radiation is still being released by the venting of steam from reactors 1 and 3 (and 2 which may not even be contained). This radioactivity was observed before any issues arose with the spent fuel pools at 3 and 4. However, this radioactivity was a lower level (didn't require removing plant workers) and was blowing out to sea at that time. 75.41.110.200 (talk) 14:42, 17 March 2011 (UTC)

Thank you all for your responses. A followup question: Is it known whether the spent fuel at the site is recently spent fuel, or has some of it been sitting there in a swimming pool for a couple of decades? Mr.98 mentioned that Japan reprocesses their fuel, so it sounds like it's probably recent; but do we have an article on the lifecycle of fuel uranium and plutonium in Japan? Comet Tuttle (talk) 16:25, 17 March 2011 (UTC)

I doubt we have an article on it. It should be information that is "out there" though — it's the kind of thing the IAEA would know definitely. My mangled German + Google Translate of this article seems to indicate that there are 50, 81, and 88 tons of fuel rods in the three pools, but that this is not their full capacity, and in fact they are relatively empty. (By comparison, the spent fuel at some US reactors is around ten times that amount — because we don't reprocess, and we don't have any long-term waste disposal options worked out.) This suggests to me that they are pretty recent, but I'm not sure. --Mr.98 (talk) 17:31, 17 March 2011 (UTC)

The most resent rods were removed in November and December. These two pages out line the problems. Danger of Spent Fuel Outweighs Reactor Threat . I guestimate that a 13 foot long rod must weigh about 5 or 6 2½ to 5 hundredweight. Zirconium alloy is a wondrous material and hopefully it will resist the contents of the rods or the pellets themselves from forming a 'pile' on the floor. If not, then it wont just be the cherry bosoms glowing in the sunset this spring and Japan will be off my itinerary for the foreseeable future. Came across this handy little chart showing the current state of play at a glance. Status of nuclear power plants in Fukushima as of 16:00 March 17--Aspro (talk) 18:18, 17 March 2011 (UTC)

I don't think you need to be flip about the risks (cherry "bosoms" and etc.) — there are real people's lives here at stake. We are not quite in the "joke about it" stage yet. --Mr.98 (talk) 19:59, 17 March 2011 (UTC)

And if I had worded the possible out come more accurately would you have then accused me of over exaggeration and scaremongering? --Aspro (talk) 21:09, 17 March 2011 (UTC)

In fact, no. I think your comment was in extremely bad taste. That's a different category from whether I think it was accurate or not. --Mr.98 (talk) 21:34, 17 March 2011 (UTC)

DANGER WILL ROBINSON! DANGER! DANGER! The THOUGHT POLICE are EVERYWHERE!! (and Mr.98 ALWAYS has to have the last word) I personally am looking forward to those delicious sushi legs and BBQ frogs wings! YUM220.233.166.18 (talk) 07:16, 1 April 2011 (UTC)

Iodized salt instead of iodide tablets

I have seen recent news stories about paranoid people hoarding potassium iodide tablets. I know that iodized salt is widely used for cooking, and contains either potassium iodide or sodium iodide (the two shouldn't really matter, right, since they all just disassociate to iodide ions in solution), couldn't one achieve the same effect by eating a lot of iodized salt? Or is there insufficient quantity of iodide in iodized salt? --98.210.210.193 (talk) 06:55, 17 March 2011 (UTC)

Right! My salt contains 0.0025% of potassium iodate. 1g would than be 2.5mg. Somebody said that a dose can be above 100mg of potassium iodate. This would be 40g of table salt. This is a deadly dose of salt for children and very unpleasant for adults. --Stone (talk) 07:33, 17 March 2011 (UTC)

The concentration apparently varies in iodized salt in important ways. I just read that Switzerland raised its concentration to 20 mg/kg from 15 mg/kg - your container appears to be just 15 mg/kg. Fortunately the article Thyrosafe I started is still knocking around, despite being deleted last December :( :), so I can see that the tablets are 130 mg for adults or 65 mg for children. So a child's dose of iodized salt required would be just, 8.6 kg?! Hmmm, I think you missed the % up there when you did the math before, unless I just fouled up.

Right! I missed the %. --Stone (talk) 13:52, 17 March 2011 (UTC)

Ooops, I messed up myself - the pills are labeled for 130 mg of KI, not 130 mg iodine, so it's only equivalent to 6.6 kg of iodized salt. If you pace yourself.... ;) Wnt (talk) 16:00, 17 March 2011 (UTC)

Anyway, since it's not needed in the U.S. where the crazy rush is, tossing a pinch of iodized salt over your shoulder would do no harm. And maybe that 8.6 kilogram figure will make people think twice about hammering their poor thyroids with that kind of iodine for no reason. Wnt (talk) 07:44, 17 March 2011 (UTC)

Can we react Tincture of iodine with something commonly available (baking soda?) to make sodium or potassium iodide? Ariel. (talk) 09:17, 17 March 2011 (UTC)

Just don't react it with ammonia or you'd get a pill with a kick to it. No, scratch that, I would say don't try this at all! Who knows what kind of impurities you'd choke down, not the least of which being iodine itself. But as you know, I'm not giving medical advice here. Wnt (talk) 10:30, 17 March 2011 (UTC)

"Japan radiation fears spark panic salt buying in China" -- Finlay McWalter ☻ Talk 15:08, 17 March 2011 (UTC)

Would eating some tinned fish or other seafood be of any use in an emergency situation? (Seafood - contains iodine). 2.97.215.199 (talk) 23:42, 17 March 2011 (UTC)

Well, for edible seaweeds e.g. kelp: "12 different species of seaweeds were analyzed for iodine content, and found to range from 16 microg/g (+/-2) in nori (Porphyra tenera) to over 8165 +/- 373 microg/g in one sample of processed kelp granules (a salt substitute) made from Laminaria digitata.";^[5] "Edible seaweed contained I levels of between 4300 and 2,660,000 micrograms/kg";^[6] (summarizing these two) "the average iodine content of kelp of 1,500 to 2,500 μg/g".^[7] So we're looking at roughly 2 mg of iodine per gram of kelp (I assume these are all dry weight), if you happen to get an average sample, with a just ridiculous amount of variation. So eating 65 grams, a plausible dose, would be equivalent to the 130 mg tablet - though you might end up getting four times as much if you are unlucky. Or you might get less than a mg. Wnt (talk) 02:38, 18 March 2011 (UTC)

My ex (who is a third year undergraduate) has made over $1000 selling KI on eBay... John Riemann Soong (talk) 18:48, 19 March 2011 (UTC)

Why does the World suffer from nuclear phobia?

Ever since Chernobyl, people have had a strong irrational fear of nuclear power. The public prefers coal fired power plants over modern ultrasafe nuclear powerplants, even though the dangers of global warming are far, far worse than that of a Chernobyl-type disaster. People are now fleeing Tokyo in airplanes, when merely being aboard the airplane at 40,000 feet altitude will expose people to 100 times more radiation than they would get if they were to stay in Tokyo. How can we explain this irrational behavior? Count Iblis (talk) 16:45, 17 March 2011 (UTC)

Just because the reading on a Geiger counter is the same doesn't mean the exposure is the same. In an airplane, you get off and the exposure ends. But in Tokyo the counter would be clicking due to various isotopes in the air, water, environmental surfaces which you might inhale or ingest and become exposed to for years to come.

Still, I think it is reasonable to assume many of the people fleeing are convinced that the radioactivity will become much worse, or that basic necessities will become even harder to find than they are now. After all, many people would have left the tsunami-disrupted country even without a nuclear situation. Wnt (talk) 16:52, 17 March 2011 (UTC)

Your premise is that people's fear of the ongoing nuclear crisis is irrational, but you would have to cite a source for that. What makes you think it is irrational? The actual situation at the site is very unclear; right now, nobody in the world, including you, can even assess the probability of Tokyo becoming increasingly irradiated, or of a criticality accident, in the coming week; and the Japanese government's and Tokyo Electric's shameful avoidance of disturbing the public with the scary details they do have only exacerbates the (rational, I'd argue) fears that already exist. Comet Tuttle (talk) 17:07, 17 March 2011 (UTC)

(ec) A better question would be why people have an irrational belief in the safety of nuclear power. Put simply, nuclear power isn't safe and it never has been. Even when operating correctly, nuclear power plants produce radioactive waste that will be dangerous for the next 10,000 years. A Quest For Knowledge (talk) 17:08, 17 March 2011 (UTC)

I think the question is why people seem to be more afraid of a rare leak of radioactive carcinogens from a nuclear plant than they are of the routine dumping of radioactive carcinogens into the air by coal plants; and seem to be more upset about a 1% increase in lifetime cancer risk for the nuclear workers than about the horrible lung diseases and fatal accidents that routinely afflict coal miners; and seem to be more afraid that a nuclear plant will render a hundred square kilometers uninhabitable than that coal plants will stop the gulf stream and render all of Western Europe unsuitable for agriculture. People do worry about those things, but I'm not sure that will stop them from demanding the closing of nuclear plants after this disaster, which will inevitably (as far as I can tell) lead to an increased demand for fossil fuels at a time when we desperately need the opposite. That's my fear. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

There is quite an advanced literature on risk perception, esp. in relation to nuclear power. In particular you might find the work of Paul Slovic quite interesting — he charts out how fears of technology generally chart onto two axis: "unknown risk" and "dread risk". "Unknown risks" are things that are invisible hazards, with delayed effects, or exceptionally new. Think contamination, poisoning, irradiation. "Dread risks" are global, uncontrollable, catastrophic, involuntary. Think big disasters, or small disasters that you feel like you can't control. If you plot out how people judge various hazards on this scale, you get a nice graph of risk perception. On the bottom left (low dread, low unknown) are actually some quite dangerous things: bicycles, home electrics, automobiles, smoking (all things with very local effects, where you feel "in control", where by itself, one "accident" isn't going to kill more than a person or two). On the top right (high dread, high unknown) sits all of the radioactive fears (waste, weapons, meltdowns) — they trip up our psychological systems in a big way, and we've always viewed them (even before nuclear power) in rather mythological terms. Humans have ancient stories about evil rays, contaminated lands, and deformed children — the nuclear threat fit into these fears quite nicely. (On this point, my favorite book on the subject, though it is now a few decades out of date, is Spencer Weart's Nuclear Fear: A History of Images.) Note that I have generalized quite a bit regarding that chart. Weapons actually are somewhat less "unknown" than waste/power related things.)

None of this is correlated at all with what we might call actual risk (which can be tricky to calculate, but let's assume it exists). (This is not to say that all things considered dangerous are safe, or vice versa. Just that there isn't necessarily a meaningful correlation here in any individual case.) It is psychological. It is not a straightforward case of people not being "educated" enough on actual risks — that can itself backfire quite heavily (if you say, "it's safe, it's safe, it's safe!", and you're wrong in a BIG WAY one time... then your credibility is shot, and it's worse than if you hadn't said anything). Anyway, it is an interesting field. Whether people's risk perceptions are "rational" or not is entirely beside the point: human beings are not "rational" when it comes to our fears, and wishing they were will never make that so. --Mr.98 (talk) 17:15, 17 March 2011 (UTC)

An excellent way to assess risk in a rational way is to attach a price tag to it and see what a free market does with it. It's called the insurance industry and they're pros at weighing the cost of paying a claim versus the likelihood of having to do so.

When private companies in the USA wanted to start operating nuclear plants they asked insurance companies to take on some of their risk. The pros at the insurance companies looked at the payout vs. likelihood equation and said "no thanks". The industry should have ended there, but unfortunately it was important enough to national self-esteem that Uncle Sam stepped in and said "you guys just stash away a little money for minor accidents and if shit ever hits the fan my taxpayers will pick up the tab".

When the nuclear industry can cover its own risks then you can fairly claim that its skeptics are irrational. --Sean 18:12, 17 March 2011 (UTC)

Sean, nobody wants to insure against rare, large losses because that's risky. Insuring against many frequent, small (at the scale of the insurance company) losses is safe; you can build a business on that. The market is great at some things, but it's terrible at pricing rare, long-term risks. The actual, scientific cost of nuclear power versus the alternatives is such that we have to keep building nuclear power plants. The government steps in in these situations because that's why governments exist: to do the things that the market does badly. I know there are people who believe that the market does everything well and governments should be abolished, but those people are wrong, just like the people who think that homeopathy works, etc. This is the science desk. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

I'm pretty sure those people fleeing Tokyo are actually at a greater risk of being injured getting to the airport or the train station, than they are of being injured by a small amount of radiation. Astronaut (talk) 18:15, 17 March 2011 (UTC)

At the moment, maybe yes. But the situation is fluid, and if shit goes bad, which it can very quickly, it can go very bad. Thousands and likely millions of people had measurable and sometimes drastic health outcomes from the Chernobyl disaster, and while right now things are not Chernobyl bad, people may not want to be around when it does. To get back to answering the first questions, the real reason is that there is something in the general human psyche that fears disaster and catastrophe, that is events where dramatic and large damage occurs in the very short term, but does not really fear small, incremental, or common dangers which only show their harm in the long term after many years. Thus, people really fear plane crashes, but car crashes aren't that scary, since plane crashes, though rarer, are more dramatic and catastrophic. And people fear being fat even less than getting in a car crash, even though being fat is going to kill many more people, and cause much more measurably bad health outcomes than car wrecks will, if only because not many people die or get hurt instantly from being fat. It's the same deal with nuclear power vs. coal power. What worries people is not nuclear waste (even though THAT is the real danger), what worries people is their local nuclear power plant blowing up like a bomb and killing all of them isntantly. Coal power, which has very little danger of blowing up and spreading instant death around the country side, feels safer because of that reason, even though we know that it is actually worse for our health, and for the health of the earth, than Nuclear. --Jayron32 18:42, 17 March 2011 (UTC)

I'm not sure why you think waste is "the real danger." It is a difficult technical problem only because we'd like to be able to say that it will be totally containable for thousands of years. In the short term, dry storage of waste is extremely safe, providing you don't live right next to it. (Wet storage is a different question, of course.) The political difficulties of waste siting are vastly overblown compared to the technical risks. (Which is not to say there aren't technical risks, but they are very minor. You can see this when you look at the actual engineering assessments of the hazards — it's things like, "will 100 people get cancer in the next 100 years" — not great, but hardly public enemy #1.) --Mr.98 (talk) 19:04, 17 March 2011 (UTC)

It's relative danger, again. In the long term, in accumulative effects, more problematic outcomes are likely to occur from nuclear waste than from power plants blowing up. Nuclear waste may be more safe than say, coal slag or greenhouse gas emissions from ordinary cars, but it is also probably the more problematic part of the nuclear equation picture, when compared to the dangers of catastrophic nuclear plant failure. But because it is cumulative and slow moving, it tends to get ignored. The point is not that nuclear waste is either perfectly safe, or the worst thing ever to have occured to humanity; people want to paint the world in dichotomies like that, much as you just charactized my arguement. Its that, taken in comparison, we can say that nuclear waste is more problematic than some stuff (like say, plant failure) but less so than other stuff (like, say, smoking cigarettes). --Jayron32 19:41, 17 March 2011 (UTC)

I think I read (a WP article?) about the over-reporting of train crashes (rare, kill more, overall death rate lower) and car crashes. Seems to be similar here. Can't find it now, though. Grandiose (me, talk, contribs) 18:53, 17 March 2011 (UTC)

The world needs energy, and all have environmental impact. You decide:

• Oil: Greenhouse-gas pollutant, limited amount to drill safely, Deepwater Horizon and Exxon-Valdez.
• Coal: Dirtiest greenhouse gases, over 20,000 miner instant deaths per year (most in China, fewer in US, but major long-term health impact), and more radioactive than nuclear waste.
• Nuclear: only three major accidents in 60 years, extremely expensive start-up, but so far the only "wasteland" area is in Chernobyl - atmospheric radiation accidents disperse quickly.
• Hydroelectricity has major ecosystem impact and is not universally available or unlimited, as with renewables like solar, wind, and wave.

So indeed, take your pick. SamuelRiv (talk) 19:32, 17 March 2011 (UTC)

I disagree about the nuclear waste impact you've given, as we are still experiencing effects in the UK, hundreds of miles from Chernobyl: Chernobyl_disaster_effects#24_years_after_the_catastrophe. I also notice you refrain from mentioning the environmental impacts of renewable energy. --TammyMoet (talk) 21:27, 17 March 2011 (UTC)

I don't see that data on coal miner instant deaths in the article cited. Yes, it's dangerous, both in the ground and downwind, but would it be if we spent the kind of money we spend making nuclear plants "safe"? Wnt (talk) 23:41, 17 March 2011 (UTC)

If you spent that kind of money on coal, it would no longer be cost effective. Nuclear energy is far more cost effective, to start, allowing you to add lots of safety precautions and still have it be competitive. StuRat (talk) 00:23, 18 March 2011 (UTC)

I have never seen an economic justification for nuclear that includes the real cost to future generations of managing the waste. HiLo48 (talk) 07:06, 18 March 2011 (UTC)

Well, then, you'd have to compare that with the real cost to future generations of the alternatives. In the case of fossil fuels, that would include moving the populations of major cities on the oceans inland some 50 miles to deal with rising sea levels from global warming, or building massive dikes around them. I think that's several trillion dollars right there. Then there's the increased damage from hurricanes and tornadoes to consider. StuRat (talk) 07:31, 18 March 2011 (UTC)

The 'real cost to future generations' is usually negligible. Assuming an annual real rate of return of 7% (a conservative 10% growth, less 3% inflation) a dollar paid in 2050 is worth about seven cents today. A dollar in 2100 is worth about a fifth of a cent today. A dollar in the year 2500 is worth a bit less than a billionth of a cent. If one honestly figures the cost of processing and safely storing the waste for the next fifty or sixty years, then the real cost to store it forever is only trivially greater. TenOfAllTrades(talk) 13:55, 18 March 2011 (UTC)

I disagree. Yes, each dollar spent in 2050 will be worth less, but presumably more dollars will need to be spent in 2050 for the same activity as today. If the inflation rate of minding nuclear waste is the same as the general inflation rate, then they should cancel out. The only reason I could see why it would have a lower inflation rate is if electronics to detect radiation levels become relatively cheaper. While the cost of electronics does tend to fall relative to other items with time, radiation detectors may be an exception, since too much miniaturization (the primary driver of cost savings) may cause them to fail when exposed to radiation. As for your 10% annual economic growth rate, that's absurdly high, except maybe in China, but even there it's unsustainable in the long term. Perhaps you meant the 10% to be the returns from investing money now, say in the stock market, to cover later costs ? That logic would only apply if such investments were actually being made, and, even then, one would need to consider the opportunity cost versus investing that money elsewhere. StuRat (talk) 18:47, 18 March 2011 (UTC)

I'm not sure you understand how future costs are evaluated (and discounted) for the purposes of making comparisons between expenditures that occur in the future versus those which take place immediately. As to whether or not such investments are being made, for the United States, at least, the Nuclear Waste Policy Act requires utilities to contribute to the Nuclear Waste Fund; the Fund currently has about $25 billion in assets. TenOfAllTrades(talk) 19:25, 18 March 2011 (UTC)

And is it currently invested in a financial instrument earning a conservative 10% growth per year ? StuRat (talk) 19:29, 18 March 2011 (UTC)

The data regarding yearly international coal miner deaths is taken from the "China" section. Official China Labor Bulletin statistics cite 6000 deaths per year, and the number is adjusted to reflect the vast number of mines with few or no records (particularly those of accidental deaths). Additionally, I get sources for 400 deaths/yr in the US from black lung disease, which of course is an immediately-identifiable etiology (as opposed to cancer). I don't mention environmental impact of renewables, just that they can't be tapped wherever and whenever you want and thus will not replace all power, but you're right that like anything else they have environmental impact as well. Regarding long-term Chernobyl effects outside of the immediate area, fair enough. I will note, though, with respect to the compare-two-evils fallacy, that the amount of atmospheric fallout from Chernobyl is negligible to that of the above-ground nuclear tests. Regarding investment, in the US where coal is king we invest heavily in safety, which is why miner deaths per year has gone from thousands 50 years ago to 30 today. SamuelRiv (talk) 00:45, 18 March 2011 (UTC)

I am skeptical that China really has ~13000 deaths a year from coal mining that they don't know about; [8] sounds like a confident source. Obviously 6000 deaths is already intolerable, and perhaps the question of nuclear power in China might go a different way. Then again, Nuclear power in the People's Republic of China is only 1% currently, and who knows how it will work out for them (especially in the same poor regions of the country)? Wnt (talk) 01:51, 18 March 2011 (UTC)

The answer to the OP's question is quite simple. People display irrational behavior because people are irrational. Does that really surprise anybody? Dauto (talk) 23:57, 17 March 2011 (UTC)

Displaying an irrational fear takes a lot less effort than learning the science so that you can display a rational fear. HiLo48 (talk) 00:04, 18 March 2011 (UTC)

That's just a tautology. It fails to explain why the nuclear fears touch off such irrationality in particular. --Mr.98 (talk) 02:08, 18 March 2011 (UTC)

My point is that people in general are irrational just about all the time, so it is not surprising that they are also irrational about that particular subject. Dauto (talk) 12:55, 18 March 2011 (UTC)

Some thoughts as to why nuclear power feeds irrational fears:

1) Radiation is invisible. Thus, people don't believe when politicians and "experts" tell them everything is safe. If radiation was visible, they would know if an area was safe or not. Perhaps if everyone had Geiger counters, they would feel safer, both because they would know if radiation levels went up, and would realize that there's background radiation everywhere, and it's nothing to worry about. Maybe portable pollution detectors would also be a good idea, so they would know when they are in an areas of (fossil fuel) air pollution, and would see how much worse that problem is.

2) Nuclear waste is concentrated, versus fossil fuel pollution, which is widely distributed. It's easier to point to a barrel of nuclear waste and think "that's dangerous" than to point at the sky and think "that's dangerous". If, at some point, fossil fuel pollution is also concentrated into barrels of toxic waste, then this difference may disappear, when people compare millions of barrels of FF waste with a few of nuclear waste. StuRat (talk) 00:32, 18 March 2011 (UTC)

I think of several things:

• Nuclear power is very expensive if you calculate the absolute cost. Reprocessing is extremely expensive. Storage for 10000 years is also very expensive. It only works when the military and the government pays for the expenses.
• I like to imagine a conflict like that in Libya in a country with a lot of nuclear power plants. All people leave and one after the other explodes. Or in like in Yugoslavia. When one party shells the nuclear power plant instead of a bridge. Or like in Egypt. When after an election a fundamentalist government Israel bombs the power plants as a friendly first gesture.--Stone (talk) 08:15, 18 March 2011 (UTC)

Bombing a neighbor's nuclear plants isn't a good strategy, as the radiation would be likely to spread back to you, and also piss off other neighbors. Terrorists, on the other hand, might not care if they poison everyone, although PR is still a concern, even for them. I have always been an advocate of building nuclear plants more safely, though, such as in old mines, far from population centers (the cooling towers can still be above ground, but the radioactive portions should be safely hidden). The nuclear waste can then be kept in the mine permanently, after the plant is decommissioned. This does require transporting the power further, with more losses, but this cost can be justified both by improving public safety and preventing the nuclear power industry from suffering these periodic black eyes which threaten to destroy it. In an age of terrorism, we have yet another reason. The distant, underground construction also gets by the NIMBY problem. StuRat (talk) 17:56, 18 March 2011 (UTC)

A recent (er, future...?) piece in the New Yorker ("The Nuclear Risk," March 28 2011) also discusses the general issue of risk assessment of nuclear energy, concluding: "As the disaster in Japan illustrates, so starkly and so tragically, people have a hard time planning for events that they don’t want to imagine happening. But these are precisely the events that must be taken into account in a realistic assessment of risk. We’ve more or less pretended that our nuclear plants are safe, and so far we have got away with it. The Japanese have not." WikiDao ☯ 17:13, 18 March 2011 (UTC)

Elastic - is it okay to keep it stretched?

I need to know how bad it is for elastic to be kept it in its stretched state for a very extended period of time. Thanks. 71.220.225.153 (talk) 19:49, 17 March 2011 (UTC)

I'm not sure if that would effect how long it will last, as, for many elastomers, "aging" is due to mainly exposure to UV light or evaporation of volatile components. However, one concern is that when it does finally give way, it may injure somebody, say by snapping them in the eye or dropping whatever it was holding. Can you tell us what you had in mind as far as the type of elastic and load ? StuRat (talk) 00:09, 18 March 2011 (UTC)

I recently bought a bandoleer to hold a bunch of shotgun shells. The holders for the shell are made out of elastic and I was going to store the bandoleer with shells loaded in it unless it would wear out the elastic and make it unusable. As of right now I'd say the elastic is far too tight. It is fairly difficult to get shells in and out of it. 71.220.225.153 (talk) 05:43, 18 March 2011 (UTC)

Well, then you want to stretch the elastic, right ? I think that might work. However, certain types of elastic might also leave residue on the shotgun shells, as the elastic deteriorates, and this could interfere with performance when the shells are used. A safer approach might be to remove the shells, and replace them with something as large or larger, like rolled up newspaper bits, to do the stretching. A similar method is often used to help shoes in storage keep their shape. StuRat (talk) 07:22, 18 March 2011 (UTC)

Virgil C. Summer

who was Virgil C. Summer? a nuclear plant is named after him?? — Preceding unsigned comment added by Timc321 (talk • contribs) 20:01, 17 March 2011 (UTC)

He was a president of the South Carolina Electric and Gas Company, see [9] for a very brief statement as such. Since they built and own said nuclear plant, it makes sense they would name it after a former president of the company. --Jayron32 20:16, 17 March 2011 (UTC)

And this Google Books search turns up a few more scanty refs: [10]. --Jayron32 20:19, 17 March 2011 (UTC)

I've added a reference (from SCANA's own website) to that effect to the Virgil C. Summer Nuclear Generating Station article. Unfortunately there's no more worthwhile info, beyond what Jayron32 has found already, there. -- Finlay McWalter ☻ Talk 20:27, 17 March 2011 (UTC)

High oxidation numbers: above 8?

Is there any reason why transition metals' oxidation numbers always seem to cut out at eight (in group 8 elements)? For instance, why can't you get nine on a group 9 element (I'm thinking rhodium, iridium, possibly also americium where the d electrons are replaced with f) to make it d⁰? Like say iridium(IX) hydride (IrH₉), which is isoelectronic with the real complex ReH₉^2–. Or I could certainly imagine a hyper-periridate anion IrO₅^–. Os(VIII) forms readily and it's nearly identical. (Feel free to get really in-depth; I'm three years into a chemistry masters degree.) 137.205.222.209 (talk) 20:40, 17 March 2011 (UTC)

Might if have to do with the geometry of 9-ligand complexes? Once you get over 6 ligands, the Octahedral molecular geometry, things get weird. There are occasional higher order bonding schemes, like Pentagonal bipyramid molecular geometry but they are quite rare. You almost never find bare transition metal ions in solution or in crystal networks, especially with the higher oxidation number metals; even low-oxidantion number metals like copper-(I) and copper-(II) form complexes very regularly. Admitedly, my chemistry is a bit older than yours, since you are in it, and it's been 15 years or so for me since I studied this stuff in depth. There's probably some combination of electrostatics and orbital geometry that makes high oxidation number transition metals to be highly unlikely. The article Ligand field theory hints on some of the problems with considering what happens in d-orbitals; at first approximation, and under normal circumstances, all 5 d-orbitals are degenerate, which is true energetically, but in real bonding situations, the three d(xy), d(xz), and d(yz) operate differently than do the d(z²) and d(x²- y²) orbitals. Making a WAG, my guess is that due to these differences in d-orbital organization, there's some barrier towards, say, removing all 9 electrons from the 6s and 5d electrons in Iridium; in other words theres something in the way that the d-orbitals are organized that presents a large jump in ionization energy between the 8+ state and the 9+ state. f-electrons are so deep, I doubt they participate to any great end in hybridization, in bonding, or in ion formation in the way that s, p, and d orbitals can. Again, this is just me riffing on my admittedly underused 1990's era inorganic chemistry knowledge... --Jayron32 02:32, 18 March 2011 (UTC)

More than just that they "seem to cut out at eight" (emphasis mine), that is citedly the actual highest known (at least as of a little over a year ago), although there are groups studying that limit. See for example doi:10.1002/cphc.200900910. DMacks (talk) 03:05, 18 March 2011 (UTC)

Deliberate meltdown

Lets say some psycho wants to create a doomsday device. What would happen if someone made a reactor that had no coolant, turned it on full power, and deliberately let it meltdown. Could this have global effects or would the effects be relatively localized near the point of meltdown? ScienceApe (talk) 20:41, 17 March 2011 (UTC)

Basically what you are describing is a type of dirty bomb. Looie496 (talk) 20:57, 17 March 2011 (UTC)

There are two hugely relevant variables. How large is the device, and where is it located. Googlemeister (talk) 20:58, 17 March 2011 (UTC)

A meltdown would certainly be no worse than a nuclear bomb with the same amount of material. The nuclear bombs used, either for wars (hiroshima) or for Nuclear weapons testing, do not appear to have had global effects. 83.134.176.57 (talk) 21:08, 17 March 2011 (UTC)

You really cannot compare reactor meltdowns and nuclear weapons. (What do you even mean by "the same amount of material" in such a comparison? Reactors use tons of fissionable materials; nuclear weapons use kilogram quantities.) The comparison is highly misleading in every way. They are very different types of events. The only similarity is that both involve distributions of fission products. And there is some dispute as to whether the years of atmospheric nuclear testing did have global effects (e.g. increased thyroid cancers, etc.). They certainly had national effects. But again, this is kind of irrelevant, because it tells you very little about meltdowns. --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

This is essentially what happened at Chernobyl, albeit not "mad men" so much as "fools." The acute effects are "regional" — not global, but certainly not just "local". There are some "global" effects, but they are very hard to measure (statistical up-tick in cancers, for example — hard to figure out what the causes of those are). --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

The cobalt bomb was proposed as a similar device; one could translate its principles into a reactor, but a bomb would be more effective at creating and distributing the fission products. I believe (the article doesn't mention it, but its references do) that one advantage of such a device would be that it would not have to be transported to the target and could be arbitrarily large, providing, of course, that the device is understood to be a "doomsday weapon." Acroterion _(talk) 21:37, 17 March 2011 (UTC)

After encountering cobalt bomb, I ran across some unusual claims that the Russians had actually built a Doctor Strangelove type device. These emanate from Bruce G. Blair. I encourage anyone to take a look at the evidence and try to figure out if this is plausible or not; I've added a brief mention of what I found in the article. Wnt (talk) 00:28, 18 March 2011 (UTC)

He's referring to Perimetr, the so-called "Dead Hand" system. It's not really the same thing as the doomsday device. It was a command and control system that would allow the top Soviet leaders to say, "we're in a very tight time, and nuclear war could start any minute, so if you need to, launch the bombs." Then the Soviet army heads could, if they felt things were really bad, could say to a specific base, "look, if you lose contact with us, assume we're toast, and launch the nukes." Then the specific base would send up a special ICBM that had a radio transmitter on it that would say to all of the other ICBM bases, "go ahead and launch 'em, boys!" and then they'd all launch at the USA or whomever. So it's that last bit that makes it sound Strangelovian — it's a one-way trip at that point if a bomb goes off (or if for other reasons they lose contact). But it's a few more steps than that. The reason to make it was not some sort of MAD pact; it was due to the fact that in the 1970s the Soviet army realized their leaders were a bit dotty (Brezhnev and Chernenko being the obvious ones) and might not be able to order the nuke attack if it came down to it, and also they realized that a very weak point in the Soviet ICBM system was the communication system between individual missile bases. (For more information, I heavily recommend David Hoffman's The Dead Hand, which came out a year or so ago, and is pretty well-researched. --Mr.98 (talk) 01:28, 18 March 2011 (UTC)

Ach! I got hit by the oldest trick in the book that time. The first 'sources' I came across in the blogosphere made it sound like the system set off cobalt bombs automatically, but the ones closer to the source I actually cited didn't actually make that link, even though they talk about both things. (They're just both reminiscent of Doctor Strangelove. That one catches me more than any other. Wnt (talk) 01:41, 18 March 2011 (UTC)

I've run across references (don't ask me where, it's been a while) to a similar last-ditch American system, going by the codename Last Dance. Acroterion _(talk) 02:09, 18 March 2011 (UTC)

Just a pointer - I once read an article on history of nuclear wepons. According to it at first the concept existed, but no one was sure how it should look like, so some developed concepts similar to nuclear reactors (it seems everyone might have used reactors to explore the process, but I think it said that Nazis at least wanted to make an acctual bomb that way) ~~Xil (talk) 10:36, 18 March 2011 (UTC)

It's true that the initial conception of a nuclear bomb by Heisenberg was something in between a reactor and a bomb. But it was very ill-conceived, and was reflective of the fact that they didn't realize they could do a fast-neutron chain reaction. There is a lot on this in Heisenberg and the Nazi atomic bomb project by Paul Lawrence Rose (he calls it the "reactor-bomb" if you want to skim through the Google Books edition). --Mr.98 (talk) 12:54, 18 March 2011 (UTC)

March 18

Breast milk and iron

According to this site: [11], human breast milk is almost devoid of iron, and many other vital nutrients. So then, how do babies which are exclusively breast fed get their iron, and those other nutrients ? StuRat (talk) 00:40, 18 March 2011 (UTC)

They store it before they are born. Especially non-c section babies get filled with extra blood from the placenta by the contractions (sometimes causing jaundice when the extra blood is broken down). The iron in blood is almost completely recycled, and the store of iron lasts them till they start eating solids. Ariel. (talk) 00:44, 18 March 2011 (UTC)

Where is this "excess blood" stored ? Even with perfect recycling, they would need more iron to account for their growth. And, if babies can recycle iron so well, why can't adults (especially men, most of whom don't menstruate :-) )? Why do adults need dietary iron ? StuRat (talk) 03:32, 18 March 2011 (UTC)

(edit conflict)Two things:

1. When reality seems to be in conflict with "experts", trust reality. In this case, since humans for millions of years fed their infants breast milk, and yet we as a species survived; and since today, still, the majority of humans still feed their infants breast milk, and those babies keep growing into healthy adults, there must be something right about breast milk. Regardless of what the "label" says, or the list of ingredients or anything else, its not that breast milk is deficient, it must be that what you are presupposing to be necessary OR what you are presupposing to be actually in breast milk, per that label, is really there, that is what is deficient. Breast milk is not deficient, obviously, so we need to figure out what is going on here.
2. Read the label again. The % of iron is the % of the daily requirement an adult eating a balanced 2000 calorie diet would get out of taking in 172 of those calories in breast milk. Instead what you have is an infant, who is eating much less (say 500 calories or less), and getting all 500 of those calories from the breast milk. In that case, the infant may be getting 100% of their daily requirment for iron, since a) their iron requirements are likely different b) American food labels are rounded somewhat, so what might be, say 0.44% for an adult would still show up as zero. That doesn't mean there is no iron, just a small amount when compared to an adult requirement, but likely suffient for what an infant needs. And that is all dependent on the fact that you can trust what that website is telling you...

That's how I read the situation. (post EC extra stuff) what Ariel said makes sense regarding how infants work out their iron situation. Makes sense. I knew it had to work out, because of point 1.--Jayron32 00:54, 18 March 2011 (UTC)

To your point 1, if a baby has only 1/4 the calorie requirements, and also only 1/4th the iron requirements, then 0.44% of an adult RDA would become 1.76% of a baby's RDA, still grossly insufficient. And I suspect that more iron is needed, proportionally, when growing, than as an adult. StuRat (talk) 03:28, 18 March 2011 (UTC)

Apparently not; again your assumption that small babies need, proportionally, the same amount of iron as adults is not borne out by the fact that breast fed babies aren't all dead, and are perfectly healthy, even with regards for the kinds of reasons that, you, as an adult, need iron. Breast milk is empirically not deficient, so either a) that "nutritional facts" label is wrong or b) babies need a lot less iron in their diets than adults. Ariel, above, provided ample evidence that the real answer is b, though I have my suspicions that there may be some option a at play as well. Again, you can't start with the supposition that breast milk is deficient when there's ample empirical evidence (nearly all of humanity for all of history; indeed even more than that, we have nearly all of mammalia for even longer). The experiment has been run trillions upon trillions of times and milk works. So we have to rephrase the question: What in your supposition is wrong, or what is it about how babies need iron that is different than adults? Ariel answered that succinctly: they don't need dietary iron during their first several months because of the massive iron boost they get during normal birth. --Jayron32 03:50, 18 March 2011 (UTC)

It's patently obvious that it has to work out somehow, so stating that over and over doesn't help much. I want to know HOW it works out. The only assumption I made in my initial post is that the nutrition site I listed has correct info. If you have another site which disputes that info, then that would be useful. If babies are born with "excess blood", I'd like to see a site which supports and describes that. Also, I believe some cultures have babies who are exclusively breast fed for years, so how can the iron last that long ? StuRat (talk) 07:11, 18 March 2011 (UTC)

The extra blood is stored as rather red-looking babies (at first, till the excess red blood cells are digested in the spleen). Iron is also be stored in the liver and other places from before they are born. Normally elements diffuse from a higher concentration to a lower across the placenta, but iron is actually pulled against the gradient if necessary (potentially leaving the mother anemic). This iron is then stored. The primary loss of iron is mucousal irritation of the bowels (red blood cells are recycled basically perfectly in the spleen), but that doesn't happen to breastfed babies, so their need is lower. That's one of the reasons their feces have such a strange (light) color. This page says more or less the same things: http://www.kellymom.com/nutrition/vitamins/iron.html It also mentions that breastmilk is not as deficient as it might appear - the iron is in a form that is extremely well absorbed. Normally an adult will need 20-100 times as much iron in their food as they actually need since it's so poorly absorbed, but in breast milk you only need twice as much. The net result is that breastmilk effectively has 10 (or more) times as much iron as it might appear. Ariel. (talk) 11:53, 18 March 2011 (UTC)

Thanks. It looks like human breast-milk is still deficient in iron, even after the better absorption is considered, since babies do gradually use up their excess stores. Do children in societies that breast-feed longer suffer from anemia ? Has anyone attempted to create iron supplements in the more absorbable form, similar to breast-milk ? Do any other mammals create such milk ? StuRat (talk) 17:44, 18 March 2011 (UTC)

Yes, they do eventually run out, but by then they are eating solids. I don't think even in those societies that it is exclusive, but rather it's a supplement. Presumably they would get iron from the other foods they eat. It looks like Iron Glycinate (or any iron attached to an amino acid) is best absorbed. It's also important to eat the iron together with vitamin-c. Ariel. (talk) 18:27, 18 March 2011 (UTC)

There's an advert for a toddler follow-on milk on British TV which goes on about how little iron breast-milk has and how much their product has, conveniently ignoring the fact that toddlers will (or should) be eating a varied diet including several sources of iron, and not relying only or mainly on milk. DuncanHill (talk) 12:08, 18 March 2011 (UTC)

Thanks, everyone. I'm glad I can trust the nutritional info on human breast milk I've found, as I've never been able to find a nutrition label directly on the natural package. :-) StuRat (talk) 02:48, 22 March 2011 (UTC)

How the following time dilation senario in three frames of reference can be explained?

Let we have A and B transparent spaceships such that B is inside back of A as the size of A is greater than B. Also there is an observer at the middle of A who is stationary for B.

Now both spaceships ignited and set out at same time (with speed close to the speed of light) for space journey. The front of A is open so that B may leave A if want. The reading of speedometer of B may or may not be the same with that of A. Light clocks installed in each ship with top and bottom mirrors,  is also starts automatically with ignition.  

We have following three reference frames

1-  within B (with light clock LC2)

2- within A (with light clock LC1 and moving spaceship B in which LC2 is installed)

3- for outside observer who is not co moving on asteroid

Now

1- LC2 is making time dilation triangle for (a) for observer at the middle of A who is stationary for B (b) for outside observer who is on asteroid.

2- LC1 is making for (a) for outside observer on asteroid (b) may be for onboard observer B.74.198.150.213 (talk) 02:48, 18 March 2011 (UTC)Eccentric Khattak#1

I think I understand the setup, but what is the question? You only asked "how can it be explained?", which is not specific enough. -- BenRG (talk) 03:25, 18 March 2011 (UTC)

Then you understand more than me. The explanation above about the setup is quite confused in my opinion. Dauto (talk) 03:48, 18 March 2011 (UTC)

I don't understand what the point is of making the spaceships transparent or allowing one to enter the other. Couldn't they simply be normal spaceships that pass by one another? More to the point, can't you just say that A is the surface of the Earth and only look at B (i.e. usual twin paradox?) But I don't understand the acceleration that A and B might undergo. Wnt (talk) 05:34, 18 March 2011 (UTC)

I don't know what it is that you want to know or you have trouble understanding, but maybe you should have a look at Bell's spaceship paradox. If you are asking whether 2 spaceships, initially at rest, and starting at the same time with the same acceleration, are moving relative to each other while they are accelerating, then the answer is yes (specifically, in the reference frame of an observer at the position of one spaceship with the velocity of this spaceship at any point in time while they are accelerating, as we only look at non-accelerating reference frames). Icek (talk) 08:07, 18 March 2011 (UTC)

I want to make it a little more clear if all above is incomprehensible. Let Spaceship B is at rest  in A while  A is moving with speed close to the speed of light. When A is about to pass by an asteroid,  B take off in A in the same direction. Thus an observer at middle of A will see a ship B is moving with light clock LC2 in his frame of reference. An outside observer will see B is moving in moving reference frame  (with light clock LC1)  of A. The direction of both A and B is same. Thus there are three reference frames

1- Within B (with LC2) 2- Within A (with LC1 and moving ship B) 3- For outside observer (with moving A inside which B is moving).

My question is how the aforementioned clocks (two time dilation triangle) can be analyzed w,r.t both onboard observers, observer at the middle of ship A and outside on asteroid. 

I don't know how to post a question with diagram therefore it's a little confusing but I hope I have explained things clearly enough for you all  to understand74.198.150.213 (talk)Eccentric Khattak#1 —Preceding undated comment added 23:09, 18 March 2011 (UTC).

Is spaceship A accelerating? Anyway, you can always analyze the situation by applying the Lorentz transformation to the time and space coordinates (and if you are specifically asking what the velocity of B is with respect to the asteroid if you only know the velocity of A with respect to the asteroid and the velocity of B with respect to A then you can use the velocity-addition formula). Icek (talk) 12:37, 19 March 2011 (UTC)

It makes no different whether one spaceship is inside the other. The analysis is the same as if they were side by side. Does that help? -- BenRG (talk) 20:31, 19 March 2011 (UTC)

No A is not accelerating. The speed of B may be  1- less than A  2- equal to A 3- greater than A

An observer on asteroid will see his local clock is correct as compared to the moving one (LC1of A) that is slow.

Similarly an observer at the middle of A will see his clock is correct as compared to that of the moving one (LC2 of B) that is slow.

So for observer on asteroid would LC2 = LC1 or LC2 slower than LC1 or vice versa OR..... 

Thus, how the following  clocks can be described in terms of slower and faster w.r.t each other while keeping in mind the aforesaid different speed of B.

  1- of an outside observer on asteroid  2-  of LC1 of A 3- of LC2 of B

74.198.150.213 (talk) 01:03, 21 March 2011 (UTC)Eccentric Khattak#1

For quantitative details, see Special relativity#Time dilation and length contraction and Time dilation. But qualitatively, the rule is that "moving clocks run slow," and the faster a clock moves, the slower it runs. So the clocks on both rockets A and B will be observed to be running slow as observed in the asteroid's frame of reference, with the clock on the fastest rocket (as measured in the asteroid's frame of reference) being observed to be running the slowest. If A and B are traveling at the same velocity, then their clocks will agree with each other.

Of course, there's nothing special about the asteroid's frame of reference, just because it happens to be the largest object of the three objects whose comoving frames are of interest (assuming the asteroid isn't so large that its gravity starts becoming significant to the problem). So for example, in A's frame of reference, a clock on the asteroid will be observed to be running slow, and A will observe B's clock to be running slow as long as B is moving relative to A. And which of the asteroid's clock and B's clock is observed by A to be running the slowest depends on which of the asteroid or rocket B is moving at the highest speed, as measured in A's comoving frame. Red Act (talk) 12:37, 21 March 2011 (UTC)

Three more simple questions

1- For outside observer: would B be touching/ hitting the end/ tail of A if B is hovering inside A or it's speed is less than A

2- For both onboard observer A and outside on asteroid

"Would B be escaped through the front of A at the same time (or different) if it's speedometer reading is greater than A

3- is it possible for outside observer to see

Speed of A = 0.8c and that of B greater than 0.20 c ? "74.198.150.220 (talk) 02:37, 22 March 2011 (UTC)Eccentric Khattak #1-420

1- If B is inside A and only the front of A is open, then relative to the asteroid, B must be traveling at least as fast as A, or B will soon be resting on the back of A and hence go the same speed as A.

2- You haven't specified how B's "speedometer" measures speed. It's possible to create an accelerometer, which can measure acceleration independent of any outside object. But in contrast, there is no such thing as absolute speed. You can only measure the speed of an object relative to some other object. For example, a car's speedometer measures the car's speed relative to whatever the car is driving on, which is usually the car's speed relative to the Earth's surface, but might be different if for example the car is on a ferry at the time. But I will take your question as meaning that B's speed relative to the asteroid is greater than A's speed relative to the asteroid.

All observers will agree that there exists an event at which the front of rocket B passes the front of rocket A. Whether all observer's clocks that are present at that event read the same time or not depends on how the observers go about setting their clocks. That specific event may as well be the arbitrary event that all observers use as defining what the "zero" point of their clocks is. In other words, that event may as well be the event that all observers use as defining the origin of their coordinate systems. When dealing with two different events that are separated by a space-like interval, relativity of simultaneity makes it such that which of the two events is considered to have occurred first depends on the observer. But when there's only one event involved in a question, whether or not observers agree on the time that the event occurs depends only on an arbitrary choice as to how the clocks are zeroed out.

3- Yes to the question as asked, but I think you aren't phrasing the question to mean what you are intending it to mean. As asked, an example situation that meets your criterion would simply be rockets A and B both traveling at 0.8c as observed in the asteroid's reference frame.

What I think is more along the lines of what you're intending to ask would be a situation in which rocket A is traveling at 0.8c as measured in the asteroid's frame of reference, and rocket B is traveling at, say, 0.9c as measured in A's frame of reference. It's certainly possible for that situation to occur. However, in that situation, B will still not be measured to be going faster than c in the asteroid's (or any other) frame of reference. Instead, B's speed as measured in the asteroid's frame of reference will be as per the velocity addition formula. Red Act (talk) 23:39, 24 March 2011 (UTC)

Efficiency of nuclear reactor

Hello, What % of the heat generated by a nuclear reactor is converted to electricity?(whats the efficiency of the turbine-cooling circuit i mean) TY DST DSTiamat (talk) 08:53, 18 March 2011 (UTC)

See the list at List_of_BWRs. For example, the Fukushima Daiichi reactor 1 had a MWth of 1380 and a MWe of 460, or 33% efficency. F (talk) 10:22, 18 March 2011 (UTC)

The efficiency is usually in the range of 30 to 35 percent which is the same efficiency of a coal power plant since they work the same way, only with a different source of heat. Dauto (talk) 12:44, 18 March 2011 (UTC)

Some of the newer designs are above 40%. Dragons flight (talk) 16:25, 18 March 2011 (UTC)

Radiofrequency ablation for typical atrial flutter

Is there any term which is addressed by "drag and burn" and it is related to cavotricuspid isthmus. Cavotricuspid radiofrequency ablation for typical atrial flutter is a proceudre and something on the lines the term "drag and burn" gets mentioned. Is "drag and burn" the right term, or there is something else related to the radiofrequency ablation for typical atrial flutter and Cavotricuspid. aniketnik 10:27, 18 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

I'm not sure I understand the question. The term "drag and burn" is widely used in the literature for a method of pulling a probe across the atrium in a linear series of steps and creating a lesion at each point. My understanding from a Google search, though, is that the technique does not work very well and is not widely used. Looie496 (talk) 17:13, 18 March 2011 (UTC)

Resource starvation or Maximum throughput scheduling for doing office paperwork?

I spend nearly all my working hours doing non-routine paperwork. The paperwork varies in importance. Doing the most important things (which also require the most time to do and are the most difficult) would result in not being able to do anything else for months, as described in the Resource starvation article. Currently I do Maximum throughput scheduling where I do the quick easy jobs. However this leaves the big difficult jobs undone.

What method of scheduling should I use, that does not have the diadvantages of the two extremes above? Thanks 92.15.2.23 (talk) 11:54, 18 March 2011 (UTC)

This reminds me of the Time Manager scheduling system, used by an IT department I used to work for. It involves setting goals, identifying key tasks identified with each of these goals along with milestones and deadlines, and scheduling tasks associated with each of the goals every day until the deadlines/milestones were met. (As far as I understand - you see I was a mere untrained secretary...) You might like to investigate this further. --TammyMoet (talk) 12:46, 18 March 2011 (UTC)

Which tasks, if left undone, will prevent other employees from doing their work? Which bits of paperwork are likely to have the most (and least) serious consequences for your employer? Is there a reason why you can't break up your day or week into blocks of time which can be allocated to different tasks, instead of your described all-or-nothing approach? (Do long-term projects in the morning while you're fresh, and do the quicker tasks in the afternoon. Or make Monday through Wednesday 'major project' days, and do small stuff Thursday and Friday. Or whatever.) Which tasks do the supervisors who evaluate your performance think are most important? Seriously; the people who pay your salary get the ultimate say in your work priorities—what happens if you ask your boss? TenOfAllTrades(talk) 13:05, 18 March 2011 (UTC)

There is nobody else - just me. No other employees, no supervisor, no employer, but only me. 92.15.2.23 (talk) 13:53, 18 March 2011 (UTC)

Ah, so your question is really "How do I do twelve hours' work in eight hours per day?" The answer, of course, is "You can't." At least, not forever. Either find a way to reduce/streamline the workload, hire additional help, or subcontract some tasks. It's difficult to advise you further without knowing what line of work you're in. TenOfAllTrades(talk) 16:55, 18 March 2011 (UTC)

Maybe the single machine/total tardiness sections of Scheduling: theory, algorithms, and systems By Michael Pinedo might be of interest. Sean.hoyland - talk 13:48, 18 March 2011 (UTC)

I had a similar situation, for writing computer programs, although I did have a boss. They gave me so many assignments they knew I couldn't do them all, and they realized I couldn't do all of them, but they did allow me to set my own priorities. I decided to write those programs which I found most enjoyable, and leave the rest to fester. StuRat (talk) 17:30, 18 March 2011 (UTC)

I think you already answered your own question by saying certain tasks were "most important". The only alternative consideration is whether you value getting more tasks done or more important tasks done. But as long as the less important (though perhaps more numerous) ones don't block other work (even your own) then I say let 'em fester, since by definition they are not as important as the other ones to accomplish (and as others noted, you apparently cannot get it all done). DMacks (talk) 17:53, 19 March 2011 (UTC)

One way which I have seen is for all the managers (you in this case) make a big pile of all the projects and decide which are the most urgent, every week. Do those first. Eventually the jobs that weren't regarded as important will become urgent, if you are gaining on the stack of work. Greglocock (talk) 03:07, 23 March 2011 (UTC)

How much warning of the Japanese tsunami was given?

Did the coastal Japanese get any prior warning of the tsunami, or was it unexpected? If yes, how long did they get? I appreciate that even if an official warning was given, not everyone may have recieved it in time. Thanks 92.15.2.23 (talk) 12:36, 18 March 2011 (UTC)

I don't know, but the quake was a warning in itself. --85.77.4.120 (talk) 14:20, 18 March 2011 (UTC)

The news reports I heard said that in the hardest hit areas, a tsunami warning was immediately and automatically issued as soon as the earthquake struck. The tsunami then first hit land only 15 minutes later. 148.177.1.210 (talk) 14:24, 18 March 2011 (UTC)

Some places had more than a half hour warning. Rmhermen (talk) 14:41, 18 March 2011 (UTC)

How much radiation protection from an Armored car (military), Armored Personnel Carrier or Tank?

I understand that modern APCs and tanks are sealed from chemical weapon attack. How much protection from radiation would a modern tank, armoured car or APC such as the Type 96 Armored Personnel Carrier give? I'm wondering why they are not being used to drag fire hoses to approriate positions in the Japanese nuclear emergency. Thanks 92.15.2.23 (talk) 12:43, 18 March 2011 (UTC)

I don't think they need that level of radiation protection to drag hoses. Around the plant, it is not "zap you dead" amounts of radiation, it is "the equivalent of lots of chest x-rays" amount (and the latter, while not good, is still only a probabilistic rise in the chance of developing cancer). The people who are probably getting way too much are the people working in the control rooms (where they are getting a year's allowed exposure in an hour, and sometimes having quite dangerous spikes of radiation), not the people dragging hoses around. I don't think the nature of the problem is not being able to drag hoses around, either. --Mr.98 (talk) 13:24, 18 March 2011 (UTC)

I wonder if there is any such thing as anti-radiation armour? It would be heavy. Radiographers in hospitals wear an apron, perhaps lead-lined. 92.15.2.23 (talk) 13:56, 18 March 2011 (UTC)

I don't think the heroic workers and fire fighters on the Japanese reactors site are at risk of being zapped by bursts of gamma rays or X-rays. Long-term health risks arising from contanimation from fallout must be a bigger concern. In this respect, the best prophylactic measures are surely a well filtered or self contained air supply and thorough decontanimation procedures. Gandalf61 (talk) 14:12, 18 March 2011 (UTC)

There is certainly radiation outside the buildings (hence the evacuation of most workers, the suspension of outside work several times during radiation spikes, etc.) There also is certainly gamma radiation - and alpha and beta. Their suits and respirators are only to keep radioactive particles off their skin and out of their lungs, altough they will stop alpha and some beta. Mainly the suits are so they don't need to be decontaminated so often. Rmhermen (talk) 14:41, 18 March 2011 (UTC)

Some tanks, such as the Abrams M1, have depleted uranium armour, but that's intended for extra resistance to armour-piercing projectiles, not gamma radiation. The primary radiological hazard isn't radiation external to the vehicle (there aren't nuclear bombs going off or big chunks of gamma emitters lying around. The danger is instead from particles of radioactive material getting onto people and contaminating surfaces: these are carried in the plume from a burning reactor (which is why the exposure in helicopters above the reactor is so great) and they fall out onto the land under the plume. Modern main battle tanks have air filtration systems and some (such as the Abrams) run an overpressure a/c system (fed through extensive filters) which are designed to keep out smoke, chemical agents, sand, dust, and other contaminants. Those fitted for urban or desert warfare have yet more filtering. But a tank is massive, and incredibly heavy, and the places to which the water needs to be delivered are inside ruined buildings. So instead they're using military fire engines - I think that means modern aviation-style ones, which have hoses on turrets that can be operated without the firefighter leaving the cabin, and have air filter systems designed to allow them to operate close to burning aircraft (which should help to keep out those radioactive particulates). -- Finlay McWalter ☻ Talk 14:27, 18 March 2011 (UTC)

I understood that the helicopter pilots problem was that they were in a direct-line from the gamma emmisions from the exposed fuel rods in the spent fuel tanks (now that the building roofs are gone while those on the ground are still somewhat protected by the large mass of the concrete pool walls. Not sure how absorbtive concrete is, though, maybe they are lead-lined as well? Rmhermen (talk) 14:41, 18 March 2011 (UTC)

Lead is only a little more effective than concrete. A 10 cm layer of either of them will be quite effective to block most gamma rays. (Equivalent to about 1 km of air). Dauto (talk) 00:48, 19 March 2011 (UTC)

It appears they are steel-lined anyway. Rmhermen (talk) 04:55, 19 March 2011 (UTC)

Levels of 400 millisieverts per hour of radiation were reported at some time during the past week. That does pose an immediate radiation hazard, with radiation sickness likely after 2.5 hours of exposure. This is aside from any danger of inhaling particles, ingesting them, or taking them home on your clothes. A tank may have thick armor on the turret and parts of the hull, but the floor is typically quite thin, and radioactive isotopes on the ground would "shine" through the bottom and harm the personnel inside if they stayed there very long, unless the tank provided shielding or unless shielding such as lead plates were added. Radiation protection says that 2.5 cm of steel would cut the radiation in half, the same as 1 cm of lead, 0.2 cm of depleted uranium, or 6 cm of concrete. Cutting the dose in half would mean radiation sickness after 5 hours rather than 2.5 at the extreme hotspot. More thickness would give proportionately more shielding. M1 Abrams#Armor says it has "chobham armor," layers of steel, ceramic, plastic and kevlar. Only the steel would provide much shielding. The article says some tanks have depleted uranium mesh only at the front of the turret and front of the hull, not particularly helpful if the radiation is coming from stuff on the ground under the tank. Armoured personnel carrier says "Armour on APCs are usually composed of simple steel or aluminium, sufficient for protection against small fire arms and most shell fragments." Thin steel or or around an inch of aluminum armor way would provide only slight reduction in the radiation the crew was exposed to. The M113 APC had 2.86 cm of aluminum on the floor and 4.45 cm on the top.I could not find a ref for the thickness of aluminum to cut the ionizing radiation dose in half. The best bet would be to operate a device remotely. Howe & Howe Tech has converted many of their tracked vehicles to full remote control, for firefighting or combat applications, and the nuclear industry would do well to similarly develop remote operated firefighting, demolition, and observation equipment. You do not need a human in the cab of a crane, or behind the wheel of a firetruck, to operate the hydraulic controls to move the vehicle around, or to move a boom or to aim a nozzle. Even the guys on Mythbusters regularly convert cars and trucks to full remote control. See also Military robot, "Thermite" fire fighting unmanned ground vehicle, which could observe and could likely be modified to deploy a hose. Edison (talk) 14:53, 18 March 2011 (UTC)

Messenger Mercury orbiter

A new "MESSENGER" orbiter has just gone into orbit around Mercury. History shows the lifetime of Mercury landers is very short because of the high heat. How does the solar heating in Mercury orbit compare to that in Earth orbit? Mercury appears to have an average distance from the Sun of about 58 million km, (avg of aphelion and perihelion) compared to about 150 million km for Earth. Inverse square law would then suggest about 6.7 times the solar radiation intensity falling on a Mercury orbiter, than if it were in orbit around the Earth. An earth orbiter gets very hot on the Sun side and very cold on the other side, if not rotated. The Mercury orbiter has solar panels, so "barbecue mode" seems to be out. It looks like they have a white heat shield on the "back" of the instrument package, and a gold covered instrument package facing Mercury. Would the "Mercury shine" be a significant infrared heating source, leading to the designers not painting the non-sun side black for better heat radiation, with lots of surface area to radiate off heat? I realize that "space has no temperature," but things in space certainly do. Edison (talk) 17:15, 18 March 2011 (UTC)

"Mercury shine" is an issue: "The spacecraft’s orbit is elliptical rather than circular because the planet’s surface radiates back heat from the Sun. At an altitude of 124 miles, the re-radiated heat from the planet alone is four times the solar intensity at Earth. “By spending only a short portion of each orbit flying this close to the planet, the temperature of the spacecraft can be better regulated,” NASA documents explained."[12] Rmhermen (talk) 17:32, 18 March 2011 (UTC)

"MESSENGER will operate at room temperature behind a sunshade made of heat-resistant ceramic cloth."[13] but "the sunshade is made of Nextel™ AF-10 fabric[7], which not only can withstand extreme temperatures, but also has excellent thermal properties that limit the spacecraft’s temperature to below 140 C."[14] 140 C is a bit warmer than I keep my room! Rmhermen (talk) 17:42, 18 March 2011 (UTC)

Is that made out of crushed Nextel cell phones ? :-) StuRat (talk) 18:39, 18 March 2011 (UTC)

Operating the spacecraft close to the hot surface of mercury it is like opening an oven and looking into it. The temperature is only 250°C but your face gets hot. The sun is more like a normal light bulb at the same distance. The tungsten filament is 1500°C or more but the heat you get is much smaller. The spacecraft orbit is designed in a way that they heat up in close approach . (They have to do it on the day side because they want to take pictures). And than they go out into space to cool down. A lander was proposed landing at the day night boarder and slowly moving away from the sunrise, but upto now nobody dared to go to mercury to land. --Stone (talk) 19:16, 19 March 2011 (UTC)

Isn't the dark side of Mercury cool enough for a landing ? (I realize that Mercury doesn't have a permanent dark side, but I believe night is very long there, allowing a mission to complete in that time). StuRat (talk) 20:37, 19 March 2011 (UTC)

The dark side isn't cool, it's freezing cold. It can get down to nearly -200C. There is no atmosphere (or at least, no atmosphere worth mentioning - there is a little outgassing, etc.) so once you are out of direct sunlight, it gets very cold very quickly. The terminator (the day/night border) is the only place with reasonable temperatures for a long-lasting lander. --Tango (talk) 02:23, 20 March 2011 (UTC)

Tango, I don't think cold weather matters much at all for these probes unless we're at cryogenic levels. The problem is that Mercury is at a 3:2 (3 rotations per 2 revolutions) tidal-lock with the sun and has an orbital period of about 100 days. This means that the dark side of Mercury will become the scorching side after only 60 days, way too short for a science mission. SamuelRiv (talk) 05:25, 20 March 2011 (UTC)

60 days doesn't seem too short, to me. For an unmanned mission, the robot could explore, pick up some good samples, and leave with them, in that time. Alternatively, they could drill a hole and climb down inside to survive the heat when day comes. Or, for a second alternative, how about rolling towards the darkness continuously to increase the length of the mission while "seeing the sights". Let's see, at the equator Mercury has a semi-circumference of about 7665 km. Divide that by 60 days to get 128 km per day. If that's too much, land closer to either pole, to shorten it, as needed. Of course, a straight path may not work, since dangerous craters may be in the way, and that would need to be taken into account, too. StuRat (talk) 08:53, 20 March 2011 (UTC)

-200C is crygenic levels, isn't it? While those kind of temperatures aren't a problem in space, since you lose heat quite slowly in a vacuum, you wouldn't be able to maintain a reasonable temperature while in physical contact with rock at -200C. --Tango (talk) 20:46, 20 March 2011 (UTC)

Driving to stay ahead of sunrise? Ha! In seven years on Mars Opportunity has driven about 26 km. Opportunity's minimum operating temperature is -40 C (with heaters to keep it that warm), so -200 C is far below current spacecraft standards. Operating on the dark side of a planet requires an energy source other than solar. So it seems landing on the dark side is not reasonable at all. anonymous6494 21:57, 20 March 2011 (UTC)

We certainly have another choice for energy: nuclear. Many spaceships have had nuclear power, so it doesn't seem impossible to put it on a rover. (The only reason it's not practical on cars is the safety concern, and, once it's on Mercury, we needn't be worried about it poisoning anyone, except maybe the little green men. :-) ). If you land it quite near a pole, say 10 km away, then it wouldn't have to move far to stay on the dark side, and it could perhaps still get solar power with a solar panel on a long vertical mast. If you can find a polar crater, it might always stay in darkness as Mercury rotates, without needing to move. So, there are plenty of options. StuRat (talk) 05:23, 21 March 2011 (UTC)

Using nuclear bombs to generate power

I remember reading about a concept to use nuclear bombs detonated in a deep underground cavity to generate power. I can't remember what it's called though, does anyone know? There's an article on wikipedia about it... ScienceApe (talk) 19:39, 18 March 2011 (UTC)

Studying that was one of the objectives of Project Gnome. In a vaguely related vein, the Soviet Union's Nuclear Explosions for the National Economy programme included explosions designed to help the harvest of fossil fuels. -- Finlay McWalter ☻ Talk 19:51, 18 March 2011 (UTC)

I think what you want is PACER. --Mr.98 (talk) 20:02, 18 March 2011 (UTC)

Thanks. Does anyone know what the advantages/disadvantages of this would be compared to conventional reactors? Would this be safer?ScienceApe (talk) 01:35, 19 March 2011 (UTC)

It's terribly uneconomical, requires you to be constantly producing nuclear weapons, and while I'm not sure the risks have been fully worked out, they are certainly not non-existant, both from an exposure point of view and a theft point of view. It's the kind of thing that weapons designers think is a really great idea, but it is most certainly not the best way to do things. Keep in mind that to produce said weapons, you still have to run reactors or enrichment facilities anyway. --Mr.98 (talk) 02:40, 19 March 2011 (UTC)

I wonder how much is known about stress fatigue in large geologic formations. Wnt (talk) 21:28, 19 March 2011 (UTC)

Not only do you need enrichment facilities, you need much greater enrichment. For a bomb, you need about 90% U-235. For a reactor, 3% will do. (The starting point is 0.7%.) See Enriched uranium for details. I can imagine that using existing nuclear bombs to generate power as a way to make use of them while getting rid of them could be worthwhile (although even that seems unlikely to me), but creating bombs specifically for power generation is just ridiculous. --Tango (talk) 02:29, 20 March 2011 (UTC)

It would be interesting to calculate how much electricity would be used to enrich uranium for a bomb versus how much energy you could produce by blowing it up in a PACER scenario. Presumably these numbers are out there, somewhere. You might end up in the black if you did this — generating more energy than it takes to enrich. I don't know. (That still wouldn't make it a good idea.) --Mr.98 (talk) 17:23, 20 March 2011 (UTC)

I'm not sure what the energy requires for uranium enrichment are. It wouldn't surprise me if you would end up in the black. However, you would be far better off with a conventional nuclear reactor. --Tango (talk) 21:30, 20 March 2011 (UTC)

Agreed. --Mr.98 (talk) 16:59, 21 March 2011 (UTC)

Evolution and sex

Male early humans were obviously more likely to use weapons and tools than female early humans. Tool usage selects for intelligence, dexterity, etc. To what extent will these traits be males, but not females? The reason I ask is that my friend tried to use this argument to "explain" why men were better than women (I think Darwin did the same)...the argument seems specious, but I don't know enough to rebuke it.

Also, more generally, when will the inheritance of some trait be sex-specific? 74.15.137.130 (talk) 20:09, 18 March 2011 (UTC)

Men only have one chromosome that women lack, the Y chromosome, so any difference between the sexes would have to lie there (or in lacking one of women's two X chromosomes). However, a "trigger" can exist there which turns on larger sections of any of the other chromosomes.

As for the argument, that would only make men better at use of weapons and tools. Women, on the other hand, seem to have developed superior communications skills and social intelligence, those being more important for living in a group while raising children. StuRat (talk) 20:23, 18 March 2011 (UTC)

I don't think it is obviously true that early human males were more likely to use tools than early human females. Assuming that the typical gender stereotypes hold (I'm not a paleosociologist, so I don't know how accurate this assumption is), men were probably more likely to use tools such as spears and axes, but women were probably more likely to use tools such as mortars and pestles and sewing needles. If anything, the smaller tools used by women might encourage more dexterity than the larger tools used by men. So it's not clear to me that the hypothesis has merit—it really requires better evidence and justification. —Bkell (talk) 20:33, 18 March 2011 (UTC)

I agree with StuRat. By default anything that changes in the human genome will affect men and women equally -- you have to add a dependence on sex hormones such as estrogen or testosterone in order to cause a feature to be sex-specific. Looie496 (talk) 20:52, 18 March 2011 (UTC)

There are many traits that are sex dependent. In fact, I remember reading somewhere that women are believed to have BETTER fine skills than men (for things such as weaving) while men are better at wider movements (For things such as throwing spears). If you ask my opinion, I don't believe it either way. Dauto (talk) 00:16, 19 March 2011 (UTC)

Yes, there are many traits that are sex dependent. But this is mainly because there are a large number of genes whose transcription is regulated, either directly or indirectly, by sex hormones. To get such regulation, though, there has to be a binding site in the DNA either for one of the hormones or for something regulated by one of the hormones; the default state is not to have such a binding site. Looie496 (talk) 00:34, 19 March 2011 (UTC)

I don't remember seeing anything like that in Darwin, and I frankly don't believe it. Darwin was one clever, perceptive writer. Wnt (talk) 23:03, 18 March 2011 (UTC)

http://en.wikipedia.org/wiki/The_descent_of_man#Part_II_and_III:_Sexual_selection

Yes, that sounds more like Social Darwinism, to me. StuRat (talk) 23:27, 18 March 2011 (UTC)

Reading [15], to me it sounds like Darwin recognizes some rather sexist assertions by his colleagues, but again and again blunts them - accepting only that men might be driven toward greater competitiveness, but not greater intelligence. For example, "It is, indeed, fortunate that the law of the equal transmission of characters to both sexes prevails with mammals; otherwise, it is probable that man would have become as superior in mental endowment to woman, as the peacock is in ornamental plumage to the peahen." Wnt (talk) 09:48, 21 March 2011 (UTC)

So, based on the comments, would it be safe to say that men using tools more frequently (if that was indeed the case) would likely benefit the species as a whole? 74.15.137.130 (talk) 01:39, 19 March 2011 (UTC)

Both men and women used tools. They may have used different tools for different jobs, but the use of tools has been a human trait for a very long time. As for the gender difference commonly cited in hunter-gatherer societies, it does not have to be genetic. Humans were smart enough to know that if a man dies, it doesn't have a large effect on the ability of the group to have children. If a woman dies, that reduces the number of children that can be born. So, men were tasked with risking their life for the betterment of the group while women were kept in relative safety. Because children must be safe also, it meant that women were kept with children while men went out to see if they would be lucky enough to return home. Of course, it could be a combination of genetic difference and social knowledge about child-birthing. Very few things are clearly one thing or another. Most things are a combination of causes. -- kainaw™ 04:31, 19 March 2011 (UTC)

Then why do female lions do the hunting? 74.15.137.130 (talk) 04:38, 19 March 2011 (UTC)

Compare the number of lions who die while hunting to the number of humans who died back when they were trying to take down large game with rocks and sticks. It is not comparable. You may as well argue "Then why do worms crawl underground?" as it is just as nonsensical. -- kainaw™ 17:08, 19 March 2011 (UTC)

Also interesting to consider perhaps: why do men have nipples? WikiDao ☯ 04:05, 19 March 2011 (UTC)

Earth going in a straight line while spacetime is curved

I read somewhere that objects under the influence of gravity (like the Earth) are actually travelling in straight lines while the massive object is bending spacetime. What is the meaning of "straight line" in this context? And how does one picture (or explain) this phenomenon? Thanks. 41.132.13.180 (talk) 20:46, 18 March 2011 (UTC)

General relativity says that objects move along geodesics; see that article for an explanation of why geodesics are considered "locally straight". Looie496 (talk) 20:49, 18 March 2011 (UTC)

I just think of that as a way to describe it, not that the objects really do travel in straight lines. StuRat (talk) 21:55, 18 March 2011 (UTC)

As Looie explained above, objects follow a geodesic which is the equivalent of a straight line for a curved space. For instance, if I say to somebody: "Follow a straight line due north and eventually you will get to the north pole", it is tacitly understood that a mean that person to stay on the earth's surface which means they are really not following a straight line because that would send them into space given that the surface of the earth is curved (curved space). I really mean that person to follow a geodesic and keep their feet on the ground. But in a sense their path is still straight. As straight as it can be without leaving the surface of the planet which is curved. Well, under the action of gravity objects follow a path that is as straight as it can be without leaving the universe which is curved by the action of gravity.

(EC) The Earth's world line is a "straight line" in the sense that it's as straight as possible, given that spacetime is curved. It's a straight line in the same sense that a line of latitude or longitude or a great circle on the Earth's surface is as straight as possible, given that the line is constrained to lie on the Earth's surface. However, it's important to note that the "straight line" that the Earth travels along is a line in a four-dimensional spacetime, in which straightness is measured using a pseudo-Riemannian metric, and is not a straight line in a three-dimensional Euclidean space. Three-dimensional Euclidean space does not physically exist, although Euclidean space can be used as a very good approximation in the common case of dealing with low speeds (compared to the speed of light) and little gravity. See also Geodesic (general relativity). Red Act (talk) 23:33, 18 March 2011 (UTC)

Thanks for your answers. I read the articles (as best I could!) and I have one follow up question. Let's say we collapse the the 3 space dimensions into 2 and then the time dimension is perpendicular to these two (ie pointing upwards) and look at this from the sun's perspective. So at t=0 the sun is at the origin and it goes straight upwards through time and the earth starts some distance away and moves in a helix so that at t= 1year it is back at the same point in space. My question is: does the mathematics say that this helix is a straight line? And what about the vertical line connecting the earths position at t=0 and t=1; is this also a straight line? 41.132.13.180 (talk) 10:39, 19 March 2011 (UTC)

Yes (the earth's orbit is a geodesic) and no (the "vertical" line is not a geodesic).

But -- and this is a rather large "but" -- your picture is not accurate. It is okay, so far as it goes, to remove one space dimension, but the result will not be the ordinary familiar 3-dimensional space you're picturing your helix in. The underlying four-dimensional space is curved, and the three-dimensional one you get by removing one dimension is still curved. If you squeeze it to make it fit into an Euclidean model, what used to be geodesics (such as the helix of the earth's orbit) will bend, but that is a product of your squeezing and doesn't say anything about the unsqueezed situation.

Also, the appropriate conversion factor between time and space is the speed of light, so the "vertical" height of one revolution in your helix would be one light year. That's huge compared to the earth-sun distance, so your helix does look extremely straight except in when you consider large times/distance (which is when the squeezing becomes relevant). –Henning Makholm (talk) 13:16, 19 March 2011 (UTC)

Here's an analogy. If you idealize the Earth as a sphere, a geodesic on the surface is a great circle. So let one person travel along the equator (which is a geodesic, i.e., "straight") and let another person set out at a slight angle to that, also in a "straight" line. Their paths will diverge at first, but they will start to converge a quarter of the way around the globe, and cross halfway around the globe, then diverge again until they start to reconverge 3/4 of the way around the globe... even though they're both traveling in straight lines. This is surprisingly close to what happens in general relativity. -- BenRG (talk) 20:27, 19 March 2011 (UTC)

transmutation of nitrogen

Since oxygen(8)has greater mass than nitrogen(7),how could Rutherford's transmutation of nitrogen into hydrogen and oxygen by iradiation have produced oxygen without a high temperature fusion event? Is fusion NOT always neccessary to produce a heavier element? Where does the extra proton come from?190.148.132.226 (talk) 21:25, 18 March 2011 (UTC)

Note that oxygen doesn't have to have a greater mass than nitrogen. It just has more protons than nitrogen. If you convert a neutron to a proton, you can increase the atomic number with no gain in mass (a slight loss, actually, at least on average). Wnt (talk) 22:57, 18 March 2011 (UTC)

For your specific instance, according to Ernest Rutherford, "In Cambridge in 1919, after taking over the Cavendish laboratory, Rutherford became the first person to transmute one element into another when he converted nitrogen into oxygen through the nuclear reaction ¹⁴N + α → ¹⁷O + p". Note that the alpha particle is a helium nucleus, making this a case of nuclear fusion. Wnt (talk) 23:01, 18 March 2011 (UTC)

Note also that the alpha particle was produced by some radioactive decay and had a lot of kinetic energy allowing the fusion to happen. Dauto (talk) 01:39, 19 March 2011 (UTC)

Thank you Wnt. for confirming that the said transmutation did involve fusion. However, since cold fusion (as a theoretical process)has been soundly debunked over the last 20years or so by uiversities, independent reserchers, governments and the U.S. patent office, the original quandary remains. ie.that Rutherford (according to historical record)achieved this fusion by the simple expedient of leaving a piece radio active material in a sealed jar of air. No heat was applied to the sample. Therefore is seems that fusion was achieved without temperatures of millions or billions of degrees, which current scientific wisdom declares to be neccessary. Question, how is this possible.190.148.136.72 (talk) 17:07, 21 March 2011 (UTC)

Thank you Dauto. Are you saying that the kinetic energy in that radioactive decay would be sufficient to overcome the proton to proton repulsion.190.148.133.58 (talk) 23:13, 21 March 2011 (UTC)

There's a difference between cold fusion and coupling a fission and a fusion event. Cold fusion is a chain reaction involving fusion of low-mass nuclei at low temperatures. The energy released by this reaction entirely sustains future reactions. At low temperatures this is simply not possible (not enough collisions per second). You do however have alpha ray emitters -- alpha particles that are released by already unstable nuclei with well-defined half lives. In cold fusion, you start with nuclei with very very long half lives (i.e. they are stable). 137.54.20.172 (talk) 17:28, 22 March 2011 (UTC)

Safe energy?

Is any form of energy totally safe when improperly handled? Which is the safest (in the broadest sense) form of energy for human use? --78.150.226.145 (talk) 21:44, 18 March 2011 (UTC)

If you mean source of energy, there are plenty, such as solar and wind, but they have other disadvantages, like not always being available.

If you mean ways to store energy, then probably not, if they store large amounts. This implies unstable chemical or nuclear bonds (otherwise you would need to use more energy to break those bonds than you would get from them, once broken), which can then catch fire and/or explode, like wood, gasoline or hydrogen gas. StuRat (talk) 21:49, 18 March 2011 (UTC)

No, the whole point of energy is that it has energy, and if you handle it in such a way that the energy is released uncontrolled it causes damage. The safest in the broadest sense is nuclear power. By far. It releases the least amount of waste, and has killed the fewest people. (Adjusting by amount of energy produced from that type of energy of course.) Ariel. (talk) 21:51, 18 March 2011 (UTC)

In declaring nuclear power's safety, I doubt that you have factored in future deaths from exposure to poorly managed nuclear waste. HiLo48 (talk) 22:29, 18 March 2011 (UTC)

We haven't had any in 60 years (from waste, poorly managed or not), and I have no crystal ball. Have you factored in future deaths from pollution generated by other forms of energy? Ariel. (talk) 22:52, 18 March 2011 (UTC)

Haven't had any? I'd love to see proof of that. And anyway, 60 years is a tiny fraction of the period for which this stuff remains dangerous. Given world political history for the past thousand years, can you tell me with certainty who will be managing India's nuclear waste in a thousand years time? HiLo48 (talk) 22:59, 18 March 2011 (UTC)

You're asking me to prove a negative? And given the world political history for the past thousand years it will be the human descendants of the current generation who will be managing the stuff. And they will be highly technical. Sorry, but I don't believe in theories that think humans will regress. Historically it may happen at a regional level, but it has never happened globally, and as long as a reasonably sized group exists anywhere in the world, dangerous places like waste sites will be managed. Ariel. (talk) 23:16, 18 March 2011 (UTC)

You made the negative claim as a point on your side of the debate, so of course I'm asking you to prove a negative. And yes, problems will occur at a regional level. That's why my question was explicitly regional. Most of your argument seems to be based on faith that we can mange a very complex science. HiLo48 (talk) 23:22, 18 March 2011 (UTC)

For nuclear waste-related illnesses/death, see Mayak. While tracing any individual death to waste exposure is hard, the odds are very high that waste exposure there has led to quite a number of deaths amongst workers and those living in the area. It's probably the most polluted place in the world from a radiological point of view. I don't think it's indicative of how radioactive waste hazards have to be — they were exceptionally poorly managed there, by a government that cared not at all what happened to the people who lived there — but it certainly is indicative of what happens if you don't try to be responsible about it. Let's not forget that we're not just talking about the US and Europe here. --Mr.98 (talk) 00:45, 19 March 2011 (UTC)

Excluding renewable sources like solar and wind, presumably? They haven't killed anyone to my knowledge! Regards, --—Cyclonenim | Chat  21:59, 18 March 2011 (UTC)

During BBC Radio 4's prestigious political debate programme Any Questions? yesterday, panellist Toby Young stated (and was not challenged by fellow panellists environmental lobbyist Jonathon Porritt, Minister of State for Energy and Climate Change Greg Barker, or Shadow Health Secretary Diane Abbott) that over the last 10 years the Nuclear industry had averaged 7 worker deaths per year, while the Wind Energy industry had averaged 44 deaths per year. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 02:23, 19 March 2011 (UTC)

And presumably also excluding the people who died from political infighting over control of uranium supplies, or in mining accidents, or mining-related illnesses. --Stephan Schulz (talk) 22:05, 18 March 2011 (UTC)

Who died from infighting over control of uranium supplies? --Mr.98 (talk) 00:46, 19 March 2011 (UTC)

I would be very cautious about raw, unqualified figures like these. Over what time period? Over what geographical area UK, Europe, worldwide? How do the number of employees in the industries compare? Richard Avery (talk) 08:21, 19 March 2011 (UTC)

Solar and wind have not generated enough energy to count (over the last 50 years or so). And I did include mining accidents - on the plus side for nuclear power, since all other forms of energy require much more mining. And has there really been that much infighting for control of uranium supplies? Ariel. (talk) 22:52, 18 March 2011 (UTC)

The safest energy source is conservation. The next safest is investments in efficiency, but perhaps I'm just confused because "tax cuts" have been renamed "tax expenditures". Hcobb (talk) 22:15, 18 March 2011 (UTC)

Conservation isn't an energy source, it's an energy-saving proposition. Investing in efficiency isn't an energy source either. Regards, --—Cyclonenim | Chat  22:20, 18 March 2011 (UTC)

Nuclear energy chain is the safest form of energy production world-wide, but in the EU hydroelectricity is yet safer (ref). Comparison of "safety" is hard because standards vary accross the globe, nuclear might be safer because the West has large reserves of uranium. --85.77.98.144 (talk) 14:24, 19 March 2011 (UTC)

I found an article with numbers: http://nextbigfuture.com/2011/03/deaths-per-twh-by-energy-source.html I can't vouch for its reliability, but it does agree with my position that nuclear is the safest. Ariel. (talk) 23:58, 20 March 2011 (UTC)

Leg injury

Hey all! I'm writing a short story for a composition class and I want it to at least make sense on the surface. Are there any leg muscle injuries that one could sustain that would prohibit the riding of a bicycle but that would not be noticed or impede with other activities such as walking, jumping, or climbing stairs (etc)? Thank you. 72.128.95.0 (talk) 22:48, 18 March 2011 (UTC)

Not that I can think of. How about an injury to the buttocks that makes sitting painful ? StuRat (talk) 22:53, 18 March 2011 (UTC)

I don't think there is any leg injury that has zero effect on walking, but it's pretty easy to get a knee injury that makes riding a bike impossible but has only a minor effect on walking, because of the much greater bending of the knee required for bicycling. Injuries of that type also make climbing stairs a problem, though -- at least in my experience. A strain of the gluteus maximus can also have a larger effect on bicycling than on walking -- but it will also making rising from a chair painful. Looie496 (talk) 00:00, 19 March 2011 (UTC)

Bruising of the soft tissues covering the medial surface of the inferior ramus of the ischium often makes it difficult to ride a bike, but has little effect on walking. -- Scray (talk) 02:44, 19 March 2011 (UTC)

Would painting your pool bottom and sides black made the water any warmer?

Just a random thought. Topic says it all. I can't recall ever seeing a pool that wasn't white-bottomed, though I suspect this is more to aid in cleaning than anything else. The Masked Booby (talk) 23:02, 18 March 2011 (UTC)

Yes, it would make the water slightly warmer. I think the reason for white pools is that they are safer, since you can see when you're about to hit bottom or the side. In a black pool people would also run into each other, as there would be less reflected light for them to see each other. StuRat (talk) 23:30, 18 March 2011 (UTC)

If you do a Google Image search for "black bottom pool," you can see examples of this. Some people prefer it. I have swam in such a thing. --Mr.98 (talk) 01:34, 19 March 2011 (UTC)

I'm not sure why people would RUN in a swimming pool but certainly many HAVE SWUM in one. Cuddlyable3 (talk) 11:55, 19 March 2011 (UTC)

Athletes or anyone in rehab might run in or near the shallow end of a pool, as part of their strengthening and conditioning program. The reason is because the water offers some resistance or "pushback" which helps develop muscle strength. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:03, 21 March 2011 (UTC)

run into: (intransitive but with prepositional object) To collide with / To cause to collide with. Perfectly correct use of the term by StuRat; it does not have to mean literal running took place (as many who have ran their cars into various things know). The only thing worse than a pedant is an incorrect pedant. --Mr.98 (talk) 13:58, 19 March 2011 (UTC)

While we're on the subject of pedantry (aka knowledge of basic English), it should be "have run their cars". 86.183.1.249 (talk) 14:47, 19 March 2011 (UTC)

Indeed. See List of English irregular verbs. Cuddlyable3 (talk) 01:35, 20 March 2011 (UTC)

cudnt help laughingg out loud, you guys are indeed pedantic :)))--Fragrantforever 05:16, 20 March 2011 (UTC) — Preceding unsigned comment added by Fragrantforever (talk • contribs)

According to this black-bottom pool enthusiast, the black bottom is used more for a classy "mirror" effect. My guess is that the water looks more mirrored because there is much more contrast when looking at a reflection of a colored object on it, but it does make me wonder if the diffraction in water might cause a different effect with a black bottom? I am reminded, however, of the solar oven. SamuelRiv (talk) 05:32, 20 March 2011 (UTC)

Diffraction occurs at the surface of the water. It can't possibly be affected by the bottom. — DanielLC 05:09, 21 March 2011 (UTC)

I think I understand the argument. The surface of water has the ability to act like a "one-way mirror", if there's significantly more light on one side than the other. Therefore, if all the light below the water line is absorbed by the black bottom, then there is no light reflected back to a viewer above, so the reflections on the water surface become far more visible, and hence it seems more "mirror-like", especially while the water is calm. StuRat (talk) 02:40, 22 March 2011 (UTC)

March 19

car

what brand car is in this vid http://www.youtube.com/watch?v=4vS4U1xXQwQ — Preceding unsigned comment added by Wdk789 (talk • contribs) 02:00, 19 March 2011 (UTC)

This is a video clip running for 3 minutes and 10 seconds. It shows a very un-funny prank in numerous fast-food driveways. The car is entirely irrelevant to the prank. You can't see enough of the car to determine its brand. I suggest no-one even bothers to download the video or watch it. Life is short enough as it is without wasting a few minutes on boring stuff like this. Dolphin (t) 04:25, 19 March 2011 (UTC)

It is pretty funny. At points it sounds like this. Bus stop (talk) 01:54, 20 March 2011 (UTC)

lights

how do they change the head lights in this http://img.ibtimes.com/www/data/images/full/2011/03/17/75371-dd.jpg — Preceding unsigned comment added by Wdk789 (talk • contribs) 04:26, 19 March 2011 (UTC)

This is just a link to a photograph of spent fuel rods at the bottom of a pool of water in a nuclear reactor. There is no car, or any other vehicle, visible in the photograph so there are no head lights. Don't bother. Instead, spend the time checking out the contributions from Wdk789. Dolphin (t) 04:31, 19 March 2011 (UTC)

Perhaps he meant to ask how they change the lights in the radioactive areas of a nuclear plant, and mistakenly called them "headlights" ? StuRat (talk) 17:22, 19 March 2011 (UTC)

yes— Preceding unsigned comment added by Wdk789 (talk • contribs) 22:06, 19 March 2011

The glow on that reactor, though, is Cherenkov Radiation and a natural effect in the air above energetic particles flying about. Whatever additional lights are used are probably fluorescent tubes energized also by the reactions themselves, thus not needing to be changed. Of course, the nature of such a reactor design is such that it's actually safe to walk around it with an open top. SamuelRiv (talk) 05:34, 20 March 2011 (UTC)

Assuming those are ordinary electric lights, I would change them by lowering the level of the water (they keep the water level higher than necessary as a safety margin). Then I would suspend someone in harness from a crane or hoist in the ceiling and have them change the light. Ariel. (talk) 00:38, 21 March 2011 (UTC)

Liver question

What is difference between compensatory hyperplasia and regenration of liver? —Preceding unsigned comment added by 210.2.181.244 (talk) 07:47, 19 March 2011 (UTC)

Does bicarb remove the acidity of acetic acid (apple cider vinegar)?

Can I just confirm that adding any amount of bicarbonate of soda would lower the acidity affects of vinegar (acetic acid)? The fact that bicarb is an 'amphoteric' (react as an acid as well as a base) doesn't clarify whether it would make vinegar more effective or less? 220.244.35.181 (talk) 09:43, 19 March 2011 (UTC)

It reduces the acidity of acids, because it acts like a base when in contact with acids. Grandiose (me, talk, contribs) 10:40, 19 March 2011 (UTC)

Thanks! you know what's also interesting and confusing, is that there is a formula for getting rid of mould/mildew in showers - and it instructs that you mix white vinegar with bicarb: the vinegar is to kill the mildew and the bicarb is to eliminate the odour of the vinegar - but how would that work if the two cancel eachother out???

220.244.35.181 (talk) 10:49, 19 March 2011 (UTC)

It confuses me too, when the ingredients are mixed, they no longer act as two substances with distinct properties. The new substance produced, is a solution of sodium acetate with completely different properties. Plasmic Physics (talk) 11:15, 19 March 2011 (UTC)

that's simplistic. vinegar + bicarbonate forms a buffer solution at some fixed pH (so long as there is not an overwhelming amount of either the vinegar or the bicarbonate.). This pH is still acidic enough to kill unprotected mildew. The free acid CH3COOH is what is smelling like vinegar (vinegar is volatile and evaporates). That's because it's at a considerably low pH (vinegar has around a pH of ~2.4) so there's a lot of free acid. A buffer solution of sodium acetate and acetic acid I believe, has a pH of around 4.76. That's still acidic enough to hinder growth, but not that acidic. Also, the acetate ions help sequester the free acid RCOOH molecules from evaporating. 199.111.169.216 (talk) 16:34, 19 March 2011 (UTC)

Just remember that mixing the two gives you a nice release of CO2, making it ooze bubbly foamy stuff. Fun thing to show your kids. SamuelRiv (talk) 05:36, 20 March 2011 (UTC)

• OP here. Thanks for the help. Then it's confirmed, I won't be mixing any bicarb with the vinegar because we want a lower pH level. Thanks 220.244.35.181 (talk)

What does the atmospheric pressure of CO2 have to be for the dominant equilibrium to be: carbonic acid + acetate <------ -----> acetic acid + bicarbonate? 199.111.185.182 (talk) 16:40, 20 March 2011 (UTC)

Identifying an actual triquetral bone

Triquetral is marked "D"

On File:RightHumanAnteriorDistalRadiusUlnaCarpals.jpg and File:RightHumanPosteriorDistalRadiusUlnaCarpals.jpg, which bone is the triquetral? I've left an image note on the anterior image for what I think is the triquetral, but I can't be sure, and I don't think it's visible in the posterior image. Nyttend (talk) 12:00, 19 March 2011 (UTC)

According to the article triquetral bone, it is the triangular bone marked C, not D. See the summary notes here.. Cuddlyable3 (talk) 13:50, 19 March 2011 (UTC)

According to Gray's Anatomy here the small bone marked 'D' is the pisiform and the other bone, 'C', is called the triangular or os triquetrum. Richard Avery (talk) 14:46, 19 March 2011 (UTC)

So I marked the bone labelled D? I know that it's C — my problem is that I can't easily figure out which bones in the diagram correspond to which bones in the photograph. If I marked the wrong one, would you please remove the note and place it on the correct bone? Nyttend (talk) 17:43, 19 March 2011 (UTC)

Oh, I just realised that I gave the wrong caption to the image here. Sorry — that was a typo, and I meant to say "C" on the caption. Nyttend (talk) 17:55, 19 March 2011 (UTC)

Which is this?

Video. Is this a MiG-23 or a MiG-27? 1:16 in the video or so is probably the best image. These are very similar aircraft, so maybe we can't tell. SDY (talk) 13:53, 19 March 2011 (UTC)

Libyan air force#Current air force equipment says "On 19 March 2011, the rebels shot down one of their captured MiG-23BN over Benghazi", but only sites as a reference that same video, which doesn't explicitly make that identification. -- Finlay McWalter ☻ Talk 14:00, 19 March 2011 (UTC)

Agenzia Giornalistica Italia identifies it as a MiG-23 (but doesn't specify which type) here, but the Sydney Morning Herald says it was later identified as a Mirage here. -- Finlay McWalter ☻ Talk 14:20, 19 March 2011 (UTC)

Sky News also claims it's a MiG-23 here. -- Finlay McWalter ☻ Talk 14:25, 19 March 2011 (UTC)

It can't be a Mirage, the planform is completely wrong. SDY (talk) 14:37, 19 March 2011 (UTC)

Matter to energy

If matter is converted to energy, and the matter happens to be in a gravitational field, then what happens to the matter's gravitational potential energy? —Preceding unsigned comment added by 86.183.1.249 (talk) 14:36, 19 March 2011 (UTC)

See gravitational redshift. Icek (talk) 15:29, 19 March 2011 (UTC)

Matter is NOT converted to energy. Matter IS a form of energy. When matter is converted to a different form of energy its potential energy remains there because the new form of energy still possesses a relativistic mass given by the famous formula E=mc² identical to the mass that the matter had before. Dauto (talk) 16:07, 19 March 2011 (UTC)

Is this connected to the fact that an object weighs more when it is heated? The gravitational potential of the heat energy is manifested as extra weight? 86.160.211.135 (talk) 18:47, 19 March 2011 (UTC)

Yes, that's it. Any form of energy has a mass given by E=mc². Dauto (talk) 19:29, 19 March 2011 (UTC)

Thanks for your help. 86.160.211.135 (talk) 20:05, 19 March 2011 (UTC)

Aquatic minibeasts

Okay, this is a long shot. What minibeasts might I have seen in a sunny ditch in Oxfordshire? The ditch was calm and a sort of temporary (but recurring) pond in the middle of a field. It still had alive-looking grass at the bottom. There were a few minibeasts that looked like pale mites or ticks, gliding through the water, but the ones I'm most interested in were there in large numbers, and looked like small ants although I didn't see legs. They were reddish-brown and moved constantly in a jerking motion: their movement was made up of lots of little straight-line pushes, a bit like Brownian motion but with acceleration that looked like little repeated pushing glides. Perhaps they move by releasing something suddenly behind them?

I'm aware this may not be possible without a picture, but I appreciate any information. 212.183.128.107 (talk) 15:03, 19 March 2011 (UTC)

I'm not sure about jet-type propulsion, but at that size class*, a high density critter in an ephemeral pool is likely an aquatic insect larva. See a visual overview of shapes here [16]. Did they look at all like mosquito larvae? Some sort of Dipteran larvae would be my guess with such limited info. *I assume 'small ant' size is ~1-2mm. SemanticMantis (talk) 16:50, 19 March 2011 (UTC)

Another guess which fits with "moved constantly in a jerking motion" is Daphnia which are very common even in quite small pools in the UK. Country folk call them "water fleas". Mosquito larvae tend to wriggle and it may be too early in the year for them. Another slightly smaller relative is the Cyclops. They both have a little pair of arms with which they do a sort of butterfly stroke - hence the jerking action. The best thing is to fish some out in a jam jar next time you're passing and have a look with an ordinary magnifying glass. This page is a simple key to pond invertibrates; click on the drawing for more details. This page is more comprehensive, but not so easy-peasy. Alansplodge (talk) 19:50, 19 March 2011 (UTC)

Me again. Looking at the naturegrid.org.uk page linked above, it says that "Daphnia contain haemoglobin - which is also found in human blood. This substance can hold and process a lot of oxygen. It turns red when it contains oxygen." That fits with the reddish-brown colour that you reported. Alansplodge (talk) 20:16, 19 March 2011 (UTC)

Thanks (I'm the OP), this is all really good. I agree that a jamjar and magnifying glass would make this a lot easier: I might be able to try that in a couple of days. I was pretty sure they weren't mosquito larvae, partly because it seems too early, but also because I first went to look closer because of the sparkles on the water: I wanted to see if it was air bubbles or little creatures like mosquito larvae. And these weren't doing the tube-to-the-surface thing that mosquito larvae do (unless they don't always do that: I shall look it up). I didn't think they were water flea or triops/cyclops shape, although maybe the angle they are in the water makes them look different. 86.164.66.59 (talk) 23:25, 19 March 2011 (UTC)

Daphnia are roughly disc-shaped, so viewed from above they would look different to the linked photos which all show the side view. However it may well be something else; I'm an amateur at pond-dipping. Good hunting! Alansplodge (talk) 01:51, 20 March 2011 (UTC)

Ocular dominance vs. amblyopia

If one cannot read (discern letters) with his left eye when the right eye is closed, is this an ocular dominance or rather amblyopia?--89.76.224.253 (talk) 16:01, 19 March 2011 (UTC)

It isn't either one of those things. Ocular dominance and amblyopia are both conditions in which one eye dominates the other when both are open -- neither says anything about what happens when one eye is closed. See ocular dominance and amblyopia for more information. Looie496 (talk) 18:20, 19 March 2011 (UTC)

Um, let me correct that. Amblyopia is a condition in which one of the two eyes sees poorly in an absolute sense -- but there are many conditions other than amblyopia that can cause one of the two eyes to see poorly. Looie496 (talk) 20:08, 19 March 2011 (UTC)

I recently spent some time reading about various eye conditions. Lazy eye seems to present in a way that it can be observed by other people (check google for images). Eye dominance is natural preference of one eye over another (muck like beeing right or left handed). What you describe might as well be something else (say, a refraction error in left eye) ~~Xil (talk) 10:07, 20 March 2011 (UTC)

Identifying the contents of a 55-gallon drum by the torn remnants of its MSDS

During a recent binge of idiocy my friend decided 55-gallon drums would make awesome trash bins. Except he didn't want to buy them new, so he dumpster-dived a few. The several we already have work fine (as their MSDSes were intact and didn't show anything freaky)... but one of them is kind of worrying. This particular black plastic 55-gallon drum was discarded by a now-defunct steel and wire processing company and most of the attached MSDS was destroyed by the elements. From what we can read though it's kind of awful, so I really want to know what's on the rest of the MSDS. I know there are different categories of danger based on the wording of the sentence (i.e. "may be harmful if ingested" and "harmful if ingested" and "toxic if ingested" and "poisonous if ingested" denote totally different levels of toxicity). So can anyone get an idea of what this crap is (or give me tips as to doing the same) based on this meager information? (Words that have worn off replaced with #)

On the barrel itself was a stamped sequence of numbers "USA/R-1608/RL/03/10".

SKIN CONTACT
Remove contaminated clothing. Wash affected #### with soap and water for at least 15 minutes #### medical attention of irritation persists.
EYE CONTACT
Remove contact lenses. Hold eyelids apart and flush with plenty of water for at least 15 minutes. Seek immediate medical attention if irritation persists.
INHALATION
Remove victim to fresh air. Restore breathing if necessary. Seek medical attention if irritation persists.
INGESTION
Seek prompt medical attention. Do NOT induce vomiting. Never give anything by mouth to an unconscious person.
########
########
## be harmful if swallowed. May cause mild to severe eye irritation upon prolonged, repeated exposures. Prolonged or repeated exposure may cause skin ### defatting and irritation ranging from mild to severe. May cause mild to severe respiratory irritation with repeated, prolonged exposures.
See MATERIAL SAFETY DATA SHEET for additional health-related information.
OTHER PRECAUTIONS
Use all personal protective equipment. Observe good personal hygiene practices, such as washing after handling and before eating, drinking and/or smoking.
KEEP OUT OF REACH OF CHILDREN
##################
##################
appl##############
enter s###########
has enter#########
exte##############
WASTE ############
Uncontaminated ###
tim### Recyclin###
disposal. Foll####
H#################
Keep from freezing. Store######
area away from all ignition s##
incompatibles. Keep containe###
MSDS Rev No. 01 MSDS Date: 03/12/10

I'm thinking of just googling the longest intact segments or running them through a MSDS search engine, but anything else that works better would be a hell of a great help. ZigSaw 20:41, 19 March 2011 (UTC)

One hopes R-1608 might be a product number (no guarantees). But isn't there a company name on the barrel (not the wire company that bought it, but the manufacturer)? Wnt (talk) 21:23, 19 March 2011 (UTC)

Let's just hope he doesn't find the number 311-555-8674 stenciled on it. ;) Wnt (talk) 21:26, 19 March 2011 (UTC)

You've forgotten to put the thing canvcelling the small type. 92.24.178.214 (talk) 23:23, 19 March 2011 (UTC)

R-1608 is one of the names for an herbicide more commonly known as EPTC or eptam. It appears to have toxicity data similar to that on the label. Looie496 (talk) 23:26, 19 March 2011 (UTC)

The points listed above are on just about every MSDS ever made. I would suggest looking for a different drum. Or at least rinse it out and line the drum with a couple garbage bags to keep a barrier between your nice new garbage and whatever was originally in it. 50.92.121.76 (talk) 22:39, 20 March 2011 (UTC)

Humans from Africa

When humans spread out from Africa, were there already some human-like creatures (such as Neandertals and others) in the land they expanded into? Thanks 92.24.178.214 (talk) 23:20, 19 March 2011 (UTC)

The answer is yes. Just be careful to define what you mean by human. Neanderthals may also be considered human depending on your definition. Dauto (talk) 23:39, 19 March 2011 (UTC)

The article Early human migrations will get you started on this question, and you may find further relevant details by following links from it. You will also find a useful table of the different known Human/Homo species in the Homo article, and further details towards the end of Timeline of human evolution.

Briefly, when the only (known) now-surviving human subspecies Homo sapiens sapiens first spread beyond Africa (though many stayed there), there were likely still some closely related sub-species in Africa such as Homo sapiens idaltu, perhaps also some of the last Homo antecessor and/or Homo heidelbergensis whose earlier emigrants to Europe had evolved into Neanderthals, and possibly some surviving Homo ergaster (aka "African erectus") from whom H sapiens had evolved (also via H antecessor and heidelbergensis), and Homo rhodesiensis.

(Remember, when one species evolves "from" another, it often does so in one particular locality because of special conditions there, leaving populations of the first species still continuing to live elsewhere, from whom further species may subsequently evolve - there is not necessarily a strict line of succession and immediate replacement.)

Beyond Africa there were already: the species/subspecies Homo neanderthalensis/Homo sapiens neanderthalensis in the Levant and Europe (with whom H sapiens sapiens then interbred); Homo denisovan (or H sapiens denisovan?) in parts of Eurasia, (with whom some H sapiens sapiens also interbred); Homo erectus (divided into several localised sub-species) throughout Eurasia, Indonesia and possibly parts of Australasia (with whom H s s probably did not interbreed - though see Homo erectus soloensis - and whom we replaced), and Homo floresiensis (perhaps a descendant from erectus, perhaps from an Australopithecus species, perhaps something else - the jury is still out) in Flores and perhaps elsewhere.

There may well have been other localised Homo species and subspecies that we have not yet discovered. Several of the above-mentioned varieties of humans are known only from very few fossils, so future finds may well extend their currently confirmed time spans nearer to the present day. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 01:24, 20 March 2011 (UTC)

March 20

What would it take to invent a vacuum-operated toilet?

If we don't have enough time in the day to even answer the call of nature the normal way, could there be a vacuum toilet that sucks out all the bodily wastes so that we wouldn't have to spend as much effort pushing it out ourselves? How much faster could this process be if this was vacuum assisted? Would it do a better job than normal? Would it be able to suck out more waste than we can push out?

So how come there hasn't been a vacuum-operated toilet yet? --70.179.169.115 (talk) 02:33, 20 March 2011 (UTC)

Astronauts use something similar, but you don't want so much suction that it can do damage. A minimal vacuum, just to suck the stench out, might work. StuRat (talk) 02:40, 20 March 2011 (UTC)

Before anyone goes through the effort, can you show that it's even necessary? Who says that we don't have enough time in the day to go the normal way? Dismas|^(talk) 03:08, 20 March 2011 (UTC)

It wouldn't work as you expect. To avoid disgusting mental images, think of this scenario: You have a plastic bag full of liquid. It has a narrow rubber hose so the liquid can drip out. To get it out, you squeeze the bag. That is how it should work. To make it faster, you suck the liquid out. The result is that the rubber hose collapses. Sucking harder makes the rubber hose squeeze tight. Nothing come out. The solution is to shove a stiff straw up the rubber hose to keep it from collapsing. Then, you have no problem sucking the liquid out (that's how those juice bags that kids drink work - they use a hard straw, not a flimsy little tube). So, your vacuum would actual keep you from evacuating your bladder or bowels instead of making it faster. The solution would be a stiff tube shoved in one hole or the other before attaching the vacuum - which will likely take longer than just going to the bathroom. So, what do people do? That's why they make magazine racks for bathrooms. Some people have televisions in their bathroom. Whatever you need to do, find something that allows you to sit for a while. -- kainaw™ 04:16, 20 March 2011 (UTC)

Well then Kainaw, I guess I'll have to resort to a liquid-based "straw" called the Washlet. I wonder if that's what they have in the space stations. --70.179.169.115 (talk) 08:09, 20 March 2011 (UTC)

Read Packing for Mars by Mary Roach; she discusses this stuff in enjoyable detail. --jpgordon^{::==( o )} 04:56, 20 March 2011 (UTC)

Death of Abigail Taylor tells me that no one should ever attempt sucking his or her butt. If the issue is that you just don`t want to go to bathroom, you might try catheter (not sure if it would work for moving bowels though) ~~Xil (talk) 10:48, 20 March 2011 (UTC)

If you are concerned about the time and effort involved in voiding waste, those are both related to diet, notably dietary fiber intake. SemanticMantis (talk) 14:22, 20 March 2011 (UTC)

I agree, if you have this problem, then its a sign that you should be eating more vegetables fruit and wholemeal grains. 92.15.21.23 (talk) 23:08, 20 March 2011 (UTC)

I think they already exist, front side anyway. Fighter pilots like these http://www.bbc.co.uk/news/uk-12798613 have white tubes as part of their jumpsuit. On an eight-hour trip they are going to need one. Perhaps they are required to have an enema before leaving too. 92.28.241.202 (talk) 15:52, 20 March 2011 (UTC)

But note that any vacuum used in such suits is low, only sufficient to remove the waste once voided, not to actually pull it out of the body. StuRat (talk) 19:23, 20 March 2011 (UTC)

Likewise for the ones astronauts use. The vacuums in "space toilets" just replace gravity, they don't replace the body's own forces. --Tango (talk) 21:35, 20 March 2011 (UTC)

How do Tomahawk missiles get to the target without getting shot down?

The Tomahawk cruse missile was used in several recent conflicts against countries with late Soviet air defense systems. They apparently reached their targets without interference, even before radar, antiaircraft defense, and fighter jets were incapacitated. The Tomahawk is a jet powered drone rather than a ballistic missile or rocket. The WW2 V1 flying bomb flew along at 400 mph, and WW propeller fighters could sometimes shoot them down, even with the primitive radar of the time. The Tomahawk only flies at 550 mph, comparable to a commercial airliner, and a fraction of the speed of even the old Mig and Mirage fighters operated by such countries as Iraq and Libya. Flying at low level to avoid radar was a common practice even in WW2, and did not really protect bombers from detection and damage. The ability to fly at 100 feet through canyons or whatever would not help while they are still out over the Mediterranean, where fighters might be deployed as a defense. Do second rate air defenses like Libya rely on ground based radar, and have nothing comparable to Awacs to "look down" and detect the Tomahawk in tome to fire a ground to air or air to air missile at one? Do the best Libyan fighter planes have "look down, shoot down" systems? Would a first rate world power be able to detect and shoot down Tomahawk quality missiles? This report from the Gulf War claims that only 60% of the Tomahawks actually hit their targets. Were some of the "misses" actually shootdowns? Edison (talk) 03:12, 20 March 2011 (UTC)

They are sometimes shot down. This PBS page says that as many as 6 were shot down in the Gulf War (out of 297 fired). It also lists counts for many other reasons they didn't reach the target. The point of the Tomahawk is that it is cheap and dependable (and what they blow up costs a lot more than a few Tomahawk missiles). -- kainaw™ 04:10, 20 March 2011 (UTC)

Cheap and dependable? The things cost $569,000 each in 1999 dollars,[17] which for a single-use weapon makes "cheap" a stretch. And according to the source cited by Edison, more than 40% of the time Tomahawks don't hit their intended target (often blowing up innocent civilians instead), which makes "dependable" a stretch. Red Act (talk) 09:39, 20 March 2011 (UTC)

Cheap depends on context. If the alternative is even a 1% chance that your billion dollar bomber is shot down, then a cruise missile would look cheap. Dragons flight (talk) 11:12, 20 March 2011 (UTC)

Is that really how much one of those missiles cost? I would have guessed a much higher price in the range of several million dollars. I think that's a relatively cheap price tag. Dauto (talk) 14:21, 20 March 2011 (UTC)

I think you've identified some of the deficiencies in third rate militaries. Another big one is the lack of communication between systems. You need the radar systems (ground, sea, air, and satellite), to all be hooked to each other, so they can identify a "bogey", track it, and fire a missile at it when it comes into range. Even if you have all the components, if they aren't connected properly, it's just about useless. StuRat (talk) 08:37, 20 March 2011 (UTC)

News media sometimes give the impression that when a destroyer or sub fires one of these things at a country, the target is doomed, but I still haven't seen arguments as to whether a country such as India, Pakistan, or the UK or US, for that matter could spot and intercept one or more fired, say from a submarine a hundred km offshore. If they are following a canyon or flying between hill, a few might be expected to hit those geographic features or even powerlines, and skimming treetops and wavetops was certainly a WW2 tactic. Radar at 30,000 feet looking down should spot it better than ground based radar, and jet fighters for the past several decades have flown much faster than these devices. If everything works right, the GPS should let the launching country put 1000 pounds of high explosive close enough to a target to blow it up, at about a million dollars per explosion, but I wonder if it has a positional uncertainty in tens or hundreds of meters, making it less effective against hardened targets than laser guided bombs, which (at least in selected footage from the attacks on Iraq) could be flown right in a window. They tend to use about 5 Tomahawks per target. Edison (talk) 20:13, 20 March 2011 (UTC)

Then there's the additional problem that the Israelis had when using the US-built Patriot missile, during the Gulf War, to shoot down Iraqi SCUDs. The SCUDs were inaccurate, and carried minimal warheads, meaning they weren't likely to create much damage when they hit. Shooting them down meant that both the remnants of the SCUD and the Patriot would then fall, frequently in a populated region, causing as much damage as the intact SCUD would have. StuRat (talk) 20:50, 20 March 2011 (UTC)

There is a significant difference in the consequences of shooting down a low flying cruise missile and that of shooting down a ballistic missile during its terminal phase. -- 119.31.121.89 (talk) 23:02, 20 March 2011 (UTC)

A reasonable proportion of them are shot down, equally a proportion of them crash or miss. There are percentages out there for the various elements of that but you can track them down yourself. The real success figures are classified.

The targeting process accounts for the likelihood of losing weapons and enough are launched to assure a sufficiently high number reach the target to deliver an effect.

ALR (talk) 10:43, 21 March 2011 (UTC)

Knowing where the enemy radar and missile sites are and their performance parameters allows a route to be planned that avoids as many of these defences as possible. Flying very low and using terrain masking also helps. A Tomahawk flying at or below 100 feet and 500+ mph will only be in the line of sight of someone on the ground for a matter of seconds - rendering manual weapons such as MANPADS or anti-aircraft guns fairly ineffective. Roger (talk) 14:42, 21 March 2011 (UTC)

Not a conspiracy theory question but a true scientific question

Was reading about the conspiracy theories floating around about the Earthquake and Tsunami in Japan. This is not a political or a conspiracy theory question, neither is it in any way intended to insult the suffering people now. I would like to know, is it possible( does technology exist) to artificially create earthquakes at an intended site and plan a tsunami? Whats the science behind this, how does this work?--Fragrantforever 05:13, 20 March 2011 (UTC) — Preceding unsigned comment added by Fragrantforever (talk • contribs)

No, it is not possible for mankind to create earthquakes or tsunamis. The technology does not exist. The technology does exist to pinpoint the epicentre of any earthquake, and it is now known that earthquakes occur many kilometres below the Earth's surface. This is a depth at which mankind has never had any influence. Also, the energy involved in an earthquake is truly immense. It makes manmade sources of energy look miniscule.

Psychology is the science of behavior. This science does exist. It is known that when people are deeply distressed they display a range of emotions (anger etc) not normally seen in people who are free from distress. Some of these emotions are demonstrably irrational, and can be of extreme intensity. One of the characteristics of anger is the ability to display antipathy towards another person, or other people. When people are angry they often display a readiness to accept suggestions and rumors about how another person has, or other people have, deliberately brought about the event that caused the deep distress in the first place. For example, during a war people have displayed a naive readiness to accept suggestions and rumors that the enemy is extremely bad and wants to cause extreme suffering and hardship. After the war, these suggestions and rumors have usually been found to have no foundation. Similarly, in the aftermath of an accident the victims often display a naive readiness to target a person or group of people, and to believe that the accident was either deliberate or solely due to the criminal negligence of this person or group of people.

With this in mind, it is to be expected in the aftermath of the truly tragic earthquake, tsunami and nuclear radiation problems in Japan that conspiracy theories will quickly take root and circulate rapidly. Some of the victims of these tragedies will derive a little comfort from focussing on the idea that their tribulations were actually designed and caused by one or more very bad people. A conspiracy theory that the earthquake and tsunami were deliberately caused by human action is entirely consistent with some elements of our understanding of human psychology. Dolphin (t) 05:38, 20 March 2011 (UTC)

It appears to be possible to induce very small earthquakes at a site by using injection wellbores to inject fluids. It can be a problem in oil and gas field development amongst other things. That's about it. Getting a fault to move by several metres over hundreds of kilometres of its length is a bit out of our league although I suppose it's theoretically possible in the same sense that dropping a copy of Yilmaz's Seismic Data Processing book out of a window in the middle of a city could, in prinicpal at least, make all of the buildings fall down if you were really very exceptionally unlucky... Sean.hoyland - talk 06:38, 20 March 2011 (UTC)

An explosion can cause seismic wave and water waves, which probably is the reasoning behind conspiracy theories. Not sure, though, if explosion can mimic devastation of earthquake and tsunami ~~Xil (talk) 10:59, 20 March 2011 (UTC)

The closest we can get to an artificial earthquake is to detonate a nuclear bomb underground, even this is of many orders of magnitude weaker than the earthquake that did happen in Japan. Besides, it's not something you can prepare and execute without drawing a lot of attention.

Some kind of "Tesla-earthquake-machine" present in some cheap science fiction or video games is completely absurd. The Earth is not of uniform density to allow waves to resonate enough, and even if such thing would be possible, it's utter nonsense to be the cause of the current events: such a thing would need a lot of resources, a lot of scientists working on it, which needs a huge infrastructure, a lot of people who support this infrastructure, then the whole international scientific community, all current ad future university professors and students who would find out what caused it, and soon we get to a point where millions of people would need to be involved in such a conspiracy all over the world, from every country. For such a conspiracy to remain a secret is completely implausible, even if the technology required for it would be possible, which I highly doubt. The problem with most conspiracy theorists is, that if what they believe has a 0.001% chance of being true, they regard it as proof of it being true.

Another "possibility" would be to deliberately not stop the reactor in time, but as in the above discussion, it would need millions upon millions of people from all over the world to be involved, so it's stupid to even consider it as a possibility.

Conspiracies can and do happen in the world, but they are mostly in the range of "bribe a politician to buy a property cheaper", or "manipulate the media to get a slightly better image of your company or ideology", or "steal some money by misusing legislative loopholes". To invent some completely new technology, or manipulate the currently existing highest technology, and hope no one will find out, is complete nonsense. --87.169.11.121 (talk) 15:51, 20 March 2011 (UTC)

A great deal of effort has been made to distinguish between earthquakes and underground explosions as part of monitoring the Test Ban Treaty using seismometers. Basically the computed focal mechanism shows whether the event involved movement on fault plane (producing the classic 'beachball plot') or was the result of an explosion (or in some cases an implosion such as in the collapse of old mine workings) where the plot is uniformly compressional (or tensional in the other case). Mikenorton (talk) 18:12, 20 March 2011 (UTC)

One of the top results of a Google search claims that the nuclear accident was much bigger than we believe it to be, and happened before the earthquake, killing many thousands, and irradiating even more. The whole tsunami was than artificially created as a cover-up, just to wash away the bodies, and to add to the realism, some agents were later planted as "survivors" to be rescued. The proof: so few bodies have been found, because the water washed away most of them.

The problem is, that there is no known technology to cause an earthquake this big, so the conspirators either managed to create, deploy and use it in a matter of hours, or they invested those horrible amounts of resources to build such an installation in the past, on the off chance that a nuclear meltdown might happen and than they could use that device to cover it up, while not using such groundbreaking new technology for anything else. --87.169.11.121 (talk) 18:54, 20 March 2011 (UTC)

That is an amazingly silly conspiracy theory. --Mr.98 (talk) 22:05, 20 March 2011 (UTC)

See: tautology. ;) --Tango (talk) 00:44, 21 March 2011 (UTC)

The energy of the recent earthquake in Japan was about 3x10²² joules. The largest nuclear bomb (and nuclear bombs are the closest we've ever got to making our own earthquakes) ever tested had an energy of about 2x10¹⁷ joules. That's more than 10,000 times smaller. There is no way we could create our own earthquake on that scale. I guess it might be possible to trigger an earthquake that would have happened sooner or later anyway. There have been proposals to try and do that before too much energy builds up so we can trigger a small, harmless earthquake instead of the very large earthquake we would get instead. However, no-one has come close to inventing a way to actually do that. --Tango (talk) 21:51, 20 March 2011 (UTC)

Thanks for all the answers. The article I was reading mentioned something about HAARP Project in Alaska being behind the quake and tsunami. When I read the wikipedia page on HAARP i ended up more confused. As a secondary question to my initial question - AGREED ALL THIS IS BASELESS ASSUMPTION AND CONSPIRACY- where does HAARP fit into this? And let me remind everyone I dont beleive in these theories I was asking these questions for better understanding of the scientific issues behind this. Even when I posed my initial question, there was not an iota of doubt in me about all this being baseless theories but the idea of this reference desk is to spread the correct and valuable info and I decided to ask this so the informed would answer the less informed. thanks again. — Preceding unsigned comment added by Fragrantforever (talk • contribs) 06:30, 21 March 2011 (UTC)

global warming

one big argument for nuclear power is it is better than coal for greenhouse gasses that cause "global warming," but what about all the excess "heat" that nuclear power releases plus the warming of the cool liquid used to keep the core cool? Isn't that contributing to global warming by definition, or has that already been considered in the comparison?98.221.254.154 (talk) 05:27, 20 March 2011 (UTC)

Nuclear fission does produce heat, just as coal does, but the concern about global warming comes from the carbon dioxide produced, not the initial heat produced. Carbon dioxide keeps sunlight from escaping Earth's atmosphere, reflecting it back toward the Earth's surface. So when you release CO2 into the air, it contributes to global warming via sunlight for as long as it is there. Nuclear fission does not produce CO2, so it doesn't really contribute to global warming.Aaron (talk) 05:51, 20 March 2011 (UTC)

Aaron's last sentence makes more sense as Nuclear fission does not produce CO2, so it doesn't really contribute to the Greenhouse effect. Greenhouse effect is retardation of the escape of heat from the Earth. Nuclear fission produces heat so it contributes to warming, but it doesn't produce CO2 so it doesn't contribute to the greenhouse effect. Dolphin (t) 07:03, 20 March 2011 (UTC)

Is there some way to relate the global warming effects of greenhouse gas emission to that of heat production? That is, how many joules of heat would I have to add to the atmosphere to bring about an equivalent warming to that caused by the release of one ton of CO2? -- 119.31.126.66 (talk) 08:19, 20 March 2011 (UTC)

Total global energy consumption is about 15 terawatts. The man-made effect of accumulated greenhouse gases is about 820 terawatts. So the man-made greenhouse effect is about 50 times the direct heating effect. Also, because greenhouse gases accumulate and have a long residence time in the atmosphere, that ratio is likely to increase over time. Dragons flight (talk) 08:42, 20 March 2011 (UTC)

Also any direct heating increases the amount of infrared radiation emitted by the earth's surface which has a cooling effect which substantially cancels the direct heating. That's why any direct heating is essentially negligible. Dauto (talk) 14:07, 20 March 2011 (UTC)

(It should be noted, of course, that while the act of fission releases no greenhouse gases, the full fuel cycle is not carbon neutral. It's just tremendously better, per megawatt of energy produced, than fossil fuels. It produces about .5-4% the CO₂ emissions as coal.[18]) --Mr.98 (talk) 15:34, 20 March 2011 (UTC)

May I suggest that the IAEA is not a particularly non-partisan source, and that any paper that starts with "the Uranium Institute (UI) decided to examine these claims and to attempt to refute them in more detail" is dubious as a scientific source. --Stephan Schulz (talk) 15:52, 20 March 2011 (UTC)

IAEA is a global independent organisation that reports to the UN. It's as unbiased as it gets. --85.77.43.229 (talk) 16:20, 20 March 2011 (UTC)

The numbers they cite look fairly legit to me. If you have better numbers, have at it. The real bait and switch here is obviously comparing it to coal and coal only — it would be more useful to compare it to things other than the dirtiest form of energy production we have. However I find it completely plausible that nuclear does pretty good when stacked up against coal when measured in terms of CO₂ emissions — or practically anything else. Coal is bad news. --Mr.98 (talk) 17:25, 20 March 2011 (UTC)

I don't think anybody needs to actually read that paper to realize that nuclear power produces much less Co2 than coal. Dauto (talk) 18:03, 20 March 2011 (UTC)

Expression for Thrust and Power coefficients

Hey, can anyone tell me the expression for Thrust Coefficient and Power Coefficient for a propeller in terms of Re, Mach Number and J ? Yes Michael? •^Talk 10:45, 20 March 2011 (UTC)

$T=C_{T}\rho n^{2}d^{4}$

$P=C_{P}\rho n^{3}d^{5}$

The relationship between these two coefficients and advance ratio J is shown graphically. I am looking at Chapter XI of Theory of Flight by Richard von Mises (1959), Dover Publications. This is now a very old book and I'm sure this information is available in all modern books on practical aerodynamics. Dolphin (t) 11:03, 20 March 2011 (UTC)

In Aerodynamics by L.J. Clancy (1975), Pitman Publishing Ltd, Section 17.3, there is also a definition of the Torque Coefficient, C_Q:

$Q=C_{Q}\rho n^{2}d^{5}$

Dolphin (t) 11:14, 20 March 2011 (UTC)

Well, I was looking for an expression for $C_{T}andC_{P}$ itself. Also, if there is an expression for Thrust by Torque, can you let me know? Yes Michael? •^Talk 11:32, 20 March 2011 (UTC)

These three coefficients vary with advance ratio in a way that is unique for any given design of propeller. There is not a mathematical relationship between coefficient and advance ratio, and the relationships must be determined empirically (ie by experiment) in the same way that the lift coefficient of a particular airfoil section varies with angle of attack and must be determined empirically. Firstly, determine exactly which propeller you want to consider, then go looking for three diagrams which show the relationship between advance ratio and each of the three coefficients for this propeller. Such diagrams will be available for a range of advance ratios from zero up to some maximum value, just as the lift coefficient of an airfoil can be shown on a diagram for a range of angles of attack from zero (or even negative) up to the stalling angle and a bit beyond.

Propeller manufacturers are likely to be reluctant to supply this information about their products, but all advanced text books about propellers should contain this information for at least one design of propeller. Dolphin (t) 21:47, 20 March 2011 (UTC)

Have a look at Figure 2 in THIS web article. Dolphin (t) 03:43, 21 March 2011 (UTC)

Flat roof vs. sloped roof

Where is each of the options necessary? Can you have a flat roof in places where it snows?

Snow ifself is not an absolute showstopper. If only the snow melts in the summer, all you need to do is make the roof construction strong enough to carry the weight of one winter's worth of snowfall.

Liquid water is much more of a problem. Even slight deviations from perfect flatness will make rainwater (or meltwater) stand in shallow pools on the roof instead of running off, and it's hard to construct a roof surface that is watertight enough not to be damaged by this in the long run -- especially if temperatures reach freezing in the winter.

Anecdotally, flat roofs were popular in Denmark abound 1970, but most of them have since been overbuilt with peaked roofs due to recurring water damage. –Henning Makholm (talk) 15:06, 20 March 2011 (UTC)

OR: We have a flat roof in southern Ontario (Canada) where we get a lot of winter snow and a lot of days below freezing. Parts of the tar-and-gravel roof are 30 years old and parts only about 5 years old. We had one problem with a leak along one seam when storms came driving out of the east. It was repaired with an overlay of tar. Aside from that, we are warm and dry. The norm, however, is a pitched roof in such climates. Bielle (talk) 15:16, 20 March 2011 (UTC) P.S. Almost all commercial buildings of whatever floor area or height have flat roofs, and it is a rare one (though it does happen) that collapses under a snow load or leaks. Bielle (talk) 15:24, 20 March 2011 (UTC)

One factor seems to be the width of the building (by width I mean the direction in which the roof would have an elevation difference, if sloped, which is usually the narrowest dimesnion). The wider the roof, the higher it has to be, if sloped, so snow will tumble off. This means the material required varies roughly with the square (width×height) of the width. (It just varies linearly with the length, as expected.) So, if a building is 10x as wide, a sloped roof would take 100x as much material, cost 100x as much, etc. This quickly makes sloped roofs impractical for large buildings (an exception being perhaps the pyramids, where the roof and the building are one in the same ?). StuRat (talk) 19:16, 20 March 2011 (UTC)

As StuRat says, for a building of significant width, say more than 80 feet (24 m), one finds that the volume of structure for an appreciable slope becomes expensive. Multiple adjoining sloped roofs have issues with snow and water retention in the valleys that tend to discourage the use of that configuration. Simple sloped roofs are in general less vulnerable to leakage, since water doesn't linger. However, nobody nowadays designs a "flat" roof - there's always a modest slope to encourage drainage, although it may not be obvious on casual examination. Acroterion (talk) 22:09, 20 March 2011 (UTC)

In addition to the roof installation being more expensive, having a sloped roof on a large building would cost more to heat/insulate/etc. If you have a sloped roof, the heat is going to want to accumulate in the peak of the roof. That's not where the people are in a large building. And if you have a ceiling with attic, then you have to insulate the floor of the attic as well. Dismas|^(talk) 07:15, 21 March 2011 (UTC)

Flat roofs are not actually flat normally. It may only be a 1 in 200 slope or even less for a hard concrete roof where it isn't going to sag and form ponds but a slope is put in so any water runs off. Dmcq (talk) 16:24, 21 March 2011 (UTC)

Birdsong, UK

Yesterday in the suburbs and the countryside of south-eastern England I heard a lot of bird calls similar to this: Low-High-Low-High-Low-High-Low-High. Different birds sang between four and nine notes, all done quickly and without any pause in between the notes. The notes sounded more like something being plucked or twanged rather than whistled.

Is this sufficient to identify a particular species, or are there several species that sound similar? Is there anything like a Flora for birdsong? Thanks 92.28.241.202 (talk) 16:08, 20 March 2011 (UTC)

Basically this is the call of the Tit species. Great Tits sound like "teacher, teacher". The smaller tits call higher and quicker. --TammyMoet (talk) 16:57, 20 March 2011 (UTC)

Thanks, the song description matched. I did not realise there were so many of them. Perhaps they have been eating the bees. Does anyone know which are the commonest tit species in SE England? 92.28.241.202 (talk) 17:05, 20 March 2011 (UTC)

I suspect the blue tit is the commonest in SE England, but populations can fluctuate wildly from year to year. By the way, there are a number of websites where you can check out bird songs. This is one.--Shantavira|^{feed me} 18:01, 20 March 2011 (UTC)

From that wonderful link of Shantavira's, it must have been a great tit. 92.28.241.202 (talk) 19:35, 20 March 2011 (UTC)

Why do old AA batteries appear to sweat?

I've often found that old batteries in transistor radios etc are often covered in tiny drops of clear fluid, like sweat. The batteries that I've just looked at are metal-covered alkali batteries, so the "sweat" may be simply condensation. But very old zinc-carbon batteries often appear to have moisture underneath their plastic sleeve.

Why do batteries appear to sweat? Thanks 92.28.241.202 (talk) 16:57, 20 March 2011 (UTC)

Probably because they build up deposits of some sort of salt, which draws moisture out of the air, especially if you live in a very humid place such as Great Britain. Looie496 (talk) 17:42, 20 March 2011 (UTC)

Thanks, but GB is not a "very humid place" as our American chums seem to believe. Fogs are infrequent or rare. 92.28.241.202 (talk) 18:23, 20 March 2011 (UTC)

Oh please. I live in Britain, and it is indeed a damp, humid place most of the time. It has lower precipitation rates than many places in the USA, but it spreads them out over many days so we get days of mist, drizzle and, yes, fog. Fogs are not infrequent, especially in the cooler part of the year in the early morning and evening. We get river-mist here most mornings. How are our houses traditionally built? With sloping roofs that protrude past the walls, and with gutters when people can afford them. Because of all the rain. Recent improvements? Cavity walls anywhere even slightly exposed, because of all the rain and drizzle that gets driven against the walls by the wind. We have damp coursing as standard, and basements are rare. Mould and damp are common in certain parts of houses, because we live in a damp country. It is humid here most of the time: it is considered noteworthy when it is warm and dry, and people get over-excited.

This is why we were good at growing corn for the Romans. This is why we did so well at wool manufacture. This is probably why your batteries behave this way. Unless you live somewhere with a specially dry microclimate? 86.164.66.59 (talk) 19:42, 20 March 2011 (UTC)

Your experience is very different from mine - where are you? What you describe sounds like an extreme exaggeration. (I detect the Northern/Midlands mantra of "We're miserable, and it's all your (comfy southerners) fault!") You must be living in one the wettest parts of the country, somewhere like Manchester or the Lake District, or Scotland. In London its about 20 inches of precipitation a year. Its hardly a rain forest or the kind of place where they have monsoons - they are "very humid places", and has less rain that most parts of europe or the western side of the US. Corn needs a dry climate to ripen by the way - as far as I understand it will not grow in Scotland, hence the oats. Wool thread manufacture was purposedly done in a damp rainy part of the country. You forgot to mention the mushrooms growing out of the carpet, lol. 92.28.241.202 (talk) 20:05, 20 March 2011 (UTC)

This image of unclear provenance seems to support the claim that London is a humid place. It's true that London is not very foggy. According to Wikipedia, London fog was pea soup fog, which is actually smog, and disappeared with the end of the coal-burning era. -- BenRG (talk) 20:44, 20 March 2011 (UTC)

I agree that in mid-winter it may be more humid than it is in most parts of North America, the reason being because in England its above freezing most of the time, and so the water vapour in the air does not freeze into snow etc. 92.15.21.23 (talk) 22:20, 20 March 2011 (UTC)

That humidity scale is grossly exaggerated. Where I am now, the humidity is only 42%, which is fairly typical. Its 42% indoors: outdoors it would be less. "Mould and damp are common in certain parts of houses" says our friend above - rubbish! Only if you are living in a cave or a slum. According to that image, a "wet day" is a day with more than 0.1mm of precipitation - you would have great difficulty measuring a tenth of a millimetre. I think that image is a fraud, as it also says that the hottest temperature is only about 60 degrees farehnheit in the summer ...... hey, is this London, Canada? Very funny. 92.15.21.23 (talk) 21:49, 20 March 2011 (UTC)

Who in Britian can't afford gutters? They are just a few bits of plastic... --Tango (talk) 22:03, 20 March 2011 (UTC)

Britons are not pieces of plastic. Their Rain gutters are constructed from materials such as cast iron, lead, zinc, galvanised steel, painted steel, copper, painted aluminium, require an outflow channel leading away from the building at ground level, need leaves to be cleared in case of blockage, and occasionally need repair e.g. after loading by snow or leaves. None of this comes free. Cuddlyable3 (talk) 09:44, 21 March 2011 (UTC)

If we didnt have gutters we'd be living in a desert. And even primitive houses in deserts have rudimentary gutters. The picture linked to above was taken in Australia. 92.15.25.108 (talk) 11:27, 21 March 2011 (UTC)

The UK has a wide range of annual rainfall (from about 15 inches to more than 200 inches). In an area such as the one where I live, with up to 100 inches a year, it does tend to feel damp (with high humidity) for most of the year, and it is very difficult to keep damp out of houses, though mould growth tends to be quickly dealt with to avoid slum conditions. Yesterday was 100% humidity all day in the low cloud. Dbfirs 14:36, 21 March 2011 (UTC)

100 inches a year is very rare and is almost the worst rainfall you can find in Britain, and is nearly five times worse than what you get in London. I think there is somewhere on top of a hill in the Lake District that gets 150, 200 or more inches a year, but apart from a farmhouse or two nobody lives there. 92.15.25.108 (talk) 16:56, 21 March 2011 (UTC)

Most modern gutters in Britain are plastic. They aren't free, sure, but they aren't something only rich people have by any stretch of the imagination. Any modern house will be built with gutters. Almost all old houses have gutters too. If you don't have any gutters, rain just falls straight off the roof onto the ground, which isn't a good idea. The ground around your house would get very wet and so would you when you walked past. --Tango (talk) 19:51, 21 March 2011 (UTC)

See Alkaline battery#Leaks Potassium hydroxide electrolyte can leak out of old alkaline batteries. When it dries it can leave a white residue I would expect electrolyte leakage is the source of moisture on an old failed alkaline battery, rathre than condensation of atmospheric moisture, unless the battery was brought into a moist place from a cold place. Carbon zinc batteries were worse in this respect in terms of destroying an device when the batteries were left in it too long. Edison (talk) 20:00, 20 March 2011 (UTC)

"This is why we were good at growing corn for the Romans.": your assertion is ridiculous. The Roman didn't know corn until the XVI century, when there were not Romans anymore... 212.169.178.75 (talk) 22:55, 20 March 2011 (UTC)

"Corn" was (and still is) the generic term used in the Old World to cover all cereal crops, including wheat, barley, rye and others. When John Constable painted "The Cornfield" he wasn't looking at maize. (The term could also refer to non-food granular particles - "corned beef" is so called because it is preserved using salt in the form of coarse grains, or corns). As applied to New World maize, "corn" is a contraction of the original "Indian corn", i.e. a particular type of cereal. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:37, 21 March 2011 (UTC)

Please make at least a small attempt to stay on topic. "Corn" has nothing to do with alkaline batteries. Edison (talk) 02:04, 21 March 2011 (UTC)

However they were responding to an incorrect or confused assertion (which IMO shouldn't have gone unchallenged) by 212 (who were responding to a point by 86). Edit: Forgot to mention this but the big long discussion up there which has gotten longer since I first posted about whether or not the UK can be considered a 'wet' country (which considering 'wet' is subjective seems a bit pointless) is IMHO a bigger issue then the clarification that the Romans did grow corn. Nil Einne (talk) 08:53, 21 March 2011 (UTC)

About duck being a red meat...

With all the current hoopla about the risks of red meat, I'm trying to determine if duck is counted as one for the purposes of said elevated health risks. The article about red meat is unclear here... Egg Centric 18:52, 20 March 2011 (UTC)

That's a good question, and I agree that the article may be contradictory. It says that red meat includes 'duck' but then goes on to talk about a bunch of health risks associated with 'red meat' when in fact the studies may or may not have included duck. What you'd have to do is go to the studies themselves. 220.244.35.181 (talk) 19:16, 20 March 2011 (UTC)

Red meat is a phrase that was invented and pushed by the beef industry to refer to "beef" whenever health risks of eating beef are discussed. Thus, when beef is bad for you, it is called "red meat", but when beef is good for you, it is called "beef". Sort of a form of reverse marketing, so in your mind, you don't associate beef with unhealthy qualities. Duck does not fit into the "Standard" American triumverate of meat protein (Beef, Pork, and Chicken), so I am not sure that most people would think of duck as being substantially different from Chicken, excepting that ALL duck is, culinarily and probably nutritionally, closer to "dark meat chicken" (i.e. lower quarters, thigh and leg), even duck breast is more like chicken legs than anything. Whiter meats (including chicken breast meat, turkey breast meat, and some parts of the pork, like the loin and the tenderloin) are lower in fat, so for people who care about fat intake, they advise people to stick to "whiter" meats. Also, with regard to duck being "red meat", it can be culinarily treated more like "beef" than "chicken", so for example, duck is still tasty when cooked to "medium rare", like beef is, but unlike chicken where "medium rare" chicken is disgusting. Nutritionally, however, I don't know that duck is distinctly more like beef or chicken. --Jayron32 22:35, 20 March 2011 (UTC)

I disagree with your contention about the origin of the term "red meat", Jayron, though I agree some anti-meat nutritionalists may use it in that way now. I can recall many references to "good red meat" or just "red meat" in an approving tone from writings going back many decades: the term simply distinguished redder mammalian meats from the whiter meat typically found in domesticated birds. Wild birds' meat tends to be darker than that of domesticated fowl, though not "red", because the wild birds exercise it more. Although some domesticated ducks are bred for meat, they are less distant from their wild forebears than domestic chickens, and of course wild ducks are also often killed for the table. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:49, 21 March 2011 (UTC)

Origins aside, many kiwis are probably familiar with the promotion of red meat (sometimes under that name) by Beef & Lamb NZ [19] some of which are available here [20] Nil Einne (talk) 08:30, 21 March 2011 (UTC)

Potassium Iodide

Would it be bad to store potassium iodide in water? I diluted potassium iodide (SSKI) in water, would it make the shelf like any less or would it make it less effective if it was stores like this overtime? —Preceding unsigned comment added by 76.169.33.234 (talk) 20:54, 20 March 2011 (UTC)

Potassium iodide is fully soluble, highly stable, and not likely to be a food source for any microbes. In other words, I can't see anything happening to it whether it is in solution or solid form. In either solution or solid form, it should outlive all of us. --Jayron32 22:26, 20 March 2011 (UTC)

Sea kelp and iodine

If I have sea kelp that says it has 0.06% iodine, how much would I have to take for it to be equivalent to 100mg of iodine which is what I read is equivalent to the amount of iodine in a 130mg tablet of potassium iodine pill? Thanks —Preceding unsigned comment added by 76.169.33.234 (talk) 21:01, 20 March 2011 (UTC)

0.06% of what? Is it 0.06% of the total mass of the seakelp or 0.06% of the Recommended Daily Allowance of iodine for an adult human? If it is the former, you would need to eat 100mg/.0006 = 16,667 mg or 16.667 grams. If it is the latter, you would first need to know what the RDA for iodine was... --Jayron32 22:24, 20 March 2011 (UTC)

I think you slipped a decimal place somewhere, Jayron: I make it 166.67g both on my calculation and on your figures. Happy munching, OP! Incidently, this all assumes that the iodine in the kelp is as assimilable as that in the potassuim iodide in the tablet, which is unlikely. {The poster formerly known as 87.81.230.195} 90.201.110.155 (talk) 00:23, 21 March 2011 (UTC)

You shouldnt take any iodine, unless you are in Japan close to the reactors. See http://www.bbc.co.uk/news/health-12784774 92.15.21.23 (talk) 22:33, 20 March 2011 (UTC)

Or you have some medical condition for which your doctor has prescribed iodine supplements. (And, by the way, when we say "close to the reactors" we mean actually being one of the people working on fixing them. Even if you are just a few hundred metres away, you shouldn't need iodine supplements.) --Tango (talk) 00:40, 21 March 2011 (UTC)

Not to be pendandic, but this conversation should be about iodide, not iodine. If you are considering consuming them, mixing up the two could be dangerous. 71.185.49.174 (talk) 22:40, 20 March 2011 (UTC)

No, it couldn't. Iodide is just iodine with an extra electron. The best way to get extra iodine into your body is taking ionic compounds of iodine and something else, usually potassium, so it that context we say "iodide", but it's the same thing. --Tango (talk) 00:40, 21 March 2011 (UTC)

Um, excuse me, but chloride is just chlorine with an extra electron, and its effects on the body are quite different. That extra electron makes a big difference. Looie496 (talk) 01:14, 21 March 2011 (UTC)

I just went into this above, but since this is a more appropriate title I'll paste it here for the archive: "for edible seaweeds e.g. kelp: "12 different species of seaweeds were analyzed for iodine content, and found to range from 16 microg/g (+/-2) in nori (Porphyra tenera) to over 8165 +/- 373 microg/g in one sample of processed kelp granules (a salt substitute) made from Laminaria digitata.";^[21] "Edible seaweed contained I levels of between 4300 and 2,660,000 micrograms/kg";^[22] (summarizing these two) "the average iodine content of kelp of 1,500 to 2,500 μg/g".^[23] So we're looking at roughly 2 mg of iodine per gram of kelp (I assume these are all dry weight), if you happen to get an average sample, with a just ridiculous amount of variation. So eating 65 grams, a plausible dose, would be equivalent to the 130 mg tablet - though you might end up getting four times as much if you are unlucky. Or you might get less than a mg. Wnt (talk) 02:38, 18 March 2011 (UTC)"

In some sources I read while preparing that last, iodine and iodide were used almost interchangeably, in the sense that the weight of iodide is the same as the weight of iodine. (neglecting the minisule electron mass) Actually eating iodine in its elemental form (or as tincture of iodine) is inadvisable for a variety of reasons, the least of which being that whatever physically reacts with and stains your sorry gullet is not going to your thyroid. Wnt (talk) 02:21, 21 March 2011 (UTC)

A quick raid on NCBI suggests that kelp stores iodide as just plain iodide, noncovalently associated with other molecules.^[24] So its iodide should be interchangeable with that from KI, at least in theory. Wnt (talk) 02:34, 21 March 2011 (UTC)

Tidal energy from the Wash and the Severn

How many typical nuclear power stations would harnessing the tides of the Wash and Severn be equivalent to? 92.15.21.23 (talk) 22:01, 20 March 2011 (UTC)

It would depend on the placement of the barrages and also which types of nuclear power stations you wish to compare them to. For instance, the proposed Severn Barrage may generate from 0.75-15GW depending on which plan you read. The proposed Hinkley Point C nuclear power station could produce 1.6GW. Nanonic (talk) 22:21, 20 March 2011 (UTC)

The 15GW figure is peak power, which isn't terribly informative when you're costing it, compared with a source with a fairly steady rate. Unfortunately the article isn't very good at giving idea (beyond the rough "average" numbers below) as to how long a given barrier would spend delivering power at that level, at the average level, and at lower levels. -- Finlay McWalter ☻ Talk 22:31, 20 March 2011 (UTC)

There are many different proposals for designs for a Severn Barrage, with quite a range of costs, power levels, and impacts. Looking at that article, the 1987 proposal would generate 313 MW on average, the 1989 design 2,000 MW on average. If you compare that to Torness Nuclear Power Station, the most productive of the UK's Advanced gas-cooled reactors, which produces at 1250 MW over two reactors. the Severn Barrage article, using those 1989 figures, puts the yield at 3 reactors worth, and observes that the estimated cost is "about the same as six nuclear reactors, but different lifespan". If Torness serves its planned 35 years of service, you'd expect a Barrage of the 1989 design to pass nuclear at some age shy of 70 years. But that's a hopelessly simplistic calculation: on the nuclear side it doesn't count the comparative cost of operating and maintaining both plants, and the cost of the fuel cycle; on the tidal side it doesn't count the (presumably fairly low) running and maintenance cost, or the (difficult to put into numbers, but not trivial) cost of the environmental impact the barrier would bring. So, handwaving a bit, power yield of 1 1/2 nuclear stations, more expensive in the short term but cheaper in the long term. -- Finlay McWalter ☻ Talk 22:24, 20 March 2011 (UTC)

I hate this "environmental impact" twaddle - who cares about a few ducks. 92.15.21.23 (talk) 22:30, 20 March 2011 (UTC)

Nobody cares that you don't care about a few ducks. This is a reference desk. Personal opinions are off-topic. --Tango (talk) 23:09, 20 March 2011 (UTC)

The ducks probably care. Sean.hoyland - talk 04:00, 21 March 2011 (UTC)

Personal opinions from the OP about what the OP is or isn't interested in are perfectly on topic, and in fact define the topic. Turns out the scope of the question does not include impact on ducks. Now we know. 81.131.35.68 (talk) 06:08, 21 March 2011 (UTC)

Ducks and the pro-duck lobby are relevant because they can scupper plans to use tidal energy instead of building more nuclear reactors. However the plans to end repair of coastal defenses along the east coast may introduce more habitat for them, although the crowd-pleasing current government seems to be appearing to reverse that policy. If you've ever been to Hunstanton you can see how ugly the mud beaches are (Old Hunstanton on the corner of the coast is much nicer) so damming the Wash will be a big improvement for recreation. 92.15.25.108 (talk) 12:08, 21 March 2011 (UTC)

By "the pro-duck lobby" you may mean the Ramsar Convention, which is an international treaty designed to protect the fundamental ecological functions of wetlands. Both the Severn Estuary and the Wash are listed here as being of international environmental importance. Perceived "ugliness" has nothing to do with it. Ghmyrtle (talk) 12:21, 21 March 2011 (UTC)

See what I mean? 92.15.25.108 (talk) 13:47, 21 March 2011 (UTC)

Not really. Many people including some locals consider the protection of wetlands in Malaysia and Indonesia important. I don't believe ducks are even commonly present in these Nil Einne (talk) 16:06, 21 March 2011 (UTC)

Chernobyl vs Deepwater Horizon

In terms of environmental damage (both present and predicted by environmentalists), how does the Deepwater Horizon incident compare to Chernobyl? Thanks. 72.128.95.0 (talk) 23:06, 20 March 2011 (UTC)

They're not really comparable. --Tango (talk) 23:11, 20 March 2011 (UTC)

Deepwater did almost nothing - it requires intense study to find any negative effects at all. Chernobyl caused a 30km area to be uninhabitable for centuries. I should point out that the environmental damage from hydrocarbons comes in the burning, not the extraction, so comparing accidents is not very meaningful. Ariel. (talk) 00:01, 21 March 2011 (UTC)

I wouldn't say it did almost nothing, see Deepwater_Horizon_oil_spill#Consequences. --Jayron32 03:55, 21 March 2011 (UTC)

Yes, broadly Chernobyl was devastating and Deepwater comparatively marginal, after all oil is a biological product which degrades in a few years. However in one case there is a government wanting to deny it and move on, a lobby industry to try to downplay it and no one except people too poor to move to care. Interesting that a single NGO medical centre is still treating 200 new children a year for radiation sickness in 2011 [25] whereas based on reliable sources (cough) Wikipedia claims only 237 people have suffered from radiation sickness since 1986. In the case of Deepwater by contrast there is a well funded government and media desperately searching for "animal touch stories" to try to make cash from them. --BozMo talk 06:24, 21 March 2011 (UTC)

The charity says it's treating children for "cancer and other diseases related to radiation exposure"; this is not the same as radiation sickness. -- BenRG (talk) 10:31, 21 March 2011 (UTC)

As BenRG notes, there is a world of difference between radiation sickness and diseases (potentially) related to radiation exposure. As well, I do wonder – and this is not to in any way negate the value of the work they do – if there isn't a significant fundraising advantage that the charity enjoys from stating that they treat "cancer and other diseases related to radiation exposure" instead of just "childhood cancer". Belarus has a population of roughly ten million people; even in the absence of any unusual radiation exposure, a few hundred childhood cancers per year wouldn't be abnormally high. The number might be even less remarkable if we knew exactly what "other diseases" were included. (Some very quick searching seems to indicate that there was the expected increase in thyroid cancer due to radioiodine exposure, but that accounted for most of the increase in total cancer rates following Chernobyl. Cancer incidence in most categories appears to be comparable to that observed in the United States: [26]. No increase in childhood leukemia was observed: [27].)

Incidentally, BozMo, do you really think that there aren't lobby groups and governments who would benefit from denying and downplaying the effects of the Deepwater spill? (When I started to read your comment, I initially thought you were talking about Big Oil and its lobbyists.) For that matter, aren't there well-funded, multinational, media-savvy pressure groups who are very active in publicizing the disaster at Chernobyl? TenOfAllTrades(talk) 13:18, 21 March 2011 (UTC)

There is a valid criticism of my comparison above since our article just quotes radiation sickness in the immediate aftermath as 237, whereas the chronic stuff is further down the page. There is quite of lot of info on the types of illness in the medical centre but it all needs translating; it looks to me as though chronic radiation sickness is the main problem but I have sent off a few queries. On the fundraising and lobby groups as far as I know this is the only major NGO working in Belarus, and you do not get to be an orphan NGO working in Zimbabwe, Sudan, Israel, Gaza Strip, Somalia etc by saying things which governments don't like. As for "Big Oil" (I left working there 6 years ago) compared to the money vultures in the USA I regard the BP lobbying group as scoring about 0.1 on the Geoffrey Howe scale of savage dead sheep. --BozMo talk 13:42, 21 March 2011 (UTC)

March 21

Why aren't Washlets common in the US yet?

It's popular in Japan; what's wrong with it being sold in US stores? Why do we still have to deal with it the old way when a newer form of hygiene already exists? --70.179.169.115 (talk) 04:07, 21 March 2011 (UTC)

This was recently asked here: [28]. (Based on the similarity in the I/P address, it looks like it was asked by you.) StuRat (talk) 05:06, 21 March 2011 (UTC)

As soon as I read the article I said "I want one." Maybe you should try importing some and try to sell them. You would soon find either the answer to your question or you would make a profit.--Shantavira|^{feed me} 09:04, 21 March 2011 (UTC)

Shanta, you can get a varying range of cost of bidet-seats at http://www.BioBidet.com. —Preceding unsigned comment added by 70.179.169.115 (talk) 22:35, 21 March 2011 (UTC)

The cost of importing a washlet is high, reportedly $660 or so[29] bought online. It requires behind the toilet an electric outlet that is properly installed for use near water, with a ground fault interruptor. A Google search for "Washlet" finds many suppliers. Low enthusiasm for washlets in USA is comparable to the low acceptance of a similar bathroom accessory, the bidet. Cuddlyable3 (talk) 09:28, 21 March 2011 (UTC)

Are showers as common in Japan as in the U.S.? It is not unheard of for someone in the U.S. to duck into the shower after an especially... sticky... experience. Wnt (talk) 09:33, 21 March 2011 (UTC)

When someone was promoting bidets in Australia some years ago it was discovered that plumbing rules demanded an independent warm water supply because of the possibility of gravity allowing unwanted solids to enter the water supply. Cost then became a big issue. HiLo48 (talk) 11:12, 21 March 2011 (UTC)

Radiation dose inside a working nuclear reactor?

If you can get inside a working nuclear reactor without disrupting the reaction and stay there for a minute, what dose of radiation would you get? F (talk) 09:48, 21 March 2011 (UTC)

Based on this chart which breaks down lots of various radiation dosages, standing next to the Chernobyl reactor for one minute during the meltdown would give you about a 5 Sv dose. I'd say that's a good ballpark number for normally-operating reactors, too. That's on the very upper edge of "if you're lucky, you don't die straightaway of radiation poisoning." — Lomn 12:38, 21 March 2011 (UTC)

Even with the author's caveat, I'm not sure that xkcd cartoon is a "reliable source," let alone encyclopedic. Here's Radiation in Perspective from the Department of Energy's Radiation Protection Policy. Each reactor type is different; usually, if you were working with a reactor, you'd have to take a DOE or an OSHA training course. Radiation levels inside the reactor would probably be fatal, maybe or maybe not instantaneously; but if you were actually inside the reactor, you'd have other problems besides radiation to worry about! The temperature isn't comfortable for human life in there, either - and there's not much breathable air - in fact, the nuclear reactor core is not a suitable place for you to go inside, even for a minute. You might equally well ask about environmental safety hazards if you were inside the combustion chamber in an automobile's engine cylinder. Nimur (talk) 14:24, 21 March 2011 (UTC)

Indeed. The inside of a boiling water reactor such as those at Fukushima contains superheated water and steam at a temperature of about 285 °C and a pressure of about 75 atmospheres. It is basically a huge pressure cooker. Gandalf61 (talk) 14:39, 21 March 2011 (UTC)

Even inside a tiny research reactor, the radiation would be quickly toxic if you were inside the unshielded core while it was undergoing criticality. The amount of neutrons alone in an operating reactor, much less gammas and other nasty things, is just fantastic. That's the whole point of a reactor. --Mr.98 (talk) 16:23, 21 March 2011 (UTC)

The sievert article has some interesting equivalent dose values. Sean.hoyland - talk 17:19, 21 March 2011 (UTC)

An alternative interpretation of the question would be if you were inside the containment building of a reactor while it was operating. Early on in the Three Mile Island accident, a spokesman for Metropolitan Edison asserted that he could "walk around inside the containment building, right now, without harm from radiation," implying that the radiation level in the building (and outside the reactor) would not be impossibly high. (He was later shown to be quite wrong: he would have gotten a lethal dose in less than an hour). When a reactor is being refueled, humans work in the containment building and around the reactor, since the valves, switches and pipes do not fix themselves, and a reactor is a very high maintenance device, with constant testing repairs, replacements, and retrofits. While the reactor is operating, I doubt that it is considered safe to wander around in the containment building. Edison (talk) 18:35, 21 March 2011 (UTC)

Containment building says that you can be in the containment building while it is on full power, but implies you are getting a non-negligible amount of radiation (you can only stay in there a limited amount of time before getting your safe dose). That is about what I would guess. A reactor, even one on full power, is still relatively shielded by the water and the reactor vessel. --Mr.98 (talk) 00:26, 22 March 2011 (UTC)

Some people saw this short blue flash when something goes supercritical for example in the Cecil Kelley criticality accident or things while Tickling the dragon's tail. This is only a few microseconds and they die relative soon (days), so with a full blast nuclear reactor it should be over in seconds.--Stone (talk) 18:52, 21 March 2011 (UTC)

Buffalo

Is it true that Buffaloes do not have sweat glands ?  Jon Ascton  (talk)

Not quite. According to this report, "buffalo skin has one-sixth the density of sweat glands that cattle skin has, so buffaloes dissipate heat poorly by sweating." Ghmyrtle (talk) 14:16, 21 March 2011 (UTC)

Which of the various bovine species commonly called ""buffalo" are you referring to? Roger (talk) 14:23, 21 March 2011 (UTC)

The OP is from India so probably Water Buffalo or perhaps the Wild water buffalo Nil Einne (talk) 16:04, 21 March 2011 (UTC)

Neurons and memories

Are memories believed to be stored with the same set of neurons throughout the years? Is an individual neuron believed to be able to be a part of multiple completely different memories? 20.137.18.50 (talk) 13:10, 21 March 2011 (UTC)

I think the answers are both "no", but we await an expert to confirm and expand the answer. Meanwhile our article Neuroanatomy of memory might be of interest. Dbfirs 14:19, 21 March 2011 (UTC)

It's basically impossible for us to know the real answer right now, but some have hypothesized the existence of specific neurons that store a representation of a complex concept or object (presumably by linking up a whole network of neurons that "remember" different aspects of that concept or object). The classic example is the grandmother neuron which is hypothesized to fire whenever you think of your grandmother, or whenever a stimulus (such as a scent, or the memory of a particular location) evokes a memory of your grandmother. --- Medical geneticist (talk) 15:19, 21 March 2011 (UTC)

Most neuroscientists believe that memories are stored, not in neurons per se, but rather by altering the strength of the synapses that connect neurons to each other. An individual neuron in the cerebral cortex makes on the order of 10,000 synaptic connections to other neurons, so this gives quite a large potential storage capacity. With synaptic storage, each individual neuron can participate potentially in thousands of memories, or conceivably even millions. Whether a memory is stored in the same set of synapses across the years is a controversial issue -- some neuroscientists think that memories need to be "refreshed" periodically and that this may involve bringing new synapses into play. Our article on synaptic plasticity contains some relevant information, although most of it is pretty technical. Looie496 (talk) 17:50, 21 March 2011 (UTC)

Expiry date of bottled water

Looking at some bottled water today, I was surprised to notice an expiry date printed on the bottle. Does pure water become unfit for drinking after long periods, assuming the seal of the bottle is not broken? The label on the bottle read 'purified tap water'. 60.48.212.9 (talk) 17:34, 21 March 2011 (UTC)

Plastic bottles can contaminate the water over time via leaching (chemistry) of chemicals from the plastic. 82.43.90.38 (talk) 17:40, 21 March 2011 (UTC)

Good to know, thank you. 60.48.212.9 (talk) 17:51, 21 March 2011 (UTC)

A follow-up question: what are those expiration dates based on? Do the manufacturers or maybe the professional organizations have studies that show the leaching rates or demonstrate safety after known periods? Are they just arbitrary? SDY (talk) 17:55, 21 March 2011 (UTC)

They may have reason to believe that it's of "Acceptable" quality up to that point, but don't study it much beyond that. Still, how long something lasts is so dependent on the conditions under which it is stored that a "look, smell, and taste" test is far better than a date stamped on the package. If your water bottle spent time on the dashboard of your car in the bright summer sun, then it would deteriorate far quicker than in a fridge, probably quicker than the date. There also could sometimes be a sleazy angle to them printing short expiration dates, if they want consumers to toss out their product, while it's still good, and buy more. StuRat (talk) 18:38, 21 March 2011 (UTC)

Here in the UK there is a difference between Use by dates and Best before. Here's some guidance from the FSA about the difference (http://www.eatwell.gov.uk/foodlabels/labellingterms/bestbefore/). In terms of 'leaching' from plastic you may be interested in EFSAs opinion on the safety (http://www.efsa.europa.eu/en/efsajournal/pub/428.htm), the concerns of leaching from plastics (from my limited understanding) are not particularly high. ny156uk (talk) 18:44, 21 March 2011 (UTC)

As far as I know, in some markets (*cough*EU*cough*) there is a requirement that all material for human consumption has an expiry date. And there also is a requirement that prescribes maximum and minimum expiry times, independent of the product (probably in a directive invented by a different, but similar committee). Put the two together, and... --Stephan Schulz (talk) 19:04, 21 March 2011 (UTC)

Do you have a citation for that? I ask because we don't have "expiry dates" in the EU, some products have "use by" dates and some have "best before" dates, as noted by Ny156uk above. DuncanHill (talk) 22:55, 21 March 2011 (UTC)

Annoying. Annoying. Annoying.

Most or all people eventually become annoyed by a sound or short phrase that is repeated ad nauseum. Can anyone point me to any studies or articles about this phenomenon? The closest thing I could find on Wikipedia that was at all related was our semantic satiation stubby article, which isn't really about the same thing. Comet Tuttle (talk) 18:30, 21 March 2011 (UTC)

"HeadOn. Apply directly to the forehead ..." hydnjo (talk) 22:39, 21 March 2011 (UTC)

vacuum electricity

Nikola Tesla observed that electrons transmitted through a near perfect vacuum in his vacuum tubes appeared as corona several feet through the air surrounding the tube. If there is nothing in the tube between the electrode and the glass, then how do the electrons convey through the vacuum and into the surrounding air. could this be explained by http://en.wikipedia.org/wiki/Electric_current#Vacuum — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:12, 21 March 2011 (UTC)

I think that's somewhat of a red herring. The vacuum is an insulator unless electrons are moving through it, yes - but that doesn't answer the issue of why the electrons move through it.

In a vague sense, my impression is that the metal anode fills with extra electrons, typically positioned at the boundary of the conductor, which fill up the conduction band to a level high enough that they can escape it. Once free, the electrons will be pushed away from the electrode and can move in response to any small electric field in the area. But someone with a better understanding of articles like Electronic band structure, Nearly-free electron model, Empty Lattice Approximation, and so on needs to give a better answer. Wnt (talk) 20:59, 21 March 2011 (UTC)

Solar radiation

Do black people aborb more energy from the sun than white people and therfore become hotter? If not, why not?-- —Preceding unsigned comment added by 89.243.141.57 (talk) 19:27, 21 March 2011 (UTC)

Yes, they do. That's why they have more sweat glands. 212.169.178.98 (talk) 20:33, 21 March 2011 (UTC)

Do you have a reference for that? I've never heard of there being a difference in the number of sweat glands. --Tango (talk) 20:46, 21 March 2011 (UTC)

In direct sunlight, I guess they would. When not in direct sunlight, though, they will radiate more energy so become cooler. (The same applies to parts of the body that aren't in direct sunlight, even if other parts are.) --Tango (talk) 20:46, 21 March 2011 (UTC)

It looks like it's kind of debatable. According to this book by an MD,[30] "darker pigments retain heat," which would be consistent with your guess. However, according to Red hair#Origins, "studies by Bodmer and Cavalli-Sforza (1976) hypothesized that lighter skin pigmentation ... allows the individual to retain heat better than someone with darker skin." So it's far from clear that there is an answer to your question that's actually known with any certainty. Also, there are other things like sweat production and dermal vasodilation that would vary between people and affect heat retention, so it would be iffy to assume that pigmentation is the variable that causes the largest variation in solar heat retention between people. Red Act (talk) 20:51, 21 March 2011 (UTC)

Thanks (NOT) for feeding the IP troll. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:53, 22 March 2011 (UTC)

Abnormal darkness

There are some sources claiming that there were relatively short periods of abnormally intense, unexplained darkness, sometimes even spread over the cities (specifically over Wimbledon, London on April 2, 1904 and over Louisville on March 7, 1911). Is there any explanation for that or it's indeed abnormal?--89.76.224.253 (talk) 21:46, 21 March 2011 (UTC)

(The book linked to by the querent is a compilation of The Book of the Damned, which is also available to read on Wikisource, along with other books by the same author.) Comet Tuttle (talk) 22:17, 21 March 2011 (UTC)

Big Bang echo

Just watching Dr Jim Al-Khalili's latest BBC programme, in which he explains about the microwave background radiation being the remnant of the Big Bang. I've known about this for some time, but the following question has just popped into my head. Is it possible to calculate at what point this radiation was in visible light, and what would the sky have looked like at that point? Or is it possible to say when the sound waves from the Big Bang would have stopped being audible to human ears? (OK I know humans weren't around then. Humour me, it's a thought experiment!) --TammyMoet (talk) 21:58, 21 March 2011 (UTC)

Sound waves only take on meaning in a medium, such as air. In the hard vacuum of space, there is no sound. --Jayron32 22:23, 21 March 2011 (UTC)

Isn't space a gas?

I was going to smugly reply to the previous question (about the big bang) with "sound waves can't propagate through the vacuum of space, duh". Space isn't a perfect vacuum, though, and it contains a certain amount of hydrogen, so is space actually a very sparse gas, through which sound could travel? 213.122.13.4 (talk) 22:27, 21 March 2011 (UTC)

Lower density, implies higher isolation. Quest09 (talk) 22:55, 21 March 2011 (UTC)

Does that mean yes, sound could travel through space, extremely poorly? 213.122.13.4 (talk) 23:07, 21 March 2011 (UTC)

I don't see why not, though it would soon get lost amongst the random jostling between whatever atoms and compounds are out there. So, even if you scream really loudly, nobody is likely to be able to hear you. However, there's also this intriguing article (okay, a preview of an article). Clarityfiend (talk) 23:56, 21 March 2011 (UTC)

The interstellar medium does propagate pressure waves - in essence "sound" - provided the wavelength is large enough. The typical example is the pressure waves associated with the galactic spiral arms, which have a length scale measured in thousands of light years. Of course, this is a "sound" that is so low frequency that no organic ear could ever hear it. Typically to avoid dispersion, one wants the wavelength of the pressure wave to be much larger than the distance that individual particles will travel between collisions. In the interstellar medium, with about ~10 atom / cm^3, one would expect a wave to propagate successfully (rather than dissipate) if the wavelength is greater than ~20 AU. The intergalactic medium (with only 1 atom / m^3) would require the pressure front to be thousands of times larger than that, but it is possible if you had an astrophysical process capable of generating a large enough perturbation. Dragons flight (talk) 00:01, 22 March 2011 (UTC)

Why is work - often - not enjoyable?

During evolution, only humans who enjoyed working could have survived. So, shouldn't we have a "I love work" gen? Quest09 (talk) 22:52, 21 March 2011 (UTC)

Conserving as much energy as possible by doing as little work as needed to survive is beneficial in situations where food is in short supply 82.43.90.38 (talk) 22:58, 21 March 2011 (UTC)

Not all work is equal. Humans love certain types of tasks — and you'll find that the jobs people love the most are the ones that satisfy them. For example (per Temple Grandin), we are hard-wired (like most mammals) to love seeking things out. We love the search, love the hunt, love the pursuit, love the flirtation, love the chase. We love the act of finding things more than we like the things found. I think most of us have experienced this in one way or another. That's a definitely genetic predisposition (though not unique to humans at all, which makes sense), but whether we enjoy "working" generally probably is not one. We like certain types of jobs. --Mr.98 (talk) 00:22, 22 March 2011 (UTC)

Earth's tilt and space radiaton.

Greetings!

I have a rather complicated question concerning the tilt of the Earth, the way the atmosphere protects us from radiation, and the effects—for a limited time—of exposure to said radiation.

Right now, our planet's orbit is tilted 23-1/2 degrees to the ecliptic. (This is why the Sun rises 23-1/2 degrees north and south of due east on the solstices.) In the (northern) summer solstice, the Earth approaches perihelion—the closest it will get to the Sun—and approaches aphelion—the farthest away it will get—at the (northern) winter solstice.

In spite of this, however, the southern hemisphere gets just as hot a summer (and just as cold a winter) as the northern hemisphere. This suggests to me that it is not distance per se, but a property of the atmosphere that gives us our tellurian seasons. I'm not an expert at all in the sciences, but I do know that the atmosphere absorbs virtually all Gamma Rays, X-Rays, Ultraviolet Rays, and most Infrared Waves from space. (Only Visible Light, Radio Waves, and some Infrared Waves make it all the way down to the surface). And I also know that around the polar regions, there are "holes"—for lack of a more proper term—where space radiation penetrates far more freely.

Now, suppose that the Earth were tilted on its axis as, or more severely than, Uranus. For simplicity's sake, let's say at an even 90 degrees to the ecliptic. (Also, for all intents and purposes, let's say that all other factors remained unchanged: orbital speed, distance from the Sun, etc.) How would that change the way that space radiation affects us?

Over the course of one Earth day (23 hours and 56 minutes) the Sun would pass through both poles on each of the solstices.

Here are my questions:

As the Sun's radiation penetrated to the surface of the Earth through the "ozone hole" and other "holes" that exist at high lattitudes, what would change about life on Earth?

—Would we see an abundance of natural disasters? (floods, volcanic erruptions, cyclones, earthquakes, etc.)

—Would anatomy and physiology of Earthly lifeforms change? (We know for a fact, the photosynthesis in plants depends on the Sun, and even we humans synthesize Vitamin D from it.)

—Would geology change in any way; to wit, would rocks become lighter or more porous, or some way different. Would the magnetic field change direction or become stronger (or less strong)?

—Would the seasons change in length or demeanor, since the atmosphere would factor differently?

And finally:

—Can such a state be replicated today, under laboratory conditions, in a small, self-contained experiment?

--Thank You! Pine (talk) 00:31, 22 March 2011 (UTC)