Jump to content

Great Filter: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
{{fact}} per talk
Line 2: Line 2:
The '''Great Filter''' is a hypothesis that concerns the implications of the [[Fermi paradox]], and can be considered an explanation for what is called the "[[silencium universi|Great Silence]]". The failure to find any extraterrestrial civilizations in the observable universe implies the possibility that a "Great Filter" might act to reduce the great number of sites where intelligent extraterrestrial life might arise to the tiny number of intelligent species actually observed (currently just one: ours).<ref>Hanson 1998: "No alien civilizations have substantially colonized our solar system or systems nearby. Thus among the billion trillion stars in our past universe, none has reached the level of technology and growth that we may soon reach. This one data point implies that a Great Filter stands between ordinary dead matter and advanced exploding lasting life. And the big question is: How far along this filter are we?"</ref> This probability threshold, which could lie behind us or in front of us, might work as a barrier to the evolution of intelligent life, or a high probability of self-destruction.<ref name="Hanson">{{cite web |url=http://hanson.gmu.edu/greatfilter.html |title=The Great Filter &mdash; Are We Almost Past It? |author= [[Robin Hanson]] |year=1998}}</ref><ref>{{cite web |url=http://www.nickbostrom.com/extraterrestrial.pdf |format=PDF|title=Where Are They? Why I hope the search for extraterrestrial life finds nothing |author=Nick Bostrom |publisher=MIT Technology Review |date=May/June 2008 |accessdate=2008-05-01}}</ref> The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.
The '''Great Filter''' is a hypothesis that concerns the implications of the [[Fermi paradox]], and can be considered an explanation for what is called the "[[silencium universi|Great Silence]]". The failure to find any extraterrestrial civilizations in the observable universe implies the possibility that a "Great Filter" might act to reduce the great number of sites where intelligent extraterrestrial life might arise to the tiny number of intelligent species actually observed (currently just one: ours).<ref>Hanson 1998: "No alien civilizations have substantially colonized our solar system or systems nearby. Thus among the billion trillion stars in our past universe, none has reached the level of technology and growth that we may soon reach. This one data point implies that a Great Filter stands between ordinary dead matter and advanced exploding lasting life. And the big question is: How far along this filter are we?"</ref> This probability threshold, which could lie behind us or in front of us, might work as a barrier to the evolution of intelligent life, or a high probability of self-destruction.<ref name="Hanson">{{cite web |url=http://hanson.gmu.edu/greatfilter.html |title=The Great Filter &mdash; Are We Almost Past It? |author= [[Robin Hanson]] |year=1998}}</ref><ref>{{cite web |url=http://www.nickbostrom.com/extraterrestrial.pdf |format=PDF|title=Where Are They? Why I hope the search for extraterrestrial life finds nothing |author=Nick Bostrom |publisher=MIT Technology Review |date=May/June 2008 |accessdate=2008-05-01}}</ref> The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.


The hypothesis was first proposed in an online essay titled, "The Great Filter - Are We Almost Past It?" written by [[futurist]] [[Robin Hanson]], a professor of economics at [[George Mason University]]. The first version of the proposal was written in August 1996 and was last updated on September 15, 1998. Since that time, Hanson's hypothesis has received recognition in several published sources discussing the Fermi paradox and its implications.
The hypothesis was first proposed in an online essay titled, "The Great Filter - Are We Almost Past It?" written by [[futurist]]{{fact}} [[Robin Hanson]], a professor of economics at [[George Mason University]]. The first version of the proposal was written in August 1996 and was last updated on September 15, 1998. Since that time, Hanson's hypothesis has received recognition in several published sources discussing the Fermi paradox and its implications.


== Main argument ==
== Main argument ==

Revision as of 12:14, 28 January 2010

This article is about an implication of the Fermi paradox. For the music album by Tub Ring, see The Great Filter (album).

The Great Filter is a hypothesis that concerns the implications of the Fermi paradox, and can be considered an explanation for what is called the "Great Silence". The failure to find any extraterrestrial civilizations in the observable universe implies the possibility that a "Great Filter" might act to reduce the great number of sites where intelligent extraterrestrial life might arise to the tiny number of intelligent species actually observed (currently just one: ours).[1] This probability threshold, which could lie behind us or in front of us, might work as a barrier to the evolution of intelligent life, or a high probability of self-destruction.[2][3] The main counter-intuitive conclusion of this observation is that the easier it was for life to evolve to our stage, the bleaker our future chances probably are.

The hypothesis was first proposed in an online essay titled, "The Great Filter - Are We Almost Past It?" written by futurist[citation needed] Robin Hanson, a professor of economics at George Mason University. The first version of the proposal was written in August 1996 and was last updated on September 15, 1998. Since that time, Hanson's hypothesis has received recognition in several published sources discussing the Fermi paradox and its implications.

Main argument

Fermi paradox

Main article: Fermi paradox

There is no evidence aliens have colonized earth. Furthermore, we have found no intelligent extraterrestrial life elsewhere despite centuries of astronomical observations,[non-primary source needed] including SETI. The universe, apart from the Earth, seems "dead"; Hanson states:[2]

Our planet and solar system, however, don't look substantially colonized by advanced competitive life from the stars, and neither does anything else we see. To the contrary, we have had great success at explaining the behavior of our planet and solar system, nearby stars, our galaxy, and even other galaxies, via simple "dead" physical processes, rather than the complex purposeful processes of advanced life.

All life expands to fill all available niches. With technology, such as self-replicating spacecraft, these niches would include neigbouring star systems and even, on longer time scales which are still small compared to the age of the universe, other galaxies. Hanson notes, "If such advanced life had substantially colonized our planet, we would know it by now."[2]

The Great Filter

With no evidence of intelligent life other than ourselves, it appears that the process of starting with a star and ending with "advanced explosive lasting life" must be unlikely. This implies that at least one step in this process must be improbable. Hanson's list, while incomplete, describes the following eight steps in an "evolutionary path" that results in the colonization of the observable universe:

  1. The right star system (including organics & potentially habitable planets)
  2. Reproductive molecules (e.g. RNA)
  3. Simple (prokaryotic) single-cell life
  4. Complex (archaeatic & eukaryotic) single-cell life
  5. Sexual reproduction
  6. Multi-cell life
  7. Tool-using animals with big brains
  8. Colonization explosion

According to the Great Filter hypothesis at least one of these steps - if the list were complete - must be improbable. If it's not an early step (i.e. in our past), then the implication is that the improbable step lies in our future and our prospects of reaching step 8 (interstellar colonization) are still bleak. If the past steps are likely, then many civilizations would have developed to the current level of the human race. However, none appear to have made it to step 8, or the Milky Way would be full of colonies. So perhaps step 8 is the unlikely one, and the only thing that appears likely to keep us from step 8 is some sort of catastrophe. So by this argument, finding multicellular life on Mars (provided it evolved independently) would be bad news, since it would imply steps 2–6 are easy, and hence only 1, 7 or 8 (or some unknown step) could be the big problem.

Although steps 1–7 have occurred on Earth any one of these may be unlikely. If the first seven steps are necessary preconditions to calculating the likelihood (using the local environment) then an anthropically biased observer can infer nothing about the general probabilities from its (pre-determined) surroundings.

See also

References

  1. ^ Hanson 1998: "No alien civilizations have substantially colonized our solar system or systems nearby. Thus among the billion trillion stars in our past universe, none has reached the level of technology and growth that we may soon reach. This one data point implies that a Great Filter stands between ordinary dead matter and advanced exploding lasting life. And the big question is: How far along this filter are we?"
  2. ^ a b c Robin Hanson (1998). "The Great Filter — Are We Almost Past It?".
  3. ^ Nick Bostrom (May/June 2008). "Where Are They? Why I hope the search for extraterrestrial life finds nothing" (PDF). MIT Technology Review. Retrieved 2008-05-01. {{cite web}}: Check date values in: |date= (help)

Further reading

Retrieved from "https://en.wikipedia.org/w/index.php?title=Great_Filter&oldid=340514781"