This might be very unclear, but in pictures explaining the great filter, there is an evolutionary leap that the civilisation is most likely not to be able to pass through. But what is that leap? Is it something specific we humans will NOT be able to do? The concept itself is never specified. Is it nuclear war leading extinction of humanity?
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1$\begingroup$ And what's the relation to astronomy? $\endgroup$– planetmakerCommented Nov 9, 2022 at 14:02
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2$\begingroup$ bro where will I post it on then, instead of saying that provide me a location $\endgroup$– schrodingerscatCommented Nov 9, 2022 at 14:08
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1$\begingroup$ I added a link to the wikipedia article on the great filter to the question. The relation to astronomy is at least twofold, astrobiology (which is on topic), and the Fermi paradox (which might or might not be on topic). There are astrobiology and fermi-paradox tags at the site. $\endgroup$– David HammenCommented Nov 9, 2022 at 14:13
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2$\begingroup$ ok thanks I didn't know :p $\endgroup$– schrodingerscatCommented Nov 9, 2022 at 14:19
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1$\begingroup$ Unfortunately, an answer that goes beyond saying what the "great filter" hypothesis is will inherently be opinion-based, a type of question that is not liked on this part of the StackExchange network. $\endgroup$– David HammenCommented Nov 9, 2022 at 15:21
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1 Answer
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The great filter hypothesis is one of the proposed answers to the Fermi paradox, which asks "where is everybody?" (referring to intelligent alien species).
The great filter hypothesis is essentially a variant on the rare earth hypothesis, which posits that intelligent life is rare. The great filter hypothesis posits that there are multiple filters that make intelligent life rare. A planet needs to be orbiting the right kind of star and in the right place. Then it has to develop precursors to life, then primitive life, then complex life, then sexual reproduction, then multicellular life, then tool-building life, then civilization, then technological civilization, then space exploration, and finally, space exploration outside of the star system.
Each of those steps might be very easy or very hard steps for life to take. Each of those steps might take one step forward, two steps back (e.g., something much bigger than the dinosaur killer asteroid). We have a sample size of one (the Earth) on which to base opinions, so we just do not know if any of those many steps are hard or easy.
Any of those steps might be easy or hard. Based on a sample size of one, life and then primitive life appear to have arisen fairly quickly, shortly after the Earth cooled to a temperature where it could support life. Maybe the Earth got lucky? It then took a long time to develop complex single-celled life, a long time to develop complex multicellular life, and a long time to develop tool-building life. There have been multiple mass extinction events that came close to wiping out life. Maybe the Earth got lucky? The jump from tool-building life to civilization took only a few million years, and the jump to technological civilization was only a few tens of thousands of years, so maybe those steps are easy -- for a planet that gets lucky such as by not being an ocean planet, or by life simply stalling at one of those steps. (Those are the 'filters' in the great filter hypothesis.) There is no telling given a sample size of one.
answered Nov 9, 2022 at 16:45
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1$\begingroup$ Good answer, although I would argue that, despite being a sample size of one, the history of life on Earth still gives some extra information about some filter probabilities: liebertpub.com/doi/10.1089/ast.2019.2149 $\endgroup$ Commented Nov 10, 2022 at 8:29