Revisiting the Fermi Paradox

[ignorantianescia]

Three authors, Anders Sandberg, Eric Drexler and Toby Ord, have a recent paper out on arxiv.org called "Dissolving the Fermi Paradox", in which they argue for a much lower probability of intelligent life than the Drake Equation would suggest.

arxiv.org/pdf/1806.02404.pdf

From the abstract:

The Fermi paradox is the conflict between an expectation of a high ex ante probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties t
hat span multiple orders of magnitude. This makes a stark difference. When the model is recast to represent realistic distributions of uncertainty, we find a substantial ex ante probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.

From the introduction:

Our main result is to show that proper treatment of scientific uncertainties dissolves the Fermi paradox by showing that it is not at all unlikely [ex ante for us to be alone in the Milky Way, or in the observable universe. Our second result is to show that, taking account of observational bounds on the prevalence of other civilizations, our updated probabilities suggest that there is a substantial probability that we are alone. Our third result is that pessimism for the survival of humanity based on the Fermi paradox is unfounded.

[unkleE]

I was interested in this too. I came across it via this Vox article.

From what I can tell, the Drake Equation as usually interpreted represents the optimistic end of the range of possibilities. Some time ago now, Ward and Brownlee, investigated the same questions and developed the Rare Earth Equation, and came to the conclusion that - the title gives the game away - the earth is indeed a rare place and that life is "exceedingly rare in our galaxy and in the universe".

[ignorantianescia]

Yes, I read their book, too, though I think their statement about rarity (like that of the authors of this paper) is specifically about intelligent life - Ward and Brownlee think that microbal life is quite common.

One facet that interests me are the implications of the Rare Earth hypothesis for the fine-tuning argument. Obviously it doesn't negate all the points about how complex chemistry is a precondition for life and how fine-tuning is necessary for that, but it can fairly be said to reduce its force to some degree.

[unkleE]

Can you explain how it reduces the force, for I don't see it? It doesn't make any difference to the argument, as far as I can see, whether there is only one life form in the entire cosmos, or million s. It is the im probability of the numbers that allow life at all that is the basis of the argument.

[himself]

Discussions of probabilities are just whistling in the dark
wmbriggs.com/post/24888/

[ignorantianescia]

Jul 15, 2018 4:41:49 GMT unkleE said:

Can you explain how it reduces the force, for I don't see it? It doesn't make any difference to the argument, as far as I can see, whether there is only one life form in the entire cosmos, or million s. It is the im probability of the numbers that allow life at all that is the basis of the argument.

I don't dispute that, but I think that "the universe is fine-tuned for life" will speak less to people when the universe is completely lifeless save for our planet.

[unkleE]

I think you are right that some people think that the inhospitality of most of the universe tells against fine-tuning, but it is a misunderstanding of the fine-tuning claim. The fine-tuning claim is not that the universe is highly hospitable to life, but that of all the possible universes allowed by theoretical physics, an astonishingly small number have physical characteristics that permit any life at all to form. The focus isn't on the amount of life, but on the apparently improbable fact that the cosmic parameters take on such unlikely values.