Tuesday, October 27, 2009

Fermi Paradox: life is extremely rare

My preferred Fermi Paradox solution is that technological societies have only a short-lived interest in roaming the physical universe. A more common explanation, now that rocky planets seem ordinary, is that life is extremely rare. I liked the way this physics professor came to that conclusion ...
Information Processing: Evolution, Design and the Fermi Paradox - Stephen Hsu

... What is the time scale for evolution of complex organisms such as ourselves? On Earth complex life evolved in about 5 billion years (5 Gyr), but one can make an argument that we were probably lucky and that the typical time scale T under similar circumstances is much longer.

There is an interesting coincidence at work: 5 Gyr is remarkably close to the 10 Gyr lifetime of main sequence stars (and to the 14 Gyr age of the universe). This is unexpected, as evolution proceeds by molecular processes and natural selection among complex organisms, whereas stellar lifetimes are determined by nuclear physics.

If T were much smaller than 5 Gyr then it would be improbable for evolution to have been so slow on Earth...
Basic Bayesian reasoning, and a new perspective for me. Good one Dr. Hsu!

Update 10/29/09: Some nice comments, but, above all, Charlie Stross drops the hammer. It's an intellectual tour de force from someone who gets paid to think about these sorts of questions. Charlie flips the question around, and shows that waiting-time-for-stuff-like-us is actually very short. He doesn't fess up to his answer to the Fermi Paradox though.

Update 10/29/09b: Through some back and forth in Charlie's comments section, I end up searching on his treatment of the FP in Accelerando -- and one of the top hits is my 2006 Amazon review of his book. He's very much in the church of "post-singular societies don't go a wandering" (me too), but he explains why. According to Charlie Stross, life without bandwidth is intolerable ...

9 comments:

Craig said...

"My preferred Fermi Paradox solution is that technological societies have only a short-lived interest in roaming the physical universe."

The optimist in me would very much like to agree with you, but, in truth, I think it's much more likely that planets are only able to sustain high-technology civilizations for vanishingly short intervals of time.

Occam's Razor, in it's original and purest form comes into play: "Entia non sunt multiplicanda praeter necessitatem." Entities must not be multiplied beyond necessity. Apotheosis requires us to assume a new and conjectural mechanism, but the fall of civilizations is so commonplace that the world is choked with their ruins and artifacts. In particular, we have only a few short decades to work out a completely new regime of energy production, or our civilization also goes into the dustbin...and the next one to come along won't have the easy access to petrochemicals that we did.

The horror of Niven and Pournelle's _The Mote in God's Eye_ is that _we_ are the Moties.

John Gordon said...

I love "we are the Moties". Great tag line.

Jared Diamond's Collapse is a good companion to your position. When I look at all the things humans will have to do to deal with climate change I wonder if we need a low cost fusion power miracle.

My guess is that humans technological civilization is more robust than we think, but it's only a desperate guess.

On the other hand, I do think we'll have a non-biological sentience within this century. Once that happens the future is even more unknowable.

Scott said...

I've always gone back and forth on the Fermi Paradox (It is good fun thinking about, and don't let anyone tell you different). But I've constantly returned to the fact that a solution is just unknowable.

In 5Gyr, we've had one observable intelligent species evolve. But I think it's a bit of a leap to assign a T value of 5Gyr, because we have no object of comparison. Are we very early, or very late, in the evolution of intelligent life? Or like Pinkner suggests, have we just fallen into the fallacy of the evolutionary ladder, and intelligence is just a random happstance of natural selection that rarely if ever repeats?

I mean, seriously. We have a single intelligent species on one world, and then a few hundred billion worlds we can't yet evaluate. Could you imagine writing a paper and saying, "This occured once in 250 billion instances in this timeframe, therefore it's logical to reason that it's an average representation?" You'd be laughed out of the place.

There's just not enough information to form any conclusion.

John Gordon said...

Yes, what we do is basically push uncertainty around the Drake equation. We squeezed some out of the planetary frequency questions, but have lots left around life, intelligent life, civilization lifespan, etc.

So it's tantalizing, but still in the fun domain.

On the other hand within the next 20 years we hope to get spectrum data from some of the solid planets -- that may start to fill in the life questions.

Of course a single SETI positive would change things a bit, but I think we'll get spectrum data first.

rhc said...

I want to second how great the "We are the Moties" comment is. In Fermi Paradox discussions it always intrigues me that rarely does anyone bring up UFOs. It would be the ultimate irony if all those pilot, policemen, military visual/radar and other hard to dismiss sightings turn out to be real. Play with the Drake equation, read science fiction but totally ignore the elephant in the room. Dont misunderstand, im not even remotely saying that its an absolute certainty that some UFOS are ETs, just that its really interesting to me that conceptually they cross some kind of consensus reality border beyond which phenomena are treated as essentially taboo. There are some articles related to the Fermi Paradox here you might enjoy. http://www.ufoskeptic.org/

John Gordon said...

Personally I don't worry about the UFO sightings because I assume anything that could cross interstellar space who didn't want to be seen by us wouldn't be seen by us.

Additionally, anything that could cross stars, whether sentient or not, would probably be measured in centimeters ...

John Gordon said...

Charlie Stross comments big time:

http://www.antipope.org/charlie/blog-static/2009/10/how_habitable_is_the_earth.html

stefano said...

Since I don't see any reference to it in this thread, I'd like to put in a mention of the Cosmic Quarantine hypothesis summarized by Steven Soter here: http://www.astrobio.net/index.php?option=com_retrospection&task=detail&id=1745

It is a variation on the idea that a technological singularity selects against aggression. What appeals to me here is that it provides one answer for the FP which allows for the possibility of civilizations of immense scope whose existence would not be apparent to us. The probability of our surmounting our own singularity, while low, is perhaps not zero.

John Gordon said...

Thanks Stefano, I liked the article. I wrote about it ...

http://notes.kateva.org/2009/11/fermi-paradox-review-article-2005.html