[fsloth]

I suppose if we take the philosophical position of Bayesian statistics, where even one sample is sufficient basis for estimating results from some sane priori model, I would say this topic is within reach of some sane postulation. Some factors we can take into account:

1. Life can evolve into us. Therefore life on other planets has p>0 to evolve agglomerations of matter we would call "alien civilization"

2. Evolution seems to be driven through external constraints, and seems to generate similar structures to solve similar problems. Hence it's not insane to postulate organelles and their function are a particular energy minima to a complex set of constraints - ie. evolution on any earth like planet might reach similar patterns as earth life.

3. Neurological function seems to be driven by laws of mathematical dynamics up to a point - if it's math, we will see it everywhere in the universe. What sort of math - I suppose nobody completely understands yet.

4. I use the above to postulate that familiar modes of existence and familiar neurological function can emerge anywhere in the universe

5. If a species is to survive, it needs to have innate drive to do so. Unless species innate drive to survive perishes, an intelligent species will realize it's chances of survival are better if it is not limited to one planet. Then, one solar system and so on. Therefore we can postulate a "natural tendency" to start interstellar expansion.

6. Humans have already launched an interstellar space craft (Voyager). Therefore p>0 that life can evolve to develop vehicles that exceeds the escape velocity form their home star

Or something like that. The thing is, I don't understand the problem well enough to know if it's impossible to probe by statistics or not. I just know I'm not smart enough to solve the matter - when I did a course on Bayesian statistics the thing that left me astounded time and again was that one could create sane and accurate models from incredibly thin amount of data if one just had a good enough grasp of some of the factors at play.

[mannykannot]

> I suppose if we take the philosophical position of Bayesian statistics, where even one sample is sufficient basis for estimating results from some sane priori model...

Some care should be taken to see that this principle is not being used to excuse just making things up. Bayesian statistics is rational but not magical, and it cannot create information out of nothing.

In practice, this comes down to the question of whether the model is plausible, accurate, complete and constrained enough to deliver an answer that is informative about the external world, as opposed to the choices made in modeling. Something more than reasons to believe various probabilities are non-zero is needed.

I feel that, in your final paragraph, you are grappling with this issue.

[fsloth]

I totally agree with you. My intent was not to promote pseudoscience but just to try sketch out why I don't intuitively feel the question would be totally beyond the scope of rational discourse.

[nl]

Why is this any different to the Drake Equation?

https://en.wikipedia.org/wiki/Fermi_paradox#Drake_equation

[fsloth]

I suppose it isn't, but the categorization is a bit different. For example, Drake takes a concept called "civilization" as given, wheres I stated it's plausible extraterrestrial life would take similar pathways as in terrestrial evolution, and that other terrestrial species have minds that give them in some ways behaviours quite similar to our own (hence increasing the likelihood of extrasolar life having familiar characteristics). The categorizations I listed were in the "self organization emerging from complex systems" tune of things while Drake equation is a bit more hierarchical. But yes, same thing I guess.

[chiefalchemist]

> If a species is to survive, it needs to have innate drive to do so....

It's worth pointing out, that's not how natural selection works. NS would be: If a species has an innate drive to survive, it will do so. Yes, subtle. But essential.

That aside, how would you account for an asteroid strike?

[DangitBobby]

This all falls apart at 1.

> 1. Life can evolve into us. Therefore life on other planets has p>0 to evolve agglomerations of matter we would call "alien civilization"

In any universe that we can observe, we must exist. That strips away any useful a priori probability estimations about how likely we were to come into existence. p ~= 0 is still p > 0. There could have been a trillion trillion trillion trillion universes before this one where no life evolved that we would never know about because we were not around to observe them. And there could be a trillion trillion trillion universes after this one in which no life arises.

[fsloth]

I think this in the category of things that would be plausible to estimate. AFAIK there has never been a Manhattan Project level investment in abiogenesis.

Of course there are quite a few steps from suitable RNA synthesis mechanism emerging to LUCA.

But until we get CERN level investment into research on abiognenesis I don't think the matter can be considered impossible to solve.

The outcome might very well be that chance of life emerging is close to zero (I don't believe it, but it's just a belief, nothing more). At this point we can only conclusively say more research is needed.

If someone is in the field I would love to hear recent details.

[ekianjo]

For 1, Life has more chance to evolve in milliona of other species that dont o serve space, master fire or launch rockets. pretty bad odds once you look around you. plus we have been graced by having fairly mild cosmic conditions for a long time. other planets may not be so lucky

[giantrobot]

Sure, but space is mind-bogglingly large. Our galaxy alone has hundreds of billions of stars. Even one in a billion odds ends up with hundreds of systems that develop just like ours did. And that's just one galaxy out of billions.

That however circles back to space being large. While a galaxy might host hundreds of civilizations just like ours at any given time, the distances between them can be insurmountable. Time is also pretty large so even a civilization that survives thousands or even millions of years might never overlap with another that they can contact.

[roywiggins]

Part of the problem is, you just need one civilization in this galaxy to invent von Neumann probes to expect to see their robot offspring everywhere, even if that civilization is half a billion years dead.

[giantrobot]

The word "just" is doing some pretty heavy lifting in that statement.

It pre-supposes you can event build a bunch of invincible perfectly programmed micro/nanobots in the first place. Then you can identify a target body in a solar system a long ways away. Then predict that system's position with an accuracy your probe could land on it after a trip of hundreds of light years (or launch a probe with a bunch of fuel to do terminal maneuvering). Then those probes would function after millennia of dormancy.

It's all possible. But the concept shouldn't be treated as inevitable.

It also runs right up against panspermia theories. What's the practical difference between a single celled organism and a self-replicating nanobot?

[roywiggins]

Well, yeah. It's really hard to do, so maybe nobody does it, or it's just impossible. But with several billions of years of galactic history it has to be pretty hard if civilizations are common.

Really it's just one example of a technosignature that is longer-lasting than radio waves, that extends the amount of detectable overlap we might expect to have with an older civilization, and the lack of observation either says that sort of technology is either not feasible or there aren't many civilizations in the galactic past or present.