On Facebook, in response to this article that's been circulating today for some inscrutable reason, one A. Melaragni said:
Apparently the guy is just talking about our own galaxy; there are BILLIONS AND BILLIONS of galaxies in the universe. Not to mention that even if other life doesn't exist in our galaxy now, that doesn't mean it never did or never will. There is just so much room out there that I think it would be bizarre if life DIDN'T exist elsewhere.
Which got me thinking. In the absence of proof positive one way or another about the existence of life elsewhere or elsewhen, we can still do some perfectly legitimate Bayesian reasoning based on what we've [not] observed, and how the universe seems to work.
While I don't really buy it, I'll concede there are some legitimate reasons to think we might be the only life anywhere. The only other plausible option is that there is an abundance of life: is, was, and will be.
My reasoning is that physics doesn't do one-offs. You don't see a new kind of particle exactly once and never again, you don't see one wildly unique type of stellar body sitting among trillions of others in our galaxy. In general, there are strong mathematical reasons why if anything happens once, it (or something similar enough) will most likely happen twice. And if there's anything less likely than someone happening just once, it's something happening just twice, which would make a mockery of probability.
So, I figure it's probably not just us out here, and if that's the case, it's certainly not going to be just us and one or two other planets of life. Let's consider the two main possibilities.
Let there be life.
In the scenario where intelligent life happens, and where you accept my assertion that there will probably be a lot of it, we can draw some conclusions. Crucially, we are unlikely to be unusual, within the range of all life that eventually takes form. Barring a meddling God, the various salient characteristics of a lifeform—longevity, intelligence, size, high reliance on optical/EM sensory input, overall temperament—are gonna end up distributed as big fat Gaussians, and we're gonna be right near the big fat middle of them for most of these things. Yes, there will be truly alien and bizarre creatures out on the fringes, so that's fun, but it's not us.
This also applies to our timeline of development of technology relative to others. We are one species selected at random from all those who have or will exist. There are some cosmological reasons why we might be one of the earlier ones, but I feel that's heavily outweighed by the implicit probabilistic evidence under discussion; if there are to be a million different life-bearing planets, what are the odds we're the very first to start to get our shit together?
Then of course you run into your Fermi paradox, which on the whole is pretty ominous. Without getting too sidetracked in that, it strongly suggests that either we'll never make it to the stars, or when we do, it will be in a form or mode unrecognizable by present-day us.
- If there's any life besides us, there's probably a shitload of it.
- If there's a shitload of it, lots of them probably have a huge head start.
- For whatever reason, they're all gone, unrecognizable, or (at best) undetectable. Without exception. This implies that whatever the attractor at work might ultimately be, it is likely inevitable and undeniable.
Basically, for anyone who dreams of 50s-scifi-style cruising around the galaxy and meeting aliens, give it up. Either there aren't any out there, or there is some overwhelmingly strong reason not to make contact on those sorts of terms, or there'll be some pesky obstacle like inexorable self-annihilation in the way. If we ever do make it to the tipping point where we have the social and engineering infrastructure for interstellar flight, and start doing it up in earnest, I figure that's the nail in the coffin for there being any other life out there. So, the other scenario:
Let there be no life.
In this scenario we are, somehow, a black swan—most likely, there would still be an infinite number of aliens in our infinite universe, but they'd be so negligibly rare as to essentially guarantee none in our light cone, which means they effectively don't exist. There's not a whole lot to say on this other than to point out the silver lining—that the massive, invisible, all-subsuming agent watching us hungrily from behind the curtain of the Fermi paradox would suddenly become a non-issue.
It may be a lonely existence, but this scenario is one in which there's no especially good reason why we can't go exploring all over observable space and spread like cancer. There just won't be all that much more to do out there, at least until we say "okay, fuck it" and seed some new form of life deliberately. I think that, of the two scenarios, this is actually the better deal, as it sidesteps the many and sundry sinister explanations for the current deafening silence.
Note to self: there was something worth exploring there that I skipped by. Given certain kinds of systems governed by a relatively small set of rules but seeded with some level of random initial conditions or ongoing perturbations, is it in fact true that it can be less likely for something to happen twice than to happen once? And if so, how much must a thing have to happen before the probabilities pull even again? I think there could be depth there. Maybe more weight behind %0%, %1%, and %oo% being the only relevant quantities of things. Which is arguably already well established. And %oo% is just a gussied-up %0%.
But I'll go digress.