Are we alone in the universe? Big question. A very clever fellow named Drake once calculated the odds of intelligent life arising in the universe, and this figure is often quoted as ‘proof’ that alien life exists. The problem is that the Drake equation is based on assumptions that he (meaning no disrespect) basically pulled out of his ass. In other words he’s totally guessing- that hardly constitutes ‘proof.’
Time and science march on however. We’ve now identified thousands of exoplanets (planets in other solar systems) and we have a much better basis to guess. On the average there appears to be about one planet per solar system that is theoretically capable of supporting life- hugely more than anyone would ever have believed previously, but it is what it is. This means that there are around two-hundred billion other places in our galaxy alone where life might have emerged. And what is outside of our galaxy? Billions of other galaxies. Even if the odds are vanishingly small that life will emerge that’s still a lot of chances- it would be bound to happen somewhere.
So what are the odds that life would emerge in these environments? We cannot even guess; our sample size is simply too small. Currently it’s a sample of one. That will inevitably expand as time marches on- there are some indications that there may have been life on Mars. A couple of moons here in our own solar system have potential for liquid water- which as far as we know is essential for life. Certainly for life as we know it. But for now we have no rational basis for guessing.
Or do we?
So far we have found life virtually everywhere on earth that we’ve looked. Poisonous, ridiculously hot volcanic sea-floor vents? Life. Solid rock kilometers deep in the ground? Life. In fact there are almost no environments we have encountered on earth where life does not exist in some form. Life is stunningly robust and adaptable, and at a guess if there ever was life on Mars we will eventually find that there still is… but it might be far underground and likely microbial. I guess we’ll know someday. The problem is that all of this life on earth may have adapted from a common source, so for life to adapt to all of these unlikely environments it had to have existed to begin with– and we’re back to guessing.
I’m guessing that as we expand into space we will find life, of some sort, everywhere that it can theoretically exist, but that guess and a couple of bucks will get you cuppa Joe.
What about intelligent life? Again, we have no way of estimating the odds. Sample size: One. Sure, it seems likely that with the ridiculously large number of potentially life-bearing planets that intelligence would arise elsewhere in the universe, but we don’t know and cannot even make a reasonable guess.
Enrico Fermi said no to intelligent aliens, his argument being that if the galaxy is about ten billion years old, surely in that time someone would have spread out across the cosmos. Shouldn’t we see evidence of them, or at least their stuff? With all that time wouldn’t they have left some observable trace of themselves? After all even with our technology we have already launched two ‘ambassadors’ into interstellar space. If we keep doing this we, even with no more technology than we have already used, could have junk spread across the entire galaxy in about twenty million years. So surely alien races would have left some traces of their presence, right? The fact that we haven’t seen any of this stuff seems to Fermi to be persuasive evidence that there isn’t intelligent life elsewhere in the galaxy. Enrico Fermi- very smart guy. Very accomplished scientist. Totally talking out his ass.
‘But Tinker, how can you- who are after all just some schmuck- say that about a great scientist?’ I hear you cry. To which I respond, “You don’t have to be an expert to know a train-crash when you see one.” First of all we have made a lot of stuff. I mean, we covered a planet with our stuff, right? So say you took all of our stuff and scattered it randomly across the solar system. We, with our current technology, would be unlikely to notice it. Because space is BIG. Seriously big. Bigger than you can imagine. Big on a scale that even out biggest stuff is infinitesimally tiny by comparison. Grand Coulee Dam is sub-microscopically tiny on that scale. We could be literally surrounded by evidence of intelligent aliens and never know it. Then there’s that time thing- humanity has only been around in a state of technology where it would even be possible for us to spot alien junk for less than a hundred years- with billions of years to play with we could have been visited thousands of times before humanity even existed, and our own natural environmental processes would have done for the evidence before the first proto-human wondered if he could walk upright.
Even really, really big stuff is small on the scale of space. Our galaxy is tens of thousands of light-years across, and it’s only one galaxy among billions spanning an unimaginably large and continuously expanding universe.
Much of science is predicated on things not being ‘special.’ Things in one place work pretty much like things in another place. So far this seems to be true, therefore if life can happen here it can, and almost certainly has, happened elsewhere. If intelligent life can arise here it can, and almost certainly has, arisen elsewhere. It seems inevitable from that perspective, but we don’t really know and until ET lands and says hello we still won’t know. Even when ET does do this a lot of people will be convinced it’s a hoax and part of some elaborate conspiracy. Because internet.
So are we alone? We can only guess, but I am guessing we aren’t– and that someday we’ll find out.