I'm sure my readers are familiar with Fermi's paradox. Some of you may even feel it's debated to death lately, but in this great memorial year (Darwin's 200th birthday, among other things) we'll be hearing a lot more about the origins of life and the trajectory of evolution. Fermi's paradox connects with all that, and I'll get to the connection in Part 2.
Here's a quick refresher. Enrico Fermi observed that there seems to be a contradiction between the fact that we have not encountered alien civilisations and facts about the scale of the universe (and, indeed, our own galaxy). The vastness of space, the enormous number of stars and planets, and the age of the stars all add up to a presumption that there should be plenty of life Out There, some of it much older than life on Earth. If there are intelligent beings in space that began with millions of years of head start over us, why don't they have technological civilisations far more advanced than our own? But if they do, why have we never encountered such things as alien space craft, probes, or radio signals?
Colonising the galaxy
Consider that the diameter of the galaxy is about 100,000 light years. Imagine for the sake of argument that there's a technological civilisation somewhere near the galactic centre. Then imagine that it has the capacity to send out space ships or self-replicating probes or similar devices at even 1 per cent of the speed of light. It could get a ship or a probe out to the galactic rim in something like five million years.
If the alien civilisation sends out a few ships every thousand years, they will soon mount up in numbers. Over a few million years, it could send out many thousands of ships. If the colonies founded by those ships themselves got in on the act and sent out ships of their own, and the colonies they founded sent out ships, we get ourselves an exponential increase.
It looks as if a sufficiently advanced and determined civilisation could colonise the galaxy, to a greater or lesser level of density, in "only" a few million years (a tiny amount of time in geological or astrophysical terms). Perhaps not all advanced technological civilisations have that ambition, but it would only take one that has the ambition plus a few million years' start on us, and the galaxy should be widely colonised by now – at least to some density level that we’d notice. Where are the space craft, the probes, the signals, maybe even the astrophysical engineering projects?
There seems to be good evidence that the galaxy doesn't contain even one civilisation that is old enough, advanced enough, and determined enough. So, why?
You might think that if the evolution of technological civilisations were a common event in the universe, there'd be at least one civilisation like this somewhere in the galaxy, with its billions of stars. Even if it started out on the distant rim, far away from us on the other side, that's just going to make it take a few million more years to reach us. So allow ten million years of head start – that's still nothing in the kind of timeframe we're talking about. If technological civilisations are commonplace, there should be some that are those millions of years ahead of us (and some will come along behind us, trailing by a few million years).
So, where are they?
Might it be that creating space craft that can travel reliably at even 1 per cent of the speed of light is harder than we assume? Or maybe advanced technological civilisations tend to destroy themselves? Or do they tend to stop expanding their populations, as human beings are doing? We're really guessing.
The most pessimistic solution is that they tend to destroy themselves. From the point of view of our own species, that solution would suggest that our self-destuction lies ahead. If we discover life elsewhere, then, it's bad news: the more common life is, the more common technological civilisations should be, and hence the more likely it is that the reason we don't see them is that they destroy themselves. QED.
But I don't think that's the best way to look at it. There are other possibilities. Perhaps technological civilisations tend to reach a technological singularity point, at which stage they are transformed so comprehensively and deeply that we wouldn't even recognise them. They might miniaturise themselves in some way that makes expansion into space pointless, or they might switch over to some kind of substrate that we would never recognise as a form of life (partly, no doubt, for their own convenience, but perhaps partly to avoid interfering with vulnerable civilisations at our level).
Another possibility – one that might bother my transhumanist friends almost as much as the self-destruction account – is that the rate of advance of technology does not accelerate to a singularity. I.e., the mathematical relationship between time and technological capacity may not be an exponential function . Perhaps it will turn out that we are now somewhere on the relatively steep part of a sigmoid curve. In that case, perhaps advanced technological civilisations never obtain the level of technological capacity that enables them to go out and colonise galaxies. Maybe there are hard limits to what is possible, or perhaps there are universal limits to desire. If this is the correct picture, transhumanists should be disappointed – what lies ahead for the human species may not be anywhere near as radical as they hope.
The sigmoid curve interpretation has a kind of intuitive rightness about it (which doesn't mean it's correct). First, when science fiction writers describe the future they tend to imagine reaching some higher technological level and things then going on without huge change for millions of years. But of course the content of science fiction might just be evidence of limits to our current imaginative capacities.
We might also be impressed by the now-embarrassing question, "Dude, where's my jet car?" It sometimes seems that, even as the power of computer hardware continues to follow Moore's Law, progress in what we can actually do with it seems to be slowing down. "Where's my robot maid?" If so, human technological potential may be limited, and we need to imagine the future of the world with bounded horizons. Not that that need lead to crippling pessimism – it would not demonstrate our inability to produce great advances in, say, health and life span. What is and is not possible may be different from what we intuit in advance.
I think, though, that there's another way to look at this. I'll be back in a few hours to go deeper into the Drake equation.
Russell Blackford is an Australian philosopher. He has published extensively (novels, short stories, academic monographs and articles, and book reviews) and is editor-in-chief of The Journal of Evolution and Technology. His home blog is Metamagician and the Hellfire Club.