(Russell is guestblogging for George) 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.
Fermi’s paradox
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.
Deeper into Drake’s equation
I suspect that the evidence that we’re on a sigmoid curve is pretty much illusory. E.g., the evidence from science fiction is probably just evidence of limits to our imaginative capacities. Still, it’s not a scenario that can be ruled out (and it seems just as possible to me as the technological singularity scenario). It’s certainly conceivable that at least some kinds of technological progress flatten out. At 1 per cent of the speed of light it would take us over 400 years to reach the nearest stars. We don’t know how much longer to reach the nearest worlds that could easily be colonised. We tend to think that the problems will be solved in millions of years of future progress, but we may not be good at working out what problems can and cannot be solved, at least easily enough to be worth the effort, even over very long tracts of time.
That said, I’d prefer to look for an explanation deeper in the Drake equation, which uses several variables to calculate the number of technologically advanced species in our galaxy. The variables include the average rate of star formation, the fraction of stars that have planets, the fraction of planets that can potentially support life, the fraction of these that actually develop life, the fraction of these where intelligent life evolves, the fraction of these that develop civilisations that send detectable signs of themselves into space, and the length of time that such civilisations exist.
Some of the fractions that feed into the Drake equation may be very small indeed, so small as to make technologically advanced species, and the civilisations they create, incredibly rare. It’s consistent with what we now know that the conditions required for life to form are extremely fortuitous and unusual. It may need very rare combinations of environmental factors. And even then, you can have life staying at levels of neurological complexity that don’t lead to technology.
We know that life can stay at levels of intelligence well below our own pretty much indefinitely. If not for one or more catastrophic events at the end of the Cretaceous Period, including the bolide impact that caused the Chicxulub Crater, Earth might still be dominated by dinosaurs, which might not have developed any impressive levels of intelligence. They hadn’t done so in the previous 150-odd million years, so there’s no reason to think they would have in the past 65 million years.
We really need to know a lot more, and we soon reach a point where people are relying on nothing more than hunches. With that disclaimer, my hunch is that the evolution of a technological civilisation to our sort of level or beyond is a statistically improbable event. I.e., it is an event that takes place quite infrequently in an average galaxy. I can’t be much more precise about what “quite infrequently” means, except to say that I wouldn’t be at all surprised if human beings were the only species in our galaxy to have created technological civilisations.
There’s a lot of things we’d need to know before we could say anything more confidently, or more precise, than that. E.g., we’d need a well-corroborated theory of the origin of life to give us an idea of how rare the conditions for it really are. We just don’t have one. We have a well-corroborated theory of how life diversifies - neo-Darwinian evolutionary biology - but not of how it gets started. The best we have is an idea of what sort of theory would be a workable account of abiogenesis – some kind of theory of early kinds of self-replicating molecules that were able to develop into the building blocks for the kinds of life forms from which we, and the rest of contemporary life on Earth, all eventually diversified.
There are so many unknowns about all this that I think we’re a long way from being able to deduce any pessimistic conclusions about humanity’s future. Even if life itself is more common in the universe than appears so far, the evolution of human-level intelligence might be very rare indeed. Even if technological change ends up following a sigmoid curve, we don’t know how to unpack the detail of that – it might mean that space travel at appreciable fractions of the speed of light is going to turn out more difficult than we commonly assume … but, for all that, our ability to transform our capacities may reach levels far beyond what is current. We can’t predict the future, though we can forecast and consider various possibilities and scenarios.
Still waiting
Meanwhile, I’m still waiting for my alien civilisation. I’m also waiting for my jet car. If it doesn’t turn up before I shuffle off this mortal coil, I don’t know if that’s a reason for pessimism or optimism.
Where has the damn thing gone?
IEET Blog