(Crossposted from Metamagician and the Hellfire Club.)

There's been a lot of fuss over the past week or so about the discovery of an Earth-like planet "only" 20.5 light years away - detected by the European Southern Observatory's telescope in La Silla, Chile. Circling the red dwarf Gliese 581, the new planet has been christened "581 c". It is at a distance from its sun that suggests a temperature range compatible with life, and it is conjectured that it may have plenty of liquid water - another precondition for life.

It would be exciting if it turned out that the new planet actually contains life, and even the discovery of such a planet in the galactic neighbourhood is pretty damn sensational: it suggests that life-ready planets may be more common than is usually thought.

Some commentators, including my pal George Dvorsky, have raised the question of what this means for the Fermi paradox (the question of why the aliens aren't seen here if they're out there somewhere). George is worried about whether it means that civilisations are doomed to extinction before they reach the exponential technological take-off point that has frequently been conjectured and dubbed "the Singularity". 

I must say that I can't get so worked up about this. I'd love it if 581 c contained life, though my betting is that any life will turn out to be at a very primitive stage, if we find it at all. From the limited evidence we have, it takes a very long time for multicellular life to evolve, even once life gets going, and it may not happen in all cases, or even in typical cases. Furthermore, life of any kind may appear on only a tiny minority of so-called "Earth-like" planets. The degree of fine-tuning necessary for life to appear is likely to be many orders of magnitude rarer, in the universe, than the relatively crude set of indicators that get a planet classified as "Earth-like". Even if Earth-like planets should now be thought a few times more common than we previously believed, this may have little effect on the extraordinarily long odds against life existing in any particular block of space-time. In short, there's no warrant to go from the discovery of a nearby "Earth-like" planet to a conjecture that our galaxy is teeming with life, let alone multi-celled life, or life that's well on the way to evolving intelligence.

Even if fairly complex life forms come into existence on a particular planet, what are the odds of evolution leading to something as smart as us, and then to a technological civilisation capable of expanding into space? Bear in mind that, if things had been a bit different, our own planet might still be ruled by dumb dinosaurs: it's widely accepted that the Cretaceous-Tertiary extinction had something to do with the asteroid impact that caused the Chicxulub Crater, perhaps coinciding with other contingencies (by itself, the asteroid may not have been enough). This gave life on Earth a second chance - as it were - to take a path that eventually led to the development of big-brained mammals.

Even when human beings appeared on Earth a couple of hundred thousand years ago, it took us almost all of that time to develop science and an industrial civilisation. There's no reason in principle why we couldn't have stayed with stone-age technology for a few more hundreds of thousands of years. Indeed, it's easy to imagine that the evolution of intelligence could have culminated in creatures like dolphins and orcas, which show no sign of ever inventing a technological civilisation, or of evolving into something that will.

There are so many contingencies involved that I'm led to betting - not that I know how I'm going to pick up my winnings - that we are currently the most technologically-advanced species in our galaxy. There may be worlds out there teeming with something like algae, or with something analogous to dinosaurs - and I'd love to see those worlds. Somewhere in the galaxy, there may be a world whose watery surface is dominated by the equivalent of whales and dolphins, or something even more majestic. But there's every reason to think that few planets ever produce something that resembles us as a technological species.

Of course, the universe is a big place. There's probably a more technologically-advanced species than us out there ... well ... somewhere; I'd be crazy to bet against that. Hey, there's probably lots of them. But the odds are, I reckon, that they're in galaxies far away, so far away that they and we will never come in contact.

I also question the assumption in the Fermi paradox that a species like us, with consciousness and the ability to rebel against its selfish replicators, will end up colonising the universe, or travelling in it en masse. The claim is often made that we are destined, beyond a certain point in technological development, to expand into new volumes of inter-stellar space at an exponential rate, and that intelligent species just do this once they obtain space-travel technology. That scenario sounds most unlikely to me. We are more likely to stay home, consciously matching our population size to the carrying capacity of our own planet and the resources available in the local solar system.

That observation may sound as if I'm against space travel and the colonisation of space, which is certainly not true. I don't doubt that we'll eventually explore the solar system and beyond, and I certainly hope there'll be some off-Earth colonisation in the mix of human civilisations as the decades, centuries, and millennia roll by. That could produce an attractive kind of innovation and diversity.

But the whole exponential-colonisation-of-the-galaxy thing always sounds monstrously improbable to me: I don't understand what would drive it, given that we are conscious beings who can make a decision to limit our own population growth to match the habitat that is easily available to us - which is the Earth, so far, and is not likely to extend beyond the local solar system in the foreseeable future. I can understand why it might be fun to send out probes, and even explorers, to find those planets filled with algae or dinosaurs or dolphins. Sure. But why would we want to interfere with those planets? They will be a wonderful interstellar wilderness that we'll want to preserve.

I can't understand why anyone would ever consider the exponential colonisation of the galaxy to be desirable in itself, or why the species as a whole would decide to go down that path. Maybe I'm wrong about that, and it has some value that I'm blind to; but even if I am, I can see us staying in our home solar system pretty much indefinitely until some unimaginable contingency shakes us out of it. Why would that not be a typical response of those technological species with rationality and consciousness? It may be very rare for such species to advance exponentially into surrounding space, even when they do come into existence.

There's a huge, exciting universe out there, and eventually we'll explore it - but we may never try to remake it in our own image. Furthermore, we may well be the most technologically-advanced species that this galaxy has ever known. That seems to me like a reasonable answer to the Fermi paradox, and nothing about the discovery of planet 581 c makes me change my opinion.