It鈥檚 fun to speculate about aliens (see 鈥�The human universe: If aliens exist, do they know we鈥檙e here?鈥�). But what if there are no aliens? It鈥檚 been 65 years since Enrico Fermi first pointed out our solitude. Fermi estimated that it would take an advanced technological civilisation 10 million years or so to fill the galaxy with its spawn. Our galaxy is 10,000 times older than that. Where is everybody?
It鈥檚 not as though we haven鈥檛 been looking. Not for long, perhaps, and not very hard, but even a crude estimate suggests there should be other advanced civilisations capable of signalling over interstellar distances. And yet 鈥� nothing.
So what if we really are alone, or so isolated as to amount to the same thing? 鈥淚f we think we are the only life in the universe, we have a huge responsibility to spread life to the stars,鈥� says Anders Sandberg of the University of Oxford鈥檚 Future of Humanity Institute. 鈥淚f we are the only intelligence, we may have an almost equal responsibility to spread that, too.鈥�
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NASA astronomer David Grinspoon agrees, although he hasn鈥檛 given up on finding ET yet. 鈥淲e have these powers that no other species has had before,鈥� he says. 鈥淚f we are it, if we are the best the universe has got, if we are the universe鈥檚 sole repository of intelligence and wisdom and scientific insight and technology, it ups the ante quite a bit. We have a responsibility to preserve our civilisation.鈥�
It won鈥檛 be easy. First, we need to decide where to boldly go (see diagram). We don鈥檛 know if humans can survive for any meaningful length of time anywhere except the surface of Earth. 鈥淣owhere in our solar system offers an environment even as clement as the Antarctic or the top of Everest,鈥� says the UK鈥檚 Astronomer Royal Martin Rees. But some pioneers aim to give it a go anyway. Billionaire inventor Elon Musk is aiming to establish a self-sustaining colony on Mars in the next 50 years. 鈥淏y 2100, groups of pioneers may have established bases entirely independent from Earth,鈥� Rees says.
Second, we are going to need some serious propulsion power but we don鈥檛 yet know what that will look like. Third, we have to have some way to deal with interstellar dust, which could create catastrophic collisions with our craft at the speeds we would need to attain. Fourth, we would need some kind of artificial gravity onboard, otherwise the crew will suffer massive, possibly fatal, health issues.
There will undoubtedly be many more obstacles that we have yet to confront or even imagine. But Sandberg and others are optimistic we can overcome them.
Even if we can鈥檛, we could play the longer game and attempt to seed the galaxy with life via 鈥渄irected panspermia鈥�. The basic idea is to launch microorganisms into space in the hope that they will crash-land on a planet or moon suitable for life, and eventually evolve into a self-aware, intelligent species.
Science fiction author Charlie Stross suggests isolating spore-forming archaea and photosynthetic bacteria that can survive for long periods in the harshest of environments. 鈥淧ut them on rockets and fire them out of the solar system,鈥� he says. 鈥淎lmost all will perish, but if you launch a hundred tonnes of spores every year for a century, maybe sooner or later something will work.鈥�
There would be no real payback for us, except perhaps returning a favour. Life on Earth may have started by directed panspermia. If so, our ultimate purpose may be to pass it on again, like a chain letter through the cosmos.
Read more: 鈥�The human universe: Exploring our place in space鈥�
This article appeared in print under the headline 鈥淐ould we colonise the stars?鈥�
