I’ve often heard the idea that humanity’s survival depends upon finding a way to leave this planet. Most recently it was Stephen Hawking, who said after a visit to zero gravity that:
I think life on Earth is at an increased risk of being wiped out by disaster, such as sudden global warming, nuclear war or a genetically engineered virus or other dangers. I think the human race has no future if it doesn’t go into space.
To my mind this is not only wrong but terribly dangerous.
In the long term it is trivially correct. At some point in the future the earth will be hit by an asteroid large enough to make it uninhabitable. Mankind can build defenses against such things – to me these most simply involve predicting potential collisions very accurately and applying a small amount of propulsion to those which present a threat so that their orbit is changed. Even so, as Hawkins says, there are other dangers and we have all our eggs in one basket. If nothing else gets us the sun will go nova in a few billion years.
But when people talk about colonising other planets they are thinking of the next few hundred years. It’s a seductive thought. We’ve messed up the earth with pollution, climate change, and so on. We’re running out of oil, there are too many people to sustain the population growth we are genetically programmed to seek, and it’s a great big universe out there. Why not replay the last couple of hundred years of western history on a truly grand scale. Set those space-wagons rolling and carve out a presence on the universal stage!
I grew up on science fiction and I love astronomy, but this attitude makes me cringe because it just hasn’t been thought through properly. First of all there is the technological challenge of getting some people into space in an environment which can support them for the many years or even generations it will take to reach a nearby earth-like planet in another solar system. Let’s assume they take a mini-environment with them plus a bunch of microbes and seeds so as to set up a pared-down version of an earth eco-system on the new planet. Let’s assume that the new planet is so like our own in climate that it doesn’t need “terraforming” as the old sci-fi stories called it. Let’s assume that planet doesn’t have its own life. [And just to be clear, Fred Holye aside, any life it does have will not be "the same" or "compatible" with ours, that's simply impossibly unlikely. So we're not going to a planet with alien trees and grasses that we can eat, we need to bring our ecology with us.]
In this best reasonable scenario we send a small expedition of a few tens of people and a proto-environment along, and they introduce microbes and flora to the bare bones of a planet. After a while they drop down out of orbit in person and, if all has gone well, they can live there. That means they can grow food and start to rebuild a technological base. After many decades one might expect that if the introduction of a new environment has been wildly successful there would be a place that other humans could travel to from earth and live upon. They too would be travelling very slowly in super-recycling mini-environments.
The Apollo program and the International Space Station have shown how expensive it is to get a few men and women into space. This to me is the second big difficulty. Assuming we can overcome the technological challenge, the biggest part of which is biology, it simply takes an enormous amount of energy even to get humans out of our gravity well (*). So the question becomes: who will get to go?
Because if we don’t solve our problems here on earth before we try to leave, we’re going to be selling very few tickets on very few life rafts from a ship which is sinking.
This is why I call the “escape pods” idea dangerous. There are a number of challenges which the human race must solve, right now, to ensure that 99.9999% of us survive. These include global warming, world peace, hunger, pandemic, and so on. To devote our efforts instead to getting 0.0001% of us off the planet, into an uncertain future in space, seems like madness unless there is no other option whatsoever.
So by all means let’s pursue a space program. I’m in favour of extending our knowlege and our reach. But we have a responsibility to our planet and our children to take our time and put our house in order before we think about leaving. If we were to rush to get even a few hundred humans set up in a viable extrasolar colony we would probably fail and we would certainly be leaving behind a smoking wreckage and untold human misery. Just to get all mystical on you for a moment, I also think we have a responsibility to export what we could be, rather than the “ugly human” we mostly are now. Once we are willing to fix what we have broken and learn to get on with one another, we will be the sort of aliens we would like to meet.