The narrative of mankindâ€™s inevitable expansion into the Milky Way has become veryÂ common, and at first glance it seems to make sense. The frontier mentality is supposedly part of human nature; we have an instinctive urge to explore beyond that hill. I actually agree with that. But those who believe that this metaphor can be applied to the stars are trapped in several fatal category errors, and they know little about the technological challenges involved in interstellar journeys. Let me explain why.
When we travelled to the moon 40 years ago, it took just a couple of days to get there. Indeed, a little under 400,000km is a distance we can manage. When it comes to reaching a nearby star, however, we are dealing with an entirely different order of magnitude. Alpha Centauri, our closest stellar neighbour, is 4 light years away: 36 trillion kilometres, a billion times further than the moon. Even if, by some miracle of technology, we manage to speed up a space ship to 10% the speed of light, it would take us approximately 80 years to get there (considering the time it would take for acceleration and deceleration).
If we find another earth in a nearby solar system, it is likely to be even further away, at least 10 light years. It becomes obvious that a single human lifetime is not enough to bridge such a distance, and we would have to send so-called generation ships: giant arks capable to supporting an entire ecosystem as well as at least a thousand travellers. Such a system would become subject to the phenomena associated with island ecology.
Sorry for becoming a bit technical, but the rate of mutation of bacteria would far exceed the rate at which human physiology could adapt. At the same time, the ark would never be entirely sealed off. There is no perfect system. Some materials would be lost to space, while others would accumulate excessively. Over a 200-year period, the environment would turn poisonous.
By the way, the energy required to move a ship like that is far beyond our wildest dreams. A smaller ship however, which would require less energy, would not be large enough to host the required ecosystem. We are stuck with a problem which cannot be solved.
The idea that we are incapable of reaching beyond the solar system allows me to sleep at night.
And letâ€™s not forget sociology. As Kim Stanley Robinson vividly demonstrates in his stunning novel Aurora, the politics in a generational ship would be totalitarian, as the limited food supply requires tight controls on birth rates. Moreover, some jobs would just be indispensable, and it is the governmentâ€™s responsibility to make sure that someoneâ€™s doing them. A rebellion on a ship like that would have disastrous consequences.
One criticism that could be raised against me here, is that I have no idea about what kinds of technologies we will eventually come to master. That may be true, but I have two arguments for you.
Firstly, if you believe that technological progress can be maintained indefinitely, you are most likely wrong. Pretty much every basic technology we use today had already been around 40 years ago â€“ we have only refined them. Mooreâ€™s law no longer holds, and the increase in computational power has already slowed down. We still treat cancer with radiation and chemotherapy, just like we did in the 70s. As our technologies become more advanced, it becomes more and more difficult to control their parameters â€“ and eventually we reach an impasse.
Secondly, the idea that we are incapable of reaching beyond the solar system allows me to sleep at night. As far as we know, the laws of physics apply everywhere, so there should be countless civilizations out there. Why havenâ€™t they reached us? Why havenâ€™t we found them? Well, I presume because they are faced with the same problems we are â€“ it is not feasible to reach the stars.
Yes, we can colonise the solar system. Probes have been sent to every planet and there are currently seven robots doing science on Mars. A manned mission to the red planet is well within our reach and we may see the emergence of an enormous asteroid mining industry within our lifetimes. I support such endeavours whole-heartedly.
Getting to another star however, is a different matter. For the time being, we need to solve our problems here on earth. We cannot just escape to another planet if the earth turns poisonous, gets struck by a comet, or if we blow ourselves up. We need to take climate change seriously, to become sustainable, and to live in harmony with the earthâ€™s ecosystem if we want to survive as a species. At least for now, there’s no place like home.