Trapped on Spaceship Earth

earth-from-spaceIn the last post, I summarized arguments from Nick Bostrum about the Fermi Paradox (the surprising absence of evidence for extraterrestrial civilizations). Bostrum suggested that there may be a ‘Great Filter’, that is, that there is a problem (or problems) inherent in the evolution of intelligence that leads civilizations to self-destruct before they can begin spacefaring. I suggested that energy problems may constitute this ‘existential risk’.

In response, Ben Geer made an excellent point about the Great Filter.
“Isn’t a possible Great Filter simply the fact that interstellar distances are too great for travel between stars to be practical, regardless of how techologically advanced you are?”

That is: The Great Filter doesn’t have to be a cataclysm. This is a really interesting point, but the moral consequences are in a sense the same.

Ben’s premise that interstellar travel might be impossible is credible, to me at least. To my limited knowledge:

  • There is no possibility of faster-than-light travel.
  • No one knows how to sufficiently armour a spaceship against the chronic exposure of its occupants to the hard radiation of space.
  • The plausible stories about how to explore the galaxy involve von Neumann machines. These are robots that get someplace, colonize it, replicate themselves, and send out copies of themselves to inhabit the next X neighbouring planets, and so on. This assumes the development of AI that is more intelligent, autonomous, and competent than homo sapiens sapiens. We haven’t seen evidence of such Cylons. So perhaps the Great Filter is the impossibility of fully autonomous AI.
  • The list of unsolved problems can be extended almost indefinitely…

The upshot is that although Bostrum assumes that the Great Filter must involve disaster, non-catastrophic great filters are plausible. But there is the obvious rejoinder that a very few hundred years ago, no one had the faintest idea how to engineer heavier-than-air flight or light speed communication beyond line of sight. So there are strong reasons to doubt our intuitions about the technical impossibility of interstellar travel.

If the Great Filter is the impossibility of interstellar space travel, the upshot is that Earth itself is our only spaceship. This means we cannot escape economic externalities. So we are in exactly the same place of needing to avoid the existential risks entailed by exponential economic growth.

This brings us back to egalitarianism and global justice. We need to understand how to live together on a very small planet.


About Bill Gardner

A health care researcher and a child and quantitative psychologist by training. I am an American living in Canada and am Professor of Paediatrics, Obstetrics & Gynaecology, and Community Health & Epidemiology at Dalhousie University; and Professor of Pediatrics, Psychology, and Psychiatry at The Ohio State University. I also blog at The Incidental Economist ( and you can follow me @Bill_Gardner on Twitter.
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One Response to Trapped on Spaceship Earth

  1. Thanks for picking up this train of thought. I was especially thinking about the social problems involved in long-distance space travel. Getting to even the nearest star systems would take tens or hundreds of thousands of years with current technology. Even if someone invents a way to travel close to the speed of light, most interstellar voyages would still take many lifetimes. This would involve raising generations of travellers on a spaceship. There are all sorts of things that could go wrong in this process. Intermediate generations would have no memory of their home planet, no contact with it, and no hope of seeing the destination planet, either. They might well lose all interest in the mission, or rebel against it. Perhaps they would cease to believe that the home planet ever existed. They would have to transmit a great deal of scientific and technical knowledge from one generation to the next, without having any motivation for doing so. Mastering, say, architecture wouldn’t help a young person have a better life on a spaceship, so why bother? One could also imagine a “Lord of the Flies” scenario, with the development of tribalism, superstition, slavery, and religious wars. As a result, the space travellers might destroy themselves before ever reaching the destination planet, or arrive there utterly unprepared to settle it.

    Other technical problems: the spaceship itself would have to be maintained for an extraordinarily long time. Experience shows that the more complex a piece of technology is, and the longer it has to run, the more likely failure becomes. The number of spare parts that could be brought along would be limited. Software bugs might crop up hundreds or thousands of years into the mission; who would be competent to fix them by then? Very little could be known in advance about the destination planet; perhaps it would turn out to be uninhabitable after all. Even if the mission was successful, radio signals from the colonists would only reach the home planet thousands of years later. This would make it impossible for subsequent missions to learn from the failures of earlier ones. Would people be willing to bear the huge cost of sending out additional missions without even knowing whether the travellers on the first one survived?

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