Will traveling to the stars be possible?

Latest post in my blog on popular science:
Will traveling to the stars be possible?


I don’t think most people understand, or even can understand, the vastness of space (and I’m not sure I really do). Douglas Adams did pretty well, writing as The Hitchhikers’ Guide to the Galaxy:

“Space,” it says, “is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”

As an illustration (OK, and maybe to show off a little), here’s a picture I took the other night of the Great Globular Cluster in Hercules:

It consists of several hundred thousand stars, has a diameter of about 145 light-years, and is about 22,000 light-years away. That sounds like (and indeed is) a long way away. But in this picture, in the red circle just down and to the left of the cluster, is IC 4617, another galaxy almost 500 million light-years away. Barring something like wormholes or hyperspace, it’s just not going to happen.

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In my post for next week (next plus one) I reason that wormholes or hyperspace are not going to happen. If they did, destructive paradoxes could take place. It’s the same with time travel. And in both cases, the Fermi paradox is also a good inkling that those ways of traveling are impossible.


Of course, at least in the case of fiction, it’s simply a way of getting the characters to where the action’s going to happen, and it is (or can be) easy to hand-wave away the science-y stuff. But in the real world, it gets harder, to the point of “might as well be impossible” (which I expect is also going to be your conclusion).

  • Generational travel, even if technically possible (which it isn’t, quite, but it’s closer to possible than anything else), would take far too long to be feasible. Using a rough number of 5M km/day (toward the high end, I think, of what you’d approximated) as a possible speed, and rounding the distance to Proxima Centauri b to 40T km, that trip would take 8M days, or just under 22,000 years. That’s considerably longer than the entirety of recorded human history. The problems are too numerous to count:
    • We’d have very little idea what the travelers would expect when they arrived, even assuming conditions on the destination planet didn’t change while they were en route. We can estimate temperature by what we know about the star, and the planet’s distance from the star. We can estimate the planet’s mass (and thus its gravity) from its size. Maybe we could learn something about the atmosphere (assuming there is one) through spectroscopy. But to learn anything else, we’d need to send a probe, which would take another 22,000 years or so. So the travelers would need to be equipped and trained to build something like Biosphere, though on a much larger scale. And if they’re going to have to live in a bubble anyway, they might as well stay in the ship.
    • How would we expect to build a ship (and all its systems) that could remain operational for that long? What machines do we have that have lasted a tenth as long? Much less something as complicated as a spaceship? Sure, its occupants could handle some degree of maintenance and repairs, but with what parts and materials? And how are you going to handle major hull repairs, should they be necessary?
    • What about medical care? Supposing there are no pathogens aboard the ship when it departs, that still leaves plenty of potential diseases to treat, cavities to fill, injuries to address, babies to deliver, etc. That means medical professionals (and maintaining them, and training new ones), equipment (and keeping the equipment operating), medication, and supplies. For 22,000 years.
    • Will the population be large enough to avoid genetic abnormalities after around 1,000 generations?
      • And will the environment introduce additional risks of mutation? What are the radiation levels, for example, in interstellar space?
    • And, as you mention, the sociological problems (or at least concerns), which are the sort of thing that produce the main conflict in Space Mutiny, and doubtless many other stories.
  • Hibernation has the potential to avoid, or at least minimize, most of these points, though of course we have no idea how to do it.
    • The first two bullets above still apply, and the second becomes more critical–if all the passengers are hibernating, the ship needs to detect and repair its own failures (which increases its complexity, which increases its risk of failures, which increases…).
    • You also need whatever hibernation support systems may be required to be self-diagnosing and self-repairing.
    • You need sufficiently-sophisticated automated controls to manage the voyage and respond to any possible risks–given your earlier writings on AI, this seems problematic.
    • A rotating system of caretakers can reduce some of the above difficulties, but that’s going to require that every person onboard be thoroughly trained in, well, pretty much everything. It’s also going to require a sort of hibernation where people can leave and reenter that state while onboard, the inability to do which was a significant part of the plot of Passengers.
  • I’ll leave the theoretical problems with wormholes, hyperspace, and the rest to those more scientifically literate than I, saying only that I’m a little skeptical about them.

Your comments are apposite. That’s why I said in my posts that “very critical circumstances would have to concur that would make it necessary to leave the solar system, for this solution to the problem of interstellar travel to be considered, and even then, it would only be a last resort, a desperate flight.”