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Comment by tzs | Hacker News Reader

Here's a shot at an upper limit (idea ripped off from an Isaac Asimov essay I read a long time ago--late '70s most likely, but I re-did the calculations myself since I couldn't remember his numbers).

Imagine all humanity packed into a very large sphere, with each human allocated a mere 1 cubic meter of space. As the population expands, we have to enlarge the sphere to make room.

Starting with the current population, how long can a 1% growth rate be sustained before the frontier of the human sphere would have to expand faster than the speed of light to make room for the new humans?

That's a pretty good hard upper bound on long 1% growth can be sustained. If my calculations are right, it's about 9000 years from now. (That fits with my recollection of Asimov's result).

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It's a nice math problem, but it misses one key element: Relativity. If most of the universe's human population is expanding away from earth at a speed approaching c, the population growth rate in the earth's frame of reference would slow down -- people might still be breeding at the same rate in their own reference frames, but from the perspective of the earth all the fast-moving people would be living their lives very slowly.

Fast-moving people will also be Lorentz contracted, so there will be plenty of room... if there's enough energy.

I'd say the chances that the speed of light is still infinite, 9000 years from now, are rather slim. After all, Newton's system was radically corrected after 320 years, and even Aristotle's only held sway for about 2000. Einstein's has held well for the past 106 years, but an additional 9000 years of observation, experiment and theorizing will probably improve it a bit.

Speed of light as a limit on speed of information or matter is a universal constant. There is a reason why it is called a universal constant, no amount of observation or experimentation would change this universal fact. Of course, the science and technology would change, we would have better understanding of the universe but I doubt we would find anything that would defy the speed of light.

If there's some neat trick we are going to figure out in 9000 years to get around the speed of light then the galaxy / universe would have been overrun by advanced alien civilizations already. Who knows, we may have "sublimed" or been uploaded, but we won't be tooling around at warp 9 in velour uniforms.

That same argument goes for sub-lightspeed galactic colonization. The time between the disappearance of the dinosaurs and today (65 mil years) is more than enough to colonize the entire galaxy with simple rocket ships.

Good point – some kind of near light speed travel is as magic as FTL for most intents and purposes. So, no star trek.

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