Most space-travel science fiction I know falls into two groups: Either people have found a way to travel faster than light (Star Trek, Star Wars and many others), or people travel for decades or centuries in sleeper ships (Jon Bing’s novels about the starship Alexandria, for instance).
However, it seems to me (I’m not a physicist, though!) that a fairly likely scenario would be the invention of spaceships travelling at a speed slightly slower than that of light. First of all, it doesn’t contradict the laws of physics as we know them, and secondly, we don’t get all these messy problems with deep-freezing people.
The big advantage would be that travel would be nearly instant for people on the spaceships, because time slows down when you’re moving very rapidly.
However, it would have some interesting consequences. First of all, it would be fairly boring for people back on earth because we wouldn’t hear anything back for a very long time (if we sent a spaceship to a planet 100 lightyears away, it would take more than 200 years before we’d find out whether the mission had been a success). It also means some people could visit all of the known galaxy, but if they ever returned back home, so many years would have passed that it wouldn’t be like coming home at all.
I guess the consequence would be that we’d only bother exploring the nearest star systems. Sure, we might also send colonisation ships to planets much further away, but that would mean cutting off all contact with them in practice, so I think only fanatics would want to do that.
I’m a bit surprised that I’ve never come across science fiction exploring this scenario – does anybody else here know more?