Is Interstellar Travel Impossible?

[Kralizec]

I think both high speeds and high acceleration causes watches to go slower.

Edit: At least high speed does http://en.wikipedia.org/wiki/Time_Di...d_space_flight

From the little that I know of these things, I remember that all movement is relative. Our solar system is moving away from the point where the big bang would have taken place, but we don't feel it. If a spaceship is accelerating, away from our system and towards this "point of origin", viewed from that point of view the spaceship is still moving away but at a decreasing speed ( eventually standing still and then moving towards it). But from our point of view, we're motionless and the ship is moving away at increasing speed.

From a PDF file linked to on that wiki page:

In conclusion, in the case of a purely accelerated motion of the clock which moves to-and-fro along a spatial straight line, a differential aging with respect to the rest clock takes place.

So traveling away from and back to Earth does make you age less compared to the people on Earth, but it's because you have to accelerate (and decelerate when you want to go back) to do it.