It is clear from the Lorentz Parameters, applied to Einstein's Equations, that as velocity, v approaches speed-of-light, c, the denominator (1 - [v/c]) tends to zero; when v=c, time, t=0: time stops?!
This accounts for the theory that an astronaut, travelling at almost the speed-of-light, for what he conceives to be a short time, returns to find that x-number of years have passed by, on Earth (bit of a shock).
Is this true; or, is it a quirk of mathematics; or, is it impossible to say?
Time does not stop. In the frame of the astronaut, time continues to flow as normal - nothing will start happening in slow motion or anything like that. As such, you will not be forever young or somehow manage to experience "more time" in your own frame of reference by moving at near the speed of light.
What does happen, however, is time passes slower in the astronauts frame of reference than it does in the stationary observer's frame of reference. This means that, depending on how fast the astronaut is travelling, for every 1 minute the astronaut experiences someone on the Earth may experience 1 hour passing. You could then return to Earth after a long period of travelling and find that years had passed for your friends and family, while only weeks had past for you.
The problem is that travelling at speeds large enough for this effect to be noticed on a "macroscopic" scale presents an enormous task. It would be nigh on impossible to accelerate a spaceship to 99.97% of the speed of light, which would recover a time dilation factor of ~60.
