Alidar Jarok wrote:
There are practical reasons to not want to go on a craft that can travel that fast. It's not the 10 years or so it would take to travel to Alpha Centauri, but the thousands of years that would pass back on Earth that would prevent me from wanting to take the trip.
At .1c a little over 40 years would pass on earth for you to reach Proxima Centauri at 4.2 light years distance. Time dilation on board ship at that speed would be negligible.
At .5c, 8 years would pass on earth while on board only about 7 years would pass.
I think you have some confusion as to how time dilation works.
I know how this is going to sound, but I've worked with the numbers often enough to hold the opinion that the relativistic time dilation thing is probably more of an illusion than an actual distortion of time; that is, if your kids on Earth were watching you with a telescope it would LOOK like time was slowing down on your ship relative to them, even though this would not actually be the case (so if you immediately turned around and flew back, your clocks would synch up again when you arrived).
Primarily this is because the equation holds true in both directions regardless of which one of them actually accelerates; both the traveler AND his point of origin will each observe the other's clock running faster relative to their own, so long as their relative velocity remains high. Meanwhile, it still takes you 40 years to get to Alpha Centauri no matter where you're measuring from.