posted on Jul, 1 2013 @ 03:19 PM
Yeah I guess there must be some limitation on how many people can travel back in time because, if time travel is physically possible, then we should
be overrun with people coming back from the year 2100, 3100, 4100 up to infinity.
Maybe that limitation is resource-based, like the scarcity of anti-matter, or maybe its an ethical constraint, like machines or dare I say it, humans
behaving more responsibly in the future. Or maybe it's due to an escalating risk factor.
If I understand relativity right, every object in the universe is constantly travelling at the speed of light through spacetime. In normal situations,
like us here on earth, most of our velocity is through time, because we are going very slow through space. As you go faster through space, you slow
down in time so that your overall velocity through spacetime remains exactly c - the speed of light.
As you speed up, time slows down until you reach the speed of light at which point you are going 1c through space and zero through time. When you pass
the speed of light barrier, then time begins speeding up again but is now running backwards. As your velocity increases, time runs backwards faster
and faster until you reach 2c at which point you are going 1c backwards through time and 2c through space.
So when travelling at 2c, time would run backwards at the same rate that it's currently running forwards. If you wanted to go back in time by one
century then it would take one century of your life when travelling at 2c.
You could speed up even more to 4c and then it would take 50 years of your life to go back one century. Clearly there is a limitation on how far back
in time a human can travel before he expires due to old age.
Speeding up even more to 100c and it would take only two years to go back one century but I wonder, at what point does it become too risky to send
humans at such high speeds, and we send robots instead?