h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

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It's already been proven that time travel into the future is possible. NASA bods used two atomic clocks with the same time, and put one of them in the shuttle and sent it into orbit for a few days. When they brought it back, the atomic clock that had been in orbit was a few milliseconds behind the one that had been on terra firma, the clock in orbit was technically "younger" than the one that stayed behind, due to time dialation.

Let's now thake this to the exteme. Take two astronauts who are identical twins, and put one of them on a spaceship going to Alpha Centauri. If the spaceship can travel at 80% the speed of light, it would appear to the twin on the spaceship that the round trip to Alpha and back was made in about 10 years. For the twin that remained on Earth it would be a lot longer than that, in from his/her perspective the journey would be so long that he/she would most likely be drawing their pension by the time the other got back.

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The problematic thing would be to attempt to travel backwards in time. For that you'd probably have to exploit black holes, worm holes, super strings, and other things like that. Technically at our current technological level, it isn't gonna happen soon.

but, as the famous physicist once said, "anything not ruled out by science is almost mandatory".

As far as I remember the experiment predated the shuttle - a high-flying bomber was enough to prove the theory.

Also, people using particle accelerators have gotten particles with half-lives of, say, 1 nanosecond, to last for 5 seconds. That's because they had the particles going 99.9999% of the speed of light, so their sense of time was messed up.

PhysicsMan