I don’t know if you knew or not, but as a kid Physics was my favorite subject (yep more than Computers), and I almost went into that line of things, but the idea of controlling a machine at my will (machine being a computer here) was more fun, so here I am many moons later. But, every now and then my old physics roots still pull me to something interesting I read about (its only reading now, no more experiments). One consequence of Einstein’s theory (E=mc²) is that a clock in motion will always appear to run slowly compared with one at rest (and since all motion is relative, the clock at rest will appear to go slowly from the vantage of the one moving).
Because of that, did you know, if you take a plane east around the world you will come back 59 nanoseconds younger than if you had stayed home. The record holder for this type of travel, is the Russian astronaut Sergei Krikalev, who came back from 748 days orbiting in the Mir space station a full one-fiftieth of a second younger than he would have if he had stayed on the ground.
Did you also know that no law of physics, that we know, prohibits time travel?
Einstein once said, “If we could go faster than light, we could telegraph into the past.” According to the theory of special relativity – which he proposed in 1905 and which ushered E=mc² into the world and set the speed of light as the cosmic speed limit – such telegraphy is not possible, and there is no way of getting back to the past.
But somewhat to Einstein’s surprise, in general relativity it is possible to beat a light beam across space. That theory, which Einstein finished in 1916, said that gravity resulted from the warping of space-time geometry by matter and energy, the way a bowling ball sags a trampoline. And all this warping and sagging can create shortcuts through space-time.