A Light Take On The Gravity-Time Relationship

Brian Greene explains the link between gravity and time.

Greene has written a short (less than 40 cardboard pages) new picture book called Icarus at the Edge of Time. It tells the story of a young boy who slips off in a space ship and cruises over to a black hole, only to discover that he’s made a terrible mistake: He forgot one of Einstein’s fundamental observations, which is that time is not the same for everybody everywhere.

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Einstein’s theories posit that as one gets closer to a center of gravity, time will “slow down.” So if you spend the rest of your life closer to the Earth’s center of gravity on 34th Street while I spend the rest of my life at the top of the Empire State Building, time for you will tick a teeny, teeny bit more slowly than time for me.

Einstein meant this not poetically, but literally. If you and I each had a watch, ticking off hundred-billionths of seconds, the watch on your wrist down below on the street would tick fewer times than the watch I was wearing up in the sky. It wouldn’t be a big difference — a few billionths of a second over 20 years — but it would be a real difference. If we decided after several decades to meet and compare watches, we’d see that they would literally differ, that time for the two of us had indeed ticked differently.

via Physics Buzz