It's All Relative

It's All Relative

This article relates to When You Reach Me

Einstein’s Theory of Relativity is, at its heart, about frames of reference. If I were in a dark, windowless train with no bumps that was going in one direction at a constant speed, then I would think I was standing still, but my sister on the train platform would see me speeding away from her. According to Einstein, if I then looked out the window, I would have every right to believe, in fact, that the world was speeding away behind me while I stood still. My sister, of course, would also be right that she was standing still. Hence, reality becomes relative to the frame of reference of the observer.

Time, as well, becomes relative to the observer’s frame of reference. This has been proven both mathematically and experimentally. One bizarre outcome of this "relativity" of time is known as "The Twin Paradox:" If I leave my sister behind on that platform while I travel far out through the universe going near the speed of light, I may age forty years in the trip out and back, but when I return, my sister will be long dead. Time will pass normally for my sister. Time will pass normally for me. But our times relative to each other are quite different.

This seems like it contradicts common sense because none of our frames of reference are traveling that much faster than each other compared to the speed of light - to a physicist walking, biking, driving, and even flying are pretty much the same speed, though time-dilation has been verified with atomic clocks on airplanes.

For a look at how quantum mechanics (another mind-bending theory that Einstein helped father) would affect us if its effects were big enough to be experienced in our day-to-day lives, take a look at The New World of Mr. Tompkins by George Gamow.

And for a readable prescription for how to actually build a time-machine by Stephen Hawking, one of the foremost physicists of our time, check out The Universe in a Nutshell.

Filed under Medicine, Science and Tech

This "beyond the book article" relates to When You Reach Me. It originally ran in September 2009 and has been updated for the December 2010 paperback edition. Go to magazine.