It's 2 a.m., and the noise from your upstairs neighbor is keeping you awake again. Take solace in the fact that by living above you he may be shortening his life, even if only by a tiny fraction of a second.
Nearly a century ago, travel up and down every day. Using the world's most precise clocks, they confirmed that our wristwatches tick at a slightly different speed when we ride an elevator, climb a flight of stairs, or even sit upright in bed.suggested that time should move faster the farther away you are from the surface of the Earth. Now scientists have tested this theory at the small distances we
According to Einstein's theory of general relativity, big objects with lots of gravity -- planets or stars -- bend the fabric of time and space, like bowling balls on a trampoline. The closer you get to these objects, the stronger the pull of gravity and the slower time moves. An astronaut watching a clock fall into a black hole, for example, would see its hands gradually slow down as the pull of gravity increases. The second hand would move tick once every hour, then once every decade, and finally appear to stop altogether.
For half a century, scientists have experimented with ways to spot this effect on Earth. In 1976, the Smithsonian Astrophysical Observatory launched a rocket that carried a clock 6,000 miles away from the ground, where the pull of gravity is weaker. When the clock returned to the surface, it had sped up -- compared to clocks on the ground -- by about one second every 70 years. Time dilation over great distances has also been measured in clocks flown around the world on airplanes and sent to Mars on spacecraft, and satellites in orbit must compensate for it to keep GPS networks functioning properly.
But spotting the subtle changes in time that happen over the smaller vertical distances we move in our daily lives -- a matter of feet and inches -- is much more difficult. It requires an exceptional clock billions and billions of time better a wristwatch.