# Atomic Clocks Measure Relative Time

Physicists at the National Institute of Standards and Technology (NIST) tested Einstein's theories about relative time in a physical setting. Time goes faster at higher elevations, and slower for moving objects. The experiments involved a comparison of two identical atomic clocks.
The NIST experiments focused on two scenarios predicted by Einstein's theories of relativity. First, when two clocks are subjected to unequal gravitational forces due to their different elevations above the surface of the Earth, the higher clock—experiencing a smaller gravitational force—runs faster. Second, when an observer is moving, a stationary clock's tick appears to last longer, so the clock appears to run slow. Scientists refer to this as the "twin paradox," in which a twin sibling who travels on a fast-moving rocket ship would return home younger than the other twin. The crucial factor is the acceleration (speeding up and slowing down) of the travelling twin in making the round-trip journey.

NIST scientists observed these effects by making specific changes in one of the two aluminum clocks and measuring the resulting differences in the two ions' relative ticking rates, or frequencies.

In one set of experiments, scientists raised one of the clocks by jacking up the laser table to a height one-third of a meter (about a foot) above the second clock. Sure enough, the higher clock ran at a slightly faster rate than the lower clock, exactly as predicted.

The second set of experiments examined the effects of altering the physical motion of the ion in one clock. (The ions are almost completely motionless during normal clock operations.) NIST scientists tweaked the one ion so that it gyrated back and forth at speeds equivalent to several meters per second. That clock ticked at a slightly slower rate than the second clock, as predicted by relativity. The moving ion acts like the traveling twin in the twin paradox.

So if you want to age more slowly, you should run as fast as you can on a beach or a valley below sea level. The time you gain would not offset the difference in the time you put in, but you might live longer due to the benefit of the physical exertion. Link -via reddit

(Image credit: Loel Barr)

I'm an over the road truck driver, I drive on average about 3,000 miles a week all over the U.S. I have always noticed on several different and expensive wrist watches being either digital or analog, when I return home, my watch is always about 2 to 3 minutes slower than my home clocks, but if I take a week off and stay home, they stay the same.
If I don't adjust the time weekly, in a month my watch would be way off time.
I really noticed it about 3 years ago when I began running a postal route, my home clocks were in sync with the postal time, and those clocks always remained accurate, my watch on the other hand would always end up about 2-3 minutes behind a week.
I even bought a new watch thinking something was wrong with it. But the problem still continued until I realized what was happening.
I was under the impression that much higher speeds, far in excess of 75-80 mph were required to affect a clock in that manner, but apparently not.
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Atomic clocks as well as mechanical clocks show the same results. So it's not just mechanical so they assume the aging process would also have similar results.
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Not that it should be surprising, but I don't understand this. Just because a clock runs slower, how do we know that "time" is actually moving slower and not just the mechanisms of the clock?
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Earth spins, it orbits around a star, that star orbits the galactic center, that galaxy also probably orbits around the central mass of a cluster of galaxies, and so on... so... outside all these superstructures upon superstructures, what reference point could we possibly use to determine how fast we're actually traveling through... whatever medium we're supposed to be traveling through? And just how fast are we traveling, anyway? What's the time dilation for that?
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