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The Question

(Submitted February 25, 2005)

Has the time dilatation been prooven in any experiments? If so how?

The Answer

Effects of the right magnitude have been measured to be consistent with time dilation to within measurement uncertainty. These are not definitive proofs of the theory but strong indications that the theory is correct. One experiment has been to fly atomic clocks in planes around the Earth in opposite directions. The difference in time between the two clocks after the flights was consistent with those predicted by time dilation. Furthermore muons, sub-atomic particles created in the upper atmosphere by cosmic rays, are unstable and fall apart after a short period of time. However because they move close to the speed of light, their lifetimes are longer, at least as seen by us on the Earth's surface. This extended life, is also consistent with the prediction of time dilation.

with regards,
Martin Still & Jay Cummings
for "Ask an Astrophysicist"

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