Atom interferometer provides best test yet of Einstein's gravitational redshift

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Washington, Feb 18 (ANI): A new experiment in an atom interferometer has provided for the most precise test yet of Albert Einstein's gravitational redshift.

A central prediction of Einstein's general theory of relativity is that gravity makes clocks tick more slowly.

Now, a new experiment in an atom interferometer measures this slowdown 10,000 times more accurately than before, and finds it to be exactly what Einstein predicted.

"This experiment demonstrates that gravity changes the flow of time, a concept fundamental to the theory of general relativity," said Holger Muller, an assistant professor of physics at the University of California, Berkeley. he phenomenon is often called the gravitational redshift because the oscillations of light waves slow down or become redder when tugged by gravity.

Muller tested Einstein's theory by taking advantage of a tenet of quantum mechanics: that matter is both a particle and a wave.

The cesium atoms used in the experiment can be represented by matter waves that oscillate 3x1025 times per second, that is, 30 million billion billion times per second.

When the cesium atom matter wave enters the experiment, it encounters a carefully tuned flash of laser light.

The laws of quantum mechanics step in, and each cesium atom enters two alternate realities, Müller said.

In one, the laser has pushed the atom up one-tenth of a millimeter - 4/1000 of an inch - giving it a tiny boost out of Earth's gravitational field.

In the other, the atom remains unmoved inside Earth's gravitational well, where time flies by less quickly.

While the frequency of cesium matter waves is too high to measure, Muller and his colleagues used the interference between the cesium matter waves in the alternate realities to measure the resulting difference between their oscillations, and thus the redshift.

The equations of general relativity predicted precisely the measured slowing of time, to an accuracy of about one part in 100 million - 10,000 times more accurate than the measurements made 30 years ago using two hydrogen maser clocks, one on Earth and the other launched via rocket to a height of 10,000 kilometers.

Far from merely theoretical, the results have implications for Earth's global positioning satellite system, for precision timekeeping and for gravitational wave detectors, according to Muller. (ANI)

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