The flow of time is affected by gravity.

Credit: Wikimedia

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PARIS: Einstein's theory of relativity, which states that gravity affects the flow of time, just got 10,000 times more accurate.

How quickly time passes depends on where you are, a lesson learnt the hard way by that first-time reviewer of Wagner who observed: "After two hours, I looked at my watch and found that 20 minutes had gone by."

For physicists rather than opera-lovers, relativity was famously expressed in 1915 by Albert Einstein who suggested, among other things, that the flow of time was affected by the force of gravity.

Flow of time gets tested

Clocks will run faster the farther they are from a large gravitational source and run slower they closer they are to it, goes the theory.

Various experiments have been carried out to explore Einstein's insight.

They include a 1976 exploit in which an atomic clock was taken on a 115-minute rocket ride to a point some 10,000 km above Earth, and was found to measure more time compared to a counterpart on Earth.

Now 10,000 times more accurate

Now physicists in the United States have gone a step further.

They have proved Einstein's theory with an accuracy 10,000 times greater than before, according to a paper published in the British journal Nature.

A team that included Nobel winner Steven Chu - now U.S. energy secretary - used a trap that involved three lasers that zapped waves of caesium atoms, making them move up and down like a fountain.

The waves were used as super-fast clocks, oscillating at nearly a million billion billion times per second.

The team's technique invoked a strange-but-true phenomenon of quantum mechanics: that an atom can be excited into two states at the same time.

In one of the states, the atom was "pushed" by laser pulse one tenth of a millimeter (0.004 of an inch), giving it a minute boost away from Earth's gravitational field. In the other, it remained unmoved.