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Scientists have created an atomic clock that is so precise that it can detect tiny changes in the speed of its ticks depending on whether it is 2 centimeters closer or farther from the center of Earth.
"Time can be intricately connected to gravity," said Jun Ye, a physicist at JILA, a joint institute of the National Institute of Standards and Technology and the University of Colorado, Boulder. "It sounds like science fiction, but these measurements are a reality."
The ability of a hyper-sensitive clock to determine small differences in altitude is based on Einstein's prediction that the farther one gets from the center of an attractor (like Earth), the faster time moves.
Researchers have long ago proved this theory by comparing the speed of clocks separated by vast differences, either on board satellites in orbits a few dozen miles apart, or by comparing the ticks of clocks telling time at sea level and those placed on a mountain top.
Five years ago researchers at NIST created a clock so sensitive that it could detect the difference in time between two elevations just a foot from each other.
But the new clock is even better.
"Now when we measure this very weird property of time fabric in the laboratory, even a 2-centimeter change will result in a detectable time change in the clock," Ye said.
The clock is described Tuesday in Nature Communications. It is a tweaked version of an optical lattice clock that measures the oscillations of strontium atoms that have been trapped in a network of lasers.
A clock with this extreme level of precision may seem like overkill, but it could be used to improve our understanding of the shape of Earth, help to conduct tests of the fundamental laws that govern space and time, and provide a new pathway for investigating dark matter.
And the possibilities grow as the clocks grow more precise.
"If we can make a clock 1,000 times more accurate, we could hear the symphony of the universe."
