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Researchers to test Einstein's general theory of relativity at Tokyo Skytree


TOKYO -- A team of researchers from the University of Tokyo will test famed physicist Albert Einstein's theory that gravity affects time's passage in an experiment this month at Tokyo Skytree, the world's tallest free-standing broadcasting tower.

On the evening of Oct. 2, the team, led by professor Hidetoshi Katori, set up high-performance clocks on the tower's 450-meter-high observation deck and in the first-floor meeting room of the structure in Tokyo's Sumida Ward. After slightly adjusting the clocks, the team members will start the test in mid-October or later.

The optical lattice clocks, which were developed by Katori in 2005, are able to measure times less than one second with a staggering accuracy down to 18 decimal places, based on the vibration of numerous strontium atoms.

The force of gravity gets smaller as a body travels further away from the Earth's center. It is theorized that the speed of time's passage increases slightly in higher places, where the effect of gravity is weakened. According to researchers' calculations based on this theory, the speed of time's passage would differ by four nanoseconds (four billionths of a second) per day between measurements taken at the observation deck and at the meeting room, which are 450 meters apart in elevation.

"If we succeed in the test at Tokyo Skytree, I would like to try a test at Mount Fuji," Katori said. "We could also go the other way to calculate differences in height from the time difference. I would like to utilize the results to improve surveying techniques."

(Japanese original by Suzuko Araki, Science & Environment News Department)

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