2026-02-25 米国国立標準技術研究所（NIST）
NIST physicist Laura Sinclair works to link an atomic clock on Mount Blue Sky to a location outside Boulder, Colorado, as part of an experiment to test whether clocks tick faster in lower gravity.Credit: G. Asakawa/University of Colorado
＜関連情報＞
- https://www.nist.gov/blogs/taking-measure/putting-einstein-test-worlds-most-accurate-clocks
- https://tiisys.com/blog/2020/04/07/post-63496/
2019年、東京大学のスカイツリーにおける光格子時計計測
Tower Testpermalink
In 2019, a research team led by Hidetoshi Katori, a physicist at the University of Tokyo, took an optical lattice clock up the Tokyo Skytree, Japan’s tallest building. The optical lattice clock, invented by Katori in the early 2000s, is one of the most sophisticated atomic clock designs, capable of measuring time to 18 digits of accuracy.
Optical clocks typically require cumbersome arrays of lasers, mirrors and electronics, often sprawling across multiple laboratories. But scientists such as Katori have found ways to shrink them without sacrificing accuracy.
For the experiment, the scientists connected their tower clock to a second lattice clock on the ground with an optical fiber, so they could compare the clocks’ ticking rates and look for slight deviations. As predicted, the elevated clock ran a tiny bit faster — four nanoseconds (billionths of a second) faster per day, to be precise.
Although Katori’s result was less precise than the earlier Galileo experiment, it notched another win for Einstein: It became the most precise test of gravity’s effect on time ever conducted on Earth — and an inspiration for even more ambitious experiments to come.
