Quicksilver Clock Could 'Revolutionize' Physics

Feb. 19, 2008 -- Researchers are set to test a new mercury-based clock expected to be the world's most accurate timepiece.

The Tokyo-based research should improve measurements of everything from the speed of light to the strength of electromagnetic forces. It could also improve the accuracy of GPS signals.

"We hope that the proposed clock...will be the most accurate one, although it is not experimentally demonstrated yet," said team leader Hidetoshi Katori, a physicist at the University of Tokyo. The clock will have to run for several weeks before researchers can determine its accuracy.

The study was published recently in Physical Review Letters.

The researchers propose what is called an optical lattice clock, where a set of lasers creates a wave that holds atoms of mercury at rest. Another set of lasers reads the atoms' energy levels to determine the time.

Current clocks are based on the oscillation of the metal cesium, a technology which is more than 50 years old, notes Andrei Derevianko, a professor of physics at the University of Reno and one of the new study's authors. The problem with the cesium clock is that after 30 million years or so, the clock will be off by about one second.

While this might not seem like a big deal, the Global Positioning System (GPS) finds a location based on the very tiny, fractions of a second differences between the signals of orbiting satellites.