International Space Station to host space’s most accurate clock

The International Space Station is about to get a new clock, one that will officially hold the title of “most accurate clock ever launched into space.” It’ll be a whopping 100 times more accurate than even the fantastically accurate clocks on GPS satellites.

Both the ISS’s new clock and some terrestrial clocks, like the one used by the National Institute of Standards and Technology to keep the US’s official time, are cesium (also spelled caesium) clocks. Cesium clocks work by cooling cesium atoms, then measuring the frequency of the microwave signals emitted by their electrons when that energy level is changed. It’s a fantastically precise way of telling time–but it could be better.

The problem with terrestrial cesium clocks is gravity. Says New Scientist:

On Earth, the accuracy of caesium clocks is limited by gravity. The atoms are cooled by using lasers to slow them down, then tossed upwards into a cavity where measurements are made to determine the precise frequency of microwave radiation that they absorb and emit. In microgravity, the atoms linger in the cavity, allowing for longer and more accurate measurements, explains John Prestage of NASA’s Jet Propulsion Laboratory in Pasadena, California, who is not involved in the project.

That tiny anomaly caused by gravity may not seem like a big deal–after all, the NIST’s cesium clock is gauged to only lose or gain one second in 60 million years–but you can always be more accurate. The ISS’s cesium clock is estimated to be “at least” 100 times more accurate than the clocks on GPS satellites, which are already used for syncing on Earth.

When the ISS’s clock is launched in 2014, it’ll provide a single source for incredibly accurate time, allowing us to better synchronize ourselves here on Earth.