World's first space cold atom clock

BEIJING - The cylinder-shaped black object bears no resemblance to any ordinary clock, but it is one of the most advanced timepieces ever.

It was sent to space with the Space Laboratory of China's Tiangong-2 on Thursday, becoming the first ever cold atom clock working in space.

"This clock is so accurate that it should not lose one second in 30 to 300 million years in space," says Liu Liang, professor and director of the Key Laboratory of Quantum Optics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences.

Unlike ordinary clocks, the timekeeping device is based on atomic physics.

And unlike the most atomic clocks, this clock uses more advanced "cold atom" technology, ensuring its ultra precision.

A mechanical watch loses almost one second a day; a quartz watch loses about one second every 10 days; the hydrogen atomic clock loses about one second over millions of years; the cold atom clock exceeds all in accuracy, Liu says.

Scientists attribute its accuracy to the microgravity environment in space as well as the coldness of the atoms the clock uses.

Under microgravity conditions, the cold atoms, pushed by lasers, perform a uniform motion in a straight line. By observing their performance, scientists get more precise atomic clock signal than under the gravity conditions on Earth.

Moreover, the laser cooling technology helps to eliminate the influence of atomic thermal motion on the clock's performance.

"Though molecules and atoms can't be seen in a room, they are actually moving at high-speed, and the speed is equivalent to temperature," Liu explains.

"We use laser cooling technology to slow down the atoms to a temperature that a refrigerator could never reach, so they nearly stay still," Liu says. "By observing the almost static atoms we make our measurements more precise."

Scientists believe that putting such a clock in space will help set a time standard to synchronize other atomic clocks in space more precisely.

"A more accurate clock system in space will benefit us on Earth," Liu says, citing possible substantial improvements in navigation and positioning accuracy.

Scientists say the development of cold atom technology could also make many experiments possible, such as deep space navigation and positioning, dark matter probes, and even gravitational wave exploration.

"A lot of research is based on our measurement of time and space. If we could detect subtle changes in time and space, we could make discoveries beyond the range of existing technology," Liu says.

"In the future, there will be more accurate clocks than this cold atom clock and our ultimate goal is to make a clock that will never be a second fast or slow over the life of the universe."