China's atomic clock is only one second wrong after 30 billion years

The American atomic clock uses strontium to keep track of time.

If it passes the assessment, the atomic clock, led by a team of experts at the National Time Service Center in Xi'an, will be sent to the Tiangong space station in October for advanced physics research. The device will also contribute to the network of chronographs along with BeiDou navigation satellites and ground-based facilities over the next few years, increasing accuracy by more than fourfold. Optical atomic clocks enable faster communications and positioning, and are vital to national defense.

Now, researchers are waiting for test results to see how well the device performs in space. Testing begins at the end of April 2022. Jun Ye, a physicist at the US National Institute of Standards and Technology and the University of Colorado Boulder, says achieving the same precision in space is difficult. Ye is the leader of the research team that develops the world's most accurate optical clock in the laboratory.

According to him, developing a smaller and lighter optical clock for use in space is very different from using it in a laboratory. The main challenge is how to achieve compact size and durable performance. According to Xinhua, the optical clock developed for the Tiangong station must be 20 times smaller than in the laboratory to fit on the station's laboratory stand.

Historically, humans have used natural phenomena with regular oscillations to keep track of time, such as the Earth's rotation and the movement of stars over thousands of years. The first atomic clock was invented in 1949 to measure time by tracking the radiation frequency of an atom which was extremely stable. Today, satellite navigation and timekeeping on the Internet are indispensable for atomic clocks. European scientists are also participating in a project called Atomic Clock Ensemble in Space to bring the atomic clock network to the International Space Station.