Chinese software calculates time on the moon

In the age of mechanical clocks, if a timepiece was significantly wrong, the malicious remark was often made that it was going according to the moon. In fact, clocks on the moon run differently due to lower gravity. A team from China has developed software to synchronize timekeeping on Earth and the moon.

LTE440 is the name of the software developed by a team from the traditional Purple Mountain Observatory in Nanjing, and it is available on GitHub. It calculates coordinated lunar time (Coordinated Lunar Time, LTC) and its relationship to barycentric coordinate time (TCB) and barycentric dynamical time (TDB), the team writes in the journal Astronomy & Astrophysics.

The software automates the complex calculations for the time deviation between Earth and the moon. It is based on data about the moon's movement and thus determines the growing difference to the time on Earth.

Thus, the software can output the time difference between Earth and the moon for any given point in time. This eliminates the need to recalculate it every time years in advance for the preparation of a lunar mission. According to the researchers, the system's deviation is estimated to be “conservatively” less than 0.15 nanoseconds in 2050.

Time depends on gravity

According to Einstein's General Theory of Relativity, time depends on gravity; if gravity is stronger, time passes more slowly. Conversely, it passes faster with lower gravity – as on the moon: there, a clock gains 58.7 microseconds in 24 hours compared to an Earth clock. In about 50 years, the time difference would add up to one second.

However, navigation and communication systems require accurate time. Currently, lunar missions use Coordinated Universal Time (UTC), which is based on atomic clocks, for communication with Earth. With a planned permanent human presence on the moon, the time problem is gaining importance: this deviation would be too large for coordinating spacecraft on the moon or a lunar satellite navigation system.

The US government under former President Joe Biden instructed NASA in 2024 to develop a coordinated lunar time that should be traceable to Coordinated Universal Time UTC, to set a standard here. The European Space Agency (ESA) is also dealing with the topic. However, it appears that the competition from China was faster.

(wpl)