The push to establish “coordinated lunar time” is gaining momentum. The International Astronomical Union (IAU) is the latest organization to call for its own standard time for the Moon to coordinate future lunar missions.
On August 15, at its XXXII General Assembly in Cape Town, South Africa, the IAU adopted a proposal to introduce a unified lunar-sky reference system and lunar coordinate time. A follow-up resolution stated that the new time zone should be established by “international agreement.”
“As we leave Cape Town and reflect on the legacy of this event, let us remember that together we are pushing the boundaries of astronomical knowledge, in a collective effort to better understand the universe we live in, our origins and our future, and to make the world a better place for all,” Willy Benz, the IAU’s president-elect, said in a statement.
There is currently no agreed time zone on the Moon – and this is becoming a growing problem. Unmanned missions typically use the time zone of the spacecraft’s country of origin, while the manned Apollo missions from 1968 to 1972 used Ground Elapsed Time, counted from the moment of launch.
As humanity (hopefully) returns to the Moon in the near future and more countries and private companies launch space missions, the need to coordinate lunar observations with a unified clock is increasing.
Time dilation throws a further spanner in the works. Due to the general and special theory of relativity, the duration of a second on the moon appears distorted to an observer on earth, since there is less gravity on the lunar surface and time therefore passes more quickly.
On the lunar surface, time passes an average of 57.5 microseconds faster per Earth day than on the surface of our planet. That may seem tiny, but it could make a difference in high-precision experiments. Moreover, these tiny differences can add up; if an astronaut spends 50 years on the moon, he would be about 1 second older than if he had stayed on Earth.
Discussions about “coordinated lunar time” have increased recently. As early as April 2024, the White House directed NASA and other agencies to develop a plan to implement a new lunar time system by the end of 2026.
While it is still unclear how the world will accomplish this, it is clear that now is the right time.
“I think the community has recognized that this needs to be done. And this is the beginning,” Bijunath Patla, a physicist at the National Institute of Standards and Technology, told the Associated Press.
