The Moon Will Get its Own Time Zone

White House officials have directed NASA to begin work on establishing a standard time for the Moon, according to a report from Reuters this week. Coordinated Lunar Time (LTC) is intended to help ensure synchronization between the various lunar activities planned under the Artemis program.

Timekeeping is essential to space travel. It ensures orbital maneuvers occur correctly, it helps communications between spacecraft remain secure, and it prevents errors in positioning and mapping. Without it, in other words, lunar exploration would get very complicated.

We can blame Einstein and his theory of relativity for part of the problem. Time is experienced differently under different gravitational conditions, an effect known as time dilation.

“The same clock that we have on Earth would move at a different rate on the moon,” Kevin Coggins, NASA’s space communications and navigation chief, told Reuters.

On the Moon, clocks move faster than their Earthly counterparts by 58.7 microseconds per day. While most humans wouldn’t notice such a tiny difference, spacecraft certainly do.

Currently, spacecraft in low Earth orbit, like GPS satellites and the International Space Station, run on Coordinated Universal Time (UTC). But even in these cases, periodic corrections need to be made for time dilation, otherwise GPS systems would lose precision and ultimately fail.

Canadian astronaut David Saint-Jacques shows his watch, set to UTC, aboard the International Space Station. Credit: CSA.

The Apollo program’s moon missions in the 1960s-70s relied on Houston time. Mission control was the astronauts’ timekeeper – though astronauts made sidereal measurements using the stars to ensure they were on course and on time – that was enough for short-term lunar visits with only two vehicles (a command module and a lander).

But with dozens of countries and private companies vying to engage in long-term lunar exploration under the Artemis program, a shared timekeeping system is going to be vital.

“Think of the atomic clocks at the U.S. Naval Observatory (in Washington). They’re the heartbeat of the nation, synchronizing everything. You’re going to want a heartbeat on the moon,” Coggins said.

NASA will need international cooperation to bring LTC into being. UTC, the global standard for Earthly timekeeping, is managed by the International Bureau of Weights and Measures, and LTC will likely need to be brought before the same body to ensure its implementation is accepted internationally.

The White House memo proposing LTC recognized the need for international agreements to bring it to fruition. It suggested facilitating LTC through existing international bodies, but also through the Artemis Accords, a recent 36-nation agreement that outlines guidelines for cooperative space exploration.

According to the memo, plans for LTC are expected to be finalized by the end of 2026.

Scott Alan Johnston

Scott Alan Johnston is a science writer/editor at the Perimeter Institute for Theoretical Physics, a contributor at Universe Today, and a historian of science. He is the author of "The Clocks are Telling Lies," which tells the story of the early days of global timekeeping, when 19th-century astronomers and engineers struggled to organize time in a newly interconnected world. You can follow Scott on Twitter @ScottyJ_PhD

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