
It wasn’t easy for earthlings to devise a uniform system for telling time around the world in the 19th century, and it may not be much easier on the Moon in the 21st. Tom Brown writes in Space that the U.S. and China don’t agree on how to do it.
Telling precise time — not in minutes and seconds, but in microseconds — is deemed critical for coordinating satellites and spacecraft using GPS, which works by broadcasting time signals. On Earth, we’ve resolved the challenge by using “atomic clocks” based on the oscillations of cesium atoms. But even atomic clocks, which are infinitely more precise than the industrial-era system built around Greenwich Mean Time, have their limitations. Time is relative. It is affected by gravity. And Earth has stronger gravity than the Moon. The consequence is that clocks on the Moon run faster than clocks on Earth by about 1 to 2 microsecond per year, according Copilot AI.
The challenge of space-faring powers is to translate Moon time into Earth-based Coordinated Universal Time (UTC).
NASA is working on establishing a Coordinated Lunar Time (CLT), which could set the standard for the U.S.-based LunaNet satellite system. But China, which already has active lunar relay satellites capable of communicating with the far side of the Moon, has its own protocol. Will one standard prevail over the other? I have no idea.
But I do have a question that the article does not address. How will people living on the Moon tell time? Humans are diurnal creatures that evolved over millions of years to adapt to the 24-hour cycle of the Earth’s rotation. They will construct habitations that mimic that 24-hour cycle, not the Moon’s 28-day cycle. much less oscillations of the cesium atom. They also will have to interact with people on Earth, with whose societies and economies they will be inextricably linked.
In “Dust Mites,” I assumed that that the U.S. lunar colonies time is synchronous with Earth’s Eastern Standard Time because that’s the time zone of Washington, D.C. Although I did not address the point in the novel, it seems plausible that a European, Chinese or Indian colony based near U.S. colonies would calibrate their time configurations to optimize interaction with Brussels, Beijing, or New Delhi. On the other hand, if the colonies come to be connected by MagLev trains, the demands of commerce would push for a uniform system. What would that look like?
I asked AI.
Copilot proposed a three-tier model for tracking time on Galileo Station, the largest lunar colony in the “Dust Mites” universe. The schema pays special attention to the implications for bots, which play an elevated role in the upcoming “Trogs” and an unnamed sequel.
more “Telling Time on the Moon”






