What time is it?

To answer that, you’d probably look at your smartphone or a watch linked to your phone. And using orbiting satellites, those devices would provide the time with an accuracy of a few billionths of a second.

With dozens of missions planned for the next few years, scientists are looking at setting up a similar system for the Moon. It would provide precise timing for probes and astronauts in orbit and on the surface. That would help with navigation, science observations, and more. To make it work, though, everyone will have to agree on some basics of time.

One question is whether the entire Moon should be one big time zone, so clocks would read the same around the entire world. Another is whether lunar time should be linked to an earthly time system.

Clocks on the Moon tick at a different rate than those on Earth. GPS satellites compensate for the effects of Earth’s gravity and their own speed. But the Moon’s gravitational pull is weaker than Earth’s, and satellites move slower. That means a clock on the Moon gains about 56 millionths of a second per day relative to clocks on Earth. For precise navigation and science, that’s critical — a big difference in the ticking of a lunar clock.

The Moon is in the early morning sky right now. Tomorrow, it climbs into good view by a couple of hours before sunrise. And it has a close companion — the planet Saturn looks like a bright star to the upper left of the Moon.
 

Script by Damond Benningfield

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