Right now, there are a few missions - a rover by the United Arab Emirates, a lander by Japan's ispace, and a NASA experiment, on the way to the moon and will arrive there at the end of this month.
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As many as 10 missions - from the US, Mexico, Netherlands, India, Japan, and Russia are planned to head to the moon this year. SpaceX is aiming to send a group of tourists around the moon late this year or early next year. NASA's Artemis II will take astronauts around the moon early next year, and Artemis III will land astronauts on the moon in 2025. China has also announced this week it is developing its lander to land two Chinese taikonauts on the moon by 2030.
The moon is going to get awfully busy and one thing we don't have an agreement on is - what time is it there?
On Earth, we have time zones so that we can adjust our clocks so that the beginning of the day is when sunrise occurs, the end of the day is when sunset happens, and we can have 24 hours in a day.
On Mars, this isn't really an issue either. A Sol (Martian day), lasts for 24 hours and 37 minutes. To account for this, scientists work on Mars missions adopt Mars time - meaning their clocks go slightly longer, but this means the mission day starts when sunrise occurs on Mars, and ends around sunset.
On the International Space Station, astronauts are orbiting Earth every 92 minutes, meaning they have about 15 sunrises and sunsets every day. To deal with this, the astronauts keep their daily schedule relative to the country they are from. American astronauts are on Houston time, Russians on Moscow time, and so on.
The instruments themselves, like a lot on Earth, operate on UT, or Greenwich Mean Time, a time zone of 0.
However, the moon is a different situation. Right now, countries choose which time zone, and system, to run missions on, and groups are calling to sort out a standard.
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Clocks themselves run slower on the moon that Earth, due to less gravity. While it is only about 55 millionths of a second per day compared to Earth, that can quickly add up and precision measurements as well as computers may get out of sync, or stop working all together.
A lunar day, the time it takes the moon to rotate on its axis, which on Earth is 24 hours, is the same as a lunar year, the time it takes to go around the Earth, much like it takes 365.2564 days for the Earth to go around the sun.
This is all because the moon is tidally locked to the Earth. Over millions of years, the gravity between the Earth and moon has slowed the rotation of the moon to reach the point where its rotation (day) and orbit (year) are happening at the same rate.
Relative to the stars and rest of the sky, the moon does one orbit around the Earth every 27.29 days. And since its spin and orbit locked, that means "daytime" would last about 14 days, and night-time, 14 days. Using time like on Earth, or even Mars, will not work.
- Brad Tucker is an astrophysicist and cosmologist at Mount Stromlo Observatory and the National Centre for the Public Awareness of Science at the ANU.
