Does the moon have its own time? Why this question concerns science

What time is it on the moon? This is a question that scientists are increasingly concerned with. Why? Because Coordinated Universal Time (UTC) is commonly used in missions, spacecraft are getting more and more trouble. Because they don’t sync with each other.

With the currently manageable number of probes and missiles, this is not so tragic. But: the more vehicles and in the future also fixed bases are added, the more necessary it becomes to find a uniform system for measuring time.

After all, five countries (China, US, Russia, South Korea, Israel and India) and the EU are currently planning a moon mission, manned and unmanned. The American space agency NASA even wants to send astronauts to the moon again this decade.

Scientists like Jörg Hahn, an expert at the European Space Agency Esa, see the need for a common lunar time to enable cooperation and communication: “All this must be reduced to some kind of time reference, otherwise chaos reigns.” and things don’t fit together,” Hahn said in an interview with “Nature” magazine.

This is especially important in order to be able to determine positions on the moon using a GPS-like technique. The coordinates of a person or a vehicle are displayed in combination with three satellites.

The time it takes for the signals from each of the satellites to reach that point indicates the position. However, for this to work, time must be measured in exactly the same way.

But it’s not that simple. Because according to the theory of relativity, the clocks on the moon tick a little faster. Because the moon has a weaker gravitational field than Earth, NASA scientist Cheryl Gramling estimates that time there moves 56 microseconds — or 56 millionths of a second — faster every 24 hours. What doesn’t sound dramatic at first can make a big difference when it comes to positioning and communication.

Based on these principles, there are several ways to set the new moon time. On the one hand, the time measured by various atomic clocks on the celestial body could be adjusted at regular intervals to the coordinated universal time. This is how the Earth and Moon would be synchronized.

On the other hand, one could, for example, run a (minimally faster) time on the moon independently and show the growing difference from coordinated universal time.

According to “Nature,” independent times could make sense in the future — especially in view of possible colonization — if a temporal synchronization with Earth is logistically more difficult.

Another question that arises is whether regions of the moon should be divided into different time zones as on Earth. In any case, it is plausible that Earth’s 24-hour system will continue to be important to humans in space as well.

One reason is the natural sleep rhythm. Since the moon rotates on its own axis about every 29 days, a day is also about 29 Earth days and not 24 hours long.

(t-online, dpa, lhe)