Why the Moon should have its own time zone – 04/04/2024 – Science

The White House wants NASA, the American space agency, to develop a new time zone for the Moon, called Lunar Coordinated Time (LTC).

Due to the different strength of the gravitational field on the Moon, time passes faster there than on Earth — 58.7 microseconds each day.

It might not seem like much, but it can have a significant impact when you’re trying to synchronize spacecraft.

The United States government hopes that the new schedule will help coordinate national and private initiatives to reach the Moon.

“This fundamental theory of gravity in our Universe has an important consequence: time passes differently in different places in the Universe”, explains Professor Catherine Heymans, Astronomer Royal of Scotland (an honorary title).

“Gravity on the Moon is a little weaker, and the clocks work differently.”

Time is currently measured on Earth by hundreds of atomic clocks located around our planet, which measure the changing energy state of atoms to record time in nanoseconds. If they were placed on the Moon, they would be one second faster for 50 years.

“The ticking of an atomic clock on the Moon will have a different rhythm than a clock on Earth,” says Kevin Coggins, a senior official in NASA’s space communications and navigation program.

“It makes sense that when you go to another (celestial) body, like the Moon or Mars, they each have their own heartbeat.”

But NASA isn’t the only one trying to make lunar time a reality. The European Space Agency (ESA) has also been developing a new time system for some time.

There will then need to be an agreement between countries, and a centralized coordination body — currently, this is done by the International Bureau of Weights and Measures (BIPM, its French acronym) for time on Earth.

Right now, the International Space Station uses Coordinated Universal Time because it is in low Earth orbit. But the same would not be suitable for the Moon.

Another aspect on which countries will need to reach agreement is where the new time zone begins and how far it extends.

The US wants the LTC to be ready by 2026, in time for its manned mission to the Moon.

Artemis 3 will be the first mission to return to the Moon’s surface since Apollo 17 in 1972. It is scheduled to land at the lunar south pole, which is believed to contain large reserves of frozen water in craters that never receive sunlight.

Locating and directing this mission requires extreme precision, at the nanosecond level — errors in navigation can put the spacecraft at risk of entering the wrong orbits.

But Artemis 3 is also one of a series of national missions planned for the Moon, as well as private ventures. If the time is not coordinated between them, this can interfere with data sending and communication between spacecraft, satellites and Earth.

Greater gravity = slower time

As we explained previously, time passes differently in different places in the Universe.

There is no common universal time for all celestial bodies, in the same way that the force of gravity is not the same for all.

The idea that time is relative comes from Albert Einstein’s theory of general relativity.

It assumes that where gravity is stronger, time passes slower.

And gravity is stronger as an object’s mass increases.

For example, a container filled with a dense material, such as granite rock, has more mass and therefore more gravitational force than the same container filled with water.

In space, the Moon has less mass than the Earth — therefore, the Moon’s gravitational force is smaller than that of the Earth.

This explains why a person weighs less on the Moon.

This weaker gravity is why we have the famous images of the Apollo astronauts taking “one giant leap for humanity” on the surface of the Moon.

So, the greater the mass of a body, the greater its gravity — and the slower time will pass.

On Jupiter, for example, time passes more slowly than on Earth, because gravity is greater.

But on the Moon, time passes faster because its gravitational force is smaller.

What is a time zone?

Time is divided around the globe into time zones using imaginary lines called meridians. They go from the North Pole to the South Pole.

One of these imaginary lines passes through Greenwich, London, in the United Kingdom, which establishes Greenwich Mean Time, or GMT.

Countries that are east of the United Kingdom (like Japan) are ahead of this base time — and countries that are west (like Brazil) are behind.

Brazil has more than one time zone, but what is followed in most of the country is the Brasília time zone, equivalent to minus three hours from Greenwich Mean Time, that is, -3 GMT.

This means that when it is 8 am in Brazil, it is 11 am in London (unless it is summer time in one of the countries).