Faster-moving Moon needs own time zone

Nasa says every fractional second counts when it comes to the impact on future space missions

GAZE up at the Moon at night and it may surprise you to learn that time on the lunar surface is moving ever so slightly faster than on Earth.

The effect, caused because the satellite’s gravity does not bend spacetime as much as on Earth, is barely noticeable even for astronauts on the surface.

But the US government is so concerned about the potential impact to future space missions that it has asked Nasa to establish an entirely new time standard for the Moon.

Space missions are based on Earth time, but time on the Moon moves around 58.7 microseconds faster each day, an anomaly that could end up causing major glitches in navigation systems and would require constant corrections.

To counter the problem, Nasa wants to establish Coordinated Lunar Time (LTC), which orbiting satellites and lunar ground technology would be synched to, instead of running on Earth time.

The head of the White House Office of Science and Technology Policy has instructed the space agency to work with the US government to devise a plan by the end of 2026.

“The same clock that we have on Earth would move at a different rate on the Moon,” Kevin Coggins, Nasa’s space communications and navigation chief, told Reuters.

“Imagine if the world wasn’t syncing their clocks to the same time – how disruptive that might be and how challenging everyday things become.

“An atomic clock on the Moon would tick at a different rate to a clock on Earth. It makes sense that when you go to another body, like the Moon or Mars, that each one gets its own heartbeat.”

On Earth, most clocks and time zones are based on Coordinated Universal Time, or UTC/GMT, an internationally recognised standard that relies on a vast global network of atomic clocks placed in different locations around the world.

Accurate navigation depends on rigorous timekeeping because a satnav calculates position by triangulating a speed of light signal from at least three satellites. If the timing is off even a little, positioning can be vastly off.

Up until now Moon missions have operated on Earth time, with deep space antennas used to keep onboard chronometers synchronised with terrestrial time.

But experts say that is unsustainable as humans spend more time on the Moon and beyond.

Einstein’s theory of general relativity predicts that where gravity is stronger, time passes more slowly, a process known as time dilation.

On Earth gravity is stronger closer to the core, with even mountaineers or airline passengers experiencing slightly faster time. Clocks on GPS satellites run ahead by about 0.000038 seconds per day, an issue that must be continuously taken into account.

These quirks of relativity make it tricky to synchronise clocks between the Moon and Earth because an observer on the Moon would see time as moving more slowly back home.

Nasa is planning to send astronauts back to the lunar surface in 2026. It wants to set up a Moon base as well as a new lunar space station with the European Space Agency.

The agency is also working on an orbiting satellite communications system called Moonlight which would allow lunar navigation, fast file transfer and even video calls.

But without a Moon time standard all technology on the lunar surface would require constant adjustments. Discrepancies in timekeeping could lead to errors in mapping making navigation, operations and spacecraft docking difficult and putting astronauts at risk.

However, deciding what LTC will be is likely to be tricky because time on the surface of the Moon runs more slowly than in orbit. It is likely that atomic clocks on the lunar surface will eventually measure accurate Moon time.