Since the astronauts last left the lunar surface Time passed 52 years ago. Compared to us Earthlings, the Moon has longed for our return just a bit longer – about 1.1 seconds.
That doesn’t sound like much, and neither does the 57 millionths (0.0000575) of a second that lunar time is stretched forward each day compared to our home planet’s time.
But the key finding of a new study by NASA scientists could be the difference between synchronizing navigation systems as the US space agency launches its long-awaited manned missions to the moon and beyond.
We have known about gravity’s ability to slow down time since Albert Einstein postulated his general theory of relativity. However, the practicality of measuring any temporal distortions that come with differences in gravity—such as the contrast between Earth’s gravity and the Moon’s—falls far short.
Only in the last decade or so have we had atomic clocks sensitive enough to detect small differences in time between two objects moving relative to each other or under different gravitational attractions.
And with a half-century gap between manned moon landings, scientists have had no pressing reason to figure out how these small time differences between Earth and our lunar companion play out. The moon has one-sixth the gravity of Earth, but astronauts only stopped by it briefly, so it wasn’t a big deal.
Now scientists have a deadline: NASA is aiming to return astronauts to the moon by 2026 as part of its Artemis missions, where they will begin exploring possible sites for lunar bases that could one day serve as a springboard to Mars.
“We’re looking at a permanent presence on the moon,” said NASA’s Cheryl Gramling, a navigation systems engineer at Goddard Space Flight Center in Maryland. New Scientist’s Jonathan O’Callaghan.
“Infrastructure on Earth like GPS provides time down to the nanosecond level,” Gramling continued. “If you’re trying to navigate or land on the moon and avoid dangerous areas, then accuracy matters.”
Earlier this year, in April, NASA and other US agencies were tasked with developing a uniform time reference system for the moon that other space agencies could agree on.
This new finding helps in this regard and has been in the works for some time. Slava Turyshev, a physicist at NASA’s Jet Propulsion Laboratory who led the study, told O’Callaghan, “Someone needed to sit down and do the math.”
From Earth, it looks like the Moon gains 57 millionths of a second per Earth day. Turyshev and colleagues arrived at this number by calculating the sliding scale of time for Earth and the Moon relative to the barycenter of the Solar System. This is the common center of mass of the Solar System, around which the Sun, planets and satellites orbit in delicate balance.
Turyshev and colleagues’ calculations are close to the 56.02 microseconds another team of researchers at the US National Institute of Standards and Technology landed on in February. But tiny fractions of a second are over such a long distance, so there’s still work to be done.
Neither result has been reviewed, and the final definition of lunar time will have to be confirmed by a number of agencies and international bodies, such as the International Bureau of Weights and Measures and the International Astronomical Union, which plan to meet in August. .
We will also have to watch how the rotation of our planet Earth strangely slows down, making our days a little longer – and how extractive human activities have changed its rotation.
The research was published on arXiv preprint server before peer review.