NASA and international partners are collaborating to establish a new timekeeping system for the moon, addressing the complexities of lunar time as astronauts prepare for future missions.
The fundamental issue with timekeeping is perhaps the most mind-boggling peculiarity of our universe: seconds pass by ever so slightly more quickly at the peak of a mountain than they do in Earth’s valleys.
Practically speaking, most people don’t need to be concerned about those distinctions.
However, a resurgent space competition has China, the US, and its allies racing to establish permanent settlements on the moon, which has once again highlighted the peculiarities of time.
A single Earth day on the moon would last around 56 microseconds less than it does on Earth, a negligible difference that over time could cause major discrepancies.
This is a dilemma that NASA and its international partners are now attempting to solve.
According to Cheryl Gramling, the lunar position, navigation, timing, and standards lead at NASA’s Goddard Space Flight Center in Maryland, scientists aren’t only trying to establish a new “time zone” on the moon, unlike what some headlines have implied. According to Gramling, the space agency and its allies are instead attempting to develop a completely new “time scale,” or unit of measurement, to take into consideration the fact that time passes more quickly on the moon.
The organization wants to collaborate with international partners to establish a new timekeeping system for the moon that space-faring countries will all agree to follow.
The White House recently sent out a memo directing NASA to begin planning for this new time frame by December 31. The statement described the new time frame as “foundational” to US efforts to resume lunar surface exploration. In addition, the document requests that NASA put in place this kind of system by the end of 2026, the year that the space agency hopes to send people back to the moon for the first time in fifty years.
To reliably maintain lunar time and come to a consensus on the location, timing, and method of placing clocks on the moon, the world’s timekeepers may find that the upcoming months will be extremely important.
According to Gramling, such a structure will be essential for people traveling to our nearest planetary neighbor.
For example, she said, astronauts on the moon will go from their shelters to conduct scientific research and explore the surface. While on the moon, they will also be interacting with one another and operating their moon buggies.
“When they’re navigating relative to the moon,” Gramling said, “time needs to be relative to the moon.”
A brief history of Earth time
Just as the changing phases of the moon can record the passage of a month on Earth, so too can simple sundials or stone formations trace shadows as the sun passes overhead to chronicle the progression of a day. For thousands of years, the inbuilt clocks have helped people stay on schedule.
But possibly clockmakers have become more meticulous about accuracy since mechanical clocks were popular in the early 14th century.
In the early 1900s, the precision of measuring seconds became increasingly challenging due to the contributions of German-born scientist Albert Einstein, whose ideas of special and general relativity profoundly affected the scientific community.
“Darn that Einstein guy — he came up with general relativity, and many strange things come out of it,” said Dr. Bruce Betts, chief scientist at The Planetary Society, a nonprofit space interest group. “One of them is that gravity slows time down.”
Though it is a complex theory, general relativity provides a general explanation of how gravity influences space and time.
Consider the solar system as a piece of cloth that is dangling in midair. That fabric is made up of space and time, which are intrinsically intertwined according to Einstein’s theories. Furthermore, everybody in the solar system—from the sun to the planets—is like a bulky ball perched on top of the material. The divot the ball makes is deeper and distorts space and time the heavier it is.
Even the concept of an earthly “second” is artificial and difficult to quantify. And because gravity is greater near a big object (like our home planet), Einstein’s theory of general relativity explains why time seems to move a little more slowly at lower elevations.
Researchers have discovered a contemporary way to resolve every issue with relativity that arises while determining time on Earth: To correct for subtle variations, many hundred atomic clocks have been installed in different parts of the world. According to Einstein’s beliefs, atomic clocks, which are incredibly accurate devices that measure time by measuring the vibration of atoms, tick more slowly the closer they are to the surface of the Earth.
Coordinated Universal Time (UTC) is the result of averaging the global readings from atomic clocks to provide a broad yet precise sense of time for the entire planet Earth. Nevertheless, “leap seconds” are periodically added to UTC to keep it in sync with minute variations in Earth’s rotational speed.
In a metaphorical sense, Kevin Coggins, deputy associate administrator and program manager for NASA’s Space Communications and Navigation Program, stated that this meticulous timekeeping contributes to the smooth operation of modern society.
“If you’ve researched time on the Earth, you realize it is the critical enabler for everything: the economy, food security, trading, the financial community, even oil exploration. They use precise clocks,” Coggins said. “It’s in everything that matters in modern society.”
Space, time: The continual question
You can only imagine how strange things get the further you are from Earth since time moves differently on the tops of mountains than on the ocean’s coastlines.
To further complicate matters, consider that according to Einstein’s theory of special relativity, time moves more slowly the faster a person or spaceship is moving.
In a phone conversation, Dr. Bijunath Patla, a theoretical physicist of the US National Institute of Standards and Technology, stated that astronauts on the International Space Station, for instance, are fortunate. According to Patla, the space station travels at great speeds, looping the planet 16 times a day, so even though it circles roughly 200 miles (322 kilometers) above Earth’s surface, the effects of relativity are slightly offset. Because of this, Earth Time makes it simple for astronauts working in the orbiting laboratory to stick to their schedule.
Other missions require more complexity.
Thankfully, scientists have decades of experience dealing with these kinds of difficulties.
According to Gramling, spacecraft, for instance, include oscillators, which are internal clocks.
“They maintain their own time,” Gramling said. “And most of our operations for spacecraft — even spacecraft that are all the way out at Pluto, or the Kuiper Belt, like New Horizons — (rely on) ground stations that are back on Earth. So everything they’re doing has to correlate with UTC.”
However, according to Gramling, those spacecraft also rely on their own time. She continued, “Vehicles traveling deep into the solar system, for instance, must be able to determine when they are approaching a planet based on their time scale in case the spacecraft needs to use that planetary body for navigational purposes.”
Over the last fifty years, researchers have also been able to monitor atomic clocks hidden within GPS satellites, which circle Earth at a distance of roughly 12,550 miles (20,200 kilometers), or roughly one-nineteenth of the distance between Earth and the moon.
As they set out to build a new time scale for the moon, studying those clocks has provided scientists with a perfect starting place to start extrapolating further, according to Patla.
“We can easily compare (GPS) clocks to clocks on the ground,” Patla said, adding that scientists have found a way to gently slow GPS clocks down, making them tick more in line with Earth-bound clocks. “Obviously, it’s not as easy as it sounds, but it’s easier than making a mess.”
But scientists probably won’t try to slow down clocks for the moon. According to Patla, who co-authored a study outlining a framework for lunar time, they aim to measure lunar time exactly as it is while also making sure it can be connected back to Earth time.
For the record, the study also made an effort to determine the precise separation between Earth time and the moon, with estimations ranging from 56 to 59 microseconds per day.
The report states that clocks at the equator of the moon would tick 56.02 microseconds quicker each day than clocks at the equator of the Earth.
Lunar clockwork
Scientists are persuaded that precise timekeeping gadgets must be sent to the moon.
It’s unclear exactly who will pay for lunar clocks, what kind they will use, and where they will be placed, according to Gramling.
“We have to work all of this out,” she said. “I don’t think we know yet. I think it will be an amalgamation of several different things.”
Gramling pointed out that whereas crystal oscillators have an edge for short-term stability, atomic clocks are excellent for long-term stability.
“You never trust one clock,” Gramling added. “And you never trust two clocks.”
Different kinds of clocks could be installed in lunar orbiting satellites or even at specific sites on the moon that astronauts will eventually visit.
According to Gramling, the cost of an atomic clock suitable for space flight could reach several million dollars, while crystal oscillators would be significantly less expensive.
You get what you pay for, though, Patla added.
“The very cheap oscillators may be off by milliseconds or even 10s of milliseconds,” he added. “And that is important because for navigation purposes — we need to have the clocks synchronized to 10s of nanoseconds.”
The new lunar time scale might be determined via a cooperative system of clocks on the moon, similar to how atomic clocks on Earth determine UTC.
(There will not, Gramling added, be different time zones on the moon. “There have been conversations about creating different zones, with the answer: ‘No,’” she said. “But that could change in the future.”)
The entire lunar network, known as LunaNet by NASA and its partners, would be supported by the new time scale.
“You can think of LunaNet like the internet — or the internet and a global navigation satellite system all combined,” Gramling said. It’s “a framework of standards that contributors to LunaNet (such as NASA or the European Space Agency) would follow.”
“And you can think of the contributors maybe as your internet service provider,” Gramling added.
It will take a large number of participants from all around the world to create such a framework. Conversations with US partners have been “very, very positive” thus far, according to Gramling.
It is unclear whether countries like China that are not US friends will support NASA and its collaborators on this project, which also includes the European Space Agency. Gramling pointed out that international standard-setting organizations like the International Astronomical Union would facilitate those discussions.
‘A whole different mindset’
Precise timekeeping is one thing. It is quite different, though, how future astronauts who live and operate on the lunar surface would perceive time.
Because the Earth completes one rotation every 24 hours, most places on Earth experience a constant cycle of daylight and gloomy nights. This phenomenon governs our perception of a single day. On the other hand, the equator of the moon experiences about 14 days of sunlight and 14 days of darkness.
“It’s just a very, very different concept” on the moon, Betts said. “And (NASA is) talking about landing astronauts in the very interesting south polar region (of the moon), where you have permanently lit and permanently shadowed areas. So, that’s a whole other set of confusion.”
“It’ll be challenging” for those astronauts, Betts added. “It’s so different than Earth, and it’s just a whole different mindset.”
That will remain accurate regardless of the time that appears on the astronauts’ timepieces.
However, accurate timekeeping is important for setting up all the equipment required to carry out missions as well as for scientifically understanding how time passes on the moon.
According to Gramling, the advantage of building a time scale from scratch is that it allows scientists to use all of their knowledge of timekeeping on Earth to a new system on the moon.
She also said that if NASA succeeds in its mission of launching astronauts farther into the solar system, scientists would be able to replicate the success they had on the moon.
“We are very much looking at executing this on the moon, learning what we can learn,” Gramling said, “so that we are prepared to do the same thing on Mars or other future bodies.”
Recently, GreatGameIndia reported that Yuri Borisov, head of Roscosmos, revealed Russia’s plans to construct a nuclear power plant on the Moon, with construction slated to begin between 2033 and 2035.
Support GreatGameIndia
