Efforts to establish a lunar time standard have been initiated as part of preparations for increased international presence on the Moon under NASA's Artemis programme. According to reports, the White House in April 2024 called for the creation of a unified lunar time system, essential for future missions and potential human bases. The core challenge involves understanding how time flows differently on the Moon compared to Earth, a phenomenon rooted in Einstein's theory of general relativity.
Understanding the Time Drift
The study was published in The Astronomical Journal by Bijunath Patla and Neil Ashby from the National Institute of Standards and Technology (NIST). The researchers calculated that clocks on the Moon would tick 56 microseconds faster per day than those on Earth. This discrepancy arises due to two factors: the Moon's lower gravity, which causes clocks to run faster and its motion relative to Earth, which slows them down. In a statement, Patla noted that precise navigation requires addressing this drift, as even a seemingly minor difference of 56 microseconds could lead to navigational errors spanning 17 kilometres daily.
Implications for Lunar Navigation
Cheryl Gramling, a systems engineer at NASA's Goddard Space Flight Center, highlighted the importance of accurate timekeeping for mission safety and operational precision in another statement. In reports, she explained that future lunar missions will require the exact positions of rovers, landers and astronauts to be determined within 10 metres, making even nanosecond-level timing errors unacceptable.
Broader Context of Relativity
Separate calculations by Sergei Kopeikin of the University of Missouri and George Kaplan of the U.S. Naval Observatory confirmed the 56-microsecond drift. These findings, reported in various publications, also addressed minor fluctuations caused by tidal forces from the Sun and Jupiter, which need consideration for high-precision lunar operations.
Scientists acknowledge the complexity of this endeavour, but standardising lunar time is viewed as a critical step. Although such precision may not be immediately required, laying the groundwork now ensures readiness for a more active lunar ecosystem in the coming decades.
