If you placed two perfectly identical atomic clocks — one on Earth's surface and one on the Moon — and checked them after exactly one Earth day, the Moon clock would be ahead by about 56.02 microseconds. This is not a flaw in the clocks. It is a fundamental property of the universe, predicted by Albert Einstein's general theory of relativity over a century ago.
Gravitational Time Dilation Explained
Einstein's general relativity, published in 1915, describes gravity not as a force but as a curvature of spacetime. Massive objects like Earth and the Moon warp the fabric of spacetime around them, and this curvature affects how time passes.
The key principle is simple: the stronger the gravitational field, the slower time passes. This effect is called gravitational time dilation. Earth's surface gravity is about 9.8 m/s², while the Moon's is only about 1.62 m/s² — roughly one-sixth as strong. Because the Moon's gravitational pull is weaker, spacetime is less curved there, and clocks tick faster.
Nomor 56 Microdetik
The precise rate at which lunar clocks run faster depends on the difference in gravitational potential between Earth's surface and the Moon's surface, plus smaller corrections for orbital velocity and Earth's rotation.
The gravitational blueshift — clocks running faster in weaker gravity — contributes about +58.7 microseconds per day. However, the Moon's orbital velocity (about 1.022 km/s) causes a small time dilation in the opposite direction (the velocity-dependent effect from special relativity), reducing the net gain by about 2.7 microseconds per day. The combined result is approximately +56.02 microseconds per day.
This number has been confirmed by multiple independent analyses, including work by NASA's Jet Propulsion Laboratory and the National Institute of Standards and Technology.
Ieu Teu Teoritis — Éta Dipamadé
Gravitational time dilation is one of the most precisely tested predictions in all of physics. GPS satellites, which orbit at about 20,200 km altitude where gravity is weaker, gain about 45 microseconds per day relative to Earth's surface. Without correcting for this, GPS positions would drift by roughly 10 km per day.
The same physics applies to the Moon. While we haven't yet placed atomic clocks on the lunar surface, the effect is calculated from the same well-tested equations. The gravitational time dilation formula yields predictions that have been confirmed to better than one part in a trillion.
Naha 56 Microdetik Pentingna
For everyday human activities, 56 microseconds is imperceptible. But for precision systems, it adds up quickly:
After one month, the Moon clock is ahead by about 1.7 milliseconds. After one year, the offset grows to roughly 20 milliseconds. Since the J2000.0 epoch (January 1, 2000), the accumulated drift has exceeded 0.5 seconds.
For navigation, light travels about 300 meters per microsecond. A 56-microsecond timing error corresponds to about 16 meters of position uncertainty per day. For the precision landings required by Artemis missions — targeting specific sites near the lunar south pole — this level of drift is unacceptable without correction.
This is exactly why Coordinated Lunar Time (LTC) is being developed: to provide a time standard that accounts for the relativistic difference and keeps all lunar systems synchronized.