Earth's Days Shrinking Due to Faster Rotation, Is Moon's Gravitational Effect Responsible?

Moon’s Gravitational Pull Steals Milliseconds, Shortening 2025’s Days 

Time appears to be speeding up. On July 9, 2025, the Earth rotated slightly faster than usual, resulting in a day that was 1.3 milliseconds shorter. Two additional days, July 22 and August 5, are expected to join the list of the shortest days in recorded history. This change is influenced by the shifting orbit of the Moon, which subtly affects the Earth's rotation.

Although a millisecond seems insignificant, it plays a crucial role in atomic clocks, GPS systems, and global timekeeping. Scientists are considering a step they had not previously taken: adding a negative leap second by 2029 to realign our clocks with the Earth's irregular rotation. This raises an important question: What is causing this acceleration, and should we be concerned?

Is Earth Spinning Faster? The Moon May Be Behind It 

The rotation of Earth is never completely uniform. Standard geophysical calculations define a solar day as 86,400 seconds (24 hours). Still, there are very slight variations in its actual length due to the gravitational influences of the Moon and the Sun.

Major Issues for the Moon: On July 9, 22, and August 5, the Moon occurs at the maximum distance from the Earth's equator, and the effect of its gravity will take on new characteristics. With the lowering of tidal friction, Earth can speed up. Think of this as a figure skater drawing in their arms to spin fast.  

In History Immense Time: Over billions of years, an effect would have slowed the Earth's rotation, assisted by the drifting of the Moon to a farther position away from Earth. Scientists, however, have concluded since the year 2020 that the planet is in an inconstant state of acceleration. For instance, an example of the phenomenon happened on July 5, 2024; the shortest day was noted at 1.66 ms faster than was previously thought. 

The phenomenon was shown on March 11, 2011, when the earthquake off the coast of Japan caused the day to shorten by 1.8 microseconds. 

The Leap-Second Dilemma: The Clock Will Change?

The atomic clock, which is used for worldwide timekeeping, is regulated with such precision. These clocks are bound to go out of sync if the Earth’s rotation speeds beyond a certain limit. 

Explaining leap seconds: Since the 1970s, 27 previous leap seconds have been added to give Earth's slightly slower pace. For the first time, a negative leap second, i.e., taking away a second, may need to be established by 2029.  

Tech Disruption: Even a slight shift in time by milliseconds can affect GPS navigation, stock trading, and satellite communication.

The IERS (International Earth Rotation and Reference Systems Service) watches these changes to keep clocks across the globe correctly timed.

The caesium atomic clock was the first successful atomic clock when it was developed in 1955. (source: space.com) 

What does this mean for us?  

For most of us, a 1.5-millisecond shorter day is nothing we would ever notice in our daily lives. But, as we have shown, the long-term trends could change how we measure time.

Future Considerations: If Earth continues to accelerate, we may see more negative leap seconds, which could change how our tech systems operate.  

Climate Change: Glaciers melt, and the mass of our planet changes, adding 1.33 milliseconds to the length of the day per century, which could offset the current speed up.  

A Cosmic Tug-of-War: What the Future Holds for Earth’s Clock 

The Earth's orbit is a complex interplay of planetary evolution and celestial events. In the short term, the moon's position in the solar system is expected to shorten the length of days in 2025. However, the long-term trend indicates that Earth's rotation will continue to slow down. Researchers will continue to monitor the changing sky and clocks to ensure that our measurement of time remains aligned with the rhythms of our planet.