Earth's Rotation Speeding Up: Scientists Consider Deleting a Second from Atomic Clocks by 2029

Scientists have observed that the Earth's rotation is slightly faster than usual, resulting in days that are a few milliseconds shorter. This seemingly minor change has significant implications for global timekeeping. Traditionally, leap seconds are added to atomic clocks to compensate for the Earth's slowing rotation. However, if the current acceleration persists, experts predict that we may need to subtract a leap second by 2029 – a historic first. This adjustment would represent a significant shift in how we synchronize human-made time with the natural rhythms of our planet, underscoring the impact of even subtle changes on time itself.

The Evolving Length of Earth's Day

The Earth's rotation takes approximately 86,400 seconds, defining a 24-hour day. However, this duration isn't constant. Natural phenomena, from gravitational forces to internal geophysical changes, cause minor variations in the Earth's spin.

Historically, the Earth's rotation has gradually slowed. During the dinosaur era, days were only about 23 hours long. By the Bronze Age, they had lengthened but were still about half a second shorter than today. While the Earth may eventually experience 25-hour days, scientists estimate this will take another 200 million years.

Earth's Changing Rotation: Implications for Day Length

Since 2020, the Earth's spin has been accelerating, surprising scientists. According to the International Earth Rotation and Reference Systems Service (IERS), this trend has continued steadily.

This acceleration results in shorter days, albeit by milliseconds. If the trend continues, experts suggest we might need to remove a leap second from Coordinated Universal Time (UTC) by 2029. This would mark the first time a leap second is subtracted rather than added. A leap second is a periodic one-second adjustment to atomic clocks, aligning them with the Earth's irregular rotation. Since the Earth's spin isn't perfectly synchronized with atomic time, leap seconds bridge that gap.

Currently, leap seconds have only been added to account for the Earth's slowing rotation. However, if the Earth's spin continues to accelerate, we may have to remove a second from atomic time, ensuring clocks accurately reflect the Earth's actual rotation.

Shortest Days Anticipated in July and August 2025

Timeanddate.com predicts the trend of shorter days will persist into 2025. Scientists have identified three specific dates when the Earth's spin is expected to be at its fastest:

• July 9, 2025
• July 22, 2025
• August 5, 2025

Reports from USA Today indicate that on August 5, the length of a day could be 1.51 milliseconds shorter than the standard 24 hours—a scientifically significant deviation, even if imperceptible to humans.

The Cause of Earth's Accelerated Spin

The precise cause of this recent acceleration remains unclear. Scientists are investigating several potential factors:

• Seismic activity
• Changes in the Earth's core dynamics
• Glacial rebound (land rising after ice melt)
• Shifts in ocean currents or atmospheric pressure

Leonid Zotov, a researcher at Moscow State University, admitted that no current model fully explains the phenomenon. While changes in the oceans and atmosphere may contribute to fluctuations in the Earth's spin, they are likely insufficient to account for this significant acceleration. Some researchers believe movement within the Earth's molten outer core could be influencing rotational speed.

Leap Second Removal: A Routine Adjustment

Despite these unusual findings, scientists are not alarmed. While it is rare for the Earth's rotation to speed up, such fluctuations are not unprecedented. Over centuries, the planet still trends toward a gradual slowdown.

The potential removal of a leap second in 2029 is simply a technical correction, helping keep atomic clocks synchronized with the Earth's rotation. It will not affect daily life, devices, or global operations. However, it is a reminder that even something as seemingly constant as time is influenced by complex natural forces.