Earth Days are Becoming Longer. Why?

For billions of years, the Moon has been Earth's timekeeper, its slow gravitational tug gently adding fractions of a second to every passing day. But in March 2026, scientists published findings that changed that story. For the first time in recorded geological history, something else is now competing with the Moon for control of the planet's spin: us.

The research, published in the Journal of Geophysical Research: Solid Earth, found that days on Earth have been growing longer since the year 2000 by roughly 1.33 milliseconds per century. That sounds small. It is small. But placed against 3.6 million years of planetary history, it is extraordinary.

The mechanism is deceptively simple. As ice sheets in Greenland and Antarctica melt, that water does not stay at the poles it spreads outward into the oceans, pooling near the equator. More mass at the equator means a wider, fatter planet. And a wider planet spins more slowly, just like a figure skater who stretches out their arms mid-spin.

From its position at 175 statute miles above Earth, the Space Shuttle Endeavour has encountered some colorful and attractive scenes heading into sunsets and sunrises. [Photo: NASA]

"A figure skater spins more slowly once they stretch their arms and more rapidly once they keep their hands close to their body," Mostafa Kiani Shahvandi, University of Vienna, lead study author, explained.

For Shahvandi and his colleague, ETH Zurich professor Benedikt Soja, the most alarming part was not the speed of the change itself, but what it signals. To understand just how unusual this era is, the team analysed fossils of tiny marine organisms called benthic foraminifera, which preserve chemical signals of ancient sea levels. What they found placed today's shift in a sobering context.

According to Prof. Benedikt Soja, ETH Zurich, study co-author (March 2026), "This rapid increase in day length implies that the rate of modern climate change has been unprecedented at least since the late Pliocene, 3.6 million years ago. The current rapid rise in day length can thus be attributed primarily to human influences."

The findings carry practical consequences too. Systems that depend on precise knowledge of Earth's rotation GPS satellites, space navigation, financial trading networks, and global telecommunications all require constant recalibration. A leap second that was supposed to be subtracted from the calendar in 2026 has already been pushed to 2029, a delay scientists attribute directly to the mass of meltwater now riding Earth's equatorial belt.

"By the end of this century, climate change is expected to affect day length even more strongly than the Moon, which has been driving Earth's rotation for the past few billion years,” added Prof. Benedikt Soja, ETH Zurich.

Climate scientist Michael Mann of the University of Pennsylvania, who was not involved in the study, called the findings a powerful reminder of scale. "This isn't just about longer days," one researcher involved in wider coverage noted. "It's about recognising that human-driven climate change is affecting Earth on a planetary scale."