If you have ever heard that Earth will soon start having 25-hour days, it might be right. The idea itself is not wrong. Scientists do expect Earth’s rotation to keep slowing. What often gets lost is the pace. These changes unfold so slowly that they slip past daily life without leaving a mark. No clocks will suddenly fall behind. No calendars need rewriting. What is happening is subtle, measured across decades and centuries using instruments most people never see. The story is not about a dramatic flip in how time works. It is about tiny shifts, pulled along by gravity, water, and ice, building up quietly over spans of time that far exceed a human lifetime.
Is a day really fixed at 24 hours
A day feels constant because we organise life around it. School starts, work ends, and alarms ring according to a 24 hour cycle. But this is only one way to define a day.If Earth’s rotation is measured against distant stars rather than the Sun, the result is a slightly shorter unit known as a sidereal day. The difference exists because Earth is not only spinning but also moving along its orbit. To bring the Sun back to the same point in the sky, the planet must rotate a little further.Even then, the solar day itself is not perfectly steady. It stretches and shrinks by tiny amounts. Over very long periods, the trend points in one direction. Days get longer.
Why the Moon is slowing Earth’s spin
The Moon plays a large role in this slow change. Its gravity pulls on Earth’s oceans, creating tidal bulges that rise and fall as the planet rotates. These bulges do not line up perfectly with the Moon because water moving across the seabed creates friction.NASA states that friction drains a small amount of rotational energy from Earth. Over time, the planet spins more slowly. The energy does not vanish. It is transferred outward, causing the Moon to drift farther away.A simple way to picture this is a spinning chair with a foot brushing the floor. The spin continues, but it gradually loses speed.
Can climate change affect Earth’s rotation
Beyond the Moon, scientists have found that changes on Earth’s surface also matter. NASA funded studies examining more than 120 years of data show that melting ice, shrinking glaciers, falling groundwater levels, and rising seas all shift how mass is distributed around the planet.When large amounts of ice melt or water moves from land to ocean, Earth’s balance changes. This causes the spin axis to wander slightly, a motion known as polar motion. It also lengthens the day by a very small amount.Since around 2000, the pace of this change has increased. Researchers link this acceleration to faster ice loss in Greenland and Antarctica driven by greenhouse gas emissions.
How scientists measure tiny changes in Earth’s spin
Early researchers tracked polar motion by observing the apparent movement of stars. Today, techniques are more precise. They include analysing radio signals from distant quasars and firing lasers at satellites to measure their exact positions.Using machine learning tools, scientists separated the causes of polar motion over 12 decades. Most repeating fluctuations were tied to changes in ice, groundwater, glaciers, and sea level. A smaller portion came from deep Earth processes, such as subtle shifts in the planet’s interior.Some patterns repeat roughly every 25 years. Others show long term drift.
Are humans responsible for all of it
The answer is mixed. Natural climate cycles have driven much of the historical variation. At the same time, recent decades show strong links between human activity and faster mass loss from ice sheets and aquifers.Scientists stress that both forces are at work. Natural systems set the rhythm. Human actions are now adding weight to the scale.
When would Earth actually reach a 25 hour day
This is where headlines often lose perspective. There is no date to circle. Based on current understanding of the Earth Moon system, reaching a 25 hour day would likely take around 200 million years.That future lies so far ahead that it has no practical effect on people, societies, or timekeeping. The idea is real, but the timescale is almost unimaginable.For now, the length of the day continues to change by milliseconds. Quietly. Almost imperceptibly.