Jul 09, 2025 21:00:00

The Earth's rotation speed will speed up, making the days of July 9th, July 22nd, and August 5th shorter, just a little.

The Earth's rotation has been gradually slowing down due to

tidal forces , which are the gravitational interactions between the Earth and the Moon. However, the Earth's rotation is expected to speed up over a few weeks in July 2025, which will result in three days on July 9, July 22, and August 5 that are shorter than usual.

Earth is going to spin much faster over the next few months — so fast that several days are going to get shorter | Live Science
https://www.livescience.com/planet-earth/earth-is-going-to-spin-much-faster-over-the-next-few-months-so-fast-that-several-days-are-going-to-get-shorter

A day on Earth is the time it takes for the Earth to make a complete revolution on its axis, which is approximately 86,400 seconds, or 24 hours, but the Earth's rotation is influenced by many factors, including the positions of the Sun and Moon, changes in the Earth's magnetic field, and the balance of mass on the Earth.

Since the relatively early days of the Earth's birth, the Earth's rotation speed has slowed down, and as a result, the days have become longer. Past research has revealed that about 1 to 2 billion years ago, a day on Earth was only 19 hours long. This was because the Earth was close to the Moon, and the Moon's gravitational influence was stronger, causing the Earth to rotate faster than it does today.

Since then, as the Moon has moved away from Earth, its rotation has gradually slowed, causing days to get longer, but in 2020 it was revealed that the Earth's rotation was the fastest it had been since measurements began in the 1970s.

The Earth's rotation is getting faster and the day is getting shorter - GIGAZINE

In addition, July 5, 2024 will be the shortest day in history, missing 1.66 milliseconds in 24 hours, which has led to the idea that a negative leap second may have to be inserted into a day in the future.

As the Earth's rotation speed increases, a 'negative leap second' may be necessary by 2029, and there is a risk that the internet and IT services will be disrupted - GIGAZINE

This time, the Moon will be farthest from the Earth's equator on July 9, July 22, and August 5, 2025, so the effect of the Moon's gravity on the Earth's axis will change, increasing the Earth's rotation speed and shortening the length of the day. The three days on July 9, July 22, and August 5 are expected to be 1.3 to 1.51 milliseconds shorter than usual.

Recent studies suggest that human activity is also contributing to changes in the Earth's rotation: NASA researchers calculated that climate change-related ice and groundwater movement increased the length of the day by 1.33 milliseconds per century between 2000 and 2018.

The Earth's rotation can also be affected by single events - for example, research has shown that the length of a day shortened by 1.8 microseconds following the Great East Japan Earthquake in 2011.

Even seasonal changes affect the Earth's rotation, according to geophysicist Richard Holm of the University of Liverpool. Because the Northern Hemisphere has more land than the Southern Hemisphere, more trees have leaves during the Northern Hemisphere summer. This means mass moves from the surface to above the surface, further away from the Earth's axis. Just as an ice skater spins in place with their arms tightly pressed against their chest, they spin faster, and with their arms outstretched they spin slower, 'in summer, the Earth's mass should move away from its axis and slow down,' Holm said.

However, on July 9th, July 22nd, and August 5th in 2025, clocks will continue to count 24 hours as usual, so no individual will notice any difference.