Earth's Days Getting Shorter: What's Happening?
Earth's spin is about to pick up speed, making some days shorter than usual. This change is due to the moon's position relative to Earth. On three specific days in the coming months, the moon's gravitational pull will cause Earth to rotate faster, making each day up to 1.51 milliseconds shorter.
Factors Influencing Earth's Rotation
Normally, a day on Earth is about 24 hours, but this can change. Earth's rotation is influenced by many factors, including:
- Positions of the sun and moon
- Changes in Earth's magnetic field
- Shifts in mass distribution
Over time, Earth's rotation has been slowing down, making days longer. About 1 to 2 billion years ago, a day was only 19 hours long. This was because the moon was closer to Earth, causing a stronger gravitational pull and a faster spin.
Recent Observations
Recently, scientists have noticed variations in Earth's rotation. In 2020, Earth spun faster than ever recorded since the 1970s. The shortest day ever recorded was on July 5, 2024, which was 1.66 milliseconds short of 24 hours.
On July 9, July 22, and August 5, 2025, the moon will be at its furthest distance from Earth's equator. This changes the gravitational pull on Earth's axis, making the planet spin faster and days shorter.
Human Impact on Earth's Rotation
Human activities are also affecting Earth's rotation. Researchers at NASA found that the movement of ice and groundwater, linked to climate change, has increased the length of our days by 1.33 milliseconds per century between 2000 and 2018.
Even single events like the 2011 earthquake in Japan can affect Earth's spin. The earthquake shortened the length of the day by 1.8 microseconds. Seasons also play a role. In northern summer, trees grow leaves, moving mass away from Earth's core and slowing down the planet's rotation.
Impact on Daily Life
Despite these changes, our clocks will still show 24 hours. The difference is too small to notice in daily life. However, over time, clocks can fall out of sync with Earth's position.
The International Earth Rotation and Reference Systems Service (IERS) monitors this and adds a "leap second" to UTC as needed to keep everything in line.
