Earth's Spin: Tiny Changes You Won't Notice

Earth's spin is not constant. It changes slightly every day. This summer, it will speed up on three days. The changes are so small that people won't notice them. The days will be shorter by a fraction of a second.

The Moon's Influence

The moon's position affects Earth's spin. When the moon is far from Earth's equator, Earth spins faster. Other factors like earthquakes and volcanoes also influence the spin. In 2011, a big earthquake in Japan made Earth spin faster. It shortened the day by a tiny amount.

Measuring the Changes

Scientists have been measuring these changes since the 1950s. They use atomic clocks to track the length of a day. The shortest day recorded was in July 2024. Earth completed its rotation 1.66 milliseconds faster than usual.

This Summer's Speed-Ups

This summer, Earth will spin faster on three days:

• July 9: Shorter by 1.30 milliseconds
• July 22: Shorter by 1.38 milliseconds
• August 5: Shorter by 1.51 milliseconds

The Winter Solstice

The winter solstice is the shortest day of the year. It has the fewest daylight hours. But the changes in Earth's spin are different. They are not noticeable to people.

A Glimpse into the Past and Future

Earth's spin has changed over time. In the Jurassic period, a day was shorter. Scientists think that in the future, days will be longer. They predict that in 200 million years, a day will have 25 hours.