Earth Days Are Getting Longer As The Moon Slowly Drifts Out Of Orbit

A standard 24-hour Earth day is slowly but surely getting longer. Researchers at the University of Wisconsin and Columbia University calculated that a day on Earth is slowly growing at one-74,000th of a second each year and will continue to increase at this pace for the next few million years.

In the study published in Proceedings of the National Academy of Sciences, the scientists explained the length of a day is increasing as the planet’s rotation has been slowing and the moon keeps drifting farther away. Per an Inverse article, the speed of Earth spinning on its axis is directly influenced by the gravitational pull of the moon.

The larger the distance between the Earth and the moon, the slower the Earth spins. Right now, the moon is moving away from the Earth at 1.5 inches per year.

“As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out,” explains study co-author Stephen Meyers, as cited by a Science Daily report.

Approximately 1.4 billion years ago, the Earth spun much faster, and the moon was closer, which made the day just under 19 hours. Today, the Earth takes 23 hours, 56 minutes, and 4 seconds to complete one rotation.

Known as Milankovitch cycles, the researchers analyzed the changes in the orbit, tilt, and wobble of the Earth over millions of years. These cycles directly determine what parts of the Earth receive sunlight. As a result, they are partially responsible for changes in climate throughout the planet’s history. A computer model was created to compare the cycles to other geological events like ice ages.

“We were interested in reconstructing the Milankovitch cycles because they provide a powerful tool for evaluating the history of our planet, and the solar system. They are like signposts on a trail, allowing us to navigate geological history,” said Meyers, per The Guardian.

Except by some cosmic catastrophe, the moon will never completely drift away from Earth’s grasp. Millions of years from now, our celestial neighbor will move to a stable orbit and remain. However, it will only be observable from one half of the Earth.