The rate of Earth's rotation has slowed down significantly since the Moon formed about 4.5 billion years ago, according to new research. Analyses of ancient rocks and computer simulations by geophysicists have revealed that the length of a day increased by about 2.3 hours every million years during the Precambrian eon, which spanned from about 4.6 billion years ago to 541 million years ago.
By the end of the Precambrian, a day was about 19.5 hours long. Earth's rotation rate has continued to slow down, but at a much slower pace, since then. Today, a day is 24 hours long, and it is estimated to increase by about 1.7 milliseconds every century.
The scientists behind the new study, which was published in the journal Nature Geoscience, say that the Moon's gravitational pull is the primary cause of Earth's slowing rotation. The Moon's gravity exerts a force on Earth's equatorial bulge, causing it to deform and creating tidal forces. This tidal force causes the Earth to wobble as it rotates, and this wobble causes the Earth's rotation to slow down.
"The Moon's gravity is like a brake on Earth's rotation," said Stephen Meyers, a professor of geology at the University of Wisconsin-Madison and lead author of the study. "It's been braking the Earth's rotation ever since the Moon formed."
The researchers used computer simulations to calculate the rate at which Earth's rotation slowed down over time. They also analyzed the ancient rocks to measure the length of a day during the Precambrian eon. The rocks contain microscopic crystals that formed when the sun was at its highest point in the sky, and by measuring the distances between these crystals, the scientists were able to calculate the length of a day.
The new study provides insights into the early history of Earth and the role of the Moon in shaping our planet. It also has implications for understanding the evolution of life, as the length of day has a profound effect on the planet's climate and other conditions that affect the survival of organisms.
