Moon Causing Days on Earth to Get Longer

The moon is moving away from the Earth over time, lengthening our days. Jonathan Pagel/Flickr

As most of us age, the days in our lives usually seem to get shorter and shorter. (In fact, scientists have studied this psychological phenomenon, and it's real!) But it turns out that our experiences couldn't be any further from the truth. Days on Earth are actually getting longer, and it's all the fault of the moon, reports

A new study has analyzed our planet's relationship with its satellite neighbor in unprecedented detail, using not only astronomical theory, but also geological observation. It turns out that Earth's once-intimate relationship with the moon has been precariously growing distant over the millennia. In fact, the moon has been moving away from the Earth at a rate of 3.82 centimeters per year.

That might not sound like much, but over the course of a couple billion years, it adds up. And it can have a dramatic effect on Earth's spin. For instance, 1.4 billion years ago, a day on Earth lasted just over 18 hours compared to the roughly 24 hours that it lasts now.

Stephen Meyers, professor of geoscience at the University of Wisconsin-Madison and co-author of the study, explains how the moon's orbit influences our planet's spin as follows: "As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out."

As the moon continues to pull away, days on Earth will only get longer and longer.

Using geology to solve a space mystery

What makes this study so unique is how researchers were able to study these changes geologically, and the key to cracking that code came from a new kind of statistical method that could take into account the chaotic interplay between astronomical theory, geologic data, and a branch of analysis known as Bayesian inversion. The method was then tested on the 1.4 billion-year-old Xiamaling Formation from Northern China.

The study was able to determine the length of day and the distance between the Earth and the moon throughout history in unprecedented precision.

"The geologic record is an astronomical observatory for the early solar system," said Meyers. "We are looking at its pulsing rhythm, preserved in the rock and the history of life."

Meyers and colleagues are hopeful that the method can eventually be expanded to make more accurate calculations over even longer periods of time. One way or another, it's a reminder that our solar system is a dynamic place, and it's anything but the fine-tuned clock that we once might have thought it was.