New Study Shows Days on Earth Have Been Getting Longer, Thanks to The Moon


If you’re one of those that wished to have a few more hours in the day to finish your tasks, then geoscientists have some good news: the days are getting longer.

Stephen Meyers is a professor of geoscience at the University of Wisconsin-Madison and the co-author of the study, which was published on 4 June in the Proceedings of the National Academy of Sciences. He found that 1.4 billion years ago, a day on Earth was just a bit over 18 hours. Back then, the moon was closer, making the Earth spin faster around its axis:


Looking back to Earth’s past, he used a statistical method called astrochronology to reconstruct the history of the solar system and understand the Earth’s geologic past:

“One of our ambitions was to use astrochronology to tell time in the most distant past, to develop very ancient geological time scales. We want to be able to study rocks that are billions of years old in a way that is comparable to how we study modern geologic processes.”

In 2017, Meyers and his colleagues studied sediments from a 90 million-year-old rock formation which revealed how climate changed on Earth – based on how it orbited around the Sun. Meyers explained that the further they went back into time, the less accurate were their findings.

Today, the Earth moves 3.82 centimeters per year. Using this date, scientists calculated what would have been the speed in the past. Meyers explained that “beyond about 1.5 billion years ago, the moon would have been close enough that its gravitational interactions with the Earth would have ripped the moon apart.” But they all know that the moon is 4.5 billion years old.

“A Solution Looking for a Problem”

So, Meyers and his colleagues had to find a different way to account for what happened in the solar system billions of years ago. One day, as Meyers went to Columbia University’s Lamont-Doherty Earth Observatory and gave a speech, he met Alberto Malinverno, Lamont Research Professor at Columbia. Malinverno said:

“I was sitting there when I said to myself, ‘I think I know how to do it! Let’s get together!’ It was exciting because, in a way, you dream of this all the time; I was a solution looking for a problem.”

That’s how Meyers and Malinverno teamed up to find a new statistical method to solve the uncertainty. They used astronomical theory, geologic data and a statistical approach called Bayesian inversion.

Testing the approach on two rock layers, they found the answer. Malinverno said that:

“In the future, we want to expand the work into different intervals of geologic time.”