Days on Earth are getting longer as the moon slowly moves farther away from us, new research shows.
According to the new study was published Monday (June 4) in the journal Proceedings of the National Academy of Sciences, a day on Earth lasted only 18 hours about 1.4 billion years ago.
Scientists believe that when Earth and the moon were barely formed some 4.5 billion years ago, days were only five hours long.
As the moon slowly drifts away from Earth, its influence on our planet’s spin around its axis is waning, thereby making days last longer, said a report on science new portal ZME Science.
“As the moon moves away, the Earth is like a spinning figure skater who slows down as they stretch their arms out,” explains Stephen Meyers, professor of geoscience at the University of Wisconsin-Madison and co-author of the new study published in the Proceedings of the National Academy of Sciences.
The moon is about 4.5 billion years old and is some 239,000 miles (385,000 kilometers) away from Earth, on average. However, due to tidal forces between our planet and the moon, the natural satellite slowly spirals away from Earth at a rate of 3.78cm (1.48in) per year, or at about the same speed at which our fingernails grow. The migration of the Moon away from the Earth is mainly due to the action of the Earth’s tides.
Without the moon, Earth could slow down enough to become unstable, but this would take billions of years and it may never happen at all.
The slowing of earth’s rotation and lengthening of days as the satellite drifted farther away is traceable in the fossil records of some creatures. For instance, the daily growth bands of corals record the number of days that occurred per year in ancient times. By one estimate, days are getting longer at a rate of 19 hours every 4.5 bn years.
Now, using a new method, called astrochronology, Meyers and colleagues were able to devise a novel way to calculate the moon’s influence on the days on Earth. Astrochronology combines astronomical theory with geological observation, allowing researchers to reconstruct the history of the solar system and better understand ancient climate change as captured in the rock record, according to a statement from the University of Wisconsin-Madison, reported Space.com.
“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,” said study co-author Stephen Meyers, a professor of geoscience at UW-Madison, in the statement.
The moon and other bodies in the solar system largely influence Earth’s rotation, creating orbital variations called Milankovitch cycles. These variations ultimately determine where sunlight is distributed on Earth, based on the planet’s rotation and tilt.
Earth’s climate rhythms are captured in the rock record, going back hundreds of millions of years. However, regarding our planet’s ancient past, which spans billions of years, this geological record is fairly limited, researchers said in the statement.
This can lead to some uncertainty and confusion. For example, the current rate at which the moon is moving away from Earth suggests 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,” Meyers said.
Using their new statistical method, the researchers were able to compensate for the uncertainty across time. This approach was tested on two stratigraphic rock layers: The 1.4-billion-year-old Xiamaling Formation from northern China and a 55-million-year-old record from Walvis Ridge, in the southern Atlantic Ocean.
Examining the geologic record captured in the rock layers and integrating the measure of uncertainty revealed changes in Earth’s rotation, orbit and distance from the moon throughout history, as well as how the length of day on Earth has steadily increased.
“The geologic record is an astronomical observatory for the early solar system,” Meyers said in the statement. “We are looking at its pulsing rhythm, preserved in the rock and the history of life.”
The new study was published Monday (June 4) in the journal Proceedings of the National Academy of Sciences.