Days feel longer? Blame the Moon for moving slowly away from Earth


The Moon is moving slowly further away from the Earth and this is causing days to get longer by the year. The Moon is actually moving by about 4 cm a year away from Earth.

New research into the relationship between Earth and the Moon has delved deep into the history of the Moon which showed that the Moon was so close the Earth about 1.4 billion years ago that a day on Earth was only 18 hours long, notes a report by

“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 study.

Planet Earth in space moves under the influence of other astronomical bodies that exert their own gravitational forces on it, this includes other planets as well as the Moon. Variations in the Earth’s rotation on its axis, its orbit around the Sun, and the wobbling it exhibits can be determined using these external forces, notes the report.

All of these variations are known as the Milankovitch cycles and they are used to find out where sunlight reaches Earth and also determine the planet’s climate patterns. Scientists have previously seen this climate pattern in rock records that span through the history of Earth, notes the report.

To understand the Moon’s influence, one needs to go back billions of years, says the report, but rock samples are no longer accurate on those scales, notes the report. At that time scale, even redioisotope dating will not work.

This is why researchers looked to the Moon. “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 explains. However, it is a fact that the moon is about 4.5 billion years old- similar in age to the Earth and the Solar System.

These complications and the number of variables that went into accurately measuring Milankovitch cycles and the Earth on the whole. This study by Meyers led to a collaboration with Alberto Malinverno of Columbia University, notes the report.

The two researchers then developed a statistical model which linked astronomical theory with geological observations. Using this model, they tested two rock layers from the 1.4 billion-year-old Xiamaling Formation in northern China and another from the 55 million year old record from Walvis Ridge, in the south Atlantic Ocean. Results of the experiment helped the duo look far back at the history of the Earth.

Meyers and Malinverno were able to identify variations in Earth’s orbit, as well as how the distance between Earth and the moon as well as the length of day changed over the aeons. They also found that the Moon has moved about 44,000 kilometres away from Earth over the last 1.4 billion years or so and continues to drift away at a rate of 3.82 centimetres year after year. That means in about 200 million years, the average day on Earth will be about 25 hours long.

The study was first published in the journal Proceedings of the National Academy of Sciences.

Looking further out, if the Sun hasn’t already swallowed the Earth, in about 600 million years, the Moon will be so far out that there will be no chance of eclipses. A few million years after this happens, when the Moon finally breaks free of the Earth’s gravity, the Sun’s gravity is likely to push the Moon a lot closer to the Earth than it is now, after which the Earth’s gravity will completely rip it apart, it will then settle like a ring around the planet, according to an unrelated study published in August last year.

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