What do you think of this fact?
Ever wished you had more hours in the day? Then you were born about 1.4 billion years too late. Back then it was the other way around: a day on Earth lasted just over 18 hours, about 18.7 according to the study. Blame the Moon.
The Moon was closer
The number comes from a study by Stephen Meyers (University of Wisconsin–Madison) and Alberto Malinverno (Columbia University), published in 2018 in the “Proceedings of the National Academy of Sciences.” Their result: 1.4 billion years ago, the Moon was only about 341,000 kilometers from Earth. Today the average distance is around 385,000 kilometers.
According to the researchers, the shorter day was at least partly because the Moon was closer and changed the way Earth spun. Meyers compares it to a figure skater spinning: stretch your arms out and you slow down. The Moon is basically Earth’s arm, and it has been drifting outward for ages.
Clocks made of rock
How do you measure a day that ended more than a billion years ago? With rocks. Earth’s orbit and tilt wobble in regular cycles called Milankovitch cycles. They control how sunlight is distributed on Earth and leave patterns in layers of rock. The team analyzed these patterns statistically, including in the 1.4 billion-year-old Xiamaling Formation in northern China. From that, they worked out the length of the day and the Earth–Moon distance back then.
It’s still leaving
The Moon isn’t done running away. According to NASA, the distance between Earth and the Moon grows by about 3.8 centimeters (1.5 inches) a year. Tides are behind it: the pull between Earth’s tidal bulges and the Moon slows Earth’s rotation and at the same time pulls the Moon forward along its orbit. Earth slows down, the Moon drifts outward. That’s why our days keep getting a tiny bit longer.
The distance is measured with lasers: telescopes in New Mexico, France, Italy and Germany fire laser pulses at reflectors that Apollo 11, 14 and 15 astronauts set up on the Moon.
So every morning your alarm goes off in a day that’s a tiny bit longer than ever before. Sleeping in still doesn’t get any easier.