How many hours make up a day on Earth? The average toddler knows this by heart. Kidding! But it really seems like there are fewer hours in a day nowadays. Truth is: days are actually getting longer instead — but that’s to a very less degree for you to ever notice. However, for several reasons, Earth’s rotation is slowing down gradually, and new research estimates just how much.
Related media: Are Days Getting Longer? Why? By How Much? Is The Earth Slowing Down Or Faster?
A Tale Of Two Gravitational Friends
It has been a known fact for quite a time now that the Earth’s rotation is gradually slowing down; and scientists have used all means of determining what’s keeping the foot on the brakes. By timing and measuring the locations of ancient eclipses to precisely measuring how long a day is, actually. As a matter of fact, a century is even long enough for changes to be noticed in the rotation of the Earth.
The planet has been slowing down and speeding up ever so slightly due to precession of the planets axis (the poles), and glitches in the core. However, the biggest culprit that most scientists blame for this slow motion is our very own planetary neighbor, the Moon — whose gravitational influence affects the Earth’s tidal bulge. Its like a spinning figure skater stretching her arms to slow down.
We’re Pulling Over
Scientists from the University of Wisconsin at Madison have used statistical tools together with geological analysis to determine way back in the history of the Earth, and have been able to extrapolate just how much we’ve slowed down. It turns out that the moon isn’t the only culprit slowing us down, other interplanetary bodies in our solar system are to blame as well.
Together, these interplanetary forces create slight variations in the orbit of the Earth around the sun, it’s rotation, and even precession — the wobble on it’s axis. These variations are known as Milankovitch cycles: they determine factors like how the Earth is impacted by solar radiation, thereby the climate of Earth. These variations also leave behind some evidence of geologic activity, which scientists can analyze to determine the climate history of Earth, thereby it’s Milankovitch cycles, roughly within the last hundred million years.
But here’s the catch: scientists can’t look any further back in time with precision. However, if you could figure out just how the moon and planets together with the Earth moved around eons ago, you might be able to figure out these variations as well. That’s the catch: its complicated. Fortunately enough, a professor from the Columbia Lamont Research developed a statistical method that could do just that.
How Long Is A Day Today?
In a 2018 study published in the Proceedings of the National Academy of Sciences, two professors: geoscience professor Stephen Meyers of the University of Wisconsin in Madison, and Columbia Lamont Research professor Alberto Malinverno teamed up and applied Malinverno’s method with astronomical theory, some geologic data, and crunched the number to reveal some magic.
Analyzing two ancient rock layers: a 1.4 billion-year-old layer from the Xiamaling Formation in Northern China, and a a 55 million-year-old layer from Walvis Ridge in the southern Atlantic Ocean, they determined how long days on Earth have gotten longer due to precession. Their find? (Cue the drum roll!) Roughly 1.4 billion years ago, a day on Earth lasted a little more than 18 hours, and the moon was roughly 43,500 kilometers (27,030 miles) closer — the Moon is currently 384,400 kilometer (238,855 miles) away. Thank goodness things slowing down.
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Written by: Nana Kwadwo, Sun, Jul 14, 2019.