An Earth day for a billion years was 19.5 hours

An Earth day for a billion years was 19.5 hours


As the moon moves away from the earth at a slow speed, the days on earth are getting longer; But from about 2 billion to about 600 million years ago, an Earth day was about 19.5 hours long. Now scientists have found the reason for this problem: the effect of the sun on the earth’s atmosphere to counteract the lethal effect of the moon.

According to ScienceAlerta group led by Hanbo Wu And Norman MurrayAstrophysicists at the University of Toronto, Canada, believe that if there was no effect of the Sun and the Moon, an Earth day would last more than 60 hours today; Therefore, we should consider this issue when building climate models.

About 4.5 billion years ago when the Moon formed, the length of an Earth day, defined by the rotation of the Earth on its axis, was much shorter. Geological records show that the length of the Earth’s day has increased over time, and the reason for this is the gradual retreat of the moon at a rate of 3.78 cm per year.

The gravitational influence of the moon on the earth is responsible for the tidal forces of the oceans. As the moon revolves around the earth, its gravitational pull on the waters has led to the rise of the oceans on both sides of the earth. The influence of the moon’s gravity on these bulges acts like a brake and slows down the rotation of the earth. Scientists often liken this effect to the spin of a figure skater opening his arms to slow down. Thus, 1.7 milliseconds are added to the Earth day every hundred years.

However, the ocean is not the only fluid that surrounds the earth. Gas is also a type of fluid that the earth has a lot of. According to Murray’s explanation, sunlight causes atmospheric drag with the same type of bulges. The effect of the Sun’s gravitational pull on these atmospheric bulges creates a kind of torque force on the Earth, with the difference that it speeds up the Earth’s rotation instead of slowing it down.


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