The Earth has been rotating since its birth, four and a half billion years ago. It was formed from the debris created when the Sun was formed by the collapse of a huge cloud of matter. The debris that became the Earth revolved around the Sun, like the water around the hole in the tub when you empty your bath, spinning on itself.
Our planet continued to orbit the Sun after its formation and will continue to do so for a long time to come.
The Earth rotates regularly, once every 23 hours and 56 minutes. During this time, the Earth is also moving a little further along its orbit around the Sun, which lasts one year. This means that it must turn a little more – for four minutes – until it faces the Sun again. That’s why a day on Earth lasts 24 hours.
If the Earth keeps spinning, it’s because there’s practically nothing to stop it. If you spin a top in the schoolyard, it will eventually stop. This is because as it spins, the air and surface of the playground exert pressure, causing friction and slowing it down.
The Earth rotates in space, which is practically empty. In space, there isn’t even air to slow the Earth’s rotation.
However, there is one thing that slows down the Earth’s rotation: the Moon. The motion on the side of the Earth facing the Moon is not perfectly balanced by gravity, nor is that on the side of the Earth opposite the Moon. This imbalance creates ocean tides, which cause the oceans to swell on either side of the Earth.
The Moon affects the rotation of the Earth. | Yuki Ho via Unsplash
As the Earth spins, these bulges move across the Earth’s surface like a wave, pushing against the Earth’s rotation. This slows down the Earth’s rotation. This means that the length of a day on Earth increases by one second every 50,000 years.
The only thing that could stop Earth’s rotation would be for another planet to crash into it. Even if that happened, it would certainly alter the rotation of the Earth, without stopping it completely.
A day that lasts six months
If the Earth stopped spinning, we wouldn’t suddenly be thrown into space. Gravity would hold us firmly to the ground.
But there would be many changes. If the Earth stopped rotating but continued to revolve around the Sun, the “day” would last for half a year, just like the night. It could heat up much more during the day and cool much more during the night. The Earth’s climate would be greatly disrupted.
A large temperature difference between day and night would cause strong winds, which would move warm air to the cooler night side of the Earth. The wind would also blow from the warm regions around the equator towards the cold polar regions. East and west winds, as well as winds towards the poles, would meet. They could eventually create huge whirlpools the size of entire continents.
On another aspect, you should know that the core of the Earth is partly made up of molten iron. The rotational movement of the Earth turns this molten iron into a magnet and gives the Earth a magnetic field. This protects us against harmful radiation, which comes from particles from the Sun and cosmic rays from outside the solar system.
Without the magnetic field, this radiation would reach the Earth’s surface and make people sick. Some birds use the magnetic field to find their way, so if the Earth stopped rotating, they would get lost.
Finally, if the Earth did not rotate, the night sky would always show the same constellations of stars, because we would always be looking into space in the same direction.
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This article is republished from The Conversation under a Creative Commons license. Read the original article.