The story of why the Earth spins goes back to the formation of the Solar System. Roughly 4.7 billion years ago, the Solar System was a large swirling cloud of dust and gas. Over time this gradually coalesced into stars and planets, being drawn into these shapes by gravity. Being pulled inwards increased the angular momentum of the various bodies, and made them rotate faster. The law of inertia states that anything stationary or moving with a constant speed wants to continue doing so until it is acted upon by another body/force. Considering the Earth rotates in space, which is a vacuum, there is nothing to drastically slow the Earth down, which is why it continues to spin. Interestingly, early in its formation, the Earth spun up to five times faster than it does now – so it has slowed down. The culprit is the moon, via something known as tidal locking. To understand tidal locking, imagine you and a friend both pull on a rope, but at the same time you spin in a circle around a pivot at the centre of the rope. As you tug harder, you are eventually able to spin less and less fast. Eventually, you will be stuck simply pulling on the rope, unable to move as your pulling force is too great; this is essentially what happened between Earth and the moon. As the moon orbits Earth it exerts a pull on the planet, responsible for causing tides. The Earth is much bigger so continues to spin freely, but the moon’s rotation now matches the time it takes to complete one orbit. Small as it is, the moon will continue to effect the Earth and, in millions of years, a day could last up to 26 hours.
Answers
Amit budhalakoti
The story of why the Earth spins goes back to the formation of the Solar System. Roughly 4.7 billion years ago, the Solar System was a large swirling cloud of dust and gas. Over time this gradually coalesced into stars and planets, being drawn into these shapes by gravity. Being pulled inwards increased the angular momentum of the various bodies, and made them rotate faster. The law of inertia states that anything stationary or moving with a constant speed wants to continue doing so until it is acted upon by another body/force. Considering the Earth rotates in space, which is a vacuum, there is nothing to drastically slow the Earth down, which is why it continues to spin. Interestingly, early in its formation, the Earth spun up to five times faster than it does now – so it has slowed down. The culprit is the moon, via something known as tidal locking. To understand tidal locking, imagine you and a friend both pull on a rope, but at the same time you spin in a circle around a pivot at the centre of the rope. As you tug harder, you are eventually able to spin less and less fast. Eventually, you will be stuck simply pulling on the rope, unable to move as your pulling force is too great; this is essentially what happened between Earth and the moon. As the moon orbits Earth it exerts a pull on the planet, responsible for causing tides. The Earth is much bigger so continues to spin freely, but the moon’s rotation now matches the time it takes to complete one orbit. Small as it is, the moon will continue to effect the Earth and, in millions of years, a day could last up to 26 hours.