When planets are coalescing not all debris falls straight smack bang into the centre of mass some will hit off centre and like kicking a football (the proper round ones) if you kick it off centre you introduce a spin.
The hundreds of billions of impacts to a forming planet will give it a spin and without anything to stop it it will continue to spin.
This is why Earth’s days are slowly getting longer because the tides cause drag slowing the earth’s rotation.
Conservation of angular momentum. Its an observation and law of nature that things continue moving unless acted on by external forces.
When the gas cloud the formed the sun and earth collapsed, it had some net angular momentum, and that caused the initial spin. Once it is spinning, we need some external force to stop it. There are some force like tidal forces from the moon and sun, but those a small and insufficient to stop the Earth’s spin, though it has slowed down a bit.
In other words “Why do you expect the earth stop spinning?”
Conservation of angular momentum. Its an observation and law of nature that things continue moving unless acted on by external forces.
When the gas cloud the formed the sun and earth collapsed, it had some net angular momentum, and that caused the initial spin. Once it is spinning, we need some external force to stop it. There are some force like tidal forces from the moon and sun, but those a small and insufficient to stop the Earth’s spin, though it has slowed down a bit.
In other words “Why do you expect the earth stop spinning?”
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