Eli5 on why do planets spin?
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Mostly, it’s due to how they form. Have you ever been on a roundabout in a playground? If so, you’ll probably know about how reducing the distance of your mass for the center increases the rate of rotation, or in other words, focusing all the mass from a wide spread to a small spread increases angular momentum!
Well, this is what happens when all things form in space. You start with a cloud of random dust and gas and whatnot that is drawn together over huge amounts of time by gravity. Except all of the little bits would have been travelling in some direction to begin with. So, as the cloud forms, the sum total of different particles’ momentum creates a very slight rotation. As the cloud condenses, that very slight rotation increases due to the focusing of mass towards the center of rotation. And then hey presto, bingo bongo, you eventually have a rotating planet!
Then you ask, but what about the moon? We only ever see one side of that
The moon is actually rotating, just perfectly in time, its orbit around the world! Amazing really
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