What causes the Earth to spin so consistently?
In: Physics
Earth is a ball suspended in nothingness. Rotational energy was given to earth as it was forming and since there is no friction in space there is nothing to really slow it down.
*Inertia, and absence of any meaningful external forces.*
**Inertia** is just the “will” of things to keep going the way they are going; or, on this case, to keep spinning. That’s something *mass* does: the more the mass, the stronger the will. That’s literally what mass *means*.
**Forces**, on the contrary, is what wants to change the way things move (or spin); for example, they want to make them stop, or go faster, or spin differently, etc. That’s literally what defines force.
Small spinning things we are familiar with, like a spinning top or a fidget spinner, have a little mass; that is, they have only a little will to keep spinning in the same way. Meanwhile, they are subject to substantial forces (such as friction with the table surface, and even with air). In total, they don’t keep spinning in the same way for long (or, after a short while, at all). This experience makes us think that, as a general rule, spinning stuff doesn’t go on for long… but that’s not true; in reality, it depends.
Earth has an enourmous mass, wa-a-a-ay bigger that any object we deal with, and much bigger still than objects we consider enoumuolsy massive, like a boulder or a mountain. That enormous mass means an incredible will to keep spinning just in the same way. Meanwhile, forces that pushes against that will are basically non existent. Gravity from sun affects spin very little, from the moon very little as well, frictions with space dust is basically zero, and ther’s not much else.
(the first two factors I mentioned do have a little effect, especially the moon, and they are making Earth slow down its spin a bit… just not enough to see it in one lifetime).
It actually slows down over time, the moon affects the earth’s rotation speed and vice-versa. I remember vsauce had a video talking about it…
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