Why is the moon moving away from the earth/why are the days getting longer?
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You’ve probably learned the moon causes the ocean tides. The moon’s gravity pulls on the oceans and causes it to bunch up a little bit. Well, more mass means more gravity. So this area of bunched up ocean has slightly more gravity, pulling back on the moon. As the Earth rotates and drags this bunched up water forward, that extra bit of gravity also pulls the moon forward a little bit. And a faster orbit also means a bigger orbit.
You know how you get pushed into the side of a car if it takes a turn too quickly? The earth is doing that to the moon.
But wait, there’s more. Newton’s third law states that for every action, there’s an equal an opposite reaction. As the Earth is pulling the moon forward, the moon is dragging backwards on the Earth’s rotation (aka longer days).
Eventually, they’ll meet in the middle and become tidally locked. The moon’s orbit will exactly match the Earth’s rotation. One side of the Earth will always see the moon, and the other side will never see it again. (Well, the death of the Sun will mean they’ll never survive to get to that point).
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