Like how does it shrink and expand?
In: Physics
Water doesn’t shrink and expand. It’s always the same volume. Because of the moon’s gravitational pull, water is constantly sloshing around the Earth like water in a cup. It’s not “high tide” everywhere on Earth at once, then low tide everywhere at once. It’s high tide on one side of the ocean and low tide on the other.
[Here’s a gif of the process.](https://cdn.shopify.com/s/files/1/1140/6118/files/TideAnimation.gif?v=1496773572) Basically the water is always bulging out towards the moon, but the Earth is spinning “underneath” that. So from the land perspective, the water goes up and down.
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