Edit to clarify: I understand the moons gravity pulls on the water on the side of the earth that’s closest to it. But there’s also a bulge on the opposite side of the earth and I don’t understand how that second bulge happens.
In: Planetary Science
There are three levels of answer:
1) Gravity is everything is attracted to everything else. Since the Earth moves as a single object, the motion of the Earth only depends on the overall gravity from the moon. However, the side closest to the moon is attracted more than average, and the side that is farthest is attracted less than average. You can intuitively see why this creates a tidal bulge on the near side. For the far side, the Moon is swinging the Earth around, and not pulling on that far side hard enough to keep it swinging, so it bulges out.
2) Gravity pulls every point on Earth toward the center of the moon. This means that the north pole is pulled a little south, the south pole is pulled a little north, and overall a belt running around the Earth is being squeezed by the gravity of the Moon. This creates a bulge on the non-squeezed parts, which are the point closest to the moon and the point farthest from the moon
3) If you fill up a bathtub, you can make the water slosh around by sticking your hand in and wiggling it around. The same thing happens with the oceans. However, the oceans are really big, so the sloshing takes longer. The Gravity from the moon is playing the part of your hand in that analogy.
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