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
Remember that the Earth is pulled toward the moon as well. The water facing the moon is closest to it and thus pulled toward the moon **more strongly** than the Earth is, making it go away from Earth, and the water opposite the moon is farthest from it and thus pulled toward the moon **less strongly** than the Earth is, again making it go away from Earth.
[More detail](https://www.youtube.com/watch?v=bPhhYhN0FAc)
[here you go](https://youtu.be/4ykH5kt4j3k?si=-wCuoL-OK0d3M-q6)
TLDW: the moons gravity pulls water
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.
It’s a bit counter intuitive, but here it goes: The moon pulls on the water on Earth. But it also pulls on the Earth itself.
And that pull is a bit stronger (because it’s closer and the earth is rigid compared to water) on the Earth than on the water on the far side of the Earth. So basically the Earth’s surface “falls away” from the water on the far side because this water is subjected to the least of the moon’s gravity of all the elements in this system.
Best description I heard. Let’s say you are spinning your 5 year old in circles by their arms. We have all done this. Kids love it. You are pulling on your child’s arms. That’s the front side of earth and your the moon. You are pulling that water towards you.
Now on the back side of earth, your child’s feet, you’re slinging them around. If your child’s shoes come off, which way to they go? They don’t fly at you. They fly away from you.
So the moon is pulling the water closest to the moon and slinging the water away from the moon on the backside.
What will really blow your mind is that the water is only moving at the speed of the moon. Earth is turning into those bulges of water.
The moon is pulling the water towards itself on the side of the earth facing the moon. On the opposite side, it’s pulling less as the gravity is weaker way over on that side. Think of the earth like a stretchy ball and the side opposite the earth is stuck a little bit (representing the weaker gravity).
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