With pushing in the opposite direction, the angular momentum decreases. This means that the overall rotation rate becomes smaller. The moon did not completely stop revolving, but it is now revolving slowly enough that it is more like a rock falling on the earth and almost hitting the earth.
(Yes, in the illustration, they look like they have collided-but remember, I made the earth and moon bigger than they should be so that you can see them. In fact, it’s more Like a fluke.)
The best way to crash the earth and moon is to freeze their orbits completely, or to use physics terms, to reduce the moon’s speed to zero (relative to the earth). Once the moon stops revolving, it will directly fall into the planet, because the gravity from the earth will pull it and increase its speed as it moves towards the planet. This is basically the same as throwing a rock on the earth, except that it is much larger and you can make a movie about it.
To do this, you either need greater “mysterious” power or a longer push. (If there are aliens reading this article, please do not use this as a blueprint to destroy the earth.)
Can the moon pull the earth’s oceans away?
But impact is not the only way the moon can destroy us. At one point in the trailer, the moon appears to be so close to the earth that its gravity pulls the ocean away from the planet’s surface. Does that really happen?
Let’s start with the simplest case, the moon and the earth are stationary and almost touching. It looks like this:
Now suppose I put a 1 kg water ball on the surface of the earth. Because water has mass, it interacts gravitationally with the earth, pulling the water toward the center of the earth. But there are also gravitational pulls from the moon in the opposite direction. Which force will be greater?
We can use the same universal gravitation to calculate the moon’s orbit. For the interaction with the earth, we will use the mass of the earth and the mass of the water. (I chose 1 kg to make it easier.) Distance (r) From the center of the earth to the surface-this is just the radius of the earth. For the interaction with the moon, I will use the mass of the moon and the radius of the moon (plus a little extra because they don’t touch too much).