For reasons like relativity, a person on the moon will most likely think that earth is spinning around them. Evidence used by these conspiracy theorists backing up that inaccurate statement has a lot to do with relativity. Earth does not orbit the moon and this has a lot to do with how gravity works in the first place. Gravity is what decides what spins around what’s in space and is responsible for the movement of celestial bodies in space-time. Relativity has offered a huge chunk of knowledge in science about the mechanisms of quite several natural secrets; using it to override gravitation is wrong. However, people did not have an understanding of how gravity works but understood relativity, saying that the earth spins around the moon would be correct too.
Why individuals have this opinion is not a reason based on facts but based on an illusion of relative motion. A man standing on the moon who has never been to earth will most likely see the situation that’s opposite from facts. They would say that it’s the earth spinning around the moon since, relatively, that’s what it seems; This is not true, and understanding why requires an understanding of gravitation. Earth together with its moon, and every other heavenly body exists in space-time. These bodies are always in a state of motion of two types, either inflicted or due to gravity action.
Inflicted motion in space is caused by an object hitting another object and giving it energy expressed as motion. There are different forms of it, but that is what it is. Movement due to gravitation happens under strange rules of physics meaning that calculation is possible. What causes these bodies to gravitate around each other has a lot to do with mass and the structure of space-time. The heavier a body is, the more that body is likely to attract objects into its orbit. This behavior is so because anytime a body is in space, it curves it.
Think of space like a long spread fabric that’s fully stretched and flat. Placing an object on such a fabric causes a curvature to happen and it’s this curvature that scientists refer to as gravity. They call it that because if the curvature is big enough, it means that any object that gets close will fall towards the body. In the 2D version, that object will fall until it’s in contact with the body responsible for curving. But in a 3D version, such behavior is not always the case. Odd things like continuous falling start to happen since there is no specific surface that is governing the falling. The surface is spread out in a 3D version and as a result orbiting happens.
What is orbiting just gets described as continuous falling. It happens because there is no concept of down to these matters. Having that knowledge, it’s now easier to explain which of the two, earth and moon, rotates about the other. Earth has more mass than the moon. A translation is that it will cause a deeper curvature of space than how the moon would. Since the moon is close, it would turn to continuously falling. The result only happens the other way when the moon has more mass than the earth, except that is not the case.