Any ball shaped object in its "center of gravity" has zero gravitation because the vectors of gravitational forces compensate each other in the center. If two objects attract each other the vector of one object being directed to the other add each other the one being directed to the outside substract from each other. That can make an object spin on its orbit or prevent it from halting its spin.
The moon has a strange spin which is related to its orbit. Relatively to us it does not spin at all. That makes us see only one and the same side of the Moon. We never see its back side. Theoretically the Moon should have a spin that we see all sides by his own, independent spin. Assuming that there is no rope between Moon and Earth that behavior can only be explained by another, smaller moon which is exactly on the opposite side, stabilizing the moon's spin and constantly "hiding" relatively to ourselves on the Earth on the "backside of the Moon" (relative to the Earth). Where is my mistake?