 Researchers who study seismology were able to get a very clear idea of the interior of the moon, and it's generally solid and filled. This is a planet that's pretty much solid with solid lava. They do not think it has a liquid core at all. So that's right. There's no hollow moon. That's just not the case. As for the China on the far side of the moon, remember, it's not dark. It's the side that we can't see because it never faces the Earth.