Hollow Moon Theory

I am not sure that i have ever seen anyone actually try to deal with this possibity before. I know that there is some school of thought that the Earth might be hollow. I expect it could be but i doubt anyone is going to go down there to find out, since it seems like it should be very hot or molten down there.
The Moon might be an entirely different kind of story. While planets and moons are held together by gravity, they are not held together by a gravity field coming from the center of the object. In fact it would seem that the force of gravity at the center of these bodies should add up to zero, or the sum total of all the gravity that the astral body generates is necessarily going to decrease as one moves toward the center. Depending on the mass density distribution, the force of gravity on the outer surface of the body should be similar if "the moon" or whatever body should be similar on the surface whether the body was uniformly solid or if it has a large hollow or gaseous center.
The Moon or Earth's moon seems to have been formed by a large collision at high enough velocity to actually have bashed the Earth with such energy and force to "knock off a chunk" driving it into orbit.
If one were to imaging that this were so, then at least part of the body might be molten or plastic in nature.
If the inner energies were similar to the inner energies of the earth, there would likely be a great deal of extremely high pressure and heat trapped within it as it was carreening off into a stabile orbit.
Now let's guess that the moon could have similar mass density to that of the Earth, or the origional body that smashed into the earth 4 to 4.5 billion years ago. If superficial Earth forces can create Himalayas and super volcanos, perhaps there could have been similar internal forces on the Moon.
Now given these realities and possibilities, the Moon could well have been expanded from the inside by outward pushing forces that would only be "countered" by gravity as it the mass displaces outward from the center. There could be something that might be likened to a balloon effect where the containing force of gravity only begins to increase as one moves away from the zero gravity center.
Now if this is possible, then there arises the possibilty that the moon continued to expand until a moon volcano could have released the internal pressure.
The entire Moon could be hollow in the center with very low gravity aligning toward the center space on the inner surface. Probably technologically adept creatures could live or have a contained living space within the hollow space in the moon. And this could easily be more than half the volume of the Moon.
You probably heard it here first. Aside from my own mind meanderings, i have actually never heard of this before. It seems both obvious and then not really clear.
My guess is that a good theoretical astro physicist might be able to analyze the moons oscillation and theorize futher on this matter. I understand that there is a sizable "hole" on the far side of the Moon.
It might be an interesting problem (however old), that some smart person could solve. As far as it being a place to live; there is probably enough energy from the sun to engineer a living space within the moon if the protected space or volume was already there.
A likely scenario might be that if it were pushed out and then solidified water would probably be one of the pressurizing gases, then if it were to push through the surface, it could do a kind of rapid cooling of the internal fires of the moon as it escaped into space.