Using Newton’s shell theorem as it relates to gravity, we come to the conclusion that there is no gravitational force at the center of large bodies like moons, planets and stars.
As a consequence, all these bodies are likely to be hollow. A cavity, once formed at the center of such a body, will have no way of disappearing.
Add to this that the internal wall of any cavity inside our planet is likely to repel itself due to electrostatic charge, we get the possibility that the atmospheric pressure at the core of our planet may be relatively low.
There will be enormous pressure in the wall surrounding such a cavity. Gravity pushing in towards the center and electrostatic repulsion pushing the other way will put the shell under enormous stress. However, the pressure in the cavity itself may be low enough to allow for a gas filled core.
Should a part of the internal wall come loose, the cavity will not become smaller. The loose matter will simply float about in the atmosphere of the cavity until it falls back against the wall. Unless the entire planet collapses in on itself, the cavity will remain, and with internal electrostatic pressure balancing out the gravitational pressure, there is little chance of this ever happening.
Cross section of a hollow planet with internal electrostatic pressure
An important point that can be gleaned from Newton’s shell theorem is that there will be an overall tendency towards less density at the center of large bodies. The theorem implies a one way mechanism in which things can become less dense at the center, but never more dense.
High density matter expelled from the core will not return. Low density matter will tend to stay.
This means that planets can be modeled as being at their most dense at some distance from the center, after which they become less dense.
When Jan Lamprecth wrote his paper on hollow planet seismology vs. solid Earth seismology, he noted that this kind of planets will yield the easiest and most straight forward explanation for seismic data.
Jan Lamprect concluded therefore that Earth is hollow, with a low density interior wrapped in a high density crust.
This happens to be the exact same conclusion that we can draw from an open minded consideration of Newton’s shell theorem as it applies to planets.
Furthermore, a gas filled hollow at the center of our planet would make it all the more easy to explain the expanding Earth. With a gas filled hollow, there is no need to have a great deal of new matter being synthesized for expansion to occur. The gas will simply expand to fill the growing internal cavity.
With pressures from both radioactivity and internal electric repulsion acting on the crust, we can expect expansion to accelerate for some time after it has started. This happens to be exactly what Dr. James Maxlow, a prominent proponent of expansion tectonics, has arrived at from his analysis of geological evidence for expansion.