I'm sure the math explains the actual mechanisms involved. I hope it does.
Here is the obvious thing about "black holes" and gravitational collapse. To use an example, we have a neutron star, say three solar masses. It has blown off all the light elements, and doesn't have enough fuel to create the energy to keep the molecules/atoms from being crushed by gravity.
Obviously there is a huge amount of EM energy released as electrons and protons and neutrons are shoved together, with protons and electrons forming neutrons, and all kinds of changes occur in the nature of the matter.
(I looked it up, there are all kinds of things involved)
Bottom line is, when the same mass, or actually less, because of all the loss from radiant energy and explosive outbursts, ejecta, etc, the same mass that was there, is now much much denser, compressed down into a smaller amount of spacetime. Because of the desnity, the gravity is more concentrated, leading to our warped spacetime, so extreme EM curves and never leaves the spacetime area.
And any matter/energy getting too close also curves in, and can't be seen.
The thing rolling around in my mind, (and I can't seem to find any published stuff about this), is at the core, we are saying dense material has more gravity than less dense matter. Not an increase, (that would violate physical law), but the gravity is more concentrated.
What I'm wondering, is there experimental evidence to show this is true?
Or to use a thought experiment. Take a sphere of neon, or some other inert gas, large enough to have gravity we can measure. Say the mass of the earth. Put a moon around it, so we have an orbiting body to observe.
Obviously this sphere is going to be huge, due to the low density of Neon. But we have the same mass, it equals the planet earth in mass. The moon orbits at the right distance, so it is a regular ellipse, not a decaying orbit.
Now, we freeze the Neon, so it becomes a liquid, a much much smaller mass, but the exact same amount. Now we have a small sphere, but with the same mass. Does this effect the moon's orbit? Has the gravity of the Neon planet changed? Because it is denser? Is the center of gravity different?
Would the moon change orbit?
I hope you see what I'm getting at. Is the gravity of our Neon planet more concentrated now? Is there less gravity effecting the moon? More gravity?
Like with a black hole, does the change cause object orbiting at a distance to change? Does the gravity change, because of density?
Or is it only real close to the dense object that gravity gets stronger?
The thing is, we say it isn't the density of an object, but the mass, that determines the gravitational energy, or interaction, with other bodies. A Kilo of lead has the same mass as a Kilo of Hydrogen.
But is that true? Is matter that is spread out over a larger area, is the gravity different because of that?
Obviously we are interested in the Black Hole issue. One minute we have a star with 3 solar masses, that doesn't have enough gravity to capture light, warp spacetime to that degree. But when it is all concentrated at a single point, now it does.
Is it about the distance to the center of gravity?
I apologize if this isn't clear. I just can't seem to find any papers that discuss this. I'm sure it has come up before.
