1) Black holes size is determinate by how much matter has been drawn into it, correct? (or, to start, the size of the collapsing star that formed it to begin with of course)
The Schwartzchild radius of the a non-spinning black hole event horizon is a function of its mass, and nothing else. Black holes are defined by exactly three parameters: mass, rotation and charge. Know those three, everything else around them is deductible from that. Iannis mentioned a kugelblitz which is formed from energy instead of matter, with the e=mc2 usual equivalence, but that falls under the general case of mass. In theory, you can't determine, from observing a black hole, what specific mass came into its "composition". Just the total amount.
Which is where those quantum physicists start tearing their hair, since information cannot be destroyed in quantum physics, except it appears to be when shoveled into a black hole.
(oh, and a rotating blackhole is not exactly spherical)
2) But as more matter is drawn into it and pulled past the event horizon, it *does* grow bigger, correct?
Yes.
3) Or, is this the part where they say Einsteinian physics breaks down and we simply don't know what happens once past the event horizon?
4) If it's nothing special (i.e. wormholes, tesseracts and sci-fi type of speculatory happenstances) and matter just keeps being packed onto matter and the black hole grows in size, would that mean that even past the event horizon that Einsteinian physics applies? Or is it, again, we just don't really know?
We don't really know how physics exactly work beyond an event horizon since nothing that happens inside is measurable outside. But as far as we know, the physics inside a blackhole don't seem to matter to the physics outside one.
that radius denotes an area of change. Black holes shouldn't grow quickly, even if we naively assume they don't radiate. Think about the ratio. You're considering density, which is mass over volume. Mass has to grow faster than volume, volume is a cube.
Fun fact is that the Schwartzchild radius equation is linear with mass. radius = M x 2G/c2. Double the mass, double the radius of the black hole. That's why the "imaged" black hole is so huge, despite being "only" a few hundred billion masses of the sun.
5) What is the relationship between black holes and dark matter? What's the general leading hypothesis of how they interact (or don't)?
Since no one knows what dark matter exactly is...
(cf the recent observation of a second galaxy that appears to have zero dark matter in it)
One thing to remember, is that the repulsion between sub atomic particles (neutrons or quarks) is not infinite in strength, so when mass piles on mass, the pressure increases until this point is passed. At that point the pressure forces all the sub atomic particles to compress toward a dimensionless point. I think.
That's the neutron star limit. Neutron stars can't be bigger than about 3 solar masses. At that point, the quantum physics that prevent neutrons from being in the same place are overtaken, the quarks start to pile up and you cross the Schwarzchild radius, and boom: you go black hole.
Vanessa
