Comments on: I Banish You To The Black Hole.

By: Chris Venus

Chris Venus — Tue, 20 Mar 2012 16:27:53 +0000

I have to admit I will probably go and tinker with the maths myself. In particular rearranging that tidal equation to try to make it more obvious what the relative effects of L and X are. And because I remember in school working out stuff to do with the escape velocity and stuff and I can’t offhand remember how to do it. And because its fun. It’ll give me something to do on the bus on the way home.

By: Chris Venus

Chris Venus — Tue, 20 Mar 2012 16:25:14 +0000

If I remember correctly Pauli’s exclusion principle is quantum in itself in that it is about not allowing two particles to have the same quantum state. And I suspect its this gap betwen relativity and quantum mechanics which is why there is so much speculation with respect to exciting effects of black holes. After all, nobody can prove me wrong(TM).

By: hentzau

hentzau — Tue, 20 Mar 2012 15:36:30 +0000

I’ll be going into more detail on this on Thursday but: the gravity of a black hole is so great that it’s not just scrunching up atoms into a very small space, but it’s actually breaking down the structure of the atoms themselves. All those electrons, protons and neutrons are crushed together and the Pauli exclusion principle ceases to apply. Once you’ve overcome the natural repulsive forces keeping the component parts of atoms — and atoms themselves — separate, there’s nothing stopping you from compressing any amount of matter down into a single point. As Chris says quantum mechanics would probably have something to say about this, but this is one of the areas where general relativity does not mesh well with quantum mechanics.

By: hentzau

hentzau — Tue, 20 Mar 2012 15:27:39 +0000

Both valid criticisms; the first is a result of me unconsciously thinking that way anyway and forgetting that few other people do as well, and the second is because I wrote this post in two sessions and the bit on the Schwarzchild radius was something I forgot to come back to. I’ll have a tinker with it in a bit.

By: Chris Venus

Chris Venus — Tue, 20 Mar 2012 15:25:33 +0000

If lots of matter goes into a black hole the mass increases and so does the “size” of it (ie the event horizon expands). However, the singularity remains singularityish. The simple way (though not necessarily strictly accurate) way to think of it is that the gravity of the singularity is strong enough that the new matter is compressed into the same space as the singularity. Of course, a singularity sort of doesn’t have a volume by its nature but I think you probably get a bit quantum when you get down to that level.

By: Chris Venus

Chris Venus — Tue, 20 Mar 2012 15:17:11 +0000

Rather than saying “m is the mass of the smaller body (usually negligible where massive stellar bodies are concerned)” I think it would be much better if you instead just commented that acceleration is force over mass so removing m from the right side gives you the acceleration (which is something much more meaningful for most people). That way your later equation of the difference in force would be difference in acceleration.

Also I was sad that you didn’t actually do anything with that second equation except quote it there. I can do the maths myself but you did seem to just quote the equation without actually then talking about it much.

By: innokenti

innokenti — Tue, 20 Mar 2012 15:03:51 +0000

Do we have any idea what would happen if lots and lots of matter splattered onto the singularity. Lots and lots and lots and lots until it all became much bigger? Does it then become less black-holey?

Or am I missing something obvious?

By: Smurf

Smurf — Tue, 20 Mar 2012 11:12:50 +0000

See, I read and understand that but my brain still goes “bleurghh”.

By: hentzau

hentzau — Tue, 20 Mar 2012 10:58:05 +0000

It may be ethereal and intangible and very, very nippy, but it still has to travel along the fabric of space-time to get to where it’s going. If that’s distorted by a large gravity well it gets deflected just like everything else.

By: Smurf

Smurf — Tue, 20 Mar 2012 10:50:16 +0000

I can never get my head around the fact that light is a thing which can be affected by gravity. Light seems to be so intangible that a physical force being able to affect it is completely alien to me.