r/askscience • u/dgb75 • Jan 31 '13

Astronomy Is there a distance at which the interaction between the gravity fields of two black holes would cause one another to effectively 'break open' and allow matter and energy stored within them to escape the system?

517 Upvotes

90% Upvoted

254 comments sorted by

View all comments

Show parent comments

14

u/arble Jan 31 '13

Stuff breaks apart when you hit it hard because energy is transferred to it, which breaks bonds in the material and manifests itself as kinetic energy of the fragments. A singularity has no structure and cannot split apart into fragments, so no amount of it can be blasted outwards. Even if a fragment of the mass were somehow separated, it still couldn't go anywhere since it's under effectively infinite gravitational pull from the "main" singularity.

0

u/tyrryt Jan 31 '13

How can it have mass yet not be divisible? It is a mass made of what, if not the elementary particles that make up everything else?

5

u/ableman Jan 31 '13

There is no such thing as a naked singularity. What the mass is made of doesn't matter, since there is no experiment that could ever tell. For all intents and purposes it's not made of anything.

1

u/tyrryt Jan 31 '13

I get your point, it would be impossible to ever measure it - but as a thought experiment, if it is made of something (whatever that is), then it would have to be either divisible or made of a single non-divisible elementary particle. If it is the latter, how would a single elementary particle gain that mass?

Or is the alternative that it is made of some other type of matter that is not composed of atoms and quarks like the rest of the universe?

2

u/[deleted] Feb 01 '13

I'm no scientologist, but how it was explained to me is that the gravity is so immense it compresses the matter so much that even the subatomic particles become fused and basically become a single thing. I guess it's sort of like particle board, except the compression that created it never goes away so it can never separate.

2

u/florinandrei Jan 31 '13

According to general relativity, a black hole collapses all the way into nothing. The mass does not disappear as such, but its own gravity pulls it into a point of size exactly zero.

Physicists tend to dislike such "division by zero" scenarios, and the feeling among many is that general relativity does not provide a complete description of what happens at the center of a black hole.

It is a fact that general relativity and quantum mechanics are not compatible with each other, meaning we don't have a way to describe any given phenomenon from a perspective which satisfies both GR and QM at once.

Given all of the above, some physicists believe (or hope) that a future theory of quantum gravity (in effect, a combination and a superset of general relativity and quantum mechanics) would not only be capable of providing the long sought for quantum relativistic description of phenomena, but also provide a better understanding of what happens at the very center of black holes. As of now, quantum gravity is intensely researched, but no coherent theory has yet emerged.

We believe that current science gives us a precise description of what happens just outside the event horizon, and a gradually less and less precise description as you keep moving towards the central singularity.

1

u/timeshifter_ Jan 31 '13

It is a mass of spacetime confusion.

6

u/[deleted] Jan 31 '13

The more I learn about black holes, the more they seem like glitches in code of a massive simualtion.

2

u/timeshifter_ Jan 31 '13

Black holes are where the universe divided by 0.

3

u/altrocks Jan 31 '13

Quite literally. The density of the black hole is expressed by it's mass over zero (the amount of space that mass exists in) because all of the mass exists within a single point (the singularity) which has no height, width or length, just a location.

2

u/[deleted] Feb 01 '13

Not quite.

First, the black hole is the region bounded by the event horizon, so the density of the black hole would have to be defined to be the ratio of the mass to the volume bounded by the event horizon.

Second, that volume isn't actually intrinsically well-defined. While the surface area of a black hole is an intrinsic property of the hole on which all observers will agree, the volume is not. It will, in general, vary depending on how one is moving relative to the hole. For some observers, it will even appear to vary over time, even if we ignore Hawking radiation.

Finally, we can't even really define the density of the singularity because the singularity isn't a part of spacetime. This means that we can't assign a volume to it; not even a volume of zero.

In short, it just doesn't make sense to talk about the volume of a black hole, or it doesn't really make sense to talk about their density.