# Blackhole question

#### izzie

Hello everyone!
I'm a student in the UK who just finished my GCSE's and im very interesting in physics particularly quantum physics, though i have little knowledge of it. So a blackhole is also called a "quantum singularity"? And it is an object with near infite mass and little/no volume (correct me if im wrong). What i don't understand is, the shape of a black hole is like that of a funnel, with the singularity at the bottom of this funnel and an acceleration disc at the top, and this suggests its a 3d shape but is it. How can it be if the matter is being pulled into the singualirty and there is only one acceleration disc? Surely if you were to go around the back of a black hole it would appear empty? I don't know if i make sense and i know i sound stupid but im just interested to find out.

Izz

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In general relativity, which is non-quantum, the center of the black hole is just a classical singularity; the density goes to infinity there. But there is current effort to quantize GR gravity (see the subforum "Strings Branes and LQG" for news about that). And in some of these quantization programs, the singularity goes away, due to, for example, the operation of the uncertainty principle at short ranges.

#### pervect

Staff Emeritus
izzie said:
Hello everyone!
I'm a student in the UK who just finished my GCSE's and im very interesting in physics particularly quantum physics, though i have little knowledge of it. So a blackhole is also called a "quantum singularity"? And it is an object with near infite mass and little/no volume (correct me if im wrong). What i don't understand is, the shape of a black hole is like that of a funnel, with the singularity at the bottom of this funnel and an acceleration disc at the top, and this suggests its a 3d shape but is it. How can it be if the matter is being pulled into the singualirty and there is only one acceleration disc? Surely if you were to go around the back of a black hole it would appear empty? I don't know if i make sense and i know i sound stupid but im just interested to find out.

Izz
To address some other points - non-rotating black holes are really spherical. The funnel shape that you see associated with them is an embedding diagram, not what they really look like.

For a description of what the term "embedding diagram" means, and a java applet, see

http://www.opensourcephysics.org/talks/osp_curriculum/applet_html/embedding.html [Broken]

Last edited by a moderator:

#### izzie

the applet doesn't load but, so that means that the singularity is at the core of a black hole? thanks anyway, now i feel stupid

delete this topic someone

#### pervect

Staff Emeritus
Chill out a bit, izzie - having your browser fail to load a java applet may be a bummer and a bit frustrating, but it doesn't make you stupid.

#### professor

it looks like the specific type of black hole that you are speaking of is a classical swarzchild blackhole (i hope i spelled his mane right) in such an instance there would be a conained singularity, and this could be described in such a way as you have mentioned, though this is only one theory, not all include the necessity of a singularity

#### professor

and ohh yeah, in such a case the singularity would be at the core of a black hole and would most likely consist of a mainly neutron comprised matter

#### amt

From the diagram applet, it seems like the singularity bottoms out when the Mass=1.

What's happening there? Is 1 some critical point?

#### pervect

Staff Emeritus
When M=1, the object becomes a black hole. The embedding diagram then stops at the event horizon, where the equations used to derive it become singular. (This is the coordinate singularity at the event horizon, not to be confused with the true physical singularity at r=0).

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