Exploring Black Holes

[pmb]

There is a new version of Exploring Black Holes comming out in the future. It's located at http://www.eftaylor.com/. See http://www.eftaylor.com/comments/ and http://exploringblackholes.com/.

 

Once again I'll be proof reading for the authors. It'll be a great deal of fun. You can do the same thing if you wish. In any case it will be fun to talk about. Download the book and bind it and read it and let's chat!

 

 

[between3and26characterslon]

As you mention black holes I have a question.

 

Please keep in mind my knowledge of maths is very limited, also, this question might be utter nonsense for reasons I don't understand.

 

However;

 

The centre of a black hole is a singularity and at this singularity our understanding of physics breaks down because things tend to infinity. But why is the centre a singularity, why isn't this singularity also governed by the uncertainty principle? Is it therefore not a singularity?

 

**http://www.youtube.com/watch?v=hydDhUNvva8** in the first minute of this vid

 

i.e. does r not = 0

 

can you not just throw some uncertainty into the equation

Edited May 23, 2012 by between3and26characterslon

[pmb]

<br />As you mention black holes I have a question.<br /><br />Please keep in mind my knowledge of maths is very limited, also, this question might be utter nonsense for reasons I don't understand.<br /><br />However;<br /><br />The centre of a black hole is a singularity and at this singularity our understanding of physics breaks down because things tend to infinity. But why is the centre a singularity, why isn't this singularity also governed by the uncertainty principle? Is it therefore not a singularity?<br /><br />**http://www.youtube.com/watch?v=hydDhUNvva8** in the first minute of this vid<br /><br />i.e. does r not = 0<br /><br />can you not just throw some uncertainty into the equation<br />

<br /><br /><br />

 

The text is on black holes and that is my extent of knowledge. What you're asking about is outside my area of expertise. You want someone versed in quantum gravity. Hopefully someone will chime in.

 

I have a luncheon on friday where I'll be around a lot of experts. I'll raise the question if I remember it.

[elfmotat]

As you mention black holes I have a question.

 

Please keep in mind my knowledge of maths is very limited, also, this question might be utter nonsense for reasons I don't understand.

 

However;

 

The centre of a black hole is a singularity and at this singularity our understanding of physics breaks down because things tend to infinity. But why is the centre a singularity, why isn't this singularity also governed by the uncertainty principle? Is it therefore not a singularity?

 

**http://www.youtube.com/watch?v=hydDhUNvva8** in the first minute of this vid

 

i.e. does r not = 0

 

can you not just throw some uncertainty into the equation

 

I'm not a quantum gravity expert by any stretch of the imagination, but I believe your impression that the singularity should obey uncertainty principle is valid. General relativity is a classical theory, and as such does not account for such effects. A good quantum gravity theory would need be invented to make reasonable predictions about quantum effects near the singularity.

[juanrga]

The centre of a black hole is a singularity and at this singularity our understanding of physics breaks down because things tend to infinity. But why is the centre a singularity, why isn't this singularity also governed by the uncertainty principle? Is it therefore not a singularity?

 

That singularity is merely indicating that general relativity (a classical theory) breaks and ceases to be applicable. This is not something special of general relativity. Each theory has a range of applicability. There is not singularity when quantum effects are taken into account.

[MigL]

More like 'a singularity is not allowed when quantum effects are taken into account', since the singularity would, by definition, localize an amount of energy into an infinitely small space, and that is not allowed.

 

I myself like to think of the possible singularity as an edge to space-time. Our current ( non quantum ) theory ceases to be valid at or very close to this 'edge'.

[between3and26characterslon]

So does GR make the assumption that r=0 or is it derived from GR that r(must)=0?

 

If so;

 

How valid is this conclusion if we can't prove it in reality? i.e. actually measure the radius.

 

Also (and I think I've asked this before)

 

How does gravity extend beyond the event horizon? If I had an indestructable stick and poked it into a blackhole I would not be able to pull it out again for to do so would require the end inside the blackhole to travel faster than light. Or, if a blackhole is there and we know it's there then we have some information, how does this information get from the singularity to the event horizon to us?

[MigL]

Certain properties of the collapsed star that formed the black hole are conserved on the event horizon, not in the possible singularity. Properties like mass ( and so gravity ), angular momentum and charge and a semi-QM argument can be made for the preservation of entropy information ( and so temperature ) on the event horizon.

The event horizon has no physicality, you cannot see it or touch it. It is defined as the radial distance from the possible singularity where the velocity needed to escape ( move infinitely far away ) is equivalent to the speed of light. Alternately, an object infinitely far away will, in the absence of any other forces, have accelerated to the speed of light upon crossing the event horizon ( note that this is then an impossibility ).