The discussion revolves around the nature of black holes and whether light can be trapped by them. Participants explore concepts from general relativity, the behavior of light in gravitational fields, and the properties of black holes, including their structure and the implications of singularities.
Participants do not reach consensus on several points, including the nature of black holes, the behavior of light in extreme gravitational fields, and the implications of singularities. Multiple competing views remain throughout the discussion.
Some claims rely on specific interpretations of general relativity and the definitions of mass and matter, which may not be universally accepted. The discussion includes speculative elements regarding the structure of black holes and the nature of singularities.
re-undefined said:I have been thinking about this for a few weeks and can not come up with an answer. As I understand it a black hole is essentially a gravitational field so powerful not even light can escape it. The last part is what I don't understand. I thought light(photons) was massless. If light has no mass how can it possibly be trapped by a gravitational field? Sorry if this is a trivial question.
With the exception of the last sentence, this is all incorrect.Aer-ki said:A black hole is NOT a gravitational field. It is a spherical body, like a planet or star, whose mass is so great that the gravity produced is enough to pull in light.
We know that gravity affects light, and some believe that light does indeed carry a small amount of mass, but reguardless, we know it is affected. Thus, a black hole is a gravity sphere with enough pull to keep any light emitted from its surface from getting free of its gravity field. Think of it like throwing a baseball straight up into the air...it gets away from the surface, but then gravity pulls it back in. Same thing with light.
But a black hole is definitely a mass...not just a gravity field.
DaveC426913 said:With the exception of the last sentence, this is all incorrect.
A BH is not a spherical body and not like a planet or star. It is a singularity, theoretically zero-size. There is a radius defined - the event horizon, defined as the radius below which nothing can escape. This radius has no physical manifestation; it is entirely a definition.
A BH does not treat light like a baseball. Light paths within the EH will bend back towards the BH, true, but a light beam that managed to find itself pointing directly out of the BH would not be pulled back down, it would be inifinitely red-shifted.
We have mathematical models of what matter does under the extreme forces in a BH. This is the prevailing model, which is what Physics Forums supports, and what you agreed to when you registered.Aer-ki said:Well, given that we have ZERO information from inside the event horizon all of this is speculation, but we do know that gravity pulls matter into spheres, so my assertion of the shape shouldn't be an issue.
As for matter, it exists, therefore it has some volume no matter how densely packed it becomes. So, the discussion can be how small of a sphere, but there has got to be one at the center.
DaveC426913 said:We have mathematical models of what matter does under the extreme forces in a BH. This is the prevailing model, which is what Physics Forums supports, and what you agreed to when you registered.
If you have some other ideas, you are welcome to publish them in a journal.
This is not true. You may be on the wrong board.Aer-ki said:Mathematical models are just guesses.
It is currently understood that, at the centre of the black hole, the singularity, mass is compressed to zero volume and infinite density. Your second statement is false.Aer-ki said:We know that gravity results from mass...mass has volume...therefore a black hole must have volume. It's simple logic.
DaveC426913 said:... It is currently understood that, at the centre of the black hole, the singularity, mass is compressed to zero volume and infinite density. Your second statement is false.
Good point.Nickelodeon said:I think you should be using the word 'matter' here. You can't compress mass as mass is a property of matter, think I'm right in saying that.
Yes. Our understadning of atomic structure says that the atoms will lose their identity and be compressed to a point.Nickelodeon said:I would have thought that in the extreme environment of a black hole matter could not structurally exist. Possible a mathematical model could be contrived to allow the individual atomic components to get ever closer but it would seem unlikely in reality.