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Post by principled on May 5, 2011 4:15:00 GMT 1
From the outset, I have to admit that I don't fully understand the concept of a hole in space. So perhaps someone could help.
As I understand it, the diameter of the hole and therefore its sphere of "influence" on surrounding masses can be calculated. These masses and all other forms of energy (eg light) enter the hole, never to exit.
I assume a black hole must be three dimensional, so is it possible that the hole could eventually be filled if enough mass enters it? Or is this another case where the mass is so great that the distortion of space within the hole means that it is infinitely deep?
Confused as always P PS: Good to see you're back STA
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Post by nickcosmosonde on May 5, 2011 6:51:45 GMT 1
From the outset, I have to admit that I don't fully understand the concept of a hole in space. So perhaps someone could help. As I understand it, the diameter of the hole and therefore its sphere of "influence" on surrounding masses can be calculated. These masses and all other forms of energy (eg light) enter the hole, never to exit. Hi P, I'm happy to admit the same thing with you! As I understand it, the "hole" part is not meant to be a literal term. The curvature of space-time given a certain amount of mass becomes theoretically infinite - there's a singularity in the equations. This is the "hole". The latter, I suppose. There is a theory that postulates that the infinity in the equations actually does imply a rupture, a literal hole, and that the space-time metric eventually curves outwards again, with all physical parameters of opposite sign - it merges into an anti-universe, in other words: a "white hole". I believe it was Halton Arp who suggested that this is what quasars are - or maybe that was John Wheeler, I forget. Hear hear!
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Post by abacus9900 on May 5, 2011 14:23:48 GMT 1
The fact is, the normal laws of spacetime break down in the centre of a black hole so that all that can be offered at the moment is speculation. Some think our universe originated in a black (white?) hole but we need further mathematical and experimental models to be more confident.
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Post by speakertoanimals on May 9, 2011 14:52:53 GMT 1
Black holes themselves DON'T really require all that weird curved space stuff, or 'holes' in spacetime..............
All that ia really required is:
Gravity adds, so you pile up more stuff, the weight on top of the stuff at the bottom of the pile increases and increases.
Matter isn't infinitely strong.
To look at it another way, since light is effected by gravity, AND has a measurable finite speed, then no surprise if you can contemplate an object where the 'escape velocity' at the surface is so great that even light can't get out.
The exact details of what such an object 'looks like' depends on your exact physical theory for space and for gravity. So, with classical theories of gravity, we have infinite-curvature singularity at the centre in simplest case. For other possible theories (ie spacetime not actually continuous at smallest scales), then what is at the centre of such an object is going to look rather different.
But a 'no escape even for light' kind of object was postulated way before general relativity.
Not quite -- big bang singularity of a different type to usual black hole singularity.
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