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<blockquote data-quote="wolsty" data-source="post: 21194" data-attributes="member: 175166">There's little doubt that black holes play a crucial role in holding galaxies together. As to the size of the one at the centre of ours, I'd be surprised if it's as small as a football, although the compression of matter in black holes is very intense.&nbsp; So intense, that 'normal' laws of physics break down.&nbsp; It's possible to work out the mass and dimension if you have good enough Maths.&nbsp; I'm not proficient at hard sums, so I leave it to the boffins and just read the popular science.&nbsp; Dark matter accounts for about 90% of the matter in the universe - at least if current theories about expansion/contraction/big bang/big crunch are valid.&nbsp; But what it's composed of is still open to considerable debate.&nbsp; I've seen it suggested that black holes can 'end' in one of two ways: by 'explosion' when they reach a 'critical mass' - scattering matter of all descriptions across the universe, or by 'evaporation' ie the gradual loss of matter through quantum processes.&nbsp; The 'explosion' hypothesis seems to have a strong similarity to the Big Bang, in that some authorities suspect that the centre of a black hole is a singularity and the BB is supposed to have begun with the 'explosion' of a singularity.I'm with you, BC; my money's on a cycle of events being the explanation.Some difficult ideas here.&nbsp; But it's as good a way of straining your brain as any I know of.<img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/smile.png"&nbsp; class="smilie" loading="lazy" alt=":)" title="Smile&nbsp; &nbsp; :)" data-shortname=":)" /> <img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/smile.png"&nbsp; class="smilie" loading="lazy" alt=":)" title="Smile&nbsp; &nbsp; :)" data-shortname=":)" /> <img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/smile.png"&nbsp; class="smilie" loading="lazy" alt=":)" title="Smile&nbsp; &nbsp; :)" data-shortname=":)" /></blockquote>

[QUOTE="wolsty, post: 21194, member: 175166"] There's little doubt that black holes play a crucial role in holding galaxies together. As to the size of the one at the centre of ours, I'd be surprised if it's as small as a football, although the compression of matter in black holes is very intense. So intense, that 'normal' laws of physics break down. It's possible to work out the mass and dimension if you have good enough Maths. I'm not proficient at hard sums, so I leave it to the boffins and just read the popular science. Dark matter accounts for about 90% of the matter in the universe - at least if current theories about expansion/contraction/big bang/big crunch are valid. But what it's composed of is still open to considerable debate. I've seen it suggested that black holes can 'end' in one of two ways: by 'explosion' when they reach a 'critical mass' - scattering matter of all descriptions across the universe, or by 'evaporation' ie the gradual loss of matter through quantum processes. The 'explosion' hypothesis seems to have a strong similarity to the Big Bang, in that some authorities suspect that the centre of a black hole is a singularity and the BB is supposed to have begun with the 'explosion' of a singularity. I'm with you, BC; my money's on a cycle of events being the explanation. Some difficult ideas here. But it's as good a way of straining your brain as any I know of. :) :) :) [/QUOTE]

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