Indeed. However, I was implying that there is no such thing as "infinite density", but that the matter would compress in on itself when achieving specific points in mass up to a point where the mass would reach a critical state where a massive explosion would be triggered instead.
I thought we did Black Holes to death earlier... but evidently they still lure us "siren-like" onto the rocks. 
Surely the only issue with them is the two (accelerating) relativistic observer reference frames we use, which happen to involve that troublesome infinity. And extreme tidal forces, which is not something we usually worry about too much. But as a sea-faring Pompey lad, I am OK on tides.
Einstein Field Equations - for beginners! - YouTube
Taking a break at 53:12 in the Einstein Field Equations for Beginners. Getting a bit heavy, but we have got the metric tensor (which distorts triangles, AFAIK) out of the way. Onto the Ricci tensor. Can't wait!
Surely the only issue with them is the two (accelerating) relativistic observer reference frames we use, which happen to involve that troublesome infinity. And extreme tidal forces, which is not something we usually worry about too much. But as a sea-faring Pompey lad, I am OK on tides.
Einstein Field Equations - for beginners! - YouTube
Taking a break at 53:12 in the Einstein Field Equations for Beginners. Getting a bit heavy, but we have got the metric tensor (which distorts triangles, AFAIK) out of the way. Onto the Ricci tensor. Can't wait!
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Come on Steve! We mere mortals need an explanation of what a metric tensor is!
On a Flat Space, the Pythagoras Theorum (you know, the square on the hypoteneuse equals the sum of the squares on the other two sides) holds true. You can draw a right angled triangle on a flat piece of paper to prove it.
However, things get interesting when we try to draw right angled triangles on a Curved Space such as a Sphere. Then we can even draw triangles where all three angles are right angles and the Pythagoras Theorum no longer holds true!
And that's where the Metric Tensor comes in!
The Metric Tensor can be thought of as the device which makes corrections to the Pythagoras Theorem when the Right Angled Triangle is on a Curved Space instead of a Flat Space!
The Ricci Tensor is the mathematical device that controls the growth rate of the volume of space bounded by a sphere and is a contraction of the Riemann Curvature Tensor.Onto the Ricci tensor. Can't wait!
I'll not even attempt to explain the significance of the Ricci Tensor!
What's all this Curvature stuff got to do with General Relativity? 
At school we were taught Euclidean Geometry. That's the geometry in which the three angles of a triangle add to 180 degrees.
However, the geometry of spacetime is non-Euclidean. For example, if a triangle is constructed out of three rays of light, then the angles do not necessarily add up to 180 degrees because of the effect of gravity.
This led Einstein, in his theory of General Relativity, to introduce the idea of spacetime Curvature.
Einstein's idea that spacetime is curved was later verified by the observation of the slight bending of starlight by the Sun during a solar eclipse in 1919.
At school we were taught Euclidean Geometry. That's the geometry in which the three angles of a triangle add to 180 degrees.
However, the geometry of spacetime is non-Euclidean. For example, if a triangle is constructed out of three rays of light, then the angles do not necessarily add up to 180 degrees because of the effect of gravity.
This led Einstein, in his theory of General Relativity, to introduce the idea of spacetime Curvature.
Einstein's idea that spacetime is curved was later verified by the observation of the slight bending of starlight by the Sun during a solar eclipse in 1919.
For light grazing the surface of the sun, the approximate angular deflection is roughly 1.75 arcseconds (approximately 0.0005 degrees).
Eddington experiment - Wikipedia
The more massive the object, the more the light will bend, of course.
Gravitational lens - Wikipedia
Eddington experiment - Wikipedia
The more massive the object, the more the light will bend, of course.
Gravitational lens - Wikipedia
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If we can see its event horizon is it as physically large as a typical galaxy, or a tiny point that's as massive as a typical galaxy?
Daniel Fleisch gives a very succinct introduction to what tensors are here (12 minutes)
What's a Tensor? - YouTube
I have his 'Introduction to Maxwell's Equations' and 'Introduction to Schrodinger's Equation' student books - fantastic if you want to get up to speed as a budding armchair amateur physicist like me!
What's a Tensor? - YouTube
I have his 'Introduction to Maxwell's Equations' and 'Introduction to Schrodinger's Equation' student books - fantastic if you want to get up to speed as a budding armchair amateur physicist like me!
I gave a similar link and referred to SLABs in post #4666.
'Stupendously large' black holes could grow to truly monstrous sizes | Space
Mind boggling!
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When we talk about the size of a black hole, we mean the radius of the event horizon, or Schwarzschild radius.
It is the Schwarzchild radius that might possibly (its only sensationalist conjecture) be as large as a galaxy, but it is a geometrical largeness, not a physical largeness.
All of the mass of a SLAB is concentrated at the singularity which has no physical dimensions whatsoever.
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P.S. There's currently no evidence that stupendously large black holes (SLABS) are real.
And they "could be as large as a entire galaxy" is simply sensationalism!
My link looks at the idea sensibly. 'Stupendously large' black holes could grow to truly monstrous sizes | Space
And they "could be as large as a entire galaxy" is simply sensationalism!
My link looks at the idea sensibly. 'Stupendously large' black holes could grow to truly monstrous sizes | Space
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