cortezthekiller said:

Au contraire.  The theory that predicts black holes actually do predict them to infinitely dense.  That, I believe, is actually in the definition of a black hole.  Because it is so (infinitely) dense, the gravity well it creates literally rips a hole in space time.

I know it's hard to put your mind around, and it is definitely counter-intuitive.  Even physicists have a hard time with this one, but if black holes do exist (and we are nearly 100% certain they do), they are infinitely dense!

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Seuss said:

> "The center of a black hole is infinitely dense."

The issue is a disconnect between the mathematical meaning of infinite and the layman meaning of infinite.  Most people think of infinite as a quantity, which is incorrect from a mathematical viewpoint.

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The word either has meaning or it doesn't. Density is determined by a ratio between mass and size. It's measurable. If they said something like 'beyond our capacity to measure' I could dig it. If it's not a quantity then they shouldn't use it to describe density.

Btw, from a mathematical viewpoint, can you explain the word to me, as you understand it?

Quote:

To a distant observer clocks near a black hole appear to tick more slowly than those further away from the black hole. Due to this effect (known as gravitational time dilation) the distant observer will see an object falling into a black hole slow down as it approaches the event horizon, taking an infinite time to reach it. At the same time all processes on this object slow down causing emitted light to appear redder and dimmer, an effect known as gravitational red shift. Eventually, the falling object becomes so dim that it can no longer be seen, at a point just before it reaches the event horizon.

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TheFakeSunRa said:

If they were really infinitely dense they would have infinite gravitational pull which would create a situation where I wouldn't be able to type this response.

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VoidMasamune said:

...Why do they have event horizons?

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Doc_T said:

Because of the definition of event horizon. A black hole has an event horizon the way a planet has an equator. It's part of how we talk about it.

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Quote:

Mass merely increases linearly, the volume increases at a greater rate than mass. Thus, density decreases for increasingly larger radii of black holes. One should be aware however that this phenomenon results from scientific definitions and does not necessarily manifest itself as a real physical property.

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Seuss said:

> Btw, from a mathematical viewpoint, can you explain the word to me, as you understand it?

Although different areas of mathematics use it (or define it) differently, the typical definition used in most calculus treats infinity as an unbound limit.  You would never have "infinite density", instead "density approaches infinity" or "the limit of density is infinity".

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DieCommie said:

TheFakeSunRa said:

If they were really infinitely dense they would have infinite gravitational pull which would create a situation where I wouldn't be able to type this response.

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I dont think so.  The center of a black hole is infinity dense because the space there is infinitely 'compacted' and you get a singularity (a discontinuity in space-time).  A singularity happens when you divide by zero.  Mass density is mass divided by volume, so the structure of space-time bends so much that it has no volume at the center.  It still has a finite amount of mass though.

Remember - nature need not conform to our intuition or our preconceived notions.  This is one of the big stumbling blocks many students have to studying science.

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That might be a bit over my head but it's really well explained and cool to consider. Thanks.

DieCommie said:

Remember - nature need not conform to our intuition or our preconceived notions.

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That about says it all right there.  If you refuse to accept a black hole's calculated density, make sure you steer clear of quantum physics because that will have you pulling your hair out by the handful