Black Hole problems?!??!

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HexHammer
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Black Hole problems?!??!

Postby HexHammer » Fri Apr 21, 2017 4:40 am

I've often heard that laws of physics breaks down at Black Holes ..but they never describe the problems, anyone could shed some light on this?

Thanks!

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Greta
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Re: Black Hole problems?!??!

Postby Greta » Fri Apr 21, 2017 8:19 am

My simple understanding, that more educated members can flesh out (or contradict) is that the singularity is the anomaly:
In the centre of a black hole is a gravitational singularity, a one-dimensional point which contains a huge mass in an infinitely small space, where density and gravity become infinite and space-time curves infinitely, and where the laws of physics as we know them cease to operate.


The theoretical singularity that comes from black hole equations is of zero size, infinite density and gravity. Clearly something else is going on that we don't understand because those kinds of infinities are seemingly impossible.

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henry quirk
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Postby henry quirk » Fri Apr 21, 2017 3:01 pm

The laws of physics are really just descriptions of how matter works and interacts in certain (currently uniform and apparently universal) conditions.

A singularity is a point where conditions differ from the (current) norm leading to different descriptions.

Bottom line: 'laws of physics' is a sloppy, misleading, construct.

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Cerveny
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Re: Black Hole problems?!??!

Postby Cerveny » Fri Apr 21, 2017 9:48 pm

There are no singularities in the real world. Consider (for example) the black hole as a substantial defect (cavity?) in the structure of aether (in physical space/vacuum)...

Impenitent
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Re: Black Hole problems?!??!

Postby Impenitent » Sat Apr 22, 2017 1:23 am

irresistible black holes are centered in chocolate donuts...

-Imp

uwot
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Re: Black Hole problems?!??!

Postby uwot » Sat Apr 22, 2017 1:53 pm

HexHammer wrote:I've often heard that laws of physics breaks down at Black Holes ..but they never describe the problems, anyone could shed some light on this?

Thanks!

It's a load of hyperbolic bollocks, really. It's not the blackhole so much as the hypothetical 'singularity'. A singularity is a point which has no physical dimensions: no height, no width, no depth. You can describe a point like that mathematically, but to say it exists physically is nonsense. Then to make it even sillier, there is no volume, but it contains matter, so the density, or curvature of spacetime, is infinite. It is just showboating when physicists talk in terms of 'The Laws of Physics' in this way. All it really means is that you can describe things in maths that simply don't happen. There is no perfect triangle. You cannot travel at the speed of light. You can't have x oranges, where x is the square root of minus one. What we call the laws of physics are mathematical relationships that we have discovered; maths includes 0 and infinity; reality doesn't.

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Noax
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Re: Black Hole problems?!??!

Postby Noax » Sat Apr 22, 2017 2:54 pm

uwot wrote:It's a load of hyperbolic bollocks, really. It's not the blackhole so much as the hypothetical 'singularity'. A singularity is a point which has no physical dimensions: no height, no width, no depth. You can describe a point like that mathematically, but to say it exists physically is nonsense. Then to make it even sillier, there is no volume, but it contains matter, so the density, or curvature of spacetime, is infinite. It is just showboating when physicists talk in terms of 'The Laws of Physics' in this way. All it really means is that you can describe things in maths that simply don't happen. There is no perfect triangle. You cannot travel at the speed of light. You can't have x oranges, where x is the square root of minus one. What we call the laws of physics are mathematical relationships that we have discovered; maths includes 0 and infinity; reality doesn't.
Interesting assertion, especially since no spatial extension has ever been measured for matter, so it is interesting to assert that actual volume must be consumed by it.
Suppose I drop a 1KG water balloon into a black hole. What would be its finite weight when (what's left of) it reaches the bottom? What force would supply this weight? On Earth, EM force supplies weight. Without EM, everything would be in freefall and weigh nothing, as does everything in orbit. OK, if we had no orbital velocity, eventually nuclear forces would resist falling beyond a certain density, and we'd have weight again, about a billion times the weight given with EM. There must be a 5th force that is repulsive and stronger than gravity at these densities, that would prevent further collapse of any finite volume of matter. Absent that force, no finite volume can be maintained.

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Re: Black Hole problems?!??!

Postby uwot » Sat Apr 22, 2017 3:45 pm

Noax wrote:Interesting assertion, especially since no spatial extension has ever been measured for matter, so it is interesting to assert that actual volume must be consumed by it.

Well, yes and no. See what you make of this: https://www.theguardian.com/science/lif ... is-a-quark We can go into the actual papers if you'd rather.
Noax wrote:Suppose I drop a 1KG water balloon into a black hole. What would be its finite weight when (what's left of) it reaches the bottom?

Nothing. If it's in the middle, there is little or no net force in any direction.
Noax wrote:What force would supply this weight? On Earth, EM force supplies weight. Without EM, everything would be in freefall and weigh nothing, as does everything in orbit.

What is different about EM on the surface of Earth or in orbit?
Noax wrote:OK, if we had no orbital velocity, eventually nuclear forces would resist falling beyond a certain density, and we'd have weight again, about a billion times the weight given with EM. There must be a 5th force that is repulsive and stronger than gravity at these densities, that would prevent further collapse of any finite volume of matter. Absent that force, no finite volume can be maintained.

So you are asserting that there is such a thing as finite volume?

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Noax
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Re: Black Hole problems?!??!

Postby Noax » Sat Apr 22, 2017 9:32 pm

uwot wrote:Well, yes and no. See what you make of this: https://www.theguardian.com/science/lif ... is-a-quark We can go into the actual papers if you'd rather.
Says there's an upper limit, and found no lower one. Physics has an interesting definition of what it means to 'hit' something. It doesn't mean physical contact.
Nothing. If it's in the middle, there is little or no net force in any direction.
Not in the middle, since there's a finite size thingy in the middle on which our water sits and has weight. Or does the ocean weigh little to nothing because it is distributed? Weight is not net force.
[/quote]What is different about EM on the surface of Earth or in orbit?[/quote]In orbit, EM does not resist the force of gravity. You fall. On the surface, EM force prevents you from falling, thus giving you weight. That EM force prevents gravity from smushing Earth into a clump about the size of a sports stadium where other forces will eventually halt the collapse to even smaller sizes.
Noax wrote:OK, if we had no orbital velocity, eventually nuclear forces would resist falling beyond a certain density, and we'd have weight again, about a billion times the weight given with EM. There must be a 5th force that is repulsive and stronger than gravity at these densities, that would prevent further collapse of any finite volume of matter. Absent that force, no finite volume can be maintained.

So you are asserting that there is such a thing as finite volume?
What?? A 1-meter cube has a finite volume of a cubic meter. So sure, but not sure how you got that from the above statement, where I was asking what would prevent gravity from collapsing a sufficiently dense thing down to a singularity? Why is that absurd?

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Re: Black Hole problems?!??!

Postby uwot » Sun Apr 23, 2017 3:10 am

Noax wrote:Says there's an upper limit, and found no lower one. Physics has an interesting definition of what it means to 'hit' something. It doesn't mean physical contact.

I've tried to illustrate this on the 5th page of What is the universe made of? http://willijbouwman.blogspot.co.id
Noax wrote:Not in the middle, since there's a finite size thingy in the middle on which our water sits and has weight.

Well, that is the issue that HexHammer was asking about. Does a singularity have finite size? Mathematically, it doesn't have to. When you are dealing with numbers, popping a 0 in isn't a problem; it only gets silly, if you are talking about something physical existing, but which has no physical size.
Noax wrote:Or does the ocean weigh little to nothing because it is distributed? Weight is not net force.

Weight, as I understand it, is the net force a given gravitational field exerts on a mass.
Noax wrote:In orbit, EM does not resist the force of gravity. You fall. On the surface, EM force prevents you from falling, thus giving you weight. That EM force prevents gravity from smushing Earth into a clump about the size of a sports stadium where other forces will eventually halt the collapse to even smaller sizes.

EM is the stuff that keeps the thing in orbit together. I get that EM is the force that overcomes gravity, but that's because of its role in making 'solid' objects, like planets and people.
Noax wrote:What?? A 1-meter cube has a finite volume of a cubic meter. So sure, but not sure how you got that from the above statement, where I was asking what would prevent gravity from collapsing a sufficiently dense thing down to a singularity? Why is that absurd?
Sorry, left out the context; we were talking about subatomic particles and singularities.

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Noax
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Re: Black Hole problems?!??!

Postby Noax » Sun Apr 23, 2017 3:44 am

uwot wrote:Well, that is the issue that HexHammer was asking about. Does a singularity have finite size? Mathematically, it doesn't have to. When you are dealing with numbers, popping a 0 in isn't a problem; it only gets silly, if you are talking about something physical existing, but which has no physical size.
It does admittedly push the definition of 'to exist'. For instance, time ends at the center of a black hole. How can you say something exists anymore at the end of time? The usual rules don't apply, and that's what they mean by the singularity: A boundary beyond which the rules do not apply.

Weight, as I understand it, is the net force a given gravitational field exerts on a mass.
Then the people on the space station would not be weightless. There's definitely a gravitational force on them (and nothing countering that force, so it is all net-force), but weight comes from something resisting the acceleration the gravitational force would otherwise give you. The space station guys accelerate much more than I do here on the surface, so I have weight and they don't. My net-force is much less, since EM of the floor counters the gravity pulling the other way.

Sorry, left out the context; we were talking about subatomic particles and singularities.
OK. No actual volume consumed by mass has ever been measured. Your link describes an upper limit to it, but efforts to 'hit' a quark just means getting close enough to it to deflect something most unlikely to hit it. What, a neutrino or something? Not sure what they were throwing at the quarks to determine their target cross section.

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Re: Black Hole problems?!??!

Postby uwot » Mon Apr 24, 2017 10:09 am

Noax wrote:It does admittedly push the definition of 'to exist'. For instance, time ends at the center of a black hole.

What do you suppose this means?
Noax wrote:How can you say something exists anymore at the end of time? The usual rules don't apply, and that's what they mean by the singularity: A boundary beyond which the rules do not apply.

In my view, it is just gibberish from people who by profession, explain things in abstract terms, and while some do this brilliantly, they're not always great at using natural language. Putting it into simple terms, it just means nothing can move, so nothing happens.
Noax wrote:...but weight comes from something resisting the acceleration the gravitational force would otherwise give you.
Well yes, I get what you are saying about EM, but if a space station suddenly stops, the fact that an astronaut weighs nothing isn't going to prevent them being splattered against the wall.

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Noax
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Re: Black Hole problems?!??!

Postby Noax » Mon Apr 24, 2017 2:59 pm

uwot wrote:
Noax wrote:It does admittedly push the definition of 'to exist'. For instance, time ends at the center of a black hole.
What do you suppose this means?
In natural language with time separate from space, I think it means the singularity in black holes do not yet exist, so don't worry about the math not describing reality.
In my view, it is just gibberish from people who by profession, explain things in abstract terms, and while some do this brilliantly, they're not always great at using natural language. Putting it into simple terms, it just means nothing can move, so nothing happens.
A reasonable example of why natural language fails. Change defines time in physics, so time is indistinguishable from not-time without something happening. The natural language description becomes the meaningless mathematical description, describing nothing real. The cosmological argument rests on applying natural language description beyond the bounds of what the language describes.
Well yes, I get what you are saying about EM, but if a space station suddenly stops, the fact that an astronaut weighs nothing isn't going to prevent them being splattered against the wall.
That's weight due to massive acceleration, not due to resistance to gravity. If the space station was stationary, whatever force held it stationary would be the force responsible for weight. In a black hole, no force is strong enough to prevent further reduction of any displacement between matter.
It is like the expansion of space in reverse. Galaxies are not actually moving away from us, its just that the space between them is expanding. Similarly, in a black hole, the space is contracting, and at the end of time, there will only be one place for everything to be. That's about the best grasp I have on it, in as natural as I can make my terms.


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