Physics geekery

[demagogue]

I only wonder what other problems it would have though. wink.gif

 

On that, one of the most interesting thing I read ("know" is too strong a word ) about black holes, sort of related to what you guys were talking about, is that the measure of its entropy is proportional not to its volume/density (like you'd think; like practically every other body of stuff out there), but to the surface area of the event horizon.

 

This is how I understand it (somebody correct me if I'm off). So a shorthand way to understand entropy is like a measure of the amount of "signal information" that will be lost as it goes up; e.g., melting ice or heating air in a balloon, the organization/information it holds gets dispersed or smoothed out (to more undifferentiated stuff) by the amount entropy goes up. Usually, it's proportional to overall volume/density changes; and it's supposed to always net increase over time.

 

So with black holes, entropy would be going down because everything is getting compacted into a singularity, about as pure a "signal" as you can get. But it's counteracted by the Hawking radiation raising entropy, as some mass gets scattered back out into space virtually at random (very high entropy). But that radiation comes off, for the same reasons mentioned above, in proportion to the surface area of the event horizon. When stuff crosses it, you get the radiation, not when it gets "inside" (unlike a star, where you get fusion radiation when its volume is squeezed).

 

But, so the paradox goes, if that's right, then you still have a problem because entropy is going down according to the volume -/density +, but back up according to just the surface area increase, which is less. Still some missing entropy to account for somewhere to balance it out. But even aside from that paradox, it's still just weird that the amount of information in a black hole is set by its surface area, not what's inside. How does that work out?

 

I remember one guy comparing it to a movie screen. What's important as far as the signal is what gets projected onto the screen (the event horizon), not the "real movie" itself (the mass inside the singularity, or whatever it is). The information of a movie only makes sense as its displayed on the 2D screen, so to speak. Whatever's going on, it's very interesting and very different from the way most everything else works. I guess we'll have to wait until they come up with quantum gravity to hear the answer.

Edited June 27, 2007 by demagogue

[Schatten]

Yup! That's what I meant. I only wonder what other problems it would have though.

I talked with a quantum-mechanist (I just made that word up, it has a nice steam-punk ring to it) about it, and he cauterized it with ockham's razor: why should massive particles behave like that?

While for an outside observer the particles would slow down infinitely due to general realtivity, from the POV of the particle, the event horizon is no barrier whatsoever.

[sparhawk]

Let's assume that the speed of light is the highest speed anything can achieve. It would require an infinite amount of energy to accelerate a particle up to the speed of light. Now where should the energy come from? The event horizon of a black hole is assumed to be the area where the speed of light is exceeded, which also would mean that inside that event horizon, either the speed always stays there, or is even higher. Nevertheless, if a particle is grabbed by a black hole, we would have to think that it managed to gain the speed of light, right? But we know that that shouldn't be possible. On the other hand, if a particle accelerates towards the event horizon it can get nearer and nearer but never actually reaches it ebcause time slows down more and more, the nearer it gets. The result would be an object as you said. It has a surface, but no inside.

Mathematically the infinity arises, because from Newton we know that we can treat matter as if all it's gravitational force is contained in an infitly small center point, but this is just a convention. Obviously this is not true for real matter, because the matter is distributed throughout the whole object but it's more convenient to assume that the force is in a point.

 

Where did you find that quantum physicist?

[Schatten]

Let's assume that the speed of light is the highest speed anything can achieve. It would require an infinite amount of energy to accelerate a particle up to the speed of light. Now where should the energy come from?

Up to the Limes (german math term, not citrus fruit) of SOL, that would be gravity.

 

The event horizon of a black hole is assumed to be the area where the speed of light is exceeded, which also would mean that inside that event horizon, either the speed always stays there, or is even higher.

IIRC, the event horizon is the point where the escape velocity gets to high for light to get away- I don't think that this assumes that speeds in excess of SOL are involved at all.

 

Nevertheless, if a particle is grabbed by a black hole, we would have to think that it managed to gain the speed of light, right? But we know that that shouldn't be possible. On the other hand, if a particle accelerates towards the event horizon it can get nearer and nearer but never actually reaches it ebcause time slows down more and more, the nearer it gets. The result would be an object as you said. It has a surface, but no inside.

For an outside observer, yes. From POV of the particle, nothing happens since time relative to itself moves normaly. It would accellerate to near SOL, pass the evnt horizon and then fall into that damned singularity.

 

Mathematically the infinity arises, because from Newton we know that we can treat matter as if all it's gravitational force is contained in an infitly small center point, but this is just a convention. Obviously this is not true for real matter, because the matter is distributed throughout the whole object but it's more convenient to assume that the force is in a point.

That's one of the main problems of the whole thing. All observations above depend on relativity and the standard model. Both models can't describe the physics involved accurately, so we can't even apply theories based on them.

 

Where did you find that quantum physicist?

On IRC.

He's currently busy researching a modulation in the hadron jets produced in quark/anti-quark creation when two protons collide. Fascinating stuff, he thinks the modulation isn't caused by the jets themselves, so I guess there must be an external force causing it.

[sparhawk]

IIRC, the event horizon is the point where the escape velocity gets to high for light to get away- I don't think that this assumes that speeds in excess of SOL are involved at all.

 

Well, I don't know. But even if inside there is still only SOL as a limit, it would apply. Doesn't really matter IMO. On the other hand, if you consider how our universe must appear to an outside observer, I think it would also look like a black hole to it.

 

For an outside observer, yes. From POV of the particle, nothing happens since time relative to itself moves normaly. It would accellerate to near SOL, pass the evnt horizon and then fall into that damned singularity.

 

But it would never reach it. That's the point. Time is slowing down. From the point of view of the particle, it means that it would continue to fall, but it would take ever longer and longer to to get even a tiny fraction further. If the particle is sped up to approach the center, the outside world would speed by in incredible speed as well. This means that either the universe might collapse before it reaches the infinity, or the black hole might evaporate. In either case the particle doesn't need to reach any infinite center point, because it can not reach it. There is not enough energy. From this conclusion, I would expect that a black hole's event horizon would only be populated by massless particles. Any massive particle, would be stopped before it could reach that event horizon, and thus would create a kind of second layer around it.

 

That's one of the main problems of the whole thing. All observations above depend on relativity and the standard model. Both models can't describe the physics involved accurately, so we can't even apply theories based on them.

 

This would be only true if you apply it all the way down. Maybe there is a another term involved, that would stop it and avoid the infitism.

 

 

On IRC.

 

Guess I should also use IRC: