JEROME - Black holes do not exist

[aggle-rithm]

Nobody, including Phil Plait of Bad Astronomy, has been able to explain to me how they can ever form. My problem: as matter approaches the even horizon, where the escape velocity reaches the speed of light, from OUR point of view it falls at an asymptotically slower rate... in fact, from our point of view, nothing ever reaches it.

The perception of time between the observer and the observed depends not only on the relative speeds of the two, but on the Doppler distortion of the light bouncing back and forth between them. From the point of view of a person approaching an event horizon, light coming from behind him is extremely red-shifted by the increased gravity, while light coming from the edge of the event horizon to the outside universe would be extremely blue-shifted. The effect would be that time would appear to speed up for the observed (the one crossing the event horizon), and slow down for the observer.

In fact, in a very real sense, time IS slowing down and speeding up, since the frequency of the light waves serves as a clock that marks events in time.

AT the event horizon, the distortion becomes infinite, so of course time comes to a stop completely from the viewer's perspective.

To the more knowledgeable people than I in this group (and I know you're out there), feel free to correct me if I'm wrong on any of these points.

 

[aggle-rithm]

Obviously, I find this a fascinating topic. However, it's entirely possible that my knowledge of physics, astronomy, etc., is not as comprehensive as I think it is. I would appreciate anyone correcting me if I'm wrong, and I apologize if I've unwittingly misled anyone.

 

[sol invictus]

In fact, in a very real sense, time IS slowing down and speeding up, since the frequency of the light waves serves as a clock that marks events in time.

AT the event horizon, the distortion becomes infinite, so of course time comes to a stop completely from the viewer's perspective.

To the more knowledgeable people than I in this group (and I know you're out there), feel free to correct me if I'm wrong on any of these points.

That's perfectly correct. But one should remember that there is more than one kind of clock we could use. Light rays bouncing back and forth between a distant observer and something near the horizon are one kind of clock, and that kind does indeed stop at the horizon (because the light rays take forever to bounce back).

But that is exactly what would happen to sound waves in water at a sonic horizon (where the water flow speed becomes equal to the speed of sound) - if you used sonar pulses as a clock, you'd say times stops at a sonic horizon, for the same reason. Clearly if you used a different kind of clock, like an ordinary watch, nothing like that would happen. But the thing about general relativity is that there is no preferred way to measure time - different observers will disagree on the time-ordering of events, for example - so you just want to pick a convenient one for the problem at hand.

 

[GreyICE]

That's perfectly correct. But one should remember that there is more than one kind of clock we could use. Light rays bouncing back and forth between a distant observer and something near the horizon are one kind of clock, and that kind does indeed stop at the horizon (because the light rays take forever to bounce back).

But that is exactly what would happen to sound waves in water at a sonic horizon (where the water flow speed becomes equal to the speed of sound) - if you used sonar pulses as a clock, you'd say times stops at a sonic horizon, for the same reason. Clearly if you used a different kind of clock, like an ordinary watch, nothing like that would happen. But the thing about general relativity is that there is no preferred way to measure time - different observers will disagree on the time-ordering of events, for example - so you just want to pick a convenient one for the problem at hand.

Actually, there is a preferential way - cause precedes effect. All observers always agree on this, whatever else they may or may not agree on. Event horizons, if you could see past them, would violate this rule - effect would precede cause.

 

[Ziggurat]

Actually, there is a preferential way - cause precedes effect. All observers always agree on this, whatever else they may or may not agree on. Event horizons, if you could see past them, would violate this rule - effect would precede cause.

So what? If you could travel faster than light, causality would also be violated. But it doesn't matter, because you can't. The idea that it takes an infinite amount of time to cross the event horizon is largely an artifact of using the Schwarzchild metric, which has a coordinate singularity at the even horizon. The important question is the proper time, and if you pick a coordinate system (like Kruskal coordinates) which don't have a coordinate singularity at the event horizon, you find that nothing funny happens when crossing.

 

[GreyICE]

So what? If you could travel faster than light, causality would also be violated. But it doesn't matter, because you can't.

I find that faster than light travel is not ruled out by General Relativity, actually. Just accelerating to faster than light velocity.

The idea that it takes an infinite amount of time to cross the event horizon is largely an artifact of using the Schwarzchild metric, which has a coordinate singularity at the even horizon. The important question is the proper time, and if you pick a coordinate system (like Kruskal coordinates) which don't have a coordinate singularity at the event horizon, you find that nothing funny happens when crossing.

Of course that leads to wormholes. I really question your definition of "Nothing funny." So odd things happen in whatever coordinate system.

 

[sol invictus]

Actually, there is a preferential way - cause precedes effect. All observers always agree on this, whatever else they may or may not agree on. Event horizons, if you could see past them, would violate this rule - effect would precede cause.

The choice of coordinates has nothing to do with whether you can see the horizon. Seeing the horizon or not is a physical fact, which cannot (and does not) depend on coordinates.

The point is that the statement that time stops at the horizon is true only in one coordinate system - the one in which you measure time by lightrays bounding back and forth. But there's no particular reason to measure time that way.

Another way to debunk this is to notice that even in flat, empty space, one can pick coordinates (they're called Rindler coordinates) which at an arbitary surface behave precisely like those coordinates in the black hole metric near the horizon. So time appears to stop, etc., but just at some imaginary surface you can choose as you like.

Remember - coordinates are just labels for points in spacetime. You can choose them so they have a singularity somewhere, but that doesn't necessarily mean a thing about the underlying spacetime.

 

[Ziggurat]

I find that faster than light travel is not ruled out by General Relativity, actually. Just accelerating to faster than light velocity.

That's true under special relativity as well. It still violates causality. While relativity alone does not enforce causality, I think it's still a pretty good bet that nothing violates it.

Of course that leads to wormholes.

Not really. It demonstrates that wormholes are valid solutions, but solutions which evolve from collapsing stars never produce worm holes.

 

[arthwollipot]

I find that faster than light travel is not ruled out by General Relativity, actually. Just accelerating to faster than light velocity.

AFAIK, it is ruled out by Special Relativity, which is, as the name suggests, a special case of GR.

 

[GreyICE]

That's true under special relativity as well. It still violates causality. While relativity alone does not enforce causality, I think it's still a pretty good bet that nothing violates it.

I would hope not. Except quantum mechanics of course, since certain elements of causality there seem to propegate faster than light. Or maybe not. All in all, we really hope nothing violates linear causality, because that opens headache territory.

Not really. It demonstrates that wormholes are valid solutions, but solutions which evolve from collapsing stars never produce worm holes.

Still, saying nothing funny happens is not, strictly speaking, true. In any coordinate system, Black Holes produce funny solutions.

AFAIK, it is ruled out by Special Relativity, which is, as the name suggests, a special case of GR.

Yes, in that it cannot be applied to anything that is moving, at all (or more accurately, in a non-inertial reference frame). Or in a gravitational field. So it is VERY special relativity, as in trying to apply it too far makes you Special.

Don't mistake an approximation that is useful for an actual theory. It breaks down on very small scales or in varying gravitational fields. It definitely is more widely applicable than Newtonian Mechanics, and is similarly internally consistant, but it's not perfect.

 

[arthwollipot]

Yes, in that it cannot be applied to anything that is moving, at all (or more accurately, in a non-inertial reference frame). Or in a gravitational field. So it is VERY special relativity, as in trying to apply it too far makes you Special.

Don't mistake an approximation that is useful for an actual theory. It breaks down on very small scales or in varying gravitational fields. It definitely is more widely applicable than Newtonian Mechanics, and is similarly internally consistant, but it's not perfect.

I don't think I (or anyone else) ever claimed that it was.

 

[GreyICE]

I don't think I (or anyone else) ever claimed that it was.

Well then why claim it rules out anything? Approximations, by definition, can never rule out anything, because they're wrong. It's like saying newtonian mechanics rules out objects having an increased mass as they accelerate (from an inertial frame of reference). It's true, but it's also meaningless.

What I guess I am trying to ask is, if you know that special relativity isn't a theory, then why say it rules out anything?

 

[arthwollipot]

Well then why claim it rules out anything? Approximations, by definition, can never rule out anything, because they're wrong. It's like saying newtonian mechanics rules out objects having an increased mass as they accelerate (from an inertial frame of reference). It's true, but it's also meaningless.

What I guess I am trying to ask is, if you know that special relativity isn't a theory, then why say it rules out anything?

Not too sure exactly what it is you're asking here. Special relativity is a theory, as far as I know, and as far as I know it rules out travelling faster than light. But I'm not an expert, and would be happy to be corrected by someone with letters after their name.

 

[MattusMaximus]

Ii is not my fault that you do not know what redshift is and why it is important to understand what it means if it is not an accurate measurement.

Wow... you're just sooo smart... Bravo.



I know precisely what redshift is and is not - if I didn't know what it was I wouldn't be qualified to teach college-level physics & astronomy courses on the topic.

I'm trying to gauge whether or not you have any clue as to what you're saying. And since you seem to refuse to even define the terms involved in this discussion (such as your vague reference to some kind of "redshift anomaly"), I can only conclude that you either cannot or will not define it. Leaving the term vague and ambiguous allows you to sound (to the uninformed) like you know what you're saying in addition to moving the goalposts in the discussion whenever you like. Sorry, no dice.

Based upon your refusal to take part in any kind of meaningful and/or constructive discussion on this point means that our conversation is at an end.

If/when you ever feel like actually talking seriously about the topic, I'll be here... lurking.

 

[MattusMaximus]

I think what we have learned is that for Jerome evidence is meaningless. His arguments are simply props in his ritualized self-deluding performance. The substance of the arguments themselves are, I think it's safe to conclude, relatively meaningless to him. All that matters is that he be in disagreement with some fundamental, well established and widely accepted aspect of learning. This allows him to imagine himself as uniquely insightful and superior in intelligence to others.

I think Jerome has the Galileo Syndrome

 

[GreyICE]

I don't think I (or anyone else) ever claimed that it was.

Not too sure exactly what it is you're asking here. Special relativity is a theory, as far as I know, and as far as I know it rules out travelling faster than light. But I'm not an expert, and would be happy to be corrected by someone with letters after their name.

I don't even know what you're talking about anymore. These don't follow in any way. Either you didn't claim its a theory, or you did.

In any case, Special Relativity is a special case of relativity (inertial frame of reference, no gravity effects) that is useful for calculation purposes. It is much easier to work with than general relativity.

The assumption of no gravity should steer you in the direction of how great it is at ruling things out. Like newtonian mechanics, it has a broader frame of usefulness than the limitations would first suggest, but its still just... newtonian mechanics.

 

[arthwollipot]

I don't even know what you're talking about anymore. These don't follow in any way. Either you didn't claim its a theory, or you did.

Make that both of us. I think we may be talking at cross purposes. I claimed that my understanding was that special relativity rules out things moving faster than light. That's all. I think it's time to move on.

 

[sol invictus]

Special relativity is a theory, as far as I know, and as far as I know it rules out travelling faster than light. But I'm not an expert, and would be happy to be corrected by someone with letters after their name.

You are absolutely correct. General relativity reduces to special relativity at short distances, in the sense that all non-singular spacetimes look flat (and therefore Lorentz invariant) on sufficiently small scales. Since causality must hold locally for the theory to be consistent, special relativity does indeed rule out faster than light travel.

 

[GreyICE]

You are absolutely correct. General relativity reduces to special relativity at short distances, in the sense that all non-singular spacetimes look flat (and therefore Lorentz invariant) on sufficiently small scales. Since causality must hold locally for the theory to be consistent, special relativity does indeed rule out faster than light travel.

Unless quantum gravity is correct, at which point general relativity only reduces to special relativity on scales that are neither too large nor too small. In any case a theory that is merely a useful approximation of another theory is a poor tool to be ruling anything out.

 

[arthwollipot]

Unless quantum gravity is correct, at which point general relativity only reduces to special relativity on scales that are neither too large nor too small. In any case a theory that is merely a useful approximation of another theory is a poor tool to be ruling anything out.

Well, there has to be some form of quantum gravity, right? If and when we find out what it is, it will make both special and general relativity redundant.