Black holes

[Farsight]

Sol's analogy is a good one. Reality Check is busting out with the bullet-point lists, and we have one unconvinced person reiterating something. Looks like we have another Electric Sun thread brewing, though it has a long way to go before its magnitude is anything like that one.

It isn't like that. I'm opposing something which isn't in line with general relativity. Take a good look at this waterfall analogy. Be skeptical about it, and ask around elsewhere.

I love how you use the term 'hiding behind calculations' as a pejorative here. It doesn't deflect from the fact that you hide from calculations at every opportunity.

I don't. See for example this post. What happens on a forum like this is that some self-professed "expert" feeds you guys hogwash. When I come along with scientific evidence and a sound argument to challenge the hogwash, the fallback position is "you don't understand the mathematics". It's bull. Don't fall for it.

 

[Brian-M]

And we know that a light beam emitted vertically from a massive star does not slow down,

Of course it doesn't slow down, it can't. But it does lose energy, which for photons is the equivalent of slowing down.

We also know that the space around this star is not moving inwards towards the star, and that we can extend this scenario to the black hole situation.

How do we know this?

 

[Farsight]

Coordinates actually exist, Farsight. They are what observers use to measure with.

No they don't. They are an artefact of measurement. Can you point up to the clear night sky and say Oh look! There's a coordinate system! No you can't. Light exists, and it certainly moves. That's what observers use to measure with. Now drop this point, coordinates don't actually exist, and sol has already conceded it.

But different coordinates will give different measurements. That is the point of GR being expressed in coordinate free mathematics.

And the original frozen star black-hole interpretation accurately reflects GR in that at the event horizon, the coordinate speed of light is zero. That means light doesn't move, so observers can't observe anything at that location. Simple stuff.

What GR shows (without coordinates) is that

• An external observer will observe a clock ticking slower and slower as it gets closer and closer to the event horizon.
• An external observer can never see a clock get to the event horizon.
• An observer with the clock will see it tick as normal as they pass through the event horizon.

Point 1 is no problem, point 2 is debateable in that the external observer will note that the clock is no longer ticking, and can only verify that by waiting an infinite length of time. Point 3 is a myth. The observer with the clock slows down like the clock, and stops like the clock stops. That means he doesn't see anything. The things you think he sees occur only in a never-neverland beyond the end of time, not in the real world.

 

[Farsight]

Of course it doesn't slow down, it can't. But it does lose energy, which for photons is the equivalent of slowing down.

It speeds up, and it doesn't lose energy. Think it through:

An optical clock at the surface of a massive body runs slower than it does in free space. And it's an optical clock. So light near the surface of the body moves slower than it does in free space.

Now emit one photon vertically from the surface of the body. It starts off moving slowly, and as is gets away, it moves faster. Meanwhile conservation of energy applies. The only particle present is the photon, it doesn't magiucally lose energy to other particles or to the gravitational field. If you're not happy with this think about two bodies falling towards one another. Conservation of energy applies there too, the bodies don't gain energy from each other such that the net system energy increases.

How do we know this?

Because we understand general relativity, it's a well tested theory, see Clifford M Will's paper, and it does not include specious nonsense like the sky is falling in.

 

[Mashuna]

I don't. See for example this post. What happens on a forum like this is that some self-professed "expert" feeds you guys hogwash. When I come along with scientific evidence and a sound argument to challenge the hogwash, the fallback position is "you don't understand the mathematics". It's bull. Don't fall for it.

Did you mean to link to that post?

It's not only that you don't understand the mathematics, you've also not supplied the scientific evidence or the sound argument. I realise that you think you have, but whereas other people are supplying both the analogy or thought experiment and the supporting calculations, you're just giving the thought experiment. It's not enough.

 

[sol invictus]

You asserted that the sonic analogue of black holes is "absolutely wrong".

No I didn't.

Yes, you did:

The waterfall analogy is absolutely wrong, sol, and a travesty of relativity.

As for the physics:

I've given the evidence of the Shapiro delay and optical clocks which demonstrate that the coordinate speed of light varies:

|----------------|
|----------------|

All of that works in precisely the same way in the waterfall analogy, Farsight. Fail.

And we know that a light beam emitted vertically from a massive star does not slow down, does not fall back, and does not curve.

Neither does a sound wave propagating straight upriver. Fail.

We also know that the space around this star is not moving inwards towards the star, and that we can extend this scenario to the black hole situation. There is no waterfall!

Again, assertions with no evidence. Fail.

 

[W.D.Clinger]

Looks like we have another Electric Sun thread brewing, though it has a long way to go before its magnitude is anything like that one.

Yep. As in the Electric Sun thread, the iconoclast is denying the relevance of mathematics even as he occasionally claims to be the only one who's doing the math correctly.

Surely you're not going to hide behind calculations

You're advancing specious pseudoscience that says it is, and taking cover behind mathematics.

What happens on a forum like this is that some self-professed "expert" feeds you guys hogwash.

Farsight is the self-professed "expert" who's feeding us hogwash.

When I come along with scientific evidence and a sound argument to challenge the hogwash, the fallback position is "you don't understand the mathematics". It's bull. Don't fall for it.

I'm sorry, but the problem with Farsight's argument is that he really doesn't understand the mathematics.

Although Farsight often says coordinates don't really exist, he founded his argument upon a meaningless coordinate singularity that occurs in one particular coordinate system (Schwarzschild coordinates), which Farsight implicitly assumes to be canonical even as he claims not to have assumed any particular coordinate system.

Consider, for example, Farsight's "$64,000 question" about the coordinate speed of light at the event horizon, according to observers at a great distance. Farsight thinks that speed of light is zero, but I've done the calculation myself and gotten a different answer: unity.

Does that contradict Farsight's belief that the coordinate speed of light is zero at the event horizon? No, because Farsight and I are distant observers who have chosen to use different coordinate systems.

Both of our coordinate systems are equally correct, and both describe exactly the same spacetime manifold.

Farsight doesn't understand that, because he hasn't done his homework. We've already been through this on another thread, but it's even more on-topic for this thread so we might as well continue that discussion here.

• Starting with the most basic definitions, I explained that a chart is not the manifold.
• I applied those definitions to the familiar example of a 2-sphere (which approximates the surface of the earth).
• I gave examples of what happens as coordinates approach a coordinate singularity. Those examples show why we should suspect Schwarzschild's r=2M singularity of being a mere coordinate singularity.
• I used Lemaître coordinates to prove that Schwarzschild's r=2M singularity is a mere coordinate singularity.
• I pointed out that your argument rests on two related errors:
  • You assume Schwarzschild charts cover the entire spacetime manifold.
  • You assume there is some global, observer-independent notion of time that could justify your use of the word "yet".
  (By the way, you repeated your "yet" error at the end of the first paragraph of your post #166.)
• I identified five recent mistakes that you made because you haven't done your homework.
• I also pointed out that anyone who's proficient in high school algebra and differential calculus can work this out for themselves well enough to identify the major mistakes you've been making.

General relativity is a difficult subject. Once upon a time, people like Lemaître published research papers about the very matters we're discussing.

It's okay to make beginner's mistakes when you're first learning a difficult subject. No one expects an amateur or student to get everything right.

It's also okay to give up on a difficult subject when you discover you just don't have the mathematical and/or scientific background required to understand it. Life is short. You can't learn everything.

It's not okay to pretend to understand a difficult subject while making beginner's mistakes and ignoring expert correction. That pretense and willful ignorance is what distinguishes cranks and crackpots from students and amateurs.

 

[sol invictus]

It speeds up, and it doesn't lose energy. Think it through:

An optical clock at the surface of a massive body runs slower than it does in free space. And it's an optical clock. So light near the surface of the body moves slower than it does in free space.

That is true in exactly the same sense as for a sonic clock near the waterfall. A sonic clock held in place near the sound horizon ticks slowly, because sound takes a long time to propagate against the current to the upriver reflector.

Now emit one photon vertically from the surface of the body. It starts off moving slowly, and as is gets away, it moves faster.

Again, exactly like a sound pulse going upriver - its speed relative to the banks increases as it moves, because the current weakens further from the waterfall.

The only particle present is the photon, it doesn't magiucally lose energy to other particles or to the gravitational field. If you're not happy with this think about two bodies falling towards one another. Conservation of energy applies there too, the bodies don't gain energy from each other such that the net system energy increases.

That's nonsense, of course. Total energy is conserved, but a photon climbing out of a gravitational well certainly loses energy. The change in the energy of the field compensates for that loss.

Because we understand general relativity, it's a well tested theory, see Clifford M Will's paper, and it does not include specious nonsense like the sky is falling in.

The relevant mathematics of the waterfall are identical to those of general relativity near a black hole horizon. You have not addressed that, because you cannot.

 

[Farsight]

Did you mean to link to that post?

Yes. here it is again: The WAR: Susskind-Hawking battle.

It's not only that you don't understand the mathematics, you've also not supplied the scientific evidence or the sound argument. I realise that you think you have, but whereas other people are supplying both the analogy or thought experiment and the supporting calculations, you're just giving the thought experiment. It's not enough.

What tosh, Mashuna. The expression is straightforward, I understand the mathematics, I've given the numbers, and I've supplied rock-solid scientific evidence. If you'd like me to repeat anything or explain it another way I'll only be too happy to do so.

 

[Farsight]

You asserted that the sonic analogue of black holes is "absolutely wrong".

No I didn't.

Yes, you did:

The waterfall analogy is absolutely wrong, sol, and a travesty of relativity.

I said the waterfall analogy was absolutely wrong. See the rest of my post #67 where I referred to sonar. It's quite clear I don't have an issue with sonic.

As for the physics:

All of that works in precisely the same way in the waterfall analogy, Farsight. Fail.

Neither does a sound wave propagating straight upriver. Fail.

It doesn't work the same way at all. There is no inward motion of the medium in a gravitational field.

We also know that the space around this star is not moving inwards towards the star, and that we can extend this scenario to the black hole situation. There is no waterfall!

Again, assertions with no evidence. Fail.

LOL! You want me to provide evidence that this waterfall of infalling space does not exist? Sol, really, you've dug yourself into a hole on this one, and again you aren't in line with general relativity. So stop digging.

 

[D'rok]

As a public service to other lurkers, I'd just like to point out that when overconfident amatuers say things like "you aren't in line with general relativity" to professional physicists, this can be translated accurately as "you aren't in line with my boutique, personal version of general relativity which I consider to be the true and correct version of general relativity". Same goes for special relativity.

In this particular case, the most accurate translation would be "you aren't in line with Relativity+".

 

[sol invictus]

It doesn't work the same way at all. There is no inward motion of the medium in a gravitational field.

Yet another assertion with no evidence. You're quite a specialist in those, I see.

LOL! You want me to provide evidence that this waterfall of infalling space does not exist?

Sure - go ahead and try. On the pro side, we have the fact that the mathematics of sound propagating in a flowing fluid is essentially identical to that of light propagating near a black hole horizon. On your side, we have...?

For the lurkers, in general relativity space is a funny thing. It can distort in response to stress and energy, and propagate waves both of itself and of other forms of radiation. But if it is a substance (an aether) then it's of a very strange and diaphanous type, because there is no preferred rest frame.

On the other hand, even in a fluid there is no rest frame as far as experiments conducted with (low-frequency) sound can determine. You can even define "Lorentz transformations" based on the speed of sound rather than light. That is the physical reason why the math of the waterfall works out so nicely, and why this analogy is so powerful.

 

[ben m]

Let me point out, also, that Farsight took his ideas on an outing in this thread:

http://www.internationalskeptics.com/forums/showthread.php?t=227470

where he revealed, basically, that "a flat-space inertial observer sees clocks stop at the horizon" is quite literally the only GR calculation Farsight has ever done (or looked up) and the only one he's willing or able to do. He posted that "|-------|" diagram about fifty times.

On the other thread, he gradually slid from "hey, look at this interesting fact" to "silly physicists, I will disabuse you of your GR mistakes" to "you are all morons".

 

[Farsight]

As a public service to other lurkers, I'd just like to point out that when overconfident amatuers say things like "you aren't in line with general relativity" to professional physicists, this can be translated accurately as "you aren't in line with my boutique, personal version of general relativity which I consider to be the true and correct version of general relativity". Same goes for special relativity.

Nope, it's translated accurately as you aren't in line with general relativity with this sky-falling-in waterfall nonsense. I would urge other lurkers to check this elsewhere. And I would urge D'rok to learn how to spell amateur.

 

[D'rok]

Nope, it's translated accurately as you aren't in line with general relativity with this sky-falling-in waterfall nonsense. I would urge other lurkers to check this elsewhere. And I would urge D'rok to learn how to spell amateur.

Ignore my previous post everyone. It has a typo in it. Clearly, this means we must now acknowledge that Relativty+ is correct.

 

[Farsight]

Let me point out, also, that Farsight took his ideas on an outing in this thread:

http://www.internationalskeptics.com/forums/showthread.php?t=227470

where he revealed, basically, that "a flat-space inertial observer sees clocks stop at the horizon" is quite literally the only GR calculation Farsight has ever done (or looked up) and the only one he's willing or able to do. He posted that "|-------|" diagram about fifty times.

On the other thread, he gradually slid from "hey, look at this interesting fact" to "silly physicists, I will disabuse you of your GR mistakes" to "you are all morons".

Take care ben, people might read that thread and see that I remained civil whilst you became abusive when you couldn't defend your position.

 

[Farsight]

Ignore my previous post everyone. It has a typo in it. Clearly, this means we must now acknowledge that Relativty+ is correct.

LOL. You can't even spell relativity.

 

[D'rok]

LOL. You can't even spell relativity.

Whoosh. I guess that was too subtle.

Let's suppose I'm a semi-literate ignoramus. Does this in any way affect your inability to produce a proper scientific argument?

 

[Farsight]

Yep. As in the Electric Sun thread, the iconoclast is denying the relevance of mathematics even as he occasionally claims to be the only one who's doing the math correctly.

Not me, Clinger. I'm on record as saying mathematics is a vital tool for physics, and I have responded on mathematical points, as per this example. Yes I'm an iconoclast destroying dogma, but I'm doing it by pointing out the issues with the mathematics and giving scientific evidence to back that up.

Farsight is the self-professed "expert" who's feeding us hogwash.

I'm giving you scientific evidence and straightforward logic.

I'm sorry, but the problem with Farsight's argument is that he really doesn't understand the mathematics.

What erudite arrogant tosh.

Although Farsight often says coordinates don't really exist, he founded his argument...

Sol agrees with me on this. We all know that we cannot look to the clear night sky and point out a coordinate system. It is an artefact of measurement.

Consider, for example, Farsight's "$64,000 question" about the coordinate speed of light at the event horizon, according to observers at a great distance. Farsight thinks that speed of light is zero, but I've done the calculation myself and gotten a different answer: unity.

Your calculation is wrong. Whether you're at the event horizon or not, the speed of light is zero in all respects. Your "calculation" omits the undefined result at R=2M, it features a stopped observer and a stopped light-clock, and you mistakenly think that this observer sees the clock ticking normally. He does not. Light is stopped. He doesn't see anything.

Farsight doesn't understand that, because he hasn't done his homework. We've already been through this on another thread, but it's even more on-topic for this thread so we might as well continue that discussion here.

I was appalled to see that waterfall twaddle being peddled here, so here I am. The waterfall is specious pseudoscience, and I'm surprised to see people defending it. Very badly, might I add.

 

[ben m]

Take care ben, people might read that thread and see that I remained civil whilst you became abusive when you couldn't defend your position.

What erudite arrogant tosh.

How civil.

I was appalled to see that waterfall twaddle being peddled here, so here I am. The waterfall is specious pseudoscience

And yet you haven't identified one single error in any of Visser's detailed mathematical maps between GR and the waterfall parallel. This is a common crackpot difficulty, which Wilfred Hodges discusses in "An Editor Recalls Some Hopeless Papers":

It was surprising how many of our authors failed to realise that to attack an argument, you must find something wrong in it. Several authors believed that you can avoid a proof by simply doing something else ...

How does anybody get into a state of mind where they persuade themselves
that you can criticise an argument by suggesting a different argument which
doesn't reach the same conclusion?