Black holes

[Farsight]

Not according to you.

Yes according to me. The world is painted in light according to me. And so is the canvas.

Suppose that we start out standing next to each other. Apparently you believe that if I start moving and you remain stationary, and I only perceive that you are moving, even though you are not in fact moving. Thus your motion is not relative to mine: you really are stationary, and I'm wrong to believe that you are now moving. Your motion is absolute, according to your own reasoning.

No it isn't. My motion is relative to you. When you and I are in deep dark space with no stars, and no galaxies, and no CMBR, and nothing to refer to, I can't say whether it's me moving or you. All I can say is that we are moving with respect to each other.

You are simultaneously grasping onto and rejecting central aspects not just of general and special relativity, but even Galilean relativity.

I grasp this Zig, don't try to make me out to be some damn fool kid just because you don't. Just think for yourself. Look to the evidence. Take it at face value, don't reject it because of what some book says.

 

[sol invictus]

OK, but as we will be doing our experiments in many different environments, including in deep space, we need a way to establish what "horizontal" is; how do you recommend we do that?

You note which way things fall down, then you take an orthogonal direction.

In deep space, things don't "fall down". They move with constant velocity unless subject to some applied force. If you could detect the (tiny) cosmological effects on the motion of objects and ignore other forces or local gravitational effects, things would "fall down" (i.e. accelerate) radially away from you, again making your definition useless for defining a special "horizontal" plane.

I'm still waiting for you to explain how you can confidently make statements about the Schwarzschild metric, while being unable to say anything about a simpler metric (that is identical to Schwarzschild near-horizon). Have you considered the possibility that you might not understand this very well, Farsight?

 

[tensordyne]

Looking back, I see that I might have misread this - by "set of space" do you mean those are the ranges of your coordinates? If so, the region is just as I said above: "a section of an annulus (two straight, radial sides, and two sides that are arcs of concentric circles)".

A more picturesque description would be the following: take a pineapple ring, and cut it twice with two radial cuts separated by a bit less than 60 degrees. The section you cut out is your region.

The sound of a trap snapping closed is appropriate right about now. You did guess correctly as per my intentions. I did not want any kind of out of the ordinary topology for the region and the whole of the space other than simply connected. Sorry, should have added that in but sometimes you can not think of everything.

That said, the answer is no, that is not the shape, or, more appropriately, until I say how p and q are determined, no one has a right to say what the shape is like.

You can have p and q being Cartesian(-like) (I put like because, to be honest, it is very annoying trying to explain how coordinates and geometry are independent to someone who just does not have that level of mathematical abstraction yet. Not that you can't get it sol, but put yourself in my shoes, or don't. For an explanation of Cartesian-like (which, come on, let's be honest, is Cartesian), see the previous post of mine in this thread).

If p and q are Cartesian, then we have the shape of a square. Use some other coordinate system and it will probably be a different shape all together. More later. I am going sailing.

 

[sol invictus]

The sound of a trap snapping closed is appropriate right about now.

Closing on who?

If p and q are Cartesian, then we have the shape of a square. Use some other coordinate system and it will probably be a different shape all together. More later. I am going sailing.

Nonsense. p and q are not Cartesian. The boundaries of your surface with constant p are not geodesics, as straight lines in a Cartesian coordinate system are. Instead, they are constant (extrinsic) curvature lines. Therefore, drawn in any Cartesian or locally Cartesian coordinate system, the shape is precisely what I described.

Perhaps your "trap" is that if you plot that region in p,q space, it will look square? That's trivially obvious, but it doesn't change anything about the geometric shape. In fact, it illustrates precisely the point I'm trying to get across to you - you need both the coordinate ranges that define the region and the metric to determine the geometric shape. With both, you can find all the geometrical facts (and hence its physics, given a physical theory) about the region - its intrinsic curvature, the extrinsic curvature of its boundary, the angles of its corners, etc. With the given metric lines of constant p are not straight; that's a geometrical fact that one can immediately see from the metric.

Thinking about maps of the earth might help you there. Would you say that the surface of the earth is rectangular or cylindrical because it can be represented that way with a Mercator projection? If so, you are again using standard terminology in a completely non-standard way.

 

[DeiRenDopa]

As far as I know, Fizeau used several different experimental setups, each with light and mirrors.

And we need to be pretty specific, I think, so would you mind spelling out the actual setup you recommend, in more detail?

Yes I would, stop wasting my time. Everybody knows the setup, see English Wikipedia.

I'm not sure if you've read this post of mine yet; here's an extract:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
me: From our exchanges so far I've learned that you have some very different understandings of key terms and concepts than what I find in standard textbooks. To be sure I do not misunderstand you, I will - often - ask you to define key terms, in your own words. If you reply by pointing to definitions that are standard (or nearly so as never mind), I can be confident of at least that commonality in our mutual understanding.

you: I don't mind putting some time into this, but if it turns into evasion and distraction on your part, forget it.

me: Fair enough. May I take it that the reverse is also acceptable to you? If I find our exchanges turning into evasion and distraction on your part, forget it?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

If you're not interested in trying to explain your ideas, that's fine with me.

OK, but as we will be doing our experiments in many different environments, including in deep space, we need a way to establish what "horizontal" is; how do you recommend we do that?

You note which way things fall down, then you take an orthogonal direction.

And if they don't (fall down)? Which they won't, if we're in deep space.

Also, this doesn't help if we choose to conduct our experiments in free fall; how do you propose to determine horizontal if we're in a stable, circular orbit around the Earth (to take but one example)?

We may have a problem here Houston. Or not; can you explain how we "time it [the back-and-forth travel time, in some Fizeau-like set-up] using the distant pulsar"?

Are you for real? Go do some research.

Not good, Farsight, not good.

You might like to look in a mirror, and tell your reflected self to go do some research.

For other readers: there are, already, known limits on the stability of any particular pulsar, and the optical clock Farsight mentioned is far more accurate/stable than any pulsar. Further, Farsight has been rather sloppy here; he said exactly this (bold added): "However we are not so stupid as to use our parallel-mirror light clock to time the back-and-forth travel time. Or [...] We time it using the distant pulsar." He didn't say which distant pulsar he intended/proposed to use, and if he meant to say something like 'a set, or array, of distant pulsars', he omitted to say how he'd use such an array as a clock.

If you have a few hours to spare, you can peruse the (astrophysics) literature on this topic, and discover that it is very far from trivial how to set up such a thing. Curiously, the Wikipedia link Farsight gives as his source has, itself, two papers as sources, dated 1997 and 1984. This particular area in astrophysics (and physics, no doubt) is very active, and 1984 is like the distant past. Oh, and the current SI definition of the second dates to 1997. Perhaps Farsight is simply not conversant with the relevant literature?

 

[DeiRenDopa]

OK, but as we will be doing our experiments in many different environments, including in deep space, we need a way to establish what "horizontal" is; how do you recommend we do that?

You note which way things fall down, then you take an orthogonal direction.

ETA: Farsight's definition of horizontal is observer-dependent, therefore coordinate-dependent. As the dialogue above continues, DeiRenDopa will explain the significance of that coordinate-dependence, and its implications for signals coming from the distant pulsar.​

It's a somewhat strange experience having a dialog with Farsight.

On the one hand, what he writes seems to imply a pretty deep knowledge and understanding of the subject; on the other, he replies to relatively straight-forward - but very pertinent - questions with curveball answers (like this).

Perhaps he's simply not paying attention ...

Oh, and it may be that we (Farsight and I) never get to discuss observer-dependence, and coordinate-dependence; for example, he may bail out before we establish a sufficiently solid, mutually agreed basis to even begin discussing that ...

 

[DeiRenDopa]

....So, re-writing F's original sentence with these clarifications, and adding back the full context (I've had to do some paraphrasing):

F: The optical clock uses aluminium rather than caesium, and a UV frequency rather than a microwave frequency, but it works along the same lines, and employs electromagnetic phenomena. When electrons move by doing a spin-flip, they emit electromagnetic waves, which move away more slowly from an optical clock at an elevation of a foot (or so) above an otherwise identical optical clock.

Right?

Sigh. Wrong. They move away faster. Remember this: they're slower when they're lower.

OK, how about this then?

F: The optical clock uses aluminium rather than caesium, and a UV frequency rather than a microwave frequency, but it works along the same lines, and employs electromagnetic phenomena. When electrons move by doing a spin-flip, they emit electromagnetic waves, which move away more slowly quickly from an optical clock at an elevation of a foot (or so) above an otherwise identical optical clock.

 

[Ziggurat]

No it isn't. My motion is relative to you. When you and I are in deep dark space with no stars, and no galaxies, and no CMBR, and nothing to refer to, I can't say whether it's me moving or you. All I can say is that we are moving with respect to each other.

If I accelerate, your motion becomes curved. If motion is truly relative, then this curvature is real in my reference frame. Yes, it's reference-frame dependent, but so is your velocity. That doesn't make it illusory.

And don't come back with that whole "reference frames aren't real" nonsense. They are as real as motion is. They are what motion is relative to. You cannot even define motion without a reference frame, even if you only want to define that frame implicitly.

 

[Farsight]

I'm going to skip a couple of posts, because this one is important:

Um, no. You've got it backwards. First we find waves that we say are oscillating at exactly 9,192,631,770 Hertz, and then we count 9,192,631,770 cycles to find out how long second is.

No, you've got it backwards. If we find waves oscillating at 9,192,631,770 Hertz we already know what the second is. That's because Hertz is cycles per second.

We're not basing the definition of the second on the speed of light, we're basing the definition of the second on a particular frequency of light.

No we aren't. Frequency is measured in Hertz, which is cycles per second, so if we were truly using frequency we'd be defining the second when we already knew what the second was. Look again at the water-wave bobbing-boat analogy.

If the speed of light was to slow down by half, the photons used for determining the second would need to have half the wavelength in order to have the right energy level to react with the caesium-133. This means that light would only be able to travel half the distance before the count reaches 9,192,631,770 cycles, or one second.

You can't say this because it assumes that the electromagnetic hyperfine transition is unaffected by whatever it was that caused the light to slow down.

Okay, you've got me there. The speed of light is used to define the metre... nowadays. But the speed of light wasn't used to define the metre until 1983, long after the speed of light in a vacuum was determined to be invariant. (In fact, that's why the speed of light was chosen.)

It isn't an issue. Where light goes slower the second is bigger, then you use the slower light and the bigger second to define the metre, so that metre is the same metre regardless of how fast the light is going.

And it wouldn't affect any direct attempt at measuring light in different conditions, since you're not altering the physical dimensions of the measuring device between measurements (which would defeat the point). The device would be built in units of the metre determined by the speed of light through a vacuum in earth-gravity. So any actual variation in the speed of light would be detected by the device.

No it wouldn't, because your definition of the second relies upon the speed of light. It's really simple. Where the light goes slower your second is bigger, and you use that bigger second on the slower light and hence measure the same speed. Even though you can look at parallel-mirror light clocks and see this going on:

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

Just think of them as racehorses. They aren't going at the same speed.

You can't see light moving any more than you can see time passing. When you "see" a photon, it's no longer moving. It's been absorbed by an atom or molecule in your eye or detection device.

These two things really aren't in the same league Brian. You know you could shine a laser at a series of objects in space and watch them light up one after the other. Light moves is a description of what happens, time passes is a figure of speech.

Why this obsession about not being able to see time passing? It's obvious that this assertion holds some special meaning for you, but until you explain your underlying reasoning, this repeated declaration is little more than a non-sequitur for the rest of us.

It's a save the planet thing. I'm trying to get you to see the scientific evidence of what's actually there, instead of not seeing it because you're obsessed with something you can't see. It's to do with A World Without Time: The Forgotten Legacy of Godel and Einstein. It's not that "time does not exist". It just isn't something that actually flows or passes.

 

[DeiRenDopa]

[...]
I've given you ample evidence and a sound argument, and you can't counter it. [...]

I'm not ben m (duh!), but I have been following what you've written (presented) here Farsight.

I do not doubt that, in your own mind, you have done precisely what you say (i.e. given ample evidence and a sound argument).

However, I can also say that for me what you have presented, so far, is very far from ample evidence and a sound argument. Worse, perhaps, you seem (sometimes) to make completely unwarranted assumptions, and write in a way that leaves the reader (well, at least this reader) quite confused over what you're trying to say.

 

[Ziggurat]

If p and q are Cartesian, then we have the shape of a square.

You can plot the space like a square, but it does not have the geometry of a square. For example, the length of the sides are not equal. Perhaps you are using "shape" to mean something different than I understand it to mean, but from where I sit, you can't make that space a square.

 

[Ziggurat]

Um, no. You've got it backwards. First we find waves that we say are oscillating at exactly 9,192,631,770 Hertz, and then we count 9,192,631,770 cycles to find out how long second is.

No, you've got it backwards. If we find waves oscillating at 9,192,631,770 Hertz we already know what the second is. That's because Hertz is cycles per second.

We're not basing the definition of the second on the speed of light, we're basing the definition of the second on a particular frequency of light.

No we aren't. Frequency is measured in Hertz, which is cycles per second, so if we were truly using frequency we'd be defining the second when we already knew what the second was. Look again at the water-wave bobbing-boat analogy.

Brian is right, you are wrong.
Current definitions of the SI units
"The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom."

 

[Farsight]

If you only need to detect a change in the speed of light, you can forget about units of distance, and use any units of time you want, as long is it's precise. Just measure the difference in the delay it takes for the light to be detected by the photo-sensor with an atomic clock. If the tube is long enough, you might be able to get by with a high precision quartz timer instead.

So, you measure the speed of electromagnetic wave propagation using an atomic clock... which employs microwaves? Or a quartz time that employs the piezoelectric effect?

Anybody spot a problem with that?

 

[Farsight]

In deep space, things don't "fall down". They move with constant velocity unless subject to some applied force. If you could detect the (tiny) cosmological effects on the motion of objects and ignore other forces or local gravitational effects, things would "fall down" (i.e. accelerate) radially away from you, again making your definition useless for defining a special "horizontal" plane.

Don't be so pompous sol. Pick up a pencil. Let go. It falls down thataway. Horizontal is thisaway.

I'm still waiting for you to explain how you can confidently make statements about the Schwarzschild metric, while being unable to say anything about a simpler metric (that is identical to Schwarzschild near-horizon). Have you considered the possibility that you might not understand this very well, Farsight?

I understand it, and your mystery expression is no substitute for addressing scientific evidence. You can't blind 'em with maths. It isn't going to work any more.

You too Clinger. An attempt at ridicule doesn't cut it.

 

[sol invictus]

Don't be so pompous sol. Pick up a pencil. Let go. It falls down thataway. Horizontal is thisaway.

Are you serious??

Things don't fall in deep space, Farsight. They don't even fall when you're in orbit.

 

[Farsight]

Let me know if I've skipped any posts. Backtracking to the top of the page:

The second as-yet-unaddressed of Farsight's posts.

For my own purposes, I shall call "what Farsight says is the original GR that Farsight has read" Farsight's GR, FGR for short.

Point of clarification: do Wald and/or MTW contain the "what people say GR says"?

I'll let others answer that.

The use of double quotes, as in ""artefacts of measurement"", by convention, means you are giving this term a meaning that is non-standard, one that is different from what a reader would normally infer.

The quotes were merely to highlight a phrase that some might find unfamiliar.

What do you intend this term to mean, in this context?

That a reference frame is not something you can actually measure, but is instead a convention used for measurement.

We most certainly need to get to a clear, mutual understanding of this!

It's quite clear enough. I can point up to the clear night sky and say "Look, that's a star. You cannot do the same for a reference frame.

I take a hard-headed approach: time is what a clock measures. The unit of time is the second, which is defined in the relevant SI standard. Two clocks are the same - for the purpose of measuring time - if they agree, when co-located. For me, the rest is philosophical fluff that we would all be better off without.

I take an even more hard-headed approach. I look inside the clock and I look at what it actually does measure.

But, if what clocks "actually do is clock up some form of regular motion", according to you, does that mean that you cannot - even in principle - build a clock based on the nuclear decay of an unstable isotope (to take one example)?

Stop wasting everybody's time Dopa. We all know about carbon dating.

I wasn't aware that there are objective independently verifiable experimental and/or observational results about Hawking radiation. Can you cite some please?

No. There's no evidence for Hawking radiation, and yet it's bandied about as if it's settled science.

How does one measure the impedance of space? And is the impedance of space the same as vacuum impedance?

You measure the speed of light then apply c = √(1/ε₀μ₀) and Z₀ = √(μ₀/ε₀).

I thought it was photons which created charged particles via pair production, and that particle-antiparticle annihilation produces photons.

Would you like to read my paragraph again? Here it is:

Impedance is an electrical property of say a cable, but it applies to space too, which electromagnetic waves propagate through. It applies to alternating current rather than direct current, these both being associated with conduction current, which is the motion of charged particles. You can create such charged particles via pair production, and get the electromagnetic waves back again via annihilation. Those electromagnetic waves are displacement current rather than conduction current, and they wave. They're alternating.

And to study photons, we need to use QED, rather than Maxwell's equations.

To study photons, we need to use experiment. Like this.

What am I missing?

Honesty, it would seem. And you're boring everybody to death. Is that your intention?

 

[Farsight]

Scientific evidence, eh? You think the evidence agrees with F-Einstein and disagrees with Wheeler? Be more specific.

Look at the thread title, and read the early posts. Black holes do not contain a central point singularity. And they do not suck in the surrounding space.

a) Perihelion of mercury.
b) Gravitational redshift.
c) Gravitational lensing.
d) Shapiro delay.
e) The Nordtvedt effect in (e.g.) Apollo lunar laser ranging
f) the Lense-Thirring effect, seen by Gravity Probe B and LAGEOS
g) Binary pulsar spindown

All fine.

Are you saying that the experimental evidence on these points agrees with "Einstein's original method" and disagrees with relativity-as-it-is-taught?

No. I'm saying that the interpretation of general relativity is now wrong, and that this has acted as a bar to scientific progress.

Sorry, Farsight. When you read a Gravity Probe B paper, and you see a plot showing the data points, and a plot showing the GR prediction, that prediction was generated from modern relativity---MTW-style relativity. If you think MTW is doing something "wrong" for some reason, then you're in trouble---because whatever MTW is doing is the thing that's actually out in the field passing experimental tests.

Not where black holes is concerned it isn't. We should talk about Gravity Probe B and gravitomagnetism sometime. Along with electromagnetism.

Unlike you, Farsight, I actually know these people, personally. I know experimental-gravity people at UW, MIT, UCSD, Harvard. Do you think they're out there learning crackpot-Farsight-relativity, bowing down before Schwarzschild coordinates, and devising experimental tests for that? No, they're learning mainstream general relativity theory, including the undergrad-level idea that coordinate-transformations are valid, and testing *that*.

Wake up ben. Some of the things some of them come out with are wrong. My scientific evidence trumps your argument from authority and your abuse. Go talk to them about what I've been telling you. Get them along here, see if they can put up any counter argument. You can't. They won't be able to either. Where does that leave you?

 

[Ziggurat]

Wake up ben. Some of the things some of them come out with are wrong. My scientific evidence trumps your argument from authority and your abuse.

Wrong about what? What scientific evidence?

The only thing I can figure out is that you think any coordinate transforms which eliminate the coordinate singularity of the Schwarzchild coordinates is wrong. But since the only evidence you've presented (what a distant observer will see) actually agrees with the predictions using other coordinates, that hardly proves them wrong.

So your scientific evidence hasn't trumped anything.

 

[Farsight]

Third of three.

Sorta.

No, not really.

I'm going to table this disagreement for now, and focus on your proposal concerning how to measure the speed of light, using a distant pulsar.

Noted.

Noted.

All points noted.

That's strange. You start with "No", but end up agreeing with me! I can't "follow the reasoning [you] offer" if I am unsure of the meaning of key terms you use in that reasoning.

It's not strange at all. You said those who seek to understand you need to be confident your understanding of key terms you use is the same as their own, right? I said No. You need to be confident that the scientific evidence I present is correct, and then you should be confident in your own ability to think for yourself and follow the reasoning I offer. Key terms aren't the issue here, the scientific evidence is.

There are several examples of this already, in this thread alone, for just me. For example, your notions of what clocks are, and how the microwave cavity works in the NIST cesium fountain clock. Others have pointed out that your use of 'speed of light' is, at times, inconsistent (and that's just one example). You apply classical electromagnetism to quantum phenomena (e.g. pair production and annihilation). And so on.

I apply experimental physics. You are raising spurious issues and presenting a straw-man argument instead of addressing the scientific evidence offered by that experimental physics.

May I take it that the reverse is also acceptable to you? If I find our exchanges turning into evasion and distraction on your part, forget it?

Please feel free to do so.

Last time I checked, I was not you.

So what I need, and don't need, is not really within your power to determine, is it?

And it's even less in your power to determine what I should need (or should not need)!

I've not read it, but I realize that we're talking at cross-purposes.

For some people, the word pictures (etc) are extremely important.

For example, they matter a great deal to teachers.

You're saying nothing. Address the scientific evidence.

 

[ben m]

Wake up ben. Some of the things some of them come out with are wrong. My scientific evidence trumps your argument from authority and your abuse.

This is what I'm asking you: what scientific evidence? I have a bunch of data from well-known gravity experiments. I have bunch of well-known mainstream-GR predictions for those experiments. I have a bunch of statistical data analysis saying that the experiments agree with the predictions. That's "scientific evidence"---the behavior of nature agrees with actual GR calculations performed by normal MTW-trained physicists.

On your side, even if you were right about GR coordinates (and I don't think you are) you've only discussed a strictly untestable problem---you've claimed that a black-hole-infall victim simply freezes at the horizon. Given the lack of data on black-hole-infall-victims and their post-horizon experiences, you do NOT have "scientific evidence". You have "an alternative hypothesis".