At Rest with our Hubble view

[Tach]

It has everything to do with the fact that it's the Shapiro delay. The out-and-back signal duration increases when the light skims the Sun. Nine-tenths of this is because the light goes slower near the Sun. You can contrive a thought-experiment where light passes between two nearby stars wherein the beam doesn't bend at all. Then all of the delay is because the light goes slower near the stars.

The above is , of course, false (like the rest of the post). The Shapiro delay is:

$$\Delta t=\frac{x_1+x_2}{c}+\frac{1}{c} ln (\frac{x_1x_2}{R})$$*

where $$c$$ is the light of speed in vacuum. No, "light going slower near the Sun", nor "because the light goes slower near the stars". Perhaps you and Undefined can stop making up stuff and posting it here as if it were science.

--------------------------------------------------------------------------------------------------
* see for example Rindler: "Relativity: Special, General and Cosmological"

 

[PhysBang]

Please don't attempt to hide behind mathematical demands because you're losing the argument.

The argument is mathematical. Einstein helped invent an entire field of mathematics in order to be able to make his argument.

It is a sign of bad character to constantly avoid the actual argument and then insult others when they want to actually address it.

 

[Markus Hanke]

You can contrive a thought-experiment where light passes between two nearby stars wherein the beam doesn't bend at all.

No you can't. The beam always bends in space-time. Hence the Shapiro delay.

And this tells you that refraction in a prism does not occur because c is reduced

Of course it does. Did you even read my reply ? While c never changes microscopically, it does change on macroscopic scales. Or are you trying to tell us that glass has the same permittivity and permeability as vacuum ? Are you taking us for fools by saying that glass is in fact vacuum ?

You know full well that the coordinate speed of light varies in a non-inertial reference frame such as a gravitational field. The speed of light does vary with the radial coordinate from the massive body.

If that were so, then we'd expect to see refraction. Which we don't.
So how would you quantify this relationship ? Why are you avoiding this very simple question ?

We observe the Shapiro delay.

Of course we do, because space-time is curved.

It's a strawman. Refraction in a prism is not caused by a reduction in c, so claiming that a varying speed of light must result in rainbow gravitational lensing is specious.

No, it's basic high school physics. In glass the values for permittivity and permeability are not the same as in vacuum, resulting in a different phase velocity, and hence in refraction. This is called Snell's law. Hard to believe that you are not aware of even such basic principles !

So let's recap - first you were saying that space must be inhomogeneous in that permittivity and permeability change ( funny though that they are called "fundamental constants"... ); then, pressed for details in the form of a relation between radial coordinate and the above values, you are unable to do so, and instead accuse us of "hiding behind mathematical demands". So all you do is make unsubstantiated assertions, and then refuse to back them up if further questioned - hardly surprising though, since they can't be backed up. The field equation of GR is a simple relation between the Einstein tensor and the stress-energy-momentum tensor, and it states that these are equal up to a proportionality constant; the point is that the Einstein tensor has no relation whatsoever to either the speed of light, permittivity or permeability of vacuum. Rather, it can be visualized as the average Riemann curvature across a small region of space-time in the immediate neighbourhood of a given point. Again, nothing to do with speeds of light, or imaginary inhomogeneities of space. What you are trying to push here is in no way connected to GR, it is your own little pet theory, and as such does not even belong in the main physics section.

In any case, until such time when you can provide a quantitative relationship between the speed of light and the source of the gravity in the scenario, and furthermore show us that the predictions such a model gives is equivalent to GR's curved space-time, you have exactly nothing. Accusing others of using "strawman arguments" and then failing to back up such accusations just doesn't cut it, you know.

Please don't attempt to hide behind mathematical demands because you're losing the argument.

It was forseeable that you'd say that, because the relation I asked you for does not exist. There is no law of physics which states that the speed of light changes in the vicinity of massive bodies. You just invented this to attempt to back up your own warped view of space-time ( see what I did here ). See above.

 

[Read-Only]

You just invented this to attempt to back up your own warped view of space-time ( see what I did here ).

HAR-HAR!!! "warped view of space-time." I *love* it!!

 

[Tach]

No you can't. The beam always bends in space-time. Hence the Shapiro delay.



Of course it does. Did you even read my reply ? While c never changes microscopically, it does change on macroscopic scales. Or are you trying to tell us that glass has the same permittivity and permeability as vacuum ? Are you taking us for fools by saying that glass is in fact vacuum ?



If that were so, then we'd expect to see refraction. Which we don't.
So how would you quantify this relationship ? Why are you avoiding this very simple question ?



Of course we do, because space-time is curved.



No, it's basic high school physics. In glass the values for permittivity and permeability are not the same as in vacuum, resulting in a different phase velocity, and hence in refraction. This is called Snell's law. Hard to believe that you are not aware of even such basic principles !

So let's recap - first you were saying that space must be inhomogeneous in that permittivity and permeability change ( funny though that they are called "fundamental constants"... ); then, pressed for details in the form of a relation between radial coordinate and the above values, you are unable to do so, and instead accuse us of "hiding behind mathematical demands". So all you do is make unsubstantiated assertions, and then refuse to back them up if further questioned - hardly surprising though, since they can't be backed up. The field equation of GR is a simple relation between the Einstein tensor and the stress-energy-momentum tensor, and it states that these are equal up to a proportionality constant; the point is that the Einstein tensor has no relation whatsoever to either the speed of light, permittivity or permeability of vacuum. Rather, it can be visualized as the average Riemann curvature across a small region of space-time in the immediate neighbourhood of a given point. Again, nothing to do with speeds of light, or imaginary inhomogeneities of space. What you are trying to push here is in no way connected to GR, it is your own little pet theory, and as such does not even belong in the main physics section.

In any case, until such time when you can provide a quantitative relationship between the speed of light and the source of the gravity in the scenario, and furthermore show us that the predictions such a model gives is equivalent to GR's curved space-time, you have exactly nothing. Accusing others of using "strawman arguments" and then failing to back up such accusations just doesn't cut it, you know.



It was forseeable that you'd say that, because the relation I asked you for does not exist. There is no law of physics which states that the speed of light changes in the vicinity of massive bodies. You just invented this to attempt to back up your own warped view of space-time ( see what I did here ). See above.

Excellent post. Unfortunately, it will not stop the steam of nonsense coming from John Duffield (Farsight). He's been doing this for years.

 

[AlexG]

Excellent post. Unfortunately, it will not stop the steam of nonsense coming from John Duffield (Farsight). He's been doing this for years.

Well if a crank could learn, he wouldn't be a crank, would he?

 

[Tach]

Well if a crank could learn, he wouldn't be a crank, would he?

I think that the most disturbing aspect is that he (John) thinks he's "teaching mainstream science, in the true spirit of Einstein".

 

[Beer w/Straw]

I've stopped reading Farsight's posts a long time ago. (Ever since physforum)

It is far more constructive for me to go on a different forum and talk about video games.

 

[Farsight]

No you can't. The beam always bends in space-time. Hence the Shapiro delay.

Spacetime is a mathematical space which presents all times at once, and in which there is no motion. I explained the distinction between curved spacetime and curved space here in response to your ?!?. And I reiterate: you can contrive a thought-experiment where light passes between two nearby stars wherein the beam doesn't bend at all. Then all of the delay is because the light goes slower near the stars. That light doesn't go slower near the stars because your plot of light-clock rates is curved. You are confusing cause and effect. The light goes slower near the stars because space there is different to space a long way away from the stars, because as Einstein said “empty space” in its physical relation is neither homogeneous nor isotropic. Again see this post for details.

Of course it does. Did you even read my reply? While c never changes microscopically, it does change on macroscopic scales. Or are you trying to tell us that glass has the same permittivity and permeability as vacuum ? Are you taking us for fools by saying that glass is in fact vacuum?

Yes I read your reply. When c doesn't change microscopically, it doesn't change on macroscopic scales either, and it doesn't change in a different fashion for different wavelengths. Again, your assertion is a straw man because the mechanism for refraction in glass does not involve a variable c.

If that were so, then we'd expect to see refraction. Which we don't.

We see gravitational lensing.

So how would you quantify this relationship ? Why are you avoiding this very simple question?

I'm not avoiding anything, I'm pointing out what Einstein actually said. He quantified it. And he didn't say light curves because spacetime is curved, he said light curves because the speed of light varies with position.

Of course we do, because space-time is curved.

No, we see it because the speed of light varies with position.

No, it's basic high school physics. In glass the values for permittivity and permeability are not the same as in vacuum, resulting in a different phase velocity, and hence in refraction. This is called Snell's law. Hard to believe that you are not aware of even such basic principles!

I'm fully aware of it. Just as you're aware that c = √(1/ε0μ0) and that in vacuum, c does not depend on wavelength. We do not see red light from a nova before blue light, we do not see a wavelength-dependent Shapiro delay.

So let's recap - first you were saying that space must be inhomogeneous in that permittivity and permeability change ( funny though that they are called "fundamental constants"... )

They aren't constant. Einstein said repeatedly that c wasn't constant, as per the Baez article which said "This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity". So if this interpretation is perfectly valid and c = √(1/ε0μ0), it's perfectly valid that vacuum permittivity and permeability are not constant.

then, pressed for details in the form of a relation between radial coordinate and the above values, you are unable to do so, and instead accuse us of "hiding behind mathematical demands". So all you do is make unsubstantiated assertions, and then refuse to back them up if further questioned - hardly surprising though, since they can't be backed up.

I've backed up what I've said with hard scientific evidence and references to Einstein. You've dismissed this, you attempted a straw-man argument with refraction in glass, and now it appears that you're being abusive. This does you no credit Markus.

The field equation of GR is a simple relation between the Einstein tensor and the stress-energy-momentum tensor, and it states that these are equal up to a proportionality constant; the point is that the Einstein tensor has no relation whatsoever to either the speed of light, permittivity or permeability of vacuum. Rather, it can be visualized as the average Riemann curvature across a small region of space-time in the immediate neighbourhood of a given point. Again, nothing to do with speeds of light, or imaginary inhomogeneities of space. What you are trying to push here is in no way connected to GR, it is your own little pet theory, and as such does not even belong in the main physics section.

It isn't my pet theory. This is GR.

In any case, until such time when you can provide a quantitative relationship between the speed of light and the source of the gravity in the scenario, and furthermore show us that the predictions such a model gives is equivalent to GR's curved space-time, you have exactly nothing. Accusing others of using "strawman arguments" and then failing to back up such accusations just doesn't cut it, you know.

It cut it. You were forced to admit that c in glass doesn't change, and you will be forced to admit that c does not vary with frequency, and that refraction in glass operates via a mechanism that does not involve a change in c.

It was forseeable that you'd say that, because the relation I asked you for does not exist. There is no law of physics which states that the speed of light changes in the vicinity of massive bodies. You just invented this to attempt to back up your own warped view of space-time ( see what I did here ). See above.

I didn't invent it. Einstein did. See below. You know what geschwindigkeit means, you know the postulate concerned the constant speed of light. I'm afraid you're in denial Markus. Your emotion betrays it.

1911: If we call the velocity of light at the origin of co-ordinates cₒ, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = cₒ(1 + Φ/c²).
1912: On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential.
1913: I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis.
1915: the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned.
1916: In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of light varies with position.

 

[Farsight]

Excellent post. Unfortunately, it will not stop the steam of nonsense coming from John Duffield (Farsight). He's been doing this for years.

Shame I demolished Markus's "excellent post". Would you like to enter into this discussion, Tach? Or would you prefer to snipe from the sidelines and play the troll as usual?

Well if a crank could learn, he wouldn't be a crank, would he?

I'm no crank. It's not me who can't learn here. It's Markus. Try to tell him something, and despite all the evidence and references, all we get is a denial followed by a straw-man followed by hostility. Not good. But that's how it generally is with self-appointed "experts". Such is life.

 

[Markus Hanke]

Shame I demolished Markus's "excellent post".

The only thing you have demolished here is your credibility by once again completely ignoring the points made, and by just repeating the same old, tired, meaningless phrases as you have for years now. But that's fine, because no one here was expecting anything else. So, I am going to repeat my "abuse", and once again give you GR in a nutshell :

$$\displaystyle{G_{\mu \nu }=\kappa T_{\mu \nu }}$$

Each reader may attempt him/herself to find where exactly this hints at a variable speed of light. At the end of the day there really isn't any other point to be made except the above; GR is a beautiful thing, because it can be written down so easily and unambiguously.

Enough said

 

[Markus Hanke]

I'm no crank. It's not me who can't learn here.

Let's put it this way - while everybody else learns and progresses, you have just been repeating the same nonsense for years.
Go figure.

The thing is - I am not an expert by any stretch of the imagination, yet I do understand the meaning of the simple tensor relation given in my previous post. How difficult is it, really ? One must be wearing blindfolds to not grasp the idea behind it, or, more likely, simple not want to understand it. At the end of the day it boils down to personal choice, I suppose...

 

[Markus Hanke]

Yes I read your reply. When c doesn't change microscopically, it doesn't change on macroscopic scales either, and it doesn't change in a different fashion for different wavelengths. Again, your assertion is a straw man because the mechanism for refraction in glass does not involve a variable c.

Ha ! Now this is a true little gem
Not only is this an as-per-yet unsurpassed example of ignorance of basic physics, but also a marvelous demonstration of your way of trying to worm yourself out of having been shown as who you truly are.

Since the above speaks for itself, we'll quite simple let it stand as-is.

 

[Tach]

Shame I demolished Markus's "excellent post".

Your delusions run very deep.

Would you like to enter into this discussion, Tach?

I already debunked your errors, read here.

I'm no crank. It's not me who can't learn here. It's Markus.

Everybody else has the opposite opinion, Duffield.

 

[Tach]

1911: If we call the velocity of light at the origin of co-ordinates cₒ, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = cₒ(1 + Φ/c²).
1912: On the other hand I am of the view that the principle of the constancy of the velocity of light can be maintained only insofar as one restricts oneself to spatio-temporal regions of constant gravitational potential.
1913: I arrived at the result that the velocity of light is not to be regarded as independent of the gravitational potential. Thus the principle of the constancy of the velocity of light is incompatible with the equivalence hypothesis.
1915: the writer of these lines is of the opinion that the theory of relativity is still in need of generalization, in the sense that the principle of the constancy of the velocity of light is to be abandoned.

Duffield, the above were written before Einstein discovered GR, he was simply trying to add gravitation to SR. You have been told multiple times that "science via quote-picking" doesn't work.

1916: In the second place our result shows that, according to the general theory of relativity, the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity and to which we have already frequently referred, cannot claim any unlimited validity. A curvature of rays of light can only take place when the velocity of light varies with position.

Duffield, do you se the word velocity in the text? I highlighted it for you. In GR, the speed of light is $$c$$. It is the velocity that changes in the presence of gravitating bodies. Google "gravitational light bending". You have been told multiple times that "science via quote-picking" doesn't work.....but you can't do anything but trawl for quotes (whose meaning you clearly do not understand).

 

[PhysBang]

Spacetime is a mathematical space which presents all times at once, and in which there is no motion. I explained the distinction between curved spacetime and curved space here in response to your ?!?. And I reiterate: you can contrive a thought-experiment where light passes between two nearby stars wherein the beam doesn't bend at all. Then all of the delay is because the light goes slower near the stars. That light doesn't go slower near the stars because your plot of light-clock rates is curved. You are confusing cause and effect. The light goes slower near the stars because space there is different to space a long way away from the stars, because as Einstein said “empty space” in its physical relation is neither homogeneous nor isotropic. Again see this post for details.

Why should anyone do this when it is clear that you are, at best, entirely deluded about the facts and at worst are lying? Anyone who reads Einstein's own work on GR discovers that he uses spacetime and that he does use solutions to the Einstein field equation in which space-like hypersurfaces are homogeneous. That you fail to understand this or you are lying about it is fairly pathetic.

Yes I read your reply. When c doesn't change microscopically, it doesn't change on macroscopic scales either, and it doesn't change in a different fashion for different wavelengths. Again, your assertion is a straw man because the mechanism for refraction in glass does not involve a variable c.

But we can all see that you have refused to actually work out any details, that you are trying to cover for your guess without any study.

We see gravitational lensing.

Which does not work like you say. You are dodging answering questions, which is something that you do for years and years. You have been banned from boards for dodging questions and insulting people who ask questions merely because they ask you questions and you have to figure out some new way to dodge the questions.

I'm not avoiding anything, I'm pointing out what Einstein actually said.

Except that you are obviously avoiding what Einstein actually did with spacetime and with homogeneous space.

He quantified it. And he didn't say light curves because spacetime is curved, he said light curves because the speed of light varies with position.

He said this in one paper in which he was speculating and before he finally abandoned the idea and developed GR. Since you have been corrected on this many time, again we see that you must be deluded or lying.

They aren't constant. Einstein said repeatedly that c wasn't constant, as per the Baez article which said "This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity". So if this interpretation is perfectly valid and c = √(1/ε0μ0), it's perfectly valid that vacuum permittivity and permeability are not constant.

You are lying about the content of that article, as anyone can read. The Baez article is clearly speaking of the vector speed of light and the change in direction, not the scalar speed as you are indicating. A more representative (not lying) quotation of the quotation you cherry-picked would be: "Since Einstein talks of velocity (a vector quantity: speed with direction) rather than speed alone, it is not clear that he meant the speed will change, but the reference to special relativity suggests that he did mean so. This interpretation is perfectly valid and makes good physical sense, but a more modern interpretation is that the speed of light is constant in general relativity."

I've backed up what I've said with hard scientific evidence and references to Einstein.

This is a lie. You have provided no scientific evidence. When asked for specific scientific evidence in the form of actually showing the equations that govern the behavior you describe, you dodged the question. When you referenced Einstein, you referenced an approach to light that Einstein abandoned.

You've dismissed this, you attempted a straw-man argument with refraction in glass, and now it appears that you're being abusive. This does you no credit Markus.

Classic: you lie to us and then you claim that others are abusing you.

It isn't my pet theory. This is GR.

Then you should be able to demonstrate a simple gravitational lensing the shows your principles in action. If you are lying to us, then you won't be able to do this.

But I note: if you apologize and no longer make these false claims about Einstein and GR, then you will be forgiven.

1911: If we call the velocity of light at the origin of co-ordinates cₒ, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = cₒ(1 + Φ/c²).

Even you know that the above something that is not GR, since that did not come until 1916! You are proving to everyone that you are lying. Please, just apologize and move on with your life.

 

[Farsight]

I already debunked your errors, read here.

LOL! That's no debunk!

Duffield, the above were written before Einstein discovered GR, he was simply trying to add gravitation to SR. You have been told multiple times that "science via quote-picking" doesn't work.

Einstein said what he said. Dismiss Einstein if you like. I prefer not to.

Duffield, do you se the word velocity in the text? I highlighted it for you. In GR, the speed of light is $$c$$. It is the velocity that changes in the presence of gravitating bodies. Google "gravitational light bending". You have been told multiple times that "science via quote-picking" doesn't work.....but you can't do anything but trawl for quotes (whose meaning you clearly do not understand).

The word Einstein used was geschwindigkeit, which means speed. He referred to the SR postulate, which was the constant speed of light. Markus knows this, and I'm afraid he's being evasive. The 1920 English translation employs the common-usage velocity, as in "high-velocity bullet". That's obvious, because if you try to use the vector-quantity version, Einstein's statement is reduced to tautological nonsense of the form: light curves because it curves. Note by the way that Einstein didn't say light curves because spacetime is curved.

 

[Beer w/Straw]

OK. Imma say something dumb.

But AlphaNumeric doesn't even trash Farsight so um... readily as before. I was feeling a little bad for Farsight. Even though I can't say I've ever agreed with Farsight on anything. I feel a bit bad for trashing him.

I really don't know what I'm saying, but I feel bad for being mean.

 

[OnlyMe]

Duffield, the above were written before Einstein discovered GR, he was simply trying to add gravitation to SR. You have been told multiple times that "science via quote-picking" doesn't work.

That is not entirely accurate Tach. While they are from a time prior to the publication of GR, they were a part of the conceptual process that Einstein went through in developing the final publication... And even after publication the issue of a variable (speed)/velocity of light in GR came up more than once.

Duffield, do you se the word velocity in the text? I highlighted it for you. In GR, the speed of light is $$c$$. It is the velocity that changes in the presence of gravitating bodies. Google "gravitational light bending". You have been told multiple times that "science via quote-picking" doesn't work.....but you can't do anything but trawl for quotes (whose meaning you clearly do not understand).

Above, I think you are confusing the current consensus view with the historical record. If you put the last part of the first reference to the constancy of the velocity of in bold, it suggests a different interpretation. By adding that last association with SR, Einstein reduced his use of velocity to a definition consistent with speed.., at least within the context, of that statement.

.., the law of the constancy of the velocity of light in vacuo, which constitutes one of the two fundamental assumptions in the special theory of relativity..,​

Generally speaking I don't agree with Farsight's conceptual interpretation, of Einstein's intent... That does not mean that historical references suddenly take on modern consensus interpretations. The issue of a variable speed of light within the context of GR was and to some extent remains debatable, along with the mechanisms responsible for that variability.

 

[Farsight]

The only thing you have demolished here is your credibility by once again completely ignoring the points made

I certainly haven't ignored them. You repeatedly claimed that gravitational lensing cannot involve inhomogeneous space and a variable speed of light because this would result in rainbow refraction, when we now all know that c in glass does not vary with wavelength. Au contraire, you've ignored Einstein, and basic physics.

and by just repeating the same old, tired, meaningless phrases as you have for years now. But that's fine, because no one here was expecting anything else. So, I am going to repeat my "abuse", and once again give you GR in a nutshell :

$$\displaystyle{G_{\mu \nu }=\kappa T_{\mu \nu }}$$

Each reader may attempt him/herself to find where exactly this hints at a variable speed of light. At the end of the day there really isn't any other point to be made except the above; GR is a beautiful thing, because it can be written down so easily and unambiguously.

It's even more beautiful when you don't ignore Einstein.

Ha ! Now this is a true little gem
Not only is this an as-per-yet unsurpassed example of ignorance of basic physics, but also a marvelous demonstration of your way of trying to worm yourself out of having been shown as who you truly are.

Since the above speaks for itself, we'll quite simple let it stand as-is.

I'm not worming out of anything. We all know that c does not vary with wavelength. Don't we?

Let's put it this way - while everybody else learns and progresses, you have just been repeating the same nonsense for years. Go figure.

Einstein didn't talk nonsense. And again, try not to be abusive when you lose an argument. It does you no credit.

The thing is - I am not an expert by any stretch of the imagination, yet I do understand the meaning of the simple tensor relation given in my previous post.

No, you don't. You think spacetime is space, you think light curves because light curves, and you dismiss Einstein. You don't understand the meaning at all.