At Rest with our Hubble view

[Farsight]

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.

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.

Well said, OnlyMe. It's good to see somebody being honest for a change.

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 That does not mean that historical references suddenly take on modern consensus interpretations.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.

Haven't we discussed optical clocks going slower when they're lower which can be simplified to the parallel mirror gif: View attachment 6349?

 

[Tach]

LOL! That's no debunk!

Duffield,

I did not expect you to admit it. For anybody who knows physics (that excludes you), it is very clear.

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

You can't do any physics by cherry-picking quotes, Duffield.

The word Einstein used was geschwindigkeit, which means speed.

Nope, it means velocity , Duffield. The math (that you clearly do not comprehend) deals with the velocity , not the speed. You've been doing this for years, Duffield, will you ever learn?

 

[Tach]

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.

It does? Coming from you, why I am not surprised?

Well said, OnlyMe. It's good to see somebody being honest for a change.

It is entertaining, yet not surprising, to see you two agree.

 

[Farsight]

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...

I'm not lying. I don't lie. I've read Einstein's own work and I'm pointing out what he said, and pointing to the hard scientific evidence that shows he was right.

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 dodging, and I haven't been banned from boards for dodging or insulting people. Apart from some foolishness on my part in the early days on Physicsforums, I've only been banned for knowing more physics than self-appointed "experts" who brook no challenge. Now please try to contribute to the discussion instead of making accusations of dishonesty.

 

[Farsight]

It does? Coming from you, why I am not surprised?

So Tach, are these two light pulses moving at the same speed?

The answer is no. And you know that the NIST optical clock runs measurably slower when it's only 30cm lower. And that parallel-mirror light-clocks will do the same. And that the mirrors don't move further apart. And that there's no time flitting back and forth between those mirrors. It's obvious what Einstein said, we all know that the coordinate speed of light varies in a non-inertial reference frame such as a gravitational field, and here we have it. The speed of light is not constant, just like Einstein said.

 

[PhysBang]

I'm not lying. I don't lie. I've read Einstein's own work and I'm pointing out what he said, and pointing to the hard scientific evidence that shows he was right.

You have clearly lied again. Hard scientific evidence would be you showing us how your kind of gravitational lensing works and how any of them many examples publicly available match your account.

I'm not dodging, and I haven't been banned from boards for dodging or insulting people.

BAUT Forums seems to disagree.

Apart from some foolishness on my part in the early days on Physicsforums, I've only been banned for knowing more physics than self-appointed "experts" who brook no challenge. Now please try to contribute to the discussion instead of making accusations of dishonesty.

Self-appointed experts like you who haven't answered any of my questions in this thread?

 

[PhysBang]

So Tach, are these two light pulses moving at the same speed?

This is either the dumbest thing I have seen on the internet or the dumbest lie I have seen on the internet. The image clearly doesn't represent anything in physics.

 

[Tach]

So Tach, are these two light pulses moving at the same speed?

The answer is no. And you know that the NIST optical clock runs measurably slower when it's only 30cm lower. And that parallel-mirror light-clocks will do the same. And that the mirrors don't move further apart. And that there's no time flitting back and forth between those mirrors. It's obvious what Einstein said, we all know that the coordinate speed of light varies in a non-inertial reference frame such as a gravitational field, and here we have it. The speed of light is not constant, just like Einstein said.

Ahh, the "classical" Duffield misconception. You see, in GR the photon speed is not calculated naively as $$\frac{distance}{time}$$. I can see now where your persistent misconception is coming from. You see two light clocks positioned at two different points in a gravitational field. You have managed to learn that the clock lower in the gravitational well ticks slower, you reckon that the photons must be bouncing at a "lower speed" between the mirrors. I think I have captured your misconception correctly.

 

[Tach]

I'm not lying. I don't lie.

The physics community disagrees. See here

 

[Farsight]

Ahh, the "classical" Duffield misconception. You see, in GR the photon speed is not calculated naively as $$\frac{distance}{time}$$. I can see now where your persistent misconception is coming from. You see two light clocks positioned at two different points in a gravitational field. You have managed to learn that the clock lower in the gravitational well ticks slower, you reckon that the photons must be bouncing at a "lower speed" between the mirrors. I think I have captured your misconception correctly.

It's no misconception. Clocks don't literally "measure the flow of time". All clocks feature some kind of regular cyclical internal motion and display a cumulative result called the time. Whether it's a mechanical clock, a quartz wristwatch, or an atomic clock, that's what clocks do. So when a clock goes slower, it's because the internal motion is going slower. It's that simple, Tach. The speed of light varies with gravitational potential, just like Einstein said. Look at the gif. Do you really prefer to believe that those two light pulses are moving at the same speed?

NB: Your link to a 2008 troll-thread contains the scurrilous accusation that I was harassing CERN over the use of the LHC. No way did I do that. Now come on, address the physics.

 

[PhysBang]

It's no misconception. Clocks don't literally "measure the flow of time". All clocks feature some kind of regular cyclical internal motion and display a cumulative result called the time. Whether it's a mechanical clock, a quartz wristwatch, or an atomic clock, that's what clocks do. So when a clock goes slower, it's because the internal motion is going slower. It's that simple, Tach. The speed of light varies with gravitational potential, just like Einstein said. Look at the gif. Do you really prefer to believe that those two light pulses are moving at the same speed?

If you would please attempt to describe the relevant picture with GR, you could easily see where you are grossly mistaken.

NB: Your link to a 2008 troll-thread contains the scurrilous accusation that I was harassing CERN over the use of the LHC. No way did I do that. Now come on, address the physics.

So you are saying that someone just cut-and-pasted your claims about physics into their emails to CERN? Do you still stand by the claims made in those emails?

A cursory google search shows that, despite not being able to explain the relationship of the Higgs field to GR, you do continue to claim that the Higgs boson violates GR.

 

[Tach]

The speed of light varies with gravitational potential, just like Einstein said.

He said id BEFORE he knew better, repeating the same error over and over doesn't make it right, Duffield.

Look at the gif. Do you really prefer to believe that those two light pulses are moving at the same speed?

Luckily, physics is not done via gifs, Duffield.

The way real physicists derive the gravitational time dilation is as follows:

Start with the Schwarzschild solution to EFEs:

$$(cd\tau)^2=(1-r_s/r)(cdt)^2-dr^2/(1-r_s/r)$$


For stationary clocks $$dr=0$$ so:

$$(cd\tau)^2=(1-r_s/r)(cdt)^2$$

A distant observer would consider two clocks , situated at radial coordinates $$r_A$$ and $$r_B$$ to be ticking at the rates:

$$(cd\tau_A)^2=(1-r_s/r_A)(cdt)^2$$

$$(cd\tau_B)^2=(1-r_s/r_B)(cdt)^2$$

Therefore, the ratio of the clock rates is:

$$\frac{(cd\tau_A)^2}{(cd\tau_B)^2}=\frac{1-r_s/r_A}{1-r_s/r_B}$$

Since the speed of light at BOTH locations (A and B) is the same, we can simplify by $$c$$ and we get the formula supported by countless experiments:

$$\frac{(d\tau_A)^2}{(d\tau_B)^2}=\frac{1-r_s/r_A}{1-r_s/r_B}$$

This is how science is done, what you are doing isn't science, Duffield.

NB: Your link to a 2008 troll-thread contains the scurrilous accusation that I was harassing CERN over the use of the LHC. No way did I do that. Now come on, address the physics.

The people posting in that thread got you right, Duffield. Same with the forums that banned you for your incessant trolling.

 

[OnlyMe]

The way real physicists derive the gravitational time dilation is as follows:

Start with the Schwarzschild solution to EFEs:

$$(cd\tau)^2=(1-r_s/r)(cdt)^2-dr^2/(1-r_s/r)$$


For stationary clocks $$dr=0$$ so:

$$(cd\tau)^2=(1-r_s/r)(cdt)^2$$

A distant observer would consider two clocks , situated at radial coordinates $$r_A$$ and $$r_B$$ to be ticking at the rates:

$$(cd\tau_A)^2=(1-r_s/r_A)(cdt)^2$$

$$(cd\tau_B)^2=(1-r_s/r_B)(cdt)^2$$

Therefore, the ratio of the clock rates is:

$$\frac{(cd\tau_A)^2}{(cd\tau_B)^2}=\frac{1-r_s/r_A}{1-r_s/r_B}$$

Since the speed of light at BOTH locations (A and B) is the same, we can simplify by $$c$$ and we get the formula supported by countless experiments:

$$\frac{(d\tau_A)^2}{(d\tau_B)^2}=\frac{1-r_s/r_A}{1-r_s/r_B}$$

This is how science is done,...

Tach, I am not sure your logic above is flawless...

In this first, quote below, you seem to be talking about coordinate speed or at least some determination of speed from a distant observer's perspective.

A distant observer would consider two clocks , situated at radial coordinates $$r_A$$ and $$r_B$$ to be ticking at the rates:

You follow that with a statement that seems to reference the speed of light as it would be measured locally.

Since the speed of light at BOTH locations (A and B) is the same, we can simplify by $$c$$ and we get the formula supported by countless experiments:

That seems to be mixing things up without any explanation, connecting them.

In the second instance above are you just assuming a constant speed based on SR? Or how did you determine that the speed of light was in fact the same in both locations and not just that it would be measured to be the same due to time dilation and length contraction? I don't remember any local tests of the speed of light, sufficiently removed from oneanother (gravitationally), to make that an experimentally proven assumption. That would require a lab type speed of light measurement.., have they done that sort of test on a sattelite, or the space station?


If I am not mistaken, the rate a light clock ticks at, has been experimentally observed as measurably different with as little as a one meter difference in height above the lab floor. Why present an arguement dependent on theory, ie. calculations based on the Schwarzschild solution (itself only an approximation of reality), when changes in clock rates has been experimentally proven?...

Instead, explain the rate change. There is an explanation,.. At least one if not more than one possible.

 

[Tach]

Tach, I am not sure your logic above is flawless...

In this first, quote below, you seem to be talking about coordinate speed or at least some determination of speed from a distant observer's perspective.

Nope, $$c$$ is the local speed of light, you obviously know nothing about the EFEs or about their solution(s). Not surprising.

Why present an arguement dependent on theory, ie. calculations based on the Schwarzschild solution (itself only an approximation of reality), when changes in clock rates has been experimentally proven?...

Because the theory predicted (correctly) that outcome of the experiment. Do you think that you can drop the pretenses of knowing what you are talking about?

 

[Farsight]

You have clearly lied again. Hard scientific evidence would be you showing us how your kind of gravitational lensing works and how any of them many examples publicly available match your account.

I haven't lied. Stick to the physics, PhysBang.

BAUT Forums seems to disagree.

Here's the thread concerned. I answered over a hundred questions and was suspended for not answering questions, and despite being a model poster was later banned on specious grounds. Because I was winning.

Self-appointed experts like you who haven't answered any of my questions in this thread?

I've just checked back through the thread. You haven't asked questions of me. You've cast aspersions, that's all. Everybody can see that, PhysBang. Do you have a question? If so, ask it.

 

[Tach]

because i was winning.

lol

 

[Farsight]

If you would please attempt to describe the relevant picture with GR, you could easily see where you are grossly mistaken.

I'm not grossly mistaken. The NIST optical clocks go slower when they're lower. Einstein said repeatedly that the speed of light varies with gravitational potential. The Shapiro delay is where an out-and-back signal takes longer when it skims the Sun.

So you are saying that someone just cut-and-pasted your claims about physics into their emails to CERN?

Ah, a question. Yes, somebody copied and pasted some of my Dawkins forum posts into their email.

Do you still stand by the claims made in those emails?

I stand by my forum posts. I've made some mistakes and received some correction, but those posts concern mass and the photon, I stand by them, though I must say they're difficult to read.

A cursory google search shows that, despite not being able to explain the relationship of the Higgs field to GR, you do continue to claim that the Higgs boson violates GR.

You have misunderstood my position. I claim that the mass of a body is a measure of its energy-content, not the measure of its interaction with the Higgs field, and thus that the Higgs mechanism as it stands contradicts E=mc². If you search further you can find me saying that the Higgs field has to be responsible for photon momentum as well as electron mass, and therefore the Higgs mechanism would be responsible for 100% of the mass of matter rather than 1%.

 

[Tach]

Einstein said repeatedly that the speed of light varies with gravitational potential.The Shapiro delay is where an out-and-back signal takes longer when it skims the Sun.

Making the same false statement over and over doesn't make it right. Especially when your false statement has just been debunked.

 

[OnlyMe]

Nope, $$c$$ is the local speed of light, you obviously know nothing about the EFEs or about their solution(s). Not surprising.

Huh? Here is the quote I was referring too,

A distant observer would consider two clocks , situated at radial coordinates $$r_A$$ and $$r_B$$ to be ticking at the rates:

How does "A distant observer would consider" refer to a locally measured speed of light.., of a distant location?

Aside from that my point was, if you can reference theory or experimental proof, which is the better reference?

 

[AlexG]

Making the same false statement over and over doesn't make it right. Especially when your false statement has just been debunked.

He's been doing it for years. Why would he stop now?