The Speed of Light is Not Constant

[OnlyMe]

No! It isn't the frequency of the hyperfine transitions, it's the frequency of the emitted light. Think of one electron dropping to a lower energy state. That's one event. That one event has no frequency. But emitted light does.

You are correct, at least in part above. I got caught up in your objection to the use of the word frequency. The cesium clock rate is based on the microwave transmission, but there is also a hyperfine electron transition occurring and it does have an associated frequency. If it occurred only one way, as a single transition we would not get enough data for the clock to be of any use.

The point is that when you are defining the second using some light, you cannot say "this light has a frequency of x" because frequency is cycles per second and you haven't defined the second yet.

This is circular reasoning. Others have already elaborated on the fact that a second was defined before cesium clocks were available. The second did not change, its definition was just refined, to a more accurate standard. If this were not true your position would suggest that temperature or magnetic fields, cause time dilation because they affect the microwave emission of the cesium atom.

Have no doubt that gravitational time dilation is proven.

I never said that evidence we now have does not support time dilation. What I said or intended was that time dilation had not been proven in any universal context.

Farsight, what happens to the microwave frequency associated with a hyperfine transition of a cesium atom if you change anything about its environment? Say, temperature or magnetic field... The clock rate of atomic clocks can be affected by more than just location in a gravity well. I accept that the experimental evidence demonstrates that the clock rate of an atomic clock based on hyperfine electron transitions, is time dilated in a manner consistent with the predictions of GR. That does not prove that all change is likewise time dilated in an equally consistent manner. For time dilation to be proven, universally it must be demonstrated to affect more than one type of change in a manner consistent with prediction.

My original objection to your use of the parallel mirror light clocks, was and is that you use it as if it is some evidence of fact. It is a hypothetical clock and remains a hypothetical clock no matter who or how many "people" believe the underlying assumptions and theory, and/or that the hypothetical can be used to communicate the theory...

Using that hypothetical as some sort of proof is like using the bowling ball analogy as a proof of gravity curving spacetime. You cannot with today's technology build a light clock with the accuracy of the real optical clocks available... And your use of the hypothetical parallel mirror light clock is based on the assumption the the speed of light or distances change in a gravity well. That is not how it is used in the references cited by your Wiki reference.

To be honest I don't know if the speed of light is universally constant or not. I understand some of the arguments on both sides of the debate, but so far it has not been accurately measured except in the essentially uniform inertial frame we experience in our earth bound laboratories.

 

[Trippy]

The current definition is relevant. And it's a better definition than the old definitions because it's in line with relativity and pair production and electron diffraction and the wave nature of matter.

No it isn't, because the results are the same regardless, and they were initially derived using a system of measurement that was independent of the speed of light.

And as for Einstein and his papers, pay attention to what the guy said:

1911: "If we call the velocity of light at the origin of coordinates c₀, then the velocity of light c at a place with the gravitation potential Φ will be given by the relation c = c₀(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 propagation of light varies with position”.

All of these quotes talk about velocity, not speed. Velocity is a vector, it has a direction and a magnitude, speed is a scalar, it has only a magnitude. If the direction of motion changes while the magnitude stays the same then the velocity has changed while the speed remains constant.

 

[nimbus]

Thanks nimbus.

OMG…I hope I’m not going in his next vanity press effort as some kind of expert agreeing with him.
Maybe I will get a mention on the next junk tv show his on, if so, don't forget my title farsight... Professor Nimbus.

 

[przyk]

No it isn't.

Yes it is. Science isn't like a court of law where a prosecutor promotes one side of the story and a defence attorney promotes the other. You're supposed to be your own worst critic in science. If you choose to ignore complications that don't fit with your story, you fail as a scientist. This is non negotiable.

Don't try to make it complicated to satisfy some kind of hubristic arrogant sense of superiority.

I don't.

I understand Einstein, he said what he said, don't dismiss it as quote-mining argument-from-authority because it doesn't tally with what you've been taught.

I don't. I dismiss it as quote mining because it doesn't tally with how Einstein actually formulated general relativity in 1915-1916 and it doesn't tally with how detailed predictions are made from the theory (a topic that you consistently avoid like a plague).

There is no way to quantitatively explain that the speed of light is not constant.

Yes there is: you specify by how much the speed of light varies and under what circumstances and influences. That's the sort of thing we expect from a properly formulated theory.

Oh for God's sake przyk, we know all about SR slowdown and GR speedup as per Phil Fraundorf's image.

So you agree it's not always true that the lower clock ticks slower?

No, you're evading mine.

I pointed out that gravitational time dilation mostly disappears under free-fall conditions. You retorted with a hypothetical situation in which you were not in free-fall. That is evasion.

Now look at the thread title, look at the Einstein quotes, look at the OP, look at the evidence, and face up to it.

Look at this forum's name and the forum rules. SciForums is not your personal playground. If you say "lower clocks tick slower" and use a GIF depicting that in an argument, then I'm allowed to say "actually, that's coordinate-dependent and it isn't true in free-fall frames", and you don't get to shut down that line of discussion just because it's inconvenient for you.

See above. Don't try to evade Einstein and the evidence by hiding behind mathematics.

The mathematics you dismiss is where Einstein formulates and explains the logic of general relativity in by far the most detail. It's where you see all the little important details and caveats that don't make it to the wordy popular science presentations. It's also what makes general relativity a useful quantitatively predictive and falsifiable theory.

In trying to preemptively stifle any discussion of the mathematics, you admit you do not care how Einstein actually structured the theory logically or how experimentally testable predictions are actually derived from it.

 

[Farsight]

You are correct, at least in part above. I got caught up in your objection to the use of the word frequency. The cesium clock rate is based on the microwave transmission, but there is also a hyperfine electron transition occurring and it does have an associated frequency.

And again, the light has the frequency, not the hyperfine transition.

This is circular reasoning. Others have already elaborated on the fact that a second was defined before cesium clocks were available. The second did not change, its definition was just refined, to a more accurate standard. If this were not true your position would suggest that temperature or magnetic fields, cause time dilation because they affect the microwave emission of the cesium atom.

It isn't circular reasoning. The more accurate standard is in line with relativity and the wave nature of matter. We can diffract electrons, and we can make them out of light (along with positrons) in pair production. The circular reasoning is saying the speed of light is constant when Einstein and the evidence says it isn't, and then insisting that the speed of light is constant because we define the second and the metre from the motion of light.

I never said that evidence we now have does not support time dilation. What I said or intended was that time dilation had not been proven in any universal context.

Noted.

Farsight, what happens to the microwave frequency associated with a hyperfine transition of a cesium atom if you change anything about its environment? Say, temperature or magnetic field... The clock rate of atomic clocks can be affected by more than just location in a gravity well. I accept that the experimental evidence demonstrates that the clock rate of an atomic clock based on hyperfine electron transitions, is time dilated in a manner consistent with the predictions of GR. That does not prove that all change is likewise time dilated in an equally consistent manner. For time dilation to be proven, universally it must be demonstrated to affect more than one type of change in a manner consistent with prediction.

I'm sorry, but I don't want to discuss your doubts about time dilation.

My original objection to your use of the parallel mirror light clocks, was and is that you use it as if it is some evidence of fact. It is a hypothetical clock and remains a hypothetical clock no matter who or how many "people" believe the underlying assumptions and theory, and/or that the hypothetical can be used to communicate the theory... Using that hypothetical as some sort of proof is like using the bowling ball analogy as a proof of gravity curving spacetime. You cannot with today's technology build a light clock with the accuracy of the real optical clocks available... And your use of the hypothetical parallel mirror light clock is based on the assumption the the speed of light or distances change in a gravity well. That is not how it is used in the references cited by your Wiki reference.

It isn't proof, it's showing you the bleedin' obvious. Again, there is no river of time flowing through an optical clock. So when that clock goes slower, it's because light goes slower. I can't make it any simpler than that.

To be honest I don't know if the speed of light is universally constant or not. I understand some of the arguments on both sides of the debate, but so far it has not been accurately measured except in the essentially uniform inertial frame we experience in our earth bound laboratories.

Noted.

 

[Farsight]

No it isn't, because the results are the same regardless, and they were initially derived using a system of measurement that was independent of the speed of light.

Your metre stick is made of electrons and other particles. We can make those electrons (along with positrons) out of light in pair production. So at the fundamental level there's not a lot of difference between using light to define your metre, or a metre stick.

All of these quotes talk about velocity, not speed. Velocity is a vector, it has a direction and a magnitude, speed is a scalar, it has only a magnitude. If the direction of motion changes while the magnitude stays the same then the velocity has changed while the speed remains constant.

Read the OP, Trippy. The word velocity in the English translation is the common-usage, as per "high velocity bullet". Go back to the original German, and what Einstein actually said was that a curvature of rays of light can only take place when die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert. That translates to the propagation speed of the light with the place varies. It just doesn't make sense if you insist on vector-quantity velocity. Einstein would have been saying light curves because it curves. No, it's crystal clear that Einstein meant speed because he referred to c which is the speed of light, and to "one of the two fundamental assumptions". That’s the special relativity postulate of the constant speed of light.

 

[Farsight]

Yes it is. Science isn't like a court of law where a prosecutor promotes one side of the story and a defence attorney promotes the other. You're supposed to be your own worst critic in science. If you choose to ignore complications that don't fit with your story, you fail as a scientist. This is non negotiable.

What's non-negotiable is that there is no river of time flowing through an optical clock. So when that clock goes slower it's because the light goes slower. That's it przyk. We got Einstein too, and the Shapiro delay, and the coordinate speed of light varying in a gravitational field, you're ignoring all of it because you've been taught that the speed of light is constant.

I don't. I dismiss it as quote mining because it doesn't tally with how Einstein actually formulated general relativity in 1915-1916 and it doesn't tally with how detailed predictions are made from the theory (a topic that you consistently avoid like a plague).

You dismiss what Einstein said and all the evidence because it doesn't tally with what you've been taught.

Yes there is: you specify by how much the speed of light varies and under what circumstances and influences. That's the sort of thing we expect from a properly formulated theory.

See what I said about the optical clock above and replace t by c, like this:

$$c_0 = c_f \sqrt{1 - \frac{2GM}{rc^2}}$$

But then you've got a problem because of the c in the $$rc^2$$. Reformulating GR to give the God's eye view instead of the local view isn't easy. Again see http://arxiv.org/abs/0705.4507 along with http://arxiv.org/abs/astro-ph/0703751 where Ellis said "any proposed variation of the speed of light has major consequences for almost all physics". Magueijo and Moffat said this: "As correctly pointed out by Ellis, within the current protocol for measuring time and space the answer is no. The unit of time is defined by an oscillating system or the frequency of an atomic transition, and the unit of space is defined in terms of the distance travelled by light in the unit of time. We therefore have a situation akin to saying that the speed of light is “one light-year per year”, i.e. its constancy has become a tautology or a definition".

So you agree it's not always true that the lower clock ticks slower?

The lower clock ticks slower, stop this ducking and diving.

I pointed out that gravitational time dilation mostly disappears under free-fall conditions. You retorted with a hypothetical situation in which you were not in free-fall. That is evasion.

I didn't. The situation started with you suspended, then we let you go. Then you were in free fall. And you are testing my patience.

Look at this forum's name and the forum rules. SciForums is not your personal playground. If you say "lower clocks tick slower" and use a GIF depicting that in an argument, then I'm allowed to say "actually, that's coordinate-dependent and it isn't true in free-fall frames", and you don't get to shut down that line of discussion just because it's inconvenient for you.

It is true. We all understand gravitational time dilation. Clocks run slower when they're lower. That's it. Stop trying to suggest it isn't true.

The mathematics you dismiss is where Einstein formulates and explains the logic of general relativity in by far the most detail. It's where you see all the little important details and caveats that don't make it to the wordy popular science presentations. It's also what makes general relativity a useful quantitatively predictive and falsifiable theory.

I don't dismiss mathematics. I just can't use mathematics to prove that there is no river of time flowing through an optical clock.

In trying to preemptively stifle any discussion of the mathematics, you admit you do not care how Einstein actually structured the theory logically or how experimentally testable predictions are actually derived from it.

Not so. See above. And note what Einstein said. It's clear that you don't care what the guy said.

 

[Trippy]

Your metre stick is made of electrons and other particles. We can make those electrons (along with positrons) out of light in pair production. So at the fundamental level there's not a lot of difference between using light to define your metre, or a metre stick.

:Sigh:
Really?
You're that desperate to be right?

I just don't know where to start, aside from the blatant misrepresentation of what I said.

Read the OP, Trippy. The word velocity in the English translation is the common-usage, as per "high velocity bullet".

Right, because clearly a bullet doesn't travel in a direction?

Go back to the original German, and what Einstein actually said was that a curvature of rays of light can only take place when die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert. That translates to the propagation speed of the light with the place varies.

It also translates as The propagation velocity of the light varies with the places, because geschwindigkeit translates from german to english as both speed and velocity.

It just doesn't make sense if you insist on vector-quantity velocity. Einstein would have been saying light curves because it curves. No, it's crystal clear that Einstein meant speed because he referred to c which is the speed of light, and to "one of the two fundamental assumptions". That’s the special relativity postulate of the constant speed of light.

Zweitens aber zeigt diese Konsequenz, dass nach der allgemeinen Relativitätstheorie das schon oft erwähnte Gesetz von der Konstanz der Vakuumlichtgeschwindigkeit, das eine der beiden grundlegenden Annahmen der speziellen Relativitätstheorie bildet, keine unbegrenzte Gültigkeit beanspruchen kann. Eine Krümmung der Lichtstrahlen kann nämlich nur dann eintreten, wenn die Ausbreitungsgeschwindigkeit des Lichtes mit dem Orte variiert. Man könnte nun denken, dass durch diese Konsequenz die spezielle Relativitätstheorie, und mit ihr die Relativitätstheorie überhaupt, zu Fall gebracht würde. Dies trifft aber in Wahrheit nicht zu. Es lässt sich nur schließen, dass die spezielle Relativitätstheorie kein unbegrenztes Gültigkeitsgebiet beanspruchen kann; ihre Ergebnisse gelten nur insoweit, als man von den Einflüssen der Gravitationsfelder auf die Erscheinungen (z. B. des Lichtes) absehen kann.

Secondly, however, this conclusion shows that according to the general theory of relativity the often-mentioned law of the constancy of the vacuum speed of light, which forms one of the two basic assumptions of special relativity, can not claim any unlimited validity. A curvature of rays of light can occur namely only when the velocity of propagation of light varies with the place One might think that would ever, brought down by this consequence of special relativity theory, and with it the theory of relativity. This is true but not in truth. It can only conclude that the special theory of relativity can not claim any unlimited validity area and their results are valid only in so far as one can foresee (eg of light) from the influences of gravitational fields on the phenomena.

No, he would not be saying "light curves because it curves", that's just a bone-headed misrepresentation. He's not stating how it occurs, but rather, when it can occur IE: when the velocity - the direction as well as the magnitude, is free to vary with location, under the inlfuence of a gravitational field. This precisely describes gravitational lensing.

 

[Farsight]

No Trippy. He said the speed varies. That's why he kept banging on about the SR postulate.

Let's have a laugh shall we? See Is The Speed of Light Constant? on Baez's website. It isn't written by Baez. Anyway, see this bit in the general relativity section:

"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..."

OK with that? Einstein really was talking about the speed of light varying. Now look at the next bit:

"but a more modern interpretation is that the speed of light is constant in general relativity".

The interpretation has changed. Einstein said the speed of light changes, but that's not what's taught any more. And look at the last line:

"Finally, we come to the conclusion that the speed of light is not only observed to be constant; in the light of well tested theories of physics, it does not even make any sense to say that it varies."

So Einstein said it varies, which makes good physical sense, but it doesn't? Run that by me again?

LOL.

 

[Russ_Watters]

Again, there is no river of time flowing through an optical clock. So when that clock goes slower, it's because light goes slower. I can't make it any simpler than that.

Repeating it over and over again will never make either of those two sentences true. No one claims that there is a "river of time flowing through an optical clock." That's something you made up for the purpose of ridicule that doesn't match what the description of time is. It's exactly as ridiculous as saying you'd need to shovel "space" out of the way before pulling your car out of your garage.

So at the fundamental level there's not a lot of difference between using light to define your metre, or a metre stick.

If that were true, it should be possible to see it with an experiment. Since it can't be seen (or, rather, since the opposite is seen), it is not true.

As pointed out, your thought experiment is not a real experiment. And as per Relativity and reality, your thought experiment is wrong.

Reformulating GR to give the God's eye view instead of the local view isn't easy.

So you believe there is an absolute frame from which "c" can be measured to be "real". Fine, you can do that and the equations still work, but you can pick any frame and it will still work, so it doesn't imply that one of them is the "God's Eye View".

Worse, it will still utilize the locally constant speed of light, so all you are doing is adding complexity that cancels itself out. You aren't actually changing anything of value except making yourself feel better about the philosophy. The "God's Eye View" of C is still exactly the same locally constant C utilized in the equations.

By the way, what did Einstein have to say about the "gods eye view"? Where are his equations and calculations about it? What did he calculate the "real" speed of light on earth to be?

 

[Xmo1]

The sol is variable. The constant is not. Don't read into it. Just believe it. You don't know what light is anyway. Is it a particle or a wave. You claim to know, but even the people who made up the constant ... useless trying to talk to u scientists. Too bad Curie is dead. She could have corrected a lot of idjotry that exists today.

 

[Farsight]

Repeating it over and over again will never make either of those two sentences true. No one claims that there is a "river of time flowing through an optical clock"...

But people do claim that clocks measure the flow of time. When actually they feature some kind of regular cyclic motion. So when the clock goes slower it's because that motion is going slower. Not because "time is going slower". And there is such a thing as an optical clock.

If that were true, it should be possible to see it with an experiment. Since it can't be seen (or, rather, since the opposite is seen), it is not true.

It is true. See gravitational time dilation on Wikipedia and note this:

"Every infinitesimal region of space time may have its own proper time that corresponds to the gravitational time dilation there, where electromagnetic radiation and matter may be equally affected, since they are made of the same essence[5] (as shown in many tests involving the famous equation E=mc²)".

As pointed out, your thought experiment is not a real experiment. And as per Relativity and reality, your thought experiment is wrong.

The idealised parallel-mirror light clock is used extensively in relativity, and if you have two such clocks, the lower clock will go slower.

So you believe there is an absolute frame from which "c" can be measured to be "real". Fine, you can do that and the equations still work, but you can pick any frame and it will still work, so it doesn't imply that one of them is the "God's Eye View".

You use the CMB rest frame. It isn't an absolute reference frame in that you can't gauge your motion if you're inside some box. But it is the rest frame of the universe.

Worse, it will still utilize the locally constant speed of light, so all you are doing is adding complexity that cancels itself out. You aren't actually changing anything of value except making yourself feel better about the philosophy. The "God's Eye View" of C is still exactly the same locally constant C utilized in the equations.

Huh? The coordinate speed of light varies in a gravitational field. This "God's Eye View" gives that some priority, that's all.

By the way, what did Einstein have to say about it? Where are his equations and calculations about it? What did he calculate the "real" speed of light on earth to be?

He said the speed of light varied, but he described general relativity from the point of view of the local observer. See the foundation of the general theory of relativity. See the bit that says this:

"Since he cannot allow the velocity of light to depend explicitly upon the time in the way under consideration he will interpret his observation by saying that the clock on the periphery 'actually' goes slower than the clock at the origin".

 

[origin]

But people do claim that clocks measure the flow of time. When actually they feature some kind of regular cyclic motion. So when the clock goes slower it's because that motion is going slower. Not because "time is going slower". And there is such a thing as an optical clock.

What is that suppose to mean? In general in a gravity well when the "clock goes slower" these will also occur; a chemical reaction will go slower, the decay of radiactive materials will go slower and you will age slower and all of these will match the slower clock. But this does not mean to you that time is going slower?

 

[OnlyMe]

And again, the light has the frequency, not the hyperfine transition.

Again, your understanding of the word, seems limited by some attention bias. Here is just one definition of frequency, The number of complete cycles of a periodic process occurring per unit time. Note the word time! Not second!

Are you attempting to say that the electron transition(s) that result in a measurable microwave frequency, occur only once?

In order for any microwave source frequency to be detected and measured over time it has to have originated from more than one photon, which means that there was a series of emission events that occurred over time with some frequency.

This whole objection to your limiting the interpretation of that word, is a relation to your insistence that it is has only one meaning. Do you ever read anything attempting to understand the authors intent? (I won't go again into your obvious biased interpretation of Einstein's Leyden address, ignoring the contextual background of the time and place it was presented.)

So to get your stance straight and clear, you are saying that the hyper fine transitions occur just once and do not repeat over any measurable time frame?

The way I have always understood the process was that the environment of a group of atoms, was controlled in a way that the hyper fine transitions of the group as a whole, occur at a measurable microwave frequency, over a detectable period of time.

 

[OnlyMe]

It isn't circular reasoning.

Really! You suggest that because the accurate measurement of the second, currently involves the frequency of EM emissions.., the second never existed before the technology to detect and measure those frequencies of time were available.

The rest of your comment on this issue is no more than opinion and belief.

The fact that you or I or anyone, including Einstein, believe or believed anything at any time, does not make it anything more than what we believed at that moment.

 

[OnlyMe]

It isn't proof, it's showing you the bleedin' obvious. Again, there is no river of time flowing through an optical clock. So when that clock goes slower, it's because light goes slower. I can't make it any simpler than that.

The following is not an expression of what is happening or what I might think is happening. It is offered only to demonstrate that there might be other reasons and mechanisms involved....

Maybe what is happening with optical clocks is that, as one is moved to a different elevation within a gravitational field, it is also moved into a dynamically different zero-point energy. The dynamics of the zero-point energy and associated zero-point filed being relative to the proximity of, in this case, the charged particles the mass of the earth is composed of.

If the Casimir effect which involves a detectable force on (by comparison to the cesium atoms of an optical clock), massive parallel plates, can be explained as an interaction between the plates and the zero-point field, how can we not consider that the dynamics of that same zero-point field has some affect on the operation of optical clocks.

 

[Russ_Watters]

But people do claim that clocks measure the flow of time.

Right, that's much better. But next you'll say that if it is "flowing" then it needs to be a physical substance, like water. But then that would just mean that you don't know what an analogy is - or are pretending not to know what an analogy is. I think you do know what an analogy is and are just pretending not to so you can misconstrue the analogy by taking it literally. In other words; trolling.

When actually they feature some kind of regular cyclic motion. So when the clock goes slower it's because that motion is going slower.

Yes, time going slower (in one frame vs another) is measured by clocks. You've actually split here to a different argument without knowing it (or maybe you do know it and are just playing games by jumping around?). On the one hand you are arguing that time doesn't exist. On the other hand you acknowledge it exists and claim that clocks are just bad at measuring it. so why even bother with the claim that time doesn't eixst? It is null (has no value unto itself) and worse, it contradicts your own follow-up claim! I'm really not sure why you even bother with it, frankly. It isn't relevant to and doesn't help your main argument and just makes you look like you are trolling.

And there is such a thing as an optical clock.

Again, since by definition clocks measure time you are again contradicting your claim that time does not exist. Setting that aside...

You are using the word "optical clock" wrong (or, rather, using two definitions at once) and you know it because we discussed it before. The clock in your animation measures time by bouncing a light beam off of two mirrors. That isn't how an atomic clock works; atomic clocks depend on the frequency of the light, not the speed of light. So my point was that the clock in your diagram does not exist.

Now with that said, there is no fundamental reason why it couldn't. It would need to have some way of reading it, which isn't clear from the diagram how that would work. Namely, it isn't clear from the diagram that the clock is being observed remotely. Two ways of doing it:

1. If the clock is just tied to a display and the display is read with a telescope, it will show time dilation as the theory predicts. The clock would use the equation t=d/s, using the invariant/local speed of light and the local distance. Simple.

2. But that doesn't work for you since you want time to be absolute and speed of light to be frame dependent and therefore can't use the local speed of light. So you would need a way to have the clock report the bounces to you remotely, so you could then calculate the time using the same equation but using the the clock's local distance and your invariant/local speed of light. Of course, that still assumes your local speed of light is valid and if you want to be consistent with your beliefs you'd need to transform all of that to your preferred God Frame, which would be a mess but wouldn't acutally change the results of the experiment in a useful way.

It is true. [that "there's not a lot of difference between using light to define your metre, or a metre stick."]

You made a mess there and I didn't clean it up properly. Yes, you are right that it is true that there is little difference between using light to define the meter or vice versa. That's why it was so easy to switch from one standard to the other. But that statement is a dodge of your own position. Your position is that since the constant speed of light is assumed, if we switch back to the old system and drop the assumption, the constancy of the speed of light goes away. But it doesn't. The point is that there is no local experiment that can show length, time or C to vary. That's the ancient Principle of Relativity that has been an integral part of science since science was created -- with only the constancy of the speed of light added to it by Einstein.

You use the CMB rest frame.

The CMB is *a* useful rest frame, yes. But for most purposes, I prefer to consider myself at rest; and I'm quite sure you do too. It makes the math so much easier and doesn't cause any problems other than imply a philosophy you find unpalatable. The point is, there is no measurement or math you can do to prove that the CMB is "God's Frame". For all you know, God is a little kid pushing a toy car containing the universe across the floor of his nursery, which means the CMB is moving with respect to God's rest frame.

Which I think you recognize, since:

It isn't an absolute reference frame in that you can't gauge your motion if you're inside some box. But it is the rest frame of the universe.

And if the universe is in a box on the back of God's Tonka Truck, then it isn't God's Frame either.

You just accidentally acknowledged that SR's version of the Principle of Relativity is true: there is no local experiment you can do that can detect that motion. We're agreed there. So you've proven your own position moot (valueless).

The idealised parallel-mirror light clock is used extensively in relativity, and if you have to such clocks, the lower clock will go slower.

Agreed, but your animation of how it works is still wrong - or, at least, purposely misleading to where it doesn't match the typical use of the thought experiment. In typical use, it is the distance that is different and the speed is the same. You are utilizing a different set of assumptions from the typical way it is described, without specifying them.

Huh? The coordinate speed of light varies in a gravitational field. This "God's Eye View" gives that some priority, that's all.

Yes, but the point is that in order to measure and calculate it, you still need to know and use the local/invariant speed of light. No matter what you do, you can never escape the fact that the local/invariant speed of light is constant and is useful in the equations.

He said the speed of light varied, but he described general relativity from the point of view of the local observer.

Is that valid? It must be, since Einstein said it, right? So if Einstein doesn't describe GR from the "God Frame", why do you? I thought you were always with Einstein?

 

[OnlyMe]

We can make those electrons (along with positrons) out of light in pair production.

Could you provide a reference to where we have made electrons out of light, through pair production? I find reference to observations of natural events that can be explained, as such, but no reference where we have experimentally done so.

 

[Russ_Watters]

Slight expansion on a bit of that for emphasis:

You seem to be aware/acknowledging that what you are saying has no impact on the results of local experiments and no ultimate impact on the math (you keep citing the same accepted equations), so what does it matter? After all, our technology works fine the way it is, right? It is a philosophical difference, that's all - and a philosophy based on an undetectable God/God Frame is just a religion.

Or do you think there is a difference you haven't stated? Do you believe people age differently in time dilated frames? Ie, do you believe that in the twins paradox, the traveling twin comes back looking the same as his earth-bound twin?

 

[origin]

Could you provide a reference to where we have made electrons out of light, through pair production? I find reference to observations of natural events that can be explained, as such, but no reference where we have experimentally done so.

check out this article.
From the article:

Photon-nucleus pair production can only occur if the photons have an energy exceeding twice the rest energy (mec2) of an electron (1.022 MeV). These interactions were first observed in Patrick Blackett's counter-controlled cloud chamber, leading to the 1948 Nobel Prize in Physics.