# The Speed of Light Is Variable, Not Constant

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#### Pentcho Valev

Consider Doppler (moving observer):

The speed of the light pulses relative to the stationary observer is

c = df

where d is the distance between subsequent pulses and f is the frequency at the stationary observer. The speed of the pulses relative to the moving observer is

c'= df' > c

where f' > f is the frequency at the moving observer.

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#### Classical Motion

I don't think EM radiation has a "Doppler" shift. A Doppler shift comes from a continuous stream. It piles and stretches. And it's reversible. One can put the whistle at the station, listener on moving train, and get the exact same effect.

But one can not do that with the shift in light. Light is not a continuous stream. It blinks. It's intermittent.

It has duty cycle. And it's asymmetric. The motion of the detector can change the F. BUT the motion of the emitter will not change F. This is because not only is light intermittent, but light has an instant emission duration. Sound and other media waves, has a full period of emission streaming time. A full period of propagation pass by time, and a full period of detection time.

But light has an instant emission time, a 1/2 period of propagation fly by time, and a full period of detection time. If the motion of the detector, changes the interaction time from 1 full period, the detector will output the interaction time, not the propagation time. This will appear as a frequency shift. A moving reflector works the same way....to change the propagation duration, and thus the F.

EM radiation emits a solitary chunk, not a stream. It strobes. It blinks. The instant emission time is why, the V of c is constant, if the detector is stationary. The motion of emitter will not change F. But the motion of detector will. Because the detector needs a full period duration for detection. Detection requires time, the emission does not.

The so called F of "wave" of light comes from detection, not propagation. It's from the action - reaction property of mass.

#### Maui

If the speed of light in free space was variable, then the permittivity of free space would also have to be variable (it isn't) and Einstein's special theory of relativity would be wrong.

Dragrath and Helio

#### Pentcho Valev

Albert Einstein: "If the speed of light depends even in the least on the speed of the light source, then my whole theory of relativity, including the theory of gravitation, is wrong." https://einsteinpapers.press.princeton.edu/vol5-trans/376

The speed of light does depend on the speed of the light source, as posited by Newton's theory and proved by the Michelson-Morley experiment in 1887 (prior to the introduction of the length-contraction fudge factor):

"Emission theory, also called emitter theory or ballistic theory of light, was a competing theory for the special theory of relativity, explaining the results of the Michelson–Morley experiment of 1887...The name most often associated with emission theory is Isaac Newton. In his corpuscular theory Newton visualized light "corpuscles" being thrown off from hot bodies at a nominal speed of c with respect to the emitting object, and obeying the usual laws of Newtonian mechanics, and we then expect light to be moving towards us with a speed that is offset by the speed of the distant emitter (c ± v)." https://en.wikipedia.org/wiki/Emission_theory

Banesh Hoffmann, Einstein's co-author, admits that, originally ("without recourse to contracting lengths, local time, or Lorentz transformations"), the Michelson-Morley experiment was compatible with Newton's variable speed of light, c'=c±v, and incompatible with the constant speed of light, c'=c:

"Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether." Banesh Hoffmann, Relativity and Its Roots, p.92 https://www.amazon.com/Relativity-Its-Roots-Banesh-Hoffmann/dp/0486406768

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#### Maui

"The speed of light does depend on the speed of the light source" - in an inertial frame of reference it does not.

#### Helio

The speed of light can only be measured to have one speed, regardless of the motion of either the receiver or the emitter. Even the definition of a meter is now based on this fact. This is the basis to SR (Special Relativity), and has been confirmed in, perhaps, countless experiments.

One can choose either a length or time dilation to accomplish this constancy.

Light is not a particle of matter, which do impart more, or less, energy on a moving surface.

#### Classical Motion

I have often wondered why science uses light to measure the velocity of light. No matter how accurate and precise, or what method we use, light is a flux, and any result will be an average. Measure 5 seconds apart, and it will be different. Because a flux is a moving average. If you ever get the same result with a flux, that proves you are not looking close enough. Or sampling fast enough. Even a one path measurement of flux would always be fuzzy.

A single emitter with just one phase should be used. And a reflection adds duration and acceleration, a direction acceleration at the least. One path measurement is needed.

We based all of our physical relationships, terms and theories on this constant velocity premise. This constant average.

#### Pentcho Valev

The texts below imply that, if the speed of light is variable (it is!), modern physics, predicated on Einstein's 1905 constant-speed-of-light falsehood, is long dead (exists in a zombie state):

"He opened by explaining how Einstein's theory of relativity is the foundation of every other theory in modern physics and that the assumption that the speed of light is constant is the foundation of that theory. Thus a constant speed of light is embedded in all of modern physics and to propose a varying speed of light (VSL) is worse than swearing! It is like proposing a language without vowels." http://www.thegreatdebate.org.uk/VSLRevPrnt.html

"If there's one thing every schoolboy knows about Einstein and his theory of relativity, it is that the speed of light in vacuum is constant. No matter what the circumstances, light in vacuum travels at the same speed...The speed of light is the very keystone of physics, the seemingly sure foundation upon which every modern cosmological theory is built, the yardstick by which everything in the universe is measured...The constancy of the speed of light has been woven into the very fabric of physics, into the way physics equations are written, even into the notation used. Nowadays, to "vary" the speed of light is not even a swear word: It is simply not present in the vocabulary of physics." https://www.amazon.com/Faster-Than-Speed-Light-Speculation/dp/0738205257

"The whole of physics is predicated on the constancy of the speed of light...So we had to find ways to change the speed of light without wrecking the whole thing too much." https://motherboard.vice.com/en_us/article/8q87gk/light-speed-slowed

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rod

#### rod

The texts below imply that, if the speed of light is variable (it is!), modern physics, predicated on Einstein's 1905 constant-speed-of-light falsehood, is long dead (exists in a zombie state):

"He opened by explaining how Einstein's theory of relativity is the foundation of every other theory in modern physics and that the assumption that the speed of light is constant is the foundation of that theory. Thus a constant speed of light is embedded in all of modern physics and to propose a varying speed of light (VSL) is worse than swearing! It is like proposing a language without vowels." http://www.thegreatdebate.org.uk/VSLRevPrnt.html

"If there's one thing every schoolboy knows about Einstein and his theory of relativity, it is that the speed of light in vacuum is constant. No matter what the circumstances, light in vacuum travels at the same speed...The speed of light is the very keystone of physics, the seemingly sure foundation upon which every modern cosmological theory is built, the yardstick by which everything in the universe is measured...The constancy of the speed of light has been woven into the very fabric of physics, into the way physics equations are written, even into the notation used. Nowadays, to "vary" the speed of light is not even a swear word: It is simply not present in the vocabulary of physics." https://www.amazon.com/Faster-Than-Speed-Light-Speculation/dp/0738205257

"The whole of physics is predicated on the constancy of the speed of light...So we had to find ways to change the speed of light without wrecking the whole thing too much." https://motherboard.vice.com/en_us/article/8q87gk/light-speed-slowed

VSL in the past was used to argue against inflation. If light speed is indeed VSL, what happens to light-travel-time to Earth from the stars and galaxies? Does it indeed take millions and billions of years to reach Earth, or does it take a much shorter time period?

#### Maui

Precisely what is the argument supporting why light speed would be variable in the vacuum of free space?

#### ASTROSTONER

If the universe is expanding, is there really such a thing as an inertial frame of reference? Isnt everything accelerating away from everything else?

the speed of light is only constant in inertial frames of reference.

#### Helio

The success of SR (Special Relativity) and GR, along with countless tests, leaves little doubt as to the veracity that c has one and only one value (for any specific medium). This speed is independent of inertial frames. It's easy to calculate the equation for time dilation using two inertial frames if one knows the Pythagorean equation.

This speed was first determined for em waves by James Maxwell by using several known constants. [This was before light was determined to be an EM wave. I think Lord Rayleigh discovered this, IIRC.] Also, that and the null result from the Michelson-Morley experiments helped Einstein in his development of SR.

Dragrath and rod

#### rod

The success of SR (Special Relativity) and GR, along with countless tests, leaves little doubt as to the veracity that c has one and only one value (for any specific medium). This speed is independent of inertial frames. It's easy to calculate the equation for time dilation using two inertial frames if one knows the Pythagorean equation.

This speed was first determined for em waves by James Maxwell by using several known constants. [This was before light was determined to be an EM wave. I think Lord Rayleigh discovered this, IIRC.] Also, that and the null result from the Michelson-Morley experiments helped Einstein in his development of SR.
"leaves little doubt as to the veracity that c has one and only one value (for any specific medium). This speed is independent of inertial frames."

Helio, this is known as the Einstein Synchrony Convention or ESC what you stated. Do you have examples of testing the one-way speed of light from different sources and distances to Earth, one-way velocity? ESC is not based upon a one-way speed of c test; Einstein knew this.

#### Helio

From Maxwell's equations, the speed of light is given c=1/√(ε0μ0) where ε0 is permittivity of vacuum and μ0 is vacuum permeability.

Are these variables?

SR uses only one value for c, which does not require a round trip for an accurate measurement, AFAIK. Take the example case of the person shining a flashlight straight down on the deck of a train. The timing of the sensors are all in the same inertial frame and will get one result... c. This doesn't require a mirror. The person at the station, however, must include the distance the train has moved forward during the time the light traveled downward. Fixing c as a constant requires that time must be dilated. This is SR in a nutshell.

The atomic clock experiments verified time dilation which did not require a round trip.

Perhaps there's something more to this idea you've mentioned, but objective evidence for variability will be required. If such evidence is found, it will be huge news, no doubt. Until then....

rod

#### rod

From Maxwell's equations, the speed of light is given c=1/√(ε0μ0) where ε0 is permittivity of vacuum and μ0 is vacuum permeability.

Are these variables?

SR uses only one value for c, which does not require a round trip for an accurate measurement, AFAIK. Take the example case of the person shining a flashlight straight down on the deck of a train. The timing of the sensors are all in the same inertial frame and will get one result... c. This doesn't require a mirror. The person at the station, however, must include the distance the train has moved forward during the time the light traveled downward. Fixing c as a constant requires that time must be dilated. This is SR in a nutshell.

The atomic clock experiments verified time dilation which did not require a round trip.

Perhaps there's something more to this idea you've mentioned, but objective evidence for variability will be required. If such evidence is found, it will be huge news, no doubt. Until then....
Helio, do you have sources showing what you said here is correct? The info I have on anistropic synchrony convention (ASC) for c velocity, indicate there are no one-way velocity of c measurements presently, e.g., post #7 reference. Even atomic clock time dilation uses ESC, and that always requires a two-way velocity measurement. The same for using lunar reflectors and bouncing lasers off them. Any one-way velocity of c requires synchronized clocks, point of origin, and point of reception. The same is true for measuring velocity of c using Jupiter's Galilean moon events. In the 1670s, speed of light was unknown until observations of events at Jupiter, but always a two-way measurement for c used. I am not aware of a synchronized clock on the surface of the Sun and here on Earth that counts the seconds for sunlight, one-way travel time to Earth. ESC is used to interpret.

So far, I have not read a single verified paper that shows experiments conducted on velocity of light using one-way measurement with synchronized clocks in different locations. That requires synchronized clocks, and the time difference must be compared between the two.

Calling attention to reference in post #7, "In Einstein's Special Theory of Relativity, all observers measure the speed of light, c, to be the same. However, this refers to the round trip speed, where a clock at the origin times the outward and return trip of light reflecting off a distant mirror. Measuring the one-way speed of light is fraught with issues of clock synchronisation, and, as long as the average speed of light remains c, the speeds on the outward and return legs could be different."

Astronomy using light-years for star light travel time to Earth does not use synchronized clocks but ESC interpretation. This should be clearly presented to the public when discussion how long it took light from the stars to reach Earth.

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Helio

#### Helio

The same is true for measuring velocity of c using Jupiter's Galilean moon events. In the 1670s, speed of light was unknown until observations of events at Jupiter, but always a two-way measurement for c used.
Yes, that was by Romer who kept noticing the periodic time delays and advances in the orbital times for the moons of Jupiter. He reasoned that the light from those moons had to travel farther to reach a are more distant Earth when farther in its orbit from Jupiter. Knowing the time variation and the distance changes quickly produces the speed of light. He didn't use a mirror so how was that a two-way experiment?

So far, I have not read a single verified paper that shows experiments conducted on velocity of light using one-way measurement with synchronized clocks in different locations. That requires synchronized clocks, and the time difference must be compared between the two.
An atomic clock in space will report, while orbiting, the time dilation effect when compared to the atomic clock on Earth. Of course, to get it to extreme accuracies does require synchronization, but I don't think there are hiccups in this process. Wouldn't GPS, which requires both SR and GR, as well as, the set value of c, notice anomalies?

Measuring the one-way speed of light is fraught with issues of clock synchronisation, and, as long as the average speed of light remains c, the speeds on the outward and return legs could be different."
Synchronization is real headache in relativity, admittedly, so I don't want to discount it too much. But, again, what objective evidence demonstrates the variability? Math is not science, but it could lead to science. So does it? The burden isn't with mainstream physics to demonstrate a new theory.

Astronomy using light-years for star light travel time to Earth does not use synchronized clocks but ESC interpretation. This should be clearly presented to the public when discussion how long it took light from the stars to reach Earth.
If the results are the same, why should science offer something undemonstrated?

rod

#### rod

"If the results are the same, why should science offer something undemonstrated?"

The problem can be seen in post #11 reference. ESC time values for remote starlight travel times like from M31 to Earth is a convention interpretation of time, not a one-way synchronized clock measurement of the actual, elapsed time. ESC makes it easier to understand and calculate but is not a fact. It is a good interpretation.

Post #11 ref, One-way speed of light, https://en.wikipedia.org/wiki/One-way_speed_of_light

I feel this is important to inform the public correctly. Many folks I know think astronomy accurately measured light-time between various stars or galaxies to Earth, that is not factual. Astronomy uses the ESC model for interpreting light-time to Earth. This is okay but not as ironclad as many may think.

#### Helio

"If the results are the same, why should science offer something undemonstrated?"

The problem can be seen in post #11 reference. ESC time values for remote starlight travel times like from M31 to Earth is a convention interpretation of time, not a one-way synchronized clock measurement of the actual, elapsed time. ESC makes it easier to understand and calculate but is not a fact. It is a good interpretation.
I'm still confused by it. If only the average round trip speed is accurate, then doesn't this imply the time to the mirror one way is different than traveling the same path on the return? Why is that likely? One isn't uphill and the other downhill, is it?

The math likley works, but again, is this claim of variability demonstrated objectively anywhere?

The Wiki article states, "The constancy of the one-way speed in any given inertial frame is the basis of his special theory of relativity,..." [This is what I was saying earlier.] If so, and variability exists, then the basis of SR is wrong, hence SR is wrong? How could this be a mainstream view of relativity?

rod

#### Helio

It's been mentioned in the past, in other synchronization discussions, that an observer exactly halfway between two others could determine variability, but has any been found.

#### rod

It's been mentioned in the past, in other synchronization discussions, that an observer exactly halfway between two others could determine variability, but has any been found.
"I'm still confused by it. If only the average round trip speed is accurate, then doesn't this imply the time to the mirror one way is different than traveling the same path on the return? Why is that likely? One isn't uphill and the other downhill, is it?"

I agree Helio, it is confusing From what I understand in ASC, the speed of light can be anisotropic - one way (even much faster than c in SR), thus the one-way travel time can be shorter than the return time but when we measure c velocity, we see it as a constant, thus SR and ESC. However, demonstrating VSL or anisotropic one-way velocity for light is not there today. ESC and SR makes it easier in astronomy The thing I keep in mind is that light-time from distant stars to Earth is ESC interpretation, thus a very long time for most stars. It looks good but advocates for ASC or VSL are saying we see a hole here. I came to the conclusion there is a hole here in light-time from distant stars to Earth using ESC, but ESC is easier to work with and use vs. ASC or VSL, that remain to be firmly shown. My understanding of VSL was in cosmology where VSL proposed in the early epoch of the universe to avoid inflation of 4D space model. The VSL approach shows light traveling perhaps 10^20 current value and then slows down so the horizon problem in BB model is answered without rapid expansion of 4D space. VSL in cosmology postulated c very fast in the early universe, all before stars and galaxies appear. Some folks are tinkering around in the physics department when I read stuff like this

#### Helio

The VSL approach shows light traveling perhaps 10^20 current value and then slows down so the horizon problem in BB model is answered without rapid expansion of 4D space.
This is tough to swallow without evidence.

We are seeing immature galaxies the farther out we look. The 13.8 Gyr value seems plausible for what is observed. If light gets here instantly, then we would see things quite differently.

Then there is the point mentioned that Maxwell, where other things would have to accommodate a variable or two of other "constants". This seems unlikely.

It seems ad hoc, though I admit I don't understand that well, partly because I can't see why I would without evidence that it is something other than math salad.

rod

#### rod

This is tough to swallow without evidence.

We are seeing immature galaxies the farther out we look. The 13.8 Gyr value seems plausible for what is observed. If light gets here instantly, then we would see things quite differently.

Then there is the point mentioned that Maxwell, where other things would have to accommodate a variable or two of other "constants". This seems unlikely.

It seems ad hoc, though I admit I don't understand that well, partly because I can't see why I would without evidence that it is something other than math salad.
Helio, keep in mind the VSL model I read about, published in Scientific American sometime back in 2000 and other sources like NASA ADS Abstract, the very fast speed of light took place in the universe, long before the CMBR forms, stars, and galaxies, so perhaps no issues here with what we see today in astronomy. By the time those stars and galaxies appear, c would already be at the slower rate used in SR today. VSL was used to solve the horizon problem - without inflation and inflaton field or particles.

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