Why is the Speed of Light Constant in All Inertial Frames?

[Kannan Kailas]

Hi All,

It is Experimentally very evident that the speed of light in any any frame of reference is constant. But is there any explanation for why this happens.

Velocity of light seems to be like zero in mathematics. Any thing multiplied my zero results in zero irrespective of the number you are using for multiplication.

If there is any explanation for the consistancy of speed of light,can anyone please explain me?

Thanks,
Kannan

 

[wolram]

http://en.wikipedia.org/wiki/Light

the online dictionary is a good source for this
kind of information.

enjoy.

 

[mathman]

The constancy of the speed of light is a given in special relativity. The theory is in excellent agreement with all experiments. "Why" is impossible to answer. I would say this (can't answer "why") is probably true for any basic theory in physics.

 

[Loren Booda]

Because physical perspective requires a constant speed of light at some level?

Because a constant speed of light helps define spherical (highly symmetric) macroscopic and microscopic horizons?

Because the tautology of constant c, h, e, kappa and G provides the illusion of a complete physics?

 

[Kannan Kailas]

Thanks for the replies,

But if we say E=hu, or F=GMm/r2 ,the constants here is not making any kind of nonsense to us.

But the consistancy of the velocity of light is TRUE, but still it remains to be a nonsense.
There is something in the universe which make this happens, else i can say there is some predefined property which make this, and most probable it was set when the universe set out in big bang.

And i positively think all the constants are related to each other, else i can say it is related to one basic constant, which we can say the "primary constant". Hope the TOE will come up with one.

 

[GijXiXj]

My inkling too ...

There is something in the universe which make this happens, else i can say there is some predefined property which make this, and most probable it was set when the universe set out in big bang.

May be it's related to the initial amount of energy, or energy "release" that kicked it all off.

Whatever "energy" means.'

Whatever "kicked it all off" means.

;-)

 

[Integral]

Yet again.

Einstein did not choose to make the speed of light constant. He was able to postulate its constancy because of Maxwells work. According to Electoromagnetic Theory

c = \frac {1} {\sqrt {\epsilon_0 \mu_0}}

Where \epsilon_0 is the permitivity of free space and \mu_0 is the permeability of free space. So the speed of light is related to the fundamental electrical properties of space itself.

 

[yogi]

The Measured speed of light appears to be constant in the Earth centered reference frame. It is postulated to be constant in SR. Does this mean "constant for all time" ... or is it maybe a variable that could change as the universe ages - or perhaps it could vary if the experiments were accurate enough to measure the effect of gravitation on the speed of light - or if experiments were made between a source and receiver moving with respect to one another in a free space (non gravitationally centered) environment. Many experiments have been made and so far SR has survived - but the search for an underlying physical dynamic is still unrevealed.

 

[selfAdjoint]

In special relativity, constant means "measured the same by all inertial observers". From this this is deduced "Constant in all physical interactions" - but that tacitly means short time (less than a million years?) interactions. Also variations that are too small to detect would not be covered.

 

[kawikdx225]

Do these laws also apply near the event horizon of a black hole.
If light on the outside of the event horizon can escape the gravity of a black hole and light on the inside is destined for the singularity then can't we assume there is a balance point somewhere inbetween where we would observe the speed of light to be 0?

Go easy, I'm new to physics and still learning.

 

[jcsd]

A remote (infintely seperated) observer would view the velocity of light at the evnt horizon as zero.

 

[russ_watters]

Originally posted by yogi
Does this mean "constant for all time" ... or is it maybe a variable that could change as the universe ages -

There are people looking at that possibility right now. It appears that IF is isn't constant in time, it doesn't change by very much.

or perhaps it could vary if the experiments were accurate enough to measure the effect of gravitation on the speed of light

Already been done. Gravitational lensing allows us to study that.

 

[yogi]

Russ Waters - question - I have never been able to find an unequivocal proof as to whether gravity simply bends light or slows it - seems it depends a lot on the interpreter - Shipero for example seems to take the view that the effect associated with his name is merely a bending whereas others have regarded the delay as due to gravitational slowing - same as to gravitational lensing - do you have a good reference?

 

[TheAtheistKing]

Originally posted by Kannan Kailas
Hi All,

It is Experimentally very evident that the speed of light in any any frame of reference is constant. But is there any explanation for why this happens.

Velocity of light seems to be like zero in mathematics. Any thing multiplied my zero results in zero irrespective of the number you are using for multiplication.

If there is any explanation for the consistancy of speed of light,can anyone please explain me?

Thanks,
Kannan

Kannan, it has not been experimentally verified that the speed of light in any frame of reference is constant. Furthermore, it has not been experimentally verified that the speed of light in any inertial reference frame is a constant (which was Einstein's postulate).


The fact of the matter is, that the speed of light in the reference frames we have measured it results in approximately 299792458 meters per second, with some degree of experimental uncertainty. In fact, the speed of light is now defined as exactly 299792458 meters per second with zero uncertainty, and the uncertainty has been pushed onto the length of the meter itself, rather than the speed of light.

In maxwellian electrodynamics, one of the speeds of light is related to the permittivity of free space constant, and the permeability of free space constant, which both showed up in magnetic and electric theory before maxwell came along. The relationship is:

c = \frac {1} {\sqrt {\epsilon_0 \mu_0}} = 299792458 m/s

Maxwell keenly noticed that this was roughly Fizeau's measurment on the speed of light relative to that which emits light, and so he knew this was more than coincidence. Now, there is no question whatsoever, that Maxwell learned that there is some connection between the three constants. When Einstein came along, he just wondered what c was measured relative to? In other words he was asking himself, "The speed of light is c relative to what?"

There is no clear answer for this in Maxwellian electrodynamics, the constant just sort of shows up out of the blue, when the equations of electrodynamics are written as second order partial differential equations. But, because the solutions of the equation are mathematical expressions of wave phenomena, his conclusion was that light is a wave. A ripple in the electromagnetic field. Now, empty space was assumed to be a vacuum, and so there was nothing that could ripple, as light moves outwards from a source, so a luminiferous ether was postulated. That idea necessarily dictates that the speed of light would depend upon ones relative motion toward or away from the source (if you are moving with respect to the medium you come up with one speed, and if you are at rest in the medium you measure a different speed). Experiments were done by Albert Michelson using a refined device similar to the one Fizeau used to measure the speed of light. The Michelson experiments did not measure different speeds, but rather always resulted in 299792458 meters per second (approximately). The real conclusion then, is that relative motion of Earth and ether was not detected. Hence, there is no ether, space is a vaccum, and light is a particle.

So at this point, Einstein then came along with his postulate:

Postulate of SR: The speed of light is 299792458 meters per second, in any inertial reference frame.

The previous postulate did explain the results of the Michelson experiment, but it also says more, which was not verified by experiment. It is the 'more' part which is still in question. This needs to be explained.


The Einstein postulate is ludicrous, because it requires that simultaneity be relative, rather than absolute. In the other thread, I am trying to show that if you assume the Lorentz formula is true, then you can reach a contradiction mathematically, at which point you have absolute knowledge that the Lorentz formula is false. It will then immediately follow that the time dilation formula is also false, and that simultaneity is absolute and not relative, and it will also follow that the speed of light is relative, rather than absolute. Note that c=299792458 is defined to be a constant, hence dc/dt=0 even if the speed of light is a variable.

Now granted that the speed of light is relative, that still leaves us with the question as to what the constant c really represents. The simplest answer of all is contained in a new postulate:

Postulate I: The speed of a photon is 299792458 meters per second, relative to that which emits the photon.

So then, this would still mean that the constant c is intriguing, because we would then wonder why all bodies must emit photons at the same speed relative to their center of mass. The answer would almost definitely have to do with the initial conditions of the universe. At any rate, this is really where all the attention should be focused.

If the postulate above is right, then the speed of light is only c in some reference frames, specifically reference frames at rest with respect to the center of mass of the emitter, regardless of whether the emitter is in an inertial or non inertial frame when the photon is emitted.

To show you clearly why Einstein's postulate is ludicrous consider the following:

A body is about to emit a photon in the direction of two observers. One observer is at rest with respect to the emitting body, and the other observer is moving away from the emitting body at 3/4 c.

Now, by my postulate, once the body emits the photon, that photon must be moving away from the body at 299792458 meters per second. Thus, the observer at rest with respect to the emitting body must measure this speed. So let his ruler tell him that he is a distance d away from the emitting body, and let his clock tell him that the time of travel of the photon from the emitting body to him is t. He must get the following result:

299792458 m/s = d/t

Now consider the other observer who was initially moving away from the emitting body at the constant speed 3/4 c. Since he was moving away from the emitting body, it follows that the speed of the photon would be different from the other guy's measurement. In fact, he should measure the speed of the photon as being slower than 299792458 meters per second. In fact, he should come up with c/4 as the photon's speed as it moves by him. However, according to the theory of relativity, he must come up with the same value as the other guy, simply because he is in an inertial reference frame.

Now, suppose that initially he was moving away at a speed of 29979458 meters per second from the emitting body. Common sense tells you that the photon should never reach him, that the distance between him and the photon should remain constant. Again relativity says that not only will the photon pass him, but it will pass him at a speed of 299792458 meters per second, simply because he is in an inertial reference frame.

The above conclusions show why the assumption that the speed of light is the same in ALL inertial reference frames is nonsensical.

Anyways, my point is that the speed of light has not been proven to be 299792458 meters per second in all frames, but only some. If you investigate experiments designed to test my postulate, you will see that there is too much experimental uncertainty in them to be conclusive. Hence, neither SR nor state theory have been experimentally verified yet.

In order to experimentally verify that state theory is correct, one would simply have to fire a photon at a mirror which is moving very fast towards the emitter. If state theory is correct, the experimental results will show a speed of light in excess of c. In order to detect this, the mirror has to be moving towards the source extremely fast. The point is, we cannot construct an experiment this delicate. How can we get a mirror to approach a photon emitter at say c/2, and know precisly when the photon is emitted, and when it strikes the mirror? (Hence it is easier to logically verify state theory).

The customary way to measure the speed of light is to use a stationary mirror and measure the time it takes light to move to the mirror and back. Thus, the time of travel can be measured by a single clock. However, this kind of experiment will not validate relativity, since the same result will be obtained under my postulate I.

You may find experimenter's who claim that they have ruled out my postulate I, but if you investigate the uncertainties in their experimental setup, not only uncertainties in 'amounts of time' but uncertainties in 'distance traveled by photon' as well, you will see that state theory has not been invalidated by experiment, from which it follows that relativity theory has not been validated by experiment.

 

[Hurkyl]

The fact of the matter is, that the speed of light in the reference frames we have measured it results in approximately 299792458 meters per second, with some degree of experimental uncertainty.

True, though you appear to understate the accuracy of such experiments. Was that intentional?

That idea necessarily dictates that the speed of light would depend upon ones relative motion toward or away from the source

You meant one's relative motion through the medium, right? One's motion WRT the source would only affect frequency.

Postulate of SR: The speed of light is 299792458 meters per second, in any inertial reference frame.

The previous postulate did explain the results of the Michelson experiment, but it also says more, which was not verified by experiment. It is the 'more' part which is still in question. This needs to be explained.

You verify Maxwell's 4 laws, and you have a verification of this postulate. *shrug*

The Einstein postulate is ludicrous, because it requires that simultaneity be relative, rather than absolute.

Why does that make the Einstein postulate ludicrous?

It will then immediately follow that the time dilation formula is also false

I would like to point out that time dilation has been experimentally verified quite well.

In order to experimentally verify that state theory is correct, one would simply have to...

Or, have a particle in a particle accelerator emit a photon... wait, I think they've done that before.

 

[yogi]

Time dilation works in such a way as to equalize inertial reference frames - it may seem counterinitve that all observers measure the velocity of light as having the same value - but if this were not the case, we could not explain how GPS satellite signals always arise "on time" irrespective of the direction of the signal with respect to the Earth's motion vis-a-vis space. As I have said - there are still tests that need to be perform to validate SR in all cases - but this does not mean that its postulates are flawed per se.

 

[Loren Booda]

jcsd,

How can a remote observer view light traveling at c=0? That light would get nowhere, and never reach her.

 

[TheAtheistKing]

Originally posted by Hurkyl

The fact of the matter is, that the speed of light in the reference frames we have measured it results in approximately 299792458 meters per second, with some degree of experimental uncertainty.

True, though you appear to understate the accuracy of such experiments. Was that intentional?

Not intentional or unintentional, I didn't think it mattered right now. Cesium clocks are accurate to one part in 10^14, and hence the limiting factor in a speed measurement will be uncertainty in distance. The point is, better measurements will only result in a more accurate definition of a 'meter' rather than a more accurate measurement of the speed of light.



Now, empty space was assumed to be a vacuum, and so there was nothing that could ripple, as light moves outwards from a source, so a luminiferous ether was postulated. That idea necessarily dictates that the speed of light would depend upon ones relative motion toward or away from the source (if you are moving with respect to the medium you come up with one speed, and if you are at rest in the medium you measure a different speed).

You meant one's relative motion through the medium, right? One's motion WRT the source would only affect frequency.

No, I meant what I said, but I will explain it better later.


Postulate of SR: The speed of light is 299792458 meters per second, in any inertial reference frame.

The previous postulate did explain the results of the Michelson experiment, but it also says more, which was not verified by experiment. It is the 'more' part which is still in question. This needs to be explained.


You verify Maxwell's 4 laws, and you have a verification of this postulate. *shrug*

Incorrect, how does one verify maxwell's four laws? This brings me back to my original point of departure, which is that simultaneity is absolute, which fact can be proved algebraically, and is the starting point of the entire analysis. If the Lorentz contraction formula is derivable from Maxwell's four laws (and it is), then Maxwellian electrodynamics ends in contradiction.


The Einstein postulate is ludicrous, because it requires that simultaneity be relative, rather than absolute.

Why does that make the Einstein postulate ludicrous?

It makes it ludicrous, because the assumption that simultaneity is relative leads to a mathematical contradiction, the only logical thing left to do is negate the assumption, and conclude that simultaneity is absolute. Again, this puts the burden on the logic of the other thread.



It will then immediately follow that the time dilation formula is also false.

I would like to point out that time dilation has been experimentally verified quite well.

Something is verified, or not verified. There is no such thing as 'verified quite well'. Choose the exact experiment, and give me the day on which is was performed, that proved conclusively that the time dilation formula is true.

In order to experimentally verify that state theory is correct, one would simply have to fire a photon at a mirror which is moving very fast towards the emitter. If state theory is correct, the experimental results will show a speed of light in excess of c.

Or, have a particle in a particle accelerator emit a photon... wait, I think they've done that before.

Yes we have done that before, I've used the accelerator at Brookhaven national labs to perform experiments using synchrotron radiation. But, I do not see how such experiments verify or falsify state theory. Perhaps you will show me?

 

[russ_watters]

Originally posted by TheAtheistKing
Something is verified, or not verified. There is no such thing as 'verified quite well'.

That isn't how science works. Since there is no such thing as a perfectly accurate experiment, you can only verify a calculation to within the sensitivity of the instruments used to measure the effect. This is part of the reason no theory can ever be said to be 100% correct.

Choose the exact experiment, and give me the day on which is was performed, that proved conclusively that the time dilation formula is true.

There have been many, many, many, many experiments. Clocks on towers, clocks on planes, clocks in space, etc. I'll give my favorite SR/GR evidence example:http://www.metaresearch.org/cosmology/gps-relativity.asp is what the GPS system tells us about Relativity. A few snippets:

3. Does the GPS confirm the clock rate changes predicted by GR and SR?

The initial clock rate errors just after launch would give the best indication of the absolute accuracy of the predictions of relativity because they would be least affected by accumulated random errors in clock rates over time. Unfortunately, these have not yet been studied. But if the errors were significantly greater than the rate variance among the 24 GPS satellites, which is less than 200 ns/day under normal circumstances, it would have been noticed even without a study. So we can state that the clock rate effect predicted by GR is confirmed to within no worse than ±200 / 45,900 or about 0.7%, and that predicted by SR is confirmed to within ±200 / 7,200 or about 3%. This is a very conservative estimate. In an actual study, most of that maximum 200 ns/day variance would almost certainly be accounted for by differences between planned and achieved orbits, and the predictions of relativity would be confirmed with much better precision.

Basically, the point of that is the confirmation given is what you can assume just by the fact that GPS works and without doing a more in depth study.

Russ Waters - question - I have never been able to find an unequivocal proof as to whether gravity simply bends light or slows it - seems it depends a lot on the interpreter - Shipero for example seems to take the view that the effect associated with his name is merely a bending whereas others have regarded the delay as due to gravitational slowing - same as to gravitational lensing - do you have a good reference?

The GPS link also talks about the speed of light. If it slowed down or sped up due to gravity, it would be noticeable in the GPS system.

4. Is the speed of light constant?

Other studies using GPS data have placed far more stringent limits than we will here. But our goal here is not to set the most stringent limit on possible variations in the speed of light, but rather to determine what the maximum possible variation might be that can remain consistent with the data. The GPS operates by sending atomic clock signals from orbital altitudes to the ground. This takes a mere 0.08 seconds from our human perspective, but a very long (although equivalent) 80,000,000 ns from the perspective of an atomic clock. Because of this precision, the system has shown that the speed of radio signals (identical to the "speed of light") is the same from all satellites to all ground stations at all times of day and in all directions to within ±12 meters per second (m/s). The same numerical value for the speed of light works equally well at any season of the year.

 

[TheAtheistKing]

quote:
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Originally posted by TheAtheistKing
Something is verified, or not verified. There is no such thing as 'verified quite well'.
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That isn't how science works. Since there is no such thing as a perfectly accurate experiment, you can only verify a calculation to within the sensitivity of the instruments used to measure the effect. This is part of the reason no theory can ever be said to be 100% correct.


Law Of The Excluded Middle (LEM):
For any statement X, X or not X

Let S denote something that we can say has been verified. It follows from the law of the excluded middle that either S has been verified or not (S has been verified).

Let S denote something that we can say has been verified quite well. It follows from LEM that either S has been verified quite well or not (S has been verified quite well).

So now the issue is what is the meaning of 'verify'. To say that something has been verified, is to say that its truth value has been determined.(As a side note, veritas is the latin word for truth, of which verify is an English derivative).

Please note I do not wish to get into semantical games, but semantics is an issue here.

Only statements can be true, and only statements can be false. Let us set aside the issue of what a statement is for now, and focus on the word 'verify'. We have some statement S, whose truth value we in particular do not know. We wish to know the truth value of S. Presuming the truth value of S can be known by us, it now follows that at the moment we know the truth value of S, we can say that S has been verified by us. I see no room whatsoever to say that a statement has been verified quite well. To understand me consider this:

At least one person knows the truth value of S.

Suppose the previous statement is true. Now even if you don't happen to know the truth value of S, if you know that someone else does, then you can honestly say that S has been verified. You wouldn't need to say that S has been verified quite well. But, if you cannot personally verify the truth value of S, how can you know that someone else has?

So, to say that something has been verified quite well, is semantically equivalent to saying that something hasn't been verified.

Now, you don't use the word 'verify' as an operator on the set of statements, rather you talk about 'calculations' as being verifiable. Perhaps you know what you mean here, but I do not. I am interested in the idea you are trying to express here though, perhaps you can make yourself clearer?

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Choose the exact experiment, and give me the day on which is was performed, that proved conclusively that the time dilation formula is true.
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There have been many, many, many, many experiments. Clocks on towers, clocks on planes, clocks in space, etc. I'll give my favorite SR/GR evidence exampleERE is what the GPS system tells us about Relativity. A few snippets:


Let me state my position clearly. Simultaneity must be absolute for logical reasons alone, and therefore it is impossible for time to dilate. Therefore, no experiment has ever confirmed time dilation.


One final word on the speed of light. To even say "THE speed of light" you have already biased yourself. In point of fact, there are many speeds of light, because the speed of a photon in an inertial reference frame is different from the speed of the same photon in a non inertial reference frame.

And even if you modify your phrase to "THE speed of light in an inertial reference frame" you are still biased, because you have already assumed there is only one such speed for ALL inertial reference frames, and I am arguing that the speed of a photon relative to that which emitted it, is not the same in a system which is moving with respect to the source.

 

[Integral]

Let me state my position clearly. Simultaneity must be absolute for logical reasons alone, and therefore it is impossible for time to dilate.

Simultaneous events can indeed happen and do all the time. What is restricted is our ABILITY to determine if 2 events are simultaneous. Your logical arguments cannot make that distinction. If physical measurements are made, the only way to determine if two events are simultaneous is to use the calculations provided be SR.

 

[chroot]

This thread seems to be firmly Theory Development material at this point. "Simultaneity must be absolute for logical reasons alone?" Give me a break.

- Warren

 

[Nereid]

Another source with oodles of references to experimental tests of GR (and SR), including time dilation:
http://relativity.livingreviews.org/Articles/lrr-2001-4/

 

[TheAtheistKing]

quote:
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Let me state my position clearly. Simultaneity must be absolute for logical reasons alone, and therefore it is impossible for time to dilate.
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Simultaneous events can indeed happen and do all the time. What is restricted is our ABILITY to determine if 2 events are simultaneous. Your logical arguments cannot make that distinction. If physical measurements are made, the only way to determine if two events are simultaneous is to use the calculations provided be SR.


You are slightly confused on simultaneity. Each state of the universe is a singular entity. So using set theory, we can discuss the set of states from the beginning of time up until the current state. The number of elements of that set is finite, and increasing without bound. That being said, it follows that it is two different descriptions of a single state that are concluded to be simultaneous, you can never conclude that 'two states' are simultaneous, because if they are two then they were not simultaneous. This makes any analysis of simultaneity very tricky.

So you aren't out to conclude that "two events are simultaneous" as your first few sentences imply, but rather you are out to conclude that "two different descriptions of a single state are simultaneous". Another way of putting this, is that you are out to conclude that what you thought were two states, is actually one. IN state theory, we say this by saying "simultaneity is an equivalence relation on the set of states."

As for our ability to determine if two different descriptions of a single state are simultaneous, I know what you mean here. Consider two different observers, at two different locations in the universe. Each is watching a clock tick. Now, one observer watches his clock tick out the number 7 at a certain moment in time, and the other observer watches his clock tick out the number 11 at some moment in time. Later the two observers get together and they wish to determine whether or not their observations were of the same moment in time or not. Now, if their clocks were synchronized perfectly, then the answer is no. On the other hand, suppose their clocks are not synchronized, then it is possible that the moment the one guy's clock struck 11, the other guys clock struck 7. And so yes you are right, there is no way to experimentally determine if both observations were made simultaneously, hence synchronization is a practical impossibility. But this experimental limitation has nothing whatsoever to do with a logical or mathematical analysis of simultaneity.

It is totally possible to logically and mathematically analyze 'simultaneity'. In case you didn't notice, the meaning of simultaneity is actually contained in the logical operator AND.

The compound statement "X and Y" is true precisely if the simple statement X, and the simple statement Y are true simultaneously. Otherwise the statement is false. Hence, the meaning of simultaneity is embedded in the very fabric of binary logic itself, in case you hadn't noticed.

 

[TheAtheistKing]

Originally posted by chroot
This thread seems to be firmly Theory Development material at this point. "Simultaneity must be absolute for logical reasons alone?" Give me a break.

- Warren

Actually warren I am correct, but to argue that simultaneity is absolute for logical reasons alone, is logic and not physics. The issue here is one of physics. Specifically, we have an assertion that the Lorentz Fitzgerald length contraction formula is true. Now, in any argument for relativity algebra will be used, as well as binary logic. So we can add them to the 'assumptions' made in relativity. Basically, there is an argument which goes like this:

If the Lorentz formula is true, then (X and not X), for some statement X.

In order to run the argument smoothly, you really have to have some excellent logical ability.

 

[Hurkyl]

The point is, better measurements will only result in a more accurate definition of a 'meter' rather than a more accurate measurement of the speed of light.

And if the speed of light varied, then one meter under one circumstance would be different than one meter under another circumstance, so better measurements still allow better verification of the constancy of the speed of light.

Incorrect, how does one verify maxwell's four laws?

Same way you verify anything else.

This brings me back to my original point of departure, which is that simultaneity is absolute, which fact can be proved algebraically, and is the starting point of the entire analysis. If the Lorentz contraction formula is derivable from Maxwell's four laws (and it is), then Maxwellian electrodynamics ends in contradiction.

We're still waiting for the proof.

It makes it ludicrous, because the assumption that simultaneity is relative leads to a mathematical contradiction, the only logical thing left to do is negate the assumption, and conclude that simultaneity is absolute. Again, this puts the burden on the logic of the other thread.

Assuming for the sake of argument that you do show that special relativity is self-contradictory, how does that show that simultaneity is absolute?

Something is verified, or not verified.

Ever hear of statistics?

 

[TheAtheistKing]

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The point is, better measurements will only result in a more accurate definition of a 'meter' rather than a more accurate measurement of the speed of light.
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And if the speed of light varied, then one meter under one circumstance would be different than one meter under another circumstance, so better measurements still allow better verification of the constancy of the speed of light.

No, your meterstick is one meter.



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Incorrect, how does one verify maxwell's four laws?
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Same way you verify anything else.

This made me smile.

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This brings me back to my original point of departure, which is that simultaneity is absolute, which fact can be proved algebraically, and is the starting point of the entire analysis. If the Lorentz contraction formula is derivable from Maxwell's four laws (and it is), then Maxwellian electrodynamics ends in contradiction.
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We're still waiting for the proof.

I know, and I will get it down eventually.

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It makes it ludicrous, because the assumption that simultaneity is relative leads to a mathematical contradiction, the only logical thing left to do is negate the assumption, and conclude that simultaneity is absolute. Again, this puts the burden on the logic of the other thread.
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Assuming for the sake of argument that you do show that special relativity is self-contradictory, how does that show that simultaneity is absolute?

It won't. In the proof I am working on in the other thread, all that will be accomplished, is that it will be shown that the lorentz length contraction formula, and the time dilation formula are false. Doing that will not prove that simultaneity is absolute. In order to prove that simultaneity is absolute, one must show that for any Length formula which is a function of speed, a contradiction will be arrived at, not just the Lorentz formula. Indeed, if you start out by proving simply that the length of an object cannot be a function of speed, for any formula L(v), you will have instantly overthrown SR, as well as proving that simultaneity is absolute.

The most important axiom of state theory, is that for any state x, and any state y, not (x before y and y before x). So now, if you go back and reconsider the first three state diagrams, you will see that a contradiction to this axiom arises, regardless of the exact amount of length contraction in a frame. Thus, any formula L(v) will lead to a contradiction, not just the Lorentz Fitzgerald formula, hence simultaneity is absolute.





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Something is verified, or not verified.
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Ever hear of statistics?

Yes, didn't like it, alpha and beta seem fudgable to me, seems to make conclusions relative.

 

[chroot]

Originally posted by TheAtheistKing
Actually warren I am correct

I guess you've got your very own universe over there. This one seems indifferent to your beliefs.

- Warren

 

[Kanelous]

According to my belief light does not bend, but Primary Force accelerates near heavenly bodies causing the appearance of light bending.

It's a distortion of the force field that has been stimulated by a light source.

 

[yogi]

Relativity is about measuration - whatever the speed of a photon in free space, there do not appear to be any unambiguous experiments that reveal light velocity to be other than isotropic in an inertial frame. The Silvertooth experiment purported to detect the Earth's motion relative to the ether - but that is contrary to all of the daily GPS results that do not detect the velocity of the Earth relative to local space. That is - we do not detect speed when both the transmitter and receiver are comoving - we do detect something akin to the one way Sagnac affect when the receiver moves relative to the transmitter - but this is not a relativity effect - it is simply the classical result of the fact that the distance the signal travels between transmission and reception must be accounted for when the receiver is moving relative to the source.

 

[Hurkyl]

No, your meterstick is one meter.

Right. No matter how I move the meterstick, no matter what reference frame I put the meter stick in, its proper length is always one meter.


If the speed of light varied, and the length of a meter was defined by the speed of light, then we would measure the proper length of the meterstick as something other than a meter.

In order to prove that simultaneity is absolute, one must show that for any Length formula which is a function of speed, a contradiction will be arrived at, not just the Lorentz formula.

I don't see how that follows either.

The most important axiom of state theory, is that for any state x, and any state y, not (x before y and y before x)

Relativity of simultaneity doesn't contradict that axiom. In each reference frame, defining "before" in the classical way obeys this axiom. If you're doing what you "should" be doing relativistically and say that if two events, x and y, are space-like seperated, then it is false that x is before y and it is false that y is before x, thus the axiom holds.

Relativistic causality is a partial order, not a total order.

(IOW, in terms of relativistic causality, "x before y" only if x and y have a timelike separation... though this could probably be safely extended to lightlike separations as well)

Yes, didn't like it, alpha and beta seem fudgable to me, seems to make conclusions relative.

Well, you need to learn to tolerate it; no experiment can prove anything in the mathematical sense... you can only prove things to certain levels of accuracy and confidence.

(to be pedantic, the same is true about mathematical proofs; e.g. there's always the remote possibility that everyone in the history of mathematics overlooked a subtle mistake in the calculation that 2 + 3 = 5)

 

[russ_watters]

Originally posted by chroot
I guess you've got your very own universe over there. This one seems indifferent to your beliefs.

- Warren

I believe that the Eagles are going to the Super Bowl. I believe the universe agrees with me.

I also believe that you (TheAthiestKing) are allowing your beliefs and desires (the way you WANT the universe to work) cloud your ability to objectively interpret the evidence presented to you.

You have to let it all go - your fear, doubt, and disbelief. Free your mind. [/Morpheus]

the daily GPS results that do not detect the velocity of the Earth relative to local space. That is - we do not detect speed when both the transmitter and receiver are comoving...

GPS transmitters and recievers are NOT comoving and the observed relativistic effects of their independent motions fit with the theory to a high degree of accuracy.

 

[yogi]

There is a comoving aspect with respect to space - both the GPS satellite and the receiver are carried along with the Earth and adjusted for height and velocity relative to the Earth centered reference frame - but the Earth is also moving relative to space, yet there is no variation in the measured time between signals that travel from the GPS satellite to the Earth bound receiver that depend upon the direction of the Earth's motion vector relative to space. The receiver on the Earth does move with respect to the GPS satellite (due to the Earth's's rotation) and this change in the position of the receiver from the time the signal is transmitted must be corrected for - and of course the receiver and GPS satellite are not comoving in that context... so the change in the receivers position during the transit time must be compensated for... but not the change in the direction of the transmission relative to the Earth's motion with respect to the Sun or the CBR or Milky Way, whatever. I call this the comoving frame since it moves with the Earth - this is the significance of the GPS as a test of "one way isotropy" ... an issue that eluded satisfactory experimental confirmation for many years.

 

[russ_watters]

Originally posted by yogi
...but the Earth is also moving relative to space, yet there is no variation in the measured time between signals that travel from the GPS satellite to the Earth bound receiver that depend upon the direction of the Earth's motion vector relative to space.

Thus we conclude there is no ether.

 

[TheAtheistKing]

Original quote TheAtheistKing:
--------------------------------------------------------------------------------
The most important axiom of state theory, is that for any state x, and any state y, not (x before y and y before x)
--------------------------------------------------------------------------------

Quote: Hurkyl

Relativity of simultaneity doesn't contradict that axiom. In each reference frame, defining "before" in the classical way obeys this axiom. If you're doing what you "should" be doing relativistically and say that if two events, x and y, are space-like seperated, then it is false that x is before y and it is false that y is before x, thus the axiom holds.

Relativistic causality is a partial order, not a total order.

(IOW, in terms of relativistic causality, "x before y" only if x and y have a timelike separation... though this could probably be safely extended to lightlike separations as well)

Yes relativity does contradict that, and showing this to be true is the purpose of the primary thread I made. And what on Earth is the classical way of defining 'before'? I explained the operational definition of 'before' somewhere.

 

[yogi]

R Waters - yes - GPS dealt a blow to traditional ether theory as a detectable particle wind - but not necessarily a fatel blow to all ether concepts - there are still possibilities that satisfy this result - Selleri transformations and Modified Lorentz Ether Theory both comport with one-way isotrophy - and as we have discussed previously, there is the idea that mass conditions space so as to create a local comoving inertial frame... What is needed is a theory that explains all aspects of space - why it has a characteristic impedance, a capacitance, an inductance, and why it can be modified by matter as per GR.

 

[Nereid]

Fatal blow to all aether theories?

Originally posted by yogi
R Waters - yes - GPS dealt a blow to traditional ether theory as a detectable particle wind - but not necessarily a fatel blow to all ether concepts - there are still possibilities that satisfy this result - Selleri transformations and Modified Lorentz Ether Theory both comport with one-way isotrophy - and as we have discussed previously, there is the idea that mass conditions space so as to create a local comoving inertial frame... What is needed is a theory that explains all aspects of space - why it has a characteristic impedance, a capacitance, an inductance, and why it can be modified by matter as per GR.

What experiments would be fatal for the remaining aether theories?

Presumably only those conducted with small spacecraft from from massive bodies like the Earth, or are there others?

 

[yogi]

Good question Nereid - I read everything I can on this subject - but the analogy to anything physical that we are familiar with always seems unattainable - as Einstein said - there is an ether - but the idea of motion cannot be applied to it - obviously it has properties, but its make up is "sui generis" When we get a model that is testable - then perhaps experiments can be devised that will confirm or demolish competing theories... at least to the satisfaction of rational thinkers.

 

[russ_watters]

Originally posted by yogi
as Einstein said - there is an ether - but the idea of motion cannot be applied to it

The quote is used a lot by people favoring an ether, but if motion can't be applied to it (as E said) then it isn't the same "ether" as is generally discussed. Its not the same "ether" that M&M searched unsuccessfully for. Its unfortunate that he didn't use a different word.

In any case, I liken the various ether theories to the attempts to keep a geocentric universe (and indeed that's one of the goals some people have with ether). But how many epicycles on epicycles on epicycles does it take before it has reached the point of absurdity and should be discarded? I think ether has passed that point.

 

[yogi]

R. Waters -- The word ether has been given bad press - space is something - your analogy to Geocentricity is unfounded - before you throw out the baby with the bath water, perhaps you should ponder how "nothing" can be so rich in properties - how do you explain CBR dipole anisotrophy, both globally and yearly variations, stellar aberration, spatial dimensional changes due to matter, spatial permeability and permittivity, the characteristic spatial impedance, the manifestation of fleeting particles from the vacuum, the inertial reaction that is exhibited by every mass when it is accelerated relative to space, the attraction of two closely spaced parallel plates, and so on. To give up is easy - to pursue the real nature of space, call it whatever you want, is probably the greatest challenge facing 21 century physics - In order to understand the universe, we must comprehend space and time - for that is the stuff of which it is made (My own quote).

 

[Loren Booda]

yogi,

Just a guess - if there exists an ether effect, it is too small to account for almost all, if not all, of the familiar phenonema you mention. What standard velocity do their measurements yield for the ether and why, more simply than relativity?

 

[russ_watters]

Originally posted by yogi
...before you throw out the baby with the bath water, perhaps you should ponder how "nothing" can be so rich in properties.

This is the crux of the problem. No one has ever said that space is devoid of properties. But that does NOT make it a medium for the transmission of waves in the manner of air transmitting sound.

The "ether" Einstein was talking about is space having properties. No one disagrees.

The "ether" relevant to M&M and light transmission experiments is a transmission medium. It does not exist.

Two different ethers. Or maybe, one ether with some properties that exist and some that don't.

 

[yogi]

Loren - Russ - Let me put it this way - we all agree that space has a lot of properties - and we all agree that we have not been able to make an experiment that (when fairly evaluated by most of the physics community) reveals the motion of the Earth relative thereto (at least there appears to be no motion relative to the local ether). The 64 dollar question is why? If relativity is totally kinametic, it is puzzling how these many properties of space are obscured in our velocity experiments.

 

[russ_watters]

Originally posted by yogi
If relativity is totally kinametic, it is puzzling how these many properties of space are obscured in our velocity experiments.

Why? Why do these properties of space have to have some connection to motion?

 

[yogi]

Russ - if space in any sense is energy - whether it be in the form of fields or in the stress tensor of Einstein that is postulated to condition space in consequence of local matter - then - stress - in its traditional understanding, is a form of energy - energy is mass - and therefore why is motion with respect to this mass containing medium not revealed. In SR we accept the idea of observational measurements made on other masses relative to an inertial frame - so why should we not expect to ascertain motion relative to a mass endowed medium?

 

[russ_watters]

Spacetime itself has mass? I don't think I've ever heard that before.

 

[yogi]

Russ - Einstein's stress energy tensor implies what it says - stress-energy. Whether there is a separate spatial stress apart from that induced by matter is debatable - but as you well know, there is energy in the field of a gravitational body - the energy density is inversely proportional to the 4th power of the distance - so when you integrate over the entire volume of the universe for every particle of mass - you get some average spatial energy density. Feynman once analysed the charging of a capacitor in terms of the field energy flowing into the device - as opposed to the electrons flowing to the plates via the wires that supplied the charging potential. Its been urged by some that all energy lies in the field and not in the objective particle.

Of course - the very fact that the spatial energy tends to be uniformly distributed - or nearly so - may be the very thing that prevents detection - hmm - maybe that answers may query

 

[David]

Originally posted by Kannan Kailas
Hi All,

It is Experimentally very evident that the speed of light in any any frame of reference is constant. But is there any explanation for why this happens.

Velocity of light seems to be like zero in mathematics. Any thing multiplied my zero results in zero irrespective of the number you are using for multiplication.

If there is any explanation for the consistancy of speed of light,can anyone please explain me?

Thanks,
Kannan

Why this happens has to do with the location of the photons and the location of an atomic clock used to measure the speed of the photons at that particular clock. Einstein made this clear in his 1911 gravitational redshift paper.

An atomic clock slows down in a stronger gravitational potential, and so does the speed of light. So, when local photon speed is measured in a certain gravitational potential by an atomic clock in that same gravitational potential, the speed is measured as being “c”. But when the photon speed is measured by an atomic clock that is located in a different gravitational potential, the speed of the photons relative to that second clock is not “c”. It can be more or less than “c”. So the original 1905 concept of “the constancy of the speed of light” is not correct. The updated 1911 version seems to be correct, but the speed of the photons must be locally measured by a local atomic clock resting on the surface of an astronomical body right where the speed of the photons are measured, ie, at that particular atomic clock.

 

[David]

Originally posted by yogi
Good question Nereid - I read everything I can on this subject - but the analogy to anything physical that we are familiar with always seems unattainable - as Einstein said - there is an ether - but the idea of motion cannot be applied to it - obviously it has properties, but its make up is "sui generis" When we get a model that is testable - then perhaps experiments can be devised that will confirm or demolish competing theories... at least to the satisfaction of rational thinkers.

In 1920 he didn’t attribute any “motion” to it, but I think that was a premature statement based on the incorrect information he had then about the universe being “static” and non-expanding and all the starts were pretty much “fixed” in space, with only small motions being attributed to the planets, while large motions were not attributed to the stars or galaxies in 1920.

If you merely say that Einstein’s 1920 “ether” is the local group of “fields” (magnetic, electric, and gravitational) that are generated by astronomical bodies and that travel through space with the bodies, then there is the local “ether” which regulates the speed of light locally, at the bodies. Local areas of this “ether” travel through space with the bodies. Local light speed then would be measured at an by an atomic clock that is resting on the surface of an individual astronomical body, as the light photons pass that particular clock.

 

[David]

Originally posted by russ_watters
If it slowed down or sped up due to gravity, it would be noticeable in the GPS system.

Not necessarily. It depends on which atomic clock you use to measure its speed and where the photons are located when you measure their speed with that particular atomic clock. Apparently, atomic clocks slow down and speed up at different gravitational potentials in the same amount that light slows down and speeds up at those same potentials.

question - I have never been able to find an unequivocal proof as to whether gravity simply bends light or slows it - seems it depends a lot on the interpreter

I think it does both. A beam of light passing the sun acts like a plane wave. The area of the wave nearest the sun is slowed down, while the area of the wave fartherest from the sun is not slowed down as much. Thus, the light beam bends toward the sun. This is very much like a light beam being bent as it enters water from an angle. The part of the plane wave hitting the water first slows down first. This results in the bending of the plane wave when it enters water.

But, there is something else to consider about light passing the sun. If its speed while nearest the sun is measured by atomic clocks at that same place, the gravitational potential at that place slows down the atomic clocks, so they measure the speed of “c” for the passing light waves. The light slows down at those clocks but the rate of the clocks slows down too, so those clocks measure the local speed of light at “c”. The light would appear to be slowed down when the speed of the photons at the sun are measured by an atomic clock located at the earth.

These various phenomena have led to a lot of confusion about what really happens when light passes the sun. It does slow down relative to the Earth and earth-based atomic clocks, but relative to atomic clocks at the sun, it doesn’t slow down. However, once the photons leave that area of the sun and move into deeper space, they speed up when their speeds are measured by the atomic clocks that are located at the sun. So, the sun-based atomic clocks measure the deep-space speed of light to be greater than “c”, while they measure the speed of the passing photons, passing right at the clocks, to be “c”.