AbstractDreamer

There is speculation that the next new particle discovered will be called the ALB particle.  It's properties are best described in terms of colors.  Predictions are already abound for the existence of an anti-ALB particle called the ALBino.  It is colorless.

On 6/3/2018 at 7:49 AM, Markus Hanke said:

for a region of spacetime to be considered special relativistic, its geometry has to be Minkowskian - in practical terms this means that any two neighbouring events will always be related to one another in the same way, regardless of where and when you are within the region in question.  This means that a number of restrictions apply:

1. There is no curvature (i.e. the Riemann tensor vanishes everywhere in that region)
2. The temporal and spatial parts of the metric have opposite sign
3. The spacetime is everywhere smooth, continuous, and differentiable

Among some other, more technical ones. Essentially, (1) means that gravitation can be neglected in the scenario in question; (2) means we are dealing with a type of hyperbolic geometry, so inertial frames are related by hyperbolic rotations in spacetime; (3) means that spacetime can be described as a manifold, so it’s a continuum of events, and all world lines are continuous and differentiable everywhere.

Note that there is no mention here of acceleration, because SR is more general than just inertial frames; it can also handle accelerated observers just fine, so long as the above three criteria apply. For a frame to be inertial is a more restrictive condition, because we also need to add the requirement that proper acceleration vanishes everywhere, meaning we consider only geodesics in spacetime, as opposed to just any arbitrary world line.

GR then generalises this by abandoning (1), allowing non-vanishing curvature, and hence non-trivial relationships between events. The limits of GR then would be given by (3) - if we have a situation where energies are so high that spacetime itself becomes subject to quantum fluctuations, we can no longer describe it as a smooth and differentiable manifold, making even simple notions such as distance etc problematic. This is where QG has to step in, then.

Given observers in an Minkowskian volume of empty space, are there any limits to how large this volume is or how much time this volume exists for before one of the three restrictions that define such a space is violated?

What if this volume of space was so large such that observers on opposite sides of this volume are moving away from each other at superluminal speeds due to expansion?  What if this volume of space is not so large, but over eons grew via expansion to such a size that observers on opposite sides of this volume are moving away from each other at superluminal speeds?

How does volume or time limit the range of Minkowskian geometry around such observers?

3 minutes ago, Strange said:

What do you base that on?

ALL theories are approximations.

In the cases where SR applies, yes. Otherwise it would make different predictions than SR and would therefore be wrong.

Well, the benefit could be (or it could be a disadvantage) is that you appear to know more than you do by showing the equation for space-time intervals.

But that isn't relevant: If you quote something it is good manners to both your audience and the person you are copying to (1) make it clear you are copying something and (2) provide the source. 

Based on an understanding the laws of physics don't apply beyond the EH.

By definition invariance in only select cases, albeit most cases, is not invariance.     Your answer belies your bias in affecting your critical thinking.

It could find invariance, make different predictions and still be more complete, because it could make predictions on relationships not addressed with SR. 

It could find variance, make the same predictions and still be more complete, because it might include unknown unknowns.

Well if its a disadvantage, its not plagiarism.  With the nature of responses i have received, I think most would agree its a disadvantage.

What is relevant is that you stay on topic.  If you want to preach about manners, you can open your own thread.

I'm trying to find where the local limitation between inertial frames of reference are stated.   The only thing i can find is that as long as any frame is not accelerating then c will be invariant

Thanks for the oklo info, showing c has been constant for 2 billion years.

6 minutes ago, beecee said:

We all know where GR fails us....at the quantum/Planck level at the BH's center where the non physical singularity exists.Not at the EH.

 

No one has ever denied that GR is an apporoximation. But any validated QGT will give the same answers as GR within the parameters of applicability of GR.

 

 

That's great and I'm glad I am mistaken with my suggestion. Your next step now is to understand the answers you have been given and the science it entails. And of course the expertise of the people giving you those answers.

GR is incomplete  because it is an approximation. A future validated  QGT will almost certainly encompass the BB and GR and extend the parameters at which they operate. Just as GR extended and improved accuracies beyond Newtonian gravity.

Anywhere within a BH is not empty free space and therefore not a valid  spatial frame of reference to test invariance of c, irrespective of whether or not the theory is valid.  Only at the EH and outside can there be empty space between which light can pass at invariant c for the 2nd postulate to hold and for it still to be a valid frame of reference, and also a point where the theory fails.

Your first post was about time dilation as evidence that c must be invariant.   Now you're saying of course its an approximation. Had you actually read my #1 post and listened, we could have saved 3 pages of missing the point.   Given that there a limits at where GR/SR fails, is it not scientifically valid to question the postulates as the reason why it fails?

Must any future validated QGT also specify that c must be invariant?

25 minutes ago, Strange said:

Are there? Citation needed.

Quoting something without credit is called plagiarism. It is generally considered a Bd Thing.

Oh good grief, really... Here:

It took a long time to convince you that you were wrong.

 

 

No that's not the full meaning of plagiarism.   You are missing the key concept of benefit to the plagiator.

How have you interpreted that as a refusal to accept an answer?

I'm not refusing to accept that alpha readings show invariant c?  I'm contesting a point about the measured observable.  Can you really not see the difference?

16 minutes ago, Strange said:

You were told, repeatedly, that various observations of distant objects would give us information about the fundamental constants at that time. You refused, repeatedly (1) to accept that such differences occurred (2) or that we are actually observing effects from the past (3) invoked non-existent physics to hide any effects.

I didn't say that you needed to provide a reference to the postulates of special relativity.

But: YOU QUOTED SOMETHING.

1. It was not obvious you had quoted anything. I assumed that equation and the surrounding text was your own work.

2. Even if I suspected that you had quoted / copied something, I would have to do a Google search of the ENTIRE FRICKING WEB to try and work out where it had come from.

If you quote something, provide the source. It is as simple as that.

Wrong.  Please quote me where i refused to accept such differences.  Simply continuing a line of questions does not imply a refusal to accept.  My point remains valid on the measurement of the observable.  Just because I'm arguing one position, doesn't mean I am refusing to accept the opposite position.  My point was to show there might be lots of opportunities for unknown physics be operating in, and to highlight the fallibility of such answers NOT to refuse to accept them.  There is a difference between critical thinking and opinion.

I quoted something that was so mainstream popular and accepted, i thought it would be easily familiar with people that i expected that could answer my question and who could readily correct me, such as someone else who has told me its not actually the second postulate.  I didn't think it needed a quote.  Why would i re-work a postulate of the most well known theory and then ask questions on my own work?

7 minutes ago, beecee said:

 

Why do you suppose that you need an alternative?

Its not that I don't suppose we need an alternative.  Its that I cannot offer one.  I do not have the grasp of all the mathematical concepts, equations and relationships that is required.  For me to give an alternative would be just so you can laugh at me, why would waste your time with a baseless alternative?

11 minutes ago, beecee said:

 

All aspects of SR have been verified. We have no evidence of "c' being anything else but invariable and constant. Why do you doubt that? Do you have evidence to support your hypothesis?

I have already stated my evidence. There are spatial frames of reference around black hole event horizons where GR is incomplete.  There are frame of reference over time, when t=10^-43 seconds where GR is incomplete.  Those were my thoughts recently after maybe watching something on youtube or reading something somewhere or talking to someone i cant remember.  I looked up both GR and SR on wiki to understand further.   I examined the postulates i thought i found.  I looked for anything that might explain where the limits of SR might be and found none in the postulates.  I proceeded to this forum to ask further questions.  THAT is my agenda.

18 minutes ago, beecee said:

 

 Do you have access to the state of the art scientific equipement available to the professionals? If you were told by a professional you needed a life saving operation by a trusted professional, along with a second agreeable professional opinion, would you question him? or take his opinion on faith? Yes in essence you have the right to question any professional accepted mainstream opinion as you see fit...but first enroll your self in the necessary appropriate courses...get your masters and all the other qualifications...Then come back and tell us your seemingly objections to what mainstream is proposing.

I would take his opinion because I'm not looking to understand medicine, I just want to live.  Here, i'm not looking to practice science, i want to understand it.  The analogy is incompatible.  There is a difference between being a student and being a patient.  

6 minutes ago, studiot said:

But it wasn't the second postulate itself and is not a good way to present it.

 

I have been responding to other speculations ( negative mass and earth science) this morning as they are easier than preparing a sensible guide to the chain of reasoning that leads to special relativity.

I will take the time today, so look again later on - it is a fascinating story that leads eventually to the maths stated. But, as Einstein said, the Physics must come first.

Well its from wiki and it looked more mathematical than the postulate that was purely in English at the top of the page, so i figured it would be more accurate.

I have since read a few things on how Einstein initially was toying with the idea of variable c, but couldn't get the equations to fit.  Then something about reconciling with gravity.  My conclusion then is he put contraints and assumptions on GR and SR to make it work, which then turned out to fit empirical evidence.  I'm more interested into what thought processes he had and what made him initially modelled c as variable.

5 minutes ago, beecee said:

Yes you are. And so far you seem to have rejected all reasons and answers offered. I have seen this similar methodology in the past elsewhere, where someone presumes to ask a question and as it turns out, that someone also refuses all reasonable answers, and as it further turns out there is always inevitabley some agenda or baggage behind theeeeir question and behind why they will not accept an answer.

 

Well that is your error of judgement then.  What answer have i refused to accept?  What is this agenda you think i have?  You think I'm here to antagonise by questioning a cornerstone of accepted science? Then why even post a comment on my thread if you believe i have an agenda?   Are you sure this agenda you're speaking of is not yours?  Are you sure you're not on an agenda to antagonise me?  What answers have i rejected?  What answers have i not accepted?

2 minutes ago, Strange said:

Asking questions is not the problem. Refusing to accept answers because you have knowledge of the subject and therefore no basis to reject them is the problem.

You either need to accept current science (which means either learning it yourself, or taking on faith the answers of those who have) or you need to propose an alternative. I don't see what other choice there is.

You mean "no knowledge", and that is wrong, i do have some knowledge just not very much.  What answers have i refused to accept ?-  or are you assuming Im refusing to except them simply because i continue to ask questions?  One answer cannot answer all the questions i have.  I will refuse to accept answers such as "its not science", or "my ideas are random".

I can go on wiki and and read the facts if i wanted to just accept current science with no understanding.  The reason people come on a forum to ask questions is to get more than a 1 sentence answer and a link to something that the linker hopes will go way over their head and will shut the person up.

Its complete cop out statement saying we need to learn it ourselves.  Its basically saying you don't know how or cant be bothered to explain it in laymans terms.  If you don't want to give an explanation fine, but don't make the comment of saying i just need to accept it or learn it myself.   If nobody here wants to teach, Ill go somewhere else.

Tell me, how do you think someone who is asking questions and trying to learn going to possibly PROPOSE AN ALTERNATIVE?  You want the student to come up with an alternative, while you expect them to accept your answers on faith?

28 minutes ago, Strange said:

The trouble is, all these constants appear in multiple places and in different combinations. It is impossible to tweak them to get one result to stay the same but not have other results change.

So, in the absence of any evidence to the contrary it is simpler to assume they haven't changed.

Note that people have looked for evidence of fundamental constants changing over time. So it is not like there is some "dogma" meaning it can't be considered. It is just there is not evidence for this at the moment.

I can accept this answer, because I have already suspected as such from even before my original post.  But my curiosity wants to know some examples of these places and combinations, or some numerical examples to show why a tweak would be impossible, to get my thought processes going.  How can i possibly learn it myself if i don't know where to look?  I want to get some kind of idea how impossible it is.  The evidence is that we know that GR and SR are incomplete.  Isn't that enough?

36 minutes ago, Strange said:

Then you should have provided a link, or at least a reference. (I assume "wiki" means Wikipedia?)

How is anyone supposed to guess that (a) you copied it from somewhere and (b) where from.

I really would have thought anyone who could answer my questions, would not need to be shown the postulates to know them and what the typical questions such as those that im asking might be, and not actually need them to provide the same answer they have no doubt given many times before, or even asked themselves when they were students.

https://en.wikipedia.org/wiki/Postulates_of_special_relativity

Do the postulates of SR hold for when \( t<=10^{-43}seconds )\?

If the answer is No, then not all frames of reference over time are valid, and that special relativity at best is incomplete.

Do the postulates of SR hold for when \( (x_{1},x_{2},x_{3} \) are spatial coordinates that fall precisely on the event horizon of a black hole, where there is still empty vacuum between that position and \( (y_{1},y_{2},y_{3} \)

If the answer is No, then not all frames of reference over space are valid, and that special relativity at best is incomplete.

The idea of inflation in the extended \( \lambaCDM \) standard model of Big Bang cosmology employs fine tuned parameters to preserve the apparent homogeneity and isotropism the flatness of the CMB, and scarcity of magnetic monopoles that we observe in the universe today.

Amongst the criticisms are untestable predictions, lack of experimental data, and arbitrary parametising of initial conditions that only increase as you go back in time if entropy from thermalisation increases as time progresses (Occam's Razor should seek simplification, not more initial conditions).

A variable c theory can also preserve homogeneity, isotropism, and flatness of the CMB, if, instead of inflation, that c was faster from say 32 to 60 orders of magnitude 

But while these criticisms have been accepted by the community to support the standard model, the same arguments are used to refute ideas of a variable c.  The hypocrisy is surprising.

Eternal inflation is one of the many models of inflation theory, and some variants include the prediction of different volumes, or multiverses, that are interactably exclusive each other, and each running with different values for the physical constants.  

15 hours ago, swansont said:

 

https://en.wikipedia.org/wiki/Fine-structure_constant

"[it] characterizes the strength of the coupling of an elementary charged particle with the electromagnetic field, by the formula 4πε₀ħcα = e² "

I think you may find that this complaint carries little weight, since it's the result of not being familiar with the subject that you are critiquing. The people answering you, OTOH, have spent more time becoming familiar with the subject.

So you can either defer to their expertise or educate yourself.   

 

Is this the kind of forum where everyone has to get familiar with a subject before asking a question or face being scorned?  Does my complaint carry less weight because I'm a novice?

While the people answering me have spent more time on the subject, they seem more intent to focus their attention on telling me how wrong I am on some irrelevant point, or how its not science, or how i need to come up with a theory, or that I cant accept some answers, or missing my point, not reading my posts, asking me define something I already defined, jumping to an absurd conclusion about me wanting to test every electron in the universe, accusing me of random ideas, resorting to ridicule using analogies of flying unicorns; instead of actually answering any of my questions.

Having read a little on fine-structured constant and spectral emission lines of hydrogen, I now understand it something to do with the how the energy levels of an elementary particle such as an electron may be excited and jump to a level above ground state due to spin orbit interactions between the electrons magnetic dipole and the magnetic field created by its orbit around a positively charged nucleus; and in doing so release mission spectra lines that are very close but separate.

\( \alpha = \frac{e^(2)/\hbar c}{4 \pi \epsilon_{0}}= \frac{\mu_{0} c e^{2}}{2 h} \)

13 hours ago, Strange said:

Maybe c has changed and the value of pi has changed by just the right amount to keep the result the same ... 

It would be far more sensible to change the value of the reduced Planck's constant seeing as it is related to the porportionality between  a quantum particle's energy and frequency, or momentum and wavelength.   On a new-magical note, if \( \hbar \) is also a function of time or space, or time is a function space, wouldn't c necessarily be variable?
 

15 hours ago, swansont said:

That only matters if you think something happened to the photon on its way, and something else happened to exactly cancel the alleged effect, since the result is consistent with c being constant. 

Doesn't everything matter if you're trying to accurately model quantum physics?  Or is it safe to assume nothing happens whatsoever while in transit over billions of years light years for billions of years, through numerous quantum fields that mutually interact , other than redshift from expansion and lensing from gravity?

15 hours ago, swansont said:

• Variable c has consequences beyond what you are discussing, and we don't observe results consistent with those other consequences.
• But a varying c will have implications, because we can make observations from different distances (and therefore times) and different directions.  

What kind of consequences? What kind of implications?  How would the universe look if c was constant, but a different value?  How would the universe behave if c was not constant?

Is it not possible for there to be a reasonably simple solution to balancing all the equations to consider a variable c that varies only in special situations, yet only alter the consequence in those special circumstances?

11 hours ago, beecee said:

What scant knowledge I have on string theory and its many derivatives, is that it is mathematically beautiful and seems to answer questions at the scale of which at this time we are unable to observe or probe at, and which according to present scientific knowledge, we have no reason to outright reject. In essence they are still hypothetical. What you are suggesting and/or claiming is a variable "c" which scientists  have many reasons to reject. Researching stuff, that is unable to be observed certainly is part of science, as is any other speculative scenario, until reasons are forthcoming that invalidate them.

  I'm asking questions on the invariance of c.  That's not the same as suggesting or claiming that c is variable.  In order to question the invariance of c, and seeing as there is no persons in support of that position, someone has to be devils advocate.  You can jump to any conclusion that you want to believe, but you're mistaken.

16 hours ago, studiot said:

But what about the first postulate of special relativity?

The mathematical expression you quoted is neither the first nor the second postulate.

So where do you want to start to understand where it comes from?

I took the mathematical expression for the 2nd postulate from wiki.   Sure, by all means help me understand.

3 minutes ago, Strange said:

And you are quite obviously wrong. What is being observed is the spectrum from distant (and therefore a long time in the past) stars. The values of c, alpha, etc would affect the spectrum at the time it was generated. The spectrum could not magically change as it passed through space.

 

No one is against it in principle. But tests have shown it has't changed. The fact that you reject these observations is irrelevant.

Experiments have been done which could have detected some types of supersymmetric particles. The fact that none have been detected yet rules out certain classes of theories. Eventually we will either detect such particles or rule out all theories that allow for them.

That is how science works.

 

There is a difference between measuring an observable that is really old, and measuring an observable (instantaneously) from a long way away.

There's no reason to believe that the spectrum must have changed, perhaps the observable has a different relationship?  Why could the spectrum have not changed as it passed through space?   Why does any change have to be magical? Again I have not done enough reading into alpha or fine structure, so you are forcing me into simply taking your word for granted, which ironically is how religion works, not science.

You need a theory before you can experimentally test it.

You need an idea before you can build a theory.

That is how science works.

3 minutes ago, StringJunky said:

I'm saying, or pondering, that if the velocity was 1% less then, those photons would be  1% less now.

Well that is another of many alternatives.  But my main position is that No, any photon measured locally in space and time must be c.  But measured across significant time or space, FROM any position, there is no experimental evidence that it must be invariant.  Other than this alpha or fine structure constant explanation that i need to explore, or the Occam's razor argument where various constants are all changing in some extravagant dance of deception such that c is invariant is more complicated than the simpler answer that c is always invariant across time and space.

1 hour ago, beecee said:

I don't believe I am. Science is not about proof. It is about the scientific method, observational and experimental evidence, and supporting theories based on that.

1 hour ago, beecee said:

Scientific theories stand until they are falsified. 

No evidence for either actually. Sorry for the science lesson. 

1 hour ago, Strange said:

Yes, there may be unobservable situations where the speed of light changes. But because they are unobservable, that is not science.

 

Supersymmetric string theories consists of ideas that cannot be observed.  So accordingly is it not science then?  All those physicists and mathematicians... are you calling them non scientists because they are researching stuff that cannot be observed?  That is a poor definition of science, if that is your lesson.

1 hour ago, Strange said:

That doesn't change the fact that the speed of light and other fundamental constants AT THAT TIME would have affected the behaviour of atoms and photons at the time. When we observe the photons (now) we would see that the atoms behaved differently then. (We don't.)

Here is an article on how the fine structure constant affects the spectrum of hydrogen, and how it is related to c and other constants: https://physics.nist.gov/cgi-bin/cuu/Info/Constants/alpha.html

I suppose once could come up with a complicated story where all of the constants in nature changed together so that everything behaved identically even though the speed of light was different. As this would, necessarily, be indistinguishable from all the constants being, well ... constant, then Occam's Razor comes into play.

 

And, at the time scales and distance accessible to us, we see that the speed of light doesn't change. That is all science can say.

And you have been given the answers we get when this is tested. 

Your refusal to accept them is your problem, not science's.

Occam's Razor, I'm in favor of the simplified solution, if it is indistinguishable.

I have been given the an answer in "alpha" whatever that is and the fine structure constant.  I will have to do research into their connection with a constant c.  It's not that i refuse to accept your answers, its that none of your answers have justifiably shown me why i should accept them, other than your word.  It's not that I don't believe you, its that you haven't explained why.  Neither do I believe you have given much thought into my position about its plausibility, and I have little confidence that you have brought about any significant weight of your expertise in the field into this thread other than fobbing it off as my problem, because even as you are convinced c is invariant, you have not actually shown me why.

17 minutes ago, StringJunky said:

If the photons velocity was different eons ago, those same photons would still have the same  velocity if they were measured now, would they not?

That is close to the point i am making!  The velocity may have been different eons ago in time, or eons away in distance, BUT we cannot measure it to be anything other than the velocity that c is today around here.  We are experimentally limited to measurements of observables that are locked in local space and local time, such that any measurement must inevitably result in an invariant c.

19 minutes ago, swansont said:

We can't do that. But demanding impossible tests isn't going to get you anywhere.

We're limited to the test we can actually perform, and they tell is that alpha is the same as it was billions of years ago, in all directions, and is not currently changing here.

Yes, it is. That's when the interactions that produced the photons occurred.

 

Ok I don't know what alpha is.  The interactions you are observing are billions of years old, but that's because the OBSERVABLES are billions of years old. You are NOT measuring the interactions as they were then from billions of light years away.  You are measuring them after their observable has traveled through billions of light years for billions of years.   If you do not acknowledge the difference, theoretical physics is the poorer.

I'm not demanding impossible tests.  I'm curious as to why the community is so against the idea of a variable c, when the possibility of one doesn't necessarily have to have such an drastic affect on currently accepted models,  and yet the only arguments I'm hearing is impossible to test, flying unicorns, circulus in probando, and argumentum ad hominem

17 minutes ago, Strange said:

You can't. SR only applies locally. You need to use GR to compare frames of reference on that scale. And GR has been amazingly successful in that regard.

Nonsense. Alpha determines the behaviour of the atoms that emitted the light.

Correct. But then you need to come up with a model for what those circumstances are and how it would change the predictions of SR. 

Without that you are just imaging that there might be invisible flying unicorns in some part of the world we haven't explored yet.

No, flying unicorns is crazy.  Variable c is within the domain of questionable physics.

14 minutes ago, Strange said:

But until you can define what those "special circumstance" are and make a prediction of the effect they have and then propose an experiment to test it, you are not doing science.

You can imagine all sots of things might be possible. Maybe the speed light changes when we are not measuring it. Or perhaps it is not invariant on very short timescales. Or maybe ...

But if you have no evidence for these random ideas, and no way of testing them, and all the evidence we currently have shows the opposite, then the speculation is a bit pointless.

I already have defined those special circumstances.  When time is a long time ago, or a long time in future.  Or when distance is a long way away.  I'm not here to do science, i'm here to ask questions about science.

Its not a random idea.  It taken from the 2nd postulate of special relativity where there is no limitation stated on (s-t), nor is there any limitation on inertial frames of reference.  I am simply questioning those limitations.  You have already hinted that during inflation, there are some theories to a varying speed of light.  So when t=very early on, physics were different and special relativity fails, but the postulates do not reference these limitations either.

7 minutes ago, swansont said:

Light traveling at c takes time to get here. If the galaxy was a billion LY away when the photon was sent, the photon is a billion LY old (ignoring expansion effects here), not 400 years old.

 

The frequency of the emitted photon is dictated by the value of c (and other constants) at the time it was emitted. Seeing the expected value of frequency, in relation to other expected values, tells us that c has not changed with time or distance.

If c were different and other constants unchanged, then alpha would be different, and atoms would behave differently. Nuclei would behave differently.

 

 

 

The photon is a billion years old, but the MEASUREMENT is 400 years old of a photon that has aged a billion years.  It is NOT the measurement of the photon a billion years AGO.

By frequency do you mean intensity?  What is the equation that is dictated by c?  What are the other constants are involved?

1 minute ago, Strange said:

That is not really how science works. We can say, for example, that electrons have a charge of e without testing every single electron in the universe.

That IS looking at alpha hundreds, thousands or even billions of ears in the past.We are looking at the processes with generated the photons.

If the speed of light were not invariant, then tests of special relativity would not match the predictions (which are based on c being invariant).

People would love to find evidence that SR is wrong or incomplete and so tests have been done to extraordinary levels of accuracy and they are perfectly consistent with the speed of light being invariant.

Because c is a factor in so many things (e=mc², for an obvious example) so the nuclear fusion processes in distant stars  would be different than in modern stars. And we don't observe that.

 

But I'm not asking to test every electron in the universe.  I'm not asking to test every inertial frame of reference.  I'm asking to test ONE inertial frame of reference 10 billion light years away.

It is NOT looking at alpha as it was then billions of years ago.  It is looking at alpha today that has already aged billions of years.

If the speed of light were invariant under circumstances beyond that tests for special relativity, then none of the tests would fail to match predictions.

11 minutes ago, beecee said:

You want to prove a negative? Secondly, science isn't about "proof" ...It's about scientific theories that are the best explanation at the time, and are open for possible modification and or total change: Of course those scientific theories such as SR GR and the BB, that continue to explain and make successful predictions, do gain in certainty over time.

It is a postulate of SR because it is required to explain length contraction and time dilation.

Again scientific theories are not about proof. Read the first answer.

You are entirely missing my point.  You're attacking me with all the usual "science is not about proof" spiel, even though it might be a mistake I have made in my comments, is not the message I'm trying to convey.

I have valid questions on the invariance and constance of c, and instead of trying to answer them or tell me why they are not valid, you are trying to school me on what science is about.

Telling me to read your first answer when you yourself haven't understood mine is frustrating.  But I will say it again.

Length contraction and time dilation are both predicted by special relativity, and proved to real phenomena through experimental tests.  Both also rely on c being "constant" and "invariant".  This does NOT necessarily mean that if c was NOT invariant or NOT constant under special circumstances, that time dilation and length contraction would no longer be real phenomena under other circumstances.  

37 minutes ago, Strange said:

Why not? This is true of electromagnetic forces. 

Well correct me if I'm wrong.  Because if gravity is quantum, then there must be some distance where it falls below the threshold for a measurable observation, even if it is beyond the distance of the cosmic event horizon for that observer.  And at that distance where no measurable observation of the gravity field of an object can be made, it can no longer gravitationally interact with anything.  If such a limitation to gravitational range exists, how can it also work over infinite distance unless you are talking about distances in dimensions above the 3 spatial dimensions.

1 hour ago, beecee said:

We have observational evidence  of length contraction and also time dilation: I pretty sure they both denote and require an invariant "c" 

Length contraction and time dilation are both predicted by special relativity, and proved to real phenomena through experimental tests.  Both also rely on c being "constant" and "invariant" - over the limitations of the tests.    None of this am I questioning.

1 hour ago, beecee said:

Invariant over time?, what reason do we have to presume that "c"changes over time? How about the other physical constants?

I have no evidence whatsoever to presume c changes over time.  I'm asking what evidence is there prove it doesn't, to make it the 2nd postulate of special relativity.

I don't have knowledge of these tests, and do not understand these limitations. 

It is my guess that these test were not - can not - be done on EM radiation that is older than 400 years, because humans did not start testing until 400 years ago. 

• I'm not talking about measuring the velocity of an EM radiation being measured today, here at velocity c originating from the source a 10 billion years ago,
• I'm talking about measuring the velocity of EM radiation a few billion years ago - as it was THEN 10 billion years ago.

It is also my guess is that these tests were not - can not- be done on EM radiation further than 0.0019 light years from earth, as that is the distance that Voyager 1 (the furthest spacecraft to date) has managed to reach. 

• I'm not talking about measuring the velocity of an EM radiation being measured today, here at velocity c originating from a source 10 billion light years away
• I'm talking about measuring the velocity of EM radiation 10 billion light years away - as it is NOW, over THERE, from HERE, 10 billion light years away.

13 minutes ago, swansont said:

As has already been stated, c shows up in a lot of places. One is in the fine structure constant (alpha). If c was varying in time or position, it would show up as a change in electromagnetic coupling. We have pretty stringent limits on both. We observe spectra from distant galaxies, and don't see the changes you would expect if alpha was varying. We can look at different atoms in atomic clocks and see that alpha isn't changing in time, both within experimental limits, of course. (meaning the experiments place a very small upper bound on possible changes) 

Showing up in a lot of places, and there being a lot of evidence that c is constant and invariant I don't disagree.  But logically, that simply does not prove that in ANY inertial frame of reference and ALL time coordinates that it is invariant and constant.  We observe spectra from distant galaxies yes.  But we can only observe them today at time t=now.  Which of course is the same c as it was since experiments began 400 years ago.  Looking at alpha today is not looking at alpha a long time ago nor is it looking at alpha a long way away.

Is there any proof that if c was not constant or not invariable, that special relativity is necessarily wrong and not simply incomplete?

What would happen if c is invariant and constant, but simply a different value?  Are there any theories or equations that would cease to work?  Would that change anything about the laws of physics?

1 hour ago, YaDinghus said:

A change in c would be quite a drastic change in the laws of nature. The only time I can imagine this happening is the first planck time after the big bang, but that doesn't mean that this would have been the case. 

Why would it drastically change the laws of nature, if these changes were simply beyond anything that might affect you?  Unless you were to travel a cosmologically long distance or time away, you wouldn't know any different.

Well yes when the reference is hard to find.  But this is wiki.  https://en.wikipedia.org/wiki/Quantum_gravity

If gravitational effects only appear at length scales near the Planck scale, it didn't sound wrong to say quantum gravity operates over distances of Planck length. 

43 minutes ago, Strange said:

Gravity will still work over infinite distance. 

If gravity works over infinite distance as you say, and its strength is proportional to inverse square law, then it cannot be quantum. 

if gravity is quantum, then there must be some distance where it falls below the threshold for a measurable observation, even if it is beyond the distance of the cosmic event horizon for that observer.

"One of the difficulties of formulating a quantum gravity theory is that quantum gravitational effects only appear at length scales near the Planck scale, around 10⁻³⁵meter"

maybe my interpretation was wrong.

Invariant means it doesn't vary.  Constant means it stays the same.  Essentially, in language, the two words are synonyms and have the same meaning.  I'm not mixing up two separate ideas here, I'm asking two separate questions, though I might be using the wrong words.  But now I understand in physics semantics invariance is specifically related to a transformation reference and constant is related to a time reference.  However I had hoped my explanation was clear what I was asking, but maybe not.

a) If c is invariant in all frames of spatial reference - including extra-galactic distances.  How has this been tested?  If every test of SR has been done over relatively short distances, doesn't that leave an obvious question to be answered?

b) If c is constant in all frames of time reference - including a long time ago and a long time in the future.  If it has changed, what effects might we see?