Velocity of light

[ajb]

As I mentioned to Swansont, that the vel. of light should be constant contravenes the general theory of relativity.

 

But this should come as no surprise to anyone as speed depends on the coordinates employed. You have the same phenomena in special relativity when using non-inertial coordinates.

 

Locally in general relativity we always have an inertial frame, and thus locally (given the strong equivalence principle) we have consistence with special relativity.

 

In general relativity, c is more like a "conversion factor" between space and time. "Travelling at c" means following a null path. The speed of light is really tied into space-time geometry and how we decide to assign units.

[Craig Dilworth]

Otis's work - some of which can be found on questia (I won't post link due to possible copyright problems) - directly contradicts maxwell, einstein etc. many seemingly consistent theories can be posited, however a constant speed of light which follows from maxwell's equations and is the basis of special relativity is the theory which matches experimental data. special and general relativity have been tested to an enormous extent, its predictions work, and real-world applications rely on the equations and physics it generates. From my very brief reading Otis claims that light does not have constant speed regardless of the motion of the observer/source - SR is based on the fact that it does. One is right, the other is wrong; I don't know if Otis's work can be mathematically self-consistent (he was/is a far greater mathematician than I) but even presuming that it is self-consistent it doesn't comply with known experimental results.

 

 

Well, as you use the term, both the special and general relativity theories "contradict" Maxwell; and the special theory "contradicts" the general theory. I don't understand how you can mean that light's having a constant velocity is a theory. Or do you mean the special theory? As I've mentioned elsewhere, all experimental results "supporting" the special theory equally well support the Maxwell-Lorentz theory, with which the special theory is incompatible. I don't believe the special theory has in fact been tested (which tests did you have in mind). The "tests" of the general theory were all second-order and inconclusive, as far as I understand.

 

As I read Otis, that light should have a constant speed relative to its source is quite possible. But its velocity should be affected by the motion of the receiver with respect to it (i.e. to the moving light ray).

 

I don't think SR is based on any facts. As I understand it, it's an attempt to save Maxwell's theory using the Lorentz transformation and at the same time introducing relativity and thereby excluding the ether, which ends up making it incompatible with Maxwell's theory.

 

Which experimental results are you referring to?

 

http://xkcd.com/675/

 

 

 

Great! (Only if it's to refer to me, I've been considering the special theory for more than 30 years ...)

[imatfaal]

Take your pick http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#moving-source_tests You doubt SR has been tested! - as one example, the time dilation effects of SR can be shown with a good clock, a few jet rides and two willing physicists (Hafele and Keating) - it has now been shown to be consistent for almost walking pace.

 

a question for you - can you provide one peer reviewed article in a science publication that provides good experimental data that light speed is not constant in a vacuum and varies with the movement of the source/observer. I know this is a reversal of the normal burden of proof, but you are challenging a concept that has withstood all that could be thrown at it for best part of a century. I am not sure of the self-contradictions you are talking about - perhaps you could elucidate?

[ajb]

I don't think SR is based on any facts. As I understand it, it's an attempt to save Maxwell's theory using the Lorentz transformation and at the same time introducing relativity and thereby excluding the ether, which ends up making it incompatible with Maxwell's theory.

 

I would view it slightly differently.

 

Maxwell's equations were the start of special relativity. The equations are invariant under the Lorentz transformations and not Galilean transformations as found in Newtonian mechanics. To my knowledge there were the first theory that has this property, though it was not properly recognised at first. The other important symmetry that Maxwell's equations ushered in is gauge symmetry, but that is another story.

[swansont]

No, I should say, fcy and vel are variables; wavelength is not. At least this is what I think I've leared from my study of the subject. Cf e.g Otis (1963), p. 10. The motion of a spectroscope towards or away from a star, caused by the orbital and rotational motions of the earth, cannot in any way affect the ‘wavelength’ (λ) of the light coming from the star.

 

This is a bald assertion with no science to back it up. It is also wrong. It's not clear the extent to which you are quoting your reference, or misunderstanding it and relaying it incorrectly. All I can say is that the answer you give is wrong.

 

"Otis (1963), p. 10" isn't sufficient as a reference. We need a title, or better still, a link to the section in question or a fair use copy-paste of the relevant part.

 

Yes, it presents a conundrum. But I'd appreciate your showing how Otis' (and and at least one so-far unmentioned other's) reasoning on this point is mistaken, rather than just referring to "a hundred years of research." Modern physics is a very tricky business, particularly since physicists now seem to accept such things as (Maxwellian, Lorentzian, Hertzian) electrodynamics (your GSP reference), which presupposes the existence of waves in a medium, and at the same time special relativity, which excludes the medium, as well as both the special and general theories of relativity, which are incompatible. By the way, by advocating the constancy of the speed of light you're denying the viability of the general theory of relativity, according to which the speed of light is variable. I think that much of this confusion stems from physicists' inclination to apply either wave or particle thinking whenever convenient (as QM has institutionalised).

 

No, the transmission of EM waves does not presuppose a medium. That notion is a century out of date.

 

General relativity reduces to special relativity when you have locally flat spacetime.

 

Your suggestion of re-writing a lot of physics is interesting, since that's precisely what I'm engaged in!

 

There's a name for people who want to rewrite physics, without first understanding the physics they wish to rewrite. I suggest that it is not a title to which one should aspire.

 

As regards the GPS business, of course, logically, the results of Maxwellian electrodynamics could well be right while the theory itself is wrong.

 

 

It's not logical at all. That's where the hundred years of experimentation come in. Your request suggests that you wish to elevate your claim to be equal with empirically confirmed physics. Science doesn't work that way.

[Craig Dilworth]

Color can be thought of as frequency or wavelength. They are really just different expressions of the same thing because light always travels at c in a vacuum. One just has units of length while the other has units of count/time.

 

If c isn't constant in a vacuum, the majority of modern physics would have to be overturned.

 

 

You'd better check this out. Colour is fcy, not wavelength.

 

it has been experimentally shown to be constant time and time again. the literature on the subject is overwhelmingly in support of a constant speed of light.

 

 

Could you please mention for me a few of these expts?

[insane_alien]

You'd better check this out. Colour is fcy, not wavelength.

 

but frequency and wavelength are equivalent as they are inversely related.

 

 

 

Could you please mention for me a few of these expts?

 

 

look up ANY experiment where the spead of light is measured. it has been done in all sorts of wavelengths from radio to gamma. seriously, go pick up a physics book. high school level will be fine.

[swansont]

You'd better check this out. Colour is fcy, not wavelength.

 

 

It's both. Their product is a constant.

[IM Egdall]

In the over 100 years since Einstein first proposed his light postulate, literally "thousands of scientific observations" have confirmed its validity. In one example, a vastly more accurate version of the famous de Sitter experiment was performed by MIT physicist Kenneth Brecher in 1977. His tests using Uhuru satellite images of X-ray pulsars verified Einstein's light postulate to one part in a billion!

 

See link to his article: http://www.ekkehard-friebe.de/Brecher-K-1977.pdf

References:

 

Victor J. Stenger, Quantum Gods, Creation, Chaos, and the Search for Cosmic Consciousness, p. 74.

 

Nigel Calder, Einstein's Universe, The Layperson's Guide, p. 176-178.

Edited December 7, 2010 by I ME

[between3and26characterslon]

I would have replied sooner to this topic but as I'm using wifi it's taking a couple of hours for the signal to travel the 24 feet to the reciever. What's really annoying is that I've got the radio on and all I get is yesterdays news. On a brighter note it's going to be sunny tomorrow so I'm going to go out now and get a tan, after all the UV, which travels that much faster, is already here and I can work on my new theory of gravity, spacetime isn't flat it's downhill

[imatfaal]

I would have replied sooner to this topic but as I'm using wifi it's taking a couple of hours for the signal to travel the 24 feet to the reciever. What's really annoying is that I've got the radio on and all I get is yesterdays news. On a brighter note it's going to be sunny tomorrow so I'm going to go out now and get a tan, after all the UV, which travels that much faster, is already here and I can work on my new theory of gravity, spacetime isn't flat it's downhill

 

Very good - I laughed out loud (I wont use the abbreviation)

[A Tripolation]

Your suggestion of re-writing a lot of physics is interesting, since that's precisely what I'm engaged in!

 

Ah. I see. I thought you were simply misunderstanding the answers given by the SFN community. But you have an agenda. In spite of what you wish were true, we're near as certain as certain gets that the speed of light is constant in a vacuum. Like others have said, it changes within mediums, but otherwise, it's constant.

 

You truly have no hope of contending that without a groundbreaking hypothesis, supported by a lot of math, that explains everything that the current theories do, and more.

[rigney]

Ah. I see. I thought you were simply misunderstanding the answers given by the SFN community. But you have an agenda. In spite of what you wish were true, we're near as certain as certain gets that the speed of light is constant in a vacuum. Like others have said, it changes within mediums, but otherwise, it's constant.

 

You truly have no hope of contending that without a groundbreaking hypothesis, supported by a lot of math, that explains everything that the current theories do, and more.

 

I'm only sticking my two cents in because I have no idea? But does antimatter, anti energy, dark matter etc..,throughout the universe; have an effect on LS? And is the universe such a vacuum? Edited December 13, 2010 by rigney

[swansont]

Ah. I see. I thought you were simply misunderstanding the answers given by the SFN community. But you have an agenda. In spite of what you wish were true, we're near as certain as certain gets that the speed of light is constant in a vacuum. Like others have said, it changes within mediums, but otherwise, it's constant.

 

You truly have no hope of contending that without a groundbreaking hypothesis, supported by a lot of math, that explains everything that the current theories do, and more.

 

And on top of all that, it has to agree with observation.

[between3and26characterslon]

Very good - I laughed out loud (I wont use the abbreviation)

 

Then my work here is done.