Variable speed of light

[VanillaGorilla]

I THINK, the speed of light may be variable. Now I know your all saying that im crazy or I dont understand the properties of light. I wont argue those points, because you may be right to some degree. But The rapid expansion of the early universe points in this direction. Now light is a wave, so it can be affected by gravity, so who's to say that that the photons aren't pushed and pulled a tiny bit during the time it takes to reach their desitination. What if it is pulled toward a black hole faster that the 'accepted' speed of light , how would we know? O.K. now that I've expressed my thoughts ,please tell me what you think, without beating me up too bad!!

[austintorn@aol.com]

I don't know really what I am talking about, but perhaps the speed of a photon depends not on gravity, but at the speed at which it began as 'thrown off' as some excess from a spinning thing. We know the speed now, but was something different 'back then'?

Here's a joke: The speed of lightning would be faster if it didn't have to zig-zag.

[dleviwing]

Well, since gravity propagates at the speed of light, it cannot cause light to move faster than it’s already moving. The best way to visualize the speed of light is to imagine that it moves through the same quantity (density) of its medium for a defined increment of time. Compress the medium such to double its density and it will take twice as long for the light to travel the same distance; this is about the spatial density of glass or a refractive index of about 1.5.

Even though the speed of light is faster in the vacuum of space than it would be in a vacuum chamber on earth, the MEASUREMENT of the speed of light would produce the same number in both vacuums; that’s why gravity produces a lens effect. Are you confused yet?

Once you comprehend this, Relativity should be a piece of cake.

[Yeltsin]

I THINK, the speed of light may be variable. Now I know your all saying that im crazy or I dont understand the properties of light. I wont argue those points, because you may be right to some degree. But The rapid expansion of the early universe points in this direction. Now light is a wave, so it can be affected by gravity, so who's to say that that the photons aren't pushed and pulled a tiny bit during the time it takes to reach their desitination. What if it is pulled toward a black hole faster that the 'accepted' speed of light , how would we know? O.K. now that I've expressed my thoughts ,please tell me what you think, without beating me up too bad!!

If that's what you think, you would be right.

When the speed of light is measured it's always the same no matter
how far away it came from.

But far away, it's variable, and due to gravity, as you've been guessing.
This is a result of projecting our idea of uncurved space out to distance
locations.

Say, we calculate the speed of light somewhere distant by noticing when
it is emitted and where it is absorbed. We come up with a value that's
different than c.

Now, someone else at that distant location where the light was emmitted
and absorbed would still measure it as c.

In general relativity, the speed of light is locally always c. At a distance,
it could be something else, as a result of the curvature of spacetime.

Say we have a dial and could change the speed of light everywhere.
Would there be a measurable difference? If not, it would be called a global
gauge invariance.

It's called a gauge invariance because it's like measuring the pressure in a
vessel with a nonometer guage. A nanometer still measures the same
pressure even when the atmospheric pressure is different, because it
measures pressure differences. Turnin the dial to change the speed of
light is like changing the atmospheric pressure, with no resultant measurable
difference--the gauge reads the same.

Where the speed of light can be different from place to place (and from one
time to another) as general relativity predicts, you have have something
called a local gauge invariance.

I'd like to know if one can begin by assuming a local gauge invariance for the
speed of light, and obtain the general theory of relativity as one possible
result. In other words, instead of beginning by premising a local Minkowski
space and the Weak Equivalence Principle, can one, instead, premise a local
Minkowski space and that the speed c variable. Anyone know?

[Farsight]

VanillaGorilla: the speed of light most definitely is variable. People think of c as a constant, but actually it's a running constant. Here's how it works. We use the speed of light to define our time: Under the International System of Units, the second is currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom... Now, clocks clock up motion, not time. When atomic clocks or light clocks or any other clocks "run slow" in a high-gravity location, they do this because the speed of light at that location less than it is in a low-gravity location. But the speed of light defines our time, so we can't measure any difference. The measured speed of light is always 299,792,458 m/s. But the seconds at one location are different to the seconds at another location, so c at those two locations is not the same. Instead it's different, and there's a gradient in between. The pseudoforce that we call gravity is the result of this gradient in c. It's actually a gradient in the impedance of space which affects the propagation of the "alternating current" photon and everything else.

[Farsight]

Here's some background reading re VSL that demonstrates you aren't crazy, and you aren't alone.

[34] Variable speed of light
John Moffat was the first physicists in modern times to talk about a variable speed of light. That was in 1992, but he was largely ignored. He’s Emeritus Professor of Physics at Toronto, and thankfully people now pay more attention. See the wikipedia article on him at http://en.wikipedia.org/wiki/John_Mo...28physicist%29 and his paper Moffat, J.; "Superluminary Universe: A Possible Solution to the Initial Value Problem in Cosmology", Int.J.Mod.Phys. D2 351-366 (1993). URL: http://arxiv.org/abs/gr-qc/9211020v2. A few years later in 1998 Joao Magueijo and Andreas Albrecht had similar ideas, not knowing about Moffat. See Albrecht, A. ; Magueijo, J. ; "A time varying speed of light as a solution to cosmological puzzles", Phys.Rev. D59 (1999) 043516. URL: http://xxx.lanl.gov/abs/astro-ph/9811018v2. I might as well quote from wiki: “Their paper made it into the more prestigious journal, Physical Review D, which had rejected Moffat's paper years earlier. When Moffat saw this, he was upset and contacted Magueijo. But after Magueijo realized what had happened, he was quick to give Moffat due credit for having first proposed the idea. In fact, Moffat and Magueijo became friends, and Magueijo even devoted a whole chapter to Moffat in his 2002 book titled “Faster Than the Speed of Light”. After that, the number of physicists citing Moffat's work in academic journals skyrocketed”. Joao Magueijo is professor of physics at UCL. Check out his book Faster Than the Speed of Light: The Story of a Scientific Speculation first published by Heinemann in 2003. It's quite critical of modern science, but it tells you what it's like, and is a really good read. He's talking here about c being greater in the early universe, not lower, and he doesn't make the connection between variable c and gravity. But I imagine he does now. See Magueijo, J ; "New varying speed of light theories", Rept. Prog. Phys. 66 (2003). URL: http://arxiv.org/abs/astro-ph/0305457v3. It's an interesting paper, see this quote: Ironically, the first “varying-constant” was the speed of light, as suggested by Kelvin and Tait in 1874. Some 30 years before Einstein’s proposal of special relativity, a varying c did not shock anyone.

[baudrunner]

the devil's wing said...

Well, since gravity propagates at the speed of light..

Dave, isn't that still theoretical? To date, no gravity waves have been detected and billions of euros, dollars, and pounds have been spent trying to detect them, all based on theory. To my mind, money wasted. The only conclusion we can draw from this is that gravity does not, cannot, exhibit wave behavior because it is a different animal. Now, I'm not surprised. Are you?

The way I dee it, gravity doesn't produce the lens effect. It is the presence of a mass and the medium around which light waves are refracted that provides that illusion. There will always be a mass present to justify the perceived bending of light waves. A mass will have a denser aura of particles around it providing the medium through which light waves are propagated. Gravity is circumstantial to this process.

[dleviwing]

You’re right Steven; “propagates” may have been the wrong way to put it. How about just saying that gravity cannot accelerate anything faster than light? I agree on your point that gravity is not a propagated wave. I view gravity as being the opposite of “inflation”.

[baudrunner]

“propagates” may have been the wrong way to put it.

I haven't found a better way to express the way that the energy producing those EM oscillations are transferred from particle to particle in the medium. "Photonic transmission" might be better, but that's two words, plus it implies that the same photon passes from one particle to another, which is a misconception.

Incidentally, the dimensions at that scale, 10^-15 roughly, for the space between the particles, don't exactly concur with the frequencies which we detect in the optical spectrum. This is a "problem" (There are no "problems", only "issues". There are no "issues", only "situations"), which has never actually been discussed, in my readings or in this forum. More hysteresis, in my opinion. And most importantly, in addition, the concept of fundamentals and their harmonics probably play a role, which just goes to show what Einstein told us, that there is a whole lot of energy in even a single atom.

What we perceive as the frequencies of light waves are what reality permits us to observe of this quantum phenomenon, like the waves of the sea, or the waves of sound.

[Farsight]

I can tell you all about gravity, and "gravity waves", why they propagate at the speed of light, and why LIGO will never detect them. It's very simple once you understand it. What's important here is that energy causes gravity, whatever its form. A mass only causes gravity because of its energy content. Yes, gravity is a refraction. It is the result of a gradient in the speed of light. But it's an immersive scale change, we can't measure it locally, because the speed of light defines our time. And time is the key.