Has it ever occured to anyone that the speed of light can be greater or smaller than c in a vacuum??

I'm asking this question because I've recently been studying how the Michelson-Morley inferometer works, and found that the lack of interference patterns is much easier to explain by assuming that the speed of light in the moving inferometer is actually larger than c. (speed of light in inferometer=c + speed of inferometer through aether)

This would, as a result, give an explanation why their are no interference patterns in the Michelson-Morley experiment without having to introduce two new factors into physics (time dilation and length contraction). This would also seem to be a more logical explanation.

If we were to assume that the speed of light in a vacuum can be higher (or lower) than c, red shifting and blue shifting can then also be easily explained. From the formula:

f=c/wavelength

you can see that if the speed of the light increased, so that it's faster than c, it's frequency would increase (blue-shifting). However, if the speed of the light decreased, it's frequency would then be decreased (red-shifted).

The reason that I'm bringing this up is because Crisp provided a link, on another thread, that shows experimental proof of photons travelling faster than c. If the experiment isn't flawed, wouldn't it be better to explain the results of inferometer experiments as being the result of the increased speed of light, rather than such objectionable effects as time dilation and length contraction??

Now, I would assume that the only way to verify if light is travelling faster (or slower) than c in a vaccum would be if the speed of light was measured from an emmiting source that is moving towards or away from us at high speeds (like stars). Does anyone know if anyone has ever measured the speed of light comming from a star or galaxy that is moving away from the Earth at high speeds?? If not, how would a device be constructed that would measure this speed?

Tom

All experiments confirm that the speed of light in a vacuum is constant. No experiments show that that speed can change, even those experiments which show pusles of light travelling faster than c. Those experiments deal with a change in group velocity of a wavepacket, not in a change in velocity of individual photons.

James,

All experiments confirm that the speed of light in a vacuum is constant. No experiments show that that speed can change, even those experiments which show pusles of light travelling faster than c.

How do those experiments measure the speed of light? Do they divide the distance travelled by the amount of time it took light to travel that distance? If so, did those experiments account for the increased distance in a moving frame of reference that light must travel?

You see, in a moving frame of reference, the distance light must travel increases. However, if the speed of light increases as well, then the light will hit the target in the same amount of time as it would of took it in a stationairy frame of reference. The invariance of light in this case is not the result of time dilation and length contraction, but an effect resulting from the increased distance being compensated for by the increased speed of light.

This would mean that the speed of light in all inertial frames of reference would be measured to be equal, even though its actual speed changes. If this is true, then the only way to measure if the speed of light increases (or decreases) would be to measure light from a source that is moving. For example, the redshifted light from a star would be a good example of this.

James, if you had an assumption that the light coming from a star was moving slower than c (in a vacuum), what device would you use to test your assumption??

Tom

Originally posted by Prosoothus
If so, did those experiments account for the increased distance in a moving frame of reference that light must travel?
Yes, the Lorentz transformation comes from the assumption that the time taken forwards and backwards through a moving apparatus is possibly different. Any book will explain this to you. Read a book. You'll be able to answer all your own pea-brained questions.
James, if you had an assumption that the light coming from a star was moving slower than c (in a vacuum), what device would you use to test your assumption??
Experiments with the decay of neutral pions moving at ultrarelativistic speeds has demonstrated that emitter theory is wrong. The light emitted by a particle (even if the particle itself is moving almost the speed of light) always travels the same speed, to all observers.

- Warren

Originally posted by James R
All experiments confirm that the speed of light in a vacuum is constant. No experiments show that that speed can change, even those experiments which show pusles of light travelling faster than c. Those experiments deal with a change in group velocity of a wavepacket, not in a change in velocity of individual photons.

Haven't there been observations - debatable, as Chroot says - that C may have changed over a very long time?

Originally posted by Adam
Haven't there been observations - debatable, as Chroot says - that C may have changed over a very long time?
None that are reputable.

- Warren

Tom,

<i>How do those experiments measure the speed of light? Do they divide the distance travelled by the amount of time it took light to travel that distance?</i>

Yes.

<i>If so, did those experiments account for the increased distance in a moving frame of reference that light must travel?</i>

They didn't need to. A measurement in the laboratory frame gives exactly the same result regardless of the speed of the lab. That's relativity.

<i>You see, in a moving frame of reference, the distance light must travel increases.</i>

Not in that frame.

<i>James, if you had an assumption that the light coming from a star was moving slower than c (in a vacuum), what device would you use to test your assumption??</i>

I guess you mean "hypothesis" rather than "assumption". One way would be to observe eclipses or something similar and compare the apparent and expected position of the star to determine the speed of its light.

chroot,

Yes, the Lorentz transformation comes from the assumption that the time taken forwards and backwards through a moving apparatus is possibly different. Any book will explain this to you. Read a book. You'll be able to answer all your own pea-brained questions.

Yes, I'm well aware of the Lorentz transformations. However, the Lorentz transformations were derived from the assumption that light is influenced by time dilation and length contraction in a moving frame of reference. I am suggesting that a simpler explanation would be if the speed of light changes in a moving frame of reference.

Experiments with the decay of neutral pions moving at ultrarelativistic speeds has demonstrated that emitter theory is wrong. The light emitted by a particle (even if the particle itself is moving almost the speed of light) always travels the same speed, to all observers.

Thanks. I knew that an experiment was done, but I couldn't remember which particles were used. I will have to take a closer look to see if there were any flaws in that experiment.

Tom

James,

I guess you mean "hypothesis" rather than "assumption". One way would be to observe eclipses or something similar and compare the apparent and expected position of the star to determine the speed of its light.

How would you calculate the location of a star by just using its redshifted light?? I assume from its light, you can only tell if the star is moving towards you or away from you, and not it's exact location.

Tom

Adam,

Haven't there been observations - debatable, as Chroot says - that C may have changed over a very long time?

I started this thread because of a link that Crisp posted that shows experimental proof that photons, under certain conditions, can travel faster than c. Here is the link if you're interested:

http://xxx.lanl.gov/abs/quant-ph/9811019

Tom

Originally posted by Prosoothus
However, the Lorentz transformations were derived from the assumption that light is influenced by time dilation and length contraction in a moving frame of reference.
Wrong.

The Lorentz transform was originally found to be the transform (as opposed to the simpler Galilean transform) that is invariant when plugged into Maxwell's equations -- it was found by essentially guesswork. For a long time, people thought that Maxwell's equations were wrong, because they didn't satisy the Galilean transform -- but in fact, changing Maxwell's equations to make the Galilean transform work meant they had to add terms that predicted effects that were not seen. Thus Maxwell's equations were correct, and so was this weirdo Lorentz transform. No one knew quite what to make of this.

Then, from an analysis of the light path through the Michelson-Morley experiment, with the only assumption that light travels at different speeds in different directions through the aether wind, the Lorentz transform was found again -- rather independently. This added some weight to the issue, and puzzled people for quite some time. Eventually Lorentz asserted that the M-M experiment would come up with a null conclusion if one supposed that the weirdo effects of length contraction and time dilation happened, according to his namesake transform. No one was sure what to make of this advice either, and most people didn't think it made any physical sense. A bit later, Einstein came along and packaged the whole mess up into a single, comprehensible, and amazingly predictive theory: special relativity.

We now have unquestionable experimental validation of relativity (and the length contraction and time dilation which comes naturally from the math). We now understand that magnetism is really just a relativistic effect of moving electrical charges, which is why the Lorentz transform appeared (ad hoc) to fit Maxwell's equations. We discovered relativity in magnetism long before we knew what relativity was.

- Warren

chroot. it has always been my opinion that special relativity was really ripe for the picking by the time einstein tackled the problem. i think lorentz or someone else would have figured it out within a few years. what do you think?

Tom:

<i>How would you calculate the location of a star by just using its redshifted light??</i>

You couldn't. You'd have to use some other method (of which there are several commonly used by astronomers).


lethe:

I think that's true of special relativity, but it is much more debateable as to whether general rel. would have been invented by now if Einstein had done it in 1916.

I guess you have all read about those experiments involving light being slowed down a lot through various means. I recall one in Germany, I think, claimed to slow light to 65 miles per hour. If you drive along beside the experiment at 70 miles per hour, are you considered to be travelling faster than light? Or not, because you're in different mediums?

Originally posted by James R

lethe:

I think that's true of special relativity, but it is much more debateable as to whether general rel. would have been invented by now if Einstein had done it in 1916.

yeah, i guess that s what i think too. although, i have this idea that someone, riemann perhaps, once tried to devise a model where forces were due to curvature of space. only he used 3 dimensions, which would never work, and he didn t restrict himself to gravity. so no equivalence principle. thus he was doomed to fail.

however, anyone looking at his work later, after lorentz had devised special relativity (assuming einstein never existed), might have come up with general relativity.

chroot,

I looked into the neutral pion experiment, that you suggested, that supposedly proved that the "emitter theory" was wrong, and I see some problems with it.

The main problem with the experiment is that the neutral pions DO NOT emit gamma ray photons, they DECAY into gamma ray photons.

I see a big difference between a moving object emitting photons, and a moving object decaying into photons. I would assume that the "summing" of speeds would occur in the first case, but not in the second.

Were there any other experiments done that disprove the "emmiter theory"? (Ones in which something is actually emitted)

Tom

Originally posted by Prosoothus
Were there any other experiments done that disprove the "emmiter theory"? (Ones in which something is actually emitted)

I'm proud of you for actually doing some research and attempting to educate yourself. :)

Your question is actually a good one. The answer is that yes, many experiments have been done on electrons moving relativistically in particle accelerators. The fast electrons, being accelerated by magnetic fields, emit radiation. This radiation is known as "synchrotron radiation." The properties of this radiation, including, among other things, its spectrum, mechanism, and yes, velocity, have all been measured by various experimenters. I cannot recall the specific experimenters, but I'll be glad to rustle up some citations for you.

What you're not realizing, though, is that the neutral pion experiment is even stronger evidence than the synchrotron radiation evidence. Not only does the speed of light emitted by an electron not change when you move the electron relativistically -- the speed of light does not change even when the fundamental physical process by which it is created is entirely different! It seems natural that all forms of emission occur by the same process, and thus all emitted light should travel at the same speed -- and this is experimentally true. The synchrotron radiation and the light coming out of your light bulb share the same physical process, so you'd expect their light to be the same. However, there was no specific reason to believe the light coming from a decay process of an ultrarelativistic particle should necessarily be exactly the same -- but indeed it is. The speed of light seems to have nothing to do with the process that produced it -- it's always the same.

- Warren

The link was about quantum tunnelling, which implies (by it`s nature ) it`s left our normal space. A particle can disappear and pop up several light years away, ( action at a distance, EPR experiments), instantaneously.
I imagine that particles are probability fields and that there is a speed limit on the `information` not on the field.