Proof of the Constancy of the Speed of Light

Michael said:

I don't think that he necessarily manipulated Maxwell's formulas to produce a favored outcome, but he certainly did make a few important "assumptions" as he made various substitutions/simplifications to Maxwell's equations, as sjastro rightly pointed out:

Click to expand...

I never said that he did. I only pointed out that based upon how he reached his conclusion, it may give those skeptical of his claim that impression.

gabemaiberger said:

Science doesn't deal in facts. It is a method of knowing more than it is a body of knowledge. We can never prove hypotheses. We can only attempt to falsify them. When a hypothesis has failed to have been falsified through experimentation, it is provisionally accepted as a potential explanation for a phenomenon. When this happens enough times, the hypothesis is inductively proven due to a lack of falsification.

Click to expand...

If that is the case, you could never be sure of anything regarding the present workings of the natural world.

usexpat97 said:

What exactly is proven here? That a photon travelling in free space, free of external forces travels at a constant speed, according to classical physics? Was that ever in doubt? With all the assumptions taken to derive the solution, you could have just made one assumption: that light in free space travels at a constant rate.

Click to expand...

Sure, but then it wouldn't have had all that melodramatic mathematical pizazz.

Ophiolite said:

I suggest there are four categories of people in matters such as this:
1. Individuals smart enough and committed enough to develop an understanding of such complex matters through experiment and hypothesis formation.
2. Individuals smart enough and committed enough to understand and, perhaps, explain the work done by the first group.
3. Individuals smart enough to recognise they don't belong in the first two groups and yet still smart enough to recognise the strength of the scientific method employed by the first two groups and so are ready to, provisionally, accept their findings.
4. Individuals who figure if they can't understand it, it's probably not true and who aren't smart enough to understand selection bias, Dunning-Kruger effect and the like.

I suggest that, in the matter of science, the members of group 4 could be safely disregarded had we not already made the mistake of giving them the vote.

(For the record I clawed my way into group 3. Does that make me an elitist? If so, may I wear the T-shirt?)

Click to expand...

Elitists are those of great influence and power who feel they know better than everyone else, placing their judgment beyond questioning and feel that they do not have to answer to those over whom they wield influence and authority, nor do they believe it to be necessary to explain themselves, thinking that their wealth, fame, academic degrees, professed expertise, and authority is enough to buy the trust of the masses who are stupid and ignorant enough to blindly trust them.

If you think you are that kind of an Elitist, then by all means go ahead and wear that T-Shirt which will proclaim you to be superior to the common man simply because he cannot understand a set of equations unless it is explain to him in a way that he can easily understand.

Belk said:

You think people are trying to convince you? Be ignorant, that is your own choice and no one is going to stop you.

Click to expand...

If convincing people that the speed of light is constant and never changes was not the intent of the original post, then the writing and posting of this thread would then be nothing more than a waste of time for the one who began this thread.

And if you feel that a set of unexplained equations is enough to prove the poster's point, then that is your choice.

sjastro said:

Argument from personal incredulity.

Click to expand...

Whatever that means, but in my defense, I made a fair point about the need for an explanation of what the equations are supposed to tell us so that we can all understand how the original poster reached his conclusion.

Contenders Edge said:

Sounds like the speed of light can be affected by a number of variables and circumstances and therefore what the speed of light may appear to be under one set of circumstances may be different under circumstances that are different.

Click to expand...

This is pretty much the case. For example, neutrinos (which have a mean free path of a light year of lead - in other words, it can go through a light year of lead without interacting with matter) travel faster than the speed of light in the medium of heavy water. The Super Kamiokande did excellent research in neutrinos almost by accident. When things go faster than light in a medium, they create a "photonic boom" much like a sonic boom - in this case, it is called Cherenkov radiation.

The neutrinos don't actually travel faster than light in a vacuum (although, depending on who you speak to, this statement isn't necessarily true) - they have mass and travel at bradyonic (slower than light) speeds. However, in Post #37, I am saying we could have an event in which a massive body does, in fact, reach a desired point faster than a photon beginning from the same location.

Sounds subjective. Overall, an informative response post.

Click to expand...

Who knows?

Kaon said:

This is pretty much the case. For example, neutrinos (which have a mean free path of a light year of lead - in other words, it can go through a light year of lead without interacting with matter) travel faster than the speed of light in the medium of heavy water. The Super Kaminokande did excellent research in neutrinos almost by accident. When things go faster than light in a medium, they create a "photonic boom" much like a sonic boom - in this case, it is called Cherenkov radiation.

The neutrinos don't actually travel faster than light in a vacuum (although, depending on who you speak to, this statement isn't necessarily true) - they have mass and travel at bradyonic (slower than light) speeds. However, in Post #37, I am saying we could have an event in which a massive body does, in fact, reach a desired point faster than a photon beginning from the same location.
Who knows?

Click to expand...

Now you've got me wanting to experiment something.

What if we accelerate BCS cooper pairs to travel faster than photons in niobium condensate? I see one paper written on the effects of cherenkov radiation in that instance. It seems like a phenomenon we could exploit, except that we have to reduce cooper pair density (normally around 10^28 per cubic meter) down to something where we don't exceed the critical current Jc of type II superconductor. I could see that photon boom changing the phonon and thus potentially changing the cooper pair behavior. I wonder...could we use this to produce new high temperature superconductors?? Seems worth a shot.

usexpat97 said:

Now you've got me wanting to experiment something.

What if we accelerate BCS cooper pairs to travel faster than photons in niobium condensate? I see one paper written on the effects of cherenkov radiation in that instance. It seems like a phenomenon we could exploit, except that we have to reduce cooper pair density (normally around 10^28 per cubic meter) down to something where we don't exceed the critical current Jc of type II superconductor. I could see that photon boom changing the phonon and thus potentially changing the cooper pair behavior. I wonder...could we use this to produce new high temperature superconductors?? Seems worth a shot.

Click to expand...

In essence, you are suggesting we force the pairs bound to field quanta to "stay ahead" of the photons - freezing in the superconductivity (fields)? (It would be as if they never left initial superconductivity state.) If so, this is similar to my post about a space ship that is not a tachyon, but ends up at a moment before a photon - by manipulating the world space.


In theory, absolutely I think its an interesting idea and, it is pretty elegant (never considered this, really). In practice, I think you bring up decent points (re. density) but there is always a way to scale from macro or meso to micro.

But please let me know if I (mis)understand you.

Freezing in the superconductivity fields would be best-case scenario. Worst-case is that the pairs cease to superconduct at superluminal speeds, current-density or no current-density. I think that might be ameliorated, however, by gradually easing in the velocity. Similar to slowly pouring out water out of a spigot. I think what'll happen is that the momentum of the cooper pairs will overcome the weak forces of the phonon, and cease to superconduct. But if the electrons are already locked into orbit--zero error--it may not matter.

usexpat97 said:

Freezing in the superconductivity fields would be best-case scenario. Worst-case is that the pairs cease to superconduct at superluminal speeds, current-density or no current-density. I think that might be ameliorated, however, by gradually easing in the velocity. Similar to slowly pouring out water out of a spigot. I think what'll happen is that the momentum of the cooper pairs will overcome the weak forces of the phonon, and cease to superconduct. But if the electrons are already locked into orbit--zero error--it may not matter.

Click to expand...

It would be interesting to - in the lab - test the critical limit.

Contenders Edge said:

Elitists are those of great influence and power who feel they know better than everyone else, placing their judgment beyond questioning and feel that they do not have to answer to those over whom they wield influence and authority, nor do they believe it to be necessary to explain themselves, thinking that their wealth, fame, academic degrees, professed expertise, and authority is enough to buy the trust of the masses who are stupid and ignorant enough to blindly trust them.

If you think you are that kind of an Elitist, then by all means go ahead and wear that T-Shirt which will proclaim you to be superior to the common man simply because he cannot understand a set of equations unless it is explain to him in a way that he can easily understand.

Click to expand...

I take it you've been put down a lot and haven't yet got used to it. Perhaps when you do your sense of humour will return. Send me a pm when and if it happens and we can talk some more.

usexpat97 said:

What exactly is proven here? That a photon travelling in free space, free of external forces travels at a constant speed, according to classical physics? Was that ever in doubt?

Click to expand...

Not seriously.

But some Young Earth Creationists have toyed with the idea that light moved faster in the past, so that (for instance) light from stars more than 6000 light years away could 'get to' us.

With all the assumptions taken to derive the solution

Click to expand...

There are not that many assumptions there, really. However, I agree that there is a big one that turns this argument into something akin to begging the question.

Assumption: μ₀ and ε₀ are constants.
Therefore, c is a constant.

I don't know that toying with the idea is pinned down to solely Young Earth Creationists. In fact, I hope not. What made Einstein successful is that he threw away all the assumptions of classical physics and wanted to see what would happen if we start over. Relativity.

So if anyone wants to toy with the assumption that μ₀ and ε₀ may have changed, go for it. For my purposes, though, they are constant.

usexpat97 said:

Freezing in the superconductivity fields would be best-case scenario. Worst-case is that the pairs cease to superconduct at superluminal speeds, current-density or no current-density. I think that might be ameliorated, however, by gradually easing in the velocity. Similar to slowly pouring out water out of a spigot. I think what'll happen is that the momentum of the cooper pairs will overcome the weak forces of the phonon, and cease to superconduct. But if the electrons are already locked into orbit--zero error--it may not matter.

Click to expand...

By the way, if you are a professional, perhaps you should protect this intellectual property. It has long-term, and profound implications if you are on to something.

I know, but right now, it's strictly academic, and I don't think the odds are high.

Ophiolite said:

I take it you've been put down a lot and haven't yet got used to it. Perhaps when you do your sense of humour will return. Send me a pm when and if it happens and we can talk some more.

Click to expand...

It seems like your professed promotion to "elitist" status has gotten to your head. I'll be happy to talk again, when you've learned a lesson in humility.

Kaon said:

The context is the speed of light in a vacuum - which is implied to be not only constant, but a maximum of c in all inertial frames. The math being used to get to part of that conclusion is the Lorentz Factor - which is source-independent. That is the problem, not whether or not it is a limit - the self-independence of the critical velocity.

Click to expand...

As stated previously the Lorentz factor was not introduced by Einstein but was proposed to explain the null result of the MM experiment through length contraction.
It was an attempt to save the ether absolute frame of reference where the speed of light was source dependent.
It is the Lorentz transformations not the Lorentz factor in isolation that defines SR, since the Lorentz factor is dimensionless.

The Hubble Constant is seriously flawed. But I admire GR.

Click to expand...

Irrespective of the value of the Hubble constant, recession velocities can exceed the speed of light as galaxies are being carried by the Hubble flow.
Galaxies (=objects with mass) moving in space-time cannot reach the speed of light let alone exceed it as it would require an infinite amount of KE.

That there is no experimental evidence for the existence of superluinal inertial frame is a testament to our crude physics - not to its impossibility. Have we been able to reproduce a galaxy in the lab to test its dynamics in the same manner it would occur in real-time nature? That doesn't stop the mathematical theory from evolving things we will/hope to see later on (things we are incapable of realizing now, for whatever reason).

Click to expand...

It doesn’t matter how crude or refined the physics is, the facts are there is no observational evidence that indicates information can travel faster than light through space-time.

Ok. Let's create an example that is in the middle - an alternative (where one front is superluminal, and one is not); we don't even need the particle to be superluminal for this example. Define alternative as superluminal if both fronts are superluminal, and semi-superluminal if only one front is superluminal.

Lets say in "world" M1 there is a photon sent from the Earth (call this event E1) to arrive at a distant star at some moment T1 by the clock of that star. Let M2 be the world that was initially the same as M1 but instead of the photon assume the "Enterprise" is sent (the start of the spaceship is event E2). On its way to the star the spaceship "warps" and tears spacetime by travelling very fast passing stars, merging binary black holes and triggering other imaginable powerful processes.

We are still assuming no tachyonic matter.

Despite all of this, the spaceship arrives at the star later than the photon emitted in E2. However, we can still entertain that the spaceship arrives in time T2 less than T1. So, the speed of the
spaceship in one world (M2) would "exceed" the speed of light in another (M1), which
would not contradict the non-tachyonic nature of the spaceship. It also wouldn't break the ‘light barrier’ in M1: the inequality T2 < T1 implies the front (call it N1) is superluminal, but no matter signal in M1 corresponds to the front. Particularly no spaceship in that space-time is associated with N1.

These two "worlds" would be considered the alternative of semi-superluminar speed, and if one can accept these conditions it shows such an alternative allows "superluminal" signalling without tachyons.

Its "superluminal" character does not contradict the principle of causality in M1, because in the space M1 (Minkowski space) the surface N1 does not correspond to any signal. The front N2 is not superluminal, so the alternative is semi-superluminal. The spaceship reaches the destination at a moment preceding the arrival of any photon emitted in E1, but no tachyons are involved. Even though the photons are in M1, the spaceship belongs to the universe M2, where its trajectory is timelike.

If/When we get the opportunity to build a spaceship like this and test it, we would be inclined to confirm what we would have already known.

Click to expand...

There are a number of problems with this argument.
The photon is travelling through space-time; the Enterprise isn’t but moving along with space-time (using your tearing space-time description).
Since there is an element of sci-fi we can take this a step further and claim the Enterprise is using an Alcubierre drive which is the only piece of science fiction I know of which is a solution to Einstein’s field equations.
Since the Enterprise is not moving through space-time it is stationary in its frame of reference, even though it is being carried by space-time.
As a result you can’t draw any conclusions by making comparisons to the photon’s world line or trajectory through space-time.

Furthermore your illustrated Minkowski(?) space-time diagram isn’t relevant either.
In fact it doesn’t make sense.
How does the blue region labelled “casual future” extend into the region t < 0 which represents the past?
The “casual future” only applies to the region where t > 0 while the present is defined for t=0.
Minkowski space-time diagrams represent flat static space-time and can only describe the world lines of particles travelling through it.
It can’t be used to describe the world lines of objects carried by the Hubble flow.
The photon’s world line is at a 45⁰ angle that passes through the origin and forms the past and future light cones.
The Enterprise’s world line cannot be represented in the diagram as space-time is not static due to the Alcubierre drive.

If the Enterprise did move through space-time, it would be travelling at less than c and within the light cones in the time-like region where causality is not violated as illustrated.

Contenders Edge said:

If convincing people that the speed of light is constant and never changes was not the intent of the original post, then the writing and posting of this thread would then be nothing more than a waste of time for the one who began this thread.

And if you feel that a set of unexplained equations is enough to prove the poster's point, then that is your choice.

Click to expand...

For me, the consistency of the logic was the point I took away from the OP content. Its pretty well 'airtight', but to see that, requires a fair amount of math knowledge.

The physical model it describes is another matter again. Whether that model produces predictions which can be verified, is a matter of testing .. and it does produce that (ie: it tests out very well in its specified physical contexts), but to see that, requires a fair amount of physics knowledge.

Assuming that the OP's point was to convince people 'that the speed of light is constant and never changes' was only an assumption and at the end of the day, it would be the OP's own personal choice as to whether to waste their time on that (or not).

sjastro said:

.. Minkowski space-time diagrams represent flat static space-time and can only describe the world lines of particles travelling through it.
It can’t be used to describe the world lines of objects carried by the Hubble flow.

Click to expand...

Perhaps the Enterprise's jump to warp speed took it into another universe (MWI) where our known laws of physics and physical constants differ. What happens when it comes back into our universe when it arrives, would be a doozy to explain though ..