Speed of Light Constant? NOT!

Light in a vacuum travels at approximately 186,000 miles per second. This has been a standard that we have been taught for generations now. Now though scientists Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland have been able to speed up, slow down and even stop light at any wavelength.
What is next? FTL Drives?


Scientists Mess with the Speed of Light

Well if you had read the article properly you would have seen it said;

By tweaking the relationship between phase velocities, it’s possible to adjust the group velocity and create the illusion that parts of the pulse are travelling faster than the speed of light.

They are not really speeding it up just faking it. It’s all to do with point of reference.
Still interesting though and useful.

[edit on 23-8-2005 by Elfwood]

[edit on 23-8-2005 by Elfwood]

The vicious forum terrorist Bin Postedalready strikes again.

Well there are a few experiments that suggest that Faster than light maybe possible due to Quantum Tunnelling...

on closer inspection of the results however shows that Information cannot travel faster than light....

However if you want to know of light is always constant then the answer is NO....

Firstly we have been able to capture a single photon inside a Qbit (A part of a Quantum computer)

And secondly there is evidence that C is not as constant throughout the history of the universe as we might have thought.

It appears that the cosmological constant C (Speed of light) has been slowing down, and as such what may be a result of that is once the speed of light reaches a critical speed that this may cause a second wave big bang.... Complicated theory here.... this is due to the continued speed of the expanding universe and so in reality it is stretching the frequency of light which has a considerable effect of the speed that light travels.

In this model of the universe the matter in the universe is like an ever-increasing ripple on a pond and the big bang is the epicentre.

So Einstein was right to a degree in his time slice but over a much larger slice of time he was wrong.

NeoN HaZe

The effect discussed in the original posted article is well-known to physics and has been for years.

There is no change in the accepted speed of light in a vacuum.

What these researchers are doing are messing around with relative phase velocities (group velocities). As it turns out due to interference effects, group velocity CAN actually propagate faster than the speed of light.

But is this helpful? Not really, as the article points out. First of all any practical medium (such as fiber optics) will slow light down (the propagation of light through glass fiber is slower than in a vacuum). Second of all, we do not have (yet) commercially viable methods to convert the fiber signals to electrical signals (which are necessary for actual communication devices) in an effective manner. Electricity (electrons in metal conducting wires) flows on several orders of magnitude slower than light.

The main thrust of this article is actually a new device that does not require this electrical coupling.

Unfortunately, we still have electrical based bus terminals and CPU's in our computers and other peripherals, so it's not quite as fantastic as it may appear.


On the other hand, the speed of light constant is in fact not entirely constant. It's constant today and will be tomorrow, and for a long long time, but eventually the expansion of the universe and the cooling associated with it will modify the resistance (permittivity) of free space which will indeed change this constant, but not by a whole lot. This is a revolutionary new concept in cosmology that is only being developed in recent years.

I subscribe to a physics (online) newsletter, i'm not sure where to link you to the info. on the web...so i guess i'll have to take the 'excessive quote' shot for the team.

This one is WAY over my head, but (somewhat) related to this discussion....i think

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 733 June 15, 2005 by Phillip F. Schewe, Ben Stein

LIGHT MAY ARISE FROM TINY RELATIVITY VIOLATIONS, according to a new
theory. Speaking most recently at last month's American Physical
Society meeting of the Division of Atomic, Molecular, and Optical
Physics in Nebraska, Alan Kostelecky of Indiana University (812
855-1485, [email protected]) described how light might exist as a
result of breaking an assumption of relativity theory known as
Lorentz symmetry. In Lorentz symmetry, the laws of physics stay the
same even when you change the orientation of a physical system (such
as a barbell-shaped molecule) or alter its velocity. According to
special relativity, the speed of light is the same in every
direction, a notion that current experiments verify to a few parts
in 10^16. However, if physicists find variations in the speed of
light with direction, this would provide evidence for broken Lorentz
symmetry, which would radically revise notions of the universe.
Broken Lorentz symmetry would give spacetime a preferred direction.
In its simplest form, broken Lorentz symmetry could be visualized as
a field of vectors (arrows) existing everywhere in the universe. In
such a picture, objects might behave slightly differently depending
upon their orientation with respect to the vectors. In a recent
paper, published in Physical Review D (Bluhm and Kostelecky,
Physical Review D, 71, 065008, published 22 March 2005), the authors
propose that the veryexistence of light is made possible through a
vector field arising
from broken Lorentz symmetry. In this picture, light is a
shimmering of the vector field analogous to a wave blowing through a
field of grain (see animation at
www.physics.indiana.edu...). The researchers
have shown that this picture would hold in empty space as well as in
the presence of gravity (curved spacetime) which is often ignored in
conventional theories of light. This theory is in contrast to the
conventional view of light, which arises in a space without a
preferred direction and as a result of underlying symmetries in
particles and force fields. Kostelecky says that the new theory can
be tested by looking for minute changes in the way light interacts
with matter as the earth rotates (and changes its orientation with
respect to the putative vector field). In addition, Kostelecky says
that neutrino oscillations might arise from interactions between
neutrinos and the background vector field, as opposed to the
conventional explanation, which invokes neutrino mass as the
explanation for the oscillations. Experimentalist Ron Walsworth of
Harvard-Smithsonian comments that the nice thing about Kostelecky's
work is that he proposes detailed experiments to test his theories;
and that the results of such experiments, no matter how they turn
out, promise to deepen our understanding of physics. (For more
information, see article by Kostelecky in the Scientific American,
September 2004; as well as Indiana University Press Release, March
21).

Hope this helps ...'course this is probably old news for you guys

Yes, broken symmetry is a big research topic right now in cosmology. The Lorentz gauging is a simplification of a more complex theory. Physics has done quite well with the symmetrical Lorenz gauging of electrodynamics, however, certain quirks that we have been looking at in recent years is leading the physics community to "rediscover" asymmetrical lorentz gauging.

The mathematics were invented 100 years ago ... it's only now that we have powerful computers that we can play thought experiments and run simulations, and build apparatus to attempt to "see" the broken symmetry.

The 1957 Nobel prize in physics was awarded to some scientists investigating these sorts of effects.

Incidentally, the statement in your quote:

"described how light might exist as a result of breaking an assumption of relativity theory known as Lorentz symmetry"

Should be better explained ... first of all "light" really means "electromagnetic radiation."

Visible light of course is only in a narrow frequency range. The existence of light is not in question ... whether we model our world with or without the Lorenz symmetry simplications will not change the way "light" exists, but it will certainly change the equations we use to predict it.

Also, the idea that light propagates equally in all directions is a theory that has been tested for 100 years.

The new studies will be examining these ideas at a small scale and with more accurate equipment.

Since the new studies will be focusing on quantum effects, it's quite possible they will discover something.

The "speed" of light in a vacuum is sort of a macroscopic property. It has to do with density of matter in some cube of space.

However, there is really no such thing as a "vacuum" even "free space" has baryons and other particles in it.

Originally posted by Rren

www.physics.indiana.edu...

Good link ... there are some books posted on his website that look like good introductions to this topic.

I'm a programmer turned electrical engineer turned quantum physics fan, and I've taken enough courses to get me to the basic levels, but am always looking around for new directions to get my curiosity tweaked.

Currently, I can explain to you that the basic difference between symmetrical and asymmetrical Lorentz gauging is akin to looking at a cube of material (or fluid).

Engineers that study fluid dynamics (for example) with tensors consider the stress and strain from many different angles. You can measure the change of a certain property (such as shear stress) with respect to a certain direction (such as x y or z).

There are a set of equations that describe classical electrodynamics known as Maxwell's Equations. There are 4 of them. They assume symmetrical Lorentz gauging.

However, some people claim that his original set of equations was 12. He had included asymmetrical effects. Since we have 3 physical dimensions, the # of equations goes to 12 instead of 4.

So the story goes, it was so complicated that no one believed him. It was only after Lorentz proposed symmetrical gauging that they were simplified to 4 equations. These are quite good enough for all electrical engineering and most physics.

It is only in recent time that we are beginning to take another look at this.

grad_student

Thanks for explaining that to me, i had read it several times since receiving it and had the 'jist' of it. But did/do not understand the implications.


A bit off topic but you said:

Visible light of course is only in a narrow frequency range. The existence of light is not in question ... whether we model our world with or without the Lorenz symmetry simplications will not change the way "light" exists, but it will certainly change the equations we use to predict it.

When you say "..it will certainly change the equations we use to predict it.", could you elaborate on that? Are we talking about fundamental changes like the age of the stars/universe? I'm not 'fishing' for a possible "young-Earth" scenario...i promise

My question is based on what you said in your earlier post(had also heard of this before).

grad_student
On the other hand, the speed of light constant is in fact not entirely constant. It's constant today and will be tomorrow, and for a long long time, but eventually the expansion of the universe and the cooling associated with it will modify the resistance (permittivity) of free space which will indeed change this constant, but not by a whole lot. This is a revolutionary new concept in cosmology that is only being developed in recent years.

Is this change in constancy of light(?) and Lorenz symmetry already taken into account when 'dating' distant stars and galaxies? Again i assure you i'm not a "young-Earther" just the dating of say a 10bill. year old star would be affected by both/either of of these variables, no? It would affect parralax measurements and perceived brightness of cepheid variable stars would it not? Both key in 'dating' distant stars, correct? I like to read alot about physics and cosmology but am not formally educated in either, so sorry if this was a stupid question.

Originally posted by Rren

1) When you say "..it will certainly change the equations we use to predict it.", could you elaborate on that?

2) Are we talking about fundamental changes like the age of the stars/universe?

3) Is this change in constancy of light(?) and Lorenz symmetry already taken into account when 'dating' distant stars and galaxies?

4) It would affect parralax measurements and perceived brightness of cepheid variable stars would it not? Both key in 'dating' distant stars, correct?

I like to read alot about physics and cosmology but am not formally educated in either, so sorry if this was a stupid question.

First of all let me say that it's not at all a stupid question. Questions actually. But most of my knowledge comes from conversations with my quantum mechanics professor Dr. Marcelo Gleiser who happens to be a cosmologist. I think if I had it to do all over again I would get into that field, it is some cool stuff indeed.

So don't take me as an expert's expert, but here are my responses:

1) What the symmetry breaking means is that we have to consider additional equations when we solve for the field. If you incorporate Lorentz symmetry gauging it simplifies the math, which can get ridiculously deep. I was checking out some of the papers on the website you found, and they are rather hairy, such as:

arxiv.org...

I just printed this out and am going to talk to a buddy of mine about it to try to get through some of it. Cool stuff!


2) Yes. We gauge the age of the universe on the amount of time it would take light to travel distances. However, the change only happens on very short time scales in the age of the universe. We're talking about back to the time before matter existed, when everything was pure energy. As things started to cool off and atoms started forming, and planets and so on, things settled into what we now have as the cosmic microwave background energy (you can do google searches on those keywords to learn more). So the difference overall is likely not a huge factor, but it certainly has a distinct shift in the explanations of the geometry of the big bang. That's about when it starts to go over my head as well.


3) No it's not. That's why it's a hot research topic right now. No one really knows the answers yet.


4) Possibly. No one knows to what extent. Probably not huge. But the fact that until recently we have never questioned this value as a constant means that we are overlooking something. Anytime physics realizes it's forgotten something or made assumptions that are not necessarily true, it usually ends up with a major breakthrough in subsequent years (or decades).