New Studies Suggest the Speed of Light is Variable

[Redfairen]

According to the Alpha Galileo Foundation, Two new studies slotted for publication in the European Physical Journal D demonstrate that the speed of light is actually variable. The authors of the studies include March Urban of the University of Paris-Sud, along with Gerd Leuchs and Luis L. Sanchez-Soto from the Max Planck Institute for the Physics of Light in Erlangen, Germany.

A major part of the discussion in both studies is the nature of a vacuum, which on a quantum level is not, as most believe, empty. Rather, it is filled with the particle pairs.

First, Urban and his team propose that there are in fact a limited number of particle pairs including electron-positron or quark-antiquark pairs within a vacuum. This opens the possibility that the speed of light can then fluctuate at a level independent of the energy of each light quantom or photon. In other words, the speed of light would depend on the vacuum properties of space and time.

In their study, Leuchs and Sanchez-Soto found that variations in the speed of light can reveal the number of charged elementary particles in any given space. If correct, the value of the speed of light can then be combined with the value of vacuum impedance in order to determine the total number of charged elementary particles that exist in nature.

http://www.natureworldnews.com/articles/1010/20130325/speed-of-light-variable.htm

[longship]

1. See! I told you evolution is a fraud!

The earth really is 6,000 years old!! The literal truth of the Bible is vindicated by science!

A variable speed of light falsifies all of biology and all of any other physics so we get to make up any shit we want!

Furthermore, Hitler thought the speed of light was constant!!!!!!


You see! The inevitable Conservapedia entry writes itself. No intelligence or education required (only being the evil spawn of Phyllis Schlafly).

[Demo_Chris]

6. LOL! :)

[Dragonbreathp9d]

2. Kick due to how interesting this is

[loudsue]

3. That is interesting. Kickin' for exposure.

[bananas]

4. Here's the alphagalileo article, with journal references

The article in the OP didn't have a direct link to the alphagalileo article so I searched for it.

http://www.alphagalileo.org/ViewItem.aspx?ItemId=129690&CultureCode=en

Ephemeral vacuum particles induce speed-of-light fluctuations

25 March 2013 Springer Science+Business Media

New research shows that the speed of light may not be fixed after all, but rather fluctuates

<snip>

Full bibliographic information

M. Urban et al. (2013), The quantum vacuum as the origin of the speed of light, European Physical Journal D, DOI 10.1140/epjd/e2013-30578-7

Gerd Leuchs and Luis L. Sánchez-Soto (2013), A sum rule for charged elementary particles, European Physical Journal D, DOI 10.1140/epjd/e2013-30577-8

[bananas]

5. A snippet about the second paper

Leuchs and Sanchez-Soto, on the other hand, modelled virtual charged particle pairs as electric dipoles responsible for the polarisation of the vacuum.. They found that a specific property of vacuum called the impedance, which is crucial to determining the speed of light, depends only on the sum of the square of the electric charges of particles but not on their masses. If their idea is correct, the value of the speed of light combined with the value of vacuum impedance gives an indication of the total number of charged elementary particles existing in nature. Experimental results support this hypothesis.

[Jim__]

7. Why is the fluctuation in the speed of light given in square meters?

The speed of light is usually given as a linear measure. From the paper cited in the OP:

In all, the fluctuations in time are estimated to be somewhere around the realm of 50 attoseconds per square meter (scientists estimate that it takes 320 attoseconds for electrons to transfer between atoms) and may in fact be testable with the help of ultra-fast lasers. Up until this point, light was considered to move at a constant 186,000 miles per second.

Is that because the light is not actually travelling through a true vacuum and so the wave properties of light have to be accounted for in the distance that the light is traveling?

[caraher]

9. Actually, the paper claims something very different from what the article says

The actual claim reads,

In our simple model where K_W = 31.9, the predicted fluctuation is:
?_T ? 5 10^?2 (fs) (m)^?1/2

In other words, in their model they estimate the fluctuation in the time it takes for a photon to transit a distance L varies with with the square root (not the square) of the distance. So there would be a fluctuation whose standard deviation is 50 attoseconds for a photon traversing 1 m, 500 attoseconds over a 100 m distance, etc.

[Jim__]

10. Ah! Thanks.

[caraher]

8. The preprints are available free on arXiv

The quantum vacuum as the origin of the speed of light

A sum rule for charged elementary particles

Lobos Motl is pretty steamed about the hype both papers receive and dismisses them both as crackpot nonsense.

[Jim__]

11. Do you agree that these papers are crackpot nonsense?

Maybe if I knew who Lobos Motl was, I would know better than to ask. But, I don't, so ... I have some specific questions about the paper on the speed of light.

About that paper, Motl says:

But science doesn't work like that. We actually know that the speed of light has to be completely constant and free of any fundamental "noise". In fact, our definition of one meter is such that the speed of light in the vacuum is tautologically 299,792,458m/s. So it's obviously constant. The constancy of the vacuum speed of light follows directly from special relativity and special relativity is what we actually know to be true from the observations. So all the speculations must adjust to this knowledge – and all other empirical knowledge we have. The authors' approach is just the opposite: they want the empirical knowledge to be adjusted to their unconstrained fantasies. They simply don't understand the basic point of science that the self-consistency of a hypothesis isn't enough for such a hypothesis to be a good scientific theory. Empirical knowledge actually matters and kills most of the conceivable guesses.

The paper is proposing that their model can be empirically tested:

Abstract.
We show that the vacuum permeability ?₀ and permittivity
?₀ may originate from the magnetization and the polarization of continuously appearing and
disappearing fermion pairs. We then show that if we simply model the propagation of the photon in vacuum as a
series of transient captures within these ephemeral pairs, we can derive a finite photon velocity. Requiring
that this velocity is equal to the speed of light constrains our model of vacuum. Within this approach,
the propagation of a photon is a statistical process at scales much larger than the Planck scale. Therefore
we expect its time of flight to fluctuate. We propose an experimental test of this prediction

So Motl is saying that the speed of light is tautologically constant. The authors say that the vacuum is not really
empty causing a statistical variance to the speed of light through a vacuum. If the instruments exist, it would seem
that this could be tested. If the paper is right, then the definition of a meter would have to be adjusted. If the
variance in the speed of light is due to interaction between photons and these particles, does this have any
implications for the Theory of Relativity?

This is what I get from reading the different articles and not understanding the physics of it all.

[caraher]

12. I'm skeptical that they amount to much

I haven't done more than skim them, so it's fair to say that I wouldn't condemn them in the terms Lubos does. Yet.

Lubos Motl is an interesting character. He's a former Harvard faculty member and string theorist with utterly abhorrent politics. He definitely has the training to evaluate this work; at the same time, he never lets the facts stand in the way of boldly pronouncing his opinion (as in his skepticism regarding global climate change).

[caraher]

13. Upon further review

I agree with Lubos. While they talk about deriving electromagnetic properties of the vacuum from quantum theory and some basic information about fermion properties, the paper reflects a very peculiar understanding of both basic quantum mechanics and classical electrodynamics, and basically ignores the most successful theory in physics, quantum electrodynamics.

For example, the authors suggest there is something counterintuitive about the fact that a parallel-plate capacitor with a vacuum between the plates has a finite, rather than zero, capacitance. They claim that the only way to explain this nonzero capacitance is through polarization of the vacuum:

Consider a parallel-plate capacitor with a gas inside. When the pressure of the gas decreases, the capacitance decreases too until there are no more molecules in between the plates. The strange thing is that the capacitance is not zero when we hit the vacuum. In fact the capacitance has a very sizeable value as if the vacuum were a usual material body. The dielectric constant of a medium is coming from the existence of opposite electric charges that can be separated under the influence of an applied electric field E. Furthermore the opposite charges separation stays finite because they are bound in a molecule. These opposite translations result in opposite charges appearing on the dielectric surfaces in regard to the metallic plates. This leads to a decrease of the effective charge, which implies a decrease of the voltage across the dielectric slab and finally to an increase of the capacitance. In our model of the vacuum the ephemeral charged fermion pairs are the pairs of opposite charge and the separation stays finite because the electric field acts only during the lifetime of the pairs. In an absolute empty vacuum, the induced charges would be null because there would be no charges to be separated and the capacitance of a parallel-plate capacitor would go to zero when one removes all molecules from the gas.

This is almost complete nonsense! They do give a qualitatively decent explanation of why inserting a dielectric material between the plates of a capacitor does increase the capacitance; however, it is utterly false that the capacitance would go to zero in the absence of a material between the plates.

There are many elementary mistakes of this nature in the paper. It's rubbish.

[caraher]

14. One more tidbit

They don't even do the basic math correctly on their experimental test proposal. Yes, the standard deviation for the jitter in propagation time, under their theory, for 30 round-trips in a 100 m evacuated tube would be about 4 fs. But if you are using a 9 fs duration pulse and randomize the travel times via a process whose spread is about 4 fs, you estimate the broadening of the pulse not by the sum of those two times but by adding them in quadrature (that is, by taking the square root of the sum of the squares). So leaving aside some more fussing about the difference between full width at half maximum (the usual way of talking about short pulses) and the standard deviation of a distribution of times, the effect would be to take a 9 fs pulse and make it more like sqrt(9^2 + 4^2)=sqrt(97)=9.8 fs, not 13 fs.

The reason you have to add in quadrature is that whether a given photon in the pulse arrives earlier or later would be random for each photon in the pulse, whether it's in the leading edge or trailing edge of the pulse. Some of the early photons will be delayed and some of the late photons will arrive earlier than expected. Their calculation would be accurate if the leading edge photons always arrived sooner than they would without this broadening and the trailing photons were always delayed.

[Jim__]

15. Thanks for that very informative response!

[dimbear]

16. Most important practical application: appealing radar speeding tickets.

Bound to be cited soon.

[Fantastic Anarchist]

17. This is actually nothing new ...

I remember reading several theories on VSL 15 years ago. I especially remember a bright new physicist who came up with his own - can't remember his name - he was from Portugal, if I recall.

[caraher]

19. I think he had more than one VSL theory

You're probably thinking of Joao Magueijo who wrote "Faster than the Speed of Light"

It's a very entertaining read, as much for his critique of how theoretical physics functions as a profession as for the theories he describes.

The difference is that Magueijo knows what he's talking about. These folks seem to be very naive, at best, in their approach.

[Fantastic Anarchist]

21. Yep, that's him!

Thanks for the link.

[Wounded Bear]

18. Doesn't this actually say....

that the density of the universe (the "vacuum of space&quot is variable. It has long been shown how the SOL varies in differing media.

I don't see how this shows a variation in the basic SOL.

[caraher]

20. It's not even that

You have a good approach to thinking about this, but I think there's even less to it than meets the eye. In one of the papers it's clear that their model include no "bare" speed of light. Instead, they posit that the propagation time of light consists of something like the sum of the lifetimes of all the virtual particles one might expect to encounter along a light beam's path.

The conventional way of talking about this, that you've picked up on, would still result in the speed of light equal to "c" in the limit of taking the density of your medium to zero. The usual index of refraction arises from the interaction of light with real particles (with virtual particles coming into the picture only in the sense that those interactions can be described by QED). And you never get light traveling faster than c.

By contrast, in this work, the transit time for light has a random element, and can be either faster or slower than c.