A reply to Motl’s post on Variable Speed of Light (VSL) theories.

Motl wrote a blog post calling the idea of a variable speed of light stupid.

Any flat space gravity theory must involve a variable speed of light. While
the Cambridge geometry group’s Gauge Gravity is not normally described as
a VSL theory, I’ve nevertheless written a defense of the idea of VSL and
put it on my gauge gravity website here.


Filed under heresy, physics

13 responses to “A reply to Motl’s post on Variable Speed of Light (VSL) theories.

  1. Kea

    Well, Lubos doesn’t strike me as someone who would shy away from dissing respectable Cambridge dons, although no doubt that was not his intention here!

  2. Doug

    1 – I was looking for posts on your old blog ‘Snuarks_N_Binons’ not realizing that ‘Mass’ is your new blog. [Mass is hard to find by google search.]

    2 – I am unsure if VSL [>c] is possible except perhaps in a plasma phase of phase transitions.

    3 – I wonder if these are different perspectives of the same phenomena:
    a – David Hestenes, ‘The Kinematic Origin of Complex Wave Functions’
    b – Lisa Randall and R Sundrum, ‘A Large Mass Hierarchy from a Small Extra Dimension’
    c – Nima Arkani-Hamed, S Dimopoulos, and G Dvali, ‘Phenomenology, Astrophysics and Cosmology of Theories with Sub-Millimeter Dimensions and TeV Scale Quantum Gravity’

    4 – Speculation on orbits, planetary and atomic.?.?

    Suppose planetary orbits or multiple electron shells are Parallel One Loops functioning as a type of Solenoid?

    Biot-Savart Law and Applications
    Some examples of geometries where the Biot-Savart law can be used to advantage in calculating the magnetic field resulting from an electric current distribution.


    Iron Core Solenoid
    An iron core has the effect of multiplying greatly the magnetic field of a solenoid compared to the air core solenoid on the left.


  3. In the past LM has spoken kindly of GM=tc^3, which does predict a changing speed of light. What he and Ellis are complaining about is the ad hoc nature of some VSL theories.

  4. ryan

    You made some excellent replies to Motl’s post. Motl is one of the few physicists who is even more abrasive than Magueijo (though I still enjoyed Magueijo’s book, “Faster than the Speed of Light”).

    I just found your blog, and it’s great. I love the fact that you’ve done some real research and got some citations (for neutrino mass paper) despite being out of academia. It gives a grad student like me hope.

  5. I just don’t know how I can explain you the basic thing that whether or not the speed of light is constant depends on the choice of units. It is not a physical question. If I e.g. use the Hubble radius as my unit of length but keep the second for time, the speed of light will be time-dependent. There is no physics in this trick whatsoever. I insist that you don’t understand what it means to choose units and why it is a matter of convention while real physics only starts with statements that are independent of the choice of units.

  6. nc

    I think that strictly speaking, Lubos should say “choice of definitions of light speed”, rather than “choice of units”. There was a definition of light speed around 1963 which defined it as a constant, and according to that definition it is simply equal to a fixed distance (a certain number of wavelengths of light emitted from Krypton atoms) divided into a fixed time (say the time taken for light to transverse the ground state orbit of a particular atom). In such a definition, “light speed” is fixed.

    Since 1983, however, the SI unit of length, the metre, has been defined as the distance light travels in 1/299,792,458 of a second, where the speed of light is believed to be 299,792,458 m/s.

    So under the 1983 SI definition, Lubos is correct technically, and it’s not really possible for the speed of light to change, because the unit of distance is now dependent on the speed of light!

    If the speed of light actually increased, the unit of length would actually decrease in this scheme, keeping the official speed, as reported in the revised units of length that would result from changing c, just the same as it had been before.

    For example, if c increased to c + a, then the definition of the metre would increase by a factor of (c + a)/c, and in the new units the new value of c, which is c + a, would need to be corrected for the new bigger unit of the metre, giving you a revised new speed of light equal to (c + a)/[(c + a)/c] = c in the new units for the metre.

    Hence, any change in c automatically cancels itself out once you correct the new value of c for the effect that the new value of c will have upon the definition of the unit for length, the metre, which is dependent upon c.

    This kind of parlour game has nothing to do with physics of the type I’m interested in. Instead, it is all about red-tape and bureaucracy. I think Lubos’ argument about the Hubble radius is similar.

    The Hubble radius is R = c/H metres, ignoring gravitational deceleration of the universe, where c is light velocity and H is Hubble constant. So if Lubos uses R = c/H as his unit of distance, then he has built c into that unit of distance. If he then defines

    c = R/t = R/(1/H) = RH,

    he gets

    c = RH = (c/H)H = c.

    This is not telling us anything. You are just going around in circles.

    If there was gravitational deceleration of the big bang, then R would be smaller (depending on the value of omega, i.e., the density of the universe compared to the critical density). However, there simply isn’t observable gravitational deceleration, as proved by Perlmutter’s supernova redshift data show. Allegedly this lack of gravitational deceleration on the big bang expansion rate is because dark energy is accelerating the universe just enough to cancel out the expected gravitational deceleration … a simpler explanation is just that there gravity gets weaker over very long distances due effects like the to the energy depletion of gravitational field interactions as a result of redshift of gravitons being received after being exchanged between receding masses, which would reduce the gravitational force coupling G.

  7. carlbrannen

    My reason for delving into this matter is not because philosophically I care much about how speeds and distances are defined. I got dragged into this by looking at the meaning of time, and then by analyzing the masses of particles as a force. The end of the long story is that I think that gravity can be modeled as a force that is proportional to a flux of “gravitons.”

    When I get around to it, I’ll devote (a) a blog post to the derivation of the equations of motion around a non rotating black hole in Painleve coordinates, then (b) a blog post about why it is that Painleve coordinates are special, then (c) showing how writing gravity as a force in Painleve coordinates allows gravity to be interpreted naturally as a particle flux with the force proportional to the flux, and a very simple diagram showing particles interact with themselves to increase the strength of gravity near black holes (and from that derive Einstein’s corrections to Newton’s equations of motion in Painleve coordinates).

    But right now I’m busy finishing up the E8 stuff, and after that, I thought I would write a few blog posts devoted to the concept of “ignoring gauge bosons” in the mass interaction. This should be particularly effective at annoying the old folks because the idea for it is from Feynman, LOL, and the mathematics is undeniably simpler than the Higgs mechanism.

    So sure, the old folks are right that it logically consistent to define the speed of light as a constant, but the consequence of this is that they conclude that space is drastically curved even on short distances. It’s consistent, but calculations are more difficult, and it gives them theoretical problems that they haven’t been able to solve. The most obvious problem is combining QFT which works best on flat space, with general relativity. Working on a flat space GR cuts that Gordion knot clean through.

  8. Making it clear what one means with speed of light is essential. In general relativity one cannot speak of varying speed of light. The challenge of VSL theorists is to define operationally what they mean with the velocity of light and how GRT should be modified.

    For instance, VSL makes sense in “sub-manifold gravity” with many-sheeted space-time identified as a 4-surface in say H=M^4xCP_2. Consider two space-time sheets and travel of topologically condensed photons (particle like topological inhomogenities that I have christened CP_2 type extremals) along them. The lightlike geodesics are with respect to the induced metric and the time taken to travel from A to B depends on space-time sheet. Travelling along very wiggly space-time surface takes much longer time than along canonically imbedded M^4. Warped imbeddings of M^4 represent the simplest example of reduction of velocity of light in this sense. Also anomalously large time dilation in absence of gravitational fields is predicted for them.

    Geometrically this means that the paths of photons are in general time-like as curves of the imbedding space and one can even have a situation in which photon does not move at all in M^4 but rotates in CP_2 degrees of freedom with velocity of light. As a matter fact, classical description of Higgs mechanism for fermions is based on this kind of zitterbewegung for CP_2 type extremals having random light like curve as M^4 projection.

  9. carlbrannen

    Matti, re: “In general relativity one cannot speak of varying speed of light”. Not at all true. For any given set of coordinates, the speed of light is defined in the very obvious way in that set of coordinates. The absence of a “varying speed of light” in GR amounts to the fact that as one chooses different coordinates, one obtains different velocities.

    Therefore, the assumption that in GR, one cannot speak of a varying speed of light, depends on the fact that in GR, there is no preferred coordinate system. And for the usual write-up of GR, this is true.

    However, there is a version of GR that matches the usual version in all particulars (except for details about what happens inside event horizons and other esoterica that are not of concern to experimentalists at this time), and that does imply a particular choice of coordinates. I didn’t go to great lengths to stress the details, but I did give the link in my short write up. I will give it again here, since it’s clear that no one bothered to read it carefully the first time:

    David Hestenes (~2003), “Gauge Theory Gravity with Geometric

    Furthermore, the “preferred coordinates” turn out to be flat, or more precisely, Minkowski. The paper uses the word “flat” 26 times, please read it carefully and reconsider.

    I realize that the above paper was published only in “Foundations of Physics”, but this is a subject that has been carefully reviewed by a lot of physicists. It’s ignored because, well, physicists are happy with the sloppy GR that they already have and they’re not particularly interested in an improvement which gives the same results, but makes it easier to calculate because this would require effort on their part to forget tensors and learn geometric calculus.

    I should also mention that it is not original with Hestenes; I chose his paper to link in because I think it is the best description of the theory. It originated with the Cambridge Geometry Group physicists Lasenby, Doran, and Gull.

    From the point of view of particle physics, you need to have a flat space to make gravity be a gauge boson mediated force (like all the other forces that are so well understood), and for starting out on this problem, this “gauge gravity” has no peers.

  10. Pingback: Predicting the future (Updated 3 December 2007) « SU(2)xSU(3) for QFT

  11. Any minds open to totally new theory based on mass as a count of Higgs particles forming the spin surface of a material point or other body in space-time? Mass is then a surface quality not a volume quality —and we need to start over. The atom as we know it is a spherical suface that reflects impinging electrons. Properly assume the atom is a gravity field that has maximally volatile center of a certain finite radius -say ten the exp. minus 14 centimeter- which one here calls an immutable maximally spinning black hole that is the same for all atoms – but that its radius grows and decays with the absorption and emission of large numbers of electrons. Next assume Bohr model is totally wrong and that the frequency, f, wavelength, lambda, speed, v, relation holds for electrons orbiting inside the atom. Now assume that spectrta data are all molecule (multiple atom) generated. Correct Einstein as he wanted but failed; to G =R/(3axis energy of R as a spin surface whose mass is the count of G populating the surface of R). Newton’s G is Einstien’s G and both are Higgs particles. Newton’s G is constant & atom sized as atoms populate the solid surface of the spinning Earth of radius R. Einstein’s G is variable without limit. R for Earth in Newtons potential energy law for a unit mass at the boundary of M can be reduced to the above space curvatue eq. if Mass is the square of 3axis energy and a count of G-size Higgs forming the surface of R.

  12. mark dyson

    If the Speed of Light could be increased, then the mass component of Light momentum definitely
    has to be ruduced by the same propotion.
    I have studied just a few equations, and have found this to be an absolute requirement. There is no other way for the physical relationships to be changed. Also the Hubble constant cannot be changed either, along with many other specifics of quantum equations. Some changes are forced but in a specific way, there simply is no other way round it.

  13. dbs

    Read “The Farce of Physics”, by Bryan G. Wallace, November 1994 — http://patric.framsteget.net/bibliotek/Wallace%20-%20The%20Farce%20of%20Physics%20(1994).pdf

    Main points: 1. Newton right, Einstein wrong; 2. Venus radar SL measurements show SL is variable; 3. Big Bang, dark matter, et al are wrong; 4. The Universe is WYSIWYG; 5. Establishment “science” is corrupt.

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