I've looked at many papers on VSL (Variable Speed of Light) Relativity on the Internet and they are all beyond me. I've asked about VSL at the newsgroup sci.physics.relativity and have never received a specific answer. Surely you know the answer. What are the transformation equations between inertial _frame_s of reference that modify SR and preserve a variable speed of light? What are the physical interpretations and implications of these equations that make sense to students of physics and math at the undergraduate level? Do these equations imply that the relative velocities between different inertial _frame_s of reference are speeding up or slowing down? And finally, is there any possibility that VSL justifies the unorthodox tired light hypothesis? Thanks. Eugene Shubert http://www.everythingimportant.org/relativity/

I've looked at many papers on VSL (Variable Speed of Light) Hi there, you might like my little file/tutorial I've put together on current measurments of light. Lab tests tenets' limits http://www.nature.com/nsu/030428/030428-20.html   Seven years ago, the US physicist Freeman Dyson looked at the radioactive decay products of a spontaneous nuclear chain reaction about two billion years ago in natural uranium deposits in Gabon. He used the results to estimate the value of alpha at that time. He concluded that it could not have differed from the present-day value by a factor of more than one ten-billionth - a rate of change of around 0.5x10-16 per year. Harold Marion and colleagues at the Observatoire de Paris in France, and James Bergquist and co-workers at the National Institute of Standards and Technology in Boulder, Colorado, have ruled out any change greater than between 7x10-15 and 7x10-16 per year. New Experimental Limit on the Photon Rest Mass with a Rotating Torsion Balance http://_link_.aps.org/abstract/PRL/v90/e081801 New upper limit on photon mass of 1.2×10-51g A New Limit on Photon Mass http://www.aip.org/enews/physnews/2003/split/625-2.html A new limit on photon mass, less than 10-51 grams or 7 x 10-19 electron volts, has been established by an experiment in which light is aimed at a sensitive torsion balance The speed of light is constant in all directions Lorentz Violations? Not Yet http://www.aip.org/enews/physnews/2003/split/623-2.html The Stanford group sees no such anisotropy at the level of 10-13 for velocity-independent terms, and at the 10-9 level for velocity-dependent terms. Finding the Speed of Light with Marshmallows http://www.bowlesphysics.com/marsh.htm

What are the transformation equations between inertial _frame_s of reference that modify SR and preserve a variable speed of light? -snip- An indirectly related theme to the idea of VSL is something that is sometimes called the Optical-Analogy. Within GR, there exists some Euclidean interpretations, one of which is the optical analogy.  In this interpretation, the gravitational field is represented as an optical medium with an effective index of refraction [7-9].  Although different from the more common Geometric interpretation, this interpretation has been shown to be consistent with physical observables, and transformation rules between these two perspectives have also been published [8].  Little attention is typically focused on this perspective because it does not predict any new effects that aren't already covered by the more common Geometric perspective of GR, and because it raises unanswered issues with coordinate systems choices. I hope that this adds to your repertoire of knowledge rather than to your confusion.  This particular approach is easier to visualize. 7.      de Felice, ?On the Gravitational Field Acting as an Optical Medium?, in Gen. Rel. and Gravitation, 2, 347-357, (1971). 8.    Evans, J., Nandi, and Islam, ?The Optical-Mechanical Analogy in General Relativity: Exact Newtonian Forms for the Equations of Motion of Particles and Photons?, In General Relativity and Gravitation, 28, 413-439, (1995). 9.  Nandi, Kamal and Islam, ?On the optical-mechanical analogy in general relativity?, In Am. J. Phys. 36 (3) (March 1995) Also, I welcome comments from the other readers to highlight the strengths and weaknesses of this perspective.  In particular, does anyone know a reference that critiques these from the point of view of issues with coordinate systems choices? Marc

I've looked at many papers on VSL (Variable Speed of Light) Relativity on the Internet and they are all beyond me. I've asked about VSL at the newsgroup sci.physics.relativity and have never received a specific answer. Surely you know the answer. What are the transformation equations between inertial _frame_s of reference that modify SR and preserve a variable speed of light? What are the physical interpretations and implications of these equations that make sense to students of physics and math at the undergraduate level? Do these equations imply that the relative velocities between different inertial _frame_s of reference are speeding up or slowing down? And finally, is there any possibility that VSL justifies the unorthodox tired light hypothesis? Inertial reference _frame_s are homogeneous and isotropic in space and homogeneous in time.  Homogeneous means exactly the same experiment yields exactly the same results.  This means if I shine a torch at time t and measure the speed of light I will measure exactly the same speed as if I shine it at another time.  The way the speed of light can vary under normal SR is it having a very small mass which means its speed is not the same as the speed in the Lorentz transformation.  That speed must, by its definition, remain unchanged. Although I have not gone into the details of the papers Bilge and others have referred you to as far as I can make out they 'modify' the property's of  inertial reference _frame_s.  Just why do you want a variable light speed when it is at such odds with the homogeneity property?  The papers you were referred to cited applications to cosmological models.  Is that your reason? If so why? Thanks Bill

-snip- What are the transformation equations between inertial _frame_s of reference that modify SR and preserve a variable speed of light? -snip- An indirectly related theme to the idea of VSL is something that is sometimes called the Optical-Analogy. Within GR, there exists some Euclidean interpretations, one of which is the optical analogy.  In this interpretation, the gravitational field is represented as an optical medium with an effective index of refraction [7-9].  Although different from the more common Geometric interpretation, this interpretation has been shown to be consistent with physical observables, and transformation rules between these two perspectives have also been published [8].  Little attention is typically focused on this perspective because it does not predict any new effects that aren't already covered by the more common Geometric perspective of GR, and because it raises unanswered issues with coordinate systems choices. I hope that this adds to your repertoire of knowledge rather than to your confusion.  This particular approach is easier to visualize. 7.      de Felice, ?On the Gravitational Field Acting as an Optical Medium?, in Gen. Rel. and Gravitation, 2, 347-357, (1971). 8.    Evans, J., Nandi, and Islam, ?The Optical-Mechanical Analogy in General Relativity: Exact Newtonian Forms for the Equations of Motion of Particles and Photons?, In General Relativity and Gravitation, 28, 413-439, (1995). 9.  Nandi, Kamal and Islam, ?On the optical-mechanical analogy in general relativity?, In Am. J. Phys. 36 (3) (March 1995) Also, I welcome comments from the other readers to highlight the strengths and weaknesses of this perspective.  In particular, does anyone know a reference that critiques these from the point of view of issues with coordinate systems choices? Let's ask some questions outside the box to challenge the ansatz where it lacks a Chobham armor glacis plate.    1) Does the optical model include birefringence?  If one can erect one refractive index in a medium, one can erect multiple refractive indices (anisotropic in space) by the same mechanism.  Gravitation suddenly has new testable predictions.  Spatial anistropy symmetry-breaks conservation of angular momentum.    2) If you can have birefringence then you can have circular birefringence (optical chirality, gyrotropy) by at least three internal physical mechanisms fundamental to a lattice (J. Chem. Phys. 65(4) 1522 (1976)):         1. Pseudoscalar, from local chirality that persists in disordered distribution (e.g., solution).         2. Vector.  A property of pyroelectric lattices.         3. Pseudodeviator, from lattice symmetry - requires absence of a point of symmetry but tolerates mirror planes of symmetry (optical chirality without physical chirality).  Silver thiogallate (J. Appl. Cryst. 33 126 (2000)), AgGaS2 with non-polar achiral tetragonal space group I-42d (#122), has immense optical rotatory power: 522 degrees/millimeter along [100] at 497.4 nm, reversed along [010]. plus external field-imposed asymmetries - Faraday effect, electrogyration, piezogyration, electro-Faraday effect, magneto-activity, and magneto-electrogyration.   Mica crystal (muscovite, phlogopite) is birefringent and it easily splits into supremely thin atomically-smooth _layer_s (isinglass).  Make a compressed stack of mica films each plane being slightly rotated about the same axis vs. the previous one, all in the same helical sense.  You now have a powerful optical rotator crafted of a sheaf of *achiral* components. If we erect an optical model then all the attendant optical baggage tags along as potential observables.  If we erect an optical model, then we have a potent handle into quantitatively modeling optical properties of a lattice-_base_d medium (J. Appl. Cryst. 19 108 (1986)). If we erect an optical model, then we can geometrically assault its geometric basis and look for unavoidable outputs, http://www.mazepath.com/uncleal/eotvos.htm It uses the same apparatus and the same experimental protocol.  The novel test masses cost about the same as those in a classical experiment.  Somebody should look.

An indirectly related theme to the idea of VSL is something that is sometimes called the Optical-Analogy. Within GR, there exists some Euclidean interpretations, one of which is the optical analogy.  In this interpretation, the gravitational field is represented as an optical medium with an effective index of refraction [7-9].  Although different from the more common Geometric interpretation, this interpretation has been shown to be consistent with physical observables, and transformation rules between these two perspectives have also been published [8].  Little attention is typically focused on this perspective because it does not predict any new effects that aren't already covered by the more common Geometric perspective of GR, and because it raises unanswered issues with coordinate systems choices. And also, I suspect, because such an Euclidean interpretation cannot possibly hold in a region with strong gravitation....         [I have not looked at your references.] Tom Roberts     This e-mail address is being protected from spam bots, you need JavaScript enabled to view it