12 thoughts on “The Speed Of Light”

  2. *Displays my Al Gore science ribbon*

    If light starts traveling slower, then infrared radiation from the sun will take longer to escape the Earth’s atmosphere, and the longer residence time will increase the rate of warming from anthropogenic CO2!

    Remember, you read it here first.

  3. If she’s right about GM=tc^3 (and the dimensions of the equation work), then either light is slowing down or else G or M are a function of time – G, M, and c cannot all be constants if t is changing.

  4. The numbers work out to within a factor of two of the current estimates of the age and mass of the universe, but I can’t say if it’s physics or numerology. Why would a lonely photon care how much the entire universe weighs?

    But if you change G and c, what other real yardstick do you have for length? Could you just as well say that G and c are constant but length is changing?

    1. The aficionados of Mach’s Principle claim that the distribution of matter in the universe is what determines how matter moves. The idea being that acceleration is, itself, a relative quantity. When we say an object is accelerating, we are implicitly stating that it is accelerating with respect to something. If the universe were “empty”, then there would be no acceleration possible, because there would be nothing relative to which one could measure one’s acceleration. What we sense as acceleration is acceleration with respect to the “fixed” stars.

      Under this paradigm, the resistance to acceleration, which we commonly view as imparted by inertial mass, is due to the distribution of matter both near and far. Standard GR, moreover, holds that the geodesics of spacetime are determined by the distribution of matter in the communicable universe. Taken together, these two models imply that inertial mass should indeed be equivalent to gravitational mass, which is commonly observed.

      It seems consistent overall, but the idea of far remote mass influencing the local motion of other bodies is a bit of a mental hurdle for me, even if the somewhat hazy mathematical framework appears to work out that way. One of these days, I’m going to get around to reading up on the Higg’s mechanism, and learn how or if it fits into the Mach paradigm.

      1. Einstein’s response to Mach was that while space nor time are fixed, space-time is indeed fixed. In a space-time universe, even if empty, an object will experience acceleraton related forces regardless of distant somethings being there or not to measure acceleration against.

        1. I am not familiar with that criticism, or whether it was based on anything beyond intuition, notwithstanding that Einstein’s intuitions tended so often to be confirmed. Of course, they didn’t play out all that well with regard to QM.

          Would appreciate a citation, as everything I have ever read suggested Einstein was a big fan of Mach.

    2. In a universe where “amplituhedrons” may be the best way to calculate particle interactions, the requirement to give up both locality (separated particles/fields being the things that act) and unitarity (that all the probabilities of an interaction must add up to 1.0) may make it *necessary* that the photon cares what the universes masses.

  5. You know how the older you are, the faster a year goes by? Perhaps the speed of light hasn’t changed but time has sped up.

  6. My question is:
    Does this open up any insights into separating ‘inertial mass’ from ‘gravitational mass’?

    Quite crucial for having fun farther from Earth.

  7. Good for her.

    G and c are constant but length is changing

    Relativity says mass, length and time all change with speed (not just the near the speed of light where it’s more noticeable.)

    We have results that suggest c is not constant. We just have to accept the implications. If we can live with quantum mechanics we aught to be able to get our heads around this.

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