Einstein deduced that the speed of light is constant from how our world behaves, not from a theory that explains why, so why does light travel at a constant speed? If light is particles moving, why can’t we nudge them to go just a bit faster, at the speed of light plus one? Why does our universe have a speed limit? The answer, according to current physics, is that:
“… the speed of light is a constant because it just is, and because light is not made of anything simpler.” (Laughlin, 2005), p15.
Yet “because it just is” isn’t a very good reason in science. Particles move according to their mass, so shouldn’t photons with no mass go at any speed? In contrast, if a photon is a wave, its speed should depend on the medium that transmits it. It follows that if light is a wave on a network, it should move at the rate of that network. How fast then is the quantum network?
A 5GHz computer network runs at 5,000,000,000 cycles per second. That seems very fast but Planck time suggests that the quantum network cycles at an astonishing 1045 times a second! Planck time is the smallest possible time scale in our universe, and Planck length is the smallest possible distance, so dividing this distance by this time should give the speed of light, and sure enough it does (Note 1). The speed of light then, like every wave, is limited by the speed of the medium that transmits it.
Yet even the term speed of light betrays our particle bias, as it assumes that light sets its own pace, but waves don’t do that. They only move as fast as their medium allows, so if space is the medium of light, what we call the speed of light is actually the speed of space. Light, like every wave, moves as fast as its medium does, so the speed of light is constant because space everywhere is the same.
Why then does light slow down when it moves in water? Again, it is our particle bias that says it is in the water. If light moves in water, we say the medium is water, and if it moves in glass, we say the medium is glass, but if it moves in space, we say it is a wave of nothing, which is inconsistent! Surely light has the same medium in every case. If the medium of light in space is the quantum network, it is also the medium when it moves through water or glass. Light then doesn’t slow down because water is a denser medium, but because the quantum network has to also generate the water. When the quantum network is doing other things, it slows down, so light slows down in water for the same reason that a game slows down when the computer running it has other things to do.
Light then moves at different speeds through different materials because the quantum network handling it has other things to do as well. Fortunately, the network still processes photons in strict sequence, one after the other, like cars in a queue. Each point handles the photon it has before accepting the next one, so even if it runs slower, they still arrive in lock-step order. This maintains causality, as if one photon could overtake another, we could see an object arrive before it left! Causality requires photons to stay in sequence and the quantum engine rigorously maintains this.
Note 1: The speed of light c = LP/TP, where LP is a Planck length of 1.616×10−35meters and TP is Planck time of 5.39 × 10−44 of a second. This gives the speed of light as 299,792,458 meters per second (see here).
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