A nice video that explains the paper: https://www.youtube.com/watch?v=UHKZMGdj7cI
> Science educators love to make videos about relativity, but surprisingly few of them seem to understand what this stuff really means.
The two examples the video gives of science educators that don't "know what this stuff means" are Don Lincoln and Matt O'Dowd. Both have PhDs in physics. Lincoln was on the team that discovered the Higgs boson. O'Dowd is a professor at CUNY. They know what they're talking about.
Then the video gives as an example of a bad explanation the PBS Space Time on the speed of light. But that video makes pretty much the same argument. That the speed of light/causality falls out logically even if you don't postulate it. The author clearly didn't watch that video carefully https://www.youtube.com/watch?v=msVuCEs8Ydo
I would have subscribed to this channel, but this tone is a bad look.
Clickbait as in "Only this channel author Knows The Truth".
Both the paper and the video then finish off by ontologically tying this maximum speed, notation 'c', to the interesting physical E&M phenomenon we happen to call 'light'. My question - in this framework where we are deconstructing everything (which I applaud), then why make that leap to associate this 'c' with the phenomenon known as light?
Inference, sure why not until any future evidence suggests otherwise, but why do so in the intentionally limited scope of the paper & video's derivations?
That's an excellent question! And there are two answers.
1. If you apply the principle of relativity to Maxwell's equations, that's the result you get. Maxwell's equations predict a wave phenomenon that propagates at a constant speed in a vacuum. If the laws of physics, including the laws of electromagnetism, are the same for all inertial observers, then the speed at which those waves propagate have to be the Lorentz-invariant speed.
2. Experiments bear out this prediction! :-)
Note that it did not have to be this way, but if it were not, then EM experiments would give different results for observers in different inertial frames, which would falsify the relativity assumption. The different results for EM experiments would allow you to identify a privileged inertial frame. For a long time, physicists thought this would turn out to be the case, that there was a medium, a "luminiferous aether", through which EM waves propagated, and this medium would define a privileged frame (at least for electromagnetism). It just turns out by experiment that this is wrong, at least in our universe.
Yes, of course. First principles only leads you to the conclusion that there is a reference speed. It tells you nothing about its actual value. In fact, first principles cannot rule out the possibility that the reference speed is infinite. They can only lead you to suspect that it might not be.
Therefore, once you show that the speed of light in a vacuum is Lorentz-invariant, then it has to be the unique Lorentz-invariant speed (i.e., the universal speed limit).
I mean, historically yes. But you can define the fields as purely postulates if you like. The theory actually requires very little input to derive.
I’ve always had a problem with the speed of light being the ultimate speed limit in the universe. I would think “who granted the photon this authority?”. It wasn’t until I watched a lot of pbs space time YouTube’s that I learned what people really meant was the speed of causality is the ultimate speed limit. That makes more sense to me.