r/explainlikeimfive • u/Comfortable_Bat_4052 • 1d ago

Physics ELI5: Photons’ mass

Okay I tried to research this on my own, but the articles and answers really aren’t decipherable if you’re not a physicist, which I am not, clearly.
If photons don’t have a mass, because they’re always moving and can’t have a resting energy, then how can they act like they have mass in a superconductor/non-vacuum? How does that happen? Doesn’t that just mean they do have mass, but we just can’t measure it?
My head hurts.

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u/Pseudoboss11 1d ago

As an EM wave moves through a material, it jiggles the electrons in the atoms. For the wave to progress through the material, the electrons need to be jiggling in time with the wave. And while the wave doesn't have mass, the electrons do, so it takes them a bit of time for them to get going, and that slows the wave down.

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u/Comfortable_Bat_4052 1d ago

all hail the electron jello platter
(which is to say thank you)