Sound is funny. At lower frequencies it behaves increasingly similarly to air i.e. wrapping around obstacles instead of just reflecting. At 0Hz sound is just the local air pressure and the weather forecast is technically sheet music.
At 0Hz sound is just the local air pressure and the weather forecast is technically sheet music.
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Thought this was from the hover text for a second!
Stands to reason. Vivaldi did compose the seasons after all
Speed of light in fiber is ~0.66c₀. Light is slowed down a bit by air, too. So...
iirc light does move through the fiber itself at more or less 1c its just that it doesn't take straight path due to all the internal reflections which is what causes the slow down.
c is speed of light in a vacuum. Light does go slower in other media. This is why refraction, among other things, exists. I'm not sure what the speed of light in fiber is, and it may be very close to c, but it will not be c.
That is not the speed of light through fiber. That is the speed of light bouncing at diagonal angles as it travels through fiber.

It appears to travel slower because it's not traveling in a straight line. But I promise, every individual photon is traveling at exactly c. Photons emmited simultaneously will not all arrive at a destination at the same time, but this isn't because they're traveling at different speeds, it's because they're taking different paths, reflecting and refracting slightly differently.
xkcd
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