What are the ranges for the speed of light?

Someone who knows for sure will certainly answer.

I’m fairly certain it’s a constant. It’s used to gage all sorts of other things.

Constant but I’ll deferred to @Caravavfan.

Maximum speed is c in vacuum. Minimum speed technically is zero or close to zero in mediums such as a Bose-Einstein condensate.

According to this article, light has been slowed down to 38 mph (about 61 km/hr).

@LostInParadise Yes, that’s the Bose-Einstein condensate that I mentioned. Good find.

Light slows by 25% when travelling through water. Mediums such as air or glass slow it by similar amounts.

Fascinating.
In deep space, space is not a vacuum, which may mean our measurements of the distance to some stars may be way off.

@filmfann Your real name is Spock!