So does light speed up again when it reenters a vacuum?
So just where are the police to give these reckless fools speeding tickets????????
THe speed quoted in the article and discussed in general is the speed of light in a vacuum.
When photons hit another medium, air, glass, etc., it slows down a tiny bit.
As an example, if light passes from vacuum to the atmosphere then through a piece of glass and then back to vacuum, the measured speed of light will slow down in the air, slow down more in the glass and then jump back up upon returning to the vacuum.
The speed quoted in the article and discussed in general is the speed of light in a vacuum.
When photons hit another medium, air, glass, etc., it slows down a tiny bit.
As an example, if light passes from vacuum to the atmosphere then through a piece of glass and then back to vacuum, the measured speed of light will slow down in the air, slow down more in the glass and then jump back up upon returning to the vacuum.