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randy23
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When light enters in Earth's atmosphere, how fast does it go? Or does it change at all?
Danger said:The speed of individual photons doesn't change, but the propogation rate of the 'beam' does so in accordance with the composition and density of the air that it's passing through. That varies.
The photons themselves travel at standard c over inter-atomic distances. It's the absorbtion and re-emission thereof by the atoms that slows down the overall propogation.cliowa said:As far as I can tell the light beam (you're referring to) is made up of individual photons, isn't it? So what do you mean the individual photons don't change speed?
Alright, thanks. Just wanted to know what exactly you're referring to.Danger said:The photons themselves travel at standard c over inter-atomic distances. It's the absorbtion and re-emission thereof by the atoms that slows down the overall propogation.
Danger, how would you describe light propagation is glass then?The photons themselves travel at standard c over inter-atomic distances. It's the absorbtion and re-emission thereof by the atoms that slows down the overall propogation.
randy23, the reason that Integral suggested this search is that the index of refraction tells you how much light slows down in a given medium with respect to its speed in vacuum.Integral said:You might try seareching on "index of refraction of air"
I'm afraid that's outside of my knowledge. I've never had much of a chance to study QM. One thing about it is that the photon isn't necessarily absorbed by a directly-neighbouring atom, so the uninterrupted propogation length would be variable. I'm not familiar with the exact QM interactions between electrons and photons.lalbatros said:Danger, how would you describe light propagation is glass then?
The speed of light on Earth is approximately 299,792,458 meters per second or 670,616,629 miles per hour.
Yes, the speed of light is considered a constant in a vacuum and does not change on Earth.
The speed of light on Earth was first measured by Ole Rømer in 1676 using observations of the moons of Jupiter and their eclipses.
According to the theory of relativity, it is not possible for anything to travel faster than the speed of light on Earth.
No, the speed of light is the same on Earth's surface as it is in the atmosphere or in space, as long as there are no obstructions or changes in medium.