Quote:
Originally Posted by shakran
No, but then I'm a physics layman. If something's moving in a straight line at speed X, and it goes through a medium still in a straight line, and the time it took to traverse that distance indicates that it had to be moving at X-10, and on the other side of that medium it's back to speed X, I don't see how it didn't slow down. I've read other articles on this, that didn't indicate the medium caused the light to take a circuitous path through the braking medium, so I've been assuming that the light travels a straight line through it. Is that where I'm hung up?
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Think of someone walking through a crowd.
Before you get to the crowd, you take a 1m step each second, meaning you travel at 1m/s.
When you hit the crowd, you take a 1m step each second, but instead of straight line, you now have to jink and bob through the people, so your speed is still 1m/s, but your progress through the crowd has dropped to >1m/s.
On the micro scale, your SPEED is unchanged, but on a macro scale your VELOCITY has dropped.
Latices that trap photons are like this - the photons move at C, but because they bounce back and forth past atoms in the lattice, their path length is massively increased, and so they take longer to get through the lattice than L/C, where L is the external size of the lattice.