How can light be slowed?

Light can be slowed by making it pass through a physical medium such as glass, air, water, etc.

 

Light can be slowed when emitted from a gravitational well. This is not effective for light passing by a gravitational well since it is blue shifted on the way in.

 

You mean it gets red shifted? [en.wikipedia.org]. Speed is the same I believe, unless you run it through anything other than vacuum/air.

 

Shooting a lazer through super-cooled sodium atoms will slow the light to 34mph.

 

You can think of light in the particle sense as an important man walking in a room. If he is just walking through an empty room, he is not really affected, as in, he is not bouncing around. If he just made an important speech, he will be shaking peoples hands a lot, just bouncing around, always going the speed of light, just in a zig-zag path. I don't think light will ever look like it is going completely at 0 speed relative to anyone else.

 

When the lazer is suddenly turned off the light freezes for a fraction of a second within the gas only to resume after the lazer is turned back on .