What is the Speed of Dark?

Most recent answer: 03/30/2011

sir, all of us know that the speed of light in vaccume is 300000000m/s.. but please could you tell the s of speed dark??????????????
- kewal sharma (age 21)
We usually don't think of it this way, but if you made a dark region in a beam of light, maybe by waving an dark cloth through it, the dark region would travel along with the light at the same speed.

Mike W.

(published on 03/30/2011)