OK, so what's the speed of dark?
The speed of light is frightful,
To attain it would be delightful.
..but I must confess
The possibility is un-sight-ful. (anon.)
If the speed of light is roughly 186,000 miles per second and with the premise that you can’t have light without dark, then the speed of dark must be greater than the speed of light; to my knowledge none has ever tried to measure the speed of dark, so I propose that the government grant me a large sum of money to conduct the study.