The magic twirly thing in the Engine Room is labeled the "Radion Accelerator Core," which is a fancier way of saying "Magic Twirly Thing."

Face it, Joss knows beans about science and has been making it up as he goes along. It says a lot about his talent that he makes it look good anyway.

The Magic Twirly Thing twirls so that you know it's working. A real nuclear reactor just sits there no matter what it's doing, and the only way you can tell things are running right is if all the lights are green.

Geeks will remember that the ends of the warp nacelles on the U.S.S. Enterprise also used twirly things to let you know they were working.

Other parts of the warp engine thrummed, and pulsed with lights to indicate proper operation.

When I was a kid, nothing said "power" to me like the original thundering drone of the original Enterprise going into warp drive. The "whiz-snap" of the later series had nothing on it.