NASA scientist and Battlestar Galactica science advisor Kevin Grazier and colleague Patrick Di Justo have written a book called "The Science of Battlestar Galactica". You can read more about it at The Register.
In their book, Grazier and Di Justo span physics, computer science, navigation systems, metals, propulsion systems, weapons and warfare, and biology, as they explain what's going on behind the scenes in BSG.
Take lasers, a staple of any sci-fi. Grazier's book explains the physical limitations of firing the equivalent of an M-16 round in laser terms. He also dispatches the idea depicted in some sci-fi that being pulled into the vacuum of space will suck your eyeballs from their sockets or cause your organs to explode (thanks, Total Recall and Outland). Rather, you'll get a wicked case of the bends, which occurs when nitrogen bubbles enter the bloodstream. It can prove lethal to ocean divers who surface too quickly..