How do spy satellites work? Is it true the US Military can control our GPS? How do we know the centre of the earth is so hot? How can we identify counterfeit money? We answer these questions on this week's Ask the Naked Scientists. We also investigate why venus doesn't rotate like the planets in the rest of our solar system, reveal why some technology is so reliant on remote control and we also reveal if a domino chain has the potential to go on forever!