Anyone can build a cart propelled by a falling lead weight, but this one, originally designed by a Greek inventor named Hero way back in 60 AD, responds to a series of commands "programmed" into the axle. The string pulled by the weight goes forward and back depending on where it has been wrapped around pegs in the axle, producing a handy tool for moving actors on and off stage. (Those Greeks sure loved their drama.) [New Scientist]