Imagine that frames r us, inc., is constructing an economy reference frame whose price will be below every water g with ers on ection other frame on the market. placing a clock at every point in the frame lattice is too expensive, so the company decides to place one clock at the origin. at all other positions, the company simply places a flag that springs up when an object goes by. the flag has the lattice location printed or it, so an observer sitting at the origin can assign spacetime coordinates to every event by noting when he or she sees o the the flag spring up (according to the clock at the origin) and in a noting the spatial coordinates indicated by the flag. why mov- doesn't this method yield the same spacetime coordinates sthe as having a clock at every location would? pinpoint the gali- assumption that the engineers at frames r us are making pic- that is incorrect. (see problem r1r.2 for a further explora- nsfor- lative hich hich tion of the problems with this reference frame.) r1m.