An urban legend is that there are spy satellites which can be employed to read license plates on cars on the ground. Find out the minimum size of the telescope aperture needed to read a license plate. Suppose that the resolution required is 1 cm and that the satellite is orbiting at 300 km over the surface of the Earth, and views in visible light, 550 nm. Even supposing that some spy somewhere even cares concerning your license plate, does this appear practical?