March 4, 1959 — The moon is a fat, slow, lazy target; it ought to be easy to hit. The problem is, it's also nearly a quarter-million miles away and in constant motion. Take a bead on it and fire, and by the time your spacecraft has gotten where it's going, the moon will have long since glided by. NASA got a fast start in the space race, taking some early target practice with the 13-lb., 23-in. Pioneer 4 spacecraft. The probe was successfully launched into orbit around the sun — a trajectory that's hard to avoid if you point your booster correctly — and aimed to pass as close to the moon as possible. Pioneer 4 came close indeed, flying by the great lunar mass at a distance of just 37,300 miles — 85% of the way to what was fast becoming the first great prize of space exploration.