Hidden in the woods two miles from Princeton University’s main campus sits a drab white building easily mistakable for a warehouse. Inside is one of the Ivy League school’s most expensive experiments: a 22-foot-tall metal spheroid surrounded by Crayola-colored magnets. About half a dozen blue beams ring the sphere horizontally, while another set, painted red, rise vertically from the floor to wrap the contraption, like fingers clutching a ball.