HOUSTON — Beyond the security gate at the Johnson Space Center’s 1960s-era campus here, inside a two-story glass and concrete building with winding corridors, there is a floating laboratory. Harold G. White, a physicist and advanced propulsion engineer at NASA, beckoned toward a table full of equipment there on a recent afternoon: a laser, a camera, some small mirrors, a ring made of ceramic capacitors and a few other objects. He and other NASA engineers have been designing and redesigning these instruments, with the goal of using them to slightly warp the trajectory of a photon, changing the distance it...