Artificial Gravity (AG): initially developed to address shipboard crew concerns about the relativistic effects of long-distance space travel. Crews under zero-G experience time at a faster rate than people in gravity wells, such as planets. They age faster than their families. While a complete explanation of the mechanics of AG would require several textbooks, an AG engine converts electrical energy into four-dimensional potential energy, increasing the local gravity in a diffuse area. Early generators were only able to create weak fields, equivalent to one or two standard gravities. This had the additional side effect of allowing humans to withstand sustained seven G forces without G suits when AG was used to counteract the effects of the acceleration. While still used on planets, Icarus engines (negative-gravity generators) have largely replaced AG generators in space.
Artificial -gravity was initially developed for the military as a backup parachute, and then used more extensively on planets without an atmosphere.