High Quality Content by WIKIPEDIA articles! A Jonbar Hinge (also referred to as a Jon Bar Hinge or change-point) is a science fiction concept derived from the Jack Williamson novel The Legion of Time. Specifically it comes from the short story John Barr, when picking up one of two objects (a magnet and a pebble) is a major turning point in history: choosing one will lead to a utopian civilization named Jonbar, while the other to the tyranny of the state of Gyronchi.