Jonbar hinge

In science-fiction criticism, a Jonbar hinge or Jonbar point^[1] is the fictional concept of a crucial point of divergence between two outcomes, especially in time-travel stories. It is sometimes referred to as a Jon Bar hinge or change-point.^[2]

It is derived from the Jack Williamson novel The Legion of Time (serialized 1938, collected 1952). Specifically it comes from one action from its character John Barr, in which 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.

Jonbar hinges often refer to small non-descript events that had an important effect on history, but because of time travel the outcome of the choice or event was changed leading to a different future or an alternate history.^[3][4] It can, however, refer to any kind of change in history without having to deal with time travel, as Paul Di Filippo used the term when reviewing S. M. Stirling's In the Courts of the Crimson Kings.^[5] In Michael Chabon's The Yiddish Policemen's Union the jonbar hinge was the death of the main opponent to the King-Havenner Bill, which if passed would have allowed Jewish refugees to settle in Alaska.^[6] The term is also used when describing an important upcoming event or decision humanity will have to make in the future.^[7]

Jonbar Hinges are often the subject of professional, journalistic, and amateur speculation.^[8]

• Alien space bats
• Counterfactual history
• Butterfly effect
• For Want of a Nail