Credit: Image by Andrew Friedman and David Leon
Diagram of a run of the Cosmic Bell test. The regions of space and time where an alternative, non-quantum mechanism could still have acted (limited to the red and/or blue regions) corresponds to at least 7.78 billion years ago (blue region). Light from the more distant quasar was emitted 12.21 billion years ago (red region). Compared to the gray region, representing all of space and time prior to the experiment, the alternatives are limited to within four percent of the space-time volume since the Big Bang.