...in a Boltzmann-dominated universe, most Boltzmann brains have "abnormal" experiences, but most observers with only "normal" experiences are Boltzmann brains, due to the overwhelming vastness of the population of Boltzmann brains in such a universe.

citation

Wikipedia contributors. (2024, January 30). Boltzmann brain. In Wikipedia, The Free Encyclopedia. Retrieved February 5, 2024, from https://en.wikipedia.org/w/index.php?title=Boltzmann_brain&oldid=1201101868

Boltzmann brain (Wikipedia) The Boltzmann brain thought experiment suggests that it might be more likely for a single brain to spontaneously form in a void, complete with a memory of having existed in our universe, rather than for the entire universe to come about in the manner cosmologists think it actually did. Physicists use the Boltzmann brain thought experiment as a reductio ad absurdum argument for evaluating competing scientific theories.