Boltzmann brain
physics thought experiment pointing out the improbability of the universe as described by thermodynamics
The Boltzmann brain thought experiment suggests that it's more likely for a random brain (or even an entire body or galaxy) to spontaneously form with false memories in a vast, fluctuating universe than for the entire universe to develop as cosmologists believe. This idea is named after physicist Ludwig Boltzmann. It is used to challenge our assumptions about thermodynamics and the universe's evolution.