Ludwig Eduard Boltzmann (1844 – 1906) was an Austrian physicist and philosopher whose greatest achievement was in the development of statistical mechanics, which explains and predicts how the properties of atoms (such as mass, charge, and structure) determine the physical properties of matter (such as viscosity, thermal conductivity, and diffusion).
Isolated brains could randomly fluctuate into existence: Imagine you're an isolated brain floating lonely through the vast expanse of the Universe with all your thoughts and perceptions just figments of your imagination. There'd even be a name for you: you'd be a Boltzmann brain. Boltzmann brains are of interest to physicists, in particular to cosmologists. The idea is that, according to quantum mechanics, there is energy in empty space which can fluctuate, producing particles as it does so.
The history of cosmology has its fair share of whacky ideas, but one of the strangest has to be the Boltzmann brain hypothesis – which suggests your mind is the result of a spontaneous, random assortment of particles.