Paul Langevin, On the theory of brownian motion
“ The theorem of the equipartition of the kinetic energy between the various degrees of freedom of a system in thermal equilibrium requires that a particle suspended in any kind of liquid possesses, in the direction x, an average kinetic energy RT/2N equal to that of a gas molecule of any sort, in a given direction, at the same temperature. ”
Paul Langevin, On the theory of brownian motion
“ We are indebted to this physicist for having clearly formulated the hypothesis which sees in this continual movement of particles suspended in a fluid an echo of molecular-thermal agitation, and for having demonstrated this experimentally, at least in a qualitative manner, by showing the perfect permanence of Brownian motion, and its indifference to external forces when the latter do not modify the temperature of the environment. ”
Paul Langevin, On the theory of brownian motion
“ A particle such as the one we are considering, large relative to the average distance between the molecules of the liquid, and moving with respect to the latter at the speed ksi, experiences a viscous resistance equal to -6*Pi*m*a*ksi according to Stokes’ formula. ”
