Brownian motion linear and angular momenta remain null over time. It is important also to note that the kinetic energies of the molecular Brownian motions, together with those of molecular rotations and vibrations sum up to the caloric component of a fluid's internal energy. This motion is named after the botanist Robert Brown, who was the most eminent microscopist of his time. In 1827, while looking through a microscope at pollen of the plant "Clarkia pulchella" immersed in water, the triangular shaped pollen burst at the corners, emitting particles which he noted jiggled around in the water in random fashion. He was
Brownian motion left then after "N" collisions the particle's velocity will have changed by Δ"V"(2"N" − "N"). The multiplicity is then simply given by: and the total number of possible states is given by 2. Therefore, the probability of the particle being hit from the right "N" times is: As a result of its simplicity, Smoluchowski's 1D model can only qualitatively describe Brownian motion. For a realistic particle undergoing Brownian motion in a fluid many of the assumptions cannot be made. For example, the assumption that on average occurs an equal number of collisions from the right as from the left falls