Work

Einstein’s theory of Brownian motion—the random movements of small particles in a liquid—explained that the movements are due to collisions between particles and molecules. Theodor Svedberg’s studies helped confirm the theory and thus provided evidence of the physical existence of molecules. In 1925 he also developed the ultracentrifuge, which spins mixtures of different substances at very high speeds. The heavier elements are pulled to the outer edge, and various measurements then allow the calculation of the weight of different molecules.