In 1907, the reality of atoms was still disputed but Albert Einstein and Marian Smoluchowski had both recently given accounts of Brownian motion in liquids, strongly supporting the atomic theory. Though Theodor Svedberg had made important demonstrations of Brownian motion in colloids, Ehrenhaft extended the work to make observations of particles of silver in air. The greater mean free path of air made for a sterner test of the reality of atoms. Ehrenhaft was awarded the Lieben Prize of the Vienna Academy of Sciences for his work.