At that time Friedmann was working on hydrodynamics writing his two part thesis The Hydromechanics of a Compressible Fluid; the first part was on the kinematics of vortices and the second on the dynamics of a compressible fluid.
Sa panahon na Friedmann ay nagtatrabaho sa haydrodinamika pagsusulat ng kanyang dalawang bahagi tesis Ang haydromekanika ng isang napipiga likido; ang unang bahagi ay sa kinematika ng vortices at ang pangalawa sa dinamika ng isang napipiga likido.