Working model of Hero's Aeolipile and steam boiler based on Sketches in 16th century Manuscripts, 1914

Hero of Alexandria was a Greek mathematician. He described the aeolipile in his treatise on pneumatics (the study of the mechanical properties of gases) c. 100 BC. It consists of a hollow ball mounted on its axis between two pivots, one of which serves as a steam pipe from the cauldron below, supporting the whole. The ball is provided with two bent nozzles in a plane at right angles to the line joining the pivots. The escape of jets of high pressure steam causes the ball to rotate. Hero considered the Aeolipile to be little more than a toy, but it could be regarded as an elementary form of steam turbine.