Tuesday, February 24, 2009

Hero (62–152 CE)

The Alexandrian inventor, physicist, and mathematician Hero was a creative mind of the second century CE. Hero lived, worked, and taught at Alexandria. Influenced by Aristotle and the atomists, he also built on the work of the mechanical engineer Ctesibius. Hero wrote Pneumatica and Automatapoeica, which described his ideas on physical forces and mechanisms to displace weight, water, and air. He was interested in land measurement, wrote on surveying, and invented a forerunner of the theodolite, a surveyor’s instrument for measuring angles.

Hero was fascinated by actions upon air and water. He argued that air is a material substance that exists within an apparently empty container. He analyzed the displacement of air by pouring water into a jar. He experimented with compression and argued for the presence of vacuums in nature. He was one of the founders of theories of kinetic energy. He explained the action of fire on substances according to the Aristotelian theory that heavy objects fall toward the center while lighter objects ascend toward the heavens. Hero invented a steam mechanism that featured a cauldron of boiling water that released steam through a small tube entering a sphere with two pipes at right angles. As the steam was forced through the pipes the sphere rotated.Another device heated air that filled a container of oil; the oil was forced by the air into tubes held within statues; the oil dripped from the stone hands holding cups for libations. Hero also experimented with pistons, valves, pneumatics, and hydraulics. Most of his inventions were, however, used as toys or for tricks to amuse the rich. For example, Hero contrived a device that, by forcing air through small valves, would produce the appearance and sound of bird’s singing. Another device used principles of heat and air pressure: it was a device made of an iron cauldron filled with water that was heated by a fire. Steam was forced through a small opening at the top of the device, which provided sufficient force to cause a small ball to hang and dance just above the opening.

Hero’s devices were built at a time of slavery when there was no demand for such labor-saving machines. Hero, like most ancient engineers, also turned his skills to military science, working on siege engines, slings, missiles and other ballistics. He also invented an odometer and designed “An Altar Organ blown by the agency of a Wind-mill.”


Boardman, John, Jasper Griffin, and Oswyn Murray. Oxford History of the Classical World.

Oxford: Oxford University Press, 1986.

Hero of Alexandria. The Pneumatics.Translated by Bennet Woodcroft. London: C.Whittingham, 1851.

Leicester, Henry M. The Historical Background of Chemistry. New York: Dover Books, 1971.


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