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Hero of Alexandria

Hero (or Heron) of Alexandria (roughly A.D. 10 to roughly A.D. 70) was a Greek engineer. His most famous invention was the first documented steam engine, the aeolipile. He is said to have been a follower of the Atomists[?]. Some of his ideas were derived from the works of Ctesibius[?].

A number of references mention dates around 150 BC, but these are inconsistent with the dates of his publications and inventions. Perhaps this is due to a misinterpretation of the phrase "first century".


The complete surviving works are:
  • Pneumatica (Greek, c. A.D. 60)
  • Automata (Greek)
  • Mechanics (Arabic)
  • Metrics (Arabic)
  • Dioptra (Arabic)

In optics, Hero proposed that light travels along the shortest geometric path. This view is no longer accepted, having been replaced by least-time principle.

In geometry, he wrote down the formula (Heron's formula) for calculating the area of a triangle in terms of its sides.


  • compressed-air fountain
  • siphons
  • automated puppets
  • machine for threading wooden screws
  • steam turbine (A.D. 50/62/70) (aeolipile)
  • density of air
  • water organ or hydraulic organ
  • odometer


The Technology Museum of Thessaloniki has a good web page on Hero at http://www.tmth.edu.gr/en/aet/5/55.

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