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Born fl. 10 AD
Residence Alexandria, Ptolemaic Egypt
Fields Mathematics
Known for aeolipile

Hero (or Heron) of Alexandria (Greek: Ἥρων ὁ Ἀλεξανδρεύς) (c. 10–70 AD). was an ancient Greek mathematician who was a resident of a Roman province (Ptolemaic Egypt); he was also an engineer who was active in his native city of Alexandria. He is considered the greatest experimenter of antiquity[1] and his work is representative of the Hellenistic scientific tradition.[2]

Hero published a well recognized description of a steam-powered device called an aeolipile (hence sometimes called a "Hero engine"). Among his most famous inventions was a windwheel, constituting one of the earliest instances of wind harnessing.[3][4] He is said to have been a follower of the Atomists. Some of his ideas were derived from the works of Ctesibius.

Much of Hero's original writings and designs have been lost, having been burned by anti-pagan Christians sometime in the late 4th to 5th century—whether intentionally or unintentionally, as many of the writings from the Library of Alexandria were housed in pagan temples later burned by Christian leaders such as Pope Theophilus of Alexandria. Fortunately, some of his works were preserved in Arab manuscripts.[5][6]



Due to strong Babylonian influence in Hero's work, it was once speculated by a minority of scholars that Hero may have been a Greek of Egyptian or Phoenician origin,[7] but the modern scholarly consensus is that he was a pure Greek.[1][8][9] The historian of mathematics C. B. Boyer explains that Hero's identification as an Egyptian or a Phoenician was largely due to the strong Babylonian influence on his work. However at least from the days of Alexander the Great to the close of the classical world, there undoubtedly was much intercommunication between Greece and Mesopotamia, and it seems to be clear that the Babylonian arithmetic and algebraic geometry continued to exert considerable influence in the Hellenistic world.[8]


A number of references mention dates around 150 BC, but these are inconsistent with the dates of his publications and inventions. This may be due to a misinterpretation of the phrase "first century" or because Hero was a common name.

It is almost certain that Hero taught at the Musaeum which included the famous Library of Alexandria, because most of his writings appear as lecture notes for courses in mathematics, mechanics, physics and pneumatics. Although the field was not formalized until the 20th century, it is thought that the work of Hero, his "programmable" automated devices in particular, represents some of the first formal research into cybernetics.[10]

Inventions and achievements

Heron's Aeolipile
  • Hero described construction of the aeolipile (a version of which is known as Hero's engine) which was a rocket-like reaction engine and the first-recorded steam engine (although Vitruvius mentioned the aeolipile in De Architectura some 100 years earlier than Hero). It was created almost two millennia before the industrial revolution. Another engine used air from a closed chamber heated by an altar fire to displace water from a sealed vessel; the water was collected and its weight, pulling on a rope, opened temple doors.[11] Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work.[12]
Hero's wind-powered organ (reconstruction)
  • The first vending machine was also one of his constructions, when a coin was introduced via a slot on the top of the machine, a set amount of holy water was dispensed. This was included in his list of inventions in his book, "Mechanics and Optics". When the coin was deposited, it fell upon a pan attached to a lever. The lever opened up a valve which let some water flow out. The pan continued to tilt with the weight of the coin until it fell off, at which point a counter-weight would snap the lever back up and turn off the valve.[13]
  • A windwheel operating an organ, marking probably the first instance of wind powering a machine in history.[3][4]
  • Hero also invented many mechanisms for the Greek theater, including an entirely mechanical play almost ten minutes in length, powered by a binary-like system of ropes, knots, and simple machines operated by a rotating cylindrical cogwheel. The sound of thunder was produced by the mechanically-timed dropping of metal balls onto a hidden drum.
Hero's fire-engine
  • The force pump was widely used in the Roman world, and one application was in a fire-engine.
  • A syringe-like device was described by Heron to control the delivery of air or liquids.[14]
The syringe
  • In Optics, Hero formulated the Principle of the Shortest Path of Light: If a ray of light propagates from point A to point B within the same medium, the path-length followed is the shortest possible. It was nearly 1000 years later that Ibn al-Haytham expanded the principle to both reflection and refraction, and the principle was later stated in this form by Pierre de Fermat in 1662; the most modern form is that the path is at an extremum.
  • A standalone fountain that operates under self-contained hydrostatic energy. (Heron's fountain)


Heron described a method of iteratively computing the square root.[15] It is also called the Babylonian method, because the Babylonians also knew of it before Hero wrote it down. Today, though, his name is most closely associated with Heron's Formula for finding the area of a triangle from its side lengths.

The imaginary number, or imaginary unit, is also noted to have been first observed by Heron while calculating the volume of a pyramidal frustum.[16]


The most comprehensive edition of Hero's works was published in 5 volumes in Leipzig by the publishing house Teubner in 1903.

Works known to be written by Heron:

  • Pneumatica, a description of machines working on air, steam or water pressure, including the hydraulis or water organ.[17]
  • Automata, a description of machines which enable wonders in temples by mechanical or pneumatical means (e.g. automatic opening or closing of temple doors, statues that pour wine, etc.). See Automaton.
  • Mechanica, preserved only in Arabic, written for architects, containing means to lift heavy objects.
  • Metrica, a description of how to calculate surfaces and volumes of diverse objects.
  • On the Dioptra, a collection of methods to measure lengths. In this work the odometer and the dioptra, an apparatus which resembles the theodolite, are described.
  • Belopoeica, a description of war machines.
  • Catoptrica, about the progression of light, reflection and the use of mirrors.

Works which have sometimes been attributed to Hero, but are now thought to have most likely been written by someone else:[18]

  • Geometria, a collection of equations based on the first chapter of Metrica.
  • Stereometrica, examples of three dimensional calculations based on the second chapter of Metrica.
  • Mensurae, tools which can be used to conduct measurements based on Stereometrica and Metrica.
  • Cheirobalistra, about catapults.
  • Definitiones, containing definitions of terms for geometry.

Works which are preserved only in fragments:

  • Geodesia
  • Geoponica

Latest paper on Hero:

  • Schellenberg, H.M.: Anmerkungen zu Heron von Alexandria und seinem Werk über den Geschützbau, in: Schellenberg, H.M./ Hirschmann, V.E./ Krieckhaus, A.(edd.): A Roman Miscellany. Essays in Honour of Anthony R. Birley on his Seventieth Birthday, Gdansk 2008, 92-130 (with a huge bibliography of over 300 titles and discussion of the communis opinio on Hero).


A 2007 The History Channel television show Ancient Discoveries includes recreations of most of Heron's devices.

A 2008 The History Channel television show Ancient Discoveries - "Ancient New York" includes a short recreation of a fountain device that made water flow uphill.

A 1979 Soviet animated short film focuses on Heron's invention of the aeolipile, showing him as a plain craftsman who invented the turbine accidentally. [19]

See also


  1. ^ a b Research Machines plc. (2004). The Hutchinson dictionary of scientific biography. Abingdon, Oxon: Helicon Publishing. pp. 546. "Hero of Alexandria (lived c. AD 60) Greek mathematician and engineer, the greatest experimentalist of antiquity" 
  2. ^ Marie Boas, "Hero's Pneumatica: A Study of Its Transmission and Influence", Isis, Vol. 40, No. 1 (Feb., 1949), p. 38 and supra
  3. ^ a b A.G. Drachmann, "Heron's Windmill", Centaurus, 7 (1961), pp. 145-151
  4. ^ a b Dietrich Lohrmann, "Von der östlichen zur westlichen Windmühle", Archiv für Kulturgeschichte, Vol. 77, Issue 1 (1995), pp.1-30 (10f.)
  5. ^ Chesser, Preston. "The Burning of the Library of Alexandria". OSU Department of History. 
  6. ^ Terry Jones, Daniel Percival. (1998). Ancient Inventions: City Life. [Mini-Series]. Seventh Art Productions. 
  7. ^ George Sarton (1936). "The Unity and Diversity of the Mediterranean World", Osiris 2, p. 406-463 [429].
    "Hero of Alexandria". John H. Lienhard. The Engines of Our Ingenuity. NPR. KUHF-FM Houston. 1995. No. 1038. Transcript.
    T. D. De Marco (1974). "Gas-Turbine Standby-Power Generation for Water-Treatment Plants", Journal American Water Works Association 66 (2), p. 133-138.
    Victor J. Katz (1998). A History of Mathematics: An Introduction, p. 184. Addison Wesley. ISBN 0321016181.
    Justin E. Wilson (2006). Heron’s Formula, University of North Carolina at Charlotte.
  8. ^ a b Boyer (1968 [1991]). "Greek Trigonometry and Mensuration". A History of Mathematics. pp. 171–172. "At least from the days of Alexander the Great to the close of the classical world, there undoubtedly was much intercommunication between Greece and Mesopotamia, and it seems to be clear that the Babylonian arithmetic and algebraic geometry continued to exert considerable influence in the Hellenistic world. This aspect of mathematics, for example, appears so strongly in Heron of Alexandria (fl. ca. A.D. 100) that Heron once was thought to be Egyptian or Phoenician rather than Greek. Now it is thought that Heron portrays a type of mathematics that had long been present in Greece but does not find a representative among the great figures - except perhaps as betrayed by Ptolemy in the Tetrabiblos." 
  9. ^ Gregory A Tokaty (1994). A History and Philosophy of Fluid Mechanics. Courier Dover Publications. pp. 26. ISBN 0486681033. 
    Grolier Incorporated (1989). Academic American Encyclopedia. Grolier University of Michigan. pp. 144. ISBN 0717220249. 
    Encyclopædia Britannica Online - Heron of Alexandria
    Israel Shatzman, Michael Avi-Yonah (1975). Illustrated Encyclopedia of the Classical World. Harper and Row. pp. 234. ISBN 0060101784. 
    Gillian Clements (2005). The Picture History of Great Inventors. frances lincoln ltd. pp. 13. ISBN 0711216053. 
    Enc. Britannica 2007, "Heron of Alexandria"
  10. ^ Kelly, Kevin (1994). Out of control: the new biology of machines, social systems and the economic world. Boston: Addison-Wesley. ISBN 0-201-48340-8. 
  11. ^ Hero of Alexandria; Bennet Woodcroft (trans.) (1851). "Temple Doors opened by Fire on an Altar". Pneumatics of Hero of Alexandria. London: Taylor Walton and Maberly (online edition from University of Rochester, Rochester, NY). Retrieved 2008-04-23. 
  12. ^ for example: Mokyr, Joel (2001). Twenty-five centuries of technological change. London: Routledge. p. 11. ISBN 0-415-26931-8. "Among the devices credited to Hero are the aeolipile, a working steam engine used to open temple doors"  and Wood, Chris M.; McDonald, D. Gordon (1997). "History of propulsion devices and turbo machines". Global Warming. Cambridge, England: Cambridge University Press. p. 3. ISBN 0-521-49532-6. "Two exhaust nozzles...were used to direct the steam with high velocity and rotate the sphere...By attaching ropes to the axial shaft Heron used the developed power to perform tasks such as opening temple doors" 
  13. ^ Humphrey, John W.; John P. Oleson, Andrew N. Sherwood (1998). Greek and Roman technology: A Sourcebook. Annotated translations of Greek and Latin texts and documents. Routledge Sourcebooks for the Ancient World. London and New York: Routledge. ISBN 9-780-415-06137-7. , pp.66–67
  14. ^ Hero of Alexandria; Bennet Woodcroft (trans.) (1851). "No. 57. Description of a Syringe.". Pneumatics of Hero of Alexandria. London: Taylor Walton and Maberly (online edition from University of Rochester, Rochester, NY). [1] Retrieved 2010 January 27
  15. ^ Heath, Thomas (1921). A History of Greek Mathematics, Vol. 2. Oxford: Clarendon Press. pp. 323–324. 
  16. ^ Nahin, Paul."An Imaginary Tale: The story of [the square root of minus one]. Princeton University Press. 1998"
  17. ^ Jamies W. McKinnon. "Hero of Alexandria and Hydraulis", Grove Music Online, ed. L. Macy (accessed January 17 2007), (subscription access).
  18. ^ O'Connor, J.J. and E.F. Robertson. "Heron biography". The MacTutor History of Mathematics archive. Retrieved 2006-06-18. 
  19. ^

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