Hero of Alexandria

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Hero of Alexandria
Hero of Alexandria.png
17th-century German depiction of Hero
Native name Ἥρων
Born c. 10 AD
Died c. 70 AD (aged around 60)
Citizenship Alexandria, Roman Egypt
Fields Mathematics
Physics
Pneumatic and hydraulic engineering
Known for Aeolipile
Heron's fountain
Heron's formula
Vending machine

Hero of Alexandria (/ˈhɪər/; Greek: Ἥρων[1] ὁ Ἀλεξανδρεύς, Heron ho Alexandreus; also known as Heron of Alexandria /ˈhɛrən/; c. 10 AD – c. 70 AD) was a Greco-Egyptian mathematician and engineer who was active in his native city of Alexandria, Roman Egypt. He is often considered the greatest experimenter of antiquity[2] and his work is representative of the Hellenistic scientific tradition.[3]

Hero published a well-recognized description of a steam-powered device called an aeolipile (sometimes called a "Hero engine"). Among his most famous inventions was a windwheel, constituting the earliest instance of wind harnessing on land.[4][5] He is said to have been a follower of the atomists. In his work Mechanics, he described pantographs.[6] Some of his ideas were derived from the works of Ctesibius.

In mathematics he is mostly remembered for Heron's formula, a way to calculate the area of a triangle using only the lengths of its sides.

Much of Hero's original writings and designs have been lost, but some of his works were preserved including in manuscripts from the Eastern Roman Empire and to a lesser extent, in Latin or Arabic translations.

Life and career

Hero's ethnicity may have been either Greek[2] or Hellenized Egyptian.[7][8][9][10] 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 twentieth century, it is thought that the work of Hero, in particular his automated devices, represented some of the first formal research into cybernetics.[11]

Inventions

Hero's aeolipile

Hero described[12] the 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 described 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.[13] Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work.[14]

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.[15]
  • A wind-wheel operating an organ, marking the first instance in history of wind powering a machine.[4][5]
  • Hero also invented many mechanisms for the Greek theatre, 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.
  • 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 Hero to control the delivery of air or liquids.[16]
  • 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 Alhacen 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 optical path is stationary.
  • A stand-alone fountain that operates under self-contained hydro-static energy; now called Heron's fountain.
  • A programmable cart that was powered by a falling weight. The "program" consisted of strings wrapped around the drive axle.[17]

Mathematics

Hero described a method for iteratively computing the square root of a number.[18] Today, however, his name is most closely associated with Heron's formula for finding the area of a triangle from its side lengths. He also devised a method for calculating cube roots.[19] He also designed a shortest path algorithm, that is, given two points A and B on one side of a line, find C a point on the straight line that minimizes AC+BC. "No one discovery forms the basis for 3D geometry. However Heron of Alexandria is one of the major contributors" Herons work, Metrica discusses the properties of regular polygons, circles, and conic sections, and thus opened up the exploration and understanding of the third dimension. Heron, father of 3D[20] can be attributed to him.

Cultural references

  • A 1979 Soviet animated short film focuses on Hero's invention of the aeolipile,[20] showing him as a plain craftsman who invented the turbine accidentally[21]
  • A 2007 The History Channel television show Ancient Discoveries includes recreations of most of Hero's devices
  • A 2010 The History Channel television show Ancient Aliens episode "Alien Tech" includes a discussion of Hero's steam engine
  • A 2014 The History Channel television show Ancient Impossible episode "Ancient Einstein"

Bibliography

File:Hero - De automatis, 1589 - 116959.jpg
The book About automata by Hero of Alexandria (1589 edition)

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

Works known to have been written by Hero include:

  • Pneumatica (Πνευματικά), a description of machines working on air, steam or water pressure, including the hydraulis or water organ[22]
  • Automata, a description of machines which enable wonders in banquets and possibly also theatrical contexts by mechanical or pneumatical means (e.g. automatic opening or closing of temple doors, statues that pour wine and milk, etc.)[23]
  • 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, a work in which 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 that sometimes have been attributed to Hero, but are now thought most likely to have been written by someone else:[24]

  • Geometrica, 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
  • Cheiroballistra, about catapults
  • Definitiones, containing definitions of terms for geometry

Works that are preserved only in fragments:

  • Geodesia
  • Geoponica

See also

References

  1. Genitive: Ἥρωνος.
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  3. Marie Boas, "Hero's Pneumatica: A Study of Its Transmission and Influence", Isis, Vol. 40, No. 1 (Feb., 1949), p. 38 and supra
  4. 4.0 4.1 A.G. Drachmann, "Heron's Windmill", Centaurus, 7 (1961), pp. 145–151
  5. 5.0 5.1 Dietrich Lohrmann, "Von der östlichen zur westlichen Windmühle", Archiv für Kulturgeschichte, Vol. 77, Issue 1 (1995), pp. 1–30 (10f.)
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  7. George Sarton (1936). "The Unity and Diversity of the Mediterranean World", Osiris 2, p. 406-463 [429]
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  9. T. D. De Marco (1974). "Gas-Turbine Standby-Power Generation for Water-Treatment Plants", Journal American Water Works Association 66 (2), p. 133-138.
  10. Victor J. Katz (1998). A History of Mathematics: An Introduction, p. 184. Addison Wesley, ISBN 0-321-01618-1: "But what we really want to know is to what extent the Alexandrian mathematicians of the period from the first to the fifth centuries C.E. were Greek. Certainly, all of them wrote in Greek and were part of the Greek intellectual community of Alexandria. And most modern studies conclude that the Greek community coexisted [...] So should we assume that Ptolemy and Diophantus, Pappus and Hypatia were ethnically Greek, that their ancestors had come from Greece at some point in the past but had remained effectively isolated from the Egyptians? It is, of course, impossible to answer this question definitively. But research in papyri dating from the early centuries of the common era demonstrates that a significant amount of intermarriage took place between the Greek and Egyptian communities [...] And it is known that Greek marriage contracts increasingly came to resemble Egyptian ones. In addition, even from the founding of Alexandria, small numbers of Egyptians were admitted to the privileged classes in the city to fulfill numerous civic roles. Of course, it was essential in such cases for the Egyptians to become "Hellenized," to adopt Greek habits and the Greek language. Given that the Alexandrian mathematicians mentioned here were active several hundred years after the founding of the city, it would seem at least equally possible that they were ethnically Egyptian as that they remained ethnically Greek. In any case, it is unreasonable to portray them with purely European features when no physical descriptions exist."
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  15. Lua error in package.lua at line 80: module 'strict' not found., pp. 66–67
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  23. On the main translations of the treatise, including Bernardino Baldi's 1589 translation into Italian, see now the discussion in Francesco Grillo (2019). Hero of Alexandria's Automata. A Critical Edition and Translation, Including a Commentary on Book One, PhD thesis, Univ. of Glasgow, pp. xxviii-xli.
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Further reading

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  • Schellenberg, H.M.: Anmerkungen zu Hero 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).

External links