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 and his work is representative of the Hellenistic scientific tradition.
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 the earliest instance of wind harnessing on land. 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, but fortunately, some of his works were preserved in Arab manuscripts.
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, but the modern scholarly consensus is that he was ethnically Greek. 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.
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.
Inventions and achievements
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. Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work.
* 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.
* A windwheel operating an organ, marking probably the first instance of wind powering a machine in history.
* 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.
* 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.
* 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)
Hero described a method of iteratively computing the square root. 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 Hero'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 Hero while calculating the volume of a pyramidal frustum.
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 Hero:
* Pneumatica, a description of machines working on air, steam or water pressure, including the hydraulis or water organ.
* 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:
* 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:
Latest paper on Hero:
* 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).
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.
A native of Alexandria and disciple of Ctesibius, who flourished about B.C. 125. He placed engineering and land-surveying on a scientific basis, and was celebrated as a mechanician, and invented the hydraulic clock, the machine called "the fountain of Hero ," and a forcing-pump used as a fire-engine. (See Ctesibica Machina.) He enjoyed a high reputation, and is mentioned by Gregory Nazianzen with Euclid and Ptolemy. He is now, however, principally known by some remains of his writings on mechanics. His extant writings are: (a) "On the Machine Called the Chiroballistra" (Χειροβαλλίστρας κατασκευὴ καὶ συμμετρία); (b) "Barulcus" (Βαροῦλκος), a treatise on the raising of heavy weights, which is mentioned by Pappus, and was found by Golius in Arabic; (c） "Belopoeica" (Βελοποιϊκά), a treatise on the manufacture of darts; (d) "On Pneumatic Machines" (Πνευματικά). In this work is the first and only notice among the ancient writers of the application of steam as a moving power. There is an English translation by Greenwood (London, 1851). (e) "On the Construction of Automata" (Περὶ Αὐτοματοποιητικῶν), contained in the Math. Veteres; it describes a number of small machines and mechanical toys. (f) "On Dioptrics," from which Heliodorus, a mathematician who flourished after the commencement of the Christian era, has left an extract. (g) Μετρικά, consisting of geometrical and trigonometrical problems and solutions. Other works of Hero , now lost, are mentioned by Pappus, Eutocius, Heliodorus, etc. Hero describes the theodolite, the cyclometer, and the steam-engine; and discusses the centre of gravity. His works have been edited by F. Hultsch (Berlin, 1864). See the treatise on Hero by T. H. Martin (Paris, 1854); and the account in Ball's Short History of Mathematics (London, 1888).
Of Constantinople, commonly called the Younger, who is supposed to have flourished about A.D. 900. In a work attributed to him (on Geodesy), he states that the precession of the equinoxes had produced seven degrees of effect since the time of Ptolemy, so that he must have been about 500 years later than Ptolemy. The writings of Hero the Younger relate to warlike machines, tactics, and practical geometry.
A mathematician, who flourished about the middle of the fifth century.
(Myth) (Ἡρώ). See Leander.