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Heron
Born	fl. 10 AD
Residence	Alexandria, Egypt
Nationality	Greek
Field	Mathematics
Known for	aeolipile

Hero (or Heron) of Alexandria (Greek: Ήρων ο Αλεξανδρεύς) (c. 10 – 70 AD) was a mathematician and engineer who flourished in Alexandria, Roman Egypt and is said to be the greatest experimenter of antiquity.^[1]

Among his most famous inventions were the first documented steam-powered device, the aeolipile, and a windwheel, constituting one the earliest instances of wind harnessing.^[2][3] He is said to have been a follower of the Atomists. Some of his ideas were derived from the works of Ctesibius.

Contents 1 Background 2 Career 3 Inventions and Achievements 4 Mathematics 5 Bibliography 6 Media 7 See also 8 References 9 External links

Heron's origins were not recorded in ancient times, but a careful analysis of history allows historians to make conjectures about his origins. It was once the general agreement that Hero was an Egyptian or a Phoenician, a view that is still held by some scholars,^[4] but the modern scholarly consensus is that he was a Greek.^[5][1][6] 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 and that the current consensus is that Hero was a Greek.^[5]

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.^[7]

Hero was known for his amazing mechanical ingenuity in the ancient world, to include his contributions in military technology and theatre. He also created devices used in temples to instill faith by deceiving believers with "magical acts of the gods."

• The aeolipile (known as Hero's engine) was a rocket-like reaction engine and the first recorded steam engine. It was created almost two millennia before the industrial revolution. Hero's steam engine was used to open temple doors, and as a toy, but the principles behind it were not well understood, and its full potential was not realized for well over a millennium.

• 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.^{[2] [3]}

• 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.

• 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 not stated in this form until Pierre de Fermat did so in 1662; the most modern form is that the path is at an extremum.

• A standalone fountain that operates under self-contained hydrostatic energy. (Hero's Fountain)

Heron described a method of iteratively computing the square root. It is also called the Babylonian method, because the Babylonians also probably knew of it before Heron wrote it down.

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.^[8]
• 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 Automata.
• 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 is described, an apparatus which resembles the theodolite.
• 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:^[9]

• 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 preserverd only in fragments:

• Geodesia
• Geoponica

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

• Heron's formula
• Heronian triangle
• Hero's engine
• Heron's fountain

• Webpage about Hero by The Technology Museum of Thessaloniki
• A translation of Pneumatica with diagrams
• Heron, and a translation of Pneumatica in German
• Heron biography, The MacTutor History of Mathematics archive

v • d • e Greek mathematics
Mathematicians	Anaxagoras · Anthemius · Archytas · Aristaeus the Elder · Aristarchus · Apollonius · Archimedes · Autolycus · Boethius · Bryson · Callippus · Chrysippus · Cleomedes · Conon · Ctesibius · Democritus · Dicaearchus · Diocles · Diophantus · Dinostratus · Dionysodorus · Domninus · Eratosthenes · Eudemus · Euclid · Eudoxus · Eutocius · Geminus · Heron · Hipparchus · Hippasus · Hippias · Hippocrates · Hypatia · Hypsicles · Marinus · Menaechmus · Menelaus · Nicomachus · Nicomedes · Nicoteles · Oenopides · Pappus · Perseus · Philolaus · Philon · Porphyry · Posidonius · Proclus · Ptolemy · Pythagoras · Pytheas · Serenus  · Simplicius · Sosigenes · Sporus · Thales · Theaetetus · Theano · Theodorus · Theodosius · Theon of Alexandria · Theon of Smyrna · Thymaridas · Xenocrates · Zeno of Elea · Zeno of Sidon · Zenodorus
Treatises	Almagest · Archimedes Palimpsest · Arithmetica · Conics · Elements · On the Sizes and Distances (Aristarchus) · On Sizes and Distances (Hipparchus)
Centers	Academy of Athens · Library of Alexandria · Cyrene
Influences	Babylonian mathematics  · Egyptian mathematics
Influenced	Islamic mathematics  · Indian mathematics