Hero of Alexandria

Inspired by the comments of Alan Mason.

Hero (or Heronof Alexandria  (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 theAtomists. 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 orPhoenician 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 theBabylonian 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 engineand 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.

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 also described a method of iteratively computing the square root. Today, though, his name is most closely associated with Hero’s Formula for finding the area of a triangle from its side lengths.

Via Wikipedia

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