It was nearly 1,000 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. 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.A syringe-like device was described by Hero to control the delivery of air or liquids.The force pump was widely used in the Roman world, and one application was in a fire-engine.The sound of thunder was produced by the mechanically-timed dropping of metal balls onto a hidden drum. 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.A wind-wheel operating an organ, marking the first instance in history of wind powering a machine.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. The lever opened up a valve which let some water flow out. When the coin was deposited, it fell upon a pan attached to a lever. This was included in his list of inventions in his book Mechanics and Optics. 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.Hero's wind-powered organ (reconstruction) However, this engine is far from a pure aeolipile.
Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work, which is not entirely false, air containing a trace of water vapor. 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. It was described almost two millennia before the industrial revolution. Hero described 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). 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. 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. Hero's ethnicity may have been either Greek or Hellenized Egyptian. 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. 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. Some of his ideas were derived from the works of Ctesibius. In his work Mechanics, he described pantographs. He is said to have been a follower of the atomists. Among his most famous inventions was a windwheel, constituting the earliest instance of wind harnessing on land. Hero published a well-recognized description of a steam-powered device called an aeolipile (sometimes called a "Hero engine"). He is often considered the greatest experimenter of antiquity and his work is representative of the Hellenistic scientific tradition. 60 AD) was a Greek mathematician and engineer who was active in his native city of Alexandria in Egypt during the Roman era. Hero of Alexandria ( / ˈ h ɪər oʊ/ Greek: Ἥρων ὁ Ἀλεξανδρεύς, Hērōn hò Alexandreús, also known as Heron of Alexandria / ˈ h ɛr ən/ fl.
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