Hero of Alexandria

Geometer and inventor, lived 62 AD (Alexandria).

Although Hero of Alexandria left many books and is mentioned by others, little is known about his life. his most important work on geometry Metrica was lost and only rediscovered in 1896. It describes methods for the calculation of the areas of regular polygons with 3 - 12 sides, segments of circles, ellipses, cones, spheres and several other areas and contains the proof for what is now known as Hero's formula for the area of a triangle. It gives also a method for the approximation of the square root of any number, already known to the Babylonians in about 2000 BC and used as an algorithm in modern computers.

Among Hero's other works on geometry are Definitiones, Geometrica, Geodesia, Stereometrica, Mensurae, Liber Geëponicus and Dioptra, which describes the principle and use of the dioptra, a surveying instrument similar in purpose to the modern theodolite.

Hero showed a great interest in mechanical inventions, in which he showed great ingenuity. His books on mechanics that survived are Pneumatica, Automatopoietica, Belopoeica (Engines of War) and Cheirobalistra. Among the amazing range of machines described in these books are inventions that can only be described as toys for the rich.

Other works are only known from fragments and translations. His Mechanics in three volumes, which exists in Arabic translation, contains descriptions of machines useful for daily life and a range of other machines of all sorts. A book on water clocks mentioned in the fifth century has been lost.

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