Héron of Alexandria or Héron Old the (Ήρων ο Αλεξανδρεύς) was a Engineer, a mechanic and a Greek Mathématicien of the 1st century after J. - C.

Presentation

Youth of Héron of Alexandria (known as also Héron the Old one) one does not know large thing, if it is not that it is originating in Alexandria. The dates of its birth and its death are not known with certainty, according to the majority of the historians it would have lived during the first century before J. - C.Héron of Alexandria (125 av. J. - C.) creative of automats driven by water, was also interested in the vapor and the compressed air. Known for the machineries described in his Treaty of the tires, one in addition owes him a project of machine intended automatically to open the doors of a temple.

He would thus have lived probably under the Roman Empire. Its work was transmitted to us via some of its treaties of Physique and Mathématiques. Many its writings were found in Latin and Arab. During centuries, they were retranscribed many times and the authenticity of these texts is sometimes called into question.

Achievements

In mathematics

One allots to Héron of Alexandria several mathematical formulas of which one of calculation of the surface of a Triangle starting from the length on its sides (the formula of Héron), like another allowing to approach the square Racine of any Nombre in a recursive way. It was also in Stereometrica the author of formulas of measurements of Length, of Surface and of Volume for objects in three Dimension S. the mathematical searchs for Héron of Alexandria aimed mainly the practical aspect of the measurement of the objects.

Formula to calculate the surface of a triangle :

That is to say ABC an unspecified triangle having for sides $a$, $b$ and $c$.

That is to say p the half-perimeter of this triangle, i.e. $p\; =\; (a+b+c)/2$.

That is to say $A$ the surface of the triangle.

$A^2\; =\; p\; (Pa)\; (Pb)\; (PC)$

Caution: The surface is high squared in this formula.

In optics

Héron the Old one studies in Catoptrica the Lumière and its reflections. It states thus the principles of reflection of the light (principles guided by the rule according to which the Nature always chooses the shortest way). He believed at the time the Vision was possible thanks to luminous rays emitted by the eyes and being propagated with a Speed Infini E.

In mechanics and tire

Héron of Alexandria conceived many hydraulic machines. It is at the origin of the éolipyle, pneumatic machine consisted of a Sphère fixed on a outgoing axis and equipped with two bent tubes in an opposite way; by heating the Eau contained in the metal sphere the Steam formed gave while escaping a rotation movement from the sphere.

It also conceived a automatic fountain which made spout out water via a clever system of communicating vases. In Pneumatica it describes an opening system of automatic doors when one lights a Feu on a furnace bridge; fire, heating a volume of water, created vapor which put moving the doors of a Temple.

Within the framework of sound Traité automats it also designed mechanisms for Théâtre containing Poids and Contrepoids putting moving a series of platforms and small characters.

Thanks to these inventions, Héron of Alexandria is often retained like the inventor of the first automats.

Others

Héron the Old one was also the inventor of a pseudo Thermomètre and Odomètre making it possible to measure the distance covered. One allots the hydraulic manufacture of Horloge to him to measure time, and the realization of works on the Astrolabe allowing to measure the angular Distance between two Astre S.

Publications

• Pneumatica ( Two books on the pressure of the air and the steam )
• Mécanica ( Three books on the means of raising object and on their center of gravity )
• Métrica ( Three books on the various metric systems )
• Géométrica ( Illustration for examples of the theory developed in Métrica )
• Catoptrica ( Book on the problems of mirrors )
• Stereometrica ( Collection of problems )
• Belopoica ( Book on the machines of jet )
• Treated automats

See too

• Triangle of Héron
• Greek Sciences
• Concept of module
• Formula of Héron
• Method of Héron

External bonds

• the full text and illustrated of a translation of the {{XIXe}} century in English of the '' Pneumatiques ''
• Diagram of the fountain of Héron
• Diagram of the Theater of Héron of Alexandria

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