Johann Andreas Segner

Johann Andreas Segner of, Andrej Segner, Jan or János András Segner, ( born October 9, 1704 Bratislava, † October 5, 1777 in Halle) was a mathematician, physicist and physician, named after him waterwheel is considered the forerunner of the Pelton turbine.

Life

Johann Andreas Segner was born the son of the Bratislava city treasurer and tax collector Johann Michael von Segner. From 1714 he attended the urban school, early showed special talents in mathematics and physics. In 1725 he entered the University of Jena to study medicine, philosophy and mathematics. Even before his graduation, he published several smaller items. As a PhD doctor, he worked from 1730 back in his hometown. However, this work did not prove to be satisfactory for him, and so he returned two years later ( 1732) back to Jena back, earned his MA at the University and held as a lecturer from 1733 lectures in mathematics and medicine. A call to Göttingen to specially created for him professor of mathematics and natural philosophy ( science ), he followed in 1735. Was one of the first scientists he considered experimental lectures in chemistry from, and he was responsible for the construction of the University Observatory in Göttingen. In 1754 he was appointed professor of mathematics and physics as the successor of the philosopher and mathematician Christian Wolff at the University of Halle. Again he left the observatory hall building. Among his students, the doctorate with him in Halle, were Christian Garve (1766) and August Niemeyer (1777 ).

As one of the most important scientists of his time was Segner member of the Prussian Academy of Sciences, Berlin ( 1746 ), the Royal Society, London ( 1738) and the Russian Academy of Sciences, St. Petersburg (1753 ).

His grave is located on the Halle Stadtgottesacker.

Work

During his time in Göttingen Segner 1750 published two scientific papers that dealt with problems of hydrodynamics.

In it, he introduced the principle of a water wheel, which was the forerunner of the water wheel as Segnersches turbine technology. The wheel utilizes Reaktionswasserrad than the potential energy. The water pressure creates a circular motion with a correspondingly arranged nozzles. The principle use some sprinklers that rotate through the recoil of the tangential outlet water. For the first time the application came this principle in ancient times in the Aeolipile, the operation Heron of Alexandria steam. The blade tip drive used on some helicopters is also closely related. Segner construction was taken up, among others, by Leonhard Euler and given suggestions for improvement. The figure shows the basic structure in longitudinal section ( A, B: water inlet, B: axis of rotation; C: nozzles; F, G: decoupling of the rotational movement ) and cross section ( D: tangential curved nozzles).

Further studies led Segner to symmetry axes of solid bodies, the air pressure, the surface tension of liquids ( particularly for capillarity ) and solar eclipses. In Hall, he worked on the Weekly Hallischen ads outside the university.

Segner is in psychology often associated with the first investigation of the iconic memory; In 1740 he is said to have conducted an experiment on this, in which he caused to rotate glowing coal on a wheel; in a dark room was found for the observer at about 100 ms steady image; then called visual persistence.

Tributes

In Hall, a street and a school named after Segner, 1956 Segnerstraße in Vienna was named after him.

On the Moon, the crater Segner bears his name.

Writings

• Pergit In contemplationibus hydraulicis. (God Ingae 1746 )
• Clarity and completeness of Lectures on the arithmetic and geometry: for the use of those who want to practice these sciences through their own hard work. ( Lemgo 1747 )
• Introduction to the theory of nature. (Göttingen 1750)
• Superficies fluidorum concavas ostendit. (God Ingae 1750)
• Programma QVO Principivm Parsimoniae Vniversaliter Demonstratvr Atqve Dissertatio Medica Inavgvralis Indicitvr. (God Ingae 1754)
• Cursus mathematici. (5 volumes, 1758-1768 Hall )
• Foundations of Arithmetic, geometry and geometric calculations from d Lat. transl. (Hall 1773)