# Johann Andreas Segner

c1775-1880. | |

Born |
October 9, 1704 Pressburg (Bratislava), Kingdom of Hungary |
---|---|

Died |
October 5, 1777 Halle, Duchy of Magdeburg | (aged 72)

Johann Segner (Johann Andreas von Segner, Ján Andrej Segner, János András Segner, Iohannes Andreas de Segner) was a 18th-century physicist, physician, astronomer, botanist, mathematician and inventor. One of the best-known scientists of his age, Segner was a member of the St Petersburg Academy of Sciences, the Berlin Academy and the Royal Society in London.

## Contents

## Early life

Segner was born in 1704 in Pressburg, then capital of Kingdom of Hungary (today Bratislava, Slovakia) as the son of a tax collector and city treasurer Johann Michael von Segner. His ancestors came to Pressburg from Styria in the 16th century. His birthplace, Segner Mansion located on Michalska Street 7 in Bratislava is now a protected cultural monument.[1]

## Studies

Segner attended school at Pressburg's Lyceum where he showed special talents for medicine and mathematics. One of his teachers there was Matej Bel. He also attended school in Győr and, while it is not completely certain, it does seem highly probable that he spent the year 1724 at the College in Debrecen.

In 1725 he went to Germany and entered the University of Jena, studying medicine there. While he was an undergraduate he published essays on a wide variety of topics including mathematics, philosophy, physics, astronomy, chemistry, and medicine. He qualified as a medical doctor in 1729 and returned to Pressburg planning to pursue in his profession. However he was employed as a doctor by the authorities in Debrecen (recommended by Matej Bel), taking up his new post in November 1730. He did not find being a doctor of medicine to his liking and, after spending eighteen months in the job in Debrecen, he returned to the academic world returning to the University of Jena to take a Master's Degree. His studies at Jena were so successful that he was soon offered a post at the university.

## Teaching

He had the great distinction of becoming the first professor of mathematics at Göttingen taking up the chair in 1735. Segner's was therefore the first to fill what was to become one of the foremost chairs of mathematics in the world. In 1743 Segner was put in charge of the construction of the university observatory which was finished in 1751.

He left Göttingen in 1755 and, with Euler's assistance, became professor in Halle, successor of professor Christian Wolff. There he lectured on mathematics, physics and medicine. He continued to write good textbooks and, as in Göttingen, established an observatory.

## Work and inventions

Segner was the first scientist to use the reactive force of water. While at Göttingen he discovered that every solid body has three axes of symmetry. He used Daniel Bernoulli's theoretical work on the 'reaction effect' to produce a simple-reaction horizontal waterwheel (**Segner wheel**) using the same principle which drives one type of modern lawn sprinkler. The study of this machine by the mathematician Leonhard Euler led to the development of a crude turbine.

In 1751 Segner introduced the concept of the surface tension of liquids, likening it to a stretched membrane. His view that minute and imperceptible attractive forces maintain surface tension laid the foundation for the subsequent development of surface tension theory. He made an unsuccessful attempt to give a mathematical description of capillary action.

Segner developed his own theory of light and its properties, researched refraction of light passing environment, described the refraction of light in water drop as well as the formation of rainbow as decay of light in nature. He explained the functioning of the glass optics, the principle of the magic lantern, camera obscura and principles of curved mirrors. His work was later studied by distinguished scholars, notably by Joseph Petzval and his brother Otto Petzval, Štefan Anián Jedlík, Gabriel Kováč-Martiny, and astronomers Maximilián Hell and František Xaver Zach.

He also studied the theory of spinning top.

Segner produced the first proof of Descartes' rule of signs.

## Death

He died in 1777 in Halle, Duchy of Magdeburg. He is buried at Stadtgottesacker Cemetery in Halle.[2]

## Legacy

According to Mathematics Genealogy Project, as of February 2013, he has over 66 thousand academic descendants, out of the total 170 thousand mathematicians in the database.[3]

The lunar crater Segner is named after him, as is asteroid 28878 Segner, and a street and school in Halle.

## Literature

- By Segner

*In contemplationibus hydraulicis pergit*, Gottingae, 1746. (Latin)*Deutliche und vollständige Vorlesungen über die Rechenkunst und Geometrie: zum Gebrauche derjenigen, welche sich in diesen Wissenschaften durch eigenen Fleiß üben wollen*, Lemgo, 1747. (German)*Einleitung in die Naturlehre*, Göttingen, 1750. (German)*Superficies fluidorum concavas ostendit*[Geometry and Nature of Liquid Surfaces], Gottingen, 1750. (Latin)*Programma Qvo Principivm Parsimoniae Vniversaliter Demonstratvr Atqve Dissertatio Inavgvralis Medica Indicitvr*, Gottingen, 1754. (Latin)*Cursus mathematici*, 5 Volumes, Halle, 1758–1768. (Latin)*Anfangsgründe der Arithmetic, Geometrie und der geometrischen Berechnungen*[Elements of Arithmetic], translated from Latin, Halle, 1773. (German)

- On Segner

- Wolfram Kaiser,
*Johann Andreas Segner. Der Vater der Turbine*, Teubner, Leipzig 1977. (German) - Barna Szénássy,
*History of Mathematics in Hungary until the 20th Century*, Heidelberg, Springer, 1992. - Andreas Kleinert, "Johann Andreas Segner",
*Reports on Didactics and History of Mathematics*19 (2002), pp 15-20. (German)