Johann Georg von Soldner

Johann Georg von Soldner (16 July 1776 - 13 May 1833) was a German physicist, mathematician and astronomer first in Berlin and later in 1808 in Munich.

Life

He was born in Feuchtwangen in Ansbach as the son of the farmer Johann Andreas Soldner. He received two years teaching at the Feuchtwanger Latin School. Soon Soldner's mathematical talent was discovered: Soldner managed to measure the fields of his faters by self-built instruments. Through many nights he studied math textbooks and maps. Since he never had visited a high school, he began 1796 with private studies of languages and mathematics in Ansbach. 1797 he came to Berlin, where he worked under the astronomer Johann Elert Bode as a geometer and was involved there with astronomical and geodetic studies. From 1804-1806 he was the leader of a team, which worked on the survey of Ansbach. 1808 he was invited by Joseph von Utzschneider to Munich to work in the field of Trigonometry for the newly formed Tax Survey Commission. For his services to the theoretical basis for the Bavarian land surveying Soldner was knighted. 1815 he was appointed as a astronomer and he was a member of the Academy of Sciences at Munich. In 1816 Soldner was appointed as the director of the observatory in Bogenhausen in Munich, which was built from 1816-1818 due to the co-operation of Utzschneider, Georg Friedrich von Reichenbach and Joseph von Fraunhofer. From 1828 Soldner was unable to completely fulfill his duties because of a Liver disease. As a result, his young assistant Johann Lamont (under his supervision) lead the operations of the observatory. Soldner died in Bogenhausen and was buried on the cemetery on the western side of the St. Georg church. [Bauernfeind 1892]

Work

The Ramanujan-Soldner constant and the Soldner coordinate system are named for him. The latter was used until the middle of the 20th century in Germany. In 1809, Soldner managed to calculate the Euler–Mascheroni constant's value to 24 decimal places. He also publisehd on Logarithmic integral function.

;Light bendingSoldner is now mostly remembered for having concluded due to the Newton's Corpuscular theory of light that light would be diverted by heavenly bodies. In a paper written in 1801 and published in 1804, he calculated the amount of deflection of a light ray by a star and wrote: "If one substitute into tang ω the acceleration of gravity on the surface of the sun, and the radius on that body is set to unity, one finds ω=0,84"". Soldner already noted that if it were possible to observe fixed stars in close distance to the sun, it might be important to take this effect into consideration. However, because (at that time) such observations were impossible, Soldner concluded that those effects can be neglected. [Soldner 1804]

Soldner's work on the effect of gravity on light became considered less relevant during the Nineteenth Century, as "corpuscular" theories and calculations based on them were increasingly considered to have been discredited in favour of wave theories of light — it was not immediately obvious that the more "fashionable" wave theories should predict similar effects. Other prescient work that became unpopular and largely forgotten for similar reasons included Henry Cavendish's light-bending calculations, John Michell's 1783 study of gravitational horizons and the spectral shifting of light by gravity, and even Isaac Newton's study in "Principia" of the gravitational bending of the paths of "corpuscles", and his description of lightbending in "Opticks". [Jaki 1978] [Treder 1981] [Will 1988]

Albert Einstein calculated and published a numerically-similar value for the amount of gravitational light-bending in light skimming the Sun in 1911, leading Phillipp Lenard to accuse Einstein of plagiarising Soldner's result. Lenard's accusation against Einstein is usually considered to have been at least partly motivated by Lenard's Nazi sympathies and his enthusiasm for the Deutsche Physik movement. At the time, Einstein may well have been genuinely unaware of it, or he may have considered his own calculations to be independent and free-standing, requiring no references to earlier research (Einstein's 1911 calculation was based on the idea of gravitational time dilation): in any case, Einstein's subsequent 1915 general theory of relativity quickly argued that "all" these calculations had been incomplete, and that the "classic" Newtonian arguments, combined with light-bending effects due to gravitational time dilation, gave a combined prediction that was twice as strong as the earlier predictions. [Laue 1921] [Will 2006]

References

;Soldner's publications
*Cite journal
last=Soldner, J. G. v.
year=1804
title=Ueber die Ablenkung eines Lichtstrahls von seiner geradlinigen Bewegung, durch die Attraktion eines Weltkörpers, an welchem er nahe vorbei geht
journal=Berliner Astronomisches Jahrbuch
pages =161-172
url=http://de.wikisource.org/wiki/Ueber_die_Ablenkung_eines_Lichtstrals_von_seiner_geradlinigen_Bewegung

*Cite journal
last=Soldner, J. G. v.; (Lenard, P.)
year=1921
title=Über die Ablenkung eines Lichtstrahls von seiner geradlinigen Bewegung durch die Attraktion eines Weltkörpers, an welchem er nahe vorbeigeht; von J. Soldner, 1801
journal=Annalen der Physik
volume =65
pages =593–604
doi=10.1002/andp.19213701503

*Cite book
last=Soldner, J. G. v.
year=1809
title=Théorie et tables d'une nouvelle fonction transcendante
publisher=Lindauer
location=München

;Secondary sources
*de-ADB|34|557|563|Soldner, Johann Georg von|Carl Maximilian von Bauernfeind

*Cite journal
last=Laue, M.v.
year=1921
title=Erwiderung auf Hrn. Lenards Vorbemerkungen zur Soldnerschen Arbeit von 1801
journal=Annalen der Physik
volume =66
pages = 283–284
doi=10.1002/andp.19213712005

*Cite journal
last=Jaki, S.L.
year=1978
title=Johann Georg von Soldner and the Gravitational Bending of Light, with an English Translation of His Essay on It Published in 1801
journal=Foundations of Physics
volume =8
pages = 927–950
doi=10.1007/BF00715064

*Cite journal
last=Treder, H. J.; Jackisch, G.
year=1981
title=On Soldners Value of Newtonian Deflection of Light
journal=Astronomische Nachrichten
volume =302
pages = 275–277
url=http://adsabs.harvard.edu/abs/1981AN....302..275T
doi=10.1002/asna.2103020603

*Cite journal
last=Will, C.M.
year=1988
title=Henry Cavendish, Johann von Soldner, and the deflection of light
journal=Am. J.Phys.
volume =56
pages = 413–415
doi=10.1119/1.15622

*Cite journal
last=Will, C.M.
year=2006
title=The Confrontation between General Relativity and Experiment
journal=Living Rev. Relativity
volume =9
url=http://www.livingreviews.org/lrr-2006-3

;Endnotes