Willebrord Snellius

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Willebrord Snellius
Willebrord Snel van Royen (1580–1626)
Born13 June 1580
Died30 October 1626(1626-10-30) (aged 46)
NationalityDutch
Alma materUniversity of Leiden
Known forSnell's law, Snellius's triangulation, Snellius–Pothenot problem
Scientific career
FieldsAstronomy and mathematics
InstitutionsUniversity of Leiden
Academic advisorsLudolph van Ceulen
Rudolph Snellius
Notable studentsJacobus Golius

Willebrord Snellius[1][2] (born Willebrord Snel van Royen[3] (13 June 1580[4] – 30 October 1626), commonly known as Snell, was a Dutch astronomer and mathematician.

His name is usually associated with the law of refraction of light known as Snell's law.[5]

Early life

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Willebrord Snellius was born in Leiden, Netherlands. In 1613 he succeeded his father, Rudolph Snel van Royen (1546–1613) as professor of mathematics at the University of Leiden.[6]

Surveying

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Quadrant of Snellius, Museum Boerhaave, Leiden
Snellius's Triangulation (1615)
Commemorative plaque on Snellius's house in Leiden

In 1615, Snellius, after the work of Eratosthenes in Ptolemaic Egypt in the 3rd century BC, probably was the first to use triangulation to do a large-scale arc measurement for determining the circumference of the earth.[7][8]

In his work The terrae Ambitus vera quantitate (1617) under the author's name ("The Dutch Eratosthenes") Snellius describes the methods he used. Snellius came to his result by calculating the distances between a number of high points in the plain west and southwest of the Netherlands using triangulation. By necessity Snellius's high points were nearly all church spires. There were hardly any other tall buildings at that time in the west of the Netherlands. More or less ordered from north to south and/or in successive order of measuring, Snellius used a network of fourteen measure points: Alkmaar: St. Laurenskerk; Haarlem: Sint-Bavokerk; Leiden: a then new part (built in 1599) of the city walls;[9] The Hague: Sint-Jacobskerk; Amsterdam: Oude Kerk; Utrecht: Cathedral of Utrecht; Zaltbommel: Sint-Maartenskerk [nl; de]; Gouda: Sint Janskerk; Oudewater: Sint-Michaelskerk [nl]; Rotterdam: Sint-Laurenskerk; Dordrecht: Grote Kerk; Willemstad: Koepelkerk [nl; de]; Bergen-op-Zoom: Gertrudiskerk; Breda: Grote Kerk. In a network of fourteen cities a total of 53 triangulation measurements were made. He was helped in his measurements by two of his students, the Austrian barons Erasmus and Casparus Sterrenberg. In several cities he also received support of friends among the city leaders (regenten).[citation needed]

In order to carry out these measurements accurately Snellius had a large quadrant built, with which he could accurately measure angles in tenths of degrees. This quadrant can still be seen in the Museum Boerhaave in Leiden. In his calculations Snellius made use of a solution for what is now called the Snellius–Pothenot problem.

He came up with an estimate of 28,500 Rhineland rods – in modern units 107.37 km[10] for one degree of latitude. 360 times 107.37 then gives a circumference of the Earth of 38,653 km. The actual circumference is 40,075 kilometers, so Snellius underestimated the circumference of the earth by 3.5%.

Mathematics and physics

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Snellius was also a distinguished mathematician, producing a new method for calculating π—the first such improvement since ancient times. He discovered the law of refraction in 1621.[11]

Other works

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Cyclometricus, 1621

In addition to the Eratosthenes Batavus, he published Cyclometricus, de circuli dimensione (1621), and Tiphys Batavus (1624). He also edited Coeli et siderum in eo errantium observationes Hassiacae (1618), containing the astronomical observations of Landgrave William IV of Hesse. A work on trigonometry (Doctrina triangulorum) authored by Snellius was published a year after his death.[6]

Death

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Coeli et siderum in eo errantium observationes Hassicae, 1618

Snellius died in Leiden in October 1626, at the age of 46 from an illness diagnosed as colic.[12] His grave can be seen in the Pieterskerk, Leiden.

Legacy

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Snellius Glacier in Antarctica is named after Willebrord Snellius.

The lunar crater Snellius is named after Willebrord Snellius.

The Royal Netherlands Navy has named three survey ships after Snellius, including a currently-serving vessel.

Works

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  • Eratosthenes Batavus (in Latin). Lugduni Batavorum: Joost van Colster, Joris Abrahamsz van der Marsce. 1617.
  • Coeli et siderum in eo errantium observationes Hassicae (in Latin). Lugduni Batauorum: Joost van Colster. 1618.
  • Cyclometricus (in Latin). Lugduni Batavorum: Matthijs Elzevier, Bonaventura Elzevier. 1621.
  • Doctrinae triangulorum canonicae libri quatuor (in Latin). Lugduni Batavorum: Joannes Maire. 1627.

See also

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Notes

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  1. ^ Willebrord Snellius at the Leiden Digital Family Tree.
  2. ^ Eerste Nederlandse Systematisch Ingerichte Encyclopaedie
  3. ^ Encarta Winkler Prins, Grote Oosthoek, Eerste Nederlandse Systematisch Ingerichte Encyclopaedie
  4. ^ Sometimes mistakenly noted as 1590 or 1591; Cf. P.C. Molhuysen; P.J. Blok, eds. (1927). "Snellius, Willebrord". Nieuw Nederlandsch biografisch woordenboek. Leiden..
  5. ^ For a reconstruction of this discovery see Hentschel 2001. It is now known that this law was already known to Ibn Sahl in 984. The same law was also investigated by Ptolemy and in the Middle Ages by Witelo, but due to lack of adequate mathematical instruments (i.e. trigonometric functions) their results were saved as tables, not functions.
  6. ^ a b Chisholm 1911.
  7. ^ Haasbroek, N.D. (1968): Gemma Frisius, Tycho Brahe and Snellius and their triangulation. Publ. Netherl. Geod. Comm., Delft. [1]
  8. ^ Torge, W.; Müller, J. (2012). Geodesy. De Gruyter Textbook. De Gruyter. p. 5. ISBN 978-3-11-025000-8. Retrieved 2 May 2021.
  9. ^ the tower of the Sint-Pieterskerk had collapsed in 1512
  10. ^ a Rhenish rod is in this calculation considered as 3.767358 meter
  11. ^ "Snellius biographies" (PDF), dwc.knaw.nl, retrieved 15 August 2019.
  12. ^ De Wreede, L. C. (2007). Willebrord Snellius (1580–1626): a humanist reshaping the mathematical sciences. Utrecht University

References

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