Willebrord Snel van Royen (1580–1626)
|Born||13 June 1580
Leiden, Dutch Republic
|Died||30 October 1626
Leiden, Dutch Republic
|Fields||Astronomer and mathematician|
|Institutions||University of Leiden|
|Alma mater||University of Leiden|
|Academic advisors||Ludolph van Ceulen
|Notable students||Jacobus Golius|
|Known for||Snell's law|
Willebrord Snellius (born Willebrord Snel van Royen) (1580 – 30 October 1626, Leiden) was a Dutch astronomer and mathematician, known in the English-speaking world as Snell. In the west, especially the English speaking countries, his name has been attached to the law of refraction of light for several centuries, but it is now known that this law was first discovered by 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 (trigonometric functions) their results were saved as tables, not functions.
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. In 1615 he planned and carried into practice a new method of finding the radius of the earth, by determining the distance of one point on its surface from the parallel of latitude of another, by means of triangulation. His work Eratosthenes Batavus ("The Dutch Eratosthenes"), published in 1617, describes the method and gives as the result of his operations between Alkmaar and Bergen op Zoom—two towns separated by one degree of the meridian—which he measured to be equal to 117,449 yards (107.395 km). The actual distance is approximately 111 km. Snellius was also a distinguished mathematician, producing a new method for calculating π—the first such improvement since ancient times. He rediscovered the law of refraction in 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 trigonometry (Doctrina triangulorum) authored by Snellius was published a year after his death.
- Willebrord Snellius at the Leiden Digital Family Tree.
- Eerste Nederlandse Systematisch Ingerichte Encyclopaedie
- Encarta Winkler Prins, Grote Oosthoek, Eerste Nederlandse Systematisch Ingerichte Encyclopaedie
- Sometimes mistakenly noted as 1590 or 1591; P.C. Molhuysen and P.J. Blok (edd.), Nieuw Nederlandsch biografisch woordenboek, part 7, Leyden 1927.
- N. Haasbroek: Gemma Frisius, Tycho Brahe and Snellius and their triangulations. Delft 1968.
- Struik, Dirk Jan (1970–80). "Snel, Willebrord". Dictionary of Scientific Biography XII. New York: Charles Scribner's Sons. ISBN 978-0-684-10114-9.
- "Snellius (Willebrord)". Nieuw Nederlandsch Biografisch Woordenboek VII.
- O'Connor, John J.; Robertson, Edmund F., "Willebrord van Royen Snell", MacTutor History of Mathematics archive, University of St Andrews.
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Snell, Willebrord". Encyclopædia Britannica (11th ed.). Cambridge University Press.