Willebrord Snellius
Encyclopedia
Willebrord Snellius (1580 – 30 October 1626, Leiden) was a Dutch
astronomer
and mathematician
. 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 instrument
s (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..jpg)
In addition to the Eratosthenes Batavus, he published Cyclometria sive 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.
The lunar crater Snellius
is named after Willebrord Snellius.
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
astronomer
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
and mathematician
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
. 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
Ibn Sahl
This article is about the physicist. For the physician, see Ali ibn Sahl Rabban al-Tabari. For the poet, see Ibn Sahl of Sevilla.Ibn Sahl was a Muslim Persian mathematician, physicist and optics engineer of the Islamic Golden Age associated with the Abbasid court of Baghdad...
in 984. The same law was also investigated by Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
and in the Middle Ages by Witelo
Witelo
Witelo was a friar, theologian and scientist: a physicist, natural philosopher, mathematician. He is an important figure in the history of philosophy in Poland...
, but due to lack of adequate mathematical instrument
Mathematical instrument
A mathematical instrument is a tool or device used in the study or practice of mathematics.Most instruments are used within the field of geometry, including the ruler, dividers, protractor, set square, compass, ellipsograph and opisometer...
s (trigonometric functions) their results were saved as tables, not functions.
Willebrord Snellius was born in Leiden, Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
. In 1613 he succeeded his father, Rudolph Snel van Royen
Rudolph Snellius
Rudolph Snellius Rudolph Snellius Rudolph Snellius (Rudolph Snel van Royen (Oudewater, 5 October 1546 – Leiden, 2 March 1613) was a Dutch linguist and mathematician who held appointments at the University of Marburg and the University of Leiden...
(1546–1613) as professor of mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
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
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...
of another, by means of triangulation
Triangulation
In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...
. His work Eratosthenes Batavus ("The Dutch Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...
"), published in 1617, describes the method and gives as the result of his operations between Alkmaar
Alkmaar
Alkmaar is a municipality and a city in the Netherlands, in the province of Noord Holland. Alkmaar is well known for its traditional cheese market. For tourists, it is a popular cultural destination.-History:...
and Bergen op Zoom
Bergen op Zoom
Bergen op Zoom is a municipality and a city located in the south of the Netherlands.-History:Bergen op Zoom was granted city status probably in 1266. In 1287 the city and its surroundings became a lordship as it was separated from the lordship of Breda. The lordship was elevated to a margraviate...
—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
Pi
' is a mathematical constant that is the ratio of any circle's circumference to its diameter. is approximately equal to 3.14. Many formulae in mathematics, science, and engineering involve , which makes it one of the most important mathematical constants...
—the first such improvement since ancient times. He rediscovered the law of refraction in 1621.
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...
(Doctrina triangulorum) authored by Snellius was published a year after his death.
The lunar crater Snellius
Snellius (crater)
Snellius is a lunar crater located near the southeast limb of the Moon. Because of foreshortening the crater appears oval in shape, although it is actually nearly round. To the northeast is the large crater Petavius. South of Snellius is the crater Stevinus....
is named after Willebrord Snellius.
External links
- Willebord Snell in Archimedes to Hawking: Laws of Science and the Great Minds Behind Them (Clifford A. Pickover, 2008).
- Snell's Law Song