Willebrord Snell was born on June 13, 1580 in Leiden, Dutch Republic, Dutch, is Astronomer & Mathematician. Willebrord Snel van Royen, also referred to as Willebrordus Snellius in most of his publications, was a 17thcentury Dutch astronomer and mathematician. Over the centuries, people recall him for one of the greatest findings in the world of science—thelaw of refraction. Until recently, it was believed that he was the proprietor of the theory; however, it was discovered that the law was actually formulated by Ibn Sahl and that Snell had only rediscovered it.Although he had originally studied law, he was a mathematical genius and made numerous contributions to the field. Snell, as he was called by the western world, brought about a major revolution when he developed a new method to calculate the mathematical function ‘Pi’, which led to tremendous development in the field of mathematics. Snell had published several of his works; the two most acknowledged and acclaimed are ‘Eratosthenes Batavus’ and ‘Tiphys Batavus’. At the peak of his career, he travelled all through Europe making more discoveries and working on several findings, especially in the field of astronomy. It was at this time that he collaborated with the best in the astronomical world, such as Johannes Kepler and Tycho Brahe.

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Who is it? | Astronomer & Mathematician |

Birth Day | June 13, 1580 |

Birth Place | Leiden, Dutch Republic, Dutch |

Age | 439 YEARS OLD |

Died On | 30 October 1626(1626-10-30) (aged 46)\nLeiden, Dutch Republic |

Birth Sign | Cancer |

Alma mater | University of Leiden |

Known for | Snell's law |

Fields | Astronomer and mathematician |

Institutions | University of Leiden |

Academic advisors | Ludolph van Ceulen Rudolph Snellius |

Notable students | Jacobus Golius |

1599

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; The Hague : Sint-Jacobskerk; Amsterdam : Oude Kerk; Utrecht : Cathedral of Utrecht; Zaltbommel : Sint-Maartenskerk; Gouda : Sint Janskerk; Oudewater : Sint-Michaelskerk; Rotterdam : Sint-Laurenskerk; Dordrecht : Grote Kerk; Willemstad : Koepelkerk; Bergen-op-Zoom : Gertrudiskerk; Breda : Grote Kerk

1613

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.

1615

In 1615 Snellius, after the work of Eratosthenes in Ptolemaic Egypt in the 3rd century BC, probably was the first to try to do a large-scale experiment to measure the circumference of the earth using triangulation. 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*). In his work *The terrae Ambitus vera quantitate* (1617) under the author's name ("The Dutch Eratosthenes") Snellius describes the methods he used. He came up with an estimate of 28,500 Rhineland rods – in modern units 107.37 km 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%.

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.

1626

Snellius died at Leiden on October 1626, at the age of 46 from an illness diagnosed as colic. His grave can be seen in the Pieterskerk, Leiden, which has since been deconsecrated.

2013

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. 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 a network of fourteen cities a total of 53 triangulation measurements were made. In his calculations Snellius made use of a solution for what is now called the Snellius–Pothenot Problem.

2014

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.

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