# Mathematician:Willebrord van Royen Snell

## Mathematician

Dutch applied mathematician and astronomer who founded the modern science of geodesy, by pioneering the technique of triangulation.

Developed an improved method for determining the value of $\pi$ (pi) using polygons.

Discovered the Sine Law.

Known today for rediscovering the Snell-Descartes Law in 1621, governing the refraction of light. He did not publish himself. It first appeared in 1703 when it was published in Christiaan Huygens' *Dioptrica*.

**Note:** Several source works (notably the 1911 Encyclopedia Britannica) give his birth year as 1591. It is apparent that this is an error.

## Nationality

Dutch

## History

- Born: 13 June 1580, Leiden, South Holland, Union of Utrecht (what is now known in English as the Netherlands).
- From 1600: Travelled to various European countries, mostly discussing astronomy.
- 1602: Went to Paris to continue studies
- 1604: Visited Switzerland with his father
- 1607: Received degree from Leiden
- 1613: Succeeded his father as professor of mathematics in the university of Leiden
- 1615: Planned and executed a new method of finding the dimensions of the earth, by triangulation
- Died: 30 Oct 1626, Leiden

## Theorems

- Snell-Descartes Law (independently of RenĂ© Descartes)

Results named for **Willebrord van Royen Snell** can be found here.

## Publications

- 1617:
*Eratosthenes Batavus*(the Dutch Eratosthenes) - 1618:
*Coeli et siderum in eo errantium observationes Hassiacae*by William IV of Hesse (edited) - 1621:
*Cyclometria sive de circuli dimensione* - 1624:
*Tiphys Batavus* - 1627:
*Doctrina triangulorum*(posthumous)

## Also known as

**Willebrord van Royen Snell** can also be rendered **Willebrord Snel van Royen**.

He is also known by his Latinized name **Willebrord Snellius**.

## Sources

- John J. O'Connor and Edmund F. Robertson: "Willebrord van Royen Snell": MacTutor History of Mathematics archive

- 1972: George F. Simmons:
*Differential Equations*... (previous) ... (next): $1$: The Nature of Differential Equations: $\S 6$: The Brachistochrone. Fermat and the Bernoullis: Footnote - 1998: David Nelson:
*The Penguin Dictionary of Mathematics*(2nd ed.) ... (previous) ... (next):**Snell, Willebrord van Royen**(1591-1626) - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next):**Snell, Willebrord van Royen**(1591-1626)