- For the crater, see Gemma Frisius (crater).
Gemma Frisius (born Jemme Reinerszoon) (December 9, 1508 – May 25, 1555), was a physician, mathematician, cartographer, philosopher, and instrument maker. He created important globes, improved the mathematical instruments of his day and applied mathematics in new ways to surveying and navigation.
Frisius was born in Dokkum, Friesland (present-day Netherlands) of poor parents, who died when he was young. He moved to Groningen and studied at the University in Leuven beginning in 1525. He received the degree of MD in 1536 and remained on the faculty of medicine in Leuven for the rest of his life. His oldest son, Cornelius Gemma, edited a posthumous volume of his work and continued to work with Ptolemaic astrological models.
While still a student, Frisius set up a workshop to produce globes and mathematical instruments. He became noted for the quality and accuracy of his instruments, which were praised by Tycho Brahe, among others. In 1533, he described for the first time the method of triangulation still used today in surveying. Twenty years later, he was the first to describe how an accurate clock could be used to determine longitude. Jean-Baptiste Morin (1583–1656) did not believe that Frisius' method for calculating longitude would work, remarking, "I do not know if the Devil will succeed in making a longitude timekeeper but it is folly for man to try."
Frisius created or improved many instruments, including the cross-staff, the astrolabe and the astronomical rings. His students included Gerardus Mercator (who became his collaborator), Johannes Stadius, John Dee, Andreas Vesalius and Rembert Dodoens.
Frisius died in Leuven.
A lunar crater has been named after him.
- Cosmographia (1529) von Petrus Apianus, annotated by Gemma Frisius
- De principiis astronomiae et cosmographiae (1530)
- De usu globi (1530)
- Libellus de locorum describendorum ratione (1533)
- Arithmeticae practicae methodus facilis (1540)
- De annuli astronomici usu (1540)
- De radio astronomico et geometrico (1545)
- De astrolabio catholico (1556)
- He was cited as Jemme Reinersz in the 1533 edition of Peter Apian's Cosmographia.
- "Longitude1". Groups.dcs.st-and.ac.uk. Retrieved 2013-03-19.
- Usus annuli astronomici - Rainer Gemma Frisius - Google Books. Books.google.com. Retrieved 2013-03-19.
Further reading 
- N. Haasbroek: Gemma Frisius, Tycho Brahe and Snellius and their triangulations. Delft 1968.
- Robert Haardt: The globe of Gemma Frisius. Imago mundi, Bd. 9, 1952.
- W. Karrow: Mapmakers of the Sixteenth Century and Their Maps. Chicago 1993.
- G. Kish: Medicina, mensura, mathematica: The Life and Works of Gemma Frisius. Minneapolis 1967, sowie sein Artikel in Dictionary of Scientific Biography
- A. Pogo: Gemma Frisius, his method of determining longitude. In: Isis. Bd. 22, 1935, S.469-485.
- Moritz Cantor (1878), "Gemma-Frisius, Rainer", Allgemeine Deutsche Biographie (ADB) (in German) 8, Leipzig: Duncker & Humblot, pp. 555–556
|Wikimedia Commons has media related to: Gemma Frisius|
- O'Connor, John J.; Robertson, Edmund F., "Regnier Gemma Frisius", MacTutor History of Mathematics archive, University of St Andrews.
- Gemma (Jemme Reinerszoon) Frisius at the Mathematics Genealogy Project
- Description of the Camera Obscura in 1544 by Frisius