Johannes Phocylides Holwarda

Johannes Phocylides Holwarda ("Jan Fokkesz, Jan Fokker, Johann Holwarda, Johannes Fokkes Holwarda, Jan Fokkens Holwarda, Jan Fokkes van Holwerd") (1618—January 22, 1651) was a Frisian astronomer, physician, and philosopher. He was professor of philosophy at the University of Franeker from 1639 to 1651. [Pieter Willem van der Horst, "The Sentences of Pseudo-Phocylides" (Brill, 1978), 63.]

Born in Holwerd, he is best remembered for his survey of Mira stars. In a systematic study in 1638, he found that Mira stars, such as Cetus, disappeared and reappeared in a varying cycle of about 330 days. [ [http://www.britannica.com/eb/topic-269721/Phocylides-Holwarda Phocylides Holwarda (Dutch astronomer) - Britannica Online Encyclopedia ] ] [ [http://www.astro.utu.fi/zubi/people/holwarda.htm Holwarda, Johannes Phocylides ] ] [ [http://subdomainname.yurisnight.net/~spider/spider/Vars/mira.html Mira, Omicron Ceti ] ]

He was a supporter of “atomism”. His "Philosophia Naturalis, seu Physica Vetus-Nova", published posthumously in 1651, defines matter and form: matter is extended and divided into atoms while form is the texture of atoms. According to Phocylides, bodies are formed of atoms and void. Atoms, which he distinguished as simple or compound, are solid corpuscles that receive motion directly from God. [Antonio Clericuzio, "Elements, Principles and Corpuscles: A Study of Atomism and Chemistry in the Seventeeth Century" (Springer, 2001), p. 187).]

The lunar crater Phocylides is named after him. [ [http://the-moon.wikispaces.com/Phocylides the-moon » Phocylides ] ]

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