Johannes Phocylides Holwarda Explained

Johannes Phocylides Holwarda (Jan Fokkesz, Jan Fokker, Johann Holwarda, Johannes Fokkes Holwarda, Jan Fokkens Holwarda, Jan Fokkes van haylen) (February 19, 1618—January 22, 1651)[1] was a Frisian astronomer, physician, and philosopher. He was a professor of philosophy at the University of Franeker from 1639 to 1651.[2]

Born in Holwerd, he is best remembered for his discovery of the length of Mira's (Omicron Ceti's) varying appearance cycle. In a systematic study in 1638, he found that Mira disappeared and reappeared in a varying cycle of about 330 days.[3] [4]

Holwarda was also 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 from atoms and a lack of atoms. Atoms, which he distinguished as simple or compound, are solid corpuscles that receive motion directly from God.[5]

The lunar crater Phocylides is named after him.[6]

Notes and References

  1. Book: The Biographical Encyclopedia of Astronomers . Hockey . Thomas . 2009 . . 978-0-387-31022-0 . August 22, 2012 .
  2. [Pieter Willem van der Horst]
  3. http://www.astro.utu.fi/zubi/people/holwarda.htm Holwarda, Johannes Phocylides
  4. http://subdomainname.yurisnight.net/~spider/spider/Vars/mira.html Mira, Omicron Ceti
  5. Antonio Clericuzio, Elements, Principles and Corpuscles: A Study of Atomism and Chemistry in the Seventeenth Century (Springer, 2001), p. 187.
  6. https://the-moon.us/wiki/Phocylides the-moon » Phocylides