Johannes Phocylides Holwarda

Who was Johannes Phocylides Holwarda?

Johannes Phocylides Holwarda was a Frisian astronomer, physician, and philosopher. He was professor of philosophy at the University of Franeker from 1639 to 1651.

Born in Holwerd, he is best remembered for his discovery of Mira's variation in brightness. In a systematic study in 1638, he found that Mira disappeared and reappeared in a varying cycle of about 330 days.

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.

The lunar crater Phocylides is named after him.