c. 370-c. 300 B.C.

Greek Astronomer and Mathematician

Callipus is famous for refining the planetary theory of Eudoxus by adding additional spheres. He also made accurate determinations of the lengths of the seasons and constructed a 76-year period to more accurately align the solar and lunar cycles. This Callipic cycle remained the standard for dating and correcting astronomical observations for many centuries.

One of the greatest astronomers of ancient Greece, Callipus was born sometime around 370 B.C. in Cyzicus, located in Hellespontine Phrygia on the southern shores of the Propontis (known today as the Sea of Marmara). According to Simplicius, he studied with Polemarchus (fl. c. 340 B.C.), a former student of Eudoxus (c. 408-c. 355 B.C.). Callipus followed Polemarchus to Athens. He eventually came to live with Aristotle (384-322 B.C.), who encouraged him to devote his efforts to improving the Eudoxean system of concentric spheres.

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