Callippus (or Calippus) (ca. 370 BC–ca. 300 BC) was a Greek astronomer and mathematician. Callippus Calippus was a tyrant of Syracuse who ruled briefly for thirteen months [1] from 354 to 352 BC. He was a native Athenian, who traveled with Dion to Sicily to capture Syracuse, where Dion became the tyrant. ... Centuries: 5th century BC - 4th century BC - 3rd century BC Decades: 420s BC 410s BC 400s BC 390s BC 380s BC - 370s BC - 360s BC 350s BC 340s BC 330s BC 320s BC 375 BC 374 BC 373 BC 372 BC 371 BC - 370 BC - 369 BC 368 BC 367... Centuries: 4th century BC - 3rd century BC - 2nd century BC Decades: 350s BC 340s BC 330s BC 320s BC 310s BC - 300s BC - 290s BC 280s BC 270s BC 260s BC 250s BC Years: 305 BC 304 BC 303 BC 302 BC 301 BC - 300 BC - 299 BC 298 BC... A recreation of the famous Library of Alexandria Greek astronomy is the astronomy of those who spoke Greek in classical antiquity. ... Leonhard Euler, one of the greatest mathematicians of all time A mathematician is a person whose primary area of study and research is the field of mathematics. ...

He was born at Cyzicus, and studied under Eudoxus of Cnidus at the Academy of Plato. He also worked with Aristotle at the Lyceum, which means that he was active in Athens prior to Aristotle's death in 322. He observed the movements of the planets and attempted to use Eudoxus' scheme of connected spheres to account for their movements. However he found that 27 spheres was insufficient to account for the planetary movements, and so he added seven more for a total of 34. According to the description in Aristotle's Metaphysics (XII.8), he added two spheres for the Sun, two for the Moon, and one each for Mercury, Venus, and Mars. Cyzicus was an ancient town of Mysia in Asia Minor, situated on the shoreward side of the present peninsula of Kapu-Dagh (Arctonnesus), which is said to have been originally an island in the Sea of Marmara, and to have been artificially connected with the mainland in historic times. ... Eudoxus of Cnidus (Greek Εύδοξος) (410 or 408 BC – 355 or 347 BC) was a Greek astronomer, mathematician, physician, scholar and friend of Plato. ... Raphaels fresco The School of Athens An academy is an institution of higher learning, research, or honorary membership. ... PLATO was one of the first generalized Computer assisted instruction systems, originally built by the University of Illinois (U of I) and later taken over by Control Data Corporation (CDC), who provided the machines it ran on. ... Aristotle (Greek: Aristotélēs) (384 BC – 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ... A Lyceum can be an educational institution (often a school of secondary education in Europe), or a public hall used for cultural events like concerts. ... Athens (Greek: Αθήνα - Athína) is the largest city and capital of Greece, located in the Attica periphery of central Greece. ... Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. ...

He made careful measurements of the lengths of the seasons, finding them (starting with the spring equinox) to be 94 days, 92 days, 89 days, and 90 days. This variation in the seasons implies a variation in the speed of the Sun, called the solar anomaly. He also followed up on the work done by Meton of Athens to measure the length of the year and construct an accurate lunisolar calendar. The Metonic cycle has 19 tropical years and 235 synodic months in 6940 days. The Callippic cycle synchronized the lunar and solar years better than the Metonic cycle, by dropping 1 day after 4 Metonic cycles, a duration of 76 years, making the Callippic 19 year cycle equal to 6439 3/4 days, or exactly 365 1/4 days per year, nearly 3 centuries before Julius Caesar. Illumination of the Earth by the Sun on the day of equinox, (ignoring twilight). ... Meton of Athens was a Greek mathematician, astronomer, geometer, and engineer who lived in Athens in the 5th century BCE. He is best known for the 19-year Metonic cycle which he introduced in 432 BCE into the lunisolar Attic calendar as a method of calculating dates. ... A lunisolar calendar is a calendar whose date indicates both the moon phase and the time of the solar year. ... The Metonic cycle or Enneadecaeteris in astronomy and calendar studies is a particular approximate common multiple of the year (specifically, the seasonal tropical year) and the synodic month. ... A tropical year is the length of time that the Sun, as viewed from the Earth, takes to return to the same position along the ecliptic (its path among the stars on the celestial sphere). ... In Egyptian mythology, Month is an alternate spelling for Menthu. ... Eclipses may occur repeatedly, separated by some specific interval of time: this interval is called an eclipse cycle. ...

Dividing Meton's and Callippus's periods by 235 produces their calendars' lengths of the month, in error by 1.9 minutes and 22 seconds, respectively. There is no evidence for anyone's knowledge of the later-canonical Babylonian month of length 29 days 12 hours and 44+¹/₁₈ minutes, until well after 300 B. C., by which time both Meton and Callippus were deceased.

Calippus had his first cycle start at the summer solstice of 330 BC (28 June in the proleptic Julian calendar). These cycles were used by later astronomers for dating observations. Centuries: 5th century BC - 4th century BC - 3rd century BC Decades: 380s BC 370s BC 360s BC 350s BC 340s BC - 330s BC - 320s BC 310s BC 300s BC 290s BC 280s BC 335 BC 334 BC 333 BC 332 BC 331 BC - 330 BC - 329 BC 328 BC 327... June 28 is the 179th day of the year (180th in leap years) in the Gregorian calendar. ... The proleptic Julian calendar is produced by extending the Julian calendar to dates preceding its official introduction in 45 BC. Historians since Bede have traditionally represented the years preceding AD 1 as 1 BC, 2 BC, etc. ...

Calippus crater on the Moon is named for him. Calippus is a small lunar crater that is located on the eastern edge of the rugged Montes Caucasus mountain range in the northern part of the Moon. ... Apparent magnitude: up to -12. ...

Reference

• Kieffer, John S. "Callippus." Dictionary of Scientific Biography 3:21-22.

External links

• O'Connor, John J; Edmund F. Robertson "Callippus". MacTutor History of Mathematics archive.