Geminus of Rhodes was a Greek astronomer and mathematician. The dates of his birth and death are still under debate, but are generally accepted as approximately 110 - 40 BCE. Rhodes, Greek Ρόδος (pron. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ... A mathematician is a person whose primary area of study and research is mathematics. ... The Common Era (CE), sometimes known as the Christian Era or Current Era, is the period of measured time beginning with the year 1 until the present. ...

He was a stoic philosopher and scholar, thought to have studied at the school in Rhodes and then later under Posidonius. During his career he wrote introductory works in mathematics and astronomy, and is typically credited with the construction of the Antikythera mechanism. His astronomical observations noted that the length of a day varied in different parts of the world. His book Isagoge was based on the work of Hipparchus. Stoicism is a school of philosophy commonly associated with such Greek philosophers as Zeno of Citium, Cleanthes, or Chrysippus and with such later Romans as Cicero, Seneca, Marcus Aurelius, and Epictetus. ... A philosopher is a person who thinks deeply regarding people, society, the world, and/or the universe. ... Rhodes, Greek Ρόδος (pron. ... The bust of Posidonius as an older man depects his character as a Stoic philosopher. ... Schematic of the artifacts mechanism The Antikythera mechanism is an ancient artifact believed to be an early clockwork mechanism. ... A day (symbol: d) is a unit of time equal to 24 hours. ... Hipparchus (Greek ) (ca. ...

His mathematical work divided the field into pure and applied mathematics. Pure mathematics included number theory and the various properties of numbers. In applied mathematics he included surveying, musical harmony, optics, astronomy, mechanics, and accounting. Number theory is the formal study of numbers. ... Surveyor at work with a leveling instrument. ... Music is a human activity which involves structured and audible sounds, which is used for artistic or aesthetic, entertainment, or ceremonial purposes. ... Harmony is the use and study of pitch simultaneity and chords, actual or implied, in music. ... Table of Opticks, 1728 Cyclopaedia Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ... Mechanics refers to: a craft relating to machinery (from the Latin mechanicus, from the Greek mechanikos, meaning one skilled in machines), or a range of disciplines in science and engineering. ... Accountancy (British English) or accounting (American English) is the process of maintaining, auditing, and processing financial information for business purposes. ...

The Geminus crater on the Earth's Moon is named for him. Geminus is a lunar impact crater that is located near the northeast limb of the visible Moon. ... Earth is the third planet in the Solar system. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ...

Bibliography

• Isagoge (or Introduction to Astronomy)
• Theory of Mathematics (now lost but cited in many other works)

External links

• Technology Museum of Thessaloniki entry
• University of St. Andrews biography