Cleomedes was a Greek astronomer who is known chiefly for his book On the Circular Motions of the Celestial Bodies. An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ...

Placing his work chronologically

His birth and death dates are not known--historians have suggested that he wrote his work sometime between the mid-1st Century B.C. and 400 C.E. The earlier estimates rely on the fact that Cleomedes refers extensively in his writing to the work of mathematician and astronomer Posidonius of Rhodes (135 BC-51 BC), and yet seemingly not at all to the work of Ptolemy (85-165 C.E.). These conclusions have been challenged on the grounds that Cleomedes' work was in relatively elementary astronomy, and that reference to Ptolemy would not necessarily be expected. The 20th Century mathematician Otto Neugebauer, however, looked closely at the astronomical observations made by Cleomedes, and concluded that a date of 371 C.E. (±50 years) better explains what is found there. Neugebauer's estimate has been challenged on the grounds that Cleomedes makes observational errors with enough frequency that there is difficulty in deciding which observations to trust for the purpose of dating his work. Events First invasion of Italy by Alaric (probable date). ... A mathematician is a person whose area of study and research is mathematics. ... The bust of Posidonius as an older man depects his character as a Stoic philosopher. ... Jump to: navigation, search Main entrance to the medieval city of Rhodes Rhodes, Greek Ρόδος (Rhodos; see also List of traditional Greek place names), is the largest of the Dodecanese islands, and easternmost of the major islands of Greece in the Aegean Sea. ... Centuries: 3rd century BC - 2nd century BC - 1st century BC Decades: 180s BC 170s BC 160s BC 150s BC 140s BC - 130s BC - 120s BC 110s BC 100s BC 90s BC 80s BC Years: 140 BC 139 BC 138 BC 137 BC 136 BC - 135 BC - 134 BC 133 BC... Centuries: 2nd century BC - 1st century BC - 1st century Decades: 100s BC 90s BC 80s BC 70s BC 60s BC - 50s BC - 40s BC 30s BC 20s BC 10s BC 0s BC Years: 56 BC 55 BC 54 BC 53 BC 52 BC 51 BC 50 BC 49 BC 48... Claudius Ptolemaeus, given contemporary German styling, in a 16th century engraved book frontispiece. ... Centuries: 1st century BC - 1st century - 2nd century Decades: 0s BC - 0s - 10s - 20s - 30s - 40s - 50s - 60s - 70s - 80s - 90s - 100s Years: 80 81 82 83 84 85 86 87 88 89 90 Events Dacians under Decebalus engaged in two wars against the Romans from this year to AD... Events A pandemic breaks out in Rome after the Roman army returns from Parthia. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Events Martin of Tours becomes Bishop of Tours _ year approximate Baekje forces storm the Goguryeo capital in Pyongyang Births Valentinian II - titular Roman emperor - year approximate Deaths August 1 - St Eusebius of Vercelli St Hilarion - year approximate Lucifer of Cagliari - bishop King Gogugwon of Goguryeo Categories: 371 ...

On the Circular Motions of the Celestial Bodies

The book for which Cleomedes is known is a fairly basic astronomy textbook in two volumes. His purpose in writing seems to have been as philosophical as it was scientific--he spends an extensive amount of time criticizing the (admittedly fallacious) scientific ideas of the Epicureans (Cleomedes appears to have been a dedicated Stoic). Jump to: navigation, search Two textbooks A textbook is a manual of instruction or a standard book in any branch of study. ... Epicureanism is a system of philosophy based upon the teachings of Epicurus (c340-c270 BC), founded around 307 BC. Epicurus was an atomic materialist, following in the steps of Democritus. ... 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. ...

Cleomedes' book is criticized by most modern astronomers as being poorly written--it is valued primarily for preserving, apparently verbatim, much of Posidonius' writings on astronomy (none of Posidonius' books have survived to the modern day). Cleomedes is accurate in some of his remarks on lunar eclipses, especially his conjecture that the shadow on the Moon suggests a spherical Earth. He also remarks presciently that the absolute size of many stars may exceed that of the Sun (and that the Earth might appear as a very small star, if viewed from the surface of the Sun). Jump to: navigation, search An eclipse occurs whenever the Sun, Earth and Moon line up exactly. ... Jump to: navigation, search Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... A sphere is a perfectly symmetrical geometrical object. ... Jump to: navigation, search Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ... Jump to: navigation, search The Sun is the star at the centre of our Solar system. ...

This book is the original source for the well-known story of how Eratosthenes measured the Earth's circumference. Although the story is now believed by some to be purely legendary, many modern mathematicians and astronomers believe the description to be reasonable (and believe Eratosthenes' achievement to be one of the more impressive accomplishments of ancient astronomy). Jump to: navigation, search Eratosthenes (Ερατοσθένης) Eratosthenes (Ερατοσθένης) (276 BC - 194 BC) was a Greek mathematician, geographer and astronomer. ... The circumference is the distance around a closed curve. ... Jump to: navigation, search A legend (Latin, legenda, things to be read) is a narrative of human actions that are perceived both by teller and listeners to take place within human history and to possess certain qualities that give the tale verisimilitude. ...

His legacy

Cleomedes is now memorialized in the name of the Cleomedes crater, a prominent feature in the northeast portion of the visible moon. Cleomedes is a prominent lunar crater located in the northeast part of the visible Moon, to the north of Mare Crisium. ... This article is about impact craters, also known as meteor craters. ...

External links

• A biography of Cleomedes on a mathematical site
• An article on Cleomedes' description of atmospheric enlargement from Perception (2000)