Dionysodorus of Caunus ( grc-gre, Διονυσόδωρος ὁ Καύνειος, c. 250 BC – c. 190 BC) was an ancient

Greek mathematician Greek mathematics refers to mathematics texts and ideas stemming from the Archaic through the Hellenistic and Roman periods, mostly extant from the 7th century BC to the 4th century AD, around the shores of the Eastern Mediterranean. Greek mathem ...

Life and work

Little is known about the life of Dionysodorus.

Pliny the Elder Gaius Plinius Secundus (AD 23/2479), called Pliny the Elder (), was a Roman author, naturalist and natural philosopher, and naval and army commander of the early Roman Empire, and a friend of the emperor Vespasian. He wrote the encyclopedic '' ...

writes about a Dionysodorus who measured the earth's circumference, however he is probably the one from Pontus and different from the one from

Caunus Kaunos (Carian: ''Kbid'';. Translator Chris Markham. Lycian: ''Khbide''; Ancient Greek: ; la, Caunus) was a city of ancient Caria and in Anatolia, a few kilometres west of the modern town of Dalyan, Muğla Province, Turkey. The Calbys riv ...

Strabo Strabo''Strabo'' (meaning "squinty", as in strabismus) was a term employed by the Romans for anyone whose eyes were distorted or deformed. The father of Pompey was called "Pompeius Strabo". A native of Sicily so clear-sighted that he could see ...

differentiates between the two mathematicians. Dionysodorus is remembered for solving the cubic equation by means of the intersection of a rectangular

hyperbola In mathematics, a hyperbola (; pl. hyperbolas or hyperbolae ; adj. hyperbolic ) is a type of smooth curve lying in a plane, defined by its geometric properties or by equations for which it is the solution set. A hyperbola has two pieces, cal ...

and a

parabola In mathematics, a parabola is a plane curve which is mirror-symmetrical and is approximately U-shaped. It fits several superficially different mathematical descriptions, which can all be proved to define exactly the same curves. One descript ...

Eutocius Eutocius of Ascalon (; el, Εὐτόκιος ὁ Ἀσκαλωνίτης; 480s – 520s) was a Palestinian-Greek mathematician who wrote commentaries on several Archimedean treatises and on the Apollonian ''Conics''. Life and work Little is ...

credits Dionysodorus with the method of cutting a sphere into a given ratio, as described by him.

Heron The herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 72 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genera ''Botaurus'' and ''Ixobrychus ...

mentions a work by Dionysauras entitled ''On the Tore'', in which the volume of a

torus In geometry, a torus (plural tori, colloquially donut or doughnut) is a surface of revolution generated by revolving a circle in three-dimensional space about an axis that is coplanar with the circle. If the axis of revolution does not tou ...

is calculated and found to be equal to the area of the generating circle multiplied by the circumference of the circle created by tracing the center of the generating circle as it rotates about the torus's axis of revolution. Dionysodorus used

Archimedes Archimedes of Syracuse (;; ) was a Greek mathematician, physicist, engineer, astronomer, and inventor from the ancient city of Syracuse in Sicily. Although few details of his life are known, he is regarded as one of the leading scientists ...

' methods to prove this result. It is also likely that this Dionysodorus was the inventor of a conical

sundial A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat ...

. Pliny's mentioning tells of an inscription placed on his tomb, addressed to the world above, stating that he had been to the centre of the earth and found it 42 thousand

stadia Stadia may refer to: * One of the plurals of stadium, along with "stadiums" * The plural of stadion, an ancient Greek unit of distance, which equals to 600 Greek feet (''podes''). * Stadia (Caria), a town of ancient Caria, now in Turkey * Stadi ...

distant.Pliny, ''Hist. Nat.'' ii. 109 Pliny calls this a striking instance of Greek vanity; but this figure compares well with the modern measurement.

Citations and footnotes

References

T. L. Heath Sir Thomas Little Heath (; 5 October 1861 – 16 March 1940) was a British civil servant, mathematician, classical scholar, historian of ancient Greek mathematics, translator, and mountaineer. He was educated at Clifton College. Heath transla ...

, A History of Greek Mathematics II (Oxford, 1921). * Netz, Reviel
''The Transformations of Mathematics in the Early Mediterranean World''
Cambridge University Press, 2004. . Pags. 29-39.

External links

* {{Authority control 250s BC births 190s BC deaths Ancient Greek mathematicians Ancient Greeks in Caria 3rd-century BC mathematicians 2nd-century BC mathematicians