Dionysodorus of Caunus (, c. 250 BC – c. 190 BC) was an ancient Greek mathematician.

Life and work

Little is known about the life of Dionysodorus.

Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...

writes about a Dionysodorus who measured the Earth's circumference, however he is probably the one from

Melos Milos or Melos (; , ; ) is a volcanic Greek island in the Aegean Sea, just north of the Sea of Crete. It is the southwestern-most island of the Cyclades group. The ''Venus de Milo'' (now in the Louvre), the '' Poseidon of Melos'' (now in the ...

and different both from the one from Caunus and from Dionysodorus of Amisene;

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 "Gnaeus Pompeius Strabo, Pompeius Strabo". A native of Sicily so clear-si ...

differentiates between the latter two mathematicians. Dionysodorus is remembered for solving the

cubic equation In algebra, a cubic equation in one variable is an equation of the form ax^3+bx^2+cx+d=0 in which is not zero. The solutions of this equation are called roots of the cubic function defined by the left-hand side of the equation. If all of th ...

by means of the intersection of a rectangular

hyperbola In mathematics, a hyperbola is a type of smooth function, smooth plane curve, 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, called connected component ( ...

and a

parabola In mathematics, a parabola is a plane curve which is Reflection symmetry, mirror-symmetrical and is approximately U-shaped. It fits several superficially different Mathematics, mathematical descriptions, which can all be proved to define exactl ...

Eutocius Eutocius of Ascalon (; ; 480s – 520s) was a Greek mathematician who wrote commentaries on several Archimedean treatises and on the Apollonian ''Conics''. Life and work Little is known about the life of Eutocius. He was born in Ascalon, t ...

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

Heron Herons are long-legged, long-necked, freshwater and coastal birds in the family Ardeidae, with 75 recognised species, some of which are referred to as egrets or bitterns rather than herons. Members of the genus ''Botaurus'' are referred to as bi ...

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

torus In geometry, a torus (: tori or toruses) is a surface of revolution generated by revolving a circle in three-dimensional space one full revolution about an axis that is coplanarity, coplanar with the circle. The main types of toruses inclu ...

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 an Ancient Greece, Ancient Greek Greek mathematics, mathematician, physicist, engineer, astronomer, and Invention, inventor from the ancient city of Syracuse, Sicily, Syracuse in History of Greek and Hellenis ...

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

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

. 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 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 transl ...

, 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 geometers Ancient Greeks in Caria 3rd-century BC Greek mathematicians 2nd-century BC Greek mathematicians