Dionysodorus of Caunus ( grc-gre, Διονυσόδωρος ὁ Καύνειος, 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 23/2479), 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
Pontus or Pontos may refer to:
* Short Latin name for the Pontus Euxinus, the Greek name for the Black Sea (aka the Euxine sea)
* Pontus (mythology), a sea god in Greek mythology
* Pontus (region), on the southern coast of the Black Sea, in modern ...
and different from the one from
Caunus as
Strabo 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, ca ...
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 exact ...
.
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 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' methods to prove this result.
It is also likely that this Dionysodorus was the inventor of a conical
sundial.
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,
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