Theodorus of Cyrene
Theodoros of Cyrene (Greek Θεόδωρος Theodoros; * to 475/460 BC; † after 399 BC ) was an ancient Greek mathematician.
Life
Theodore was born in Cyrene, a Greek city in what is now Libya. After Plato's presentation, he belonged to the generation of Socrates. This is consistent with the information provided by the Eudemus of Rhodes in his " History of Geometry " match. This gives a date of his birth to 475/460 BC Since he survived Socrates, he died after 399 BC.
Theodore was a pupil and friend of the famous sophist Protagoras, but he turned away early on by the sophistry and from the geometry. He was not only a mathematician, but was also in astronomy and music as an outstanding professional. In these subjects he gave lessons. Among his students was one of the mathematician Theaetetus. Perhaps Plato was taught by him. Whether he's in Athens, where Plato lived, stopped, or whether Plato has visited him in Cyrene, like philosophy Diogenes Laertius historian asserts is unclear. Perhaps his stay in Athens, reported by Plato, a literary invention. The late ancient philosopher Iamblichus counted Theodoros to the Pythagoreans, but will question the credibility of this message in research. Apparently Theodoros was not a philosopher; according to Plato's presentation he did not want to participate in philosophical investigations, since he did not consider themselves to be competent in this field.
Theodoros Plato has reportedly shown that not only - as the Pythagoreans had recognized - the square root of 2, but also the square roots of non-square natural numbers 3-17 are irrational. He went on geometric, by showing that the side length of a square of area 3 square feet with 1 foot of unit length is therefore incommensurable and an irrational number. This he also performed for the square roots of 5, 6, 7 and so on until he broke off at 17. As Theodore led the evidence has not been preserved; in research is even doubted that it is in fact a mathematical proof. Holger Thesleff, which takes up one in 1941 put forward by Jakob Heinrich Anderhub idea, says Theodore had his assumption is not proven, but demonstrates drawing only on the basis of a design, and he had to stop at 17, because the spiral drawing offers only for 17 triangles Place. This is the formula used to construct roots " root worm ," which is called "Wheel of Theodorus " or " spiral of Theodorus ".
Furthermore, Theodoros dealt with curves. The late ancient philosopher Proclus reported Theodoros have called the helix as a "merger" ( crasis ) a straight and a circular line. In contrast, Proclus, who said protested the blend of straight and circular line come in the helix into being neither composition nor merger. The identity of the mentioned by Proclus Theodoros with Theodoros of Cyrene is controversial in research.
Literary reception
Theodoros is caller in Plato's fictional literary dialogue Theaetetus. The dialogue takes place in the year 399 BC, Theodoros is already an old man. Even in Plato's dialogues Sophist and Statesman Theodoros is among those present, he plays in conversation but only a minor role.
Source collections
- Hermann Diels, Walther Kranz (ed.): The fragments of the Presocratics. Volume 1, 6th edition, Weidmann, Berlin 1951, pp. 397 (No. 43)
- Maria Timpanaro Cardini: Pitagorici. Testimonianze e frammenti. Vol 2, La Nuova Italia, Florence 1962, pp. 74-81 ( Greek source texts with Italian translation and commentary )