PART II. ARISTARCHUS OF SAMOS.

We are told that Aristarchus of Samos was a pupil of Strato of Lampsacus, a natural philosopher of originality, who succeeded Theophrastus as head of the Peripatetic school in 288 or 287 B.C., and held that position for eighteen years. Two other facts enable us to fix Aristarchus’s date approximately. In 281–280 he made an observation of the summer solstice; and the book in which he formulated his heliocentric hypothesis was published before the date of Archimedes’s Psammites or Sandreckoner, a work written before 216 B.C. Aristarchus therefore probably lived circa 310–230 B.C., that is, he came about seventy-five years later than Heraclides and was older than Archimedes by about twenty-five years.

Aristarchus was called “the mathematician,” no doubt in order to distinguish him from the many other persons of the same name; Vitruvius includes him among the few great men who possessed an equally profound knowledge of all branches of science, geometry, astronomy, music, etc. “Men of this type are rare, men such as were in times past Aristarchus of Samos, Philolaus and Archytas of Tarentum, Apollonius of Perga, Eratosthenes of Cyrene, Archimedes and Scopinas of Syracuse, who left to posterity many mechanical and gnomonic appliances which they invented and explained on mathematical and natural principles.” That Aristarchus was a very capable geometer is proved by his extant book, On the sizes and distances of the sun and moon, presently to be described. In the mechanical line he is credited with the invention of an improved sun-dial, the so-called scaphe, which had not a plane but a concave hemispherical surface, with a pointer erected vertically in the middle, throwing shadows and so enabling the direction and height of the sun to be read off by means of lines marked on the surface of the hemisphere. He also wrote on vision, light, and colours. His views on the latter subjects were no doubt largely influenced by the teaching of Strato. Strato held that colours were emanations from bodies, material molecules as it were, which imparted to the intervening air the same colour as that possessed by the body. Aristarchus said that colours are “shapes or forms stamping the air with impressions like themselves as it were,” that “colours in darkness have no colouring,” and that “light is the colour impinging on a substratum”.