“The sun is a circle many times larger than the earth, and its fire is like the fire of a wheel with an opening.”
— Anaximander[commonly attributed] Testimony in Hippolytus, Refutation of All Heresies 1.6, and Ps.-Plutarch; paraphrase, not verbatim

Commentary

This report describes the sun as a circular body of fire many times the size of the earth, a figure that the doxographers give in specific numerical terms. The claim, if authentic, shows an ambition to estimate the scale of celestial bodies, which is a notable feature of early Milesian astronomy. G. S. Kirk, J. E. Raven, and M. Schofield caution that the numerical figures in the doxography are late and may be schematic. Charles Kahn argues that the sun's size and fiery character follow from the ring model, and that the figures reflect an attempt to make the cosmos commensurable with the earth. Jonathan Barnes notes that the precise size attributed to the sun is a detail whose reliability cannot be established. W. K. C. Guthrie observes that the sun's size was a common subject of early Greek speculation and that the attribution to Anaximander is traditional. The sentence is a paraphrase of late doxography and should be labelled as a commonly attributed doctrine.