Resumen de Bright stars and wide whorls
Plato’s Republic culminates in a model of the cosmos based on a spindle, with eight nested cups (‘whorls’) representing the moon, sun, planets, and fixed stars (10, 616E). The whorls differ in width, in colour, and in speed. The model is evidently qualitative and imprecise, but addresses observable features. The colours and speeds correspond accurately to what Plato and his contemporaries could have observed, so the widths of the whorls should correspond to some visual feature of the heavenly bodies observable in Plato’s era. Observable features in that era were speed, colour, and brightness; speed and colour are accounted for. Ancient observers were well aware of the differences in brightness between stars. The widths, in the received text of Plato’s Republic, represent the range of brightness differences as perceived among the fixed stars, or respectively, the range of brightness variations as perceived for each of the seven wandering stars.
