Search Results

Geocentricity is the theory that the Earth is located at the center of the cosmos. The theory was espoused first by Parmenides in the fifth century BCE and then became the standard view from the fourth century BCE onward. Eudoxus and his student Callippus devised geometrical models based on the geocentric hypothesis. In these models, the heavens consist of a series of homocentric spheres, centred on the Earth, that account for the movements of the Sun, Moon, stars, and five planets visible with the naked eye: Mercury, Venus, Mars, Jupiter, and Saturn. Aristotle modified this cosmological system and developed an element theory consistent with geocentricity. Some ancient Greek intellectuals offered alternative cosmologies—notably Philolaus, Heraclides of Pontus, and Aristarchus of Samos—but the geocentric conception of the cosmos remained the standard view. Cleomedes and Claudius Ptolemy offer proofs of the geocentric hypothesis in their astronomical texts. In addition, Ptolemy puts forward complex astronomical models that incorporate the eccentric and epicyclic hypotheses as well as the equant, a feature of his own invention. Ptolemy’s geocentric astronomy was authoritative until the seventeenth century, when mathematicians came to espouse a Copernican conception of a heliocentric cosmos, where the Sun is situated at the centre of the cosmos and the Earth orbits the Sun. Isaac Newton developed a physics consistent with heliocentricity and thus prepared the way for the demise of the geocentric theory and the widespread acceptance of heliocentricity.

Greco-Roman meteorology included the study of what we today consider to be atmospheric, astronomical, and seismological phenomena; wind, rain, comets, and earthquakes were subjects of meteorological study, as were many other phenomena. For the most part, those authors and texts that treated meteorology were not concerned with weather prediction but rather with explaining phenomena. Various philosophers, including the Presocratics, Aristotle, Theophrastus, and Epicurus, as well as other philosophically-minded authors such as Lucretius and Seneca, approached the topic from the standpoint of their own interests, including ethics as well as physics. The traditional gods were not wholly absent from philosophical accounts, but they were not thought responsible for weather. Various authors and texts addressed weather prediction, providing lists of weather signs. Ancient Greco-Roman meteorology and weather prediction were both characterized by conservatism and a valorization of tradition, but nevertheless permitted a degree of innovation and originality.

“Meteorology” strictly means “the study of things aloft,” but the term was widely used in antiquity to cover the study of what might now be called meteorological phenomena, as well as comets (today treated as astronomical) and phenomena on and within the earth itself, such as tides and earthquakes (the latter now described as “seismological”). The Homeric and Hesiodic poems describe meteorological phenomena as linked to gods, often as epiphanies. The long-lived authority of the poets on meteorological topics is attested by many quotations and allusions in the writings of later authors, even in prose works on meteorology. Notwithstanding this, later Greek and Roman thinkers offered explanations of meteorological phenomena with no mention of gods.