Shakman, S. H., Nature 338, 456 (1989):

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SIR -- The heliocentric hypothesis, so able championed by Copernicus and Galileo(1), is authoritatively said to have originated with Aristarchus of Samos in the third century BC. Sand-Reckoner, written by Aristarchus's younger contemporary Archimedes before 216 BC(2), attributed to Aristarchus a book containing the hypotheses "that the fixed stars and the sun remain unmoved, [and] that the earth revolves about the sun in the circumference of a circle, the sun lying in the middle of the orbit...". Aristarchus's (lost) book is thought to have "clearly...also included some kind of geometrical proof"(3). Aristarchus had also produced a treatise On the sizes and distances of the Sun and Moon, which has survived intact. Its "excellent" methodology confirms that Aristarchus's (probably later) heliocentric hypothesis was similarly "not irresponsible" but rather the work of a conscientious astronomer"(2). Nicholas Copernicus's De Revolutionibus (1543) acknowledged Aristarchus but not his heliocentric hypothesis(4); however, it seems certain that Copernicus was also acquainted with the latter. For example, his original manuscript had referred to the opinion of Aristarchus on the movement of the Earth, but this reference was subsequently "suppressed" or "scored out"(4). Moreover, in relating the views of Philolaus, Heracleides and Ecphantus on the question of movement of the Earth, Copernicus's Preface quoted from De Placitis Philosophorum of pseudo-Plutarch, a work in which may also be found: "Aristarchus places the Sun among the fixed stars, and holds that the EArth moves around the Sun's circle"(4). And De Revolutionibus (IV, 32) cites Archimedes' Measurement of the Circle, a treatise commonly found in the company of Sand- Reckoner(5). Copernicus's unquestionably pivotal contribution to astronomy was his grand revival of the heliocentric hypothesis as a systematic planetary theory(4). But in order to fit theory to observation, Copernicus had retained the geometric devices used by Ptolemy (the deferent, epicycle and excentric), and had referred details of planetary movements not to the Sun but rather to the centre of the Earth's orbit. Because of technical and other difficulties with the copernican system, the astronomer Tycho Brahe (1546-1601) rejected it. Brahe had compiled an unrivalled set of observations, which he thought would demonstrate that the Sun and Moon travel around the Earth while the other planets travel round the Sun(6). After Brahe's death, Johannes Kepler (1571-1630) invested years in the analysis of Brahe's data, culminating in the derivation of Kepler's three laws of planetary motion. These provided a precise and enduring mathematical characterization of the heliocentric hypothesis, thus serving to support the position of Copernicus while ironically refuting that of Brahe. STUART HALE SHAKMAN 1. Nature 337, 101 (1989). 2. Sarton, G. A History of Science: Hellenistic Science and Culture in the Last Three Centuries BC, 54-57 (Harvard University, Cambridge, 1959). 3. Heath, T. Aristarchus of Samos, 301-302 (Clarendon, Oxford, 1913). 4. Armitage, A. Copernicus (Allen & Unwin, London, 1938). 5. Heath, T., The Works of Archimedes xxiv-xxvi (Dover, N.Y., 1912). 6. Armitage, A. Sun Thou Stand Still 149, 169-175 (Sigma, London, 1947).HOME Copyright SHShakman 1996