Early Greek Philosophy by John Burnet, with Burnet's notes
179. The Weight of the Atoms 181. The Earth and the Heavenly Bodies

From Chapter IX., Leukippos of Miletos

180. The Vortex
But what are we to say of the vortex itself which produces these effects? Gomperz observes that they seem to be "the precise contrary of what they should have been by the laws of physics"; for, "as every centrifugal machine would show, it is the heaviest substances which are hurled to the greatest distance."47 Are we to suppose that Leukippos was ignorant of this fact, which was known to Empedokles and Anaxagoras?48 We know from Aristotle that all those who accounted for the earth being in the centre of the world by means of a vortex appealed to the analogy of eddies in wind or water,49 and Gomperz supposes that the whole theory was an erroneous generalisation of this observation. If we look at the matter more closely, we can see, I think, that there is no error at all.

We must remember that all the parts of the vortex are in contact, and that it is just this contact (ἐπίψαυσις) by which the motion of the outermost parts is communicated to those within them. The larger bodies are more able to resist this communicated motion than the smaller, and in this way they make their way to the centre where the motion is least, and force the smaller bodies out. This resistance is surely just the ἀντέρεισις τοῦ μέσου which is mentioned in the doxography of Leukippos,50 and it is quite in accordance with this that, on the atomist theory, the nearer a heavenly body is to the centre, the slower is its revolution.51 That is just the point which, as we have seen,52 Anaximander would seem not to have observed. There is no question of "centrifugal force" at all, and the analogy of eddies in air and water is in reality quite satisfactory.

Burnet's Notes


47. Gomperz, Greek Thinkers, i. p. 339.

48. For Empedokles, see Chap. V. p. 237; Anaxagoras, see Chap. VI. p. 269.

49. Arist. De caelo, B, 13. 295 a 10 ταύτην γὰρ τὴν αἰτίαν (sc. τὴν δίνησιν) πάντες λέγουσιν ἐκ τῶν ἐν τοῖς ὑγροῖς καὶ περὶ τὸν ἀέρα συμβαινόντων· ἐν τούτοις γὰρ ἀεὶ φέρεται τὰ μείζω καὶ τὰ βαρύτερα πρὸς τὸ μέσον τῆς δίνης.

50. Diog. ix. 32. Cf. especially the phrases ὧν κατὰ τὴν τοῦ μέσου ἀντέρεισιν περιδινουμένων, συμμενόντων ἀεὶ τῶν συνεχῶν κατ' ἐπίψαυσιν τῆς δίνης, and συμμενόντων τῶν ἐνεχθέντων ἐπὶ τὸ μέσον.

51. Cf. Lucr. v. 621 sqq

52. See p. 69.

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