Anima motrix

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The anima motrix is a - but not applicable - concept used by the astronomer Johannes Kepler in the context of his planetary theory, from which the connections known today as Kepler's laws have been preserved.

Kepler did not know the theory of gravity that keeps planets in orbit. Instead, he speculated that the sun had a radiating, magnet-like effect that would do just that.

Anima motrix:

He called it the anima motrix , "soul of the mover", a concept that goes back to Scaliger's teaching of the moving soul forces , which is still deeply rooted in the impetus teaching of scholasticism . Kepler described it as a “certain divine power” (KGW I, 56), to which the soul of the heavenly bodies is added, on which the motor anima can act (KGW I, 77), and thus creates the heavenly orbits.

He thought the relationship between the intensity of the anima motrix and the distance between the sun and the planet to be analogous to the decrease in the intensity of light with distance from a light source, whereby the effect of the anima motrix was limited to the orbit of the planets. He called this effect vigor motus , the "(life) force of movement". Kepler expressly states that this connection would be “very clearly the same law for the currents of light and power emerging from the sun” (KGW XIV, 280.653–657).

Kepler is the first to distance himself from the Aristotelian concept of the first mover ( Greek proton kinoun akineton , primum movens ), the primordial ground that flows through all spheres of the cosmos and has the same effect everywhere: He should have given every body a constant angular velocity (Aristotle: De Caelo  II.10), which he later refuted with his Lex secunda , and he should have worked proportionally to the distance from the center of the world, while Kepler needed the square-proportional effect to formulate his planetary theory. To the extent to which the anima decreases from the sun, the impulse to move ( motus impressio , KGW V, 121) of the heavenly bodies decreases.

Kepler formulated the anima motrix very early, as early as 1600 (documented in correspondence) it was changed to the designation virtus motrix " fortune of the mover" or vis motrix "power of the mover" (KGW III, 113). Bialas sees this as a very fundamental step away from Aristotelian metaphysical concepts of the soul to that of the theory of forces , and thus a physically based celestial mechanics instead of cosmogonically caused phenomena.

Kepler recognized the quadratic proportionality, the mass dependence, and also the mutual effect of the bodies on one another (the character of the interaction ), which was still unthinkable for Kepler, was only introduced by Newton with his law of gravitation of the 1680s. The field theories of the late 19th century erroneously assume that gravity does not propagate (spreads), but is an action at a distance - and therefore something fundamentally different from light. With his association with magnetism , which was also just being formulated in his time, Kepler was closer to this. In the general theory of relativity , however, gravitational waves , i.e. the spread of gravitation, are predicted.

literature

  • Johannes Kepler: Harmonices Mundi Libri V . In: Max Caspar (Ed.): Collected Works (KGW) . CH Beck, Munich 1990, ISBN 3-406-01648-0 (first edition: 1938).
  • Volker Bialas: Johannes Kepler . 566 Beck's series. CH Beck, Munich 2004, ISBN 978-3-406-51085-4 , 2.2 The physicalization of astronomy in the trinitarian cosmos c)  Physical justification of the celestial movement , p. 88-96 .

Individual evidence

  1. ↑ cit. Trans. Bialas: Kepler . 2004, p. 91 .
  2. ↑ cf. First mover in: Microsoft Encarta
  3. ↑ Bialas: Kepler . 2004, p. 88 .
  4. ↑ Siegmund Günther pointed out in 1888 that Kepler was familiar with the studies of Domenico Maria da Novara , the Bolognese teacher of Copernicus , on terrestrial magnetism . Siegmund Günther, Wilhelm Windelband: History of ancient natural science and philosophy . Beck, Nördlingen 1888. After Bialas: Kepler . 2004, p. 90 .