3 ms·

does it matter whether you have a heliocentric or a geocentric worldview when using this method?

• herodotus 4y ago
  No. Babylonian astronomers created arithmetical techniques for predicting key events of the moon and planets, such as the date that Jupiter reached a stationary point in the sky. (The stationary point is the positions where Jupiter starts its retrograde motion). They were not trying to explain the nature of the universe (cosmology). Ptolemy derived cosmological models based on geometry, but even he was interested in prediction, not explanation. In both cases, it does not matter whether the astronomer's view is helio- or geo- centric. Ptolemy used a geocentric model, but he did point out that a heliocentric version was a possible alternative. Even Copernicus was not really that concerned with cosmology: he was showing an alternative to Ptolemy based on the heliocentric view of what he thought was the universe (now known to be the solar system). In my view it was Galileo who really first proposed that these models went beyond prediction to describe the reality of the cosmos.
  • trasz 4y ago
    Do we know why they tried to predict, but not explain? Or would prediction simply be a prerequisite for explanation?
    • rosetremiere 4y ago
      I heard (iirc in the “In our time” podcast) that they associated rare/unusual cosmological events (say, a solar eclipse) with signs from the gods. Hence, to better read the signs, you want to know what's normal/predicted. Don't quote me on this, though :)
    • herodotus 4y ago
      The most likely reason was because there was an obvious correlation between astronomical events and things that happened on earth. The most obvious are seasonal weather events, which are obviously important for agriculture. Having noticed that these earthly events correlated with certain astronomical events, it was natural to extend this to predicting other events based on astronomical "omens" such as conjunctions, risings, stationary points and so on. It is likely that Babylonian rulers used astrologers when making decisions such as the best time to attack a neighbour.
    • ncmncm 4y ago
      We know that, at various times, explanation was a strictly and vigorously defended priestly prerogative, and encroaching on that was a good way to get oneself dragged behind a chariot all through town.
    • FastMonkey 4y ago
      The periodic back and forth movement of a pendulum can be modelled as a circular rotation with constant angular velocity. We "know" that it just goes over and back so we "know" that the circular motion is just a model. All the same, maybe in the future, they'll figure out that pendulums actually move in 4 dimensions. Then they'll look back at us and think "surely they should have known that pendulums really moved in 4 dimensional circles, because they knew about this model". I'd imagine it's similar looking at the sky. If you "knew" the motion of the planets was related to some Gods moving around, you might expect that circular motion was just a model there too.
• qubex 4y ago
  Orbits are always periodic functions, so quite amusingly heliocentric and geocentric models are equivalent (because of Fourier transformations).