Sunday, August 03, 2008

Robert Grosseteste, Albumasar, and Medieval Tidal Theory

The article by Edgar Laird, Robert Grosseteste, Albumasar, and Medieval Tidal Theory, seeks to articulate the influence of the medieval islamic astrologer Albumasar, on the work of Robert Grosseteste's tidal theory.

Grosseteste's work on tidal theory, De Fluxa, preceded the Hexamearon, which he is best known for. What is most interesting is the appliance of cosmological principles to the special problem of tides. The cosmological principle of rarefaction and condensation are part of a complete and coherent cosmology, despite the integration of Albumasar's work which was the best available account of the tides.

The cosmogonic principle of rarefraction and condensation implies the material cause of the tides is a rectilinear motion away or towards the center of the universe. Light is the source of motion and the tides are moved by the light of the moon, hence an astrological interpretation of tidal movement. The light from the moon rarefies the sea in the same manner that the stars rarefy the air at night; if not the air would be so condensed that human and plant life would be impossible.

What I find most important is the articualtion of tidal movement within a cosmology, and the articulation of tidal movement as a cosmogony.

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