Tycho Brahe and Weather Prediction

In 1573, Tycho Brahe included in his De nova stella an introduction to an almanac for the year which set out the principles he favoured for the production of such a document. Although criticising other astrologers for a number of reasons, Tycho made it clear that the probable weather for each day should be predicted on the basis of the heavenly configurations. Tycho's own meteorological theory attributed most weight to the Moon in varying the solar-controlled climate, on account of its proximity to the Earth. However, he warned readers not to expect too much from weather predictions, both because the motions and effects of the heavenly bodies had yet to be properly explored, and because the fluidity of sub-lunary matter can sometimes hasten events or delay them. He recommended that weather observations be kept so that prediction could be placed on a sounder footing in the future.

Tycho's own attempts to provide an empirical basis for astro-meteorology date from 1564, when he observed the heavens during the twelve days of Christmas in order to test the theory that these presaged the monthly weather phenomena of the coming year. From 1582 onwards, Tycho kept a daily record of the weather on Hven, and in 1585 published, under the name of one of his students, an astrological calendar for the coming year. Another book, issued from the Uraniborg press in 1591, contained 399 aphorisms for weather prediction on the basis of the sky's appearance, the motions of the heavenly bodies, and the behaviour of animals. Although this work was also presented under the name of a disciple, it was later revealed that Tycho composed its preface, which displays an enthusiasm for astrological weather prediction undimmed by the realisation that local meteorological variation was much greater than could be attributed to heavenly influences alone.