Meteors

Summary

The field of “meteorology” (as it was traditionally understood) is circumscribed by Aristotle's Meteorologica – one of the smaller physical treatises. According to Aristotle, it is concerned with “events that are natural, even though their order is less perfect,” which take place “in the region nearest to the motion of the stars.” More particularly, it would make a study of “the properties shared by air and water, and the kinds and parts of the earth and the affections of its parts,” so light can be thrown “on the causes of winds and earthquakes … thunderbolts, whirlwinds and fire-winds,” as well as an account given of more complex substances – more complex, that is, than earth, water, and air. Finally, Aristotle admits that meteorology is not a perfect science because the causal scheme that was believed to be essential for explanation does not completely apply (final causes in particular – the idea that meteorological phenomena have a purpose was seen as unphilosophical) (I.i.338a20–339a9). In any case, the subject matter of meteorology could be defined in different ways: either as the study of all phenomena that occur between the earth's surface and the moon, or as a discussion of the elements, or as the study of the various forms taken by water and vapor.

Descartes started work on his Météores in the late summer of 1629, after reading a description of the parhelia (sundogs or mock suns) observed earlier that year by the Jesuit Scheiner (1573/75–1650). He first gave his own explanation of the same phenomenon, then proceeded to the rainbow and eventually added explanations of wind, rain, and snow, of elementary chemical processes, and of atmospheric phenomena. The basis of most of these explanations is formed by a few “suppositions,” necessary because as yet Descartes was not prepared to disclose his principles. It is assumed, first, that all qualitative differences between the elements can be reduced to differences in form, mass, and motion of elementary particles; and, second, that there is no vacuum and that the room between the particles is filled with what Descartes calls subtle matter – a very fine and pliable substance, composed of the same matter as the other elements.