Atmospheric tides and other relationships: »Interpreting the Phenomena« at the time of the Seeberg conference

Wolfgang Kokott, Munich

Complete text (abstract only):

Lalande's account of his experiences at Gotha and on his journey back to France [AGE 2 (1798), 381-382] contains an interesting attempt to explain the extremely rainy September weather (»at a time of the year when it is raining more rarely in our countries«) by means of the Moon's southern declination. Actually, there are several other documents on the same subject; Lagrange was trying to prove his version of lunar influence against Lamarck who claimed exactly the opposite correlation to be true.

In the light of Lalande's own work on oceanic tides, his interest in this meteorological problem is readily understood. While stringent limits for tidal variations of air pressure had already been established by d'Alembert (1747) and Toaldo (1779), no consistent theory of tidal mechanics was yet available. Theoretical and empirical investigations of alleged lunar influences on our weather did remain on the agenda well into the 19th century - the names of Olbers and Arago stand for many contemporaries.

Moreover, the Earth's atmosphere was an object of fundamental interest to astronomers not only because of its influence on observational results, but also because it was the only accessible planetary atmosphere. Not only were sizeable gaseous envelopes of planetary bodies (with the apparent exception of only the Moon) considered as commonplace (Herschel, Schröter, etc.); the quest for understanding them was also an importent issue. As early as 1780, J. E. Bode tried (following Euler) to explain the blue colour of the sky by means of blue (scattering?) particles in the upper atmosphere; consequently, he raised the question of whether the red colour of Mars was due to this planet's surface materials or rather to a different atmospheric composition. In our time and age, a new and very successful branch of science called Comparative Planetology did emerge from apparently very modern roots; two centuries ago, its basic objectives were an undisputed part of everyday astronomical research.

The Seeberg conference took place in an environment of (prolonged) change from natural history to modern science. In astronomy, the interaction between descriptive, phenomenological methods and quantitative investigations and results was particularly fruitful. Many of the results did emerge slowly: Seemingly atmospheric phenomena, like meteors, did turn out to be of extraterrestrial origin; objects like ejecta from lunar volcanoes eventually became mere figments of imagination. In both cases, unprejudiced observations and their theoretical evaluation were necessary. Chladni's work (1794) on the origin of meteorites did need to be verified by the »stone shower« of l'Aigle (1803). And the quest for the missing planet between Mars and Jupiter did not only produce literally many results - it also led to the »Theoria Motus«.

Bibliographical details:

Wolfgang Kokott: Atmospheric tides and other relationships: »Interpreting the Phenomena« at the time of the Seeberg conference. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae ; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. 87-88.