2 - Examination of the question whether the rotation of the Earth on its axis by which it brings about the alternation of day and night has undergone any change since its origin and how one can be certain of this, which [question] was set by the Royal Academy of Sciences in Berlin as the prize question for the current year (1754)

Summary

EDITOR'S INTRODUCTION

In 1752, the Prussian Royal Academy of Sciences in Berlin announced its prize essay question on whether the rate of rotation of the Earth on its axis would decrease over time and if so, how one could know this to be the case. The deadline for submissions was initially set for 1754, though it was later extended, unbeknown to Kant, to 1756. During the summer of 1754, after leaving his employment as house tutor for Count Keyserlingk's three sons and returning to Königsberg (possibly supervising a member of the Keyserlingk family studying at the university then), Kant wrote an essay in response to the prize essay question. However, instead of submitting this essay to the Academy, he published it, in two parts, in the June 8 and June 15, 1754 issues of the Wöchentliche Königsbergische Frag- und Anzeigungs-Nachrichten, a weekly newspaper with articles on sundry topics of interest to the citizens of Königsberg. The essay that eventually won the prize for this question was written by Paolo Frisi (1728–84), an Italian mathematician and astronomer, who argued that the Earth's rate of rotation would not decrease over time.

Rather than pursuing historical comparisons of potentially unreliable data on the length of years and days in the past, Kant, following Newtonian principles, considers what external causes could effect any changes in the rotation of the earth. If the earth were a completely solid and homogeneous spherical mass, the Sun and the Moon (which are the two bodies that have the greatest gravitational effect on the earth) would act equally on all parts of the Earth and there would be no (cause for a) diminution of its rotation. However, given that the Earth contains a considerable amount of liquid (primarily water in the form of oceans, seas, and lakes), it is not a perfectly solid mass, and for that reason, the gravitational effect of the Sun and the Moon causes tides. But the tides that are caused by the Sun and Moon move contrary to the direction of rotation of the Earth and thus cause a decrease in the rotation around its axis.