Adolf Marcuse

Adolf Marcuse (1860 - 1930) was an observer throughout the 1890s in a program to measure the amount and direction of the very slight oscillations of Earth's axis of rotation, now known as the Chandler wobble (named after Seth Carlo Chandler).

Chandler wobble
These motions had first been detected in Berlin in 1884-1885, though they had been predicted theoretically by Leonhard Euler in 1765. In the years 1889 - 1891, Marcuse worked at the Royal Observatory (Berlin - Postdam) with a universal transit instrument, a telescope mounted in such a way that it could rotate in any direction and swivel so that it could look straight up. It also equipped with vernier scales and micrometers capable of delicate adjustments and measurements of angles.

Marcuse was looking for repeated, minute variations in the apparent positions of pairs of stars. These variations could be interpreted as indications of slight variations of the latitude of the observatory. These were what one would expect if Earth's pole of rotation was slightly and continuously displaced. The phenomenon provided a necessary correction when preparing maps of star positions, and the Royal Observatory was at that time preparing such a map.

In 1891, Marcuse had traveled to the Hawaiian Islands and made the same observations. If Earth's pole were wobbling in an irregularly circular path over a period of months, the same latitude variations should be seen in Hawaii that were seen in Berlin, but they should be in the opposite direction. Marcuse showed that this was the case. The measurements confirmed an oscillation of Earth's axis of 0.3 arcseconds over a period of 14 months. This was a displacement of the pole of just under 10 meters.

Astronomers greeted these measurements with great interest. The amplitudes of the oscillations were exactly confirmed by those measured by Seth Chandler at Harvard Observatory. Meanwhile, Chandler also made an attempt to confirm the motion historically by going back to look at observatory records of the past 150 years indicating similar shifts of star positions. These historical researches uncovered a 12-month variation superimposed on the 14-month period and set off a controversy even more absorbing than the measurements themselves. What could be causing the variation? Since it was a "free motion", it should ultimately "damp out" and cease, unless re-excited. But 150 years of records showed no damping. There was no candidate mechanism for the excitation to keep the motion alive.

The phenomenon was of sufficient interest that in 1899 an agreement was reached to establish the International Latitude Service, with four observatories to be constructed in the Northern Hemisphere, 90° of longitude apart from one another, all four at the same latitude, to measure continuously the shifting of the pole.