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Abstract
Uranus and Neptune are two planets not known in ancient times. Once discovered, however, astronomers were eager to obtain their vital statistics. Of course once Voyager flew by them everyone had the information, but before there was Voyager, there were many attempts to measure things like the rotational period, the mass, the brightness, etc. This is the story of the two people who obtained the rotational period of both planets before Voyager got there. They confirmed that the spin of Uranus is retrograde and that of Neptune direct. Uranus rotates on its side. Their estimates for the periods of rotation are, for Uranus, 24 ±3 hr., and for Neptune, 15 ±3 hr.
Introduction
FOR MOST OF HUMAN HISTORY humanity knew of only five planets (plus our own): Mercury, Venus, Mars, Jupiter, and Saturn. These are the planets that are visible to the naked eye at various times during the year. We learned relatively recently that there are two other planets in our Solar System: Uranus and Neptune. Note the proper pronunciation of Uranus (accent on the first syllable).
First a little history on Uranus and Neptune. The question being what did we know before the Voyager flyby of Uranus.
Uranus had been observed on many occasions before its recognition as a planet, but it was generally mistaken for a star. Then Sir William Herschel observed the planet qua planet on March 13, 1781. This was the first planet added to the Solar System since the dawn of history. See Figure 1 for a drawing of the telescope he used. He decided to name the new planet Georgium Sidus (George's Star), in honor of his new patron, King George III of England. As one might expect, this was not popular outside England. Bode (a German astronomer) opted for Uranus, the Latinized version of the Greek god of the sky, Ouranos (the only planet with a name of Greek origin). Bode argued that just as Saturn was the father of Jupiter, the new planet should be named after the father of Saturn. Ultimately, Bode's suggestion became the most widely used, and became universal in 1850 when Her Majesty's Nautical Almanac Office, the final holdout, switched from using Georgium Sidus to Uranus.
Uranus is the...