Today every schoolchild learns that our solar system contains nine planets in orbit around the sun--plus a variety of other bodies such as asteroids--but as Richard Baum and William Sheehan describe in In Search of Planet Vulcan,
the discovery of these facts was far from straightforward. In a book rich with historical anecdotes, Baum and Sheehan depict centuries of efforts to enumerate the inhabitants of our solar system. In some cases the successes are stunning proof of the veracity of Newtonian mechanics; in others, such as the quest for a hypothetical planet "Vulcan" orbiting well inside Mercury, the fallacies and failures are equally staggering.
Before it spawned Spock, the "planet" Vulcan was proposed to orbit inside Mercury to account for a chronic deviation in Mercury's predicted orbit. When amateur astronomer Edmond Lescarbault claimed to see the culprit, case closed, right? But try as they might, no one else could observe the fugitive; still, theoretically, its existence suited world-class mathematician Urbain Jean Joseph Le Verrier, so he offered proof. A curiosity in the history of astronomy, the case demonstrates how a scientific authority can get the whole world barking up the wrong tree. Baum and Sheehan readably recount how Le Verrier made his name by explaining perturbations in Uranus' orbit in terms of an unknown planet, duly discovered as Neptune in 1846. The authors give a merry rendition of astronomers tramping to solar eclipses to glimpse Vulcan, the repeated futility of which finished it off, but the problem of Mercury's orbit persisted. Einstein eventually solved it: a curvature of space-time, not a planet, explained Mercury's orbit. Enjoyable recreational reading for astro-buffs. Gilbert Taylor