Or old words with new definitions. Like ‘planet’. The row over Pluto’s status was considerable, mainly because ‘planet’ had never been formally defined. When the hunt for Planet X found not one tidily orbiting tenth planet, but hosts and shoals of remote objects, some on the same scale as Pluto, argument raged, but as of 2006, we do have a definition (of sorts).
The arguments are to some extent ridiculous. Whatever we call it, Pluto will orbit exactly as it did. But if detailed inventory and classification was the necessary starting point for zoology and botany, it’s also important in understanding the formation and behaviour of the solar system.
Schilling samples the lives, careers, dedication, and rivalries of the astronomers who searched for new planets – the earliest group formed as early as 1800 and called themselves the ‘Celestial Police’! He lists the discoveries of the major asteroids and bodies in the outer solar system, and gives a little of what is so far known about them, plus theories for their creation and interaction. There are insights into the politics of the IAU – our current celestial police. We also get a taste of the speculations generated by a febrile collection of crackpots (still ongoing, of course).
The main work in reading the book is to sort out in one’s own head the terminology of it all: asteroids, certainly, but also centaurs, plutinos, ice dwarfs, minor planets, Kuiper Belt objects, the scattered disk, the Oort cloud, cubewanos, plutoids, vulcanoids, long- and short-period comets, trojans, Earth-grazers, planetesimals.
Confused? So am I. But the story of the Solar System is all the richer for the details, and in 2015 the New Horizons probe will be looking at Pluto and its moons. If the technology works, it should be fascinating.