Pisces: expect bad news

According to the publishers, this book is the first in a series on bad science. "Bad Medicine" is promised next, and the scope for more must be endless. "Bad Genetics" is certainly one to look forward to.

Unlike ill-informed medicine, bad astronomy does not kill anyone. But the planet is still awash with people who think Nasa faked the Moon landings, that summer occurs because the Earth is nearer the Sun at some times of year, or that the universe is 6,000 years old. And that is before we even get to the horoscope page.

Philip Plait collects ill-thought-through astronomy and runs a website, badastronomy.com, to point up some of the worst. The number of ways in which people can misunderstand the universe is impressive. Plait uses them in two ways - first as canards to be dismissed, but also as ways of communicating sound science. The fact that the Earth rotates at an angle to its orbit round the Sun, the true cause of the seasons, is well explained, as is the fact that southern hemisphere summers are indeed slightly hotter than those in the northern hemisphere, because the Earth is closest to the Sun in January. But he does not tell us that because planets move faster when nearer the Sun, northern hemisphere summers may be cooler, but they are also a few days longer than those in the south.

Another basic case he tackles is why the sky is blue. The simple answer is that blue light is scattered in the atmosphere much more than light of longer wavelengths. So red light from the sun comes straight at us while blue light comes from all directions. But this leads to more worthwhile questions about how our eyes work and what sunlight is. It also brings us to the question of why the sea is blue. A blue sea is reflecting a blue sky (not the other way round as some imagine); and, more important, water preferentially absorbs red light and reflects blue, a non-astronomical insight that Plait explains well.

But Plait really gets into his stride with bigger and better delusions, expressing special scorn for astrology (perhaps something of an open goal for him to shoot at) and the folk who think people never went to the Moon. Their arguments - for example, that no stars are seen in pictures showing Apollo astronauts on the Moon - are quickly dismissed, as is the man who thinks Nasa will not allow the Hubble telescope to observe the Moon because of the aliens it would reveal. Plait even has a go at creationists, though he wisely limits his attack to their astronomical arguments. All this and UFOs, the origin of the universe, eye damage through eclipse watching, and the claims of Immanuel Velikovsky (where, as he shows, science shot itself in the foot by over-reacting to a totally risible book) make Bad Astronomy a rich stew.

There are problems of style, and some less-than-accurate astronomy. The writing is baggy, telling more than one might care to learn about famille Plait, has too many exclamation marks and uses "spastic" as a colloquialism without good reason. It is not true that asteroids are traditionally named after women; number 8380 is named after Tooting, the London suburb. Refracting telescopes bigger than 20 inches are highly feasible; and the 200-inch telescope at Mount Palomar was finished in 1948, not 1936. Yet the book might be a better student introduction than many more sober tomes.

Martin Ince is deputy editor, The THES .