Wonder of day turned into night

A total eclipse of the Sun is about as astonishing a treat as nature provides. For a few minutes, the Moon exactly covers the Sun, making night from day and displaying the otherwise invisible solar atmosphere. This book celebrates eclipses of both Sun and Moon (the rather less spectacular sweeping of Earth's shadow across the lunar surface) from many directions, including the complex history of eclipse observations and their declining but still real scientific value.

Serge Brunier and Jean-Pierre Luminet are respectively a science journalist and photographer, and a senior astronomer. This book, well translated from French by Storm Dunlop, makes the most of their strengths. It displays a deep understanding of history, some gripping science and a wealth of images, both of eclipses and of the many ways in which they have been represented over the years.

The vast amount of eclipse wisdom they uncover raises one question straight away. Why does it exist? Belgian astro-mathematician Jean Meuss has shown that it takes 4,000 years for a total solar eclipse to be seen from every spot on Earth. If people do not travel to see eclipses, their chance of seeing one at home is minute. So how did, say, the Chippewa Indians develop customs about what to do when one occurs? Is it possible that European reporters happened to see how the Indians responded on one occasion rather than a deeply embedded tradition?

By contrast, it seems certain that most cultures that did not know why eclipses happened feared them. Even in modern times, one of the authors saw villagers in Colombia go indoors as a total solar eclipse approached, leaving the tourists to witness it. Emergency steps to persuade the Sun or Moon to reappear, or to get the creature that had swallowed one or other to regurgitate it, are widely reported. Rare exceptions included the Eskimos and Aleuts, who thought eclipses were caused by the Sun and Moon gods paying a quick visit to Earth to check things were going well here.

The cultural power of eclipses may be one reason why they seem to have marked so many significant events, including the birth of Mohammed, the fall of Constantinople, the death of Gordon of Khartoum and, most famously, the Crucifixion. The latter lunar eclipse may have been that of November 24 AD29, visible at Jerusalem, which a Greek historian says coincided with an earthquake, agreeing with the biblical account.

More recent eclipses have become scientific rather than spiritual landmarks, none more so than that of 1919. It was used to show the pull of the Sun's gravitation on passing starlight, confirming the theory of special relativity. Asked what he would have thought if the effect had not appeared, Einstein answered that he would have known the experiment had gone wrong.

In the modern era, spacecraft allow the Sun's atmosphere to be observed continuously, eroding the value of observations snatched during eclipses. But observations from bigger and better equipment at ground level are still valuable for research and teaching. In 1991, a total eclipse swept across Hawaii and gave the world's biggest collection of great telescopes, the Mauna Kea observatory, a grandstand view that will not be repeated for centuries.

Yet as eclipses have lost some of their scientific importance, they have regained their aesthetic value as a miracle unique in the solar system. Nowadays, eclipse tourists cross the Earth to see them, a development that astronomer Camille Flammarion anticipated in 1880. Because the Sun's shadow lands on Earth at random, dedicated eclipse viewers see the world without regard for normal tourist considerations. A few eclipses, such as the 1999 eclipse that passed from England to India, visit many major cities, as a special chapter in this book shows. But most do not. Aficionados can find themselves in the Arctic for one trip, on a ship in mid-ocean for another, and in Africa for the next. Brunier is an addict, and readers might well catch the bug from his accounts of eclipses seen from the Altiplano of Bolivia, the temples of India and the volcanoes of Hawaii.

If you want to take up eclipse chasing, the book's maps of future eclipses will tell you when and where to be, and its illustrations will tell you what to expect and how to observe in safety. There are explanations of the eclipse cycle, or Saros, and of the fact that in the far future, there will be no more solar eclipses as the Moon's distance from the Earth increases.

The book also provides generous coverage of lunar eclipses and of related events such as occultations and transits. There is even space to reveal how planets in other solar systems are being detected as they eclipse their own star as seen from Earth. Eclipses still make cutting-edge science thousands of years after they first caused dismay to our ancestors.

Martin Ince is deputy editor, The THES .