The passage of the moon’s shadow across the face of the Earth is a strange mixture of normally separate scales and sensibilities, personal and astronomical at once. Total eclipses of the sun are outstandingly romantic yet remarkably regular, measuring out time in periods precise to the second and longer than lifetimes. Indeed, it is possible to predict eclipses farther off into the future than it is possible to predict there will be humans to see them.
The celestial clock ticks regularly. It also ticks slowly. There are fewer than a hundred total eclipses of the sun every century, and each visits only a thin swath of the world. There are exceptions–the coast of Angola will see total eclipses in both 2001 and 2002, and some parts of Turkey graced by the forthcoming eclipse on Aug. 11 will see another one on March 29, 2006–but on average a given spot on the globe will be passed over by a total eclipse only once every 410 years. The brief eclipse Woolf saw from the grouse moors of Yorkshire was the first to cross England since 1724.
Woolf and her companions, like the millions who will rush around Europe for the eclipse of Aug. 11, were helped by a tourism industry wise to the eclipse’s potential. Earlier scientific enthusiasts, drawn by the possibility of observing the atmosphere of the sun–only visible when its brilliant disk is blotted out–and the mountains of the moon–which break the edge of the sun into a chain of brilliant beads as the eclipse begins and ends–traveled farther in harder conditions. Jules Janssen, a 19th-century French ophthalmologist turned astronomer, tracked down eclipses and related astronomical phenomena to the far corners of Siam, Japan and Peru, not to mention establishing a solar observatory high up on Mont Blanc. During an Indian eclipse he made observations of the corona–the sun’s outer atmosphere–which were later to show the existence of a new element. Not detected on Earth for a generation after that, helium, named for the Greek sun god, is now known to be the second most common substance in the universe. Janssen was so drawn by eclipses that he would not let a little thing like a war get in his way. In 1870, like a hero from Jules Verne, he drifted over the heads of the Prussian Army in a balloon to escape besieged Paris for an eclipse in Algeria.
Today eclipses excite less scientific interest. Telescopes in orbit can block out the sun any time they want with a simple shutter, and while our nearest star still has its mysteries–what exactly is it that makes the corona so much hotter than the surface below it?–they are not so profound as once they were. We know why the sun shines; we have visited the mountains of the moon. But that does not detract from the experience of the eclipse. It is still the most striking illustration of the workings of the cosmic clockwork that most of us will ever see: an astonishing moment in which the everyday world falls apart and cold darkness reveals the unearthly scale of creation. Then the day bounces back–and it is all over, for Western Europe, till 2081.
