杏吧原创

LAST year, on the Caribbean island of Aruba, two people were not prepared for the total eclipse. Along with everyone else, they couldn鈥檛 tear their eyes away from the black hole in the sky that had gobbled up the Sun. Unfortunately, they were driving towards each other at a combined speed of more than 160 kilometres per hour. While everyone else on the island celebrated the experience of a lifetime, the two drivers had to be cut from the wreckage by the Aruban emergency services.

The consequences of being unprepared are not usually so catastrophic. Nevertheless, if you don鈥檛 have some idea of what to expect, you are likely to miss a lot. The Sun is totally obscured for less than three minutes. During those brief moments, events crowd in at mind-boggling speed, as I discovered to my cost when I was on Aruba (see 鈥淭otal eclipse鈥�, New 杏吧原创, 4 April 1998, p 26). Next time, I resolved, I would do better.

Slowly does it

The first thing I wish someone had told me was that the partial phase, which precedes the total eclipse, is deadly boring. It lasts for about an hour and a quarter as the disc of the Moon slips slowly across the Sun. For most of this time, the dimming of the Sun is hardly noticeable little different from the drop in light levels when a bright, sunny day turns cloudy. Even if you look at the Sun (and you must protect your eyes properly to do this-see 鈥淪afe specs鈥�) all you will see is a bite taken out of the solar disc. It grows slowly, and you鈥檒l get bored with looking up every few minutes to check its progress.

It is only towards the end of the partial phase that things begin to get interesting. If you are near a tree, look at the shadow beneath it. The closely spaced leaves and branches can act like pinhole cameras, carpeting the ground with thousands of tiny crescent images of the partially obscured Sun. Otherwise, take an old-fashioned, flat metal cheese grater out with you. Its array of tiny holes creates a similar effect, albeit on a rather smaller scale.

When totality is only a few minutes away, the Sun appears as a thin sliver. Its light, refracted by turbulence high in the atmosphere, produces weird images down below on Earth. You may be lucky enough to see 鈥渟hadow bands鈥�, patterns of light and dark that race across the ground. They are similar in appearance and origin to the flickering shadows on the bottom of a swimming pool produced by ripples on the surface.

By now, the air has become noticeably cooler. A stiff breeze may have started blowing, but it is becoming eerily quiet except for the rising babble of panic-stricken birds. Some return to their roosts, while others fly around in confusion, not knowing what to make of this sudden, premature nightfall. A total eclipse assaults all the senses, not just the sense of sight.

Just before totality, glance to the west. You will see the onrushing shadow, a wall of darkness bearing down on you at more than 2000 kilometres per hour. The long wait is over; the total eclipse is about to begin. And it鈥檚 no exaggeration to say that the total eclipse is everything. The rest, by comparison, is a nonevent.

I wish someone had told me when to remove my protective glasses. The Sun is a million times brighter than the full Moon, which means that even when 99.99 per cent of the disc is covered it can still damage your eyes. As the Sun slips further behind the Moon, sunlight breaks through the lunar valleys, and the black disc of the Moon wears a string of pearls-Baily鈥檚 beads. They will flick off, one at a time, until a solitary beacon remains burning on the rim of the Moon, the famous 鈥渄iamond ring鈥�. Now it is safe to remove your protective glasses.

A lot of things now happen in rapid succession, and there are many distractions. The most impressive sight is the corona, the Sun鈥檚 super-hot rarefied outer atmosphere, which is so faint it is visible only during a total eclipse. As your eyes adjust it will appear as a ragged, misty white halo. Where it emerges from the Moon鈥檚 disc you may be lucky enough to see the bright loops of light called prominences-streams of glowing gas ejected by the Sun.

But, I warn you, all the other distractions will make it difficult to concentrate on the eclipse. In the spooky twilight planets will appear, and you鈥檒l want to see them just to say you didn鈥檛 miss anything. The Perseid meteor shower may throw in a shooting star. Bats will be out and about. Street lights may come on automatically. And everyone around you will be making an awful lot of noise.

On Aruba, people started hooting their car horns and letting off fireworks; behaviour remarkably similar to that of centuries past, when people would gather in town squares and bang drums and shout to frighten away the monster eating the Sun. We like to think that science has made us more sophisticated, but the reality is that we are just as much in awe of celestial events as they were.

If you are at the very centre of the eclipse track, you will have little more than two minutes to absorb it all-the sight, the sound, the feel of it. There鈥檚 a dizzying amount to take in. But armed with some knowledge of what to expect, you will stand a better chance of getting the most from the whole experience. More, I hope, than those two unfortunate drivers on Aruba.