"Five minutes before totality, everything became strangely still, and over the hills we could see the approaching area of gloom. Then, suddenly, totality was upon us. The corona flashed into view round the dark body of the moon, a glorious aureole of light which made one realise the inadequacy of mere photographs." This is how the astronomer Patrick Moore describes an eclipse of the sun, the phenomenon due to occur next Wednesday morning, when the moon will move in front of the sun's face as seen from earth.
Unfortunately, Ireland lies just outside the "path of totality" - the sliver of the earth's surface, about 60 miles wide, where the sun will be totally obscured for about two minutes at any given point. As a result, no part of the island will experience the awesome sight described by Moore, and indeed the diminution in sunlight may be barely perceptible. The same is true for most of Britain, except for Cornwall and parts of Devon, which are expected to be invaded by up to two million visitors eager for the experience of a lifetime. For although a total eclipse of the sun happens somewhere or other in the world every 18 months or so, the last one visible from Britain occurred in 1927 and the next is not due until 2090.
Indeed, the track of next week's eclipse - from southern England through northern France, central and eastern Europe, Turkey, the Middle East, Pakistan and India - means that it will probably be watched by more people than any other in history. "Eclipse tourism" is in full swing in several countries - notably Romania, which has been promoting the event for the past two years in the hope that it will boost the country's nascent tourist industry. Attractions on offer include eclipse-day tours of "Dracula's castle" and a concert in Bucharest by Pavarotti.
The eclipse will bring dangers as well as opportunities. In particular, there are fears that people will cause serious and irreversible damage to their eyes by gazing directly at the sun. In Britain, there has been some conflict between the chief medical officer of the Department of Health, who has advised people to watch the event only on television, and a number of astronomers, who have pointed out that during "totality" - the short period when the sun is completely blocked by the moon - it is safe to view the eclipse with the naked eye. But here in Ireland, where the degree of eclipse will vary from 85 per cent in Derry to 90 per cent in Dublin and over 95 per cent in Cork, there is no such dispute: all experts agree that people must not look at the sun at any time, and that even the darkest sunglasses offer no protection against retinal burning. Many authorities have cautioned even against using the special mylar lenses on offer (which should carry a CE symbol to show they have been properly made) because of the risk of a tiny scratch or hole, invisible to the eye, which would allow dangerous ultra-violet radiation to reach the retina.
There are two safe ways to watch the eclipse: by using a card with a pinhole in it to project an image of the sun onto a sheet of paper; or on television. These may sound like a poor second-best to the experience of "totality" (impossible in Ireland, anyway); but they are infinitely preferable to lasting loss of sight.