Oh, what a beautiful morning!

I refer, of course, not to this morning as you read your Irish Times, which for all I know may well be dreary, dark and dismal…

I refer, of course, not to this morning as you read your Irish Times, which for all I know may well be dreary, dark and dismal, but to the time at which I write, the first morning of the first new millennium. It augurs well: the sky is blue, the wind is calm, the sun is shining on dew-laden lawns, and as you walk outside in the bright, crisp air you scatter round you, as you lightly pass, A shower of diamonds from each blade of grass.

It is these dew-diamonds, rather than the sunshine or my surviving to the third millennium, that account for my euphoria. I have just observed for the first time a phenomenon memorably and somewhat idiosyncratically described by Benvenuto Cellini in his autobiography. Cellini is best remembered as a goldsmith and sculptor of quite awesome talent, but among the many, often bizarre, theories recorded in his book is his personal interpretation of the heiligenschein.

"An aureole of glory," writes Cellini, "has rested on my head. This halo can be observed about my shadow in the morning from the rising of the sun for about two hours, and far better when the grass is drenched with dew." It is, he continues, "perhaps the most remarkable circumstance which has ever happened to anyone. I relate it in order to justify the divinity of God and of his secrets, who deigned to grant me this great favour."

Your humble scribe, alas, can claim no corresponding godly preferment. The heiligenschein is a well recognised occurrence, comprising a very noticeable brightness surrounding the shadow of the head, which occurs when the early morning sun casts our long shadow on the dewy grass.

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Drops of dew are like little spheres of water. They act like lenses, and rays of sunlight falling on them come to a sharp focus just behind the drop, on the surface of a blade of grass. When we look at the dewdrop from a certain angle, the water again acts as a lens to allow us to see this shining image very clearly - and the geometry of the whole ensemble is such that we can see this image only when our eyes are pretty much on a line between the sun behind us and the drop of dew.

This, of course, almost coincidentally is the position which allows the shadow of the head to appear just beside the drop in question. It was the amalgamation of a myriad of such images that gave the halo around the shadow of Cellini's head - and mine.