SPEAKING of the Pope's weathermen, as Weather Eye did yesterday if you remember, it is worth noting that one of the most eminent of them in the present century was Irish - well, almost Irish, anyway - as Irish, perhaps, as the average player on our national soccer team.
Daniel O'Connell was born of Irish parents in Rugby, England, and studied for the priesthood here in Ireland. He joined the Jesuits and, specialising in astronomy, was for 14 years in charge of the Riverview Observatory in Australia before reaching the pinnacle of his career as Director of the Specola Vaticana, the Pontifical Astronomical and Meteorological Observatory as Castel Gandolfo, outside Rome. There Father O'Connell became an expert on the green flash. Let me hasten to explain.
The green flash is a very rarely observed momentary eruption of green light emanating from the upper edge of the setting sun. As rays of light pass through the atmosphere, they are bent or "refracted" a little, causing the image of the sun that we see near the horizon to be slightly higher than it ought to be. But the amount of refraction depends on the wavelength of light - so the "blue image" of the sun is displaced "slightly higher in the sky than its "red image". In the absence of any other complication, therefore, the setting sun ought to have blue rim along the top.
But blue light is "filtered" very effectively by the molecules of air and dust, leaving the colour green as the shortest wavelength to survive the long trip through the atmosphere when the sun is near the horizon. Normally, however, this green upper rim cannot be seen with the naked eye. It only becomes visible when a very rare, almost freck, thermal structure of the atmosphere makes the air act like a "glant magnifying glass then, as "the green rim passes through this magnifying region it is momentarily enlarged to producing the hauntingly beautiful and spectacular green flash.
As it happens the Vatican observatory, 1,200 feet above sea level on the rim of the crater lake of Albano, and with a clear view across the Roman campagna to the western horizon 50 miles away on the Tyrrhenian Sea, is ideal for observing this phenomenon.
Father O'Connell studied it very closely during the 1950s he also investigated many historical sightings over the centuries and compiled his knowledge into a book which is still the standard work upon the subject. Rarely, indeed, will you see the phenomenon mentioned in scientific circles without reference being made to The Green Flash and Other Law Sun Phenomena, by D. J. K. O'Connell, 1958.