`The Little Flower" has been lying low of late. Her relics, however, are presumably still on tour around the country, and will no doubt depart our island in due course with as much pomp and circumstance as they arrived with.
But it is not St Therese of Lisieux who concerns "Weather Eye" this morning, but her namesake, St Teresa of Avila, or to be more precise, Bernini's sculpture of the Ecstasy of same.
The story is a strange one. St Teresa, according to her, was quietly saying her prayers one day when an angel came to her: "In his hands I saw a long golden spear and at the end of the iron tip I seemed to see a point of fire. With this he seemed to pierce my heart several times, so that it penetrated my entrails. When he drew it out, I thought he was drawing them out with it, and he left me afire with the love of God."
Now whatever one's interpretation of this incident, it has left a tangible and magnificent legacy in the form of The Ecstasy of St Teresa of Avila by Bernini in the Cornaro Chapel in Rome. The sculpted figures of the ecstatic St Teresa and her aggressive visitor are perfection in their execution. To a meteorologist, however, the most striking aspect of the work is a brilliant representation in the background of the optical phenomenon of crepuscular rays. A crepuscular ray occurs when a beam of sunlight passes through a gap in the clouds, and the contrast between brightness and shadow provides a well-defined shaft of light.
When the sun is high in the sky on a day that is almost overcast, crepuscular rays can sometimes be seen directed downwards at a slight angle to the vertical. They stand out clearly because the light is scattered by mist and dust suspended in the atmosphere.
But it is when the sun is low in the sky in the late evening or early morning that crepuscular rays can be seen at their most spectacular and brilliant best. The rose-coloured sunbeams often appear to diverge upwards from behind a distant cumulus or cumulonimbus, spreading their crimson stripes of light and shadow in a huge fan.
This fan-like shape is an optical illusion, deriving from the same quirk of linear perspective that makes straight railway lines, or the two sides of a long wide street, appear to meet in the very far distance. It is from its striking appearance in this particular guise, when the sun is near the horizon, that the phenomenon gets its name; crepusculum is the Latin word for twilight".