Sea fog is an eerie, persistent and claustrophobic phenomenon. Unlike its inland counterpart, fog at sea is not dependant on calm weather for its formation; on the contrary, it requires a certain movement of the air as a necessary condition for its occurrence. It is a particular case of a general phenomenon known to meteorologists as advection fog.
Advection fog occurs when warm, moist air finds itself carried, or "advected", over a cold surface. Air, as we know, gradually adopts the temperature of the surface underneath it, and if this temperature happens to be below the dew point of the air - the temperature at which condensation takes place - then fog may form. This type of fog is a frequent visitor to the US coast stretching from Massachusetts up to Newfoundland, when warm, moist, southerly winds, having absorbed an abundance of moisture from the Gulf Stream, suddenly find themselves over chillier waters as they move north.
Forty-five years ago yesterday, there was sea fog near Nantucket Island, off Cape Cod, and two ocean liners, steaming in opposite directions, moved through it at considerable speed. One was the Stockholm, which had just recently left New York on its way to Scandinavia. The other was a luxurious Italian liner, designed "as a living testament to the importance of beauty in the everyday world". It was headed for New York, and was called the Andrea Doria. The Andrea Doria was headed south-east with engines running at full speed, her captain anxious, despite the fog, to make up time that had been lost earlier in the voyage. He was confident the ship's powerful radar would identify any other vessels in the area in ample time to alter course. Indeed as the two vessels approached each other, each appeared clearly on the other's radar, but confusion seems to have arisen as to whether the "Rules of the Road" - which require ships to pass each other "port-to-port" - should apply in this particular case or not.
At 11:06 p.m. both ships finally sighted each other through the thickening fog, and a tragic pas-de-deux ensued. The Stockholm swung to starboard, while the captain of the Andrea Doria called "All left!" and brought his ship directly into the other's path. At 11:09 p.m. the reinforced bow of the Stockholm pierced the starboard side of the Andrea Doria, inflicting a gash that was more than 30 feet in length. It was a fatal wound; 12 hours later the Andrea Doria slipped forever below the surface of the sea, and 50 of the 1,700 souls aboard were drowned.