If the appearance of a ship apparently floating above sea level is a very rare event in the UK, two within two weeks should be an even more unlikely event.
But 13 days after a giant tanker drifted in front of the water off Cornwall, the effect of an optical illusion known as a superior mirror image, similar images of the cruise ship, the Jewel of the Seas, on the Dorset coast appear.
When the Cornwall illusion took place, BBC meteorologist David Braine said it was common in the Arctic, but that it could occur “very rarely” in the UK during the winter.
This is caused by a meteorological phenomenon called a temperature inversion. Normally the air temperature drops with increasing altitude, making mountain peaks colder than the foothills. But in a temperature inversion, hot air sits on top of a band of colder air and destroys our visual perception. Both the cases in Cornwall and Bournemouth were caused by cold air that lay over the relatively cold sea, with warmer air above.
The coronavirus pandemic led to cruise ships that would normally be in distant places being anchored off the English coast.
The Bournemouth Echo published photos taken Wednesday night of the Jewel of the Seas and Anthem of the Seas, many of which were shared on the camera club’s Facebook page.
David Morris said he was ‘stunned’ when he spotted a giant tanker floating above the water on March 4 as he looked out to sea from a hamlet near Falmouth in Cornwall and took a photo for posterity.
Excellent aerial reflection has long enabled photographers around the world to take striking images of ships, yachts and other vessels that seem to be floating in the air. One possible clue that the face is an aerial mirror is the lack of detail below the waterline of the vessel: for example, an aerial mirror of a ‘floating’ yacht lacked the lower hull and keel.
More optical illusions are the “inferior air mirrors” that give rise to apparent oasis in the desert and puddles on hot summer roads, caused by cooler air sitting on a layer of warm air, directly above a road. When sunlight comes out of the sky, the air approaches near the hot surface, and is then bent upwards again towards the eye of the observer, and it seems as if the air is reflected on the road.