Camera conjures up the horizon

It was Christmas on December 25. Many experienced subdued moments around the Christmas tree and Christmas brunch, but editor Hans Steketee walked on the beach of Kijkduin around noon. The weather was sunny and clear but cold and there was an easterly wind. Steketee looked downwind at the water and saw something strange in the distance. The horizon was not straight and straight as in drawings and paintings, it was jagged. He took a picture and sent it on. “What do you think of this?”

You could clearly see wave crests sticking out above the horizon. Those must be the tops of huge waves because you calculates easily that a person of average build standing close to the water on the beach has his horizon three miles away. Even more so if you take into account that light rays in the lower air layer are always weakly curved. This is because the density of the air decreases with height.

After some digital back-and-forth, the conclusion was reached that distant waves do not necessarily have to be extremely high to rise above the horizon. You could call it the Gerrit Krol insight. Writing mathematician Gerrit Krol stood on Mont Blanc in the early 1990s and was surprised to see the much lower Matterhorn well above the horizon. On a Flat Earth this had couldn’t, but the spherical shape makes it possible. That’s one.

Special temperature distribution

Another effect may also play a role in the Kijkduin case. The air temperature on December 25 was 1 to 2 degrees Celsius, it had frozen at night. The sea water was still at 7 or 8 degrees. The offshore wind thus carried cold air over relatively warm seawater. That may have reduced the curvature of the light rays just mentioned and brought the horizon closer. Minnaert, often quoted here, discusses that in part I of The physics of the free field, nota bene in relation to waves protruding above the horizon. He calls it “the convex surface of water.” Due to the special temperature distribution in the lower air layer above the sea, the earth appears more spherical than usual. Especially if you look at the horizon from a low position.

Whether this actually happened is unclear, but in any case the considerations bring us compulsively to the ghostly floating ships in the photo. On September 21, editor Arlen Poort photographed a cruise ship sailing up the Loire. Poort sat on the north side of the estuary, at the Pointe de Chémoulin, shooting from a fairly steep beach. He estimates the height of the camera above the water at more than 2.5 meters. “Nothing seemed out of the ordinary until I looked at the photo and saw the ship hovering over the water.” Poort attributes it to imperfections of his smartphone with some hesitation.

Practically on the horizon

The glare on the water shows that the photo was taken in the direction of the sun. It was 2:19 p.m., according to the site suncalc.org, the sun was 6 degrees past the south. The intersection of the Port-ship sightline and the concreted fairway to Saint-Nazaire (to be found on nautical charts) provides the position of the cruise ship. It feeds 7 km away. A camera height of more than 2.5 meters puts the horizon at about 6 km. Practically sail the ship on the horizon and that’s how Poort remembers it. But the photo shows the horizon a lot lower. Weird.

There is a relationship with the Kijkduin observation. Also in France, the land wind, which was northeast, blew from the camera to the object. But this wind brought relatively warm air (22 degrees) over a relatively cold sea (estimated 18 degrees). So chance on a where water surface à la Minnaert. That could raise the horizon a bit in relation to the ship.

It remains to be guessed what it represents in practice. Time to contact physicist Siebren van der Werf who was in at the time The Nova Zembla phenomenon (Historische Uitgeverij, 2011) explained why, and reconstructed how, Barentsz and Van Heemskerck in January 1597 saw the sun after their hibernation two weeks earlier than seemed possible. It was a mirage, caused by an unusual temperature build-up in the low air layers around the Behoudt Huys.

What does Van der Werf think of the floating ship at Saint-Nazaire? It looks familiar to him. Last year there was attention for a floating ship at FalmouthSuffolk was added later. Both ships floated a relatively short distance above a calm sea. There was no distortion whatsoever in the image of the ship, which is usually the case with mirages. Meteorologists tried to explain the hovering, but it turned out to be a weakness of the cameras. Van der Werf: “The distant sea probably functions as a mirror, so that you can no longer distinguish between sky and mirrored sky. If you play with contrast, brightness, gamma correction and saturation in a photo editing program, you can often make the true horizon visible.” Then he conjured up the horizon.

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