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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Mirages, was: Refraction
From: Trevor Kenchington
Date: 2004 Jul 12, 08:44 +0000
From: Trevor Kenchington
Date: 2004 Jul 12, 08:44 +0000
Fred, An image sunk below the horizon could not be seen and thus could not be an image. However, I think what you are getting at is a converse of the classic mirage seen in hot, desert areas. Low-latitude mirages involve light rays bending upwards very near the ground, so that we see light from the sky apparently rising from the ground. But high-latitude mirages involve the reverse bend, so that surface light appears to come from the sky. They are perhaps most common in the form of "ice blink", where sunlight reflected off ice beyond the horizon is visible as a whiteness in the sky. However, there are reports of people seeing, in the sky, inverted images of ships which, in reality, are hull-down over the horizon. I have characterized the two types as "low" and "high" latitude but they are, of course, respectively the result of (1) intense solar heating of a land surface under cooler air and (2) the presence of warmer air overlying a very cold surface. Trevor Kenchington Fred Hebard wrote: > OK ladies & gentlemen. We have the case of a mirage, where the image > rises above the desert floor. Are there any counter examples of an > image sinking below the horizon? -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus