Topic
Mirage
About: Mirage is a research topic. Over the lifetime, 11 publications have been published within this topic receiving 84 citations.
Papers
TL;DR: In this article, a simpler and more consistent theory is developed, namely, that the hafgerdingar are an optical phenomenon, specifically, a superior mirage, which can produce an appearance fully consistent with the original description, as illustrated by several photographs and a computer simulation.
Abstract: The medieval King's Mirror describes Iceland and Greenland with a scientific accuracy that is remarkable. One of the very few exceptions is the hafgerdingar in the Greenland Sea. The term translates as ‘sea hedges,’ within which a mariner may become trapped at great peril. Many have believed that a real event was being described, although none of the proposed explanations has been totally satisfactory. The most common view currently is based on Steenstrup (1871), who explained the phenomenon as a tidal wave following a submarine earthquake. A simpler and more consistent theory is developed here: that the hafgerdingar are an optical phenomenon, specifically, a superior mirage. Such mirages, quite common in the polar regions, can produce an appearance fully consistent with the original description, as illustrated by several photographs and a computer simulation. Even the peril to seafarers has been corroborated, in the sense that such a mirage is frequently followed by a storm.
12 citations
TL;DR: In this article, a mirage is created indoors using an electric hotplate and a saucepan filled with ice water, which is known as an inferior mirage; a superior mirage occurs when cooler air is underneath.
Abstract: Most people have witnessed mirages such as the distant “puddles” that appear on a highway when the pavement is warmed by the Sun. The warmed surface heats the nearby air creating a temperature gradient with the cooler (and more dense) air above. The apparent displacement of distant objects occurs as light refracts through the different air densities. Rays of light from the sky that are originally directed toward the ground can be bent upward, appearing to a viewer as though coming from the ground. This effect is known as an inferior mirage; a superior mirage occurs when cooler air is underneath.1,2 In this paper, a mirage is created indoors using an electric hotplate and a saucepan filled with ice water.
8 citations
TL;DR: In this paper, the authors extend their analysis by introducing a periodic time dependence in the properties of the inversion layer, and show that also the illusion of incoming waves and an immediate danger may so be explained.
Abstract: A 13th-century text in Old Norse, Konungs Skuggsja (translated as The King’s Mirror), tells about a phenomenon that may be encountered in the Greenland Sea. It is called hafgerðingar (sea fences). The horizon is raised, and from there three giant waves come rolling in. Recently Lehn and Schroeder have explained the phenomenon as a superior mirage. I extend their analysis by introducing a periodic time dependence in the properties of the inversion layer, and show that also the illusion of incoming waves and an immediate danger may so be explained.
6 citations
1 Jan 2004
5 citations
TL;DR: In this article, the effects of ray refraction and atmospheric distortion on the maximum intervision range (MIVR) of distant low-altitude targets are discussed. But, although horizontal inhomogeneity may influence superior mirage formation, it is not necessary to explain features such as numerous mirages or multiple (three) horizons.
Abstract: Atmospheric effects at low elevation angles can complicate shipboard infrared search and tracking (SIRST) of distant low altitude targets, such as sea skimming cruise missiles. Here we focus upon the effects of ray refraction and atmospheric distortion. For constant-flux surface layer conditions we discuss target magnification and demagnification and atmospheric distortions. For sufficiently negative air-sea temperature differences (ASTD), the maximum intervision range (MIVR) of low altitude targets is reduced, but the target is significantly magnified compared to no-refraction predictions. Negative ASTD can give rise to an inferior mirage which we discuss with a model-data comparison. Positive ASTD extends a target MIVR, but the target image is severely demagnified, closer to the horizon, and more degraded by atmospheric turbulence. We discuss environments that are likely to violate constant-flux conditions and include an example of a superior mirage. Although horizontal inhomogeneity may well influence superior mirage formation, we show that inhomogeneity is not necessary to explain features such as numerous mirages or multiple (three) horizons.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
5 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2017 | 1 |
| 2006 | 1 |
| 2004 | 1 |
| 2003 | 1 |
| 1996 | 1 |
| 1990 | 1 |