April Fools?

March 30, 2001


Provided by: Pekka Parvianinen, Turku University
Summary authors & editors: Jim Foster

The picture above is not an April Fools prank - it's an actual photograph taken by Pekka Parviainen, a lecturer in mathematics at Turku University in Finland. Mirages are commonly seen on many water bodies if clear skies and calm winds prevail. The photo above is a classic example of a superior mirage - the image of a distant object is always displaced upward. In the early spring, when the water is still cold but the air has begun to warm, it's often possible to see superior mirages. Cold water and warm air above creates an atmospheric inversion that can result in the deviation of the usually straight-line movement of light rays. Under such conditions, an object can seem to be displaced or distorted from where we expect it to be or how we expect it to appear. That's the case with this photo. The sailboat in the foreground seems normal, but the island in the background is severely distorted.

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