Marine Fact of the Moment: Mirages and Fata Moragana
Light is refracted as it passes through the atmosphere; when refraction is normal, objects appear slightly elevated, and the visible horizon is farther from the observer than it otherwise would be. A mirage is an optical phenomenon in which objects appear distorted, displaced (raised or lowered), magnified, multiplied, or inverted due to varying atmospheric refraction which occurs when a layer of air near the Earth's surface differs greatly in density from surrounding air. If there is a temperature inversion (increase of temperature with height), particularly if accompanied by a rapid decrease in humidity, the refraction is greater than normal; objects appear elevated, and the visible horizon is further away. When refraction is not uniformly progressive, objects may appear distorted, taking an almost endless variety of shapes. The Sun, when near the horizon, is one of the objects most noticeably affected. A fata morgana is a complex mirage characterized by marked distortion, generally in the vertical. It may cause objects to appear towering, magnified, and at times even multiplied
Fact for 2025/02/27. Old facts will be archived in the ship knowledge section.
