SUNSET SCIENCE .1. THE MOCK MIRAGE

A previously unrecognized phenomenon, which we call the mock mirage, p roduces inverted images of the Sun and Moon near the horizon when the observer looks downward through a thermal inversion. No ducting is inv olved; the rays can be concave toward the Earth throughout their lengt h, with a radius of curvature larger than the radius of the Earth. Qui te mild inversions produce surprisingly large effects, which increase with the height of the observer. Although the phenomenon has frequentl y been photographed, published pictures have been misinterpreted. Fina lly, we distinguish between features that are due to waves on inversio n layers and the larger features that are due to the inversions themse lves. (C) 1997 Optical Society of America.