Anticrepuscular Rays Over Colorado

What's happening over the horizon? Although the scene may appear somehow supernatural , nothing more unusual is occurring than a setting Sun and some well placed clouds. Pictured above are anticrepuscular rays . To understand them, start by picturing common crepuscular rays that are seen any time that sunlight pours though scattered clouds. Now although sunlight indeed travels along straight lines , the projections of these lines onto the spherical sky are great circles . Therefore, the crepuscular rays from a setting (or rising) sun will appear to re-converge on the other side of the sky. At the anti-solar point 180 degrees around from the Sun , they are referred to as anticrepuscular rays . Pictured above is a particularly striking set of anticrepuscular rays photographed in 2001 from a moving car just outside of Boulder, Colorado , USA .