Two aspects of crepuscular rays, both imaged by Jonathan Shock (more images). Images ©Jonathan Shock, shown with permission. Cloud shadows, the dark parts of crepuscular rays, are long parallel tunnels of shadowed air. Here their true form can be seen as they extend tens or even hundreds of miles away from the clouds. From the ground they appear to radiate in all directions outwards from the sun - the same perspective effect that makes a road or railroad tracks converge.