Sun below horizon
Light dark contrast
Rayleigh scattering
On the earth’s curved edge, air particles scatter short wavelength light allowing longer wavelengths to differentially pass through cloud formations. Although it takes effort and planning, being active during twilight hours offers substantial reward.
“From the first opening of our eyes, it is the light that attracts us. We clutch aimlessly with our baby fingers at the gossamer-motes in the sunbeam, and we die reaching out after an ineffable blending of earthly and heavenly beauty which we shall never fully comprehend.” – Lucy Larcom