Clouds Lit From Below

The illumination of the underside of clouds is a popular discussion topic. There are a number of possible causes for this effect.

Earth Reflection
According to the Universities Space Research Association the clouds can appear to be lit from below as result of a reflection of sunlight off of the surface of the earth. The sunlight reflecting off of the ocean can pass through so much atmosphere, absorption by atmospheric water vapor and aerosols may render it much redder. See the following images from usra.edu:

https://epod.usra.edu/blog/2017/02/clouds-lit-from-below.html (Archive)





Electromagnetic Acceleration
According to the theory of the Electromagnetic Accelerator, light is bending upwards over very long distances and can illuminate the underside of clouds during sunrise or sunset.