Clouds Lit From Below

The illumination of the underside of clouds is a popular discussion topic. There are a number of potential causes for this observation which do not invoke a sphericity to the earth.

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. Absorption by atmospheric water vapor and aerosols may render the sun's light much redder. See the following images and quote from usra.edu:

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





Caption:

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