How can I tell how far away a cloud is by sight?

Question

I noticed today that there was the top of a large cumulo-nimbus cloud on the horizon at sunset today. I could only see the top of the cloud. Obviously the main reason this cloud was visible because the sun was bouncing off the outline of it. Supposing this cloud was 35,000 feet tall what formula would I use to figure out the distance from where I was standing to the center of the clouds base. It easy to figure out if the earth was flat but I am having trouble with the equation seeing as the Earth is round.

Answer 1

You don't have enough information to determine the clouds distance.

Anyway, I don't think arc length would affect the distance, only the time and travel distance to you.