One day many years ago my boys and I were lying on our backs in the yard watching the clouds drift by. “Dad,” one asked, “why do clouds float?” “Well, son,” I began, intending to give him the benefit of my vast knowledge, but then I lapsed into silence. “I don’t know,” I admitted, “but I’ll find out for you.”

The answer, I discovered, is that condensed moisture, descending by gravity, meets warmer temperatures rising from the land. That moisture then changes into vapor and ascends back into the air. That’s a natural explanation for the phenomenon.

But natural explanations are not…