Rainmaking is the oldest form of geo-engineering, although there is little evidence it actually worked until the middle of the 20th century. It has always held a powerful spot in people’s imagination. The Mayans and other people sacrificed many people an animals in the mistaken belief that it would entice rain. The belief held sway among more advanced people too. the Nash play “The Rainmakers”, about the Midwest United States during a drought, was also made into a hit movie. Whether rainmaking is effective or not, the belief that it could work is a powerful political and cultural phenomena.