For centuries we've made sacrifices, sent prayers to gods and summoned witches, in an attempt to bend the weather to our will. Science suggests now we might actually be able to do it. Weather modifiers are employed to make it rain, suppress hail and enhance snow packs. It is big business, from the UAE to Chile, Thailand to China, interest and investment is global. Kim Chakanetsa asks what the weather changers are actually doing, if it really works and if so, is it problem free?