Whenever there's a drought, someone will come up with the idea of finding a rain maker, or holding a day of prayer for rain.

Now far be it for me to make light of people who are in truly desperate straits and who are prepared to try anything to relieve their precarious situation. The worst that can happen, assuming no deliberate or unknowing fraud, is that everyone has something else to think about for a day or so. For a while they have some cause for hope.

And it may indeed rain and the drought will be over. But in most cases not.

For more information on droughts, visit http://www.home-weather-stations-guide.com/drought.html

Rain making can be divided into two types - cloud seeding, which has strong scientific and engineering reasoning behind it, and, for the moment, everything else.

Cloud seeding has been used to create or increase rain for over 50 years, and while the results are a little patchy and rarely spectacular, when the right combination of cloud seeding method and clouds is present, it has been shown to work many times over, and in a cost effective way.

But what of the rest? I don't wish to question the power of prayer, which presumably transcends all physical rules, but it is worth looking at just what it would take to change the weather pattern before it is ready to change.

But first let's take a look at the rain maker's methods.

They can be divided into two parts - local knowledge and rainmaking techniques or ceremonies.

Firstly, rainmakers with a good reputation will generally be folk with a strong knowledge of local weather, climate, and seasonal changes. Some of these may be subconscious, but I think we can give them some credit for astuteness and good observational powers. This allows the rainmaker to practise his or her rituals at a time when a change in the weather seems most likely. With good local weather knowledge, chances of success will be high, and in any event, payment is usually dependent on success. It is also human nature to remember (and advertise) the successes and forget the failures.

In primitive societies, rain makers usually have an inbuilt "get out" clause. The rain making ceremony consists of certain things done by the rain maker, supported by other rituals, requirements, or prohibitions required of the community the rain maker is serving.

These may be bans on certain foods or practices, but if the rain doesn't come, who is to say that someone in the community failed to play their part, destroying the rain maker's good efforts?

And eventually, with persistence, the rain will come.

So, in a very general way, that's how the rain maker works.

But let's see what he or she is up against.

Weather is the local end result of the effects of the vast atmospheric circulation system, which works towards creating some sort of balance between unequal heating of the earths surface, the planet's rotation, transferring water from the oceans to the atmosphere and back again, variable distribution of warm and cold water currents in the oceans, and much, much more.

All this takes a huge amount of energy. Let's put it in perspective. In 1945, an atomic bomb was dropped on the Japanese city of Hiroshima, effectively destroying it. That bomb was the equivalent of 12,500 tons of TNT, or 12.5 kilotons. An average thunderstorm generates the equivalent of 20 kilotons.

A hurricane generates the equivalent of a 10 megaton bomb - 10 million tons of TNT - every 20 minutes. Some people have asked why large bombs aren't used to divert or destroy hurricanes. Others have suggested that would be about as effective as throwing a ping-pong ball at a charging elephant.

To create rain out of nothing, a rain maker would need to control huge amounts of energy to overcome the inertia of the stable weather systems associated with droughts. With that sort of power, why hasn't the rain maker taken over the world, hopefully for the good of all, or at the very least made his fortune by affecting the results of horse races?