Blasting Thunder

How many people do you know, that literally jump out of their skins at the "clap" of thunder? Is it the sudden noise, or the volume of sound? Or the idea of the storm that follows?

Thunder is one of nature's loudest and most nerve-shattering noises. It occurs following lightning, which may or may not be seen as a flash of light, or a bolt. The air around the lightning is superheated to approximately five times that of the Sun, causing it to expand faster than the speed of sound, then compressing the air to make the boom that you hear.

At times, you see lightning without thunder. Or see something often referred to as "heat lightning". Both of these phenomenon are due to your distance from the actual weather disturbance. And considering that at any given moment, there are about 2,000 storms taking place around the world, chances are pretty good of observing or hearing one, without the other.

The cause of thunder has been the subject of centuries of speculation and scientific inquiry. The first recorded theory is attributed to the Greek philosopher Aristotle in the third century BC, and an early speculation was that it was caused by the collision of clouds. Subsequently, numerous other theories have been proposed. By the mid-19th century, the accepted theory was that lightning produced a vacuum. In the 20th century a consensus evolved that thunder must begin with a shock wave in the air due to the sudden thermal expansion of the plasma in the lightning channel. In a fraction of a second the air is heated to a temperature approaching 28,000 °C (50,000 °F). This heating causes it to expand outward, plowing into the surrounding cooler air at a speed faster than sound would travel in that cooler air. The outward-moving pulse that results is a shock wave, similar in principle to the shock wave formed by an explosion, or at the front of a supersonic aircraft.

More recently, this consensus has been eroded by the observation that measured overpressures in simulated lightning are greater than what could be achieved by the amount of heating found. Alternative proposals rely on electrodynamic effects of the massive current acting on the plasma in the bolt of lightning.

In a strange quirk of Nature, the town Tororo,Uganda suffered an average 251 days of thunder a year, from 1967-1976, the highest incidence ever recorded.