Atmosphere And Weather

What causes Lightning



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Lightning is a natural phenomenon that is as lethal as it is an incredibly beautiful display of nature at work. Dazzling in a brilliant show of light and random patterns yet deceptively dangerous as a source of power and raw energy, lightning is a continuing mystery worthy of study as we continue seeking possible methods through which we can harness thi force of nature.

The most basic description of lightning is that it is a static discharge of stupendous magnitude between the earth's surface and the atmosphere. That is the basics of a ground strike where the discharge is unpredictable and can manifest in many different forms ranging from balls of light and energy to the violent and destructive forks of destruction.

Clouds are the source of the electrical charge necessary for lightning to occur because of air movement at varying rates through and across the upper and lower sections. This does not sound like much but consider the thousands of square miles of surface involved and it puts some perspective into what is occurring.

Moisture from evaporation moving rapidly upwards will contribute to this energising process because of friction and by collision with other suspended particles that form the clouds. This creates a difference in rate of charge where one section of cloud acquires a higher charge than another the effect is like a giant capacitor charging up with one plate building a more positive charge than the other. Moist air acts as a dielectric that separates the two charges until either one builds up enough energy to overwhelm the insulating properties of the dielectric. What we see from the ground is a bright flash followed by a sharp cracking rumble. This sound is the shockwave resulting from a sudden and very powerful electrical discharge.

If the rate of charge is sufficient and rapid enough, the path of discharge occurs between the cloud base and the earth. This happens as a result of the electrical charge building up sufficient energy to ionise the air. Ionisation is where air molecules breakdown into positive ions and electrons with the result being a conductive medium through which the violent discharge is released. The path is unpredictable and despite the popular belief suggesting lightning will always strike the tallest object, the fact is that lightning can strike anywhere irrespective of the presence of tall objects. There is of course a higher probability that the strike point will be the closest conductive path that is; the tallest object!

The dangerous part about a lightning strike is the incredibly powerful electric charge accompanied by tremendous heat. The power of a lightning strike can literally blow a good size hole in solid rock, explode trees of a significant size and a direct hit on humans is more often that not a fatal occurrence. Few survivors of a lightning strike will live beyond a few more years because of the internal damage caused. Some exceptionally lucky survivors seem relatively unaffected but generally the chances of surviving a lightning strike are not good.

Lightning is as fascinating as it is dangerous, and demonstrates the awesome power of natural forces at work on this planet. It could be said that we exist inside gigantic dielectric of a global size capacitor where the earth is one plate and clouds the other. Lightning strikes occur somewhere on the earths surface many times every second of every day yet few people realise we live in such an unstable; and unpredictable atmosphere. Each lightning strike discharges enough electrical energy to power a small city for several hours yet the power of a single strike is far more than our technology can possibly control. Our best efforts in the 21st century are barely enough to deflect the damaging effects and that is only most of the time!

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