Lightning is one of the great mysteries of nature that man fears most. What, after all, could possibly be scarier than a massive, sudden bolt of electricity from the sky that can kill a human being in a split second? At least with other natural phenomenon we have more time to react. There's no avoiding a lightning bolt if it's coming down at you.
Despite the danger lightning poses to people on a daily basis, however, there is still no conclusive process through which lightning is formed. What CAN be said is that lightning is generated by the formation of rain clouds, which are created through the water cycle.
The water cycle is one in which water on the ground is evaporated by heat from the sun or some other, man-made source and released into the air. As this vapor rises into the air the temperature around it decreases and the vapor begins to change back from a gas and into a liquid again, causing rain and the creation of clouds.
So where does the lightning come from in this equation? That's still debatable. The clouds in a lightning storm as been positively or negatively charged during the water cycle process, though how this happens remains a mystery to mankind. There are quite a few theories floating about as to how lightning is created, however, including the following:
- The Electrostatic Induction Theory states that updrafts, warm wind traveling upward, send the water molecules up through a cloud to collide with ice crystals. This triggers the creation of graupels, an ice and water combination that becomes negatively charged as gravity pulls it down through the cloud. This negative charge continues to accumulate until a lightning strike occurs, the result of the electrical field trying to balance itself out by bleeding off the excess charge.
- Polarization Mechanism Hypothesis, on the other hand, would have it that the electrical charges are created by the ice and water falling through Earth's natural magnetic field, which again the cloud must bleed off through lightning to balance the charge in the cloud with whatever the lightning is striking (which can often be the ground).
- A third, Gurevich's Runaway Breakdown Theory, involves cosmic rays that ionize storms and cause the above-mentioned effects.
So how is lightning formed? In short, we don't know, not for certain. All that's really known at this point is that the cloud becomes positively or negatively charged (positively-charged clouds producing much more powerful lightning bolts on average) and creates lightning. Given that this lightning is often drawn to the ground, it's safe to say that the most important information to know about a lightning storm is that, when lightning is forming, it's best to stay indoors.