Lightning Striking Again
What's hotter than the surface of the sun, moves with incredible speed, lasts a few seconds and goes out with a bang? If you said lightning, you're right. Lightning strikes cause thousands of forest fires every year and occasionally cause the death of people. Few who have been hit by lightning live to tell the tale. Yet the process that causes lightning is not really any different than what makes static electricity jump when we walk on a carpet and touch a metal doorknob.
Within thunder clouds, air and water vapor, snow and ice crystals are in constant motion. This motion causes the accumulation of positive and negative charges within the particles of snow and ice. As the cloud continues to churn, the areas of charged particles become larger and separate, with the positively-charged particles moving upward, and heavier negatively-charged particles falling downward. This imbalance, in turn, causes the ground below the thunderstorm to become positively charged. Once this process is set in motion, it isn't long before the areas of positive and negative particles attempt to balance each other out. What we call lightning is nothing more than the process of reconciling the positive and negative charges back to a neutral state.
A common misconception is that lightning moves from the sky to the ground. Actually, the process is much more interesting. In the seconds before a lightning strike, negatively-charged air rapidly moves towards the ground. In reaction, positively-charged particles in tall objects on the ground (church steeples, trees, electrical towers) begin to flow upward toward the descending air. When the two connect, a giant rush of visible electrical energy leaps from the ground. This is what we see as lightning. And the thunderclap we hear soon after is the shockwave caused by the sudden heating of the air near the lightning bolt.
