Chet Green, age 11, of Emmaus, Pennsylvania, for his question:
What exactly causes lightning?
A raging thunderhead is a powerhouse of electricity, which is why we call it an electric storm. It can generate enough power to light a city and maybe someday its energy can be tamed to do useful work for us. Thunderstorms seem rare, even where they happen most often. But at any time, day or night, hundreds of them are raging here and there around the globe.
The electric energy in a thunderhead is the activity of electrons, those tiny particles charged with negative electricity that normally swarm around the atomic nucleus. Each atom has a quota of positively charged protons in its nucleus. Normally the number of electrons equals the number of protons and the atom has a balanced quota of positive and negative charges.
Positive and negative electricity attract each other, somewhat like the opposite north and south poles of two magnets. A normal atom is electrically neutral and its nucleus likes to keep things this way. The protons locked within the nucleus cannot leave home. When a footloose electron strays away, the lopsided atom becomes a positive ion, seeking to regain its electrical balance. And ¬electrons often behave like runaways, frantically dashing from atom to atom.
When ions have extra electrons, naturally they have surplus charges of negative electricity. When a substance loses large numbers of light footed electrons, it is left with a positive charge. When either of these situations becomes intense, the surplus charges must be exchanged, or discharged. In a small way, this happens on a frosty morning when you touch something and a spark flies. In a big way, the same thing happens when lightning flashes from a thunderhead.
The storm cloud is a raging whirl of hot and cold, dry and damp regions. In the wild turmoil, countless electrons are stripped from their atoms creating pockets of negative and positive ions.
When these electrical charges build to a peak, they must be discharged. In a flash, the discharged electricity becomes a fiery finger, strong enough to sunder a mighty tree and start a forest fire.
The flash lasts less than a second, though several streaks may zoom along the same path. The first flash cuts a wavy path through the moist, turbulent cloud and other flashy discharges follow the leader. Heat from the fiery flash forces the moist, resisting air to expand in a great hurry. Actually it expands in an airy explosion ¬with a roaring clap of thunder.
Summer thunderstorms happen often, so we may tend to forget that they can be dangerous. Every year many people are injured by lightning, some of them fatally. So let's beware. The safest shelter is a building armed with proper lightning conductors.
A parked car also is fairly safe, so long as you do not touch the radio or metal fixtures. The safest part of a forest is under one of its smallest trees. Tall trees attract lightning, so do hilltops. Swimming is unsafe and running through the storm outdoors can be downright dangerous. Even when indoors it is wise to avoid electrical gadgets such as TV, and stay away from the water pipes.