Spring is here, and with the warmer weather come thunderstorms. And, as we know, there would be no thunder without lightning. On any given day on Earth, there are approximately eight million lightning strikes. Though they can easily light up the whole sky, and they appear as thick, jagged lines of electricity, each lightning bolt only lasts a few thousandths of a second and is only about a centimeter wide (though they can be up to three miles long).
What Causes Lightning?
A lightning strike is actually an extremely powerful discharge of static electricity, like the spark you get after sliding across the carpet in socks and touching a doorknob (but turned up by several billion percent).
Instead of socks on carpet, however, the friction that leads to lightning is caused by areas of warm and cold air moving against each other in rising and falling air currents. Negative charges build up in the lower portions of thunderclouds, while positive charges build up in the upper portions.
Most lightning is discharged between clouds, but if a negative charge becomes large enough it will seek an easier discharge path by shooting out to the positively charged ground below.
Make Your Own Indoor Mini-Lightning
A fun, easy, and safe weather science experiment to do with kids (or by yourself for the fun of it) is a DIY lightning show. All you need is two balloons, a smooth wall, and one of Maria von Trapp’s favorite things, a woolen mitten.
All you need to do is inflate the balloons to roughly the same size, then vigorously rub one of them against the wall and the other with the mitten. Then turn out the lights and hold one balloon in each hand, about a foot or so apart. Move them closer together slowly… slowly… slowly… until SHAZAM! Miniature lightning.
How Does It Work?
After you inflate them, the balloons will have be carrying both positive and negative static charges. By rubbing them on the wall and with the mitten, respectively, you’ll change their overall charges—one will gain a more negative charge, while the other will gain a more positive charge.
As you move them together, the static will jump from the negative balloon to the positive one, just as lightning jumps from negatively charged clouds to the positively charged ground.
- Science in Seconds for Kids, Jean Potter, 1995. ISBN 978-0471044567