BACKGROUND: Lightning is a common phenomenon but there are still a lot of things scientists don't know about it. A pair of modern Ben Franklins -- a physicist and an electrical engineer -- are studying lightning at the Florida Institute of Technology by sending rockets into the air to seek out and capture lightning.
ABOUT ELECTRICITY: The secret to electricity lies in the structure of an atom. Negatively-charged electrons spin around the nucleus of the atom. The nucleus is made up of positively charged protons and neutrons, which are neutral. In stable atoms, such as carbon, the positive and negative charges are balanced; that is, there is the same number of protons and electrons. But some atoms have electrons that are more loosely attached and can be knocked free, flowing between atoms of matter to create a current of electricity. For instance, the atoms that make up the dry asphalt are stable and non-conductive, and the electron charges from a downed power line cant' travel very far. But what if the road is wet? Water is highly conductive, and the electric charge can easily travel from the power line to your feet. Unless you happen to be wearing thick rubber soles (rubber is also non-conductive), you'll likely be electrocuted.
WHAT IS LIGHTNING? Lightning is a form of static electricity. We experience static electricity every time we drag our feet on the carpet and then touch a conducting surface, like a metal doorknob. The shuffling causes our bodies to pick up extra electrons. Touching something with a positive charge, like metal, causes the electrons to "jump" across the small gap from our fingers to the object, and we experience a tiny electric shock. Similarly, lightning occurs because clouds become negatively charged as the water droplets inside rub up against each other during the natural process of evaporation and condensation, when moisture accumulates in the clouds. This charge seeks out something with a positive charge -- the ground, ideally -- and the lightning is the "spark" closing the gap between the two.
As more and more water droplets collide inside a cloud, the friction between them produces enough extra energy to knock off electrons. The ousted electrons gather at the lower portion of the cloud, giving it a negative charge. Eventually the charge becomes so intense that electrons on the Earth's surface are repelled by the growing negative charge and burrow deeper into the Earth. The Earth's surface becomes positively charged, and hence very attractive to the negative charge accumulating in the bottom of the cloud. All that is needed is a conductive path between cloud and Earth, in the form of ionized air -- another byproduct of the collision process. When the two charges finally meet, current jumps between the earth and the cloud, producing lightning.
EYE ON HISTORY: Benjamin Franklin reportedly performed his famous kite experiment during a thunderstorm in June 1752, on the outskirts of Philadelphia. But he wasn't the first to do so. One month earlier, a Frenchman named Thomas Francois D'Alibard had read Franklin's published paper, and used a 50-foot-long vertical rod to draw down lightning in Paris on May 10, 1752.
The American Meteorological Society contributed to the information contained in the TV portion of this report.
