Counting Thunder
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Have trouble falling asleep on a stormy night? Then count the seconds between the flash and the thunder and multiply that by 1,000 feet and you'll come up with how far away the lightening is (Remember that sound travels at a 1000 feet a second? ). Okay, so this may not actually put you to sleep but it sure will entertain! Hi! I'm Dave Thurlow and this is the Weather Notebook.

As correspondent Jeff Rice reports today, you can learn an advanced trick to figure out the length of the lightning bolt itself.

Next time you hear a thunder crash, try this-- count the number of seconds that the stroke of thunder rolls across the sky. When a stroke starts and stops, that length can be used to tell you how long it is.

That's William Bickel , professor of physics and acoustics at the University of Arizona in Tucson, a place known for its dramatic lightning displays. Contrary to what you might think, Bickell says lightning actually begins at the ground when electrical charges build. It then shoots up into the air at about a third of the speed of light.

As the electrically supercharged lightning moves through up through the sky, it heats the air around it to more than 43,000 degrees, creating a series of explosions commonly known as rolling thunder.

The sound that was created all along the stroke is further and further away, and that sound comes at you successively later and later times. So that's why you hear this crackling whoom! like that.

Remember that the speed of sound is 1,000 feet per second. Start counting from the beginning of the rolling thunder until the end and multiply that by 1,000. That tells you the rough length of a lightning bolt.

Thanks today to correspondent Jeff Rice of Boise, Idaho. The Weather Notebook is a production of the Mount Washington Observatory and is underwritten by Subaru of America.