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Question: What is thunder?
Answer: Have you ever heard the sonic boom of a modern fighter aircraft as it zooms overhead? Or maybe you have attended the Binghamton Air Show and experienced first hand the excitement of the Thunderbirds or Blue Angels racing across the sky? One of the highlights of such shows is the passage of a sonic boom which rattles the buildings and shakes you to your very core. But what does all this have to do with thunder? In fact, thunder is nature's sonic boom. Let's see how it happens!
When supersonic aircraft fly, a sonic boom is generated through a phenomenon known as a shock wave. The aircraft essentially creates a hole in the fabric of the atmosphere. Nature hates vacuums so there is an immediate rush of air back into this tear. The tearing and subsequent refilling of the atmosphere generates an incredibly loud sound wave which is what we hear when the aircraft passes overhead. Thunder is nature's equivalent. A bolt of lightning fills the role of the supersonic aircraft. Lightning, which is approximately 54,000 degrees Fahrenheit and six times hotter than the surface of the sun, seems to be clear or a white-yellow color, but it really depends on the background. When a lightning bolt travels from the cloud to the ground it tears a hole in the air. When the lightning bolt is gone the air collapses back into the tear or hole in the atmosphere and creates a sound wave that we hear as thunder.
Thunder, as it is a sound wave, travels at the speed of sound which at sea level is approximately 725 miles per hour. Contrast this speed with the speed of a lightning bolt which travels at approximately 186,000 miles per second! Is there any doubt as to why we see the lightning bolt before we hear the thunder? Thunder and lightning can help us tell how far away a storm is. Next time you see a storm coming, count the number of seconds between when you see the lightning and hear the thunder. Take the number of seconds and divide by 5 and that will tell you how far away the storm is in miles. For example, if you counted 10 seconds between seeing the lightning and hearing the thunder, the storm is approximately 2 miles away.
Though the heavenly displays of lightning and the accompanying symphony of thunder can be awe-inspiring, a word of caution is important. All thunderstorms produce lightning and are very dangerous. If you hear the sound of thunder, then you are in danger from lightning. Lightning kills and injures between 75 and 100 people each year which is often more than hurricanes or tornadoes.
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