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Thunder

physical science Maturity 7-9 Next article →

Thunder is the powerful sound made by lightning. It is a very loud noise that can sound like a sharp crack or a low rumble. This sound happens because lightning is incredibly hot. The heat causes the air to expand very quickly in the path of the bolt. This rapid expansion creates a sonic shock wave in the air. People often call this sound a thunderclap or a peal of thunder.

To understand how it works, we must look at the heat. Inside a lightning bolt, the temperature rises very fast. It can jump from 20,000 K to 30,000 K in just 50 microseconds. The average temperature is about 25,000 K. This intense heat makes the air expand outward faster than the speed of sound. This moving pulse is a shock wave. It works much like the shock wave from a large explosion.

People have wondered about thunder for a very long time. Ancient Greeks like Aristotle thought wind struck the clouds to make the sound. Other thinkers thought it was hail hitting things inside clouds. In the mid-19th century, people thought lightning made a vacuum. They believed thunder was the sound of that vacuum collapsing. Now, scientists use brontology to study these sounds. Brontology is the scientific study of thunder.

Thunder can take many different shapes and sounds. A clap is a loud sound that lasts 0.2 to 2 seconds. It usually has a high pitch. A peal changes in both loudness and pitch. A roll is a mixture of different pitches and loudness. Rumbles are low and can last for more than 30 seconds. Near the source, thunder can reach 165 to 180 dB. Sometimes it can even go over 200 dB.

You always see lightning before you hear the thunder. This happens because light travels much faster than sound. Sound moves at about 343 meters per second. You can use this to find how far away a storm is. Count the seconds between the flash and the sound. Divide that number by five to find the miles. You can also divide by three to find kilometers.

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