1. Lightning! How far away is it?

    Thunderstorms produce powerful flashes of lightning. Let’s find the distance between you and a bolt of lightning by measuring the time between the lightning’s flash and the thunder that follows.

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    You can use any of three methods to find the distance between you and a lightning bolt. In each method you will count or measure the time in seconds between a lightning flash and the thunder it causes. You will then multiply this time by the speed of sound to learn the distance. 

    Lightning is a giant electrical discharge between clouds or between a cloud and something on the ground. According to the US National Lightning Safety Institute, a lightning bolt almost instantly heats the air to as much as 39,000° Celsius (70,000° Fahrenheit). The heated air expands so rapidly that it creates a shock wave in the atmosphere that we hear as thunder.

    Lightning can explode trees and kill people and animals. Sometimes lightning strikes high in a tree and removes a strip of bark all the way to the ground as shown in this photo of a tree behind my barn:

    The bottom of the tree in this photo was split into three sections by the lightning. Pieces of wood as tall as a person were thrown several meters (yards) away.

    Lightning can strike high on mountains. The photo below shows a power pole along the road to Hawaii's Mauna Loa Observatory that was struck by lightning. This pole is at an elevation of about 3.2 kilometers (10,500 feet).

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