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How Is Lightning Made?
08.19.04
 
Animated drawing of lightning coming from a cloud
Image above: How would you explain lightning? Credit: NASA
How is lightning made? People used to make up stories to answer that question. Today, science tells us how.

You have heard of Ben Franklin. Did you know he flew a kite during a thunderstorm? He wanted to prove that lightning is a form of electricity. We know now that flying a kite in a storm is not safe. But, Ben was right. Lightning is a form of electricity. How does this "electricity" form?

What do You Need to Make Lightning?
Drawing of a dark cloud with snow flakes and drops of water and small circles with either a plus or minus sign in them
Image above: Ice crystals and water droplets bump together and move apart to cause electricity. Credit: NASA


You need cold air and warm air. When they meet, the warm air goes up. It makes thunderstorm clouds! The cold air has ice crystals. The warm air has water droplets. During the storm, the droplets and crystals bump together and move apart in the air. This rubbing makes static electrical charges in the clouds.

Just like a battery, these clouds have a "plus" end and a "minus" end. The plus, or positive, charges in the cloud are at the top. The minus, or negative, charges are at the bottom. When the charge at the bottom gets strong enough, the cloud lets out energy.
Cartoon battery standing up with a plus sign near the top and a minus sign near the bottom
Image above: Look at a battery and find the plus end and the minus end. Credit: NASA


The energy goes through the air. It goes to a place that has the opposite charge. This lightning bolt of energy that is let out is called a leader stroke. It can go from the cloud to the ground. Or, a leader stroke can go from the cloud to another cloud. No one is sure why lightning bolts follow a zigzag path as they move. The main bolt or stroke will go back up to the cloud. It will make a flash of lightning. It will also heat the air. The air will spread quickly. It will make the sound we hear as thunder.

Be Safe in a Storm

Lightning is dangerous. Here are some safety rules.
    Animation of cartoon mole hit by lightning so that you can see his skeleton
    Image above: Do not stand outside during a storm. Credit: NASA

  • Stay away from open spaces. But, do not stand under a tree. The best place is inside a building.
  • If you are swimming, get out of the water. Get out as soon as you see a storm coming. The storm may seem far away, but lightning can travel over 20 miles!
  • During a thunderstorm, shut off or unplug all electrical items. Do not use the phone.
  • Never walk in a thunderstorm carrying a metal pole. Don't even carry an umbrella!
  • How will you know if a lightning strike is near you? You will feel the hair on your head or body start to stand up. If this happens, go to a safe place. Go quickly! If there is no safe place near, get as close to the ground as you can.
Drawing of lightning in a night sky
Image above: A special camera can show that one lightning flash is made of many bolts of lightning. Credit: NASA


Scientists have learned some facts about lightning from pictures. Some lightning flashes are made up of as many as 25 or more lightning bolts (strokes). They move so fast that your eyes only see one flash!

Lightning is fun to watch. But, make sure you do so safely.
 
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Adapted from What Causes a Lightning Flash?
 
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