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A SciShow Kids viewer wants to know, “Why do lightning and thunder happen?” Get your raincoat, because Jessi will take you inside a thunderstorm to give you the answer!
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Squeaks, where are you?  Squeaks, where are you?  Squeaks?  Oh there you are Squeaks!  It's okay Squeaks, thunderstorms can get kind of loud, and maybe even a little scary sometimes.  But you know what?  Sometimes things that are frightening are a little less scary when we understand what causes them, and we can learn what causes things by asking questions.  That's why we're so glad that we heard from our friend four year old Eleanor, who asked, "Why do lighting and thunder happen?"  I'm sure Squeaks would like to know.

Experts called meteorologists study the science of weather, including lightening and thunder.  We can use what they've learned to explain what causes these bright flashes of light and the big booms that follow.  And you may not know it, but the science of what causes lightening can happen right in your own home.  

Have you ever walked across a fuzzy carpet, and then when you reach for a door knob gotten a little shock?  If so, then you've been part of making a mini lightening bolt.  That shock that you felt was caused by the buildup of what's known as a static electrical charge.  A static electrical charge is just a little bit of electricity that stays in one place for a little while.  Static electricity can build up any time two things are rubbed together.  When you walk across the carpet your body picks up tiny bits of charge, then when you reach for that door knob these charges jump into the metal door knob and ZAP.   Lightening is caused by the same thing, only on a much bigger scale.  
The kinds of clouds we see in thunderstorms have tiny bits of ice in them, and these little bits of ice bump into each other.  They cause an electrical charge to build up inside the cloud.  And as this charge keeps building up it gets stronger.  But there are two kinds of electrical charge.  We call them positive and negative.  Charges that are different from one another will attract, or pull toward one another, a lot like magnets.  But in our case the charge of the cloud is negative.  The negative charge of the cloud makes some spots on the ground get a positive charge.  And when the charges in the cloud and the charges on the ground are just right, a bolt of lightening jumps between the cloud and the earth.

And meteorologists have discovered that there are different kinds of lightening too.  Some lightening goes from one part of a cloud to another.  Some jumps from cloud to cloud.  And some goes between the sky and the ground.  But it's all caused by a moving electrical charge and all lightening is hot.  Really hot!  And that heat is what causes thunder.

Thunder starts with the fact that air is made of tiny particles.  When these little particles get heated up they start to move around more quickly.  So when that hot lightening bolt suddenly moves through the air it's heat makes the air particles around it all excited.  All those particles of suddenly hot air start to move around quickly.  They push hard against the cooler air around them.  That air then flies away really fast from where the lightening was with a lot of energy.  Our ears hear this movement of the air particles as a loud bang or crackle.  That's thunder.

So now you know.  Lightening happens when an electrical charge builds up inside a cloud and moves to an opposite charge.  And thunder happens when the heat from lightening causes the particles that make up air to push away from the lightening bolt.  And remember, when you're not sure about something, ask questions.  It just might make you feel better.

Thanks for asking Eleanor, and if you have a question for any of us here at the fort, let us know by leaving a comment or emailing us at  Until next time.