Dear Dr. Universe: What causes lightning?
-Monica, 10, Costa Rica

And while we’re at it, let’s answer these questions:
When lightning strikes the ocean, what happens to the fish? –Olivia, 12, Manchester, UK
Why is lightning attracted to metal objects? –Grant, 11, Pullman, Wash.
Why does lightning sometimes just happen in clouds? –Leo, 11, Cayman Islands

Dear Monica, Olivia, Grant, and Leo:

While you are probably not in the middle of an electrical storm right now, there are more than 1,000 happening at any given moment on our planet. They happen on Saturn, Venus, and Jupiter, too.

These big, grey storms we see on Earth give us the chance to see electrical charges in action, said my friend Nic Loyd, a meteorologist at Washington State University.

Pretty much everything has a charge. You have a charge. I have a charge. These charges interact with each other. Founding Father and inventor Ben Franklin, who was really curious about lightning, is credited with giving these charges names: negative and positive.

They work kind of like the different ends of a magnet. Two charges that are the same will move away from each other. But put a negative and positive charge near each other and they are like best buds. Opposite charges attract.

Of course, even though we have charges, we aren’t walking around repelling and attracting different objects. Most of the time, objects have both positive and negative charges. They cancel each other out, leaving a neutral charge.

But sometimes, these charges are out of balance. Lightning is one way nature balances out these charges on our planet. Loyd told me about the ingredients.

As the sun heats the earth’s surface, the air above it warms up, too. Warm air rises. As the air rises, very tiny droplets of water, or vapor, rise up and form into a cloud. Air continues to rise and the cloud gets bigger and bigger. At the top of the cloud the temperature is really cold. The tiny droplets of water there turn into ice.

One idea is that bits of ice bump into each other to create electrical charge. Exactly how they do this is still a bit of a mystery. But when these charges in the sky interact with opposite charges on the ground, current runs between them and we see a bright flash of lightning. Lightning can happen within a cloud or it can happen between the cloud and the ground. It all depends on how these charges are jumping around.

Now, for a final lightning round of answers to the remaining questions. It turns out metal doesn’t necessarily attract lightning. But it is a good conductor of electricity. That means electricity can easily flow through it. Lighting will take the shortest path possible. Water can also be a good conductor. That’s why it’s important to stay away from water when there’s an electrical storm. Most of the electricity flows along the top of the water. A fish’s fate may depend on how close to the surface it swims.

Finally, thunderstorms happen more often in spring and summer, as the ingredients—especially warm air– are more likely to exist. Now that you know more about the electrical charge we can see in the sky, what about the sound we hear at or near the same time? What causes thunder? Send your idea to Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe