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Why do you have to wear a helmet when you’re skateboarding? – Artie, age 13, Queens, New York

Back when I was 13, I was an avid skateboarder – the kickflip was my go-to trick. And I didn’t see why I needed to strap on a helmet before practicing my ollies.

But now, doing the work I do, I get it.

My research is centered on understanding how physical forces cause brain injury and how to best protect against it. So I spend a lot of time thinking about how the brain gets hurt and how to improve helmets. This includes work focusing on protecting members of the United States military in training and active combat zones.

So why is it so important to wear a helmet when skateboarding, and also riding your bike, and really any sport or activity where your head could get hurt?

Your very own supercomputer

Inside your head sits probably your most amazing organ – your brain. It allows you to do everything you love, such as tasting ice cream, watching movies, listening to music and, of course, skateboarding.

Your brain is the world’s mightiest supercomputer. Everything it does requires billions of tiny brain cells, called neurons, working together in unison. These cells send messages to the rest of your body that regulate everything from body processes you’re not even aware of – such as your heartbeat – to moving your muscles, to helping you think and talk.

Some researchers estimate that humans have about 86 billion neurons, although scientists are still working on finding the exact number. That’s more than 10 times the number of all the people living on earth. And they’re all crammed inside a space the size of a melon, working together tirelessly, day in and day out.

Of course, your brain is not just made up of neurons. There are a lot of other cells supporting the neurons, including astrocytes and microglia, which are important helper cells to the neurons.

But as busy as your brain cells are, they are also incredibly soft and squishy. In fact, your brain has the consistency of jello. And like jello, it is very vulnerable, especially to physical forces, such as a fall or a sudden jolt.

The physical forces of a fall

Now, you might be thinking, doesn’t my skull protect my brain? And, yes, it does offer some protection. But your skull is a layer of cortical bone only about .28 inches (7 millimeters) thick, making it a useful barrier that prevents dirt and other objects from getting into your brain, but it’s too thin and too stiff to keep your brain safe in case of a fall while skateboarding.

Why is that? It helps to break down what happens when your unprotected head hits the pavement: Upon impact, your skull deforms, or changes shape, and often rotates. But your skull is not capable of fully absorbing that impact. So the remaining energy is transferred through the hard bone of your skull and absorbed by your soft, squishy brain.

Imagine squeezing and wiggling a block of jello to change its shape. This is similar to what happens to your brain: Like the block of jello, when your skull deforms, your brain can be compressed and change shape. This can cause your neurons to stretch and move in ways they aren’t designed to, causing damage.

This is why wearing a helmet is so important. If you look at your helmet, you will see that it has two parts – an outer shell that is usually hard and an inner shell liner, usually made from stiff foam. The shell is meant to protect your brain from penetrating objects. It also holds the liner, which is there to absorb most of the energy from an impact so it doesn’t reach your brain.

Recovering from a brain injury

If you fall off your skateboard and you’re not wearing knee and wrist pads, you might skin your knee or break your wrist. But unlike your skin and bones, your brain doesn’t tend to heal easily.

Without a helmet, much of the energy from your fall gets absorbed by your brain. Depending on the amount of energy that enters your brain, your brain cells can be injured. Even a mild traumatic brain injury, such as a concussion, can cause significant damage to the cells inside your brain. This could mean that you lose some of those brain cells or that they won’t work properly anymore.

If too many of your brain cells are damaged or die, you may lose really important brain functions, such as walking, talking or seeing clearly. The brain cells you have now are largely the same ones you had when you were born. And once you lose them, there is no way to get them back.

When you lose brain cells, the remaining cells have to work extra hard to keep your brain function intact. While modern medicine has gotten really good at repairing most of the tissues and organs in your body, the brain is still a major challenge for researchers.

This is why researchers like me spend so much time trying to find ways to protect the brain from trauma: A protected brain doesn’t need to be healed. In fact, according to one study of bicyclists, those who wear helmets are 65% to 88% less likely to get a brain injury.

So next time you step onto your skateboard, remember that you need your brain to do all the amazing things it does for you, and do what you can to protect it. Helmet on!

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Christian Franck is director of the Office of Naval Research sponsored PANTHER program through which his research group at UW-Madison receives funding.