Out there in space there is no air. Cindy Zhi NY-BD-CC, CC BY-SA

Curious Kids: Why do you have to wear a helmet in space?

Curious Kids: Why do you have to wear a helmet in space?

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Out there in space there is no air.
Cindy Zhi NY-BD-CC, CC BY-SA

David Blair, University of Western Australia

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!


Why do you have to wear a helmet in space? – Leonardo, age 3, Curtin, ACT.


Hi there Leonardo. What a great question.

There is an easy answer: it’s just that out there in space there is no air. We need air to breath to keep us alive.

Here on our planet, the gravity holds the air down close to Earth so we can all share it. Gravity is the force that stops everything on Earth from floating away. The bigger a planet is, the stronger its gravity.

But up there in space all the air has been sucked up closer to big planets like Earth because of their gravity.

It’s also really cold in space.

That’s the short answer. If you want the long answer, ask your parents to read you the story below.

Not so long ago, in a galaxy not too far away…

Once upon a time, there was a boy named Leonardo. He won a competition to go to space!

When he got to space, he put on his space suit and helmet and went outside to float around for a little while. He was tied to his spaceship, so he would not float away.

Suddenly, he saw an alien on a nearby floating rock. The alien was inside a big glass dome, waving at Leonardo.

“Hi there Earth boy. My name is Ein,” the alien said. “Welcome to space. What’s your name?”

“I’m Leonardo. I’m the very first kid to visit space. I won a space competition,” he said.

“Wow!” said the alien. “Why don’t you float over to my rock? Just push off gently, one finger only.”

Leonardo pushed off from his spaceship with one finger. That was all it took to get him heading over toward the alien’s rock. It was so easy to float – so slow, so steady, so gentle!

Stopping the air whooshing out

As he drifted over, he asked the alien: “Ein, why do you live in a big glass dome?”

“Same reason you are wearing a space suit and helmet,” said Ein. “You need to keep the air in. If you took your helmet off, all the air would whoosh out and you wouldn’t be able to breathe.”

Leonardo was still drifting closer.

“I could never understand that,” he said. “When I open my front door at home the air doesn’t whoosh out. What is so different about space?”

“Well, first, do you know what air is made of?” said Ein.

“Yes, it’s made of atoms. They are teeny weeny things, too small to see. Everything is made of atoms,” said Leonardo. He was a very smart boy.

“You know, the atoms in the air you are breathing are moving at the speed of a jet plane,” said Ein. “They are bouncing all around inside your helmet, and are bouncing off your skin right now.”

“That’s crazy. They would be hurting my skin!” said Leonardo.

“No. There are so many trillions of them. They are super-tiny. They bounce off,” said Ein.

“But if you took off your helmet, the air atoms would have nothing to stop them. They would go shooting off at the speed of a jet plane.”

Air sticks close to planets

Leonardo was confused. “Then why doesn’t all the air shoot off Earth the same way?” he asked.

“The gravity of Earth holds it in,” explained Ein.

“A rocket – like the one that brought your spaceship to space – can go fast enough to escape Earth’s gravity. But atoms aren’t going that fast, so they stick close to Earth.”

Leonardo was nearly at Ein’s rock now. “So air sticks close to all the other big planets, because they have gravity?”

Ein smiled. “Yep,” she said. “It’s got a bit to do with how our universe was created when the Big Bang happened. But I’ll explain that after morning tea.”

A special air lock door on Ein’s dome opened, so Leonardo could come in without all of Ein’s air whooshing out.

Leonardo couldn’t wait to tell his Earth friends all about his new alien friend – and what he had learned about why an astronaut must always wear a helmet in space.


Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to us. They can:

* Email your question to [email protected]

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The ConversationPlease tell us your name, age, and which city you live in. You can send an audio recording of your question too, if you want. Send as many questions as you like! We won’t be able to answer every question but we will do our best.

David Blair, Emeritus Professor, ARC Centre of Excellence for Gravitational Wave Discovery, OzGrav, University of Western Australia

This article was originally published on The Conversation. Read the original article.

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