As Byeol-maru drifted closer to Earth, a faint green outline appeared on the screen, wrapped gently around the whole planet, as if Earth were carefully tucked inside a thin, transparent soap bubble.
“Byeoli, what’s that green outline? It looks like Earth has some kind of shield wrapped around it.”
“That’s Earth’s magnetic field. You can’t see it with your eyes, but it wraps around the whole planet like an invisible shield.”
“A shield? What is it protecting Earth from?”
“The Sun is constantly sending out tiny, dangerous particles in every direction through space, something called solar wind. If that hit Earth directly, it wouldn’t be good for us. But deep inside Earth, a huge ball of hot metal spins around and around, and that spinning creates a magnetic field, one that pushes most of the solar wind away before it ever reaches us.”
Hyeongseop stared for a long while at the image of the field wrapped around Earth. It was hard to believe something completely invisible was doing such an enormous job.
“How long has this shield been protecting Earth?”
“Pretty much since Earth was first formed. As long as that molten metal core keeps spinning inside, this shield keeps being made, nonstop. It’s been protecting Earth since long before you were born, even before your grandmother’s grandmother was born.”
“Wait, remember when you told me about the green lights dancing in the sky? Does that have something to do with this shield?”
“Exactly right. The magnetic field blocks most of the solar wind, but a small amount still leaks in through gaps near the North and South Poles. When those particles crash into the air high above Earth, they glow, and that glow is the aurora. So really, the aurora is proof that this invisible shield is working hard.”
“What would happen if the shield disappeared?”
“If it vanished, the solar wind would gradually strip away Earth’s air. Luckily, that molten core will keep generating this shield for a very, very long time to come, so you can sleep easy tonight.”
“Do other planets have a shield like this too?”
“Not all of them. Mars used to have a magnetic field a long time ago, but it’s mostly gone now, so Mars takes the full hit from the solar wind. Some scientists think that’s part of why Mars ended up with such a thin atmosphere. The thick air and water Earth has might be a gift from this very shield.”
Hyeongseop looked at Earth again. Knowing that an invisible shield was quietly protecting him and everyone on the planet, right at this very moment, made the blue glow of Earth feel even more comforting. Every ordinary moment, running around outside, looking up at the sky, falling asleep at night, something unseen had been watching over him the whole time. The thought warmed a small corner of his heart.
“Earth’s core generates a magnetic field that acts as an invisible shield against solar wind, and particles that leak through the gaps create the aurora.”
Your Turn Now
Share with someone today what you remember.
- What’s Earth’s invisible shield called?
- What does it protect Earth from?
- How is the aurora related to this shield?
(Check when ready: 1. The magnetic field. 2. Solar wind from the Sun. 3. Leaked solar wind particles glowing is the aurora.)
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