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  • Here's a story: Now imagine there's an invisible force field around our planet. And now imagine that

  • for billions of years, that force field has been protecting us from a beam of supercharged

  • plasma that otherwise wipe out life on Earth as we know it. You might think this

  • is some kind of science fiction story, but it's all true. And it's what gives us this:

  • The aurora!

  • So the auroras are one of mankind's oldest mysteries, and we've come up with some pretty crazy theories

  • of how to explain it along the way. Take Aristotle, he thought they aurora was the sky vomiting

  • little bits of flame! But it wasn't until the 1600's that we figured out two key things

  • that helped us explain the aurora. One, Earth is really just one big magnet,

  • and second, it turns out the sun gives of a lot more than just light.

  • Long before any sunlight hits Earth, it's born at the edge of the Sun. And the edge

  • of the Sun, the corona, is a busy, beautiful place, full of churning whirlpools of plasma

  • and huge magnetic arcs. All of that action is constantly releasing waves of energized

  • particles, creating what we call the "solar wind". A few days after leaving the Sun,

  • travelling at a whopping 400 kilometers per second, that blast of charged particles reaches

  • Earth. But luckily, we've got a secret weapon on our side: Earth's swirling, molten core.

  • Our core is the key to life on Earth. It creates a magnetic

  • force field around us that deflects that solar wind up and away, making life down here much

  • more enjoyable. Then because that magnetic field we have nice things like an atmosphere and we're much less burnt-to-a-crisp

  • thanks to wave after wave of planet-sterilizing radiation. But despite all that . . . A

  • tiiiiiny bit of that solar wind does hop on the magnetic field and rided

  • it up or down to the Earth's poles, and that's where we get the auroras.

  • When those energized particles smash into gases wayyyyy up high in our atmosphere, they

  • "excite" them, which means the gas atoms grab on to a bit of energy. But they don't

  • stay excited for long. They give off that stored energy in a bright burst of

  • light. Different atoms in our atmosphere each give off different colors.

  • Excited oxygen would give off that familiar green and red that most of us think of when

  • we hear "aurora". But there's also nitrogen up there, and it can give off a really cool

  • mix of red and blue light that makes the sky glow this incredible purplish-pink. Now, we

  • can only see this happening at night, but it's happening 24 hours a day, every day of every year! It's

  • also happening on Saturn and Jupiter.

  • Sometimes the Sun takes that wind and turns up to eleven, and that can be a very dangerous sight

  • to behold. Extreme solar storms called coronal mass ejections can erupt into space almost

  • without warning, unleashing huge waves of charged particles. If they happen to be pointed

  • at Earth, then . . . look out.

  • These storms are incredibly powerful. Astronauts that are working outside of the Earth's magnetic field

  • say that if you close your eyes during one of these solar storms, you see bright

  • flashes of light when the charged particles reacting with the fluid inside your eye. In 1859, a storm

  • so powerful hit Earth that it powered a telegram from Boston to Portland, Maine

  • . . . with the equipment unplugged.

  • But, when those rare violent storms hit Earth's magnetic field and ride up to the

  • polar atmosphere, we are treated to an aurora show like no other. Now these images are more than just

  • works of art, they give scientists to study how solar storms affect life here on

  • Earth, like our electronics and communications. Some of the best views of Earth's auroras

  • have been captured from the International Space Station, the Space Station passes near the north

  • and south poles of our planet about once every 90 minutes. So if they pass by the poles while

  • it's dark? The auroras are close enough to touch! Although I wouldn't recommend that.

  • NASA makes sure that the astronauts that work on the ISS are highly trained photographers.

  • And artists down here on Earth are taking their photos and remixing them into creations

  • that are enough blow your mind.

  • This celestial light show has been burning bright for perhaps billions of years, and

  • it's more than just Earth's private art show. It's painted by this invisible

  • force surrounding our living planet, a force that catches wind from the Sun, and turns

  • it into light. It gives humans a constant reminder of the beauty of the night sky, and

  • it's right in our planetary backyard. And that's pretty awesome.

Here's a story: Now imagine there's an invisible force field around our planet. And now imagine that

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オーロラの科学と美しさ (The Science and Beauty of Auroras)

  • 191 38
    Anita Yeung に公開 2021 年 01 月 14 日
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