Here's a story: Imagine there's an invisible force field around our planet.
Now imagine that for billions of years, that force field
has been protecting us from a beam of supercharged
plasma that would 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!
The auroras are one of mankind's oldest mysteries, and we've come up with some crazy theories
of how to explain it along the way. Take Aristotle, he thought they aurora was the sky vomiting
little bits of flames! But it wasn't until the 1600's that we figured out two key things
that helped us explain the aurora. One, the 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,
traveling 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.
Because of 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 tiny bit of that solar wind does hops on the magnetic field and rides
it up or down to the Earth's poles, and that's where we get the auroras.
When those energized particles smash into gases way 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 little burst of
light. Different atoms in our atmosphere each give off different colors.
Excited oxygen is what gives 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 take that wind and turns it 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 working outside of Earth's magnetic field
said that if you close your eyes during one of those solar storms, you
see bright flashes of light, from 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.
When those rare violent storms hit our magnetic field and ride up to the
polar atmosphere, we are treated to an aurora show like no other. These images are more
works of art, they let scientists a 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, which 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 reach out and touch! Although I wouldn't recommend it.
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 there in our planetary backyard. And that's pretty awesome.
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