BrainStuff Classic: What Creates the Northern Lights?

There are lots of misconceptions out there about what causes the stunning Aurora Borealis. Learn what's really up with the Northern Lights in this classic episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff production of I Heart Radio. Hey
brain Stuff, Lauren Bogelbaum here with a classic episode for
you from our former host, Christian Sagar, about the stunning
science behind the Northern Lights. I wanted to run this
one because well, hey, it's really cool. But b I'm
loving the series His Dark Materials from the BBC and HBO,

(00:22):
so they've been on my mind and they're not a sponsor.
I just dig the show anyway. Here's Christian. Hey brain Stuff,
this is Christian Sagar. We've all heard of the Northern lights, right,
those beautiful manifestations of colors that are in the sky. Well,
they've inspired many myths in Viking legends. They were considered

(00:44):
the by Frost, the many colored bridge between Earth and Asgard,
the home of the gods, and in Finland they actually
believed the lights were a sign of the archangel Michael
battling the devil bills above. Scandinavians believed that they were
reflect actions off of the shields of the Valkyries. But
despite being observed for thousands of years, there are still

(01:06):
many misconceptions about what the Northern lights are. First of all,
it's false that their sunlight reflecting off of polar ice caps.
It's also false that their moonlight reflecting off of ice
crystals in the air. The Aurora borealis, as it was
coined by Galileo Galilei and means northern dawn or dawn
of the North in Latin, is also at the South pole,

(01:30):
known as the Aurora Australia's. In eighteen nine six, their
real origin was discovered by Norwegian scientist Christian Burkeland. He
tested his theory in controlled experiments, and here's the truth
of the matter. Solar winds stream away from the Sun
and flow around the Earth's magneto sphere. They're charged electrons

(01:53):
interact with elements in our atmosphere at points where the
magneto sphere is weakest, the no in the south poles.
So these solar winds the Sun's corona continuously amidst them
a stream of electrically charged particles. They stream away from
the Sun at speeds of one million miles per hour.

(02:16):
They reach Earth in forty hours from the Sun. Now,
this is forty times faster than a spacecraft needs to
be to escape Earth's gravity. It's pretty fast. Solar activity
currently follows an eleven years cycle and longer cycles affect
the aurora, and we've actually seen them increased solar activity
in the last few centuries. When they get here, though,

(02:38):
these solar winds strike the magnetic force generated by the
Earth's core. Then they flow through this magneto sphere, a
shield area of charged electrical and magnetic fields. This shield
is then blown into a tear drop shape by the
solar winds. The magneto sphere protects Earth from danger is

(03:00):
solar and interstellar particles, and most are directed away from Earth,
but some are trapped near the magnetic poles. The electrons
from these solar winds interact with elements in Earth's atmosphere
somewhere between sixty to two hundred miles up in the air.
This is ten times higher, by the way than most

(03:21):
airlines fly. These electrons collide with oxygen and nitrogen, transferring
energy into these gases and making them excited. When they
calm down, they emit photons and small little bursts of
energy form light. The shifts and flow of this energy
can reach twenty million ampiers at fifty thousand volts. Compare

(03:46):
that to your circuit breaker at home disengaging over fifteen
to thirty ampiers at one volts, so it's a lot
of energy. Now, the color of the aurora depends on
which element, whether it's oxygen or nitrogen, that is struck
and at what altitude it's struck at. Since it's dimmer
than sunlight, the aurora actually can't be seen during the day.

(04:10):
But oxygen emits either a greenish yellow light somewhere around
up to a hundred and fifty miles up in the air,
or a red light over a hundred and fifty miles
up in the air. Nitrogen, however, emits a blue light
up to sixty miles up in the air. If you
blend them all together, however, you can produce purples, pinks,

(04:31):
and white light. But one note. While some say they
have quote heard the Northern lights, the air where they're
formed is actually too thin to conduct sounds, so that's
not possible. It would be impossible for sound to travel
from the upper atmosphere to the ground. So you're probably
asking yourself, these sound pretty cool. Where do I get
to see the Northern lights? Where do they occur? Well,

(04:53):
they center around Earth's magnetic poles, not the geographic polls,
and they're in ring shaped spots called auroral ovals. These
are between five hundred and fifteen hundred kilometers wide and
expand during geomagnetic storms. These roughly correspond to the Arctic
and Antarctic circles and can be seen from space, so

(05:17):
the best places to see them are Central Canada, Alaska, Greenland,
Northern Scandinavia, and northern Russia. And yes, if you're asking,
other planets also have auroras. They've also been observed on Saturn, Jupiter,
and Urineus. Today's episode was written by Christian and produced

(05:41):
by Tyler Klang. Brain Stuff is a production of I
Heart Radio's How Stuff Works. For more in this and
lots of other colorful topics, visit our home planet, how
stuff Works dot com. And for more podcasts in my
heart Radio, visit my heart Radio app, Apple Podcasts, or
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