WEBVTT - BrainStuff Classic: What Creates the Northern Lights?

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<v Speaker 1>Welcome to brain Stuff production of I Heart Radio. Hey

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<v Speaker 1>brain Stuff, Lauren Bogelbaum here with a classic episode for

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<v Speaker 1>you from our former host, Christian Sagar, about the stunning

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<v Speaker 1>science behind the Northern Lights. I wanted to run this

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<v Speaker 1>one because well, hey, it's really cool. But b I'm

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<v Speaker 1>loving the series His Dark Materials from the BBC and HBO,

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<v Speaker 1>so they've been on my mind and they're not a sponsor.

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<v Speaker 1>I just dig the show anyway. Here's Christian. Hey brain Stuff,

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<v Speaker 1>this is Christian Sagar. We've all heard of the Northern lights, right,

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<v Speaker 1>those beautiful manifestations of colors that are in the sky. Well,

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<v Speaker 1>they've inspired many myths in Viking legends. They were considered

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<v Speaker 1>the by Frost, the many colored bridge between Earth and Asgard,

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<v Speaker 1>the home of the gods, and in Finland they actually

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<v Speaker 1>believed the lights were a sign of the archangel Michael

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<v Speaker 1>battling the devil bills above. Scandinavians believed that they were

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<v Speaker 1>reflect actions off of the shields of the Valkyries. But

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<v Speaker 1>despite being observed for thousands of years, there are still

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<v Speaker 1>many misconceptions about what the Northern lights are. First of all,

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<v Speaker 1>it's false that their sunlight reflecting off of polar ice caps.

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<v Speaker 1>It's also false that their moonlight reflecting off of ice

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<v Speaker 1>crystals in the air. The Aurora borealis, as it was

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<v Speaker 1>coined by Galileo Galilei and means northern dawn or dawn

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<v Speaker 1>of the North in Latin, is also at the South pole,

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<v Speaker 1>known as the Aurora Australia's. In eighteen nine six, their

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<v Speaker 1>real origin was discovered by Norwegian scientist Christian Burkeland. He

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<v Speaker 1>tested his theory in controlled experiments, and here's the truth

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<v Speaker 1>of the matter. Solar winds stream away from the Sun

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<v Speaker 1>and flow around the Earth's magneto sphere. They're charged electrons

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<v Speaker 1>interact with elements in our atmosphere at points where the

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<v Speaker 1>magneto sphere is weakest, the no in the south poles.

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<v Speaker 1>So these solar winds the Sun's corona continuously amidst them

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<v Speaker 1>a stream of electrically charged particles. They stream away from

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<v Speaker 1>the Sun at speeds of one million miles per hour.

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<v Speaker 1>They reach Earth in forty hours from the Sun. Now,

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<v Speaker 1>this is forty times faster than a spacecraft needs to

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<v Speaker 1>be to escape Earth's gravity. It's pretty fast. Solar activity

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<v Speaker 1>currently follows an eleven years cycle and longer cycles affect

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<v Speaker 1>the aurora, and we've actually seen them increased solar activity

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<v Speaker 1>in the last few centuries. When they get here, though,

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<v Speaker 1>these solar winds strike the magnetic force generated by the

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<v Speaker 1>Earth's core. Then they flow through this magneto sphere, a

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<v Speaker 1>shield area of charged electrical and magnetic fields. This shield

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<v Speaker 1>is then blown into a tear drop shape by the

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<v Speaker 1>solar winds. The magneto sphere protects Earth from danger is

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<v Speaker 1>solar and interstellar particles, and most are directed away from Earth,

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<v Speaker 1>but some are trapped near the magnetic poles. The electrons

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<v Speaker 1>from these solar winds interact with elements in Earth's atmosphere

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<v Speaker 1>somewhere between sixty to two hundred miles up in the air.

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<v Speaker 1>This is ten times higher, by the way than most

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<v Speaker 1>airlines fly. These electrons collide with oxygen and nitrogen, transferring

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<v Speaker 1>energy into these gases and making them excited. When they

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<v Speaker 1>calm down, they emit photons and small little bursts of

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<v Speaker 1>energy form light. The shifts and flow of this energy

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<v Speaker 1>can reach twenty million ampiers at fifty thousand volts. Compare

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<v Speaker 1>that to your circuit breaker at home disengaging over fifteen

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<v Speaker 1>to thirty ampiers at one volts, so it's a lot

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<v Speaker 1>of energy. Now, the color of the aurora depends on

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<v Speaker 1>which element, whether it's oxygen or nitrogen, that is struck

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<v Speaker 1>and at what altitude it's struck at. Since it's dimmer

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<v Speaker 1>than sunlight, the aurora actually can't be seen during the day.

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<v Speaker 1>But oxygen emits either a greenish yellow light somewhere around

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<v Speaker 1>up to a hundred and fifty miles up in the air,

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<v Speaker 1>or a red light over a hundred and fifty miles

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<v Speaker 1>up in the air. Nitrogen, however, emits a blue light

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<v Speaker 1>up to sixty miles up in the air. If you

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<v Speaker 1>blend them all together, however, you can produce purples, pinks,

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<v Speaker 1>and white light. But one note. While some say they

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<v Speaker 1>have quote heard the Northern lights, the air where they're

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<v Speaker 1>formed is actually too thin to conduct sounds, so that's

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<v Speaker 1>not possible. It would be impossible for sound to travel

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<v Speaker 1>from the upper atmosphere to the ground. So you're probably

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<v Speaker 1>asking yourself, these sound pretty cool. Where do I get

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<v Speaker 1>to see the Northern lights? Where do they occur? Well,

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<v Speaker 1>they center around Earth's magnetic poles, not the geographic polls,

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<v Speaker 1>and they're in ring shaped spots called auroral ovals. These

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<v Speaker 1>are between five hundred and fifteen hundred kilometers wide and

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<v Speaker 1>expand during geomagnetic storms. These roughly correspond to the Arctic

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<v Speaker 1>and Antarctic circles and can be seen from space, so

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<v Speaker 1>the best places to see them are Central Canada, Alaska, Greenland,

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<v Speaker 1>Northern Scandinavia, and northern Russia. And yes, if you're asking,

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<v Speaker 1>other planets also have auroras. They've also been observed on Saturn, Jupiter,

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<v Speaker 1>and Urineus. Today's episode was written by Christian and produced

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<v Speaker 1>by Tyler Klang. Brain Stuff is a production of I

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<v Speaker 1>Heart Radio's How Stuff Works. For more in this and

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<v Speaker 1>lots of other colorful topics, visit our home planet, how

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<v Speaker 1>stuff Works dot com. And for more podcasts in my

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<v Speaker 1>heart Radio, visit my heart Radio app, Apple Podcasts, or

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