WEBVTT - What Causes the Northern Lights?

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<v Speaker 1>I'm at, I'm no, I'm Ben, and we are stuff

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<v Speaker 1>Stuff Works. Hey, brain Stuff, this is Christian Sager. We've

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<v Speaker 1>all heard of the Northern lights, right, those beautiful manifestations

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<v Speaker 1>of colors that are in the sky. Well, they've inspired

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<v Speaker 1>many myths. In Viking legends. They were considered the by Frost,

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<v Speaker 1>the many colored bridge between Earth and Asgar, the home

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

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

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<v Speaker 1>devil bills above. Scandinavians believed that they were reflections off

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<v Speaker 1>of the shields of the Valkyries. But despite being observed

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<v Speaker 1>for thousands of years, there are still many misconceptions about

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<v Speaker 1>what the Northern lights are. First of all, it's false

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

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<v Speaker 1>also false that their moonlight reflecting off of ice crystals

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

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

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<v Speaker 1>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 nineties 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 magnetosphere. They're charged electrons interact

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

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<v Speaker 1>sphere is weakest, the North and the South poles. So

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

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

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

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

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

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

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<v Speaker 1>follows an eleven years cycle, and longer cycles affect the Aurora,

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<v Speaker 1>and we've actually seen them increased Solar activity in the

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<v Speaker 1>last few centuries. When they get here, though, these solar

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<v Speaker 1>winds strike the magnetic force generated by the Earth's core.

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<v Speaker 1>Then they flow through this magneto sphere, a shield area

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

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<v Speaker 1>blown into a tear drop shape by the solar winds.

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<v Speaker 1>The magneto sphere protects Earth from dangerous solar and interstellar particles,

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<v Speaker 1>and most are directed away from Earth, but some are

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<v Speaker 1>trapped near the magnetic poles. The electrons from these solar

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<v Speaker 1>winds interact with elements in Earth's atmosphere somewhere between sixty

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<v Speaker 1>to two hundred miles up in the air. This is

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<v Speaker 1>ten times higher, by the way, than most airlines fly.

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<v Speaker 1>These electrons collide with oxygen and nitrogen, transferring energy into

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<v Speaker 1>these gases and making them excited. When they calm down,

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<v Speaker 1>they emit photons and small little bursts of energy form light.

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<v Speaker 1>The shifts and flow of this energy can reach twenty

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<v Speaker 1>million ampiers at fifty thousand volts. Compare that to your

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<v Speaker 1>circuit breaker at home disengaging over fifteen to thirty ampiers

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<v Speaker 1>at one volts. So it's a lot of energy. Now,

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<v Speaker 1>the color of the aurora depends on which element, whether

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<v Speaker 1>it's oxygen or nitrogen, that is struck, and at what

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<v Speaker 1>altitude it's struck at. Since it's dimmer than sunlight, the

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<v Speaker 1>aurora actually can't be seen during the day. But oxygen

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<v Speaker 1>emits either a greenish yellow light somewhere around up to

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

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

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

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

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

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

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

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<v Speaker 1>is actually too thin to conduct sounds, so that's not possible.

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<v Speaker 1>It would be impossible for sound to travel from the

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

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<v Speaker 1>these sound pretty cool. Where do I get to see

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

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

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<v Speaker 1>in ring shaped spots called auroral oval. These are between

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<v Speaker 1>five hundred and fifteen hundred kilometers wide and expand during

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<v Speaker 1>geomagnetic storms. These roughly correspond to the Arctic and Antarctic

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

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<v Speaker 1>places to see them are Central Canada, Alaska, Greenland, northern Scandinavia,

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

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

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<v Speaker 1>and Urinus. Check out the brain stuff channel on YouTube,

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<v Speaker 1>and for more on this and thousands of other topics,

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<v Speaker 1>visit how stuff works dot com.