Speaker 1: I'm at, I'm no, I'm Ben, and we are stuff
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Speaker 1: you get your podcasts. Welcome to brain Stuff from How
Speaker 1: Stuff Works. Hey, brain Stuff, this is Christian Sager. We've
Speaker 1: all heard of the Northern lights, right, those beautiful manifestations
Speaker 1: of colors that are in the sky. Well, they've inspired
Speaker 1: many myths. In Viking legends. They were considered the by Frost,
Speaker 1: the many colored bridge between Earth and Asgar, the home
Speaker 1: of the gods, and in Finland they actually believe the
Speaker 1: lights were a sign of the archangel Michael battling the
Speaker 1: devil bills above. Scandinavians believed that they were reflections off
Speaker 1: of the shields of the Valkyries. But despite being observed
Speaker 1: for thousands of years, there are still many misconceptions about
Speaker 1: what the Northern lights are. First of all, it's false
Speaker 1: that their sunlight reflecting off of polar ice caps. It's
Speaker 1: also false that their moonlight reflecting off of ice crystals
Speaker 1: in the air. The Aurora borealis, as it was coined
Speaker 1: by Galileo Galilei and means northern dawn or dawn of
Speaker 1: the North in Latin, is also at the South pole,
Speaker 1: known as the Aurora Australia's. In eighteen nineties six, their
Speaker 1: real origin was discovered by Norwegian scientist Christian Burkeland. He
Speaker 1: tested his theory in controlled experiments and here's the truth
Speaker 1: of the matter. Solar winds stream away from the Sun
Speaker 1: and flow around the Earth's magnetosphere. They're charged electrons interact
Speaker 1: with elements in our atmosphere at points where the magneto
Speaker 1: sphere is weakest, the North and the South poles. So
Speaker 1: these solar winds the Sun's corona continuously amidst them a
Speaker 1: stream of electrically charged particles. They stream away from the
Speaker 1: Sun at speeds of one million miles per hour. They
Speaker 1: reach Earth in forty hours from the Sun. Now, this
Speaker 1: is forty times faster than a spacecraft needs to be
Speaker 1: to escape Earth's gravity. It's pretty fast. Solar activity currently
Speaker 1: follows an eleven years cycle, and longer cycles affect the Aurora,
Speaker 1: and we've actually seen them increased Solar activity in the
Speaker 1: last few centuries. When they get here, though, these solar
Speaker 1: winds strike the magnetic force generated by the Earth's core.
Speaker 1: Then they flow through this magneto sphere, a shield area
Speaker 1: of charged electrical and magnetic fields. This shield is then
Speaker 1: blown into a tear drop shape by the solar winds.
Speaker 1: The magneto sphere protects Earth from dangerous solar and interstellar particles,
Speaker 1: and most are directed away from Earth, but some are
Speaker 1: trapped near the magnetic poles. The electrons from these solar
Speaker 1: winds interact with elements in Earth's atmosphere somewhere between sixty
Speaker 1: to two hundred miles up in the air. This is
Speaker 1: ten times higher, by the way, than most airlines fly.
Speaker 1: These electrons collide with oxygen and nitrogen, transferring energy into
Speaker 1: these gases and making them excited. When they calm down,
Speaker 1: they emit photons and small little bursts of energy form light.
Speaker 1: The shifts and flow of this energy can reach twenty
Speaker 1: million ampiers at fifty thousand volts. Compare that to your
Speaker 1: circuit breaker at home disengaging over fifteen to thirty ampiers
Speaker 1: at one volts. So it's a lot of energy. Now,
Speaker 1: the color of the aurora depends on which element, whether
Speaker 1: it's oxygen or nitrogen, that is struck, and at what
Speaker 1: altitude it's struck at. Since it's dimmer than sunlight, the
Speaker 1: aurora actually can't be seen during the day. But oxygen
Speaker 1: emits either a greenish yellow light somewhere around up to
Speaker 1: a hundred and fifty miles up in the air, or
Speaker 1: a red light over a hundred and fifty miles up
Speaker 1: in the air. Nitrogen, however, emits a blue light up
Speaker 1: to sixty miles up in the air. If you blend
Speaker 1: them all together, however, you can produce purples, pinks, and
Speaker 1: white light. But one note. While some say they have
Speaker 1: quote heard the Northern lights, the air where they're formed
Speaker 1: is actually too thin to conduct sounds, so that's not possible.
Speaker 1: It would be impossible for sound to travel from the
Speaker 1: upper atmosphere to the ground. So you're probably asking yourself,
Speaker 1: these sound pretty cool. Where do I get to see
Speaker 1: the Northern lights? Where do they occur? Well, they center
Speaker 1: around Earth's magnetic poles, not the geographic polls, and they're
Speaker 1: in ring shaped spots called auroral oval. These are between
Speaker 1: five hundred and fifteen hundred kilometers wide and expand during
Speaker 1: geomagnetic storms. These roughly correspond to the Arctic and Antarctic
Speaker 1: circles and can be seen from space, so the best
Speaker 1: places to see them are Central Canada, Alaska, Greenland, northern Scandinavia,
Speaker 1: and northern Russia. And yes, if you're asking, other planets
Speaker 1: also have auroras. They've also been observed on Saturn, Jupiter,
Speaker 1: and Urinus. Check out the brain stuff channel on YouTube,
Speaker 1: and for more on this and thousands of other topics,
Speaker 1: visit how stuff works dot com.