Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey
Speaker 1: brain Stuff, Lauren Bogelbaum here with a classic episode for
Speaker 1: you from our former host, Christian Sagar, about the stunning
Speaker 1: science behind the Northern Lights. I wanted to run this
Speaker 1: one because well, hey, it's really cool. But b I'm
Speaker 1: loving the series His Dark Materials from the BBC and HBO,
Speaker 1: so they've been on my mind and they're not a sponsor.
Speaker 1: I just dig the show anyway. Here's Christian. Hey brain Stuff,
Speaker 1: this is Christian Sagar. We've all heard of the Northern lights, right,
Speaker 1: those beautiful manifestations of colors that are in the sky. Well,
Speaker 1: they've inspired many myths in Viking legends. They were considered
Speaker 1: the by Frost, the many colored bridge between Earth and Asgard,
Speaker 1: the home of the gods, and in Finland they actually
Speaker 1: believed the lights were a sign of the archangel Michael
Speaker 1: battling the devil bills above. Scandinavians believed that they were
Speaker 1: reflect actions off of the shields of the Valkyries. But
Speaker 1: despite being observed for thousands of years, there are still
Speaker 1: many misconceptions about what the Northern lights are. First of all,
Speaker 1: it's false that their sunlight reflecting off of polar ice caps.
Speaker 1: It's also false that their moonlight reflecting off of ice
Speaker 1: crystals in the air. The Aurora borealis, as it was
Speaker 1: coined by Galileo Galilei and means northern dawn or dawn
Speaker 1: of the North in Latin, is also at the South pole,
Speaker 1: known as the Aurora Australia's. In eighteen nine 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 magneto sphere. They're charged electrons
Speaker 1: interact with elements in our atmosphere at points where the
Speaker 1: magneto sphere is weakest, the no in the south poles.
Speaker 1: So these solar winds the Sun's corona continuously amidst them
Speaker 1: a stream of electrically charged particles. They stream away from
Speaker 1: the Sun at speeds of one million miles per hour.
Speaker 1: They reach Earth in forty hours from the Sun. Now,
Speaker 1: this is forty times faster than a spacecraft needs to
Speaker 1: be to escape Earth's gravity. It's pretty fast. Solar activity
Speaker 1: currently follows an eleven years cycle and longer cycles affect
Speaker 1: the aurora, and we've actually seen them increased solar activity
Speaker 1: in the last few centuries. When they get here, though,
Speaker 1: these solar winds strike the magnetic force generated by the
Speaker 1: Earth's core. Then they flow through this magneto sphere, a
Speaker 1: shield area of charged electrical and magnetic fields. This shield
Speaker 1: is then blown into a tear drop shape by the
Speaker 1: solar winds. The magneto sphere protects Earth from danger is
Speaker 1: solar and interstellar particles, and most are directed away from Earth,
Speaker 1: but some are trapped near the magnetic poles. The electrons
Speaker 1: from these solar winds interact with elements in Earth's atmosphere
Speaker 1: somewhere between sixty to two hundred miles up in the air.
Speaker 1: This is ten times higher, by the way than most
Speaker 1: airlines fly. These electrons collide with oxygen and nitrogen, transferring
Speaker 1: energy into these gases and making them excited. When they
Speaker 1: calm down, they emit photons and small little bursts of
Speaker 1: energy form light. The shifts and flow of this energy
Speaker 1: can reach twenty million ampiers at fifty thousand volts. Compare
Speaker 1: that to your circuit breaker at home disengaging over fifteen
Speaker 1: to thirty ampiers at one volts, so it's a lot
Speaker 1: of energy. Now, the color of the aurora depends on
Speaker 1: which element, whether it's oxygen or nitrogen, that is struck
Speaker 1: and at what altitude it's struck at. Since it's dimmer
Speaker 1: than sunlight, the aurora actually can't be seen during the day.
Speaker 1: But oxygen emits either a greenish yellow light somewhere around
Speaker 1: up to a hundred and fifty miles up in the air,
Speaker 1: or a red light over a hundred and fifty miles
Speaker 1: up in the air. Nitrogen, however, emits a blue light
Speaker 1: up to sixty miles up in the air. If you
Speaker 1: blend them all together, however, you can produce purples, pinks,
Speaker 1: and white light. But one note. While some say they
Speaker 1: have quote heard the Northern lights, the air where they're
Speaker 1: formed is actually too thin to conduct sounds, so that's
Speaker 1: not possible. It would be impossible for sound to travel
Speaker 1: from the upper atmosphere to the ground. So you're probably
Speaker 1: asking yourself, these sound pretty cool. Where do I get
Speaker 1: to see the Northern lights? Where do they occur? Well,
Speaker 1: they center around Earth's magnetic poles, not the geographic polls,
Speaker 1: and they're in ring shaped spots called auroral ovals. These
Speaker 1: are between five hundred and fifteen hundred kilometers wide and
Speaker 1: expand during geomagnetic storms. These roughly correspond to the Arctic
Speaker 1: and Antarctic circles and can be seen from space, so
Speaker 1: the best places to see them are Central Canada, Alaska, Greenland,
Speaker 1: Northern Scandinavia, and northern Russia. And yes, if you're asking,
Speaker 1: other planets also have auroras. They've also been observed on Saturn, Jupiter,
Speaker 1: and Urineus. Today's episode was written by Christian and produced
Speaker 1: by Tyler Klang. Brain Stuff is a production of I
Speaker 1: Heart Radio's How Stuff Works. For more in this and
Speaker 1: lots of other colorful topics, visit our home planet, how
Speaker 1: stuff Works dot com. And for more podcasts in my
Speaker 1: heart Radio, visit my heart Radio app, Apple Podcasts, or
Speaker 1: wherever you listen to your favorite shows.