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Speaker 1: Welcome to brain Stuff from How Stuff Works. Hey, brain Stuff,

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Speaker 1: it's Christian Sager. On September five, nineteen seventy seven, NASA's

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Speaker 1: historic Voyager one mission launched, joining its identical robotic twin

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Speaker 1: Voyager two, on what would turn out to be a

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Speaker 1: forty year odyssey through the Solar System and into interstellar space.

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Speaker 1: Voyager two had launched more than two weeks earlier on

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Speaker 1: August nineteen seventy seven, and both spacecraft completed the dazzling

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Speaker 1: grand tour of the Outer Solar System's planets. Voyager one

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Speaker 1: has now left our sons heliosphere, becoming a bona fide

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Speaker 1: interstellar probe and the most distant human made vehicle, and

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Speaker 1: Voyager two is about to flirt with the outermost boundary

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Speaker 1: of the Heliosphere the Helio Pause. But exploring interstellar space

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Speaker 1: wasn't a mission objective back in nineteen seventy seven. Back then,

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Speaker 1: the twin probes aim was to reveal the rich, diversity

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Speaker 1: and mystery of the Outer Solar System's planets. For Ed Stone,

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Speaker 1: who has been project scientists for the Voyagers since nineteen

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Speaker 1: seventy two, his favorite memory was the jaw dropping discovery

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Speaker 1: of volcanoes on Jupiter's moon Io in nineteen seventy nine.

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Speaker 1: He said the eruptions on Io were the first direct

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Speaker 1: evidence of active volcanoes elsewhere in the Solar System, and

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Speaker 1: he wasn't wrong. Both Voyager one and two changed our

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Speaker 1: perspective of our Solar System, revealing never before seeing details

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Speaker 1: in planetary atmospheres and revealing new discoveries about interplanetary space.

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Speaker 1: New insights to Saturn's beautiful rings were gleaned, and a

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Speaker 1: huge diversity of moons swarming around the gas giants was revealed.

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Speaker 1: There are few more visceral science impacts on society than

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Speaker 1: when in nineteen ninety Voyager one was commanded to turn

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Speaker 1: around and capture an image of Earth from nearly four

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Speaker 1: billion miles or six point four billion kilometers distant. This

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Speaker 1: was at the request of Superstar astronomer and science communicator

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Speaker 1: Carl Sagan. In an interview with space dot Com, Stone

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Speaker 1: estimated that both spacecraft only have about ten years supply

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Speaker 1: of power left before the plutonium heat output dwindles, two

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Speaker 1: levels that won't sustain any spacecraft instrumentation or critical subsystems.

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Speaker 1: Though the Voyagers will eventually die, they continue to take data,

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Speaker 1: and Voyager one is taking measurements of a very alien

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Speaker 1: region the interstellar medium. On August two thousand and twelve,

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Speaker 1: NASA confirmed that Voyager one had officially left the heliosphere,

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Speaker 1: speeding into interstellar space. Voyager two is traveling in a

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Speaker 1: different direction and has an encountered interstellar space. It The

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Speaker 1: mysterious outermost regions of the Solar System have now been probed,

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Speaker 1: and Voyager one was able to take measurements of the

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Speaker 1: magnetic field and particle energies, important measurements that have allowed

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Speaker 1: scientists a very privileged view of how our Son's magnetic

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Speaker 1: field and solar wind particles interact with the space between

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Speaker 1: the stars. So, after four decades of exploration, two spacecraft

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Speaker 1: built from nineteen seventies technology are still exploring, and a

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Speaker 1: new generation of scientists are using them to carry out

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Speaker 1: cutting edge research in a region of space that no

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Speaker 1: other robot that we know of has ever experienced. Even

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Speaker 1: after their power supplies dwindle and the Voyagers lose communication

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Speaker 1: with Earth, they will be silent interstellar emissaries for humanity,

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Speaker 1: carrying the Golden records as shrines of the civilization that

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Speaker 1: built these incredible machines should an extraterrestrial and elligence stumble

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Speaker 1: upon them and the eons to come. Today's episode was

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Speaker 1: written by Ian O'Neill, produced by Dylan Fagan, and For

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Speaker 1: more on this and other topics, please visit us at

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Speaker 1: how stuff works dot com