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Speaker 1: Welcome to brain Stuff, a production of I Heart Radio.

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Speaker 1: Hey brain Stuff, I'm Lauren Vogelbaum, and this is another

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Speaker 1: classic episode. When you release a helium balloon, it's freedom

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Speaker 1: is temporary. Eventually it must fall back to Earth. But

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Speaker 1: when and how I'll let former Lauren explain. Hey, brain Stuff,

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Speaker 1: I'm Lauren Vogelbaum, and today we're talking about balloons, Helium

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Speaker 1: balloons that have escaped the clutches of their human captors

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Speaker 1: to float far beyond the mortal realms, straight up into

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Speaker 1: the infinity of the stars. Well, not really. I hate

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Speaker 1: to burst your well, balloon, but that's not what balloons

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Speaker 1: do when they're released. They first blame the composition of

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Speaker 1: our atmosphere. Helium balloons float because they're buoyant in the air,

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Speaker 1: like a beach ball is buoyant in water. Balloons don't fly.

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Speaker 1: The air around them sinks pushing them upward. That's because

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Speaker 1: helium ways just zero point one eight grams per leader.

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Speaker 1: Nitrogen and oxygen, which together make up about of the

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Speaker 1: air we breathe, weigh one point to five grams and

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Speaker 1: one point for three grams per leader, respectively. And okay,

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Speaker 1: most helium balloons these days aren't filled with one pure

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Speaker 1: helium depending on the company selling it about maybe regular

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Speaker 1: old air to help keep costs down and preserve the

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Speaker 1: global helium supply. But as long as the weight of

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Speaker 1: the balloon plus the helium mixture inside of it equals

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Speaker 1: less than the weight of the air around it, it'll

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Speaker 1: keep on moving up. However, nitrogen and oxygen aren't distributed

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Speaker 1: evenly from sea level two outer space. Earth's gravity holds

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Speaker 1: air close to the surface. The higher up you go,

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Speaker 1: the thinner a k a. Less massive the air gets.

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Speaker 1: Just five miles up, there are only one third as

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Speaker 1: many nitrogen and oxygen atoms around you. Ten miles up,

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Speaker 1: there are only one tenth as many. So a helium

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Speaker 1: mixture balloon wouldn't keep floating up forever because eventually it

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Speaker 1: would be heavier than the air around it. It'll stop

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Speaker 1: when it hits the point of equilibrium. However, However, as

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Speaker 1: evidenced by the lack of a thick layer of party

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Speaker 1: balloons up in the sky, that's not how the story

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Speaker 1: ends for freed balloon enter atmospheric pressure. Since the elements

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Speaker 1: that make up our air supply hug the surface and

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Speaker 1: thin out at increasing altitudes. The pressure that the air

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Speaker 1: exerts on objects also drops, and increasing altitudes, lower atmospheric

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Speaker 1: pressure outside means the gases inside a balloon will want

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Speaker 1: to expand how much that balloon can expand depends on

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Speaker 1: what the balloon is made of. A latex rubber is

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Speaker 1: pretty common and can stretch a lot. Milar, which is

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Speaker 1: a trade name for a type of stretched polyester that's

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Speaker 1: strengthened with a film of evaporated metal, does not stretch,

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Speaker 1: So how long the balloon lasts before bursting depends on

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Speaker 1: the material and how much helium mixture is in there.

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Speaker 1: A half full balloon will last longer. Also, since latex

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Speaker 1: is porous, a bit of helium mixed your will constantly

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Speaker 1: seep out through the balloon's walls, possibly giving it a

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Speaker 1: little bit more time. And finally, how the balloon pops

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Speaker 1: will depend on the temperature of the air around it.

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Speaker 1: That temperature will decrease as the balloon rises through the troposphere.

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Speaker 1: This is the lowest layer of Earth's atmosphere, extending four

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Speaker 1: to twelve miles above the surface. At the top of

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Speaker 1: the troposphere, temperatures reach negative sixty degrees fahrenheit. That's about

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Speaker 1: negative fifty one celsius. Latex and mile are both become

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Speaker 1: brittle around negative forty degrees fahrenheit or celsius. So if

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Speaker 1: they make it up that bar, they'll lose their ability

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Speaker 1: to expand, and they won't pop, they'll shatter. So when

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Speaker 1: and how balloons burst depends on three things. What the

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Speaker 1: balloon is made of, how much gas is inside, and

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Speaker 1: the temperature around them. Today's episode is based on a

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Speaker 1: script that I wrote for a brain stuff video for

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Speaker 1: how stuff works dot Com. A brain Stuff is production

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Speaker 1: of my heart Radio in part ship with how stuff

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Speaker 1: Works dot Com, and it's produced by Tyler Klang. For

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Speaker 1: more podcasts my heart Radio, visit the I heart Radio app,

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Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows,