WEBVTT

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Everybody loves fireworks --

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the lights, the colors,

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and, of course, the big boom.

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But the history of fireworks

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isn't all hugs and celebrations.

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Long before epic fireworks displays,

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chemists in China invented the key ingredient

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that propels those bright lights into the sky.

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That invention was what we now call gunpowder.

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Our story begins back in ancient China

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in the mid-ninth century

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where early Chinese alchemists

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were trying to create a potion for immortality.

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Instead, what they created was a flammable powder

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that burned down many of their homes.

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They quickly realized that this black powder,

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which they called fire medicine,

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was precisely the opposite of something

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that would make you live forever.

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In these early days,

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the Chinese hadn't yet figured out

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how to make the powder explode;

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it was simply very flammable,

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and their armies used it

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to make flaming arrows

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and even a flamethrower.

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But once they figured out the right proportions

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of ingredients to create a blast,

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they began using the powder even more,

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creating fireworks to keep evil spirits away

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and bombs to defend themselves

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against Mongol invaders.

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It was these Mongols, most likely,

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who spread the invention of gunpowder

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across the world.

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After fielding Chinese attacks,

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they learned how to produce the powder themselves

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and brought it with them

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on their conquests in Persia and India.

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William of Rubruck,

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a European ambassador to the Mongols,

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was likely responsible for bringing gunpowder

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back to Europe around 1254.

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From there, engineers and military inventors

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created all kinds of destructive weapons.

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From bombs to guns to cannons,

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gunpowder left its mark on the world

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in some pretty terrible ways,

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in contrast to the beautiful marks

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it can leave in the air.

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So, how does black powder propel

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fireworks into the sky?

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You might have seen old Westerns or cartoons

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where a trail of gunpowder is lit

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and it leads to a large and obviously explosive barrel.

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Once the fire gets to the barrel,

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a large boom occurs.

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But why doesn't the trail itself explode?

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The reason is that burning the powder

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releases energy and gases.

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While the trail is burning,

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these are easily released into the surrounding air.

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But when the gunpowder

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is contained within the barrel,

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the energy and gases cannot easily escape

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and build up until

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BOOM!

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Firework canisters provide

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a single, upward-facing outlet

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to channel this explosive energy.

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The wick ignites the gunpowder

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and the energy takes

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the easiest exit from the canister,

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launching the firework high into the sky.

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The flame then makes its way

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through the firework's encasing

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and the same reaction occurs

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high above our heads.

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So, while the Chinese alchemists

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never found the compound for eternal life,

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they did find something

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that would go on to shape all of civilization,

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something that has caused

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many tragic moments in human history,

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and yet still gives us hope

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when we look up in celebration

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at the colorful night sky.