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Speaker 1: Welcome to brain Stuff from house Stuff works dot com,

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Speaker 1: where smart happens Him Marshall Brain with today's question, how

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Speaker 1: big does a meteor have to be to make it

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Speaker 1: to the ground. If you've spent much time looking up

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Speaker 1: at the night sky, you've probably seen some spectacular meteors

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Speaker 1: and meteor showers. One of the most amazing things about

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Speaker 1: these displays is that the majority of the space does

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Speaker 1: that causes visible meteors is tiny, between the size of

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Speaker 1: a grain of sand and the size of a small pebble.

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Speaker 1: Discussing meteor activity can be tricky because the terminology is

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Speaker 1: pretty confusing. The term meteor actually refers to the streak

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Speaker 1: of light caused by a piece of space debris burning

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Speaker 1: up in the atmosphere. The pieces of debris are called meteoroids,

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Speaker 1: and remnants of the debris that actually each Earth's surface

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Speaker 1: or another planets for that matter, are called meteorites. Meteoroids

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Speaker 1: have a pretty big size range. They include any space

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Speaker 1: debris bigger than a molecule and smaller than about three

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Speaker 1: thirty feet or a hundred meters in diameter. Space debris

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Speaker 1: bigger than this is considered an asteroid, but most of

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Speaker 1: the debris the Earth comes into contact with is dust

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Speaker 1: shed by comets traveling through the Solar System. This dust

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Speaker 1: tends to make up the small particles that we see

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Speaker 1: as meteors. So how can we see a meteor caused

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Speaker 1: by such a small bit of matter. It turns out

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Speaker 1: that what these meteoroids lack in mass, they make up

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Speaker 1: for in speed, and this is what causes the flash

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Speaker 1: of light in the sky. Meteoroids enter the atmosphere at

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Speaker 1: extremely high speeds seven to forty five miles per second

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Speaker 1: or eleven to seventy two kilometers per second. They can

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Speaker 1: travel at this rate very easily in the vacuum of

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Speaker 1: space because there's nothing to stop them. Earth's atmosphere, on

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Speaker 1: the other hand, is full of matter, which creates a

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Speaker 1: great deal of friction on the traveling object. This friction

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Speaker 1: generates enough heat up to three thousand degrees fahrenheit or

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Speaker 1: degrees celsius, to raise the meteoroid surface to its boiling point,

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Speaker 1: so the meteoroid is vaporized layer by layer. The friction

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Speaker 1: breaks the molecules of both the meteoroid material and the

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Speaker 1: atmosphere into glowing ionized particles, which then recombine, releasing light energy.

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Speaker 1: To form a bright tail. A meteor tail caused by

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Speaker 1: a grain sized meteoroid is a few feet wide about

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Speaker 1: a meter, but because of the high speed of the debris,

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Speaker 1: maybe many miles long. So how big does a meteoroid

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Speaker 1: have to be to make it to the surface of

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Speaker 1: the Earth. Surprisingly, most of the meteoroids that reach the

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Speaker 1: ground are a specially small, from microscopic debris to dust

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Speaker 1: size particle pieces. They don't get vaporized because they're light

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Speaker 1: enough that they slow down very easily, moving about one

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Speaker 1: inch or two and a half centimeters per second through

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Speaker 1: the atmosphere. They don't experience the intense friction that larger

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Speaker 1: meteoroids do. In this sense, most all meteoroids that enter

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Speaker 1: the atmosphere make it to the ground in the form

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Speaker 1: of microscopic dust. As for the meteoroids big enough to

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Speaker 1: form visible meteors, estimates for the minimum size vary. This

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Speaker 1: is because there are factors other than size involved. Most notably,

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Speaker 1: a meteoroid's entry speed affects its chances of reaching the

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Speaker 1: surface because it determines the amount of friction the meteoroid experiences. Typically,

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Speaker 1: though a meteoroid would have to be about the size

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Speaker 1: of a marble or a portion of it to reach

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Speaker 1: the Earth's surface. Smaller particles burn up in the atmosphere

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Speaker 1: about fifty seven five miles above the Earth. The fist

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Speaker 1: size meteorites a person is likely to find on the

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Speaker 1: ground probably came from something significantly larger pieces of debris

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Speaker 1: at least the size of a basketball. Since larger meteoroids

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Speaker 1: usually break up into smaller chunks as they travel through

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Speaker 1: the atmosphere, you can actually find and collect tiny meteorites

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Speaker 1: that have made it through the Earth's atmosphere. With this

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Speaker 1: simple experiment, put a pan on your back porch or

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Speaker 1: deck and catch them. You can find sites on the

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Speaker 1: web that will show you how to identify the difference

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Speaker 1: between meteorites and bits of sand and dust. For more

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