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nasa education wally take one and whoa

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hey wally we're not ready you're not on

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god

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guys are we ready

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so i see you've met our special guest

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thanks wally

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nasa's put people on the moon before and

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the lunar reconnaissance orbiter is

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mapping the moon so that we can go back

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now when you've looked at the moon from

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your backyard it looks really tiny so

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how does nasa put a spacecraft on

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something so small well that's because

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it's probably not as small as it looks

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so the question of the day is how big is

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the moon and to answer that we need to

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apply a proportion

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that's right wali a proportion is the

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relationship between things such as the

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relationship between the size of the

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earth and the size of the moon to find

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the actual diameter of the moon we can

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use two everyday objects to represent

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the relative sizes of the earth and the

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great idea guys a baseball is just about

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the right size for our moon now we need

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an earth

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wally so we could use the basketball as

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our earth and the baseball as our moon

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now a basketball is 24 centimeters in

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diameter and the baseball is seven and a

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half centimeters in diameter so let's

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apply our proportion

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over basketball equals x because that's

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what we're trying to find out over the

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earth's diameter and we know that

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because we live here so that's 12 756

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kilometers

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now cross multiply

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and solve for x

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so we just saw that the moon's diameter

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is about 3 900 kilometers but you should

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in any case the moon's plenty big to

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land a spacecraft to live and work on