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(cellphone ringing)

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(soft ethereal tone)

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- Hi, it's Jay.

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When I was in high school, I
loved running on my track team.

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Though I don't run track anymore,

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I still enjoy watching the
world's best runners compete.

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Like Brazilian runner Alan Oliveira.

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He's one of the fastest
Paralympic runners in the world.

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He once ran the a hundred
meter dash in 10.56 seconds.

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That's less than a second
away from the world record.

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Watch him running, notice anything?

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He doesn't have lower legs,

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so these prosthetic legs help him run.

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Alan's hard work and super speed
helped him win a gold medal

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at the London Paralympics.

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Pretty cool.

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Someone named Mia is
curious about running fast.

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Let's give Mia a call now.

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(cellphone ringing)

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(soft ethereal tone)

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- Hi Jay.

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- Hi Mia.

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- I have a question for you.

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Can any animal outrun a cheetah?

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- That's a great question.

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A lot of you may already know

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that the cheetah is the fastest
land animal on the planet.

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A cheetah named Sarah was once recorded

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running 61 miles per hour

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and she probably wasn't even the fastest.

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Scientists believe cheetahs in the wild

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can reach speeds over 70.

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That's faster than a lot of cars drive.

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Whoa.

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Imagine driving on the freeway

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and seeing a cheetah run past.

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That would be pretty amazing.

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But what is it about cheetahs
that make them so fast?

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Before I go on, I'm curious,

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what do you think makes a cheetah so fast?

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Now would be a good time to
pause the video and discuss.

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Okay, you ready?

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I'm not sure what you answered,
but you might have said

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that a cheetah's four
legs help it run fast,

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and you're right.

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Cheetahs have super strong leg muscles

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that help them run super fast.

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And see those claws?

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A cheetah's claws help
it grip on the ground

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when it's running.

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Kind of like soccer cleats
help a soccer player

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from slipping when they're running fast.

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But it's not just how
strong a cheetah's legs are

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that helps it go fast.

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It's how far those legs can
go with each stride or step.

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Watch this human running.

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Some Olympic runners go
about seven to eight feet

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with each stride.

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That means they can run

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down a football field in about 40 strides.

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Now, watch this cheetah running.

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A cheetah has a bendable
spine that allows its front

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and back legs to overlap
and acts like a spring.

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This helps a cheetah spring

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over 20 feet forward with each stride.

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That means they could run

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down an entire football
field in only 15 strides.

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That's a lot less steps than a human.

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It's almost as if cheetahs
are built for speed.

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Take a look at a cheetah
next to a lion and a tiger.

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Notice the difference in size?

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A cheetah is lighter than
these other wild cats,

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and that helps with speed too.

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In fact, scientists think

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that the cheetah is the
perfect size for speed.

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If it were any smaller, like a house cat,

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its muscles would be too small
to run as fast as it does.

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And if it were any bigger,

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like a lion or a tiger,
it would be too heavy.

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With all these speedy traits, it's hard to

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imagine any animal being
able to outrun a cheetah.

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I mean, they're the fastest
animals on earth, right?

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The answer may not be
as simple as it seems.

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For example, some animals can move faster

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but they don't necessarily run,

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like this white-throated needletail.

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Some scientists think
that birds like this one

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might be able to reach flying speeds

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of 100 miles per hour or more.

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Which is a lot faster than a cheetah.

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So they could definitely
out fly a cheetah.

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But what about other land
animals, like this one?

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The pronghorn is the
second fastest animal on land.

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It has a lot of the same
traits a cheetah does.

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Powerful back legs, a long stride.

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It even has cushioned toes
that help it spring forward

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at speeds of up to 60 miles per hour,

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which isn't quite as fast as a cheetah.

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But even so,

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a pronghorn might still
be able to outrun one.

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Can you guess how?

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Okay, sure, a cheetah is definitely faster

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than a pronghorn.

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But here's the thing,
cheetahs are sprinters,

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which means they can only run
super fast for a few seconds

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before they need to slow
down or stop to rest.

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But pronghorn are
long distance runners.

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They may be slower than
cheetahs, at first,

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but they can run fast
for a really long time

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before they need to stop and rest.

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Now, cheetahs and pronghorn

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live on different continents,

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so they won't be running
into each other anytime soon.

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But if a pronghorn needed
to outrun a cheetah,

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it probably could if it
had a little headstart

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and it would probably have a
headstart almost every time.

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Pronghorn have super
eyesight and can spot a predator

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up to three to four miles away,

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and when they do, their fur
sticks up and the glands

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on their back release
a special alarm smell

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which warns the rest of their
herd that danger is near.

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So a pronghorn would probably
be able to spot a cheetah

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before it got near.

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Which would probably
give them the headstart

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they need to outrun them most of the time.

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So in summary, a cheetah's powerful legs

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and long stride make it
the fastest animal on land,

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but because it can only
run fast in short bursts,

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the long distance running pronghorn

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could probably outrun it,
if it had a headstart.

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That's all for this week's question.

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Thanks Mia for asking it.

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Now for the next episode, we reached

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into our question jar and
picked out three questions sent

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into us that we're thinking
about answering next.

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When this video's done playing,

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you'll get to vote on one.

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You can choose from, do dogs sweat?

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How does a refrigerator keep things cold?

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Or, who invented hot air balloons?

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So submit your vote when the video's over.

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We want to hear from all of you watching.

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There are mysteries all around us.

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Stay curious and see you next week.