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We can learn about what's inside an apple
by slicing it in half.

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We can learn a lot about what's inside a planet by slicing it in half, but

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they're planets, you can't really slice them in half.

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So, how will the Juno
spacecraft find out what's inside Jupiter?

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We don't know what's inside Jupiter. Jupiter
could have a core made of heavy metal that's

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sunk to the center. Or it might be that Jupiter
has this exotic material that's hydrogen,

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squeezed down to such a high pressure, that the hydrogen acts like a metal: metallic hydrogen.

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Now, we can't cut Jupiter in half, we don't
have that capability, instead we have a happy little spacecraft

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in orbit around Jupiter.

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I'm a happy spacecraft orbiting a great big planet.

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Now as it orbits, we strongly believe
that there will be slight variations in its

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path due to tiny variations in the gravity
of Jupiter. And that will help us figure out

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what's inside. Now, how would we measure the
tiny variations of the orbit of a spacecraft

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around a great big planet millions of kilometers
from here? Well, we would do it by measuring

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the frequency of radio waves; radio waves
coming from the spacecraft, and radio waves

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coming from Earth. We can measure those variations like this, using the Doppler effect.

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Listen to the sound as the alarm clock moves toward you.

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[ALARM RINGING]

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Now listen to the sound as the alarm clock moves away.

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[ALARM RINGING]

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As it's moving toward you,
the sound gets higher-pitched.

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As it's moving away, the sound gets lower-pitched.

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Now this effect, or this phenomenon, was described

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at first by a man named Christian Doppler.
And to this day, my brother would like to

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have a rock-n-roll group called Christian
Doppler and the Effects.

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But my brother's first name isn't Christian.

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So, we believe that by precisely measuring the path of Juno

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as it orbits Jupiter using the Doppler effect,
we'll be able to determine, from Jupiter's