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[upbeat rock music]

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♪ ♪

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- Let's take a quick trip

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through the planets
in our solar system,

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with our last stop

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at the dwarf planet Pluto.

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So how far is the Sun
from Pluto?

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It's this.

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Does this number mean
anything to you?

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How can scientists possibly
work with numbers this big?

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- The end of the solar system
is something like

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5 trillion miles away.

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That's a lot of zeroes.

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To manage such a huge number,

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we need to scale things down
to more manageable numbers.

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"AU" is "astronomical unit."

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It's the distance between
the Earth and the Sun,

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about 93 million miles,

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and it's a convenient
yardstick

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to measure other distances
throughout the solar system.

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And the AU is very convenient.

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So the size
of the solar system in AU

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is about 50,000 AU.

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- One way to get a better idea
of the distance

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between the Sun and Pluto
is to compare it

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to something most of us
have seen and is familiar,

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like a football field.

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Let's start by placing the Sun
at the goal line

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and Earth at a distance
of 1 AU,

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which is at the second yard
line on a football field.

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We'll drop in inner planets
first to scale,

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using astronomical units.

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Mercury and Venus is less
than 1 AU from the Sun.

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Mars is beyond Earth's orbit,
at a distance of 1.5 AU.

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The outer planets begin
with Jupiter, at 5.2 AU,

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and end with Neptune,
at 30 AU,

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which is a little more than
half a football field away.

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And let's not forget
the dwarf planet Pluto.

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At 39.5 AUs, it's 79 yards
away from the Sun

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on our football field.

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Hmm, I wonder where

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the Kuiper Belt
and the Oort Cloud

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fit on this scale.

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- The Kuiper Belt is about
30-50 AUs away from the sun.

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The Oort Cloud wouldn't
even be in the stadium.

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It would be a couple
miles away,

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and it would extend
as much as 50 miles away.

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- Our solar system is so vast.

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Math and scaling helps us
shrink the solar system down

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to a physical model
that we can understand.

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To learn more
about our solar system,

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check out this website:

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Thanks for watching.

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See you next time
on "Real World."

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[exciting music]

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♪ ♪