[MUSIC]
"Okay, we've had a problem here."
"This is Houston. Say again, please."
"Houston, we've had a problem."
Fifty years ago today, three astronauts returned from 
the Moon, splashing down in the Pacific Ocean.
None of them got to land on the Moon 
as they'd planned.
On the third day of the mission, one of the oxygen 
tanks burst, seriously damaging the spacecraft.
The focus of the mission shifted from 
exploring the Moon to getting home safely,
and that mission was accomplished.
I was a 9-year-old kid, and I remember 
following the story on the television news.
Space exploration was the ultimate adventure story,
and like the stories I liked best, I waited 
for this one to have a happy ending.
I'm glad this one did.
But only looking back as an adult 
can I realize the seriousness of the risk,
and I have to admire everyone who took part.
I'm going to show you a safe and 
easy way to explore the Moon,
but if you would like to learn more 
about the Apollo 13 story,
follow the links under the 
 "Show More" button on this page.
To prepare for your exploration of the Moon,
find a ball — a light-colored ball — 
that you can carry with you
so that when you see the Moon, 
you can hold it out toward the Moon.
Imagine this is a picture of me holding 
this little cat toy out toward the Moon,
and I ask you to imagine it's a picture of me because 
today was cloudy and I couldn't take a picture like that.
This one was made in Photoshop.
Here is the actual photo.
It's me in a room with the windows 
darkened and there's a ceiling light,
and that light is shining on the ball.
But whether it's a ceiling light 
or whether it's the sunlight,
the effect of the light on the ball 
is going to be very similar.
We see the light shines on the ball, 
so the ball has a bright side,
and where the light isn't shining on it, the side is dark.
And similarly with the Moon: The sunlight 
shines on it so the Moon has a bright side,
and the side that the Sun is not shining on is dark.
And we can see that the ball in our hand 
mimics the Moon very nicely,
with the Sun hitting the ball 
and the Moon at a similar angle
so that we see a similar shape 
lit up on the ball and the Moon.
Maybe you'll find yourself in a place 
where you don't have the ball with you,
but you see something round nearby.
This is a decoration on the roof 
of a house that I visited once,
and you get extra points if you can 
identify the mystery of what that house is,
and I just gave you a clue for people 
who live in the Bay Area.
The light shines on the decoration on the
rooftop, so it has a bright and a dark side,
and similarly showing the same shape, 
the Moon has a bright side and a dark side.
Now imagine you're not using a decoration
on a rooftop or you're not using a cat toy,
but the ball that you're observing is the actual Earth.
This picture was taken by a space probe called Galileo.
It was the first space probe to get such a nice picture 
of the Earth and the Moon in the same frame.
And again, you can see the Earth has 
a bright side and a dark side.
The Moon has a bright side and a dark side.
And because the light is coming 
from the Sun on both of them,
the shape of the Earth and the shape of 
the Moon that we see mimic each other.
When you see the Moon in the sky, you can imagine
the planet we're on has the same pattern of 
brightness and darkness that we see on the Moon.
But 50 years ago, people were exploring the Moon 
the adventurous way, by going to the Moon.
And you can imagine the flight of 
Apollo 13 on its way to the Moon.
It gets about here when the accident occurs.
They can't put it in reverse to go home, 
and they have to continue around the Moon,
keeping themselves alive until they get 
home to Earth, and I'm so glad they did.
[MUSIC]
