Are There Other Planets Like Earth?

[ intro ] Squeaks was just showing me some new pictures
of different planets. We have Mars, bright red and rocky … Saturn,
with its amazing rings … Can you guess which is my favorite to learn
about, Squeaks? [Squeaks thinks, then guesses Earth] You got it! I love learning about planet Earth because
it’s so unique. Here on Earth, there’s life everywhere you
look. But the seven other planets, all their different
moons, other places like asteroids — we’ve never seen signs of life on any
of them. The sun is only one star, though, and the
universe is full of stars. Lots of those stars also have planets orbiting
them, just like Earth and Mars and Jupiter and all the other planets in our solar system
go around the sun. With so many other planets out there, lots
of astronomers — scientists who study space — wonder if some of them are like Earth and
living things could survive there. Most of the planets we’ve seen are very different
from Earth — lots of them are boiling hot, or don’t have
enough air, or don’t have any solid ground. There’s even a planet where it might /rain
diamonds!/ But there are a few planets around other stars
that scientists think are a little bit like Earth. That doesn’t mean there are living things
on them, but at least living things could survive there. So when scientists are looking to see if a
planet is like Earth, what do you think they’re looking for? What do living things need to survive? I’ll give you a hint: one of them is something
you’re standing on right now. [Squeaks guesses, the floor?] That’s a good guess — it is like the floor,
but outside. [Squeaks: the ground!] Yeah, the ground! Earth has a crust of dirt and rock around
the outside; that’s the ground where we walk and what’s
at the bottom of the sea. If a planet doesn’t have ground to walk
on, then it wouldn’t be as good for most living things. Some planets are just a big ball of gas with
nothing solid in them at all! It would be very hard to live someplace without
ground to stand on or oceans to swim in. I think you might be able to guess another
thing that we need on a planet to survive, Squeaks. It’s all around us… [Squeaks guesses air] That’s right, we need air to breathe. An Earth-like planet needs to have air for
us to breathe. That air is part of what’s called the atmosphere, a layer all around the planet with all of
the air and clouds inside. The atmosphere on a planet has to be just
right, with the right amount of air — and it has to be the type of air we can breathe. Knowing that a planet has air to breathe and
a solid crust is important, but the planet also has to be the right temperature. Planets orbit around stars like our sun, but
if the planets are too close to their star, they can be horribly, boiling hot. Yikes, I would not want to live there. But if the planet is too far from its star,
it’s way too cold. We’d freeze if we even tried to set foot
on that planet. Only planets at that perfect distance away
from their star will be at the right temperature to support
life like us. We don’t want it too hot or too cold — it
has to be just right. Does that sound familiar, Squeaks? [Squeaks] It does sound like the story of ‘Goldilocks
and the Three Bears.’ In fact, many scientists call that special,
perfectly-warm distance away from a star the Goldilocks zone. In the Goldilocks zone, it would also be possible
to find liquid water, something that all life on Earth needs. There are so many different traits that a
planet needs to share with Earth for us to live there that most of the planets we’ve found wouldn’t
work. Scientists have found some that could be like
Earth, though, like a planet called Kepler-452b. It’s much bigger than Earth, but it’s
in the Goldilocks zone! There’s still so much to learn about what
it’s like on planets like Kepler-452b. [Squeaks] I also wish we could visit those planets,
Squeaks! But they’re too far away for humans to reach
right now. Even in our fastest rocket ships, it would take thousands of years for us to
reach the closest star to the sun and the planets around it. That’s way too long a trip for people to
take. Maybe someday, people will invent a way to
travel that far quickly, but for now, we can’t reach planets like Kepler-452b. Since we can’t go visit it ourselves, we’ll just have to make our observations
from here on my favorite planet: Earth! We’re so lucky to have such a great planet
where we can live, make discoveries, and learn new things about the other planets
all around the universe. [Squeaks agrees] What do you think it would be like to live
on another planet? Do you have an idea to make spaceships move
faster, so we can visit other planets? Ask a grown-up to help you leave a comment
below, or send us your ideas on our website at We’ll see you next time, here at the Fort! [ outro ]

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