(ringing)
- Hi, it's Doug.
The planet Mars is sometimes
known as the red planet
and with good reason.
When scientists sent
robotic landers to Mars,
they found lots of red colored
rocks and even red dirt
similar to the kinds of
red rocks and red dirt
you might find here on Earth.
They even found evidence that
Mars once had a lot of water
but we've yet to find
any sign of life on Mars.
Someone named Sanskriti has a question
about life on other planets.
Let's give her a call now.
(ringing)
- Hi, Doug.
- Hi, Sanskriti.
- I have a question for you.
Is Earth the only planet with life?
- That's a great question.
You might know that our solar system
has eight planets orbiting the sun,
Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus and Neptune
but our planet, the Earth, is special.
It's the only planet that has life.
Why is that?
Why is Earth the only planet
with life in our solar system?
Now would be a good time to
pause the video and discuss.
Okay, you ready?
You might know that some
planets are really hot.
Mercury and Venus, the
planets closest to the sun,
reach temperatures over
800 degrees Fahrenheit.
At temperatures that hot,
you could cook a pizza
in about 16 seconds.
So it's no wonder there
aren't living things
on these planets.
The sun is the source of most
heat in the solar system.
So the farther you get from the sun,
the star at the center
of our solar system,
the cooler it gets.
The farthest planets are really cold.
The temperatures on Uranus and Neptune
are about 300 degrees
Fahrenheit below freezing.
On the dwarf planet Pluto,
it gets even colder.
About minus 380 degrees Fahrenheit.
Living things can't survive on planets
with extreme temperatures
that are either way
too hot or way too cold
but somewhere in between there's a zone,
a place in the solar system
where the temperature
is just right for life,
a place that's not too
hot and not too cold.
Scientists have a special name
for this zone around the sun.
They call it the Goldilocks Zone
as in Goldilocks and the Three Bears.
Have you heard the story?
Goldilocks goes into the bears' house
and tries different things
that belong to the bears
like the three bowls of porridge.
One is too hot, one is too
hold and one is just right.
Earth is in the just right
part of the solar system.
Earth is the only planet
in the solar system
with liquid water on its surface.
In fact, that's where it gets
the nickname the blue planet.
Earth is not so hot that all
of the water boils into vapor
and it's also not so cold
that all of the water freezes into ice.
It's just right for life.
So that explains how Earth
is unique in our solar system
but it's not necessarily
unique in the universe.
It's not just our sun that
has a Goldilocks Zone.
The sun is a star like
the other stars in the sky
and every star has a
Goldilocks Zone around it.
When you look up at the night sky,
there are millions of stars
meaning millions of places
where life might exist.
Many scientists like Neil deGrasse Tyson
strongly believe that Earth
probably isn't the only place
in the universe where life exists.
We just haven't found
life on other planets yet
but scientists are hunting for it.
As of now, scientists
have found over 50 planets
orbiting around other stars in
the stars' Goldilocks Zones.
Who knows, maybe life exists
on one of these planets
waiting to be discovered by
a future scientist like you.
So in summary, so far
scientists have only found life
on one planet in our
solar system, the Earth.
Earth is in the Goldilocks
Zone of our sun.
That's where it's not too hot or too cold.
Scientists are now searching
for Goldilocks Zones
around other stars to try to find life
elsewhere in the universe.
That's all for this week's question.
Thanks, Sanskriti for asking it.
Now, for the next episode, I
reached into my question jar
and found three questions submitted to me
that I'm thinking about answering.
When this video's done playing,
you'll get to vote on one.
You can choose from
what's the difference
between dry ice and ice,
what makes sloths slow
or how are pencils made?
So submit your vote when the video's over.
I wanna hear from all of you watching.
There are mysteries all around us.
Stay curious and see ya next week.
