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? [music] ?

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KIDS: Our World!

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EVAN: What’s that Globey?

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What am I doing? I’m looking
into the night sky.

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Oh, what’s with the white
beard?

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I’m doing my impersonation of
Galileo.

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Galileo was an Italian
physicist, mathematician,

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and astronomer who studied the
stars more than 400 years ago.

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People today refer to Galileo
as the "father of modern

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science” and the “father of
modern observational
astronomy."

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Galileo made major improvements
to the telescope, which today

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continues to help us see the
stars and planets in space.

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In fact, using one of his early
models of the telescope,

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Galileo was able to discover
four of the largest moons of

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Jupiter, which are called Io,
Europa, Callisto, and Ganymede.

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He was also the first to say
our Moon’s surface is not
smooth.

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It’s rough and uneven...
covered with craters and
mountains.

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Like Galileo, today’s
astronomers continue to look

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into space, hoping to make new
discoveries about our universe.

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But today’s telescopes are much
more powerful than the one’s
Galileo used.

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The large telescopes our
astronomers use can be found at
observatories around the world.

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But they can also be found in
space, such as the Hubble Space
Telescope.

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Hubble is a giant telescope
that orbits Earth and sends

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back amazing pictures of our
universe.

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Today we’re going to talk about
a special earth-based
observatory in Puerto Rico.

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It’s the Arecibo observatory.
It’s called that because it’s

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located near the town of
Arecibo in Puerto Rico, which
is a US territory.

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Puerto Rico is in the
Caribbean. It’s also an island.

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The telescope at the Arecibo
observatory is enormous!

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It measures 305 meters in
diameter.

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That’s about 1,000 feet, which
is even longer than three
football fields.

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A diameter is a line segment
that goes from one point on a

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circle through the center to
another point on the circle.

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People use this measurement to
describe how large a circle is.

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But the Arecibo telescope isn’t
like some of the other
telescopes we’ve talked about.

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You know, there are many
different types of telescopes,

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and only some of them are
optical scopes like the on used
by Galileo.

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The Arecibo telescope is a
radio telescope, which means it

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sees the radio waves given off
by large objects like planets.

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A large dish on the Arecibo
telescope focuses these waves

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so the radio data can be
collected.

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Computers than turn the data
into images or pictures.

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Radio waves are not nearly as
affected by Earth’s atmosphere
as optical telescopes.

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So it’s not necessary to build
a radio telescope on a high
mountain.

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In fact, the Arecibo telescope
was built inside a giant
natural valley.

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The largest curved telescope
dish in the world makes it the

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most sensitive radio telescope
on Earth!

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DR. KELLY HERBST: Well, a radio
wave is a wave just like you
think about waves on the ocean.

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A wave goes up and then it goes
down.

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Well a radio wave isn’t in the
water, it’s actually a kind of
light.

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So it’s light just like we
think of light from the Sun or

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light from a lamp that we would
turn on. Those also are waves.

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But in this case, it’s a radio
wave.

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EVAN: Radio waves are much
longer, and lower in energy
than visible light.

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DR. KELLY HERBST: Now a radio
wave can travel through space

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just like light waves can
travel through space, because
radio is light.

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And that’s the advantage of a
radio telescope. That wave can

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travel through space, but then
when it gets to the Earth,

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it can make it all the way down
through our atmosphere.

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The atmosphere of the earth
actually blocks a lot of

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different kinds of light that
comes to us from space.

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But there is what we call a
window of transmission at radio
frequencies.

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So radio waves can come from
space and make it all the way

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down to the ground where we can
detect them.

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EVAN: Astronomers carefully
chose the location of the
Arecibo telescope.

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Puerto Rico is near the
equator. The equator is an

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imaginary line that runs around
the center of Earth.

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You may have noticed that
objects in the sky, like stars

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or the moon, appear in
different locations at

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different times of the night.
This happens because Earth is

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actually rotating on its axis
as it revolves around the sun.

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It would be impossible to move
a telescope as big as the one

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at Arecibo to follow these
objects, so placing the

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telescope near the equator lets
astronomers observe planets and

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other objects in space for the
longest period of time.

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DR. KELLY HERBST: A telescope
that’s really really big is

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really really hard to move. So
rather than make a moving
telescope,

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the Arecibo telescope is fixed,
it doesn’t move.

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It sits in the ground and we
can’t reposition it.

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So that means the telescope can
only look at whatever passes
right over it.

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Well, if you want to be able to
look at planets and you can

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only see what’s straight
overhead, you need to be close
to the equator.

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Because near the Earth’s
equator, planets pass directly
overhead.

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EVAN: Astronomers have learned
many things from using this
giant telescope.

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For example, astronomers used
to believe it took Mercury 88

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days to make one complete
rotation on its axis.

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Every 24 hours marks one day on
Earth. That’s the time it takes

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Earth to make one complete
rotation on its imaginary axis.

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When scientists began studying
Mercury’s radio signal in 1965,

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they discovered that one day on
Mercury is only 59 Earth days
long.

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That’s really slow compared to
Earth but much faster than
astronomers first thought.

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But it’s not just planets that
interest scientists at Arecibo.

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Much about what we know about
the upper layers of our

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atmosphere has been learned
from the research done in
Puerto Rico.

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And here’s something really
cool. The Arecibo telescope is

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part of the SETI program, which
stands for the “search for
extraterrestrial intelligence.”

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DR. KELLY HERBST: The SETI
program is a scientific

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program designed to look to see
if there are any other living

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beings out in space somewhere.
They actually found pulsars and

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thought that those pulsars
might be signals from alien
civilizations.

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It turned out they were just
stars. But in 1974, when the

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Arecibo telescope was
recomissioned after an upgrade,

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they decided to do what’s
called an active SETI test.

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And they sent a message out
into space to a star cluster

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that’s about 25,000 light years
away.

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That means it will take the
message 25,000 years to get
there.

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And if anybody’s there to
answer it, it will take their

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answer 25,00 years to come 
back. So searching for life 
out in space is not easy.

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EVAN: Wow Globey, can you
imagine how incredible it would

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be if one of our telescopes
actually discovered life
outside Earth?

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After all, our astronomers,
with the help of the Arecibo

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and Hubble telescopes, as well
as other observatories on

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Earth, are discovering new
planets in our solar system and
beyond.

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What else will they discover in
the next 10, 20, 30 or 400
years?

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It will certainly be exciting.
So what do you think Globey,
should I keep the beard?

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GLOBEY: NO!

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? [music] ?

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KIDS: Our World!