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KIDS: Our World!
EVAN: Hey Globey, you’re looking a little "two
dimensional" today. Did you know that a few hundred years
ago, people actually thought you were flat? After all, they
could look out on the horizon and things looked like they
were flat for as far as humans could see.
Sailors even had the false belief that if they kept
sailing in a straight line, they would eventually
fall off the earth.
Of course today we know you’re not flat. You’re a sphere.
Did you also know Globey that people once thought you were
the center of the solar system?
That’s right. They thought the Sun and the other planets in
our solar system revolved around earth. In fact, they
thought everything in the universe revolved around Earth.
But in 1543, an astronomer named Copernicus claimed the
Sun was the center of our solar system. But not many people
thought he was right. They held strong to their
mistaken beliefs.
Then another astronomer named Galileo proved the Earth was
not the center of our solar system.
He used his telescope to observe that Venus had
different phases...like our Moon.
For example, sometimes the Moon is full in the sky and
sometimes it’s just a sliver.
This is caused by the Moon’s orbit around our Earth as well
as our planet’s orbit around the Sun.
We know the Moon does not make its own light. It can only
reflect light from the Sun.
The Sun lights one half of the Moon. The other half is always
dark. During the Moon’s orbit
around the Earth we see different fractions of the
lighted half so the Moon appears to change shape.
We call these changes phases of the Moon.
The time from one phase of the Moon until the next time it
reaches the same phase is 29.5 days
Galileo correctly assumed since Venus also displayed different
phases like our moon, then that must mean it was orbiting the
Sun and not Earth.
This was his hypothesis, and today we know he was right.
But at the time, many leaders thought Galileo was outright
crazy. In fact, they charged him with a crime
for his beliefs. And sentenced him to house arrest for the
remainder of his life. Can you imagine that?
Let’s talk about the word "hypothesis" for a moment.
A hypothesis is a statement that can be tested using the
scientific method.
That basically means a hypothesis is someone’s idea
that hasn’t yet been proven right or wrong.
When scientists are using the scientific method, they are
making observations, asking questions, and looking for
possible explanations for what they see.
They form a hypothesis, then test that hypothesis.
And that’s one of the exciting things about science.
At its very basic level, science is about the
search for truth. Scientists and astronomers develop ideas
about the universe and then set out to prove that what they
believe is right. Sometimes though, scientists prove the
hypothesis is wrong, and that forces them to revise and
change their ideas. Even a hypothesis that is right can
lead to new questions and the process begins all over again.
CARLA BITTER: On Earth our hypothesis change all the time.
Less than a hundred years ago, we had no idea that microbes
caused disease. If you think of the stories of yellow fever.
It was the hot air. It was the miasma.
It was the bad air coming off the river. And when it got
cold, people wouldn’t be sick anymore.
The outbreak would end. But nobody really knew that "oh,
it’s a mosquito." It’s this critter that’s carrying this
microbe that is biting you, getting in your bloodstream.
This is what’s making people sick. So, that’s an idea, the
hypothesis of the miasma off the river or the vapors coming
out of vents or whatever where the leading theories of what
was causing yellow fever a hundred years ago.
We know now that simply, it’s a microbe. And you can solve it.
You can fix it. You can say, let’s start developing a
vaccine. Because we know what this mechanism is now.
Let’s eradicate mosquitos so people don’t get bitten.
So you can take precautions and you can have solutions when you
start turning over hypothesis and coming up
with an idea of how things really work.
EVAN: The planet Mars is another example of where
scientists have revised their ideas. Many astronomers who had
gazed at Mars through their telescopes, believed the planet
had liquid water because they observed both dark and light
patches on its surface. They thought the dark patches were
water and the light patches were continents.
But in 1965, NASA sent the Mariner 4 to fly by the planet
and take photographs. The Mariner 4 captured the first
pictures of another planet taken from deep space.
It was during this mission that scientists realized there was
no liquid water on the surface of Mars. But had there
ever been? Some scientists believed there had been.
Some did not.
In 2008, NASA sent the Phoenix Lander to Mars.
During its mission, the robotic arm of the Phoenix Lander dug
just below the surface of Mars
and discovered frozen water... ice!
The Phoenix Lander has also discovered that the soil of
Mars was different than they originally thought.
So Globey, these are just a few examples of changing ideas.
And with all we’ve learned today, I’m going to make a
hypothesis of my own. If new discoveries are made in the
next decade, scientists will continue to revise and change
their beliefs. It’s a very exciting process. And one that
helps us discover the truth about our world
and our universe.
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KIDS: Our World!
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