(lively music)
- [Narrator] This program
is brought to you by BASF,
The Chemical Company.
- Hey, welcome to Stuff
to Blow Your Kid's Mind.
My name is Robert Lamb.
- And I'm Julie Douglas and
today we are talking about
rainbows because they are spectacular
and they seem to appear out of thin air.
- In this experiment, we're
actually going to make a rainbow
but before we do, let's talk
about where rainbows come from.
There's nothing magical,
actually, happening.
What happens is you have a
tiny little particle of water,
it's floating around on
the air, and the sunlight
hits that particle, the
particle then breaks that beam
of light out into seven
different wavelengths.
- That's right.
And we are going to do the same
thing here with this prism.
Now this one is a plastic
prism but you can get glass,
three-sided prisms as well.
You can get 'em online
or at a variety of stores
and we are going to use
a good source of light
that we've got off over here to the side
and a piece of water
paper to better illustrate
how this light, this white light,
when it's passed through this prism,
is gonna smash into these
seven different wavelengths.
- And while Julie's getting that ready,
I'm gonna point out, you can
also conduct this experiment
with just a glass of water held
up into a beam of sunlight.
- Okay, so now you can start
to see some of these colors
emerging and those seven
different colors are red,
orange, yellow, green,
blue, indigo, and violet.
- So we're actually gonna be
able to see through light here,
to see how light actually works.
- Yeah, and it's just
really cool insight to
how light behaves and how
really mysterious it is
but the actual science behind it.
In fact, if you were
to go above a rainbow,
up in the clouds and look
down, what you would discover
is that a rainbow is actually
in the shape of a halo
and not that half-arch that
we see here on the ground.
- So there's nothing magical happening,
there are no leprechauns
at all, it's just science.
- Okay so we just looked at
rainbows and how they're made
and what happens when you
take a beam of white light
and you pass it through
a prism or a rain drop
and it breaks it up into
seven different colors
with seven different wavelengths.
Even then, it was a nice
insight into what seems like
an illusion, these rainbows,
but what about the sky
above us, the blue sky?
Is that an illusion too?
- It sure looks blue but as we know,
you can look into the sky at night
and you don't see the
color blue, you see stars,
you see space, you see
into the outer universe.
We know there's not really a
big, blue barrier up there.
And as it turns out, this
all has to do with the way
that light interacts with objects
and even though the air
around us may seem empty,
it's actually filled with
lots and lots of tiny little
particles and the wavelengths
of light actually interact
with those particles and
influence what we see
in the daytime sky.
- That's right.
So you're talking about
the wavelengths of light
and what we're talking about specifically
are those colors in the rainbow.
So when you have short wavelength colors
like blue and like violet,
those tend to scatter
a lot more when they're
interacting with particles
as small as nitrogen and oxygen.
And so, therefore, when
you look up at the sky,
those are the colors that are the majority
of what your eye sees, but still,
that seems a little bit odd, right?
Because why don't we look up at a sky
with just blue and purple
splotches all over?
- Well, as it turns out,
it all comes down to
the machinery in our eyes and
the machinery in our brains
because our eyes and our
mind have to take this data
and make sense of it and they end up
combing the two colors into one.
- Yeah, so think of it kind
of like a little artist
in your brain mixing together
colors and, in this case,
you've got blue and white and purple
and coming up with a really
beautiful shade of blue
and depending on how much
sunlight is in the day
that you're looking at, if
it's either really sunny
or really cloudy, you're
gonna have a different shade
of blue every single day.
- So we've explained the
illusion of the blue sky
overhead, but what about the sun?
How does our perception of light
and the illusion of light, affect the way
that we perceive the sun?
- Yeah, let's talk a little
bit about how the sun's rays
actually reach the Earth.
- That's right.
It's important to realize that
sunlight is actually composed
of tiny particles which are called photons
and when light reaches us,
it is actually having to make
that journey, that physical journey,
from the surface of the sun to our planet.
- Yeah and the really
cool thing about this is
that we actually know how long it takes
for a little photon to
actually reach the Earth
and the reason we know
that is because we know
the speed of light and
we know the distance
from Earth to sun, that
gives us an estimate
of eight minutes and 20 seconds.
- So when we take a prism
and we break a beam of light
into those seven wavelengths,
we're getting an insight
into the illusion of light
and into how light works
but we're also getting
a better understanding
of why the sky is blue and
why the sun looks like it does
and how it actually energizes our world
and lights the world around us.
- That's right.
It's a peek into the
physics of the universe
as well as into the human mind.
(lively music)
- [Narrator] This program
is brought to you by BASF,
The Chemical Company.
