(ringing)
- Hi, it's Doug.
Saint Patrick's Day.
It's a time when people where green
and some people even dress up in costume
but for me, Saint Patrick's Day
always made me think of rainbows.
I remember when I was young
seeing a rainbow in the springtime
and getting on my bike
and riding toward it
hoping that I could find a pot of gold.
I never did get there.
Someone named Joseph has
a question about rainbows.
Let's give him a call now.
(ringing)
- Hi, Doug.
- Hi, Joseph.
- I have a question for you.
How are rainbows made?
- That's a great question.
Normally, the sky outside
doesn't have that many colors,
just blue or gray like
when it's dark and cloudy
but then sometimes a rainbow comes out.
It's such a special thing
when you get to see a rainbow.
People even know the colors
of the rainbow by heart.
You've got red, orange,
yellow, green, blue and purple.
Scientists call it violet.
But where do rainbow colors come from?
How are rainbows made?
Do you have any ideas?
Now would be a good time to
pause the video and discuss.
Okay, you ready?
For a long time, no one
had a very good idea
about where rainbows come from
and how they get all those colors.
Rainbows aren't like most colorful things
like things you can reach out and touch.
For example, think about a
red chair or a green frog.
Those things get their colors
from what they're made of.
A red chair has red paint on
it and a frog has green skin
but a rainbow is different.
It's not a thing you
can reach out and touch.
It doesn't contain colored stuff
like a chair or a frog has.
Instead, it's something that floats there
like a big arch in the sky
and rainbows don't just stay there either.
Not long after they appear,
they start to disappear.
It's really very puzzling
what a rainbow's colors are made of
or where a rainbow comes from.
The first big clue about
how rainbows are made
actually didn't come
from rainbows in the sky.
It had to do with rainbow
colors from pieces of glass.
For a long time, people had
noticed that glass pieces
especially ones with flat sides on them
would sparkle with rainbow
colors when placed in sunlight.
Scientists noticed that
one of the best ways
to get a rainbow sparkle
was using a triangle
shaped piece of glass.
It's called a prism.
It was one scientist in particular
who was very interested in this.
His name was Isaac Newton.
Isaac Newton wondered,
was there a connection
between the rainbow
colors of a glass prism
and the rainbows that we see in the sky?
To figure this out, he bought a prism
and came up with a science experiment.
In a room, he covered his window like this
to make the room really dark
then he made a hole in the covering
to let in a single beam of sunlight.
When he placed his prism in
front of the beam of sunlight,
it did this.
It created rainbow colors on the wall.
Interesting, Newton thought.
But how did it do that?
Was the prism somehow
creating those colors?
That's what some people
thought but Newton wondered,
could it be that sunlight
itself is maybe a mixture
or bundle of all the
colors of the rainbow?
If true then maybe what the
prism is doing, thought Newton,
is it's separating white sunlight
out into each color of the rainbow
but that seems unlikely, right?
I mean, sunlight itself is white.
If you had a bunch of
different colors of paint
and you mix those together, it
doesn't make anything white.
Look, you can see here it
makes sort of a brownish color
but maybe light is different
from paint, Newton thought.
This is where Newton did
something very clever.
He took another second prism
and he turned it the other way
so that it would now combine
all the rainbow colors
of light shining onto it.
When he combined all the
colors of the rainbow,
guess what he got?
This.
White light.
So Newton proved the colors of the rainbow
really do come from sunlight
but that still doesn't solve
why a rainbow appears
in the sky sometimes.
I mean, it's not like there are prisms
or pieces of glass floating
around in the sky, right?
Well, there aren't pieces of glass
but there are these, water droplets.
It's rain.
Water droplets can do
similar things as a prism.
Taking white sunlight
and separating it out
into all the colors it's made of.
When we see sunlight shining
on a bunch of water droplets,
we see a rainbow and it's
not just raindrops either.
Any drops of water in the air will do.
You can find rainbows under waterfalls
or even in the spray from sprinklers.
Check it out next time
you play with a hose.
So in summary, Isaac Newton
proved that white sunlight
is actually a combination of
all the colors of a rainbow.
A rainbow is formed when white sunlight
passes through water droplets
in the sky acting like prisms.
That's all for this week's question.
Thanks, Joseph, for asking it.
Now, we have something special
for this week's episode.
My friends and I here at Mystery Science
have created a step by step activity
where you can experiment with
sunlight and rainbow colors.
You can find a link to the activity
at the end of this video.
Okay, 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
are shooting stars really stars,
how deep does the ocean go
or how do people know what
expiration date to put on food
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 you next week.
