(light symphony music with
chalk writing on board)
- Okay, so you have this
amazing idea to start
your own business, a
licorice-themed food truck.
Genius, right?
But the bank turned you down, and your
Kickstarter campaign failed to fund.
Fortunately, you know
where you might be able
to find a large stash of gold, if only
you can get to the end of this rainbow
you've been following for six hours.
But is it actually possible to
get to the end of a rainbow?
And if so, what will you
find when you get there?
Let's start with the bad news.
Leprechauns are liars.
You cannot reach the end of the rainbow.
If you were to mark on a map the place
where the rainbow seems to meet the land
and then travel to that
location, you would not
be standing inside a
glorious pillar of colors.
There would be nothing there, except
probably the fresh smell
of a recent rain shower.
To understand why this is, we need
to look at how rainbows form.
Rainbows are created when
sunlight reflects and refracts
through water droplets
suspended in the air.
Those water droplets act like
both a mirror and a prism.
Like a mirror, they reflect
the sunlight back towards you.
But like a prism, they also
bend and disperse the light.
This is because rays of
light shining through the air
change speed when they enter a
different medium, for example, water.
This sudden change in speed bends
the trajectory of the light and disperses
white light into the
whole ROY G BIV spectrum.
The reason you see a nice,
ordered gradient of colors
within a rainbow going from red to violet
is because this refraction
bends each of the different
colors of light at a
slightly different angle.
So, for example, red
light bends at 42 degrees.
Violet light bends at 40 degrees.
And all the other colors
are somewhere in between.
So let's find a rainbow.
To do this, you need to
locate your antisolar point.
Your antisolar point is the point in space
180 degrees, or exactly
opposite from, the sun.
A simple way to find this is to go outside
and look for the shadow of your own head.
Now imagine drawing a
straight line from the sun
through your head to
the shadow of your head.
Now look up.
If there is a rainbow to
be seen, you will find it
by facing away from
the sun and looking for
an arc 42 degrees above that line
from the sun to your antisolar point.
Notice that the apparent
location of your rainbow
depends upon three
things: where the sun is,
where the water droplets
are, and where your eyes are.
Change any one of those
variables, and you'll
see a different rainbow or none at all.
So no matter where you see your rainbow,
if you try to walk out to
meet it, you'll be changing
the variable of your own position.
Trying to find the end of
a rainbow is sort of like
trying to walk to the
end of your own shadow.
Somebody else could stand at the
apparent end of your rainbow, but you will
never, ever reach that location yourself.
Here's another thing.
A rainbow isn't actually a bow.
Rainbows are circular.
Usually when you're
standing on the ground,
most of the rainbow is
blocked by the horizon.
In rare cases, like if you'e
in an airplane or something,
you'll be able to see the entire rainbow.
Rain hoop, rain hole?
But there's an obvious
take-away from this.
It doesn't actually meet
the ground anywhere.
There's just the altitude
where you can't see it anymore.
Despite all the science that
is quite well-understood,
you'll find people on
the Internet swearing
up and down that they've
found the end of a rainbow.
Not sure what's up with that.
Have you ever tried to
find the end of a rainbow?
What kind of adventures did that lead to?
Let us know in the comments.
Subscribe to our channel, and
to learn more about rainbows
and optics, head on over
to howstuffworks.com.
