Our culture, and our skies, are full of rainbows, but do you know how they form?
Do we all see the same rainbow? Could cyborg-enhanced mantis shrimp eyes
someday see a bigger rainbow?
From coloring books to record covers, rainbows are everywhere.
I bet you can even remember the colors without thinking twice.
Although in real life no one really says "indigo", although I guess ROYGBV
doesn't really have the same ring to it. As anyone who's tried to chase
one finds out, a rainbow isn't really there.
You can't go over it, and you can't get to the end of it. It's become
a mythical representation of the unattainable.
In Navajo and Norwegian mythology, it's a bridge that only gods could take
between heaven and Earth.
For Christians and Buddhists, rainbows are a state of peace and forgiveness.
And in some cultures, it's a really long and colorful unicorn.Of course,
just because a rainbow isn't really there doesn't mean we can't explain
how it works. The better question is "WHY is a rainbow?
" And that answer is "42"Let me explain. A rainbow exists because of light,
water and a little physics.Let's start with sunlight. It looks white.
To some that seems like the absence of color.
But thanks to Isaac Newton we know that white light is really the sum of all visible
wavelengths, from short to long and all the colors in between.
So we've got light,now we need water. On a rainy or misty day,
the sky is filled with tiny droplets.They aren't quite as small as the droplets
in clouds, though, which is why we don't have awesome looking clouds.
Some of you might be saying "But Joe,
I've seen a rainbow in a cloud before! Well, that's not really a rainbow.
But we'll talk about that another time.
Those suspended liquid prisms are surface tension on its smallest scale,
and they're pulled into the shape of a sphere and each one can catch sunlight
and become its own part of the rainbow factory.
Here's where we add the physics. Sunlight starts by entering a raindrop from
behind you. The light goes from one medium, air, into another, water.
And that causes it to bend slightly thanks to a process called refraction.
Different wavelengths of light bend at different angles so the white light begins
to separate. This bent sunlight then reflects off the back of the raindrop,
and refracts again on the way out. When we measure the angle between
the light that went in and the red light that comes out, the answer is 42 . . .
degrees. So how many drops does it TAKE to make a rainbow? Well, a lot.
Because each color exits at a different angle, one raindrop will send red light
into your eye and another drop will send violet light. The same thing happens
with all the colors in between, each coming from their own droplet.
And what about the shape? We call it a rainBOW for a reason.
It's not a rainLINE or a rainZIGZAG. You and your eyes are at the apex of a huge
half-cone, and at the other end is the water that makes the rainbow shape that
we all know and love. Everything that you see is because that light is refracting
right to where you are. No one else is experiencing exactly the rainbow as you.
If everyone's rainbow is unique, does your rainbow look like my rainbow? Well,
Michael from Vsauce has a great video about that, so I'll put a link in the description
to let him answer that question for you.
Could we ever see a different rainbow?
We've evolved to see only a tiny fraction of a percent of the entire electromagnetic
spectrum, what about all the rest of it, from x-rays to radio waves. What if we could
see a rainbow like the mantis shrimp, maybe we could see a rainbow that stretches
across the sky! Spoiler alert, maybe NOT.
While it's true that we only see a sliver of the spectrum, you can't make a rainbow
out of anything that doesn't make it into Earth's atmosphere.
Take the sun: It actually emits almost half of its radiation
right around the visibla range, which is exactly why we evolved to see that range.
The rest of the sunlight is mostly infrared and just a tiny bit of UV. If we could see
a rainbow made of all of that, it would only be about twice the width of the one
we're used to. Unfortunately, if we could see infrared,
we'd be blinded by the infrared radiation given off by all the warm
things around is,including the Earth itself.Cranking up the sun wouldn't
work either because most of the electromagnetic spectrum is filtered out
before it reaches Earth's surface. What about all those radio waves,
they're traveling freely through the atmosphere. Picture all those bands
way beyond the red side of our rainbow. Sadly, having radio antennas
for eyes would also be a blinding experience, because the air is filled with
the signals from our wi-fi, mobile phones,and well, radio. I guess we'll have
to be happy with the rainbow we have,because it's pretty much the best
rainbow we can make.The next time you see a rainbow,
remember that even though there's no pot of gold at the end, no one else
can see exactly same rainbow you can. That sounds like treasure to me.
1. How many colors of the rainbow? Enumerate the colors.
2. Specify the significance of rainbow in some culture and religion.
3. Explain the components of a rainbow.