Friday Joy Package (Friday Friday Night / 금요일 금요일 밤에)

Is somebody controlling him?

What are you?

He looks like a stylish old lady.

Do we have to talk about that?

Here's how we're going to start. Since our show is modeled...

after "Saturday, Saturday is Fun",

which was hosted by Lee Duk Hwa.

I'm going to open our show in Duk Hwa's tone.

Don't do things like "Please".

In that case, I'll just skip the opening today.

Professor Kim Sang Wook, give us a science lesson, please.

All right. It's good to see you all.

Who are you, by the way?

I'm Albert Einstein.

You're very fluent in Korean.

Yes.

What are you disguised for?

It's for "Mapo Hipster",

which will be aired in an hour.

P.O and I... - Whatever. I won't watch it.

Please watch it just once.

Take him out! What is this?

Why is he promoting it here? - I don't know what to say.

What is today's subject?

Today's subject is...

We see things every day, right?

But I don't think you've given...

any deep thought to what "seeing" is.

"Seeing"? - That is today's subject.

What is seeing?

When light is reflected from objects,

it falls into the iris.

That's such an exemplary answer.

Here's an example.

Apple? - It's an apple again.

Are apples available all year round?

It looks like a prop. - They will run out at some point.

When they are out of season.

You all see the apple, right?

When you think about the meaning of seeing the apple,

the first thing you need is a light source.

Which means you need light. - Right.

The light source here is up there. - Yes.

To understand how fluorescent lamps generate light,

you first need to learn quantum mechanics.

What else is there?

How about candles we talked about last time?

Now, you know how candles work, right?

Combustion. - Yes, as a result of combustion,

light can be generated too.

Natural sunlight. - Yes, sunlight from the sun.

Like these examples, we first need light from all directions.

Secondly, light must hit the object.

Since light is invisible,

we can't see it for sure.

But anyway, the moment light hits the object,

the information about the object...

will be reflected in all directions.

And some of it will be reflected into our eyes.

Solely based on analysis of the light information,

our brain determines what the object is.

This is the process of seeing.

We all know the fact...

that light travels in a straight line.

Since that's how our brain thinks,

it doesn't even know when the light is bent along the way.

For example, let's put the apple in front of the mirror.

If this apple is out of your sight,

the apple is in the mirror, right? - Yes.

The light from this apple hit the mirror first,

and it was reflected into your eyes.

Because human eyes believe that light travels in a straight line.

So they think the apple is on the opposite side.

Those who are good at billiards probably see things better.

If it's reflected multiple times between mirrors,

our brain will think there are multiple objects.

With another mirror, try reflecting it like this.

I see what you mean. - I often see this in an elevator.

One mirror is reflected in the other mirror.

It can travel back and forth between mirrors.

There are a lot of possibilities. - Gosh.

What are you doing? - As our eyes believe each image...

comes in a straight line, we see it as multiple images.

But actually, there aren't multiple objects.

Then can light be reflected infinitely?

Or will it lose its intensity every time it gets reflected?

Light will eventually fade away if it's reflected too many times.

For example, the light going into the cave doesn't bounce out.

In most cases, it's reflected numerous times...

and absorbed in the dark.

That's why the hole always seems black.

That way, you can create...

the most perfect black shade.

Recently, one of the carmakers had a collaboration with that black.

Vantablack. - Vantablack.

Vantablack is...

You seem to know everything. - He's so knowledgeable.

They developed a special atomic structure,

that reflects light numerous times.

It's completely different from black when you see with the naked eye.

As if you're getting sucked in.

It's like a black hole.

If light goes in, it gets trapped. - It won't come out.

So it creates the perfect black.

So far, I have explained a simple example with mirrors.

And mirrors bend light only once, right?

The more times it gets bent, the more complex the image looks.

As our brain thinks that light always travels in a straight line,

we can take advantage of this fact...

and do some interesting experiments.

Here are two pieces of stone.

These are special crystals called calcite.

If you see it through this, you can see a double image.

It's amazing. - This is called double refraction.

Depending on the polarization,

the light refracts in different directions.

This tendency enables us to see a double image like this.

This is so fascinating. - Right.

It's really interesting. - It's like...

we're seeing it through a digital gadget.

Like the 3D glasses. - Right.

His eye looks double too. - Really?

You can see the refracted images. - It's popping up.

Are these quite rare?

No, you can buy them.

Really? Where can I buy them? - From the science museum.

Are you reading your palm? Ji Won's reading his palm, sir.

If you see this for the first time, you may think it's like magic.

The truth is, our brain thinks light travels in a straight line,

so it creates an illusion when the light alters its path.

Although many things can happen while the light is traveling,

the second important factor is our eyes.

What happens when light enters our eyes?

We get dazzled. - Right. Your eyes get dazzled.

So when light enters our eyes,

we start detecting the light.

There are cells to detect brightness and darkness,

which are called rod cells. And there are cone cells,

which detect color.

Although there are a lot of colors out there,

human eyes are only capable of seeing three colors.

Red, blue, and green? - Yes, it's called RGB.

Red, green, and blue. - Is that all we can see?

All the colors we see...

are a combination of these three colors...

from our brain's point of view. - That's really amazing.

To prove that humans can only see three colors,

we're going to do an experiment.

We'll use this lamp.

And I brought this cube as it has the three primary colors.

Here's what we're going to do.

If I cover this with red cellophane and turn on the light,

It will be red. - the light will be red, right?

Now, if I put the blue side under the light,

here's what will happen.

Blue has no red components, right?

Only red components reflect the red light,

but there are no red components in blue.

So it has nothing to reflect and appears black.

That's amazing. - Let's start our experiment.

We need to turn the light off.

Let me shine it on this.

It really looks black.

Let's try the other colors. - That's so interesting.

For example, green. Is this green? Green also...

Is it going to look black too?

It's the same as the blue one. - That's amazing.

Because we shone the red light...