- [Caitlin] This molten material is critical to our modern world.

It is the basis of everything from incredible artwork, (metal clanking) to super tough materials.

Oh, look, it's denting.

- [Chris] The steel will dent before the glass will break.

- [Caitlin] And even fiber optic cables... - A lot of the things that we have now would not exist without glass.

- [Caitlin] That run our high speed internet.

- Life would be rather boring, in my opinion, right?

Some people might like it.

- [Arlo] (laughs) I love it.

(Desiré laughs) (upbeat music) (water burbling) - [Caitlin] Hey, Chris.

- [Chris] Hey, Caitlin.

- [Caitlin] Today, we are at the Diablo Glass School to figure out how glass is made and can be so versatile that it allows us to create everything from horses to the internet.

- [Chris] This whole studio is basically a science lab that's disguised as an art studio.

- [Caitlin] Chris starts by showing me the stuff that glass is made of.

Silica.

- This is what we call batch, and that is pure silica, mixed with a variety of materials.

- [Caitlin] Silica is made up of silicon and oxygen.

At room temperature, silica has an ordered crystalline structure.

In order to make glass, we need to loosen this structure and make it disordered.

In other words, we need to melt it.

Only problem is that by itself, silica melts at over 3,000 degrees fahrenheit.

And although Diablo's ovens are hot, they only operate at around a measly 2,000 degrees.

Ooh.

This is where additives to the batch come in.

Chemical compounds like sodium carbonate are added to lower silica's melting point, and other chemical compounds, like calcium carbonate, help stabilize this new unorganized structure.

This structure is called an amorphous solid which basically means it's something between a liquid and a solid.

This is so cool.

This is what material scientists refer to as glass.

- [Arlo] But it's also more than just an interesting material.

So while Caitlin is learning how to make glass, I'm calling material physicist Desiré Whitmore, to better understand what glass actually is.

- Glass is not just like one thing, right?

Glass is this huge class of materials.

There are many different types of glass.

You have, like, the glass you drink out of.

And then you have, like, the glass that's on your windshield.

Those are two very different glasses, and the difference between them is how they're manufactured, and what actually goes into it.

- [Arlo] Turns out, there is a ton you can add to and do to glass.

- [Caitlin] As an example, Chris shows how some additives to glass can change its color.

- So even though it looks orange, that's just clear, colorless glass.

And all I need to do is roll it lightly in this copper oxide to really achieve a visible coloration in the glass.

And now, you can see how this bit of clear glass is now an aqua blue color.

- [Caitlin] Whoa, it's like taffy.

- [Chris] Exactly.

At this temperature, it's sticky just like taffy.

It stretches and falls, just like taffy or gum.

It sticks to itself.

- [Caitlin] How hot is it right now?

- [Chris] I can show you how hot it is.

So here's a little bit of the paper and if I just put it right on it... - [Caitlin] Whoa!

Holy smokes.

Adding chemicals isn't the only way that we can change glass.

We can also alter it by controlling its cooling rate.

And the results are pretty cool.

- [Chris] I got a good feeling about this one.

- [Caitlin] This is a Prince Rupert's drop and it is the perfect example of how we can use temperature to physically alter the properties of silica glass.

- All right, so I'll show you just how strong the surface is.

(Chris laughs) So right on this metal table... (metal clanking) - [Caitlin] Wow.

- I could hit it as hard as I possibly can.

- [Caitlin] This little glass drop goes against the everyday notion that glass is a fragile material.

- And actually, what's happening is I'm denting the metal.

- [Caitlin] This is because as the droplet falls into the water, the outside cools faster than the inside.

This creates a special kind of internal tension that makes the whole droplet very hard and rigid.

But this tension is no superpower.

As soon as the pressure finds a way to be released, like, say, a single crack in the pointy end... Oh, God.

(glass shattering) The drop shatters into pieces.

Whoa!

- [Arlo] You know what they say.

Business in the front.

Explosive shattering in the back.

(glass shattering) - [Caitlin] But this way of cooling glass isn't just a cool trick.

The technique actually has real world applications.

Some that you encounter every day.

- So windshields are made of glass that have been cooled very suddenly so that that rounded exterior surface is very resistant to impact.

- [Caitlin] By chemically and physically altering the properties of silica glass, we can create the vast variety of materials that are essential to our modern world, from glasses holding our drinks, to cables sending information at the speed of light.

- [Arlo] In fact, it's so good at sending information, that thousands of miles of glass cables, called fiber optic cables, are laid down around the globe and even under the ocean, creating the global internet infrastructure we know today.

But, while it's pretty easy to see how glass can carry my drink, how exactly does it carry information?

This brings us back to Desiré Whitmore, better known as the LaserChick.

- Or Doctor LaserChick in some circles.

(laughs) I used to go out and teach kids all the time and show them my lasers.

- [Arlo] I met up with her so she can show me how glass can be able to transmit information using lasers.

- And you should see it light up.

- [Arlo] Oh, it's dope!

- Right?

- Wait, do it again.

Do it again.

Do it again.

- Okay.

- [Arlo] But first, we need a little Physics 101 to understand how information can be encoded and conveyed through light.

Desiré uses water to explain.

- [Desiré] The light is going from the laser through the bottle of water all the way into the stream, and it's traveling along the stream of water.

- [Arlo] It looks like this laser light is bending downward, following the stream of water as though it were trapped.

- And this happens because water and air have different speeds of light.

Light travels faster in air than it travels in water, right?

When the light is traveling in the water and the water is surrounded by air, it creates this kind of tunnel or a pipe so that the light gets trapped inside of the water.

- [Arlo] This property is called total internal reflection, and here is the key: when it traps light, it's actually trapping information.

In this case, it's color.

A lot of information can be conveyed this way, far more than, for example, through movement of electrons in a copper wire.

To show an example, Desiré adds another laser.

No surprise there.

- I can have two separate pieces of information.

I have a red wave and I have a green wave.

So now when I mix red and green together... Oh, look at... That's so perfect.

Look at that.

And you have mixing already.

And so now you can see the point of mixing.

It actually turns yellow.

And so this is a new piece of information.

And I know that it's real information because the yellow needs the red and the green to be there.

I'm not sending in any other colors of light.

I'm only sending in red and I'm only sending in green.

- [Arlo] Just like that, layers of information can be encoded in light and conveyed by, well, in this case by water.

But you can do this with other materials like plastic.

Although, when it comes to the largest source of information, the internet, we use glass.

- If you move to glass, you can take this amazing material and you can do the same thing.

- [Caitlin] Woah, there it goes!

- And you create these long fibers that are basically just tubes, they actually put a different piece of glass on the outside.

And so, those two have different speeds of light.

It's still glass.

It's just slightly different because it has a little bit of a different chemical in it.

And so because of that, the light gets trapped on the inside.

- [Arlo] Just as colored light got trapped inside the stream of water because it was surrounded by air, light can get trapped in a thin tube of glass if it's surrounded by a material with slightly different properties.

- [Desiré] Light can just bounce a million times through the core all the way to the other side.

- [Arlo] This is how fiber optic cables work.

Recently, scientists were able to transmit 40 terabytes of data in one second.

For reference, that means you could transmit the equivalent of every Hollywood movie released in the past twenty years in less than two seconds.

- [Voiceover] A million poles parade across the landscape.

- [Arlo] But optic fiber has not fully replaced the more traditional copper cables, which is just part of the reason why you might have to tolerate youtube buffering for a little while longer.

- [Caitlin] Glass is so common in our modern world that we can often take it for granted.

But when you take a step back and look at the wider picture, you realize how it's not only a mesmerizing material... - [Arlo] Caitlin, this is the most beautiful swan I have ever seen in my life.

(Chris laughs) - I'd say so.

- [Arlo] But it's also an incredibly practical one.

- We use light and optics in basically every aspect of our lives.

- [Arlo] And all of this is only possible because we have learned how to manipulate the properties of glass at the molecular level.

(gentle music) It's so freaky to be watching you move your hands in one, and also the other.

- Yeah.

Stand there and then I'll come over here.

Me versus me.

- Yes.

- Looks really crazy.

Yeah.

- Whoa!

(laughs)