자막 (553)
0:00- Glass is inherently brittle.
0:03It is the very symbol
we use for fragility.
0:05But these days, we expect
so much from this material.
0:09We want it to be perfectly transparent,
0:11scratch resistant,
thin, and even flexible.
0:15But most of all, we want it not to break.
0:18So is it possible to
make unbreakable glass?
0:22Well, in this video, I will make the case
0:23that glass is one of the
most important materials
0:26humans have ever made.
0:27It has transformed how we live,
0:30launched numerous scientific revolutions,
0:32and forever altered how we think
0:34about our place in the universe.
0:38Part of this video was sponsored by Saily.
0:42In mid 2006, Steve Jobs had a problem.
0:45Apple was working on the first iPhone,
0:47set to be released in January 2007.
0:50But Jobs wasn't satisfied with the screen.
0:53The prototypes he was
testing had plastic screens,
0:56which scratched easily.
0:57So Jobs wanted glass, but
regular glass wouldn't work.
1:02It too would get scratched
up and it would also shatter.
1:06Plus, he wanted the phone to be slick,
1:08so the glass had to be really thin.
1:11So he called up the CEO
of Corning, Wendell Weeks,
1:14to ask him to make the glass for Apple.
1:17And six months later, it
was on the first iPhone.
1:20This was Gorilla Glass.
1:23Gorilla Glass has been
used in phones, computers,
1:26and wearable devices
for the last 17 years.
1:28Now it's used on billions of devices,
1:31and over the years it's
become a lot more durable.
1:36So we sent Veritasium producer, Petr,
1:38to Corning's headquarters,
1:39to see for ourselves how
Gorilla Glass is made
1:43- We'll need a volunteer.
1:45- [Petr] Yeah, guess that's me.
1:48- [Demonstrator] All right,
so this is what we call
1:49our key scratch demo.
1:50In here we have a polycarbonate,
1:53which is basically a plastic,
1:55and then we have the Gorilla Glass.
1:56And what you can do is
scratch this side first,
1:59the polycarbonate, see how it goes.
2:03- [Petr] Yep, definitely scratches.
2:04- Yep.
- Try to scratch in our logo.
2:07Not quite.
- There you go.
2:09- [Petr] Are we getting it?
2:11- [Camera Operator] Yes.
2:13- [Demonstrator] So now try the same thing
2:15So this is Gorilla Glass.
2:17- [Petr] Yeah, definitely
does not scratch.
2:21- [Narrator] To break
glass requires two things,
2:25To introduce the flaw,
they sandblasted a spot
2:27in the middle of the glass
to roughen up its surface.
2:30And Petr will apply the stress.
2:33- [Demonstrator] Take that tip
and put it inside that circle
2:37See if you can break it apart.
2:42- [Demonstrator] All
right, so next we have
2:43strengthened soda lime.
2:44Strengthened as much as
you can for soda lime.
2:49- [Petr] Harder, for sure.
2:50- Harder, a little bit?
2:51Next we have Gorilla Glass.
2:53- [Petr] I'm kind of terrified.
2:59(laughing) I know like we
don't actually want to do this,
3:03but I want to do this.
3:11- There's two responses.
3:15The first response is either,
3:16"This is a really great demo,
3:18I completely understand
what you're showing me."
3:20The second response is,
3:22'I'm taking this personally,
3:24and I need to try to break this glass."
3:27It is a very good demo.
3:28I'm like genuinely really
impressed at this point.
3:31I still want to break the glass.
3:38Like, I'm bending the stylus.
3:47- Glass has existed in
nature for billions of years.
3:50It's formed by meteorite impacts,
3:53lightning strikes and volcanic eruptions.
3:55But when humans came along,
they found ways to use glass.
3:59Obsidian is volcanic glass.
4:01It forms when lava cools quickly.
4:04It's extremely brittle,
4:05so when you hit it with another rock,
4:07you can chip off sections of it
4:09to make a sharper and sharper edge.
4:11There's evidence of obsidian being used
4:14for cutting implements,
arrowheads and tips of spears,
4:17as early as 1.2 million years ago.
4:21And it hasn't gone out of fashion.
4:22Today, some surgical
scalpels have their tips
4:26sharpened to just three nanometers across,
4:29and the best material for
this purpose is obsidian.
4:34Compared to the million plus
years we've been using glass,
4:38we only started making it very recently,
4:41around 5,600 years ago.
4:43Most common glass is composed
mainly of oxygen and silicon.
4:47The two most abundant
elements in Earth's crust.
4:50In nature, you find them
in the form of quartz,
4:53crystalline silicon dioxide.
4:55Crystalline means that
the atoms are arranged
4:57in a regular repeating structure,
5:00and quartz is the primary
constituent of sand.
5:03So if you take some sand,
5:05heat it up to about 1700
degrees Celsius until it melts,
5:08and then rapidly cool it, it forms glass.
5:14During the rapid cooling process,
5:16the atoms don't have enough time
5:17to return to their periodically
arranged crystal structure.
5:21So instead they are stuck where they are,
5:23like a liquid that's been
flash frozen in place.
5:27That is why glass is
considered an amorphous solid.
5:30Amorphous just means disorganized,
5:32not in any regular arrangement.
5:35But perhaps this is where
the misconception about glass
5:38being a liquid comes from.
5:40It isn't a liquid at room temperature.
5:42Glass is solid because the
atoms are fixed in place.
5:45They can't flow past each
other like in a liquid.
5:48I even made a video about
this nine years ago.
5:51They are disordered, but they are solid.
5:56This amorphous structure is
also what makes glass so brittle
5:59because there's no way for the
structure to relieve stress.
6:03When stress is applied to the glass
6:04a small crack will form
at a flaw on the surface.
6:08And as the glass cracks,
6:09the stress is applied to
atoms with fewer neighbors.
6:12So the crack grows bigger,
6:13which eventually leads
to the glass fracturing.
6:17- [Demonstrator] So next
we'll move to what we call
6:19What we're using is sandpaper.
6:22This represents like an
asphalt type surface.
6:26- So if you were to get outta your car
6:27and you accidentally drop
your phone in the parking lot.
6:30And what we're using is this fixture.
6:34- Mm hm.
- So it's pre-stressing it.
6:36You have our rough surface
to introduce the flaw.
6:38And on here we have an alternative glass.
6:41Similar to some of the competitive stuff,
6:43different things on the market.
6:44And when you're ready, you can drop.
6:46- On three, two, one.
6:53- So it broke.
- Not what you wanna see
6:55when you pick up your
phone off the parking lot.
6:59- And then we have the Gorilla Glass
7:01and what we call the mega slap.
7:02All right, very exciting name, right?
7:05Now you can see me dramatically
increase the height.
7:08- Shall I do it from here?
7:09- Nope, from...
- The very top?
7:10- From the very top.
- Okay.
7:12So, we're not just increasing the height,
7:15we're also starting from way up here.
7:16- Right.
- All right.
7:30- While, the basic recipe for glass
7:31involves silicon dioxide,
7:33glass makers have been
adding other ingredients
7:35to change its properties
for thousands of years.
7:38Adding sodium carbonate,
also known as soda,
7:40and calcium oxide, also known as lime,
7:43lowers the temperature at
which it becomes liquid
7:45from 1700 degrees Celsius
7:47to around a thousand degrees Celsius.
7:50And that's why soda lime
glass accounts for around 90%
7:53of all glass manufactured today.
7:56Another recipe includes adding
7:57boron trioxide to the mixture,
8:00forming a borosilicate glass.
8:02Glass is usually quite sensitive
to changes in temperature.
8:05If you throw boiling water
on your car's windshield,
8:07it'll likely shatter due to
the glass rapidly expanding.
8:11But borosilicate glass
8:13has a really low coefficient
of thermal expansion.
8:15It doesn't grow or shrink very much,
8:17even with drastic temperature changes.
8:19So it's often used for
laboratory glass, like beakers.
8:23- [Group Member] Let's go.
8:26- If you want to grab a pair
of these screen glasses too?
8:30- [Camera Operator] Oh yeah.
8:32- I can't see anything.
8:36- [Narrator] And while
this specific recipe
8:37for Gorilla Glass is secret,
8:39it is based on a combination of silicon,
8:41aluminum, magnesium, and sodium.
8:46And the recipe keeps changing.
8:48The scientists are constantly
trying different formulations
8:51to find more durable and
scratch resistant glasses here.
8:57Do you ever feel like a pizza chef?
8:59(group indistinct chattering)
9:01(group indistinct chattering)
9:07- [Narrator] This facility
9:08is actually where that
experimentation takes place.
9:16The earliest human made
glass was likely an accident.
9:19People have been working
metal for thousands of years
9:22before they made glass.
9:23So it's thought that
some sand made its way
9:26into metal working furnaces,
forming small glass beads.
9:30But soon glass making
became its own art form,
9:33to make decorations, ornaments, statues,
9:36tableware and containers.
9:38Unlike clay, glass is
impermeable to water,
9:41making it an ideal material
for bowls and bottles.
9:45But then glass makers noticed
9:47that by adding other
elements into the mix,
9:49they could change the color of the glass.
9:52By adding cobalt oxide,
9:53you would get a vivid blue.
9:55Adding cuprite makes red.
9:59But all of the historical
glasses we've been talking about
10:03Which is not really what
we think of as glass today.
10:07After glass making was invented,
10:08thousands of years passed before
10:11we invented transparent glass.
10:13That's because making it is
actually pretty difficult.
10:16(light bright music)
10:17The first step came around a hundred AD,
10:19when glass makers in Alexandria
10:21added manganese dioxide into the mixture,
10:24which led to a semi opaque glass.
10:26It definitely wasn't transparent,
10:28but it did let some light through.
10:31This is when glass began
being used for windows.
10:35And glass windows were a huge deal.
10:37I mean, they provide a physical barrier
10:40that keeps the warm air in
10:41and the wind and critters out,
10:43while still allowing light
to shine into your home.
10:48But the first truly transparent glass
10:50was made many centuries later,
10:52around the Italian city of Venice.
10:54The art of glass making was thriving
10:57and bringing a lot of money into the city.
10:59(cash register dinging)
11:01There was just one problem.
11:03To make and manipulate glass
you need very hot furnaces.
11:06And at the time, Venice was a city
11:08built almost entirely out of wood.
11:11So yeah, glass makers were bringing
11:13a lot of money into the city,
11:15but they also kept
accidentally burning it down.
11:18So in 1291, the government
of Venice had had enough,
11:22so they moved all the glass
makers to the island of Murano.
11:26The island became known
as the Isle of Glass,
11:30celebrated for making the most beautiful
11:32and intricate glassware anywhere on earth.
11:35This is also where the glass
maker, Angelo Barovier,
11:38invented clear glass.
11:41He took some seaweed rich in
potassium oxide and manganese
11:44and burned it to create ash.
11:47Then he added this ash into his glass.
11:49And when it cooled, he found
that the glass was transparent.
11:56Most materials are opaque
because when photons hit them,
12:00the photons are absorbed.
12:01The photon excites an electron,
12:03pushing it up to a higher energy level.
12:05But this only happens
when the photons energy
12:07matches the energy of an
allowed electron transition.
12:11And different materials have
different energy levels.
12:13In transparent glass,
12:16the energy required to move an electron
12:18from a lower state to a higher state
12:20is higher than the amount of energy
12:22that a photon of visible light has.
12:24So the photon just passes right through.
12:28Now, while glass is
transparent to visible light,
12:30it does interact with other parts
12:32of the electromagnetic spectrum.
12:34It absorbs much of the
ultraviolet spectrum,
12:36because UV photons have more energy.
12:39Hence, they can push the electron
to the higher energy level
12:44That makes it opaque to UV.
12:48This is also how colored glass is made.
12:51You add impurities into the glass,
12:53which affects the electron energy levels,
12:55which then changes the color of the glass.
12:57If you look at a pane of glass side on,
13:00you might notice that
it looks slightly green,
13:02which is because the most
common glass used for windows,
13:05soda lime, has impurities of iron oxides,
13:08which give the glass a green tinge.
13:11The glass absorbs more of the other colors
13:14So that's why we see it.
13:19I think the only way we truly appreciate
13:22how important transparent glass is
13:24would be if all of a
sudden it disappeared.
13:26So your windows, glasses,
screens all gone.
13:30But there is another
element in our daily lives
13:32that we take for granted,
which is connectivity.
13:35I mean, we are always
connected to the internet,
13:38and losing that connection,
13:39even for a few minutes, can
be pretty uncomfortable,
13:42especially when you are traveling.
13:44Staying connected abroad requires
13:46either paying exorbitant roaming fees,
13:48or a continuous hunt for public wifi.
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14:48So I wanna thank Saily for sponsoring
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14:50And now back to transparent glass.
14:54(light upbeat music)
14:55Truly transparent glass was a massive deal
15:00Sometime in the early
1300s, in northern Italy,
15:03this clear glass was
ground, shaped and polished
15:08that were thicker in the
center than at the edges.
15:11Due to their resemblance to lentil beans,
15:13they became known as lenses.
15:17Glasses to correct farsightedness
15:19didn't seem all that
important at the time,
15:22because literacy rates were so low,
15:24they were almost
exclusively used by monks.
15:28But after the invention of the
printing press, circa 1440,
15:32glasses became a vital tool.
15:34The printing press led
to a precipitous drop
15:36in the cost of producing books,
15:38which led to a rapid
increase in literacy rates.
15:42Now a large number of people became aware
15:44that they were farsighted.
15:45Thankfully, there was
a technology available
15:48to solve the problem.
15:51150 years later, a father and son,
15:54Hans and Zacharias Janssen,
15:56put two lenses in line with each other,
15:59rather than side by side.
16:00And this was likely the
world's first microscope.
16:04It made objects appear about
20 times their original size.
16:09Antony Van Leeuwenhoek made
significant improvements
16:12on the microscope, by
grinding the lenses himself.
16:16He could magnify things 200 times,
16:18allowing him to see human cells.
16:21A few years later, Robert
Hook published "Micrographia,"
16:24a book full of beautiful sketches
of the microscopic world.
16:28And all of this was possible
because of transparent glass.
16:33And in 1608, Hans Lippershey,
an eyeglass maker,
16:37applied for a patent for a spy glass.
16:40His idea was for it to be used in warfare
16:42to spy on your enemy on the battlefield.
16:45The next year, Galileo
Galilei heard about his idea
16:49and realized that he could
point this device toward the sky
16:52to study the stars and planets.
16:55Galileo's telescope magnified
objects in the night sky
17:01In 1610, he was able to see
17:03he craters of the moon in
detail, the phases of Venus,
17:07and four of Jupiter's largest moons.
17:10These observations were the
final nail in the coffin
17:13for the geocentric model of the universe.
17:16He saw moons that were clearly
revolving around Jupiter
17:20And how else could you
explain the phases of Venus,
17:23other than to say that the
planet must go around the sun?
17:27None of this would've been discovered
17:30without the invention
of transparent glass.
17:35Four centuries later,
we can now make glass
17:38that is orders of magnitude
more transparent than water.
17:41Glass that is so transparent,
17:43that if you were able to make a column
17:45as deep as the Mariana trench,
17:47you'll be able to see all
the way to the bottom.
17:51This is the glass inside optical fibers.
17:57- Oh, this is getting real.
18:00(camera operator laughing)
18:03- [Narrator] But the
main thing we all need
18:06So how do you take a substance
18:08that is typically delicate and brittle
18:10and improve its scratch
resistance and drop resistance?
18:14First you start with an
aluminosilicate base,
18:17and then after the glass is made,
18:19you submerge it in a
potassium salt solution
18:22at 420 degrees Celsius.
18:25- [Petr] It really does look like water.
18:26- [Camera Operator] Doesn't it?
18:28I don't know if I want to drink it.
18:30- [Narrator] Potassium and sodium
18:32are chemically very similar.
18:33I mean, they both have one
electron in their outer shell.
18:36So during this process,
18:37some of the sodium atoms are
replaced by potassium atoms
18:42Now, potassium atoms are physically larger
18:46but the glass is already set.
18:47It's rigid, so it
doesn't increase in size.
18:51So now there's the larger potassium atoms
18:53all squeezed together,
18:54taking up the same amount
of space as before.
18:57This increases the compressive strength
19:00in the surface of the glass,
which makes it more durable.
19:05- [Camera Operator] Can you
see any visual difference
19:06of size between them?
19:11I have two pieces of glass.
19:13One of them has gone through
the ion exchange process.
19:16The other one hasn't.
19:18I don't know which one is which.
19:19And we're gonna figure
that out really soon.
19:30(camera operator laughing)
19:32That was really cool.
19:37Shall I hit it harder?
- Yeah.
19:40- Yeah, that was a thunk.
19:42My mind is genuinely blown.
19:44That's all just like ion exchange, right?
19:48There's no other difference, right?
19:50- Yeah.
- You put it in
19:51a bunch of salt.
- Yep, for a few hours,
19:53and voila.
- For a few hours.
19:56- I'm trying to think of
a good analogy for this.
19:59You know, I can imagine
20:00if there were just a whole bunch of people
20:02sort of standing around casually
20:03and you try to run through them,
20:06you'd probably be able to
bounce through a few of them,
20:08break through the crowd.
20:09But what if instead,
20:10all of those people
were squeezed together,
20:13shoulder to shoulder, you know,
20:14like people trying to get
into a subway or something.
20:16If you try to run through them,
20:18all of those forces are just
gonna add up and prevent you
20:22from getting in or from
making a dent, making a crack,
20:26(light groovy music)
20:28But the scientists at Corning
20:29are constantly trying
to refine the process,
20:31to make the glass even more durable.
20:33There is a whole team at the facility
20:35that is dedicated to testing and measuring
20:37different glass prototypes.
20:39- [Petr] Alright, we're displacing it
20:41by one and a half millimeters.
- Yep.
20:43- [Petr] Two millimeters.
20:46- [Narrator] And they really
put glass through its paces.
20:48Conducting bending
tests, scratching tests,
20:51and dropping heavy steel
balls onto the glass.
20:54- [Demonstrator] Three, two, one.
20:57- [Narrator] They also have replica phones
20:58with different glasses for the screen.
21:00And they drop them from
ever increasing heights.
21:03- But we can go up a little bit
21:06- We can imagine that I'm taking a selfie.
21:07- [Narrator] All of this is to make
21:10the next version of Gorilla
Glass even more durable
21:13- Like, are we doing this?
21:14- If you want to.
- Hell yeah.
21:17- That's roughly selfie height.
21:24- Amazing.
- Go down and pick that up.
21:26- Still good.
- Still survived.
21:28- [Petr] Dude, that's pretty wild.
21:30- You know, I think it's rather ironic,
21:32that we are making this video right now,
21:33while my phone looks like this.
21:39So, it's still glass, it's still cracks.
21:42It is not perfect yet.
21:44But it is constantly improving,
21:47because scientists are working on ways
21:49to make this material
more and more durable.
21:52And we have come such a long way.
21:54I am just appreciative that
I can have this material.
22:00even if it does still crack sometimes,
22:04with people who just refuse
to get a case for their phone.
22:09(electronic device whirring)
