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Dr. Helen Czerski: Everything
around us exists somewhere
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on a vast scale from
cold...to hot.
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Whether living or dead,
solid or liquid, visible or
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invisible, everything
has a temperature.
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It's the hidden energy
contained within matter.
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And the way that energy
endlessly shifts and flows
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is the architect that
has shaped our planet
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and the universe.
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Across three programs,
we're going to explore
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the extremes of the
temperature scale,
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from some of the coldest
temperatures...
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to the very hottest
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and everything in-between.
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In this program,
the incredible
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science of heat.
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What temperatures does
it reach on the inside there?
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100 million degrees.
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That's just
a ludicrous number!
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We'll reveal how our ability
to harness heat lies behind
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some of humanity's greatest
achievements...from the
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molten metals
that gave us tools...
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[Hammering]
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[Crackling]
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to the searing energy
of plasmas...
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[Loud crack]
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that offer
the promise of almost
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unlimited power.
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Temperature is in every single
story that nature has to tell,
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and in this series
we'll show you why.
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[Engine huffing]
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[Whistle blows]
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I love steam engines 'cause
they're so raw. You can see
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where the energy's coming
from and where it's going to.
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This one's called "Braveheart,"
built in 1951, but still
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going strong.
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The steam out
there is amazing!
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[Whistle blows]
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Steam locomotives like
"Braveheart" are a symbol of
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an age when it seemed that our
ability to harness heat knew
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no bounds...
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allowing us to
drive our trains, run our
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factories, and
propel our ships.
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But to get the engineering
right, people had to ask
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previously unanswered
questions about what heat
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really was.
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And with the answers came an
understanding of just how much
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heat could do for us.
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We're going past the
modern world and the houses
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and computers and technology
that we take for granted,
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all of which required
control of heat.
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But all of that is built
on the foundation
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of the Industrial Revolution,
things like this engine.
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And right at the heart of
the engine is the rawest bit
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and the first form of
heat that humans learned
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to control--
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and that is fire.
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In all of human history,
there can be few moments more
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significant than the
discovery of fire.
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A spark is so brief, such
a tiny flash of light,
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and yet the start of
such a huge story.
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A long time ago, perhaps
around a million years,
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our ancestors could sit around
a fire for the first time when
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they chose.
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And I'm sure that fire was
just as mesmerizing for them as
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it is for us, this flood of
heat and light conjured
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up at will.
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You don't need any
understanding of physics to
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appreciate this or to
be fascinated by it.
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It must have seemed amazing
that something as apparently
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dead and inert as wood could
suddenly change into flame,
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releasing so much heat.
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Our ancestors couldn't have
known it, but mastering that
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spark opened the door to a
whole new way of being human.
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The ability to create fire
provided our ancestors
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with warmth, protection,
as well as a means
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of cooking food.
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But for all the usefulness
of fire, unlocking its full
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potential was still
a long way off.
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For almost all of human
history, we had no idea what
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heat could do for us, because
we just didn't know what it
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really was.
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It wasn't that long ago
that people thought heat was
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a substance in its own right--
a weightless fluid called
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Caloric that could flow in and
out of solids and liquids,
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altering their temperature.
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Not until the early 20th
century did we, in fact,
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discover that heat isn't
a substance but something
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else entirely.
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[Kernels clattering in pan]
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What I've got here are popcorn
kernels, and each one is the
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seed of a plant, but inside
them they've got a little
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bit of water.
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And what's happening is that
energy is flowing into
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the kernels, and the water
molecules as they heat up are
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moving faster and faster.
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That water, the liquid water,
is being pulled apart,
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and so the liquid is becoming
a gas and the popcorn kernels
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are filling up with steam.
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Every single one of these
kernels is now a very small
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pressure cooker.
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And eventually....
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Oop! Ha ha ha!
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And the pressure bursts the
kernel outer shell.
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The whole kernel turns inside
out, and then you get popcorn
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that is flying everywhere!
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And the important point here
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is that the heat energy
is all about movement.
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As atoms and molecules take
energy on board, they start
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to speed up.
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The faster they're moving,
the hotter the substance is.
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And the crucial point about
all this movement or energy is
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its extraordinary ability
to transform things...
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even matter itself.
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In the year 793, Anglo-Saxon
Britain came under attack...
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[Shouting]
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when Viking raiders
first landed
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on the Northumbrian coast.
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While the Vikings' reputation
as fearsome warriors is well
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documented, what's less
well known is their skillful
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craftwork,
especially with metals.
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[Chainmail rattling]
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A skill calling for not only
a sense of design, but also
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a sophisticated understanding
of temperature.
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[Hammering metal]
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And historical blacksmith
Jason Green is going to
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show us why.
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And how hot will
it get in there?
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Around 1300 degrees.
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Czerski: Under Jason's watchful
eye, we're going to attempt to
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make a Viking dagger, a process
that starts with heating up
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a small piece of steel before
hammering it into shape.
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- That's it.
- OK.
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Ooh! Not setting
the grass on fire.
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The only way you're
gonna learn is to do it.
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Czerski: Is by doing it.
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Right. Well, there's gonna be a
lot of doing, isn't there?
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[Tapping]
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It's funny.
You can feel as it cools.
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It suddenly stops going
anywhere.
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Green: Yeah, it starts getting
harder, so...
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Czerski: Blow, by blow,
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the dagger starts to take
Shape, both externally and,
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more importantly,
deep inside the metal.
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We don't tend to think of
metals as being crystals,
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but in fact they are.
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That means their atoms
are arranged into a highly
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regular, repeating pattern.
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What's happening as we heat is
that the crystals are changing
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because the heat makes
them slightly more mobile.
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It allows you to
push atoms around.
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As the metal is hammered,
each impact rearranges
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the atoms inside creating
tiny knots within
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the crystalline structure.
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As these knots accumulate,
it becomes harder
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for the atoms to move
over each other.
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And this helps make
the metal stronger.
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And so all of this
raw action, this hammering,
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thumping, and the heating,
is changing things at a very
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tiny scale inside the metal
itself, and that's what gives
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iron and steel it's strength
and that's why it's so useful.
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But a blade's strength doesn't
come from hammering alone.
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It also requires
clever manipulation
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of its temperature.
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The knife's now back in
the forge glowing cherry-red,
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and that means it's about 800
degrees C, and that matters
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because the crystal structure
at this temperature, this is
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the one we want.
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It's very strong,
it's really useful.
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If I let it cool down slowly,
it will change back to the
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room temperature structure.
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And so in order to keep this
crystal structure so it's
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a useful knife,
this is what we do,
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which is very satisfying.
Ha ha!
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As the hot metal is
plunged into the water, its
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temperature plummets in
just a few seconds.
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By cooling it so quickly,
the atoms haven't got time to
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shift into the shape that they
want to have and so they're
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stuck, locked in, with
a very strong structure.
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Finally, one last round
of heating to remove any
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remaining brittleness.
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There we go.
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One finished fighting blade.
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Czerski: I'm so impressed that
with such simple tools you can
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make something so useful.
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That's brilliant.
Thank you very much.
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By turning wood into flames,
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rock into metal,
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and soft metal into hard,
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our ancestors' growing
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understanding that heat could
transform matter altered the
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course of human civilization.
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But for thousands of years,
this knowledge was only
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applied to solids.
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The next leap forward would
see people using heat to
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exploit another form
of matter, one
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with astonishing potential.
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[Steam hissing]
Gas.
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But to understand how gases
respond to heat, we first need
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to take a step back and look
at what gases are and how
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they work.
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Humans love a bit of
spectacle, anything
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with color and music and fun.
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But the stereotype of a
scientific experiment is
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almost exactly the opposite,
a dusty basement with someone
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who hasn't seen daylight for a
week writing down measurements
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that no one will ever read.
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But there have
been exceptions.
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There have been experiments
set up with a theatrical drama
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to match their
scientific significance.
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And one of my favorites
happened in 1654, and it was
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all organized by a man
called Otto von Guericke.
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The aim of the experiment was
to demonstrate a very specific
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and extraordinary
property of air.
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And heading up the guest list
was none other than the
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Holy Roman Emperor,
Ferdinand III.
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Once the Emperor was seated,
Von Guericke took a pair
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of metal hemispheres, placed
them together, and then began
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to pump the air
out from inside.
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This created a vacuum,
which held the two halves
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of the sphere together.
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He then attached each end to
a team of horses and gave
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the command to pull.
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To show you what happened
next, we're going to attach
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our sphere to the modern
equivalent of Von Guericke's
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horses--a pair of 4x4s.
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Man: OK, stand by!
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I'm actually
quite nervous.
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Man: 3, 2, 1, go!
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Czerski: So the tension's
out of the rope.
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So now a little bit on the
accelerator just up to 1,000.
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Feel it taking the strain.
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OK, keep going
up to 1,300.
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[Revving engine]
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Feel it in the car.
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OK, up to 1,600.
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[Revving engine]
The engine's not happy. Ha ha!
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I think we might have
established the sphere
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00:16:31,034 --> 00:16:32,275
really works.
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OK, let's pause
there, so stop.
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It's impressive!
It really is impressive.
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Just as our sphere stood up
to a pair of 4x4s,
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so Von Guericke's was also able
to resist the pull of two sets
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00:16:50,517 --> 00:16:52,310
of horses.
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To Von Guericke, it was the
proof of something he had long
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suspected, that gases like
air, exert an incredibly
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strong force.
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While the air around us may
appear calm, it is in fact
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a mass of moving molecules.
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As these molecules collide,
it produces an invisible push
250
00:17:24,931 --> 00:17:28,413
that we know as air pressure.
251
00:17:28,551 --> 00:17:31,724
That we don't notice this
pressure is because there's
252
00:17:31,862 --> 00:17:35,103
an equal pressure inside
each one of us pushing
253
00:17:35,241 --> 00:17:38,034
in the opposite direction.
254
00:17:38,172 --> 00:17:41,586
And so the two
cancel each other out.
255
00:17:45,862 --> 00:17:49,034
And that was why Von Guericke
needed to generate a vacuum.
256
00:17:49,172 --> 00:17:52,517
You can only see how strong
the air pressure really is when
257
00:17:52,655 --> 00:17:55,137
you take away the push
from the other side.
258
00:17:55,275 --> 00:17:57,275
At the end of the
demonstration, all they needed
259
00:17:57,413 --> 00:18:02,103
to do was let a little bit of
air back in, and it was almost
260
00:18:02,241 --> 00:18:04,448
as though the pressure
hadn't been there.
261
00:18:04,586 --> 00:18:06,724
[Air hissing]
262
00:18:13,275 --> 00:18:16,344
The ability of molecules
to exert pressure is one
263
00:18:16,482 --> 00:18:19,689
of the most fundamental
properties of not just air,
264
00:18:19,827 --> 00:18:22,310
but all gases.
265
00:18:24,931 --> 00:18:27,000
But Von Guericke's
discovery also raised
266
00:18:27,137 --> 00:18:30,310
an important question.
267
00:18:30,448 --> 00:18:34,482
If cold air molecules could
have such a powerful effect,
268
00:18:34,620 --> 00:18:37,586
what might be achieved if
those same molecules were
269
00:18:37,724 --> 00:18:39,620
heated up?
270
00:18:47,896 --> 00:18:50,689
I've travelled to the north
of England to meet a bunch
271
00:18:50,827 --> 00:18:54,551
of enthusiasts with
a head for heights.
272
00:19:00,862 --> 00:19:03,000
Harry Stringer is from
the Pennine Region
273
00:19:03,137 --> 00:19:06,517
Balloon Association.
274
00:19:06,655 --> 00:19:12,206
He's been flying hot air
balloons for over 25 years.
275
00:19:15,241 --> 00:19:16,896
Right, so where
are we going today?
276
00:19:17,034 --> 00:19:18,793
Well, we'll clear
the treetops here.
277
00:19:18,931 --> 00:19:20,137
That sounds like
a good start.
278
00:19:20,275 --> 00:19:21,758
Yeah, and then
we'll go up to
279
00:19:21,896 --> 00:19:23,103
about 1,000 feet.
- OK.
280
00:19:24,344 --> 00:19:26,172
Hands on!
281
00:19:26,310 --> 00:19:30,172
Czerski: The very first hot air
balloon, launched in 1783,
282
00:19:30,310 --> 00:19:33,620
was the brainchild of two
brothers called Joseph
283
00:19:33,758 --> 00:19:36,137
and Etienne Montgolfier.
284
00:19:38,241 --> 00:19:39,620
Oh! We're free!
285
00:19:39,758 --> 00:19:41,586
Stringer: OK,
we're away, John!
286
00:19:41,724 --> 00:19:44,517
One story goes that Joseph
had been staring into his
287
00:19:44,655 --> 00:19:48,310
fireplace one evening, when
he had the idea of filling
288
00:19:48,448 --> 00:19:51,344
a paper bag with hot air.
289
00:19:51,482 --> 00:19:54,034
On letting the bag go,
he observed that it
290
00:19:54,172 --> 00:19:56,724
began to rise.
291
00:19:56,862 --> 00:19:59,172
And this encouraged the
brothers to repeat
292
00:19:59,310 --> 00:20:02,931
the experiment, but this time
with a much larger,
293
00:20:03,068 --> 00:20:06,344
purpose-built balloon.
294
00:20:19,517 --> 00:20:22,517
And the really ingenious thing
about balloons is how they
295
00:20:22,655 --> 00:20:29,000
exploit a crucial
property of hot gasses.
296
00:20:29,137 --> 00:20:31,517
The mechanism of these
is beautifully simple.
297
00:20:31,655 --> 00:20:33,758
There's a bag above me
filled with hot air.
298
00:20:33,896 --> 00:20:36,344
What the burner does is
allows the balloonist to play
299
00:20:36,482 --> 00:20:38,689
around with the density of
the air by controlling
300
00:20:38,827 --> 00:20:40,620
its temperature.
301
00:20:40,758 --> 00:20:43,000
And as the air inside there is
heated up--and it could get up
302
00:20:43,137 --> 00:20:46,413
to 100 degrees
Celsius--it expands.
303
00:20:46,551 --> 00:20:50,206
As the air expands,
its individual molecules push
304
00:20:50,344 --> 00:20:56,137
outwards, making the air
inside the balloon less dense.
305
00:21:00,965 --> 00:21:03,344
Gravity is pulling everything,
everything I can see down to
306
00:21:03,482 --> 00:21:05,206
the ground.
307
00:21:05,344 --> 00:21:07,724
But because the air inside the
balloon is less dense than
308
00:21:07,862 --> 00:21:11,448
the air around it, everything
around us is being pulled down
309
00:21:11,586 --> 00:21:15,758
more, so it's squeezing the
less dense balloon upwards.
310
00:21:15,896 --> 00:21:18,413
And so balloonists are
floating on top of the denser
311
00:21:18,551 --> 00:21:21,206
air around them.
312
00:21:23,137 --> 00:21:26,896
But temperature doesn't just
enable a balloon to rise.
313
00:21:27,034 --> 00:21:30,379
It also controls how it falls.
314
00:21:36,517 --> 00:21:38,551
So how do you
make us come down?
315
00:21:38,689 --> 00:21:41,448
Stringer: We'll have a
parachute vent.
316
00:21:41,586 --> 00:21:43,551
It's massive.
You can see it.
317
00:21:43,689 --> 00:21:48,172
I could pull this red line,
and it will open the valve,
318
00:21:48,310 --> 00:21:51,379
and then I just close it and
the gulp of hot air lost will
319
00:21:51,517 --> 00:21:53,137
cause the balloon to descend.
320
00:22:07,862 --> 00:22:09,517
We are safe.
321
00:22:09,655 --> 00:22:11,517
- Can we stand up now?
- We can. We can.
322
00:22:11,655 --> 00:22:13,931
Czerski: The discovery that
heating up air could make it
323
00:22:14,068 --> 00:22:17,896
expand enough to lift people
into the skies was a milestone
324
00:22:18,034 --> 00:22:22,275
in human innovation.
325
00:22:22,413 --> 00:22:25,827
And it wasn't long before we
began to put that very same
326
00:22:25,965 --> 00:22:30,413
heat energy to a much
more practical purpose.
327
00:22:39,379 --> 00:22:41,310
It was something that
emerged from a very
328
00:22:41,448 --> 00:22:44,103
18th-century problem.
329
00:22:48,862 --> 00:22:52,793
300 years ago, mine owners
in Britain were facing
330
00:22:52,931 --> 00:22:55,068
a serious crisis.
331
00:22:59,000 --> 00:23:02,931
Since many ore deposits sat
well below the water table,
332
00:23:03,068 --> 00:23:06,137
they were finding that their
mines could only go as deep as
333
00:23:06,275 --> 00:23:11,275
the drainage technology at
the time allowed, resulting
334
00:23:11,413 --> 00:23:15,275
in many mines going
out of business.
335
00:23:18,275 --> 00:23:21,655
What was needed was a way to
haul all that water up to
336
00:23:21,793 --> 00:23:26,551
the surface so the miners
could get to the ore below.
337
00:23:26,689 --> 00:23:31,413
And in 1712, an ironmonger
called Thomas Newcomen hit
338
00:23:31,551 --> 00:23:34,517
upon the answer, with the
world's first commercial
339
00:23:34,655 --> 00:23:38,103
steam engine.
340
00:23:38,241 --> 00:23:41,827
And it worked by harnessing
the immense energy
341
00:23:41,965 --> 00:23:44,379
contained within
hot steam.
342
00:23:52,586 --> 00:23:54,862
The principle behind
Newcomen's engine is exactly
343
00:23:55,000 --> 00:23:57,793
the same one that Otto Von
Guericke had demonstrated.
344
00:23:57,931 --> 00:24:01,862
And that's just how hard air
pressure can push, especially
345
00:24:02,000 --> 00:24:04,482
when there's a vacuum
on the other side.
346
00:24:04,620 --> 00:24:07,482
I've got a plastic bottle here
with some water in the bottom,
347
00:24:07,620 --> 00:24:08,931
and I'm gonna put it in
the microwave to heat
348
00:24:09,068 --> 00:24:10,758
the water up.
349
00:24:14,448 --> 00:24:18,275
What's happening inside the
microwave is that the water
350
00:24:18,413 --> 00:24:21,448
molecules are being given
energy, and they're not just
351
00:24:21,586 --> 00:24:25,103
heating up but some of them are
turning into a gas, into steam.
352
00:24:25,241 --> 00:24:28,034
And that steam is starting
to fill up the bottle.
353
00:24:28,172 --> 00:24:31,586
And it's what happens
next that's important.
354
00:24:31,724 --> 00:24:33,034
[Microwave dings]
355
00:24:34,724 --> 00:24:38,586
Tip it into this water here.
356
00:24:38,724 --> 00:24:41,724
Ooh! Ha ha ha!
357
00:24:41,862 --> 00:24:45,448
And you can see that what
happened is that the bottle
358
00:24:45,586 --> 00:24:48,310
has been crushed, and
it's now full of water.
359
00:24:48,448 --> 00:24:50,931
And the reason for that
is that as it filled up
360
00:24:51,068 --> 00:24:53,482
with steam, the
air was pushed out.
361
00:24:53,620 --> 00:24:56,310
And then when I cooled the
steam down, it condensed from
362
00:24:56,448 --> 00:25:01,068
a gas back into a liquid,
which takes up much less space.
363
00:25:02,689 --> 00:25:04,965
And so there's a partial
vacuum left in the bottle
364
00:25:05,103 --> 00:25:08,206
and so there was all the air
pressure pushing in, nothing
365
00:25:08,344 --> 00:25:11,448
pushing back, and the
bottle was crushed.
366
00:25:18,241 --> 00:25:19,896
And this is the principle that
Newcomen used to drive
367
00:25:20,034 --> 00:25:21,551
his engine.
368
00:25:21,689 --> 00:25:24,655
At the heart of Newcomen's
engine lay a large metal
369
00:25:24,793 --> 00:25:30,172
cylinder housing a piston
and filled with hot steam.
370
00:25:30,310 --> 00:25:33,103
Cooling this steam with
water simultaneously created
371
00:25:33,241 --> 00:25:36,931
a vacuum and caused the weight
of the atmosphere to push down
372
00:25:37,068 --> 00:25:41,344
on the piston,
driving the engine.
373
00:25:41,482 --> 00:25:44,068
The cylinder was then refilled
with hot steam
374
00:25:44,206 --> 00:25:46,793
and the cycle repeated.
375
00:25:51,379 --> 00:25:54,689
Soon, Newcomen's steam engines
were popping up all over
376
00:25:54,827 --> 00:26:00,344
Britain, each one a symbol
of heat's ability to perform
377
00:26:00,482 --> 00:26:03,344
useful work.
378
00:26:06,517 --> 00:26:10,896
But Newcomen's design had
one major weakness.
379
00:26:13,275 --> 00:26:16,206
It was hugely inefficient.
380
00:26:16,344 --> 00:26:21,068
Of all the energy in the coal
that it consumed, only 1%-2%
381
00:26:21,206 --> 00:26:25,827
was converted into
useful mechanical work.
382
00:26:28,758 --> 00:26:32,103
The mystery was why?
383
00:26:32,241 --> 00:26:35,586
Where was all that
heat energy going
384
00:26:35,724 --> 00:26:39,931
and what could be
done to retrieve it?
385
00:26:40,068 --> 00:26:43,827
To discover the answer, we've
come to Coldharbour Mill
386
00:26:43,965 --> 00:26:45,793
in Devon.
387
00:26:45,931 --> 00:26:50,137
Originally built in 1797,
it's one of the oldest
388
00:26:50,275 --> 00:26:53,517
steam-powered woolen mills
left in Britain.
389
00:26:55,724 --> 00:26:59,241
Man: OK, try not to kill
anybody with the other end.
390
00:26:59,379 --> 00:27:02,896
Czerski: John Jasper runs the
mill's giant steam engine.
391
00:27:03,034 --> 00:27:04,137
- That's good.
- Like that?
392
00:27:04,275 --> 00:27:06,103
- You are a natural.
- OK.
393
00:27:06,241 --> 00:27:08,103
- Right side.
- Yes.
394
00:27:10,965 --> 00:27:13,862
[Clang]
Oop! Ha ha ha!
395
00:27:16,517 --> 00:27:18,206
So tell me
about these boilers.
396
00:27:18,344 --> 00:27:20,482
This is a
Lancashire boiler.
397
00:27:20,620 --> 00:27:23,275
It holds 20,000
gallons of water.
398
00:27:23,413 --> 00:27:26,482
Above that water level,
you have steam.
399
00:27:26,620 --> 00:27:28,448
[Steam hissing]
400
00:27:28,586 --> 00:27:31,068
- Get a bit of steam up.
- Right.
401
00:27:31,206 --> 00:27:33,000
So it's basically a
sort of steam kettle.
402
00:27:33,137 --> 00:27:34,931
So these bits are
the heating elements.
403
00:27:35,068 --> 00:27:38,310
Effectively, you're shoveling
fire into the heating element,
404
00:27:38,448 --> 00:27:40,344
and then all of this is the
kettle which is full of water.
405
00:27:40,482 --> 00:27:41,931
That's right.
406
00:27:42,068 --> 00:27:43,965
But instead of coming out
of the spout, it goes to
407
00:27:44,103 --> 00:27:45,517
a steam engine.
408
00:27:45,655 --> 00:27:47,551
It takes a little longer
to get to the boil.
409
00:27:47,689 --> 00:27:50,620
Ha ha! Better do some
more shoveling then.
410
00:27:50,758 --> 00:27:52,068
Jasper: Yeah.
411
00:27:54,310 --> 00:27:56,689
The engine here is a
descendent of a type that was
412
00:27:56,827 --> 00:28:03,206
built to address the problem
of Newcomen's lost energy.
413
00:28:03,344 --> 00:28:06,482
It was designed by a Scottish
instrument maker called
414
00:28:06,620 --> 00:28:08,896
James Watt.
415
00:28:10,689 --> 00:28:13,413
Watt had recently become
familiar with a new
416
00:28:13,551 --> 00:28:16,310
theory of heat.
417
00:28:19,793 --> 00:28:23,827
Creating steam is all about
putting heat energy into water.
418
00:28:23,965 --> 00:28:27,068
But there's this strange
observation, which is that as
419
00:28:27,206 --> 00:28:30,241
you start to heat water up,
you see the thermometer rise.
420
00:28:30,379 --> 00:28:33,206
And it goes up and up and up,
and then it gets to
421
00:28:33,344 --> 00:28:36,862
100 degrees and it won't
go any further.
422
00:28:37,000 --> 00:28:40,448
So you can be pumping in
huge amounts of heat energy,
423
00:28:40,586 --> 00:28:44,448
and yet the thermometer
isn't moving.
424
00:28:44,586 --> 00:28:48,379
And that's because once water
reaches its boiling point,
425
00:28:48,517 --> 00:28:52,689
all that heat energy is being
used up, turning the water
426
00:28:52,827 --> 00:28:55,379
into steam.
427
00:28:55,517 --> 00:29:00,068
And this led to the idea that
there are two forms of heat--
428
00:29:00,206 --> 00:29:05,620
first the sort that causes
a thermometer to rise,
429
00:29:05,758 --> 00:29:09,137
and second the heat required
to change matter from one
430
00:29:09,275 --> 00:29:14,206
state to another,
called latent heat.
431
00:29:18,068 --> 00:29:21,068
And the amount of latent heat
needed to turn water
432
00:29:21,206 --> 00:29:25,137
into a gas is enormous.
433
00:29:28,344 --> 00:29:30,172
And the reason that all this
matters for steam engines is
434
00:29:30,310 --> 00:29:33,206
that steam is expensive
in terms of energy.
435
00:29:33,344 --> 00:29:35,586
And when you've got it,
you certainly don't want
436
00:29:35,724 --> 00:29:37,137
to waste it.
437
00:29:40,931 --> 00:29:44,551
It was this revelation that
creating steam requires huge
438
00:29:44,689 --> 00:29:48,482
amounts of latent heat that
was one of the main reasons
439
00:29:48,620 --> 00:29:52,482
why Newcomen's engine
was so wasteful.
440
00:29:57,137 --> 00:30:00,689
At the heart of every steam
engine, there's a piston.
441
00:30:00,827 --> 00:30:03,620
That's where the hot gas
molecules are pushing to
442
00:30:03,758 --> 00:30:06,413
create mechanical work.
443
00:30:06,551 --> 00:30:08,655
And the problem with
Newcomen's engine was that
444
00:30:08,793 --> 00:30:12,827
in order to reset, the water
needed to be condensed, cooled
445
00:30:12,965 --> 00:30:15,827
down, and that happened
inside the pistons.
446
00:30:15,965 --> 00:30:18,724
So the metal itself had to
be cooled down as well.
447
00:30:18,862 --> 00:30:21,724
And then you needed to use
more steam energy to heat it
448
00:30:21,862 --> 00:30:25,103
up again to create
the next stroke.
449
00:30:25,241 --> 00:30:29,517
In order to conserve all that
valuable steam, Watt came up
450
00:30:29,655 --> 00:30:32,413
with an ingenious invention.
451
00:30:36,689 --> 00:30:41,758
Watt's solution was a
condenser, and this is it.
452
00:30:41,896 --> 00:30:44,206
So instead of having the
condensation happening inside
453
00:30:44,344 --> 00:30:48,206
the piston, the steam was
vented out to a separate
454
00:30:48,344 --> 00:30:53,448
chamber, and that was where
the condensation occurred.
455
00:30:53,586 --> 00:30:56,344
And the reason it was a
brilliant solution was that
456
00:30:56,482 --> 00:30:59,310
the hot parts of the engine
stayed hot, and the cool parts
457
00:30:59,448 --> 00:31:03,862
of the engine stayed cool and
much less heat was wasted.
458
00:31:07,103 --> 00:31:10,413
Watt's great insight that the
more an engine can conserve
459
00:31:10,551 --> 00:31:15,586
heat, the more efficient it
will be was a watershed moment
460
00:31:15,724 --> 00:31:19,103
in the history of steam power.
461
00:31:19,241 --> 00:31:22,448
Other improvements followed,
such as the introduction
462
00:31:22,586 --> 00:31:29,413
of steam at high pressure to
generate even greater force.
463
00:31:29,551 --> 00:31:34,241
These innovations ushered in a
mechanical revolution, founded
464
00:31:34,379 --> 00:31:38,241
upon the energy of
hot gas molecules.
465
00:31:40,931 --> 00:31:45,103
But as our population grew and
our coal supplies dwindled,
466
00:31:45,241 --> 00:31:49,551
so we began to turn
elsewhere for our energy.
467
00:31:52,689 --> 00:31:55,448
And in some places, that
has involved tapping into
468
00:31:55,586 --> 00:31:58,310
a different source of heat...
469
00:32:00,517 --> 00:32:02,000
one that's responsible
470
00:32:02,137 --> 00:32:04,482
for some of the most
violent natural phenomena
471
00:32:04,620 --> 00:32:06,827
on the planet.
472
00:32:19,758 --> 00:32:22,620
Just a short distance
from Reykjavik lies one
473
00:32:22,758 --> 00:32:26,482
of Iceland's top tourist
attractions...
474
00:32:28,275 --> 00:32:32,517
an outdoor health
spa known as the Blue Lagoon.
475
00:32:36,413 --> 00:32:39,517
This is the real attraction
round here, lovely warm water
476
00:32:39,655 --> 00:32:43,344
at 38 degrees Celsius and
full of minerals, which are
477
00:32:43,482 --> 00:32:45,275
apparently very good for you.
478
00:32:45,413 --> 00:32:48,241
So, on a day like today and
in a country with a reputation
479
00:32:48,379 --> 00:32:50,275
for being chilly, this
is clearly the perfect
480
00:32:50,413 --> 00:32:53,206
place to relax.
481
00:32:59,655 --> 00:33:02,241
But despite appearances,
this is no natural
482
00:33:02,379 --> 00:33:04,275
beauty spot.
483
00:33:04,413 --> 00:33:09,103
In fact, the Blue Lagoon is
entirely manmade...
484
00:33:12,724 --> 00:33:16,793
fed by hot water from the nearby
Svartsengi Geothermal
485
00:33:16,931 --> 00:33:19,206
Power Station.
486
00:33:24,724 --> 00:33:27,931
Every day, Svartsengi
produces enough electricity
487
00:33:28,068 --> 00:33:32,172
for around 130,000 homes.
488
00:33:35,827 --> 00:33:39,655
And the source of all that
power is the same heat energy
489
00:33:39,793 --> 00:33:43,206
that created Iceland
in the first place.
490
00:33:54,827 --> 00:33:58,344
Directly below Iceland lies a
giant column of super-heated
491
00:33:58,482 --> 00:34:03,448
rock, known as a mantel plume,
fed by heat rising up from
492
00:34:03,586 --> 00:34:07,379
the Earth's core.
493
00:34:07,517 --> 00:34:11,620
To tap into this immense
source of energy, Svartsengi
494
00:34:11,758 --> 00:34:15,931
sits above 13 bore holes,
stretching 2 kilometers into
495
00:34:16,068 --> 00:34:18,206
the rock below.
496
00:34:21,517 --> 00:34:24,206
The basic premise here is
that a mixture of hot water
497
00:34:24,344 --> 00:34:27,896
and steam is pumped up from
deep down, and the steam is
498
00:34:28,034 --> 00:34:30,793
separated out and sent through
a turbine that generates
499
00:34:30,931 --> 00:34:33,344
75 megawatts of electricity.
500
00:34:33,482 --> 00:34:35,172
That goes into the grid.
501
00:34:35,310 --> 00:34:38,103
And then the same steam comes
back around and reheats
502
00:34:38,241 --> 00:34:41,068
the water, and that supplies
domestic hot water
503
00:34:41,206 --> 00:34:45,793
for about 20,000 homes
on this peninsula.
504
00:34:45,931 --> 00:34:49,103
For the engineers around here,
the hot water beneath their
505
00:34:49,241 --> 00:34:53,344
feet is just one
massive treasure trove.
506
00:34:55,689 --> 00:34:58,793
Channeling the heat of the
planet itself has allowed us
507
00:34:58,931 --> 00:35:02,517
to take steam power to
a new level.
508
00:35:07,931 --> 00:35:11,862
But today, scientists are
attempting to harness another,
509
00:35:12,000 --> 00:35:18,344
even hotter, form of energy...
derived from a strange type
510
00:35:18,482 --> 00:35:22,586
of matter that here on Earth
makes the occasional,
511
00:35:22,724 --> 00:35:24,896
spectacular appearance.
512
00:35:35,724 --> 00:35:37,517
[Footsteps climbing stairs]
513
00:35:41,137 --> 00:35:44,689
Inside the University of
Manchester's High Voltage Lab,
514
00:35:44,827 --> 00:35:48,103
a team of researchers is getting
ready to re-create one
515
00:35:48,241 --> 00:35:52,620
of the most awesome natural
phenomena on the planet...
516
00:35:55,689 --> 00:35:57,448
[Loud crack]
Lightning.
517
00:36:05,379 --> 00:36:08,827
This beast of a device is an
impulse generator, and this
518
00:36:08,965 --> 00:36:11,758
one is capable of generating
2 million volts between
519
00:36:11,896 --> 00:36:14,793
the bottom and the top,
and here's how it works.
520
00:36:14,931 --> 00:36:17,793
Normally when you get a
voltage, electric charge will
521
00:36:17,931 --> 00:36:22,103
flow, but here, each of these
red things is a capacitor,
522
00:36:22,241 --> 00:36:24,482
and so the electric charge
can't go anywhere.
523
00:36:24,620 --> 00:36:27,793
It's stored on the plates,
and that means that energy is
524
00:36:27,931 --> 00:36:30,103
building up.
525
00:36:36,103 --> 00:36:38,206
And it's this point here
that's the important bit,
526
00:36:38,344 --> 00:36:41,655
because when the switch over
there is pressed, all of that
527
00:36:41,793 --> 00:36:44,586
charge is gonna get dumped
through that point
528
00:36:44,724 --> 00:36:48,241
in around a millionth
of a second.
529
00:36:48,379 --> 00:36:53,344
In charge of the controls
is Dr. Viddy Peesapati.
530
00:36:55,275 --> 00:36:56,965
So what we're going to do
right now is make sure that
531
00:36:57,103 --> 00:36:58,862
no one else can walk in.
532
00:36:59,000 --> 00:37:01,551
So if you want to press the
black button on the interlock.
533
00:37:01,689 --> 00:37:03,586
- That?
- Yes, that's the one.
534
00:37:03,724 --> 00:37:05,000
[Buzzer]
Now it's ready.
535
00:37:05,137 --> 00:37:06,620
Czerski: Under Viddy's
supervision,
536
00:37:06,758 --> 00:37:10,965
we're going to
trigger a lightning strike...
537
00:37:11,103 --> 00:37:13,758
You wanna press
F4 on the keyboard.
538
00:37:13,896 --> 00:37:18,275
which we'll also capture
using a high-speed camera.
539
00:37:20,620 --> 00:37:22,310
Peesapati: Now it's charging.
540
00:37:22,448 --> 00:37:24,275
Czerski: So we can see the
voltage going up here.
541
00:37:24,413 --> 00:37:25,655
Peesapati: Absolutely, so it
takes around 60 seconds
542
00:37:25,793 --> 00:37:28,172
for the entire kit
to be charged up.
543
00:37:28,310 --> 00:37:30,413
When this gets to the
end, we'll be ready to go.
544
00:37:30,551 --> 00:37:32,931
Peesapati: We'll let the siren
go telling us that there's going
545
00:37:33,068 --> 00:37:34,413
to be a flash-over, and it
automatically triggers
546
00:37:34,551 --> 00:37:36,413
the first stage.
547
00:37:36,551 --> 00:37:40,724
Czerski: 60 seconds later, and
the generator is ready to fire.
548
00:37:44,206 --> 00:37:45,206
So when I hear the siren--
549
00:37:45,344 --> 00:37:48,068
[Siren blares]
550
00:37:50,862 --> 00:37:53,413
[Loud crack]
551
00:37:53,551 --> 00:37:55,655
That is an echo
and a half, isn't it? Wow!
552
00:37:55,793 --> 00:37:58,344
It is very loud, and that is
basically a sonic boom.
553
00:37:58,482 --> 00:38:00,172
It's like a giant
electric whip-crack.
554
00:38:00,310 --> 00:38:01,758
It is, absolutely.
555
00:38:01,896 --> 00:38:03,931
Czerski: But it's only
when you play back
556
00:38:04,068 --> 00:38:05,862
the slow-motion video
557
00:38:06,000 --> 00:38:11,000
that you begin to see exactly
what lightning really is...
558
00:38:11,137 --> 00:38:12,965
[Loud crack]
559
00:38:13,103 --> 00:38:16,965
a super-heated channel of air,
with so much energy that it's
560
00:38:17,103 --> 00:38:21,172
become an entirely
different form of matter.
561
00:38:21,310 --> 00:38:23,310
[Loud crack]
562
00:38:24,620 --> 00:38:26,448
We're used to the idea of
3 states of matter--
563
00:38:26,586 --> 00:38:28,448
solid, liquid, and gas.
564
00:38:28,586 --> 00:38:31,586
But what we've got here,
is a 4th, because the source
565
00:38:31,724 --> 00:38:35,000
of all of that
light is a plasma.
566
00:38:35,137 --> 00:38:37,275
[Crackling]
567
00:38:39,000 --> 00:38:43,724
From the Sun's fiery surface...
568
00:38:43,862 --> 00:38:45,551
to the clouds of interstellar
569
00:38:45,689 --> 00:38:49,482
gas known as nebulae, plasmas
are found across our solar
570
00:38:49,620 --> 00:38:52,206
system and beyond.
571
00:38:53,862 --> 00:38:57,206
And it's this super-heated
form of matter that scientists
572
00:38:57,344 --> 00:39:01,034
are hoping will enable them
to unlock a brand-new type
573
00:39:01,172 --> 00:39:02,862
of energy...
574
00:39:05,965 --> 00:39:10,103
by manipulating one of its
strangest properties.
575
00:39:13,379 --> 00:39:15,206
This is a Crookes Tube,
named after the British
576
00:39:15,344 --> 00:39:17,379
physicist William Crookes
who was one of the people to
577
00:39:17,517 --> 00:39:20,275
design and use
it in the 1870s.
578
00:39:20,413 --> 00:39:22,758
This was the piece of
equipment that opened the door
579
00:39:22,896 --> 00:39:24,827
to plasma physics.
580
00:39:24,965 --> 00:39:28,344
It's a sealed glass vessel,
and it's got two electrodes--
581
00:39:28,482 --> 00:39:31,206
the negative one here and
a positive one here.
582
00:39:31,344 --> 00:39:34,172
And on the inside, there's
just a little bit of gas
583
00:39:34,310 --> 00:39:36,310
at very low pressure.
584
00:39:38,827 --> 00:39:42,724
And when Crookes turned up the
voltage, this is what he saw.
585
00:39:42,862 --> 00:39:45,068
[Loud crackling]
586
00:39:48,448 --> 00:39:52,379
You can see that this is quite
noisy, but there's a green
587
00:39:52,517 --> 00:39:55,896
glow down this
end of the tube.
588
00:39:56,034 --> 00:40:00,724
Crookes called this eerie
light "radiant matter."
589
00:40:04,000 --> 00:40:06,758
But Crookes didn't understand
what was going on, but we do,
590
00:40:06,896 --> 00:40:08,586
and it's this.
591
00:40:08,724 --> 00:40:11,793
When high voltage is applied
across the two electrodes,
592
00:40:11,931 --> 00:40:16,172
it frees up negatively charged
electrons from the gas inside
593
00:40:16,310 --> 00:40:19,206
that are then accelerated
towards the flat end
594
00:40:19,344 --> 00:40:21,620
of the tube.
595
00:40:21,758 --> 00:40:24,551
As they strike the glass,
they excite the molecules
596
00:40:24,689 --> 00:40:29,241
on the surface, causing
them to give off light.
597
00:40:34,103 --> 00:40:36,758
And it's the free movement of
electrons like this that is
598
00:40:36,896 --> 00:40:41,068
the defining characteristic
of a plasma and which gives it
599
00:40:41,206 --> 00:40:45,034
one of its most
distinctive properties.
600
00:40:45,172 --> 00:40:47,379
I've got a magnet here,
just a small one.
601
00:40:47,517 --> 00:40:50,827
So when I bring the magnet in
here, you can see that that
602
00:40:50,965 --> 00:40:55,000
beam of electrons is being
pushed to one side or the other.
603
00:40:55,137 --> 00:40:58,034
It's being deflected
by the magnet.
604
00:41:01,241 --> 00:41:03,517
So I can actually control
what's going on inside
605
00:41:03,655 --> 00:41:07,206
a plasma using electric and
magnetic fields, and that is
606
00:41:07,344 --> 00:41:10,724
what makes a plasma
really interesting.
607
00:41:15,620 --> 00:41:18,206
It's this in-built
electromagnetism that's opened
608
00:41:18,344 --> 00:41:22,137
up the possibility of one
day channeling the enormous
609
00:41:22,275 --> 00:41:28,448
energy inside super-hot plasma
and putting it to use...
610
00:41:28,586 --> 00:41:33,413
by exploiting here on Earth a
different source of energy,
611
00:41:33,551 --> 00:41:38,103
the same type of
energy that powers our Sun.
612
00:41:47,689 --> 00:41:50,965
Inside a vast hanger at the
Culham Science Centre near
613
00:41:51,103 --> 00:41:55,620
Oxford sits a machine so
complex, it contains well over
614
00:41:55,758 --> 00:41:59,103
100,000 separate parts.
615
00:42:01,034 --> 00:42:04,586
This is a fusion reactor.
616
00:42:04,724 --> 00:42:08,275
Its job is to channel streams
of extremely hot plasma
617
00:42:08,413 --> 00:42:13,310
and use them to manipulate
matter at the atomic scale.
618
00:42:15,586 --> 00:42:19,931
The aim is to unleash the
power of the atom itself
619
00:42:20,068 --> 00:42:24,724
and reach the holy
grail of physics--
620
00:42:24,862 --> 00:42:27,206
nuclear fusion.
621
00:42:35,000 --> 00:42:38,241
There's no way anyone would be
this close to a fusion reactor
622
00:42:38,379 --> 00:42:41,551
if it was running, because it
throws off enormous numbers
623
00:42:41,689 --> 00:42:43,724
of neutrons which can
do a lot of damage.
624
00:42:43,862 --> 00:42:46,275
And that's why everything
around me here is surrounded
625
00:42:46,413 --> 00:42:48,689
in concrete 3 meters thick.
626
00:42:48,827 --> 00:42:51,275
Just at the moment, they're in
a maintenance phase so we can
627
00:42:51,413 --> 00:42:53,379
get a little bit closer.
628
00:42:53,517 --> 00:42:57,551
Showing us around the
reactor is Dr. Joanne Flanagan.
629
00:43:00,344 --> 00:43:02,448
Czerski: What exactly is it
that all of this kit is
630
00:43:02,586 --> 00:43:04,482
trying to do?
631
00:43:04,620 --> 00:43:07,413
We are essentially trying to
create an artificial star.
632
00:43:07,551 --> 00:43:10,034
Actually we do.
We create artificial stars.
633
00:43:14,413 --> 00:43:18,103
We take hydrogen gas
and heat it up to very high
634
00:43:18,241 --> 00:43:20,172
temperatures, where
it becomes ionized.
635
00:43:20,310 --> 00:43:21,862
It becomes a plasma.
636
00:43:22,000 --> 00:43:23,137
Czerski: What sort of
temperatures does it reach
637
00:43:23,275 --> 00:43:24,655
on the inside there?
638
00:43:24,793 --> 00:43:26,551
We routinely reach
temperatures of about
639
00:43:26,689 --> 00:43:29,551
100 million degrees, which is
about 10 times hotter than
640
00:43:29,689 --> 00:43:30,965
the center of the Sun.
641
00:43:31,103 --> 00:43:32,689
That's just
a ludicrous number!
642
00:43:32,827 --> 00:43:34,793
It's a number you can't
even get your head around.
643
00:43:34,931 --> 00:43:36,620
It's a crazy
hot temperature.
644
00:43:36,758 --> 00:43:38,482
We need such high temperatures
because hydrogen nuclei
645
00:43:38,620 --> 00:43:40,448
repel each other.
646
00:43:40,586 --> 00:43:43,310
To get them to stick, we need
them to collide at high speed,
647
00:43:43,448 --> 00:43:45,689
and that's fundamentally
what temperature is--
648
00:43:45,827 --> 00:43:47,103
high-speed particles.
- Right.
649
00:43:47,241 --> 00:43:49,689
How do you make
anything that hot?
650
00:43:49,827 --> 00:43:52,586
A first step is to run
a current through the plasma.
651
00:43:52,724 --> 00:43:55,103
It's like an old-style
electrical light bulb.
652
00:43:55,241 --> 00:43:59,241
And that gets us to a few
tens of millions of degrees.
653
00:44:01,965 --> 00:44:04,034
But then we need
to pull additional heating
654
00:44:04,172 --> 00:44:06,827
systems online to boost us
the rest of the way.
655
00:44:06,965 --> 00:44:08,344
So you're just throwing
everything at it to get
656
00:44:08,482 --> 00:44:10,310
energy into it.
657
00:44:10,448 --> 00:44:13,034
Since there is no material
on earth that can withstand
658
00:44:13,172 --> 00:44:17,551
temperatures of 100 million
degrees, the scientists
659
00:44:17,689 --> 00:44:23,137
instead contain the plasma by
using its electromagnetism.
660
00:44:26,344 --> 00:44:30,206
At the heart of the reactor
lies a giant metal doughnut
661
00:44:30,344 --> 00:44:34,586
called a Tokamak that uses
a powerful magnetic field to
662
00:44:34,724 --> 00:44:38,206
keep the plasma confined long
enough for the collisions that
663
00:44:38,344 --> 00:44:41,172
cause fusion to happen.
664
00:44:48,206 --> 00:44:50,000
The plasma would be in the
space that we're in here
665
00:44:50,137 --> 00:44:53,068
and the magnetic fields,
where do they go?
666
00:44:53,206 --> 00:44:54,586
The magnetic fields
curve around in the shape
667
00:44:54,724 --> 00:44:56,275
of the vessel.
668
00:44:56,413 --> 00:44:59,103
They have a sort of
an onion-like structure.
669
00:44:59,241 --> 00:45:02,172
And they hold the plasma to
the shape of this vessel,
670
00:45:02,310 --> 00:45:04,482
about 5 centimeters
away from the edges.
671
00:45:04,620 --> 00:45:07,241
And the plasma is then
here in the middle, is it?
672
00:45:07,379 --> 00:45:09,103
Right where you are.
673
00:45:09,241 --> 00:45:11,896
Czerski: As all this plasma
is heated up,
674
00:45:12,034 --> 00:45:13,793
so the hydrogen nuclei
675
00:45:13,931 --> 00:45:18,241
inside accelerate, getting
faster and faster, until they
676
00:45:18,379 --> 00:45:23,068
reach a speed where they can
get close enough to fuse.
677
00:45:26,206 --> 00:45:27,517
So once you've had
a successful collision,
678
00:45:27,655 --> 00:45:29,206
what happens next?
679
00:45:29,344 --> 00:45:32,000
Then you have a very
fast neutron that comes out
680
00:45:32,137 --> 00:45:33,758
of that reaction.
681
00:45:33,896 --> 00:45:36,379
So it's the neutrons that are
carrying the energy out.
682
00:45:36,517 --> 00:45:38,448
It's the speed, yes.
683
00:45:38,586 --> 00:45:40,586
Czerski: Yeah, that would go
flying off, and it would heat
684
00:45:40,724 --> 00:45:42,551
something up.
- Yeah.
685
00:45:46,241 --> 00:45:49,000
Flanagan: The idea is that you
would have a lithium blanket
686
00:45:49,137 --> 00:45:51,689
surrounding the entire device,
which would capture those
687
00:45:51,827 --> 00:45:54,310
neutrons and heat up,
and you'd have heat exchanger
688
00:45:54,448 --> 00:45:58,000
pipes that run through that
blanket that would then heat
689
00:45:58,137 --> 00:46:01,241
water to drive steam turbines.
690
00:46:03,586 --> 00:46:06,344
Czerski: But if we're ever to
master the searing temperatures
691
00:46:06,482 --> 00:46:10,448
of fusion, then there's one
major obstacle that still has
692
00:46:10,586 --> 00:46:12,620
to be overcome...
693
00:46:15,275 --> 00:46:18,103
because for now, at least,
we've yet to find a way
694
00:46:18,241 --> 00:46:23,206
of getting more energy out
from a fusion reactor than
695
00:46:23,344 --> 00:46:25,344
we put in.
696
00:46:28,689 --> 00:46:32,379
Until then, commercial-scale
nuclear fusion lies
697
00:46:32,517 --> 00:46:36,206
tantalizingly
just out of reach.
698
00:46:39,896 --> 00:46:42,517
I think it's very likely that
fusion energy, this technology
699
00:46:42,655 --> 00:46:46,586
made possible by fantastically
high temperatures, will form
700
00:46:46,724 --> 00:46:48,655
a significant power
source in the future
701
00:46:48,793 --> 00:46:51,586
of our civilization.
702
00:46:51,724 --> 00:46:55,620
Even though there's not yet
one clear solution, when it
703
00:46:55,758 --> 00:46:59,172
comes to fusion,
the game is afoot.
704
00:47:04,172 --> 00:47:08,275
From the searing heat of the
early Earth to the cooling
705
00:47:08,413 --> 00:47:13,034
that transformed it and
allowed life to flourish,
706
00:47:13,172 --> 00:47:15,758
temperature has been
fundamental to the story
707
00:47:15,896 --> 00:47:20,241
of our planet,
708
00:47:20,379 --> 00:47:24,103
but it's
also driven our story.
709
00:47:26,000 --> 00:47:29,137
As our understanding of
temperature has grown,
710
00:47:29,275 --> 00:47:32,206
so we've learnt
how to use it
711
00:47:34,241 --> 00:47:37,344
to create new materials...
712
00:47:37,482 --> 00:47:40,517
drive our machines...
713
00:47:40,655 --> 00:47:45,310
and advance technology.
714
00:47:45,448 --> 00:47:48,586
Temperature is such a big
idea encapsulated in just
715
00:47:48,724 --> 00:47:50,310
one number.
716
00:47:50,448 --> 00:47:53,310
As a physicist, it's the
first thing I measure.
717
00:47:53,448 --> 00:47:56,689
And as a human, it's
the first thing I feel.
718
00:47:56,827 --> 00:47:59,586
And yet our direct experience
of temperature is limited to
719
00:47:59,724 --> 00:48:01,931
a really narrow range.
720
00:48:02,068 --> 00:48:04,344
But once you learn about
what's beyond that--
721
00:48:04,482 --> 00:48:07,655
the extreme heat, the extreme
cold, and all the subtleties
722
00:48:07,793 --> 00:48:11,000
in-between--it's clear
that the possibilities that
723
00:48:11,137 --> 00:48:14,068
temperature
offers are endless.
58772
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