Kind: captions
Language: en
are you ready to explore nothing less
than the entire universe three
two
one
welcome to nova now universe revealed a
five-part companion podcast series to
the nova mini series on pbs
humanity's view of the vast cosmos is
part of our global heritage you can
check it out anywhere on earth
take stars
we typically think of them as part of
the night sky but it's a star that
dominates our days the sun our primary
provider of light and heat
look around outside
plants from the tallest trees to the
shortest sprouts stretch out reaching
towards the light and these plants
convert our star's energy into fuel that
we can consume to power ourselves
but have you ever looked up and wondered
what exactly is a star and why is it
shining
well timon and pumbaa have from the lion
king
to moon
yeah
ever wonder what those sparkly darts are
up there
they're fireflies
fireflies that got stuck up in that big
bluish flat thing oh
gee
i always thought they were balls of gas
burning billions of miles away
sorry timon pumbaa got this one right
but plot twist fusion scientists today
are trying to capture the power of the
stars in a magnetic bottle
feeling starry-eyed yet
today on nova now universe revealed
stars what makes them shine how we're
trying to recreate that energy source
here on earth and how you and i are
composed of stardust i'm alok patel
solar energy
is indirectly responsible for dam near
every process on earth right when you
eat
that's the sun this is hakeem olu
he's an astrophysicist and cosmologist
and as he puts it i am a science
mercenary i called on hakeem to help me
understand those twinkling lights in the
sky and how they shine
[Music]
so
a star
is a self-sustained
nuclear fusion reaction in the center of
a giant ball of gas
or plasma so it's the fusion reaction
that's the key thing for those of us who
aren't nuclear physicists can i get a
show of hands people let's do a quick
refresher on atoms
they're the basic units of matter made
up of three types of particles protons
electrons and neutrons
protons have a positive charge and the
number of them in an atom's nucleus
determines which element it is
you might remember the periodic table of
elements from science class
one proton means you have hydrogen two
protons helium three lithium and down
the line
the second kind of particle electrons
have a negative charge whereas neutrons
the third type of particle have no
charge
so when it comes to fusion a fusion
reaction is nothing more than two
lighter atoms merging to form a heavier
atom an entirely new element it's the
nuclei of the atoms that fuse together
and this process releases energy because
the total mass of the resulting element
is slightly less than the sum of the two
originals that leftover mass is released
as energy
[Music]
but nuclei don't just fuse together on
their own in fact their protons
naturally repel each other due to their
positive electric charge
so to get fusion to happen you have to
meet certain conditions
and the primary conditions there are two
of them like with many things that occur
that involve matter
the two things are almost always the
most important are the temperature
and the density how much stuff is packed
together and the temperatures and
densities required for fusion are found
inside the cores of stars when you think
about a star a star really has two major
parts
it has a core where the fusion reaction
is going to occur and then between the
core and the surface
that region of the star we call that the
envelope it's the gravity of the star
that keeps its core hot and dense
as you pour more and more matter onto
that envelope it's compressing that core
more and more making it hotter and
hotter and hotter
imagine two protons
that are in that core
and they're flying around and they're
coming towards each other
what's gonna happen is they're gonna
veer away from each other
now
as the temperature gets hotter and
hotter that means the particles are
moving faster and faster
this means that when those two protons
are encountering each other they get
closer
at a higher speed than they would get at
a lower speed and the key thing for them
is to get within a certain distance of
each other then there is a strong
attractive force that kicks in that we
call the strong force that's 137 times
more powerful than the electrostatic
repulsive force so instead of veering
away they'll be pulled together
these two protons now in this core
getting crushed by this envelope
scream towards each other the
temperature is 10 million degrees kelvin
and so now
boom
meaning once atoms start fusing together
you've got yourself a star
that's the first step of what we call
the pp chain
p the letter p for papa stands for
proton proton chain
right and so we typically say
hydrogen combines to form helium but
it's a series of steps where ultimately
you end up with
two protons and two neutrons bound
together in what we call a helium-4
nucleus in other words two one-proton
hydrogen atoms have fused into one two
proton helium atom and in that process
you kick out light in the form of gamma
rays and neutrinos fuse enough hydrogen
into helium and you get a star that
shines
stellar fusions also responsible for
fusing nuclei into not just helium but
even heavier elements like oxygen carbon
nitrogen if you look at the order in
which stars build atoms in their cores
and you look at the
abundance of the elements in the
universe you'll see directly that stars
built
the stuff you know what boggles my mind
is every time you take a breath
you're inhaling the cores of long dead
stars
now before these atoms came from
so is it it's fair to say like stars
play an important part in terms of the
formation of elements in our universe oh
they play the primary part so basically
there are several processes by which
elements are created and the creation of
the elements we call nucleosynthesis so
there are processes that occur in the
cores of stars
now there's another way that's more
sneaky
and that's when neutrons sneak into a
nucleus neutrons do not have an
electromagnetic repulsion right so they
can you know i'm flying out of the core
and i'm flying around the envelope boom
i hit a nucleus i am now part of that
nucleus and sometimes that neutron
converts into a proton which transforms
the atom into a different element and
that way you build up heavier elements
right then there is the process of
a supernova explosion
a supernova the end times for giant
stars
when a massive star much larger than our
sun runs out of nuclear fuel the energy
from the fusion no longer balances the
force of gravity and some of its mass
from the envelope falls into its core
eventually the core gets so heavy that
it can't withstand its own gravitational
force
the core collapses in on itself and the
massive star explodes in a giant
supernova
you know the inner core goes out so the
outer layers just fall in at you know
some fraction of the speed of light and
so now you can really once again sneak
protons into nuclei
which generates heavier elements
another thing is when neutron stars
collide after a massive star goes
supernova its core can become a tiny and
incredibly dense object just one
teaspoon of that material weighs four
billion tons these super dense cores of
exploded stars are called neutron stars
so if you have neutron stars that's a
lot of neutrons to be packing the you
know boom right you can make some really
big nuclei and that's when you know our
first time we observed two neutron stars
collide
more than an earth's mass of gold was
produced in the collision wow
yeah it's hard to even fathom exactly
right it's crazy thankfully our sun
doesn't have enough mass to go supernova
but there's still the question of what's
going to happen when it runs out of
hydrogen fuel to fuse it's more than a
factor of it running out of its gas
because there's other dynamics that are
occurring so when a star is burning
hydrogen like the sun is doing right now
they're really stable and well behaved
before they start burning hydrogen they
can be crazy
and when they go from burning hydrogen
to burning other things like helium
carbon oxygen they can behave crazy then
right but one of the things they will do
is they'll swell up
and many of them will pulsate
and some of them will have periodic
pulses that originate in the core and
throw off the outer layers the envelope
just starts going wacky you know what i
mean after the star gets a bit old
and how far away is this reality from
our sun our sun is at the halfway point
so we got about another four and a half
billion years
but you know we are not going to be
there earth is going to be uninhabitable
in another billion years because as you
burn hydrogen to make helium
remember the core of the sun is not hot
enough to burn helium so that helium
that is sitting in the core of the sun
right now it's just sitting there in the
core and it's not burning as the core
gets crushed down smaller and smaller
that means that
the outer layers the envelope is
responding to what the core is doing
right so if the core is hotter and
putting out more energy and more heat
the envelope expands so in a billion
years the earth is going to be
uninhabitable because the sun will have
swollen to such a size that the amount
of radiation reaching earth will have
you know boiled off the oceans and
you know once you do that it's bad
life is short that's even more reason
people have to party you only have a
billion years left here and when we
return i'll give you a different reason
to party
how scientists are creating a star in a
bottle using fusion inside a lab
in the past hundred years our
understanding of nuclear fusion the
process we've been discussing that
powers our sun and sustains life on
earth has exploded
given that it generates immense power
and is responsible for the creation of
elements across the universe
fusion's gotten some people wondering if
maybe we can harness that power right
here on earth as a new source of clean
energy
here's maria zuber vice president for
research at mit
well there's a big push right now in
decarbonizing the grid with renewables
solar wind but at some point
probably around 2040 we're going to max
out with renewables and we won't be able
to decarbonize further we're going to
need another zero carbon option
this is a video from mit its plasma
science infusion center has partnered
with the commonwealth fusion systems
startup company to develop commercial
fusion as a clean energy source
dennis white directs the plasma science
infusion center it's like the prometheus
myth we're going to bring the fire of
the gods down here
to earth although we don't want to end
up like prometheus that is with an eagle
eating our livers for eternity that
doesn't sound great but fusion energy
isn't as zany as it sounds almost every
energy source that we actually have on
earth actually originates with fusion
because
wind comes from heating the atmosphere
solar very evident which is the radiant
energy which comes from the sun
but even fossil fuels are actually
fusion energy because they were from
plants accumulating stored energy from
sunlight coming down to the earth but
recreating actual nuclear fusion as a
sustainable energy source would be
groundbreaking the main goal is to bring
that fundamental energy source that
power stars
to earth for use by mankind to provide
an inexhaustible supply of energy
i have a thousand questions
i mean that's
[Laughter]
sometimes it's a simple answer and yet
it's so um
like well that that's kind of ambitious
first we need to differentiate fusion
from fission which is the process
traditionally associated with the term
nuclear energy they're literally the
opposite of each other
so
fusion as they described combines or
fuses the lightest elements like
hydrogen into helium fission
actually breaks apart the largest and
most unstable elements mostly uranium
so the thing that they share in common
is that because they're making new kinds
of atoms
it releases very large amounts of energy
per unit mass
and that's almost like where the
similarity ends
so in fusion it's inherently safe
because you cannot get a runaway process
the process itself does not produce
nuclear waste
fission has to by the rules of physics i
would point out the universe already
voted the universe runs on fusion
quick rewind to hakeem on nuclear fusion
in stars these two protons now in this
core getting crushed by this envelope
scream towards each other the
temperature is 10 million degrees kelvin
and so now
boom
and get this this is exactly what
scientists like dennis white are trying
to do
in the lab
so to get that fusion to happen the
first order of business is to recreate
the conditions of a star that's all
that's easy enough right
first let's talk about gravity to force
nuclei to fuse together you need your
lab to be the size of a star
because you need that much mass to
create a sufficient gravity force
so that can't be directly translated
obviously onto earth so we have to
replace the gravitational force with
another kind of force
and our main line of doing this is
replacing it with the magnetic force or
the electromagnetic force
next consider the temperature the fusion
reaction needs high temperatures to
occur
and the way that this works is what
provides the high temperature must be in
the end the fusion reactions themselves
in stars the temperature remains high
due to both the pressure from gravity
and the energy released by fusion
reactions in the core
in other words fusion powers more fusion
allowing stars to be self-sustaining at
least for a time it's like a fire you
need more than just a match
you know you need more than something
that's just hot temporarily you need the
wood to actually burn the other parts of
the wood as well too by keeping them hot
sufficiently hot so it's the same thing
in fusion actually it works on the same
physical principle you're just trying to
keep it hot enough that the fusion in
fact will occur in stars the temperature
has to be at least 10 million degrees
kelvin for fusion to occur
our sun's core is around 15 million
degrees celsius but when dennis says hot
he means even hotter roughly 100 million
degrees celsius in fact the temperature
of 100 million degrees was achieved many
decades ago so the natural question is
what kind of container can hold
something on earth that is a 100 million
degrees the answer is nothing for
comparison imagine an oven
so you turn on the element in there
there's heat being released so you put
some insulation around on the oven kind
of put some energy into it don't let it
escape out into the kitchen and it's
going to get hot but no oven no matter
what the infomercial says could contain
a hundred million degrees celsius so
what we have to do is actually isolate
the fuel from anything that has to do
with it being on earth in a terrestrial
environment
and so what does that entail so first of
all we get rid of all the air it's gone
so this is why i said it's not like a
container then we think of like a bottle
or an oven
we build a different kind of container
and the container is the magnetic field
the magnetic field because it exerts an
action at a distance
allows you to exert a force on those hot
particles
without physically touching it
what could possibly survive at such
scorching temperatures we call it a
plasma
remember matter exists naturally in four
states liquid solid gas and plasma think
of plasma as superheated matter since
the fuel dennis and his team are using
has to be heated in the lab to around
100 million degrees celsius it exists as
plasma and just because i'm thinking
through doomsday lab scenarios what
would happen if the magnetic fields were
to i don't know if it actually would
break but if it lost its integrity and
the plasma escaped in your lab so it
immediately turns back into a room
temperature gas
because it will touch normal matter
and then it cools so rapidly that
instantly all fusion reactions stop
because it's not hot anymore and in fact
it gets so cold it's not even a plasma
anymore it'll just turn back into
regular gas in fact the challenge about
fusion has been to keep it going
because it always wants to go back
actually to room temperature gas we just
don't allow it by holding it with that
magnetic field so this is why
fusion is inherently safe
you were talking about
the fuel now the fuel in a star is
hydrogen in those specific conditions is
that the same fuel you're using or that
nuclear fusion
labs are using on earth yeah
almost that so what we use
is actually a different fusion reaction
than occurs in stars it turns out that
the process that occurs in stars is is
actually too weak and too slow for us to
use for a practical power plant which
you would think of as like wow isn't the
sun making a lot of power but it's also
enormous in terms of its volume so we
actually use a different
reaction than what's used in the sun so
we use a heavier form of hydrogen it's
called deuterium that's around one in
every 5 000 hydrogen atoms is a
deuterium one it's just twice as heavy
so it's abundant everywhere that there's
water and we extract that one small
percentage of it and you go well that
doesn't sound very effective because
it's going to use a lot of water well no
because this has to do with the
effectiveness of fusion is that like as
you were picking up your coffee like the
amount of deuterium
that is in that cup of coffee is
approximately like what's needed to
power
all of your personal energy needs for a
year is just in that one cup of coffee
and yet you're extracting essentially an
infinitesimal amount of water so this is
why we say for that fuel source it's
essentially limitless because just think
of the amount of water that's around
everywhere the amount of water in my
coffee the deuterium in there was enough
to power my apartment for a year and
what's funny is the coffee itself is
barely enough to power this podcast hose
for a couple hours
scientists have been able to fuse
elements in the lab
but one of the challenges they still
face is reaching net energy gain
or getting more energy out than they put
in
so before fusion becomes the power
source feeding the outlets in the walls
of our homes
we have to address the question of how
to get fusion to power itself to become
self-sustaining like it is in stars we
call this the burning plasma which again
goes back to the analogy of a pile of
wood sitting in your fireplace is
different than when it's burning so when
it's burning this means the fusion
reactions and the particles which are
being released in fusion are themselves
then keeping the medium hot so that more
fusion reactions can occur
that has not been achieved yet
then you say okay so once you achieve
that are you all the way there you know
we're not all the way there because the
other part of it is that as a practical
energy source you have to meet obvious
things of reliability and particularly
economics
so can you build them fast enough can
you build them cheaply enough that you
can actually pay yourself back for the
resources that are took to build this
object
we honestly don't know the answers to
those yet
but we are working very hard
at understanding about what is needed to
get there
i was gonna ask you
like what's taking so long like why
aren't we there yet what is so hard and
it i'm curious to get your blunt answer
and like what is the limiting step right
now
it's the perfect question like why is it
taking so long
it's not because we don't understand the
science of fusion in my opinion
what happened was the objects that we
had to build these very special objects
of magnets became so big and complex
that it just kind of really stopped in
my opinion innovation and it also slowed
down the time scale of actually
achieving
these conditions that were necessary but
on september 5th 2021 dennis and his
research team demonstrated a
breakthrough in fusion technology
we have in fact achieved 20 tesla for
the first time in a large bore fusion
relevant coil and what this means is
that we're going to change the
trajectory of fusion energy and we hope
the world by supplying clean energy to
mankind forever
that's dennis speaking at the
commonwealth fusion systems
demonstration event that was live
streamed on september 5th along with our
private sector you know partner
commonwealth fusion systems we
demonstrated
a magnet technology that basically put
us on a completely different path the
same science path to fusion but a
totally different scale
and economic viability path to fusion
and brace yourself here was their big
breakthrough we made a magnetic field
that has a unit of around four hundred
thousand
so it's four hundred thousand times the
earth's magnetic field
and why is this important the simple
answer is that of doubling the magnetic
field strength
increases the amount of fusion power
that you get in a fixed volume
to the fourth power of that doubling
so that's what we did we basically
doubled the magnetic field compared to
the previous technology which means a
16-fold increase in the amount of fusion
power
and they did it using high-temperature
superconductors extremely powerful
magnets that consume negligible amounts
of energy now i can build an object
a lot smaller and make the same amount
diffusion power which is good from a
speed point of view but also obviously
critical from an economic point of view
it also allows you to get to that
special science condition that i talked
about that we haven't crossed over the
threshold yet of when the plasma starts
to heat itself and we get net energy
gain but it actually has a real shot at
meeting economic targets for the first
time
so we think that this is why it's the
game changer you know to use an overused
word but it is a game changer i mean i
don't think it's overused if the game
changer is a limitless source of green
energy that could basically power
mankind until we cease to exist yes yes
i would call that the game changer of
course i worry what do i worry about
it's easy we're not going fast enough
it's mostly motivated by climate change
and the timelines of climate change
scientists at mit have estimated that to
avoid the most detrimental effects of
climate change the world's electrical
energy systems must stop producing
carbon by 2050
with that deadline in mind dennis and
his research team are racing to start
making fusion available as a clean
energy source starting in the 2030s
that way they'll have time to integrate
fusion energy into our existing
electrical grids but our biggest hurdle
is or our biggest enemy is time
because we're running out of time
if we're able to develop fusion as a
clean power source dennis says it'll
fundamentally change humanity's
relationship with energy fusion is just
a completely unique arrow in the quiver
and the battle against climate change
imagine that humanity's curiosity of
those sparkling little dots in the sky
led to scientific discoveries about
stars which may soon save our planet
nova now universe revealed is a
production of gbh and prx it's produced
by terence bernardo jenny cataldo r.a
daniel caitlin falls and jocelyn
gonzalez julia court and chris schmidt
are the co-executive producers of nova
suki bennett is senior digital editor
christina moden is associate researcher
robin kasmer is science editor robert
boyd is digital associate producer shyla
duff is digital video intern and devon
maverick robbins is managing producer of
podcasts at gbh
special thanks to our guests hakeem
olusey author of a quantum life and
dennis white director of mit's plasma
science and fusion center
i'm alok patel we'll be back next week
which should be plenty of time for you
to brush up on your out of this world
cooking skills before our next episode
where we'll share the recipe for
creating a galaxy
it's like interstellar top chef
if you're interested in learning more
about the science behind the universe
visit pbs.org nova now podcast this
podcast has been made possible by the
gordon and betty moore foundation
gbh
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