Atom (2007–…): Season 1, Episode 2 - The Key to the Cosmos - full transcript
As we gazed up at the heavens,
we asked where we had come from,
how all the stars were created,
how all the elements were made,
even how the universe itself had begun.
One of mankind's greatest
achievements is that we've
answered these questions.
What is truly remarkable
is that this understanding has come
through the study of the smallest
building blocks of matter - atoms.
As we peered inwards, we realised
we could explain what we saw
when we peered outwards.
The atom has helped us solve
the greatest mysteries of existence.
Everything in the world we see is
made out of tiny objects called atoms
and yet
we only proved their existence
at the beginning of the 20th century.
The first shock was to discover
how small they were,
less than
a millionth of a millimetre across,
there are trillions
in a single grain of sand.
Amazingly, we now have
a pretty good idea of the number
of atoms in the known universe.
Now, given
the vastness of the universe
and the minuteness of the atom,
it's not surprising that this
is a mind-numbingly huge number,
it's one
followed by over 70 zeros,
that's a trillion,
trillion, trillion,
trillion, trillion, trillion atoms.
We don't only know the raw number
of atoms in the cosmos
we also know that they come
in 92 different flavours.
These are called the elements
and you'll recognise many of them
as familiar parts
of the world around us.
Oxygen, iron, carbon,
tin, gold and so on.
Everything in the universe,
the stars, the planets,
the mountains,
the seas, the animals, you and me,
we're all made of these atoms
or combinations of them.
It's an astonishing human achievement
that we now know,
not only how many atoms
there are in the universe
and how many different types there
are, but why they exist at all.
We can now explain how every one of
those trillion, trillion, trillion,
trillion, trillion, trillion atoms
was created.
It turns out that the answer
to the mystery of creation itself
lies within the heart of each
and every atom in the universe.
The story of how we came
to understand creation itself
started over 100 years ago
in a small laboratory
in south-east Paris.
GEIGER COUNTER CLICKS RAPIDLY
This piece of paper
is a remarkable artefact.
It's from the notebook of the woman
who first studied radioactivity,
the chemist Marie Curie.
It's incredible, 100 years later
and this piece of paper is still
spitting out radioactive particles.
The photograph on the left
shows the concentration
of the radioactivity,
you can actually see
Marie Curie's thumbprints on it
but what's really incredible
is the sheer power,
the energy given off by radioactivity
that this piece of paper
is still spitting out these particles
100 years later.
Still stuck to the paper are
tiny but intensely radioactive
particles of a substance
that Marie Curie discovered in 1898,
a substance she called radium.
It was a sensational discovery
for one primary reason.
Though radium looks like
an unremarkable grey metal,
it contradicted
all the then-known laws of science.
Because radium pumps out
invisible yet powerful rays of energy
which could fog sealed photographic
paper and burn human flesh.
They're a little like radio waves
which is why
Curie called radium radioactive
but the waves were millions of times
more powerful than any radio wave
previously encountered.
Also,
radium appeared to contain within it
an inexhaustible store of energy,
Curie worked out that
a gram of radium,
a piece much smaller than a penny
contains more energy
than 100 tons of coal.
By the turn of the century,
the French public and the tabloid
press were fascinated by radium
and, rather touchingly
though no-one had a clue
was radioactivity really was,
everyone assumed it must
be wholesome and healthy.
When radium was first discovered,
they found all sorts of weird and
wonderful commercial uses for it.
Here is the Radium bath products,
there's the Radium Eau de Cologne,
Atomic Perfume and Radium Face Cream
apparently enhancing beauty
through healthy skin.
There's even the Radium
razor blade, I'm not quite sure
how that's supposed to work.
Ah, the good old days, clearly
when ignorance really was bliss.
Whatever the public made of it,
to the scientific community
radioactivity was just about
the most exciting thing possible.
The brightest minds of a generation
clamoured to study it
and the price of radium,
it's most potent source,
soared to thousands of pounds
per ounce and radioactivity
didn't disappoint.
In 1919, it produced its greatest
revelation yet,
a revelation that would ultimately
lead to a fundamental understanding
of the atomic world.
The revelation was that radioactivity
allowed humanity to fulfil
an age-old dream...
to become alchemists.
Alchemy, the power to change
base metals into gold,
the quest for the so-called
Philosopher's Stone
which has the magical ability
to transmute one substance
into another,
has been an obsession for centuries.
It conjures up wonderful tales of
sorcery and wizardry, as anyone who's
read Harry Potter knows very well.
The power and wealth that would
surely come to anyone who mastered
alchemy seduced many great scientists
and thinkers like Isaac Newton,
Robert Boyle and John Locke.
All of them tried to change
one element into another
and all of them failed.
Then in 1919, the secret of alchemy,
the mystery of
the Philosopher's Stone
was finally revealed,
not in a wizard's den
but in the physics department
at Manchester University.
The world's first true alchemist
was Ernest Rutherford.
A loud, straight-talking
New Zealander,
Rutherford had come to dominate
the study of radioactivity.
He had wonderful intuition and was
fearlessly prepared to challenge
conventional wisdom and alchemy
would require Ernest Rutherford
to follow his intuition
deep into the unknown.
The discovery was almost accidental.
It began when one of
Rutherford's students noticed that
when radioactive materials like
radium were placed inside a sealed
container of ordinary air,
mysteriously, small amounts of
the gas hydrogen begin to appear.
Now this was bizarre. Ordinary air
contains virtually no hydrogen
and yet in the presence
of radioactivity
it was appearing out of nowhere.
This was precisely
the kind of problem that Rutherford,
now at the height of his powers
as an experimental physicist, loved,
and he flung himself at it.
He began by isolating
all the different gases
that make up the air we breathe,
nitrogen, oxygen, water vapour
and carbon dioxide
and studied how each of them behaved
in the presence of radioactivity.
And then...eureka!
Rutherford realised
that in the presence of
powerful radioactive rays,
the gas nitrogen, which makes up
about 80% of the air we breathe,
changes into two new substances,
the gases oxygen and hydrogen.
Then and there
Rutherford had transmuted
one element into two others.
He'd become an alchemist and radium,
with its powerful radioactivity,
was the Philosopher's Stone.
The press hailed Rutherford
as the first alchemist,
but in fact that was the least of it.
What alchemy had shown him was
the inside, not just of the atom,
but of the strange object
at its centre,
its tiny beating heart, the nucleus.
To get a sense of this achievement,
remember Rutherford
and his contemporaries at Cambridge
had only a sketchy idea of
what an atom was but they did have
an idea of its size.
And it's mind-numbingly tiny,
one tenth of a millionth
of a millimetre across.
Let me put it another way, there are
more atoms in a single glass of water
than there are glasses of water
in all the oceans of the world.
And Rutherford now also knew
that the atom had structure,
that within the atom
there was a sub-atomic world.
He pictured each atom
like a tiny solar system.
At its centre, 100,000 times smaller
than the atom itself
was an object
which Rutherford called the nucleus.
Orbiting this, like planets,
were the electrons
but what on earth WAS the nucleus?
Rutherford was convinced that
alchemy had shown him the answer.
To understand how Rutherford did this
we have to get inside his head
to think like he did.
Rutherford had fantastic intuition
coupled with an intensely
practical approach to science
so he hated ideas that relied
on complicated mathematics.
When it came to the atomic nucleus,
Rutherford looked for
the simplest idea that worked
and what worked was to imagine
that the nucleus is made of tiny,
rigid spheres, like snooker balls.
Using this incredibly simple image,
Rutherford could construct
all the elements in the universe.
He could explain how the huge variety
of different atoms are made
of the same basic components.
So here's how it works.
Hydrogen, which is the simplest
element, consists of just one sphere
which Rutherford called a proton,
which is the Greek word for "first".
All the other elements are made by
adding more protons to the nucleus.
It's as simple as that.
So helium,
which is the second lightest element,
comprises of two protons,
lithium has three.
Carbon, which is the element
that's the basis of all life,
has six protons.
The oxygen that we breathe
has eight
and uranium, which is the heaviest
naturally-occurring element,
has 92 protons.
This was Rutherford's
inspirational idea,
that each element is defined by
the number of protons in its nucleus.
It's a wonderfully elegant
and simple idea,
an idea that explains
how so much of the universe
we see around us is constructed.
But as scientists often find,
nature is never quite as simple
as it seems at first sight.
Sure enough, a big problem
emerged with Rutherford's proton.
A problem which threatened
to derail the whole atom project
and it was to be
one of Rutherford's own proteges
who was the first to identify it.
Francis Aston
was an interesting character.
As a young man he enjoyed
the adventurous outdoors
and was into skiing and motor racing
and apparently in about 1909
he discovered surfing
off Waikiki Beach in Hawaii.
But he soon realised the call
of the physics laboratory was greater
than the call of the waves
and it was while at Cambridge
that he invented
an incredible piece of equipment.
That's now housed here in this rather
austere and plain-looking building,
the Cavendish Laboratory.
This is
Aston's original spectrograph.
It's an amazing piece of equipment
because with it, for the first time,
scientists were able
to weigh individual atoms.
It's incredible, it looks a bit like
a gun, it's a very strange shape.
I guess basically, you'd have
the atoms that you wanted to weigh
in this glass tube
and the electrically-charged atoms
would be fired in this direction.
Round about here there'd be electric
plates which would bend those atoms.
Because the atoms had electric charge
they'd get bent in the electric field
down in this direction
and then what we're not seeing here
would have been a huge magnetic coil
that would sit around this arm
and the magnet would bend those atoms
back up again in this direction.
Now round about here at the end
would be a photographic plate,
I'm not quite sure if we can see it,
no.
But the plate would sit here
and atoms of a particular weight
would be focused in a line
and so Aston was able to see
individual lines for atoms
of different weights.
It was remarkable that round about,
just after the First World War,
scientists were finally able
to weigh atoms.
Now they could weigh atoms
accurately, they discovered that
there was a fundamental problem
with Rutherford's model
of the nucleus.
Basically the numbers
didn't quite add up.
All the atoms of the known elements,
apart from hydrogen, were
much heavier than they should be.
For instance, helium,
with two protons should weigh twice
as much as hydrogen, with just one.
In fact it's four times as heavy.
Rutherford realised
this could mean just one thing -
apart from the proton
there's something else inside
the atomic nucleus. But what?
It took 12 years to find the answer.
Now, as head of the prestigious
Cavendish Laboratory in Cambridge,
Rutherford threw
all his resources into the project.
He bullied and cajoled his students
and researchers until one,
a northern lad from humble origins
called James Chadwick,
hit the nuclear physics
equivalent of gold.
Chadwick built this in 1932
and to think that with just
this tiny little piece of equipment
he discovered
the missing ingredient of the atom.
For me
as a practising nuclear physicist
this really is an amazing device.
When I think of the huge accelerators
that are built today
to conduct experiments to probe
the nucleus of the atom,
it's really awe-inspiring
in its simplicity, really.
He put a source of radioactivity
at this end of the tube
and the radioactivity then struck
a small target in the middle here
and then out of the target
came new particles that sprayed
out of this end here.
It's a bit like an atomic gun,
shooting out
Rutherford's missing particles.
What Chadwick discovered was that
along with the proton there's another
kind of particle inside the nucleus.
It weighs almost exactly the same
as a proton but is much more elusive
because it carries
no electrical charge.
Technically we say it's electrically
neutral hence its name, the neutron,
and it immediately solved
the problem of the weight of atoms.
So, helium
is four times as heavy as hydrogen
because along with its two protons
it contains two neutrons
and oxygen has eight neutrons
along with its eight protons,
making it 16 times
as heavy as hydrogen.
So in 1932,
the atomic family was complete.
Scientists announced that
every atom in the universe is made
of just three basic components -
electrons,
tiny particles orbiting a nucleus
which in turn
is made of protons and neutrons.
WALTZ PLAYS
# Neutron, neutron... #
Over Christmas 1932,
physicists at the other great centre
of atomic physics,
the Niels Bohr Institute
in Copenhagen celebrated
the neutron's discovery
and the completion
of the nuclear trinity
by writing a musical about it.
# That which experiment has found
# For theory had no part in
# Is always reckoned more than sound
# To put your mind and heart in
# Good luck, you heavyweight Ersatz
# We welcome you with pleasure
# But passion ever spins our plot
# And Gretchen is my treasure. #
Some of the great names in
physics took part in this musical.
Their excitement
was primarily due to one thing.
They knew they stood at the threshold
of an entirely new kind of science
with entirely new rules,
what we now call nuclear physics.
The first challenge
for nuclear physics was this.
Although physicists now knew
what the tiny nucleus was made of
they couldn't explain
how it all held together.
In fact it was worse than that,
the existing laws of physics
predicted that every atomic nucleus
should self-destruct instantly.
# Eternal neutrality
pulls us alo-o-o-ng. #
The main problem was this.
All protons, the key ingredient
of the atomic nucleus
have positive electric charge
and things with the same charge
repel each other
just like these magnets. Look.
So just like these magnets,
if two protons get close together
they should then just fly apart
but weirdly,
inside the atomic nucleus they don't.
Dozens of protons can stick
together alongside each other.
So what sticks them together?
What stops the protons
from flying apart?
The answer was big news,
it was nothing less than
an entirely new force of nature.
For centuries humans had only ever
encountered two natural forces,
gravity which pulls us down
to the Earth and electromagnetism.
But now, hidden inside
the atomic nucleus
was something completely new,
it was called
the strong nuclear force
and the easiest way to imagine it
is with some Velcro.
If I put Velcro around these magnets,
they start to behave
slightly differently.
At first they repel
each other just as before
but when they get close enough
the Velcro kicks in and they stick.
The effect is very short range
but very, very strong
and it's exactly the same
with protons.
The strong nuclear force explains
what holds the nucleus together.
The strong nuclear force works
between all protons and neutrons
but what is truly surprising about it
is its strength.
It's by far the most powerful force
in the universe...
more than a trillion, trillion,
trillion times stronger than gravity.
Think about it this way, if I was
pulled down the earth, not by gravity
but by the strong nuclear force
then I'd weigh trillions of times
more than I actually do, in fact I'd
weigh more than the entire galaxy.
But the reason
I don't weigh that much
is because the strong nuclear force
is only felt down at a distance
of a trillionth of a millimetre.
With the strong nuclear force,
humans finally began to get a glimpse
of what was actually going on
inside the atomic nucleus.
Roughly speaking, all nuclear
behaviour is down to a balance
between the strong nuclear force
squashing the protons and neutrons
together
and the electric charge
on the protons forcing them apart.
Physicists realised that picturing
the nucleus as a battlefield
between different elemental forces
solved one of the oldest mysteries
of all time.
It's this.
A question that humans have asked
ever since the dawn of time
is, how does the sun shine?
Now sunlight is the source of
all life on Earth but how is it made?
It's all to do with the forces
inside the atoms that make up most of
the sun - hydrogen.
This is how it works.
The nucleus of a single atom of
hydrogen consists of just a proton
and every now and again inside
the high-pressure, high-temperature
cauldron of the sun,
this proton can get squeezed up close
to another and bang!
The strong nuclear force kicks in
and fuses them together.
CYMBALS CRASH
Now this is a process that
eventually leads to the creation
of a helium atom
and it's accompanied
by the release of energy
as a burst of light and heat.
It's a bit like
slamming two cymbals together
and releasing a burst of sound.
Hydrogen fusing into helium
and the energy released
is what we see and feel as sunshine.
This process of
two hydrogen nuclei slamming together
and releasing energy
became known as nuclear fusion.
The turmoil between the strong
nuclear and electromagnetic forces
as they strive
to dominate the nucleus
does more than just power the sun.
It's at the heart of everything
but in the late 1930s
before people figured out that story,
nuclear physics did something
much closer to home.
In no uncertain terms,
it redefined the history of mankind
right here on Earth
and led to one of our darkest hours
and that story began
with the study of the humble neutron.
In the years immediately following
its discovery the neutron
became the focus of atomic research
in laboratories across Europe
and the reason for the excitement
was this.
See, the neutron is the stealth
bomber of the atomic world because
unlike the other particles
that make up the atom,
the proton and the electron,
the neutron is, as its name suggests,
electrically neutral
so it can fly
undetected and undeflected
into the very heart of the atom
and collide with the nucleus.
Now physicists knew that these
collisions would be spectacular
because by atomic standards
the neutron is heavy
so when it collides with
the nucleus, it deals a mighty blow.
It's a bit like the Moon
smashing into the Earth.
Now physicists in the 1930s
knew that this held up all sorts
of tantalising possibilities.
Such collisions might chip bits off
the nucleus and create new elements.
They might -
and this is the Holy Grail -
even create new radioactive elements
like Marie Curie's radium
which was the source
of unlimited energy.
In their excitement
about this new science,
physicists in labs across Europe
fired neutrons into every element
they could find.
In a laboratory in the Kaiser Wilhelm
Institute in Berlin,
a chemist called Otto Hahn
finally got round to firing neutrons
at the last, heaviest element
in the periodic table,
the metal uranium.
This is some of the equipment
that he used in the late 1930s.
So, what they would have would be
a source of neutrons sitting here
surrounded by a block of paraffin wax
that would slow down the neutrons so
they'd be more likely to be absorbed
by the uranium sitting on the side.
This electronic equipment was used
to detect the particles coming out
from these radioactive elements.
What Otto Hahn tried to do was
to analyse chemically
the new elements being produced
from the reaction.
What he found was what appeared to be
Marie Curie's radium being produced
but when he tried to isolate it
he didn't find any at all.
Instead it seemed that what was
being produced was the element barium
which was much lighter than uranium.
How could barium be produced?
It was a puzzle,
he simply couldn't explain it.
Nevertheless, Hahn meticulously
catalogued his results.
Hahn was a chemist not a physicist
but, even so, he knew that
according to all laws of science
there was no way barium would be
coming out of his experiment.
It was simply
too different from uranium,
the only person
who Hahn thought might be able
to explain what was going on
was his old assistant,
the physicist Lise Meitner.
But she'd been forced to flee
Nazi Germany a few months earlier
because she was Jewish so Hahn
sent her his controversial findings.
Lise Meitner was in Sweden
with her nephew, Otto Frisch
who was also a nuclear physicist,
when she received the letter
from Hahn.
On Christmas Eve 1938
they went for a walk in the woods
where they discussed long and hard
the results of Hahn's experiment.
They realised
that the uranium nucleus
wasn't just having a small piece
chipped off the edge.
The nucleus was literally splitting
into two equal halves.
Meitner and Frisch were shocked
beyond belief.
The idea that uranium
could literally split into two
had never been considered remotely
possible but after Hahn's experiment
it was the only explanation.
Right then, Meitner and Frisch
realised this had astonishing
and terrifying consequences.
The huge uranium nucleus
splits into two
because the strong nuclear force
loses its battle to hold
the nucleus together.
The electrical repulsion
then tears the nucleus apart
and the amount of energy released
would be on a scale
never seen before.
The energy released from
a single uranium nucleus would be
enough to move a grain of sand.
Now this is an incredible
amount of energy
because a grain of sand itself
contains trillions and trillions
of atoms.
It's a bit like
kicking a football at the Moon
and knocking the Moon off its orbit.
For me, this heralded
the birth of the atomic age.
What Frisch and Meitner
had discovered was nuclear fission.
Nuclear fission was the first time
anyone had released
the enormous forces
inside the nucleus artificially.
Uranium gave mankind the means
to tap into the vast, seething energy
inside the nucleus
and turn it to its own uses.
The timing of the discovery -
it coincided with the beginning
of the Second World War -
meant that Allied scientists
under Robert Oppenheimer
worked day and night
to figure out how nuclear fission
could be exploited
as a weapon of mass destruction
and the final manifestation of this
research came in 1945
over Hiroshima and Nagasaki.
ATOM BOMB BLASTS
The atom bomb changed everything.
The excitement of
pre-war scientific research,
the days when physicists sang songs
about their discoveries, were over.
Robert Oppenheimer summed up
the grim mood with these words.
"The physicists have known sin
and this is a knowledge
which they cannot lose."
The terrible irony
of the atomic bomb is that
because of the scientists' sin,
because of that knowledge
that cannot be lost, something
of great significance did emerge.
Something that would ultimately
reveal the full story
of the 14 billion years
of the entire universe.
The war had caused
a massive two billion dollars
to be poured into nuclear research.
People now knew an astonishing amount
about the atom and its nucleus.
Specifically,
scientists had detailed measurements
of how stable or unstable
different atomic nuclei were.
That stability was a direct result of
the battle between the strong nuclear
force holding the nucleus together
and the electromagnetic force
pushing it apart.
In some atoms, the balance
tipped towards the strong force
making them very stable
but when the electromagnetic force
had the upper hand
they were inherently unstable.
By the late '40s, scientists
began to investigate the implications
of the way
nuclear stability of atoms varies.
They noticed one very strange fact
about the nuclear stability
of one particular atom.
IRON CLANGS
Of all the 92 different elements,
of the 92 different types of atoms
that make up
the universe around us,
gases like hydrogen and oxygen,
solids like carbon and silicon,
metals like gold and silver,
one is special...
iron.
So what makes iron so special?
It stems from the unique structure
of its nucleus.
The 26 protons
along with the neutrons
combine in a very special way
to make iron incredibly stable.
For some reason,
nature has decreed this as the number
that allows the strong force
and the electromagnetic force
to balance each other perfectly.
It makes iron the most stable element
in the universe.
Now we can understand
why fusion occurs.
Lighter atoms can combine together
to become more iron-like
and fission is the opposite process,
atoms heavier than iron
can split apart into lighter,
more iron-like pieces.
So all elements seek
the stability of iron
and that fact underpins
the whole history of the cosmos.
The best way to understand this
is to imagine the relative stability
of atoms as a couple of graphs.
Here's what they show.
The very lightest elements,
hydrogen and helium
are not quite as stable as they could
be, they'd like to be something else,
something even more stable.
Similarly, the heaviest elements
like uranium and polonium
are actually unstable,
in fact they're so unstable
that they fall to pieces
naturally through radioactivity.
And here, in the middle
are the most stable atoms of all,
nickel, cobalt and iron.
So far, so good.
Now, here's the amazing bit,
this nuclear stability graph
turned out to be uncannily similar
to a different graph altogether
but it was a similarity
that no-one had ever suspected.
That's because data from this other
graph came not from the tiny nucleus
but from as different
an arena as you can imagine...
the vast expanses of space.
This other graph
came from astronomers
who studied
the blazing light from stars
and shows the abundances
of the different types of atoms
in the universe.
By far the most common atom of all
is that of hydrogen
followed closely by helium but
not a great deal of anything else.
Now look at this, it really
is of cosmic significance.
Both graphs, the stability graph
and the abundances graph
show the same strange
but very noticeable peak
The first scientists who spotted this
were blown away.
One graph from the tiny nucleus and
the other from the vastness of space
point to the same magical atom.
The atom that provided the key
to unlocking the secrets
of the entire universe.
Iron, the atom which was the key
to understanding the atomic nucleus,
also turned out to be
one of the most abundant atoms
in the entire universe.
Amazingly the properties of
its nucleus seem to lead directly
to how much of it there is
and it's not just true of iron.
Radium, which is very unstable,
turns out to be incredibly rare.
Aluminium which is relatively stable
turned out to be relatively common.
It's a pattern which appears
right across the list of elements.
The signature of their nuclei
is written in the skies above us...
..and deciphering the meaning of
this connection would require
the greatest minds of a generation.
The first of these was a rebel
and a maverick called Fred Hoyle.
He loved walking the hills
and dales of his native Yorkshire.
Hoyle always spoke his mind
even though it brought him
into conflict with his peers.
He became something
of a scientific pariah.
More than almost any other scientist,
he explored the strange overlap
between the science of the atom
and the science of the cosmos.
Hoyle realised what the graphs
revealed is that the underlying theme
of the universe
was ultimately change.
Everything in the universe
is in a state of flux.
The atoms are trying
to gain or lose protons
in an attempt to become more stable.
What Hoyle and his colleagues did
was to ask
how and where in the cosmos
all this atomic transformation,
all this alchemy, takes place.
Hoyle knew that
in stars like our sun,
hydrogen turns into helium by
a process called nuclear fusion.
But could nuclear fusion
also be the way all the other atoms
in the universe are made?
Fred Hoyle's great insight
was to work out precisely
how the heaviest elements
are created through nuclear fusion.
Hoyle worked out that this process
can only take place
at unimaginably high pressures
and temperatures of
millions of degrees centigrade.
In our universe
there's only one place where
such conditions exist...in stars.
Fred Hoyle's problem
was with the details.
To explain how fusion could create
atoms heavier than helium
was tricky and complicated.
Hoyle had to explain precisely
how in the fierce heat inside stars,
light atoms might fuse
to become heavier ones.
EXPLOSION
In the '40s, Hoyle worked out that
our sun is hot enough to fuse atoms
like oxygen, carbon and nitrogen
but what about heavier atoms
like copper, zinc or iron?
His calculations showed that
they could be made inside stars
but these would have to be
much hotter than our sun
and he knew exactly
where to find them.
These huge, bloated stars
near the end of their lives
were called red giants.
Astronomers had discovered that there
were hundreds of millions of these
monsters throughout the universe.
Fred Hoyle reasoned that
they were hot enough to allow
weightier atoms to be fused
but there was still a problem.
Even the mighty red giants
weren't hot enough
to make the really heavy stuff,
atoms like gold and uranium.
To make these heavier than iron atoms
would mean forcing them
to fuse together,
becoming more and more unstable.
It would require unimaginable
temperatures and pressures.
His only hope was that somewhere
out there in the vastness of space
were things so big and so hot
they made our sun look like
a birthday candle.
And towards the end
of the Second World War,
during a research trip to Southern
California, Fred Hoyle found them.
This is the 100-inch telescope
at the Mount Wilson Observatory
outside Los Angeles.
When it was first built
in 1917, it was without doubt
the largest telescope in the world
and it was while he was here
he met up with the great astronomer,
Walter Baade who told him about
supernovae.
Now these are processes
when massive stars explode
with an incredible intensity
and in a flash of inspiration
Hoyle realised that here, at last,
were the extreme conditions necessary
to produce all the heavy elements.
What Baade was referring to was
an explosion of simply cosmic scale.
BANG!
When the larger stars run out
of hydrogen to fuse into helium,
they come to the end of their lives
and they collapse under
the weight of their own gravity
and then explode outwards.
In a blinding flash of inspiration,
Hoyle and his colleague
William Fowler
realised that supernovae might be
the hottest places in the universe,
hot enough to fuse together
even the heaviest of atoms.
Hoyle and Fowler
had found the furnaces
in which everything was made.
The discovery of how atoms are made
in stars is surely one of
humanity's greatest achievements,
except for one glaring problem.
One that Hoyle could never
explain away and it was this.
Stellar nuclear fusion can explain
how all the elements in the universe
are made...except for two,
two very important ones.
The two simplest elements,
hydrogen and helium.
In the 1940s, using
increasingly accurate equipment,
scientists found that a quarter
of the sun was in fact helium
which was considerably more
than they thought.
They realised that to fuse that
amount of helium would mean the sun
would have to be burning at billions
of degrees but the truth was,
the sun only burns
at 15 million degrees.
The sun just wasn't hot enough
to have made all that helium.
In fact,
it turns out that per cubic metre,
the sun actually generates less heat
than a human being
so I produce more heat than a piece
of the sun the same size as me.
This means that the sun
is just not hot enough
to make all the helium
we know that it contains.
If all the helium wasn't made in
the sun then where did it come from?
And even more crucial
was the question
Hoyle was in denial about.
If all the atoms in the universe
started off as hydrogen,
where did THAT come from?
All that hydrogen and all that helium
needed an explanation.
This problem catalysed
one of the most vicious fights
in post-war science.
That's because it turned
into a much bigger question,
in fact, the ultimate question.
Was the entire universe
created in a single instant
or has it always been there?
Nearly every post-war physicist
was sucked into this controversy
but two men were at its centre.
One was Fred Hoyle,
the other was an eccentric Ukrainian
called George Gamow.
6'4", a practical joker
and a refugee from Stalin's Russia.
Another physicist said of Gamow,
"even when he's wrong,
he's interesting".
Both men would stake their careers on
this mother of all physics battles.
It all began innocently enough.
Gamow had recently
been appointed a professor
at George Washington University and
thought the hydrogen and helium
riddle might be worth exploring.
This was George Gamow's office
at the George Washington University.
It's really pokey!
It was here that Gamow worked on
the problem of why there seemed
to be too much helium gas in the sun
than could be accounted for
from the fusion of hydrogen.
Gamow came up with the crazy idea
that maybe most of this helium
had been around
before the sun was even formed.
This is the moment
it gets controversial and leads us
inexorably into a row over creation.
For Gamow to assert that helium
existed in the universe before
the sun and the stars were formed
he had to come up with another place
that was capable of making helium.
Gamow knew wherever this process was,
it needed to be staggeringly hot,
a searing billion degrees centigrade,
millions of times hotter
than the sun.
At this temperature, matter,
as we know it, is ripped apart.
Hydrogen nuclei move about
manically, constantly colliding,
making helium at a prodigious rate.
But what cosmic event was capable
of reaching such an epic,
terrifying temperature?
To explain this,
he used a speculative theory
that was doing the rounds
at the time that suggested that
the whole universe had been created
in a single cataclysmic explosion
billions of years ago, a theory
that today we call the Big Bang.
For decades astronomers have known
that the galaxies are flying away
from each other
at astonishing speeds.
The universe is getting bigger.
This means that in the past
the universe must have been
much smaller
and in the very, very distant past
the entire universe
must have been a tiny,
almost infinitesimally minute dot.
And the implication of this
is a single moment of creation,
an instant at which all matter,
even time and space, came into being.
In 1945, most scientists were
uncomfortable with this idea
but not Gamow.
He spotted that it might solve
the mystery of the excess helium
in the sun and stars.
Gamow worked out that if
the entire cosmos was squeezed down
to a tiny dot
it would be immensely hot.
In the first few minutes after
the creation the universe would have
been hot enough for hydrogen nuclei
to squeeze together
to make all the excess helium
in the sun and stars.
Now, after those first few minutes
the universe would have expanded
and would have been too cool but
a few minutes were all Gamow needed.
In that time, all the hydrogen
and almost all the helium was made.
That's about 98% of all the atoms
in the universe today
or as Gamow put it,
our universe was cooked in less time
than it takes to cook a dish
of duck and roast potatoes!
BANG!
But by arguing that the Big Bang,
a deeply controversial idea,
had created most of the hydrogen
and helium in the universe
Gamow ignited an enormous row
over creation.
Fred Hoyle soon became the most vocal
of Gamow's critics.
Fred Hoyle hated
the idea of the Big Bang
with every fibre of his being.
You see, as a committed atheist
he objected to the theory
because a single moment of creation
to him smacked of a divine creator.
Gamow hit back saying that
without the Big Bang,
Hoyle couldn't properly explain
why there was so much hydrogen
and helium in the universe.
Both men had their supporters and
the argument between the rival camps
became quite shrill and personal.
Hoyle was deemed as
an old-fashioned, crusty old Brit
by the Big Bang supporters
and Gamow was condemned as a closet
creationist by Hoyle's supporters.
The argument raged in scientific
conferences and in the popular press.
Secretly, each side knew
that they had a compelling argument
but both lacked
the killer piece of evidence
that would settle things decisively.
The conflict seemed destined
to remain unresolved.
Then south of New York, close
to the mean streets of New Jersey,
an unlikely piece of equipment
was to make one of the most important
discoveries of the century
and settle the argument
once and for all.
This giant piece
of sadly rusting machinery
is the Bell Labs horn antenna
in New Jersey.
It's in fact a radio telescope
but rather than looking like
the more traditional satellite dish
it has this huge horn-like structure
that could be rotated round
to face the sky
and pick up radio signals from space.
It's a bit like a giant hearing aid
but it could pinpoint very, very
weak signals extremely accurately.
It was originally built for research
into satellite communication
but instead it was used
in the mid-1960s
to make
one of the most important discoveries
in the history of science.
Two researchers,
Arno Penzias and Robert Wilson
had got hold of this antenna
in 1963 from Bell Laboratories
with the intention of doing research
into the faint halo of hydrogen
around the Milky Way.
Before Penzias and Wilson
could begin their experiment,
they had to make sure they got rid
of all the background noise
the antenna was picking up.
It's a bit like the hiss
on radios in between stations.
They spent the best part of a year
checking all the equipment
and the electronics,
they even got down on
their hands and knees inside the dish
to scrub it clean of what they called
white dielectric material
which was basically pigeon crap.
But even after all this there was
still a faint persistent hiss
they couldn't get rid of
and it was there whichever direction
the antenna pointed.
There was
only one viable explanation.
The noise was the sound of radiation,
the afterglow of Gamow's Big Bang.
THUNDEROUS BANG
Here at last was final proof
that Gamow was right,
the Big Bang had to have happened.
You see,
soon after the universe was created
about 300,000 years
after the Big Bang
it had expanded and cooled enough
for the atoms of
the lightest elements to form,
leaving the whole universe
awash with light.
Now George Gamow
had earlier predicted
that this afterglow of creation
would today be in
the form of weak microwave radiation.
You can actually hear this radiation
as a tiny fraction of the hiss on
your radio or TV in between channels.
The detection
of this cosmic background radiation
by Penzias and Wilson
showed that Gamow's Big Bang theory
was correct and that he was right
about how hydrogen and helium
were formed in the early universe.
So this, together with Hoyle
and Fowler's theories about how
the atoms of all the heavier elements
were cooked inside stars
gave us the complete picture.
We finally understood how the atoms
of all the elements in the universe
were made.
In less than 100 years,
science has performed a miracle.
It had truly explained where
we come from and was able to describe
the entire 14 billion year history
of the cosmos.
In the beginning was the Big Bang...
BANG!
..an explosion of unimaginable power.
In the following ten minutes
in the searing heat,
the nuclei of just two types of atom
emerged, hydrogen and helium.
For the next 300,000 years
the universe expanded.
At that point
another cosmic chapter began.
Individual atoms separated out
from each other,
as they did this,
they released light.
It's the remnants of this light
that Penzias and Wilson
picked up with their horn antenna.
Then, millions of years after this,
massive clouds of hydrogen
coalesced into the first stars.
In here they began to fuse,
producing starlight and eventually
all the other types of atoms
that exist in the universe today.
Our Earth and everything on it,
including our own bodies, was forged
long ago in the crucibles of space.
For instance, my body
is almost three-quarters water
which we know is made up
of oxygen and hydrogen atoms.
We now understand that hydrogen
was formed 13 billion years ago,
soon after the Big Bang itself
whereas oxygen had to wait
to be cooked
inside stars like our sun.
The same is true of another
important element in my body, carbon,
the element on which
all life forms on Earth are based.
But my body also contains
other elements in smaller amounts,
like iron.
This element was formed
during the dying embers
of gigantic stars as they ground
towards the ends of their lives.
There are also
trace elements like zinc.
There are only two grams of zinc
in my body but this element
had to be created during a supernova,
the explosion of a giant star
with cosmic violence
during which lighter atoms
are fused together to form
heavier elements.
The same is true for all naturally
occurring elements, they are
all cooked in cosmic cauldrons.
Romantically, you could say
that we're all made of stardust
but the truth is also
that we're all just nuclear waste.
Subtitles by Red Bee Media
we asked where we had come from,
how all the stars were created,
how all the elements were made,
even how the universe itself had begun.
One of mankind's greatest
achievements is that we've
answered these questions.
What is truly remarkable
is that this understanding has come
through the study of the smallest
building blocks of matter - atoms.
As we peered inwards, we realised
we could explain what we saw
when we peered outwards.
The atom has helped us solve
the greatest mysteries of existence.
Everything in the world we see is
made out of tiny objects called atoms
and yet
we only proved their existence
at the beginning of the 20th century.
The first shock was to discover
how small they were,
less than
a millionth of a millimetre across,
there are trillions
in a single grain of sand.
Amazingly, we now have
a pretty good idea of the number
of atoms in the known universe.
Now, given
the vastness of the universe
and the minuteness of the atom,
it's not surprising that this
is a mind-numbingly huge number,
it's one
followed by over 70 zeros,
that's a trillion,
trillion, trillion,
trillion, trillion, trillion atoms.
We don't only know the raw number
of atoms in the cosmos
we also know that they come
in 92 different flavours.
These are called the elements
and you'll recognise many of them
as familiar parts
of the world around us.
Oxygen, iron, carbon,
tin, gold and so on.
Everything in the universe,
the stars, the planets,
the mountains,
the seas, the animals, you and me,
we're all made of these atoms
or combinations of them.
It's an astonishing human achievement
that we now know,
not only how many atoms
there are in the universe
and how many different types there
are, but why they exist at all.
We can now explain how every one of
those trillion, trillion, trillion,
trillion, trillion, trillion atoms
was created.
It turns out that the answer
to the mystery of creation itself
lies within the heart of each
and every atom in the universe.
The story of how we came
to understand creation itself
started over 100 years ago
in a small laboratory
in south-east Paris.
GEIGER COUNTER CLICKS RAPIDLY
This piece of paper
is a remarkable artefact.
It's from the notebook of the woman
who first studied radioactivity,
the chemist Marie Curie.
It's incredible, 100 years later
and this piece of paper is still
spitting out radioactive particles.
The photograph on the left
shows the concentration
of the radioactivity,
you can actually see
Marie Curie's thumbprints on it
but what's really incredible
is the sheer power,
the energy given off by radioactivity
that this piece of paper
is still spitting out these particles
100 years later.
Still stuck to the paper are
tiny but intensely radioactive
particles of a substance
that Marie Curie discovered in 1898,
a substance she called radium.
It was a sensational discovery
for one primary reason.
Though radium looks like
an unremarkable grey metal,
it contradicted
all the then-known laws of science.
Because radium pumps out
invisible yet powerful rays of energy
which could fog sealed photographic
paper and burn human flesh.
They're a little like radio waves
which is why
Curie called radium radioactive
but the waves were millions of times
more powerful than any radio wave
previously encountered.
Also,
radium appeared to contain within it
an inexhaustible store of energy,
Curie worked out that
a gram of radium,
a piece much smaller than a penny
contains more energy
than 100 tons of coal.
By the turn of the century,
the French public and the tabloid
press were fascinated by radium
and, rather touchingly
though no-one had a clue
was radioactivity really was,
everyone assumed it must
be wholesome and healthy.
When radium was first discovered,
they found all sorts of weird and
wonderful commercial uses for it.
Here is the Radium bath products,
there's the Radium Eau de Cologne,
Atomic Perfume and Radium Face Cream
apparently enhancing beauty
through healthy skin.
There's even the Radium
razor blade, I'm not quite sure
how that's supposed to work.
Ah, the good old days, clearly
when ignorance really was bliss.
Whatever the public made of it,
to the scientific community
radioactivity was just about
the most exciting thing possible.
The brightest minds of a generation
clamoured to study it
and the price of radium,
it's most potent source,
soared to thousands of pounds
per ounce and radioactivity
didn't disappoint.
In 1919, it produced its greatest
revelation yet,
a revelation that would ultimately
lead to a fundamental understanding
of the atomic world.
The revelation was that radioactivity
allowed humanity to fulfil
an age-old dream...
to become alchemists.
Alchemy, the power to change
base metals into gold,
the quest for the so-called
Philosopher's Stone
which has the magical ability
to transmute one substance
into another,
has been an obsession for centuries.
It conjures up wonderful tales of
sorcery and wizardry, as anyone who's
read Harry Potter knows very well.
The power and wealth that would
surely come to anyone who mastered
alchemy seduced many great scientists
and thinkers like Isaac Newton,
Robert Boyle and John Locke.
All of them tried to change
one element into another
and all of them failed.
Then in 1919, the secret of alchemy,
the mystery of
the Philosopher's Stone
was finally revealed,
not in a wizard's den
but in the physics department
at Manchester University.
The world's first true alchemist
was Ernest Rutherford.
A loud, straight-talking
New Zealander,
Rutherford had come to dominate
the study of radioactivity.
He had wonderful intuition and was
fearlessly prepared to challenge
conventional wisdom and alchemy
would require Ernest Rutherford
to follow his intuition
deep into the unknown.
The discovery was almost accidental.
It began when one of
Rutherford's students noticed that
when radioactive materials like
radium were placed inside a sealed
container of ordinary air,
mysteriously, small amounts of
the gas hydrogen begin to appear.
Now this was bizarre. Ordinary air
contains virtually no hydrogen
and yet in the presence
of radioactivity
it was appearing out of nowhere.
This was precisely
the kind of problem that Rutherford,
now at the height of his powers
as an experimental physicist, loved,
and he flung himself at it.
He began by isolating
all the different gases
that make up the air we breathe,
nitrogen, oxygen, water vapour
and carbon dioxide
and studied how each of them behaved
in the presence of radioactivity.
And then...eureka!
Rutherford realised
that in the presence of
powerful radioactive rays,
the gas nitrogen, which makes up
about 80% of the air we breathe,
changes into two new substances,
the gases oxygen and hydrogen.
Then and there
Rutherford had transmuted
one element into two others.
He'd become an alchemist and radium,
with its powerful radioactivity,
was the Philosopher's Stone.
The press hailed Rutherford
as the first alchemist,
but in fact that was the least of it.
What alchemy had shown him was
the inside, not just of the atom,
but of the strange object
at its centre,
its tiny beating heart, the nucleus.
To get a sense of this achievement,
remember Rutherford
and his contemporaries at Cambridge
had only a sketchy idea of
what an atom was but they did have
an idea of its size.
And it's mind-numbingly tiny,
one tenth of a millionth
of a millimetre across.
Let me put it another way, there are
more atoms in a single glass of water
than there are glasses of water
in all the oceans of the world.
And Rutherford now also knew
that the atom had structure,
that within the atom
there was a sub-atomic world.
He pictured each atom
like a tiny solar system.
At its centre, 100,000 times smaller
than the atom itself
was an object
which Rutherford called the nucleus.
Orbiting this, like planets,
were the electrons
but what on earth WAS the nucleus?
Rutherford was convinced that
alchemy had shown him the answer.
To understand how Rutherford did this
we have to get inside his head
to think like he did.
Rutherford had fantastic intuition
coupled with an intensely
practical approach to science
so he hated ideas that relied
on complicated mathematics.
When it came to the atomic nucleus,
Rutherford looked for
the simplest idea that worked
and what worked was to imagine
that the nucleus is made of tiny,
rigid spheres, like snooker balls.
Using this incredibly simple image,
Rutherford could construct
all the elements in the universe.
He could explain how the huge variety
of different atoms are made
of the same basic components.
So here's how it works.
Hydrogen, which is the simplest
element, consists of just one sphere
which Rutherford called a proton,
which is the Greek word for "first".
All the other elements are made by
adding more protons to the nucleus.
It's as simple as that.
So helium,
which is the second lightest element,
comprises of two protons,
lithium has three.
Carbon, which is the element
that's the basis of all life,
has six protons.
The oxygen that we breathe
has eight
and uranium, which is the heaviest
naturally-occurring element,
has 92 protons.
This was Rutherford's
inspirational idea,
that each element is defined by
the number of protons in its nucleus.
It's a wonderfully elegant
and simple idea,
an idea that explains
how so much of the universe
we see around us is constructed.
But as scientists often find,
nature is never quite as simple
as it seems at first sight.
Sure enough, a big problem
emerged with Rutherford's proton.
A problem which threatened
to derail the whole atom project
and it was to be
one of Rutherford's own proteges
who was the first to identify it.
Francis Aston
was an interesting character.
As a young man he enjoyed
the adventurous outdoors
and was into skiing and motor racing
and apparently in about 1909
he discovered surfing
off Waikiki Beach in Hawaii.
But he soon realised the call
of the physics laboratory was greater
than the call of the waves
and it was while at Cambridge
that he invented
an incredible piece of equipment.
That's now housed here in this rather
austere and plain-looking building,
the Cavendish Laboratory.
This is
Aston's original spectrograph.
It's an amazing piece of equipment
because with it, for the first time,
scientists were able
to weigh individual atoms.
It's incredible, it looks a bit like
a gun, it's a very strange shape.
I guess basically, you'd have
the atoms that you wanted to weigh
in this glass tube
and the electrically-charged atoms
would be fired in this direction.
Round about here there'd be electric
plates which would bend those atoms.
Because the atoms had electric charge
they'd get bent in the electric field
down in this direction
and then what we're not seeing here
would have been a huge magnetic coil
that would sit around this arm
and the magnet would bend those atoms
back up again in this direction.
Now round about here at the end
would be a photographic plate,
I'm not quite sure if we can see it,
no.
But the plate would sit here
and atoms of a particular weight
would be focused in a line
and so Aston was able to see
individual lines for atoms
of different weights.
It was remarkable that round about,
just after the First World War,
scientists were finally able
to weigh atoms.
Now they could weigh atoms
accurately, they discovered that
there was a fundamental problem
with Rutherford's model
of the nucleus.
Basically the numbers
didn't quite add up.
All the atoms of the known elements,
apart from hydrogen, were
much heavier than they should be.
For instance, helium,
with two protons should weigh twice
as much as hydrogen, with just one.
In fact it's four times as heavy.
Rutherford realised
this could mean just one thing -
apart from the proton
there's something else inside
the atomic nucleus. But what?
It took 12 years to find the answer.
Now, as head of the prestigious
Cavendish Laboratory in Cambridge,
Rutherford threw
all his resources into the project.
He bullied and cajoled his students
and researchers until one,
a northern lad from humble origins
called James Chadwick,
hit the nuclear physics
equivalent of gold.
Chadwick built this in 1932
and to think that with just
this tiny little piece of equipment
he discovered
the missing ingredient of the atom.
For me
as a practising nuclear physicist
this really is an amazing device.
When I think of the huge accelerators
that are built today
to conduct experiments to probe
the nucleus of the atom,
it's really awe-inspiring
in its simplicity, really.
He put a source of radioactivity
at this end of the tube
and the radioactivity then struck
a small target in the middle here
and then out of the target
came new particles that sprayed
out of this end here.
It's a bit like an atomic gun,
shooting out
Rutherford's missing particles.
What Chadwick discovered was that
along with the proton there's another
kind of particle inside the nucleus.
It weighs almost exactly the same
as a proton but is much more elusive
because it carries
no electrical charge.
Technically we say it's electrically
neutral hence its name, the neutron,
and it immediately solved
the problem of the weight of atoms.
So, helium
is four times as heavy as hydrogen
because along with its two protons
it contains two neutrons
and oxygen has eight neutrons
along with its eight protons,
making it 16 times
as heavy as hydrogen.
So in 1932,
the atomic family was complete.
Scientists announced that
every atom in the universe is made
of just three basic components -
electrons,
tiny particles orbiting a nucleus
which in turn
is made of protons and neutrons.
WALTZ PLAYS
# Neutron, neutron... #
Over Christmas 1932,
physicists at the other great centre
of atomic physics,
the Niels Bohr Institute
in Copenhagen celebrated
the neutron's discovery
and the completion
of the nuclear trinity
by writing a musical about it.
# That which experiment has found
# For theory had no part in
# Is always reckoned more than sound
# To put your mind and heart in
# Good luck, you heavyweight Ersatz
# We welcome you with pleasure
# But passion ever spins our plot
# And Gretchen is my treasure. #
Some of the great names in
physics took part in this musical.
Their excitement
was primarily due to one thing.
They knew they stood at the threshold
of an entirely new kind of science
with entirely new rules,
what we now call nuclear physics.
The first challenge
for nuclear physics was this.
Although physicists now knew
what the tiny nucleus was made of
they couldn't explain
how it all held together.
In fact it was worse than that,
the existing laws of physics
predicted that every atomic nucleus
should self-destruct instantly.
# Eternal neutrality
pulls us alo-o-o-ng. #
The main problem was this.
All protons, the key ingredient
of the atomic nucleus
have positive electric charge
and things with the same charge
repel each other
just like these magnets. Look.
So just like these magnets,
if two protons get close together
they should then just fly apart
but weirdly,
inside the atomic nucleus they don't.
Dozens of protons can stick
together alongside each other.
So what sticks them together?
What stops the protons
from flying apart?
The answer was big news,
it was nothing less than
an entirely new force of nature.
For centuries humans had only ever
encountered two natural forces,
gravity which pulls us down
to the Earth and electromagnetism.
But now, hidden inside
the atomic nucleus
was something completely new,
it was called
the strong nuclear force
and the easiest way to imagine it
is with some Velcro.
If I put Velcro around these magnets,
they start to behave
slightly differently.
At first they repel
each other just as before
but when they get close enough
the Velcro kicks in and they stick.
The effect is very short range
but very, very strong
and it's exactly the same
with protons.
The strong nuclear force explains
what holds the nucleus together.
The strong nuclear force works
between all protons and neutrons
but what is truly surprising about it
is its strength.
It's by far the most powerful force
in the universe...
more than a trillion, trillion,
trillion times stronger than gravity.
Think about it this way, if I was
pulled down the earth, not by gravity
but by the strong nuclear force
then I'd weigh trillions of times
more than I actually do, in fact I'd
weigh more than the entire galaxy.
But the reason
I don't weigh that much
is because the strong nuclear force
is only felt down at a distance
of a trillionth of a millimetre.
With the strong nuclear force,
humans finally began to get a glimpse
of what was actually going on
inside the atomic nucleus.
Roughly speaking, all nuclear
behaviour is down to a balance
between the strong nuclear force
squashing the protons and neutrons
together
and the electric charge
on the protons forcing them apart.
Physicists realised that picturing
the nucleus as a battlefield
between different elemental forces
solved one of the oldest mysteries
of all time.
It's this.
A question that humans have asked
ever since the dawn of time
is, how does the sun shine?
Now sunlight is the source of
all life on Earth but how is it made?
It's all to do with the forces
inside the atoms that make up most of
the sun - hydrogen.
This is how it works.
The nucleus of a single atom of
hydrogen consists of just a proton
and every now and again inside
the high-pressure, high-temperature
cauldron of the sun,
this proton can get squeezed up close
to another and bang!
The strong nuclear force kicks in
and fuses them together.
CYMBALS CRASH
Now this is a process that
eventually leads to the creation
of a helium atom
and it's accompanied
by the release of energy
as a burst of light and heat.
It's a bit like
slamming two cymbals together
and releasing a burst of sound.
Hydrogen fusing into helium
and the energy released
is what we see and feel as sunshine.
This process of
two hydrogen nuclei slamming together
and releasing energy
became known as nuclear fusion.
The turmoil between the strong
nuclear and electromagnetic forces
as they strive
to dominate the nucleus
does more than just power the sun.
It's at the heart of everything
but in the late 1930s
before people figured out that story,
nuclear physics did something
much closer to home.
In no uncertain terms,
it redefined the history of mankind
right here on Earth
and led to one of our darkest hours
and that story began
with the study of the humble neutron.
In the years immediately following
its discovery the neutron
became the focus of atomic research
in laboratories across Europe
and the reason for the excitement
was this.
See, the neutron is the stealth
bomber of the atomic world because
unlike the other particles
that make up the atom,
the proton and the electron,
the neutron is, as its name suggests,
electrically neutral
so it can fly
undetected and undeflected
into the very heart of the atom
and collide with the nucleus.
Now physicists knew that these
collisions would be spectacular
because by atomic standards
the neutron is heavy
so when it collides with
the nucleus, it deals a mighty blow.
It's a bit like the Moon
smashing into the Earth.
Now physicists in the 1930s
knew that this held up all sorts
of tantalising possibilities.
Such collisions might chip bits off
the nucleus and create new elements.
They might -
and this is the Holy Grail -
even create new radioactive elements
like Marie Curie's radium
which was the source
of unlimited energy.
In their excitement
about this new science,
physicists in labs across Europe
fired neutrons into every element
they could find.
In a laboratory in the Kaiser Wilhelm
Institute in Berlin,
a chemist called Otto Hahn
finally got round to firing neutrons
at the last, heaviest element
in the periodic table,
the metal uranium.
This is some of the equipment
that he used in the late 1930s.
So, what they would have would be
a source of neutrons sitting here
surrounded by a block of paraffin wax
that would slow down the neutrons so
they'd be more likely to be absorbed
by the uranium sitting on the side.
This electronic equipment was used
to detect the particles coming out
from these radioactive elements.
What Otto Hahn tried to do was
to analyse chemically
the new elements being produced
from the reaction.
What he found was what appeared to be
Marie Curie's radium being produced
but when he tried to isolate it
he didn't find any at all.
Instead it seemed that what was
being produced was the element barium
which was much lighter than uranium.
How could barium be produced?
It was a puzzle,
he simply couldn't explain it.
Nevertheless, Hahn meticulously
catalogued his results.
Hahn was a chemist not a physicist
but, even so, he knew that
according to all laws of science
there was no way barium would be
coming out of his experiment.
It was simply
too different from uranium,
the only person
who Hahn thought might be able
to explain what was going on
was his old assistant,
the physicist Lise Meitner.
But she'd been forced to flee
Nazi Germany a few months earlier
because she was Jewish so Hahn
sent her his controversial findings.
Lise Meitner was in Sweden
with her nephew, Otto Frisch
who was also a nuclear physicist,
when she received the letter
from Hahn.
On Christmas Eve 1938
they went for a walk in the woods
where they discussed long and hard
the results of Hahn's experiment.
They realised
that the uranium nucleus
wasn't just having a small piece
chipped off the edge.
The nucleus was literally splitting
into two equal halves.
Meitner and Frisch were shocked
beyond belief.
The idea that uranium
could literally split into two
had never been considered remotely
possible but after Hahn's experiment
it was the only explanation.
Right then, Meitner and Frisch
realised this had astonishing
and terrifying consequences.
The huge uranium nucleus
splits into two
because the strong nuclear force
loses its battle to hold
the nucleus together.
The electrical repulsion
then tears the nucleus apart
and the amount of energy released
would be on a scale
never seen before.
The energy released from
a single uranium nucleus would be
enough to move a grain of sand.
Now this is an incredible
amount of energy
because a grain of sand itself
contains trillions and trillions
of atoms.
It's a bit like
kicking a football at the Moon
and knocking the Moon off its orbit.
For me, this heralded
the birth of the atomic age.
What Frisch and Meitner
had discovered was nuclear fission.
Nuclear fission was the first time
anyone had released
the enormous forces
inside the nucleus artificially.
Uranium gave mankind the means
to tap into the vast, seething energy
inside the nucleus
and turn it to its own uses.
The timing of the discovery -
it coincided with the beginning
of the Second World War -
meant that Allied scientists
under Robert Oppenheimer
worked day and night
to figure out how nuclear fission
could be exploited
as a weapon of mass destruction
and the final manifestation of this
research came in 1945
over Hiroshima and Nagasaki.
ATOM BOMB BLASTS
The atom bomb changed everything.
The excitement of
pre-war scientific research,
the days when physicists sang songs
about their discoveries, were over.
Robert Oppenheimer summed up
the grim mood with these words.
"The physicists have known sin
and this is a knowledge
which they cannot lose."
The terrible irony
of the atomic bomb is that
because of the scientists' sin,
because of that knowledge
that cannot be lost, something
of great significance did emerge.
Something that would ultimately
reveal the full story
of the 14 billion years
of the entire universe.
The war had caused
a massive two billion dollars
to be poured into nuclear research.
People now knew an astonishing amount
about the atom and its nucleus.
Specifically,
scientists had detailed measurements
of how stable or unstable
different atomic nuclei were.
That stability was a direct result of
the battle between the strong nuclear
force holding the nucleus together
and the electromagnetic force
pushing it apart.
In some atoms, the balance
tipped towards the strong force
making them very stable
but when the electromagnetic force
had the upper hand
they were inherently unstable.
By the late '40s, scientists
began to investigate the implications
of the way
nuclear stability of atoms varies.
They noticed one very strange fact
about the nuclear stability
of one particular atom.
IRON CLANGS
Of all the 92 different elements,
of the 92 different types of atoms
that make up
the universe around us,
gases like hydrogen and oxygen,
solids like carbon and silicon,
metals like gold and silver,
one is special...
iron.
So what makes iron so special?
It stems from the unique structure
of its nucleus.
The 26 protons
along with the neutrons
combine in a very special way
to make iron incredibly stable.
For some reason,
nature has decreed this as the number
that allows the strong force
and the electromagnetic force
to balance each other perfectly.
It makes iron the most stable element
in the universe.
Now we can understand
why fusion occurs.
Lighter atoms can combine together
to become more iron-like
and fission is the opposite process,
atoms heavier than iron
can split apart into lighter,
more iron-like pieces.
So all elements seek
the stability of iron
and that fact underpins
the whole history of the cosmos.
The best way to understand this
is to imagine the relative stability
of atoms as a couple of graphs.
Here's what they show.
The very lightest elements,
hydrogen and helium
are not quite as stable as they could
be, they'd like to be something else,
something even more stable.
Similarly, the heaviest elements
like uranium and polonium
are actually unstable,
in fact they're so unstable
that they fall to pieces
naturally through radioactivity.
And here, in the middle
are the most stable atoms of all,
nickel, cobalt and iron.
So far, so good.
Now, here's the amazing bit,
this nuclear stability graph
turned out to be uncannily similar
to a different graph altogether
but it was a similarity
that no-one had ever suspected.
That's because data from this other
graph came not from the tiny nucleus
but from as different
an arena as you can imagine...
the vast expanses of space.
This other graph
came from astronomers
who studied
the blazing light from stars
and shows the abundances
of the different types of atoms
in the universe.
By far the most common atom of all
is that of hydrogen
followed closely by helium but
not a great deal of anything else.
Now look at this, it really
is of cosmic significance.
Both graphs, the stability graph
and the abundances graph
show the same strange
but very noticeable peak
The first scientists who spotted this
were blown away.
One graph from the tiny nucleus and
the other from the vastness of space
point to the same magical atom.
The atom that provided the key
to unlocking the secrets
of the entire universe.
Iron, the atom which was the key
to understanding the atomic nucleus,
also turned out to be
one of the most abundant atoms
in the entire universe.
Amazingly the properties of
its nucleus seem to lead directly
to how much of it there is
and it's not just true of iron.
Radium, which is very unstable,
turns out to be incredibly rare.
Aluminium which is relatively stable
turned out to be relatively common.
It's a pattern which appears
right across the list of elements.
The signature of their nuclei
is written in the skies above us...
..and deciphering the meaning of
this connection would require
the greatest minds of a generation.
The first of these was a rebel
and a maverick called Fred Hoyle.
He loved walking the hills
and dales of his native Yorkshire.
Hoyle always spoke his mind
even though it brought him
into conflict with his peers.
He became something
of a scientific pariah.
More than almost any other scientist,
he explored the strange overlap
between the science of the atom
and the science of the cosmos.
Hoyle realised what the graphs
revealed is that the underlying theme
of the universe
was ultimately change.
Everything in the universe
is in a state of flux.
The atoms are trying
to gain or lose protons
in an attempt to become more stable.
What Hoyle and his colleagues did
was to ask
how and where in the cosmos
all this atomic transformation,
all this alchemy, takes place.
Hoyle knew that
in stars like our sun,
hydrogen turns into helium by
a process called nuclear fusion.
But could nuclear fusion
also be the way all the other atoms
in the universe are made?
Fred Hoyle's great insight
was to work out precisely
how the heaviest elements
are created through nuclear fusion.
Hoyle worked out that this process
can only take place
at unimaginably high pressures
and temperatures of
millions of degrees centigrade.
In our universe
there's only one place where
such conditions exist...in stars.
Fred Hoyle's problem
was with the details.
To explain how fusion could create
atoms heavier than helium
was tricky and complicated.
Hoyle had to explain precisely
how in the fierce heat inside stars,
light atoms might fuse
to become heavier ones.
EXPLOSION
In the '40s, Hoyle worked out that
our sun is hot enough to fuse atoms
like oxygen, carbon and nitrogen
but what about heavier atoms
like copper, zinc or iron?
His calculations showed that
they could be made inside stars
but these would have to be
much hotter than our sun
and he knew exactly
where to find them.
These huge, bloated stars
near the end of their lives
were called red giants.
Astronomers had discovered that there
were hundreds of millions of these
monsters throughout the universe.
Fred Hoyle reasoned that
they were hot enough to allow
weightier atoms to be fused
but there was still a problem.
Even the mighty red giants
weren't hot enough
to make the really heavy stuff,
atoms like gold and uranium.
To make these heavier than iron atoms
would mean forcing them
to fuse together,
becoming more and more unstable.
It would require unimaginable
temperatures and pressures.
His only hope was that somewhere
out there in the vastness of space
were things so big and so hot
they made our sun look like
a birthday candle.
And towards the end
of the Second World War,
during a research trip to Southern
California, Fred Hoyle found them.
This is the 100-inch telescope
at the Mount Wilson Observatory
outside Los Angeles.
When it was first built
in 1917, it was without doubt
the largest telescope in the world
and it was while he was here
he met up with the great astronomer,
Walter Baade who told him about
supernovae.
Now these are processes
when massive stars explode
with an incredible intensity
and in a flash of inspiration
Hoyle realised that here, at last,
were the extreme conditions necessary
to produce all the heavy elements.
What Baade was referring to was
an explosion of simply cosmic scale.
BANG!
When the larger stars run out
of hydrogen to fuse into helium,
they come to the end of their lives
and they collapse under
the weight of their own gravity
and then explode outwards.
In a blinding flash of inspiration,
Hoyle and his colleague
William Fowler
realised that supernovae might be
the hottest places in the universe,
hot enough to fuse together
even the heaviest of atoms.
Hoyle and Fowler
had found the furnaces
in which everything was made.
The discovery of how atoms are made
in stars is surely one of
humanity's greatest achievements,
except for one glaring problem.
One that Hoyle could never
explain away and it was this.
Stellar nuclear fusion can explain
how all the elements in the universe
are made...except for two,
two very important ones.
The two simplest elements,
hydrogen and helium.
In the 1940s, using
increasingly accurate equipment,
scientists found that a quarter
of the sun was in fact helium
which was considerably more
than they thought.
They realised that to fuse that
amount of helium would mean the sun
would have to be burning at billions
of degrees but the truth was,
the sun only burns
at 15 million degrees.
The sun just wasn't hot enough
to have made all that helium.
In fact,
it turns out that per cubic metre,
the sun actually generates less heat
than a human being
so I produce more heat than a piece
of the sun the same size as me.
This means that the sun
is just not hot enough
to make all the helium
we know that it contains.
If all the helium wasn't made in
the sun then where did it come from?
And even more crucial
was the question
Hoyle was in denial about.
If all the atoms in the universe
started off as hydrogen,
where did THAT come from?
All that hydrogen and all that helium
needed an explanation.
This problem catalysed
one of the most vicious fights
in post-war science.
That's because it turned
into a much bigger question,
in fact, the ultimate question.
Was the entire universe
created in a single instant
or has it always been there?
Nearly every post-war physicist
was sucked into this controversy
but two men were at its centre.
One was Fred Hoyle,
the other was an eccentric Ukrainian
called George Gamow.
6'4", a practical joker
and a refugee from Stalin's Russia.
Another physicist said of Gamow,
"even when he's wrong,
he's interesting".
Both men would stake their careers on
this mother of all physics battles.
It all began innocently enough.
Gamow had recently
been appointed a professor
at George Washington University and
thought the hydrogen and helium
riddle might be worth exploring.
This was George Gamow's office
at the George Washington University.
It's really pokey!
It was here that Gamow worked on
the problem of why there seemed
to be too much helium gas in the sun
than could be accounted for
from the fusion of hydrogen.
Gamow came up with the crazy idea
that maybe most of this helium
had been around
before the sun was even formed.
This is the moment
it gets controversial and leads us
inexorably into a row over creation.
For Gamow to assert that helium
existed in the universe before
the sun and the stars were formed
he had to come up with another place
that was capable of making helium.
Gamow knew wherever this process was,
it needed to be staggeringly hot,
a searing billion degrees centigrade,
millions of times hotter
than the sun.
At this temperature, matter,
as we know it, is ripped apart.
Hydrogen nuclei move about
manically, constantly colliding,
making helium at a prodigious rate.
But what cosmic event was capable
of reaching such an epic,
terrifying temperature?
To explain this,
he used a speculative theory
that was doing the rounds
at the time that suggested that
the whole universe had been created
in a single cataclysmic explosion
billions of years ago, a theory
that today we call the Big Bang.
For decades astronomers have known
that the galaxies are flying away
from each other
at astonishing speeds.
The universe is getting bigger.
This means that in the past
the universe must have been
much smaller
and in the very, very distant past
the entire universe
must have been a tiny,
almost infinitesimally minute dot.
And the implication of this
is a single moment of creation,
an instant at which all matter,
even time and space, came into being.
In 1945, most scientists were
uncomfortable with this idea
but not Gamow.
He spotted that it might solve
the mystery of the excess helium
in the sun and stars.
Gamow worked out that if
the entire cosmos was squeezed down
to a tiny dot
it would be immensely hot.
In the first few minutes after
the creation the universe would have
been hot enough for hydrogen nuclei
to squeeze together
to make all the excess helium
in the sun and stars.
Now, after those first few minutes
the universe would have expanded
and would have been too cool but
a few minutes were all Gamow needed.
In that time, all the hydrogen
and almost all the helium was made.
That's about 98% of all the atoms
in the universe today
or as Gamow put it,
our universe was cooked in less time
than it takes to cook a dish
of duck and roast potatoes!
BANG!
But by arguing that the Big Bang,
a deeply controversial idea,
had created most of the hydrogen
and helium in the universe
Gamow ignited an enormous row
over creation.
Fred Hoyle soon became the most vocal
of Gamow's critics.
Fred Hoyle hated
the idea of the Big Bang
with every fibre of his being.
You see, as a committed atheist
he objected to the theory
because a single moment of creation
to him smacked of a divine creator.
Gamow hit back saying that
without the Big Bang,
Hoyle couldn't properly explain
why there was so much hydrogen
and helium in the universe.
Both men had their supporters and
the argument between the rival camps
became quite shrill and personal.
Hoyle was deemed as
an old-fashioned, crusty old Brit
by the Big Bang supporters
and Gamow was condemned as a closet
creationist by Hoyle's supporters.
The argument raged in scientific
conferences and in the popular press.
Secretly, each side knew
that they had a compelling argument
but both lacked
the killer piece of evidence
that would settle things decisively.
The conflict seemed destined
to remain unresolved.
Then south of New York, close
to the mean streets of New Jersey,
an unlikely piece of equipment
was to make one of the most important
discoveries of the century
and settle the argument
once and for all.
This giant piece
of sadly rusting machinery
is the Bell Labs horn antenna
in New Jersey.
It's in fact a radio telescope
but rather than looking like
the more traditional satellite dish
it has this huge horn-like structure
that could be rotated round
to face the sky
and pick up radio signals from space.
It's a bit like a giant hearing aid
but it could pinpoint very, very
weak signals extremely accurately.
It was originally built for research
into satellite communication
but instead it was used
in the mid-1960s
to make
one of the most important discoveries
in the history of science.
Two researchers,
Arno Penzias and Robert Wilson
had got hold of this antenna
in 1963 from Bell Laboratories
with the intention of doing research
into the faint halo of hydrogen
around the Milky Way.
Before Penzias and Wilson
could begin their experiment,
they had to make sure they got rid
of all the background noise
the antenna was picking up.
It's a bit like the hiss
on radios in between stations.
They spent the best part of a year
checking all the equipment
and the electronics,
they even got down on
their hands and knees inside the dish
to scrub it clean of what they called
white dielectric material
which was basically pigeon crap.
But even after all this there was
still a faint persistent hiss
they couldn't get rid of
and it was there whichever direction
the antenna pointed.
There was
only one viable explanation.
The noise was the sound of radiation,
the afterglow of Gamow's Big Bang.
THUNDEROUS BANG
Here at last was final proof
that Gamow was right,
the Big Bang had to have happened.
You see,
soon after the universe was created
about 300,000 years
after the Big Bang
it had expanded and cooled enough
for the atoms of
the lightest elements to form,
leaving the whole universe
awash with light.
Now George Gamow
had earlier predicted
that this afterglow of creation
would today be in
the form of weak microwave radiation.
You can actually hear this radiation
as a tiny fraction of the hiss on
your radio or TV in between channels.
The detection
of this cosmic background radiation
by Penzias and Wilson
showed that Gamow's Big Bang theory
was correct and that he was right
about how hydrogen and helium
were formed in the early universe.
So this, together with Hoyle
and Fowler's theories about how
the atoms of all the heavier elements
were cooked inside stars
gave us the complete picture.
We finally understood how the atoms
of all the elements in the universe
were made.
In less than 100 years,
science has performed a miracle.
It had truly explained where
we come from and was able to describe
the entire 14 billion year history
of the cosmos.
In the beginning was the Big Bang...
BANG!
..an explosion of unimaginable power.
In the following ten minutes
in the searing heat,
the nuclei of just two types of atom
emerged, hydrogen and helium.
For the next 300,000 years
the universe expanded.
At that point
another cosmic chapter began.
Individual atoms separated out
from each other,
as they did this,
they released light.
It's the remnants of this light
that Penzias and Wilson
picked up with their horn antenna.
Then, millions of years after this,
massive clouds of hydrogen
coalesced into the first stars.
In here they began to fuse,
producing starlight and eventually
all the other types of atoms
that exist in the universe today.
Our Earth and everything on it,
including our own bodies, was forged
long ago in the crucibles of space.
For instance, my body
is almost three-quarters water
which we know is made up
of oxygen and hydrogen atoms.
We now understand that hydrogen
was formed 13 billion years ago,
soon after the Big Bang itself
whereas oxygen had to wait
to be cooked
inside stars like our sun.
The same is true of another
important element in my body, carbon,
the element on which
all life forms on Earth are based.
But my body also contains
other elements in smaller amounts,
like iron.
This element was formed
during the dying embers
of gigantic stars as they ground
towards the ends of their lives.
There are also
trace elements like zinc.
There are only two grams of zinc
in my body but this element
had to be created during a supernova,
the explosion of a giant star
with cosmic violence
during which lighter atoms
are fused together to form
heavier elements.
The same is true for all naturally
occurring elements, they are
all cooked in cosmic cauldrons.
Romantically, you could say
that we're all made of stardust
but the truth is also
that we're all just nuclear waste.
Subtitles by Red Bee Media