Einstein and Hawking: Unlocking the Universe (2019) - full transcript

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In the 1960s,
radio telescopes around the world

started to pick up strange signals
from outer space.

They appeared to be coming

from tiny objects of massive density,
neutron stars.

These mysterious objects

had been predicted by Einstein's
theory of relativity

and their discovery meant
other predictions of relativity

might also exist...

objects like black holes.

Understanding these mysterious
monsters of the universe

kick-started the careers
of a young group of physicists

including Stephen Hawking.

It was a golden age, relativity,

as we sorted out,
under Hawking's leadership,

the theory of black holes.

It soon became clear that black holes
were very peculiar places.

We think of a black hole as a thing,
as an object,

but really
it's a region of space time.

A black hole is a region of space
time where gravity is so strong

that once you enter that region,
you just cannot ever leave it.

Black holes are fissures
in the fabric of the universe,

surrounded by an invisible boundary
called the event horizon.

Nothing that crosses that horizon
can ever get away.

Falling through the event horizon

is a bit like going over
Niagara Falls in a canoe.

If you are above the Falls, you can
get away if you paddle fast enough

but once you are over the edge,
you are lost.

A black hole is really defined
by that event horizon.

It separates us
fundamentally and for ever

from the inside of the black hole.

You can fall in
but you cannot come out.

The consequence is once something
has fallen into a black hole,

it appears to be lost
from the universe for ever.

From the outside, you can't tell
what is inside a black hole.

You can throw television sets,
diamond rings

or even your worst enemies
into a black hole

and all the black hole will remember

is the total mass
and the state of rotation.

It was these monsters that
Stephen Hawking was working on

in Cambridge in the mid 1970s.

And in 1974,
he made an enormous breakthrough.

Up to 1974, everyone,
including me,

thought that nothing
could get out of a black hole.

Then I discovered

that the uncertainty principle
of quantum mechanics

allowed particles to leak out.

By adding quantum mechanics, Hawking
made the stunning discovery

that actually black holes
could evaporate.

Black holes are not
what you thought they were.

Black holes can actually radiate.

Yeah, that was an in-your-face
shocking idea that he put forward.

Quantum mechanics implies
that the whole of space

is filled with pairs of virtual
particles and anti-particles

that are constantly materialising in
pairs, and annihilating each other.

Now in the presence of a black hole,

one member of a pair of virtual
particles may fall into the hole,

leaving the other member
without a partner.

As particles escape
from a black hole,

the hole will lose mass and shrink.

Eventually the black hole will lose
all its mass and disappear.

The discovery that black holes
emitted particles

was soon named Hawking Radiation.

It showed that black holes were even
stranger than we had imagined.

How can a black hole evaporate?

It seemed so peculiar and very
counter-intuitive but it made sense.

The calculations were checked over
and over again and it made sense.

This is completely counter
to everything

we thought that we understood
about black holes in the year 1970.

By combining general relativity
with quantum mechanics,

Hawking had shown the enduring power
of Einstein's theory.

But as Einstein himself
would discover,

that theory also had a dark side.

It could be used to unleash
devastation on the earth.

Back in the 1920s, Einstein found
that interest in his work

had extended beyond
the world of theoretical physics

and into the realm
of populist politics.

Long before there was even
a formal Nazi party,

as early as spring of 1920,

there were rallies to denounce
not just Albert Einstein

but rather to denounce
general relativity.

They would rent out sports arenas
and opera houses

and large, large stadiums,
thousands of people in attendance,

to basically chant
'Down with warping space time.'

It was seen as a symbol
of all that had gone wrong

with so-called Jewish physics.

It became clear it was not
going to be safe for him.

After the Nazis came to power,
Einstein fled Germany in 1933

and settled here in Princeton,
New Jersey,

working at the Institute
for Advanced Study.

And as a lifelong pacifist,

he was appalled
at the prospect of another war,

especially since he knew his own work

could have a devastating impact
on its outcome.

Einstein did not want to get
that involved in the war effort.

I think everyone was extremely
surprised that this 1905 paper,

E = MC2, could have an implication
for killing people.

So we come to Einstein's most famous
equation, E = MC2.

And like many of his equations,
it has this magical property

of equating two things that you
wouldn't expect to be equal.

On the left hand side we find E,
the energy.

On the right hand side, M, the mass.

And so this equation tells us
that energy and mass

are essentially the same.

They're equivalent.
They can be exchanged.

And the exchange rate
is C squared.

C is the speed of light,
it's huge.

So C squared
is a tremendously large number.

So one way to read the equation
is that a huge amount of energy

can be converted
into a small amount of matter

but reading the equation
from the opposite end,

it tells us that a small amount
of matter can be converted

into a huge amount of energy.

The power of E = MC2
went far beyond the theoretical.

In the early 1920s, Einstein's friend
Arthur Eddington realised

that this famous equation was the
secret to how stars, like our sun,

produced such vast amounts
of heat and light.

Deep in the hearts of stars,
pressures and temperatures

are so high that hydrogen nuclei
slam into each other,

fusing and eventually creating
helium nuclei.

And in that process, a tiny amount
of mass is converted into energy.

Albert Einstein realised

that perhaps we could harness
that process here on Earth

and create energy of our own.

Or create a weapon.

Worried the Germans had already
started a nuclear programme,

Einstein and fellow physicist
Leo Szilard

wrote to President Roosevelt,
urging him to develop a bomb.

Roosevelt responded by setting up
the Manhattan Project.

They achieved their goal
in just three years.

This is the Trinity monument.

On July 16th 1945, the world's
very first nuclear bomb

was set off right here in this spot.

The bomb, nicknamed Gadget,
was winched to the top

of a hundred foot tower
that stood right here.

The observers retreated
and just before dawn,

the bomb was detonated.

At 5.29 am, the device exploded

with an energy equivalent
to twenty kilo-tonnes of TNT.

The roar of the shock wave was felt
over one hundred miles away.

The surrounding mountains were
illuminated brighter than daytime

and the mushroom cloud reached
seven and a half miles in height.

All that power was released
when inside the bomb,

just 0.9 grams of matter
were converted into energy

and that's the power of E = MC2.

Just three weeks later, on August 6th
1945, another bomb was dropped

over the Japanese city of Hiroshima.

At exactly 8.15 in the morning,
0.6 grams of matter

was converted into energy,
incinerating seventy thousand people.

The devastating power of Einstein's
equation had been unleashed.

Now it's always been a mixed legacy
for the history of physics, right?

Like we like to think of ourselves
discovering secrets of the universe

not as blowing things up, but there
is this necessary interplay

between the discoveries we make

and the technological capabilities
that we have here on Earth

that physicists have to accept,

and of course Einstein always had
mixed feelings about it later on

because he was at heart a pacifist.

For the rest of his life,

Einstein campaigned for nuclear
disarmament and peace.

The nuclear bomb
was a devastating demonstration

of how Einstein's theories could be
used to practical effect.

Ever since then,
humanity has been building

increasingly complicated machines
that use Einstein's theory

not for destruction, but to unlock
the mysteries of the universe.

This is the entrance
to the Large Hadron Collider.

Buried deep below
the Swiss/French border,

it is the world's biggest machine.

Sudan Paramesvaran is a scientist who
uses the LHC to travel back in time.

The point of the LHC
is to try and understand

how the universe
came into its current state

from the Big Bang
all those billions of years ago,

and one way that we can do that
is to try and re-create

some of those early conditions.

Sudan's work relies on
the concept of time dilation,

developed by Albert Einstein.

Time dilation is only noticeable
at close to the speed of light

but in the LHC,
we can see it in action.

Beams of protons are fired
through these tubes

and smashed into each
other at very high speed.

In the middle of this pipe is where
the actual protons are travelling.

We accelerate them using
very powerful magnets.

They're actually
travelling round the ring

eleven thousand times a second,

very, very close
to the speed of light.

So when the protons collide,

they actually smash up into lots
of little different things.

A lot of new particles are created.

We think the particles
created in these collisions

are similar to those that existed
in the moments after the Big Bang.

Studying them can help us
understand the early universe

and that's where
time dilation comes in.

Okay, so what we have here

is a visual representation
of a collision.

The protons are colliding right
in the middle of our detector

and then everything comes out
from that point.

Each of these tracks
represents an individual particle

created in the collisions.

Many of them blink out of existence
in a fraction of a second.

This is actually
the decay of a B-meson

and its typical lifetime is only a
millionth of a millionth of a second

so it's tiny, and that would make it
very difficult for us

to actually investigate it.

It would decay very close
to the primary point here.

Now because it's travelling
close to the speed of light,

its clock is running
a little bit slower.

This means that it's actually able
to travel this distance before decay

and so the fact that
it undergoes time dilation

gives us
an avenue of physics to explore

which we otherwise
wouldn't be able to do.

The time dilation we see in the LHC

is Einstein's theory of relativity
in action...

this time for peaceful means.

We have answered many mysteries
about the universe

using Einstein's theories.

But even in the 21st century

there are still more discoveries
to be made...

discoveries that will
elegantly tie together

the work of Albert Einstein
on relativity

and Stephen Hawking on black holes.

Black holes are stranger

than anything dreamed up
by science fiction writers

but they are firmly
matters of science fact.

Despite all our advances
in technology,

we have still never seen a black hole

and it's that search for
an elusive glimpse of a black hole

that brings Dan Marrone
to the mountains of Arizona.

Black holes are one of those things

that I feel like everyone
is interested in, right?

The fact that we've never even
seen one is kind of amazing.

We're so confident they're there

but yet show me a picture
and you can't.

Dan is on a mission to do something
no one has ever done before,

take a picture of a black hole.

Ordinarily, it would be impossible
to photograph a black hole,

like picking out a shadow
on an already-dark sky.

But Dan is hoping to capture a black
hole in a particular phase of life,

while it is feeding.

The gravitation pull
of black holes is so strong

that they can consume
entire stars.

This simulation shows what we think
happens as a star is ripped apart.

What you see is the bright splatter
of the debris

falling around the black hole
from the neighbouring star,

and it turns out,
maybe even ironically,

that the darkest objects
fundamentally conceivable

become the brightest beacons
in the universe.

The event horizon, where the
whirlpool is at its fiercest,

is one of the most extreme
environments in the universe.

It is what Dan and his colleagues
are trying to take a picture of.

This is the sub-millimetre telescope
on Mount Graham in Arizona.

A radio telescope,

it can probe the depths
of the universe in broad daylight.

We'd like to see that material
circling the drain and disappearing.

We'd like to see the light itself
not escaping,

a shadow in front of the black hole

where the light
is disappearing into it.

Dan's sights are set
on the very heart of our galaxy.

Astronomers have been tracking
the motion of the stars

around the galactic core
for more than twenty years.

How's the weather this evening?

The weather's good.

The enormous speed
at which they are moving

suggests that they are orbiting
something huge and unseen.

They believe it is
a super-massive black hole,

over forty million kilometres across

and four million times
the mass of our sun.

It is known as Sagittarius A♪.

The event horizon around it

should be one of the brightest spots
in the galaxy...

but it is still so small
and so far away

that to image it takes
the largest telescope ever built.

So right now the telescope
is pointed at Sagittarius A♪.

We have to look through
the entire plain of the galaxy

and so if you look
with a visible light telescope,

you can't actually see it
as a black hole.

All the dust in the way
blocks the light

and so we have to do this
with a radio telescope.

And in fact we're not
just looking through one

but we're looking with a whole array
of them scattered over the earth.

The event horizon telescope
is a huge network.

As well as this dish on Mount Graham,
there are dishes in Europe,

on Hawaii, in Chile
and at the South Pole,

all of which are simultaneously aimed
at the very centre of the galaxy.

When the data
from all of them is combined,

it creates a telescope
the size of the Earth.

It is hoped it could soon produce

our first detailed view
of an event horizon

and the material around it
spiralling into oblivion.

But while we wait
for that first elusive image...

there is already a technology

that can detect Stephen Hawking's
beloved black holes

and may answer
one of the final great mysteries

of Einstein's theory of relativity.

These are offices at LIGO.

We can use any of these rooms
if you want

but if you want my office,
we're heading there.

It's full of junk.

This is the office they give
emeritus old professors,

that's what they do with them,

so a lot of my papers and junk
is all around.

There's a picture of my mentor
right over there.

You can see him,
his name is Jerrold Zacharias.

He's the first guy who ever
said to me that, you know,

you're not as dumb as you look.

That was very important.

You need somebody in your life
to tell you that.

Rainer Weiss, Rai to his friends,

is now a Nobel prize-winning
Emeritus Professor at MIT

but in 1967
he was just a junior faculty member

who was fascinated by a particular
piece of Einstein's theory...

gravitational waves.

In 1916,
Einstein himself had calculated

that objects moving through
the fabric of space-time

should cause it to ripple,
like waves on a pond.

At first Einstein thought
that these waves would be so tiny

they would be
impossible to measure.

Later in life, he was not sure
they existed at all.

If you ask me whether there are
gravitational waves or not,

I must answer that I don't know but
it is a highly interesting problem.

Rai thought gravitational waves
did exist

and has spent a lifetime
trying to find them

so he came up with a system
that could potentially detect

the most miniscule waves
in space-time.

It was called laser interferometry.

So here's the idea.

There's a laser
which is the cylinder.

There is something called a beam
splitter which divides the light.

Half of the light will get reflected
to a mirror that's over here,

and then sent back
to this beam splitter,

and the other half hits this mirror
and comes back to the beam splitter.

Then two beams will head
towards a photo detector

and you'll see something

No light goes to the photo detector.
Light cancels.

Now what happens is you change the
length on one arm, make it longer,

make the light shorter
on the other arm.

You see light does go
to the photo detector

when the paths are not equal
any more and that,

the fact that light goes
to the photo detector here,

when the paths are no longer equal

and may have been disturbed by that
gravitational wave to do this,

that's the way
the detection is made.

It's really as simple as that.

If Rai's calculations were right,

his system would be able to pick up
movements in the mirrors

of just
a few trillionths of a metre.

I heard about the idea,
I did some numbers

and it was obvious that Rai
had gone crazy or something.

I just couldn't believe
that he could really,

anyone could really pull this off

and then I spent the rest
of my career eating crow

and trying to help him pull it off.

When Kip Thorne,
a theoretical physicist

and close friend of Stephen Hawking,
joined the project,

his job was to work out whether there
were any events in the universe

powerful enough to produce
gravitational waves

that Rai's system could detect.

As a theorist,
I had the best handle anyone had.

It was not a great handle

but the best handle anyone had
on the strengths of the sources.

What Kip needed was a source
of gravitational energy

so strong it would shake the fabric
of the entire universe,

the sort of energy
that would be released

if two black holes collided.

You began with two massive stars.

This one collapsed
and formed a black hole

and then later that one collapsed
and formed a black hole,

and then create a binary
going around each other.

That binary emits
gravitational waves,

spirals the other closer and closer
and the black holes collide.

But we'd never seen
pairs of black holes.

We couldn't see pairs of black holes

because black holes
don't emit any electromagnetic waves

as they go round each other, they
only produce gravitational waves,

so the only way we would ever
see them was with our detectors.

To try to detect the gravitational
signals from colliding black holes,

Kip Thorne and Rai Weiss embarked

on one of the most expensive
scientific ventures ever attempted.

After years of planning,

construction started in Livingston,
Louisiana in 1994.

The lasers would be fired
up these arms,

each four kilometres long,

before reflecting off the mirrors
and returning to sensors

so finely tuned they could in theory
detect a shortening of the arms

caused by gravitational waves

of just a million million millionth
of a metre.

Three thousand miles away
in Hanford, Washington,

an identical facility was built.

For any detection to be confirmed,

it would have to be picked up by both
detectors at the same time.

The instruments were activated
in 2002.

For eight years
they listened to the universe.

By 2010, they had heard
absolutely nothing.

For the LIGO team,
the pressure was mounting.

We had convinced the NSF
and Congress

that they should spend
a billion dollars on this

and we had nothing to show for it.

Doubling down, they shut the project
for another five years

to install an even more precise
set of detectors.

It was a high stakes gamble.

In September 2015,
almost exactly a hundred years

after Einstein published
his theory of general relativity,

Rai Weiss's detectors
were reactivated.

Just two days later, both sites
recorded an unusual signal.

Ladies and gentlemen, we have
detected gravitational waves.

We did it!

After working on the problem
for almost fifty years,

it was a massive vindication
for Rai and his friend Kip.

I want to first remind you
of Einstein's 1915 big discovery,

was the, really the formulation
of these field equations.

He applied these field equations
to the idea of gravitational waves.

Almost the first day
of the real run,

we saw what is in front of you
on the screen here,

and let me play it for you.

That isn't much. It's a little blip.
That's all you heard.

But let me change, this is a trick.

We made it
so that you can hear it better

by changing the frequency
of everything.

And that chirp is the characteristic
of this particular source,

and that was something
which was quite astounding to us.

Long, long ago, in a galaxy
far, far away, a pair of black holes

each around thirty times
the mass of the sun

circled each other,
moving faster and closer.

The point when we first see
the gravitational waves,

they may be
a thousand kilometres apart,

each one roughly
a hundred kilometres in size

and they're going around and around

creating stronger and stronger
warping of space and time.

As they near each other,

they warp space and time in a wild
way, very much like a storm at sea.

And then, the black holes coalesce.

In that instant,
three times the mass of the sun

is converted into pure energy...

but none of that energy
is emitted as light.

It is all released
as gravitational waves.

So there's a huge amount of energy.

Turns out to be fifty times higher
than the total power output

of all the stars in the universe
put together.

By far the largest explosion
in terms of power output,

except the Big Bang,
that we ever had any evidence of.

As they travel through space at the
speed of light, the waves dissipate,

getting smaller and smaller
until 1.3 billion years later...

they passed through Rai's detectors.

I wish I could have
told Einstein directly

that we had seen a black hole
doing this.

That would have been
just a wonderful experience,

to see the expression on his face
after we'd told him that.

The discovery of gravitational waves

is the ultimate triumph
of Einstein's theory of relativity,

a theory that has been repeatedly
tested and proven to be correct.

Einstein died in 1955.

In just half a century, he had
re-imagined the entire universe.

Albert Einstein enters the world
when it's one way

and by the time he leaves the world,
it's completely different.

We now live in a world

where we understand
the universe had a beginning

and we can tell
how long ago it was.

Those are stunning achievements
and stunning shifts,

both in our scientific
and our cultural perspective.

He was a figure that is rare,
you know, once in a hundred years,

maybe once in five hundred years.

Stephen Hawking's greatest
contribution to physics

was his discovery
that black holes could evaporate.

If his theory of Hawking radiation
was correct,

it would have profound implications

for the way we understand
the entire universe.

In Haifa, Israel,
Jeff Steinhauer has spent a decade

searching for evidence
of Hawking radiation,

using artificial black holes
that he makes out of sound.

So here we go.
All the equipment that you see

is for the sake
of this small point right in there

where the artificial black hole is.

We start out with these very cold
atoms in this tube-like volume

and it's only .1 millimetres long.

We then apply a blue laser beam
which causes some of the atoms

to be accelerated to supersonic
speed and so in this region,

they're flowing slower
than the speed of sound

and here they're flowing faster
than the speed of sound.

So here, in the supersonic region,

a sound wave trying to move against
the flow will actually fall back.

It can't go forward
against the very fast flow.

In his artificial black hole,
Jeff has created an event horizon.

Once the sound wave is over
that line, it cannot escape,

just as light cannot
escape a real black hole,

and when Jeff takes photos
of his sonic event horizon,

he sees something very strange, the
tell-tale signs of Hawking radiation.

You see this band?

This band is an observation
of sound waves being emitted

from the horizon of the black hole.

This experiment is the first time

that Hawking radiation
has been observed.

It is an amazing discovery which
suggests that Hawking radiation

may be a fundamental feature
of black holes.

If that's true,
it means that given enough time,

all black holes will evaporate

and that prospect has troubling
implications for the rest of physics.

A central principle of all physics,

in fact it's written into
the laws of quantum theory,

is that information
cannot be destroyed.

Consider this newspaper.

It has information on every page

and if I were to throw it
on this fire,

it's quickly consumed by the flames

and it looks like the information
is destroyed

but if I were able
to take all the ashes,

collect all the smoke
and all the heat,

and analyse and reconstruct
the past of all the particles,

then I should be able
to reconstruct what's on every page.

And this is because
the laws of physics allow us

to tell the entire future
and the entire past of any system.

No one's saying it's easy

but it is possible as long
as you have all the information.

We call this determinism.

Scientists believe that
the principle of determinism

applies to all systems,
no matter how big or complex.

It should even apply
to the entire universe.

So if I were to somehow
know the position and state

of every particle in the universe,

I could apply the laws of physics

and know the entire
future of the universe

and the entire past of the universe.

But there is a catch because if,
as Hawking predicted,

black holes could evaporate in such
a way that they leave behind

no trace of the material
that was inside,

then information could be lost

and even if only a small amount
of information is lost,

then everything is lost.

You can't re-construct the past
and you can't predict the future.

It seems trivial but actually
it was a massive problem

that shook
the very foundations of physics

and this became known
as the information paradox.

If determinism, the predictability
of the universe,

breaks down with black holes,

it could break down
in other situations.

Even worse,
if determinism breaks down,

we can't be sure
of our past history either.

The history books and our memories
could just be illusions.

It is the past
that tells us who we are.

Without it, we lose our identity.

The information paradox has troubled
physicists for decades.

If Hawking was right

and black holes did destroy
the information they contained,

then they would also destroy
almost everything we know

about modern physics.

It created this big rift

between those who were adherents
to quantum thinking

and those who were
adherents to relativity,

the quantum people saying
the information must get out.

We don't know how,
we don't see how, but it must.

And the relativists saying
you know maybe,

maybe the information's just lost.

I'm inclined to suspect

that information is truly lost
down black holes

but mine is the minority
point of view.

Who cares if black holes evaporate

and swallow little bits of
information as they go?

But in the forty-plus years
since then,

it's kind of been like a snowball.

The importance of this problem
has grown and grown.

The information paradox was a problem

that Stephen Hawking worked on
for over four decades

and in 2015, he came up with
a major breakthrough.

Many scientists felt that
information should not be lost

but no one could suggest a mechanism
by which it be preserved.

The arguments went on for years.

Finally, I found what I think
is the answer.

I realised that a black hole
can store the information

in what is called super-translations
of the horizon.

Hawking's new idea was that as
objects fall into a black hole,

they disturb the event horizon,

leaving behind
a pattern of turbulence

which could preserve the information

about everything
that's fallen inside.

I am now working with my colleagues,

Malcolm Perry at Cambridge, and
Andrew Strominger at Harvard,

on whether this
can resolve the paradox.

If information
is stuck on the horizon,

it has not fallen
into the black hole

and you can't directly observe it
from outside

but what will happen is it will
influence the Hawking radiation

that comes out of the black hole

and that may be enough to help you
resolve the information paradox.

When we first came upon it,
we were up until late at night.

He said he hadn't been
this excited in forty years...

and he started working on it
basically full time.

Together, the scientists wrote
three papers on the subject...

edging closer to a solution
to the information paradox.

It was Hawking's last great idea.

Sadly this is the last paper
that Stephen wrote.

He was fully engaged with it
right till the very end.

Hawking died in March 2018
at the age of 76,

over half a century after he had been
given just two years to live.

He was kind of magical to be around.

When I miss him the most
is when we figure something out.

I'd like to tell him.

Such was his contribution to science,

his ashes were interred
in Westminster Abbey

alongside Isaac Newton
and Charles Darwin.

Stephen was one of the great minds
of the 20th century

in terms of his impact
on our understanding

of the laws that govern
the universe.

I miss Stephen greatly.

It was a tremendous loss
for me personally.

His gravestone engraved

with the equation describing
Hawking radiation.

Stephen Hawking's legacy
will clearly be a vital part

in the unfolding story

of putting gravity
and quantum mechanics together.

And as we go forward,
everything that we do

in some sense will go right back
to Stephen Hawking.


We think of it
as regular as clockwork,

ticking out the steady
progress of the universe,

but time is not constant.

It holds the key
to the secrets of the universe

and the two people who helped us
unlock those mysteries

are joined by
a cosmic coincidence of timing.

On March 14th 1879,
Albert Einstein was born.

Einstein gave to us all
a set of tools

that literally help us organise
the world around us to this day.

And on March 14th 2018,
Stephen Hawking died.

I think Stephen should be remembered

as one of the most remarkable people
of the 21st century.

He is someone who in a thousand
years from now will be remembered.

His name will be known.

That's not true for most of us.

Between them, they have transformed
our understanding

of the entire universe.

As a working physicist,
I look at these two giants

and I have nothing but gratitude.

They revealed the world to be so
much more than it would have been,

and without them,
who knows if we would have gotten

to this wondrous stage
in our understanding.

I have a real feeling of achievement

that I made a modest but significant
contribution to human knowledge

despite my condition.