Universe (2021) s01e02 Episode Script

At this precise moment,
on a planet far, far away
an alien sunrise ushers in a new day.
But will alien eyes gaze upon it?
Or will it go unseen?
Just another moment
in a vast sterile universe.
The hunt is on for the answer.
Magnificent desolation.
- Beautiful view!
- Isn't that something?
The Milky Way.
Hundreds of billions of stars
spread across
100, 000 light years of space.
Among them the Sun,
with eight planets orbiting around it,
including our home.
Until very recently, these were
the only worlds we knew of.
The only planets
we could hope to explore
for signs of life beyond Earth.
When I first got into astronomy
back in the 1970s,
we knew of no planets
beyond our solar system.
We didn't have the technology
to detect them, even if they were there.
Our neighbourhood was the only place
we could look for life.
And so the hunt for life began
in our own backyard.
Over the last few decades,
multiple missions have explored
our solar system's planets.
And even some of their moons.
But to date,
even as we continue to look,
no convincing evidence of life has
been found on any of these worlds.
Earth remains one of a kind.
The only living world around the Sun.
But as the exploration
of the solar system continued,
another search had begun
for worlds that lie
far beyond these shores.
You know, the wonderful thing
about astronomy is
that as we develop better
and better technology
and accumulate more and more knowledge
about our universe,
we turn more and more of these points
of light in the sky into worlds.
I mean, that we've known is
a world for a long time,
because that is the planet Mars.
But just above Mars tonight is
a constellation called Pegasus.
This is the square of Pegasus.
And we now know that around there is
a star called 51 Pegasi,
which has a planet orbiting around it,
a gas giant about the size ofJupiter,
that goes round that faint point
of light every four days.
It is wonderful to think
that, in my lifetime,
in fact in my adult lifetime,
in the last 25 years,
we've gone from a universe
that could have been
devoid of planets beyond
our solar system,
to a universe that we know
is teeming with places
that we can search for life.
Over the last three decades,
some of the most powerful telescopes
on Earth havejoined the hunt,
searching for planets
unimaginably far away,
hiding in the dark.
Planets like 51 Pegasi b.
The first world outside our solar system
to be detected around a Sun-like star.
51 Pegasi b is a gas giant,
around half the mass ofJupiter,
but far closer to its star.
Just imagine what that world
might be like.
A world with skies torn
by titanic winds,
where its hot interior is
bathed in rain of sapphires.
In every sense,
51 Pegasi b is an alien world.
And we soon discovered that the galaxy
is full ofplanets
unlike anything seen
in our solar system.
Planets enveloped by fierce radiation.
Their surfaces battered and stripped
by the high energy strobing light
of their star.
Worlds so cold
their atmospheres are frozen solid.
Or great swollen planets,
with the density of Styrofoam.
And fathomless atmospheres.
These discoveries prove
that in one sense
we really are not alone.
There are other worlds out there
waiting to be explored.
We estimate
that in the Milky Way Galaxy,
there are more planets than stars.
Hundreds of billions of them.
That's hundreds of billions
ofplaces to look for life.
But there's a catch.
Because not all worlds,
by a long stretch,
are like this one.
The first planets we found appeared
too bizarre,
too large,
and often too close to their stars
for living things to survive.
To find worlds where life could exist,
we needed to look
for smaller, rocky planets
in orbits further from their stars.
T-minus ten,
nine, eight, seven
We needed to look
for another earth.
three, two,
engine start, one, zero,
and lift off
of the Delta II rocket with Kepler
on a search for planets
in some way like our own.
So the hunt moved to space
with the launch
of NASA's Kepler space telescope
And we have separation.
searching for Earth-like worlds
in the galaxy beyond.
Kepler crossed 94 million miles
of space,
until it arrived in a steady orbit
around the Sun,
from where it looked out
with a fixed and clear gaze,
to a single patch of sky
in the constellation of Cygnus.
Exposing its sensitive light meter
to the light of 150, 000 stars,
it began to look
for Earth-like alien worlds.
Kepler doesn't detect planets directly.
They are far too small.
They'rejust specks of dust
relative to their parent star.
They're also very faint.
They don't emit light of their own,
so theyjust glow very dimly
in the reflective ambient light
of their stars.
So Kepler has
to detect planets indirectly.
Imagine that a moth just flew
across the beam of light
from the lighthouse.
And I wouldn't see the moth.
But if I had a sensitive enough detector
and everything was lined up properly,
I might just see
the brightness of the light dim.
And that is how Kepler detects planets.
Imagine there's an alien astronomer
in some distant solar system
looking back at the Sun,
and everything's lined up
so they see the Earth trace across
the face of our star.
They would see
the light from the sun dim
by one hundredth of one percent.
It's a tiny amount, but it's enough.
And if they saw
that dimming was regular,
if they saw the star dim
once every year in this case,
then they would infer
that there's a planet orbiting
around the star.
With its exquisitely sensitive
light meter,
Kepler sees only
the regular dimming ofpixels.
Just a few bits of information.
But from those bits, astronomers can
begin to build a picture
of the worlds that dim the starlight.
Worlds that might, in some way,
resemble our own.
Worlds like Kepler-36b.
The planet was
one of Kepler's earliest discoveries.
Orbiting a star similar to our own,
we'd found a world that at first glance,
might seem familiar.
Weighing in at around four times
the mass of our own planet,
Kepler-36b was one of the first
of a new class ofplanet,
a Super-Earth.
The Kepler data doesn't
just allow us to say
there's a planet around that star.
It allows us to characterise
those planets.
So, by looking at the precise way
that the light fades
and then rises again,
and the timing between the dips,
we can measure the orbit of the planets.
And if there are multiple planets
in the system,
we can even estimate their masses.
So, the Kepler data allows astronomers
to paint a picture
of the worlds it discovers.
But the more detailed our picture
of Kepler-36b became,
the less Earth-like
this super-Earth appeared to be.
It orbits very close to its star,
circling once every 14 days.
And, it has company.
A gigantic gaseous companion
with an orbit unusually close
to its smaller sibling.
The proximity of both its star
and sister planet,
allows us to imagine
the bizarre conditions
that may exist
on the surface of Kepler-36b.
The planet may be tidally-locked,
which would mean that one hemisphere
always faces the star.
On this side, the punishing heat could
turn the ground molten,
creating rivers of lava that would
criss-cross the surface.
The planet could experience
violent eruptions
as the gravitational pull
of the gas giant triggers
intense volcanism,
each time it passes by.
But Kepler-36b could
also be a planet of ice.
Because if it's tidally-locked,
the far side would face permanently
away from the star.
And we could imagine
a freezing, cold hemisphere
shrouded in eternal darkness.
For now, this is all
just informed speculation.
But we are beginning to build
a picture of these worlds.
I mean, imagine a world
where the sun stays at the same point
in the sky forever.
So, one side of the planet is
in eternal night
and the other side in eternal day.
And even the twilight strip
between day and night,
we think, would suffer
from extreme conditions.
So, Kepler-36b just goes to show
there's so much more
to having a habitable world
than just the composition of the planet.
There's the details of its orbit,
and also the nature of the other objects
in the solar system
that are orbiting
around the star with it.
Kepler-36b isjust one
of thousands ofplanets
that Kepler has discovered.
We now know beyond doubt
that our galaxy is home
to a diverse collection of alien worlds.
Each one of the over 4, 000 planets
that we've discovered to date,
is different from all the others.
They really are an alien
and exotic bunch,
and there's certainly no planet
that's identical to the planets
that we know of in our solar system.
And I think that reveals a deep truth
about the universe.
Because although the laws of nature
that form the planets are simple
and the same everywhere,
and the fundamental ingredients
out of which the planets are made,
are simple and the same everywhere,
the nature of a planet also depends
on the history of its formation,
and the environment
around its parent star,
out of which the planet formed.
And those are all radically different.
So, each planet has
a different story to tell.
I suppose in that sense,
planets are like human beings.
And this wholly unexpected
but exciting discovery
certainly complicates
the search for life.
We needed to narrow the search
for planets further,
but not too far away
from their parent stars.
Planets atjust the right distance
for their surfaces
potentially to be habitable.
Alien worlds
with one precious ingredient
that makes Earth a living planet.
Now, you might legitimately ask
can we transfer all the knowledge
we have of life here on earth
to planets elsewhere in the universe?
Well, I would answer emphatically
"Yes, we can,"
because the laws
of nature are universal.
So, the laws of physics
and chemistry that underpin biology
here, on this planet,
will apply to every planet
out there in the universe,
whether we've discovered it or not.
The chemistry of life requires
a few basic ingredients.
Carbon, nitrogen, oxygen, iron.
And it also requires a ready supply
of high quality energy
from heat within the planets
or perhaps from starlight.
But life here on earth also requires
one very important fundamental
extra ingredient, which is liquid water.
Liquid water is
a deceptively complicated substance.
It's a very powerful solvent.
But it also has structures
which are constantly forming
and disappearing within it,
which act as a kind of scaffolding
around which biology happens.
Organic molecules are
orientated by that scaffolding
so they can react together.
Now, it is certain
that every living thing
here on Earth requires
liquid water to survive.
And I would say it is
a very good assumption
that every living thing anywhere
out there in the universe
will require it, too.
The universe is filled with water.
Great reservoirs have been detected
throughout the galaxy,
amongst the gas clouds ofgiant nebulae.
Butjust because water is plentiful,
that doesn't mean
that it necessarily ends up
in oceans on planetary surfaces.
Of the eight planets
in our solar system,
only one has liquid water flowing
permanently on its surface today.
An ocean world where,
long ago, life began.
Around four billion years ago,
life on Earth would have begun
probably in places
not dissimilar to this,
where there's geothermal activity,
a source of energy,
in contact with rich concentrations
of reactive chemical elements
and minerals, but also crucially, that.
The magical solvent, liquid water.
Now, many rocky planets out there
in the galaxy will probably have this,
but far fewer, we think, will have that.
Large bodies of liquid water
on the surface.
So, that's why
there's a kind of a catchphrase
in the astro-biology community,
which is if you want to search for life,
follow the water.
Whilst life on Earth was evolving,
124 light years away,
amidst a collapsing cloud
ofgas, dust and ice,
a small star was born.
And the cloud's
swirling leftovers condensed
to form a brand new world.
In 2015, Kepler found a planet
orbiting comfortably
within its star's habitable zone.
More than eight times
the mass of the Earth,
K2-18b is a giant,
with a powerful gravitational pull.
If the planet is rocky,
this may have allowed it to hang on
to a thick atmosphere.
K2-18b might have
all the makings of a water world.
And a legendary space telescope had
Kepler's new discovery in its sights.
The most powerful space telescope
of them all
hadjoined the hunt.
Hubble examined the light
from K2-18b's parent star,
as the planet passed in front of it,
and detected, what may be,
a faint signature
of water vapour.
124 light years from Earth,
we may have, at last, found
the evidence of water
on an alien world.
This was the first observation
of water vapour in the atmosphere
of a planet orbiting
in the habitable zone around its star.
Now, admittedly, measurements
of the amount of water vapour
in the atmosphere is pretty wide.
It's somewhere between 0.01 percent
and 50 percent.
I mean, this is a planet
that's a long way away.
But, for comparison,
our planet has a few percent
water vapour in its atmosphere.
So, that observation is important
for two reasons.
One is, it is not zero.
There is water vapour in the atmosphere.
But, secondly, if the measurement
is at the lower end,
a few percent of water vapour
in the atmosphere,
then that is consistent
with this world being a planet
with oceans on its surface.
The nature of this planet is
currently the subject
of intense scientific debate.
The planet may be
more like a mini-Neptune,
a gas planet.
But, it is possible to dream
of a rocky alien world
with skies full of clouds,
where water droplets collect,
and eventually fall,
feeding vast oceans
that cover the surface
of a massive planet.
A water world,
where the elixir of life
is in plentiful supply.
K218-b is exciting
because it's the smallest world
with an atmosphere
that we've been able to analyse.
And we've found
that its mass and density,
and composition of its atmosphere,
and it's orbit are consistent
with it being a world with water.
And it might be a world
with oceans on its surface.
We don't know for sure,
but just imagine
what that small, faraway world
around a faint red star might be like.
Kepler went on to make
many more discoveries
until, in October 2018,
it finally ran out of fuel.
After nine years, it had found
over 2500 alien worlds
showing usjust how common
potentially Earth-like planets might be.
We estimate that there may
be around 20 billion
potentially Earth-like worlds,
that's rocky planets
in the habitable zone around a star
that may support liquid water
on the surface, in our galaxy.
That is 20 billion
potential homes for life.
Now, we don't know the probability
that given the right conditions,
life will begin on a planet.
But we do have evidence, from our world.
What we know is that here on Earth,
life began pretty much
as soon as it could
after the Earth had formed
and cooled down,
and the oceans formed on its surface.
So that might suggest
that whilst there isn't
a sense of inevitability
about the origin of life
given the right conditions,
it might, at least,
be reasonably probable.
So, I think that there is
at least a chance
that life may have begun
on some, perhaps many,
of those 20 billion Earth-like worlds
out there in our galaxy.
But, I think there are
two questions about life.
One question is about the origin,
and the existence of microbes,
but often, when we speak about aliens,
what we really mean is not microbes,
but complex creatures.
Indeed, things that we can
speak to, civilisations.
What is the probability there will be
other civilisations out there
in the Milky Way?
Well, again, the answer is,
we don't know.
But there are observations we can make.
Patterns we can see in the Milky Way
that might allow us
to make an educated guess.
We don't know precisely
how we highly-intelligent
complex creatures came to be here.
But, we do know, for certain,
that life on Earth didn't
begin this way.
We are the product of a story
that has been playing out
for over a quarter
of the age of the Universe.
From microbes
to a global technological civilisation,
reaching out for others.
For now, at least,
we remain surrounded by silence.
The messages we've sent out
into the cosmos remain unanswered,
and the telescopes we use
to scan the skies
for alien signals remain quiet.
Now, that's not to say, of course,
that there aren't
other civilisations out there.
We may have been looking
for the wrong thing, in the wrong place.
But I think the answer to the question
of the great silence can be found here,
on Earth.
Because, here, it took
four billion years of stability
for a civilisation to emerge.
That is a vast amount of time.
And when we look to the other worlds
out there in the Milky Way,
it's those two things,
stability and time,
that appear to be
very rare commodities indeed.
In 2013, the European Space Agency
launched the Gaia Space Telescope.
Its mission, to survey the stars
of our galaxy, the Milky Way.
Billions of stars have been mapped.
Each star, a potential host
for alien worlds.
And patterns are
already beginning to emerge.
Not all stars exist alone.
Some have company.
And, bizarre as they seem,
Gaia has discovered around a million
of these binary
or multiple star systems.
We've known for a long time
that binary star systems,
and indeed, multiple star systems exist,
but we didn't know
precisely how common they are.
But now, we have
a huge amount of high-precision data,
including the Gaia data, which tells us
that around 50 percent
of all sun-like stars are
in multiple star systems.
And for more massive stars,
that number is 80 percent.
So, how does the prevalence
of multiple star systems in the galaxy
shift the odds in the hunt
for another Earth?
Could Earth-like planets exist
in multiple star systems?
And, if so, what might their fate be?
In 2020, we may have found a clue.
A planet the size of Mars, floating
freely through the galaxy.
A so-called rogue world.
But planets can't form alone
in interstellar space.
So, where did it come from?
Dawn
ushered in not by one star
but two.
Perhaps the rogue world grew up
in a close binary system.
Subject to the gravitational pull
of two stars
its orbit may have been unstable
as its parent stars fought
to control its destiny.
But, even in single star systems,
the weak gravitational interactions
between the planets
can change their orbits.
Now, in a double star system,
the planets are not only subjected
to the gravitational pulls
of each other,
they're subjected
to the stronger gravitational pull
of another star.
So, even if a planet gets
into a stable orbit,
it's very likely that it won't
stay in that orbit for long.
So, in double star systems,
the line between order
and chaos is very thin indeed.
Even subtle changes
in a planet's orbit can lead
to dramatic changes in climate.
And that's why the surface conditions
on planets in double star systems may
be unlikely to remain
stable enough for long enough
for intelligent life to evolve.
And the changes
in the orbits ofplanets can
sometimes be anything but subtle.
A close encounter
may have given the rogue world
a final gravitational kick
flinging it outwards
and releasing it
from the grip of its parent stars,
setting it loose
on a journey through the galaxy.
Far from the warmth of its stars,
any liquid water the rogue world
might once have had
would have frozen solid.
Any atmosphere that once protected it
would have frozen out onto the surface.
The rogue would have become a world
with conditions
that no living thing could endure.
An entire planet alone and adrift,
only to be detected by us,
millions ofyears later.
A small Earth-like rogue planet
roaming the darkness of space
for eternity.
This lonely, wandering planet is
not a unique world.
Although rogue planets are
very difficult to detect,
it's estimated that there may be
over 100 billion of them in our galaxy.
Rogue planets might be
the most common type of planet
in the Milky Way.
And, although we think
most of them were torn away
from their star soon after formation,
this does suggest that star systems are
not always stable places,
where complex life could evolve
over billions ofyears.
Our hunt for another living planet has
onlyjust begun.
Yet, we've already learnt so much.
We found our first rocky worlds.
Some in the habitable zone
around their stars.
Some, potentially,
with liquid water on the surface.
Candidate worlds for future missions
to search for evidence of life.
But we've also found hordes
of bizarre, tortured worlds,
orbiting around violent stars,
and a multitude of rogue planets
where complex life,
as we understand it, seems impossible.
Perhaps it's these worlds
that hint at the reason why,
for now, one planet stands apart
alone.
Our planet seems to have
largely escaped the violence,
the chaos, and the constant change
that seems to characterise
a galaxy like the Milky Way.
Yes, there's been
the odd mass extinction,
but there's been
an unbroken chain of life here on Earth,
stretching back four billion years.
And if that's what you need
to go from the origin of life
to a civilisation,
then, although there may be billions
of worlds out there where life began,
there may be very few civilisations.
But that's just an opinion.
It's an educated guess.
And, given the profound nature
of the question,
no matter how educated the guess,
I think it would be ridiculous
for us to stop looking
both inside our galaxy and beyond.
For, we may havejust received
the first glimpse
of a world beyond the Milky Way
around 30 million light years away,
nestled in the spiral arms
of the Whirlpool Galaxy.
A world the size of Saturn.
A find that marks
an expansion of our horizons.
The beginning of the hunt
for extra-galactic planets.
The potential discovery
of a planet orbiting around a star,
in another galaxy is something
that I never thought I'd see.
And it opens up
the intriguing possibility
that we might be able to explore
not only the question,
"Are we alone in our galaxy?"
but, "Are we alone in the universe?"
And the answer to that question
may lie far in the future.
We might never answer that question.
But I said, the question
"Are we alone?" is profound,
because answering it would teach us
much more
about what it means to be human.
Well, I think we become
a little bit more human
with every world that we explore,
because that ability
to lay the foundations,
to explore questions to which we may
never receive answers in our lifetime,
questions for our children
or our grandchildren to answer,
is a fundamental part
of what it means to be human.
It's a fundamental part
of what makes us so special,
here on this little world,
looking up at the stars,
whether we're alone or not.
Five. Four. Three. Two.
Engines start. One. Zero.
And, lift off
of the Delta II rocket with Kepler,
on a search for planets,
in some way, like our own.
We had worked together, thousands
of people worked together,
and it's all coming together.
And we have separation.
It was so emotional to see
the project they had worked on
for so many years or decades
finally go to space,
and all that hope and promise,
all bundled up in the machinery.
Kepler was an immediate success,
discovering over 2, 000 new planets
in its first four years of operation.
But in the summer of 2012,
the team faced a challenge
that threatened the entire mission.
One of the things that
the Kepler Mission needs to operate
are reaction wheels
that spin and hold it on target.
So, it always points
at the same stars, and doesn't jiggle.
Well, we had four wheels that did that.
And we knew that we only
had a couple of spare gyroscopes,
and we knew that spacecraft tend
to have gyros fail.
And, after a while, it failed.
Three months later,
the second one failed.
And, since we needed three,
we could no longer look
at the Kepler field of view.
I had hope that they'll figure out
a way to work with two gyros,
and, indeed, they did.
So, the very clever people,
the engineers and scientists said,
"What we can use, is we'll use
the sunshine for the third wheel.
"We'll make this thing
reflect sunlight off it,
"we'll use the other two wheels,
and now, we can point in the sky."
The faint pressure of sunlight
helped stabilise the telescope.
That was, kind of,
good news, actually,
because it meant Kepler was gonna
have to go off the Kepler field now,
and we could get all kinds
of other stars and observe them,
and so, it actually was a boon
for stellar astronomy.
After another four years
of discoveries,
in total, it had found
over 2, 600 planets,
making it, by far, our most successful
planet-hunter to date.
It was sad when they sent
the command to shut everything down.
You know, it's asleep now.
It's in orbit around the sun.
It will continue that orbit.
But, since it launched from Earth,
it will come back to Earth.
It will come and visit us again
in about 40 years,
and my hope is people will say,
"This is a historic telescope.
It told us about all these planets",
and they will go up
and pick up this telescope
and bring it back to Earth,
and put in the Air and Space Museum
for us all to admire.