01x02 - Aliens: Are We Alone?

[bunniefuu]

For more than a decade,

I've made
programmes about the universe...

...and our place within it.

There it is! There it is!

I can see the parachutes.

I've had some remarkable
encounters...

I can't believe you can just stand
next to a spacecraft.

Release.

...memorable experiences...

They came down exactly the same.

Wow.

MUFFLED SHOUTING

...and explained some beautiful
science about how our planet works.

That really is the thin blue line
that protects us.

Look at that!

Now I'm taking a new
look at those past programmes.

It's surely as close as I'm
going to get to being in space.

I think our knowledge really has
moved on since we made these films.

So it's really interesting to
revisit some fundamental

questions again.

Are we alone in the universe?

What really is gravity?

Where will the exploration
of space take us?

And what is time?

BEEPING

Beeping's never good.

I'm back at the historic
Royal Institution

to re-watch some of my previous
films...

...and explore one of the most
profound questions we can ask...

...are we alone in the universe?

Arthur C Clarke famously said,

"Two possibilities exist.

"Either we are alone
in the universe,

"or we are not.

"Both are equally terrifying".

There are certain
questions in science that,

if we can answer them, I think will
have profound cultural ramifications

and the question, "Are we alone?"
is one of them.

And to be able to answer that,
I think

will change our view of our place in
the universe in a very profound way.

It's one of the most common
questions I get asked -

"Do you believe in UFOs?"

"Do you think there are aliens
out there?"

People of my generation, certainly,

I think we'd all like ET to be real.

ET, by the way.

I don't really want
Darth Vader coming down,

but I would like ET to arrive.

And as we send spacecraft to
explore the solar system,

we're beginning the scientific
search for alien life.

Just knowing that we are not alone,

that life exists elsewhere would,
I think,

be one of the greatest
discoveries in human history.

DRUMS AND SINGING

We have long sought to
communicate with beings

out there amongst the stars.

DRUMS AND SINGING

In New Mexico, the Navajo tribe
believe the stars

are home to another consciousness.

Once a year, they come together to
communicate with this entity...

DRUMS AND SINGING

...in a healing ceremony called
Yeibichai.

It's a nine-day long
festival of ritual and chanting...

...the most sacred of which is the
night chant,

performed by medicine men
in private,

never filmed,

and recorded just once.

WINDING

MUSIC PLAYS

This recording was made by Willard
Rhodes of Columbia University

in the early 19405...

SINGING

...and he could not have imagined
what was going to happen to it.

MUSIC CONTINUES

In 1977, the recording was
transferred onto four golden records

and encased in these covers.

Today, only two of them
remain on planet Earth.

The other two are bolted to the
sides of two space probes -

Voyager 1 and Voyager 2 -

and are
now travelling into deep space.

Accompanying the night chant are an
eclectic mix of images

and sounds from Earth.

ARCHIVE: Shalom.
Konnichiwa.

OPERATIC SINGING

The choice of images and sounds,
music, is very important

because it's a snapshot
of how we feel about ourselves.

It's what how would we like to
represent ourselves

to alien civilisations out there?

What ideas do we want to
communicate?

What music from Earth
and sounds from Earth

and pictures would
we like someone to find?

The Voyagers' primary mission

was to explore the outer planets
of the solar system...

...but adding the discs gave
the spacecraft an extra purpose.

They've become Earth's emissaries,

carrying postcards to our alien
neighbours,

if they exist.

I think the wonderful thing
about the act of putting images

and sounds and the songs
of Earth on this spacecraft

and sending it off
into interstellar space

is that it speaks to our need,
in a sense, not to be alone.

MUSIC: Johnny B Goode
by Chuck Berry

♪ Deep down in Louisiana close to
New Orleans

♪ Way back up in the woods among
the evergreens

♪ There stood a log
cabin made of earth and wood... ♪

The sounds of Earth may wash
up on a distant shore.

♪ Who never ever learned to read
or write so well

♪ But he could play a guitar
just like a-ringin' a bell

♪ Go, go... ♪

The question is,

will there be
anyone around to listen?

If you're going to look for life
beyond Earth

out there in the universe,

you have to know what life is

and you have to know how
to look for it.

And the best way to do that,
by far,

in fact, the only way to do that

is to understand life here on Earth.

WAVES CRASH

Floating in the Sea of Cortez
off the coast of Mexico is

the research vessel Atlantis -

the mothership for the exploration

of one of the most alien
worlds we know.

But it's an alien
world on our planet.

The Atlantis is the launch
vessel for Alvin,

one of the world's most rugged
submarines.

Built like a spacecraft,
it's designed to explore

the deepest depths of the ocean...

...and I'm lucky enough to have
hitched a ride down

to the sea floor, 2km
beneath the surface.

CHUCKLES

ARCHIVE: That has honestly got to be
the closest thing

to going into space
that you can do,

and given that I'm not going to go
into space any time soon,

I think this is the next best thing.

See you in eight hours.

INDISTINCT INSTRUCTION

WINCH SQUEAKS

WATER BABBLES

The parallels to
space flight are obvious.

As the tiny capsule descends,

we're leaving the familiar
world of the surface of our planet

and entering a strange,
hostile world.

MUFFLED SPEECH OVER COMMS

If anything goes wrong,
we will be completely on our own.

It's very rare that you get to do
something so challenging

and so alien,

and to be taken to that
environment in the very deep ocean,

it's strange

and silent and unusual.

And it's tiny, as well.

Erm, so there's three people
crammed into this little

titanium ball, which kind of
creaks a bit as it goes down!

BEEPING

Beeping's never good!

BEEPING CONTINUES

BEEPING STOPS

MUFFLED SPEECH ON COMMS

At the Earth's surface, we're used
to one atmosphere of pressure.

As we descend,
the pressure increases by another

atmosphere every ten metres

and it soon adds up.

RADIO COMMS:

So we're just approaching
a kilometre deep.

The pressure outside there is now,
what, 100 atmospheres?

That's higher than the atmospheric
pressure on the surface of Venus.

Without knowing,

if you're asked the question,
"Could life exist down here?" -

100 atmospheres,

...the cold, dark, no sign of
sunlight at all,

it's pitch-black there -

you would say, "No".

Well, I would say, "No".

But the depths of the ocean
are not lifeless.

Illuminated by Alvin's lights,

we find oases of life
in the deserts of the ocean floor.

COMMS:

So we've landed,
after about an hour of descent.

We've just stopped in the most
incredible place.

This underwater city is
one of the most bizarre

environments on our planet.

CAMERA WHIRS

It's built around
a hydrothermal vent,

a volcanic opening
in the Earth's crust

that pumps out clouds of
sulphurous chemicals

and water heated
to nearly 300 Celsius.

And somehow,
life has found a way to thrive

in these most extreme conditions.

Look at that!

It's not only just bacterial blobs,

it's real complex organisms.

Alien - I want to say that word.
Alien environment.

It really is alien to us.

For me, the fascinating
thing about finding life down here

is that the conditions on the deep
ocean floor

are more similar in many ways
to the conditions

on worlds hundreds of
millions of kilometres away

out there in the solar system

than they are to the conditions
just 2km above my head

on the Earth's surface.

You know, it's incredibly dark.

There's no sunlight. There's a
brutal mixture of hot and cold water

and just, well, rock and minerals,

so if life can not only survive

but even flourish
in these conditions,

then you've got to feel
that it's much more likely

that life can also survive
and flourish

out there in the solar system.

One of the main benefits, I think,

in looking at life in extreme
environments on Earth,

so-called extremophiles,

is that you
get a wider view of what life is

and what chemical elements or
compounds it produces.

And that is useful because, really,

if you think about life,
subsurface on Mars, for example,

if it exists,

we really don't know how that
life would behave.

BIRDSONG

This is the Cueva de Villa Luz
in Tabasco, Mexico,

the Cave of the House of Light,

and it is the definition of a
hostile environment

to me because
it's full of hydrogen sulphide gas,

which is why I've got this gas
mask in case it all gets too much.

Although the cave
is a deathtrap for us,

that doesn't mean that
nothing lives here.

In fact, it's teeming with life.

So you're looking for the chemistry.

You're looking for
seeing how life behaves,

that almost alien chemistry to us,
at least.

And that can tell us

what to look for when we're
searching for life on other planets.

Well, these things are what
I came deep underground to see.

These are snottites and you can see
why they're called that.

They're really one of the most alien
life forms that I can conceive of

on the Earth because
they metabolise hydrogen sulphide.

So they metabolise this faintly

acidic and nasty gas
that I'm just breathing

in now, you can almost feel it
on your tongue, actually,

the acidity of it.

These guys breathe in
hydrogen sulphide and oxygen

and produce sulphuric acid.

Every time we think we know

what the envelope within
which life can exist

is, every time we say, "Well, it's
got to be at this temperature

"and it's got to have these gases

"and it's got to have these
substances around",

then we tend to find somewhere
that proves that we were wrong

and life is rather more ingenious
than we thought.

But does that mean that life could
exist anywhere in the cosmos?

We live in a vast universe, which is
always an understatement.

It could well be infinite
in all directions.

We cannot look everywhere for life.

So we have to try

and narrow it down and make
an educated guess about what kind

of conditions might be prerequisites
for the existence of life.

If there's one thing - it's probably
the only thing that all biologists

agree on - it's that liquid water

is a prerequisite for life.

So in 2010, I visited
the driest place on Earth.

If you want to see how important
water is to life,

there's no better place to come
than the Atacama Desert in Chile.

There's soil here

that's more sterile than a hospital
operating theatre.

And in fact, scientists have looked
for the most basic form of life

- bacteria
- in some parts of the Atacama

and they found absolutely nothing.

All deserts are characterised
by a lack of moisture,

but the Atacama takes that
to the extremes.

The Sahara is 50 times wetter
than the Atacama.

There are weather stations here
that have measured one millimetre

of rainfall in ten years.

There are river valleys that have
been dry for 120,000 years

and there are rocks that haven't
seen rainfall for 20 million years.

It's this dryness that explains
why nothing can survive here.

Even the most primitive form of life
on Earth, the bacteria,

need water for their survival

and there are no exceptions

and this seemingly fundamental
link between water and life

is driving the search for life
out there in the solar system.

Since we filmed
Wonders of the Solar System,

which is now over a decade ago,
the science has moved on.

People have done research

and we have found bacteria
in the driest parts of the Atacama.

However, they're dormant bacteria.

They are a bacteria that can
survive without water,

in very arid conditions
for long periods of time.

And then if you sprinkle some water
on them, they are reanimated.

So if we accept that water is
one of the prerequisites for life,

it is necessary for life
anywhere in the universe,

then immediately you have
a search strategy.

We want to look for signs
that water was,

or maybe still is, present.

And fortunately, one of the places
where that's certainly

a possibility and
perhaps a probability, is Mars.

Mars is now the focus of
Nasa's Mars 2020 mission,

the latest of many attempts
to search for signs of life

on the planet.

In the 1940s and '50s,

serious astronomers thought
that there may be liquid water

flowing on the surface,
and even vegetation, because that's

sort of what it looks like when you
look at it through a telescope.

But the first time we went to Mars,
the results were quite shocking

to many people because
what we saw was a world

that looked like the Moon,
which is a barren,

lifeless world at first sight.

RADIO COMMS:

STUDIO: And there's the first piece
of information coming in.

And later missions offered
little encouragement.

So I think through the '70s,
there was

a fairly negative view of certainly
life existing today on Mars.

But as we've learned more
about the geology of Mars

and the history of Mars, I think
that sense has certainly changed.

And that's why we're sending
increasingly complex robotic

explorers to Mars today
to search for the conditions

necessary for life and ultimately
to search for life itself.

In 2012, NASA attempted a new
manoeuvre to land on Mars.

The payload was a one-tonne rover
called Curiosity.

Its final descent has become known
as the seven minutes of terror.

Curiosity touched down
in Gale Crater,

a 150-kilometre-wide impact basin

thought to have been home
to an ancient lake.

Then, 61 clays after landing,

Curiosity identified the perfect
spot to begin its primary mission.

In a sandy area of the crater called
"The Rock Nest"

the rover took its first
scoops of Martian soil.

WHIRRING

Chemical analysis of the
fine, dusty sand

revealed something quite unexpected.

Even though the surface of Mars
appears completely dry,

2% of the soil is still
made up of water.

Curiosity had found evidence
of just how wet a planet

ancient Mars had been.

For hundreds of millions
of years...

...Mars was a water world.

THUNDER CRACKLES

Rains fell.

Rivers ran.

And in the Northern Hemisphere,
water collected in a vast sea

that covered a fifth
of the Martian surface.

The Red Planet was once blue.

On Mars around
four billion years ago.

And the atmospheric pressure
was at least that of Earth today,

perhaps even higher.

Temperatures were around 25 degrees.

So I could have sat on Mars
all those years ago,

admittedly with a mask to breathe

because there was
very little oxygen,

but I could have sat there and
looked out over a view like that.

So you don't have to imagine
what Mars was like in the past,

you can experience it.

It was pretty much like this.

Perseverance, the rover for
Nasa's current mission to Mars,

landed in February 2021.

Manoeuvre has started.

Tango delta.

Touchdown confirmed.

Perseverance is safely
on the surface of Mars

ready to begin seeking...

So Perseverance is going to
prepare samples of Martian soil

from below the surface,
where there may be evidence

that life existed or could
possibly still exist.

And then we're going to send
another spacecraft there

to take those samples
prepared by that rover

and bring them back to Earth.

We wouldn't do that if we didn't
think there was a chance

that life had existed,
and may still exist, on Mars today.

But life needs more than
just water to exist.

When Earth formed,
there was no life.

So there had to be a genesis.

Life had to emerge somehow from
the geology of a lifeless planet.

And discovering how life
emerged here

gives us vital clues in our search
for alien life.

This is Lake Taal.

Despite its sleepy,
languid appearance,

this landscape has been
violently transformed.

When I think of a volcano, I usually
think of a pointy, fiery mountain

with a little crater in the top.

Probably a bit like that one.

But actually, this entire lake is
the flooded crater

of a giant volcano.

It began erupting only about
140,000 years ago.

This crater is 30km across
and in places, 150 metres deep,

and that's a cube of rock,

5km by 5km by 5km,

just blown away.

Taal Lake is testament
to the immense power

locked within the Earth
at the time of its formation.

Since the lake was created,
a series of further eruptions

formed the island in the centre.

And at its heart is a place
where you can glimpse

the turmoil of the inner Earth,

where energy from the core

still bubbles up to the surface...

...producing conditions similar
to those that may have provided

the very first spark of life.

The volcano transforms heat
from the inner Earth

into chemical energy and stores it

as a reservoir
of protons in the lake.

This reservoir of positively charged
particles is a natural battery.

These bottles contain a weak acid

and are connected by a
semipermeable membrane.

Passing an electric current
through them has a similar effect

to the volcano's energy
bubbling up into the lake.

It causes protons to build up
in one of the bottles.

You can think of it, I suppose,
like a waterfall where the protons

are up here waiting to flow down,
and all you have to do

to release that energy
and do something useful with it

is complete the circuit,
which I can do

by just connecting a motor to it.

There you go.

Look at that.

That's the protons
cascading down the waterfall

and driving the motor around.

It actually works!

Quite remarkable, actually!

Proton cascades once occurred
naturally at openings in the

Earth's crust called alkaline vents,

deep in the primordial oceans.

This could be where your
distant ancestors come from.

Places like these could be the
places where life on Earth began.

The first living things
might have started out

as part of the rock
that created them.

Simple organisms that
exploited energy

from the naturally occurring
proton gradients in the vents.

And today, this same flow of energy,

this waterfall of protons,

is found in the cells of every
living creature on this planet,

from a single bacterium cell,
to you and me.

We are now, as we speak,

recreating the conditions

that were present in a primordial
ocean of ancient Earth,

3.8 billion years ago

in the deep oceans close
to hydrothermal vents.

Why? Well, the theory is because
that's where we come from.

That was our home.

If life emerged in this way
from the energy of our planet,

this allows us to narrow down
the search

and send space probes to hunt
for places with similar geology.

And, in recent years,

we've found these conditions
in some unexpected locations.

I think one of the great revelations

and surprises in the exploration
of the solar system

has been the richness in the geology

and geochemistry of moons.

I think before we went,

before we flew out into the outer
solar system

to look at the moons of
Jupiter and Saturn in particular,

when you said, "moon", the
image conjured is that of our Moon,

which is, as Buzz Aldrin said,
"magnificent desolation",

but essentially an arid rock,
a lifeless rock,

geologically inactive.

We're not going to find life
on the Moon, right?

But as is always the case,

what we found when we flew to the
moons of the outer solar system

with spacecraft, is that the moons
are more interesting and varied

and fascinating than
we could possibly have imagined.

Jupiter's moon, Europa, has more
salt water in its ocean

below its icy surface than in all
the oceans of the Earth combined.

And we have found evidence of, um,

perhaps, fountains of ice

rising up from the surface.

So geological activity
below the surface, perhaps.

And if you have energy, geological
activity and you have water,

then perhaps you have life.

Jupiter's frozen moon, Europa,
is echoed in this spectacular

ice cave in the Vatnajokull glacier
in Iceland.

You see, the laws of nature

are universal and that may not only

apply to the laws of physics, but
also to the laws of biology as well.

If that's the case, then what we
find in these ice caves of Iceland

may tell us something about
what we could expect to find

below the frozen surface of Europa.

Now, it's hard to describe
this place.

I mean, it's absolutely magnificent.

Visually, the quality of the ice,

it's just completely transparent
and clear.

You can see straight through it.

It's what astrobiologists find
in this ice that makes us think

that Europa could be
teeming with life.

FAINT HAMMERING

NASA scientist, Richard Hoover,

has spent his career

looking for life in unlikely places.

Well, that went very well.

OK. So will any organisms
that you find in that ice

be living in a sense that I would
understand it, like, they're

actually alive now and metabolising?

For a long time, it was thought
that ice microorganisms

were present only in a state
of what is called deep antibiosis -

suspended animation.

It's now becoming quite clear
that that isn't necessarily

the case for all the
microorganisms.

There may be others that are
actually actively living in the ice.

That's quite incredible.

So in this glacier, the whole place,
this whole cave,

may be populated by actual
living things, not frozen things,

but things existing, living,
cell dividing, reproducing,

all those things.

Cell dividing, reproducing.
All of this.

It's this prospect of finding things
living in solid ice

that has had the greatest impact
on our ideas of where life could

survive in the solar system.

We're at lowest magnification.

That's 100,000 millionths
of a metre? Yeah. Yeah.

We have bacteria.

HE CHUCKLES

Look, I'm really interested there

because we found these
living things in the ice.

Tremendous.

So these are organisms that have
been trapped in that glacier for...

Yes... thousands of years?

Look at this, beautiful.

You're seeing life in ice.
So, that's amazing.

We now know that some
microorganisms are capable

of actually causing the ice to melt

because they generate essentially
antifreeze proteins.

So what are the implications
of these discoveries,

the fact that you've got living
bacteria inside ice on Earth?

What are the implications
for Europa?

You can clearly have bacteria
like this in the frozen ice

near the surface crust.

I've learned this lesson all the way
through making these programmes

over the years. Every time you send
a spacecraft somewhere new,

it discovers new stuff.

And when NASA sent space probe
Cassini to Saturn,

it stumbled upon another surprising
potential home for alien life.

Enceladus, Saturn's moon, is
one of the great discoveries,

and I think it's widely
accepted now,

it strongly suggests that
there's both liquid water

and geological activity below
the surface of that tiny moon.

If you force me to guess,

then I would guess that we may find

evidence of bacterial life,

single-cell life, simple life,

somewhere in the solar system beyond
Earth. That would be my guess.

But I am as certain as I can be

that we won't find complex life.

There won't be fish
in the oceans of Europa.

But this begs the question -

is there intelligent
life beyond our solar system?

And really,
that's a different question

that we want to know the answer to.

When we talk about aliens,

we talk about the search
for extra-terrestrial life.

We kind of mean ET, don't we?

We mean something
that we can talk to.

This desire to know
if there are other civilisations

out there in the universe

has inspired decades
of scientific research.

Right now, as we speak,

there are telescopes searching
the skies for signals, for hints,

for a sign of civilisations

or even
the signals from starships moving

through the sky, you know, whatever
it is, that we're looking for that.

Every hour of every day,

some among us scan the skies
listening for alien civilisations.

They call themselves SETI -

the Search for
Extraterrestrial Intelligence.

This is the Allen Array
in Northern California,

and it's SETl's most
ambitious instrument to date.

This collection of 42 radio
telescopes is optimised

to detect signals from
extra-terrestrial civilisations.

And it's exquisitely sensitive.

If a signal would beam to us,

with the sort of power that we
can generate using our

current technology, from any one of
the million or so sun-like stars

within a thousand light years
of Earth, then this would hear it.

This experiment has yet to
detect a call from ET.

But they live in hope

because SETI did once pick up
a tantalising signal.

PIERCING TONE

On August the 15th, 1977, a radio
telescope called a Big Ear detected

a radio signal from somewhere
in the vicinity

of the constellation Sagittarius.

And this is the printout
from that night.

You can see that
somewhere around 10.15pm,

Eastern Standard Time, a very
bright radio signal pulsed in.

It looks something like this.

I can sketch it out.

It was a pulse...

...with a width of
around 72 seconds

and the peak intensity,

the peak brightness, was over
30 times the brightness of

the background radio emission from
the galaxy, so it's fascinating.

PIERCING TONE

And it came in on a wavelength that
SETI believes an intelligent

civilisation might choose.

The wavelength was 21 centimetres.

That's the wavelength of light,

of radio waves emitted
from hydrogen atoms.

So the whole sky glows at
that wavelength,

and back in the 1950s,

radio astronomers speculated
that if an alien civilisation

wanted to communicate
with us, then they might well

choose that very special, natural
wavelength to send their message.

So surprising was this that
when it was spotted a few clays

later by an astronomer
called Jerry Ehman,

he circled that pulse,

that 72-second flash of radio waves,
and wrote, "Wow" next to it.

So this has become known
as the Wow! signal.

RUMBLING

Today, over 35 years after the
Wow! signal was detected,

there's still no
satisfactory explanation.

It doesn't seem to have been local,
a military signal or a satellite,

and indeed,
nobody's supposed to transmit

at the hydrogen line frequency.

It's reserved for radio astronomy,

Since the Wow! signal,
we've heard nothing.

We've searched in more
detail with better telescopes,

more systematically,
by no means exhaustively,

by the way,
I think we can do much more,

but we've searched
and we've heard nothing.

So the name that
astronomers give it,

the rather ominous name - The Great
Silence - still applies, right,

we listen and we look out
into the universe

for signs of others
and we see no sign.

A possible reason for that
can be found in the biology

of complex organisms here on Earth.

The story of life on this planet
shows that the transition

from single-celled life to complex
life may not have been inevitable.

Life had to overcome
a significant bottleneck.

Everything we would call a
complex living thing today

shares the same basic structure.

It's built out of cells
called eukaryotic cells.

They're, roughly speaking,
the same in every tree,

every blade of grass, every fish,
every insect, even in every

piece of skin in my knee. Every cell
in my body is a eukaryotic cell.

And they're extremely different
to the simple cells,

the bacteria.

So how did those
cells come to exist?

One popular theory is that it was
two simple cells merging together

that formed what we'd
recognise today

as the complex cells in your body.

Somehow, the invader managed to
survive the host cell's defences.

And when the cells reproduced,

they reproduced together.

We still struggle to
understand how this happened

because it's incredibly unusual.

Here's the point -
because every complex animal

and plant shares that same
basic building block,

we are very confident that it
only happened once,

somewhere in the oceans
of the primordial Earth.

And biologists call this merger

the Fateful Encounter Hypothesis
for a good reason.

It seems that that kind of merger
between two simpler life

forms may be extremely rare.

The idea that one organism can get
inside another and doesn't k*ll it,

that they both survived to produce
something that's actually capable

of doing magnificent things -
things that are far more complicated

and wonderful than the two simple
building blocks can manage

on their own - seems to be...
it seems to be unlikely,

a fateful encounter.

Now, if that's the case, then that
may suggest that complex life,

that intelligent life, is extremely
rare indeed in the universe.

But that possible rarity
hasn't stopped us

searching for signals
from intelligent civilisations.

Now, here's Frank Drake.

And this was a tremendous
privilege to me

cos I'd grown up with that name.

I mean, if you're interested
in astronomy and SETI -

the Search for
Extraterrestrial Intelligence -

you know the name Frank Drake.

When you meet someone like
that, one of your heroes,

it's a special moment.

And he did not disappoint.

So if I'd have asked you,
back in the 1960s,

"By the 21st century, do you expect
to have seen a signal?",

what would you have said?

I would have said,

"Yes, I expect to succeed",

because we were doing
a lot of searching then.

Does that make you disappointed?

I'm disappointed, yes,
but not surprised.

What we've learned over the years
is the searching has to be much

more comprehensive than
we'd realised 50 years ago. Hm.

But we know it's still doable.

It just takes much more
time than we imagined.

Let me show you something.

This is an orchid...

...a very peculiar and beautiful
orchid, it's very fragrant...

...which actually only
blooms two days a year.

If you would have been here two days
ago, you wouldn't have seen this

orchid and you might have thought
that this plant never blooms.

Well, so it is with SETl.

We've learned that we must search
over and over and over through

the years till we are in the right
place at the right time

to make the discovery.

What are they called?

This is called a Stanhopea.

It has hope in its name
and we have hope that

someday we'll be in the right
place, at the right time in SETI.

Frank Drake makes the argument that

if there are civilisations out
there, then you might imagine

that the radio waves that they
send out

are passing through the galaxy...

...and so they would be passing
through this room now.

So if only you had a
sensitive enough detector,

then maybe you could pick
up the signals.

And he's right.

The point he's making,
as a scientist,

is that the only way you're
going to know is to look.

And he doesn't think we've
looked closely enough.

And I agree with him.

But Frank wasn't content
just to hang on the line,

waiting for ET's call.

In 1961, he devised what
remains a useful scientific

framework for considering how
likely it is that we share

the galaxy with others.

The Drake Equation has become famous

because it gives us a tool to
continue the search.

It dares us to answer a series
of provocative scientific questions.

On the left-hand side, there's
the number we want to measure,

the number of
intelligent civilisations

in the galaxy that we
can communicate with,

and then there's this group of
terms that really ask questions

about ourselves - how likely is
it for life to arise on a planet?

How special is the Earth?
How special is the Sun?

How special is the solar system?

How special is intelligence?

And then there's this last term,
L, which perhaps speaks to us

most profoundly of all -

the lifetime of intelligent
civilisations.

Do civilisations live for
a long or short time?

And if it's short,
what is it that destroys them?

Is it a natural disaster?

We do after all live
in a violent universe.

Or, are they condemned to
destroy themselves?

When Frank first thought about
it, sort of 50 years ago,

for example, the number of planets
around distant stars -

how likely is it,
what's the probability,

that a star will have
planets around it?

We didn't know,
we hadn't detected any.

It's not till the 1990s that we
have the evidence for planets

around distant stars.

Now we have dedicated missions
to go and look for them.

And these missions are revealing
a universe full of possibilities.

Within the constellation
of Pegasus,

around a sun-like star,
there's a planet called Osiris.

It's way closer to its parent star
than Mercury is to our Sun.

But it's a massive gas giant,
a hotjupiter,

and by measuring the light that
shines through its atmosphere,

we found that the atmosphere's full
of hydrogen and methane... and water.

And just 24 light-years away,
in the constellation of Scorpius,

there's a small, rocky world, one of
the most Earth-like worlds we know.

It orbits around a red dwarf star,

which is one of three stars
in the system -

a planet with three suns in the sky.

So now we can say with confidence
that virtually every star

has a planetary system and
we can put numbers on the number

of potentially Earth-like
planets in a galaxy like ours.

We think it's
something like 20 billion.

So probably one in ten stars

has an Earth-like planet

potentially around it.

We're on the verge of
being able to analyse

the atmospheres of those planets.

We can very slightly now.

We have the capability to do it
and look for signs of life

and look for signs of civilisation.

Given the importance
of the question,

"Are we alone in the universe?",

it is inconceivable to
me that we would not

continue to look as hard as we can

for evidence of life beyond Earth.

But are we likely to find it?

Or are we, in fact, alone?

I would guess that simple
life is reasonably common,

but complex life is far less common.

And if we're talking about aliens,
I mean, what do we really mean?

Going back to my ten-year-old
self watching Star Wars,

aliens means Chewbacca

and spaceships and lasers!

Civilisations, right?

I think that my guess is
there are very few of those.

And it's my working assumption
that there may be, on average,

a handful, maybe one civilisation
per galaxy at any given time.

If there is only one
civilisation per galaxy,

a simple message to our
nearest alien neighbours

could take millions of
years to reach them,

making it inconceivable that
we'll ever establish contact.

So we may be,
for all intents and purposes,

alone.

Just think about what that
means for a moment.

If indeed we are the only
civilisation currently

present in our galaxy of
200 billion stars,

then I think that that means that,
notwithstanding the fact that we

are physically insignificant,
a speck of sand,

a grain of dust in this galaxy,

we are in a very real sense,
extremely valuable.

And so that, to me, is why this
question is so interesting

and so profoundly important,

because the more we hear silence,

right, the more we detect nothing,

the more we begin to think,

in my view,
about our value in this universe.

I'd be delighted if we found
anything that you could call

alive anywhere beyond Earth.

I don't care, at one level, if it's
a little microscopic organism.

But I'd be even happier

if someone sent me

the Encyclopaedia Galactica,

do you know, by radio waves,

and I knew that there were other
civilisations out there

because I'd have loads
of questions for them.

Look at that!

Gravity...

Release!

...the mysterious force of nature...

I've got to say, this is one of the
most exciting things I've ever done.

...that's challenging
our understanding of reality.

Holy mackerel!