Strange Signals from Outer Space! Horizon

'Emergency, which service?'

'Police. My husband's been attacked.'

'There's still deadlock tonight between the United States and Iran

'over the 60 American hostages held in their embassy in Tehran.

'But the Muslim students did...'

RADIO STATIC

For decades, some have suspected there might be others out there.

Beings capable of communicating with us,

even visiting our world.

HE SHOUTS

It might sound like science fiction,

but today, scientists from across the globe are scouring the universe

for signs of extraterrestrial intelligence.

My students showed me this signal that was so bright

and apparently so far away

that it was unlike anything we've ever seen before.

Then we realised this is just impossible,

unless a civilisation is way more advanced than we are.

A Kardashev Type II civilisation

would need to build a massive network of solar collectors

that would orbit their star in space.

Something we call a Dyson sphere or a Dyson structure.

Some scientists believe advanced aliens really could exist.

About 10,000 detectable civilisations

at present in our galaxy, the Milky Way.

And yet, no solid evidence has ever been found.

But recent discoveries mean that could all be about to change.

The data for the star looked nothing like any other star

that we know of today.

And so at last we might be close to answering the question

of whether we are alone in the universe.

One day my father happened to tell me, there are other worlds in space.

And, to an eight-year-old kid,

I thought that meant worlds just like mine.

Just like the Earth, creatures just like myself and I wondered,

what are they like? Are they really like that, or are they different?

And I've wondered those same questions my whole life.

The universe is thought to contain 700 million trillion rocky planets

like our own.

Countless worlds other intelligent beings might call home.

And yet, in more than 50 years of searching,

we're yet to find them.

The deafening lack of any communication from extraterrestrials

has become known as "the great silence".

Oh, I believe very strongly that they're out there.

The numbers support that.

There's so many stars in the universe,

numbers that are so large they make no sense to us.

We can be very, very wrong and yet there will be

many, many detectable civilisations.

We met in Arecibo in Puerto Rico.

There's a large radio telescope there.

I used to work at the observatory as a staff scientist

and you were a grad student at Cornell,

and they used to send their students down from Cornell.

We met at the observatory in the control room.

Husband and wife Duncan Lorimer and Maura McLaughlin

share a passion for astronomy.

Boys, it's breakfast time!

I was never, you know, the type of kid, when I was really young,

that was super into astronomy.

I still don't know, like, a single constellation.

But when I was sort of 10, 11, 12, I started reading science fiction.

So when I went to college I decided to take astronomy classes.

I still wasn't sure what I wanted to do,

but then I did research with a professor at Penn State

that took me down to Arecibo and I observed pulsars.

I was just so excited,

and I just really enjoyed doing that and I thought,

"OK, I think this is what I want to do",

and I've just stuck with it ever since.

-Nice day!

-Yeah.

What do you have today?

-Gym.

-Gym.

I got into astronomy in a different way to Maura, I guess.

I've always been fascinated with the night sky.

When I was about 16, taking my A-levels,

my physics teacher saw that myself and a few other students

were interested in astronomy and said,

"Here's the key to the school telescope. Go and fix it up."

And it was this old telescope, this early 1900s telescope,

and it had lots of things,

lots of moving parts that were fascinating to us

and we got the telescope going

and we took a picture of a lunar eclipse,

and we started a little astronomy club at school

and I went to college after that and heard about neutron stars,

and once I found out about those, I knew that's what I wanted to study.

I would have had nothing to do with him

if I'd met him like 30 years ago.

-Yes.

-That would have been it.

Oh!

We work here in the Department of Physics and Astronomy.

We're next-door neighbours, aren't we?

Yeah, our offices are right next door

and it's typically really useful.

We can just, you know, pop in and out, so it saves us a lot of time.

-See you.

-All right, then.

-Have a good day.

-You, too.

Occasionally we have disputes.

I'm in control of the temperature in both offices,

and so I like it really warm, and Duncan likes it a lot colder.

So we have occasional arguments, but generally it's really useful

being right next to each other.

Sometimes you bang your feet on the wall

and I have to tell you to stop.

But generally it's really nice.

-It's good.

-We like it.

In the summer of 2006,

Duncan and Maura began a project searching historical data

for the Park's radio telescope.

So we'd just arrived at West Virginia University.

We wanted to find some data that already existed to get working

on a project straightaway.

So we kind of like bandied around some ideas for good projects,

and one of the things we thought of was re-analysing the data

from an old survey taken, like, in the late 1990s,

of the small Magellanic cloud and this large Magellanic cloud,

to look for pulsars that had been missed before.

The project involved painstakingly searching hundreds of data plots,

work Duncan delegated to student.

Every week my student would come to me with the results of his analysis

from the previous week,

and sometimes those would be known pulsars,

sometimes we would see sources of interference or just noise.

But one week, I remember it very clearly,

he came to me and showed me this plot with a signal

that was so bright and apparently so far away

that it was completely unlike anything we'd ever seen before.

So this is the plot that my student David brought to me,

and you can see straightaway this is the pulse that he found.

This big dark feature here.

This is a graph of telescope time along the horizontal axis,

so this is almost two hours of observation here.

And on the vertical axis is basically distance.

You can see the background of noise from the telescope and the sky,

these little dots here.

So this feature really stands out

because it's so bright and so far up the plot here,

which indicates that it's a bright source that's very, very far away.

Quite frankly, it was unlike anything I'd ever seen before.

Yet, it had all the hallmarks of a signal

that was coming from deep space.

The signal, or "fast radio burst" Duncan had discovered

became affectionately known as the "Lorimer Burst".

When people started calling it the Lorimer Burst,

at first I just chuckled.

Because it seemed just so funny

to have something actually named after Dunc,

and it was even funnier when people didn't realise I was married to him,

we have different last names, so I got lots of questions,

like, "What do you think about the Lorimer Burst, is it real or not?"

So I kind of got a good chuckle out of it for a little bit,

but then that kind of stuck and so we started using the name

in proposals and things, which was kind of fun.

To have something named after me like this was really a great honour.

Yeah, not something I was expecting, but yeah, really nice.

But the Lorimer Burst was so distant and yet so bright

it didn't appear to have been produced

by any naturally occurring phenomenon.

I did think that it could be a signal from an extraterrestrial

civilisation - we create signals like that on Earth,

so it's not crazy to think that radio bursts

could be created on another planet.

Once we actually thought about it, and looked at the energetics,

you'd need to harness almost a whole solar system's worth of energy

to create something this bright.

Then we realised this is just impossible

unless the civilisation is way more advanced than we are.

We couldn't think of how to make something this energetic.

Scientists have been searching the cosmos for strange signals

like the Lorimer Burst for more than 50 years.

Ever since a secretive meeting took place

in the foothills of the Appalachian Mountains.

There have been, over the years,

a lot of claims, of sightings of extraterrestrials,

colonies on the moon.

The subject had gotten to be treated with contempt, really.

It was considered almost taboo.

But, in 1961,

Frank Drake held a conference behind closed doors in this room

at the Green Bank Observatory.

The National Academy of Sciences of the United States,

a very eminent body,

asked me to convene a meeting of all the people I knew in the world

who were actually serious thinkers on the subject

and I invited them all.

All 12 of them.

The group called themselves the Order of the Dolphin.

I could talk about all of them at length but let me just mention a few

just to give you a feel for who they were.

There was Otto Stuber,

director of the observatory here at Green Bank,

and considered perhaps the most important astronomer

of the 20th century.

Besides being a great astronomer

he was a very strong proponent of the idea that intelligent life,

and life in general, was very common in the universe.

And there was Carl Sagan, a familiar name,

who was a great proponent of extraterrestrial intelligent life.

He had popularised it, gotten support for it,

both with the general public and the scientific world.

Then there was John Lilly, not an astronomer,

a neurologist who had studied the human brain,

and then the brains of dolphins,

and was convinced that dolphins were close in intelligence to us,

and, in studying the brain, he was trying to make the case

that intelligence is inevitable in the course of evolution,

and therefore it should be very common in the universe.

Then there was Melvin Calvin,

a chemist who had successfully understood how chlorophyll works

to produce food and plants and makes life on earth thrive.

And in fact had been awarded the Nobel Prize for it.

In fact, that prize was given to him right in the middle of this meeting,

which was pretty disruptive, I have to tell you.

The purpose of the meeting was to estimate how many extraterrestrial

civilisations might be out there

using what's become known as the Drake Equation.

So, we start out with the rate of star formation,

which you write R star,

and of course the more stars more planets there will be,

the more possibilities for life.

We multiply that by the fraction of stars which actually have planets

and then again by the number of habitable planets in each system.

We then multiply this by the fraction on which life develops.

And then by the fraction by which intelligence appears.

And then by the fraction of those

which actually give a detectable technology,

one we might detect across the great distances between the stars.

What we have now in these six factors is the rate of production

of detectable civilisations.

Well, how many are there?

This rate times the average time

that these civilisations remain detectable.

'United States maintains its determination...'

For two days, the group worked out best guess values

for each term in Frank's equation.

The answer we came to for the value of N

was N equals about 10,000 detectable civilisations at present

in our galaxy, the Milky Way.

It became clear to us that it was very likely

that there were radio signals from other worlds

passing through the room in which we were sitting

and which we could detect if we but pointed our telescopes

in the right direction and tuned to the right frequency.

At the time of the meeting,

Frank thought he knew exactly what channel to listen into.

What we needed was a special place in the universe

where civilisations might contact, and we realised it wasn't a place,

but it was a radio channel.

The most common element in the universe is hydrogen.

It happens to transmit a very beautiful signal

at a certain frequency when it's in its lowest energy state.

And we decided that might be the place you meet your friends

when you can't arrange in advance where to meet.

So we decided to search the hydrogen wavelength.

My father served in the Army, and when I was in high school he really

encouraged me to join the Service, so that's what I did.

I joined the military as an intelligence officer

and after seven years I transferred to the Department of Defence.

I was in the cold case unit for four years

and during that time I would look through cases that were

20, 30 or 40 years old, and the intent for that

was to capture spies that slipped through our fingers.

The Department of Defence was just a chapter in my life,

but as a kid I always wanted be an astronomer,

so I went to school, received my degrees and I became a scientist.

Since leaving the agency,

Antonio has become obsessed with the most famous cold case

in the search for extraterrestrials.

On August 15, 1977,

astronomers at the Big Ear radio telescope in Ohio

were listening to the night sky and, at about 23:00 hours local time,

they detected a radio signal from space.

The single was strong, about 72 seconds,

but more importantly, it was detected in something known as

the hydrogen line.

That was significant because at the time,

astronomers thought that if extraterrestrials did exist

they would use that frequency.

The astronomer Jerry Ehman and was so excited

that he actually wrote the term "Wow!" on the printout.

But what exactly caused the Wow! signal?

It's a mystery that has endured for decades.

I approached the Wow! signal just like any cold case at the Pentagon.

I had multiple facts.

I had a crime scene, and in this case

we know that the crime scene is the constellation Sagittarius.

I have a time of the crime, which was at 23:17 local,

and the date of the event which was on August 15, 1977.

More importantly, we have a fingerprint of the suspect,

and that's hydrogen.

So I went back to the NASA databases

and I plugged in the date and time of the event,

and what I learned was there were two comets in the very same area

at the same time that the Wow! signal was detected.

Comets are giant rocks of ice, dust and carbon.

And, as they get closer to the sun, they begin to melt

and as they melt they give off a massive envelope of hydrogen,

that can be millions of kilometres across.

So when we put two and two together,

what we have here is a suspect that matches the fingerprint

of the Wow! signal.

But not everyone is convinced by Antonio's detective work.

Few believe that comets produce enough hydrogen

to emit such a strong signal.

If my theory proves wrong, then I won't be upset.

There are no emotions in science.

What I'll do is what any other scientist would do,

and that's move onto the next suspect.

As Antonio continues his hunt,

many believe the answer lies far closer to home.

Rather than coming from deep space,

the most likely source of the Wow! signal is thought to be interference

from passing satellites, or aircraft here on Earth.

Four years following its discovery,

people were beginning to have doubts about the Lorimer Burst, too.

Let's get to the bus stop.

Because only one had ever been detected.

So, did you bring your book?

-Yes.

-What was your favourite part of that?

When he chewed gum.

I knew you were going to say that.

So, around 2010,

people were actively looking for these bursts in other datasets

and then one day I got a call that the first few were found.

This might sound exciting, but it really wasn't because these bursts

were a lot like the Lorimer Burst, the original burst.

But they had a couple of different characteristics

which indicated that they definitely were not extragalactic,

and that they were from some source,

either on the Earth, or maybe just right in our local atmosphere.

When I got that call, my heart really did sink and I thought,

"Oh, the original burst is probably a similar thing."

Just a locally generated signal.

So it was very, very depressing.

There was also something deeply suspicious about the new bursts.

They were far more common in winter

and always appeared around lunch time.

It was eventually discovered they weren't coming from space at all.

They were being generated by the observatory's microwave.

So I think it was a hard time for him

because he felt like his original paper was discredited.

It made it harder that everyone had been calling it the Lorimer Burst

because then it felt very personal.

When I first saw the data and I compared their properties

with the Lorimer Burst properties,

they looked really similar and I thought it too much of a coincidence

for them not to be coming from the same source.

My initial conclusion was that the Lorimer Burst probably wasn't real.

But Duncan wasn't prepared to give up on his discovery so easily.

So what we're looking at here is the original burst from 2007,

and then one of the detections that was coming out in 2010,

so you can see that they have quite a lot of similarities.

Both pulses are about the same width.

But if you look at them in terms of their frequency versus time,

you'll see that they have an overall slope.

They both have the same slope,

but the structure within the pulse is quite different.

One of the new signals has this very blotchy appearance,

whereas our original signal had a smoother, continuous appearance.

And that was the thing that was really giving me hope

that this was still real.

But for the scientific community,

the most likely explanation for the Lorimer Burst

was still interference.

For now, at least, the great silence persists.

In 1989,

the International Academy of Astronautics

approved a post-detection protocol.

A code of practice to be put into play by governments

should we detect an alien transmission.

The document detailed how to control the dissemination of information

and coordinate a unilateral response.

One reason scientists believe such a protocol was required...

..is because in the mid-'70s,

we tried to make contact with aliens ourselves.

There were two purposes to the Arecibo message.

One was to demonstrate that it was possible to send a message

across the interstellar space

that would be detectable and decodable, understandable.

The other was simply to show that we had in fact reached the stage

where we ourselves could do this sort of thing.

There were like probably 200 people, they're sitting in chairs

on the edge of the big giant dish,

and we tell them we're about ready to send,

and they steer the telescope, that whole great big thing starts moving.

Which is in itself very impressive.

This giant thing is moving,

and you just have the sense that something spectacular is going on.

I will play the tape for you.

This is a recording made in the control room

of the Arecibo radio telescope at the time, in November 1974,

when we sent a message to the stars.

LONG, LOW TONE

That steady tone is the sound of the transmitter being turned on,

it's simply sending out a signal without any information on it.

To call attention to itself,

so that people who capture this will know that something is coming

and here it comes.

That sort of warbling sound you hear is actually a sequence

of 10 characters per second, being sent out with those characters

being on two slightly different radio frequencies.

When you listen to the sound, you had the impression

that there was a story being told here.

And when it finally ends, everybody was crying...

..on the actual occasion.

It was just the, um...

sense that this great big machine was talking to another world.

The message goes to 300,000 stars, so there's a good chance, actually.

The recipient of the Arecibo message is a galaxy 25,000 light years away.

But the 50,000 years it would take for a message to get there,

and for any reply to journey back to Earth,

is far beyond the lifespan of any single human.

Perhaps even the lifespan of civilisation itself.

Human civilisation is thousands of years old,

but we've only been sending strong signals into space

for really about 60 years.

The truth is, we don't know how long we'll continue to send the signals

out into space

because we don't know longa technological civilisation like ours

typically lasts.

When we look into space, searching for extraterrestrial intelligence,

in a way we're looking for a glimpse of our own future

and potentially a glimpse of how our civilisation might come to an end.

And one of the biggest dangers we face

is the threat we pose to ourselves.

In the Cold War, we were worried about nuclear annihilation.

Nowadays we worry more about climate change,

and in the future we might worry about things such as nanotechnology

or artificial intelligence.

These are all serious risks that we have to be very careful about.

As we become more advanced,

the threat we pose to ourselves increases

because we have improved ability to harness large amounts of energy

and manipulate the environment to a greater degree.

When those processes go wrong,

the damage we can inflict on ourselves and on the planet

becomes substantial.

Faced with these dangers,

advanced civilisations could be relatively short-lived.

It might be that in the 13.5 billion year history of the universe,

many have risen,

but today, nothing but ruins remain.

So if we don't find anything, that could be quite a disturbing thought

because it could mean that the reason we don't see anything

is that civilisations don't last very long,

and that the signals they produce suddenly disappear.

MUSIC: It's Not Unusual by Tom Jones

# It's not unusual to be loved by anyone... #

But if they haven't destroyed themselves,

a technologically advanced civilisation

might provide us with another way of detecting them.

Because all technology needs energy.

In 1994, Las Vegas consumed 1300 megawatts of power.

Today that figure has nearly doubled to 2400 megawatts.

That's the same trend that we see all over the world.

For the last century, every few decades,

humanity's power consumption has doubled.

As our technology has increased, so too has our need for power.

And, as demand increases,

civilisations must look beyond their home world.

Every star, just like our sun,

is basically a giant nuclear furnace,

fusing hydrogen into helium and producing energy.

The ultimate limit to the amount of energy available to any civilisation

is just the amount of energy that they can harvest

from that parent star.

Deep in the Mojave Desert,

halfway between Las Vegas and Reno...

..it's possible to glimpse the future.

So, this is the Crescent Dunes Solar Facility.

There are 10,347 of these mirrors.

They all reflect the sun's energy up to that tower.

The heat's a reservoir of molten salt,

that's then used to turn water into steam,

turning turbines, and generating electricity.

Crescent Dunes is one of the world's largest solar power plants,

but even this gigantic facility

can only collect a small fraction of the sun's energy.

In the future, we might build thousands more of these facilities,

collecting even more of the sun's energy.

The amount of energy a civilisation can harness from their star

provides an indication of their technological advancement.

And it's measured on what's known as the Kardashev scale.

A Kardashev Type I civilisation

is a civilisation that's capable of harnessing all of the energy

that falls on their planet from their parent star.

Human civilisation only consumes about 20 terawatts of power.

That's about 1000th of the amount of energy that falls on our planet

from our sun.

But the amount of sunlight that hits the Earth

is only a tiny fraction of the light that leaves the sun.

Our sun's power is 400 billion terawatts.

That's 10 million times as much energy in just one second

as the entire United States consumes over the course of the year.

Any civilisation capable of harnessing all the energy

emitted by its star would have achieved Kardashev Type II status.

But to do it

would require engineering on a truly astronomical scale.

A Kardashev Type II civilisation

would need to build a massive network of solar collectors

that would orbit their star in space.

Something we call a Dyson sphere, or a Dyson structure.

A Dyson structure is very much like the solar power plant here,

but billions of times larger, in space, orbiting an entire star.

But they needn't be a solid surface.

It could be a swarm of individual solar panels,

all interconnected, as long as they occluded a large fraction

of the light that came from the star.

To construct a Dyson sphere that enveloped the sun

would require all the matter in all the planets in the solar system.

And so until recently,

Dyson spheres were thought to be purely theoretical.

Then, in 2013,

some deeply strange observations from NASA's Kepler space telescope

fell onto the desk of astronomer Tabetha Boyajian.

Kepler looked at over 150,000 stars in our galaxy,

and the data for this star looked nothing like any of the stars,

and nothing like any other star that we know of today.

For four years, the telescope scoured the Milky Way,

hunting for evidence of exoplanets.

Meticulously measuring the brightness of stars

in search of the tell-tale dimming in light

produced as a planet passes in front of them.

So, this is what an exoplanet transit looks like.

On the left-hand side you have the amount of light,

and on the bottom you have time,

and when a Jupiter-like planet transits in front of a star,

you have this clean U-shaped dip in the star's light.

And this dip this about 1%.

So this is the Kepler data for KIC 8462852.

And it shows four years of Kepler photometry of the star.

And, as you can see, for most of the time it's pretty flat.

Nothing is going on.

But then in May 2009, you had this dip that on face value,

appears to look like what a transiting planet would look like.

But if you take a closer look,

then you actually see that the transit lasts for almost a week,

compared to a planet-sized object,

which would just last for a couple of hours.

It was also very asymmetric in shape,

meaning that, instead of having that cleanly U-shaped dip,

it had this strange slope over here on the left-hand side.

This seemed to indicate that whatever was crossing

in front of the star was not circular like a planet.

Things are pretty quiet for a couple of years,

and then in March of 2011 we have this very dramatic feature

where the star's brightness drops by 15%.

And this drop is also very asymmetric.

It gradually decreases in brightness for about a week

and it then snaps right back up to normal in just a few days.

Now, after this nothing happens again for a couple of years

until February of 2013,

when you have this huge complex of dips that last almost for 100 days.

Each of these dips have a different structure,

some are very shallow, some are very sharp,

and the deepest one here drops by over 20%.

And so it seems to indicate that there is some swarm of objects

with different sizes and shapes that were passing in front of the star.

At first, no one had any idea what those objects could be.

Then somebody came along and said,

"What if there was a giant swarm of comets that was

"swooping down towards the star and blocking out the star light?"

And this seemed to be consistent with the observations that we had,

but it seemed a little bit contrived because it would take, you know,

hundreds if not thousands of comets to block out the star's light.

But nevertheless this was kind of the best idea, theory,

that we had to explain the data.

But there was another possibility.

That Tabby had detected the deep shadows

cast by a Dyson sphere constructed around the star.

The scale of these things is kind of hard to imagine,

but you can think of it this way.

So the Earth-Moon distance is about a quarter of a million miles

and the simplest element in one of these would be 100 times this size.

Now, imagine these in orbit around the star,

and you can see how it would produce anomalies

in the data that we detect.

Scientists are still trying to determine

the precise cause of the dimming.

But they have at least settled on a name.

Star KIC 8462852

has become known as Tabby's Star.

-See you, bye!

-OK, bye.

Along with the potential discovery of alien mega structures,

2013 also brought good news for Duncan Lorimer.

A group at Manchester University

announced the discovery of four more bursts.

There were coming from all over the sky and they were clearly real,

so it was a breakthrough moment.

It meant the Lorimer Burst was real, which was just great news.

And it also meant that we could learn a lot about these bursts

that we couldn't before - we'd be able to study the population

and the energetics and try to figure out exactly what's causing them.

I think up until that moment when the confirmation came through,

I certainly every now and again, would begin to doubt myself

and think, is it really just some bizarre form of interference

that causes that one object?

But as soon as you get those other objects,

all of those doubts go away and it's a very, very liberating feeling.

Duncan was very, very excited when these other bursts were announced

because, yeah, he felt vindicated.

He was very self-satisfied and had a little bit of a high and mighty air

for a few weeks because I'd sort of started to doubt

that the Lorimer Burst was real, and he had never given up.

He always said it was real, so he'd won the argument.

And he made it well-known that he was right.

I think I told her something like, "I told you so!"

By the end of 2013,

there had been six confirmed detections of fast radio bursts.

But what was causing them was still unknown.

Now that fast radio bursts are real,

it comes back to the idea of whether they could be caused by aliens.

And I've never really subscribed to that.

If I were looking for a signal from an extraterrestrial civilisation,

I'd be looking for it coming from a single point in the sky.

We have a population of sources all over the sky

which implies that the aliens are all over the place,

all over the universe, and that just seems highly unlikely to me.

But then, mathematical analysis of the known signals

seemed to show they were all placed at regularly spaced distances.

Maybe, whatever was responsible for the fast radio bursts

were put there by extraterrestrials,

perhaps even ones on the next level of the Kardashev scale.

Communication beacons placed across the Milky Way

by a Type III civilisation.

One with the ability to harness the power of an entire galaxy.

But, if the Milky Way were home to a Type III civilisation,

its presence should be written across the sky.

We know from thermodynamics that any energy usage that does useful work

produces waste heat.

Our car engines produce waste heat,

our laptop batteries produce waste heat,

so too does any energy usage by any technology,

whether it's human technology, or an extraterrestrial technology.

If there were a civilisation in our galaxy that was using the energy

of millions or billions of stars,

we would see evidence of that energy usage in the form of waste heat.

As more fast radio bursts were discovered,

so the regular pattern disappeared.

And nothing like the heat produced by a Type III civilisation

has ever been seen in our galaxy.

There are hundreds of billions of galaxies in our universe

so there's certainly still room for these very,

very advanced civilisations to exist somewhere in our universe.

But, wherever those civilisations might be,

for as long as we have been looking...

..they have remained elusive.

In the spring of 1960,

Frank Drake arrived in Green Bank

to fulfil the dream he'd had since childhood.

I had been waiting for many, many years for this opportunity

to answer that question, are there other civilisations out there?

It was very exciting, because at that time, for all we knew,

every star had a planet that was sending intelligent signals.

We might succeed the first day, in the first hour.

It was here that Frank conducted Project Ozma,

the first scientific search for extraterrestrials.

We did in fact attach a loudspeaker just in case a miracle happened

and we actually heard someone talking to us.

It was not out of the question.

We had a tape recorder that was recording everything coming in.

So when we first turned it on,

of course everybody was wondering, what are we going to hear?

What we heard was noise.

Static, nothing.

Project Ozma heard no alien communications.

And it's been the same story for every subsequent search.

We've done a great deal of searching in the last 50-plus years,

and we've learned that we're going to have to search

perhaps a million stars and countless frequency channels

before we have a good chance of success.

But, after more than half a century,

Frank's own search is drawing to a close.

If I had this to do all over, I would still do it.

In fact, probably put more time into it because I've come to realise

that's what's required to succeed.

And to me that time is not time wasted.

Because the eventual discovery is of such importance that it justifies

not just one human life being dedicated to succeeding, but many.

Are we alone?

If we are, then that tells us something

about the preciousness of life on Earth.

And if we're not alone...

..then what discovery could possibly be more important?

Come with us.

Breakthrough Listen takes the search for intelligent life in the universe

to a completely new level.

In 2015, Russian billionaire Yuri Milner

put down 100 million of his own money

to conduct the most comprehensive search for extraterrestrials

ever undertaken.

This was once a dream,

it is now a truly scientific quest.

The 20th century...

..we stepped out from our planet to space,

to the moon,

to the solar system.

In the 21st century, we'll find out about life on a galactic scale.

And the search begins with Tabby's Star.

KIC 8462852 is one of the best targets we've had in a long time

for study searches.

We're going to be using the 100-metre Green Bank telescope,

the largest fully steerable radio telescope on the planet,

paired with a brand-new set of instrumentation we've installed

as part of the Breakthrough Listen project.

This instrumentation allows us to conduct a very sensitive search

over a huge amount of the radio spectrum.

Now, if Tabby's Star does indeed have a Dyson sphere around it,

and it is inhabited by a very advanced civilisation,

perhaps that civilisation might have technology like we use on Earth,

perhaps radio technology.

And if they do, we could detect it with this telescope.

Tonight represents perhaps the best chance humanity has ever had

to make contact with extraterrestrials.

Hey, Dave.

Could you put Vegas back in mode one?

This evening is a very exciting night.

Turned back on and then...

We've been waiting for it for over a year,

so, yeah, I think we're all pretty excited about what's happening.

What's next? Is Tabby's Star next?

Tabby's Star is next, yes.

All right, time for you to push the button!

Right, here we go.

-We're off.

-Here we go.

MOTOR WHIRS

Once it's moved into position,

the telescope begins to gather radio waves

that just might contain messages from an alien civilisation.

-There you go. It's coming in.

-Right!

For six hours, the giant dish tracks the star across the sky,

scanning billions of radio channels simultaneously.

By 3:30am, the observations are complete.

These four plots represent about 800 megahertz of the radio spectrum

and this is only about one quarter of the amount of the radio spectrum

that we're observing.

So this plot shows the shape of the radio spectrum

as a function of frequency.

And here we see the radio spectrum as a function of time.

If there was evidence of technology in these data,

what we would expect to see is a spike in one of these plots,

a lot of electromagnetic energy in just one channel.

Now we don't see that yet, but in the coming days,

weeks and months, we're going to be looking at the data

in many different ways with much higher resolution,

that will allow us to be much more sensitive to evidence of technology.

For tonight at least, Tabby's Star is holding onto its secrets.

For the Breakthrough team,

the search for extraterrestrials is only just beginning.

I don't know if they're out there or not.

As a scientist I have to admit that.

But I think that it would be a pretty strange universe

in which life only arose once, and intelligence only arose once.

I think, to me, the most interesting property of the universe

is the fact that intelligence exists at all,

that somehow the universe has evolved a capacity to know itself,

to ask questions about itself,

and ultimately I think, until we answer this question,

we won't really understand the universe at all.

Since 2013, many more fast radio bursts have been discovered.

Duncan and Maura now have a theory for what might be producing them.

So whatever it is that is causing FRBs must be both very compact

and very energetic.

It must be compact because the width of the pulses is very narrow,

and they must be very energetic

because the distances that we infer are very far away.

It's thought, in fact, the bursts could be created

during the explosive collisions of neutron stars,

some of the densest, most energetic objects in the universe.

We observe binary systems of two neutron stars

that are in orbit around each other,

and when we observe these systems, we see them getting closer

and closer together all the time.

So what will happen eventually is that they're going to collide.

And when they merge,

the neutron stars will be completely destroyed and form a black hole.

As they annihilate, the two stars release in an instant

the same energy the sun produces in an entire month.

A blinding flash visible to our telescopes as a fast radio burst.

This theory perhaps solves the mystery

of these strange signals from space.

When you look at the energetics of these events,

you can easily explain the FRB energies with them.

You can also explain the durations of the FRB pulses

with the expected durations of these merger events.

So it's quite a plausible explanation.

Then, in 2016, a new burst was detected.

The distinctive pulse of radio waves

released as the neutron stars collided and were destroyed.

Followed by nothing.

Silence.

Just as the astronomers expected.

But then, when they looked again...

..the signal came back.

# It's not unusual to be loved by anyone

# It's not unusual to have fun with anyone

# But when I see you hanging about with anyone

# It's not unusual to see me cry. #