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Stop for a moment and think of this. | 0:00:03 | 0:00:05 | |
Are we alone in the universe? | 0:00:06 | 0:00:09 | |
It's perhaps the biggest question we've ever asked. | 0:00:09 | 0:00:12 | |
It's not crazy to imagine that some hugely super-human | 0:00:12 | 0:00:16 | |
civilisation exists out there. | 0:00:16 | 0:00:18 | |
They may have been watching the earth for millions of years. | 0:00:19 | 0:00:23 | |
After a long and distinguished career | 0:00:25 | 0:00:27 | |
at the forefront of cosmology, | 0:00:27 | 0:00:30 | |
the Astronomer Royal, Martin Rees, has taken up | 0:00:30 | 0:00:34 | |
the hunt for extraterrestrials. | 0:00:34 | 0:00:36 | |
Absence of evidence is not evidence of absence. | 0:00:39 | 0:00:42 | |
Now, with the help of the BBC's archive... | 0:00:45 | 0:00:48 | |
We can't prove that bug-eyed monsters don't exist. | 0:00:48 | 0:00:52 | |
..Martin's going to take us into his world. | 0:00:52 | 0:00:54 | |
You might think hunting for aliens is just science fiction. | 0:00:56 | 0:01:00 | |
You'd be wrong. | 0:01:00 | 0:01:02 | |
Quite a sight, wasn't it, sir? | 0:01:02 | 0:01:03 | |
A sight I'd rather not be seeing. | 0:01:03 | 0:01:05 | |
It's a vibrant frontier of modern science... | 0:01:07 | 0:01:09 | |
..where fierce debates rage. | 0:01:15 | 0:01:17 | |
It's possible that we are a trillion-to-one fluke. | 0:01:18 | 0:01:23 | |
I think that's an over-hasty conclusion. | 0:01:23 | 0:01:26 | |
By exploring opposing views... | 0:01:26 | 0:01:29 | |
A lot of sloppy thinking is quite accepted about alien intelligence | 0:01:29 | 0:01:33 | |
and I think that is a problem. | 0:01:33 | 0:01:35 | |
..we'll travel to the limits of our understanding about the universe | 0:01:35 | 0:01:39 | |
and our place in it. | 0:01:39 | 0:01:40 | |
It's a journey that, for Martin, | 0:01:42 | 0:01:43 | |
leads to an extraordinary conclusion. | 0:01:43 | 0:01:46 | |
Our idea of what an alien will be is all wrong. | 0:01:46 | 0:01:49 | |
It's not organic beings we should be looking for. | 0:01:50 | 0:01:54 | |
It's machines. | 0:01:54 | 0:01:55 | |
On July 20th, 2015, | 0:02:10 | 0:02:12 | |
Professor Martin Rees joined | 0:02:13 | 0:02:15 | |
some of the greatest minds in science at the Royal Society. | 0:02:15 | 0:02:18 | |
They were launching a £70 million research programme. | 0:02:20 | 0:02:25 | |
The aim? Finding intelligent life in the universe. | 0:02:25 | 0:02:29 | |
It's a huge gamble, of course. | 0:02:29 | 0:02:31 | |
No-one would count on success, but the pay off would be so colossal. | 0:02:31 | 0:02:35 | |
The team are using some of the world's biggest telescopes to hunt for a signal. | 0:02:36 | 0:02:40 | |
It's our best chance yet of finding aliens. | 0:02:41 | 0:02:44 | |
Stakes are so high, and that's why I think there's more interest | 0:02:45 | 0:02:49 | |
and more focus - certainly among mainstream scientists - | 0:02:49 | 0:02:52 | |
on this topic than there ever was in the past. | 0:02:52 | 0:02:56 | |
And we are gradually edging closer to answers. | 0:02:56 | 0:02:59 | |
'With at least two billion stars in our universe, | 0:02:59 | 0:03:01 | |
'somewhere in deep space there are probably planets with | 0:03:01 | 0:03:04 | |
'civilisations built by living creatures.' | 0:03:04 | 0:03:07 | |
As our knowledge of the universe has increased... | 0:03:07 | 0:03:10 | |
..so has our understanding of who or what might be living out there. | 0:03:12 | 0:03:17 | |
Hello! | 0:03:17 | 0:03:19 | |
Aliens have gone mainstream. | 0:03:23 | 0:03:25 | |
That's why scientists like Martin - | 0:03:29 | 0:03:32 | |
more famous for researching the big bang and black holes - | 0:03:32 | 0:03:36 | |
have joined the hunt for extraterrestrials. | 0:03:36 | 0:03:39 | |
Are we alone? Or is there life elsewhere? | 0:03:42 | 0:03:45 | |
It's especially fascinating to us today, | 0:03:45 | 0:03:47 | |
because, for the first time, we have a real chance of answering it, | 0:03:47 | 0:03:51 | |
because of the advances in technology | 0:03:51 | 0:03:53 | |
and in our understanding of life. | 0:03:53 | 0:03:55 | |
But first, there's a problem. | 0:04:07 | 0:04:09 | |
Before we can explore Martin's ideas on aliens, | 0:04:09 | 0:04:13 | |
there's one question all those who look for ET must face. | 0:04:13 | 0:04:17 | |
It's a question famously posed in the most unlikely of settings. | 0:04:18 | 0:04:22 | |
Los Alamos. | 0:04:27 | 0:04:28 | |
Birthplace of the bomb. | 0:04:30 | 0:04:31 | |
The year is 1950... | 0:04:34 | 0:04:36 | |
..and Enrico Fermi, one of the architects of the atomic age, | 0:04:37 | 0:04:41 | |
is taking a break. | 0:04:41 | 0:04:43 | |
Fermi was having lunch with some colleagues. | 0:04:45 | 0:04:47 | |
They were talking about the existence or otherwise of aliens. | 0:04:47 | 0:04:51 | |
And midway through the lunch, Fermi just stopped and said, | 0:04:51 | 0:04:55 | |
"Where is everybody?" | 0:04:55 | 0:04:56 | |
Where indeed. | 0:04:58 | 0:05:00 | |
Fermi's point was that if there ARE lots of alien civilisations | 0:05:00 | 0:05:04 | |
out there, why haven't we found any? | 0:05:04 | 0:05:06 | |
It may seem a simple observation, but for physicist Stephen Webb, | 0:05:07 | 0:05:12 | |
it casts doubt on the idea that we have any cosmic company at all. | 0:05:12 | 0:05:16 | |
Because Fermi did more than just ask the question. | 0:05:17 | 0:05:21 | |
Like all good scientists, he did a spot of maths. | 0:05:21 | 0:05:24 | |
What he did was run through the numbers, | 0:05:25 | 0:05:29 | |
looked at the number of stars in the galaxy, number of planets. | 0:05:29 | 0:05:33 | |
He made an estimate of how many extraterrestrial civilisations | 0:05:33 | 0:05:36 | |
should be out there. | 0:05:36 | 0:05:38 | |
And he came to a large number. | 0:05:38 | 0:05:40 | |
Given the huge scale of the galaxy, Fermi calculated that | 0:05:42 | 0:05:46 | |
there should be loads of alien civilisations out there. | 0:05:46 | 0:05:50 | |
What's more, he reasoned that many of them would | 0:05:52 | 0:05:56 | |
be far more advanced than our own | 0:05:56 | 0:05:58 | |
There are many stars which are quite a bit older than the earth. | 0:06:05 | 0:06:11 | |
Indeed, in our galaxy there are stars two or three billion years older than the sun, | 0:06:11 | 0:06:16 | |
which could perfectly well have evolved planets, | 0:06:16 | 0:06:19 | |
rather like happened here on earth. | 0:06:19 | 0:06:22 | |
And of course you then have to ask, if that were the case, | 0:06:22 | 0:06:26 | |
then the life on those alien planets would have had a head start. | 0:06:26 | 0:06:30 | |
Fermi's conclusion was that aliens should easily have colonised | 0:06:32 | 0:06:35 | |
the galaxy by now - several times over. | 0:06:35 | 0:06:38 | |
In short, there should be space-faring civilisations everywhere. | 0:06:39 | 0:06:45 | |
So Fermi realised that there's something paradoxical about this. | 0:06:45 | 0:06:49 | |
We expect to see them, and we don't. | 0:06:49 | 0:06:52 | |
It's called...guess what? The Fermi Paradox. | 0:06:54 | 0:06:58 | |
And for some, it leads to a stunning conclusion. | 0:06:58 | 0:07:02 | |
It's a surprise to me. | 0:07:02 | 0:07:03 | |
I would expect, if they exist, that we would see them. | 0:07:03 | 0:07:06 | |
We would hear from them. | 0:07:06 | 0:07:08 | |
They could build large structures, | 0:07:09 | 0:07:11 | |
we could see exhaust from anti-matter rockets, | 0:07:11 | 0:07:14 | |
we could see artificial lines in a star's spectrum | 0:07:14 | 0:07:18 | |
that they've put there. | 0:07:18 | 0:07:19 | |
The conclusion that I would draw from that is that we are alone. | 0:07:19 | 0:07:23 | |
And that's a really, really sad thought. | 0:07:24 | 0:07:27 | |
I think that's an over-hasty conclusion... | 0:07:37 | 0:07:40 | |
..because we've no idea what variety the life out there might take. | 0:07:43 | 0:07:47 | |
If there are aliens out there, | 0:07:47 | 0:07:49 | |
then they're likely to be extremely different from us, in my opinion, | 0:07:49 | 0:07:52 | |
because there could be all kinds of intelligence which would not | 0:07:52 | 0:07:55 | |
manifest itself in any way that we can yet detect. | 0:07:55 | 0:07:58 | |
Indeed, Martin's not ruling out the possibility that we may | 0:07:59 | 0:08:04 | |
someday find evidence that alien civilisations | 0:08:04 | 0:08:07 | |
have visited our solar system. | 0:08:07 | 0:08:09 | |
You could certainly imagine scenarios where some alien | 0:08:11 | 0:08:14 | |
civilisation sent out lots of probes and some of them | 0:08:14 | 0:08:19 | |
came to our solar system. | 0:08:19 | 0:08:21 | |
And therefore we should keep our eyes open for any artefacts | 0:08:21 | 0:08:26 | |
that we might come across orbiting in space or even on one of the planets, | 0:08:26 | 0:08:30 | |
which could be evidence of some kind of external civilisation. | 0:08:30 | 0:08:35 | |
It's an idea that's familiar | 0:08:38 | 0:08:40 | |
from science fiction. | 0:08:40 | 0:08:42 | |
In the film 2001: A Space Odyssey, alien artefacts | 0:08:44 | 0:08:48 | |
were scattered in our solar system, | 0:08:48 | 0:08:50 | |
left by higher civilisations, waiting to be discovered. | 0:08:50 | 0:08:55 | |
It's a long shot, though. | 0:08:57 | 0:08:59 | |
And in the absence of enigmatic monoliths, | 0:08:59 | 0:09:02 | |
we need more solid foundations for our hunt. | 0:09:02 | 0:09:05 | |
Which means starting with something much simpler. | 0:09:07 | 0:09:10 | |
Because intelligence isn't everything. | 0:09:10 | 0:09:13 | |
Consider bacteria. Simple single-celled organisms. | 0:09:15 | 0:09:19 | |
Superficially, nothing special, but these humble life forms could | 0:09:19 | 0:09:23 | |
hold the key to understanding how common life is in the universe. | 0:09:23 | 0:09:27 | |
And if it's just alien bacteria we're looking for, | 0:09:29 | 0:09:33 | |
it might be right under our noses. | 0:09:33 | 0:09:35 | |
For centuries, Mars was the prime candidate for alien life | 0:09:45 | 0:09:48 | |
in our solar system. | 0:09:48 | 0:09:50 | |
In fact, in about 1900, a French foundation had set up | 0:09:50 | 0:09:54 | |
a prize of 100,000 French Francs for the first detection | 0:09:54 | 0:09:59 | |
of extraterrestrial intelligence. | 0:09:59 | 0:10:01 | |
And in the rules for that prize, they excluded Mars | 0:10:01 | 0:10:04 | |
because it was thought too easy to detect life on Mars. | 0:10:04 | 0:10:07 | |
We've just had some amazing photographs sent back | 0:10:11 | 0:10:14 | |
by the American Probe to Mars, Mariner 6. | 0:10:14 | 0:10:16 | |
Nasa's Mariner probes first took us to Mars. | 0:10:16 | 0:10:20 | |
First in 1965...then again in '69. | 0:10:20 | 0:10:24 | |
You can see there some of the dark areas, which may be vegetation. | 0:10:26 | 0:10:29 | |
And at the bottom, you can see the white polar cap, | 0:10:29 | 0:10:31 | |
which has always been thought to be due to some sort of icy or frosty deposit. | 0:10:31 | 0:10:35 | |
But close-up pictures revealed a barren world. | 0:10:35 | 0:10:39 | |
Hopes of Martian life began to slip away. | 0:10:40 | 0:10:42 | |
Well, primitive life, there may be. I don't even think so. | 0:10:45 | 0:10:48 | |
Intelligent life? Certainly not. | 0:10:48 | 0:10:49 | |
So, in other words, you think Mars is a dead planet? | 0:10:49 | 0:10:52 | |
Absolutely dead as a dodo. | 0:10:52 | 0:10:53 | |
It certainly looked as dead as a dodo. | 0:10:53 | 0:10:56 | |
There's nothing. There's not even any desert scrub | 0:10:59 | 0:11:03 | |
clinging to the edge of a cliff. | 0:11:03 | 0:11:06 | |
There's nothing. It's completely bare. | 0:11:06 | 0:11:08 | |
This is Professor Monica Grady. | 0:11:21 | 0:11:23 | |
She's one of a growing number of scientists who believe that, despite appearances, | 0:11:23 | 0:11:27 | |
our solar system may yet turn out to be home to alien life. | 0:11:27 | 0:11:32 | |
15 or so years ago, you were regarded as, at best, fringe, | 0:11:35 | 0:11:39 | |
at worst, lunatic, | 0:11:39 | 0:11:42 | |
if you were going to study these sort of subjects. | 0:11:42 | 0:11:45 | |
It's not hard to see why people were doubtful. | 0:11:46 | 0:11:49 | |
As probe after probe visited the planets in turn, | 0:11:52 | 0:11:56 | |
scientists had grown increasingly confident | 0:11:56 | 0:11:59 | |
that Earth was unique in our solar system | 0:11:59 | 0:12:01 | |
in being home to life. | 0:12:01 | 0:12:03 | |
But for Professor Grady, this just doesn't make sense. | 0:12:06 | 0:12:10 | |
The ingredients of life are really, really simple. | 0:12:11 | 0:12:14 | |
Basically, hydrogen, carbon, oxygen and nitrogen. | 0:12:16 | 0:12:19 | |
And they are the most abundant elements in the solar system. | 0:12:19 | 0:12:23 | |
The most abundant elements in the universe. | 0:12:23 | 0:12:26 | |
So there's no reason why life could not, should not | 0:12:26 | 0:12:32 | |
have got going in places beyond the Earth. | 0:12:32 | 0:12:34 | |
Because it's simply physics and chemistry. | 0:12:34 | 0:12:36 | |
But that raises a big question. | 0:12:38 | 0:12:39 | |
How did physics and chemistry... | 0:12:41 | 0:12:43 | |
..turn into biology? | 0:12:45 | 0:12:47 | |
How was life on Earth first created? | 0:12:48 | 0:12:51 | |
We know that all life on Earth is related. | 0:12:58 | 0:13:00 | |
We share DNA not just with monkeys, | 0:13:00 | 0:13:03 | |
but with all the animals and plant life we see. | 0:13:03 | 0:13:05 | |
Go back far enough | 0:13:07 | 0:13:08 | |
and all living things share the same common ancestor. | 0:13:08 | 0:13:11 | |
A single cell. | 0:13:13 | 0:13:14 | |
What nobody knows yet is where that first cell came from. | 0:13:14 | 0:13:19 | |
The origin of life, everyone has known for a century, | 0:13:21 | 0:13:24 | |
is a key problem in science. | 0:13:24 | 0:13:26 | |
At present, when we only know about life in one place, | 0:13:26 | 0:13:30 | |
we can't rule out the possibility | 0:13:30 | 0:13:32 | |
that the odds against life emerging are zillions to one. | 0:13:32 | 0:13:35 | |
So, do we know anything about how easy it was for that first cell to form? | 0:13:37 | 0:13:41 | |
Well, there is one thing. | 0:13:43 | 0:13:45 | |
On our planet, it happened very early. | 0:13:45 | 0:13:48 | |
4.5 billion years ago, the Earth was formed | 0:13:51 | 0:13:53 | |
from a collapsing cloud of gas and dust. | 0:13:53 | 0:13:56 | |
It was a violent event. | 0:13:58 | 0:14:00 | |
Volcanoes pumped out a toxic atmosphere. | 0:14:02 | 0:14:04 | |
And the young planet was bombarded by asteroids. | 0:14:06 | 0:14:09 | |
Yet in this literal hell on Earth, | 0:14:14 | 0:14:17 | |
chemistry turned into biology. | 0:14:17 | 0:14:19 | |
It was an event that Horizon investigated in 1974. | 0:14:22 | 0:14:26 | |
At the University of California, Stanley Miller is re-creating | 0:14:26 | 0:14:29 | |
the early Earth in a fourth-floor laboratory. | 0:14:29 | 0:14:32 | |
The primitive atmosphere was very different than the one | 0:14:32 | 0:14:35 | |
we have at the present time on the Earth. | 0:14:35 | 0:14:37 | |
But the major difference was that there was no oxygen | 0:14:37 | 0:14:39 | |
and there was an abundance of molecular hydrogen. | 0:14:39 | 0:14:42 | |
But nobody had ever tried an experiment | 0:14:42 | 0:14:44 | |
to see what would happen in such an atmosphere. | 0:14:44 | 0:14:48 | |
So, at the age of just 23, Stanley Miller decided to do just that. | 0:14:49 | 0:14:53 | |
It was a famous experiment | 0:14:53 | 0:14:55 | |
in our understanding of the origins of life. | 0:14:55 | 0:14:58 | |
So the experiment was to construct the model ocean, | 0:14:58 | 0:15:01 | |
which is the small flask here, | 0:15:01 | 0:15:03 | |
a model atmosphere, which is the large flask | 0:15:03 | 0:15:07 | |
containing the gases of the primitive atmosphere. | 0:15:07 | 0:15:10 | |
So he boiled up the model ocean, | 0:15:10 | 0:15:12 | |
added lightning and sat back to wait. | 0:15:12 | 0:15:15 | |
His flask contained nothing organic at all. | 0:15:16 | 0:15:19 | |
But after just a week, the miniature ocean within it | 0:15:21 | 0:15:24 | |
had turned muddy brown. | 0:15:24 | 0:15:26 | |
He'd created his very own primordial soup, | 0:15:28 | 0:15:31 | |
full of organic compounds. | 0:15:31 | 0:15:33 | |
The building blocks of life. | 0:15:33 | 0:15:35 | |
In fact, the major group of organic compounds | 0:15:38 | 0:15:41 | |
produced by the spark were amino acids. | 0:15:41 | 0:15:44 | |
And one had no right, really, to expect such a result. | 0:15:44 | 0:15:48 | |
Miller had shown just how easily the building blocks of life can form. | 0:15:51 | 0:15:55 | |
We still don't know how those organic chemicals | 0:15:57 | 0:16:00 | |
turned into a living organism. | 0:16:00 | 0:16:01 | |
But we do know that almost as soon as the planet had a solid crust, | 0:16:03 | 0:16:08 | |
life began. | 0:16:08 | 0:16:09 | |
I suspect that we will find that simple life in some form | 0:16:12 | 0:16:17 | |
is something which can form fairly readily, | 0:16:17 | 0:16:21 | |
given the amount of space and time on a young planet. | 0:16:21 | 0:16:24 | |
Biology's early emergence on Earth offers hope | 0:16:28 | 0:16:31 | |
that life might have formed elsewhere in our solar system. | 0:16:31 | 0:16:35 | |
And possibly not too far away. | 0:16:36 | 0:16:40 | |
Because our next-door neighbour had a remarkably similar early life. | 0:16:40 | 0:16:44 | |
Mars was made at the same time as the Earth was made - | 0:16:47 | 0:16:50 | |
so, roughly 4.5 billion years ago. | 0:16:50 | 0:16:53 | |
Made from the same materials, by the same processes. | 0:16:53 | 0:16:56 | |
It did have active volcanoes, it had rain, it had water, | 0:17:00 | 0:17:05 | |
water flowing over its surface. | 0:17:05 | 0:17:07 | |
So for the first billion years of its life, it was like the Earth. | 0:17:07 | 0:17:13 | |
And in the first billion years of Earth, life got going. | 0:17:13 | 0:17:17 | |
But if life did get going on Mars, | 0:17:20 | 0:17:22 | |
it would have soon found it tough-going. | 0:17:22 | 0:17:25 | |
Mars cooled down fast. | 0:17:26 | 0:17:28 | |
Its small size meant it couldn't retain its internal heat. | 0:17:28 | 0:17:32 | |
And with no magnetic field, much of its atmosphere was lost to space. | 0:17:33 | 0:17:37 | |
Could life still be there now? | 0:17:39 | 0:17:41 | |
Until recently, most people would have said no. | 0:17:42 | 0:17:46 | |
But the more we learn about simple bacterial life | 0:17:46 | 0:17:49 | |
of the kind that might have formed on Mars, | 0:17:49 | 0:17:51 | |
the more we realise it's more robust than we ever thought possible. | 0:17:51 | 0:17:56 | |
If you think of the range of environments in which people can survive - you know, | 0:17:57 | 0:18:01 | |
some of us get really sunburnt if we go out into the garden | 0:18:01 | 0:18:05 | |
and the temperature's above about 25 degrees C. | 0:18:05 | 0:18:09 | |
But bacteria is everywhere. I mean, you know, absolutely everywhere - | 0:18:09 | 0:18:14 | |
deep inside nuclear reactors, deep below the surface of the Earth, | 0:18:14 | 0:18:18 | |
in boiling-hot water, | 0:18:18 | 0:18:20 | |
frozen in Antarctica - it's all over the place. | 0:18:20 | 0:18:24 | |
These sorts of microorganisms are called extremophiles. | 0:18:24 | 0:18:27 | |
They love being at these extremes. | 0:18:27 | 0:18:29 | |
In fact, they're so hardy, scientists decided to test them | 0:18:31 | 0:18:35 | |
in the ultimate extreme environment. | 0:18:35 | 0:18:37 | |
Space. | 0:18:39 | 0:18:40 | |
Minus ten, nine, eight. Go from eight and just start. Seven, six... | 0:18:44 | 0:18:48 | |
On February 7th, 2008, the Space Shuttle Atlantis blasted off | 0:18:48 | 0:18:53 | |
with a surprising payload onboard. | 0:18:53 | 0:18:55 | |
..Space Shuttle Atlantis. | 0:18:55 | 0:18:57 | |
Bacteria, taken from the cliffs of Devon. | 0:18:57 | 0:19:01 | |
..A voyage of science to the Space Station. | 0:19:03 | 0:19:06 | |
Devon may be a holiday spot for us, | 0:19:06 | 0:19:09 | |
but for bacteria, these cliffs are a surprisingly harsh place. | 0:19:09 | 0:19:13 | |
When they're not being hit with a hammer, | 0:19:13 | 0:19:16 | |
they're being blasted by sun and salty water. | 0:19:16 | 0:19:19 | |
So a sample of these hardy bacteria | 0:19:21 | 0:19:23 | |
spent 553 days | 0:19:23 | 0:19:26 | |
outside the International Space Station. | 0:19:26 | 0:19:29 | |
Scorched by cosmic rays | 0:19:31 | 0:19:33 | |
and subjected to extreme shifts in temperatures. | 0:19:33 | 0:19:37 | |
When they returned, something was still alive. | 0:19:38 | 0:19:42 | |
Bacteria called OU-20. | 0:19:42 | 0:19:45 | |
Life could survive in space. | 0:19:45 | 0:19:49 | |
Study of extremophiles has shown that it can exist | 0:19:49 | 0:19:53 | |
over a wider range of conditions | 0:19:53 | 0:19:55 | |
than people had thought previously. | 0:19:55 | 0:19:57 | |
And that, of course, is something which is good news | 0:19:57 | 0:20:00 | |
in the sense that it widens the range of possible locations for life, | 0:20:00 | 0:20:04 | |
if we think about the wider galaxy. | 0:20:04 | 0:20:06 | |
And for Monica Grady, these hardy organisms raise a startling possibility. | 0:20:07 | 0:20:12 | |
If bacteria did form on Mars, as they did on Earth, | 0:20:13 | 0:20:17 | |
then maybe they're still there today. | 0:20:17 | 0:20:19 | |
If you look at Antarctica from the air, | 0:20:25 | 0:20:28 | |
you see a barren and desolate place. | 0:20:28 | 0:20:30 | |
You don't see any trees or vegetation. | 0:20:30 | 0:20:33 | |
When you get up close to some of the rocks and break them open, | 0:20:33 | 0:20:37 | |
you can see that there is a colony in there. | 0:20:37 | 0:20:41 | |
A colony of microorganisms called cryptoendoliths | 0:20:41 | 0:20:45 | |
hidden inside the rock. | 0:20:45 | 0:20:46 | |
Maybe they're there on Mars. | 0:20:46 | 0:20:49 | |
And we might not be too far off finding out if it's true. | 0:20:51 | 0:20:55 | |
Right now, the European ExoMars probe | 0:20:58 | 0:21:01 | |
is en route to the red planet... | 0:21:01 | 0:21:03 | |
..where it will scan for biological signatures. | 0:21:06 | 0:21:09 | |
It's then hoped a rover will follow in 2019, | 0:21:18 | 0:21:21 | |
drilling for signs of life in the Martian soil. | 0:21:21 | 0:21:24 | |
And if we find Mars has, at any time, played host to bacteria... | 0:21:27 | 0:21:31 | |
..it will be a game-changer. | 0:21:32 | 0:21:34 | |
As soon as we find a trace of some sort of biology, | 0:21:36 | 0:21:43 | |
we can be almost certain, | 0:21:43 | 0:21:47 | |
almost absolutely 100% certain maybe... | 0:21:47 | 0:21:50 | |
SHE LAUGHS | 0:21:50 | 0:21:53 | |
..that there is going to be physics turning to chemistry, | 0:21:53 | 0:21:56 | |
turning to biology on planets around stars in our own galaxy | 0:21:56 | 0:22:01 | |
and in many, many, many other galaxies. | 0:22:01 | 0:22:04 | |
I would say that finding evidence for life elsewhere | 0:22:04 | 0:22:07 | |
of independent origin would be a huge discovery - | 0:22:07 | 0:22:10 | |
one of the great discoveries of the century, if it happened. | 0:22:10 | 0:22:12 | |
Because it would have these implications about | 0:22:12 | 0:22:15 | |
the likelihood of life existing throughout the entire universe. | 0:22:15 | 0:22:20 | |
These days, most scientists think it's likely | 0:22:23 | 0:22:26 | |
that we do live in a universe teeming with simple life. | 0:22:26 | 0:22:29 | |
But a few cells in a Petri dish | 0:22:32 | 0:22:34 | |
aren't what most people think of when they imagine ET. | 0:22:34 | 0:22:37 | |
So here's the next big question. | 0:22:43 | 0:22:45 | |
If there is primitive life out there, | 0:22:45 | 0:22:47 | |
what are the chances it could have evolved into something | 0:22:47 | 0:22:51 | |
we might truly call an alien? | 0:22:51 | 0:22:53 | |
Again, our Earth offers | 0:23:06 | 0:23:08 | |
the only example of evolution that we can use as evidence. | 0:23:08 | 0:23:12 | |
But this time, things don't look so hopeful. | 0:23:13 | 0:23:16 | |
All we know from the history of life on Earth | 0:23:17 | 0:23:20 | |
is that it took a long time | 0:23:20 | 0:23:23 | |
to get from single-celled life | 0:23:23 | 0:23:25 | |
to the next stage - a multi-cellular one. | 0:23:25 | 0:23:27 | |
And that, of course, suggests that that might involve | 0:23:27 | 0:23:31 | |
some rather improbable change. | 0:23:31 | 0:23:33 | |
For two billion years, | 0:23:36 | 0:23:38 | |
the Earth was home only to simple organisms, like bacteria. | 0:23:38 | 0:23:43 | |
In short, slime. | 0:23:43 | 0:23:45 | |
But then, something happened. | 0:23:47 | 0:23:50 | |
It's thought one primitive cell swallowed another | 0:23:52 | 0:23:55 | |
and the two began working together. | 0:23:55 | 0:23:58 | |
It was the first step on the path to more and more complex organisms | 0:24:00 | 0:24:04 | |
and the huge diversity we see today. | 0:24:04 | 0:24:06 | |
What we don't know is how many of the specific features of the Earth | 0:24:08 | 0:24:13 | |
were crucial in order to allow life | 0:24:13 | 0:24:16 | |
to proceed through its stages of emerging complexity. | 0:24:16 | 0:24:19 | |
And that, therefore, means we don't know for sure | 0:24:19 | 0:24:23 | |
how likely it would be | 0:24:23 | 0:24:24 | |
that life would develop complexity on other planets. | 0:24:24 | 0:24:27 | |
This is a big debate. | 0:24:27 | 0:24:29 | |
For some, the late emergence of complex life on Earth | 0:24:31 | 0:24:34 | |
points to it being a very rare event indeed. | 0:24:34 | 0:24:37 | |
There's a hypothesis - it's called the Rare Earth hypothesis - | 0:24:42 | 0:24:46 | |
that suggests that there's something special about Earth. | 0:24:46 | 0:24:50 | |
This Rare Earth hypothesis claims that an extraordinary | 0:24:52 | 0:24:56 | |
once-in-a-galaxy run of good luck | 0:24:56 | 0:24:59 | |
led to the evolution of our planet's rich and diverse life. | 0:24:59 | 0:25:02 | |
If true, other worlds wouldn't make it past slime. | 0:25:14 | 0:25:18 | |
And slime isn't well suited to interstellar travel. | 0:25:20 | 0:25:23 | |
Some conditions that are part of the Rare Earth hypothesis | 0:25:29 | 0:25:32 | |
don't sound too rare. | 0:25:32 | 0:25:34 | |
We're looking for a star that's been stable for billions of years | 0:25:34 | 0:25:38 | |
and we're looking for a rocky planet with water on there. | 0:25:38 | 0:25:42 | |
But some are trickier. | 0:25:44 | 0:25:46 | |
One in particular takes us back once again | 0:25:47 | 0:25:51 | |
to our Earth's violent formation. | 0:25:51 | 0:25:53 | |
And a day that was responsible for much of what makes Earth so special. | 0:25:54 | 0:25:58 | |
And yet it was just a chance event. | 0:25:59 | 0:26:01 | |
It's believed the Earth once had a twin. | 0:26:03 | 0:26:05 | |
A Mars-sized planet named Theia. | 0:26:06 | 0:26:09 | |
Born in a similar orbit. | 0:26:09 | 0:26:11 | |
The result? | 0:26:12 | 0:26:14 | |
Well, be grateful you weren't there. | 0:26:16 | 0:26:18 | |
Theia was destroyed in the collision. | 0:26:23 | 0:26:25 | |
But the debris coalesced, forming our planet's travelling companion. | 0:26:28 | 0:26:33 | |
The moon. | 0:26:33 | 0:26:35 | |
It's true, moons aren't rare, | 0:26:39 | 0:26:41 | |
but our moon is huge compared to the Earth. | 0:26:41 | 0:26:44 | |
And this may have been vital for complex life. | 0:26:44 | 0:26:47 | |
Because our moon doesn't just give us tides. | 0:26:50 | 0:26:53 | |
The moon plays a key role in stabilising the Earth's axial tilt, | 0:26:55 | 0:27:02 | |
which gives rise to the nice, pleasant seasons that we enjoy. | 0:27:02 | 0:27:07 | |
There's the possibility that the existence of the moon | 0:27:07 | 0:27:10 | |
has helped a long, four-billion-year period of clement weather. | 0:27:10 | 0:27:16 | |
Without the moon, some believe our planet's tilt would have been unstable. | 0:27:22 | 0:27:26 | |
Some years, our seasons would be unbearably hot and long. | 0:27:27 | 0:27:31 | |
Other years wouldn't have seasons at all. | 0:27:31 | 0:27:34 | |
Such an unstable climate might have meant | 0:27:35 | 0:27:38 | |
that complex life never got out of the starting blocks. | 0:27:38 | 0:27:41 | |
Because evolution relies on small changes from one generation to the next. | 0:27:44 | 0:27:48 | |
If that change is useful, the creature is more likely to survive. | 0:27:48 | 0:27:53 | |
But if there were extreme swings in climate - | 0:27:55 | 0:27:58 | |
so extreme that, at times, there was no liquid water - | 0:27:58 | 0:28:02 | |
an adaptation that's useful one year may be wiped out the next. | 0:28:02 | 0:28:06 | |
No long-term stability, no natural selection. | 0:28:08 | 0:28:11 | |
And it's not just the moon. | 0:28:14 | 0:28:16 | |
There are many other examples of our planet's apparent good fortune. | 0:28:17 | 0:28:20 | |
Earth has a system of plate tectonics. | 0:28:22 | 0:28:25 | |
Plate tectonics is important for stabilising Earth's temperature. | 0:28:25 | 0:28:31 | |
The movements of the vast network of rigid plates | 0:28:32 | 0:28:34 | |
that make up our planet's surface... | 0:28:34 | 0:28:37 | |
..create massive volcanic eruptions, | 0:28:39 | 0:28:41 | |
recycling carbon dioxide into the atmosphere. | 0:28:41 | 0:28:44 | |
Today, we think of it as a nasty greenhouse gas. | 0:28:47 | 0:28:50 | |
But throughout the Earth's long history, | 0:28:50 | 0:28:52 | |
carbon dioxide has helped regulate our planet's temperature, | 0:28:52 | 0:28:57 | |
so complex life can survive. | 0:28:57 | 0:28:59 | |
The Rare Earth hypothesis also suggests | 0:29:06 | 0:29:08 | |
that we've a lot to thank Jupiter for. | 0:29:08 | 0:29:11 | |
The gas giant's huge gravitational pull might capture asteroids | 0:29:11 | 0:29:15 | |
that would otherwise be on a collision course with Earth. | 0:29:15 | 0:29:19 | |
It's hard to evolve if icy rocks | 0:29:22 | 0:29:24 | |
constantly rain down on you from above. | 0:29:24 | 0:29:26 | |
The special conditions that led to complex life on Earth go on and on. | 0:29:31 | 0:29:35 | |
And maybe there's only one conclusion. | 0:29:36 | 0:29:40 | |
It's possible that we are a trillion-to-one fluke. | 0:29:41 | 0:29:47 | |
That there's some combination of factors that make Earth special. | 0:29:47 | 0:29:51 | |
My view is that these ideas of a so-called very rare Earth are rather oversold | 0:29:56 | 0:30:01 | |
and that we've learnt that life can exist in a variety of contexts in the Earth. | 0:30:01 | 0:30:06 | |
And our observations are limited, | 0:30:06 | 0:30:08 | |
our imaginations are even more limited. | 0:30:08 | 0:30:10 | |
So my view is that we should not be put off | 0:30:10 | 0:30:14 | |
and not take too seriously | 0:30:14 | 0:30:16 | |
the fact that our particular evolutionary track here on Earth | 0:30:16 | 0:30:20 | |
depended on some special conditions. | 0:30:20 | 0:30:22 | |
There's another, more practical reason | 0:30:29 | 0:30:31 | |
that the Rare Earth hypothesis might be overplayed. | 0:30:31 | 0:30:34 | |
Perhaps it underestimates the sheer number and variety | 0:30:37 | 0:30:41 | |
of other worlds in our galaxy. | 0:30:41 | 0:30:43 | |
We've learnt, actually, just in the last few years, | 0:30:45 | 0:30:48 | |
a great deal about our universe | 0:30:48 | 0:30:50 | |
that makes the night sky far more interesting. | 0:30:50 | 0:30:53 | |
100 years ago, people thought that planets were very rare | 0:30:53 | 0:30:56 | |
around other stars. | 0:30:56 | 0:30:58 | |
No-one had found any direct evidence for a planet until 20 years ago. | 0:30:58 | 0:31:04 | |
It was once thought that detecting planets around other stars | 0:31:06 | 0:31:09 | |
would be impossible. | 0:31:09 | 0:31:11 | |
They were just too small and too far away. | 0:31:14 | 0:31:17 | |
But in 1995, the impossible happened. | 0:31:20 | 0:31:23 | |
Two Swiss scientists - Didier Queloz and Michel Mayor - | 0:31:30 | 0:31:34 | |
were monitoring the positions of some 140 stars. | 0:31:34 | 0:31:37 | |
But one of these stars was a puzzle. | 0:31:39 | 0:31:41 | |
On closer inspection, they realised | 0:31:42 | 0:31:44 | |
the sun-like star, 51 Pegasi, was on the move. | 0:31:44 | 0:31:49 | |
In fact, the first reaction that you have at that time is, | 0:31:52 | 0:31:55 | |
"Oh, something is wrong with the experiment". | 0:31:55 | 0:31:57 | |
And you observe it again the day after and the day after | 0:31:57 | 0:32:00 | |
and then it was more and more awful | 0:32:00 | 0:32:03 | |
because it was moving every day. | 0:32:03 | 0:32:06 | |
And you say, "There is really a big problem with the experiment". | 0:32:06 | 0:32:09 | |
Each time they looked, the movement had changed. | 0:32:09 | 0:32:14 | |
Gradually, a pattern emerged. | 0:32:14 | 0:32:16 | |
The star was wobbling around a point. | 0:32:18 | 0:32:21 | |
This could mean only one thing. | 0:32:24 | 0:32:27 | |
51 Peg was not alone. | 0:32:27 | 0:32:29 | |
It was being pushed and pulled by the gravity | 0:32:31 | 0:32:33 | |
of a smaller body we couldn't see. | 0:32:33 | 0:32:35 | |
This was the first planet we'd found orbiting another star. | 0:32:38 | 0:32:41 | |
A huge moment in our hunt for worlds aliens might call home. | 0:32:41 | 0:32:46 | |
It was a completely crazy time, with calls from papers, | 0:32:48 | 0:32:54 | |
from television, from radio, from...from all the world. | 0:32:54 | 0:32:59 | |
And, er...e-mail - 100 email per day, or something like this. | 0:32:59 | 0:33:03 | |
It was absolutely, completely a time | 0:33:03 | 0:33:06 | |
where we had no possibility to work at all. | 0:33:06 | 0:33:08 | |
This planet was too large and too hot to be home to life. | 0:33:11 | 0:33:15 | |
But we've got better at this planet-hunting lark. | 0:33:16 | 0:33:19 | |
Over time, we've found smaller planets, | 0:33:21 | 0:33:24 | |
further out from their parent stars. | 0:33:24 | 0:33:26 | |
Until eventually, in April 2007, | 0:33:29 | 0:33:33 | |
Gliese 581c was discovered. | 0:33:33 | 0:33:36 | |
And scientists thought it just might be capable of supporting life. | 0:33:36 | 0:33:42 | |
European astronomers have spotted a new planet outside our solar system | 0:33:42 | 0:33:46 | |
which closely resembles the planet Earth. | 0:33:46 | 0:33:48 | |
Every time somebody finds an Earth-like planet, | 0:33:50 | 0:33:52 | |
the probability that there is life | 0:33:52 | 0:33:54 | |
somewhere else in the universe goes up a bit. | 0:33:54 | 0:33:57 | |
This latest find has set the world of astronomy alight. | 0:33:57 | 0:34:01 | |
In the last few years, more and more planets have been found. | 0:34:02 | 0:34:06 | |
Many in the so-called Goldilocks Zone - | 0:34:06 | 0:34:08 | |
not too hot and not too cold for liquid water. | 0:34:08 | 0:34:11 | |
The more we look, the more we realise | 0:34:16 | 0:34:18 | |
that Earth-like planets are all over the place. | 0:34:18 | 0:34:21 | |
The universe which we now perceive | 0:34:23 | 0:34:26 | |
is far vaster than it was perceived to be in earlier centuries. | 0:34:26 | 0:34:31 | |
In our galaxy, there are probably | 0:34:31 | 0:34:33 | |
literally a billion planets like the Earth. | 0:34:33 | 0:34:36 | |
We've seen that it's possible simple life is common in the universe. | 0:34:38 | 0:34:42 | |
Complex life could be trickier. | 0:34:45 | 0:34:47 | |
Conditions need to be just right. | 0:34:50 | 0:34:52 | |
But the sheer number of planets we've discovered in our own galaxy | 0:34:56 | 0:35:00 | |
suggests that such conditions could be surprisingly common. | 0:35:00 | 0:35:04 | |
But there's one further leap that needs to happen | 0:35:07 | 0:35:09 | |
before we can hope to make contact with aliens - | 0:35:09 | 0:35:12 | |
the leap to intelligence. | 0:35:12 | 0:35:15 | |
We're not talking about the ability to bash a few rocks together. | 0:35:17 | 0:35:20 | |
We need civilisations that can communicate | 0:35:20 | 0:35:24 | |
across the vastness of space. | 0:35:24 | 0:35:26 | |
So, is it possible to predict | 0:35:46 | 0:35:47 | |
how common intelligent civilisations are in the galaxy? | 0:35:47 | 0:35:51 | |
Fortunately, thanks to astronomer Frank Drake, | 0:35:57 | 0:36:00 | |
we have an equation designed to tell us just that. | 0:36:00 | 0:36:04 | |
And, in, fact this is our number N. | 0:36:04 | 0:36:07 | |
The number of technical civilisations in the galaxy. | 0:36:07 | 0:36:10 | |
The challenge is to give each term a number | 0:36:12 | 0:36:15 | |
and simply multiply them together. | 0:36:15 | 0:36:17 | |
Into the now famous - or infamous - Drake equation | 0:36:19 | 0:36:21 | |
goes everything from astrophysics, through evolutionary biology | 0:36:21 | 0:36:25 | |
to whatever it is that governs | 0:36:25 | 0:36:27 | |
the lifetime of a detectable civilisation. | 0:36:27 | 0:36:30 | |
Not surprisingly, no-one's solved it yet, but anyone can have a go. | 0:36:30 | 0:36:34 | |
It's almost a game the whole family could play. | 0:36:34 | 0:36:37 | |
Get the numbers right, and, bingo! | 0:36:37 | 0:36:40 | |
You know how many communicating civilisations are likely to be out there. | 0:36:40 | 0:36:44 | |
So, in 1981, BBC Horizon locked some of the brightest minds in Nasa | 0:36:47 | 0:36:52 | |
in a room together and asked them to come up with a solution. | 0:36:52 | 0:36:56 | |
Team captain today is John Wolfe. | 0:36:58 | 0:37:00 | |
I think it was Frank Drake himself who said that | 0:37:00 | 0:37:03 | |
this is a rather nice way of fitting | 0:37:03 | 0:37:05 | |
a great deal of ignorance into a very small space. | 0:37:05 | 0:37:08 | |
Some of Drake's variables we know reasonably well. | 0:37:08 | 0:37:12 | |
We know how often stars form. | 0:37:12 | 0:37:15 | |
And these days, we can have a good stab at | 0:37:15 | 0:37:17 | |
how many stars have planets. | 0:37:17 | 0:37:20 | |
-Seem to have more consensus... -That was easy! | 0:37:20 | 0:37:22 | |
..more consensus there than anywhere. Quickly. | 0:37:22 | 0:37:24 | |
This may reflect the fact that we're moving to the area we know least about. | 0:37:24 | 0:37:28 | |
It's the later terms we know less well. | 0:37:28 | 0:37:31 | |
But scientists don't mind guesswork, provided it's educated guesswork. | 0:37:32 | 0:37:36 | |
And when it comes to asking if life | 0:37:36 | 0:37:38 | |
would eventually evolve intelligence, | 0:37:38 | 0:37:41 | |
the Nasa scientists were actually quite confident. | 0:37:41 | 0:37:45 | |
It's very natural, I think, to argue that intelligence | 0:37:45 | 0:37:47 | |
with the survival capability that's inherent in it will also follow. | 0:37:47 | 0:37:51 | |
I think that's the usual argument for it being an unity. | 0:37:51 | 0:37:54 | |
In fact, the first guy to get smart is the one that dominates the planet. | 0:37:55 | 0:37:59 | |
-That's right. -Thank God we were first. | 0:37:59 | 0:38:03 | |
They were equally confident that intelligent life | 0:38:03 | 0:38:06 | |
would go on to develop the ability to communicate across space. | 0:38:06 | 0:38:10 | |
Put it up there, that's good enough. Wait until we get to L. | 0:38:13 | 0:38:15 | |
THEY LAUGH | 0:38:15 | 0:38:17 | |
You might think this would mean that intelligent civilisations are ten a penny. | 0:38:17 | 0:38:22 | |
But the final term, L, causes the team some problems. | 0:38:22 | 0:38:26 | |
It asks us to estimate the lifetime of communicating civilisations. | 0:38:28 | 0:38:32 | |
It soon emerges they're going to chicken out of reaching a conclusion. | 0:38:34 | 0:38:37 | |
So if we were to take that lower value of 100, that says that N is, er... | 0:38:37 | 0:38:42 | |
The average lifetime lies somewhere between a few hundred years | 0:38:42 | 0:38:45 | |
and a few billion. | 0:38:45 | 0:38:46 | |
So the number of civilisations in the galaxy now | 0:38:46 | 0:38:49 | |
is somewhere between a few tens and a few hundred million. | 0:38:49 | 0:38:52 | |
A few tens to a few hundred million | 0:38:52 | 0:38:55 | |
isn't the most exact solution. | 0:38:55 | 0:38:57 | |
The term L is so hard to estimate | 0:39:00 | 0:39:03 | |
because it forces us to ask a very difficult | 0:39:03 | 0:39:06 | |
and rather uncomfortable question. | 0:39:06 | 0:39:08 | |
How long do intelligent civilisations like ours last? | 0:39:10 | 0:39:15 | |
Of course, we know that here on Earth, the amount of time | 0:39:16 | 0:39:19 | |
we've had any kind of civilisation is a few thousand years, | 0:39:19 | 0:39:24 | |
and that is only one millionth of the age of the Earth. | 0:39:24 | 0:39:28 | |
So it's just a sliver. | 0:39:28 | 0:39:30 | |
And we don't know how long it'll last in future. | 0:39:30 | 0:39:33 | |
If civilisations last for only a few hundred years, | 0:39:36 | 0:39:39 | |
then the window of communication is impossibly small. | 0:39:39 | 0:39:43 | |
There are actually people trying to figure out | 0:39:45 | 0:39:47 | |
just how long advanced civilisations might last. | 0:39:47 | 0:39:50 | |
Dr Anders Sandberg works at the Future of Humanity Institute | 0:39:52 | 0:39:56 | |
in Oxford University. | 0:39:56 | 0:39:58 | |
It's his job to think about the myriad ways | 0:39:59 | 0:40:02 | |
a society could destroy itself. | 0:40:02 | 0:40:04 | |
So we humans have mastered this planet, | 0:40:06 | 0:40:09 | |
but in the process, of course, | 0:40:09 | 0:40:10 | |
we caused a lot of extinctions of animals, | 0:40:10 | 0:40:12 | |
and now we're changing the climate and we're developing bioweapons | 0:40:12 | 0:40:16 | |
in the lab that could kill a lot of people. | 0:40:16 | 0:40:18 | |
So we're obviously a danger to ourselves. | 0:40:18 | 0:40:20 | |
So it might be that sufficiently-powerful technologies | 0:40:20 | 0:40:23 | |
mean that a civilisation will start blowing itself up, | 0:40:23 | 0:40:26 | |
or poisoning itself in a very effective way. | 0:40:26 | 0:40:30 | |
And let's not forget, advanced aliens | 0:40:36 | 0:40:40 | |
might have technologies that we haven't even dreamt of yet. | 0:40:40 | 0:40:44 | |
The basic problem here is that powerful technology is dangerous. | 0:40:46 | 0:40:50 | |
And advanced civilisations will have a lot of powerful technologies at their disposal. | 0:40:52 | 0:40:56 | |
Quite a sight, wasn't it, sir? | 0:40:57 | 0:40:59 | |
A sight I'd rather not be seeing. | 0:40:59 | 0:41:01 | |
The truth is, we don't know whether intelligence | 0:41:05 | 0:41:08 | |
might ultimately be fatal. | 0:41:08 | 0:41:09 | |
So we can't know how many civilisations out there | 0:41:11 | 0:41:14 | |
could hold up their end of the conversation. | 0:41:14 | 0:41:17 | |
And this makes our hunt all the more important. | 0:41:17 | 0:41:20 | |
Because if we find advanced aliens, we'll know for certain | 0:41:22 | 0:41:26 | |
that societies can survive their own powerful technologies. | 0:41:26 | 0:41:30 | |
So, how do you go about finding extraterrestrial intelligence? | 0:41:33 | 0:41:36 | |
What we know is that here on Earth, | 0:41:47 | 0:41:49 | |
life has evolved to a kind of intelligence | 0:41:49 | 0:41:52 | |
that can develop a technological civilisation | 0:41:52 | 0:41:55 | |
which would make our activities detectable in principle | 0:41:55 | 0:41:59 | |
to an alien with a big telescope. | 0:41:59 | 0:42:01 | |
So we've learnt that we have become more conspicuous | 0:42:01 | 0:42:05 | |
and that an alien watching the Earth | 0:42:05 | 0:42:07 | |
would realise that something special had happened | 0:42:07 | 0:42:09 | |
in the last few centuries. | 0:42:09 | 0:42:11 | |
Humans have existed for about 200,000 years. | 0:42:12 | 0:42:16 | |
But for most of this time, alien astronomers looking at the Earth | 0:42:16 | 0:42:20 | |
would see little to suggest there's anything intelligent down here. | 0:42:20 | 0:42:24 | |
INSTRUMENTAL | 0:42:24 | 0:42:26 | |
In fact, it wasn't until 80 years ago | 0:42:32 | 0:42:35 | |
that we really screamed our presence to the galaxy. | 0:42:35 | 0:42:38 | |
When we began leaking radio and television signals into space. | 0:42:41 | 0:42:44 | |
So if the Earth's first sign of intelligence | 0:42:48 | 0:42:50 | |
was our making a racket in the radio spectrum, | 0:42:50 | 0:42:53 | |
it's only natural to wonder whether intelligent aliens | 0:42:53 | 0:42:56 | |
would be doing the same. | 0:42:56 | 0:42:58 | |
-Listen... -CRACKLING | 0:42:59 | 0:43:02 | |
Sound picked up from outer space by radio telescope | 0:43:04 | 0:43:08 | |
for some earthly usage still unknown. | 0:43:08 | 0:43:11 | |
The '50s and '60s saw the construction of radio telescopes | 0:43:17 | 0:43:22 | |
so sensitive, they could tune into signals | 0:43:22 | 0:43:25 | |
from the other side of the galaxy. | 0:43:25 | 0:43:27 | |
The hunt was on. | 0:43:28 | 0:43:30 | |
Into such a dish one day could come a signal | 0:43:34 | 0:43:36 | |
that would reveal the existence of other creatures | 0:43:36 | 0:43:39 | |
unimaginably more intelligent than we are. | 0:43:39 | 0:43:41 | |
It was the radio astronomers who were the first to talk about | 0:43:43 | 0:43:46 | |
doing serious searches for artificial signals. | 0:43:46 | 0:43:50 | |
And the first effort to do this was pioneered by Frank Drake, | 0:43:50 | 0:43:55 | |
who is one of the pioneers of this subject | 0:43:55 | 0:43:58 | |
and is still one of the leaders of it today. | 0:43:58 | 0:44:01 | |
Before he wrote his frustrating equation, | 0:44:06 | 0:44:08 | |
Frank Drake gave birth to Seti - | 0:44:08 | 0:44:11 | |
the Search for Extraterrestrial Intelligence. | 0:44:11 | 0:44:14 | |
We used the 85-foot telescope there | 0:44:17 | 0:44:19 | |
and a special, very sensitive receiver | 0:44:19 | 0:44:21 | |
which was especially designed to detect intelligent signals | 0:44:21 | 0:44:25 | |
rather than the natural emissions radio astronomers normally study. | 0:44:25 | 0:44:29 | |
For the first time, man made a serious attempt | 0:44:29 | 0:44:32 | |
to determine whether he was alone in the universe. | 0:44:32 | 0:44:35 | |
We searched for two months | 0:44:35 | 0:44:37 | |
and studied the two nearest stars which are like the sun. | 0:44:37 | 0:44:40 | |
The stars Tau Ceti and Epsilon Eridani. | 0:44:40 | 0:44:43 | |
For all we knew then, every star had intelligent civilisations in orbit, | 0:44:46 | 0:44:51 | |
pumping out radio waves. | 0:44:51 | 0:44:53 | |
And just a few days into the search, | 0:44:53 | 0:44:55 | |
it looked like that might be the case. | 0:44:55 | 0:44:58 | |
At one point, we had a very exciting recording on our tape recorder. | 0:44:58 | 0:45:01 | |
The telescope picked up a short, but clearly artificial signal | 0:45:04 | 0:45:07 | |
on a frequency protected for radio astronomy. | 0:45:07 | 0:45:10 | |
The news leaked out. | 0:45:14 | 0:45:16 | |
Journalists started to call up, | 0:45:16 | 0:45:18 | |
asking if Drake had found an alien civilisation on his first go. | 0:45:18 | 0:45:22 | |
Could it really be so easy? | 0:45:23 | 0:45:25 | |
Ten days later and the signal came again. | 0:45:27 | 0:45:30 | |
Only this time, the source was clear. | 0:45:30 | 0:45:33 | |
Analysis of this and further study of the signal | 0:45:34 | 0:45:38 | |
showed it had come not from space, | 0:45:38 | 0:45:41 | |
but rather from a radio station on Earth. | 0:45:41 | 0:45:43 | |
What Drake had discovered was a top-secret U2 spy plane | 0:45:44 | 0:45:49 | |
flying at high altitude. | 0:45:49 | 0:45:50 | |
# I'm sorry...# | 0:45:50 | 0:45:53 | |
Not quite the distant signal they were hoping for. | 0:45:53 | 0:45:56 | |
# That I was such a fool...# | 0:45:57 | 0:46:02 | |
After 300 hours of searching, | 0:46:02 | 0:46:04 | |
we concluded that our two target stars, | 0:46:04 | 0:46:07 | |
Tau Ceti and Epsilon Eridani, | 0:46:07 | 0:46:09 | |
had produced no evidence whatsoever for extraterrestrial radio signals. | 0:46:09 | 0:46:13 | |
It was an inauspicious start to our search. | 0:46:17 | 0:46:20 | |
No aliens, and a false signal. | 0:46:20 | 0:46:23 | |
But Frank had paved the way. | 0:46:23 | 0:46:25 | |
Systematic searches were now possible. | 0:46:25 | 0:46:28 | |
More followed. This time, scanning thousands of stars. | 0:46:29 | 0:46:34 | |
-I see two glitches on this one. -Yeah, yeah. | 0:46:34 | 0:46:37 | |
Probably a car going by, | 0:46:37 | 0:46:39 | |
or the equipment's screwed up, or something like that. | 0:46:39 | 0:46:42 | |
Still nothing. | 0:46:43 | 0:46:45 | |
But maybe we don't hear anything | 0:46:45 | 0:46:47 | |
because we're going about the search all wrong. | 0:46:47 | 0:46:50 | |
A lot of sloppy thinking is quite accepted about alien intelligence. | 0:46:50 | 0:46:54 | |
And I think that is a problem. | 0:46:54 | 0:46:56 | |
A lot of people, for example, just make bland assumptions | 0:46:56 | 0:46:59 | |
that aliens must, of course, be like us. | 0:46:59 | 0:47:02 | |
Radio signals of the type we churn out | 0:47:05 | 0:47:08 | |
may have been ditched long ago by alien civilisations. | 0:47:08 | 0:47:11 | |
Who knows what technologies they're on to now? | 0:47:14 | 0:47:18 | |
But if they're super-advanced, | 0:47:18 | 0:47:20 | |
they'll probably be doing things on a big scale. | 0:47:20 | 0:47:22 | |
Maybe big enough for us to detect. | 0:47:22 | 0:47:25 | |
Maybe we should look for the side effects of activities. | 0:47:26 | 0:47:29 | |
A super civilisation might be sending off all sorts of radiation, | 0:47:29 | 0:47:32 | |
not because they want to tell us, "We're here," | 0:47:32 | 0:47:35 | |
but because that's a side effect of what they're actually doing. | 0:47:35 | 0:47:38 | |
It comes down to energy. | 0:47:41 | 0:47:43 | |
As humanity has advanced, we've needed more and more of it. | 0:47:43 | 0:47:46 | |
Fossil fuels may not be the best solution, | 0:47:48 | 0:47:51 | |
so we're turning to wind power, tidal power... | 0:47:51 | 0:47:54 | |
..and the light emitted from our star. | 0:47:56 | 0:47:58 | |
And advanced aliens might have to go to even further lengths | 0:48:01 | 0:48:04 | |
to quench their thirst for energy. | 0:48:04 | 0:48:06 | |
You can get even more energy if you put solar panels in space. | 0:48:07 | 0:48:11 | |
It's day all the time, and there is no atmosphere blocking it. | 0:48:11 | 0:48:15 | |
So the logical endpoint would be | 0:48:15 | 0:48:17 | |
to put solar panels around the entire sun. | 0:48:17 | 0:48:21 | |
Who knows what such a structure would look like? | 0:48:21 | 0:48:23 | |
Indeed, who knows what other strange, supersized technologies | 0:48:23 | 0:48:27 | |
aliens might develop? | 0:48:27 | 0:48:29 | |
But it's likely that from Earth, such megastructures would appear | 0:48:29 | 0:48:33 | |
like nothing we've ever seen before. | 0:48:33 | 0:48:36 | |
And maybe this is how an alien civilisation will reveal itself. | 0:48:36 | 0:48:39 | |
I think we look in every way we can. | 0:48:40 | 0:48:43 | |
Traditionally, we've looked for radio signals. | 0:48:43 | 0:48:46 | |
We should look for optical flashes, we should look for artefacts, | 0:48:46 | 0:48:50 | |
we should look for structures in space | 0:48:50 | 0:48:52 | |
that look manifestly artificial. | 0:48:52 | 0:48:54 | |
Whilst we wait for first contact, | 0:48:56 | 0:48:59 | |
we have time to consider another question. | 0:48:59 | 0:49:01 | |
If any aliens out there are more advanced than we are... | 0:49:03 | 0:49:06 | |
..is it a good idea for us to track them down? | 0:49:08 | 0:49:11 | |
The dangers of alien encounters have certainly | 0:49:18 | 0:49:20 | |
inspired their share of sci-fi films. | 0:49:20 | 0:49:23 | |
Whether they're galactic colonialists, | 0:49:26 | 0:49:29 | |
as in The War Of The Worlds, | 0:49:29 | 0:49:32 | |
taking over our lives one at a time... | 0:49:32 | 0:49:34 | |
You fools! You're in danger! | 0:49:34 | 0:49:36 | |
..like in the classic Invasion Of The Body Snatchers... | 0:49:36 | 0:49:40 | |
They're after all of us! My wife, my children, everyone! | 0:49:40 | 0:49:43 | |
..or simply mindless predators, like in Alien. | 0:49:43 | 0:49:47 | |
SCREAMING | 0:49:49 | 0:49:50 | |
And maybe science fiction wasn't too wide of the mark. | 0:49:50 | 0:49:53 | |
Even top scientists have their concerns. | 0:49:53 | 0:49:58 | |
If aliens decided to visit us, then the outcome might be similar | 0:49:58 | 0:50:02 | |
to when Europeans arrived in the Americas. | 0:50:02 | 0:50:06 | |
That did not turn out well for the Native Americans. | 0:50:06 | 0:50:10 | |
So should we be worried about advertising | 0:50:11 | 0:50:14 | |
our existence to the galaxy? | 0:50:14 | 0:50:16 | |
Martin's not convinced. | 0:50:16 | 0:50:18 | |
I would guess that if there are any aliens out there, | 0:50:18 | 0:50:21 | |
then, if they were advanced, they would know we're here already. | 0:50:21 | 0:50:26 | |
They may have been watching the Earth for millions of years, | 0:50:26 | 0:50:30 | |
realising it's a place where something interesting | 0:50:30 | 0:50:32 | |
might be happening. | 0:50:32 | 0:50:33 | |
So, for that reason, I find it hard to take seriously people | 0:50:33 | 0:50:36 | |
who are worried about sending out some sort of message. | 0:50:36 | 0:50:40 | |
And, anyway, it's already too late. | 0:50:40 | 0:50:43 | |
As soon as we started leaking waves into space, | 0:50:43 | 0:50:46 | |
we said to the galaxy, "We're here." | 0:50:46 | 0:50:49 | |
So what type of entities might be out there, tuning in to our signals? | 0:50:51 | 0:50:54 | |
Who, or indeed what, might we make contact with? | 0:50:56 | 0:51:00 | |
We think we'd know an alien if we saw one. | 0:51:14 | 0:51:17 | |
The classic is ET. | 0:51:17 | 0:51:19 | |
I'll be right here. | 0:51:21 | 0:51:26 | |
He might have a bigger head, short little legs | 0:51:26 | 0:51:28 | |
and long, thin fingers, but the basic body shape | 0:51:28 | 0:51:31 | |
is much like our own. | 0:51:31 | 0:51:33 | |
But Martin thinks this is about as far from what an actual alien | 0:51:37 | 0:51:40 | |
might look like as it could be. | 0:51:40 | 0:51:42 | |
A clue to what we might find, lies in our own species' future. | 0:51:44 | 0:51:49 | |
It's taken us a few hundred years to evolve | 0:51:49 | 0:51:53 | |
our technological civilisation. | 0:51:53 | 0:51:55 | |
It's changing very fast, | 0:51:55 | 0:51:56 | |
and if we think of what's going to happen in the next century, | 0:51:56 | 0:52:00 | |
one scenario is that intelligence of the organic kind | 0:52:00 | 0:52:05 | |
may be near its limit with humans. | 0:52:05 | 0:52:08 | |
We like to think we're a pretty smart species. | 0:52:09 | 0:52:12 | |
As evidence, we might point to our technological achievements. | 0:52:13 | 0:52:17 | |
Our computers and sophisticated artificial intelligence, perhaps? | 0:52:18 | 0:52:21 | |
But maybe they're getting so good that our robot servants | 0:52:23 | 0:52:28 | |
will soon be our robot masters. | 0:52:28 | 0:52:30 | |
The future intelligence in our solar system may lie | 0:52:32 | 0:52:35 | |
not with organic life on Earth, but with these entities which are | 0:52:35 | 0:52:38 | |
electronic, rather than chemical, | 0:52:38 | 0:52:41 | |
like what goes on in our human skulls. | 0:52:41 | 0:52:43 | |
Martin's point is that it looks like it won't be long | 0:52:44 | 0:52:47 | |
before the robots here on Earth are much smarter than we are. | 0:52:47 | 0:52:51 | |
And if this happens, | 0:52:52 | 0:52:54 | |
it's likely that THEIR culture will dominate ours. | 0:52:54 | 0:52:57 | |
But what does this have to do with aliens? | 0:53:03 | 0:53:06 | |
Well, if it does turn out that humanity's role is to act | 0:53:06 | 0:53:10 | |
as the midwives to a new robotic super species, | 0:53:10 | 0:53:14 | |
there's no reason other worlds won't have followed a similar path. | 0:53:14 | 0:53:17 | |
If there were another planet on which evolution had tracked | 0:53:19 | 0:53:24 | |
what happens on Earth, then there are two options. | 0:53:24 | 0:53:28 | |
Either it hasn't yet got to | 0:53:28 | 0:53:30 | |
the stage of emergent intelligence - we see no signal from it - | 0:53:30 | 0:53:34 | |
or it's got to the stage when the machines have taken over. | 0:53:34 | 0:53:38 | |
What is most unlikely is that we would find another planet | 0:53:39 | 0:53:44 | |
whose evolution was so synchronised with ours | 0:53:44 | 0:53:47 | |
that we would observe it in just the few centuries | 0:53:47 | 0:53:52 | |
when the dominant feature is organic intelligent civilisation. | 0:53:52 | 0:53:57 | |
If Martin's right, in our first encounter with aliens | 0:53:59 | 0:54:02 | |
we might be dealing not with organisms, | 0:54:02 | 0:54:05 | |
but with super-advanced artificial intelligences. | 0:54:05 | 0:54:08 | |
And this might give us cause for concern. | 0:54:10 | 0:54:13 | |
After all, in films like The Terminator, | 0:54:13 | 0:54:15 | |
when the machines took control, it didn't turn out well for the humans. | 0:54:15 | 0:54:19 | |
And, actually, maybe they underestimated the dangers. | 0:54:21 | 0:54:25 | |
It might all depend | 0:54:25 | 0:54:27 | |
on why the robots were built in the first place. | 0:54:27 | 0:54:30 | |
So you might want to use an autonomous weapon for warfare. | 0:54:30 | 0:54:35 | |
And it's very convenient if it can build more of itself. | 0:54:35 | 0:54:38 | |
And you could programme it to attack your enemies. | 0:54:38 | 0:54:40 | |
So what if you let them loose and they attacked everybody else, | 0:54:40 | 0:54:44 | |
and then you went extinct? | 0:54:44 | 0:54:45 | |
So now you have these mindless machines | 0:54:45 | 0:54:48 | |
going around killing off young civilisations. | 0:54:48 | 0:54:51 | |
The idea that self-replicating killer robots roam throughout space | 0:54:52 | 0:54:56 | |
is called the Berserker Hypothesis, after the novels by Fred Saberhagen. | 0:54:56 | 0:55:02 | |
If true, maybe we should turn off our transmitters | 0:55:03 | 0:55:07 | |
and sit in the dark with our fingers crossed, hoping the machines | 0:55:07 | 0:55:10 | |
have been too busy causing destruction elsewhere to notice us. | 0:55:10 | 0:55:14 | |
And even if the robots aren't programmed killers, | 0:55:18 | 0:55:21 | |
we could still be in trouble. | 0:55:21 | 0:55:23 | |
And this might not be deliberate at all. | 0:55:23 | 0:55:26 | |
The software is really smart and you give it an order | 0:55:26 | 0:55:29 | |
and it implements the order faultlessly, | 0:55:29 | 0:55:31 | |
except that it wasn't in the way you wanted. | 0:55:31 | 0:55:34 | |
And it converts the planet into paperclips, | 0:55:34 | 0:55:36 | |
and then the rest of the galaxy into paperclips, | 0:55:36 | 0:55:39 | |
because that was the order - "Make more paperclips." | 0:55:39 | 0:55:42 | |
Whilst we can't do anything about how aliens may create | 0:55:43 | 0:55:46 | |
their AI, Martin thinks that we at least should proceed with caution. | 0:55:46 | 0:55:51 | |
We've got to ensure that the way in which innovation leads | 0:55:52 | 0:55:56 | |
from the limited-capacity artificial intelligence we have today, | 0:55:56 | 0:56:01 | |
to the more powerful ones, is moderated and regulated, | 0:56:01 | 0:56:06 | |
just like we already have to moderate and regulate | 0:56:06 | 0:56:08 | |
the way biotech is used. | 0:56:08 | 0:56:10 | |
Whether benevolent or not, one thing's for sure - | 0:56:11 | 0:56:15 | |
if we encounter such beings, | 0:56:15 | 0:56:18 | |
they would be unlike anything we've ever seen before. | 0:56:18 | 0:56:21 | |
We are thinking about the possibility of entities who may | 0:56:23 | 0:56:28 | |
be able to grasp concepts which are as far beyond the human mind | 0:56:28 | 0:56:33 | |
as quantum theory is beyond a monkey's mind. | 0:56:33 | 0:56:36 | |
So, are these entities out there? | 0:56:38 | 0:56:40 | |
We've seen how scientists think our universe | 0:56:43 | 0:56:45 | |
might be teeming with life. | 0:56:45 | 0:56:47 | |
And perhaps somewhere it's evolved, | 0:56:49 | 0:56:52 | |
and gone on to do things that dwarf our own achievements. | 0:56:52 | 0:56:55 | |
But we've also seen that there are an awful lot of barriers | 0:56:59 | 0:57:03 | |
to intelligent civilisations. | 0:57:03 | 0:57:04 | |
It feels like we're on the brink. | 0:57:05 | 0:57:08 | |
There is a huge truth to discover. | 0:57:11 | 0:57:13 | |
A truth that tells us not just what's out there, | 0:57:14 | 0:57:19 | |
but what might lie ahead for us down here on Earth. | 0:57:19 | 0:57:23 | |
Whatever we find, one thing is certain - | 0:57:24 | 0:57:28 | |
the answer will change our understanding | 0:57:28 | 0:57:30 | |
of our place in the universe for ever. | 0:57:30 | 0:57:33 | |
Were it the case that the origin of life, | 0:57:34 | 0:57:37 | |
or the origin of intelligent life, were an extremely rare phenomenon | 0:57:37 | 0:57:41 | |
so that we were, in a sense, unique, or unique in our galaxy, | 0:57:41 | 0:57:45 | |
then our fate matters not just to us, | 0:57:45 | 0:57:48 | |
but maybe in a sense of cosmic importance, | 0:57:48 | 0:57:51 | |
and the greening of the galaxy could then start with us. | 0:57:51 | 0:57:55 | |
But, of course, if there were life everywhere in our galaxy - | 0:57:58 | 0:58:03 | |
as there may well be - | 0:58:03 | 0:58:05 | |
it would, in a sense, force us to be somewhat more cosmically modest. | 0:58:05 | 0:58:08 | |
But the upside would be that, | 0:58:11 | 0:58:13 | |
instead of there just being lifeless planets and stars | 0:58:13 | 0:58:15 | |
orbiting around in the galaxy, | 0:58:15 | 0:58:18 | |
we would realise that we were in a far more interesting cosmos | 0:58:18 | 0:58:21 | |
than one in which life is limited to one place. | 0:58:21 | 0:58:24 |