0:00:11 > 0:00:13What if we're alone in the galaxy?
0:00:15 > 0:00:18What if no other intelligent life has ever glimpsed
0:00:18 > 0:00:22the beauty of a star rising over a planet's horizon?
0:00:23 > 0:00:27For many years, this question was asked, not by scientists,
0:00:27 > 0:00:30but by philosophers and theologians.
0:00:31 > 0:00:34But then, 50 years ago, an astronomer came up with
0:00:34 > 0:00:39a mathematical equation which changed everything.
0:00:39 > 0:00:44The equation estimated the number of intelligent civilisations in our galaxy
0:00:44 > 0:00:50and it gave the possibility of their existence a scientific legitimacy.
0:00:56 > 0:00:57But more incredibly,
0:00:57 > 0:01:01this simple equation has gone on to shape the science of a generation.
0:01:03 > 0:01:10It's led to new insight into the nature of life, the cosmos and the enigma of intelligence.
0:01:11 > 0:01:13And, it's allowing us to speculate
0:01:13 > 0:01:18on the true nature of our relationship with the universe.
0:01:43 > 0:01:47My name's Dallas Campbell and ever since I first read about the Drake Equation,
0:01:47 > 0:01:52I've been intrigued that a simple scientific formula could tell us
0:01:52 > 0:01:56so much about the existence of extraterrestrial intelligence.
0:01:56 > 0:02:01That it could help us answer what is, perhaps, our most profound question.
0:02:06 > 0:02:09When you look up at a clear, desert night sky, like this,
0:02:09 > 0:02:14you can start to physically sense just how huge the universe is.
0:02:14 > 0:02:17And the few thousand stars you can see are, of course,
0:02:17 > 0:02:22just a tiny fraction of the billions of stars that make up our galaxy.
0:02:22 > 0:02:25And I don't know about you, but when I look up,
0:02:25 > 0:02:31I can't help but wonder what, or who else might be out there.
0:02:34 > 0:02:36What I want to find out, is what we do know,
0:02:36 > 0:02:40what we can know, and how close we might be to finding an answer.
0:02:40 > 0:02:43And that journey starts with a telescope.
0:02:55 > 0:02:5950 years ago, one man tried to do something that nobody had ever really tried to do before,
0:02:59 > 0:03:05and that's attempt to answer this question in a more scientific and more rational way.
0:03:05 > 0:03:07And that attempt happened here,
0:03:07 > 0:03:10at the Greenbank Observatory in West Virginia.
0:03:21 > 0:03:27In 1960, Doctor Frank Drake was a leading light in the new field of radio astronomy.
0:03:28 > 0:03:34With its huge radio dishes, it was revolutionising the way we looked at the universe.
0:03:36 > 0:03:41But in April that year, he decided to do something truly extraordinary.
0:03:41 > 0:03:44He pointed one of the radio dishes out into space
0:03:44 > 0:03:48to listen for signs of extraterrestrial intelligence.
0:03:51 > 0:03:54It was a decision that could have labelled him a crank.
0:03:54 > 0:03:57It could have ruined his career.
0:03:57 > 0:04:01But instead, it was the beginning of a lifelong obsession.
0:04:04 > 0:04:07All right, let's go take a look.
0:04:07 > 0:04:10Oh, my goodness.
0:04:10 > 0:04:15Why is this important? It's probably the most important question there is.
0:04:15 > 0:04:18What does it mean to be a human being? What is our future?
0:04:18 > 0:04:20Are there other creatures like us?
0:04:20 > 0:04:23What have they become? What can evolution produce?
0:04:23 > 0:04:26How far can it go? All of that will come out of
0:04:26 > 0:04:29learning of the extraterrestrials.
0:04:29 > 0:04:32And this will certainly enrich our lives
0:04:32 > 0:04:35in a way that nothing else could.
0:04:35 > 0:04:391960 was the beginning of radio astronomy.
0:04:39 > 0:04:45New dishes were being built which could search the heavens, not for light, but for faint radio signals
0:04:45 > 0:04:49which might reveal new insights about the nature of the universe.
0:04:49 > 0:04:57And Drake believed that this meant he could now search for radio evidence of intelligent life.
0:04:57 > 0:05:01Quite literally, aliens communicating.
0:05:03 > 0:05:08It was such a far-fetched idea, that Frank turned to mathematics,
0:05:08 > 0:05:12to create a theoretical framework for his obsession.
0:05:15 > 0:05:18Can you just explain the history of the equation?
0:05:18 > 0:05:22Well, in 1960, the National Academy of Sciences in the US
0:05:22 > 0:05:27asked me to convene a meeting to discuss this whole subject,
0:05:27 > 0:05:31to ground it in good, sound science,
0:05:31 > 0:05:34and to develop a plan for how to proceed.
0:05:34 > 0:05:35So I did that.
0:05:35 > 0:05:39I invited everyone in the world who I knew was interested in the subject
0:05:39 > 0:05:43to a meeting at Greenbank, all 12 of them.
0:05:43 > 0:05:48Just 12 people I knew who were very interested in extraterrestrial life.
0:05:48 > 0:05:54And in November of 1961 we convened at the Observatory in Greenbank
0:05:54 > 0:05:59and so I thought through what it is you need to know about to be able to
0:05:59 > 0:06:04predict how many civilisations there might be to detect in our galaxy.
0:06:04 > 0:06:10And I realised that the number of such civilisations depended on seven factors,
0:06:10 > 0:06:14and you could even use those factors to form an equation. So I did.
0:06:14 > 0:06:16And that became the agenda for the meeting.
0:06:17 > 0:06:21This is how those seven factors became the Drake Equation.
0:06:21 > 0:06:27He estimated the number of detectable, intelligent communicating civilisations
0:06:27 > 0:06:32in the galaxy to be based on the number of stars formed every year...
0:06:36 > 0:06:40..multiplied by the fraction of those stars with planets...
0:06:43 > 0:06:48..times the number of those planets per solar system with environments suitable for life...
0:06:50 > 0:06:55..times the fraction of those planets on which life actually appears...
0:06:57 > 0:07:02..multiplied by the fraction of those life-bearing planets on which intelligence arises...
0:07:04 > 0:07:06..times the fraction of those that would become
0:07:06 > 0:07:10technologically advanced and develop a desire to communicate...
0:07:12 > 0:07:18..multiplied by the length of time that they continue to transmit detectable signals into space.
0:07:20 > 0:07:26So, with the Drake Equation in place, Frank and his colleagues could start filling in the numbers
0:07:26 > 0:07:30and for the first time, make an estimate
0:07:30 > 0:07:33for the number of intelligent civilisations in the galaxy.
0:07:37 > 0:07:42Can you put the original 1961 estimates into the equation?
0:07:42 > 0:07:46One factor that was really well-known was the rate of star formation.
0:07:46 > 0:07:48It was about ten per year.
0:07:48 > 0:07:51The fraction of stars which have planets -
0:07:51 > 0:07:54we had indirect evidence from binary stars.
0:07:54 > 0:07:57It was a guess to be about 0.5.
0:07:57 > 0:08:02In those days we thought the Earth, and if Mars had been a little more massive, it would have been
0:08:02 > 0:08:05able to retain an atmosphere and be suitable for life.
0:08:05 > 0:08:07So that, based on our own system, was two.
0:08:07 > 0:08:12The chemical experiments in the laboratory suggested that to give it a planet like the Earth,
0:08:12 > 0:08:15given some time, by one way or another, life would appear.
0:08:15 > 0:08:17So that fraction was one.
0:08:17 > 0:08:20That is given enough time it would appear...always appears.
0:08:20 > 0:08:25A fraction of these which gave rise to intelligence was a big guess, and still is to this day.
0:08:25 > 0:08:280.5.
0:08:28 > 0:08:31Then when it came to the fraction which developed detectable technologies,
0:08:31 > 0:08:37was then and now based on our own history, but that one seems to be one.
0:08:37 > 0:08:42And at this point we have the rate of production of detectable civilisations.
0:08:42 > 0:08:47We conservatively assume that they do not remain detectable forever.
0:08:47 > 0:08:53But a favourite guess is 10,000 years for L.
0:08:53 > 0:08:56And if we put that in, we get a value N,
0:08:56 > 0:09:01which is equal to 50,000 civilisations.
0:09:01 > 0:09:05Now that seems like a big number, when you say 50,000.
0:09:05 > 0:09:08It is a big number and it's very exciting.
0:09:08 > 0:09:12It means there's something to be found out there. We can be far wrong and there's something to be found.
0:09:12 > 0:09:14So that's very encouraging to people.
0:09:18 > 0:09:22But even though Frank now had a theoretical justification
0:09:22 > 0:09:27for his search, he and his colleagues were still a lone voice.
0:09:27 > 0:09:31They grabbed telescope time where and when they could,
0:09:31 > 0:09:37desperate to find a signal to prove to the world they were right.
0:09:37 > 0:09:42But the deafening silence from space was a gift to their critics.
0:09:44 > 0:09:51But as the years passed, the scientific mood slowly shifted.
0:09:51 > 0:09:54As the astronomers explored more of the universe
0:09:54 > 0:09:58and biologists penetrated into the workings of life,
0:09:58 > 0:10:02and as our own evolution became clearer, the scientific community
0:10:02 > 0:10:07began to feel that Frank wasn't quite so eccentric.
0:10:07 > 0:10:09Even though ET had not been heard,
0:10:09 > 0:10:13the estimates in Frank's equation made real sense.
0:10:24 > 0:10:29And now, 50 years later, his initial radio telescope search of the heavens has become SETI -
0:10:29 > 0:10:34the Search for extraterrestrial Intelligence, and boasts its own
0:10:34 > 0:10:38multi-million dollar dedicated radio telescope array.
0:10:41 > 0:10:49And I'm off to see it with the current director of the Center for SETI Research, Doctor Jill Tarter.
0:10:49 > 0:10:54Hi, there. You aren't going anywhere near the ATA, Allen Telescope Array, by any chance, are you?
0:10:54 > 0:10:57- You must be Dallas.- Hi, Jill. - It's very nice to meet you.
0:11:04 > 0:11:09I'm on my way to the Allen Telescope Array in Hat Creek in Northern California.
0:11:09 > 0:11:12And it's the most ambitious SETI project yet.
0:11:22 > 0:11:27Built in 2007, the Array is currently made up of 42 small
0:11:27 > 0:11:31radio telescopes which can survey the galaxy 24 hours a day.
0:11:36 > 0:11:39Computers combine the signals from each dish
0:11:39 > 0:11:42to give the equivalent sensitivity of a much larger telescope.
0:11:44 > 0:11:47- Well, welcome to Hat Creek. - Thank you for having me.
0:11:47 > 0:11:53So why have you got lots of little telescopes as opposed to like a big, Arecibo style dish?
0:11:53 > 0:11:56So what we built is a fabulous survey instrument.
0:11:56 > 0:12:01You can survey much more of the sky
0:12:01 > 0:12:04to a given sensitivity than you can with a big dish.
0:12:04 > 0:12:09If you compare what we're doing here with what Frank Drake did 50 years ago,
0:12:09 > 0:12:12there's 14 orders of magnitude improvement.
0:12:12 > 0:12:13Ten to the 14.
0:12:14 > 0:12:19I really get the sense that, for Jill, these are more than just telescopes.
0:12:19 > 0:12:25They are the link between modern science and some of the oldest questions on Earth.
0:12:25 > 0:12:32After millennia of asking the priests and the philosophers and whoever else we felt was wise,
0:12:32 > 0:12:38you know, what we should believe, that suddenly we had some new technology, that is radio telescopes.
0:12:38 > 0:12:43And that those telescopes could do an experiment to find the answer.
0:12:43 > 0:12:47And I was alive in the very first generation of humans who could do this.
0:12:49 > 0:12:52Most of the modern search works in much the same way
0:12:52 > 0:12:57as it did back in Frank's day, still based on a single piece of science.
0:12:57 > 0:13:00Radio.
0:13:00 > 0:13:04Radio waves travel across the distances between the stars across the whole galaxy,
0:13:04 > 0:13:09without being absorbed by the dust that's between the stars.
0:13:09 > 0:13:15So radio waves are fantastic for long distance inter-stellar communication.
0:13:17 > 0:13:22This unique property of radio led Drake to imagine that it would be
0:13:22 > 0:13:26far and away the best medium for inter-stellar communication.
0:13:36 > 0:13:39But the trouble is that looking for radio signals
0:13:39 > 0:13:42isn't quite as simple as we might imagine.
0:13:48 > 0:13:54Radio signals, like all electro-magnetic radiation, comes in waves.
0:13:54 > 0:13:58And those waves can vary in length from trillionths of centimetres
0:13:58 > 0:14:00to kilometres and beyond.
0:14:00 > 0:14:05So imagine all those different wavelengths stretched out along this road here.
0:14:05 > 0:14:09Let's assume that here we've got visible light and in reality
0:14:09 > 0:14:13the wavelength is smaller than the radius of the finest spider silk.
0:14:13 > 0:14:17So along this side you've got all the very small stuff.
0:14:17 > 0:14:20So you've got ultraviolet. You've got x-rays.
0:14:20 > 0:14:23You've got gamma rays.
0:14:23 > 0:14:26And on the other side of visible light,
0:14:26 > 0:14:28you've got the much bigger stuff.
0:14:28 > 0:14:32So you've got infrared, you've got microwave,
0:14:32 > 0:14:35you've got radio waves, long waves,
0:14:35 > 0:14:39so you can listen to the Radio Four cricket, and very long wave.
0:14:39 > 0:14:41But the point is this.
0:14:41 > 0:14:44It's a really, really long road
0:14:44 > 0:14:48and trying to tune into ET, excuse the cliche,
0:14:48 > 0:14:54really is like trying to find a tiny needle in a cosmic-sized haystack.
0:14:58 > 0:15:04Back then, SETI could only listen to a tiny section of the spectrum at any one time.
0:15:04 > 0:15:08So Drake and his colleagues had to make an educated guess
0:15:08 > 0:15:12where to search for extraterrestrial messages.
0:15:14 > 0:15:21They knew that every element in the universe has its own unique electromagnetic frequency.
0:15:23 > 0:15:26So they made an assumption that if extraterrestrial life
0:15:26 > 0:15:32wanted to talk, then surely they'd broadcast on 1420.5 megahertz,
0:15:32 > 0:15:37the frequency of the most common atom in the universe, hydrogen.
0:15:37 > 0:15:41Hydrogen's the most abundant element in the universe.
0:15:41 > 0:15:44So when Frank Drake did his search - and he had one channel -
0:15:44 > 0:15:47he chose the frequency of hydrogen - it's universal.
0:15:47 > 0:15:51When we were able to look at a little bit more of the spectrum,
0:15:51 > 0:15:55we expanded the search to what we call "the waterhole".
0:15:55 > 0:16:00Because water is so essential to life, at least as life as we know it,
0:16:00 > 0:16:05we said, "Let's look between the hydrogen line, that Frank started at,
0:16:05 > 0:16:10"and we'll go up in frequency, 300 megahertz, to the line of the OH Radical."
0:16:10 > 0:16:12So H and OH, that's water.
0:16:12 > 0:16:15- H2O, yes.- That's a special place.
0:16:15 > 0:16:20So if you're trying to guess a magic frequency or a range, where someone
0:16:20 > 0:16:25might decide to transmit a signal, that's a good guess.
0:16:26 > 0:16:32The spectrum within the waterhole has been the focus of the search for 50 years.
0:16:35 > 0:16:38And recently, new advances in computing power have meant
0:16:38 > 0:16:42these telescopes can search billions of channels simultaneously.
0:16:52 > 0:16:54But, there's a problem.
0:16:54 > 0:17:00Since Frank Drake started looking in 1960, they've used thousands of telescope hours to search
0:17:00 > 0:17:03for hundreds of different star systems and they've found nothing.
0:17:03 > 0:17:05Not a peep.
0:17:05 > 0:17:06Silence.
0:17:16 > 0:17:19This silence, and the lack of any other evidence
0:17:19 > 0:17:24of extraterrestrial life, has become known as the Fermi Paradox.
0:17:27 > 0:17:30It's named after the physicist Enrico Fermi,
0:17:30 > 0:17:34who first boldly asked, "Where is everybody?"
0:17:37 > 0:17:40He pointed out a clear contradiction.
0:17:44 > 0:17:47If there are thousands of intelligent civilisations out there,
0:17:47 > 0:17:51then at least one must have left some sort of trace.
0:18:04 > 0:18:06So what's gone wrong?
0:18:06 > 0:18:09Have the scientists led us up the garden path?
0:18:09 > 0:18:14Is Frank Drake's Equation just a hope-driven wild overestimation?
0:18:14 > 0:18:17Isn't the simplest answer to the Fermi Paradox,
0:18:17 > 0:18:21and therefore the most likely, that are no aliens?
0:18:21 > 0:18:23We're on our own.
0:18:43 > 0:18:48The Fermi Paradox has forced scientists to look closer at the Drake Equation.
0:18:50 > 0:18:53Especially at its more speculative elements,
0:18:53 > 0:19:00the probability of life beginning and becoming intelligent enough to communicate across the galaxy.
0:19:07 > 0:19:12Professor Paul Davies, for one, believes the journey from life's beginnings
0:19:12 > 0:19:16to communicating intelligence is fraught with difficulties.
0:19:17 > 0:19:22So I asked him to explain the most important barriers to life's development.
0:19:24 > 0:19:27One way to think about this is that there's like a great filter
0:19:27 > 0:19:30that has to be passed through before you get to the point
0:19:30 > 0:19:33of an intelligent civilisation and the first step,
0:19:33 > 0:19:36first hurdle, if you like, in the filter
0:19:36 > 0:19:39is the transition from non-life to life.
0:19:39 > 0:19:43So we can think of this as the first great...
0:19:45 > 0:19:47..hurdle that nature has to cross.
0:19:47 > 0:19:51So that gives us no life this side. Life.
0:19:51 > 0:19:55- So that's the beginning of biology? - That's the beginning of biology.
0:19:55 > 0:19:59Big step. I think it could be a very unlikely step, but we don't know.
0:19:59 > 0:20:01Then the next might be, say,
0:20:01 > 0:20:03multi-cellular organisms.
0:20:03 > 0:20:07That's another hurdle that has to be crossed.
0:20:07 > 0:20:10And then to get further on,
0:20:10 > 0:20:14we need to make the transition to intelligent life.
0:20:14 > 0:20:19So intelligence is something that has to evolve, and so it's yet another line in the sand.
0:20:19 > 0:20:22That may be a very difficult step.
0:20:22 > 0:20:26At the end of this long sequence of hurdles, if you pass through this filter,
0:20:26 > 0:20:30then the final goal that we're interested in is the emergence
0:20:30 > 0:20:34of technological communicating civilisations, like that up there.
0:20:34 > 0:20:36Our lovely telescope.
0:20:47 > 0:20:52So if Drake is right, and there are extraterrestrial intelligences elsewhere in the galaxy,
0:20:52 > 0:20:56they would all have to overcome those three great filters.
0:21:00 > 0:21:02Biogenesis,
0:21:02 > 0:21:05the development of multi-cellular life,
0:21:05 > 0:21:08and the leap to intelligence.
0:21:09 > 0:21:13And that could be almost impossible.
0:21:16 > 0:21:22OK, so, this first line in the sand represents the origins of life, biogenesis.
0:21:22 > 0:21:25Everything on this side is physics doing its thing,
0:21:25 > 0:21:27chemistry doing its thing, and then suddenly...bam!
0:21:27 > 0:21:32It turns into biology, the first self-replicating molecules.
0:21:32 > 0:21:37And there's loads of good ideas, loads of good science about how this might have happened.
0:21:37 > 0:21:42The big question, of course, is, is it common? Does it spring up as soon as the conditions are right?
0:21:42 > 0:21:46Or, is life rare or very rare, or even a unique event
0:21:46 > 0:21:51that could happen only once in a 13.7 billion year blue moon?
0:21:57 > 0:22:00To begin to answer this, we first need to know whether
0:22:00 > 0:22:04the kinds of places where life can start are common,
0:22:04 > 0:22:07as Drake's Equation would suggest, or rare.
0:22:08 > 0:22:13In other words, is Earth a one-off?
0:22:17 > 0:22:22To find out, I went hunting for planets around distant stars, known as exoplanets,
0:22:22 > 0:22:25at the University of London's Mill Hill Telescope.
0:22:29 > 0:22:33One way of detecting exoplanets is what's known as the Transit Method,
0:22:33 > 0:22:36and it's a really beautifully simple idea to understand.
0:22:36 > 0:22:39If you imagine that this is your star and you're wondering,
0:22:39 > 0:22:43"What's going round my star, I can't see it, it's all too small?"
0:22:43 > 0:22:47Well, as your exoplanet passes in front of your star, there will be a dip in starlight.
0:22:47 > 0:22:53I've got a light meter here, and so imagine that's your telescope, and as the planet passes in between
0:22:53 > 0:22:58the telescope and the star, you'll actually be able to see that tiny little dip in starlight.
0:22:59 > 0:23:05In practice, even using this small telescope, we can actually see that dip
0:23:05 > 0:23:10and infer the existence of a planet orbiting a star far out in the galaxy.
0:23:10 > 0:23:12To prove it, the team showed me one
0:23:12 > 0:23:18orbiting around a star called HatP14, 650 light years from Earth.
0:23:19 > 0:23:23So we started observing just after sunset
0:23:23 > 0:23:27and we initially see the amount of light from the parent star.
0:23:27 > 0:23:29Then we see it about half an hour later,
0:23:29 > 0:23:35just starting to drop as the planet begins to cross the parent star.
0:23:37 > 0:23:40Using techniques like this and others,
0:23:40 > 0:23:45astronomers have now identified over 450 exoplanets.
0:23:45 > 0:23:48A handful of which look like they might be, as Drake put it,
0:23:48 > 0:23:51suitable for life.
0:23:53 > 0:23:59And they speculate that this is just a tiny fraction of the billions of planets in the galaxy.
0:23:59 > 0:24:03So Drake's estimate for Earth-like planets is credible.
0:24:03 > 0:24:09And yet, being suitable for life is only the starting point.
0:24:09 > 0:24:13Because life still has to actually begin.
0:24:21 > 0:24:23And to find out about that,
0:24:23 > 0:24:30I've come to southern California and the Scripps Institute in San Diego.
0:24:30 > 0:24:33Here, Professor Gerry Joyce believes he could be on the brink
0:24:33 > 0:24:37of producing artificial, self-replicating life.
0:24:37 > 0:24:44And if he's right, we may understand not only how life started here on Earth,
0:24:44 > 0:24:48but also how life might have started elsewhere in the galaxy.
0:24:50 > 0:24:53In his lab, he's producing artificial RNA,
0:24:53 > 0:24:56which is thought to be the forerunner to DNA.
0:24:59 > 0:25:02- All right, so let's replicate some RNA.- OK, fantastic.
0:25:02 > 0:25:05- In fact, let's have you replicate some RNA.- So I can do this?
0:25:05 > 0:25:07This is OK for me to do, is it?
0:25:07 > 0:25:09Yes, I trust you. It's not that hard.
0:25:09 > 0:25:12So, we have RNA molecules that can reproduce themselves
0:25:12 > 0:25:15and all you need to do is give them the food.
0:25:15 > 0:25:18And then a little test tube here that contains their food,
0:25:18 > 0:25:23- the building blocks that those molecules use to produce new copies of themselves.- OK.
0:25:23 > 0:25:27- And I actually want you to do the replication.- Sure. Just for the sake of argument,
0:25:27 > 0:25:30if I went outside and dropped them they won't suddenly devour everything around us
0:25:30 > 0:25:34- and start their own culture...- No, out in the wild they wouldn't last
0:25:34 > 0:25:36- more than a minute or two. - OK, so they're fragile.
0:25:36 > 0:25:40They're very fragile in the face of biology, yeah.
0:25:42 > 0:25:46What makes Gerry's RNA unique is that although they're completely artificial,
0:25:46 > 0:25:50they are capable of a key characteristic of life -
0:25:50 > 0:25:54replicating themselves.
0:25:54 > 0:25:56So what's in my test tube?
0:25:56 > 0:25:59- I mean, can we say it's life in any way?- They're not alive.
0:25:59 > 0:26:00They are a synthetic genetic system.
0:26:00 > 0:26:04They are undergoing Darwinian evolution in a self-sustained manner.
0:26:04 > 0:26:08And I should say, nothing in the test tube comes from biology. So there's water,
0:26:08 > 0:26:12there's some salts, there's the building blocks of RNA,
0:26:12 > 0:26:18and then there's the replicator molecules which contain about 80 or 85 different pieces of RNA.
0:26:20 > 0:26:24Here's a question. How do I know that they're actually growing?
0:26:24 > 0:26:27All I can see is a tiny bit of liquid in the bottom of a test tube?
0:26:27 > 0:26:32It is just a very small volume of a clear-coloured solution. So you don't see the molecules.
0:26:32 > 0:26:34However, what we've done is put tracers on the molecules.
0:26:34 > 0:26:38Either radioactive tracers, which - no offence - we don't trust you with that.
0:26:38 > 0:26:42- Right.- Or fluorescent tracers, and then we have analytical tools
0:26:42 > 0:26:44that lets us look at their growth characteristics.
0:26:44 > 0:26:47So there is ways of actually seeing them doing their thing.
0:26:48 > 0:26:51Now it may not look like much,
0:26:51 > 0:26:56but this is evidence that Gerry's RNA molecules are actually replicating,
0:26:56 > 0:27:00turning basic sugars in the bottom two lines into new RNA at the top.
0:27:02 > 0:27:06In terms of that line, that tantalizing line where chemistry turns into biology,
0:27:06 > 0:27:09how close are you to that line and can you see yourself going over?
0:27:09 > 0:27:14It has a lot of the properties of life, and I suppose the way I would think of things,
0:27:14 > 0:27:19even a few years ago, I would have thought something like this would be over the line.
0:27:19 > 0:27:24But now, standing right on the line, or right adjacent to the line, I feel it's not over the line.
0:27:24 > 0:27:28That it's not just a matter of having a genetic system that can replicate and evolve,
0:27:28 > 0:27:34but also the capacity to invent new solutions to new problems that the environment might pose.
0:27:34 > 0:27:38So given we've got all this understanding, can we start
0:27:38 > 0:27:41to speculate in any meaningful way about how life started on Earth?
0:27:41 > 0:27:44- I think that mystery's already put to bed.- Yeah?
0:27:44 > 0:27:47I think, you know, there are certainly no show stoppers
0:27:47 > 0:27:52in understanding how we get from inanimate chemistry to animate biology,
0:27:52 > 0:27:56even though the line hasn't been crossed, literally, in someone's hands.
0:27:56 > 0:27:59Or been witnessed other than the life form that we see on this planet.
0:27:59 > 0:28:03So I don't think there's mystery about that, but there's still much to be learned.
0:28:05 > 0:28:10Understanding the mystery of biogenesis would certainly be
0:28:10 > 0:28:15a key step to working out how it might happen elsewhere in the galaxy.
0:28:15 > 0:28:21But it doesn't necessarily make biogenesis itself any more likely.
0:28:23 > 0:28:28Let's look at the only example we really know - Earth.
0:28:30 > 0:28:35It's always been assumed life here on Earth started only once.
0:28:35 > 0:28:38So everything, every living thing around us,
0:28:38 > 0:28:42is therefore descended from that single moment of biogenesis.
0:28:44 > 0:28:47But that view is now being challenged.
0:28:50 > 0:28:56All this life around us, all what we see, we know is the same life.
0:28:56 > 0:29:01That is, this tree behind me, you and me, these flowers here, the insects and so on,
0:29:01 > 0:29:06if you dig into their innards, you look at their DNA, you find they're all interrelated.
0:29:06 > 0:29:09So we're all cousins, all life so far studied on Earth,
0:29:09 > 0:29:12is related to all other life. So it belongs to a single tree.
0:29:12 > 0:29:15And Darwin had this metaphor of a tree,
0:29:15 > 0:29:20that it sort of started with some long-ago, precursor organism
0:29:20 > 0:29:24and that over billions of years it's diversified and diversified
0:29:24 > 0:29:29- into all these different branches. Each branch representing a different species.- That's us up there.
0:29:29 > 0:29:32So you've got the mushrooms over there and, you know,
0:29:32 > 0:29:36you've got the bacteria up here and the oak trees over here, and so on.
0:29:36 > 0:29:41But that's assuming that all life came from a single common origin.
0:29:41 > 0:29:44That is, it happened only once on Earth. But how do we know that?
0:29:44 > 0:29:48Maybe life happened many times on Earth and maybe instead of being
0:29:48 > 0:29:52just one tree of life, there is actually a forest.
0:29:52 > 0:29:58So if we confirm this idea of life 2.0, if you like, the separate biogenesis on Earth, can we assume,
0:29:58 > 0:30:04with a little more certainty that life is more common in the galaxy, if not the universe, do you think?
0:30:04 > 0:30:08It would be inconceivable that life could start twice here on Earth and not at all
0:30:08 > 0:30:11on all the other Earth-like planets around the universe.
0:30:11 > 0:30:16So all we need is just one example of life, but not as we know it.
0:30:16 > 0:30:20Life 2.0. It could be here, it could be on Mars, doesn't matter where it is.
0:30:20 > 0:30:23We just want to know that life has happened more than once.
0:30:23 > 0:30:27If it's happened twice, it's going to happen all around the universe.
0:30:31 > 0:30:35So where do we start looking for life 2.0?
0:30:35 > 0:30:40Paul suggested I go looking in the murky world of microbes,
0:30:40 > 0:30:44most of which haven't even been classified, let alone analysed.
0:30:46 > 0:30:51And he suggested I visit a young biologist in San Francisco.
0:30:51 > 0:30:58Doctor Felisa Wolfe-Simon has been searching in the highly toxic depths of California's Mono Lake
0:30:58 > 0:31:03and believes she might have found something very unusual.
0:31:03 > 0:31:08A tiny microbe that can survive concentrations of arsenic
0:31:08 > 0:31:11that would kill all normal life dead.
0:31:13 > 0:31:19And this might imply that it evolved from a totally separate biogenesis.
0:31:21 > 0:31:26If it is, then life developed on Earth not once, but twice.
0:31:30 > 0:31:33Hi, Felisa. Hello, I'm Dallas.
0:31:33 > 0:31:34- Hiya, Dallas.- Nice to meet you.
0:31:34 > 0:31:37- Nice to meet you. - Thanks for seeing me.
0:31:37 > 0:31:39- So, you've been at Mono Lake.- Yes.
0:31:39 > 0:31:41And you've been studying some interesting stuff.
0:31:41 > 0:31:43- Yes.- Can I have a look at it?- Absolutely.
0:31:43 > 0:31:47Firstly, I should ask you, why Mono Lake? What's important about Mono Lake?
0:31:47 > 0:31:50Well, first, since you're in the lab, let's get you the lab coat...
0:31:50 > 0:31:54- OK.- ..so we can not just talk about it, but we can actually look at it.
0:31:54 > 0:31:58- That would be great, really fantastic.- So why go to Mono Lake?
0:31:58 > 0:32:01- Yeah.- So, Mono Lake for many years has been measured
0:32:01 > 0:32:03by many different people to be very high in arsenic.
0:32:03 > 0:32:06But this isn't polluted arsenic. Nothing has been dumped.
0:32:06 > 0:32:08This is a natural, rich arsenic lake.
0:32:08 > 0:32:11So this lake has been around for a long time.
0:32:11 > 0:32:17- Probably has been enriched in arsenic for most of that time. - So, what have you got to show me?
0:32:17 > 0:32:20So, what I wanted to do is first show you, start from kind of the
0:32:20 > 0:32:24normal thing we might see at Mono Lake, which is still very unusual.
0:32:24 > 0:32:26This is just some gunk from Mono Lake...
0:32:26 > 0:32:31Some mud from the bottom of Mono Lake, and essentially you just let it sit on a window sill,
0:32:31 > 0:32:34and over time, you see these different colours evolve or develop.
0:32:34 > 0:32:37These are different kinds of microbes.
0:32:37 > 0:32:40And this is the same source material or the same mud that we've isolated
0:32:40 > 0:32:46a potentially very unusual and interesting, let's say, arsenic-utilising organism.
0:32:46 > 0:32:48We just want to see what's there.
0:32:48 > 0:32:50- Let's have a look.- Absolutely.
0:32:50 > 0:32:53So you'll see there's nothing fancy about what we're going to do.
0:32:55 > 0:32:57Just take a little bit of the sample.
0:32:57 > 0:33:01- Put it on a microscope slide. - Can I have a look?
0:33:01 > 0:33:02Please.
0:33:02 > 0:33:06Oh, my god. Oh, my god.
0:33:06 > 0:33:11The toxic, arsenic-rich mud is actually alive with activity.
0:33:13 > 0:33:15It's almost fractal, right.
0:33:15 > 0:33:18The closer we go in, the busier it seems to get.
0:33:18 > 0:33:20That's...that is extraordinary.
0:33:20 > 0:33:24So as we zoom in, you'll see it's just teaming,
0:33:24 > 0:33:27literally teaming with life.
0:33:27 > 0:33:28That's wild, isn't it?
0:33:28 > 0:33:33- That's amazing.- So these are just organisms that were essentially laying in wait in the mud.
0:33:33 > 0:33:37Most of these microbes are normal life which have evolved
0:33:37 > 0:33:39to live in high levels of toxic arsenic.
0:33:40 > 0:33:44But by increasing the levels of arsenic even further,
0:33:44 > 0:33:48Felisa believes she may have isolated something very unusual.
0:33:48 > 0:33:50So we have, in my group, in my lab,
0:33:50 > 0:33:54I've so far looked at a bunch of different microbes, and I was...
0:33:54 > 0:33:57The way I went about doing this, we want to give it a lot of arsenic.
0:33:57 > 0:34:00- Yes.- We want to really see what can handle a lot of arsenic.
0:34:00 > 0:34:04So the more arsenic you give it, the more you're going to say,
0:34:04 > 0:34:06actually yeah, this is something different.
0:34:06 > 0:34:10It's something that... Different. It's doing something unique.
0:34:10 > 0:34:13She's convinced that anything that can survive
0:34:13 > 0:34:17this intense arsenic bath would have to be structurally different,
0:34:17 > 0:34:20would have unique DNA fundamentally separate
0:34:20 > 0:34:22from life as we know it.
0:34:22 > 0:34:27If I can concretely say to you, this organism, biochemically,
0:34:27 > 0:34:31is completely different than we are at a molecular level,
0:34:31 > 0:34:37it's either a deep root, you know, we share a common tree, but it's a deep root on the tree of life.
0:34:37 > 0:34:40- Which would be interesting in itself.- Absolutely.
0:34:40 > 0:34:46It suggests that while there was really one structural way to make DNA and to make genetic material...
0:34:46 > 0:34:47Or there were multiple...
0:34:47 > 0:34:50multiple point sources of the origins of life.
0:34:50 > 0:34:53And have you found anything like that, or do you think you've found
0:34:53 > 0:34:57something that is a prime candidate, if you like, for that?
0:34:57 > 0:35:00Well, it's very likely. We think we have an organism.
0:35:00 > 0:35:02I think that I've isolated a microbe
0:35:02 > 0:35:04that's doing something very different.
0:35:04 > 0:35:07It can survive with exceedingly high levels of arsenic
0:35:07 > 0:35:10that would be very toxic to you and I and most other life we know.
0:35:10 > 0:35:15It seems to be growing in a unique way and hopefully,
0:35:15 > 0:35:19very shortly, we'll be making a very interesting announcement.
0:35:19 > 0:35:25And that announcement could have a huge impact on the search for extraterrestrials.
0:35:28 > 0:35:32Because if life started more than once here on Earth,
0:35:32 > 0:35:36then the chances that it started elsewhere in the galaxy
0:35:36 > 0:35:38are greatly increased.
0:35:52 > 0:35:58But for Drake's estimate to be correct, it's not enough for life to just begin.
0:35:59 > 0:36:02Some of that life must develop into intelligent life
0:36:02 > 0:36:06capable of communicating across the galaxy.
0:36:07 > 0:36:10And to do that, it must first become multi-cellular.
0:36:12 > 0:36:17This is the second hurdle or great filter, so everything on this side
0:36:17 > 0:36:20is very simple, single-celled life, bacteria and such,
0:36:20 > 0:36:24and this is the junction where it suddenly becomes complex,
0:36:24 > 0:36:27ultimately blossoming into plant and animal life.
0:36:27 > 0:36:31But the big question is, how likely is that?
0:36:46 > 0:36:47This is the Mojave Desert,
0:36:47 > 0:36:51one of the hottest, most inhospitable places in the world.
0:36:53 > 0:36:58And I've been brought here by Doctor Chris McKay of NASA Ames,
0:36:58 > 0:37:02who's been studying an unexpected kind of life.
0:37:02 > 0:37:06Life that might offer tantalising clues to how we evolved
0:37:06 > 0:37:11from single-celled organisms to something much more complex.
0:37:12 > 0:37:15Just how hot and dry is it here?
0:37:15 > 0:37:18Well, this is the driest part of the Mojave Desert,
0:37:18 > 0:37:20and from a microbial point of view
0:37:20 > 0:37:23it's dryness, not hotness, that matters.
0:37:23 > 0:37:26And we can find a place like this where there's no trees,
0:37:26 > 0:37:28no plants and it seems like it's dead.
0:37:28 > 0:37:31But it's not. I want to show you something.
0:37:31 > 0:37:33Evidence that life is more clever than we think.
0:37:33 > 0:37:36Here on the surface of what looks like a barren desert
0:37:36 > 0:37:39we can pick up clear rocks and underneath them,
0:37:39 > 0:37:41you can see these layers of green.
0:37:41 > 0:37:44This is photosynthesis at its limit.
0:37:44 > 0:37:46That's extraordinary, isn't it?
0:37:46 > 0:37:48That's thick. There's a colony here.
0:37:48 > 0:37:50There's a lot going on. So what is this?
0:37:50 > 0:37:53These are single-celled cyanobacteria.
0:37:53 > 0:37:55Photosynthetic bacteria.
0:37:55 > 0:38:00They take sunlight, they make organic material, they produce oxygen.
0:38:00 > 0:38:04Yes, but how are they photosynthesising if they're underneath the rocks?
0:38:04 > 0:38:06Presumably it's dark under there.
0:38:06 > 0:38:11If you hold these quartz rocks up, you can see that light is coming through.
0:38:11 > 0:38:17You can see that sunlight, about a percent or so of the sunlight gets through the rock.
0:38:17 > 0:38:19So think of this as a greenhouse.
0:38:19 > 0:38:22Light is coming through the glass, the conditions under the rock
0:38:22 > 0:38:27are trapping moisture, they're living in little rock greenhouses.
0:38:27 > 0:38:32Chris McKay's green smudge is certainly tenacious, but he believes
0:38:32 > 0:38:34it also hints at a story much more crucial
0:38:34 > 0:38:37to my search for intelligent life in the galaxy -
0:38:37 > 0:38:40the story of how simple, single-celled life
0:38:40 > 0:38:43became multi-celled and complex.
0:38:43 > 0:38:46And that's because of its ability to photosynthesise -
0:38:46 > 0:38:51to use sunlight to turn carbon dioxide into food and oxygen.
0:38:51 > 0:38:56We think that that ability, photosynthesis,
0:38:56 > 0:38:58is going to be widespread.
0:38:58 > 0:39:02It's a natural result of living on a planet with sunlight, water...
0:39:02 > 0:39:08Combining sunlight and water is a logical thing for an organism to do if it lives on Earth.
0:39:08 > 0:39:10The result of that is oxygen.
0:39:10 > 0:39:14And that oxygen changes everything.
0:39:17 > 0:39:20For most early life, oxygen is toxic.
0:39:24 > 0:39:26But, with the arrival of photosynthesis,
0:39:26 > 0:39:30oxygen is suddenly pouring into the atmosphere.
0:39:31 > 0:39:35Some organisms survive the new levels of oxygen
0:39:35 > 0:39:40and find in the process an unexpected reward.
0:39:40 > 0:39:44Because using the energy that oxygen releases,
0:39:44 > 0:39:47single-celled organisms can supercharge their metabolism.
0:39:49 > 0:39:53These organisms are responsible for polluting the Earth.
0:39:53 > 0:39:56Billions of years ago, they produced oxygen.
0:39:56 > 0:40:00That oxygen changed the environment in a profound way.
0:40:00 > 0:40:05It changed the environment in a way that allowed for the development of huge creatures like us.
0:40:05 > 0:40:09So, in a sense, we owe our existence to these kind of organisms.
0:40:09 > 0:40:12And what's more, according to Chris McKay,
0:40:12 > 0:40:17complexity is not only a possibility, it's an inevitability.
0:40:17 > 0:40:22Do you think once life gets going, complex life will naturally follow?
0:40:22 > 0:40:27Yeah, I think, given an origin of life, photosynthesis will come,
0:40:27 > 0:40:31oxygen will come, complex life will come. I think that will be easy.
0:40:34 > 0:40:41So, if it's inevitable that simple life will become complex, what of the last great filter?
0:40:43 > 0:40:48When I look at the whole story from origin of life, development of complexity,
0:40:48 > 0:40:53development of intelligence, I think the hardest step is going to be the final one, intelligence.
0:40:53 > 0:40:56I think that's the step that's rare, that's defining.
0:40:56 > 0:41:00That separates Earth from the vast majority of other planets.
0:41:05 > 0:41:09And for Frank Drake, the likelihood of intelligence arising
0:41:09 > 0:41:12was one of the great unknowns of his equation.
0:41:12 > 0:41:15He guessed intelligence was common in the galaxy.
0:41:15 > 0:41:21But ultimately, that guess was based on a sample of just one. Us.
0:41:33 > 0:41:38So this line is what separates us from all other life on Earth,
0:41:38 > 0:41:40and I suppose we can call it intelligence.
0:41:40 > 0:41:42The big question, of course, is,
0:41:42 > 0:41:45is intelligence an evolutionary imperative,
0:41:45 > 0:41:49or are we just a once-in-a-galaxy freak of nature?
0:41:51 > 0:41:54SQUAWKING
0:41:58 > 0:42:03To answer that, I'm off to Cambridge to meet palaeontologist Professor Simon Conway Morris.
0:42:06 > 0:42:10He believes intelligence is much more common than we might think.
0:42:10 > 0:42:15In fact, to prove it, he's taking me to meet experimental psychologist
0:42:15 > 0:42:21Professor Nicky Clayton and one of the cleverest families of creatures on Earth. Corvids.
0:42:21 > 0:42:25Better known to you and me as the crow family.
0:42:25 > 0:42:28SQUAWKING
0:42:29 > 0:42:32- Hi, Nicky.- Hello.- I'm Dallas. How do you do?- Nice to meet you.
0:42:32 > 0:42:34Nice to meet you. They are amazing.
0:42:34 > 0:42:38It's quite ominous coming here. Just the kind of noise of everything.
0:42:38 > 0:42:41You understand why they make appearances in horror movies.
0:42:41 > 0:42:42But they're so beautiful.
0:42:42 > 0:42:45Are they talking? Are they communicating?
0:42:45 > 0:42:47Well, they're communicating, that's for sure,
0:42:47 > 0:42:49and there's lots of body language.
0:42:49 > 0:42:52If you meant language in a psychological sense, no.
0:42:52 > 0:42:54But in a communicative, biological sense, yes.
0:42:55 > 0:42:58Nicky and her team have been giving puzzles to
0:42:58 > 0:43:02her crows and jays and been finding some impressive results.
0:43:05 > 0:43:08So if you give them a tube of water and there's a worm,
0:43:08 > 0:43:10the Belgian truffles of the crow world,
0:43:10 > 0:43:13floating on the top, but the worm is out of beak reach
0:43:13 > 0:43:16because the water level is too low, what they will do is pick up stones
0:43:16 > 0:43:20and use the stones as tools to raise the water level
0:43:20 > 0:43:24and thereby get the juicy worm at the end of it.
0:43:30 > 0:43:37Another experiment reveals a very unexpected human characteristic.
0:43:37 > 0:43:40So, one of the things that's thought to sort of make humans special,
0:43:40 > 0:43:44of a suite of things that have been claimed, one is theory of mind.
0:43:44 > 0:43:48And that's the ability to be able to think about what other people are thinking.
0:43:48 > 0:43:54And the jays are very, very good at that. So in one of, perhaps the most striking case of that,
0:43:54 > 0:43:58is the case where they hide food, and if another bird is watching them,
0:43:58 > 0:44:01they later come back when the other birds have left
0:44:01 > 0:44:03and move the food to a new place.
0:44:07 > 0:44:08But the really cool thing is that
0:44:08 > 0:44:11not all birds do this moving of food to a new place.
0:44:11 > 0:44:13It's only those birds who themselves
0:44:13 > 0:44:16have been thieves in the past that do it.
0:44:16 > 0:44:18So it's not a hard-wired reaction.
0:44:18 > 0:44:20It takes a thief to know one, if you like.
0:44:20 > 0:44:24And the idea is that that is a special form of this experience projection.
0:44:24 > 0:44:28It's reasoning by analogy, based on your own experience.
0:44:28 > 0:44:32If I were the thief, I would do X and therefore I'll move it.
0:44:35 > 0:44:40- Your corvid is your sort of ZX81 and we're a kind of iPad, maybe. - Well, in my view...
0:44:40 > 0:44:42- Not me personally. - My view is, I mean,
0:44:42 > 0:44:45these and maybe a few other groups, maybe the elephants also,
0:44:45 > 0:44:48I think the dolphins are just on the threshold
0:44:48 > 0:44:50of what we were only 100,000 years ago.
0:44:50 > 0:44:54- This is what I want to know.- Very exciting, isn't it?- Super exciting.
0:44:54 > 0:44:59What makes this especially exciting is that crows are so far from us on the evolutionary tree.
0:45:01 > 0:45:06And this suggests that intelligence is evolutionarily convergent,
0:45:06 > 0:45:11that intelligence is such a good solution to living in our complex world
0:45:11 > 0:45:14that evolution will fall upon it time and time again
0:45:14 > 0:45:16in many different organisms.
0:45:18 > 0:45:22Just like that other great evolutionary success story, the eye.
0:45:24 > 0:45:29- What could be more different than an octopus to ourselves?- Yeah, yeah.
0:45:29 > 0:45:32But now what I'm going to show you is in fact just in this area here.
0:45:32 > 0:45:34It's not for the squeamish.
0:45:34 > 0:45:35This is the eye of the octopus.
0:45:35 > 0:45:38If I was to dissect out that eye,
0:45:38 > 0:45:40it would be, in certain respects,
0:45:40 > 0:45:42almost indistinguishable
0:45:42 > 0:45:43from our eyes.
0:45:43 > 0:45:46Built on a so-called camera principle.
0:45:46 > 0:45:50And there are many ways of building eyes, but this camera eye,
0:45:50 > 0:45:52remember, is in an animal which is
0:45:52 > 0:45:55a close relative of the garden snail.
0:45:55 > 0:45:58- So we can say that eyes are convergent.- Eyes are convergent.
0:45:58 > 0:46:01Because it happens lots of different times.
0:46:01 > 0:46:04Yeah, and we shouldn't be surprised, because eyes are a good trick.
0:46:04 > 0:46:08Now, if the crow's behaviour really implies that intelligence
0:46:08 > 0:46:12is convergent, then it has serious implications for our search.
0:46:15 > 0:46:18Because not only would it lend support to the idea
0:46:18 > 0:46:21that aliens would evolve intelligence,
0:46:21 > 0:46:24it might allow us to imagine how they think, too.
0:46:27 > 0:46:31At least, if I'm right about the convergence, one could say, you know,
0:46:31 > 0:46:35after all, they come from the same universe with the same periodic table,
0:46:35 > 0:46:37governed by the same evolution.
0:46:37 > 0:46:40Even if there wasn't a hand to shake of the alien,
0:46:40 > 0:46:42we would still know each other.
0:46:44 > 0:46:48Simon's research really lends intriguing support
0:46:48 > 0:46:51to the more speculative parts of the Drake Equation.
0:46:53 > 0:46:56But there's one final element that's less certain.
0:46:56 > 0:47:00L. The length of time a civilisation might last.
0:47:02 > 0:47:07Maybe galactic civilisations last just a short blink of the eye.
0:47:11 > 0:47:13Which means that perhaps there's
0:47:13 > 0:47:16yet another great filter ahead in our future.
0:47:25 > 0:47:28The question is, is the eerie silence
0:47:28 > 0:47:31because we're alone in the universe, or is it because
0:47:31 > 0:47:35there are many civilisations that emerge, but they don't last long?
0:47:35 > 0:47:38That they get wiped out fairly soon after they arise.
0:47:38 > 0:47:42When you say wiped out, what kind of thing are we talking about?
0:47:42 > 0:47:46Well, I suppose we can think of manmade disasters, like the release of some
0:47:46 > 0:47:52genetically-engineered organism that just infects us all,
0:47:52 > 0:47:55or nuclear war, or there could be natural disasters,
0:47:55 > 0:47:58like the impact of an asteroid or comet
0:47:58 > 0:48:00or the explosion of a nearby star as a supernova.
0:48:00 > 0:48:03There are many ways that we could meet our demise.
0:48:06 > 0:48:11Does this explain the conundrum of why we haven't heard from any extraterrestrial life?
0:48:11 > 0:48:14The so-called Fermi Paradox?
0:48:14 > 0:48:21If civilisations disappear quickly, then we are unlikely to hear their short bursts of radio.
0:48:21 > 0:48:23MUFFLED RADIO NOISE
0:48:27 > 0:48:29But there may be another reason.
0:48:29 > 0:48:34If the value of L was large, we might not hear ET because
0:48:34 > 0:48:38our radio technology might be much too primitive.
0:48:40 > 0:48:44After all, radio's only been around about 100 years
0:48:44 > 0:48:47and already it's changed many times.
0:48:47 > 0:48:50Now, this little diddy radio here is tuned to AM,
0:48:50 > 0:48:55which is where medium wave and long wave radio stations broadcast.
0:48:55 > 0:49:01And you can hear it. It's low quality and consequently rarely used now by any broadcaster.
0:49:01 > 0:49:04MURKY DISTORTION
0:49:04 > 0:49:05But nowadays, of course,
0:49:05 > 0:49:08we don't use AM as much, because we've got FM,
0:49:08 > 0:49:11Frequency Modulation, which of course gives us a much better signal.
0:49:11 > 0:49:16RAPID BURSTS OF CLEAR RECEPTION
0:49:16 > 0:49:22FM is a newer technology, it's clear as a bell, and as you can hear, it's very, very busy.
0:49:25 > 0:49:29And this is the thing. Our technology is constantly changing,
0:49:29 > 0:49:34so it's very likely that an extraterrestrial technology is going to be hugely different from ours.
0:49:34 > 0:49:40So in the same way that an AM receiver can't pick up FM, maybe SETI are listening in the wrong way.
0:49:55 > 0:49:56I always kind of assume that, well,
0:49:56 > 0:49:59we're just expecting everyone else out there
0:49:59 > 0:50:01to have our technology where we are.
0:50:01 > 0:50:05Are we being quite anthropocentric about the way we look for...?
0:50:05 > 0:50:09Well, how would you look in a way that you don't know anything about?
0:50:09 > 0:50:12- Exactly, yeah.- You have to use the tools that we have.
0:50:12 > 0:50:14We have to base it on what we know.
0:50:14 > 0:50:19And in fact, it might well be that in some other planet,
0:50:19 > 0:50:22it's the Institute of Ancient Instruments
0:50:22 > 0:50:24that is broadcasting SETI signals.
0:50:26 > 0:50:30But back at Greenbank, Frank Drake believes the real reason
0:50:30 > 0:50:35we haven't heard anything is much, much more simple.
0:50:35 > 0:50:38But even if we haven't, obviously, you know,
0:50:38 > 0:50:42despite what people may think they see or believe happens,
0:50:42 > 0:50:47you know, other civilisations haven't come here, why haven't we been able to detect them?
0:50:47 > 0:50:50I mean, forget about space travel. But why?
0:50:50 > 0:50:55Why haven't we detected them? That's easy. We just haven't tried enough.
0:50:55 > 0:50:58We, I think, have again been mislead by unfortunate...
0:50:58 > 0:51:05exuberant claims by myself and other colleagues that we've done a lot of searching, and we haven't.
0:51:05 > 0:51:11We've looked carefully at only a few thousand stars on a very small number
0:51:11 > 0:51:14of the channels that are possible in the electromagnetic spectrum.
0:51:14 > 0:51:18And that's just hardly even a start.
0:51:18 > 0:51:25If you take perhaps reasonable or even optimistic values for the factors that go into the equation,
0:51:25 > 0:51:31it suggests that right now, there maybe only 10,000 civilisations we can detect in the galaxy.
0:51:31 > 0:51:33That's one in ten million stars.
0:51:33 > 0:51:40We have to look at ten million stars before we have a good chance of succeeding. We have a long way to go.
0:51:42 > 0:51:45Hearing Frank say this made me realise
0:51:45 > 0:51:50that the one thing I hadn't done was actually look myself.
0:51:50 > 0:51:54And almost exactly 50 years after Frank's first search,
0:51:54 > 0:51:59he and I have been given an exceptional opportunity.
0:51:59 > 0:52:01This is the Robert Byrd Telescope.
0:52:01 > 0:52:05The largest, steerable radio telescope in the world.
0:52:06 > 0:52:11And we're going to use its incredible radio sensitivity
0:52:11 > 0:52:14to perform a landmark experiment.
0:52:14 > 0:52:17So here we are actually in the mission control of the Greenbank telescope.
0:52:17 > 0:52:23We're going to be redoing the original project with Frank. Frank's over here, come with me.
0:52:23 > 0:52:26We're going to look at the stars from his original search
0:52:26 > 0:52:30that Frank still believes are good candidates for intelligent life.
0:52:30 > 0:52:34Here we are, 50 years later looking at the same two stars.
0:52:34 > 0:52:40Apart from obviously the sort of anniversary, does it make sense to look at those two stars?
0:52:40 > 0:52:43Yes. But there is a catalogue called the HabCat Catalogue,
0:52:43 > 0:52:45which is the Habitable Stars Catalogue.
0:52:45 > 0:52:49And there are five stars in that catalogue that are considered
0:52:49 > 0:52:52the prime candidates, and two of them are these two.
0:52:54 > 0:53:00As the telescope locked onto the star, I had to admit to feeling a surge of adrenalin.
0:53:00 > 0:53:06- Just a single beep, beep, beep would change everything.- Here we go.
0:53:06 > 0:53:09- We've started, folks.- Are we on?
0:53:09 > 0:53:11- We're on.- OK.
0:53:11 > 0:53:14- Good luck, everyone. - So here is hydrogen
0:53:14 > 0:53:17coming from the Milky Way and so we know now that everything is OK.
0:53:17 > 0:53:21Now we're looking at the star.
0:53:21 > 0:53:26Well, you get the excitement that goes with doing SETI the first time.
0:53:26 > 0:53:29Maybe the whole world is going to change.
0:53:29 > 0:53:31I remember Carl Sagan doing this with me once and
0:53:31 > 0:53:35he was sure we were going to find something within the first hour.
0:53:35 > 0:53:38After the first hour he sort of started nodding off
0:53:38 > 0:53:42and he got the newspaper and started reading it!
0:53:44 > 0:53:48We're starting to get the first data in now.
0:53:48 > 0:53:50STATIC
0:53:50 > 0:53:52What's it doing?
0:53:52 > 0:53:56You so want there to be something. Every time you see one of those
0:53:56 > 0:53:59blips in the line, you just want it to be...to be real.
0:53:59 > 0:54:03STATIC
0:54:03 > 0:54:07Just a few minutes into the search, and an unexpected peak crops up
0:54:07 > 0:54:10amongst the normal background signal.
0:54:10 > 0:54:15- So, an extraterrestrial signal would be broader. - It would be broader.
0:54:15 > 0:54:19But disappointingly, it turns out to be merely interference.
0:54:19 > 0:54:22- So we're saying no extraterrestrials?- Yeah.
0:54:22 > 0:54:27How do you feel about... are you sort of disappointed?
0:54:27 > 0:54:30No... It's... You...
0:54:30 > 0:54:33It's like buying a ticket in the lottery.
0:54:33 > 0:54:38If you're going to be disappointed that every ticket loses,
0:54:38 > 0:54:40you shouldn't be in the business.
0:54:40 > 0:54:42That's the difference between me and you,
0:54:42 > 0:54:45because you can be very pragmatic about it
0:54:45 > 0:54:48and say, "Well, it's OK, it's like a lottery ticket.
0:54:48 > 0:54:50"Two chances a million." I'm...
0:54:50 > 0:54:54You know, that's my first search, and I'm disappointed
0:54:54 > 0:54:59because I secretly, deep down, wanted to hear a signal.
0:54:59 > 0:55:02Well, don't be depressed. Your reaction is very standard.
0:55:02 > 0:55:07Everybody thinks that there's going to be a success on the first search.
0:55:07 > 0:55:10I told you about Carl Sagan.
0:55:10 > 0:55:17It took him one hour to go from wild excitement to, "Ugh, let's go home."
0:55:17 > 0:55:20I guess that's the ultimate question, isn't it? Is it worth it?
0:55:20 > 0:55:24- Yeah. Is it worth that much effort? - And is it worth that much effort?
0:55:24 > 0:55:28Yeah. People in SETI think the ultimate impact on society
0:55:28 > 0:55:35is great enough to justify 50 years of failures.
0:55:35 > 0:55:37I shouldn't call them failures.
0:55:37 > 0:55:39- Lack of success!- Observations.
0:55:48 > 0:55:5350 years on, and that lack of success might, to some, suggest a lost cause -
0:55:53 > 0:55:57a lottery in which any jackpot might not even exist.
0:55:57 > 0:56:00But these SETI types are made of sterner stuff.
0:56:00 > 0:56:06And what's more, where some see failure, they see hope.
0:56:06 > 0:56:08I think everything we've learned about Earth
0:56:08 > 0:56:11builds in us an intuition that life is common.
0:56:11 > 0:56:15But it's important to emphasise that at this point,
0:56:15 > 0:56:16it is just an intuition.
0:56:16 > 0:56:18We don't have any hard facts,
0:56:18 > 0:56:20and that's what this horse race is all about.
0:56:20 > 0:56:23Is to get some hard facts, some scientific facts,
0:56:23 > 0:56:30to try to understand, is life on Earth a rare, unusual, unique story?
0:56:30 > 0:56:33Or is the events that unfolded on this planet
0:56:33 > 0:56:37a common story that occurred many times in many different places?
0:56:44 > 0:56:47To me, the thing that SETI brings out
0:56:47 > 0:56:52is the intrinsic connection that we have with the cosmos.
0:56:52 > 0:56:58I mean, we are star stuff studying the stars.
0:56:58 > 0:57:02If you see yourself in that kind of a larger perspective,
0:57:02 > 0:57:07it really does change what you think about other humans on this planet.
0:57:12 > 0:57:15I think Frank Drake summed it up very well when he said
0:57:15 > 0:57:18that SETI is really a search for ourselves -
0:57:18 > 0:57:20who we are and where we fit in to the universe.
0:57:20 > 0:57:24And that's why it's great to do, even if it's a needle in a haystack search
0:57:24 > 0:57:27without any guarantee there's a needle out there.
0:57:27 > 0:57:31It's good that we should ask questions like, what is life?
0:57:31 > 0:57:34What is intelligence? What is the destiny of mankind?
0:57:34 > 0:57:38These are all very healthy, particularly for young people, to deliberate on.
0:57:43 > 0:57:45So is it worth it?
0:57:45 > 0:57:47Is the optimism of Frank's estimate
0:57:47 > 0:57:51and the search for extraterrestrial intelligence naive?
0:57:51 > 0:57:53Or is it enough that through the process of looking,
0:57:53 > 0:57:57we learn more about ourselves and what it means to be human.
0:57:57 > 0:57:59To be honest, I still don't know.
0:58:02 > 0:58:08What I do know is that after some 50 years of searching, we're just beginning to find
0:58:08 > 0:58:11some real, tangible evidence that life COULD exist beyond the Earth.
0:58:11 > 0:58:13And if you want to know what I believe,
0:58:13 > 0:58:16I agree with Arthur C Clarke, when he said,
0:58:16 > 0:58:19"Sometimes I think we're alone, sometimes I think we're not.
0:58:19 > 0:58:22"But either way, the implications are staggering."