BBC The Sky at Night (1957) s25e03 Episode Script
Life
Good evening.
Our programme now is about life.
Now, I'll begin by showing you three objects.
First, a stone - no life there.
Secondly, a lemon - that's living but it can't see or think.
And thirdly, my beloved cat Ptolemy who, believe me, can see and think and is a very intelligent cat.
But, after all, why is lemon living and the stone not? What is the spark of life? If life appears, will it develop into intelligence? And very importantly, is life unique to Earth or is it widespread all through the universe? At least the are two things to guide us - first, we have absolutely no firm knowledge of life anywhere except on the Earth, and, secondly, we'll never be sure how life here began.
There are even suggestions that life was brought here by means of a comet.
My first guest now is Dr Lewis Dartnell.
Now you are an astrobiologist.
Yes.
Some people won't know what astrobiology is.
Looking at the words "astro biology", it means the life, the biology, amongst the stars, so astrobiology is a field of science.
It's relatively new, actually, but it's about looking at the possibility of there being life beyond the Earth, looking to extraterrestrial life, so as my job at University College London, I hunt for aliens, that's what I do.
One thing I'm not certain about is the origins of life on Earth.
So could you help me about that? This is one of the biggest unanswered questions of modern science, of course.
An enormous number of people are trying to address that question.
If we're talking about life on other planets, we need to know how it got started here to know what the best places to be looking or the best ways of looking for it.
Some of these locations that exist today, right on the sea floor, the so-called "black smokers" seem to be one of the best bets, so these are, essentially, underwater plumes of very, very hot super-heated water, which are very rich in dissolved minerals, so things like iron and sulphur from the crust of the planet itself are being pumped out into the sea.
How did life come from that? Well, again, we don't really know.
There's a massive gap in our understanding.
We've got quite a good handle on prebiotic chemistry.
We think we understand generally how you get from things like carbon dioxide and ammonia to amino acids and building blocks of things like DNA, but how you get from things like amino acids things like DNA, which is a chemical that can store digital information - it can store the genetic code and replicate itself - we haven't the foggiest.
It certainly happened here and therefore on a world like the Earth, going round the sun like the sun, why shouldn't it happen there too? Well, exactly.
That's why we're optimistic.
One of the reasons for thinking that life might be common in the universe is that it seemed to happen very, very quickly on the Earth.
Yes, indeed.
As soon as the environment for the Earth became potentially habitable, when the heavy bombardment had stopped pummelling and smacking the Earth with the rubble left over from the formation of the solar system, as soon as the oceans had stopped being repeatedly boiled and sterilised, life appears.
It was incredibly quick, within 200 million years, life has emerged on our planet and it ran with it then.
So the fact that it happened quickly would suggest it's a likely thing to happen, so it could emerge on other planets as well.
So my research is on extremophiles that can survive in the coldest, driest places on Earth - places like the Antarctic dry valleys, which are actually far drier than the Sahara, which is a hot desert, you get very cold dry deserts as well.
I'm working on some bacteria that can survive very, very high doses of radiation - the arch survivalists of our planet.
We found things in pools of boiling acidic water in places like Yellowstone Park when they're heated volcanically.
We found life living inside solid icebergs at minus 20 degrees Celsius, so if you look at these extremophiles in general, this broad spectrum and incredible diversity on our planet and look at the survival envelope of all life on Earth, the astounding discovery, the thing that's getting astrobiologists like me excited is that the survival envelope of life on Earth overlaps with some of the conditions we think or we know exist on extraterrestrial places, so stuff on Earth could survive some of the conditions on Mars or Europa or possibly the upper cloud decks of Venus.
It's not all that crazy at all to be talking about extraterrestrial life, because we know of terrestrial life that could survive in those situations.
What of intelligent life? Well, intelligent life takes a long time to evolve.
For the majority of Earth's history, it's been smeared with nothing more than pond scum, simple life.
You need a planet with the right conditions for very long periods of time to be able to develop intelligence.
So I personally believe that although there'll be plenty of wet rocks out there in the galaxy, plenty of Earth-like worlds smeared with microbial life, I don't think any of them have got intelligent life on them.
There might be forested worlds or worlds with animals, but not anything clever and cunning out there like us.
So far as the solar system is concerned, our best chance of finding life is certainly Mars.
We know that thousands of millions of years ago, it was a warmer, wetter world than it is now.
So could life have appeared there then? And for that matter, could there be life there now? So far, we've no evidence and we've talked about it many times on The Sky At Night.
Primitive life there may be, I don't even think so.
Intelligent life, certainly not.
You think that Mars is a dead planet.
Dead as a dodo.
I don't think we should write off Mars, even now.
If there's never been life on Mars, that's a very surprising fact.
Mars may have been benign a few million years ago.
I wonder if life had time to evolve before conditions became impossible.
It begins to look as though life can evolve very rapidly if conditions are favourable.
We know that there is life in the solar system and it may even be intelligent, but what about the rest of the galaxy? Plenty of stars there, plenty of planets.
Are there worlds like our Earth and, if so, can they support life? We're doing our best to find out.
New missions are going up all the time.
Chris went to America to find out about one of these missions - NASA's Kepler.
The first planet found around a normal star other than our sun was only discovered in 1995.
It took until then because planet-hunting is a painful process.
The signature of the planet's presence is subtle and easily hidden by changes in the star itself.
As a result, the 400 or so planets we've discovered to date are typically large - mostly bigger than Jupiter and too close to their parent star to make them suitable homes for our kind of life.
Three, two, engines start, one, zero and lift-off! Kepler is the latest mission to hunt for planets.
It's staring at millions of stars at once, looking for rocky planets like Earth that have the potential to support life.
I visited NASA's AIMS Research Center to meet the man who leads the Kepler mission, Bill Borucki.
Kepler, basically, is a space mission where we're trying to look for planets, Earth-like planets around other stars and find out whether Earths are frequent in our galaxy or very rare.
If they're frequent, there's probably a lot of life in our galaxy.
If they're rare, we may be the only extant life.
What we'd like to do is determine that frequency, the frequency of Earth's inhabitable zone - the zone where you could have liquid water on the surface of a planet, where there very well may be conditions conducive to life.
We can't find life, but we can find whether planets that could have life are frequent.
Of course, Kepler is a step along the way.
We're trying to understand the extent of life in our galaxy.
An incredibly difficult challenge - how do you detect them? Basically, the stars are so bright and the planets are so dim, you can't see them directly, so you look at some characteristic of the light from the star itself.
So we look at the brightness of over 100,000 stars constantly.
We've got a sort of giant camcorder in space called Kepler.
It's looking at each of these stars, sending that information back to us.
We're measuring whether the brightness of any of these stars changes.
If a star dims by about 1%, that's a Jupiter-size planet.
If it dims a tenth that, that's a Neptune size planet.
If it's a hundredth of what a Jupiter is, in other words, a hundred parts per million, that's Earth size.
If the orbital period is such that it's like a year, like the Earth, you're probably in the habitable zone.
Now cooler stars, and we look at a whole range of stars, have closer-in habitable zones, so their orbital period might only be a few months.
If you look at stars that are hotter than the sun and there are many such, then you have to look longer.
What do we mean by an Earth? Do you need a rocky planet or is it about the size - what's important? A couple of things are important - certainly the size, but composition is the most important thing.
When you find Jupiters and Neptunes, those are gas giants, basically fluid, you couldn't walk on them.
When you're talking about Earths, you're talking about a rocky planet you can have water on, and a super Earth is something we'll find probably before we find Earth.
That'll be a planet maybe twice the size of Earth, again rocky, you could live on it.
The first one that we might want to think about is COROT 7b.
This is a recent discovery? It's a recent discovery by the COROT ESA Mission and people are delighted to see that they found such a planet.
It's a very short-period orbit, however.
It's too hot to have life.
At least it shows these planets exist and we should find more of them.
Since that interview was recorded late last year, the Kepler team have announced their first planet discoveries.
It will take them another year or so to find any Earth-like planets, though.
We need to find planets that occupy the same comfortable niche that life does on Earth.
Our planet lies in what's called the "habitable zone" or Goldilocks Zone, if you prefer - a place not too hot and not too cold, but rather just right for life.
Venus, for example, is far too hot, and Mars, at least in the present day, is slightly too cold.
Once we find a planet in the Goldilocks Zone, scientists and everyone else will clamour to find out what Earth's cousin is like.
One critical clue will be the presence of oxygen - an indicator of life.
Remarkably, even today, we've begun to probe the atmospheres of other worlds.
Studying these worlds is by no means easy, but Dr Giovanna Tinetti is doing precisely that, particularly with regard to their atmospheres.
Giovanna, welcome to The Sky At Night.
Thank you very much.
How do you go about studying their atmospheres? OK, for probing the atmosphere, just to give you an idea, first of all, for the moment, the kind of method we can use to probe the atmosphere is the transit method.
So we basically need a system which are transiting the stars That's movement in front of a star? Exactly.
We would expect to observe at a certain point, the planet is passing in front of the star, and so is masking part of the light and the luminosity of the star.
By studying basically this process at different wavelengths, we can basically understand what's going on in the atmosphere of the planet.
Now this kind of exercise, it's far from being easy, but is doable with nowadays telescope, which is pretty amazing.
What kind of molecules? For the moment, we know that a list on four of these hot Jupiters, apart from molecular hydrogen, which is the main component of the atmosphere, molecules like water vapour, methane, carbon dioxide and carbon monoxide are present, and we have hints that in some of these hot Jupiters, even more complex molecules are present, so I guess in the next few months and years we will know even more.
So we would love to find the same kind of molecules in terrestrial planets, in the habitable zone of the star, if life is there would definitely modify the atmospheric composition, like it did for our own Earth through the Earth's history.
Just suppose now there is someone living in the Upsilon Andromeda System, and they look at our sun, can they tell there's a life-bearing planet here? Well, certainly an alien looking back at our own planet would find extremely interesting the fact that we have huge quantities of molecular oxygen in our own atmosphere, and I'm talking about 21%.
Given the fact that molecular oxygen is a very reactive type of molecule, if it finds that, it's certainly a signature that something very strange is going on and cannot be completely explained by chemistry.
And so, probably from that information, for instance, will get the hint that there is something going on on our planet, but that is not the only bio-signature that these aliens might find in our own atmosphere.
For instance, the fact that the carbon dioxide has some annual cycles, where it's increasing and increasing with the seasons in a very typical pattern - that also could be interpreted like a signature that something is going on and, in particular, this kind of patterns on the Earth is due to the fact that vegetation has some seasonal variation.
Well, I must ask this question you must have been asked millions of times, what about life there? Are there life-bearing planets? I can tell you my personal opinion, because at this point we have no evidence whatsoever, er, well, my personal opinion is life is very common in the universe.
I'm talking about not necessarily complex life, like we have in our own Earth.
I'm more talking about simple life.
I personally think it would be very arrogant to think we are the only one Quite.
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that we have the exclusive recipe for life.
Thank you so much for coming.
Thank you very much.
It was a pleasure and a great honour.
We've been talking about planets orbiting stars, but we've yet to know how far away those stars are.
Light travels at a finite speed.
Well, The Sky At Night was first broadcast way back in 1957- how long ago that seems! And since then, our programmes have been winging their way into space.
Possibly someone out there is listening to our old programme right now.
Pete and Paul are in the garden talking about just how long light takes to get there.
If I turn this torch on and point it up into the night sky, the beam of light which leaves the torch is leaving the Earth's surface at the incredible speed of 186,000 miles a second - the speed of light.
Now the distance that beam travels over the course of a year is what's known as a "light year".
Television transmissions travel at the same speed as our light beam, which means it takes them some ten-and-a-half years to reach here - Epsilon Eridani - which is located some ten-and-a-half light years away from the Earth.
That means that The Sky At Night programme that they're most likely to be watching now is our August '99 edition which was looking at the total eclipse of the sun in Cornwall.
It's a bit cloudy.
A little over five times further away than Epsilon Eridani is a star known as HD128311, not really a name which easily trips off the tongue.
Now it's thought that there is a planet around this star which is 54 light years away, and if there are beings on that planet with really sensitive reception equipment, they could pick up The Sky At Night.
Which episode would they be watching? Well, they would have just finished watching the very first episode, where Patrick described the comet Arend-Roland.
If they are watching that and they're hooked on the series, I'd like to send them out a message now which will take 54 years to get to them and that is, "Please remember to pay your television licence.
" If a rocky planet is going round this star Caro 7, located some 490 light years away from the Earth, which means they won't receive the first episode of The Sky At Night for another 437 years, but if they had a telescope powerful enough and could look back on the Earth, they would see it not as it is now but as it was in the time of the Tudors with Henry XllI still on the throne.
FIZZLING Not much to see here.
Now while Caro 7 at 490 light years' distance is a long way away, it's by no means the furthest known system with an exoplanet going round it.
That's believed to be a star located in the constellation of Scorpius estimated to be some 20,000 light years away.
Now that places it very close to the galactic centre where the oldest stars of our galaxy are located.
Now just imagine a being on a planet going round that star with a telescope powerful enough to look back at Earth.
If it looked through that telescope, it would see our tiny planet covered in ice because it would be looking back in time 20,000 years, to the time of the last ice age.
Well, Pete, it looks like communicating with extraterrestrials via radio waves is going to take just too long.
It's not a very good way of communicating over such vast distances, is it? No.
Can you think of anything better? Well HIS SPEECH BECOMES DISTORTED Well, it will certainly be some time before anyone out there watches this programme.
The main organisation looking for life elsewhere is SETI - the Search for Extra-Terrestrial Intelligence, and Chris went to see the latest SETI telescope array.
Out in the middle of rural America, a bold experiment scans the skies looking for alien radio signals.
This is the Allen Telescope Array.
It works by linking together many small dishes providing the resolution of a much bigger telescope.
The array is used for conventional astronomy too, but the team are always alert for that elusive signal.
SETI luminary Jill Tarter showed me around the array.
Built on a shoestring, it has a reassuringly homemade look.
Ready? Yep.
Got it! And here we go! OK.
So now, if you look inside here, what you're looking at is the secondary reflector.
So radio waves have bounced off the big dish up there, onto the secondary reflector and they're focussed back here.
Wow! Look at that! Isn't that amazing? I always think about the Saturday morning TV I used to watch.
Flash Gordon death rays! Zzz! Zzz! REFLECTOR BUZZES That's what that reminds me of.
So, what is it? Why is it that shape? That shape allows it to do two things - one, to capture very long wavelengths down here OK.
So that's where the half a gigahertz is picked up.
It's like a car aerial that works at half a gigahertz.
Mm-hm.
And up at this end, um, the short wavelengths, the high frequencies - the 11 gigahertz - are captured by that part of the aerial.
Recently, Jill was in England and came to the Sky At Night to give me the latest news.
Jill, it's great to see you.
Thank you for coming.
Oh, my pleasure to be here.
Now, first of all, SETI.
You've been involved now for a long time, a large part of your life, haven't you? I have.
How did you get involved? By accident, Patrick.
I knew how to programme a computer that was turned out to be given to someone to do a SETI project, when it was obsolete.
And what I learned from that was that I lived in a really special time.
I was in the first generation of humans that could stop asking the priests and the philosophers what to believe about whether we're alone and actually do an experiment and try and find the answer.
Do you personally think there's probably life elsewhere? I actually don't know the answer to that question.
I think we should do the experiment to find out.
Exactly.
If there ARE other beings, would you expect them to be anything like us? Gee, if we're going to find them, it's because they're using technology.
So they're probably not that small.
They have to manipulate big pieces of equipment to build transmitters.
Other than that, I don't know what they're going to look like.
So I wonder if we found them, how could we communicate? Well, I think it will probably be a universal language based on mathematics.
Because technology requires mathematics to do the engineering.
Um we can hope that if someone is taking the trouble to broadcast a deliberate message, that they'll make it anti-cryptographic, that they'll try and help us understand.
Have you any real hope of success in the foreseeable future? Well, Patrick, I always keep champagne on ice.
I'm very hopeful, always! The technology that we're able to use now is getting so much better.
We have an exponentially more capable system than we ever had.
And so I think within the next few decades we will have been able to search a few million, ten million stars, and that might give us a chance.
And, you know, because there's so few people in the world doing SETI, I have a passion to get more people involved and so we are about to start a new SETI project called SETI Quest where we will publish all of the code we've been writing all these years as an open source.
We'll ask all the engineering students to come up with better algorithms for finding signals, and we'll ask people around the world to use their brains to help us find patterns in noise.
And so I hope that by involving the world, we can tell the story of SETI and make people think about us and how we would look relative to some alien species.
Yes.
And understand that all earthlings are the same.
This programme of searching for extra-terrestrial intelligence can help us trivialise the differences among humans.
I hope that is so.
And make me one promise, Jill.
If you find it and I'm still around, come back to the Sky At Night and tell us.
I promise that for sure.
Promise? Absolutely! The first modern SETI experiment was carried out by Dr Frank Drake at Green Bank, West Virginia.
And in 1965 he joined the Sky At Night to tell us about it.
From what we know, there are at least 100 billion stars in our own galaxy and so many other galaxies, that there is a total of 10 to the 20th, that's 100 million million million stars in space.
So that we would expect that there are very large numbers of planetary systems.
That on many of these planetary systems, life has arisen, and given this very large number of stars with which we start and the possibilities of life developing in so many of these places, it seems virtually certain that there is intelligent life elsewhere.
That was 45 years ago, and today Frank is still involved in SETI.
To calculate the odds of SETI success, Frank came up with one of the most famous equations in science - The Drake Equation.
It's his attempt to work out the number of intelligent civilisations in the universe capable of communicating with us.
There's at least one species that can send signals across the wastes of space - our own.
But there's no evidence yet for anybody else.
Dr Drake, thank you for joining us.
You're best known as one of the people who first tried to work out what the chances of receiving a signal from another civilisation were.
What inspired you to try and make that effort? Well this occurred about 50 years ago when we had just done the first search for extra-terrestrial radio signals and this lead people to ask, "What are the chances? What is it going to take to succeed?" And the answer to that requires you to make, somehow, an estimate of how many civilisations are out there and therefore, how far the closest ones are and how much searching has to be done before you have any reasonable chance of success.
So I sat down and just took into account all the things that bear upon the number of detectable civilisations in our galaxy, turns out there's seven different things.
And when you multiply your estimates of all of these things together, the end result is our goal - the number of detectable technical civilisations in space.
So what were the seven things? The seven things are the rate of star formation.
That we know! That we know extremely well.
The second one is just the fraction of newly-born stars to have planets.
The more planets, the chances for life.
The third thing is the number of habitable planets in each planetary system, on average.
OK, so that's three.
Three of them! The next one is the probability of life actually developing on a habitable planet.
Life appeared on Earth at the earliest time it could have.
So that one is well, actually, pretty well known, even though we've not seen a life form on some other planet.
The next one is what fraction of those evolve an intelligent species.
This one is still very problematical.
And one thing we do know here is that although life appeared quickly on Earth, intelligent life took billions of years to come about.
It took billions of years and it's because we're of You have to be an extremely complex organism before you can have a brain capable of intelligence.
The next one is the, er the fraction of intelligent species which develop a detectable technology.
On Earth, technology has been developed independently many times.
In every case, first the technology of agriculture.
But in an instant in cosmic time on the cosmic timescale, that has developed into automobiles, aeroplanes and iPods and all of the things we have today.
So that fraction seems to be one with the caveat that the planet has to be suitable for the development of technology.
The last one is the length of time a civilisation continues to be detectable once it has developed its detectable technology.
In our case, we became detectable easily around the year 1950 through the development of radar.
And also through the development of television.
And these signals are leaking into space.
These signals have been leaking into space now for 50, 60 years and there's a shell around us - 60 light years in diameter - full of evidence for our existence.
People can learn all about us with very little effort from what we have very generously provided.
Disturbingly by watching our television! Maybe you should pass over that.
Yes, what bad impression do they have of us by now.
That shell is continuously growing.
Now, 50 years ago we thought we understood the limits of technology and that what we were searching for would always be there.
It was the very powerful, so-called carrier signals of television transmissions.
A thing which looks like its definitely the way of the future is some combination of cable television, and direct-to-home, as it's called, television broadcasts from satellites to little dishes on people's houses.
It turns out the typical power transmission from the satellites providing television to a whole continent is about 20 watts.
The traditional TV stations are a million watts.
All of that power goes into space.
So if this becomes the way to deliver television 100 years from now the Earth will become very difficult to find.
And that makes us stop, and say, "Whoa!" Does that mean that the typical longevity is 100 years? In which case the odds of finding another civilisation in our bubble are very small.
Very small.
During the years we've discussed the chances of life not only on Mars but even on the Moon.
When the first explorers land on the moon, are they going to find any natural life there? There's not much outward resemblance between, say, a jellyfish, an ant, and a man.
At least I very much hope not! But they are all based on carbon and all meet certain conditions.
None of those conditions exist on the Moon.
My old friend, Arthur Clarke, has his ideas about life elsewhere.
When you consider the incredible variety of life on this earth, it's obviously impossible to speculate usefully about life on any other planet.
Who could have imagined the giraffe? The giant squid? The Whale? Or indeed, if you take a dispassionate viewpoint, us.
Since on this one planet, relatively uniform environment, nature has done such fantastic things and on planets which are much hotter or colder, or have different chemical constituents, then life could take almost any imaginable form.
From the point of view of other forms of life, WE are bug-eyed monsters.
We've been talking about the chances of life elsewhere.
There are people that have very pronounced views on the general aspect of life in the universe.
One of these is one of our most regular and welcome visitors, Dr Allan Chapman.
Alan, welcome back.
What are your views on the search for extra terrestrial intelligence? To be perfectly honest, it makes looking for fairies at the bottom of the garden look like hard nuclear physics.
I have to admit there is just so much fantasy, so much impossibility in it, that I just cannot take it for serious.
I don't deny that there may be some form of intelligence up there, but the chance of us finding it after 50 years of failed searching, I see it frankly more as an aspect of the psychology of religion.
It's more an attempt to find something you can't prove exists.
Of course, religion works along a totally different line.
The idea of finding these beings at all costs, in spite of every single scrap of scientific reality against them.
I just find it - I have to speak bluntly - a complete waste of resources.
Absence's vividness is not evidence of absence! I quite agree.
But how far do you have to search for something before finally deciding it is not there? Allan, you won't recall this, I do.
I go back to the time when there was quite widespread belief in life on Mars.
And after all, it wasn't till the first spacecraft showed those dark cracks were not vegetation.
Perfectly correct.
And we've learned an enormous amount since then.
What I would suggest has happened is the real hope of there being life at least in the solar system Solar system, yes.
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stopped with the telescope.
Because all of a sudden - bearing in mind that in the ancient world they thought the planets were simply bright lights in the sky - what Galileo and Thomas Harriet and Robert Hooke all discover is that Mars, Jupiter, the Earth, everywhere, are actually worlds.
And if they are worlds, then, their religious argument was, why hadn't God put life on them? Herschel believed in beings living inside the Sun! Absolutely.
It was an idea they called plenitude.
In other words, plentifulness.
Life everywhere.
Working on the argument that you didn't build houses if there was nobody going to live in them.
So this means there is an active concern with what they call Selenites - from the Greek Goddess, Selene - moon beings, Jupiterians, and so on.
And John Wilkins, in Oxford, in the 1650s, had the bright idea of using the latest technology, clockwork, springs, levers, machinery, to build a small ship with a powerful clockwork motor inside it and a pair of wings.
This might be able to get to the Moon.
And his argument was, we would find the Moon, a long, long voyage that would take ages, like sailing to America or China, but then we would find the Selenites.
Then we could learn from them, talk to them, and the wonderful idea was they realised that the lunar night was 14 Earth nights long - it must be pretty chilly on the Moon, could we not even sell English cloth to the Moon men?! They'd be wearing English tweed overcoats to keep them warm! I grew up with the idea of aliens.
My mother was a very talented artist.
She was indeed.
She drew these lovely aliens.
And as she said, no-one could prove her wrong! Precisely.
And her drawings, of course, we have a copy of the book, there are some wonderful pictures in there.
Those pictures are highly amusing.
In particular the way she often puts a little bird in.
The bicycles going round the rings of Saturn! It's a wonderful humour.
I think it's so wonderful.
Over the years, plenty of people have suspected flying saucers, UFOs, alien visitations, and so on.
My old friend, Michael Bentine, joined me to talk about this.
Caught it! Ha! Well, Michael, we used a frisbee, obviously, because it is aerodynamically shaped.
And when these things were first reported they were always known as flying saucers.
I'm not quite sure when they changed to UFOs but a flying saucer it could be.
But people who have reported them say they are other shapes as well.
Yes, indeed.
We've got the famous Havana shape, from Cuba, like a cigar, up there, which launches the little saucers, apparently, we've got the dumbbell shape, and I like that one And the famous lampshade model! Worn on the head it looks very attractive! I think people will believe anything.
What about that famous divorce case? Is it true? Absolutely true! And I've met the chap concerned.
He was American, and wrote a book a long time ago now called Aboard a Flying Saucer.
He described his adventures aboard a craft from the planet Venus piloted by a beautiful lady whose name was, I think, Aura Rhanes.
Apparently he had a very good time indeed and his book came out as non-fiction, a true adventure, and his wife promptly sued him for divorce, cited the lady from Venus, and she won! First interplanetary scandal in history! Absolutely fabulous! Well, flying saucers are still with us.
Pete and Paul have brought along some very interesting specimens.
Yes, look, aren't these marvellous? I have here a model of George Adamski's very early flying saucer, seen in the 1950s.
It looks a bit retro now, doesn't it? Definitely.
Imagine if it actually landed.
It would be so disappointing, wouldn't it? Ha-ha! The first one, very reminiscent of the first alien abduction case, if you believe that sort of thing.
This is the Betty and Barney Hill spacecraft Oh, yes.
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which snatched them up from the road in Montreal, Canada.
Zeta Reticuli.
That's right.
The aliens showed Betty Hill a star map which she revealed under hypnosis, and it showed the Zeta Reticuli star system.
It's rather small.
Bigger inside! And finally, right up to date, we have the flying saucer seen by Billy Meier.
I like that one.
It's also known, by people who back-engineer these things, of course, as the sports model! It's quite a sleek looking craft.
Who wouldn't want to own a flying saucer looking like that?! It looks like a flying saucer should look like in the mind's eye.
Of course people do see weird things in the night sky.
They are actually quite natural, aren't they.
UFO means unidentified flying object and of course if you see something and can't identify it then it is unidentified.
And I've seen loads of things in the night sky which I haven't been able to identify, but then I've found out, so they are no longer UFOs.
These include things like, say, a bright planet down close to the horizon.
As it is flickering away, it is easy to mistake it.
So you get lots of calls coming in from people.
Sirius, too.
Sirius flashes these bright, brilliant colours.
That can be mistaken as well.
Other bright things, the International Space Station is a classic example.
It is so bright and moves across the sky, people see it, don't know what it is, and think it is a UFO.
It is quite spooky, how it brightens up as it reaches the zenith and then dims back down again.
It is very odd indeed.
The thing which almost threw me once, going outside, another artificial satellite.
But this time it was a trio of satellites, just bright enough to be able to see with the naked eye, moving across in formation together.
That was actually quite freaky to see.
You have had a UFO experience yourself! Oh! A whole crop of flying saucers going towards me! My 50 inch reflector.
"The Martians have arrived at last!" I couldn't see them, absolutely baffled.
What was it? Pollen! Oh, no! I saw, actually, a very strange sight a while back.
It was a triangular cloud.
Triangular cloud? I was quite perplexed by that.
So I took a photograph, as I would do, and then left it for a bit.
A couple of hours later it was still there.
I took another photograph of it and it turned out, after I did a bit of research, it was a fuel dump from a satellite.
Really?! Oh! So it was just up there in space, glowing away! But my all-time favourite UFO, partly because I've launched them from my own back garden, is the Chinese lanterns.
Ah, yes! These are remarkable things.
And becoming more common now.
Yeah, people don't fall for it any more.
There were quite a few reports of people reporting a meteor shower.
They actually turned out to be Chinese lanterns.
So it's just misidentification of things.
Pure coincidence! Well, can there be life elsewhere? If so, what's it going to be like? More seriously, what can life on Earth tell us about possible life elsewhere? Chris talked about this to an astrobiologist, Charles Cockell.
From here, on the surface of Planet Earth, It seems that life is everywhere, making its presence felt even in apparently barren environments like the Antarctic.
But looking at our planet as a whole destroys this illusion of abundant life.
Life, in truth, occupies only a fragile, narrow portion of the Earth's crust.
It forms no more than a thin film on the planet's surface.
Charles Cockell is a microbiologist who is looking at how life can survive even where we might no expect it.
As a human, you are used to walking around, seeing tall trees, and lots of vegetation.
It is easy to get this impression that life is very luxuriant, and covers the planet in great abundance.
But in fact, if you draw a diagram of the scope of the biosphere to the scale of Planet Earth, it's a tiny thin strip of life on the surface of the planet, and just beneath the surface, very, very thin strip of life.
It's not very abundant at all, just within that surface layer.
And it's restricted to that thin layer because it need special things to exist.
In particular, life on Earth has got very used to photosynthesis.
Well over 90% of life on Earth is there because of photosynthesis.
Photosynthesis uses sunlight and it generates huge quantities of carbon and oxygen.
And it is carbon and oxygen that most other organisms use as a source of energy.
So, for example, we eat our food.
And we burn it in the oxygen that we breathe in, So we're dependant upon photosynthesis.
And that's the case for many other organisms on Earth.
So it is photosynthesis that really accounts for that incredible spread of life over the surface of Earth that we see today.
So how can we use what we have on Earth to tell us about life elsewhere in the solar system? Most people are not that interested in microbes.
They seem to be very boring little single-cell things that you might see under a microscope back when you're at school.
But what's incredible about some of these microbes is they eat rocks.
You and I eat our food, and we breathe oxygen, but there are microbes that literally eat rocks and some of them breathe metals.
A great deal of life on Earth is microbes living inside rocks and making a living in volcanic environments, or in asteroid and comet impact craters, even microbes living in the bricks of your house, for instance, that most people are probably not aware of.
Your bricks are actually a habitat for vast numbers of microbes.
And by studying those microbes we can start to ask, could microbes live in rocks on Mars? How would they live in other rocky planets in our own solar system, or elsewhere? And it is crucial because, unlike most of life on Earth, these rock-dwelling creatures, these bacteria, don't depend on photosynthesis.
You can imagine these existing where photosynthesis hasn't evolved.
That turns out to be very important on the inside of planets.
Photosynthesis needs light.
It uses light to drive energy.
If you can get your energy without photosynthesis, you don't need to be on the surface of a planet.
You can live down in the rocks.
Many of these microbes live off rocks, live in the sub-surface right underneath our feet, and many of them have been found 2, 3 kilometres deep underground.
This is of great interest on a planet like Mars where the surface is very extreme, there's high levels of radiation, there's not much water, but perhaps under the surface of Mars, there might be water, they can be protected from the extreme conditions on the surface, and underground where there's energy in the rocks, that might be the best place to look for life on Mars.
So much for Mars, but you mentioned Europa as well, which is the other place people tend to look for life in the solar system.
What can we say about Europa based on our experience of Earth? Europa's an interesting environment because it has an ocean.
That ocean seems to be in contact with a silicate core.
So when you think about energy from rocks, you think about circulation of water through the crust, a bit like water through the deep ocean crust on the Earth.
Which produces these hydrothermal vents and so on.
Yes, and people have thought maybe that could happen on Europa.
It's a nice idea, but there are many caveats to this.
The ocean may be too salty for life.
Life has a great tolerance for different salt concentrations, but there is an upper boundary beyond which molecules can't tolerate high salt.
We also don't know the lower limit of temperature.
Maybe the Europan oceans are too cold, but that's a good reason for sending a mission there.
Even if we were to find that Europa could not harbour life, that would be just as interesting scientifically, to find a huge body of liquid water in our solar system that was not capable of harbouring life.
Not quite as exciting in terms of a newspaper headline story, but from the point of view of understanding the boundary conditions for life, that would be an equally fascinating discovery.
It illustrates what you've said.
Water isn't enough, we need We need these other ingredients and environmental conditions for life to be able to originate and then persist in a planetary environment.
Charles' work helps us set out the ingredients needed for life.
The beginning of a recipe for organisms to form elsewhere.
If life can exist in some of the most inhospitable places on earth, does it have a chance of finding a niche somewhere else in the universe? The SETI researchers looking for life have so far had no luck at all.
Merely silence.
Why is this so? Can it be that there really is nobody there? Chris went to see a cosmologist who has rather different ideas about it.
It's tempting to put SETI's failure to detect an alien signal down to bad luck, but cosmologist Paul Davies, although he's a supporter of SETI, thinks there's a more troubling reason why all we've heard so far is an eerie silence.
When we talk about life in the universe, there are many unknowns.
Which of them do you think is the most important? The quantity that we understand least is the probability that life will emerge on an Earth-like planet if you have one.
That number could be anywhere from very nearly zero to very nearly one.
The error bars are enormous.
We know it's not zero of course.
We know it's not strictly zero, but people will often use a silly argument, they'll say, "The universe is so big, there's got to be life out there somewhere.
" Even if it's unlikely, we have billions of planets so the argument is it will have happened somewhere.
It's a silly argument for the following reason, if we take the entire observable universe, as far as we can in principle see, there might be something like a 100 billion billion Earth-like planets in that volume.
100 billion billion sounds like a big number.
1 followed by 20 zeros.
Surely, even if the chances of life forming by the random shuffling of molecular building blocks, there are many planets out there where it will have happened.
This is not true.
Imagine having a soup of amino acids with everything there, and you allow it to shuffle and shuffle.
The chances of getting a particular protein is like 1 followed by 130 zeros to one against.
If that's the way life occurred on Earth, we would be unique, this would be the only planet even given the vastness of the universe.
That argument does not wash.
What we'd like to know is, is that the way it worked, or was is just chance that gave us life on Earth? Was there some process that drove quickly to the right convention? Is there some sort of life principle at work in the universe? Some cosmic imperative, in other words, is life somehow built into the nature of the laws of the universe in a fundamental way? That it is more or less automatic that is going to form when you have the right conditions.
A lot of people would like to believe that but the truth if the matter is we have absolutely no evidence whatsoever that that is actually the case.
It is a complete unknown.
What about those who argue that life happened very quickly on Earth, and therefore in some it must be likely? This is another bad argument and I can understand why people make it.
Carl Sagan famously said that no sooner was Earth ready for life then up it popped.
And that is true for about 700 million years.
Our planet was being pounded by comets and asteroids.
This merciless bombardment would have made life almost certainly impossible.
We see the scars of that on the moon.
We do not see those scars so easily on Earth.
And so we know that up until about 3.
8 billion years ago, Earth was pretty much uninhabitable.
By 3.
5 billion years ago, life had firmly established itself here.
A rather narrow window.
That makes it look like is easy to make, gets going quickly.
Unfortunately, the reason that we are going through this argument about Planet Earth is precisely because that is our home, that is where we live.
We are the observers so this is what scientists call a selection effect.
We are discussing it because we are the products of that life.
The fact that life did get going quickly on Earth, does not mean that it is a highly probable event.
Right.
It can still be an incredible fluke, but it is a fluke that had to happen for us to have this conversation.
As a subtle argument, a philosophical argument, you cannot base too much on it.
A sample of one.
But, equally, you can't use the argument the other way, and say the fact that is started quickly means it is very probable.
It doesn't.
There is a selection effect.
We are left with this crucial idea of whether there is this, what you call, the cosmic imperative towards life.
How can we test the idea of the cosmic imperative? There is one very obvious way.
We should try to find a second sample of life.
We do that if were to pick up a signal from an alien civilisation, there we have it.
But in the absence of that, there is a very simple way we can test, that is right here on Earth.
We do not even need to leave our home planet because if it is true that life, as many astro-biologists hope, does pop up very readily in Earth-like conditions, there is no planet more Earth-like than Earth itself, surely life should have happened many times over right here on our home planet? Unless you have a cosmic imperative, the chance of life being vanishingly small, that has huge implications for SETI.
I have always been a supporter of SETI.
I think that the chance of success is exceedingly small because it forces us to think about things we should be thinking about anyway.
What is life? What is intelligence? What is the destiny of mankind? We are looking for alien civilisations.
We are really looking at the future of human civilisation.
What might it be like on Earth in another thousand years? In another million years? In another ten million years? What lies in store for us because that is what we are assuming is happening out there? We are really searching for human destiny mirrored in the stars, is the way I like to put it.
When you put it like that, that sort of suggests the paradox inherent in current SETI searches.
Because we are looking for the future of human civilisation with the technology that we use today.
In my view, rather than looking for messages crafted for mankind and deliberately beamed at us.
Which I don't think is a credible notion.
The best way that we can hope to pick up anything using radio as beacons.
We can imagine a civilisation, say towards the centre of the galaxy, that might have been around for hundreds of millions of years, to have built a beacon like a lighthouse, it would sweep the plane of the galaxy, and this thing would go, "Bleep," as it comes round.
It might go, "Bleep, bleep", or something more interesting.
But it would do this once a year, once every ten years.
I don't know what it is.
But as a form of advertising their presence Right, so what we really want is a set of instruments to just stare towards the centre of the galaxy which is where most of the stars are, where the older civilisations would be.
We now know there are planets contrary to lots of expectations, planets seem common towards the centre.
It does appear to be so.
SO we should just stare at the centre of the galaxy, continuously, over many years.
The SETI program as is currently set up, does not really do that.
It is not well set up for these events.
Could we see traces of civilisation directly? One scenario is that not only are there other inhabited planets, but there will have been waves of colonisation across the galaxy.
There could have been a wave of colonisation, or at least exploration, that passed through our solar system in the past.
A lot of people are fixated on this idea, "Oh, ET came to visit within historical times.
" Sure.
That is absurd when you look at the duration of cosmic history.
There could have been advanced civilisations in our galaxy billions of years ago.
Supposing an expedition had come through our solar system 500 million years ago.
How would we know even if they had landed and made a mess? Would any of that remain today? Well, if we think very carefully, the answer could be yes.
For example, if they had used nuclear materials in some way, we might just find The radioactive traces.
That would show that there had been something else going on.
If they had dug craters on the moon, or somewhere where erosion is rather small, we might notice it if the shape was peculiar.
They may have fiddled around with the biosphere.
They may have created micro-organisms to help them with mineral refining or something of that sort.
You might see a trace in the genomes of the micro-organisms.
They may even have left a message for us in the genomes of micro-organisms.
We know that DNA is a great place to store information.
The information in your DNA and my DNA, some of the information has been around for 3.
5 billion years.
Passed down from generation to generation.
It is much better than leaving an obelisk there that is not going to survive too long.
You encode if biochemically so we can start looking in genomes.
Maybe the message is in the genome not in the sky.
All of these ideas are incredibly fanciful.
This is science fiction that we are talking about but what I really want to do is make people aware that we could see a signature of intelligence, of alien intelligence, almost anywhere.
In almost any science, and almost anywhere in the universe.
We mustn't just be fixated on this idea that it has got to be a radio signal coming our way.
Life has been present on our Earth almost since the beginning of our planet's long story.
More than four billion years ago.
Yet only in the last 50 years has our technology advanced enough to make us visible to the rest of the cosmos.
Things are happening now that would have been sheer science fiction only a few years ago.
As we have heard, the odds of there being a civilisation out there whose signals we can detect are small.
That makes it very difficult to assess if we are truly alone in the universe.
That said, there are likely to be many thousands of planets spread throughout the galaxy.
And despite the arguments against it, I still believe that there must be at least one other place out there where life is flourishing.
In this programme, we have talked to a good many people, all of who have different views.
But they are making progress on all kinds of fronts.
We are going forward and sooner than later, those fronts will gel.
What do you think? I think that's absolutely right.
The easiest way to see that, I think, is to go back 20 years.
20 years ago, we did not know of any planets beyond our own solar system.
SETI was fairly moribund.
They were doing some radio stuff but there was nothing like the telescope array.
Even the biologists who are now getting more confident about how life can have started, if you go back to Lewis, who you talked to at the start of the programme, the idea that you could do experiments in the laboratory that had direct bearing on this question as to whether there is life elsewhere, is quite impressive.
Then, of course, look at Mars.
20 years ago, Mars was a dead place.
No-one thought there was any possibility of recent water.
Europa's oceans were a hypothesis but there was not much evidence.
Enceladus was a boring moon going round Saturn.
We gained places within the solar system.
When you put all this together, what we're doing is making the problem much worse for ourselves.
We are understanding planets and life, but we still don't have the evidence we need to say, "Yes, there is intelligent life.
" In a way, in the solar system, we have found more evidence that there is no life of any intelligence at all.
The chances have increased.
There are so many planets, I can't take the idea of all the Earth-like planets, we are the only one with intelligent life.
I can't take it.
It is a strange idea.
In some ways it is I was talking to somebody who said it was inspiring because we would be the only people in the galaxy and we would have to take responsibility.
Frankly, looking around Earth, I think it is rather depressing to think we are the height the universe has managed.
I have a feeling that sooner rather than later, there is going to be a success and we'll make contact with another race.
And on a smaller scale, we may be five, ten years from pointing at a star in the night sky, and saying, "Not only do I know that star has planets, not only do I know that one of those planets is like the Earth "in that is has oceans, a rocky surface.
"But I know that there is the signature of at least primitive life.
" I think that changes our whole view of the cosmos.
Once we can point to One is all we want.
Absolutely.
Just one.
Chris, thank you very much.
Well, in this programme, we have talked about the matter in all its aspects.
Is there life there? Is it intelligent? Can we ever contact it? Will the eerie silence ever be broken? Well, I don't know.
I have a sort of feeling it will.
And finally, we may at last find out the answer to what we really want to know Are we alone in the universe? Goodnight.
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Our programme now is about life.
Now, I'll begin by showing you three objects.
First, a stone - no life there.
Secondly, a lemon - that's living but it can't see or think.
And thirdly, my beloved cat Ptolemy who, believe me, can see and think and is a very intelligent cat.
But, after all, why is lemon living and the stone not? What is the spark of life? If life appears, will it develop into intelligence? And very importantly, is life unique to Earth or is it widespread all through the universe? At least the are two things to guide us - first, we have absolutely no firm knowledge of life anywhere except on the Earth, and, secondly, we'll never be sure how life here began.
There are even suggestions that life was brought here by means of a comet.
My first guest now is Dr Lewis Dartnell.
Now you are an astrobiologist.
Yes.
Some people won't know what astrobiology is.
Looking at the words "astro biology", it means the life, the biology, amongst the stars, so astrobiology is a field of science.
It's relatively new, actually, but it's about looking at the possibility of there being life beyond the Earth, looking to extraterrestrial life, so as my job at University College London, I hunt for aliens, that's what I do.
One thing I'm not certain about is the origins of life on Earth.
So could you help me about that? This is one of the biggest unanswered questions of modern science, of course.
An enormous number of people are trying to address that question.
If we're talking about life on other planets, we need to know how it got started here to know what the best places to be looking or the best ways of looking for it.
Some of these locations that exist today, right on the sea floor, the so-called "black smokers" seem to be one of the best bets, so these are, essentially, underwater plumes of very, very hot super-heated water, which are very rich in dissolved minerals, so things like iron and sulphur from the crust of the planet itself are being pumped out into the sea.
How did life come from that? Well, again, we don't really know.
There's a massive gap in our understanding.
We've got quite a good handle on prebiotic chemistry.
We think we understand generally how you get from things like carbon dioxide and ammonia to amino acids and building blocks of things like DNA, but how you get from things like amino acids things like DNA, which is a chemical that can store digital information - it can store the genetic code and replicate itself - we haven't the foggiest.
It certainly happened here and therefore on a world like the Earth, going round the sun like the sun, why shouldn't it happen there too? Well, exactly.
That's why we're optimistic.
One of the reasons for thinking that life might be common in the universe is that it seemed to happen very, very quickly on the Earth.
Yes, indeed.
As soon as the environment for the Earth became potentially habitable, when the heavy bombardment had stopped pummelling and smacking the Earth with the rubble left over from the formation of the solar system, as soon as the oceans had stopped being repeatedly boiled and sterilised, life appears.
It was incredibly quick, within 200 million years, life has emerged on our planet and it ran with it then.
So the fact that it happened quickly would suggest it's a likely thing to happen, so it could emerge on other planets as well.
So my research is on extremophiles that can survive in the coldest, driest places on Earth - places like the Antarctic dry valleys, which are actually far drier than the Sahara, which is a hot desert, you get very cold dry deserts as well.
I'm working on some bacteria that can survive very, very high doses of radiation - the arch survivalists of our planet.
We found things in pools of boiling acidic water in places like Yellowstone Park when they're heated volcanically.
We found life living inside solid icebergs at minus 20 degrees Celsius, so if you look at these extremophiles in general, this broad spectrum and incredible diversity on our planet and look at the survival envelope of all life on Earth, the astounding discovery, the thing that's getting astrobiologists like me excited is that the survival envelope of life on Earth overlaps with some of the conditions we think or we know exist on extraterrestrial places, so stuff on Earth could survive some of the conditions on Mars or Europa or possibly the upper cloud decks of Venus.
It's not all that crazy at all to be talking about extraterrestrial life, because we know of terrestrial life that could survive in those situations.
What of intelligent life? Well, intelligent life takes a long time to evolve.
For the majority of Earth's history, it's been smeared with nothing more than pond scum, simple life.
You need a planet with the right conditions for very long periods of time to be able to develop intelligence.
So I personally believe that although there'll be plenty of wet rocks out there in the galaxy, plenty of Earth-like worlds smeared with microbial life, I don't think any of them have got intelligent life on them.
There might be forested worlds or worlds with animals, but not anything clever and cunning out there like us.
So far as the solar system is concerned, our best chance of finding life is certainly Mars.
We know that thousands of millions of years ago, it was a warmer, wetter world than it is now.
So could life have appeared there then? And for that matter, could there be life there now? So far, we've no evidence and we've talked about it many times on The Sky At Night.
Primitive life there may be, I don't even think so.
Intelligent life, certainly not.
You think that Mars is a dead planet.
Dead as a dodo.
I don't think we should write off Mars, even now.
If there's never been life on Mars, that's a very surprising fact.
Mars may have been benign a few million years ago.
I wonder if life had time to evolve before conditions became impossible.
It begins to look as though life can evolve very rapidly if conditions are favourable.
We know that there is life in the solar system and it may even be intelligent, but what about the rest of the galaxy? Plenty of stars there, plenty of planets.
Are there worlds like our Earth and, if so, can they support life? We're doing our best to find out.
New missions are going up all the time.
Chris went to America to find out about one of these missions - NASA's Kepler.
The first planet found around a normal star other than our sun was only discovered in 1995.
It took until then because planet-hunting is a painful process.
The signature of the planet's presence is subtle and easily hidden by changes in the star itself.
As a result, the 400 or so planets we've discovered to date are typically large - mostly bigger than Jupiter and too close to their parent star to make them suitable homes for our kind of life.
Three, two, engines start, one, zero and lift-off! Kepler is the latest mission to hunt for planets.
It's staring at millions of stars at once, looking for rocky planets like Earth that have the potential to support life.
I visited NASA's AIMS Research Center to meet the man who leads the Kepler mission, Bill Borucki.
Kepler, basically, is a space mission where we're trying to look for planets, Earth-like planets around other stars and find out whether Earths are frequent in our galaxy or very rare.
If they're frequent, there's probably a lot of life in our galaxy.
If they're rare, we may be the only extant life.
What we'd like to do is determine that frequency, the frequency of Earth's inhabitable zone - the zone where you could have liquid water on the surface of a planet, where there very well may be conditions conducive to life.
We can't find life, but we can find whether planets that could have life are frequent.
Of course, Kepler is a step along the way.
We're trying to understand the extent of life in our galaxy.
An incredibly difficult challenge - how do you detect them? Basically, the stars are so bright and the planets are so dim, you can't see them directly, so you look at some characteristic of the light from the star itself.
So we look at the brightness of over 100,000 stars constantly.
We've got a sort of giant camcorder in space called Kepler.
It's looking at each of these stars, sending that information back to us.
We're measuring whether the brightness of any of these stars changes.
If a star dims by about 1%, that's a Jupiter-size planet.
If it dims a tenth that, that's a Neptune size planet.
If it's a hundredth of what a Jupiter is, in other words, a hundred parts per million, that's Earth size.
If the orbital period is such that it's like a year, like the Earth, you're probably in the habitable zone.
Now cooler stars, and we look at a whole range of stars, have closer-in habitable zones, so their orbital period might only be a few months.
If you look at stars that are hotter than the sun and there are many such, then you have to look longer.
What do we mean by an Earth? Do you need a rocky planet or is it about the size - what's important? A couple of things are important - certainly the size, but composition is the most important thing.
When you find Jupiters and Neptunes, those are gas giants, basically fluid, you couldn't walk on them.
When you're talking about Earths, you're talking about a rocky planet you can have water on, and a super Earth is something we'll find probably before we find Earth.
That'll be a planet maybe twice the size of Earth, again rocky, you could live on it.
The first one that we might want to think about is COROT 7b.
This is a recent discovery? It's a recent discovery by the COROT ESA Mission and people are delighted to see that they found such a planet.
It's a very short-period orbit, however.
It's too hot to have life.
At least it shows these planets exist and we should find more of them.
Since that interview was recorded late last year, the Kepler team have announced their first planet discoveries.
It will take them another year or so to find any Earth-like planets, though.
We need to find planets that occupy the same comfortable niche that life does on Earth.
Our planet lies in what's called the "habitable zone" or Goldilocks Zone, if you prefer - a place not too hot and not too cold, but rather just right for life.
Venus, for example, is far too hot, and Mars, at least in the present day, is slightly too cold.
Once we find a planet in the Goldilocks Zone, scientists and everyone else will clamour to find out what Earth's cousin is like.
One critical clue will be the presence of oxygen - an indicator of life.
Remarkably, even today, we've begun to probe the atmospheres of other worlds.
Studying these worlds is by no means easy, but Dr Giovanna Tinetti is doing precisely that, particularly with regard to their atmospheres.
Giovanna, welcome to The Sky At Night.
Thank you very much.
How do you go about studying their atmospheres? OK, for probing the atmosphere, just to give you an idea, first of all, for the moment, the kind of method we can use to probe the atmosphere is the transit method.
So we basically need a system which are transiting the stars That's movement in front of a star? Exactly.
We would expect to observe at a certain point, the planet is passing in front of the star, and so is masking part of the light and the luminosity of the star.
By studying basically this process at different wavelengths, we can basically understand what's going on in the atmosphere of the planet.
Now this kind of exercise, it's far from being easy, but is doable with nowadays telescope, which is pretty amazing.
What kind of molecules? For the moment, we know that a list on four of these hot Jupiters, apart from molecular hydrogen, which is the main component of the atmosphere, molecules like water vapour, methane, carbon dioxide and carbon monoxide are present, and we have hints that in some of these hot Jupiters, even more complex molecules are present, so I guess in the next few months and years we will know even more.
So we would love to find the same kind of molecules in terrestrial planets, in the habitable zone of the star, if life is there would definitely modify the atmospheric composition, like it did for our own Earth through the Earth's history.
Just suppose now there is someone living in the Upsilon Andromeda System, and they look at our sun, can they tell there's a life-bearing planet here? Well, certainly an alien looking back at our own planet would find extremely interesting the fact that we have huge quantities of molecular oxygen in our own atmosphere, and I'm talking about 21%.
Given the fact that molecular oxygen is a very reactive type of molecule, if it finds that, it's certainly a signature that something very strange is going on and cannot be completely explained by chemistry.
And so, probably from that information, for instance, will get the hint that there is something going on on our planet, but that is not the only bio-signature that these aliens might find in our own atmosphere.
For instance, the fact that the carbon dioxide has some annual cycles, where it's increasing and increasing with the seasons in a very typical pattern - that also could be interpreted like a signature that something is going on and, in particular, this kind of patterns on the Earth is due to the fact that vegetation has some seasonal variation.
Well, I must ask this question you must have been asked millions of times, what about life there? Are there life-bearing planets? I can tell you my personal opinion, because at this point we have no evidence whatsoever, er, well, my personal opinion is life is very common in the universe.
I'm talking about not necessarily complex life, like we have in our own Earth.
I'm more talking about simple life.
I personally think it would be very arrogant to think we are the only one Quite.
.
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that we have the exclusive recipe for life.
Thank you so much for coming.
Thank you very much.
It was a pleasure and a great honour.
We've been talking about planets orbiting stars, but we've yet to know how far away those stars are.
Light travels at a finite speed.
Well, The Sky At Night was first broadcast way back in 1957- how long ago that seems! And since then, our programmes have been winging their way into space.
Possibly someone out there is listening to our old programme right now.
Pete and Paul are in the garden talking about just how long light takes to get there.
If I turn this torch on and point it up into the night sky, the beam of light which leaves the torch is leaving the Earth's surface at the incredible speed of 186,000 miles a second - the speed of light.
Now the distance that beam travels over the course of a year is what's known as a "light year".
Television transmissions travel at the same speed as our light beam, which means it takes them some ten-and-a-half years to reach here - Epsilon Eridani - which is located some ten-and-a-half light years away from the Earth.
That means that The Sky At Night programme that they're most likely to be watching now is our August '99 edition which was looking at the total eclipse of the sun in Cornwall.
It's a bit cloudy.
A little over five times further away than Epsilon Eridani is a star known as HD128311, not really a name which easily trips off the tongue.
Now it's thought that there is a planet around this star which is 54 light years away, and if there are beings on that planet with really sensitive reception equipment, they could pick up The Sky At Night.
Which episode would they be watching? Well, they would have just finished watching the very first episode, where Patrick described the comet Arend-Roland.
If they are watching that and they're hooked on the series, I'd like to send them out a message now which will take 54 years to get to them and that is, "Please remember to pay your television licence.
" If a rocky planet is going round this star Caro 7, located some 490 light years away from the Earth, which means they won't receive the first episode of The Sky At Night for another 437 years, but if they had a telescope powerful enough and could look back on the Earth, they would see it not as it is now but as it was in the time of the Tudors with Henry XllI still on the throne.
FIZZLING Not much to see here.
Now while Caro 7 at 490 light years' distance is a long way away, it's by no means the furthest known system with an exoplanet going round it.
That's believed to be a star located in the constellation of Scorpius estimated to be some 20,000 light years away.
Now that places it very close to the galactic centre where the oldest stars of our galaxy are located.
Now just imagine a being on a planet going round that star with a telescope powerful enough to look back at Earth.
If it looked through that telescope, it would see our tiny planet covered in ice because it would be looking back in time 20,000 years, to the time of the last ice age.
Well, Pete, it looks like communicating with extraterrestrials via radio waves is going to take just too long.
It's not a very good way of communicating over such vast distances, is it? No.
Can you think of anything better? Well HIS SPEECH BECOMES DISTORTED Well, it will certainly be some time before anyone out there watches this programme.
The main organisation looking for life elsewhere is SETI - the Search for Extra-Terrestrial Intelligence, and Chris went to see the latest SETI telescope array.
Out in the middle of rural America, a bold experiment scans the skies looking for alien radio signals.
This is the Allen Telescope Array.
It works by linking together many small dishes providing the resolution of a much bigger telescope.
The array is used for conventional astronomy too, but the team are always alert for that elusive signal.
SETI luminary Jill Tarter showed me around the array.
Built on a shoestring, it has a reassuringly homemade look.
Ready? Yep.
Got it! And here we go! OK.
So now, if you look inside here, what you're looking at is the secondary reflector.
So radio waves have bounced off the big dish up there, onto the secondary reflector and they're focussed back here.
Wow! Look at that! Isn't that amazing? I always think about the Saturday morning TV I used to watch.
Flash Gordon death rays! Zzz! Zzz! REFLECTOR BUZZES That's what that reminds me of.
So, what is it? Why is it that shape? That shape allows it to do two things - one, to capture very long wavelengths down here OK.
So that's where the half a gigahertz is picked up.
It's like a car aerial that works at half a gigahertz.
Mm-hm.
And up at this end, um, the short wavelengths, the high frequencies - the 11 gigahertz - are captured by that part of the aerial.
Recently, Jill was in England and came to the Sky At Night to give me the latest news.
Jill, it's great to see you.
Thank you for coming.
Oh, my pleasure to be here.
Now, first of all, SETI.
You've been involved now for a long time, a large part of your life, haven't you? I have.
How did you get involved? By accident, Patrick.
I knew how to programme a computer that was turned out to be given to someone to do a SETI project, when it was obsolete.
And what I learned from that was that I lived in a really special time.
I was in the first generation of humans that could stop asking the priests and the philosophers what to believe about whether we're alone and actually do an experiment and try and find the answer.
Do you personally think there's probably life elsewhere? I actually don't know the answer to that question.
I think we should do the experiment to find out.
Exactly.
If there ARE other beings, would you expect them to be anything like us? Gee, if we're going to find them, it's because they're using technology.
So they're probably not that small.
They have to manipulate big pieces of equipment to build transmitters.
Other than that, I don't know what they're going to look like.
So I wonder if we found them, how could we communicate? Well, I think it will probably be a universal language based on mathematics.
Because technology requires mathematics to do the engineering.
Um we can hope that if someone is taking the trouble to broadcast a deliberate message, that they'll make it anti-cryptographic, that they'll try and help us understand.
Have you any real hope of success in the foreseeable future? Well, Patrick, I always keep champagne on ice.
I'm very hopeful, always! The technology that we're able to use now is getting so much better.
We have an exponentially more capable system than we ever had.
And so I think within the next few decades we will have been able to search a few million, ten million stars, and that might give us a chance.
And, you know, because there's so few people in the world doing SETI, I have a passion to get more people involved and so we are about to start a new SETI project called SETI Quest where we will publish all of the code we've been writing all these years as an open source.
We'll ask all the engineering students to come up with better algorithms for finding signals, and we'll ask people around the world to use their brains to help us find patterns in noise.
And so I hope that by involving the world, we can tell the story of SETI and make people think about us and how we would look relative to some alien species.
Yes.
And understand that all earthlings are the same.
This programme of searching for extra-terrestrial intelligence can help us trivialise the differences among humans.
I hope that is so.
And make me one promise, Jill.
If you find it and I'm still around, come back to the Sky At Night and tell us.
I promise that for sure.
Promise? Absolutely! The first modern SETI experiment was carried out by Dr Frank Drake at Green Bank, West Virginia.
And in 1965 he joined the Sky At Night to tell us about it.
From what we know, there are at least 100 billion stars in our own galaxy and so many other galaxies, that there is a total of 10 to the 20th, that's 100 million million million stars in space.
So that we would expect that there are very large numbers of planetary systems.
That on many of these planetary systems, life has arisen, and given this very large number of stars with which we start and the possibilities of life developing in so many of these places, it seems virtually certain that there is intelligent life elsewhere.
That was 45 years ago, and today Frank is still involved in SETI.
To calculate the odds of SETI success, Frank came up with one of the most famous equations in science - The Drake Equation.
It's his attempt to work out the number of intelligent civilisations in the universe capable of communicating with us.
There's at least one species that can send signals across the wastes of space - our own.
But there's no evidence yet for anybody else.
Dr Drake, thank you for joining us.
You're best known as one of the people who first tried to work out what the chances of receiving a signal from another civilisation were.
What inspired you to try and make that effort? Well this occurred about 50 years ago when we had just done the first search for extra-terrestrial radio signals and this lead people to ask, "What are the chances? What is it going to take to succeed?" And the answer to that requires you to make, somehow, an estimate of how many civilisations are out there and therefore, how far the closest ones are and how much searching has to be done before you have any reasonable chance of success.
So I sat down and just took into account all the things that bear upon the number of detectable civilisations in our galaxy, turns out there's seven different things.
And when you multiply your estimates of all of these things together, the end result is our goal - the number of detectable technical civilisations in space.
So what were the seven things? The seven things are the rate of star formation.
That we know! That we know extremely well.
The second one is just the fraction of newly-born stars to have planets.
The more planets, the chances for life.
The third thing is the number of habitable planets in each planetary system, on average.
OK, so that's three.
Three of them! The next one is the probability of life actually developing on a habitable planet.
Life appeared on Earth at the earliest time it could have.
So that one is well, actually, pretty well known, even though we've not seen a life form on some other planet.
The next one is what fraction of those evolve an intelligent species.
This one is still very problematical.
And one thing we do know here is that although life appeared quickly on Earth, intelligent life took billions of years to come about.
It took billions of years and it's because we're of You have to be an extremely complex organism before you can have a brain capable of intelligence.
The next one is the, er the fraction of intelligent species which develop a detectable technology.
On Earth, technology has been developed independently many times.
In every case, first the technology of agriculture.
But in an instant in cosmic time on the cosmic timescale, that has developed into automobiles, aeroplanes and iPods and all of the things we have today.
So that fraction seems to be one with the caveat that the planet has to be suitable for the development of technology.
The last one is the length of time a civilisation continues to be detectable once it has developed its detectable technology.
In our case, we became detectable easily around the year 1950 through the development of radar.
And also through the development of television.
And these signals are leaking into space.
These signals have been leaking into space now for 50, 60 years and there's a shell around us - 60 light years in diameter - full of evidence for our existence.
People can learn all about us with very little effort from what we have very generously provided.
Disturbingly by watching our television! Maybe you should pass over that.
Yes, what bad impression do they have of us by now.
That shell is continuously growing.
Now, 50 years ago we thought we understood the limits of technology and that what we were searching for would always be there.
It was the very powerful, so-called carrier signals of television transmissions.
A thing which looks like its definitely the way of the future is some combination of cable television, and direct-to-home, as it's called, television broadcasts from satellites to little dishes on people's houses.
It turns out the typical power transmission from the satellites providing television to a whole continent is about 20 watts.
The traditional TV stations are a million watts.
All of that power goes into space.
So if this becomes the way to deliver television 100 years from now the Earth will become very difficult to find.
And that makes us stop, and say, "Whoa!" Does that mean that the typical longevity is 100 years? In which case the odds of finding another civilisation in our bubble are very small.
Very small.
During the years we've discussed the chances of life not only on Mars but even on the Moon.
When the first explorers land on the moon, are they going to find any natural life there? There's not much outward resemblance between, say, a jellyfish, an ant, and a man.
At least I very much hope not! But they are all based on carbon and all meet certain conditions.
None of those conditions exist on the Moon.
My old friend, Arthur Clarke, has his ideas about life elsewhere.
When you consider the incredible variety of life on this earth, it's obviously impossible to speculate usefully about life on any other planet.
Who could have imagined the giraffe? The giant squid? The Whale? Or indeed, if you take a dispassionate viewpoint, us.
Since on this one planet, relatively uniform environment, nature has done such fantastic things and on planets which are much hotter or colder, or have different chemical constituents, then life could take almost any imaginable form.
From the point of view of other forms of life, WE are bug-eyed monsters.
We've been talking about the chances of life elsewhere.
There are people that have very pronounced views on the general aspect of life in the universe.
One of these is one of our most regular and welcome visitors, Dr Allan Chapman.
Alan, welcome back.
What are your views on the search for extra terrestrial intelligence? To be perfectly honest, it makes looking for fairies at the bottom of the garden look like hard nuclear physics.
I have to admit there is just so much fantasy, so much impossibility in it, that I just cannot take it for serious.
I don't deny that there may be some form of intelligence up there, but the chance of us finding it after 50 years of failed searching, I see it frankly more as an aspect of the psychology of religion.
It's more an attempt to find something you can't prove exists.
Of course, religion works along a totally different line.
The idea of finding these beings at all costs, in spite of every single scrap of scientific reality against them.
I just find it - I have to speak bluntly - a complete waste of resources.
Absence's vividness is not evidence of absence! I quite agree.
But how far do you have to search for something before finally deciding it is not there? Allan, you won't recall this, I do.
I go back to the time when there was quite widespread belief in life on Mars.
And after all, it wasn't till the first spacecraft showed those dark cracks were not vegetation.
Perfectly correct.
And we've learned an enormous amount since then.
What I would suggest has happened is the real hope of there being life at least in the solar system Solar system, yes.
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stopped with the telescope.
Because all of a sudden - bearing in mind that in the ancient world they thought the planets were simply bright lights in the sky - what Galileo and Thomas Harriet and Robert Hooke all discover is that Mars, Jupiter, the Earth, everywhere, are actually worlds.
And if they are worlds, then, their religious argument was, why hadn't God put life on them? Herschel believed in beings living inside the Sun! Absolutely.
It was an idea they called plenitude.
In other words, plentifulness.
Life everywhere.
Working on the argument that you didn't build houses if there was nobody going to live in them.
So this means there is an active concern with what they call Selenites - from the Greek Goddess, Selene - moon beings, Jupiterians, and so on.
And John Wilkins, in Oxford, in the 1650s, had the bright idea of using the latest technology, clockwork, springs, levers, machinery, to build a small ship with a powerful clockwork motor inside it and a pair of wings.
This might be able to get to the Moon.
And his argument was, we would find the Moon, a long, long voyage that would take ages, like sailing to America or China, but then we would find the Selenites.
Then we could learn from them, talk to them, and the wonderful idea was they realised that the lunar night was 14 Earth nights long - it must be pretty chilly on the Moon, could we not even sell English cloth to the Moon men?! They'd be wearing English tweed overcoats to keep them warm! I grew up with the idea of aliens.
My mother was a very talented artist.
She was indeed.
She drew these lovely aliens.
And as she said, no-one could prove her wrong! Precisely.
And her drawings, of course, we have a copy of the book, there are some wonderful pictures in there.
Those pictures are highly amusing.
In particular the way she often puts a little bird in.
The bicycles going round the rings of Saturn! It's a wonderful humour.
I think it's so wonderful.
Over the years, plenty of people have suspected flying saucers, UFOs, alien visitations, and so on.
My old friend, Michael Bentine, joined me to talk about this.
Caught it! Ha! Well, Michael, we used a frisbee, obviously, because it is aerodynamically shaped.
And when these things were first reported they were always known as flying saucers.
I'm not quite sure when they changed to UFOs but a flying saucer it could be.
But people who have reported them say they are other shapes as well.
Yes, indeed.
We've got the famous Havana shape, from Cuba, like a cigar, up there, which launches the little saucers, apparently, we've got the dumbbell shape, and I like that one And the famous lampshade model! Worn on the head it looks very attractive! I think people will believe anything.
What about that famous divorce case? Is it true? Absolutely true! And I've met the chap concerned.
He was American, and wrote a book a long time ago now called Aboard a Flying Saucer.
He described his adventures aboard a craft from the planet Venus piloted by a beautiful lady whose name was, I think, Aura Rhanes.
Apparently he had a very good time indeed and his book came out as non-fiction, a true adventure, and his wife promptly sued him for divorce, cited the lady from Venus, and she won! First interplanetary scandal in history! Absolutely fabulous! Well, flying saucers are still with us.
Pete and Paul have brought along some very interesting specimens.
Yes, look, aren't these marvellous? I have here a model of George Adamski's very early flying saucer, seen in the 1950s.
It looks a bit retro now, doesn't it? Definitely.
Imagine if it actually landed.
It would be so disappointing, wouldn't it? Ha-ha! The first one, very reminiscent of the first alien abduction case, if you believe that sort of thing.
This is the Betty and Barney Hill spacecraft Oh, yes.
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which snatched them up from the road in Montreal, Canada.
Zeta Reticuli.
That's right.
The aliens showed Betty Hill a star map which she revealed under hypnosis, and it showed the Zeta Reticuli star system.
It's rather small.
Bigger inside! And finally, right up to date, we have the flying saucer seen by Billy Meier.
I like that one.
It's also known, by people who back-engineer these things, of course, as the sports model! It's quite a sleek looking craft.
Who wouldn't want to own a flying saucer looking like that?! It looks like a flying saucer should look like in the mind's eye.
Of course people do see weird things in the night sky.
They are actually quite natural, aren't they.
UFO means unidentified flying object and of course if you see something and can't identify it then it is unidentified.
And I've seen loads of things in the night sky which I haven't been able to identify, but then I've found out, so they are no longer UFOs.
These include things like, say, a bright planet down close to the horizon.
As it is flickering away, it is easy to mistake it.
So you get lots of calls coming in from people.
Sirius, too.
Sirius flashes these bright, brilliant colours.
That can be mistaken as well.
Other bright things, the International Space Station is a classic example.
It is so bright and moves across the sky, people see it, don't know what it is, and think it is a UFO.
It is quite spooky, how it brightens up as it reaches the zenith and then dims back down again.
It is very odd indeed.
The thing which almost threw me once, going outside, another artificial satellite.
But this time it was a trio of satellites, just bright enough to be able to see with the naked eye, moving across in formation together.
That was actually quite freaky to see.
You have had a UFO experience yourself! Oh! A whole crop of flying saucers going towards me! My 50 inch reflector.
"The Martians have arrived at last!" I couldn't see them, absolutely baffled.
What was it? Pollen! Oh, no! I saw, actually, a very strange sight a while back.
It was a triangular cloud.
Triangular cloud? I was quite perplexed by that.
So I took a photograph, as I would do, and then left it for a bit.
A couple of hours later it was still there.
I took another photograph of it and it turned out, after I did a bit of research, it was a fuel dump from a satellite.
Really?! Oh! So it was just up there in space, glowing away! But my all-time favourite UFO, partly because I've launched them from my own back garden, is the Chinese lanterns.
Ah, yes! These are remarkable things.
And becoming more common now.
Yeah, people don't fall for it any more.
There were quite a few reports of people reporting a meteor shower.
They actually turned out to be Chinese lanterns.
So it's just misidentification of things.
Pure coincidence! Well, can there be life elsewhere? If so, what's it going to be like? More seriously, what can life on Earth tell us about possible life elsewhere? Chris talked about this to an astrobiologist, Charles Cockell.
From here, on the surface of Planet Earth, It seems that life is everywhere, making its presence felt even in apparently barren environments like the Antarctic.
But looking at our planet as a whole destroys this illusion of abundant life.
Life, in truth, occupies only a fragile, narrow portion of the Earth's crust.
It forms no more than a thin film on the planet's surface.
Charles Cockell is a microbiologist who is looking at how life can survive even where we might no expect it.
As a human, you are used to walking around, seeing tall trees, and lots of vegetation.
It is easy to get this impression that life is very luxuriant, and covers the planet in great abundance.
But in fact, if you draw a diagram of the scope of the biosphere to the scale of Planet Earth, it's a tiny thin strip of life on the surface of the planet, and just beneath the surface, very, very thin strip of life.
It's not very abundant at all, just within that surface layer.
And it's restricted to that thin layer because it need special things to exist.
In particular, life on Earth has got very used to photosynthesis.
Well over 90% of life on Earth is there because of photosynthesis.
Photosynthesis uses sunlight and it generates huge quantities of carbon and oxygen.
And it is carbon and oxygen that most other organisms use as a source of energy.
So, for example, we eat our food.
And we burn it in the oxygen that we breathe in, So we're dependant upon photosynthesis.
And that's the case for many other organisms on Earth.
So it is photosynthesis that really accounts for that incredible spread of life over the surface of Earth that we see today.
So how can we use what we have on Earth to tell us about life elsewhere in the solar system? Most people are not that interested in microbes.
They seem to be very boring little single-cell things that you might see under a microscope back when you're at school.
But what's incredible about some of these microbes is they eat rocks.
You and I eat our food, and we breathe oxygen, but there are microbes that literally eat rocks and some of them breathe metals.
A great deal of life on Earth is microbes living inside rocks and making a living in volcanic environments, or in asteroid and comet impact craters, even microbes living in the bricks of your house, for instance, that most people are probably not aware of.
Your bricks are actually a habitat for vast numbers of microbes.
And by studying those microbes we can start to ask, could microbes live in rocks on Mars? How would they live in other rocky planets in our own solar system, or elsewhere? And it is crucial because, unlike most of life on Earth, these rock-dwelling creatures, these bacteria, don't depend on photosynthesis.
You can imagine these existing where photosynthesis hasn't evolved.
That turns out to be very important on the inside of planets.
Photosynthesis needs light.
It uses light to drive energy.
If you can get your energy without photosynthesis, you don't need to be on the surface of a planet.
You can live down in the rocks.
Many of these microbes live off rocks, live in the sub-surface right underneath our feet, and many of them have been found 2, 3 kilometres deep underground.
This is of great interest on a planet like Mars where the surface is very extreme, there's high levels of radiation, there's not much water, but perhaps under the surface of Mars, there might be water, they can be protected from the extreme conditions on the surface, and underground where there's energy in the rocks, that might be the best place to look for life on Mars.
So much for Mars, but you mentioned Europa as well, which is the other place people tend to look for life in the solar system.
What can we say about Europa based on our experience of Earth? Europa's an interesting environment because it has an ocean.
That ocean seems to be in contact with a silicate core.
So when you think about energy from rocks, you think about circulation of water through the crust, a bit like water through the deep ocean crust on the Earth.
Which produces these hydrothermal vents and so on.
Yes, and people have thought maybe that could happen on Europa.
It's a nice idea, but there are many caveats to this.
The ocean may be too salty for life.
Life has a great tolerance for different salt concentrations, but there is an upper boundary beyond which molecules can't tolerate high salt.
We also don't know the lower limit of temperature.
Maybe the Europan oceans are too cold, but that's a good reason for sending a mission there.
Even if we were to find that Europa could not harbour life, that would be just as interesting scientifically, to find a huge body of liquid water in our solar system that was not capable of harbouring life.
Not quite as exciting in terms of a newspaper headline story, but from the point of view of understanding the boundary conditions for life, that would be an equally fascinating discovery.
It illustrates what you've said.
Water isn't enough, we need We need these other ingredients and environmental conditions for life to be able to originate and then persist in a planetary environment.
Charles' work helps us set out the ingredients needed for life.
The beginning of a recipe for organisms to form elsewhere.
If life can exist in some of the most inhospitable places on earth, does it have a chance of finding a niche somewhere else in the universe? The SETI researchers looking for life have so far had no luck at all.
Merely silence.
Why is this so? Can it be that there really is nobody there? Chris went to see a cosmologist who has rather different ideas about it.
It's tempting to put SETI's failure to detect an alien signal down to bad luck, but cosmologist Paul Davies, although he's a supporter of SETI, thinks there's a more troubling reason why all we've heard so far is an eerie silence.
When we talk about life in the universe, there are many unknowns.
Which of them do you think is the most important? The quantity that we understand least is the probability that life will emerge on an Earth-like planet if you have one.
That number could be anywhere from very nearly zero to very nearly one.
The error bars are enormous.
We know it's not zero of course.
We know it's not strictly zero, but people will often use a silly argument, they'll say, "The universe is so big, there's got to be life out there somewhere.
" Even if it's unlikely, we have billions of planets so the argument is it will have happened somewhere.
It's a silly argument for the following reason, if we take the entire observable universe, as far as we can in principle see, there might be something like a 100 billion billion Earth-like planets in that volume.
100 billion billion sounds like a big number.
1 followed by 20 zeros.
Surely, even if the chances of life forming by the random shuffling of molecular building blocks, there are many planets out there where it will have happened.
This is not true.
Imagine having a soup of amino acids with everything there, and you allow it to shuffle and shuffle.
The chances of getting a particular protein is like 1 followed by 130 zeros to one against.
If that's the way life occurred on Earth, we would be unique, this would be the only planet even given the vastness of the universe.
That argument does not wash.
What we'd like to know is, is that the way it worked, or was is just chance that gave us life on Earth? Was there some process that drove quickly to the right convention? Is there some sort of life principle at work in the universe? Some cosmic imperative, in other words, is life somehow built into the nature of the laws of the universe in a fundamental way? That it is more or less automatic that is going to form when you have the right conditions.
A lot of people would like to believe that but the truth if the matter is we have absolutely no evidence whatsoever that that is actually the case.
It is a complete unknown.
What about those who argue that life happened very quickly on Earth, and therefore in some it must be likely? This is another bad argument and I can understand why people make it.
Carl Sagan famously said that no sooner was Earth ready for life then up it popped.
And that is true for about 700 million years.
Our planet was being pounded by comets and asteroids.
This merciless bombardment would have made life almost certainly impossible.
We see the scars of that on the moon.
We do not see those scars so easily on Earth.
And so we know that up until about 3.
8 billion years ago, Earth was pretty much uninhabitable.
By 3.
5 billion years ago, life had firmly established itself here.
A rather narrow window.
That makes it look like is easy to make, gets going quickly.
Unfortunately, the reason that we are going through this argument about Planet Earth is precisely because that is our home, that is where we live.
We are the observers so this is what scientists call a selection effect.
We are discussing it because we are the products of that life.
The fact that life did get going quickly on Earth, does not mean that it is a highly probable event.
Right.
It can still be an incredible fluke, but it is a fluke that had to happen for us to have this conversation.
As a subtle argument, a philosophical argument, you cannot base too much on it.
A sample of one.
But, equally, you can't use the argument the other way, and say the fact that is started quickly means it is very probable.
It doesn't.
There is a selection effect.
We are left with this crucial idea of whether there is this, what you call, the cosmic imperative towards life.
How can we test the idea of the cosmic imperative? There is one very obvious way.
We should try to find a second sample of life.
We do that if were to pick up a signal from an alien civilisation, there we have it.
But in the absence of that, there is a very simple way we can test, that is right here on Earth.
We do not even need to leave our home planet because if it is true that life, as many astro-biologists hope, does pop up very readily in Earth-like conditions, there is no planet more Earth-like than Earth itself, surely life should have happened many times over right here on our home planet? Unless you have a cosmic imperative, the chance of life being vanishingly small, that has huge implications for SETI.
I have always been a supporter of SETI.
I think that the chance of success is exceedingly small because it forces us to think about things we should be thinking about anyway.
What is life? What is intelligence? What is the destiny of mankind? We are looking for alien civilisations.
We are really looking at the future of human civilisation.
What might it be like on Earth in another thousand years? In another million years? In another ten million years? What lies in store for us because that is what we are assuming is happening out there? We are really searching for human destiny mirrored in the stars, is the way I like to put it.
When you put it like that, that sort of suggests the paradox inherent in current SETI searches.
Because we are looking for the future of human civilisation with the technology that we use today.
In my view, rather than looking for messages crafted for mankind and deliberately beamed at us.
Which I don't think is a credible notion.
The best way that we can hope to pick up anything using radio as beacons.
We can imagine a civilisation, say towards the centre of the galaxy, that might have been around for hundreds of millions of years, to have built a beacon like a lighthouse, it would sweep the plane of the galaxy, and this thing would go, "Bleep," as it comes round.
It might go, "Bleep, bleep", or something more interesting.
But it would do this once a year, once every ten years.
I don't know what it is.
But as a form of advertising their presence Right, so what we really want is a set of instruments to just stare towards the centre of the galaxy which is where most of the stars are, where the older civilisations would be.
We now know there are planets contrary to lots of expectations, planets seem common towards the centre.
It does appear to be so.
SO we should just stare at the centre of the galaxy, continuously, over many years.
The SETI program as is currently set up, does not really do that.
It is not well set up for these events.
Could we see traces of civilisation directly? One scenario is that not only are there other inhabited planets, but there will have been waves of colonisation across the galaxy.
There could have been a wave of colonisation, or at least exploration, that passed through our solar system in the past.
A lot of people are fixated on this idea, "Oh, ET came to visit within historical times.
" Sure.
That is absurd when you look at the duration of cosmic history.
There could have been advanced civilisations in our galaxy billions of years ago.
Supposing an expedition had come through our solar system 500 million years ago.
How would we know even if they had landed and made a mess? Would any of that remain today? Well, if we think very carefully, the answer could be yes.
For example, if they had used nuclear materials in some way, we might just find The radioactive traces.
That would show that there had been something else going on.
If they had dug craters on the moon, or somewhere where erosion is rather small, we might notice it if the shape was peculiar.
They may have fiddled around with the biosphere.
They may have created micro-organisms to help them with mineral refining or something of that sort.
You might see a trace in the genomes of the micro-organisms.
They may even have left a message for us in the genomes of micro-organisms.
We know that DNA is a great place to store information.
The information in your DNA and my DNA, some of the information has been around for 3.
5 billion years.
Passed down from generation to generation.
It is much better than leaving an obelisk there that is not going to survive too long.
You encode if biochemically so we can start looking in genomes.
Maybe the message is in the genome not in the sky.
All of these ideas are incredibly fanciful.
This is science fiction that we are talking about but what I really want to do is make people aware that we could see a signature of intelligence, of alien intelligence, almost anywhere.
In almost any science, and almost anywhere in the universe.
We mustn't just be fixated on this idea that it has got to be a radio signal coming our way.
Life has been present on our Earth almost since the beginning of our planet's long story.
More than four billion years ago.
Yet only in the last 50 years has our technology advanced enough to make us visible to the rest of the cosmos.
Things are happening now that would have been sheer science fiction only a few years ago.
As we have heard, the odds of there being a civilisation out there whose signals we can detect are small.
That makes it very difficult to assess if we are truly alone in the universe.
That said, there are likely to be many thousands of planets spread throughout the galaxy.
And despite the arguments against it, I still believe that there must be at least one other place out there where life is flourishing.
In this programme, we have talked to a good many people, all of who have different views.
But they are making progress on all kinds of fronts.
We are going forward and sooner than later, those fronts will gel.
What do you think? I think that's absolutely right.
The easiest way to see that, I think, is to go back 20 years.
20 years ago, we did not know of any planets beyond our own solar system.
SETI was fairly moribund.
They were doing some radio stuff but there was nothing like the telescope array.
Even the biologists who are now getting more confident about how life can have started, if you go back to Lewis, who you talked to at the start of the programme, the idea that you could do experiments in the laboratory that had direct bearing on this question as to whether there is life elsewhere, is quite impressive.
Then, of course, look at Mars.
20 years ago, Mars was a dead place.
No-one thought there was any possibility of recent water.
Europa's oceans were a hypothesis but there was not much evidence.
Enceladus was a boring moon going round Saturn.
We gained places within the solar system.
When you put all this together, what we're doing is making the problem much worse for ourselves.
We are understanding planets and life, but we still don't have the evidence we need to say, "Yes, there is intelligent life.
" In a way, in the solar system, we have found more evidence that there is no life of any intelligence at all.
The chances have increased.
There are so many planets, I can't take the idea of all the Earth-like planets, we are the only one with intelligent life.
I can't take it.
It is a strange idea.
In some ways it is I was talking to somebody who said it was inspiring because we would be the only people in the galaxy and we would have to take responsibility.
Frankly, looking around Earth, I think it is rather depressing to think we are the height the universe has managed.
I have a feeling that sooner rather than later, there is going to be a success and we'll make contact with another race.
And on a smaller scale, we may be five, ten years from pointing at a star in the night sky, and saying, "Not only do I know that star has planets, not only do I know that one of those planets is like the Earth "in that is has oceans, a rocky surface.
"But I know that there is the signature of at least primitive life.
" I think that changes our whole view of the cosmos.
Once we can point to One is all we want.
Absolutely.
Just one.
Chris, thank you very much.
Well, in this programme, we have talked about the matter in all its aspects.
Is there life there? Is it intelligent? Can we ever contact it? Will the eerie silence ever be broken? Well, I don't know.
I have a sort of feeling it will.
And finally, we may at last find out the answer to what we really want to know Are we alone in the universe? Goodnight.
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