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Do aliens really exist?

11:17 UK time, Monday, 26 April 2010

Renowned astrophysicist Stephen Hawking says aliens almost certainly exist but warns it would be a bad idea to contact them. Are we ready for them if they exist?

In a series for the Discovery Channel, Professor Hawking said it was perfectly rational to assume intelligent life exists elsewhere, but warned that aliens might simply raid Earth for resources and then move on.

He said "The real challenge is to work out what aliens might actually be like."

He said that if extraterrestrials visited the planet the outcome would be similar to when Christopher Columbus landed in America, which, he added, didn't turn out well for the Native Americans.

Are there aliens out there capable of communicating with us? If they exist, should we avoid making contact with them?

This debate is now closed. Thank you for your comments.


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  • Comment number 1.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 2.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 3.

    In order to answer this question correctly we need to know : a) the definition of existence: b) the definition of what we understand by the term 'reality; c)are we also a form of aliens? &, if we are, to whom/what?

  • Comment number 4.

    Well I'm not into all the latest technology, don't twitter, don't have a facebook page etc. Seem to be too honest for modern society and have learnt by the way I've been treated by other people all my life not to trust anyone as everyone only seems to be out to see what they can get out of you. I'm beginning to think I'm an alien as there doesn't seem to be anywhere I fit in current society.

    Beam me up Scotty - I've had enough!!

  • Comment number 5.

    If space is infinite, then it is infinitely likely that aliens do exist.

  • Comment number 6.

    Well, it seems fantastically unlikely that Earth is the only planet in Creation that contains sort-of-intelligent life. The question that intrigues me is how common it is; is it found on one planet in every hundred, a thousand, a million, a billion......

    I was going to request that people not poison this debate with dreary political references but I see that I'm already too late.

  • Comment number 7.

    Oh goodie, a conversation about the real world of ideas rather than the artificiality of politics!

    As to aliens, there are only 3 alternatives when it comes to sentient life in the universe.

    1. There isn't any.
    2. It's very rare.
    3. The place is heaving with sentient beings.

    Option 1 is generally regarded to have been disproved by our presence.

    Option 2 is possible, although WHY should it be so? Some people have speculated that you need a very specific combination of circumstances to bring about 'life' at all (although they usually mean carbon-based lifeforms who breathe oxygen and like their water in liquid form - who says aliens are anything like that?). The Moon may be the culprit here: not only the right primordial soup of chemicals on a planet just the right distance from its star, but something to stir it up... and we have an uncommonly large moon, as such things go.

    Option 3 is likewise possible. Trouble is, the universe is so big that even if it's crawling with aliens they are unlikely to drop in... and if they don't, does it really matter much if they are there or not. That light speed limit is a real problem here: we (or they!) need to figure out a way past that, be it warp drive Star Trek style or wormholes or whatever.

    I'd like Option 3, though. It would be nice to have neighbours!

  • Comment number 8.

    There is a higher probability that aliens exist than 'god'.

  • Comment number 9.

    Leaving aside the usual pointless posts that are invariably first up, the first question is whether aliens exist. Mathematically and logically, they certainly do. Or more accurately, have done, or will do.
    Many worlds will have come and gone, or life not yet evolved sufficiently, so the chances of them coinciding with our 100-years of radio capability is slim.
    Secondly, their world as to be in reasonable proximity to us, and most stars are not. The chances are that if we ever detect a signal, it is likely to have originated 100 or 1,000 light years away, so it's not going to make for much of a conversation.
    Thirdly, if anyone has the technology (or inclination) to cover such a distance for resources, they are going to have to have vastly superior technology to us - in which case they will detect us long before we detect them.
    Which leaves the question of whether advanced aliens will be peaceful, or conquering. If they are peaceful, they may have already visted, and it's not a problem.
    If they are conquering, they haven't got here yet.. but could be on their way!

  • Comment number 10.

    Oh please don't let this debate turn all political as well!
    Im sick of hearing it

  • Comment number 11.

    I doubt any alien intelligence out there would want to communicate with us.

  • Comment number 12.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 13.

    If space is infinite as we believe, then statistically there MUST be intelligent life elsewhere in the universe.
    Whether that life has the ability or desire to communicate with us is a different matter.....

  • Comment number 14.

    I don't actually see why not. Thinking inside the box, the planets we've had a look at show humans can't live there. However on our own planet fish live underwater whereas humans can't. So what evidence is there to say that aliens cannot live on planets inhospitable to humans. None. Species adapt for survival.
    Thinking outside the box says that no matter how inhospitable a planet is something will survive there. Maybe by our standards its inhospitable but for another species maybe not so?
    Personally I think its a bad idea trying to contact other forms of life. We've been trying to kill our own species for thousands of years as we have animal species. It would be poetic justice is something in the outreaches of space did the same to us. Maybe it's not a good idea poking about?

  • Comment number 15.

    Intelligent aliens do exist because the size of the universe and the odds say that they do. Unfortunately we will never meet any of them and its unlikely that we will ever see any evidence of them. This is precisely for the same reason. Space is big, unimaginably big.

  • Comment number 16.

    The odds are good, but the chances of proving it are remote. Then again alien is a broad definition. You could have sea creatures living under the ice on europa. They may not be intelligent or something we could communicate with, but they would still be aliens and thus they'd exist.

  • Comment number 17.

    Why should we pay any attention to Professor Hawkings`s views on this?.
    Anyway I thought he was preparing to go into space. Perhaps he should concentrate on that.

  • Comment number 18.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 19.

    In a series for the Discovery Channel, Professor Hawking said it was perfectly rational to assume intelligent life exists elsewhere, but warned that aliens might simply raid Earth for resources and then move on.

    Hah!!! What resources? We've almost used the wretched planet up!

    It would be foolish to continue the religiously inspired belief that we're the only planet to contain what we define as "life" and an "intelligent species".

    Considering the time and scope of the cosmos it's possible that countless intelligent civilisations have come and gone. Perhaps they passed us by in their flying saucers when the saw the huge neon sign in orbit, saying, "Welcome to Earth, a subsidiary of Microsoft Corp!"

    Once it was heresy to claim the sun didn't revolve around the Earth, or that Earth wasn't the centre of the universe. Now we have to reckon that there are billions of planets out there, mostly undetected by our current technology, and it would be weird indeed to claim that none contained intelligent life.

  • Comment number 20.

    What convinces me that alien life has already invaded is a look at some of our politicians.

  • Comment number 21.

    If space and time are infinite then yes, all the possibilities will also be infinite.

    I beleive that space may go on forever, however not all of that "space" has stars, planets and life. It's like a bubble expanding outwards if you will. In this respect and the size of space then there is a very high chance of life, i'd be very surprised if bacteria isn't found elsewhere outside Earth

    I do not beleive in UFOs or spacemen coming to visit us and that even the most weirdest things you see in the sky can often be explained

  • Comment number 22.

    "If space is infinite, then it is infinitely likely that aliens do exist."

    Space time isn't infinite though . It has a beginning ( the big bang ) and and an end .
    I don't understand why anybody ( even Stephen Hawking ) can say that given the huge number of stars in the universe life on other worlds is likely.
    Nobody yet understands how life formed on this world and how likely it was to happen. You can't make a pattern out of a single occurrence. Even if you could assign a number to this variable you would then have to know the probability of intelligent life forming and then intelligent life capable of interstellar communication and the chance that that civilisation will not wipe itself out through its own technology.
    You end up with a load of unknowns stacked on top of each other. Possibly we are the only civilisation within our own event horizon.

  • Comment number 23.

    Exist?! Of course we do!

    We have ventured to other bodies in space (the Moon), therefore WE are aliens.

  • Comment number 24.

    I realy dont think we have anything to worry about.
    The only reason an alien would come here is to take bets on the outcome of this planet.

  • Comment number 25.

    There is a greater chance of Alien Life, than a religous deity created this world. Would an intelligent life form really want to contact us ? It would be like us talking to apes in a zoo.

  • Comment number 26.

    Communicating with aliens? I thought that's what elections are for.

  • Comment number 27.

    The hitchhikers guide to the galaxy had a nice logical argument: the chances of life evolving on a planet is virtually zero. However the universe contains an almost infinite number of other worlds and virtually zero multiplied by almost infinity means that there must be thousands of civilisations out there.

    Fortunately they are almost certainly many, many light years away because I agree with Stephen Hawkins. Any alien with technology so advanced that they can get here will not come in peace. To them we'll be like rats... a much lower order of life.

    Its worth remembering that every radio wave, TV signal or wireless internet transmission we make goes into space and travels at the speed of light. Our first TV broadcasts are now 70 light years out. The human genome and details of all the things that kill us (like the Ebola virus) are ten light years out and travelling. It doesn't strike me as a terribly good idea to be broadcasting our vunerabilities to the rest of the universe.

  • Comment number 28.

    17. At 12:47pm on 26 Apr 2010, John of Weston-super-Mare wrote:
    "Why should we pay any attention to Professor Hawkings`s views on this?."

    Because he's far, far cleverer than you?

  • Comment number 29.

    In the U.S. we have about 20 millionos of undocumentated aliens.

    Why do they all come here what do they have to gain from this relocation

    is a common knowledge among American voters.

  • Comment number 30.

    I'd be amazed if they didn't. Countless billion other planets in our universe and only ours supports intelligent life (well fairly intelligent), doesn’t seem likely to me.

    Avoiding contact with them just because they MIGHT attack us seems a bit silly to me, they could just as easily turn out to be friendly, spirited types willing to share technology with us.

  • Comment number 31.

    If they do they are obviously staying well away from Earth!
    They may on the other hand already be living amongst us! Interesting thought.
    I think there must be more living things out in that vast landscape.

  • Comment number 32.

    Professor Hawking comment that aliens would colonize/use earth is most likely based on his belief that alien would have the same intellect as humans do, and the fact that space exploration might become private sector tool to expand.
    I do believe that we might have been previously visited or even monitored by aliens. Something like laboratory experiment….
    As for natural resources, aren’t we looking for off-earth resources already… meaning that we already are running low on our own resources?!

  • Comment number 33.

    I, like everybody else, do not know if there is intelligent life out there but, we should certainly look for it: were we to have taken the same attitude in previous times, America would never have been discovered, and we wouldn't have the cultural delights of the nations of the World open to us.

  • Comment number 34.

    There is a rather famous equation that correlates the liklihood of life existing on other planets, and of our detecting it, called the Drake Equation.

    Basically it states that by multiplying together the chance of life developing, becoming intelligent and creating a technological civilisation you get a very small number- lots of zeros after the decimal point.
    If you then work out the number of planets/ large moons that probably exist (a very large number with a huge number of zeros on the end) you can multiply this with the previous small number and get a reasonable estimate of how much intelligent life is out there that we have the potential to encounter.

    This number, incidentaly, is significantly big.

    But there is one problem.
    We have been 'advertising' our presence with radio/televison broadcasts since the early twentieth century. The first we considered powerful enough to have left the heliosphere (the edge of the influence of our sun) was the Berlin Olympic games. The one opened by Hitler. Hmm, possibly not putting our best foot forwards there...
    These signals were analogue. We are now going digital and using less powerful signals.

    Chances are that any culture out there could be broadcasting on systems we have yet to discover, and/or are unable to pick up and understand our broadcasts as to them it is about as advanced as smoke signals!

    So, is there life on other worlds?

    I daresay we will find primitive life in the form of microbes/mould on Europa and under the surface of Mars in the not too distant future.

    Will we ever communicate with intelligent life on other worlds?
    Now that is a harder one to predict- even if we do discover some we may well find that we are so far away that one or both of us goes extinct from self destruction before we are ever able to reply to the first message recieved!

  • Comment number 35.

    Every time I come away from a visit to the in-laws I'm convinced alien life exists.

  • Comment number 36.

    Firstly apologies for my first post. Having a bad day and I'm surprised it got past the moderators.

    Anyway, back to the question.

    Probability laws suggest that with the number of stars out there that there are likely to be a huge number with planets. Of those there is also the potential for there to be a huge number that bear life. One question is what defines life?. Just because we're carbon based doesn't mean all life forms will be. Also just because we exist in a certain temperature band doesn't mean life doesn't exist outside of that or even on planets without water (which is obviously a pre-requisite of life on our planet).

    Prof. Hawkins comments that we shouldn't contact them as they may raid us for resources. This seems a reasonable viewpoint given the way that we raid each other for resources. would an alien race have the same sensibilities as us, can't see why that would be a valid assumption, but you never know.

    However, whenever this type of thing is discussed it's always that alien races will be more advanced and will either ransack us or pass us by. My question though is, what makes anyone think we're not the first?

    Maybe that's why we've never found any sign of it (although we could have a separate discussion on why else that could be).

  • Comment number 37.

    Aliens with sufficient technology to have star-travel will not "raid the Earth and move on". What's the point? From the knowledge we have of our own solar system plus the fact that most other stars appear to have planets, physical resources are not an issue (by this I mean water, oxygen, metals, hydrocarbons etc etc).

    A star faring society will more than likey have advanced terraforming technology at their disposal (the ability to turn dead worlds into living ones), so a lack of Earth-like planets should not be an issue.

    Of course there may be aliens out there who could wish to hunt us for fun, sport or food, or some which believe all life apart from theirs is inferior and must be exterminated. Still, what are the odds of that happening against the odds of us wiping ourselves out?

  • Comment number 38.

    Consider this...
    Say there are one billion stars, if 1% of them have planets orbiting them (10 million) and 1% of those with plants have some form of life (1 hundred thousand), and just 1% of those contain sentient life then there would be a thousand sentient life forms in the universe.

    Now we know there are more than one billion stars out there so the probablility we are alone is incredibly slim. This is what Hawkins is on about.

    Plus who is conceited enough to think we are so special that in an immense universe we are the only sentient life form?

  • Comment number 39.

    if they exist, and they are capable of sucking the earth of our resources, then it would be feasible that they would be the ones who contact us, not us contacting them,as of yet, they haven't,and if they do exist,why would it be took for granted that they would be more advanced than us,if we was to make contact with aliens, maybe its the aliens who should worry,as mankind has a tendency to be the species that plunder and destroy,

  • Comment number 40.

    If the Universe is what modern science thinks it is, then it's very probable that extraterrestrial life exists. However:
    1. The Universe is estimated to be over 13 billion years old.
    1. Even the most lethargic species would spread throughout a galaxy such as ours within a hundred million years or so after achieving spaceflight. Our Galaxy is old enough to have been completely populated and repopulated many times over.
    3. We haven't found any traces of extraterrestrial civilizations (signals, megastructures, etc). Why is that? If there is or was an intelligent species somewhere in our Galaxy, it seems very strange we haven't seen any evidence of them.

    Conclusion: there is a lot we don't know. Either life is incredibly rare and fragile... or the Universe is not what we think it is.

    As for Stephen Hawking, I disagree with his views on this. An advanced space-faring civilization wouldn't need any resources Earth has. There is plenty of water and minerals in the Galaxy. The only seemingly rare thing Earth has in abundance is life.

  • Comment number 41.

    Yes, sometimes I feel like one.

  • Comment number 42.

    I think Hawking's reference to "intelligent" aliens is an oblique reference that we know of forms of life from other than Earth already. It may be unsafe to regard all of these as being microscopic either, since I have it on good authority that not all intelligent life is able to prevent itself from watching X Factor, Eastenders, or even the Simpsons.

    Now I must return to my X Files DVDs.

  • Comment number 43.

    For proof, read the comments on most HYS sites.

  • Comment number 44.

    Before Columbus the Europeans didn’t knew of America. And Hawking exactly made the logical point comparing it with our own history colonising America, Australia and N Zealand.
    But if they do exists and have observed us for long being highly advanced and haven’t yet attacked us for recourses etc., may well prove we are way lover intelligent form not fit at all amongst those far more advanced out there.

    - It may be also true their evolutionary development wasn’t at all based on our values of greed.

    - It may be also they didn’t start with informal Gods as us.

    - It may be also they don’t worship gold and material things but solely interested in knowledge and live in societies of equality, what we refer to as communism.

    - It may be also some intergalactic ethics not to interfere into the development of others.

    And if so why would they be interested contacting us?

    Look at the Hollywood productions; star wars, etc. We already brought our wars into the universe and even concurred it before being able to travel through, and imagine if we do what a disaster for the universe we might become.

  • Comment number 45.

    Considering the differences in mindsets on ths planet there is no way to predict even for someone as brillant as Hwaking, to know what a first contact would be.

    A book I read several years ago speculated one of the few avenues to communicate would be mathematics.

  • Comment number 46.

    I believe we are naïve to think that here on Earth humans will be the only intelligent life to spawn from it. This short sided thinking will ultimately be our demise. The Earth is 4 billion years old, millions of species have come and gone, more than 2/3 with no trace, completely undiscovered. It is estimated the Earth has another 4 billion years before our sun runs out of fuel. The possibility that the Earth will spawn another higher intelligence is statistically very high and there may already be species inhabiting the Earth’s crust that we are unaware of.
    The universe is estimated to be 13.5 billion years old, and is probably much older. It is not the size of the universe that is the problem, it’s the age of the universe. All species come and go, that time span could be several million years, an intelligent alien species would have to live within our time frame as well as in close proximity such as within the Milkyway for us to detect their presence. The odds are against that we are close enough and within the correct time frame.
    Bacteria traces have already been found within meteor fragments that have struck the earth. That should tell us something about the nature of solar system formation. Life is abundant.

  • Comment number 47.

    Read Ikabod Gelaty's epic "The Ninckles of Bot" for the answer to this question.

  • Comment number 48.

    " 8. At 12:23pm on 26 Apr 2010, Neil Probert wrote:

    There is a higher probability that aliens exist than 'god'. "

    Or it could be that God or Gods are themselves alien? Always a possibility, no?

  • Comment number 49.

    Statistically it is unimaginable that we are the only intelligent life in the universe.

    The likelihood of us bumping into each other depends on how close together we are positioned and the degree of technological advance.

    Given how hostile we still are to one another, life more advanced than us might either be hostile too, or have the good sense to steer clear until we settle down.

  • Comment number 50.

    Apparently the chances of anything coming from Mars are a million to one. So no worries there then.

  • Comment number 51.

    I reckon it's more likely that there are aliens than it is that there aren't, if that makes sense! Can't believe we're the only ones. Yep, I'm with Prof Hawking. Hope they don't try and colonise us though. :o)
    Though one could argue that there is already alien life that tries to colonise us, in the form of viruses? Just a thought.

  • Comment number 52.

    I believe that it is inevitable that different forms of life exist within our Universe. I also believe that they could be even more alien than some of the forms of life that exist in the extreme places on our planet. With regard to hostility, most if not all forms of life on Earth eat, dead or alive, other forms of life, including ourselves - little fleas have smaller fleas and so on, infinitum. The saving grace could be that Gaia is a closed system that could be too complex and toxic to any invading species. As human beings, for example, we have evolved complex immune systems over the millennia and are constantly under attack by bacteria and viruses. An alien species would have a huge challenge, as probably would we were we to enter an alien equivalent to Gaia. I agree with Stephen Hawking that there would be no profit in attempting to contact alien species, even if at our stage of development we are capable of recognising them!

  • Comment number 53.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 54.

    So, in a way it is good that we're unable to make that mistake of contacting the aliens and vice-versa.

  • Comment number 55.

    I agree with Dr. Hawking who certainly has a fertile mind, but I don't think this is any great revelation. I mean there are more stars in the Universe than grains of sand on the beach and it is only common sense that other star's or world's will be occupied by life forms in various states of development. As far as it being dangerous to contact them, that has been the stuff of Science Fiction since War of the Worlds was published and before.

  • Comment number 56.

    He's absolutely right. We used to do a back of the envelope calculation at college that showed these 'Generation Ships' could be used to colonise the whole galaxy in a few hundreds of thousands of years. That's no time at all in cosmic terms.
    There's lot's of really special life bearing features about this particular planet, and I'm sure an alien species would happily take it off our hands and respect it more than we currently do given half the chance.
    If we want to survive, it's also time we had our own long term plan of generation ships and colonisation of the galaxy. It'd be far more productive than building weapons to kill each other and putting rubbish plastic toys into landfill.

  • Comment number 57.

    It would be presumptuous of us to think we are the only intelligent beings in the universe and beyond. One has only to look at this world and the great differences between races and religions to cause one to think that there are some here from other planets! Were we the 'penal colony' of the universe in past times? Surely the Taliban fanatics are not from this world.

  • Comment number 58.

    I should imagine that there is other life in space. But if there was I doubt very much that they would want to communicate with us. Intelligent life would have sent out a reconnaisance party, assessed the situation and reported back. There are probably outward facing warning beacons around Earth saying avoid at all costs, any contact with these people will wreck your world as much as they have irreparably wrecked theirs. Did you see the article on the floating Pacific Garbage area. Point proven methinks.

  • Comment number 59.

    It would have been cruel for aliens (or alien, since they do not necessarily have separate minds) to reveal their presence to people.

    The result would be a deep feeling of inadequacy and despair since all we know would turn out to have been known to them hundreds of millions of years ago, and all our thoughts would be as simple to them as a couple of letters is to us.

    The conclusion that there is a moral reason for aliens to keep people unaware of them.

  • Comment number 60.

    We need only look at ourselves to answer this question. Our motivation to venture into space is to assure the survival of our own species. And once we've left our little blue marble our top priority will be to find somewhere else we may colonize. So if intelligent beings exist out in the void, then it's pretty likely when they do find our planet their top objective will be - their own survival - at the cost of our own. Or at the very least, enslaving us to do their work for them. So yeah, trying to contact intelligent life out there doesn't seem to be a very logical initiative, to me anyway.

  • Comment number 61.

    chronocompos wrote:
    Well I'm not into all the latest technology, don't twitter, don't have a facebook page etc. Seem to be too honest for modern society and have learnt by the way I've been treated by other people all my life not to trust anyone as everyone only seems to be out to see what they can get out of you. I'm beginning to think I'm an alien as there doesn't seem to be anywhere I fit in current society.

    Beam me up Scotty - I've had enough!!

    I feel the same.

    Live long and prosper!

  • Comment number 62.

    There is simply too much space out there for nothing intelligent to exists. Then again, it is called SPACE for a reason.

  • Comment number 63.

    I've believed in alien existence for some time. Whether they've visited earth is another matter altogether.
    I second Stephen Hawking's cautious approach to aliens. Perhaps that's why they're keeping a low profile?

  • Comment number 64.

    Monty Python summed up this question completly:

    The Universe Song

    Our universe itself keeps on expanding and expanding,
    In all of the directions it can whiz;
    As fast as it can go, at the speed of light, you know,
    Twelve million miles a minute and that's the fastest speed there is.
    So remember, when you're feeling very small and insecure,
    How amazingly unlikely is your birth;
    And pray that there's intelligent life somewhere out in space,
    'Cause there's bugger all down here on Earth!

  • Comment number 65.

    Of course aliens exist. They're invading Britain on May the 7th at 00:00. Watch out.

  • Comment number 66.

    Billions of solar systems and trillions of planets i would assume that we are not alone.

  • Comment number 67.

    I suppose aliens do exist somewhere, at least I like to think. I wonder though, if we can't get on with each other and have awful wars and have to suffer terrorism, how we could possibly get along with aliens.

  • Comment number 68.

    Why would intelligent aliens want to descend into a gravity well to raid our resources when there are many more easily accessible sources within the solar systems in the Asteroid and Kuiper belts as well as the Oort cloud.

    The asteroid Ceres alone contains more water than is on Earth (if it ever hit us, we really would be a waterworld!), while all the minerals on this planet are readily accessible in smaller asteroids and comets.

    Some scenarios call for our nickel-iron core to be raided. As iron is one of the most common elements in the galaxy, this is unlikely to happen.

    About the only reason alien lifeforms capable of interstellar travel would want to visit would be to subjugate humans (either in order to prevent destruction of the planetary ecosystem or to prevent us getting out of the neighbourhood), or to exchange information. Given our documented xenophobia, it's more likely to be the former than the latter.

    It's worth pointing out that the universe is rather large and rather old. The odds of any 2 spacefaring species being near the same place at the same time are slim to negligible, let alone one taking an interest in us...

  • Comment number 69.

    I always wonder why the “aliens” are always technologically advanced to us? The possibility that they missed, or made better use of the various ages, that did not advance us to “their” level, beggars the question why would they want to engage with primitives? For resources? Rubbish, exactly, space rubbish, asteroids would provide that without the hassle. For food? How do they know we taste good? For slaves? If they are that technologically advanced they have robots! (Cheaper and less lazy, argumentative and disruptive) So they only aliens we are likely to bump into are microbes, the very primitive, or the dopey! The rest will simply avoid us until we mature!

  • Comment number 70.

    This whole thing is nothing new and has been discussed many years ago. Yes there are other forms of life and Yes we should very very careful.

  • Comment number 71.

    I'm afraid that Prof. Hawking's mathematical brain has overlooked the basics of probability; It is exponential. You don't have to multiple many 1 in a few thousand probabilities (Such as having protection from solar radiation or long intervals without asteroid collision) to end up with a very big number indeed. It quickly makes the likelyhood of other intelligent life existing at the same time as us, doubtful.
    As for the massive space ships business. Total Sci-Fi nonsense. Why would a race with such advanced technology have to travel round the the universe to find resources. The universe is full of them!

  • Comment number 72.

    50. At 1:38pm on 26 Apr 2010, LippyLippo wrote:
    "Apparently the chances of anything coming from Mars are a million to one. So no worries there then"

    Prog rock refs apart 1 million to 1 is 14 times more likely to happen than winning the lottery and people win that every week.

  • Comment number 73.

    Science's view of the conditions necessary for life changed with the discovery of the life around the undersea hyperthermal vents. They are now looking at the moons around Jupiter & Saturn.
    It looks as if life can exist using different chemistries, this opens up a multitude of possiblities.
    However if by life we mean sentient life, there the argument continues.

  • Comment number 74.

    The notion, expressed by some in HYS that in an infinite universe all things are possible is misguided. If this were so then not only would we be in contact with an infinite number of intelligent aliens but there would be some who would be queuing up to meet us dressed identically. Any absurdity would be possible where statistics determines existence. As for mutual contact, science reveals that the Universe depends as much upon some things being possible as it does upon others not being possible. Even in a relativistic universe, distances are such that we can never travel millions of light years across space and anything made of matter that could would not require the material resources of this planet. The 'wormholes in space' arguments are fatuous as they are mathematical phenomena only. Accepting their existence would also mean accepting the physical constraints that would come with the theory, namely, their proximity to a near infinite mass. There is no such mass anywhere near us. Such as do exist (black holes) would tear apart anything made of matter before it came out 'the other side' if there was one. Contacting aliens would also be a protracted business indeed.
    Professor Hawking refers to 'simple microbes' but it is not at all obvious how those found on Earth developed. The simplest free-living bacteria are, biochemically, extremely complex and virtually as complex as our own. Not even the most basic self-replicating system can yet be made in the laboratory using intelligent guidance so there is no way of knowing how rare are the conditions required by 'blind' Nature to make life.

  • Comment number 75.

    I'm in agreement with pretty much everybody on here in saying that, based on probability, it is highly likely that we are not the only sentient species in the universe.

    However, the main thing that a lot of us seem to assume is that they are going to be "human" in some way, shape or form - people mention communication, but how do they communicate? People mention resources, but do they need what we need, or indeed, if they need resources at all? Do they eat? Drink? Sleep? Any of those functions that we consider to be basic to us may not be to them - the answer is that we don't know, and we may never find out in our lifetime.

    Also, everybody mentions the idea that they haven't communicated with us yet, if they are at a sentient stage - maybe they already have, but we don't understand the messages that they have sent to us.

    It's easy to assume these things, but it's possible that there are alternative explanations for it all.

  • Comment number 76.

    We have been looking on and off for intelligent extra-terrestrial life since Frank Drake first postulated his famous equation, back in the 60's. We have been looking for extra-terrestrial planets for roughly half that time.
    Within our admittedly-limited present knowledge, it seems that our Earth is unique in two different ways:-
    1) It harbours abundant land life, and (at least) one of those species has evolved intelligence.
    2) It has a uniquely-large Moon, so much so that the Earth-Moon system has been described as a double planet.
    It is certainly within the bounds of possibility that these two facts are connected. It may be that in order to have life, at least the macroscopic land-based life which most biologists seem to think is necessary for intelligence (and no, dolphins are not an exception - their ancestors were land-dwelling), you have to have a large moon, to strip away much of the prehistoric atmosphere; otherwise you end up with a planet like Venus. A large moon also means larger tidal forces, which might provide the impetus for life, which must originate in the sea, later evolving to conquer the land.
    If this is the case, then Drake's equation is likely significantly over-estimating the probability of intelligent life evolving. Microbial, or possibly marine life, may be common on worlds with temperatures consistent with liquid oceans (not necessarily water - some astronomers think methane might do the job on Saturn's moon Titan), but intelligent life may be so much rarer that statistically it would be beyond the range of our current radio telescopes.
    And surely, all the more precious here on Earth for that!

  • Comment number 77.

    I have absolutely no idea. I also have absolutely no idea if God or Dark Matter/Energy exist or whether Chelsea or Man U will win the 2009/10 Premiership.

  • Comment number 78.

    one theory is that humans are already a slave race to highly intelligent alien beings. that humans are programmed and used for energy.

    if you have ever seen the movie 'osmosis jones,' its a good example of what i think life is like. we are a part of a MACRO-cosm which breaks down infinitely into smaller MICRO-cosms. there's stuff living in us, that has stuff living on and in it, that has stuff, living on it... so... it goes on forever like that.

    so- the earth is a giant living and breathing 'alien' that bleeds lava!!

  • Comment number 79.

    I'm with Stephen Hawking. Even if you just take into account the number of Sun-like stars in our galaxy alone, the odds of Earth being the only planet capable of supporting life as we know it, without even going into other possibilities, are very small. Therefore, it is a reasonable assumption that aliens do exist.

    However, there are a couple of questions raised by that - would said aliens be more technologically advanced than us, and what are their intentions?

    If they're less technologically advanced than us, then we have little to fear from them, but they have a great deal to fear from us. As a species, we're aggressive, hostile and wouldn't blink at exploiting other races for our own benefit. For that reason, we should be seeking to avoid contact, so that we don't screw them over.

    If they're more technologically advanced, then their motivations for space exploration need to be questioned. There's only really two reasons for space exploration:
    1. For peaceful means, simply seeking to expand knowledge of the cosmos;
    2. By requirement, i.e. to hunt for resources to ensure their own survival.

    Any aliens in the first category probably wouldn't be interested in us - we're far too primitive and hostile, and not worth troubling with. Any in the second category would be seriously bad news. They wouldn't hesitate to exploit us, and you can bet it wouldn't be pleasant.

    So, generally, we really should be avoiding contact, in case we run into trouble we can't get out of, or until we're sufficiently mature so that we wouldn't interfere in other species' natural development.

  • Comment number 80.

    Oh! BBC, you've opened a can of worms here!
    My reality, using probability and taking into account the amount of galaxies (millions), stars in each of those galaxies (billions), and applying those figures rationally allows me to accept the possibility as plausible. So yes, I do think that life on other planets is a reality.

  • Comment number 81.

    How come we think that "aliens" need the same conditions to survive as we do? As far as I'm concerned they might live on thin air and be invisible to us... and they might already live on this Earth. It's only possible.

  • Comment number 82.

    If you mean sentient life at our level or below its academic as space and time is a solid brick wall barrier. If life has evolved elsewhere that can 'warp drive' anywhere in the universe they may not recognize us as 'worth the effort'. Until we can overcome space and time all we can do is watch and wait - even light speed is slow compared to the size of the universe.

  • Comment number 83.

    The aliens should watch out for us humans!! We have a known history of exploitation. If we discover them, then they are in trouble. Yes, if they discover us first and visit out territory, then we should simply hike the visa fees for them. Insist on full-body scans as they enter! Charge huge parking fees for their spacecraft. If they need fuel, put a heavy surcharge on that. Bury them in red tape! If they are indeed technologically superior it would still not be a given that we would capitulate.

  • Comment number 84.

    The possibilities are NOT finite in an infinite universe if the laws governing said universe are finite.

  • Comment number 85.

    Despite the almost certain probability of intelligent life existing out there, the vast distances of the cosmos would greatly limit the possibility of any contact. One must also remember that time creates and equal obstacle. Not only would two intelligent civilisations have to exist within a small distance from each other (on a cosmic scale at least), they would also have to evolve within the same time span. Considering the fact that human existence has only lasted for literally the last seconds on the last day of the universal calendar, the chances of two civilisations sharing both a common space AND time greatly diminishes the probability. And even if two species did exist in the same space and time, there's no guarantee that both them would have developed the technical sophistication needed to communicate with each other. With these factors, the chances become almost nil. It's not impossible, just improbable.

  • Comment number 86.

    "22. At 1:01pm on 26 Apr 2010, jimmy_the_shoe wrote:

    Space time isn't infinite though . It has a beginning ( the big bang ) and and an end ."

    The Big Bang marks the beginning of our Universe. Not Space.

  • Comment number 87.

    Who can blame Stephen Hawking for publicising his new series with a little teaser like this one?!

    I think the accuracy of our mathamatical guesses about the likelihood of intelligent life elsewhere would certainly be helped by the proven discovery of any form of life somewhere else in the solar system. So let's take a look in the likely areas. That'll take 30-50 years and who knows, maybe in that timeframe we'll detect evidence of intelligent life in deep space. Or intelligent life will detect us...

    Some great comments on here about the variables to consider. An advanced civilisation has to be close enough in space to detect, and close enough in time too!!

    The chances of an alien civilisation being even vaguely close to our level of technology is tiny. They'll/it would either be massively ahead of us or massively behind. So either still swinging in the trees, or the galatic empire has already been defeated.

    A long time ago in a galaxy far far away........

    Right up there as the best opening line to a film! But also quite profound in a 'just think what could be out there' kind of way.

  • Comment number 88.

    At 12:23pm on 26 Apr 2010, Neil Probert wrote:

    There is a higher probability that aliens exist than 'god'.

    At last! Something I can believe in.

  • Comment number 89.

    Most people seem to think aliens need a physical form and a actual physical presence to exist. I believe this to be a rather large error. Any advanced alien civilisation able to reach us would not do it initially via a large flying saucer or via any other physical object geared towards interstellar transportation. Traveling through the medium of none physical space, if you have the know-how, is much easier plus the impact at your destination is much less evident. The only reason a alien race would physically arrive at planet Earth would be to clean up the place and turn it into either a holiday resort or a high security prison.

  • Comment number 90.

    Intelligent aliens observe all the political, environmental, religious and all the other interspecies conflicts we have on Earth, and would likely have an utter lack of respect for us, and would either destroy us or avoid us altogether.

    If they themselves or their machines are capable of landing on this planet, they would also be far technologically advanced than we are today.
    What could we offer them - our art? That's usually a matter of taste. Religion? Culture? Unlikely, we don't even like each other's, never mind expecting aliens to do so.

    Perhaps they could eat us? Brings new meaning to having Indian, Chinese, Italian, Tex-Mex, Japanese, French or Thai tonight. (At least the Germans, Poles, Russians and the British will be safe).

  • Comment number 91.

    Sometimes it’s so difficult to understand a person, just like you, a human being… Imagine how would it be to meet (and what is more, to try communicating) aliens that can be so unlike us. We can only presuppose that they exist. In our imagination they’ll either contact us, or destroy us, or enslave us, or vice versa(!) It is mysterious, that is why frightening. To my mind, meeting aliens is inevitable, however, it is a prospect of a distant future. Our civilization is not ready for such a welcome yet; we’ll just be confused and start making rash steps. We need more scientific ground, more knowledge about extraterrestrial worlds to have at least the smallest notion of what to expect.

  • Comment number 92.

    Unless you are self-absorbed religious nutter then the answer is "there must be". Probably the more pertinent question is one of: "Is there alien life out there we can ever hope to interact with and, like Hawking implies, is it advisable to do so ?"

  • Comment number 93.

    I think professor Hawkings is right. Logically, if aliens were to arrive on earth, the technology they would need to travel from another solar system, would mean that they would be far in advance of us, and may well have malevolent intentions. Either that, or they could end up here by accident and be in a "District 9" situation. Either way, they and we, would probably be much better off if they avoided contact with the human race!

  • Comment number 94.

    Star Travel:

    It's not viable at sub-light speeds because it takes too much time.

    It's impossible at faster-than-light speeds since time reverses.

    So, forget space ships.

    But there is another way.

    Quantum teleportation through micro wormholes via Bose-Einstein-Condensate-generated spooky action at a distance.

    I'm currently working on a prototype.

  • Comment number 95.

    "EARTHLINGS to understand This Question, you must know "What life is"

  • Comment number 96.

    My bet's on that; they do exist and that they're not celibate either and that they'd quickly wipe that stupid little pretentious smile we carry on our faces.

  • Comment number 97.

    I read somewhere that the greatest thing alien contact would achieve is the blink of an eye..we on Earth would cease to be British or Chinese or African, and would be suddenly, and unitedly, simply HUMAN.

  • Comment number 98.

    First of all - There is a higher probability that aliens exist than 'god'. Maybe ‘god’ is an alien! God is most likely alien in many ways to humankind so your argument makes the probability of god very high.

    Second - When Dr Stephen Hawking states if or when extraterrestrials visited the earth this assumes extraterrestrials are highly intelligent and light years ahead of humankind’s technology. Yet I see no spaceship or little green aliens with laser guns flying above my head. Which would bring me to these conclusions:1 – Aliens are very intelligent, 2 – we will never know, 3 – there are no such things, 4 - they only exist existentially in our own human minds.

  • Comment number 99.

    Well im guessing there is! I dont think anyone in the modern age really doubts this! unless they still think God created the earth 6000 years!

  • Comment number 100.

    I think it is arrogant to believe that Earth is the only planet with the capability of supporting life in the cosmos. There must be other planets which have the capabilites of supporting other life, who is to say that other lifeforms need oxygen?

    Considering that even bacteria can be classed as a form of life, then the possibilities out there are endless!

    With regards to making contact with aliens? I don't know, I don't want to shatter my Trekker brother's dreams by telling him that there are no beautiful alien women out there, but merely an army of toasters hell bent on wiping out cheese on toast.

    Hmm... on that note, I think I will follow Prof. Hawking's advice :o)


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