back to article Mars, Moon, solar system could be littered with alien artifacts

It's one of the top alien-related puzzlers: Given the vast number of stars out there, and the great age of the universe, if intelligent life other than ourselves exists even very uncommonly ... why haven't we met it yet? Surely, somewhere in the multitudes of other stars, at some remote juncture in the past, some alien …


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  1. horse of a different colour

    I, for one, welcome our undiscovered alien overlords,

  2. Novex

    Aliens! Everywhere! Not!

    We simply don't know enough about the universe yet to even guess at what life may be in it. The fact that two theories exist that are polar opposites speaks volumes. We need to do much more research before we can entertain even the notion that there might be alien artifacts in our solar system to find.

    1. Rob Dobs


      Fermi Paradox is very short sighted.

      It ignores:

      - the vast size of the universe.

      - things like warring organisms and self destruction that are sure to take out many advanced civilizations before they can expand to space

      - The ethnocentric aspects of life (If a civilization were properly advanced and not using up the resources on their planet that they know and love... why spend so much time to go all over the universe? Really having just a second planet to make destruction of your species less likely would be enough to stop spending so much effort and conquering the whole universe and leaving your mark)

      - The immaturity of our species and even looking around our own solar system

      Saying there must be nothing out there just because we have launched a few satellites, is like looking out door early in the morning, seeing no one and assuming "oh I must be the only person on Earth"

      Stupid very very stupid.

      1. NomNomNom

        "The ethnocentric aspects of life (If a civilization were properly advanced and not using up the resources on their planet that they know and love... why spend so much time to go all over the universe?..."

        It's not about resources, it's about identity.

        Despite ample resources on Earth, plenty of people today would want to found their own planet, their own empire, their own "better" civilization for religious, political or other ideological reasons if they could. Maybe even because they can.

        You can bet if we as individuals had the technology to survive and travel in space that there would be a constant outflow of ships heading for "the middle of nowhere"

        You should play minecraft. Has nothing to do with space but you'll find the reason players spread all over the map has nothing to do with resources and all to do with finding their own space and territory.

        1. sisk

          As humans we have this drive to see what's just past the edge of our vision or around the next turn. It assumes this same trait in all intelligent life. Perhaps there are civilizations out there thousand of years more advanced than us who, lacking said drive, have yet to even send a manned craft into orbit around their own planet.

          1. NomNomNom

            "As humans we have this drive to see what's just past the edge of our vision or around the next turn. It assumes this same trait in all intelligent life."

            You don't need it in all. You only need it in a few. If even only a few species in the galaxy were like this they would have spread throughout the entire galaxy by now.

  3. Tom_

    OK, but...

    It's a fair point, but completely ignores the other likely and easier to spot sign of intelligence which is it's EM emmisions. SETI exists because it's easier to look for ubiquitous evidence than to turn over every stone in the solar system, looking for one small object.

    The question remains, why are we not seeing any evidence?

    1. AndrewG

      How long does a civilisation radiate EM signals

      Possibly a long time, but taking the one example we know (us) our omnidirectional EM output is actually dropping overall as we move to cable transmission, fibre optics, podcasts instead of radio and low strength wi-fi.

      Don't forget a Star is a pretty big EM emitter naturally and any source has got to be resolvable with that in the background.

    2. John Miles

      re: EM emissions

      I believe EM Emissions from Earth would be very hard to detect in the noise floor at a light year away and becoming harder as technology progresses. 150 years ago we wouldn't have been able to detect one of today's most powerful radio transmitters if it was placed on moon - maybe in before the next 100 years have passed we'll worked out how to (there was a recent idea about seeing their light)

    3. Ru

      "It depends", of course

      There's only been a fairly short period in human history with bloody great omnidirectional high power transmitters spitting out something that clearly looks like a signal. As time goes on, we're moving towards smaller transmitters, complex encoding schemes and stuff like ultra wideband with the result that in the not too distant future Earth simply won't be emitting anything that looks like a carrier wave between DC and gamma rays.

      That suggests that in order to find developing technological civilisations you have to be listening very carefully during the hundred year window in which clear signals can be seen. The sort of thing SETI could spot is a deliberate, high powered signal sent by something with the intent to communicate that came to the same conclusion as SETI when deciding on which frequencies to transmit on.

      Alternatively, black helicopters, government conspiracies, inhibitor machines, everyone hiding from R-bombs, whatever.

  4. Destroy All Monsters Silver badge

    By Chromis Pasqueflower Bowerbird's cube!

    "NASA's efforts in putting the famous plaques on them may well be wasted"


    Hoping that someone finds these plaques is like hoping that this EXTREMELY IMPORTANT PIECE OF PAPER ON THE TRUTH ABOUT THE SECRET IRANIAN PROGRAM TO BUILD NUKES AND TAKE OVER THE WORLD that I have in front of me and will now throw into the loo will somehow arrive on the desk of POTUS.

    Not gonna happen.

    One really has to invest a bit more seriously in local marketing efforts.

    1. AdamWill

      that's crazy talk

      that's crazy talk, you crazy person. Every fule kno the Iranian program to build nukes and take over the world isn't *remotely* secret.

  5. Richard Wharram

    Damn, I was gonna do the "I, for one, welcome..." thing :(

    OK - I'll do a TMA-1 thing instead !

  6. Lee Dowling Silver badge

    What, exactly, are the chances of something like Voyager getting even close to making it to another planet intact? Yes, it's likely to end up in some kind of orbit or some kind of Lagrange point but so is EVERYTHING else, including an awful lot of boring rock.

    Not to mention natural decay, corrosion, irradiation, micro-meteorites, etc. smashing the thing to pieces, after a few light years it's going to be unrecognisable junk or it's going to get captured / destroyed by something far larger and heavier. The chances of us recognising a bit of smashed technology once it's been superheated, subjected to extreme pressures, smashed repeated by rocks and other debris, and whizzed a few light years to even the nearest star are almost zero - it'll virtually be a little muddy molten puddle of it's original makeup.

    Ignoring the statistics of whether we're likely to find them or not (and this says "unlikely", and we already believe the chances of civilisations even being able to contact others across interstellar scales are so remote as to be effectively zero), when we do find them the chances of them being in any way recognisable, useful, or another other than a pile of mush are really quite slim. Also, sheer scale. If you had an Earth-size planet exhaust its entire metal supplies by launching probes in every direction for thousands of years, chances are that we'd never detect them even if they were the next star to ours.

    1. Armando 123

      "What, exactly, are the chances of something like Voyager getting even close to making it to another planet intact? "

      Very very very tiny. Small enough to be practically nil, actually, and EVEN THEN, if a Voyager/Pioneer probe does enter into a solar system, it is more likely to be shot out of it in a hyperbolic orbit than to be captured within the system.

      1. Anonymous Coward
        Anonymous Coward

        Even if something did come into contact with a planet, the chances are it would be the biggest ones in that system, just like our gas giants have hovered up vast numbers of comets and asteroids. And don't forget about that big old gravity well at the center called a star.

        Then there is the fact that such an object would be traveling really - really fast, it's not going to have a soft landing anywhere. If it didn't burn up in an atmosphere it would be nothing but fragments and dust and probably vapor after hitting anything.

    2. Ru

      natural decay, corrosion, irradiation, micro-meteorites, etc

      Decay how? metal eating mould? Interstellar space is a pretty tenuous vacuum. Probes would simply be too far from star systems to run into anything more substantial than the odd hydrogen molecule... certainly no micrometeorites, and radiation from stars would be incredibly tenuous. The only things that could cause corrosion would be its own components, and they seem stable enough... especially in the absense of any heat or light!

      You seem to envisage deep space as a busy, hostile sort of place. You're a fair old way from the truth. Voyager can and will reach *somewhere* intact, eventually. The odds of anyone ever finding it are beyond astronomical, of course.

      1. Rick Brasche

        two words

        vacuum ablation

  7. Anonymous Coward
    Anonymous Coward

    I suspect it's very unlikely that either voyager or pioneer will ever just happen to drift into another star system occupied by intelligent life capable of detecting it and determining what it is. The odds are so vanishingly small that this paradox doesn't sound like much of a paradox but common sense.

    Also with the human lack of commitment to space why assume ET decided space was the way to go? Unless it was made up of people from the Isle of Man.

    Also that isn't many aliens, if only every 1 in a million planets in the "habitable region" of a star system develops intelligent life then that's only about 500 intelligent life forms on latest guesses. So with several hundred billion stars in the galaxy, and all the debris and phenomena, what are the chances of a small unmanned unpowered probe reaching one of those 500 worlds at the right moment in a species existence for them to take notice?

  8. Sloping Shoulders

    Too many jokes

    That's no moon

    Hey - what's this large black monolith?

    What are all these alien souls doing in this volcano?

    etc. etc..

  9. Anonymous Coward

    Mass Relay

    I thought everyone knew that Charon is, in fact, a Mass Relay...

    1. Sorry that handle is already taken. Silver badge


      Of all the hand waving going on in that series, extra special bonus points for the use of that particular object as a hand wave to explain the circularity of Pluto's orbit in the system map.

  10. dotdavid

    That's no moon...

    Maybe the whole moon is an alien artefact.

    You can imagine what the beachball-shaped inhabitants of Omina Pleidie IV are saying;

    "Bloody humankind. We leave this HUGE statue of K'rug, the founder of our glorious civilisation here for you to find, with carefully-placed rock features spelling "WE COME IN PEACE" in 300 of our languages, and you land on the bloody thing, kick our carefully-arranged messages about and plant a stupid flag on K'rug's left eyebrow.

    You were supposed to look at the damn thing, not rearrange it. Why do you think we engineered it to show the one face to Earth all the time? Seriously. That's it; we give up."

    1. Anonymous Coward
      Anonymous Coward


      We may be surrounded by artefacts that we simply do not see, because we do not know how to see them or what we are looking for.

      We can only measure things we know how to measure...

      1. Anonymous Coward
        Anonymous Coward

        Maybe we are the artifacts.

        1. Bill B

          I look in the mirror every morning and think

          "God, I look like an alien"

    2. NomNomNom

      maybe I am jelly

  11. DaeDaLuS_015

    By this logic...

    If everyone has a good look around their garden tonight there is a reasonable chance one of us will find an alien probe?


  12. Ray0x6
    Paris Hilton

    yeaaaah, but also, noooo....

    saying "given that they are there, what is the probability of finding them" is not the same as "what is the probability they are there and that we also find them". the universe is very large and we are aware of only a vanishingly small amount of it, so the likelihood of there actually being anything in the bits we can see is thus also vanishingly small. i would argue that your use of "littered" is really rather optimistic, even for the el reg alien hunting desk...

  13. I've forgotten what I wanted to say...
    Big Brother


    We just haven't climbed enough lunar mountains yet...

  14. Red Dwarf

    I, for one, welcome our purely speculative alien overlords.

  15. Chemist

    There may well be millions of 'advanced civilizations..

    but space is BIG, VERY BIG.

    Consider if there were 1 million advanced civilizations in the galaxy willing to send probes - they've got a choice of ~4e11 stars to send a probe to. OK they could rule out quite a lot but it's still one very large number of which we are 1. Plus the distance. So we'd be dependant on a civilization developing in our neighbourhood, wanting to send missions, choosing us amongst many, and the probe arriving, not malfunctioning and us spotting it.

    Far fetched

    1. Anonymous Coward
      Anonymous Coward

      and that's just assuming that they ARE out there...

      which they may of course not be!

      All of these ideas like the Fermi paradox and the Drake equation are ultimately rooted in guesswork and therefore only of academic interest. Drake never intended his equation to be used to determine values - it was intended as a thought exercise, as was Fermi's paradox.

    2. Anonymous Coward
      Anonymous Coward

      What I was gonna say

      It may be that intelligent life is as numerous as grains of sand on a beach, it's just that the beach is SERIOUSLY FUCKING big!

    3. NomNomNom

      "Consider if there were 1 million advanced civilizations in the galaxy willing to send probes - they've got a choice of ~4e11 stars to send a probe to. OK they could rule out quite a lot but it's still one very large number of which we are 1."

      Why do you assume they would only build one probe? Consider probes being able to travel to multiple stars too.

      1. Chemist


        As I said "it's still one very large number ( of targets) of which we are 1."

        I assumed they may well send multiple probes it's just that the number of 'local targets' is enormous. I think probes doing 'grand tours' is rather far-fetched and in any case would take a long, long time.

  16. Heironymous Coward

    Basic maths

    If there is one "advanced" civilization per 100 solar systems, and each of these civilizations puts out 10 000 interstellar probes over it's lifetime, and 1% of these probes happen to find a useful resting place (i.e. not a star) in another solar system, that means on average that there is one extraterrestrial probe somewhere in each solar system. Fancy searching the surface of Jupiter or Saturn? Those are the most likely resting places..

    And IMHO, my assumptions are wildly optimistic - assuming 1 civ per 10 000 systems, 1000 interstellar probes, and a 0.1% chance of finding a useful resting place, you get a 0.01% chance of a probe in any one solar system.

    And we haven't begun talking about the fact that a probe landing on earth even just a few million years ago would be buried, just like a fossil.

    SETI has a much better chance of finding anything IMO... If a civ wanted to show it existed and find other civs, and had the capability, why wouldn't it send out vast numbers of probes, each with a radio sending out messages and some kind of atomic battery to ensure long life.

    1. Andrew Norton

      Modifird SETI, maybe

      A modified SETI might work, yes, but modified by what it scans.

      I don't think EM is the best thing for it to be looking at, at present. It's such a noisy enviroment in general that its like having a fire alarm at a school being a normal persons voice - it's buried in the surrounding noise.

      I'd expect it to be more like a neutrino stream, or some other near- lightspeed (or tachyon) particle, that would stand out, pentaquarks, or maybe a charmed bottom Omega baryon. something *distinctive*

      It's why you should be supporting, not SETI@Home, but projects like Muon1 (which is british, and just had it's 70Millionth result Tuesday night)

  17. Torben Mogensen

    Pure speculation

    I see little scientific value in such speculations, as the assumptions made are often rather arbitrary or chosen to support the desired conclusion. (If the calculations don't match expectations, change the assumptions until they do).

    The only way the Fermi paradox can be resolved is if hard evidence of alien civilisations are found. Otherwise, there are all sorts of more or less plausible explanations why we haven't found any evidence and it doesn't get us anywhere calculating probabilities some of those -- there will always be other explanations.

  18. Anonymous Coward
    Anonymous Coward

    "Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."

    So, effectively, finding a few specific grains of sand amongst an infinite amount of sand.

    “It is known that there are an infinte number of worlds, simply because there is an infinite amount of space for them to be in. However, not every one of them is inhabited. Any finite number divided by infinity is as near nothing as makes no odds, so the average population of all the planets in the Universe can be said to be zero. From this it follows that the population of the whole Universe is also zero, and that any people you may meet from time to time are merely products of a deranged imagination.”

    1. Chemist

      Very good but

      you should really acknowledge that the quote is from Hitchhikers

    2. Anonymous Coward
      Anonymous Coward

      ...and as far as is known, the universe is NOT infinite

      it's just very very very very big. These two things are not equivalent. An infinite universe allows an infinite number of worlds, a very very very very big one does not.

      This seems to be where all that misguided (almost religious) belief that we can't be alone comes from.

      We may be alone. We may not be alone. The question is not answerable because there are too many unknowns.

      1. Rob Dobs

        No, we don't know

        That's the whole point, its not known.

        We can assume its infinite, or we could assume its not.

        Not having seen ANY semblance of an edge or end, I tend to lean towards the theory that it is indeed infinite, but to say it's only really really big implies you've seen the edge, or seem to know the size.

        And certainly "as far as we can see" is not an edge, sure theres a point it appears to stop, but so does the land when your out in the ocean far enough. If we travel a million light years across the universe, I bet we will see more of the same in all directions.

        1. Anonymous Coward
          Anonymous Coward

          @Rob Dobs : Yes, we do know

          If the big bang theory is correct (and it seems the most likely to be), the universe exploded from a singularity about 13 billion years ago and has been expanding ever since.

          That makes it very big, not infinite.

      2. sisk

        Even if what we can see of the universe were all that there was of it I've always felt that chances are there are aliens out there somewhere. Even if our solar system is an oddity and only half the stars we can see have any planets at all and most of those only have one (both of which I think are unlikely scenarios) that's still an awful lot of planets. For this to be the only planet out of a zillion or so to have intelligent life seems extremely unlikely to me.

        1. Anonymous Coward
          Anonymous Coward


          Why do you think it's unlikely? How does life start? How likely is it to start? Of course you have no idea on either count. You have nowhere near enough information to ask the question, let alone guess at the answer.

          What you mean when you say "I've always felt" is that you *want to believe*. I'd like to believe it too, but that's not science, it's just pseudo-religion.

          Try something a little more scientific :

  19. Dr Dan Holdsworth

    See past El Reg stories

    Specifically the one about supposedly universal physical constants not being constant at all. The calculations for the number of alien civilisations all assume that the universe is EXACTLY as friendly to life elsewhere as it is here; if this is not the case, and we are in a spot which is especially nice for life, then the calculations are so much bunk.

  20. Chris Miller

    The Fermi Paradox isn't just about artifacts

    Fermi was pointing out that any civilisation only slightly more advanced than our own should be capable of spreading throughout the galaxy within a timescale << 100 million years (and that's without requiring any warp drives or other fanciful notions). Not all such civilisations would necessarily choose to spread out in this way, but it would only take a single event to populate the galaxy. So why don't we observe them?

    I personally like Fermi's own answer: alien intelligences are already on Earth, we just call them Hungarians.

    1. Stoneshop


      >I personally like Fermi's own answer: alien intelligences are already on Earth, we just call them


      Look at those names: Jacob Haqq-Misra and Ravi Kumar Kopparapu. No-one has a name like that (let them try and get a G+ account, see how far they get), so they must be aliens themselves. Although any alien worth its NaCl-equivalent would probably have chosen a more common, inconspicuous name like Ford Prefect.

  21. Anonymous Coward
    Anonymous Coward

    Mars Sandpit

    Wasn't one of the mars rovers tested in a "Mars-pit" where various obviously non-martian objects had been left behind rocks to see if the rover operators would notice them? I recall that it wasn't hugely successful which would suggest that there is some mileage in this theory. After all, Voyager et al will be stone cold dead electrically (and radioactively?) by the time they end up in some other solar system so it really would be like looking for a tiny black artificial object (that may not even be there) amongst billions of similar sized lumps of rock. Odds of spotting it accidentally would be astronomical, odds of spotting it on purpose probably not great either...

  22. Winkypop Silver badge

    Hey Mum look what I found...

    Krgghzzt, put that down, you don't know where it's been *

    * rough translation, obviously.

  23. Error Message Silver badge


    The problem with these types of academic exercises is that they make a very risky assumption at their very beginning, namely that we'd recognize an "alien" artifact if we came across one. That's like assuming a chimp would recognize a USB flash drive as a storage device for information. The chimp "culture" doesn't even contain the concept of "information", much less have the ability to progress down the road towards recognizing the USB flash drive as being unnatural, a storage device, nor any concept even one iota down the path towards reading one. And that example does not even start along the more complex path that a very logical mode for "alien artifact" propagation would be to have the artifact be biological (maybe even all life on this planet) so that the "artifacts" are self propagating.

  24. OracleUK

    The right time

    How do we know that any advanced civilisations havent already come and gone in the billions of years the universe has existed, the chances of us and them being around at the same technological point to communicate across these vast distances is has got to be low. As a race we have only in the last 60yrs been able to send/recv messages from space and now with the digital age we are broadcasting/leaking less into space as communication becomes more focased inwards rather than out into space then it doesnt really give us much of time frame for us to be detected and if other civilisations follow a simlar progression then really we have no chance in detecting each other unless we make the concious effort to either send out probes or dedicate some transmissions to outerspace.

    1. Loyal Commenter Silver badge

      I always find the numbers interesting in this sort of argument

      Age of the universe: 13.75 billion years

      Age of the Earth: 4.53 billion years

      Earliest signs of life on Earth: 3.5-4.5 billion years

      In other words, the Earth has been around for about a third of the lifetime of the universe, and has had life in some form on it form most of that time, so it has taken about a third of the lifetime of the universe for life on this planet to reach the point where we can even begin to affect or properly observe anything outside our own planet.

      Assuming any alien culture would take as long to develop, and life was able to get started somewhere within a billion years or so of the big bang, then there's only a window of 9 billion years (okay, it's a big number) before the present where this could have happened.

      Bearing in mind that our planet exists and has the abundance of elements that it does because it formed from the remains of an earlier generation of stars, then you can probably shave another 5 billion years or so off that for that generation of stars to form, burn all their fuel and go pop.

      All in all, there may be other civilisations around, but they are not likely to be vastly older than our own.

      1. NomNomNom

        "All in all, there may be other civilisations around, but they are not likely to be vastly older than our own."

        Completely wrong. If there are other civilizations around they are almost definitely vastly older than our own.

        1. FredScummer


          I don't think it fair to try and limit the equation to be based upon some point in time, like the instant the big bang occurred, and assume that civilisations have to be more or less equal in terms of time to become conversant with each other.

          Reason being that the other civilisation could potentially be significantly more advanced than we are, and have the benefit of time travel - which we do not.

          Furthermore, I imagine that most people think in terms of the two civilisations being more or less equal in terms of their intelligence. Remember the film Forbidden Planet and the Krell civilisation which had ceased to exist? A super-intelligent race which put mankind into the Mickey Mouse brigade.

          Yes I know Forbidden Planet was a film made up by a man. But the fact is that other civilisations do not have to be at the same intelligence level that mankind is at. Maybe those civilisations are out there sending broadcasts across the cosmos but using a medium which we have no idea about.

  25. Anonymous Coward
    Anonymous Coward

    "who wants to meet meat?"

    This speculation is all fun and well but not to be taken seriously until such time that we actually manage to walk out our own front door. Or, well, hop up the well and manage to scoot around a little further than the moon. Until such time this is just cheap trolling for publicity (and moar funding).

  26. Nigel 11
    Thumb Up

    More than "likely"

    It's a thermodynamic-odds certainty that we can't find any dead alien probes that are drifting in the solar system. We can just about notice rocks tens of meters across ... if they happen to come close enough to Earth's orbit to attract out attention.

    An alien interstellar probe is unlikely to be bigger than a coke can. (I'm assuming a modicum of technological advancement, but no way to beat the speed of light.) It might once have had a solar sail, but if it hadn't evaporated within a few years of its deployment, those aliens were wasting an awful lot of energy sending it here!

    I haven't had enough coffee to think about the physical limits on detectability, but there are such. Radar is probably the best bet. How far away does a coke can have toi be, before its radar reflection becomes undetectable in the universal background noise? I'd hazard a guess, inside the orbit of Mars. Tht leaves a LOT of solar system outside. Anyway, the solar system is chock-full of coke-can-sized rocks to detect. How to spot the needle in the haystack?

    BTW alien probes that landed on Earth will long ago have been destroyed by geological or biological activity. Or if neither of those, just undetectably buried in kilometers of solid rock. (I'll ignore the extra energy budget needed to send something that could land on a planet across interstellar distances!) Best hope for aliens that really, really wanted to leave a probe where the developing life on earth would find it many millions of years in their future, would be the moon. But even there, it would get covered in dust.

    An active probe, sent across interstellar space to carry on bleeping at probably non-existent locals rather than devoting all its energy budget to communicating back with its makers? Seems unlikely. That it can stay "live" for as small a span of time as a million years? Improbable squared, and we've probably still missed it by more millions of years.

    About the only thing we can rule out is hegemonising swarms of Von Neumann robots. The Fermi paradox definitely does apply to them; they aren't here so they don't exist in this galaxy.

  27. Rob

    More likely...

    ... that any space faring aliens that have seen us on Planet Earth have no doubt stuck the equivalent to a D-Notice on us and slapped our solar system with a Do Not Disturb sign followed by a bio-hazard and nuclear warning logos.

  28. Steve May 1

    Aliens don't vote

    Or it might be that all advanced civilisations evolve to the point of being run by tiny-minded bureauocrats who wouldn't dream of wasting public funds on sending probes to planets whose inhabitants don't even vote for them. Maybe they all don't boldly go anymore. Just like us.

    As for SETI.. What kind of profilgate civilisation wastes it's energy resources by radiating them away in all directions. Perhaps we should be listening for supiciously quiet planetary systems?

  29. maccy

    Well, a variant of the Fermi paradox makes it even more likely that we're alone. If we make a robot probe which a) flies to the nearest star and then b) builds two copies of itself which then fly to the next stars, you can see that once one is built, it won't take long for copies of it to have visited every star in the galaxy (basically just the width of the galaxy (100,000 light years) divided by the flight speed (with magnetic ramjets, a decent fraction of c). If 1/10 c is the best on offer, it would only take 1 million years for these probes to visit every star, including ours.

    Hence, alone.

    1. Nigel 11

      Or ...

      I'd postulate the counter-argument that any civilisation stupid enough to develop Von Neumann robots is wiped out by the consequences, long before it is able to develop them to the point where they can propagate over interstellar distances. You've seen the movies ("Terminator" etc.) The reality would probably be worse.

      Ken Macleod (SF) came up with a neat answer t the Fermi paradox. The solar system, and just about every other solar system, is already teeming with alien intelligences ("deities"). They don't like hot, they don't like oxidizing atmospheres. They live very long and very slow in the Oort clouds. They talk to each other, very slowly and quietly, across interstellar space. Another thing they don't like is radio noise. If one of those hot oxidizing planets starts emitting noise, they drop a comet on it. This has already happened several times in geological history.

      Actually the last two sentences are mine. It's a bad set-up for writing SF, so Ken gives them alien ethics, and a way to sort-of get around the speed-of-light limit . The book is "Cosmonaut Keep", featuring intelligent dinosaurs and intelligent giant squid, amongst others.

    2. Ru

      Ahh, that's easy.

      You keep your stinking replicators off my intellectual property. Royalties are due for each and every instance of your space probe... one for every star in the galaxy, you say? You'd better have deep pockets.

    3. Kubla Cant

      Visit every star

      @maccy "it would only take 1 million years for these probes to visit every star".

      Which means one hypothetical probe somewhere in a solar system. All we have to do is find it - if we don't, we're alone.

      I think this is where we came in. There might be a million of the things already in our solar system, and we still wouldn't necessarily find them.

  30. Nigel 11

    4D spaetime

    I've just realized a calculation of such odds is a good illustration of the fact that we inhabit a 4D spacetime, not just a 3D space. Adding another dimension (time) is a very good way of reducing the odds of a near-coincidence of all coordinates. It may also be the reason that almost all civilisations think about it, realize how infinitessimally unlikely it is that they'll find other intelligent life, and give up. Especially if they try hard enough to get some observational certainty as to the probability of a star having a planet bearing life. If the mean distance between life-bearing planets in this galaxy is 4000 light-years, it's a near-certainty that the universe is teeming with other intelligences. It's also a near-certainty that no two civilisations will ever get to talk to each other, provided the speed-of-light limit holds.


  31. Anonymous Coward
    Anonymous Coward

    Darwin's Theory + Fermi paradox = common sense

    If you look to nature (you know, that stuff outside) cross-species communication is an extremely rare phenomenon. There is a reason for this - it's not a good survival trait.

    So now to Fermi's Paradox. Why on earth (or any other homeworld) would any species want to broadcast their presence to another unless either

    a) They wanted to attract potential sources of handily packaged energy.

    b) They were attention seeking halfwits who thought that something might be interested in them for anything other than the fact they are handily packaged energy sources.

    c) They wanted to find themselves as nominees for the following millenia's Intergalactic Darwin Awards.

    It's not a paradox, it's logical.

    1. Ru

      Thankyou, Zach Weiner.

    2. Nigel 11
      Thumb Down

      I doubt your premise

      Inter-species communication is extremely common. Of course they can't talk in a human sense, but ...

      Birds "understand" other species alarm calls. It's in their common interest to know that there is a predator on the prowl.

      Yellow-and-black stripes mean "leave me alone, I can inject venom". Of course sometimes it's a bluff.

      The bee-eater (a bird) can't break into beehives. It has a special song and dance solely for attracting the attention of other species that can. It finds the hive and leads them to it. They break in to take the honey. It eats the bees.

      On coral reefs there are "cleaning stations" manned by fish whose role in nature is to eat parasites off bigger fish. The bigger fish could but don't eat the cleaners. Co-evolved communication for sure, but also a wider "neutral zone" around the cleaning station. Something similar around desert water-holes.

      Dolphins not infrequently rescue drowning humans to dry land. This is also evidence of high intelligence and inter-species altruism. They know that humans come from dry land, a place where no dolphin ever wants to end up.

      When human scientists went to study wolves in the far north of Canada (so far north no humans lived there, not even Inuit) they were surprised that the wolves were neither hostile nor fearful, but highly curious. Inter-species communication was so effective that in one season, the humans had been integrated into the wolf pack, and were trusted to look after the cubs while the pack went hunting! I expect this is how dogs first became "man's best friend".

      And so on ....

      (Bacteria talk to each other in RNA code packages. Does that count? :-)

      1. Spoobistle

        (un)friendly aliens

        "Dolphins not infrequently rescue drowning humans to dry land. This is also evidence of high intelligence and inter-species altruism. They know that humans come from dry land, a place where no dolphin ever wants to end up"

        As a zoologist pointed out, we never hear from the people they push out to sea...

        Bacteria - well, they're just a lifestyle choice for phages.

        I'm with Douglas Adams and the white mice theory.

      2. Anonymous Coward
        Anonymous Coward

        Ok I stand corrected

        If we're not eaten by the vastly superior intelligence then we will either become pets, skippy/flipper equivalents constantly saving extra terrestrials from deep gravity wells or useful parasite removing devices.

        I for one welcome.....

  32. Anonymous Coward
    Anonymous Coward

    Never mind the solar system ...

    The whole Earth could be littered with alien artifacts but the fact remains we are too self-centered and know so very little of our own world that we'll probably never find any.

  33. Jared Hunt

    I always liked the idea...

    ...that SETI is barking up the wrong tree. Radio is obviously no use over interstellar distances so presumably all the aliens out there would have to have figured out some other kind of faster than light comms (subspace transmission, quantum resonance, take your pick) and as soon as we figured out how to do it ourselves we'd suddently be bombarded with a vast array of interstellar chatter.

  34. Jeff 8

    Maybe we are more advanced than we think

    The assumption always seems to be that other civilizations are at the same level as us or perhaps even more advanced. What if other civilizations are no further along than we were say 200, 500, 1000 years ago. They may not even be sending out messages into space.

  35. Mumrah

    Self-replicating probes.

    Surely any advanced civilization worth its salt that bothers to send probes all over the place would make them self-replicating and self-repairing. In which case we'd expect these probes to be flying around our skies monitoring our civilization as we speak. Of course the powers that be would be shit scared and maintain for as long as possible that nothing of the kind is happening.

    Hold on a minute...

  36. Lloyd

    I heard tell of a long silver cigar shaped object in the region of Uranus.

    Sorry, I couldn't help it.

  37. Richard Wharram

    Inhibitors ?

    Body text is optional.

  38. brain_flakes

    Keep an eye on 1991 VG

    Its next close approach to earth will be in 2017. I'm not saying it's an alien probe, BUT IT'S AN ALIEN PROBE!

  39. Anonymous Coward
    Anonymous Coward

    Of course

    This is really a no brainer. All you need to do is reverse the situation.

    If we discover another world with life, we will do everything we can to get there and obseve them. We might even obduct some of them to examine up close, then drug them so they forget. Is it really so hard to imagine that we are likely already being visited?

  40. Andy Fletcher

    They're doing it wrong

    Vader managed to locate the Rebels on Hoth in a matter of hours by firing about a dozen probes.

  41. Chris Gray 1


    Aliens would be *alien*. It would be a nuisance, and perhaps quite unpleasant, for they and us to meet face to face. Differing atmospheres, unpleasant or harmful trace gasses, incompatible gravity levels, etc. To say nothing of possibly totally incompatible communication systems.

    So, how would exploring aliens want to contact a new species? How about through computers? But, look at the state of our computers today: a totally uncontrolled mess of porn, viruses, scams, unsafe programming, and zillions of bugs.

    So, the aliens may be out there, but they are patiently waiting for us to get our act together and produce a global computer network that they would be willing to connect to.

    (See, it *is* IT related!)

    1. Destroy All Monsters Silver badge
      Black Helicopters

      You are now being contacted by "Artificial Insanity"

      The most powerful pan-galactic spambot. Written by the highly dedicated team of Stellar Haxxters from Spandex IV (a species that manages multiple sex changes during their lifetime), it mercilessly penetrates any and all computer systems built by emerging civilizations - emitting physical level nanoprobes if need be - and fills data storage with alien porn, spiral arm 415 solicitations or galactic cam dross. It drives species not of the insectoid variety to extinction within a short time. Studies show that non-hive-mind hierarchical mammalian civilizations rot totally within less than half the typical lifetime of a representative, beginning with the leadership group.

    2. Anonymous Coward
      Anonymous Coward

      @ Chris Gray 1

      You've made a very interesting point here.

      Perhaps they see it as OUR role to plug into their civilisation (when, as you say, we've become smart enough) -- it is maybe somehow, for THEM, culturally a no-no to announce themselves to US first. Perhaps they see it as the role of the newest junior and latest members to find their way in.

      I honestly find this an intriguing idea.

      We take for granted that they would announce themselves first. That might be just rude!

  42. Tannah


    Who says they are not already amongst us?

    1. Graham Dawson Silver badge

      We aren't. Stop asking.

  43. Big Al

    Missing the obvious

    If they're really *intelligent*, why would they want anything to do us in the first place?

  44. Stuart 2

    The chances of voyager 1 or 2 _ever_ coming close to another object after leaving the solar system are almost zero. I have read estimates that only one star in 100 billion will ever collide with another star. In conclusion, there might be trillions of alien artefacts floating through the galaxy, but they will never come close to a star in their entire existence, let alone end up on the surface of a planet.

  45. FrankAlphaXII

    Hell, what if they're right? There could be Alien stuff all over the place on our own planet (forget the moon, next planets over, asteroids and in the Lagrange Points) and we'd never know. Because we don't explore our oceans to any meaningful extent.

    Think about how much of this particular planet is covered in water. And we've charted and directly observed like what, 2% to 10%(at most) of the seabed? And if you're some remote Alien civilization, (who probably has or had no idea there was anything interesting on land), are you going to target the land, which occupies about 25% of the surface area, or the water, which takes up the other 75%?

    Id go for the water. It would seem to be the better choice no? Our civilization's just a pissant like that, we don't do what an outside observer would expect.

  46. Nights_are_Long

    We already have them...

    We already have bit's of old space ships, NASA recovered loads of the Armour plate that fell of the Galactica when it broke apart after it's last FTL jump, that's why they where able to recreate it so well in the documentary series a few years back....

  47. Richard75
    IT Angle






    Say no more...

  48. Slim Chance

    It's life Jim

    But not as we know it... yeah all right where's my spacesuit

  49. Error Message Silver badge

    Alien Artifacts are all on Earth

    'Cause it's where we dump our trash.

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