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Space

Advanced Civilizations Probably Don't Exist In Our Galactic Neighborhood 365

schwit1 writes: New observations of the best candidate galaxies now suggest that advanced civilizations are very rare or don't exist in the local universe. Researchers looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation (abstract), which could possibly be produced as the waste heat from civilizations using energy on galactic scales.

They found: "The presence of radio emission at the levels expected from the correlation, suggests that the mid-IR emission is not heat from alien factories but more likely emission from dust — for example, dust generated and heated by regions of massive star formation. As Professor Garrett explains: 'the original research at Penn State has already told us that such systems are very rare but the new analysis suggests that this is probably an understatement, and that advanced Kardashev Type III civilizations basically don't exist in the local Universe.'"

Obviously, the uncertainty of these results is quite high. Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or advanced civilizations are far more efficient in their use of energy than is reasonable to assume.
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Advanced Civilizations Probably Don't Exist In Our Galactic Neighborhood

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  • by cunniff ( 264218 ) on Wednesday September 16, 2015 @11:15AM (#50532619) Homepage

    Planets are common. Planets within the habitable zone look like they are common. So, is this evidence of the Great Filter - https://en.wikipedia.org/wiki/... [wikipedia.org] ?

    • My personal opinion is that life is really, really, really, REALLY rare. It only seems like it ought to be common because of the Anthropic Principle. We're can observe ourselves and thus it seems like life is easy. But everything would be exactly the same if we were completely unique in the universe. In fact, if the universe were cyclic and it took 1e1035 universe cycles for life to happen, things would look exactly the same. We simply have no basis for knowing how probable it is. Given how insanely complex we are, I suspect that it's exceedingly rare.
      • by Viol8 ( 599362 ) on Wednesday September 16, 2015 @11:46AM (#50532989) Homepage

        Even if life isn't rare , theres no guarantee that the random steps that led to a human civilisation that can create radio signals, ie:

        life -> multicellular life -> dinosaurs -> asteroid impact -> mammals -> apes -> humans -> civilisation -> farming -> nation states -> discovery of coal seams -> metal refining -> industrial revolution -> electronics revolution

        would ever happen anywhere else either in another order or at all.

        There may be plenty of life in the universe but I suspect the number of technological civilisations is tiny.

        • Re: (Score:3, Interesting)

          by CastrTroy ( 595695 )

          I would tend to agree. Even within our own human population it seems that only a relatively small number of people have allowed us to advance past the age of agriculture, into the age of electronics and interconnected networks. If the average person was just a little bit dumber, we probably wouldn't be able to sustain the level of technology we currently have. If the average IQ of people was closer to where an IQ of 75 currently is, we'd probably never reach the point where the average person could read,

          • by invid ( 163714 ) on Wednesday September 16, 2015 @12:58PM (#50533725)
            A good candidate for the filter is the ability to do math. Think about how few humans can even do calculus. We might discover the universe filled with semi-intelligent species with number systems with only 3 numbers: one, two, and many.
          • by gizmo2199 ( 458329 ) on Wednesday September 16, 2015 @01:36PM (#50534111) Homepage

            Even within our own human population it seems that only a relatively small number of people have allowed us to advance past the age of agriculture, into the age of electronics and interconnected networks.

            I don't think that's true at all. Anyone who studies technological advancement, or the philosophy of science, can tell that it's a heuristic process. In other words, it's the result of many, sometimes "average" people taking a crack at a problem over a long period of time, until someone is finally able to put all that work together to get a solution.

            The oft-cited "genius" making a technological breakthrough by himself is really just a myth.

        • by invid ( 163714 )
          We can get some idea of the likelihood of some stages by looking at how long in took for them to occur on earth. For instance, it took about 1 billion years for life to form on earth, but after that it took an additional 3 billion years before the Cambrian Explosion, where we saw significant diversification of complicated lifeforms. That 3 billion year gap allows time for all sorts of global cataclysms--we had one that nearly wiped out life during the snowball earth. After the Cambrian Explosion it took a m
          • We can get some idea of the likelihood of some stages by looking at how long in took for them to occur on earth. For instance, it took about 1 billion years for life to form on earth, but after that it took an additional 3 billion years before the Cambrian Explosion, where we saw significant diversification of complicated lifeforms. That 3 billion year gap allows time for all sorts of global cataclysms--we had one that nearly wiped out life during the snowball earth. After the Cambrian Explosion it took a mere half billion years to reach technological intelligence.

            But it's very dangerous to simply extrapolate from a single data point (Earth) - there are quite a few environmental elements that could massively influence those timescales - for example the early sun was quite a bit fainter than it currently is, so those 3 billion years might just have been necessary to reach some kind of tipping point favouring the development of complex multicellular life, on another planet under slightly different conditions, this might take just a fraction of that time (or it might ne

        • by kat_skan ( 5219 ) on Wednesday September 16, 2015 @12:42PM (#50533581)

          Even if it isn't rare, and human-like civilization also isn't rare, there's still no guarantee that we would have heard from them by now. Our own radio signals have only reached a tiny fraction [postimg.org] of our galaxy, which is just one out of hundreds of billions. The Universe is just so stupefyingly, mind-blowingly enormous it's hard to say how common advanced civilizations are based on evidence from the scant few decades we've been listening for them.

          • by meglon ( 1001833 ) on Wednesday September 16, 2015 @01:19PM (#50533929)
            Exactly. Because we haven't seen them up to now, with our rather primitive, blind searching doesn't mean they're not there, just that we haven't seen them. Takes a great deal of arrogance to think we've seen all, done all, and nothing new will ever be. 35 years ago (when i was in college... how depressing) we were still trying to figure out if quasars were in our galaxy with an unknown reason for their massive redshift, or outside our galaxy with an unknown reason for their massive energy output.

            Whether life (intelligent, technologically advanced civilizations) is common or rare, the simple fact is we're not going to have a definitive search done for them in a just few decades, and the fact we haven't seen them really means nothing at all.
          • by gtall ( 79522 )

            Yep, the Universe is amazingly big. And we wouldn't want it any other way with stars exploding and boiling away adjacent systems. And then there is the in-law problem, that Universe simply isn't big enough to solve that problem yet.

        • by Ost99 ( 101831 )

          This particular study was looking for Type III civilizations.
          It's entirely conceivable that Type III civilizations doesn't exist anywhere - simply because the technology required to harness the total energy output of a galaxy cannot be created (the great filter is in our future).

          Type 0 - type I civilizations would be hard to observe from earth unless they were actively trying to get noticed or just happened to have their (probably short) window of high-power radio era just at the right time for us to observ

      • My personal opinion is that life is really, really, really, REALLY rare.

        Another factor is that high intelligence isn't necessarily a beneficial thing in terms of evolution. Cockroaches and rats will probably outlast the human species. Bacteria, algae and similar most certainly will.

      • by u38cg ( 607297 )
        I half agree with you. My opinion is that intelligence is in general not a useful evolutionary attribute and the fact we have it is simply dumb luck. In evolutionary terms, we're not much of a success; by mass, algae and amoebas are way ahead. We're more populous than monkeys, but then so are mice.
        • by Zak3056 ( 69287 )

          My opinion is that intelligence is in general not a useful evolutionary attribute and the fact we have it is simply dumb luck

          While it's not exactly good practice to make sweeping generalizations based on a sample size of one, it seems more than likely that the dominant species on our planet also being the only sentient species (that we're aware of) on that same planet is not coincidental.

          I realize that you're making this claim in the context of "success" as "biological mass" but frankly, your chosen measure is less than compelling. Humans do not in any way compete with algae from an evolutionary standpoint. If one wanted to exa

      • I'm going to head in the other direction but stop half way. I think life at the single cell level might be fairly common. But as you go up the evolutionary ladder it get more rare, with intelligent life been extremely rare.

        While I think that is the mostly likely reason there are not more advanced civilizations in the galaxy, my favourite is simply we are the first one. Why not? Somebody has to be first. I like to think that some where down the road a million or 10 million years from now some alien a

        • To answer your "why not" - because sun-like stars were around for many billions of years before our own sun formed. If intelligent life were rare enough the statistics might still play out to let us be the first, but there's precious little margin between the numbers that allow intelligent life to be *that* rare, without also making it extremely rare that any particular galaxy will ever host intelligent life at all.

          Granted, that's not exactly a really well reasoned argument, but it grows from the general f

          • While G-type stars have been around for a long time, they didn't have the same concentration of elements other than hydrogen and helium (what astronomers call metals). You can't form an Earthlike planet without a lot of stuff like iron and silicon, and you're unlikely to get robust life without carbon.

            Heavier elements are produced by supernovas, and are therefore becoming more common. It still seems likely that we're not the first intelligent life, but it didn't predate us by too many billions of years

      • by Z00L00K ( 682162 )

        I think that life isn't that rare, but intelligent life with a technological civilization is.

        When I applied the Drake equation once I got a value of 0.8 on the number of technological civilizations in the Milky Way right now. I find that plausible considering how civilized humans are.

        • by meglon ( 1001833 )
          If you base it on how civilized hoomans are, the universe is VSF.... very severely fucked.
      • by Kythe ( 4779 )
        Based on our own planet's history and what we know of biochemistry/bioenergetics, I'd go with:

        1) Life is pretty common.
        2) Anything more advanced than bacteria-like single cells is exceedingly rare.
      • I think that life is common but intelligent life is rare - which again matches up with what we see on Earth. Out of all these species there's 1 capable of building complex tools. How many other planets might have one less? Big powerful energy-guzzling brains aren't very useful in nature after all.

        I also think that any Kardashev Type 2+ civilization almost certainly doesn't, and never will exist, and that even a Type 1 would be extremely uncommon. The whole Kardashev scale assumes runaway population growth w

    • They only tested for really advanced civilisations, that are harnessing energy on a galactic scale. A civilisation building a Dyson Sphere is only Type 2 since it only harvests the energy of a whole star. Maybe these things are just impossible, or no civilisation sees a reason to do this.
  • by Mab_Mass ( 903149 ) on Wednesday September 16, 2015 @11:17AM (#50532649) Homepage Journal
    There is this huge assumption that alien civilizations will be emitting large amounts of waste heat. What happens if they are just more efficient than us?
    • by tnk1 ( 899206 ) on Wednesday September 16, 2015 @11:32AM (#50532849)

      Efficiency can only get you so far. You use enough energy, you will get waste heat as entropy, and entropy is inescapable. Of course, they might use hyperspatial redirection or subspace quantum oscillation phase modulation or something to make it look different to us or send it to another pocket dimension, but chances are, we'd have some indication of a Type III civilization.

      What we should really be calling the summary out on is the fact that they equate a Type III civilization with an "advanced civilization". Yeah, it's advanced all right, but the bloody United Federation of Planets would only be something like a Type II. You have to control the energy output of an *entire galaxy* to be a Type III.

      • by Grishnakh ( 216268 ) on Wednesday September 16, 2015 @11:54AM (#50533053)

        I don't think even the United Federation of Planets qualifies as Type II. They haven't harnessed the entire energy output of a star. The engineering implications of that are mind-boggling; we've dreamed up Dyson Spheres, but those really don't seem realistic, unless we can somehow invent "scrith".

        Our current civilization doesn't even place on the scale. We're probably like a Type 0.5 at best.

        • They don't have to harness all of one star; if they're harnessing enough of a lot of stars they can get to a Type II.
          And we are a Type 0.76 on Sagan's log scale.
        • by abies ( 607076 )

          More around 0.72.
          https://en.wikipedia.org/wiki/... [wikipedia.org]

        • I don't think even the United Federation of Planets qualifies as Type II. They haven't harnessed the entire energy output of a star.

          Which is why the entire Kardashev Type scale is trivially useless. Nobody is going to harness the entire energy output of a star unless it is more practical than just going to another star and getting the low hanging fruit there first. One the planetary scale, we do not harness the entire energy output of a single country, continent, or planet. Before we harness the entire energy output of a planet, we'll be off this rock and harnessing the energy output of the star. before we harness the entire energy outp

    • by Grishnakh ( 216268 ) on Wednesday September 16, 2015 @11:51AM (#50533035)

      This analysis seems to be completely lacking. They're looking at waste heat and saying "well, there don't appear to be any Type III civilizations around here". Then they say that humans are the only "advanced species" around here. Ok, even if we assume that Type III aliens are this inefficient with waste heat, this just doesn't make sense. On the Kardashev scale, humans don't even place! We are not an "advanced species", because we haven't even made it to Type I, let alone II or III. What about Type I or II civilizations? This analysis has no way of determining if any of those are nearby. Type I civilizations would be completely invisible to us from a distance, and even Type II civilizations would probably be very difficult to spot. A Type III would be easier, since that's a civilization that uses the entire energy output of a galaxy, but really that kind of civilization is rather difficult for us humans to even comprehend.

      Just for reference, the civilization depicted in Star Trek: TNG, with warp drive and a Federation spanning a good chunk of this galaxy's quadrant, is still only a Type I civilization. The episode where they found an abandoned Dyson Sphere (the one with Scotty) showed a Type II civilization, but it's unlikely a real Dyson Sphere would even look like that; it probably wouldn't be able to hold itself together; a real one would be lots of separate pieces orbiting in formation.

      • The Ringworld seems a bit more feasible still. And even that could be hard to detect as anything different than the heat from their sun if it were aligned so as to obscure part of their sun from our perspective, where the heat generated from the Ringworld itself might just break even with the heat (from their star) obscured. That's wild conjecture, of course, but not too unreasonable.
        • no, there is no known material that could make a ringworld, nor any known energy source that could set one spinning to have simulated 1 g field for inhabitents. its tensile strength is of the order of the atomic nucleus, and the energy to spin it would require many Jupiter sized worlds to be converted to energy

  • It's a somewhat 50's point of view that an "advanced civilisation" would produce massive amounts of waste heat. Surely an even more advanced civilisation would be so efficient as to be undetectable?
    • by Grishnakh ( 216268 ) on Wednesday September 16, 2015 @11:57AM (#50533099)

      You can't escape waste heat; it's part of entropy. Unless maybe you open a subspace portal or something like that, but obviously our understanding of physics doesn't allow for anything of that sort.

      This is the problem with trying to understand hypothetical advanced civilizations; if any really exist, most likely they're figured out things in physics which we still have no clue about. We only started figuring out quantum mechanics about a century ago, and without that we wouldn't have semiconductors, including microchips and LEDs. We've barely even gotten off our own planet.

      • by Z00L00K ( 682162 )

        Waste heat - that assumes that you actually need heat in large volume to achieve your goals. We don't know what the next world with a civilization look like so we can't tell if they actually have that need or if they have tamed plants to grow houses and don't need heat to the same extent that humans do.

      • You can't escape waste heat

        What about hiding in plain sight? What if you use semi-transparent Dyson spheres or some other mechanism that lets half the normal radiation flow outwards? It might be wasteful, but it also seems to me that it would make you undetectable.

        This is the problem with trying to understand hypothetical advanced civilizations; if any really exist, most likely they're figured out things in physics which we still have no clue about.

        Agreed. Considering that we actually know that there is something like dark matter (whatever it may be), it seems more than naive to think that an advanced civilization (Type III, no less) would still need to be messing around in the EM spectrum.

  • The issue at hand, is that the Fermi Paradox doesn't consider the probability that an intelligent alien life will suffer from RF spectrum sensitivity, and will thus build a civilization void of radio transmissions... I'm just sayin'.

    • You might be on to something. If this civilization did exist, could we ship off all the WiFi Sensitive people to go live with them?

      Though one has to wonder how sensitive the aliens are to RF, those people might not last long there as they sit wondering why their iPhones aren't getting a signal.

  • Mmmno. The research doesn't indicate anything like that at all. They were looking for civilizations that harness energy and resources at galactic scales, ie. Kardashev III - level civilizations. Mankind haven't even reached Kardashev I yet. The submitter didn't understand what they were reading and jumped to conclusions.

    • Exactly right. Just means there aren't any level III civilizations. Personal opinion is that they're not possible or feasible or there will be a better way than harnessing galaxies once you get to that knowledge level. We really have no idea how a level III civilization might work or look.
      • "Exactly right."

        Who's to say we would even be _able_ to see them? If you have all the power in the galaxy and you start noticing some pesky, lower beings starting to make camp on your door step. Either you're going to ignore them and make sure they can't bother you, or wipe them out.

        As the latter hasn't happened (yet), who's to say the former isn't true?

        • Or perhaps the light delivering information to us that they are a Type III civilization hasn't reached us yet, but might in a few hundred/thousand/million years.

    • Not to mention that it's probably a reasonable assumption that civilizations at that level might be far more efficient with their use of energy, and emit much less - either out a desire for efficiency, or because they DON'T want to call attention to themselves.

  • So it looks like they defined advanced civilization as the ones that will use energy at galactic levels at such a proportion and emit IR radiation that could be detected across the local galaxy clusters.

    Most old religions imagine God to be some supersized version of some human known to them. These people think advanced civilization to be something that wastes energy like we do, but at some galactic scale.

    • I think we are looking at this with the eyes of a 4 year old.

      We know that 2+2=4, so we presume to think that we know all there is about Math.
      We know that e=mc2, so we presume that we understand how the Universe works.

      Then, using our faulty assumptions, we presume to say that we are the only ones around.

      I expect that should we ever meet a space faring civilization, our best and brightest will be as children trying to keep track of their lunch boxes as they are escorted to their first class in Kindergarten.

  • by dmomo ( 256005 ) on Wednesday September 16, 2015 @11:26AM (#50532759)

    ...as of thousands to millions of years ago, anyway? Speed of light, and all.

    • This is still another reason why such a search should be confined to the recently discovered class of very old galaxies.

    • Exactly. The problem with looking for alien life is that the probability is that we missed the window of opportunity. They already drove themselves to extinction.
  • in a galaxy far, far away
  • Advanced civilizations just build ring worlds like in the Larry Niven novels. Then civilization collapses and they no longer produce waste heat. Or they could be like the Puppeteers, and manage massive empires while basically all living on one planet.
  • ... human presumption knows no limit.
  • by Geoffrey.landis ( 926948 ) on Wednesday September 16, 2015 @11:30AM (#50532815) Homepage

    Nonetheless, the results indicate that either humanity really is the only intelligent species in this part of the universe, or

    Incorrect conclusion.

    The analysis was about civilizations that use energy on a galactic scale. It makes no conclusions about intelligent civilizations that use energy on the scale of human civilization. There could be trillions of human-scale civilizations out there; this analysis would not notice them.

    advanced civilizations are far more efficient in their use of energy than is reasonable to assume.

    Again, bad conclusion. We have not way to estimate what is "reasonable" to assume for a galactic-scale civilization. Kardashev defined a type-III civlilzation as one that used energy on the scale of galactic energy production, but gave no reasoning as to what a civilization would do that requires this much energy.

    • Kardashev defined a type-III civlilzation as one that used energy on the scale of galactic energy production, but gave no reasoning as to what a civilization would do that requires this much energy.

      Porn

    • Build a galaxy-sized Dyson Sphere?

    • Agreed. Maybe is't just a matter of feasibility. Civilization X advances enough to realize that trapping the whole star into a Dyson sphere is simply less effective than matter/antimatter energy generation or microfusion piles, for example.

  • Researchers looked at several hundred nearby galaxies that emitted a high amount of mid-infrared radiation (abstract), which could possibly be produced as the waste heat from civilizations using energy on galactic scales.

    So, we're defining "advanced" societies according to the ability to put out more heat than their parent galaxies?

    Well, that's a pretty high bar, and I'm also not sure the assumption these societies will exist is based on, well, anything.

    From what I can see, maybe if you're talking about ene

    • If you consume that energy, it doesn't matter how you transport it; even if it's 100% efficient, you're going to consume it somewhere, doing something, and then it'll be emitted as waste heat. This is basic entropy in physics.

      The only way around this is if you find some unknown-to-us branch of physics that doesn't require entropy (maybe you divert the waste heat to a parallel universe or hyperspace or something).

      • The only way around this is if you find some unknown-to-us branch of physics that doesn't require entropy

        Sure, fine .... but presumably using energy on a scale which outshines its parent galaxy you're probably doing some things we don't understand.

        I'm pretty skeptical that we'd be talking about a freaking wood-burning civilization.

        At which point everything we say about that society is, at best, pulled out of someone's backside.

    • Actually it makes sense.
      Energy input can be photons, energy output is mid-wave Infrared.
      Uninhabited galaxy emits energy as X-Ray+Photons+mid-wave Infrared+UV+god knows whet else.
      Inhabited galaxy (by Type III) emits way less Photons but more mid-wave Infrared than the above, because the Photon energy is captured and part of it emitted as mid-wave Infrared.

      One type of emission becomes much greater than expected, not the overall energy emission.

    • by amorsen ( 7485 )

      Life is basically a way to export entropy elsewhere. Life uses low-entropy energy like sunlight and turns it into high-entropy energy like deep infrared in order to stay complex and low-entropy (unusual combination) itself.

      The assumption is that if you have more efficient processes, you use them to do more useful work, not to sit around singing Kumbayah. I.e. efficiency increases are offset by increased consumption. This certainly seems like a reasonable assumption for life as we know it.

  • ...other advanced civilizations with nearby locations looked at our planet, said "well, there goes the neighborhood" and right quickly buggered off before their property values took a nosedive?

  • If they were advanced enough to notice us, they probably moved out. Wouldn't you?
  • by jeffb (2.718) ( 1189693 ) on Wednesday September 16, 2015 @11:35AM (#50532891)

    The firmament is peppered with huge concentrations of high-density plasma, supporting computation and communication far beyond the capacity of low-temperature, low-energy, solid-state matter. The byproducts of all that computation and communication look to us like thermal and optical noise because, being advanced, the minds running on them do so efficiently. Why leak information out into the vast, cold universe before you've taken full advantage of your substrate's Shannon capacity?

    But, no, you're probably right. If there are other civilizations out there, why aren't we seeing the smoke from their cook-fires?

  • The odds of a given planet being able to support life is low to begin with, the odds of a given planet that can support life actually DEVELOPING that life is much lower, the odds of that life developing into intelligent species is even lower than that, and the odds that said intelligent life would exist in an adjusted coincidental time-frame with OUR intelligent life on earth is down infinitesimal.

    Now there are a huge number of planets in the universe so even infinitesimal odds mean that there is probably l

  • by U2xhc2hkb3QgU3Vja3M ( 4212163 ) on Wednesday September 16, 2015 @11:36AM (#50532899)
    It is known that there are an infinite 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. Therefore, there must be a finite number of inhabited worlds. Any finite number divided by infinity is as near to 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 the products of a deranged imagination.
  • Obviously, the uncertainty of these results is quite high.

    Then don't use 'probably' in the title.

  • by no1nose ( 993082 ) on Wednesday September 16, 2015 @11:49AM (#50533015)

    Perhaps intelligent civilization will originate from Earth and spread across the Universe. Everything has a beginning.

  • Why would an advanced civilization want to fry their planet? I find it more likely that they invented birth control, kept their population at reasonable level and are exploring universe by watching miniaturized robotic probes from the comfort of their beach bungalows. We are defining ourselves as an example of advanced. And civilizations that do that are usually not very advanced.

  • It's amazing that this comments section has attracted so many experts in this field! Given how many people here know enough to dismiss the findings of this analysis out-of-hand with a few sentences of a priori reckoning, I can only imagine that they will be blessing us mere mortals with the fruits of their vast knowledge and understanding soon! Maybe not through academic papers per se, but perhaps some pithy Dr. Who fan fic!

  • by Cro Magnon ( 467622 ) on Wednesday September 16, 2015 @12:18PM (#50533325) Homepage Journal

    If we're looking at other galaxies, we're seeing what happened 100,000 years ago or more. Maybe the people in the Andromeda galaxy went from living in trees scratching themselves to ruling the entire galaxy in that time. Also, who says they have to be Type III? Neither Star Trek nor Star Wars are throwing around galactic levels of energy, but they're way ahead of us. Maybe there are aliens at that level, too distant for us to detect.

  • If some alien culture were to look at Earth and try to determine if there were advanced cultures what would they determine?

    Well if they are more then 200 light years away they won't see anything. Why? Those signs of intelligent culture when applied to us would not yet have reached those cultures. Reverse that. We can say that we know of no advanced culture in an approximately 200 light year radius. Of the Milky Ways approximately 100,000 light year radius.

    What does that get us? We know that there are no ad

  • I have met several aliens, so this cannot be true.

  • It's like a bunch of savages saying their can't be other people around because we don't hear their drum messages. Technology advanced enough to produce that much detectable energy would use an energy we don't detect.
  • by WSOGMM ( 1460481 ) on Wednesday September 16, 2015 @01:46PM (#50534213)

    You couldn't detect radio signals from a planet. The electric field of a radio signal drops off inversely with the distance that it's traveled, the intensity inversely with the square of the distance. The closest large galaxy is about 2.4 million light-years away. Compare that to the measly 100 light-years that our radio signals have traveled. In Andromeda, the intensity of our radio signal will have dropped off by a factor of about a billion -- 2.4 million years from now-- compared to the already weak signals that we sent 100 years ago. So we will not likely find a signal from another civilization like our own.

    As far as detecting extremely advanced civilizations goes, it's silly to assume that they will output enough infrared heat to be detected on a galactic scale. Assuming they're able to overcome their population constraints (lack of resources, planets, living in space far from another star, etc), the heat that they generate on their own would still be negligible compared to even the dimmest brown dwarf stars that we can detect... unless you think that their population exceeds the mass of many thousands of stars. It's not downright impossible for a civilization to have spread throughout a galaxy -- it only takes about 250 million years to orbit your own galaxy -- but it's rather unlikely that we could see them from such distance.

    Furthermore, it took Earth about 4 billion years to form (mind you, just the planet... the evolution was much quicker with a bit of luck). As far as we can tell, the universe has only been churning out planets for 13.6 billion years. So you might be hard pressed to look at galaxies much farther than 9 billion light-years, since we can only receive light from civilizations that have had the time to develop on formed planets with good chemicals.

    I suspect that our best bet is looking at exoplanets within our own galaxy. As of now, we don't have a sun-sized telescope, so we'll have to stick with examining planetary atmospheres via transits (so absorption spectra of light coming from the star through the atmosphere). With some extreme amount of luck, we may be able to see the byproducts of an organic life-form within a planetary atmosphere, but there's no reason that it'd be life with advanced intelligence.

    If you wanted to search for a signal from another civilization similar to our own, they'd probably have to be directing a strong signal towards us intentionally (and from within our own galaxy). I suggested to Geoff Marcy during a colloquium that we should look for signals within our own ecliptic, since if we've been discovered as a non-advanced life-form (remember we've only been technologically 'advanced' for less than 100 years), they would most likely have discovered our atmosphere via the transiting technique. You can actually detect transits in mass simply by observing the intensity of thousands of stars over a few decades. No need to zero in on a planet with a *giant* telescope. He seemed to think it was a decent idea, but I probably would have been better off by emailing someone at seti :P

  • by sdinfoserv ( 1793266 ) on Wednesday September 16, 2015 @02:01PM (#50534327) Homepage
    All this really says is that civilizations emitting IR were not found in Y regions of the galaxy at time X in history.
    Since these regions are different 'light years' away in distance, what reaches us is not the current state of what's going on there.
    An advanced planet 500 light years from Earth looking today for other advanced race would not find us since 500 years ago we were not creating IR signatures.
    Likewise, if we found such a signature, the possibility exists that during the time the IR got here, that civilization ceased to exist.

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