Follow Slashdot blog updates by subscribing to our blog RSS feed


Forgot your password?
Space Sci-Fi Science

Fewer Than 10 ET Civilizations In Our Galaxy? 642

Al writes "The Fermi Paradox focuses on the existence of advanced civilizations elsewhere in the galaxy. If these civilizations are out there — and many analyses suggest the galaxy should be teeming with life — why haven't we seen them? Carlos Cotta and Álvaro Morales from the University of Malaga in Spain investigate another angle by considering the speed at which a sufficiently advanced civilization could colonize the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, the colonization wavefront could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain ET's absence. Cotta and Morales study how automated probes sent ahead of the colonization could explore the galaxy. If these probes left evidence of a visit that lasts for 100 million years, then there can be no more than about 10 civilizations out there."
This discussion has been archived. No new comments can be posted.

Fewer Than 10 ET Civilizations In Our Galaxy?

Comments Filter:
  • Re:Why (Score:3, Insightful)

    by Ihlosi ( 895663 ) on Friday July 31, 2009 @10:22AM (#28895825)

    I wonder why should one consider a colonisation of the whole Galaxy?

    Because someone else might have the same idea, and you need to beat them to it.

    Isn't it a too damn big territory to defend - explore - colonize?

    Well, if you manage to colonize the whole galaxy, you probably don't have to worry about defending it from external threats for quite a while.

    Without talking about the astronomical (ha ha) amount of human (E.T.) resources it would take to launch such an enterprise!

    Yes, it takes quite a bit of resources to start, but once you have it going, the law of exponential growth is on your side ... at least until you run out of galaxy to colonize.

  • by Ihlosi ( 895663 ) on Friday July 31, 2009 @10:25AM (#28895851)
    All this is assuming that we would know immediately if there were a 50-100 million year old alien probe in our solar system's backyard.

    Yes. There could be half a bajillion alien probes in the Kuiper belt, transmitting the latest antics of the Earthlings right to GalaxyTV, and we'd have no idea.

  • by Dotren ( 1449427 ) on Friday July 31, 2009 @10:25AM (#28895855)

    I remember reading an interesting book called "The Science of Star Wars" that discussed the real life issues with the technology and situations in the original trilogy. This covered everything from the theoretical sciences behind the technologies like lightsabers, blasters, and lightspeed to the possibilities of existence of other life out there. I haven't read this book in a very long time and I don't have access to it at the moment, but I seem to remember it indicating that the odds of finding another planet with water, breathable air, and the exact distance from a sun necessary to help life flourish were so extremely low as to be laughable.

    I remember thinking even then how short-sighted that was and how arrogant it seemed.

    I realize these things are supposed to be scientific so they use only what they know to be fact, however, I think when dealing with complete unknowns such as the type of life out there or what their technology level may be at, you have to start thinking outside the box and be a bit more imaganitive.

    Who is to say, for example, what form other life will take? Would we even recognize it as life if we were standing right next to it? What about their technology? Who is to say that they haven't gotten past the lightspeed issues with relativity and energy required? Perhaps they have stealth technologies... would we even be able to detect them? Just because we don't know how to do it now, and just because our current science says it probably isn't possible, doesn't mean it can't be done.

  • by Ihlosi ( 895663 ) on Friday July 31, 2009 @10:29AM (#28895893)
    Would we even recognize it as life if we were standing right next to it?

    We pretty much know what rocks and ice look like. If the aliens aren't spectacularly good at masquerading as rock and ice, we'll recognize them.

  • Probes (Score:5, Insightful)

    by UncleWilly ( 1128141 ) * <> on Friday July 31, 2009 @10:34AM (#28895973)

    I am curious as to what evidence these alien probes would leave if they don't land and stay on a planet. If they just fly around, collect data and phone it home we would never see them.

    Even landing, unless they landed on Earth, our Moon or Mars, how would we see it? I'm not even certain our own probes can spot our own rovers on Mars. Lets say they did put a probe down on earth (like our mars rover) say recently, like 100,000,000 years ago; it could easily be hidden under a kilometer of dirt and rocks and never be found. Time, like space, is vast.

  • Re:Why (Score:3, Insightful)

    by maxume ( 22995 ) on Friday July 31, 2009 @10:36AM (#28896001)

    You need to throw in a bunch of hand waving about statistics.

    It is at least possible that we are the first, most advanced civilization, out of some huge number in this vicinity (even if it is extremely unlikely...).

  • by NonUniqueNickname ( 1459477 ) on Friday July 31, 2009 @10:39AM (#28896039)
    Hard to imagine it would still be ticking and beeping 100 million years later. At least by our standards, 1000 years of operation would be a great engineering feat for a device that's subject to space travel. A silent probe in a solar system is like a drop in the ocean, maybe like single molecule in the ocean. Not surprising we haven't found one.
  • Assumptions (Score:3, Insightful)

    by I.M.O.G. ( 811163 ) <> on Friday July 31, 2009 @10:42AM (#28896085) Homepage

    This assumes a sufficiently advanced civilization could survive itself for a sufficient span. Taking the only advanced civilizations we know into account - the human race - I don't see how its realistic to expect survival into the "millions of years" range.

    I'd put forth that any civilization advanced enough to develop such technological advances, would kill itself long before such technology develops. Our current modus operandi is not sustainable millions of years out, and using the human race as a basis, I think it laughable to consider the possibility of survival for millions of years. The oldest human remains are what, about 160,000 years old? Might we be getting ahead of ourselves speaking about intelligent life colonizing the galaxy?

    Crocodiles on the other hand - those bastards are believed to be around 200 million years old. They've exhibited a much better understanding for what it takes to survive long term (of course we're doing a pretty good job of killing them too - you can say people are bad at somethings, but everyone has to admit we're really good at killing other stuff). If crocs could somehow work space travel into their lifestyle, this could lead to something...

  • by logicnazi ( 169418 ) <logicnazi AT gmail DOT com> on Friday July 31, 2009 @10:43AM (#28896097) Homepage
    It's always seemed to me that the major hole in the Fermi paradox is the assumption that technologically advanced alien civilizations would be emitting signals we would recognize.

    I mean it's kinda hubristic to assume they want to talk to us. After all we may study chimps but we don't go out of our way to show up in the middle of nowhere to say hello. That leaves the question of why we don't detect communication leakage, e.g., radio signals they use for communication. However, not only is it not obvious that they would use radio to communicate, or that we could recognize such signals, but it's not even obvious they would bother to colonize the galaxy or communicate between planets.

    For example suppose that sufficiently advanced civilizations transform themselves into some form of 'computational' life. Such a civilization couldn't care less about planents or minerals. What would matter to them is processing power per unit volume. It would therefore make sense for such civilizations to seek out the regions with the highest energy density that would allow them to access the most processing power. Rather than racing around the galaxy in starships and living at the same crawlingly slow pace we do such civilizations might exist entirely in the high energy regions in neutron stars or around black holes. So why would we expect to meet them. Hell, even if they care about meeting aliens too the aliens they care about are probably the ones who already inhabit similar regions.

    Even if we think it's reasonable to assume aliens are sending messages all over the galaxy the more efficiently such messages are encoded the harder it will be for us to identify them. The closer such transmissions approach the Shannon limit for the communications channel the harder they would be to distinguish from random noise (and we don't know enough to rule out a natural source). Also the more effective use they made of their communications equipment the less stray signal that would wash the earth, even if it was encoded in radio instead of neutrinos or something weird (some papers have suggested neutrinos would be a better long range communication method).

    The point is that even if we take for granted that there a fucktons of advanced alien civilizations around it just doesn't follow that we should be able to detect them.
  • by Ktistec Machine ( 159201 ) on Friday July 31, 2009 @10:44AM (#28896117)

    ...and we haven't been back since. Beyond the question of how long it would take a motivated civilization to expand throughout the galaxy, there's the question of "would they bother?". We don't seem to be bothering.

  • by Artifakt ( 700173 ) on Friday July 31, 2009 @10:44AM (#28896119)

    I don't remember the novel it came from, but one SF writer had a bunch of human explorers run across pretty, slowly shifting, crystaline patterns floating as thin films on the surfaces of otherwise sterile oceans in a chemically exotic environment. Human initial response was pretty much limited to 'Ooooh shiny!" After weeks of scanning the whole planet and crunching numbers, one of the ship's scientists announces there is a sophisticated civilization with billions of participants encoded in each crystal mat, and has to prepare a computer emulation translated into experiential modes the humans can better understand before anyone else will believe it.

  • Calvin (Score:5, Insightful)

    by residieu ( 577863 ) on Friday July 31, 2009 @10:54AM (#28896251)
    "Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
  • Lack of resources? (Score:2, Insightful)

    by javacowboy ( 222023 ) on Friday July 31, 2009 @10:59AM (#28896341)

    A civilization needs to devote a lot of resources to space travel:

    1) Energy
    2) Metal and other materials
    3) Human resources such as scientists and engineers

    Usually, the whole point of exploring and colonizing other planets is to make up for a lack of resources, such as minerals. It's effectively a chicken-and-egg problem.

    I'm sure once we run out of resources, we won't have enough left over to start exploring space.

  • by tzhuge ( 1031302 ) on Friday July 31, 2009 @11:04AM (#28896413)
    I would say the assumption isn't so much based on hubris as on practical considerations. We only really know our civilization, so we can only make these kinds of conjectures based on what an advanced version of our own civilization would be like (we would so trash the place with probes). If we don't make those assumptions, then there really is no starting point to get very far on this kind of 'what-ifs'. Maybe the planets are sentient...
  • Re:Why (Score:2, Insightful)

    by Anonymous Coward on Friday July 31, 2009 @11:10AM (#28896519)

    "But why, some say, the moon? Why choose this as our goal? And they may well ask why climb the highest mountain? Why, 35 years ago, fly the Atlantic? Why does Rice play Texas?

    We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard.."

    "Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there."

    Well, space is there, and we're going to climb it, and the moon and the planets are there, and new hopes for knowledge and peace are there. And, therefore, as we set sail we ask God's blessing on the most hazardous and dangerous and greatest adventure on which man has ever embarked."

    -John F. Kennedy, September 12 1962

  • Re:Why (Score:5, Insightful)

    by SatanicPuppy ( 611928 ) * <.Satanicpuppy. .at.> on Friday July 31, 2009 @11:13AM (#28896559) Journal

    "Well, if you manage to colonize the whole galaxy, you probably don't have to worry about defending it from external threats for quite a while."

    Okay, that's the funniest thing I've ever heard.

    Q: What's the biggest threat humanity has ever faced?
    A: Itself.

    Creating thousands of splinter civilizations with no emotional investment in the species homeworld is a recipe for galactic war if I've ever heard one.

  • Re:!Science (Score:2, Insightful)

    by Nitage ( 1010087 ) on Friday July 31, 2009 @11:16AM (#28896607)
    The Drake equation is maths. Just because we don't know the numbers to substitute for the terms, it doesn't make the equation itself any less valid.
  • Re:Why (Score:5, Insightful)

    by fastest fascist ( 1086001 ) on Friday July 31, 2009 @11:16AM (#28896615)
    You can't really think of colonizing a galaxy in the way you might think of colonizing a new continent. The distances alone would make sure whatever reaches the far end of the galaxy would be a completely different species than the originator of the "colonization". Barring faster-than-light travel or some kind of extreme (from our point of view) psychology and genetics, I see no way a civilization spanning an entire galaxy could exist. If we colonized Mars now, it wouldn't be very long before they started to go their own way. Hell, the Americas were lost to the parent countries in a few centuries, and that's on the same planet.

    It just doesn't make much sense to take an expansionist view of space travel, unless maybe your species is very, very patient and stable. Any colonists you send far out, you will never have meaningful contact with again. At that point you might wonder what the point of "conquering" new systems is, in terms of nationalist-type expansionism.
  • by interval1066 ( 668936 ) on Friday July 31, 2009 @11:20AM (#28896667) Homepage Journal

    @Ktistec Machine: "We don't seem to be bothering."

    Chastising ourselves for our lack of will regarding space exploration is all well and good but the fact of the matter is that space exploration is no light matter. It currently requires a great amount of effort, will, economic consumption, and resolve.

    That the US was able to go to the moon during the cold war should not be taken lightly. Of course, the only reason we were able to do both things is that we were still coasting on our fortunes gained from WWII and the economic power of the 50's, and the prestige of going to the moon before the Soviets was invaluable, at the time. Now we're like playboys living off our daddy's legacy, which has run out but our credit is still good. Yes, exploring the moon and space and all that is good but we need to keep the Ferrari gassed up for Friday Night right now, put that on the Master Card please.

    That aside, with all the money we and the other countries around the world have printed up devaluing all our economic measures of output, we simply don't have the time. We're all working very hard to pay back all that debt, and of course the US government is working overtime to suck back in all that output and turn it right back into debt. We do not have the economic means to do serious space exploration. China, for all its economic power, is in the same boat, to a lesser & different extent, so don't look to them.

    The upshot of all that is to do REAL space exploration, the world will at some point need to be united so that the entire global output can be turned to doing this exploration. If any exocultures have in fact been able to mount a serious exploration of outer space, I suspect they would have had to do the same thing. Even if they've had to hold their noses at dealing with each other, they've probably united their entire "diverse culture" nonsense and made a real, concerted effort to doing this.

    From what I can see, if we are representative of carbon-based life forms, this united effort is probably very rare, if its happened at all.

  • Re:Why (Score:4, Insightful)

    by fastest fascist ( 1086001 ) on Friday July 31, 2009 @11:28AM (#28896775)
    Thinking about this this takes me to some kind of conclusion:

    Most civilizations would not expand very quickly at all, probably not much faster than they absolutely have to. Granted, you might imagine a very adventurous species that would send ark ships thousands of light years away just for the hell of it, but for the most part that seems unlikely, perhaps used as a last chance for survival. If any faraway colony is, in essence, as good as a different civilization, it makes little sense to send ships out very far. Moving out of a solar system would be a rare incident, mostly only taken up when the survival of the species is threatened. Just as you can't currently think of colonizing other planets as a solution for overpopulation on the earth - you just can't lift enough people off the planet for it to make a difference - you can't with any reasonably conceivable technology think of colonizing new solar systems as a solution for lack of resources or living space. You can send colonists out, but that's the last you'll see of them, and any problems you have in your own system, you will need to deal with there.
  • Otherwise, societies are too self-absorbed to dedicate those sort of resources to a goal that will have ZERO benefit to them or their descendants.

    It sucks for scientific types, for sure, but the best way to get the masses emotionally committed to space flight and space exploration is through religion. There's no more historically proven way that motivates people to build and explore for future purposes than the prospect of being able to worship your lord and impose his law as your religious customs see fit to do so. In 1620, it wasn't a bunch of scientists on board the Mayflower, it was a bunch of religious fanatics. In my site I'm going to go all out religion for space exploration as a national priority and argue in this order:

    a) The Lord gave us the vast resources of the Heavens to use.
    b) The Earth is a crowd and dank cesspool of sin.
    c) You can establish a more Godly society on another planet.
    d) You can re-create the American Experiment the way the founding fathers intended.

  • by scorp1us ( 235526 ) on Friday July 31, 2009 @11:29AM (#28896799) Journal
    I think a better question is "could they bother" or the "Battlestar Galactica" problem. (Honorable mention to Trigun) Any craft, unless capable of near-luminal speeds will take a large amount of time and energy to get there. This craft will require maintenance over the duration, and after arriving at a a destination will be limited by the lack of industry at the destination. Meaning, once you get somewhere, all your technology goes away eventually, unless you transport a population large enough to build the most complex part on a ship (for us a microprocessor) You can cheat for a little while and take a small chip fab plant with you, but eventually that will need parts too. What you'll end up with ia a devolution of society. Given the problems the pilgrims had at Plymouth rock, (on the same planet) the survival of the group is far from assured. i.e. Jamestown and the the other colonies. Meanwhile your source civilization is capable of being wiped out by an asteroid or comet. Sure it may take 30 or 100 years to get the part delivered, but it to too long of delay. I think any civilization out there would focus on the much more down-to-earth effort of population and resource management. We should also be looking at populating the oceans, because given an asteroid impact, that is the safest place to be overall.
  • by thedonger ( 1317951 ) on Friday July 31, 2009 @11:31AM (#28896827)
    I propose thedonger Paradox:

    If there exists another race like earth-based humans, it proves our evolution is completely random because no intelligent, higher being would make us on purpose twice. On the other hand, if we are here our of sheer randomness then it is most probable we are, in fact, alone.
  • Re:Greed Effect (Score:3, Insightful)

    by YrWrstNtmr ( 564987 ) on Friday July 31, 2009 @11:38AM (#28896915)
    In our case, I think we should be more concerned with the slow pace in space exploration, not because that North Korea might launch a nuke, but a asteroid might be heading our way.

    Slow pace? A mere 100 years ago, we were just beginning to experiment with heavier than air vehicles. Today, we are driving RC cars around on other planets. It may seem 'slow' to the gottahaveitrightnow mindset of today's younguns, but 100 years is a drop in the bucket.

    How long was it between Columbus and the landing at Jamestown or Plymouth Rock?
    500 or 1000 years from now, historians will look back and say "Dayum! They did a lot of stuff in that century!"

    What did we as a species do between 900 and 1000 AD? Besides fight a few wars, not a whole lot.
  • Mind the gap! (Score:5, Insightful)

    by rlseaman ( 1420667 ) on Friday July 31, 2009 @11:38AM (#28896921)

    bjourne points out: "They assume that alien civilizations would grow exponentially like humanity. To maintain exponential growth the civilization would inevitably have to colonize other planets, other solar systems and even other galaxies."

    What they really assume is that the laws of physics apply broadly across the cosmos. Darwin and Malthus do the rest.

    The real question is how hard it is to jump the gap from one world to the next. Science fiction authors assume this is not only possible but relatively easy, because otherwise they would have no story to write. Travel (of the few) within the solar system seems plausible. Travel (of the many) to neighboring stars is far beyond daunting.

    Consider Malthusian growth: Our population today is 6.602 billion souls. The current growth rate is 1.167% per annum. (Numbers are a couple of years old - it doesn't change the result.) Do the math.

    Today there were 210,000 more souls and 6000 tons more human flesh pressing inward on Mother Earth than yesterday. Tomorrow there will be 210,000 more. The day after - another 210,000. In six months that will be 211,000 per day - in a year, 212,000 per day, and so forth and so on. Less than a year from now there will be another 1.8 million tons of human flesh literally shouldering other species into extinction. That's not 1.8 million tons total - that's just the additional growth of skin and hair and sinew and good red meat locked up in your mama's Soylent Green recipe.

    For space travel to matter in the solution of this problem, we have to build a fleet of ships capable of offloading 210,000 people - a new space fleet every day, year after year - forever. A space shuttle carries a crew of seven - so we need 30,000 space shuttles a day. (Of course, that only gets you to low Earth orbit.) Each year we would have to move at least that 1.8 million tons of human cold cuts - that's the equivalent of 18 Nimitz class aircraft carriers - to some other distant, unwelcoming world.

    And then, of course, you've just shifted the horizon of the always looming catastrophe to a collection of planets rather than a single planet. Since this is a doubling issue, colonizing another planet - say, a terraformed Venus - just buys you an additional 60 years.

  • by Swizec ( 978239 ) on Friday July 31, 2009 @11:44AM (#28897025) Homepage

    However, not only is it not obvious that they would use radio to communicate, or that we could recognize such signals, but it's not even obvious they would bother to colonize the galaxy or communicate between planets.

    Exactly, why would you want to communicate between planets when in a few thousand years after having populated one everybody you left there will forget they're still the aliens? Even their technology would probably start diverging from what you left them with and eventually they'd become a group of organisms looking into the sky to find aliens and wondering why there aren't any ...

    ... maybe that's why we're so adamant about finding them. Deep down somewhere we know we're aliens and would like to go home now to visit mum.

  • by qwerty shrdlu ( 799408 ) on Friday July 31, 2009 @12:01PM (#28897273)
    11. Detecting radio signals at interstellar ranges is _hard_, unless the source is as powerfull as a star.
  • by plague3106 ( 71849 ) on Friday July 31, 2009 @12:02PM (#28897283)

    You're suprised? Never heard the phrase "all the worlds a stage?"

  • by John Hasler ( 414242 ) on Friday July 31, 2009 @12:06PM (#28897335) Homepage

    Let alone evidence that would last a million years. A probe could have come through a thousand years ago, hung around taking pictures and measurements for a few years and moved on. We'd never know.

  • by FlyingSquidStudios ( 1031284 ) on Friday July 31, 2009 @12:18PM (#28897471) Homepage
    I have doubts whether SETI will ever find evidence of life on other worlds. If nothing else, the inverse square law pretty much rules out our picking up any transmission which wasn't intentionally broadcast to us and we have a very small frequency band to search since we pollute much of the EM spectrum with various electronics. On top of this, for all we know, none of the other intelligent, technologically-advanced civilizations rely on modulating EM radiation for communications. On the other hand, Carl Sagan once said that even if we have evidence that there are no other intelligent civilizations out there, we should keep looking anyway just in case we're wrong.
  • Re:Why (Score:3, Insightful)

    by Shakrai ( 717556 ) on Friday July 31, 2009 @12:30PM (#28897619) Journal

    There is no such thing as a recipe for galactic war, if you have the resources to wage interplanetary warfare, you won't care about waging interplanetary warfare.

    Human history suggests otherwise......

  • Re:Why (Score:3, Insightful)

    by stwrtpj ( 518864 ) <> on Friday July 31, 2009 @12:41PM (#28897813) Journal

    Creating thousands of splinter civilizations with no emotional investment in the species homeworld is a recipe for galactic war if I've ever heard one.

    What would be the point?

    Consider two "rival" worlds separated by a modest distance of 50 light years. Now assume that the top speed that ships can go remains 1/10 light speed as mentioned in the article. That's 500 years for your fleet to get to the other world. The time dilation at that speed would be small enough to be insignificant. Multi-generational warships anyone?

    So let's instead consider that we push the speed envelope. We're still limited in how fast we could go. Say we push it to 80% or maybe 90% lightspeed. You're still talking about taking over 50 years universe time to get there. The expenditure is not worth it. By the time they got there, people will have forgotten what they were fighting about, or would have moved on to more important matters.

  • Re:Why (Score:3, Insightful)

    by Nimey ( 114278 ) on Friday July 31, 2009 @12:58PM (#28898107) Homepage Journal

    Depends on how long it takes a Martian colony to become self-sufficient. Stuff can grow pretty well in the Americas, and it's not overly hard to extract natural resources. The same cannot be said of Mars, with its lack of atmosphere and magnetic field.

  • by bhartman34 ( 886109 ) on Friday July 31, 2009 @01:03PM (#28898197)
    There are other problems, as well. 1) This whole thing is anthropomorphic. What make us think that other intelligent life wants to explore space and find us (or other lifeforms)? They could very well be perfectly happy doing what they're doing. Who's to say? 2) The universe is big. The Earth is small. Our view of things is smaller still. It strikes me as more than a little arrogant to assume that if some planet 1000 light years away sends out a probe the size of a basketball, we're going to know anything about it at all, even if it gets within 100,000 miles of Earth. Scientists sometimes have trouble seeing meteors until they're almost on top of us, and we're supposed to believe that they'd know any time someone was to send a probe our way? 3) The universe is very old. 10,000 years ago, the universe was basically the same as it is now. We, on the other hand, were still using stone and bone tools. We've only been systematically looking at the sky for a very short time, and for most of that time, even something as close as Mars was an indistinct mass. The idea that we'd be able to detect anything like an alien technology (that might not want to be found) is a little bit ridiculous. With all the planets out there, it's inconceivable to me that none of them would have life at least as intelligent as us. (If we're the best the universe can do, how sad is that?) That doesn't mean that we'd automatically know if they were around, though. We're probably going to ahve to get lucky to find them, given the vast distances between planets (let alone inhabitable ones).
  • Re:!Science (Score:1, Insightful)

    by Anonymous Coward on Friday July 31, 2009 @01:11PM (#28898301)
    I have to disagree with you. The drake equation is accurate... we just have huge error bars on every one of the terms (though we're closing in on star formation, I think).

    It's surely ridiculous at this point to say "10 or fewer" but the concept of trying to figure out the terms of the Drake equation to reasonably small margins of errors *is* science. Yes, there might be fewer then 10 or more then 10,000 (though the latter brings back up the Fermi Paradox) ... but as we learn more, we can come up with a better estimate. Maybe in a hundred years we'll know enough about the formation of stars, planets, and life to say with 95% certainty that there are between 2 and 20 civilizations currently alive in the galaxy. Maybe not. But it's still science as long as you include the error bars.
  • by TiggertheMad ( 556308 ) on Friday July 31, 2009 @01:19PM (#28898441) Homepage Journal
    One of the reasons why we might not see the galaxy as teeming with life is beacuse all the life out there might not be capable of generating advanced technology. One of the assumptions in the equations is that all live will evolve to the point of sentience and begin building transistors. Why would this be the case?

    The dinosuars were doing pretty well as the dominant species for 100 million years without advanced technology, and if it were not for the KT event, they might have been the dominant species for another 100 million years. Evolution doesn't 'try' to evolve life to be smarter, just to be better. Big brains were a good move for us, but that may not be the case for every other life form.
  • by Sanat ( 702 ) on Friday July 31, 2009 @01:42PM (#28898791)

    "I at least hope they're getting a good laugh."

    Or weeping for what we are doing to ourselves and Earth.

  • "all your technology goes away eventually, "

    Only if they are incredible stupid and short sighted.

    Since they have space flight, I will presume they are neither.

    You know when you get there you will need to build an infrastructer.
    So you takes some fundamental resource with you.
    For example, take what is needed to build a nuclear reactor*.
    Build it, now you have power. Then you mine to replenish resources and build.
    You don't go through all the technology phases again.

    *what ever technology you are using to power the spaceship.

  • by mcrbids ( 148650 ) on Friday July 31, 2009 @01:55PM (#28898963) Journal

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

    -Hitch-hiker's Guide to the Galaxy

  • by Lostlander ( 1219708 ) on Friday July 31, 2009 @03:24PM (#28900393)
    I see a bunch of basic issues with the entire paradox and it's assumptions.

    1. It assumes that radio signal based communication is the first major communication style developed/discovered by a civilization. It's entirely possible that based on different environmental factors they were never able to get it to work in a reliable manner or through the magic of scientific breakthrough ended up with a different or superior communication style.

    2. Any number of religious or cultural decisions could get in the way.

    3. We assume that civilizations existed before we did and therefore their signals should be reaching us by now. They could be just now getting to the point we are. It could be assumed that a period of say 1-2 million years were optimal for development of life in our galaxy we simply don't have enough information.

    4. Due to additive and subtractive properties of radio waves there could be a significant amount of variables in play interfering with signals. We shouldn't assume that just because it has a straight line to us a signal won't have issues. We have significant issues of our own keeping our own signals clear from solar flares and everyday cosmic radiation.

    5. No matter how good we are at math if we base our calculations on what is essentially flawed data we will always draw the wrong conclusions. Hell we're constantly rewriting laws rules and constants in everyday physics. Until we can easily measure things on a galactic scale all this conjecture is little more than armchair quarterbacking. And since it is negative and discourages discovery it is especially harmful to put any value to it.
  • Clever is not wise (Score:2, Insightful)

    by ourcraft ( 874165 ) on Friday July 31, 2009 @05:16PM (#28902345)
    We dont see life everywhere because we (life forms) get clever enough to release radioactivity into our life envelope, long before we get clever enough to have multiple robust life envelopes. Smart enough make weapons, not wise enough to stop using them. Or in the common parlance: Glen Beck.
  • by Fantastic Lad ( 198284 ) on Saturday August 01, 2009 @12:31AM (#28905969)

    You have no idea what resources a probe built by a civilization 100,000 years ahead of us requires.

    Heck, even the assumption that "Probes" as we understand them are needed for data collection is enormously conceited on the part of humanity.

    Humans today are as thick as bricks.

    Do we try to communicate with the cows and pigs? Heck, we walk among them, breed them, cage them, kill them and EAT them. But they just graze and stand around in a daze as though it were all the most normal thing in the world. We simply use the means of containment which are necessary to counteract their ability to overcome that containment and escape our food system.

    As above, so below.

    We're smarter than cows and we have opposable thumbs, so the systems necessary to contain and manage us as a food supply are naturally going to be more complex. But those systems work well enough, and they're barely hidden if we bother to stop and notice them. But we don't. Instead we dream our lives away and discuss Fermi as though he were full of insight and wisdom. As though aliens would naturally want to shake our hands and talk with us. That burning bush spoke, did it? And did the things it told us make the world less like a meat rendering plant or more like a meat rendering plant?

    There are thousands of documented crop circles with just some of the strangest features which cannot be replicated by even the most clever human engineers we ask. And there are countless millions of children who go missing every year all over the world. For some reason, those figures are largely NOT documented. How curious.

    But we don't like to think about things like that. They are creepy and weird and our knees are designed to jerk instantly upon the mention of such things. We've been well programmed. Anybody who thinks we have not need only read the five hundred posts on this very subject. The amount of raw sewage which passes for reasoned thinking is depressing.

    It's the rare cow which escapes the food chain.


  • by jobst ( 955157 ) on Saturday August 01, 2009 @02:10AM (#28906447) Homepage

    There is 100% no proof that there is life out there. Period.
    Therefore the assumption is (for now!!!) that we are alone and that we need to take more care of this place.

  • by AzureDiamond ( 1314257 ) on Saturday August 01, 2009 @09:20AM (#28908163)

    The whole thing seems utterly bogus to me. Why should you build a probe to last for hundreds of millions of years? How do we know we haven't been visited? Who's to say a civilisation could even last for thousands of years when civilisations here have tended to collapse after mere hundreds.

    The worst problem is the economics of space travel at or less than light speed. On Earth voyages to the New World were funded by monarchs - they paid for the ship which would sale there and back in a couple of years and bring back gold, slaves or goods to pay off the investment. Later on conquistadors took over the countries and paid a members fee to the monarch. Now consider a spaceship travelling at 0.1c. That would take 80years to get to Sirius for example, 8 light years away. Once the ship arrives there is a 16 light year delay in communications, or another 80 year trip if that is possible. And when you get to Sirius there is most likely no biosphere to support you, so you pretty much stay on the ship. Even if there was it would take decades or centuries to build a technological civilisation. Basically the people that paid for the ship have no chance of getting a return on their investment.

    Even on Earth there a civilisations that were able to build ships but decided not to attempt colonisation. China in the 1400's had the technology to do it but decided not to for political reasons []

    Actually if you want a vision for something which can spread across vast distances, consider. You broadcast plans for a machine, Contact style. Unlike in Contact the machine is designed wipe out the receiving civilisation and suck up all available power and resources building copies of itself which then broadcast the plans to other civilisations. It's sort of like a computer virus, only scaled up. Maybe it could have mutated from a message sent for benign reasons. It the machine would have sensors to find nearby civilisations likely to have a SETI program and powerful lasers to beam the plan to them. It's far easier to send bits at light speed than ships.

  • by Rockoon ( 1252108 ) on Saturday August 01, 2009 @12:26PM (#28909425)
    Lets suppose that we design a small craft with a forward cross section of 10m square. Lets further suppose that craft is traveling at 0.5c.

    This craft sweeps a volume of space equivilent to 15 billion cubic meters / second. []

    Thats 9 quadrillion cubic meters / week.

    The *nearest* star will be 8 years away, at 0.5c.

    The chance of hitting such a small piece of rock approaches 100%

The only possible interpretation of any research whatever in the `social sciences' is: some do, some don't. -- Ernest Rutherford