# The Straight Dope on Fermi's Paradox... **URL:** \ **Category:** Great Debates\ **Created:** [December 9, 2009, 10:20pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647 "2009-12-09T22:20:45Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 11, 2009, 7:02pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/41 "2009-12-11T19:02:31Z")
> [@Triskadecamus](#): > > Everyone has heard the old if one in a million. . . . etc. arguments for other intelligent life. No one likes to do the math the other way. > > I did it, in a thread a while ago. > > Here it is again. > > Suppose a trillion civilizations, in the universe have each been expanding for an average of ten thousand years. Suppose these civilizations expand at the speed of light. Suppose further that this state of affairs is more or less constant, with new civilizations replacing fallen ones over the fifteen billion years of universal history. So, where are they? > > Well, given that: > > (1.5 x 10[sup]10[/sup])[sup]3[/sup], x 4/3 pi = 1.413 x 10[sup]31[/sup] cubic light years in the universal neighborhood. > > And these trillion civilizations occupy > > 4.189 x 10[sup]24[/sup] cubic light years, > > the percentage of space occupied by those civilizations is > > 0.00000296% > > It’s a big universe. > > Tris I think I see what you’re getting at, but I don’t agree. As I understand it, there is much more space inside my molecules than not, and for all I know I am only 0.00000296% of the space that is me. So? Even if there were 10 billion aliens on every single planet in the universe I wouldn’t expect that to be anything but an infinitesimal portion of the universe, just as humanity is an infinitesimal portion of the Earth. You still run into humans everywhere you go. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 11, 2009, 7:38pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/42 "2009-12-11T19:38:56Z")
> [@Half\_Man\_Half\_Wit](#): > > True, but civilizations are unlikely to be equidistributed within it – most will probably have originated within galaxies. Estimates vary, but there are probably about 100 billion galaxies within the visible universe, and, if our galaxy serves as a benchmark, each of those has, on average, a volume of around 4 \* 10[sup]13[/sup] cubic light years, making for a total habitable volume of around 4 \* 10[sup]24[/sup] cubic light years, which, according to your calculation, should all be rented out by now. True enough. Yeah, space between galaxies shouldnt be counted IMO either. But he assumed a trillion civizations. At any given time. Expanding to every star in reach at the speed of light. So, even with your correction, it doesnt take much less of any of those three to have plenty if not very mostly “unrented” space. ---
**Author:** ![Dioptre](https://avatars.discourse-cdn.com/v4/letter/d/278dde/32.png) [@Dioptre](https://boards.straightdope.com/u/Dioptre)\ **Post date:** [December 12, 2009, 12:00am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/43 "2009-12-12T00:00:45Z")
One answer to Fermi’s Paradox that has been explored is that we haven’t seen them because they are hiding. So what are they hiding from? And more importantly, why aren’t we hiding too? ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [December 12, 2009, 12:24am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/44 "2009-12-12T00:24:31Z")
Everyone seems to be working on the assumption that it is normal, or at least reasonably common, for civilizations to last for many thousands, or even millions, of years, and that it is normal for a civilization, while it exists, to experience rapid and steady growth in scientific knowledge and technological capability. All the (admittedly limited) evidence we have suggests otherwise. No Earth civilization has lasted for more than a few millennia (many for much less), and we really only have one example of a civilization that has experienced rapid, steady growth in scientific and technological capability. It has lasted, so far, maybe about 500 years,\* and there is good reason to believe that it may not last very much longer (in large part _because_ of its rapidly growing technological power, which has led to both environmental destruction and the availability of weapons quite capable of wiping the civilization out completely). Even if (as seems likely) there are intelligent beings on other planets in the galaxy, and even if (as also seems likely) some of these species have been around for much longer than human beings have, it is perfectly possible, or even (going by the limited experience the human race has had of such things) very likely that none of them would have developed a technology very much in advance of ours as it is now. * * * - All these temporal estimates are very approximate of course. It is impossible to put definite dates on when a civilization begins and ends, or on when or whether we should distinguish civilizations from successor civilizations. However, even if you went to the extreme of saying that “Western” civilization has existed continuously from the days of ancient Greece, that would still only give you about 3,000 years, and only about 400 of rapid and steady scientific and technological progress. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 12, 2009, 1:11am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/45 "2009-12-12T01:11:00Z")
> [@Dioptre](#): > > One answer to Fermi’s Paradox that has been explored is that we haven’t seen them because they are hiding. So what are they hiding from? And more importantly, why aren’t we hiding too? According to the Wiki article, it boils down to: [ul] [li]There must be other advanced civilizations, but they’re being quiet.[/li][li]Since those civilizations are advanced, there must be a good reason for being quiet.[/li][li]We should be quiet too.[/li][/ul] In other words, no advanced civilization wants to be the first to raise its hand. We aren’t really advanced enough yet to take the question seriously. ---
**Author:** ![Shawn1767](https://avatars.discourse-cdn.com/v4/letter/s/ee7513/32.png) [@Shawn1767](https://boards.straightdope.com/u/Shawn1767)\ **Post date:** [December 12, 2009, 1:42am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/46 "2009-12-12T01:42:35Z")
I never got this. I mean, we assume that because the universe isn’t overrun with self-replicating machines and galaxy-spanning civilizations, then there is no other intelligent life in the universe. Well, does that mean since humans don’t have self-replicating machines and a galaxy-spanning civilization, we don’t exist? ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [December 12, 2009, 2:09am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/47 "2009-12-12T02:09:09Z")
> [@Shawn1767](#): > > I never got this. > > I mean, we assume that because the universe isn’t overrun with self-replicating machines and galaxy-spanning civilizations, then there is no other intelligent life in the universe. Well, does that mean since humans don’t have self-replicating machines and a galaxy-spanning civilization, we don’t exist? Quiet, you are making sense, nobody wants to hear that. 😛 Personally, I would like to know where the resources come from for our galaxy expansion plan. I am not talking about simple little things like local energy resources and don’t want to get into some hippy-dippy solar energy, floating garden, sci-fi fantasy. The resources of the entire system, not just our planet, would be needed. The Fermi Paradox implys that the same forces that drove world wide exploration on this planet will continue to off-planet adventures. But what drove exploration on this planet has always been the possibility of new found wealth. Greed if you want to call it that. I would call it incentive. The application of resources for extra-solar adventures will be huge, not even a united planet could get it done. Maybe if the resources of an entire system were used you could get a fleet that might actually return after a long time with some benefit for the effort. Pure ideology, just to see what is out there, has launched not a single sailing ship on this planet. There has to be a better reason to go, or you won’t get the funding or ships built. Sorry, that is the way things work. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 12, 2009, 2:31am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/48 "2009-12-12T02:31:03Z")
> [@ghardester](#): > > Pure ideology, just to see what is out there, has launched not a single sailing ship on this planet. There has to be a better reason to go, or you won’t get the funding or ships built. > > Sorry, that is the way things work. Escape from persecution and poverty have launched a few ships, although I’m not saying that will be a system-wide problem in 5,000 years. Profit might not be a factor to a race so wealthy every single person commands their own empire of self-replicating AIs. ---
**Author:** ![Shawn1767](https://avatars.discourse-cdn.com/v4/letter/s/ee7513/32.png) [@Shawn1767](https://boards.straightdope.com/u/Shawn1767)\ **Post date:** [December 12, 2009, 3:46am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/49 "2009-12-12T03:46:22Z")
And another thing, based on the evidence we have (us) it has taken us the life of the universe so far to get to our level. Why assume there would be all these technically advanced races or assume that simply because we haven’t heard from them they aren’t there? The only evidence we have suggests that it takes around 15 billion years for intelligent life to form in the universe. (and don’t say only 4 billion because the earth is, after all, just a subset of the universe). ---
**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\ **Post date:** [December 12, 2009, 4:39am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/50 "2009-12-12T04:39:20Z")
Well, not that I know enough to support the reasoning or not, but I think part of the idea would be that other planets formed much earlier in the universe’s history, with there being no reason to suppose this wouldn’t correspondingly accelerate the development of intelligent life. That is, while it may be true that humans took 15 billion years to get here, 11 billion of those years were spent just forming our planet, which clearly has occurred in other cases much more quickly, presumably drastically shortening the development timeline of potential life elsewhere. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 12, 2009, 6:17am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/51 "2009-12-12T06:17:41Z")
> [@Shawn1767](#): > > And another thing, based on the evidence we have (us) it has taken us the life of the universe so far to get to our level. Why assume there would be all these technically advanced races or assume that simply because we haven’t heard from them they aren’t there? The only evidence we have suggests that it takes around 15 billion years for intelligent life to form in the universe. (and don’t say only 4 billion because the earth is, after all, just a subset of the universe). Yeah, but that’s a heavily biased observation. To be scientific about it we’d want a random sample of intelligent life but after we remove ourselves from the sample we’ve got zilch to work with but our own biased but well-meaning guesses. It’d help if we found unrelated life on Mars.🙂 ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [December 12, 2009, 9:08am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/52 "2009-12-12T09:08:32Z")
> [@Chronos](#): > > There’s been enough time for aliens to not just blanket the Galaxy with radio waves; there’s enough time for they, themselves, in the flesh, to have filled the Galaxy. Why haven’t we filled the galaxy so far? Why assume that aliens should be able to do so? ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [December 12, 2009, 10:50am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/53 "2009-12-12T10:50:24Z")
> [@billfish678](#): > > True enough. Yeah, space between galaxies shouldnt be counted IMO either. > But he assumed a trillion civizations. At any given time. Expanding to every star in reach at the speed of light. > > So, even with your correction, it doesnt take much less of any of those three to have plenty if not very mostly “unrented” space. Yes, obviously, those figures are easily fudged by a couple of orders of magnitude – that’s really the problem with Drake’s equation, which I guess is where the ten civilizations per galaxy and 10,000 year average lifespan came from. Personally, I’d guess ten is little and 10,000 also on the small side, but lightspeed (obviously) is a bit high, but who cares about my personal tastes? And besides, using 10,000 years as an average lifespan ignores the possibility that it only takes one civilization expanding in an exponential fashion for some geologically small amount of time (say some 10 million years) to colonize the whole galaxy, which is really why this is called a ‘paradox’ in the end. There’s also the question, if you’d started colonizing the galaxy, why would you stop? It becomes exceedingly hard to think up reasons for the disappearance of advanced civilizations the farther they got – I mean, even if your home planet central government decides that the whole colonization shtick is bullshit after all, if you’ve already made it halfway through the galaxy, the news only reach you after 50,000 years – at which point you’re even further down the line. ---
**Author:** ![The\_Second\_Stone](https://avatars.discourse-cdn.com/v4/letter/t/bbe5ce/32.png) [@The\_Second\_Stone](https://boards.straightdope.com/u/The_Second_Stone)\ **Post date:** [December 12, 2009, 6:54pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/54 "2009-12-12T18:54:57Z")
So long, and thanks for all the fish!! ---
**Author:** ![YamatoTwinkie](https://avatars.discourse-cdn.com/v4/letter/y/cc9497/32.png) [@YamatoTwinkie](https://boards.straightdope.com/u/YamatoTwinkie)\ **Post date:** [December 15, 2009, 3:04pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/55 "2009-12-15T15:04:06Z")
> [@Dog80](#): > > Why haven’t we filled the galaxy so far? Why assume that aliens should be able to do so? As a species, we’ve only had a major science program going on for the last ~300 years or so. Can you imagine what technological progress we’d make in the next **million** years (assuming we don’t blow ourselves up)? Now, get this, given the age of the galaxy (~13 billion years), if alien civilizations do exist, a vast percentage of them are bound to be _hundreds_ of millions of years older than us, or more. Even if the best they could pull off is spacecraft going 0.10c (not unreasonable), that still gives them plenty of time to colonize the galaxy several times over by now, assuming they wanted to. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [December 15, 2009, 4:13pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/56 "2009-12-15T16:13:54Z")
I’ve been interested in Super-Earths lately. This [Wiki entry](http://en.wikipedia.org/wiki/Super-Earth) is a nice overview of them. They are rocky planets generally considered to be 2-10 times the mass of Earth. Larger than that, we get ice giants. Ice giants are cool because they could easily be covered in deep oceans composed of all sorts of exotic ices. Bigger than that, we get gas giants of course. Anyhoo, here is a recent [MSNBC article](http://www.msnbc.msn.com/id/34230212/) discussing the potential habitability of Super-Earths. It also pertains to Fermi’s Paradox and the Drake Equation. It seems Super-Earths are very common, and may well be even more conducive to life than Earth is. Furthermore, Earth might be considered to be on the lower end of habitability, and Super-Earth civilizations might not even consider our system to be a priority for searching. Super-Earth civilizations also evolve under greater gravity than Earth (Superman!), and so might have a tougher time venturing out of their own gravity well. ---
**Author:** ![Roadfood](https://avatars.discourse-cdn.com/v4/letter/r/9fc348/32.png) [@Roadfood](https://boards.straightdope.com/u/Roadfood)\ **Post date:** [December 15, 2009, 11:21pm UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/57 "2009-12-15T23:21:51Z")
> [@ghardester](#): > > Quiet, you are making sense, nobody wants to hear that. 😛 > > Personally, I would like to know where the resources come from for our galaxy expansion plan. I am not talking about simple little things like local energy resources and don’t want to get into some hippy-dippy solar energy, floating garden, sci-fi fantasy. The resources of the entire system, not just our planet, would be needed. > > The Fermi Paradox implys that the same forces that drove world wide exploration on this planet will continue to off-planet adventures. But what drove exploration on this planet has always been the possibility of new found wealth. Greed if you want to call it that. I would call it incentive. > > The application of resources for extra-solar adventures will be huge, not even a united planet could get it done. Maybe if the resources of an entire system were used you could get a fleet that might actually return after a long time with some benefit for the effort. > > Pure ideology, just to see what is out there, has launched not a single sailing ship on this planet. There has to be a better reason to go, or you won’t get the funding or ships built. > > Sorry, that is the way things work. It’s the way things work, if you take the extremely short-sighted, narrow-minded view that all extraterrestrial beings will be more or less just like us and motivated solely by greed. I submit that about the only thing that another technologically advanced civilization would need to have in common with humans is basic curiosity. Because I submit that, without curiosity, intelligence would never develop technology. Beyond that, it takes no great leap of imagination to believe that an intelligent civilization that has had millions of years to evolve will have left such quaint concepts as “greed” and the need to compete far, far behind. I can imagine that, perhaps, curiosity is the only real motivation left after a hundred million years of evolving intelligence. Or perhaps that motivations that we haven’t even conceived of will come into existence. The Fermi paradox does not imply “that the same forces that drove world wide exploration on this planet will continue to off-planet adventures”. Far from it. It only implies that _some_ forces will drive advanced civilizations to explore and/or colonize. Assuming that the forces that would drive a hundred-million year-old intelligence must be the same as what drives ten-thousand year-old human intelligence is just silly. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [December 16, 2009, 12:33am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/58 "2009-12-16T00:33:08Z")
> [@Roadfood](#): > > Beyond that, it takes no great leap of imagination to believe that an intelligent civilization that has had millions of years to evolve will have left such quaint concepts as “greed” and the need to compete far, far behind. I can imagine that, perhaps, curiosity is the only real motivation left after a hundred million years of evolving intelligence. Or perhaps that motivations that we haven’t even conceived of will come into existence. Yeah, but after you’ve visited a kazillion solar systems, are you still curious about all the rest AND are movtivated to hang around them all for millions of years at every spot as well? I think calling it a “paradox” is borderline retarded. Many conditions have to be meet before space is flooded with ET’s. All it takes is “failure” of ONE these conditions before ET is virtually nowhere to be found. Don’t get me wrong. I WANT all those conditions to be “workable”. But they could easily not be. I submit to you Billfish’s “Paradox” Why isnt Santa on my roof ? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 16, 2009, 12:45am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/59 "2009-12-16T00:45:55Z")
Just noticed this from the last page: > [@](#): > > All the (admittedly limited) evidence we have suggests otherwise. No Earth civilization has lasted for more than a few millennia (many for much less), and we really only have one example of a civilization that has experienced rapid, steady growth in scientific and technological capability. It has lasted, so far, maybe about 500 years,\* and there is good reason to believe that it may not last very much longer (in large part because of its rapidly growing technological power, which has led to both environmental destruction and the availability of weapons quite capable of wiping the civilization out completely). You have to pick a definition of “civilization”, and then stick to it. You can argue that “humans” constitute a civilization, in which case we’ve already lasted for hundreds of millenia. Alternately, you can call, say, Rome a civilization, but then you’ve got to add a new factor in Drake’s equation for the number of civilizations an intelligent, tool-using species will form, and history seems to show that that factor is very large. What you can’t do is say “Well, civilization has arisen once on Earth, and history shows that civilizations on Earth only last a few hundred years”. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [December 17, 2009, 12:14am UTC](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647/60 "2009-12-17T00:14:06Z")
OK, how about a question we probably can answer. How far away could we detect ourselves? What percentage of the heavens have we examined with sufficient detail to detect life exactly like our own? Tris [Previous page](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647.md?page=2) [Next page](https://boards.straightdope.com/t/the-straight-dope-on-fermis-paradox/520647.md?page=4)