# Why haven’t we been contacted by extraterrestrials? **URL:** \ **Category:** Great Debates\ **Created:** [January 17, 2017, 7:42pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410 "2017-01-17T19:42:44Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![Bosda\_Di\_Chi\_of\_Tricor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bosda_di_chi_of_tricor/32/16845_2.png) [@Bosda\_Di\_Chi\_of\_Tricor](https://boards.straightdope.com/u/Bosda_Di_Chi_of_Tricor)\ **Post date:** [January 18, 2017, 12:42am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/41 "2017-01-18T00:42:46Z")
Planetary biosphere contamination issues could be a risk–re: _The Andromeda Strain._ ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [January 18, 2017, 12:54am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/42 "2017-01-18T00:54:28Z")
> [@Dallas\_Jones](#): > > My point was that entering any real number into any part of the Drake equation is making an unfounded assumption. A guess. Wishful thinking. None of these variables are known. . . . That is completely valid and true. The equation is valid (and true!) but the specific values put into it are not all known. (Some are!) It’s like saying that the area of a given rectangular field or building lot is equal to width times length. It’s true…but I don’t know what those two values actually are. ---
**Author:** ![aldiboronti](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@aldiboronti](https://boards.straightdope.com/u/aldiboronti)\ **Post date:** [January 18, 2017, 1:18am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/43 "2017-01-18T01:18:04Z")
As others have said, space is a big place. There could be billions upon billions upon billions of advanced civilizations out there all frantically looking for each other and the odds would still be astronomical against any of them meeting or even seeing signs of each other from light years away. In effect if aliens exist then they may as well not. We’re on our own even if we’re not. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [January 18, 2017, 4:38am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/44 "2017-01-18T04:38:28Z")
Whaddyamean “why haven’t _we_ been contacted by extraterrestrials?” Speak for yerself, bub. ---
**Author:** ![Mosier](https://avatars.discourse-cdn.com/v4/letter/m/7ea924/32.png) [@Mosier](https://boards.straightdope.com/u/Mosier)\ **Post date:** [January 18, 2017, 6:39am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/45 "2017-01-18T06:39:57Z")
> [@Dallas\_Jones](#): > > This is like asking why Jesus hasn’t returned yet. > > The question assumes unproven facts. That Jesus existed, that he was the son of God, that he can reincarnate. No scientific evidence for any of this exists. > > And there is no evidence, of any kind, that \*\*ANY life exists \*\*off the planet Earth. None at all. Beyond the absence of proof for any extraterrestrial life existing at all the question makes further assumptions, of complex life, of technological life, of an interest by this supposed life in exploration. A technological civilization could exist on a planet with permanent cloud cover and not even be aware of the galaxy beyond their world. > > Why haven’t dolphins invented airplanes? > > The whole Drake Equation is an exercise in unproven assumptions, compounded with multiple assumptions over and over. There is no scientific evidence behind any of it. > > I stick with my opinion that we are the Elder Race, at least here in the Orion Spur of the Milky Way galaxy and will never, ever, even if we survive a million more years, find any other intelligence _out there_. For the sake of argument, let’s say you’re right and there aren’t any aliens out there. What then do you suppose is the bottleneck life has somehow managed to overcome on our planet? Why would something you argue is so rare it might as well be unique end up happening here, and not anywhere else? ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [January 18, 2017, 7:26am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/46 "2017-01-18T07:26:44Z")
> [@Washoe](#): > > some people get extremely emotional about the matter. > > I need more and better possible explanations. You sound like you are speaking with emotional people, who have trouble grasping abstract concepts like the huge size of the universe, and how long it’s been around. So here’s an easy-to-explain way to physically demonstrate it: 1. Hold out your arms spread out wide.( like Jesus on the cross.) 2. Tell your friends to imagine that the distance between your fingertips is the width of the universe. 3. The earth is only as wide as about one of the hairs on the back of your hand. Go find it. This works for time, too. The distance between your fingertips is the 15 billion years of the universe. The earth has only existed for the width of, say, the width of one finger, and homo sapiens has only existed for one hair width. Either way, if alien life exists, it ain’t gonna be easy for them to meet us. And for those who want to discuss the Drake equation and the Fermi paradox, there is one simple way to disprove it, with scientific facts: Look at the facts we now know about population growth (but did not know 30 years ago.) All over the planet earth ,every advanced country is now reproducing at low levels–birth rates barely match death rate, and in many countries, the actual population is declining. Therefor, using pure scientific facts, based on the only evidence we have (i.e. ourselves), we can state that techologically advanced civilizations have NO reason to expand throughout the universe. > [@](#): > > Expanding into space is more that being just about breathing room, it is about resources. > … we will end up with the same fate as Easter Island. Easter Islanders lived for hundreds of years within their resources, till human greed and overpopulation ruined it… There is no reason to assume that an advanced alien civilization with no overpopulation would destroy its natural resources, and need to go hunting in space for new supplies. ---
**Author:** ![rat\_avatar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rat_avatar/32/255_2.png) [@rat\_avatar](https://boards.straightdope.com/u/rat_avatar)\ **Post date:** [January 18, 2017, 7:50am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/47 "2017-01-18T07:50:51Z")
You are in luck, PBS Space time just covered this in depth related to the radio wave question. [![](https://img.youtube.com/vi/Ttwl_zH_DZ8/maxresdefault.jpg "Have They Seen Us? | Space Time | PBS Digital Studios") ](https://www.youtube.com/watch?v=Ttwl_zH_DZ8) ---
**Author:** ![Malden\_Capell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/malden_capell/32/5274_2.png) [@Malden\_Capell](https://boards.straightdope.com/u/Malden_Capell)\ **Post date:** [January 18, 2017, 7:58am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/48 "2017-01-18T07:58:25Z")
The Reapers got them. ---
**Author:** ![ataraxy22](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ataraxy22/32/307_2.png) [@ataraxy22](https://boards.straightdope.com/u/ataraxy22)\ **Post date:** [January 18, 2017, 8:06am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/49 "2017-01-18T08:06:17Z")
Don’t know the answer, but I can say that there is a very good reason why we haven’t heard from aliens already. It’s not happenstance. ---
**Author:** ![foolsguinea](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foolsguinea/32/14751_2.png) [@foolsguinea](https://boards.straightdope.com/u/foolsguinea)\ **Post date:** [January 18, 2017, 8:07am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/50 "2017-01-18T08:07:17Z")
They live among us but in secret. I would have thought not a well-kept secret, but apparently you’ve never noticed. ---
**Author:** ![PatrickLondon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/patricklondon/32/4422_2.png) [@PatrickLondon](https://boards.straightdope.com/u/PatrickLondon)\ **Post date:** [January 18, 2017, 8:30am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/51 "2017-01-18T08:30:14Z")
They didn’t turn out to be what we expected and whatever attempt at contact was made, somehow it simply became an inexplicable phenomenon: [As suggested here](http://www.campaignlive.co.uk/article/thinkbox-the-broadcast-red-brick-road/1419352) Or alternatively, they’ve been watching our TV programmes and thought better of it. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 18, 2017, 11:57am UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/52 "2017-01-18T11:57:19Z")
> [@Mangetout](#): > > They’re yelling, waving and signalling at us in ways we just can’t perceive. > [@That\_Don\_Guy](#): > > I am convinced that it is a combination of these two, although I wouldn’t rule out, “Somebody has to be first; why not us?” > > Besides, what do you expect them to say - “Darmok and Jalad at Tanagra”? In all honesty, I wasn’t being very serious. I think the true answer is probably just a combination of: [ul] [li]Space is big[/li][li]Time is long[/li][li]Civilisation is a probably a relatively short-lived phenomenon in universal terms.[/li][li]Deliberate interstellar communication is not very worthwhile, so few civilisations bother doing much of it.[/li][li]Accidental spillage of radio or other transmissions is very short in terms of range and the period of development where it happens in a technologically advancing civilisation.[/li][/ul] Most technological societies that arise in the universe will find themselves _functionally_ alone, even if life, intelligence and technology is common. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [January 18, 2017, 2:20pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/53 "2017-01-18T14:20:04Z")
> [@k9bfriender](#): > > Expanding into space is more that being just about breathing room, it is about resources. So you agree with me that the argument that an intelligent species will spread to other solar systems as some kind of imperative is flawed. > [@](#): > > We will before too long (within thousands or at least tens of thousands of years), exhaust all of the extractable minerals in the crust, and will have extracted all the easily accessible ones long before that. > > If we have not at that point started a supply line of resources coming from off planet, then we will end up with the same fate as Easter Island. There’s a LOT of minerals just dissolved in the ocean and buried in the mantle, and other than minerals used for nuclear fission can all be recycled at a trivial cost compared to the enormous costs of interstellar travel. This line of thinking ignores just how much mineral wealth is easily accessible, how cheap recycling is, and how expensive interstellar travel is. Plus, if you send off people to another solar system decades or centuries from home, there is no reason to assume that the other system will decide to spend their lives in servitude to Earth, sending back resources indefinately. It seems inevitable that at some point they will decide to go independent, and if your ‘Easter Island’ thesis is true, that means the extinction of Earth. ---
**Author:** ![Fiveyearlurker](https://avatars.discourse-cdn.com/v4/letter/f/da6949/32.png) [@Fiveyearlurker](https://boards.straightdope.com/u/Fiveyearlurker)\ **Post date:** [January 18, 2017, 2:29pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/54 "2017-01-18T14:29:24Z")
> [@Scylla](#): > > We are living in a simulation, and aliens were left out. I’m more and more heading in this direction as the hypothesis that makes the most sense. If you’re running a simulation, aliens would be a huge variable to drop on top. ---
**Author:** ![Damuri\_Ajashi](https://avatars.discourse-cdn.com/v4/letter/d/898d66/32.png) [@Damuri\_Ajashi](https://boards.straightdope.com/u/Damuri_Ajashi)\ **Post date:** [January 18, 2017, 3:44pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/55 "2017-01-18T15:44:11Z")
There are less than 100 planets within 50 light years that can have water in a naturally liquid state, that is assuming that all the other shit that you need for life to exist is also present. Perhaps 4 times that many within 100 light years. We have been transmitting for less than 100 years. Time is long. They might have stopped listening millions of years ago. They may not be able to listen until millions of years in the future. We have been transmitting for less than 100 years. Perhaps they don’t think we’re ready. Some sci fi paradigms propose that communication of the future is done via ftl communication and that we will not pick up anything until we also grok ftl theories. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [January 18, 2017, 3:54pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/56 "2017-01-18T15:54:14Z")
> [@Stranger\_On\_A\_Train](#): > > Our radio emissions (including television transmission) obviously have a maximum radius of less than 120 light years, but even with that most of the signals are not going to be distinguishable from the background radio environment without extreme amplification at that range which would necessitate already looking for and knowing the format of the signal. \ > [@](#): > > Or alien civilizations may have arisen, gone through cycles of development and advancement, and have extinguished, either through conflict, depletion of resources, or have been overcome by some natural or manufactured disaster. Life has been around on Earth for ~4.2 Byr, complex (multicellular) for 1.5 Byr, terrestrial mobility for about 350 Myr, and anatomically modern humans for about 200 kyr. That is the metaphorical blink of an eye on the cosmic time scale, and there is plenty of times for a human-like civilization to have risen and fallen many times in that interval, perhaps never having attempted to convey their existance, or having shouted into the void with unheard invitations to respond. > Stranger Not only that, but humans have been using radio (and other “advanced” tools) around a century. This represents a tiny sliver of the timeline of the planet. I don’t believe evolution has stopped working on us, and I have no idea how long we are going to continue to be a tool using form (since the internet has proven that the “stupidity” gene appears to be the dominant gene in humans). Let’s say another hundred thousand years. [I wonder if the “next step” in our evolutionary future is going to be shaped by our knowledge and use of genetic manipulation, and/or cybernetic and nano-technologies.] That’s a pretty narrow window of opportunity in a Galaxy eight to nine billion years old. The chances of two species being “synced up”, and close enough to contact each other at the same space-time (in a galaxy 120,000 ly across) sounds pretty fooking small. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [January 18, 2017, 3:57pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/57 "2017-01-18T15:57:48Z")
> [@Trinopus](#): > > Someone or something is killing civilizations – cosmic berserkers – and those few that survive are keeping their heads down and maintaining radio silence. > > We’ll be contacted soon enough…and that’ll be the end of us! Imagine our surprise when the first alien radio message is “Shhhh! not so loud! Do you want _them_ to hear you??!” ---
**Author:** ![quimper](https://avatars.discourse-cdn.com/v4/letter/q/7c8e57/32.png) [@quimper](https://boards.straightdope.com/u/quimper)\ **Post date:** [January 18, 2017, 4:13pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/58 "2017-01-18T16:13:37Z")
> [@mlees](#): > > Imagine our surprise when the first alien radio message is “Shhhh! not so loud! Do you want _them_ to hear you??!” Hehe. This is (essentially) the plot for Cixin Liu’s [Three Body Problem](https://en.wikipedia.org/wiki/The_Three-Body_Problem) trilogy. I’m with Hawking: “Meeting an advanced civilization could be like Native Americans encountering Columbus. That didn’t turn out so well.” Relevant XKCD: [Fish](https://www.xkcd.com/1377/) ---
**Author:** ![Dale\_Sams](https://avatars.discourse-cdn.com/v4/letter/d/779978/32.png) [@Dale\_Sams](https://boards.straightdope.com/u/Dale_Sams)\ **Post date:** [January 18, 2017, 4:25pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/59 "2017-01-18T16:25:51Z")
> [@PatrickLondon](#): > > They didn’t turn out to be what we expected and whatever attempt at contact was made, somehow it simply became an inexplicable phenomenon: > > [As suggested here](http://www.campaignlive.co.uk/article/thinkbox-the-broadcast-red-brick-road/1419352) > > Or alternatively, they’ve been watching our TV programmes and thought better of it. Which brings up another idea. Creating fiction for amusement may be a very rare thing among sentient species. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [January 18, 2017, 5:16pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/60 "2017-01-18T17:16:28Z")
> [@chappachula](#): > > Easter Islanders lived for hundreds of years within their resources, till human greed and overpopulation ruined it… There is no reason to assume that an advanced alien civilization with no overpopulation would destroy its natural resources, and need to go hunting in space for new supplies. I suggest you check the history of easter island a bit more. It’s ecology and civilization collapsed before Europeans discovered it. Not saying that it wasn’t overpopulation and greed that caused it, just that it seems to be the natural state of things, and did not have anything to do with contact with western culture. You are correct that there is no reason to assume that an alien civ would do such, but there is evidence that our civ would, and has done such. It collapsed because they ruined their ecology by cutting down all the trees. They are actually a good analogy. They used up their resources before they were able to get to the point of bringing in new from outside. > [@Pantastic](#): > > So you agree with me that the argument that an intelligent species will spread to other solar systems as some kind of imperative is flawed. As a means to an end, I will agree that people moving to other solar systems for room is not an imperative. This does not mean that it will not happen as a consequence of other imperatives. > [@](#): > > There’s a LOT of minerals just dissolved in the ocean and buried in the mantle, and other than minerals used for nuclear fission can all be recycled at a trivial cost compared to the enormous costs of interstellar travel. This line of thinking ignores just how much mineral wealth is easily accessible, how cheap recycling is, and how expensive interstellar travel is. Yes, there are alot. But it is a finite amount, it is limited, it will be diminishing returns if we do mine the sea water as the mineral concentrations drop, and it really is not all that much compared to what is out there. > [@](#): > > Plus, if you send off people to another solar system decades or centuries from home, there is no reason to assume that the other system will decide to spend their lives in servitude to Earth, sending back resources indefinately. It seems inevitable that at some point they will decide to go independent, and if your ‘Easter Island’ thesis is true, that means the extinction of Earth. That’s assuming that you are going with the colonization imperialism model we have used on the earth. That would be a bad idea. First, we are certainly not going to start by going to other solar systems for resources, there are quite a number right here. We are going to start by mining asteroids, moons, maybe even the gas giants themselves. But, at a certain point, our space faring will have become good enough that sending a probe to a nearby star is not implausible. If our technology has advanced to the point of having self building technology (replicators), then we just send them out as well. They reproduce for a while, then start sending back raw materials. At some point, it will send off some self replicating probes to even more distant stars. It may take decades or even centuries for the first products to start flowing back, but once it does, it will be a continuous and exponentially increasing stream of material. (Well, at least until we consume the galaxy, but we should have probes out to other galaxies by then anyway.) If we want to be nice about it, we could set it up so that it doesn’t harvest any planets upon which it detects life, but that assumes that we would recognize it when we see it in all the forms it may take that we cannot even imagine. As far as how people end up there, I doubt we would use colony ships or anything that is considered transportation to get you from one point to another. We would build worlds. Hollowed out asteroids or even small moons. Take an asteroid 50 or so miles long, and just poke it on an orbit to get to another star within a few thousand years. Mine the asteroid and live and grow inside of it on the way. When you get close enough to the destination star system, your populations can move out of the mostly overcrowded and depleted asteroid, and move into new, fresh ones. I also doubt that at that point, people would be really recognizable to their 21st century ancestors as the humans that we currently know. [Previous page](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410.md?page=2) [Next page](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410.md?page=4)