# Why doesn't ET call us? **URL:** \ **Category:** Great Debates\ **Created:** [November 14, 2008, 12:38am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634 "2008-11-14T00:38:26Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [November 14, 2008, 5:44am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/21 "2008-11-14T05:44:50Z")
> [@Chronos](#): > > This is known as the [Fermi paradox](http://en.wikipedia.org/wiki/Fermi_paradox). The crux of it is that, given an intelligent species somewhere in a galaxy, it should only take a few million years (an eyeblink, compared to the time it takes for such a species to evolve) for that species to completely fill the galaxy. Given a whole bunch of assumptions, none of which have been proven. Thirty years ago, we thought interstellar travel would be relatively easy to accomplish. Bussard ramjets, Orion nuclear pulse propulsion, etc. Most of these ideas have turned out to be completely impractical. What we do know is that it takes an immense amount of energy to move between stars at anything remotely close to light speed, and if you’re not going a significant fraction of lightspeed, it’s going to take centuries. This is an enormous undertaking we as a species aren’t even close to being able to make. > [@](#): > > And once a species gets to the point where it’s spreading to multiple star systems (even just the very nearby ones), extinction should be nearly impossible. But we’ve never met any of them. Spreading to multiple star systems, in terms of establishing self-supporting colonies of the species, is something we can only guess at how to accomplish. We still don’t know how many habitable planets there are, or how far apart they are. If there is only one habitable planet for a species on average every 1000 light-years, establishing colonies would be an extremely daunting task. > [@](#): > > This leads to several possible conclusions: > 1: We’re alone in our galaxy. This pretty much requires stretching every term of the Drake equation to the limits of plausibility. Not at all. It seems increasingly likely that life is quite common in the universe, but we still don’t have a clue what it takes for intelligent life to evolve. Consider that after four billion years of evolution, only one species on this planet evolved to the point of being able to send radio waves into space. And all it would have taken would have been for one good asteroid strike in the last million years or so, or a major change in solar output, or the solar system passing through a dense cloud of gas, and our evolutionary chain could have been wiped out. We survived by the tiniest of threads. You can count down the ways in which the Earth might be very special indeed for the formation of intelligent life: - We have a stable sun - We are in an arm of the galaxy that is far enough away from the center that radiation is low enough for us to survive and matter density low enough that the sun and planets would be undisturbed for long periods of time. - We have a Jupiter-sized planet in just the right place to sweep out cosmic debris. - We have a large moon to create tides, and a tilt to our axis to give us seasons. - We managed to go four billion years without a single ecosystem destroying collision. - Our sun stayed stable enough for those billions of years to not fry or freeze life on the planet. - We avoided runaway greenhouses or other potential ecological disasters. - The dinosaurs were wiped out by a large impact, allowing mammals to thrive. And the list goes on. We still have the vaguest of notions of just how fragile our planet is, and just how unlikely the chain of events were that got us to this point. That’s because we only have a single data point. That’s why SETI is so important. > [@](#): > > 2: Intelligent species tend to go extinct before they develop the capability for interstellar travel. Maybe, but we’ve made it this far, and we’re not really all _that_ far from interstellar capability. This is a real possibility as well. Think of the flap over the new Large Hadron Collider and black holes. That concern was overwrought, but as we experiment with increasingly powerful energies and manipulate matter in increasingly sophisticated manner, perhaps we begin to walk a minefield of poorly understood forces just waiting for us to do exactly the wrong thing. > [@](#): > > 3: Other intelligent species are arising, but we just happen to be the first. This seems unlikely at first glance, but if intelligent species tend to drive almost-intelligent species extinct, then there might be an anthropic bias at work here. The universe has been around a long time, but we needed a few generations of stars to come and go to create the heavy elements we need for complex life. So we’re not that far from the theoretical start of the possibility of life, I’d think. I also think we have to consider this possibility - especially in conjunction with the notion that intelligent life may be quite rare. Let’s say a universe by this time should on average have 100 intelligent species - if so, it’s not that wildly unlikely that we’re the first. > [@](#): > > 4: Other intelligent species are out there and can reach us, but for reasons of their own choose not to. Some variant of the Prime Directive, perhaps? But while the Prime Directive makes for good stories, I’m not sure there’s any reason to expect that it’d be actually implemented. I think this is the weakest argument of all. It’s more science fiction than anything else. My gut feeling is that it’s a combination of all of the above except #4: Intelligent life is reasonably rare, it’s extremely difficult to move out of your solar system, it’s hard to maintain a technological culture long enough to create the technology needed to range out into the universe, and even if you do, it would take a very, very long time to spread out to the point where your species is essentially everywhere. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [November 14, 2008, 5:50am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/22 "2008-11-14T05:50:23Z")
It’s also worth considering that there may be Rumsfeldian ‘unknown unknowns’ that we have yet to consider. There are plenty of unknowns right now that we can’t explain - dark matter, dark energy, gaps in the standard model (still haven’t found the Higgs Boson), etc. But then there are the unknown unknowns - forces that may exist that we don’t even know about because we haven’t discovered their effects. There may be something out there yet that makes intersteller travel virtually impossible, or which makes life impossible except in very isolated areas or something. Thirty years ago, we weren’t discussing dark matter, because our science to date hadn’t uncovered any data that needed dark matter to explain it. A hundred and fifty years ago, we didn’t need relativity because we hadn’t made any observations that couldn’t be explained via Newton’s laws. Given the accelerating rate at which our understanding of the cosmos is growing, it would be presumptuous to think that we even know what all the questions are that need to be answered. ---
**Author:** ![Isamu](https://avatars.discourse-cdn.com/v4/letter/i/7c8e57/32.png) [@Isamu](https://boards.straightdope.com/u/Isamu)\ **Post date:** [November 14, 2008, 5:58am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/23 "2008-11-14T05:58:24Z")
They seeded the planet with us, a more primative version of themselves, as an organism which functions as a territorial marker, much in the same way that a dog pisses on a tree to mark it’s territory. They designed us not to be durable enough to escape the solar system, so they know we aren’t going anywhere. Why would they bother to contact _us_? Must go, it’s time for my pills now. ---
**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:** [November 14, 2008, 6:28am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/24 "2008-11-14T06:28:41Z")
Quoth **Peter Morris** : > [@](#): > > 5: They’ve been trying to call us for years, but we haven’t invented the spacephone yet, so we haven’t received their calls. > > 6: Communication across vast distances is flat out impossible at any level of technology. > > 7: cultural differences and language barriers make communication impossible. > > 8: We aren’t interesting enough to be worth talking to. > > 9: They don’t know where we are. Fermi wasn’t just talking about radio (or the equivalent) signals: He was talking about physical, in-the-flesh travel. An advanced civilization shouldn’t just have sent signals across the Galaxy, they should have sent _colonists_. Even at the much slower than light speeds that we can envision as actually being doable, it should still only take millions of years, which on cosmological or evolutionary timescales is an eyeblink. ---
**Author:** ![levdrakon](https://avatars.discourse-cdn.com/v4/letter/l/49beb7/32.png) [@levdrakon](https://boards.straightdope.com/u/levdrakon)\ **Post date:** [November 14, 2008, 6:34am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/25 "2008-11-14T06:34:35Z")
If we could do it now, we surely would. We’re explorers. We’re still learning. Hell yeah, we’d go out there. But getting to another star is pretty difficult. By the time we could reasonably do it, we may not want to anymore. Our minds might be blended with AIs so powerful we can virtually experience anything that could ever exist in our universe. Why bother actually doing it? Information-ally, or experientially, it’s meaningless. Or, perhaps we become immortal. Really immortal, like millions of years immortal. Jaunts between stars are insignificant amounts of time, and they are possibly out there right now, hiding behind our sun, or other planets, or in the asteroid belt. What’s 10,000 years or 100,000 years to them? They’re infinitely patient, and simply watching us out of idle curiosity once in awhile. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [November 14, 2008, 6:35am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/26 "2008-11-14T06:35:53Z")
> [@Sam\_Stone](#): > > The universe has been around a long time, but we needed a few generations of stars to come and go to create the heavy elements we need for complex life. So we’re not that far from the theoretical start of the possibility of life, I’d think. I also think we have to consider this possibility - especially in conjunction with the notion that intelligent life may be quite rare. Let’s say a universe by this time should on average have 100 intelligent species - if so, it’s not that wildly unlikely that we’re the first. I love that idea - that we’re the first race to develop technology and, perhaps, explore the stars. We’re the Old Ones! ---
**Author:** ![Mr\_Buttons](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Mr\_Buttons](https://boards.straightdope.com/u/Mr_Buttons)\ **Post date:** [November 14, 2008, 6:44am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/27 "2008-11-14T06:44:21Z")
> [@Peter\_Morris](#): > > 5: They’ve been trying to call us for years, but we haven’t invented the spacephone yet, so we haven’t received their calls. I kinda lean towards this one. In 1850, sending a message over anything beyond a telegraph seemed unimaginable. 160 years later we have cell phone, fiber optics, satellites, etc. So from 3 million B.C. til 1900 or so, we couldn’t receive any sort of wireless communications. That gives us about the past 106 years to pick up anything, and we never really TRIED to detect weak intergalactic signals until SETI was up and running. In another 105 years we might have discovered something from the LHC (or something else) that allows us to use the twin-particle anomaly thing (that thing where twin particles communicate faster than the speed of light) to have truly instant communication over millions of miles. We’re searching for signals that are familiar to us, that we’ve only known about for 100~ years. So we’re only going to find a civilization that’s on a similar time scale to our own. Does not carry a PhD in anything, just throwing out my WAG ---
**Author:** ![Cisco](https://avatars.discourse-cdn.com/v4/letter/c/ccd318/32.png) [@Cisco](https://boards.straightdope.com/u/Cisco)\ **Post date:** [November 14, 2008, 7:46am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/28 "2008-11-14T07:46:06Z")
> [@xtisme](#): > > Perhaps other intelligent species simply choose not to engage in exploration of space for whatever reason. After all there are lots of humans who think it’s a complete waste. Perhaps when a species gets to a certain stage of advancement they turn more inward (starting off by becoming obsessed with message board technology and eventually going to a completely virtual world :)). Maybe as certain technologies become available (like nano-tech) they don’t NEED to explore anymore and are content to simply exist on their home world, since all their material needs would be met and at least in theory they’d have control of their environment. Or maybe aliens are sufficiently different to humans that exploration isn’t a driving force in their cultures…maybe it’s even against their core beliefs or something. Perhaps to many species intelligence doesn’t translate to technology…and maybe technology itself is shunned. Like [Zenn-La](http://en.wikipedia.org/wiki/Zenn-La). > [@xtisme](#): > > I think we’ll find an earth like planet in my lifetime. Some might call me crazy but I’m starting to think we will find life or evidence of past life in our solar system in my lifetime. ---
**Author:** ![Mojo\_Pin](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mojo\_Pin](https://boards.straightdope.com/u/Mojo_Pin)\ **Post date:** [November 14, 2008, 8:11am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/29 "2008-11-14T08:11:49Z")
> [@Isamu](#): > > They seeded the planet with us, a more primative version of themselves, as an organism which functions as a territorial marker, much in the same way that a dog pisses on a tree to mark it’s territory. They designed us not to be durable enough to escape the solar system, so they know we aren’t going anywhere. Why would they bother to contact _us_? > > Must go, it’s time for my pills now. heheheh ---
**Author:** ![chowder](https://avatars.discourse-cdn.com/v4/letter/c/977dab/32.png) [@chowder](https://boards.straightdope.com/u/chowder)\ **Post date:** [November 14, 2008, 8:45am UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/30 "2008-11-14T08:45:26Z")
> [@Captain\_Carrot](#): > > They want nothing to do with us. If I were a member of a civilization that’s mastered FTL travel, I’d be hesitant to deal with Earth in any way. Exactly. “Visit Earth. are you mad?” “Those guys are fucking dangerous, stay well away” ---
**Author:** ![CutterJohn](https://avatars.discourse-cdn.com/v4/letter/c/91b2a8/32.png) [@CutterJohn](https://boards.straightdope.com/u/CutterJohn)\ **Post date:** [November 14, 2008, 12:24pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/31 "2008-11-14T12:24:48Z")
1. We’re all there is. 2. Apes and Angels. The time span between an intelligent species arising and becoming something not unlike gods is quite short on a geological time. Humans as humans have been around for 50-100k years. Another 1000 or so, and its quite possible we’ll have no need of spreading anywhere further than the solar system, or we might even all live in a computer or something, untroubled by the worries of the universe. Who knows? But regardless, its a remarkably short timespan as far as the universe is concerned, and the odds of another intelligent species reaching their climax at the same time as us is very, very slim. 3. But if there are others out there, and they know of us, they might very well leave us alone. Not because we are particularly bad creatures, as I feel confident that any species will have a similar amount of blood on their hands from growing up. Think of it… If we had an interstellar empire, and more worlds than we knew what to do with to exploit as we saw fit, we would certainly leave those that have burgeoning intelligent life alone. Theres far more planets than we need, so the tiny fraction that had the fantastic miracle of intelligent life would have a good possibility of being protected by the 31st century equivalent of the National Park Service. 1. We may simply not recognize the intelligent life when we see it, nor them, us. Imagine a race of Plasmids living on the sun, magnetohydrodynamics doing for them what chemistry does for us… Imagine one of their number being mocked for suggesting that life could form on the satellites, where temperatures are so unbelievably cold that solid matter exists! We would never have a clue about each other, In all likelihood. ---
**Author:** ![Captain\_Carrot](https://avatars.discourse-cdn.com/v4/letter/c/f0a364/32.png) [@Captain\_Carrot](https://boards.straightdope.com/u/Captain_Carrot)\ **Post date:** [November 14, 2008, 2:10pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/32 "2008-11-14T14:10:27Z")
> [@Sam Stone](#): > > - We managed to go four billion years without a single ecosystem destroying collision. Eh? To my knowledge, we’ve had several asteroid strikes that destroyed 80-95+% of life on the planet. > [@Sam Stone](#): > > - The dinosaurs were wiped out by a large impact, allowing mammals to thrive. So? What’s to say some species of dinosaur wouldn’t have developed intelligence? ---
**Author:** ![FoieGrasIsEvil](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foiegrasisevil/32/16638_2.png) [@FoieGrasIsEvil](https://boards.straightdope.com/u/FoieGrasIsEvil)\ **Post date:** [November 14, 2008, 2:21pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/33 "2008-11-14T14:21:41Z")
> [@Peter\_Morris](#): > > 8: We aren’t interesting enough to be worth talking to. This is what I keep thinking. It is the height of human hubris for us to assume that another species would desire to contact us, especially a species that has mastered interstellar space travel. Unless of course we had something they wanted, like vast water resources, or minerals or something. Or hot white women. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [November 14, 2008, 2:56pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/34 "2008-11-14T14:56:04Z")
> [@cmosdes](#): > > 1. They don’t exist (seems unlikely, but possible) In theory, the [Drake Equation](http://en.wikipedia.org/wiki/Drake_equation) could tell us how many intelligent and civilized species there are in the galaxy – but it’s useless because too many of the variables are not only unknown, but imponderable. Especially L. We don’t have any idea how long an industrial civilization can last. ---
**Author:** ![Sam\_Stone](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Sam\_Stone](https://boards.straightdope.com/u/Sam_Stone)\ **Post date:** [November 14, 2008, 2:56pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/35 "2008-11-14T14:56:28Z")
> [@Captain\_Carrot](#): > > Eh? To my knowledge, we’ve had several asteroid strikes that destroyed 80-95+% of life on the planet. > So? What’s to say some species of dinosaur wouldn’t have developed intelligence? 80 to 95% of all life is not ‘all’ life. Had one of those rocks been a little bigger, and wiped out the entire ecosystem, it could have set us back a billion years. Had it been big enough, it coudl have ended Earth’s ability to harbor life permanently. We still don’t have a handle on how likely such collisions are in other star systems. Maybe we won the galactic lottery. ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [November 14, 2008, 3:13pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/36 "2008-11-14T15:13:42Z")
I like Greg Bear’s take on it - the galaxy is full of wolves, and we’re a lost baby crying in the forest, wondering why no one is coming to help us. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [November 14, 2008, 3:16pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/37 "2008-11-14T15:16:54Z")
I recall Jodi Foster’s character in _Contact_ saying, “If we were the only sentient species in the universe, wouldn’t that be an awful waste of space?” :dubious: Yes, it would be. When rain falls on the ocean, that is an awful waste of fresh water. Nevertheless, rain falls on the ocean. ---
**Author:** ![twickster](https://avatars.discourse-cdn.com/v4/letter/t/ec9cab/32.png) [@twickster](https://boards.straightdope.com/u/twickster)\ **Post date:** [November 14, 2008, 3:19pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/38 "2008-11-14T15:19:20Z")
Why doesn’t ET call us? He/she/it is just not that into us. ---
**Author:** ![BrainGlutton](https://avatars.discourse-cdn.com/v4/letter/b/82dd89/32.png) [@BrainGlutton](https://boards.straightdope.com/u/BrainGlutton)\ **Post date:** [November 14, 2008, 3:19pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/39 "2008-11-14T15:19:59Z")
> [@FoieGrasIsEvil](#): > > This is what I keep thinking. It is the height of human hubris for us to assume that another species would desire to contact us, especially a species that has mastered interstellar space travel. > > Unless of course we had something they wanted, like vast water resources, or minerals or something. Or hot white women. Why? If **we** had mastered interstellar space travel, **we** would want to contact any sentient species that might be out there, simply out of curiosity. Or perhaps the “hubris” in the above is projecting our curiosity on other hypothetical sentient species, i.e., simply assuming it to be a concomitant of sentience. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [November 14, 2008, 3:25pm UTC](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634/40 "2008-11-14T15:25:20Z")
One possibility is that we’re unknowingly living in a preserve. Our section of the galaxy is ruled by the Interstellar Federation of Wise Aliens, who realize the importance of allowing lesser species like ourselves the independance to develop at our own rate without outside interference. So they decided to put our solar system off-limits to visitors and have blocked off any evidence of extra-solar intelligence, like interstellar radio signals, from reaching us. [Previous page](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634.md?page=1) [Next page](https://boards.straightdope.com/t/why-doesnt-et-call-us/472634.md?page=3)