# 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:** 5
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [January 19, 2017, 4:07pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/81 "2017-01-19T16:07:39Z")
> [@Pantastic](#): > > Non-mutating replicators that are built cheaply, never run into problems they can’t solve, never get out of control in your own system, and keep working forever are pure fantasy. Once you start invoking magical technologies, the answer to ‘why haven’t we been contacted…’ becomes ‘because things work according to what we understand of physics and your magic doesn’t happen’. Actually, self-replicating systems of this nature exist today, in thr form of animals. Of, course, no terrestrial animal is going to be functional for very long in the vacuum of space, but that is essentially “an engineering problem” (albeit one well beyond our current capability in biological engineering), and it is not unlikely that our first interstellar probes will be some combination of mechanical technology and highly modified organism adapted to long duration space travel. The biggest problems with travelling to another star system on any reasonable time frame are actually developing some kind of propulsion system with adequate propellant mass efficacy to achieve useful speeds, and the thermodynamics of dealing with waste heat produced by the propulsion and other systems necessary to keep the vehicle operating and instruments or occupants functioning. Stranger ---
**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 19, 2017, 4:08pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/82 "2017-01-19T16:08:11Z")
> [@Stranger\_On\_A\_Train](#): > > The reason “science” hasn’t found evidence of life elsewhere in the Universe is because I was careful to explicitly state, twice, that this was not what I was arguing. The statement to which I was responding: > [@snowthx](#): > > I find it interesting that discussions such as this often tap faith to explain why we are not alone, yet **science has not found any evidence at all to suggest there could be life anywhere else**. Do we accept science as fact or not? Emphases added. As we learn more about astronomy and organic chemistry, we get a better handle on how life _could_ exist elsewhere. At this point, it’d take an act of faith to decide that life _couldn’t_ exist elsewhere. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [January 19, 2017, 4:15pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/83 "2017-01-19T16:15:28Z")
> [@Stranger\_On\_A\_Train](#): > > Actually, self-replicating systems of this nature exist today, in thr form of animals. Of, course, no terrestrial animal is going to be functional for very long in the vacuum of space, but that is essentially “an engineering problem” (albeit one well beyond our current capability in biological engineering), So you’re denying that evolution exists, since you’re denying that animals mutate and change over time? That animals never fail to take over an environment (how does that even work if there are two competing species?)? That animals never get out of control on earth and need to be managed by humans? That animals never go extinct, maybe you’re a young earth creationist too? And dismissing the issues of animals functioning in airless void, high pressure atmospheres, high radiation environments (which increases the mutation problem BTW), no gravity, high gravity, and all of the realistic conditions as ‘an engineering problem’ is just funny. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [January 19, 2017, 4:23pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/84 "2017-01-19T16:23:41Z")
> [@k9bfriender](#): > > Now, if your contention is that civilization won’t last that long, and we will never get to that stage, then I don’t know that I disagree that that is a likely scenario. But, assuming that we manage to survive these upcoming bottlenecks, what limits do are you putting on our engineering capabilities? You’re the one putting major limits on our ability to reuse minerals, and presuming that we’re going to actually run out of materials in the solar system to the point that it makes sense to spend vast amounts of energy on interstellar resource extraction. > [@](#): > > We already have our resource extraction and preparation into consumer materials fully automated. No we don’t. We don’t have anything where you just throw a box at an uninhabited chunk of rock and builds probes, locates materials to extract, creates extraction equipment, extracts minerals, and sends them back home, then makes another starting box and sends it to another uninhabited chunk of rock. And that’s what your replicators need to be smart and capable enough to do. And also they need safeguards so they don’t accidentally try to mine inhabited areas, or mutate and start doing things other than what you want. > [@](#): > > As you claim that such technology is pure fantasy, can you quote to me the laws of physics that forbid such? It seems you are unfamiliar with Clarke’s third law. If you claim it’s not pure fantasy, can you point me to where we actually have equipment that does ALL of what you said with NONE of the problems I mentioned? Saying ‘what law of physics do my magical robots violate’ doesn’t move them out of the realm of fantasy. If it’s not fantasy, we should dump one of these on Mars as our next interplanetary project, and we’d be ready for a Mars base within a few years! ---
**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 19, 2017, 4:47pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/85 "2017-01-19T16:47:55Z")
> [@Pantastic](#): > > You’re the one putting major limits on our ability to reuse minerals, and presuming that we’re going to actually run out of materials in the solar system to the point that it makes sense to spend vast amounts of energy on interstellar resource extraction. Re-Use? Who said anything about reuse? Can you use your iphone at the same time as I use it? I think not. In that case, we are going to need to have one for each of us. The same with all other consumer materials, unless you have an idea of all of us sharing the same materials, or you are assuming that population growth will stop. And, as far as re-using them, well, there is some level of waste that is likely in every recycling cycle, so new materials will be needed to make up for this. I really don’t think you are thinking long term about this. I think you are thinking on the order of decades or centuries. This is not a long period of time. Try thinking on the scales of tens or hundreds of thousands of years to start. Then realize that there is no reason you shouldn’t be thinking on millions, tens of millions, hundreds of millions, and even billions of years. Do you realize that no matter our recycling efforts, the sun is gonna run out in just a few short billion years? Do you have a plan for re-using that? I would also point out that it is does not require vast amounts of energy, compared to the types of energy we will have access to at that time. > [@](#): > > No we don’t. We don’t have anything where you just throw a box at an uninhabited chunk of rock and builds probes, locates materials to extract, creates extraction equipment, extracts minerals, and sends them back home, then makes another starting box and sends it to another uninhabited chunk of rock. And that’s what your replicators need to be smart and capable enough to do. And also they need safeguards so they don’t accidentally try to mine inhabited areas, or mutate and start doing things other than what you want. Did I say that we have something like that? I don’t think so. I said that we have manufacturing processes where humans barely, if at all touch the product from the time it is mined to the time it goes on a shelf. Do you realize that it is computers and satellites that find mineral resources, not people with prospector picks? You do realize that it is giant automated mining machines that actually dig up the ore, not some guy with a shovel? Now, yes, humans are involved in these steps, at the moment, as computers have not advanced enough to not need the occasional judgement of a human, but that involvement is decreasing. As computer technology progresses, and they become better and smarter, humans will be more and more cut out of the loop, until we are essentially only making decisions based on our preferences and needs, not based on the best way to extract, refine and process materials. > [@](#): > > If you claim it’s not pure fantasy, can you point me to where we actually have equipment that does ALL of what you said with NONE of the problems I mentioned? Saying ‘what law of physics do my magical robots violate’ doesn’t move them out of the realm of fantasy. If it’s not fantasy, we should dump one of these on Mars as our next interplanetary project, and we’d be ready for a Mars base within a few years! You want me to point to equipment that hasn’t been invented yet? Okay… Or did you miss the part where I said that it is something that would come with technological development? Can you point me to where we had moon capable rockets in the 1820’s? That’s pretty much the same question you are asking. By your logic, if we didn’t have them in the 19th century, we could never have them. Do you not get that technology progresses? That we get better at doing things, we make better machines? Do you think that we will just suddenly stop the technological progress we have been doing the last couple hundred years? But, if you want to see where we have all that equipment, just look at the what brought your iphone to you. Look at that supply line, and tell me, what laws of physics prevent you from automating every step of the way? These are all just engineering problems, ones that are really not all that hard to solve, especially not when we are talking about thousands of years in the future, and access to a few orders of magnitude more resources than we currently have. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [January 19, 2017, 5:11pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/86 "2017-01-19T17:11:49Z")
> [@Pantastic](#): > > So you’re denying that evolution exists, since you’re denying that animals mutate and change over time? Do not ever misattribute me in this manner again, fuckwit. I said nothing of the sort and making this claim, even in some kind of jest is the height of offensiveness. Stranger ---
**Author:** ![Bone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bone/32/407_2.png) [@Bone](https://boards.straightdope.com/u/Bone)\ **Post date:** [January 19, 2017, 5:30pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/87 "2017-01-19T17:30:57Z")
> [@Stranger\_On\_A\_Train](#): > > Do not ever misattribute me in this manner again, fuckwit. I said nothing of the sort and making this claim, even in some kind of jest is the height of offensiveness. > > Stranger This is a warning for personal insults not appropriate for this forum. If you feel you must, the BBQ is right around the corner. [/moderating] ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [January 19, 2017, 5:32pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/88 "2017-01-19T17:32:56Z")
> [@Bone](#): > > This is a warning for personal insults not appropriate for this forum. If you feel you must, the BBQ is right around the corner. > > [/moderating] And the clear and unambiguous character defamation is not worthy of warning? Stranger ---
**Author:** ![Bone](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bone/32/407_2.png) [@Bone](https://boards.straightdope.com/u/Bone)\ **Post date:** [January 19, 2017, 5:34pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/89 "2017-01-19T17:34:59Z")
> [@Stranger\_On\_A\_Train](#): > > And the clear and unambiguous character defamation is not worthy of warning? If you are interested, please start a thread in ATMB and I would be glad to discuss it. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [January 19, 2017, 6:53pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/90 "2017-01-19T18:53:38Z")
> [@Bone](#): > > If you are interested, please start a thread in ATMB and I would be glad to discuss it. No, I don’t believe I’m going to do that. Between the permissiveness toward cunt-ass trolls and blatant defamation to the smash-cut modal window ads and the frequent redirect to scammy malware sites, I’m done with this board. Stranger ---
**Author:** ![Tibby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tibby/32/17030_2.png) [@Tibby](https://boards.straightdope.com/u/Tibby)\ **Post date:** [January 19, 2017, 7:11pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/91 "2017-01-19T19:11:38Z")
> [@Stranger\_On\_A\_Train](#): > > No, I don’t believe I’m going to do that. Between the permissiveness toward cunt-ass trolls and blatant defamation to the smash-cut modal window ads and the frequent redirect to scammy malware sites, I’m done with this board. > > Stranger I hope you will reconsider. You are one of a handful of posters whose input is appreciated by me and I’m sure many others on this board. ---
**Author:** ![iiandyiiii](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/iiandyiiii/32/7924_2.png) [@iiandyiiii](https://boards.straightdope.com/u/iiandyiiii)\ **Post date:** [January 19, 2017, 7:14pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/92 "2017-01-19T19:14:42Z")
> [@Tibby or Not Tibby](#): > > I hope you will reconsider. You are one of a handful of posters whose input is appreciated by me and I’m sure many others on this board. Seconded – you’re a wonderful poster, **Stranger** , and you add a lot to this board. Please don’t go! Hell, I’ll gift you a membership if you’ll stay – at least that will get rid of the ads. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [January 19, 2017, 7:25pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/93 "2017-01-19T19:25:30Z")
Thirded. **Stranger** , you are very well-known and liked here. I tried to PM you, but you don’t accept PMs. Please stick around. Pretty please. ---
**Author:** ![running\_coach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/running_coach/32/15836_2.png) [@running\_coach](https://boards.straightdope.com/u/running_coach)\ **Post date:** [January 19, 2017, 7:26pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/94 "2017-01-19T19:26:15Z")
> [@Tibby or Not Tibby](#): > > I hope you will reconsider. You are one of a handful of posters whose input is appreciated by me and I’m sure many others on this board. Couldn’t agree more. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [January 19, 2017, 7:32pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/95 "2017-01-19T19:32:20Z")
> [@Pantastic](#): > > How are you going to gather the immense resources needed to create an interstellar colony ship and go through the long and highly technical process of creating the ship when other people are lighting you on fire? . . . Seriously, the same way the Huguenots got to England. If the ships exist, they’ll find a way to get passage. Religious freedom has been behind many migrations here on earth. If interstellar passage is possible at all, this could become one of its purposes. A frontier implies frontiersmen. ---
**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 19, 2017, 8:02pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/96 "2017-01-19T20:02:31Z")
To bring this back to the OP (note this is very rough back of the envelope style math) Let us consider a space shuttle sized craft, to accelerate it to a small fraction (1/100) of the speed of light would require 10,000 \* the amount of power that it takes to launch from orbit, and with simplified math it would still take 430 years to travel the 4.3 light-years to Alpha Centauri which is the nearest star system. But if you actually want to stop at Alpha Centauri you need to also slow down which will roughly require the same amount of energy to accomplish. The combined fuel weight for the shuttle was around 4.4 million pounds, so with conventional rockets you would need to some how get the ship and 44 billion pounds moving that fast. While there are options technologies like light sails they are only useful for a flyby and not a visit within practical time frames. Think about that time scale, Sir Francis Drake invading was invading Florida 430 years ago. As the astronaut would be exposed to at least 0.66 sievert of radiation per year, and would need to be able to reproduce for at least 10 generations without succumbing to cancer a shuttle sized craft wouldn’t have the population diversity to survive that journey. Without new discoveries and new physics human interstellar travel is no where close to being practical. ---
**Author:** ![Gatopescado](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gatopescado/32/5711_2.png) [@Gatopescado](https://boards.straightdope.com/u/Gatopescado)\ **Post date:** [January 19, 2017, 8:07pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/97 "2017-01-19T20:07:56Z")
They don’t contact us because we are on the “Ignore” list. ---
**Author:** ![Pantastic](https://avatars.discourse-cdn.com/v4/letter/p/3bc359/32.png) [@Pantastic](https://boards.straightdope.com/u/Pantastic)\ **Post date:** [January 19, 2017, 8:53pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/98 "2017-01-19T20:53:59Z")
> [@Stranger\_On\_A\_Train](#): > > Do not ever misattribute me in this manner again, fuckwit. I said nothing of the sort and making this claim, even in some kind of jest is the height of offensiveness. I didn’t misattribute you, I quoted you directly. I originally said: > [@Pantastic](#): > > Non-mutating replicators that are built cheaply, never run into problems they can’t solve, never get out of control in your own system, and keep working forever are pure fantasy. Then you said: > [@Stranger\_On\_A\_Train](#): > > Actually, self-replicating systems of this nature exist today, in thr form of animals. So I then asked if you’re denying that evolution exists, because by using ‘animals’ as an example of ‘non-mutating replicators’, you’re making a claim that animals don’t mutate, but mutations are one of the major drivers of evolution. If you aren’t denying that mutations happen in animals, then they’re not actually an example of “self-replicating systems of this nature”. If you are, then you’re denying that one of the major drivers of evolution happens. But, go ahead and leave the board because you’re insulted that someone asked if you believe in evolution when you claimed that animals do not mutate, I can’t stop you. ---
**Author:** ![Ramira](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ramira/32/344_2.png) [@Ramira](https://boards.straightdope.com/u/Ramira)\ **Post date:** [January 19, 2017, 8:56pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/99 "2017-01-19T20:56:27Z")
No he was not, that is a gross distortion of his statement. ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [January 19, 2017, 9:20pm UTC](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410/100 "2017-01-19T21:20:40Z")
**Pantastic** : You’re dealing with one of the smartest people on this board. Trust me, he knows all about evolution. [Previous page](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410.md?page=4) [Next page](https://boards.straightdope.com/t/why-haven-t-we-been-contacted-by-extraterrestrials/777410.md?page=6)