Talk:Fermi paradox/Archive 6
|This page is an archive. Do not edit the contents of this page. Please direct any additional comments to the current talk page.|
- 1 "They do not exist because...humanity is the first in the universe/...they do not exist yet
- 2 Fermi principle
- 3 N~L?
- 4 Too young?
- 5 Kinda arguments
- 6 Definition of life?
- 7 UV light hitting open water, and thus a lifeless planet s l o w l y producing oxygen, which then prevents life from developing (oxygen strong reactant)
- 8 They are deliberately keeping quiet
- 9 Galactus ate them
- 10 They are deliberately keeping quiet
- 11 Reference no. 36
- 12 Stephen Webb on the transition from prokaryotic cells to eukaryotic cells
- 13 Ill advised??
- 14 Signal compression
- 15 The "Cosmic-Orgasm" hypothesis
- 16 They didn't have / ran out of oil
- 17 Clarke's law
- 18 Wordiness let loose
- 19 Non-Interference / Our Bad Assumptions
- 20 Human civilization is detectable from space pic
- 21 Source for "other unique factors"
- 22 Statement removed
- 23 Removing "critiques" of depletion argument
- 24 What about Cosmic Noise and signal degradation?
- 25 They call themselves Hungarians
- 26 Probes
- 27 European aliens
- 28 Speeding minds
- 29 The 'duh' response
- 30 Problem
- 31 Intelligence versus Sapience
- 32 The article
- 33 They are here unobserved
- 34 Earth is purposely isolated...
- 35 Both 'Rare Earth' and that life evolves in many, MANY directions.
- 36 Possible evidence
- 37 request for comment on removed text re: "Great Silence"
- 38 Nominal merge of Silencium universi [sic]
- 39 Failed speciation is systematically garbage collected
- 40 "too alien"
- 41 Under the section "Too Dangerous to Communicate".
- 42 Recent changes in the probabilities
- 43 It is pointless to try to communicate
- 44 "Humans were created"
- 45 /* as to growing evidence of reproductive problems among mammals in microgravity
"They do not exist because...humanity is the first in the universe/...they do not exist yet
This keeps getting deleted. I put in my version yesterday, and it was deleted despite the fact that I clearly marked it as a stub. I couldn't cite anything because I was in a hurry and did not feel like searching for any citations. Since, I think, the purpose of this article is to be a full list of potential explanations of the Fermi paradox, as well as defining and describing the paradox itself, this cannot be ignored. Lockesdonkey 13:03, 20 June 2006 (UTC)
- At least a second deletion along these lines has also occurred. (220.127.116.11) 24 September 2006
- It is not impossible that ET edit wiki. There is considerable evidence that ET wants us to think they exist, but not be certain ET exist. Some ET may be uncomfortable with us thinking that there are no ET. Some humans want us to keep an open mind about the existance of ET.Ccpoodle (talk) 14:15, 7 January 2008 (UTC)
- It's not the purpose of the article to include all potential explanations, because many potential explanations defy logic and/or science. The "humanity is the first", although obviously not impossible, isn't logical (and becomes stupefyingly illogical if one words it as "first in the universe" rather than "first in the galaxy"). At most, it might be worth a parenthetical aside in the "Rare Earth hypothesis" section (e.g. "Intelligent life has not arisen (or has not arisen yet) on other planets due to blah blah"). Even if you had a citation for this, I doubt it would be worth any more mention than that. KarlBunker 13:56, 20 June 2006 (UTC)
- You can't just handwave this possibility away with a quip. Life is extremely complex, and how do you know that it is not rare for this very reason? A soup full of potential amino acids along with other organic compounds is far, far more simple than a cyanobacteria, with both photosynthetic pathways, DNA, RNA, and protein synthesis, and the ability to build up many sugars, proteins, amino acids, fats, and possibly other membrane compounds or enzymes, often from scratch or carbon dioxide, with a few of the building materials possibly sometimes coming from other organisms. Most people on Earth do not know of any other planets upon which life has independantly arisen besides Earth, and the ultimate difficulty of abiogenesis is not necessesarily a completely known factor. First in the universe, well probably not, but first in the galaxy? This is at least one way to possibly explain the Fermi paradox and it is not genuinely intellectually honest to not include this possibility unless these factors are far more known and understood than they generally are. (18.104.22.168) 24 September 2006
- I actually had thought of adding it myself to the "Do not exist and never did" section. To say we are the first is just another way of saying we are alone. In Rare Earth and elsewhere you do see it noted that the Universe's first stars would likely not have planets, generally as a matter of metallicity (the first stars would not have had enough iron etc. for planet formation). Marskell 16:22, 20 June 2006 (UTC)
- This is only a special case of the "too far apart in time" concept. Doesn't matter if they come before and after, or just after, it is all just temporal displacement, and therefore is covered in the article already, otherwise we had better add "They do not exist because...humanity is the last in the universe/...they all died out already." as well - Vedexent (talk • contribs) - 19:44, 24 September 2006 (UTC)
I also think that this explanation is most likely to be the correct one. There is no reason to believe that the conditions in the galaxy is constant over time, indeed we know for certain that metallicity will increase over time. Moreover, observe that the age of planet earth (3-4 billion years) is in the same order of magnitude as the age of the universe (15-20 billion years). I wouldn't say we are the first, but we are among the first and this situation may change in future, since there is no reason to believe that once the conditions were appropriate for life to develop that it only happened on earth. Basically, if we weren't among the first ones we wouldn't wonder why we haven't met other civilisations.
To me it seems that the hypothesis is sufficently different from the rare earth or too far apart in time hypothesis. Hence, I will add it, unless somebody gives a more substantial reason why it shouldn't than just stating "it is illogical" as Karl Bunker did above. --Thorsten 20:44, 26 March 2007 (UTC)
- You've said that you find this theory the most likely, but I don't see where you've explained how it differs from "too far apart in time." You seem to be saying that because it's your favorite variation on "too far apart in time", it ought to get more attention.
- In any case, note that content added to Wikipedia is supposed to be based on WP:Reliable sources, not on "Here's my favorite theory." RedSpruce 01:38, 27 March 2007 (UTC)
It's not so much that it should get more attention, it is rather that it should be mentioned at all. As far as reliable sources go, it seems that the whole article is rather speculative and while it shouldn't cover "every possible" explanation - I do find it rather surprising that the one which I consider as the correct one is omitted. I have been looking at SETI pages and other places do find a reference but haven't found it anywhere but here. However, I agree that wikipedia shouldn't be the place to introduce new speculations. --Thorsten 21:17, 27 March 2007 (UTC)
- It should be noted that Jehovah's Witnesses hold this cosmological view to some extent with some believing that after the restoration of Earth to Paradisaic conditions humanity would then spread out into the Universe to reside on habitable planet throughout the rest of the universe. —Preceding unsigned comment added by Sochwa (talk • contribs) 03:17, 5 November 2007 (UTC)
- What we need is a "not worthy of much serious consideration" category and to focus our efforts on ths "worthy of serious consideration" categories, with due attention paid to any information relavent to the not worthy subject matter. WFPMWFPM (talk) 19:53, 2 November 2008 (UTC)
- The belief that the lack of evidence conclusively demonstrates the non-existence of extraterrestrial civilizations is known as the Fermi principle.
- Conclusively is unappropriate and unscientific. All conclusions are tentative and we don't have all possible evidence on any subject. Fermi would not have said that, unless he was drunk at the time.Ccpoodle (talk) 14:34, 7 January 2008 (UTC)
I'm having trouble finding this. Anyone know how it got this name? Is this something Fermi agreed with? 22.214.171.124 16:39, 25 July 2006 (UTC)
- I also dispute this, without a source I suggest mention of 'the Fermi principle' be removed. As far as I know Fermi had nothing to do with stating that the lack of evidence of anything conclusively demonstrates anything. A logical fallacy such as that seems to me to be foreign to any scientist or mathematician, and I can find no evidence to support its existence, therefore conclusively proving the non-existence of the Fermi principle. (forgive the jest) User:Pedant 21:42, 17 August 2006 (UTC)
- The anon already removed it. Marskell 22:19, 17 August 2006 (UTC)
The idea that N approximately equals L, that the number of civilizations in the Milky Way right now approximately equals the ratio of the average lifespan of a civilization to the entire timespan of life/civilization being possible in the Milky Way. FriendlyRiverOtter (talk) 04:44, 6 February 2008 (UTC)
Er, isn't the universe just too young to have an abundance of life?
According to various Wikipedia articles, the universe is 13.7 billion years old, while our own solar system is 4.6 billion years old: thus, following on from the mediocrity principle and assuming an average time period of about four and a half billion years from the birth of a planetary system to the evolution of a species capable of producing radio waves, we limit the actual amount of time involved to the last nine billion or so years.
Now, Big Bang nucleosynthesis had not actually produced enough elements to allow for Earth-like life in the first place, so the very first 4.x billion year old planetary systems wouldn't have produced life anyway. We would have to wait for those first stars to perform stellar and supernova nucleosynthesis. If we jump ahead another "generation", we are now reduced to only about the life time of our own solar system, ie: if there is going to be lots of life in the universe, then it would only be getting off the ground now, right? 126.96.36.199 (talk) 03:36, 15 March 2008 (UTC)
- I think this goes beyond the scope of this talk page, but briefly: that argument is based on a lot pre-suppositions. Even if we assume everything you state as a given, it still presupposes the same evolutionary rate everywhere, but in the 'generational' scheme of things, a billion or two years head start for some localities, shouldn't be underestimated. Hope that makes sense. El_C 03:44, 15 March 2008 (UTC)
- The big stars that die as supernova and spew their elements into space don't live very long. So scientist think there were plenty of elements for life and planets just a few billion years after the big bang. So it's perhaps a correction to the numbers of the Drake equation, but not nearly enough to explain the Fermi Paradox. There is at least some experimental data on this - when stars with planets are found, their age can be estimated, and so far the ones that we have found are both older and younger than the sun. Of course these are bigger gas planets, not small rocky ones, but the current thinking is that the gas planets were created around rocky cores. So there were plenty of elements at least a billion years before the sun was born, which is plenty to support the paradox, given that spread across the galaxy takes (we think) much less than this. LouScheffer (talk) 13:34, 15 March 2008 (UTC)
- Even better:
- All of the largest, brightest, and hottest stars possible in our Universe (speculated Population III stars) had already been born, lived for a million years, and died within a few hundred million years of the Big Bang. (This may be why most galaxies have supermassive black holes in their cores.) They all ended as supernovae, spewing metals liberally through a much smaller and more crowded, more active star-forming Universe than we live in today.Vendrov (talk) 05:32, 28 December 2008 (UTC)
Definition of life?
UV light hitting open water, and thus a lifeless planet s l o w l y producing oxygen, which then prevents life from developing (oxygen strong reactant)
Origins: Fourteen Billion Years of Cosmic Evolution, Neil deGrasse Tyson and Donald Goldsmith, W.W. Norton & Co.: New York, London, 2004, page 237:
“What made Earth’s atmosphere relatively rich in oxygen? Much of it came from tiny organisms floating in the seas, which released oxygen as part of their photosynthesis. Some oxygen would have appeared even in the absence of life, as UV from sunlight broke apart some of the H2O molecules at the ocean surfaces, releasing hydrogen and oxygen atoms into the air. Wherever a planet exposes significant amounts of liquid water to starlight, that planet’s atmosphere should likewise gain oxygen, slowly but surely, over hundreds of millions or billions of years. There too, atmospheric oxygen would prevent life from originating by combining with all possible nutrients that could sustain life. Oxygen kills! Not what we usually say about this eighth element on the periodic table, but for life throughout the cosmos, this verdict appears accurate: Life must begin early in a planet’s history, or else the appearance of oxygen in its atmosphere will put the kibosh on life forever.”
The reaction you are considering is: 2H2O = O2 + 2H2. The equilibrium strongly favors the reactants, that is, water. There will not be a slow build up of O2 over time, rather there will be a constant, very low level of O2, due to the very small equilibrium constant of this reaction. <<((:-:))>>0X0<<((:-:))>> (talk) 15:14, 31 December 2008 (UTC)
They are deliberately keeping quiet
Hello folks... I am a newbie at this so please forgive etiquette errors.
A while ago I tried to add the possibility that they do exist but keep a low profile because of sterilisation risk from other groups. The 'crying baby in the woods' scenario. This is certainly a possibility if not a large one. It kept getting removed.
Perhaps the quality wasn't good enough... no argument there... I would be happy to collaborate or even submit drafts until it is ready for inclusion.
If it is not article quality but rather content at issue I would like to know why this can not be mentioned when clearly it actually is a real possibility. (I do not 'believe' it is the case... but it is a possibility I am willing to consider.)
- This is a well known hypothesis, and is already covered in the section 'They choose not to communicate'. That in turn references the section which comments that perhaps civilizations destroy others, which in turn references both popular literature and science article (of which Brin's 'The Great Silence' is perhaps best known.). So it's indeed a reasonable concept, but it's already covered in the article. LouScheffer (talk) 14:38, 25 November 2008 (UTC)
Lou you have done a lot of good work here but I think you may have missed something. You are correct that this possibility is discussed, but not where and how you mentioned. (perhaps it has changed over time...) In the section on 'It is the nature of intelligent life to destroy others' the possibility of aggressive sterilisation is mentioned and the section ends with a link to 'They choose not to interact with us' but that section does not at all mention the possibility that they choose not to interact with us because 'it is potentially dangerous to communicate with other civilisations'.
So the last sentence of 'It is the nature of intelligent life to destroy others' does mention that others may keep quiet out of fear but there is no corresponding subtopic in the 'They choose not to interact with us' section. And given that the 'SEE' link indicates that you will find a discussion, or at least a mention, in the linked-to area (5.2) you would expect a subtopic called something like: 'Communicating with other civilisations is considered dangerous'
If the topics are well laid out you should be able to get a sense of the arguments by simply looking at the content headings.... if you do you will see that this possibility does not make the list. It definately should be in the area of 'They do exist but we see no evidence'.
Galactus ate them
- This is covered in detail in the article, with references. LouScheffer (talk) 19:04, 26 May 2008 (UTC)
They are deliberately keeping quiet
This is already covered in 'They choose not to communicate'. That references the section that perhaps civilizations destroy others, which in turn references both popular literature and science article (of which Brin's 'The Great Silence' is perhaps best known.).
Reference no. 36
- It took only about 30 seconds to find this article with Google, and replace the link. You might consider contributing by fixing dead links, it's a lot faster than waiting for someone else to do it, and improves the article for everyone else. LouScheffer (talk) 22:52, 26 May 2008 (UTC)
Stephen Webb on the transition from prokaryotic cells to eukaryotic cells
Prokaryotic cells have rigid cell walls or rigid cell membranes. They have a nucleus that is in contact with the rest of the cellular contents. Different prokaryotic cells often have very different biochemistries and thus adapt to different environments in this fashion, but frequently have the same external shape.
Eukaryotic cells have a flexible cell membrane. They have a separate, distinct nucleus. Different eukaryotic cells adapt to different environments with differences in size and shape. To maintain their shape and integrity, eukaryotic cells have a cytoskeleton composed of actin filaments and microtubules. Actin filaments resist pulling. Microtubules resist compression. This cytoskeleton also has the ability of being able to pull the cell into a variety of temporary shapes, such as for phagocytosis (food engulfing). The cytoskeleton can also marshall the organelles into various positions, and can also allow the eukaryotic cell to increase in size (partial summary of Stephen Webb, pages 206–208). FriendlyRiverOtter (talk) 18:02, 14 June 2008 (UTC)
And now, for one of Stephen’s main points---
If The Universe Is Teeming With Aliens . . . Where Is Everybody? Fifty Solutions To The Fermi Paradox And The Problem Of Extraterrestrial Life , Stephen Webb, Copernicus Books, Praxis Publishing: New York, 2002, page 209:
“Was it inevitable, this transition from a primitive cell to the awesome complexity of a modern eukaryotic cell? Or was it a fluke? These are difficult questions to answer, not least because the many steps involved in the transition occurred so long ago. One of the first steps must have been loss of the rigid cell wall, even though this would have been fatal to most organisms that attempted it. (Penicillin, for example, works by blocking the formation of bacterial cell walls. Without a rigid wall to protect them, most single-celled organisms are vulnerable to attacks from the environment.) Disposing of the cell wall was ultimately extremely useful because it enabled phagocytosis to occur. But phagocytosis evolved at a later date and thus could have provided no immediate benefit to the organism that lost the wall. Evolution has no foresight; unless an organism can survive in the here-and-now and pass its genes on to offspring, any potential it may possess will be lost. Somehow, in ways not yet understood, some organism managed to employ new structural proteins—actin and tubulin—and develop a cytoskeleton that helped mitigate the loss of the wall. How likely was this to happen? We simply do not know.” —Preceding unsigned comment added by FriendlyRiverOtter (talk • contribs) 18:11, 14 June 2008 (UTC)
- I think the wording is correct. If the world is indeed destroyed by some physics experiment, presumably it was ill-advised, in that it was thought to be safe, when in fact it was not. The alternative is that it was thought to be unsafe, but tried anyway. In this case it was not ill-advised (the advice was correct), but hopefully less likely... LouScheffer (talk) 19:20, 29 July 2008 (UTC)
I can't believe there is no referrable discussion to note the idea that any optimally compressed signal is indistinguishable from white noise. Nearly everybody I talk to about the Fermi Paradox is well aćquainted with this maxim. It can't be just scientific folklore, somebody must have committed it to a publication we can point to. -- Cimon Avaro; on a pogostick. (talk) 09:05, 4 August 2008 (UTC)
Shannon himself showed that any optimally compressed signal looks like noise. There has been lots of other work, but the most relevent reference (in my opinion) is probably:
The physical limits of communication or Why any sufficiently advanced technology is indistinguishable from noise, by
Michael Lachmann, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany and Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501
M. E. J. Newman, Department of Physics and Center for the Study of Complex Systems, University of Michigan, Ann Arbor, Michigan 48109 and Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501
Cristopher Moore. Computer Science Department and Department of Physics and Astronomy, University of New Mexico, Albuquerque, New Mexico 87131
The "Cosmic-Orgasm" hypothesis
There are many problems with this addition:
- It's way too specific. There are many reasons civilizations might turn inward, and hedonism of all kinds is only one of them. And even the main reason is hedonism, there are many possible sub-reasons - video games, fine dining, etc. in addition to cyber-sex.
- The reference you quote does not say anything about this hypothesis (search for cosmic, or Fermi, etc.) The point of a reference is to back up the text argument, and this one does not do that.
- Sure, the drive towards sex is strong, but people here on earth suppress it for all kinds of reasons, so to call it inevitable seems way too strong. (Even assuming aliens feel the same way we do about sex...)
- You can debate whether this goes under "technological singularity" or "They choose not to communicate". It takes both - a much improved technology, then the will (or lack of it) on their part to use it. But the same is true of many other arguments in this article - we need to decide where it fits best. At most a cross reference to the other section is needed, as used elsewhere in the article.
- The reference format is wrong, as well. Web site references should be written in Wikipedia like this "KurzweilAI.net". Retrieved 2008-09-10.. Also, this web site is quite dubious as a source. It has no owner, a person who is responsible by name for what appears on the site, and hence no-one who's reputation is on the line if any portion is not correct. There is no named publisher as well. Both of these are normally required for a backing reference.
- Without a good reference this verges on original research (OR in Wikipedia parlance). This is any idea that is covered in Wikipedia without first appearing in a fairly reputable third-party publication. There is certainly nothing wrong with original research, and it may well be correct, but Wikipedia is not the right place for it.
I just dicovered this page (I am a new user) in which you expose your reasons. There are a few issues that you got wrong, in others, I concede. I am going to make the idea more clear and also link it to an article posted to my labs web page at syracuse university. I hope this would be enough for citation's sake. On the other hand, the webpage kurzweiai.net belongs to Ray Kurzweil, if you dont know him you better stop editing articles and start reading his books. And lastly (for now), I never mentioned sex. I mentioned orgasmic-like, which refers to the extreme pleasure perceived when a reward center is highly activated (not necessarily by sex). It is in fact unrelated to any specific activity. The confusion about sex could come from the last statement, cosmic onanism, but that was a joke. You guys are too serious... —Preceding unsigned comment added by 188.8.131.52 (talk) 19:37, 11 September 2008 (UTC)
- Hi! Thanks for responding here. A few points: (1) A link to your lab's web page may or may not be enough. Unfortunately, lots of cranks have their own web pages, and otherwise publish their own ideas (generally referred to as self-publication). So the very first level of credibility is where some reasonably reputable source, not the author or their friends, discusses the idea. A link to your own page, or your groups, may also be considered a conflict of interest. (2) Of course I know of Kurzweil and it *looks* like the page is his, but it's not attributed. Most sources need to be attributed to have much credibility. After all, the whole phishing industry works by creating good reasonable looking but false web sites. (3) It's generally considered good form to make the fixes first, then put the material back. Just putting it back unchanged does not add much to the discussion. Also, a look at the history shows 3 different folks, all fairly experienced editors, have deleted it, where only you (I think) have added it. (4) You might want to consider logging in rather than editing anonymously. Of course an idea can be valid no matter where it originates, but many folks take named editors a little more seriously. (5) If you end your posts on discussion pages with four tildes - ~~~~ it will sign and date your posts automatically. LouScheffer (talk) 20:07, 11 September 2008 (UTC)
They didn't have / ran out of oil
Suppose the existence of life analogous to humans, but on a planet without petroleum. The industrial revolution never occurs, and no space programs take flight. That's why they don't visit. Or they use up all their petroleum before achieving alternative fuels, and end up ground-bound for the remainder of their lifespan. (Or perhaps they're dolphinoid, language users without hands.) --BlueNight (talk) 06:33, 15 September 2008 (UTC)
- All of these ideas are already discussed in the article. Since there are many possible reasons for the Fermi paradox, to keep the article short enough the reasons are described quite tersely. LouScheffer (talk) 13:51, 18 September 2008 (UTC)
Wordiness let loose
The Drake equation has been used by both optimists and pessimists with wildly differing results. Dr. Carl Sagan, using optimistic numbers, suggested as many as one million communicating civilizations in the Milky Way in 1966, though he later suggested that the number could be far smaller. Skeptics, such as Frank Tipler, have put in pessimistic numbers and concluded that the average number of civilizations in a galaxy is much less than one. (Note that, even though there is at least one civilization in our galaxy, the average or "most likely" number of civilizations in our galaxy as described by this equation may still be smaller than one. In other words, the fact that there is at least one civilization in our galaxy does not mean that this was a likely outcome. This is an excellent example of anthropic bias. No civilization can use itself to estimate the average number of civilizations in a galaxy, since if there was not at least one civilization the question could not arise.)
This paragraph states that the probability for life to emerge in a galaxy can be less than one. If there are 10 galaxies, and the probability is 0.1 that means, that statistically speaking, only one galaxy will inhabit life. It doesn't matter that we are a civilization that asks this question and nor does it matter that we live in a galaxy that happens to inhabit life. I don't see the point. Do you want to say that just because we are a civilization and we live in a galaxy that inhabits life, the probability still can be smaller than 1?!
In other words, the fact that there is at least one civilization in our galaxy does not mean that this was a likely outcome.
This is the same as saying the probability of intelligent life in a galaxy is less than 1. This has been stated already.
No civilization can use itself to estimate the average number of civilizations in a galaxy, since if there was not at least one civilization the question could not arise.
I don't understand this line, either. Are you trying to vaguely imply the fact that the probability can't be 0, because there is at least 1 civilization in the universe, ours? What does it have to do with anthropic bias? This is just plain, simple statistics that the average person would have already understood from the main article. You're just saying the same thing over and over again in 5 lines which has been already said before.
Yes, probability can be less than one. But no civilization can get a measurement of less than one in their own galaxy - that's the bias
??? We are speaking of probability or chances. It involves the examination of a set of elements, which includes the various outcomes of galaxies. You are mixing things up. Our galaxy is just one element in the set. Just because life exists in the Milky Way now, that does not mean the likelihood of life in a galaxy at any given time is 100%. —Preceding unsigned comment added by Bizso (talk • contribs) 22:11, 18 December 2008 (UTC)
There is nothing wrong with the probability argument. But suppose a civilization checks it's own galaxy and finds exactly one civilization, itself. What does that tell you? Very little - it's consistent with 1, 0.1, 0.01, etc. If you use your won galaxy as sample, you will always get a count of at least one, no matter what the true average is. That's the bias. LouScheffer (talk) 00:46, 19 December 2008 (UTC)
Non-Interference / Our Bad Assumptions
I believe the Fermi Paradox is flawed, for several reasons: 1) There is no conclusive evidence that intelligent life does not exist. Rather, there are plenty of witness accounts (substantiated or not) of people claiming to have been contacted by some extraterrestrial, intelligent life form here on earth. The problem is that we have not as of yet been able to definitively confirm or refute these reports. However, I believe this will happen soon. 2) I believe it is highly possible that such reports are indeed true, and that they are already here -- but they are so much more advanced than us that they view us as curious animals to be experimented on. They may view Earth as a huge petri dish and thus are trying not to disturb it too much for scientific reasons. 3) We humans do make a lot of bad assumptions, as I believe we may actually be among the more primitive of sentient beings out there, if any exist. I used to think the SETI program was cool, until I realized we may be sending out a signal inviting HOSTILES to stop by and take over our planet. Any civilization intelligent enough to get here could surely wipe us out without much problem. 4) I also think people aren't taking into enough consideration various space/time issues. Who's to say that the alleged visitors already witnessed have ALREADY answered our calls, but due to technological advances were able to get here before we even sent the signal? Why would this not be possible, based upon Einstein's theory of relativity?
|This page is an archive. Do not edit the contents of this page. Please direct any additional comments to the current talk page.|
Human civilization is detectable from space pic
"A composite picture of Earth at night. Human civilization is detectable from space." this is the words under the Earthlights dmsp.jpg picture but says in Earth it says this "The Earth at night, a composite of DMSP/OLS ground illumination data on a simulated night-time image of the world. This image is not photographic and many features are brighter than they would appear to a direct observer." so the pictrues are not "real".i think something shold be done with this image in this article.Confront (talk) 04:43, 8 March 2009 (UTC)
- I think the assumption is that any observing civilization that made it all the way over here would likely have the technology to produce at least a similar image. Equazcion (talk) 12:26, 24 September 2009 (UTC)
Source for "other unique factors"
There may also be other unique factors on which our civilization is dependent.
Who seriously believes this requires a citation? "You need some kind of proof to establish that something we do not know about could have an effect on this extremely complex issue in a way we have not noticed."
That's kind of the basis of science, isn't it? The idea that, on any given day, something you believe can be proven wrong with the right evidence? If this needs a 'citation,' that 'citation' needs to point to an article on the scientific principle... 184.108.40.206 (talk) 18:16, 24 April 2009 (UTC)
I just came in to say, radio technology is a relatively new technological achievement for humanity; I quickly checked wiki/radio and it was only developed only just over 100 years ago, which means (according to earth history) humans have been in their present form for about 200,000 years yet we only developed this radio technology in the last 100 (±50?) So there could be plenty of extraterrestrials who simply haven't spent 200,000 years evolving, no? And there are plenty of sources of 'unintelligent life' here on earth... but seriously, there could be anything that technically qualifies as life (bacteria) through aquatic life up to all the non-sentient life forms we have on earth, or even primitive hominids who just hasn't developed radio technology yet.
My one concern is, are there any naturally occurring radio waves? Maybe as a result of supernovae, pulsars, etc?
ps: just wanted to say i'm following, er 'watching' this per the checkbox above the 'save/show preview/show changes' buttons, I assume that will send me an email notification when someone else edits this discussion page?
And also I put my comment here because I wasn't sure if it should go in a new topic or not so I just put it here. Dave 01:59, 21 October 2009 (UTC) Dave 02:06, 21 October 2009 (UTC) autosine bot keeps adding stuff even tho i'm entering the 4 tildes.... Dave 02:06, 21 October 2009 (UTC)
I've taken out the following from the section "They choose not to interact with us":
"Humans can hardly communicate with species living on earth who sharing similar genetics."
I was going to correct the grammar (because I'm fussy like that), figuring that it wasn't an unreasonable point; but the more I looked at it the more I wasn't convinced it belonged where it had been put. I couldn't find anywhere else to put it, though, so I took it out for the time being. - Mithvetr (talk) 14:11, 12 June 2009 (UTC)
On earth several species have developed with varying amounts of intelligence including Dogs, Chimpanzees, Elephants, and Whales. Even with "Man's Best Friend", we have minimal, at best, understanding of their knowledge and native communication.
Removing "critiques" of depletion argument
I don't see the point of debating peak oil issues on this page. It seems to be too far away from the topic of the Fermi paradox to debate peak oil on this page. Request to remove this paragraph. —Preceding unsigned comment added by
Critics of the resource depletion argument point out that an energy-consuming civilization is not dependent solely on fossil fuels. Alternate energy sources exist, such as solar power which is renewable and has enormous potential relative to technical barriers. For depletion of fossil fuels to end the "technological phase" of a civilization, some form of technological regression would have to invariably occur, preventing the exploitation of renewable energy sources.
- I agree this is too specific. But the general argument that renewable resources might run out, and the counter argument that renewable resources exist, seem OK. I reworded to make this a little clearer, but more work might still be done. LouScheffer (talk) 06:12, 16 December 2009 (UTC)
- Definitely off topic. The idea is that civilizations might run out of resources. It's spoken of theoretically, there is no need to bother with an assessment of the likelihood of it happening. The point of the proposal is that perhaps civilizations run out of resources not that we on Earth will or won't or the likelihood of it happening. It's a fair point that the likelihood of it happening on Earth rolls up to the likelihood of it being the reason why we don't observe aliens but in my opinion, an involved discussion of this is distracting. I'll work on it too. BobKawanaka (talk) 14:38, 16 December 2009 (UTC)
Fossil Fuels are only one type of "Resource". We also have a finite quantity of metals including Uranium available; most, but not all can be recycled and reused.
One of the basic premises of the Fermi Paradox is that "Given intelligent life's ability to overcome scarcity, and its tendency to colonize new habitats, it seems likely that any advanced civilization would seek out new resources and colonize first their own star system, and then the surrounding star systems." Yet... if we used today's technology, it would take a Herculean effort that consumes extraordinary amounts of resources to send a "colony ship" to the nearest star. And, that might comprise of a few hundred individuals that endure generations of travel, confinement, risk, and scarcity, followed by an extraordinary effort to colonize a new planet. It is unlikely that any significant amount of materials will be returned in retrograde trade back to earth. Unless we arrive at a point where the sun and our solar system can no longer sustain life, it is unlikely that resource depletion would lead to interstellar colonization. Humans have an insatiable curiosity for what is on the other side of the fence, but is that alone adequate driving stimulus to colonize multiple stars?
This also depends on the inability of the "advanced civilizations" to learn to live in harmony with the nature with which they co-evolved.
Actually, if the stimulus for leaving one's solar system was something like impending supernovae, then the colonization of new stars would progress at an extremely slow rate.
What about Cosmic Noise and signal degradation?
At this point we can barely detect planets the size of Jupiter, generally by means of inferring their existence without actual direct observation.
From the nearest star, Proxima Centauri, 4.2 light years away, would any of Earth's TV, Radio, and Satellite broadcasts be detectable? What if we took a very focused laser and directed it at the projected position of the star 4.2 years from now, would that be detectable?
- It should be apparent then from these results that the detection of AM radio, FM radio, or TV pictures much beyond the orbit of Pluto will be extremely difficult even for an Arecibo-like 305 meter diameter radio telescope! Even a 3000 meter diameter radio telescope could not detect the "I Love Lucy" TV show (re-runs) at a distance of 0.01 Light-Years!
It is not clear that anything that Earth is capable of broadcasting would be detectable 5 or 500 or 500,000 or more light years away, unless it was actually directed in a very powerful, but narrow beam to the exact location where the alien star system will be centuries from now when the beam arrives.
And, if you take our current "listening technology", we scan each section of space and listen for very brief intervals before moving onward. Assuming we are broadcasting a narrow beam for a few seconds at each projected star location... would they be listing for our broadcast at the same instant?--Keelec (talk) 04:44, 14 January 2010 (UTC)
They call themselves Hungarians
This theory was jokingly suggested in response to Fermi's paradox by his fellow physicist, Leó Szilárd, who suggested to Fermi that extraterrestrials "are already among us - but they call themselves Hungarians", a humorous reference to the peculiar Hungarian language, unrelated to most other languages spoken in Europe.
- I noticed this was unsourced so I added Crick, Marx, and Webb, but the reference is about much more than just the Hungarian language, so the current version is not accurate. For a good overview, see Webb, p.28. I think this needs to be rewritten. Viriditas (talk) 09:37, 26 January 2010 (UTC)
The number in The Guardian January 18, 2007 contrasts with number on the wiki page
Guardian it would take 10bn years, roughly half the age of the universe, to explore just 4% of the galaxy.
Wiki If interstellar travel is possible, even the "slow" kind nearly within the reach of Earth technology, then it would only take from 5 million to 50 million years to colonize the galaxy.
I'm not sure, but I think most numbers are applicable to the Milky Way Galaxy alone. If so, I expect the Guardian number to be in error. As far as I understand the search for ETs in other Galaxies is another story. —Preceding unsigned comment added by 220.127.116.11 (talk) 12:42, 26 January 2010 (UTC)
- The source given in the article assumes that the colony ships travel at 0.1 c, that is hardly "nearly within the reach of Earth technology". Using a speed of 10 km/s, one gets ~2 billions years.
- The Guardian is a reliable source, don't expect it to be in error. Get another reliable source which contradicts it. Paradoctor (talk) 14:20, 26 January 2010 (UTC)
- Fermi realized that any civilization with a modest amount of rocket technology and an immodest amount of imperial incentive could rapidly colonize the entire Galaxy. Within ten million years, every star system could be brought under the wing of empire. Ten million years may sound long, but in fact it's quite short compared with the age of the Galaxy, which is roughly ten thousand million years. Colonization of the Milky Way should be a quick exercise.
- "Colonization with Von Neumann machines is exponential": I'm afraid this is a misunderstanding coming from analogy with biological exponential growth. While the latter surely exists, it is metabolic
rate"speed" that limits this kind of growth, not (locomotive) speed. In the case of space colonization, metabolic rate is insignificant as compared to probe speed. If you have a source for the "exponential" claim for von Neumann probes, please cite it.
- The SETI page referring to to Ward, Peter Douglas; Brownlee, Donald E. (16 January 2000). Rare earth: why complex life is uncommon in the universe. Springer. ISBN 9780387952895. Retrieved 27 January 2010. is certainly an RS, but IMHO it appears to presume that the probes can travel at 0.01c, which is still far from "within reach". We need a source for the "within reach" claim. A page citation, preferably a quote from the book which details the "ten million years" claim would also be a good idea.
- Just had a look at your userpage: Hi yourself! ;) Paradoctor (talk) 23:35, 27 January 2010 (UTC)
- "Colonization with Von Neumann machines is exponential": I'm afraid this is a misunderstanding coming from analogy with biological exponential growth. While the latter surely exists, it is metabolic
- It is not speed that is exponential. Regardless of self-replication, a probe at 0.01 c can still travel from one end of the Milky Way to the other in 10 million light years (which is still a short time). I would not like to dive into the technology too much, but I think a solar sail can reach speeds up to 0.3 c, which is an order of magniture faster than what we need. But I really would not like to invent the technology here to travel at those speeds, because I expect an advanced civilization to be much better in it than we are. Second, why would a Von Neumann machine not replicate at an exponential rate? In fact it's mentioned in the wiki article self-replicating spacecraft as part of the theory. It allows the machine to colonize all star systems instead of just travel from one side of the Milky Way to the other on its own. SvenPB (talk) 10:45, 31 January 2010 (UTC)
- "not speed that is exponential": That's right, and that is the problem. It is speed that limits colonization, and this speed is constant. The only question is how large it is. Any significant fraction of c is not "within reach", I'm afraid. Unless you have a source for that?
- "why would a Von Neumann machine not replicate at an exponential rate": Because it cannot get at the required resources fast enough. Starting from a given point, the volume of available material is , and the radius of the colony increases as . As you can see the growth of von Neumann colonies is polynomial, not exponential. I corrected the article correspondingly. Paradoctor (talk) 13:50, 31 January 2010 (UTC)
A person living in the Americas in 1491 might well have asked "If there are people across the ocean, why aren't they here?", and concluded that such people don't exist. The article talks about the tendency of intelligent species to colonize new habitats, but even crossing the ocean on a leaky sailing ship is tremendously easier than colonizing another planetary system. We can send millions of people across oceans to set up new colonies on Earth, but it is highly unlikely that any species could ever deal with overpopulation problems by shipping excess population into space. Truly suitable planets for colonization might be very rare - the biology might be completely incompatible. It's unlikely that a virus could infect a species from another planet, but a bacteria might to quite well against the colonists. The planet's biology might be loaded with chemicals that are poisonous to the colonists, but beneficial to the native species. This would mean that the colonisists might have to resort to terraforming, which could add centuries. A species spreading out to take over the whole galaxy would require that the species have an overwhelming compulsion to spread through the galaxy as fast as possible. We have no such compulsion, if we did, we'd be much farther along than we are with space travel. The Fermi Paradox misjudges how compulsive species are likely to be in regards to colonizing other planetary systems.--RLent (talk) 19:44, 28 January 2010 (UTC)
- I like the analogy, but I'm afraid this has little to do with the article or the literature on the Fermi paradox. I've heard the argument that they don't feel compelled to colonize before, but this has two problems: It doesn't explain why they don't communicate, and it doesn't explain the observed fact that species fill all available niches. All other arguments you mentioned fall under categories already covered by the article. If you can find reliable literature on "lacking motive even when feasible", please add it. Regards, Paradoctor (talk) 23:38, 28 January 2010 (UTC)
- I disagree and think this is in fact the answer/resolution of the paradox. Have looked over the current state of this space of articles, i.e. Seti, CETI, etc., and note that some consolidation especially performing the merge of those two is called for. Typically and if one is rationalistic, as I am, always, the resolution of paradox, involves a doxastic operation, the retraction or revision of false belief that is the basis of the paradox. Since its first expression, the concept implicit in Fermi's question, that the number of contemporary scientific civilizations in the universe as a whole must necessarily be much greater than 1 has only gained force with the discovery of extrasolar planets, the density of planet formation and so on, so the resolution by answering that there's noone there is unavailable. A resolution I'm not seeing developed is that there is a rich cosmopolitan culture which we are simply not yet advanced enough to observe by analogy with the title of this thread. Imagine a very isolated Amazonian tribe in the current time which has had no contact with the outside world. Radio frequency communications of modern society are available all around it but it is 1) beyond its means to access it and 2) in the modern era, some social advancement since the first genocidal contacts of the mainstream of world society with such groups might cause them to be protected. These two points, one of which is touched on (that communications are not observed because they would be harmful) are I believe the resolution to the paradox. If there is a rich cosmopolitan culture of independently evolved beings of widely varying kinds, it's reasonable to assume that some moral order would have arisen as it has to some degree in human society and this would condition first contact independent of the norms of a particular ET culture. As far as the nature of the contact, it seems to me this would have to be by direct mental contact, mediated by signal transmission means unknown to our level of development in order to overcome the language barrier. Returning to the Amazonian Gedankenversuch, suppose instead a tribe of Australopitihicenes who have not yet developed the physiological basis for human language were coeval with modern humans and a functioning radio or TV were to fall into their hands. Would they see it as communication? In a similar way the less tenable horn of this dilemma would, I believe, be resolved. That's the alternative I don't see developed and which would be an alternative to "They are here unobserved" which would be "There is communication but we lack the sophistication to process the signals". 18.104.22.168 (talk) 02:16, 13 February 2010 (UTC)
- "I disagree and think this is in fact the answer/resolution of the paradox": Ok, but this is an encyclopedia. What we need here is reliable sources. Are there verifiable, reliable sources holding these views? Then, by all means, add them. Otherwise, our opinions have to be considered original research, I'm afraid. Paradoctor (talk) 12:00, 13 February 2010 (UTC)
This edit mentions the idea that different "thought speeds" could prevent communication. Note that in Dragon's Egg (1980), which may very well have inspired Sagan, a ratio of 1:400000 is surmounted. A footnoted quote of Sagan's argument would be helpful. Paradoctor (talk) 18:00, 30 January 2010 (UTC)
The 'duh' response
Since the thread above sort of trails off, its point is "duh: because EM radio transmissions are limited by c". We are oblivious to the actual means by which (copious) communications are taking place which of course would have to surmount this fact. The "paradox" is that people think ET would a) wait for a signal with that time domain, b) not have been aware of it (c as a fundamental constant) or given it practical consideration, and c) not have found other means by which to effect such communications. The obvious answer for why a "Great Silence" by the means looked for is that they are not the means used. 22.214.171.124 (talk) 04:35, 14 February 2010 (UTC)
- Well, we need sources. You are more than welcome to add to the collection. :) Paradoctor (talk) 08:08, 14 February 2010 (UTC)
It is the nature of intelligent life to keep silence
It is possible that Great Silence occurs because of most civilizations in the Universe prefer surrogate Pseudo-METI profanations and do not make serious METI ???
Intelligence versus Sapience
Life may be natural and universal, and so may be intelligent behaviour, but as on Earth, where there are a number of species demonstrating intelligent behaviour, humanity is alone. That is, humans possess sapience uniquely. I think this reasoning should be added to the main entry, - --Extramural —Preceding undated comment added 01:09, 11 March 2010 (UTC).
This is a really good article, which gives the reader a well rounded, and in-depth view, of the topic. And so far I have only read half the article. Really good job. It certainly deserves the Featured Article rating.----Steve Quinn (formerly Ti-30X) (talk) 17:01, 14 March 2010 (UTC)
They are here unobserved
In reference to the following:
Rather than edit war, let's discuss it. It seems silly to keep this out entirely, as the section is clearly about theories in which alien life is present on Earth, yet unobserved. I'm in favor of mentioning that rather than it being 'possible', stating "some have claimed" instead. That seems consistent with preventing a small fringe theory from overtaking more reputable analysis. Perhaps a burden of providing more links to prove the proponents of this theory are more than simply the two listed? Bakkster Man (talk) 15:54, 25 May 2010 (UTC)
- Like, er... what is there to discuss, man? Just take a good look at this juicy list of political scandals of the United States, and also this (not quite as juicy as the previous) list of political scandals in the United Kingdom, and then ask yourself: are these people in power really capable of keeping alleged alien contact a secret when they cannot even keep their own bloody shenanigans a secret?
- Furthermore, there is not one journalist anywhere who would not fall over himself/herself to get "a scoop" over their journalistic rivals on the subject of alleged alien contact cover-up, and newspapers would pay millions to anyone who 'spilled the beans' on the matter.--IVAN3MAN (talk) 18:29, 25 May 2010 (UTC)
- Wiki isn't supposed to determine the truth, just collect the information. The only question here should be if this is notable, or a fringe group. Considering we're talking about the theory that aliens exist among us but are unobserved, one might consider the entire section fringe. The questions should really be; are there a significant number of people subscribing to this theory (or is it a fringe-of-the-fringe), and are there citable sources. If this is a sufficiently large movement amongs the group who claims aliens are here and unobserved, they should be added, probably along with a link mentioning that even the other people thinking they are here unobserved think they are crackpots (to prevent lending credibility). Bakkster Man (talk) 19:06, 25 May 2010 (UTC)
- RE: "Wiki isn't supposed to determine the truth, just collect the information."
- As far as I understand, Wikipedia's policy on fringe theories is "to separate the wheat from the chaff" by collecting information from various but reliable sources, and that Wikipedia itself does not become the validating source for non-significant subjects, such as government conspiracy theories of hiding "The Truth™" from the public -- which is what Dr. Steven M. Greer of "The Disclosure Project" is alleging.
- As to the question of whether that group is noteable or fringe, Wikipedia's statement on identifying fringe theories mentions, as an example, conspiracy theories -- ideas which purport to be scientific theories, but have little or no scientific evidence to support it.--IVAN3MAN (talk) 23:26, 25 May 2010 (UTC)
1. The "They are here unobserved" section needs expansion. This article is full of absolutely unfounded theories, random ideas and speculation, while theories that present actual proof, popular support or are much more likely are underrepresented.
2. "Conspiracy theory" is a discursive weapon which is seldomly applied according to its proposed definition. There are better was to point out weaknesses than name calling.
3. There are no peer-reviewed journals on exopolitics, so please stop to pretend that there is a scientific side of this and a pseudoscientific one.
4. The wording "it is also possible" is the most accurate one. Who is honestly disputing the fact that this is a possibility? Neither is it a fringe theory such as "Other advanced civilizations don't have radio technology" - THAT is a fringe theory. No one believes that to be true. But a large part of the population believes that aliens exist here on earth and are hidden by the government.
5. We're not even talking facts here, but theories. Still, there is proof for the theory that aliens are on this planet, but there is none supporting many of the other fringe theories.
6. The old "governments can't keep secrets secret" argument is invalid, as first of all you would have to have a list of all the crimes that were indeed kept secret (Who's got that? I see.), and second of all the Manhattan Project showed that hundereds of thousands of people can work in secrecy for a prolonged time.
7. The old "journalists will uncover it" argument is invalid, as many many horrific crimes are not covered or discussed by the media due to advertising customers, governmental orders, laws, spy plants, ownership and systematic slander. This is all verifiable, with numerous examples. See Wikileaks for an Update.
8. The theory that aliens are here unobserved should even be considered one of the most plausible ones, even regardless of the fact that there is proof supporting it. If I would be flying with an helicopter over an ant colony the reason why the ants won't recognize me won't lie in my inability to build and live in ant colonies, I just have superior technology, superior intellect and are outside of the sensoric spectrum of an ant. That doesn't mean that I don't live on the same planet. People have to resolve their personal issues, such as hubris, before looking at this. If aliens traveled here, they are extremely advanced compared to us. Consider that with all its consequences for a moment. Metaferon (talk) 17:05, 21 June 2010 (UTC)
- I don't think conspiracy theory is inaccurate here. The disambiguation page's definition is "A conspiracy theory alleges an event and/or events to be secretly influenced by a premeditated group and/or groups of powerful people or organizations working together". Yes it's dismissive, but it's also true in the case of the gov't keeping alien knowledge to itself with no firm evidence as proof. That said, it's not our job to write the argument based on our arguments, only to document notable arguments from published sources.
- I read the cited article (Google Books version here), and he gives book time to the subject of government coverup. He roundly decides that it is highly unlikely. At the same time, however, he presents that this is a popular theory, even though there is little evidence.
- "As surveys consistently show, a majority of Americans believe flying saucers are visiting Earth right now; the proportion of Europeans holding this belief is smaller, but is still significant. Many people even believe that a flying saucer crashed at Roswell, New Mexico, in late June/early July of 1947 (suspiciously close to the time of Arnold's sighting), and that the US military recovered alien bodies from the qreckage. Nevertheless, sciense is not a democratic process. No matter how many people believe in the truth of a particular hypothesis, scientists will accept the hypothesis (and then just provisionally) only if it explains many facts with a minimum of assumptions, if it can withstand vigorous criticism, and if it does not run counter to what is already known." -p. 30
- It seems reasonable to make reference to this as a 'pop-culture' hypothesis (note that even conspiracy theories can be notable) which is not considered by most scientists as valid, because it provides no evidence (despite it being one of the few hypothesis on the topic with the opportunity to provide such evidence). It seems silly to remove reference to the most commonly held view, even if it is unscientific. Let's simply add it, and mark is as popular with scientific dismissal. Thoughts? Bakkster Man (talk) 18:46, 21 June 2010 (UTC)
- I took a look at the section in question and I have discovered, what appears to be a questionable pargraph. I will paste it here:
- "Carl Sagan and Iosif Shklovsky argued for serious consideration of "paleocontact" with extraterrestrials in the early historical era, and for examination of myths and religious lore for evidence of such contact. Many religions, of course, cite "deities" from the heavens with great powers unknown to man. Old Testament stories of Gabriel's trumpet, and the giving of laws to Moses, might theoretically reflect alien efforts to guide or assist primitive man. In this view, there is in fact ample evidence of alien visitation. It is simply ignored out of habit, or because of the sacred religious traditions that have grown around those incidents."
- Here is the reference cited: <ref>Shklovski, I.S and Carl Sagan. Intelligent Life in the Universe. San Francisco: Holden-Day, 1966. </ref>
- I have read a lot of Carl Sagan, and even though it has been awhile, I am sure that he never "argued for serious consideration of 'paleocontact' with extraterrestrials in the early historical era...".
- I recall Carl Sagan stating no (scientific) evidence has been presented which proves we have been visited by intelligent extraterrestrial beings. Not one peice of phyical evidence has been presented. That was a paraphrase, because I do not recall the exact statement, or statements. Essentially, however, that is what he said. I also got the idea that he would welcome physical (empirical) evidence which proved the existence of such extraterrestrials. He was a an empirical scientist on a very deep level. That statement probably needs to be removed. Also, this is an attempt of proof by appeal to authority, and, sorry to say, has no place on Wikipedia. All the most notable astronomers can line up and say that we have been visited by extraterrestrials. That is not a problem. The problem is, where is the physcical evidence which backs up these statements?
- Next, this statement: "Old Testament stories of Gabriel's trumpet, and the giving of laws to Moses, might theoretically reflect alien efforts to guide or assist primitive man " This is WP:SYN and appears to be opinion, supposition, and is not WP:NPOV. Furthermore, I am guessing that by using the word "theoretical" it may appear that it is OK to have this statement as part of this article. That would probably be an inaccurate assumption. A scientific theory is "expressed as quantifiable properties". "A scientific theory is constructed to conform to available empirical data about such observations." In addition, anything that cannot be supported by empircal, or physical evidence, such as ideas, or concepts are in the "realm of philosophical theories as contrasted with scientific theories".
- That is followed with this: "In this view, there is in fact ample evidence of alien visitation". This statement, to begin with, is inaccurate. It essentially states that a point of view gives validity to evidence that is not evidence in the first place. There then appears to be a statement of fact "there is ample evidence...", which is unsubstantiated, and it appears to be an unsubstantiated conclusion. Sorry to say, but this borders on WP:SYN, and maybe WP:OR.
- The next statement is a point of view an not WP:NPOV. It is simply ignored out of habit, or because of the sacred religious traditions that have grown around those incidents. Also much of this statment is made up of "weasel words". WP:WEASEL
- Also the last pargraph in this section appears to have no relation to the article, or this section. It is simply off topic for one thing. Also, it can be taken as a slant (or sleight) against Hungarians and the Hungarian language.
- Thanks for your time----Steve Quinn (talk) 03:42, 22 June 2010 (UTC)
- I guess I have two more things to add here. First, if the Sagan-Shklovsky paragraph is based on a book, then that book is probably somehow based on fringe theories. On the other hand, even if such a book appears to present a balanced view, such a balanced view can only be opinons for the exsitence of visting extraterrestrials, and evidence against the existence of such beings. The books I have in mind would be authored by Jerome Clark, or any other UFO author trying to present a balanced view. Second, this book, "Intelligent Life in the Universe". by I.S. hklovski, and Carl Sagan. (San Francisco: Holden-Day, 1966), which is cited as a reference in the article, is riddled with scientific inaccuracies. See book review here by Öpik, E. - Book Reviews: Intelligent Life in the Universe. Irish Astronomical Journal, Vol. 8, p.94. 1967.
- Also a Pdf copy of this work is here. Thanks again. ----Steve Quinn (talk) 05:20, 22 June 2010 (UTC)
Earth is purposely isolated...
Under this section I read: "A related idea is that the perceived universe is a simulated reality. The planetarium hypothesis holds that beings may have.. blah blah.."
I confess, it may on first glance seem far-fetched, but when you even accommodate hypotheses in the sense of a 'simulated reality' (which, right here, is as far-fetched as it can be), there would, at least I find, be another "version" suitable to be added here. Perhaps anyone read that book "Biocentrism" by Robert Lanza? What I'm driving at, in a broader sense than depicted in the book itself, is by extension something quite similar than what Wheeler (and some others) termed the 'Participatory Universe'. Obviously this also harks back to a (very hard, or even ultimate) version of the Anthropic Principle. Well, in terms of the theory of Biocentrism, there is, and, by necessity or simple logic, can only be life on planet Earth. Especially Lanza's Biocentrism is very radical, no question, yet this alone doesn't disprove it. Moreover it wouldn't have to be considered 'hard science' in the strictest sense in order to be admitted on Wikipedia - otherwise, this article at hand should lose a lot of weight anyway. (As, for instance, the mere concept of a 'simulated reality' isn't falsifiable, and therefore certainly not science.) Biocentrism, would it be true, at any rate could easily explain the Fermi Paradox. Because this universe, as we know it, would be realized only in our (i.e. conscious beings of Earth) consciousness and be generated by it. All the stars, and galaxies "out there", wouldn't be really there as long as we don't observe them and would even then exist merely in form of images from a telescope or on a computer screen, etc. (As far as I understand, even Biocentrism wouldn't necessarily rule out ET in other universes, should they exist.) Well, yes, this, in principle, is what Lanza, and some others, do state. And maybe actually believe. So what? As I said, even J.A. Wheeler did - at least - speculate in a similar direction with his so called Participatory Anthropic Principle (PAP). Whether or not you like it: Such hypotheses are possible and legitimate solutions to the Fermi Paradox, counterintuitive, as they might feel. I would like to see something out of this line of thought be mentioned in the article, even if only briefly?! Zero Thrust (talk) 22:36, 9 July 2010 (UTC)
- Reminds me of Schrodinger's Cat! which is of course a topic of genuine investigation (if only in thought experiments) When obviously, Obviously the cat is either alive or dead and well before we look at it, . . . well, maybe not so quick.
- Only have one question, if a radio astronomer believes SETIs are likely, will he or she see what he or she expects to see? FriendlyRiverOtter (talk) 20:40, 29 July 2010 (UTC)
Both 'Rare Earth' and that life evolves in many, MANY directions.
In our No other civilizations have arisen subsection, we emphasize the 'Rare Earth' thesis, even including a free-floating, see-also blue link, and it is an important thesis, with a well-known book of that title.
SETI: A Critical History, Part III Implications of the expanded ETI discourse for SETI, Chapter 10. Inflection http://www.daviddarling.info/encyclopedia/S/SETI_critical_history_inflection.html
from a 1979 conference, second published edition of the proceedings:
"[Ernst] Mayr later elaborated on his critique.
- "It is interesting and rather characteristic that almost all the promoters of the thesis of extraterrestrial intelligence are physical scientists.... Why are ... biologists, who have the greatest expertise on evolutionary probabilities, so almost unanimously skeptical of the probability of extraterrestrial intelligence? It seems to me that this is to a large extent due to the tendency of physical scientists to think deterministically, while organismic biologists know how opportunistic and unpredictable evolution is." [ellipses at web site]
See also: http://books.google.com/books?id=EH86AAAAIAAJ&pg=PA24&lpg=PA24&dq=almost+all+the+promoters+of+the+thesis+of+extraterrestrial+intelligence+are+physical+scientists&source=bl&ots=YjzQgQV_sm&sig=MovDHjh8SAXOC6Bhtb6wQbiyD_o&hl=en&ei=tpxdTNzMEZn_lQfOvZD6CA&sa=X&oi=book_result&ct=result&resnum=1&sqi=2&ved=0CBIQ6AEwAA#v=onepage&q=almost%20all%20the%20promoters%20of%20the%20thesis%20of%20extraterrestrial%20intelligence%20are%20physical%20scientists&f=false
"Some 20 years ago when I argued a great deal with the astronomer Donald Menzel . . . "
"What is most remarkable is that for about 3000 my nothing very spectacular happened . . . "
There are some cosmological features that seem very unlikely and puzzling. I'm thinking of http://en.wikipedia.org/wiki/CMB_cold_spot (WMAP cold spot - which could be a giant array of super effective Dyson spheres or something like that) and http://en.wikipedia.org/wiki/Dark_flow (dark flow). There was another incident where a distant large radio source suddenly disappeared. I believe the article could benefit from metioning these things. —Preceding unsigned comment added by 126.96.36.199 (talk) 11:06, 13 August 2010 (UTC)
- Are you talking about the "Wow!" signal, or is this something else? FriendlyRiverOtter (talk) 01:04, 17 August 2010 (UTC)
- No, it wasn't the "WOW!" signal. It was an object - possibly a star, galaxy or new thing - that was clearly detectable for some time and then apparently disappeared. It wasn't as interesting as I had recalled because it didn't SUDDENLY disappear but just faded away, making it sound more like a super- or hypernova.
The story is here: http://www.skyandtelescope.com/community/skyblog/newsblog/28244844.html?pageSize=0 During the google search I found another SETI item I hadn't known before: http://en.wikipedia.org/wiki/Radio_source_SHGb02+14a —Preceding unsigned comment added by 188.8.131.52 (talk) 22:39, 17 August 2010 (UTC)
- DISCOVERY OF AN UNUSUAL OPTICAL TRANSIENT WITH THE HUBBLE SPACE TELESCOPE, Accepted to ApJ: September 8, 2008, Barbary, Dawson, Tokita, et al. (The Supernova Cosmology Project), page 3 (right before “3. SPECTROSCOPY” section). http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.1648v1.pdf
- “ . . . The transient increased in brightness in each of epochs four through eight before finally declining in the ninth epoch, resulting in a rise time of approximately 100 days (Fig. 2). . . ”
request for comment on removed text re: "Great Silence"
A while back, I added the text
(Note that the term "Great Silence" is often used synonymously with "Fermi paradox", as in the Brin paper which apparently coins the term.)
It has been removed. I'm not sure why. That paper is cited for the use of the term "Great Silence", and Brin uses it to mean "Fermi paradox". I haven't seen a citation for the article's current claim that the two terms mean different things, though it would be logical and I'd be happy to see the practice evolve that way. False vacuum (talk) 11:03, 23 August 2010 (UTC)
- Hi! The two are not synonymous, even in Brin's article. 'Great Silence' refers, as the name suggests, to the lack of communication. The Fermi paradox includes the fact that the Earth was not settled long ago, as well as the lack of any other evidence. This distinction is covered already earlier in the introduction - "Another closely related question is the Great Silence — even if travel is hard, if life is common, why don't we detect their radio transmissions?". If you have a reference showing that people use the two synonymously, that would be helpful, as would the opinion of others. LouScheffer (talk) 15:30, 23 August 2010 (UTC)
- Lou Scheffer, did you read Brin's paper? It never mentions any term other than "the Great Silence" for the phenomenon in question, and it addresses not only "the lack of communication" (which, as I said, I agree "the name suggests") but the whole absence of evidence for ETI. That absence of evidence is what Brin defines the term "the Great Silence" to mean. Here's the entire abstract of the paper:
- Recent discussions concerning the likelihood of encountering extraterrestrial technological civilizations have run into an apparent paradox. If, as many now contend, interstellar exploration and settlement is possible at non-relativistic speeds, then reasonable calculations suggest that space-faring species, or their machine surrogates, should pervade the Galaxy. The apparent absence of evidence for extraterrestrial civilizations, herein called 'the Great Silence' places severe burdens on present models.
- Many of the current difficulties are due to inadequate exploration of the parameters of the problem. A review of the topic shows that present approaches may be simplistic.
- So, that's one citation for the claim that "the Great Silence" is the same thing as "the Fermi Paradox" (viz., "[t]he apparent absence of evidence for extraterrestrial civilizations"), and zero citations for the claim that they are different things. I will reiterate that I agree it would be logical if they were taken to be distinct, with the former a proper subset of the latter (although there is undoubtedly room for dispute about the boundary between the two), and I will add that I'd be delighted to see a citation for this second claim. However, as much as I hate to say it, the definition of "the Great Silence" now in the article appears to be WP:OR. In the absence of a citation, it should really be stricken altogether; at the very least, it needs to be modified by something like my reverted edit. I could, perhaps, be persuaded to replace "often" with "sometimes". False vacuum (talk) 23:41, 1 September 2010 (UTC)
- Here's the first sentence of Hanson's 'Great Filter' paper:
- Fermi, Dyson, Hart, Tipler, and others [Finney & Jones, Dyson 66, Hart 75, Tipler 80] have highlighted the relevance to SETI (the search for extraterrestrial intelligence) of the "The Great Silence" [Brin 83] (also known as the Fermi paradox), the fact that extraterrestrials haven't substantially colonized Earth yet.
- Bostrom has an informal paper called 'In the Great Silence there is Great Hope', which implicitly identifies the Great Silence with the Fermi Paradox (the more formal version 'Where Are They? Why I Hope the Search for Extraterrestrial Life Finds Nothing' is about the same, though the terms are a bit harder to find and not capitalised).
- A classic paper on the ArXiv from 1999, James Annis's 'An Astrophysical Explanation for the Great Silence', begins its abstract with
- An astrophysical model is proposed to answer Fermi's question.
- I can't find any clear evidence that anyone distinguishes between the terms 'Great Silence' and 'Fermi's question'. I see no alternative to changing the article. False vacuum (talk) 22:04, 6 September 2010 (UTC)
- Here's the first sentence of Hanson's 'Great Filter' paper:
Comment about the speed-of-light limit
- Further deconstruction. I realize en.wikipedia shouldn't be rising above the intellectual niveau of some active area of important research, but once again uh, ... duh. Just as the reality of the impact of c as a fundamental constant doesn't seem to be taken seriously, so the well known facts of actual travel at or near or it don't seem to be taken seriously. Also there seems to be a simplistic splitting between utterly unique and relatively common vs. the total number of planets which only now begins to be empirically estimable. For similar reasons as with communications itself and subject to the same end conclusions, actual in person appearance by ET is impractical, at least until something has developed that makes the trip worthwhile, and that development, were it directed, could be best done by automation. As with the main "paradox", for this editor in any case, the real paradox is why these facts aren't taken into account. 184.108.40.206 (talk) 23:01, 24 August 2010 (UTC)
- (Would 220.127.116.11 mind if I moved his/her contribution to a new section? It doesn't seem to have any relevance here.)
Nominal merge of Silencium universi [sic]
Failed speciation is systematically garbage collected
Also known to me as the Religious Explanation. If the thing between a chimp and the creator(s) of the universe doubles its distance from animality but essentially tries to stay there but also steps onto the cosmic stage then the species is culled. So there actually is no chatterbox cosmic MSM since they all met the fate of Sokratis Giolias although by more natural means such as Mr. Integrity is for paupers. 18.104.22.168 (talk) 13:20, 11 September 2010 (UTC)
- In the strong version of this, said Agency is the efficient cause of all intelligent life by locally available automation which it can use to sterilize botched jobs. Lycurgus (talk) 13:34, 11 September 2010 (UTC)
I think that Donald Davidson's work on Radical Interpretation  may be relevant to the question of a civilization that is 'too alien.' It's from philosophy of mind, rather than astronomy, but makes a compelling argument that any two intelligent species should, in principle, be capable of communication. Unfortunately, the wiki on Radical Interpretation is itself not very coherent or compelling... ~Kawphy, 04:33, 21 October 2009 (UTC)
Under the section "Too Dangerous to Communicate".
Wouldn't it be wise for Humans to discover a few additional things about the Universe before blindly broadcasting our existence. For example, ascertain whether or not Faster than Light travel is in fact possible, and how common planets actually are with breathable Nitrogen/Oxygen/Water/Carbon Dioxide atmosphere with an average temperature of about 70°F. Possibly actually configure a Solar System Defense Grid & start exploring the nearest stars and star clusters... A lot of information about the potential to colonize other star systems would be gained with the process of colonizing the Moon, Ganymede, and Mars, and beginning the work on Terraforming Venus.
It is also quite possible that Human Life and Alien Life would be mutually toxic to each other, with the mixing of the two leading to the necessary extermination of one or both due to viruses, bacteria, mutually exclusive proteins, and perhaps even more voluntary means.
What if we sent a colonization ship to a nearby star and it took 2,000 years to get there (the duration of modern human civilization)... If it found an existing modern, or pre-modern civilization. Would it stop and potentially devastate the existing environment, or would it pass it on to wait another 2,000 years before arriving at the next star? Wouldn't one goal, of course, be to communicate with a novel civilization, even if doing so could bring harm to them or us?--Keelec (talk) 06:51, 14 January 2010 (UTC)
I was told by an Arecibo Scientist that the Arecibo dish and amplifer could transmit a tight radio beam with a range half the diameter of the galaxy. Current values for the drake equation suggest that the closest intelligent life is of the order of 1500 light years away. At a minimum it would take 3000 years before we could hope for a response but the odds are that we are not transmitting in the right direction, frequency or modulation and they are not even listening for us. Further, to send a space craft to them with today's technology would take about 22 million years. —Preceding unsigned comment added by 22.214.171.124 (talk) 16:15, 19 November 2010 (UTC)
Recent changes in the probabilities
Shouldn't there be some way to reflect the recent changes in the probabilities? Or is that basically irrelevant to the topic of the paradox itself? Specifically I'm thinking about such recent results as detection of extrasolar planets increasing the general odds of planetary systems and the discovery of the alternative version of DNA using arsenic. Such factors seem to make the paradox more paradoxical. My money is on Triskellion gamesters betting on our survival... Shanen (talk) 08:05, 9 December 2010 (UTC)
- The Drake Equation article does this, with sections on historical and best current estimates of the parameters. LouScheffer (talk) 14:29, 9 December 2010 (UTC)
It is pointless to try to communicate
Because of all the factors listed here, civilizations choose not to even try to "talk" or "listen". The Fermi paradox itself is what prevents communication. The last part of It is dangerous to communicate touches on this line of thought:
- Perhaps the Fermi paradox itself—or the alien equivalent of it—is the ultimate reason for any civilization to avoid contact with other civilizations, even if no other obstacles existed. From any one civilization's point of view, it would be unlikely for them to be the first ones to make first contact and therefore likely for them to face the same possibly fatal problems that supposedly prevented the earlier civilizations from contacting them. So perhaps every civilization keeps quiet because of the possibility that there is a real reason for others to do so.
- Brin's article says this directly. Since the silence *might* be due to everyone who speaks out getting killed, the prudent thing to do is to keep quiet. LouScheffer (talk) 00:55, 14 December 2010 (UTC)
"Humans were created"
Removed this section. To unscientific and not neutral. Humans were not created, we were not "placed" on Earth by somebody's god, we evolved like the rest of the lifeforms on the planet. If it happened here is probably happened elsewhere in the universe. The entire section was far to anthropocentric and wrapped up in religious belief. Removal is because this is a scientific article and belief should not even come into play when we are talking about accepted scientific theory. 126.96.36.199 (talk) 06:41, 6 February 2011 (UTC)
- I restored it as a suggestion from the history of ideas. I don't know that it belongs where it is in the article, thinking that it might better be handled in the intro or a summary, but I think removing the topic is unnecessary for the purpose of giving the scientific perspective full weight. There is no suggestion there is any evidence for the position, but there is no evidence it is false either and it doesn't imply that there is anything upon which to base a belief in this other than that somebody said so, so it's not prejudicial. Just to be sure, though, I did add a little 'the perspective is an historical and non-scientific one' at the end. If you want to discuss a resituation of this to an expanded introduction or to a new summation, I would agree it probably should not be in the middle of the article at all. I think it's an indication that wiki is not the ideal means of writing things that it is.Julzes (talk) 08:46, 6 February 2011 (UTC)
Nope. Sorry it does not belong in the article at all. First year astrobiology and astronomy class covers religious arguments fairly well. There is no place for this kind of opinion even in lose scientific article. It isn't testable. Removing again. Leave it gone this time. 188.8.131.52 (talk) 17:12, 6 February 2011 (UTC)
- To be fair, a lot of what is in this article is not scientifically testable. That doesn't mean it should be removed. I am in favor of restoring the deleted section. –CWenger (talk) 17:17, 6 February 2011 (UTC)
- I've restored it. It is sufficiently neutrally presented. There's nothing in the section that would lead the reader to choose this as a likely option; it is merely informing the reader of one other possibility, though a non-falsifiable unscientific one, and there is no good reason or need to eliminate it. You have your own opinion of what should be included, and others have theirs, but nowhere is it established that a subject scientists concern themselves with has to totally disregard/censor non-scientific mentions, 184.108.40.206, and for completeness the mention of this portion of our intellectual heritage deserves mention. As I said, it might better be placed in a better-writtten introduction or in a summation (as might be done in an article with one lead author more easily), but it's better where it is than gone. I'm not sure what the point of grinding an axe on this is. It's hardly going to bias the reader in the wrong direction to include it, and it might lead one or more readers to explore the earlier history of the handling of this general subject area.Julzes (talk) 20:04, 6 February 2011 (UTC)
- Agree on keeping this section. Right or wrong, sensible or not, it's been seriously proposed and discussed, and hence should appear on the page. LouScheffer (talk) 21:37, 6 February 2011 (UTC)
- Negative. Calling creationism a sensible argument when it isn't points out the need to have this section removed. Religion has no part in this article. If you are really going to leave it in there don't make it one religion. You need to talk about all of the religious implications dating back to the stone age and before that. Do we see the massive problem with this. You would need to cite sources for several religions and not just one. Again removing it. Will continue to remove it until the article makes sense and is not filled with belief. 220.127.116.11 (talk) 01:27, 7 February 2011 (UTC)
- Nobody said it was sensible. I'll do the 4th undo if someone else does a third. This is not a dictatorship.Julzes (talk) 03:20, 7 February 2011 (UTC) I should remark that I think it's a ludicrous idea from the past, and I'm sure it actually will be falsified, since it stands as a possible explanation for why we are the only intelligent life in the Universe if we are (but we aren't). It doesn't stand to reason that all historical perspectives need to be treated, as the reverter claims. Right now, so far as we know, it is a possible fact. Saying who thought of this possible fact does not require saying what all the alternatives are and who thought of them. If the same notion is evidenced elsewhere historically, such things should be included, but saying how other peoples did not come up with it is not relevant. It weighs in the discussion as a possible--however ludicrous--explanation for what we observe. It mostly does so because of how it biases or has biased some people not to place any emphasis on the question at issue, in my opinion, but it still belongs in the discussion if only for that reason in addition to its currently not having been established false.Julzes (talk) 03:52, 7 February 2011 (UTC). Also, while this is essentially a science article, it is not an engineering article. Science articles have a primary purpose of informing people in as broadly a relevant way as possible, while an engineering article might concern itself with whether it is a distraction to the reader leading to inefficient outcomes to include something that is relevant but not on point. You won't find here in wikipedia, for example, that an article on Chemistry is not going to talk about its historical roots in alchemy and the slow early stages of the science, though it is doubtful that such information is of any use at all to someone who needs to learn how to be a practicing chemist.Julzes (talk) 04:03, 7 February 2011 (UTC)
/* as to growing evidence of reproductive problems among mammals in microgravity
Over on http://www.centauri-dreams.org/ there is many a discussions on the "economic" effort required for a civilization to mount a interstellar mission.Economic meaning expenditure of energy required as a percent of a civilizations other priority's. A civilization that has the economic surplus to do so must have mastered the resource utilization of its solar system and this implies that any biological impediment to early solar system utilization must have been over come early. what if the economic costs of overcoming biological restraints to early solar system colonization discourages a significant portion of sentient species from proceeding further?or biological problems delay the use of robotics and AI to a time after the ecology of the home world has collapsed. the statement that, "spinning the spacecraft" will solve everything, does have some merit, a generation ship that spins would work,"spinning" the entire population of colonists and in transit beings who must spend generations building the solar system economy required to build this spinning interstellar generation ship is the question to be answered. deleting a hypothesis with out presenting opposing citations to the ones I posted will get you noticed in the wider scientific community.Deleting means that you perhaps do not want to have a discussion on the merits of a hypothesis,or perhaps of the many theory's posted in a largely untestable Fermi's paradox some theory's are more worthy then others, I posit that you my fellow wiki editors do not know enough to judge let alone delete Infocat13 (talk) 03:11, 11 January 2011 (UTC)
- WP:FA article is not a place for original research, essays, or just poorly formatted additions. Specifically: (i) section headers are to be concise and be placed at appropriate level. (ii) Sentences are to be written in normative English grammar (iii) WP:SYNTH: that reproduction is difficult in microgravity is one step, we need a reliable, secondary source to say that this is an impediment for propagation through space. Materialscientist (talk) 03:26, 11 January 2011 (UTC)
Most if not many sources for this highly, but most interesting "hypothesis" cite a great many of our civilizations great thinkers, but many of these are, science fiction authors, futurists,and others. do I need help assistance with grammar, sure, placement, you and others can move my editorial to its proper place. please use the same standard for(secondary source)for the rest of the Fermi paradox article please.even rare earth does not meet this standard, as it waits for more early solar system astrodynamics and Kepler observations. this is an exciting age! in the next decades, so called secondary sources as you call them will/may come to be for the Fermi paradox,indeed the new data is giving us data on the drake equation. your tough standard on secondary sources should meet the science standard, right? I could delete all non conforming sections as they exist in the current wiki? you will help me please? I will not do this! but you should not be a unintentional vandal please indeed who is responsible for providing these secondary proofs? I put forth an hypothesis, you refuse to answer it instead deleting it. how does wiki reconcile a anonymous editor such as you who claims to be a University of California (graduate student instructor? )with an editor such as me who could be anyone with a knowledge of our limited biological knowledge in microgravity? — Preceding unsigned comment added by Infocat13 (talk • contribs) 04:46, 11 January 2011 (UTC)
- No WP:OR, WP:SYNTH and other kind of hypotheses please. It does not matter who we are, it matters what we can write and support with verifiable and reliable sources. Materialscientist (talk) 04:54, 11 January 2011 (UTC)
- The article already states, under "It is too expensive to spread physically throughout the galaxy":
- "It is possible, however, that present scientific knowledge cannot properly gauge the feasibility and costs of such interstellar colonization. Theoretical barriers may not yet be understood and the cost of materials and energy for such ventures may be so high as to make it unlikely that any civilization could afford to attempt it."
- This is just one of the many, many factors that are not understood, or might make interstellar travel too expensive. Energy needs are shielding are two other obvious ones, and have lots of literature references. It's way too specific to add to a article where the entire difficulties of interstellar flight get only one paragraph. LouScheffer (talk) 05:44, 11 January 2011 (UTC)