Wikipedia:Reference desk/Archives/Science/2013 April 20

= April 20 =

the speed of nervous system
I have red that the speed of the nervous sistem is about 70 kph, and I don't understand how the researchers reached to this information. Can you explain me, please, how is it possible to reach to such conclusion? Thank you 80.246.130.221 (talk) 11:27, 20 April 2013 (UTC)
 * This is actually a reasonably common medical test used in diagnosing various nervous conditions. Our article is quite technical but I'll link to it here for completeness: Nerve conduction study. I have performed this test myself (actually it was on myself) as part of my physiology lab sessions in college. Basically you stimulate a nerve with an electric shock, and measure the electrical signal further down the nerve (or on the muscle the nerve connects to if it is a motor nerve) using electrodes applied to the skin. You know the distance between where you applied the shock and where you measured the nerve signal, and also the time between the shock and the downstream signal (the apparatus records theses times automatically) so you can then work out the speed using speed = distance/time. The 70 kph claim is within the range for certain types of nerve fibre (such as those that sense touch, pressure and pain) but there is really quite a large range, and some types of nerve fibre are much faster or much slower. Our article gives values for different types of nerve in m/s (70kph is about 20m/s). Equisetum (talk &#124; contributions) 12:29, 20 April 2013 (UTC)
 * Your spellings are horrible. This website will be good to you. --Yoglti (talk) 13:11, 20 April 2Equisetum
 * "Spellings", lol. 202.158.103.252 (talk) 09:37, 21 April 2013 (UTC)
 * At least he got the subject-verb agreement right: Spelling is vs. spellings are. ←Baseball Bugs What's up, Doc? carrots→ 23:10, 21 April 2013 (UTC)

First of all, thank you Equisetum for the information. It help me a lot to understand what I learn. Again, thank you :)  And thank you also for the second responser who called Yoglti, for the right comment about the incorrect speling. I hope that now it's better. 80.246.130.221 (talk) 14:23, 20 April 2013 (UTC)

Animal courtship & human flirting
From my understanding in humans there are 2 types of flirting. One occurs almost naturally when a man is attracted enough to a woman or fancies her and this can be subconscious. The other is a very conscious flirting or picking up. Which is closer to animal behaviour? Which is more natural? Or does both happen in the animal kingdom also. Clover345 (talk) 13:02, 20 April 2013 (UTC)


 * Your question can't really be answered, because it require knowing the internal mindset of animals. Instead, we can only observe how they behave. You might be interested in the courtship behavior of bower birds, which build elaborate structures to attract mates. Some of them even serve as "apprentices," helping to build structures for other birds, before they try to attract a mate on their own. David Attenborough has an excellent piece about it, available on youtube here: . While this is all very interesting, deciding how the birds feel about the whole thing is a matter of personal and unscientific opinion. SemanticMantis (talk) 14:01, 20 April 2013 (UTC)


 * You're getting into the "theory of mind" here. That is, to what extent do animals consider what others are thinking ?  Most experiments show that very few animals seem to consider this.  Of course, it's possible to mimic this, without actually knowing what the other thinks.  It's the difference between pure instinct to considering what others think, from "add blue feather here" to "add blue feather here to attract females" to "I should add a blue feather here so the females will be impressed".  The results may be similar, but the thought processes are millions of years of evolution apart. StuRat (talk) 18:49, 20 April 2013 (UTC)

Article Existence of God
I have posted following on the article Existence of God with a section named: "Prove of Existence of God via absence of extra-terrestrial life while assuming that our World is eternal and infinite." I wonder if there are any reliable sources that used such reasoning, so that we could include it in the article. As well as any critics to the reasoning. The reasoning sounds logically to me, but perhaps there are some faults, in this case kindly let me know.

"I have gave some thoughts to the previous section and decided to refine it. Here is an astonishing result.

Let's assume that we are living in a world without God. Because we have no Creator in this case, there is no first cause, so nobody has created our world and thus no point of creation. Our world is infinite, because what could possible be outside of the borders of our world? Nothing? But nothing is something. Thus our world is eternal referring to time and infinite referring to space.

Since we are existing, we can be absolutely sure, that under some circumstances life can be created. Since our world is eternal and infinite, there are infinite number of extra-terrestrial lifeforms that would come to exist because those circumstances would be repeated infinite number of times.

The extra-terrestrial lifeforms would have infinite time to mature and advance. There would be infinite number of them that would decide to migrate to other planets, galaxies and universes. Having infinite number of lifeforms migrating for infinite period of time would result in huge number of lifeforms eventually reaching our planet. We would be surrounded by extra-terrestrial life.

However, that is not happening. We haven't clearly seen even one alien, and we are absolutely not being surrounded by them, neither we have observed their existence using our scientific tools, including space telescopes. The only logical reason is the Existence of God. This is the only clear possible cause. Thus we are logically being proven in the Existence of God." Ryanspir (talk) 15:16, 20 April 2013 (UTC)


 * Wikipedia isn't a place to post original reasoning (see WP:NOR), and coming up with your own argument and then searching for others who make it, while not necessarily outside of the rules (we don't really care what your motivations are), but it seems like a way to inadvertently violate WP:NPOV. So don't be surprised when your changes to the article are reverted.
 * That being said, your argument, if I understand it, is that the lack of current evidence for extraterrestrials is somehow a positive argument in favor of God. This is problematic for a number of fairly straightforward reasons:
 * Our lack of communication with extraterrestrials does not imply that they do not exist. We are sure there are many species of animals on this planet that humans have not yet encountered (e.g. extremophiles) but it does not mean they do not exist.
 * Our lack of communication with ETs may be because of hard physical limits. If faster-than-light travel or communication is not possible, then the vast distances of space may preclude actual contact without rather extreme measures. We still know very little about long-distance space travel. Science fiction has primed us to believe that wiser beings might be able to navigate in ways that are currently excluded by physics, but this may (perhaps sadly) be completely false.
 * There are many factors involved with the question of whether we could, in fact, communicate with ETs. See the Drake equation for some of them. We don't know all of the parameters of the equation, but it underscores that we, humans, have only been around and capable of receiving remote communications for a tiny sliver of human time, much less galactic time, and we would need to overlap with similar slivers of possibility for other ETs.
 * Your assumptions about the universe being infinitely old and infinitely large are incorrect according to modern cosmology. The universe is very old, and very big, but not infinitely so. There is a big difference between "very large" and "infinite," philosophically and practically.
 * It is not a very compelling argument from a philosophical point of view, largely because absence of evidence is not proof of absence. We are nowhere near the position of knowledge to claim there is not life somewhere else in the galaxy, much less in the universe. We have seen only the tiniest of slivers of it. Perhaps, in many many centuries, if we have explored even just our galaxy to a point to get a better sense of what kinds of worlds there are, and whether they do or don't support life, and we find that there is no obvious life in our galaxy, maybe then one could postulate very broad philosophical or scientific explanations for that, but such a thing is clearly premature. --Mr.98 (talk) 15:42, 20 April 2013 (UTC)
 * The OP's editorial reminds me of a scene from Love and Death, in which a Russian Orthodox priest is explaining to the young Boris why God must necessarily exist. Then the subject of Jews comes up, and the priest shows Boris some pictures of Jews - some who have horns and some who have stripes. So much for wisdom. ←Baseball Bugs What's up, Doc? carrots→ 20:30, 20 April 2013 (UTC)
 * The OP is referring to the talk page of Existence of God, where a debate ensued. He also posted this same editorial on a Philosophy talk page and was promptly reverted for soapboxing. ←Baseball Bugs What's up, Doc? carrots→ 20:37, 20 April 2013 (UTC)


 * See Fermi paradox and Olum's paradox. Count Iblis (talk) 16:04, 20 April 2013 (UTC)


 * I think the relevant question would be, if this proof of God is correct, which God's existence does it prove? Cthulhu's?  Ba'al's?  μηδείς (talk) 00:03, 21 April 2013 (UTC)
 * Good point. How do you prove the existence of something that's undefined? ←Baseball Bugs What's up, Doc? carrots→ 07:15, 21 April 2013 (UTC)


 * So let's examine your argument point by point:
 * Let's assume that we are living in a world without God. -- OK.
 * Because we have no Creator in this case, there is no first cause, so nobody has created our world and thus no point of creation. -- By "world", I presume you really mean "universe". Both our planet and our universe have definite points of creation - we have "The Big Bang" as that singular point of creation - but no mystical being involved in that.
 * Our world is infinite, because what could possible be outside of the borders of our world? -- Again, assuming you mean "universe", it might be infinite - but it could be curved in on itself and therefor be finite. However, the speed of light imposes a practical limitation in how big that "observable universe" is - and nothing beyond that can ever affect us.
 * Nothing? But nothing is something. Thus our world is eternal referring to time and infinite referring to space. -- No, we cannot conclude that from your premise. In time, it's finite because of the definite start time imposed by the Big Bang - and whether it's infinite or not in spatial terms doesn't matter because of speed of light considerations.
 * Since we are existing, we can be absolutely sure, that under some circumstances life can be created. -- Yes, I agree.
 * Since our world is eternal and infinite,... -- No, it isn't!
 * there are infinite number of extra-terrestrial lifeforms that would come to exist because those circumstances would be repeated infinite number of times. -- That might be the case even if the universe is only spatially infinite...so it's possible (despite your earlier incorrect assumptions) that there are an infinite number of extra-terrestrial lifeforms.
 * The extra-terrestrial lifeforms would have infinite time to mature and advance. -- Even if the universe did have an infinite life-span and be infinite in extent - that claim would not be correct. Life has to appear around some kind of energy source (a star) - and all energy sources eventually expire.  Hence it's perfectly possible that every one of those infinite varieties of life eventually die out and become extinct.
 * There would be infinite number of them that would decide to migrate to other planets, galaxies and universes. -- Not necessarily. They would ultimately run into fundamental technological barriers to doing that.  Not only that, but because nothing can travel faster than light, only those lifeforms that existed within our local "observable universe" (which is most certainly finite) can possibly communicate with us - or be known to us in any way whatever.
 * Having infinite number of lifeforms migrating for infinite period of time would result in huge number of lifeforms eventually reaching our planet. We would be surrounded by extra-terrestrial life. -- No. Even in a truly infinite universe, there are only a finite number of ET's that we could ever know about because of the speed of light limitations.  If life is sufficiently rare - then we could still be the only life forms within the observable universe - despite there being a literal infinity of life forms in the extended universe.:
 * However, that is not happening. We haven't clearly seen even one alien, and we are absolutely not being surrounded by them, neither we have observed their existence using our scientific tools, including space telescopes. -- Which, sadly, proves nothing.
 * The only logical reason is the Existence of God. This is the only clear possible cause. Thus we are logically being proven in the Existence of God. -- No, even in the event that all of your false assumptions were true, there could be other reasons why not. In an infinitely large universe - containing an infinite number of objects - even without the speed-of-light restriction, the distance between any two objects is infinity divided by infinity - which is an indeterminate number and can still be infinite.  So even if every other error you made were not an error - there is still plenty of reasons why we'd never meet an alien lifeform.
 * Sorry - your argument fails at nearly every step. It has no merit whatever.
 * SteveBaker (talk) 16:44, 21 April 2013 (UTC)
 * From discussion elsewhere, the OP is apparently reluctant to accept limitations imposed by the speed of light. Also when they are saying the universe is infinite they're evidently referring to some 'multiverse' they invented or got from somewhere and are apparently assuming you can traek beyween universes in this multiverse. I would note even if we accept the OP's flawed premise based on odd and flawed assumptions, that most intelligent lifeforms will have become aware of other intelligent lifeforms after a short span of time such as ours, by the OP's own assumption of everything being infinite it's easy to theorise that the occasional lifeform will not be aware of other lifeforms after a short span of time such as ours, and we happen to be one of those. Nil Einne (talk) 17:08, 21 April 2013 (UTC)


 * Rvanpir, you clearly believe in the existence of God. Just keep on believing, that's all you need to do.  There is absolutely no purpose in convincing others this is so, but even if there were a purpose, a science or logic-based argument is an utterly wrong approach.  Even if you got the science accurate, science can never prove the existence of God, and it can certainly never disprove it.  It's beyond that.  Way, way, way beyond. --   Jack of Oz   [Talk]  17:26, 21 April 2013 (UTC)
 * The existence or non-existence of God is beyond the capabilities of science to answer. The poster(s) who occasionally bring up this subject would be better off pursuing the question of how, or if, the belief in God improves their own quality of life, etc. ←Baseball Bugs What's up, Doc? carrots→ 17:30, 21 April 2013 (UTC)


 * I can certainly understand the human need to have others believe what you believe about stuff, and share your experiences, whether it be music or movies or literature or art or politics or religion. But these things are scientifically ineffable.  You cannot prove scientifically that Pink Floyd is better than Pearl Jam, or The Godfather was better than Apocalypse Now, or Religion A is better than Religion B, or that God exists or does not exist.  Even if God appeared on a golden cloud announcing a Millennium of Peace and Love, and everybody in the world could see Him simultaneously, there'd still be those who would not believe.  As it is now, there are millions who do believe, but without ever having seen the golden cloud.  That's the essence of belief.  You're convinced something is the case, but without any scientific evidence for it.  But you don't care about that.  It's beyond evidence and logic, and way beyond science.  Involving science in these questions is just, well, pointless.  A lot of scientific types just don't get this.  They say "When you show me the proof, then I will believe".  But by that stage, belief is not only unnecessary, it's irrelevant.  We don't need to believe the Earth is (roughly) spherical, because there's abundant proof of it.  But if we discuss alien life, then we do need to bring in belief (or lack thereof), because there are scientific theories but no hard evidence.  Until it comes along, either you believe there's sentient life out there or you don't, and that's where it rests.  A lot of scientists believe in alien life despite any evidence, but pour tsunamis of cold water on anyone who believes in God because "that's unscientific thinking".  Weird.  --   Jack of Oz   [Talk]  18:10, 21 April 2013 (UTC)
 * Yes. This is where scientists and religionists, believers and non-believers, betray their personal biases. Anyone who says he "believes" that aliens exist (or not) is mixing science with religion. Until or if an E.T. actually shows up, the best any scientist can do is to theorize on what conditions might be necessary for the existence of life elsewhere, and maybe on what the probabilities are that such conditions exist elsewhere. This was the view of Carl Sagan, who continually said that there is not one iota of evidence that extraterrestrials exist, but he fully supported looking for such evidence - because, as you indicate, belief or non-belief has nothing whatsoever to do with whatever the reality is. A believer has "proven" to himself that there is a God - a non-believer has "proven" to himself that there isn't one. Neither opinion has anything to do with whether or not there really is a God. The best a believer or non-believer can do is testify as to why they believe or don't believe, and how that opinion has impacted their lives. ←Baseball Bugs What's up, Doc? carrots→ 19:50, 21 April 2013 (UTC)
 * For what its worth I think before you can even begin to discuss this subject you need to work rather hard on what the actual question on the existence of God means. When you can ask a sharp meaningful question you will find it surprisingly easy to answer. --BozMo talk 20:17, 21 April 2013 (UTC)
 * Yes. The first question I would ask to someone who asserts "There is a God" is "Define what you mean by 'God'." Because I claim that since every believer will have his own personalized answer. ←Baseball Bugs What's up, Doc? carrots→ 21:03, 21 April 2013 (UTC)
 * Non-belief doesn't necessarily imply that the nonbeliever has "proven" there is no god or that they are in anyway unscientific. In fact, the contrary is usually the case. See the atheism article and the Edwards' reference  note for the scientific details. Its a featured article and if you check my contributions, you will see its one of the few pages that I really care about. You will see from its talkpage header and its archives that the definitions of atheism have been the subject of some fairly intense debates in the past. --Modocc (talk) 23:54, 21 April 2013 (UTC)
 * Believing in alien life has at least one difference from believing in a god, in that there at least is a proof by example that environments sometimes exist in the universe which result in life evolving. Believing that life exists elsewhere isn't much more of a stretch than believing that there exist species of frogs that we don't currently know about, because there are proofs by example that frogs exist, and that sometimes previously unknown species get discovered.  But there is no comparable proof by example that sometimes one of the deities that people have worshiped turns out to actually exist.  Red Act (talk) 22:46, 21 April 2013 (UTC)
 * Believing in alien life is unscientific. The only life we know about is here. Believing in the possibility of alien life, based on various factors, is a different story. And those who believe and have felt valued by their belief in deities would take issue with your assertions about deities. That doesn't make them right nor you wrong - but to exclude someone else's experience because you haven't likewise experienced it, is not scientific either. ←Baseball Bugs What's up, Doc? carrots→ 23:09, 21 April 2013 (UTC)
 * Well put. --   Jack of Oz   [Talk]  23:20, 21 April 2013 (UTC)
 * Given the vastness of the universe, aliens are not just possible, but likely. Its a reasonable model or scientific hypothesis to study. But, of course, not yet verified as a fact though. -Modocc (talk) 00:25, 22 April 2013 (UTC)
 * (unindent)
 * Yes, of course we cannot "believe" in the definite existence of aliens. However:
 * We have no evidence that aliens don't exist.
 * Statistical evidence strongly suggests that they exist. (Drake equation is worth a read)
 * Since we exist, then somewhere in a literally infinite universe, there must be aliens...but we don't know that the universe is literally infinite...so still no absolute proof.
 * God (or gods), however are a different matter:
 * By the way most gods are defined (with literally unlimited supernatural powers) - their existence is "unfalsifiable". We can never, even theoretically, prove that there are no gods.
 * But don't take that fact as any kind of proof...quite the opposite.
 * There is a literal infinity of other unfalsifiable prospects (like: A race of pan-dimensional, hyper-intelligent, invisible, piano-playing aardvarks exist only to induce humans into making M&M's only in the color purple.)...with an infinity of this kind of random possibilities, and in the absence of other evidence, then the statistical odds of some particular unfalsifiable belief being true approaches zero.
 * That means that with rigorous scientific thinking, one should believe neither in gods nor aliens. However, humans very often have to act without perfect knowledge...I spend money to book a vacation in the summer - without knowing whether I'll be able to take it (I might die, a gigantic asteroid might wipe out my holiday destination, etc).  The rational thing to do in the absence of perfect knowledge is to assess the statistical odds and choose your path based on the overwhelmingly probable - and ignoring the overwhelmingly improbable.  Hence, I am happy to behave in all respects as if there is no god - but that there are aliens out there somewhere - and yet not be certain that there is no god or that there are aliens.
 * Humans work this way all the time. If you believed with unreasonable degrees of certainty that you'd win the lottery tomorrow - you could choose to spend all of your life's savings on...a brand new sports car...knowing that the lottery winnings will enable you to feed your family tomorrow.  We'd all agree that this is a crazy way to run your life.  Belief in gods is kinda similar...basing your life on something which, while it might be true, is a statistical non-starter.  Compare that to someone who acts as though they won't win the lottery tomorrow (although they believe that they might) - that's a much more rational way to live your life.  So I'm technically agnostic - but I choose to behave as an atheist...same deal.
 * SteveBaker (talk) 05:16, 22 April 2013 (UTC)


 * That's all good. But not everything we do in life can be boiled down to reason or rationalness (?). You fall in love with Girl A and not Girls B, C, D ... Z.  Girls B-Z might have lots more going for them in terms of prospects, intelligence, looks, etc than Girl A, but you're attracted to A and that leads wherever it leads.  There's nothing rational about human attraction, but without it, you and I and everybody else would not be here to talk about it.  There's nothing rational about what music we prefer, what political parties we support, what interests us enough to make a lifetime career out of it, and so on.  Belief in God is similarly irrational, but that doesn't make it any less of a valid thing than a preference for pink cars over black ones.  --   Jack of Oz   [Talk]  05:44, 22 April 2013 (UTC)
 * Very true - but when you tell highly religious people "You're being completely irrational" - they tend to get very upset with you! I'll admit that my undying love of my soon-to-be-wife seems largely irrational - although not entirely without overtly conscious reasons.  We humans have evolved sophisticated mechanisms for selecting and bonding with particular mates - there is scientific evidence for the idea that we tend to prefer people who share certain similar genes with us or who exhibit signs of being obviously healthy or overtly more capable of child-bearing - but there are enough cases of people falling in love with people who are obviously not in any of those categories to know that it's not a simple matter!  We certainly don't understand why we fall in love with particular people - but that doesn't make it either irrational or something that is unapproachable to science.  I'd strongly dispute that we don't support political parties for rational reasons - we might make what some would consider the "wrong" choice - but that's frequently caused by lack of information, lack of education, self-interest...that kind of thing.  It's not "irrational" though.  SteveBaker (talk) 15:33, 22 April 2013 (UTC)
 * Anent your comments: There are extremely good reasons why people do not agree on everything ... we make decisions based on game theory, and if you know about that, it is irrational for everyone to adhere to the same positions -- one "wrong position" being adopted by everyone leads to "loss of the entire game" so to speak (i.e. loss of that civilization).   And it is not "lack of information" or the like at all -- it is simply the best way to make decisions overall yet found. Collect (talk) 15:39, 22 April 2013 (UTC)
 * OP, there is no reason to deduce the existence or non-existence of God from the number of intelligent races, actual or detected, in the universe. If we assume for a moment that we humans are the only ones, that tells us literally nothing about theology. Have you ever encountered the anthropic principle? Because you exist, the question 'why are there (only) N intelligent species?' must always apply to n>0; if there were no intelligent life, you wouldn't be around to ask. And so if our existence really were a spectacularly unlikely one-off fluke, it would be no different observationally from a situation in which we were a deliberate one-off miracle. You really could not tell the difference. (Of course, you might have special revelation or something, but that's not what you're arguing.) I suggest you go and study some cosmology, some probability theory, and some theology. I've done all three, and I regard the question "Is there a God?" as pretty intractable for philosophical reasons, and the question "Are there aliens?" as very hard in practical terms. And the two are totally unrelated. AlexTiefling (talk) 07:04, 22 April 2013 (UTC)


 * Well, my observations of life tells me, that sometimes its useful to unlearn things (if that would only be possible) in order to arrive to the truth. Sometimes, an innocent 6 year old can say something that is true, while contradicting all learned men. Sometimes, extra knowledge may actually delimit our reasoning. Albert Einstein had said: Imagination is more important than knowledge.
 * "Totally unrelated" - that is interesting way of thinking I observe among the people who believe in God (or say so). They believe, believe, but when you are talking with them about actual events, suddenly the God is no longer there.
 * If there is God, and He has reasons that he wouldn't like us to interact with extra-terrestrial forms, why He just wouldn't do so? He actually have many reasons for it, as He probably would like ourselves to develop in all areas, including wisdom and technology, and not get some extra-million-years-in-making technology from some aliens in a moment.
 * All we have to do, is to assume that we are living in a world without God, and calculate the probability of us not seeing extra-terrestrial life. My hypothesis is that our time-space continuum is eternal and infinite and thus there should be infinite probability for us to encounter the aliens.
 * And I'm not necessarily saying that to provoke any discussion, though it may be useful, but to find out if there are any reliable sources that proposed such ideas (so that we could consider them to be used on the article Existence of God). I personally consider that people who agree or disagree with my hypothesis would make the discussion on my talk page for being more appropriate venue IMHO. Ryanspir (talk) 17:17, 24 April 2013 (UTC)
 * I'm not saying that this is a good idea - but we can do exactly what you said - and calculate the odds of us NOT seeing an alien. Let's just do that real quick.
 * The Drake equation is the thing you want:
 * From our article:
 * The Drake equation is:
 * $$ N = R^{\ast} \cdot f_p \cdot n_e \cdot f_{\ell} \cdot f_i \cdot f_c \cdot L$$
 * where:
 * N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);
 * and
 * R* = the average rate of star formation per year in our galaxy
 * fp = the fraction of those stars that have planets
 * ne = the average number of planets that can potentially support life per star that has planets
 * fℓ = the fraction of the above that actually go on to develop planetary life at some point
 * fi = the fraction of the above that actually go on to develop intelligent life
 * fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
 * L = the length of time for which such civilizations release detectable signals into space[8]
 * When you ask experts to plug in their best estimates for these terms into the equation (again, see our article which points out which experts gave which estimates for which of those numbers), the answer comes out to be that the number of alien civilizations that we might possibly be able to detect lies somewhere between 8x10-20 and 36.4 million. At the upper limit, it is perhaps a little surprising that we have failed to detect any aliens...but the galaxy is huge and our instruments are not very sensitive - so it's not impossible or even unbelievable that we might have missed a communication.  But at the lower limit, there is only a one in 800,000,000,000,000,000,000 chance of there being even one alien civilization that's close enough for us to detect (given the speed of light, etc).  Given that very mundane calculations produce the answer that we may never see an alien - the fact that we haven't (yet) seen one isn't much evidence for a god.
 * With perfectly normal numbers, based on reasonable scientific estimates, it's not at all unreasonable to say that the universe simply doesn't have a sufficient density of alien civilizations for them ever to meet.
 * Put more simply, the scientific evidence is that even without a god, we might very easily never come across an alien civilization...and that's independent of the size of the universe, the life of it or anything like that. It's based only on the rate of star and planet formation - and perfectly reasonable estimates of the likelyhood of various things being true.
 * SteveBaker (talk) 19:42, 24 April 2013 (UTC)


 * I think we are a bit off-topic here. Anyway, Drake's equation is considered overly simplistic by many. It should be also viewed in a way, whether some of the alien races are seeking contact, or would seek a contact would opportunity arise, and not simply play sitting ducks for us to discover them :). A question on-topic, how do you propose to define God (without getting into religions)? Ryanspir (talk) 10:51, 26 April 2013 (UTC)

taking a sample from air for test
what will happen if I'll take a sample from the air in the street anywhere, in order to find pathogenic creature. Will I find a lot pathogenic in air within 1 cm? To the best my knowledge, the air is full with pathogenic, and our bodies protect us against them. 80.246.130.20 (talk) 15:25, 20 April 2013 (UTC)


 * The book "Microbe Hunters, " by Paul de Kruif tells how in the  19th century, experimenters would take  sealed and sterilized containers of growth medium, and break the seal in various locations for different vials to let the air get in for a brief period, then reseal the vial and watch to see if microbes grew. If they did, the broth would turn cloudy and develop a bad smell, and a microscope would show vast numbers of microscopic wigglers, or microbes of various shapes. If the experiment was done on a snow-covered mountaintop, there was far less microbe colonization from the ambient air than if it was done on a city street or in a barn full of dust.  One cubic cm of air might contain pathogens, but  (original research) I wouldn't count on there being enough to culture in a medium or an agar plate. On the other hand one cannot rule out there being a pathogen in a random cc of air. Millions of operations have been done in which the internal parts of the human body were exposed to large volumes of air, without there being an infection, though airborne pathogens have in some cases caused infections, and diseases are often transmitted via coughs or sneezes through the air to the victim.  Pathogens may also drift through the air on dust. See Airborne disease. A website by Penn State University has a great deal of up-to-date information of airborne pathogens and their concentration, and on filtering and isolation systems. It says "Airborne pathogens can be removed by purging with outside air, which is naturally sterilized. Airborne bacteria and viruses pathogenic for humans rarely occur in the outdoor air, and cannot survive long if they do. Spores of fungi and actinomycetes can occur in outside air but rarely occur in hazardous concentrations," citing a 1984 study by Goodfellow. Edison (talk) 18:07, 20 April 2013 (UTC)


 * You're right about our immune system protecting us from them. Normally they can only get in a few ways, like our mouths, noses, and eyes, and those have strong protections.  But, when you get a cut or have surgery, they can get in other ways.  A strong immune system can still protect us from most of them, unless a large quantity is introduced, or it's some microbe for which we have no defense.  Unfortunately, injections also bypass the body's defenses, so, if it's not sterile, can cause severe problems, like the recent meningitis outbreak.  StuRat (talk) 18:26, 20 April 2013 (UTC)

Machine identification


What do we call the machine visible near the center of this image? I can't think of anything closer than a crane (machine), and it's not that because it hoists its load directly up (using an accordion-style lift) instead of lifting the load from pulleys. Nyttend (talk) 19:41, 20 April 2013 (UTC)


 * We have an article (or at least, a section of an article): see Aerial work platform. AndyTheGrump (talk) 19:46, 20 April 2013 (UTC)
 * Commons category added; thanks! Nyttend (talk) 20:14, 20 April 2013 (UTC)