Wikipedia:Reference desk/Archives/Science/2011 June 14

= June 14 =

Does the planet Neptune contain water? If so, is it possible that there's a chance that maybe there's life?
Does the planet Neptune contain water? If so, is it possible that there's a chance that maybe there's life? If so, what kind of life? Neptunekh2 (talk) 03:23, 14 June 2011 (UTC)
 * Read Neptune. Basic summary: Neptune's mantle is mostly water and ammonia; one could call it an ocean many times the mass of Earth. It seems improbable that life as we know it could exist there, since temperatures are above 2000K, while DNA denatures at much lower temperatures.- Running On Brains (talk) 03:28, 14 June 2011 (UTC)


 * The problem with this retort reply is carbon chauvinism, DNA is unique to Earth. The same problem is with water, water is a good solvent, but it doesn't mean all life requires it. Plasmic Physics (talk) 04:23, 14 June 2011 (UTC)
 * It is incivil to call an another editor's considered and informative reply to the OP a "retort", even when you can give supplementary information. Cuddlyable3 (talk) 07:32, 14 June 2011 (UTC)
 * For the record, I didn't consider it incivil. Also for the record, I am not a carbon chauvinist, but it is completely pointless to speculate on alternative forms of life, because science knows of no possibilities for non-carbon-and-liquid-water-based life as of now. I never say impossible unless I mean impossible, thus I said "improbable".
 * I don't think many complex molecules are stable at 2000K, carbon or not. StuRat (talk) 05:00, 14 June 2011 (UTC)
 * Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching −218 °C (55 K). Temperatures at the planet's centre are approximately 5,400 K (5,000 °C). Cuddlyable3 (talk) 07:38, 14 June 2011 (UTC)
 * Yes, but water is only in a useable liquid(ish) form in the mantle, where there are extremely high pressures and temperatures.- Running On Brains (talk) 13:38, 14 June 2011 (UTC)
 * I think there are planets and moons in our solar system which are much better suited to life, carbon based or not. I would even go as far as saying that simple life forms are quite probable on Enceladus or Europa. --helohe (talk)  22:46, 14 June 2011 (UTC)


 * The problem is that the ambient conditions are either, incredibly high atm. pressure and very hot; or low atm. pressure and incredibly cold. There is no liquid water in Neptune, only crystal vapour and super critical water. Plasmic Physics (talk) 08:05, 14 June 2011 (UTC)


 * The answer to "is it possible...there's a chance..." regardless of what you fill in the blanks with is always "yes". There is always a very tiny possibility that there is a tiny chance that something may happen or exist. For example, it is possible that there is a chance that there is a flying spaghetti monster floating around the solar system. -- k a i n a w &trade; 12:57, 14 June 2011 (UTC)
 * Don't worry, the Invisible Pink Unicorn will trap him inside Russell's teapot. Cuddlyable3 (talk) 12:07, 15 June 2011 (UTC)


 * Editor Kainaw writes "There is always a very tiny possibility that there is a tiny chance that something may happen or exist." That is a challenge I cannot resist.
 * I would assert that there is no possibility whatsoever that any of the editors involved in this topic could swim unassisted from San Francisco Bay to Tokyo Bay. Also that there is no possibility that any of us could walk unassisted from San Francisco Bay to Tokyo Bay. Also that there is no possibility that any of us could flap our arms and fly unassisted from Philadelphia to the dark side of the moon.
 * I would be pleased to read arguments that there is any chance whatsoever that one of these athletic feats might be possible. Wanderer57 (talk) 01:44, 18 June 2011 (UTC)


 * I could do it, but your lack of faith is impeding me from doing so. -- k a i n a w &trade; 22:40, 18 June 2011 (UTC)


 * O me of little faith.               Wanderer57 (talk) 23:41, 18 June 2011 (UTC)

Mystery drug
This is a question about a drug I'm almost sure we have an article for, but I can't remember the exact name of it. The name is something like "Delidamide." It was pretty wide spread in the 50's and 60's for, what I think, was menstrual pains (or something along those lines.) It turned out to cause birth defects that caused shortened limbs among other things. JFK actually made a speech in which he encouraged women to stop using this drug and to "turn it in" to medical authorities. What was the name of this drug and any related articles about it on WP. Thanks! Quinn &#10048; BEAUTIFUL DAY 04:54, 14 June 2011 (UTC)


 * Thalidamide. StuRat (talk) 04:58, 14 June 2011 (UTC)


 * Actually, it is spelled "Thalidomide", but that's a minor issue. The drug itself was a sedative that was frequently prescribed for "morning sickness", which exacerbated the birth defect problem, for obvious reasons.  The lesson of the drug shows up in organic chemistry classes when discussing the importance of knowing how stereochemistry works, in that one enantiomeric form of the compound cured morning sickness, and the other form gave your kids a third arm. the inability to give the correct answer at the reference desks.  -- Jayron  32  05:05, 14 June 2011 (UTC) (edit: struck through wrong answer and corrected -- Jayron  32  12:58, 14 June 2011 (UTC))


 * 3rd arm ? Not a side effect I'm aware of. StuRat (talk) 05:07, 14 June 2011 (UTC)


 * See Phocomelia. The symptoms of thalidomide syndrome are defined by absent or shortened limbs. Cuddlyable3 (talk) 07:28, 14 June 2011 (UTC)


 * Right, so no third arm. StuRat (talk) 07:35, 14 June 2011 (UTC)

lunar eclipse
''How full moon appers during lunar eclipse?' ' — Preceding unsigned comment added by 14.97.111.145 (talk) 08:46, 14 June 2011 (UTC)
 * See our articles lunar eclipse and full moon. I think they make sense, let us know if you have a specific question.--Lgriot (talk) 09:39, 14 June 2011 (UTC)


 * The requisite of a lunar eclipse is a completely shadow covered moon. You can't have a full moon concurrently occuring with a lunar eclipse. The moon is too big to have properties like a quantum superposition. Plasmic Physics (talk) 11:26, 14 June 2011 (UTC)
 * A lunar eclipse only happens at full moon. It usually has a reddish or brown tinge. Graeme Bartlett (talk) 12:51, 14 June 2011 (UTC)


 * Not concurrently, but in sequence. Plasmic Physics (talk) 13:13, 14 June 2011 (UTC)
 * No, really concurrently. Obviously, a lunar eclipse can only happen when the moon is on the exact opposite side of the Earth than the Sun. We call that a full moon. Just because most of the light is blocked doesn't change that - it's still considered a full moon. --Tango (talk) 22:00, 14 June 2011 (UTC)
 * Full phase might be a better term. ←Baseball Bugs What's up, Doc? carrots→ 02:21, 15 June 2011 (UTC)
 * I would argue that a lunar eclipse is the fullest possible full moon. 86.160.218.204 (talk) 13:54, 14 June 2011 (UTC)


 * It is not surprising that this question located to Hyderabad where they will experience the full glory of the June_2011_lunar_eclipse. Richard Avery (talk) 18:08, 14 June 2011 (UTC)


 * Lunar eclipses happen at Full Moon, and solar eclipses happen at New Moon. Furthermore, eclipses very often come in pairs, 2 weeks apart. ←Baseball Bugs What's up, Doc? carrots→ 02:19, 15 June 2011 (UTC)

transduction, transformation, transfection and electroporation
Is there an umbrella term for transduction, transformation, transfection and electroporation? --129.215.47.59 (talk) 11:31, 14 June 2011 (UTC)


 * Perhaps: transgenic introductive techniques. Plasmic Physics (talk) 11:56, 14 June 2011 (UTC)

Raspberries
According to the article, each raspberry contains only a single seed, so why are there so many pips in raspberry jam and yoghurt? Aren't they all seeds? As far as I recall, when I eat fresh raspberries, there are no pips.--Shantavira|feed me 13:29, 14 June 2011 (UTC)


 * The article says "An individual raspberry weighs about 4 g, on average and is made up of around 100 drupelets, each of which consists of a juicy pulp and a single central seed. " So each raspberry contains about a hundred seeds. Whenever I eat fresh raspberries (which is as often as possible), I always get pips in my teeth. DuncanHill (talk) 13:34, 14 June 2011 (UTC)


 * Oh I misread it, thanks.--Shantavira|feed me 14:57, 14 June 2011 (UTC)

Soundproofing with solids
This is something I've never understood. If sound moves fastest in solids, why are solids used for soundproofing? Metroman (talk) 13:43, 14 June 2011 (UTC)
 * Mostly, by intentionally designing a system to be poorly impedance matched to air. The key is that a large change in sound velocity means that the transfer of energy between two materials is poor.  So, even if a material like solid steel conducts sound very well, at a high speed and with low attenuation, that sound doesn't transfer well from steel to air (and back).  Most energy will be reflected at the surface.  In addition, incoherency and diffusion are exploited by shaping the surface... a good sound barrier will be a rough surface (and a great sound barrier will be diffusive acoustic cones as you see in a studio booth).  This way, you minimze the transmitted sound and the reflected sound.  Nimur (talk) 14:15, 14 June 2011 (UTC)
 * The most common type of soundproofing I'm familiar with, like the kind used in recording studios is made of sponge. sponge is elastic so the little cells of air tend to absorb and dissipate sound energy rather then propagate it like a rigid solid. Vespine (talk) 00:16, 15 June 2011 (UTC)
 * Yes. Rubber or other elastomer has pronounced elastic hysteresis by which most received vibrational (sound) energy gets converted to heat. Cuddlyable3 (talk) 11:53, 15 June 2011 (UTC)
 * What is used to block ultra low frequency sound? It doesn't seem like anything but water or heavy masonry affects it very much. Wnt (talk) 06:01, 16 June 2011 (UTC)
 * "Nothing." Ultra-low-frequency sound barely propagates in air; at very low acoustic frequencies (say, a few hertz), the pressure wave is essentially unsustainable.  (The physics of this have to do with mean free path of a gas particle).  In any case, even if the wave can propagate, very few transducers can couple to air at this frequency; so the wave is hard to generate.  You can consider thermal effects and large-scale wind patterns to be "acoustic waves" if you want; and as you can imagine, these waves propagate very slowly (far below the sound speed in air).  Mostly, they are convective propagation of pressure disturbance, not true pressure-waves.
 * In solid materials, such as rock or the internals of the earth, the very low frequency signals propagate very, very, very far (making teleseismic measurements on the other side of the Earth possible). The biggest causes of signal loss at such low frequencies are scattering, not attenuation.  Here's a research paper on this exact phenomenon: Seismic attenuation tomography using the frequency shift method; the authors outline the difference between scattering-attenuation and intrinsic-attenuation for relevant frequencies.  Nimur (talk) 00:05, 17 June 2011 (UTC)

Unstable nuclei
Hi. Is there any qualitative difference between an atomic nucleus that is extremely unstable (arbitarily so) and one that simply can't exist at all? For example, suppose I took x protons and y neutrons, for some arbitrary x and y, and stuffed them together to make a nucleus, which then blew up effectively instantly but actually in some tiny amount of time like 10^-15 seconds, or whatever value it might be. Have I thus always created a nucleus with an extremely short half-life, or might I have tried to create one that simply can't ever exist, and can't meaningfully have a "half-life" assigned? 86.160.218.204 (talk) 13:51, 14 June 2011 (UTC)
 * How do you propose to stuff them together? You don't just pick out protons and neutrons from little trays, and apply some gluons and then let go and see if it sticks.  You'd need a real possible procedure to create your proposed nuclei.  Also, something with a half-life of 10^-15 seconds is still a real amount of time, several mesons (see List of mesons) have half-lives several orders of magnitude shorter than that before they disintegrate into their constituent particles, and they "exist".  The answer is, if it exists, it exists and if it does not, it does not.  The length of time is irrelevent, all that is relevent is if you can establish evidence of its existence in the first place.  There's lots of ways to establish evidence of existing; and these don't always involve keeping a bunch of it in a jar long enough to do tests on it.  To take two examples, the neutral pion has been positively confirmed to exist, despite having a halflife of 10^-21 seconds, see Pion.  On the flipside, the Higgs boson has never been detected though many (not all, but many) models of particle physics predict, and rely upon, its existence. -- Jayron  32  15:05, 14 June 2011 (UTC)
 * The way in which they are stuffed together is not relevant to the question I want to ask. Just imagine that the requisite particles are in place in a putative nucleus and take it from there -- a kind of thought experiment, if you like. If the question can't be asked, even in principle, without knowing exactly how this state was achieved, then I guess my question makes no sense. As you can probably imagine, "if it exists, it exists and if it does not, it does not" is not the answer I was seeking. I have thought of another way to ask this which may be clearer: imagine you are compiling a table of all possible atoms -- that is, all values of my x and y -- in decreasing order of half-life. Is there some point at which you must stop and draw a line (that is, when there is a qualitative change from unstable atoms with a definable half-life, to "non-atoms" that simply aren't viable at all, even with no matter how short a half-life) -- or do you go on, in principle indefinitely, with the half-life just getting shorter and shorter? 86.179.117.174 (talk) 17:39, 14 June 2011 (UTC)
 * I believe what you are looking for can be answered in a few articles. There are ways to predict which nuclei should be stable enough to be considered to "exist" for a reasonable amount of time (reasonable as defined by Dauto below), one of the most common is the Nuclear shell model.  The table of all possible atoms also exists.  See Island of stability for a graph exactly like you want.  -- Jayron  32  18:53, 14 June 2011 (UTC)


 * Yes. A viable nucleus must, at minimum, have positive nuclear binding energy.  This means the strong nuclear forces holding the nucleus together have greater impact than the electrostatic repulsion trying to drive the protons apart.  In principle, the binding energy can be modeled via quantum chromodynamics, though in practice it is often an impractically difficult computational problem for large atoms.  Also, though this is a necessary condition, it isn't sufficient since some potential nuclei will fission without having been self-bound for any meaningful length of time (i.e. without even allowing binding forces to cross the whole nucleus).  Dragons flight (talk) 19:12, 14 June 2011 (UTC)


 * That question shouldn't be dismissed so handedly. There are two aspects that should be taken into consideration. First, if the decaying object is a composite structure such as a nucleus, as opposed to a fundamental particle such as a quark or a gauge boson, than if its life time is too short there will not be enough time for light (or anything else) to cross its length before it decays and there is no meaningful reason to call it a particle. For the nucleus example the relevant length is 10^-15 m. Light takes about 10^-23 s to cross that length therefore no nuclei can exist with a lifetime shorter than that. The second point to take into consideration is that because of the uncertainty principle a particle with a very short lifetime will have a large uncertainty to its total energy. If that uncertainty is larger than the mass of the particle itself than we should more properly talk about a Resonance (particle physics) instead of a particle. Dauto (talk) 16:25, 14 June 2011 (UTC)

Fingerprints
I read the article Fingerprint and even saw the use of the word "point" without clear definition. Nowhere did it explain what a "point" is in the context of fingerprints. On television, both in fiction and nonfiction, I've heard people speak of two fingerprints having X number of matching points, and sometimes they show a picture of a fingerprint with little squares or circles drawn on the fingerprint. Who decided to draw the points right where they are? If I draw a bunch of line curves, what's the objective method of deciding where any point is to be on any of those curves? 20.137.18.50 (talk) 18:03, 14 June 2011 (UTC)
 * A "point" is a common term which applies to an identifying characteristic of a particular print. In fingerprinting, these are often called "Minutiae" and applies to a set of "common" features which appear at specific locals in specific fingerprints.  It isn't a simple problem, which is why a "positive" connection requires a sizable number of common "points" to call it a "match".  What you have is an overall pattern of the print (a "whorl" or an "arch" or a "loop" are the three most common patterns) and within the main pattern are small features which are unique to the individual, like say you have a whorl-type print.  Lets say on a line drawn at 12:00 from the center of the whorl, you have a gap on the third ridge, and there's a connecting bit between the fifth and sixth ridges, while on the line drawn at 3:00, there's gaps on the second and fourth ridge, etc. etc.  This is in general how prints are identified; in reality the language used to describe the "points" and the manner in which they are connected between the sample print and the suspect print are much more precise than I have done here, but that should give you the idea.  -- Jayron  32  18:47, 14 June 2011 (UTC)

diffrence
how can u distinguish between Allene and Alkyne? i know about bayers reagent test but both of them give it so there is no physical distinction((both discharge color of KMnO4).So my question is is there any other test which distinguish between Alkene and Alkyne physically. Can Ozonolysis be a authentic test for them? — Preceding unsigned comment added by 175.110.91.49 (talk) 21:13, 14 June 2011 (UTC)
 * There is distinction, an allene has an "sp" carbon bonded to two "sp2" carbons, while an alkyne has an two "sp" carbons bonded to each other and one other atom. However, you are correct in that allenes and alkynes are particularly tricky to identify via "wet chemistry" analytical techniques; this is because allenes and alkynes are frequently in equilibrium, see Propadiene, which exists normally as an equilibrium mixture with propyne (likewise, propyne will exist in the same equilibrium with propadiene) called MAPD.  Any reaction which would react preferentially with the allene will simply, via Le Chatelier's principle, cause the equilibrium to shift to convert more alkyne to allene, and the same in reverse as well.  There are likely ways to use technology to do the job for you, for example they may produce distinctly different peaks in IR spectroscopy or something like NMR or mass spectrometry may be very useful in this regard; however you may be correct in that it is almost impossible distinguish them via chemical reactivity.  Ozonolysis may be an option, as you note, since ozonolysis of an alkyne should produce two carboxylic acids, while ozonolysis of an allene should produce carbon dioxide and two aldehydes.  However, given the equilibrium situation I note, that may foil whichever ozonolysis reaction of the two is slower; the equilibrium situation would just cause the faster ozonolysis reaction to drive the reaction kinetics, and the other wouldn't happen.  -- Jayron  32  23:24, 14 June 2011 (UTC)


 * Try infrared spectroscopic analysis, alkynes gives an absorption peak at a higher wave number. If you heat alkynes, they tend to polymerise easier. Plasmic Physics (talk) 23:26, 14 June 2011 (UTC)

Thank for the answer. my exams is on friday and i was a little confused.Can u suggest any links or articles.I am in 12 standard. — Preceding unsigned comment added by 175.110.91.49 (talk) 23:56, 14 June 2011 (UTC)

Physics and timetravel
I am interested in writing a short story about a scientist who creates a time machine. Instead of going to a certain year, he is accidentally catapulted to the very beginning of time billions of years ago. I know very little about physics. Was time as we know it created the very second that the big bang took place, or some other time? I'm just interested to learn if it is at least plausible for someone to go back to that exact moment (that is assuming time travel is possible in this scenario). --Ghostexorcist (talk) 22:30, 14 June 2011 (UTC)
 * At that instant the entire universe was smaller than an atomic nucleus. Looie496 (talk) 22:38, 14 June 2011 (UTC)
 * Matter as we know it could not exist until the universe was about 380,000 years old, so the physicist would instantly transform into plasma, presuming time travel possible. See Timeline of the Big Bang.
 * If we assume that he somehow shields himself from the extreme energies at that time (this is science fiction after all), you have to consider that you can't go further back than the instant the universe began (my favorite analogy: going back before the big bang is like trying to go North from the North Pole), and at that instant, it was (practically) infinitely dense. At some point backwards, the universe itself would be smaller than the time-traveling scientist himself, so you can see why this would present a problem! There really is no practical way, even in the structure of a fictional time-travel book, to plausibly go back to the instant the universe was created. For this, you need to delve more into the "fiction" part of "science fiction".- Running On Brains (talk) 22:44, 14 June 2011 (UTC)


 * What is a good book that explains the most current research on the big bang that is dumbed down enough for the average joe interested in science? --Ghostexorcist (talk) 08:04, 15 June 2011 (UTC)


 * Thanks for the informative response. As for shielding, I was thinking that some strange quark of him physically traveling back through time (he doesn't travel in a machine) makes him immortal. His body is petrified into a rock like substance, in effect becoming a living statue. Going back to the beginning of the universe is just something I thought of a second ago. I originally conceived the idea of him going back to the earliest days of human civilization. He watches the rise and fall of various cultures over the course of thousands of years. Now that you have thoroughly answered my question, I would like to pose a related query. --Ghostexorcist (talk) 23:05, 14 June 2011 (UTC)


 * My favourite for unexpected time travel effects is the scientist who built a time travel machine to find out what caused the snowball earth. As it is impossible to send matter back, he sends information to rebuild the matter (himself and the time-ship). Unfortunately part of the matter uptake was in the form of heat energy so as a result, the whole earth got frozen. 5BYv8cUJ (talk) 09:39, 15 June 2011 (UTC)

Time travel and biology
What fictional process could effect the scientist's body in such a way that it would become living stone. I imagine that it would have to effect his body's natural atomic bond. Again, I know very little of physics. --Ghostexorcist (talk) 23:05, 14 June 2011 (UTC)


 * I don't know, you tell us, it is your work fiction after all. What is a human body's natural atomic bond? For that matter, what is an atomic bond? Plasmic Physics (talk) 23:20, 14 June 2011 (UTC)


 * That's why I said "Again, I know very little of physics" above. I guess his atomic bond would be the spacial density of his atoms. Then again, I have read that this density is fixed and cannot be change, so just consider that a bad word choice. I'm just interested in some type of real world explanation that can be greatly embellished. Like for instance, if you expose a certain element to a given energy source, does it effect its density in any way? If there is none, then I'll just shoot from the hip. --Ghostexorcist (talk) 23:27, 14 June 2011 (UTC)


 * An important clarification: what properties of stone do you want this living body to have? For instance, the hardness of stone is not (primarily) due to the density, but the crystal lattice structure of the mineral components. Once you have that hardness via the crystalline structure, malleability (e.g. the ability to move around) becomes a problem... SemanticMantis (talk) 23:43, 14 June 2011 (UTC)


 * I haven't the slightest clue to tell you the truth. I know living rock can move like toothpaste given enough pressure, but it's not like the guy is trapped between tectonic plates or anything. I guess I'll have to relegate this portion of the story to the fiction side of sci-fi. --Ghostexorcist (talk) 23:52, 14 June 2011 (UTC)
 * The idea reminds me more of golems, gnomes or other fantastical creatures anyway... you can always say a wizard did it ;) SemanticMantis (talk) 00:24, 15 June 2011 (UTC)


 * How about a supersolid? Plasmic Physics (talk) 06:34, 15 June 2011 (UTC)


 * Thanks for reminding me of this. I'll look into it more. --Ghostexorcist (talk) 08:04, 15 June 2011 (UTC)


 * Since this is fiction your protagonist could meet up with the Gorgon. Insert obvious phallic joke here. You may find more scientific ideas in the article Fossil although your plot should allow plenty of time for this slow process. Note that fossilization will affect and not effect the body. Cuddlyable3 (talk) 11:37, 15 June 2011 (UTC)

phone tracing
Usually in movies it takes some time until the phone number of a caller can be traced. So they have to keep them on the line for a certain amount of time until they get the number. This sounds like BS to me, as the phone company certainly has the caller's number in real time. What are the technical reasons behind this? Is/was there at all any truth about this? --helohe (talk)  22:37, 14 June 2011 (UTC)
 * Technological capabilities at the present time may be superior to technological capabilities when the movie was made. Looie496 (talk) 22:39, 14 June 2011 (UTC)
 * No, they have pretty much always been bullshit, at least since the advent of relatively modern phone-switching systems (i.e. something better than women with headphones moving wires around a giant pegboard). Telephone_exchange indicates that digital systems have been in place since the 1980's.  Caller_ID indicates that the technology has existed, theoretically, since 1969, to instantly display a caller's phone number, though the first market-ready applications were in the mid 1980's.  I'm sure at some point in the past this really was a major undertaking to "trace" a call, but given that for at least 20 years, my phone has been able to automatically tell me who is calling, and I am not the police, then any movie in the past 20 years where the police can't do so is bullshitting us.  this article confirms that, during the days of manual switching it used to take upwards of 20 minutes to trace a call, and required the cooperation of the phone company.  However, with the advent of electronic switching techniques, tracing calls went from "20 minutes for the phone company to track someone down" to "instantaneous".  There was never a time when a call could be traced in an automated way, like you see in movies and cop shows, but did not return results essentially as soon as the connection was made.  The whole "keep him talking while we trace the call" bit has always been an invention of scriptwriters.  Either (pre-1980's) you had to get the phone company to figure out who called (and this didn't require the other person to be on the line; they could figure where it came from after they hung up) OR (modern systems) you can find out instantly as soon as the connection is made.  -- Jayron  32  23:12, 14 June 2011 (UTC)
 * I've always had the suspicion that this is the result of not just the drama involved (to avoid making things too easy on the protagonists) but also script writers not wanting to give away the FBI's tricks. For instance even on shows where it would be great to have you never see them use portable cell towers for triangulation and to lock down a hostage taker's cell phone (by forcing it to connect to YOUR tower rather than the network at large) despite the fact the technology exists. HominidMachinae (talk) 00:54, 15 June 2011 (UTC)


 * I think some of the respondents above may be making a false analogy between the telephone network and the Internet. The Internet was designed to be stateless and is based on datagrams (i.e., postcards). You have to supply a legitimate return address if you want to get a reply, unfortunately for your privacy. The telephone network doesn't work that way. It is circuit switched, which means that every switch on the network behaves more or less like a NAT router. How do you find out which of the computers behind a NAT router was the source of an outgoing connection? You don't, unless the sender identifies itself or the router exposes an interface that can be used to query that information. I'm sure that mechanisms for fast call tracing have existed for a long time, because the spooks demand it, but it's not in the nature of the telephone network to expose the caller's identity, unlike the Internet. Caller ID works by sending the calling number over the circuit once it's made, encoded as pulses. The receiving phone displays whatever information is sent, even if it's wrong. It doesn't really know who's calling. -- BenRG (talk) 06:26, 15 June 2011 (UTC)


 * It should be noted that caller ID is completely unrelated to call tracing. A trick from the old days included tandem stacking, which would let one bounce a call back and forth across the US, and then connect to a given number (which would sometimes have the effect of the local telco's central office number showing up.) Similarly, using a calling card to place a call will often give the Caller ID for the calling card company, not the pay phone from where the call was originally placed. Related to this is ANI, which is included on all 800-numbers, as well as all law enforcement phone systems. One can block their caller ID, but they cannot block the ANI function. (although ANI information can also be spoofed by proper call routing.) None of this affects call tracing, but can affect the perceived origin of a call for your average citizen (or their Caller ID equipment.) Avic ennasis  @ 09:38, 13 Sivan 5771 / 15 June 2011 (UTC)

You have to take into account the fact that the telephone company has historically kept records for billing purposes, not because they cared about tracking any single person's actual physical location. There are and have been all sorts of legacy physical situations which may simply make tracing a specific land line call from a specific land line area very difficult. It's not an either/or situation, but a hugely complex process depending on circumstances, such as flat rate and party line (telephony). μηδείς (talk) 19:28, 16 June 2011 (UTC)