Wikipedia:Reference desk/Archives/Science/2014 February 19

= February 19 =

Can bats transfer "sound maps" to each other?
This applies to biology, specifically bat echolocation. I have not been able to find any info on whether bats can sing "sound maps" - collections of sounds from echolocation that come together to form one big image - to each other, like what happened in Silverwing. It seems logical, since they are simply repeating what they heard from their clicks, although it may not be possible. Does anyone have any information on that? 173.50.125.12 (talk) 01:02, 19 February 2014 (UTC)
 * Since most of the preprocessing of sound into neural representation will no doubt occur at a very low level, it is unlikely that a bat will directly perceive all the details of a "sequence of clicks". A second challenge is the adaptation of the vocalization system to accurately repeat a waveform: it is not just sequence of clicks, but a complicated waveform consisting of millions of overlapping reflections of each click. You might be able to mimic someone singing, but imagine trying to accurately reproduce a soundscape of running water, wind and cackling geese using your voice. A further problem is that the crucial three-dimensional component (relative phase and amplitude to the two ears) would be impossible to reproduce with a single vocalization. I expect that bats would develop speech before they develop the ability to "project" an image in this way. —Quondum 04:42, 19 February 2014 (UTC)
 * Brilliantly said, Quondam. μηδείς (talk) 04:53, 19 February 2014 (UTC)
 * Thanks, though of course I have to admit that I've assumed that what was intended by the OP was that another bat would directly perceive the image. But then, a more manageable, slowed down representation (the few milliseconds of the collected reflection of a click stretched into say seconds or minutes, perhaps only incorporating simplified features of interest) would be more properly considered to be speech, ignoring all the other issues, wouldn't it?  Actually, the relationship between echolocation and the vocalization of dolphins and other cetaceans used for communication would probably be an interesting area of study, even though my observations would still apply. —Quondum 05:17, 19 February 2014 (UTC)


 * Would there also be problem in positional referencing of a particular sound-scape. Even with voice-expressed locations a mid-air position could be difficult to describe. Richard Avery (talk) 11:08, 19 February 2014 (UTC)
 * This strikes me as somewhat analogous to seismic exploration and processing in the oil and gas industry where the objective is to generate a model of the subsurface using reflection seismology. Acquiring and processing the data is a lengthy, complicated and expensive process, both financially and in terms of computing resources. For a bat it's cheap and fast. The final products that represent the 3D model of the subsurface (including positioning information), are very many orders of magnitude smaller than the data recorded. They are described using standard formats so they can be transferred between parties. So, I guess, in principal, a bat could evolve the equivalent of a SEG Y standard to organize the post-processed model and sing that. It's probably the equivalent of someone reciting the first few tens of thousands of digits of Pi.  Sean.hoyland  - talk 11:36, 19 February 2014 (UTC)


 * Merlin Donald discusses in Origins of the Modern Mind and A Mind So Rare (at the same link) the uniqueness of the phonemes of speech in that we represent them to others in the same way we perceive them. This is a highly complex skill which we execute, even then, imperfectly, and which seems to have required some exaptations unique to our lineage.  First we made and perceived hand gestures, then we adapted the same mechanism to make and understand a limited set of oral gestures, i.e., phonemes.


 * There are birds that exhibit mimicry, but in nature these are more displays like gorilla chest-pounding or peacock strutting than the communication of ideas. In nature these displays are not symbols that can be applied to conveigh arbitrary meanings (but see Alex the Parrot).  Our own abilities are very limited.  There are some very skilled voice artists short video like Michael Winslow.  But most humans don't represent complex audio portraits, just one to a few dozen phonemes and clicks and raspberries and so forth.  We can describe running water, wind, and cackling geese--but symbolically and conceptually, not by producing the sounds themselves.


 * Of note is the recent discovery that dolphins each have a unique personal signature call which they make to announce their presence, and which other dolphins reproduce in order to summon them. Dolphins are the only animals besides humans to have and use names.  What else might they be doing behind our backs? μηδείς (talk) 17:29, 19 February 2014 (UTC)


 * It strikes me that this would be like trying to use a single speaker to recreate surround sound, but where instead of trying to imitate five or seven speakers (plus subwoofer), you'd have to recreate thousands. No one speaker, no matter how good, is going to give even our poor ears the feeling of being within an orchestra. You might be able to mimic Michael Jackson's singing voice, but you're just never going to be able to mimic him standing six feet to your left and a guitarist on your right. Matt Deres (talk) 17:47, 19 February 2014 (UTC)

Unifying general relativity and quantum mechanics
What is stopping us from unifying general relativity and quantum mechanics? Concepts of Physics (talk) 06:27, 19 February 2014 (UTC)


 * A lack of practical utility? The fact that the few physicists talented enough to address such theoretical physics problems are diverted towards more alluring technical and theoretical challenges?  The immense reductive changes in the available funding and career opportunities in pure physics research?  The closure and/or realignment of major physics research institutions in the United States?  The inherent difficulty of the problem?  Reptoid conspiracy to deny knowledge of interstellar travel to pure humanoids?  What kind of answer are you looking for?  Nimur (talk) 06:56, 19 February 2014 (UTC)

I have heard somewhere that there are two equations; one from GR (Einstein field equation) and the other from QM (I don't know the name of that equation). And physicists are trying to combine those two equations into a sigle equation to formulate a single unified theory. If I am right, then what is stopping us from combining those two equations? Is the discovery of graviton also essential to formulate a single unified theory? Concepts of Physics (talk) 07:20, 19 February 2014 (UTC)


 * GR is a classical physics theory. To make it compatible with QM it must be quanitized. There are precedents for this - for example, classical electromagnetism was successfully quantized in the twentieth century, resulting in the theory of quantum electrodynamics. This involved a process called renormalization. However, when physicists try to quantize GR in the most obvious and straightforward way, this process of renormalization fails. So physicists are investigating other approaches to creating a quantized version of GR, also known as quantum gravity. Two of these approaches are string theory and loop quantum gravity. Both approaches are, so far, almost entirely hypothetical, and the question of which approach is "better" or more likely to succeed is very controversial. Both approaches predict the existence of gravitons, although I think gravitons are more fundamental in string theory than in LQG. If gravitons (or, alternatively, gravitational waves) could be observed, an investigation of their properties might give support to either string theory or LQG - or might point us towards an entirely different theory of quantum gravity. Gandalf61 (talk) 09:26, 19 February 2014 (UTC)


 * The failure of the renormalization process is not that surprising from a purely physical point of view. While it is reasonable to expect that an effective theory that describes Nature at a level far away from the Planck length should be renormalizable (because the non-renormalizable terms should have flowed to zero when renormalizing the unknown theory of everything to the effective theory), there is no reason why an (approximate) theory that describes Nature at its fundamental scale should have this property. Count Iblis (talk) 11:45, 19 February 2014 (UTC)

Take some ownership, science does not belong to the privileged few, but belongs to everyone. Don't ask "What is stopping us from unifying general relativity and quantum mechanics?" -- what is stopping you? 91.120.14.30 (talk) 18:03, 19 February 2014 (UTC)


 * For 99.99% of the population, I would assume the answer includes a lack of knowledge equivalent to a post-graduate physics education. Even among people interested in physics, most will never choose to spend to the time required to reach the forefront of physics research.  Dragons flight (talk) 19:52, 19 February 2014 (UTC)


 * ...and for the other 0.01%, the answer includes a lack of knowledge of how to unify general relativity and quantum mechanics. --Bowlhover (talk) 21:26, 19 February 2014 (UTC)


 * I'm not a physicist, but even I know they have no shortage of theoretical models. The main shortage is a shortage of fundamental experiments that they don't know what answer to expect from.  Come up with one of those, and you're bound to come up with some groundbreaking theory, whether it is describable as fusing these two or something else.  The problem is, coming up with one of those generally seems to involve a request for some exceedingly large amount of money to make absurdly high energy things happen, or to look through an absurdly large telescope to some point absurdly long ago in the past.  At least, it's absurd to some people.Wnt (talk) 22:01, 19 February 2014 (UTC)

Soft water
Where is soft water found?14.192.211.48 (talk) 12:51, 19 February 2014 (UTC)

https://simple.wikipedia.org/wiki/Soft_water Zzubnik (talk) 14:27, 19 February 2014 (UTC)
 * Or even simple:Soft water. —Tamfang (talk) 06:16, 21 February 2014 (UTC)

Soft water redirects to Water softening. Interestingly, Hard water has information on where softer water can be found. http://water.usgs.gov/owq/hardness-alkalinity.html has maps for the US. http://dwi.defra.gov.uk/consumers/advice-leaflets/hardness_map.pdf map for england and wales. http://www.doeni.gov.uk/niea/water-home/drinking_water/consumer/water_hardness.htm for northern Ireland. In Malaysia (where the IP originates from) try http://kmam.moh.gov.my/ for standards, but it looks like the government hasn't produced any surveys yet. You could try http://scholar.google.com/scholar?q=water+quality+Malaysia for scholarly articles if you are up to it. Richard-of-Earth (talk) 17:30, 19 February 2014 (UTC)

Papering window with alfoil for heat reflection - inside or outside?
I've moved back in with my Dad for a few months and I'm in the spare room which nobody has lived in before and I'm in Australia in summer and the window faces east and I'm a night owl. The Venetians are useless and by 7.00am the room is about 35 degrees Celcius (there are no trees or anything outside, it's just direct sunlight). Dad found me duct taping newspaper against the window and suggested I use aluminium foil instead. Now, one of the panes is covered by flywire which the duct tape won't stick to, so I put it on the inside of the window instead of the outside. My question is, does that affect how much heat/light it's reflecting? Because I sort of feel like the heat is entering the glass before it hits the alfoil and even though a lot of it probably gets bounced straight back out, there may be at least some element of greenhouse effect going on. 58.161.162.150 (talk) 14:28, 19 February 2014 (UTC)


 * It does make sense to put the foil outside, since glass does not transmit energy perfectly, and in particular, probably absorbs (depending on the type of glass) a substantial amount of the energy in the infrared portion of the spectrum. The infrared portion probably accounts for around half the energy in sunlight.  The effect of this is to heat the glass, which then warms the air inside and outside through conduction, and the foil would do little to stop that.  With the foil on the outside, a large percentage of the energy at all wavelengths would be reflected without heating anything.  If you further have flywire between the glass and the foil that would be on the inside, which probably absorbs quite a lot of the energy going through it, this would increase the interior heating, but it is not clear from what you said whether this was how you had it. You could try foil under external flywire if you can get it there; I expect which side of the flywire it is will have little effect.  You might even want to smooth the foil to the glass on the outside with some liquid to that it is less susceptible to wind etc., preferably something very dilute and soluble that would dry eventually acting as a weak gum, but would allow later removal through gentle scraping/washing – maybe dilute dishwash liquid? —Quondum 15:16, 19 February 2014 (UTC)


 * The aluminum foil might do some good, but I suggest inserting a Styrofoam sheet (cut to the proper dimensions) into the window frame, on the inside, then taping up the gaps along the side and bottom (I'd leave the top untaped, as you need to allow air pressure to equalize during heating and cooling cycles). I've found this makes a major difference.  You could also line that whole wall with Styrofoam.


 * I also have a powerful fan pointed at my sleeping position, with a remote dimmer switch in the bed with me, so I can adjust the fan setting from bed.


 * Also, if you can set up a sprinkler on a timer to splash water on the outside of that wall, that will make quite a difference too. StuRat (talk) 03:09, 20 February 2014 (UTC)

Arrhenius and van't Hoff equations
The Arrhenius equation, describing the rate constant, is k=Ae^(-Ea/RT). The van't Hoff equation, describing the equilibrium constant, is K=e^(-deltaG/RT). However, activation energy Ea is also the deltaG between reactants and the activated complex. This leads to my question of whether the two equations are actually related beyond the fact, as the Wikipedia article notes, that Arrhenius based his equation off of van't Hoff's? This seems to suggest to me that the equilibrium constant between reactants and the activated complex is equal to the rate of the overall reaction divided by A?  Bramble claw  x  15:31, 19 February 2014 (UTC)
 * I'm not sure that either scientist used their work as the basis for the other, but yes, you are essentially correct; insofar as the entire set of equilibrium and thermodynamics equations is internally consistent; that is they are all basically different mathematical ways to get at the same physical phenomenon. Remember that the equilibrium constant is the ratio of the forward and reverse rate constants, while the Arrhenius equation is only looking at the forward rate constant.  It's fairly simple math to show that since deltaG-forward and deltaG-reverse are the same magnitude and opposite signs, that the forward reaction to the activated complex and the reverse reaction to the same complex should be related, basically the difference between Ea-forward and Ea-reverse should be exactly equal in magnitude to deltaG.  Something like:


 * Eaforward - Eareverse = ΔGforward
 * and


 * kforward ÷ kreverse = K

With these two relations, you should be able to substitute into either of the Van't Hoff or Arrhenius equation and get the other. I'm really to tired right now to check my math, but from a logic point of view, it makes fine sense. Sketch a reaction coordinate graph and it's easy enough to prove graphically. -- Jayron  32  03:04, 20 February 2014 (UTC)


 * Thanks,  Bramble claw  x  16:27, 21 February 2014 (UTC)

Humidity weather warning for UK
Is there some service that I can use to alert my mother when outside humidity is low so she can open windows in her house? She has a dehumidifier but I imagine that swapping the air out entirely would be very effective when the conditions are right. Can humidity be accurately forecast? Forecasts would be ideal but notifications with no warning would also be useful. Seans Potato Business 20:40, 19 February 2014 (UTC)
 * Just buy her one of these. --TammyMoet (talk) 18:45, 19 February 2014 (UTC)


 * I have one of these; it shows both indoor and outdoor humidity (also "predicts" weather changes, etc. ) -- When it's nicer outside than inside, I open windows.
 * (Additional sensor required for outdoor humidity: ) ~:71.20.250.51 (talk) 19:17, 19 February 2014 (UTC)
 * P.s.: there is a cheaper version. 71.20.250.51 (talk) 19:35, 19 February 2014 (UTC)


 * Or, even cheaper (actually, **FREE**!): Use a pine-cone...the branches of the cone open out when it's dry and close up tight when it's humid. These aren't a great way to measure the absolute humidity - but all you care about is whether it's more humid indoors than out.  So stick one outside the window and one inside and you'll know whether it's significantly less humid outdoors than in. (SteveBaker) 99.96.179.150 (talk) 19:56, 19 February 2014 (UTC)


 * I should have bought this one, (includes additional humidity/temp sensor), cheaper and better than my set-up.   :(  71.20.250.51 (talk) 20:32, 19 February 2014 (UTC)


 * I've read that those hygrometers are very inaccurate. The UK government meteorological office has an automated weather station at Hawarden Airport (closest station to where my mother lives). I imagine that their instruments are far better than that cheap tat. I've found this webpage which gives me the humidity reported. I don't know how they get that information (I failed to find it on the met office website).


 * I've found the dew point forecast to be more useful for telling me when to open the windows than the humidity, as the dew point tells you when the temperature/humidity combo is good. (If you just rely on humidity, you would mistakenly open the windows when the humidity is low but the temp is hot.)  I find a dew point below 59°F (15°C) to be comfortable.   StuRat (talk) 03:03, 20 February 2014 (UTC)

Chemistry book series
Are there any "all the basics" book series on chemistry like there are on physics? Something like Landau's course on theoretical physics or the Feynman lectures. I'm not looking for anything in particular, just something to gawk at in idle time. I realize that in their very fundamentals physics and chemistry are the same. --81.175.238.65 (talk) 18:29, 19 February 2014 (UTC)
 * Here are three introductory books on Chemistry by Isaac Asimov, User:81.175.238.65. I read all his science books when I was in about sixth grade. He is very clear and engaging. μηδείς (talk) 17:19, 22 February 2014 (UTC)
 * Thanks. On another site I got recommended Chemistry: an experimental science, the first edition of which is available on archive.org for free . These aren't exactly what I was hoping for but will do nicely enough --81.175.238.65 (talk) 21:47, 22 February 2014 (UTC)

EM energy in Fourier representation
In Quantization of the electromagnetic field it is reported that, taking Fourier coefficients, the quantized fields are:

$$ \begin{align} \mathbf{A}(\mathbf{r}) &= \sum_{\mathbf{k},\mu} \sqrt{\frac{\hbar}{2 \omega V\epsilon_0}} \left(\mathbf{e}^{(\mu)} a^{(\mu)}(\mathbf{k}) e^{i\mathbf{k}\cdot\mathbf{r}} + \bar{\mathbf{e}}^{(\mu)}  {a^\dagger}^{(\mu)}(\mathbf{k}) e^{-i\mathbf{k}\cdot\mathbf{r}} \right) \\ \mathbf{E}(\mathbf{r}) &= i\sum_{\mathbf{k},\mu} \sqrt{\frac{\hbar\omega}{2 V\epsilon_0}} \left(\mathbf{e}^{(\mu)} a^{(\mu)}(\mathbf{k}) e^{i\mathbf{k}\cdot\mathbf{r}} - \bar{\mathbf{e}}^{(\mu)}  {a^\dagger}^{(\mu)}(\mathbf{k}) e^{-i\mathbf{k}\cdot\mathbf{r}} \right) \\ \mathbf{B}(\mathbf{r}) &= i\sum_{\mathbf{k},\mu} \sqrt{\frac{\hbar}{2 \omega V\epsilon_0}} \left((\mathbf{k}\times\mathbf{e}^{(\mu)}) a^{(\mu)}(\mathbf{k}) e^{i\mathbf{k}\cdot\mathbf{r}} - (\mathbf{k}\times\bar{\mathbf{e}}^{(\mu)})  {a^\dagger}^{(\mu)}(\mathbf{k}) e^{-i\mathbf{k}\cdot\mathbf{r}} \right), \\ \end{align} $$

Than the energy is reported as (taking the square of the fields):

$$ H = \frac{1}{2}\epsilon_0\iiint_V \left( E(\mathbf{r},t)^2 + c^2 B(\mathbf{r},t)^2 \right) \mathrm{d}^3 \mathbf{r} = V\epsilon_0 \sum_\mathbf{k}\sum_{\mu=1,-1} \omega^2 \big(\bar{a}^{(\mu)}_\mathbf{k}(t)a^{(\mu)}_\mathbf{k}(t)+ a^{(\mu)}_\mathbf{k}(t)\bar{a}^{(\mu)}_\mathbf{k}(t)\big). $$

However, when integrating over the volume for finding the energy, I find terms like $$a_{\mathbf{k}}^{(\mu)}a_{-\mathbf{k}}^{(\mu)}$$ as well, since the integral of $$e^{i\mathbf{k}\cdot\mathbf{r}}e^{i\mathbf{-k}\cdot\mathbf{r}}$$ does not vanish in the integral. What am I doing wrong? — Preceding unsigned comment added by 87.1.53.150 (talk) 19:11, 19 February 2014 (UTC)


 * Don't you get those terms twice, once from E^2 (with positive sign) and once from B^2 (with negative sign) so that they subtract out to zero? --Amble (talk) 19:22, 19 February 2014 (UTC)


 * I found the answer! In order for $$\mathbf{A}$$ to be real it should be $$\overline{a(\mathbf{k})^{(\mu)}}=a_(-\mathbf{k})^{(\mu)}$$. See this. --87.1.53.150 (talk) 22:52, 19 February 2014 (UTC)

Spiritual practices as alternative medicine
I know that TaiChi and QiGong and Yoga are used as alternative medicine to Western medicine, and I am familiar with TaiChi and QiGong as taking concepts from Daoism, an integral belief system in traditional Chinese culture. I am just wondering if Western spiritual practices, like praying the rosary, would also be considered alternative medicine. The Catholic rosary, in particular, seems to have a very strict structure, where the person in meditation has to recite 10 Hail Marys in each decade while thinking about other stuff. Can a non-Catholic pray the Catholic rosary as meditation, or would that be considered too sacrilegious? 140.254.227.25 (talk) 21:14, 19 February 2014 (UTC)
 * It would not be considered sacrilegious. It might be encouraged by some. It might seem puzzling by some if the one praying does not believe in what he/she is praying, but I can not see that any catholic would object. DanielDemaret (talk) 21:29, 19 February 2014 (UTC) I base this personal opinion on two tenets of the Catholic Church. 1) Catholic means approximately "universal": It is open for everyone and one does not need to believe in anything to go to heaven. 2) A basic tenet of the catholic church is that one believes in what one says. So if one were to say the words of a rosary, then I imagine it is assumed that one believes in it while one says it, at least. DanielDemaret (talk) 21:53, 19 February 2014 (UTC)
 * The religious aspects are more or less a Humanities question and might get a better answer there. Briefly though, many Protestants hold strictly to a position that the dead, even saints, stay dead until a future resurrection, and so accounts of ghosts, spirits, or even praying to Mary would be seen as superstition, or perhaps historically as some evil deception along the lines of the doppelganger (a demonic apparition which demonstrates its falseness by turning up before the person is dead; or aside from that, see Hamlet).  However, from a purely scientific point of view, they might make an interesting control in a neurotheology experiment, because they can say the same things with the same cadence and sentiment but without "true" belief.  But I think it's worth considering whether qi, like "health", is a general term without a specific meaning.  You could look through every tube, jar, refrigerator and freezer at the National Institutes of Health and not find a single specimen of "health" at any degree of purity.  They believe in health ... but it's not really the same as believing in God, or even Mary.  It's hard to compare philosophical things... Wnt (talk) 21:54, 19 February 2014 (UTC)


 * Indeed, various... enthusiastic Catholic websites encourage anyone who wants to to pray the rosary, even if they do not currently have any faith. See for example, , , so I don't think you have to worry about Catholics considering it sacrilegious unless your intention actually is sacrilegious! 86.157.25.240 (talk) 16:08, 21 February 2014 (UTC)


 * The difference between Tai Chi/Yoga and prayer is that both Tai Chi and Yoga involve some physical movements that help the physical body in some way, whereas prayer (whether chanting the rosary or just hands together and meditation) does not. Some of the yoga exercises I am familiar with were prescribed to me by a physiotherapist as part of therapy for a slipped disc, for example. However, the complementary therapy known as Reiki is actually a spiritual practice, where healing is a (welcome) by-product of spiritual practice. Make of that what you will. --TammyMoet (talk) 12:46, 20 February 2014 (UTC)


 * I'm not sure that's an entirely meaningful distinction Tammy. Many would classify the spiritual practice of yoga and tai chi as a form of prayer. The idea that "prayer" is a purely verbal activity (whether spoken or not) is relatively modern, and especially common among Protestant Christianity: traditional prayer in Christianity, Islam, Judaism, and many (most?) other religions has included the use of the body in ritual movements, as well as things like "contemplative prayer" which are forms of meditation. I don't think any of the ritual gestures commonly found in Christianity have been found to have any particular physical benefit, but meditation in its many forms is often credited with improving mental health. The rosary, as a form of meditation when properly carried out, could therefore be plausibly claimed to have mental health benefits, although I'm not aware of anyone making such claims. 86.157.25.240 (talk) 15:58, 21 February 2014 (UTC)