Wikipedia:Reference desk/Archives/Science/2012 October 18

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October 18[edit]

Redstone[edit]

Meh, could someone clarify what is redstone here (concerning the Union Soldiers and Sailors Monument)? Looks like some sort of rock, but there is virtually no info on it in the internet and everything is flooded with Minecraft stuff (and no article in Wiki either).Brandmeistertalk 10:57, 18 October 2012 (UTC)

My guess is that only a description is provided by that term rather than an identification. I would guess that what is known is only the color—red. It is some unidentified red stone. Bus stop (talk) 11:06, 18 October 2012 (UTC)
The OED simply has "stone of a red colour" for this word, but apparently it can also mean red ochre, however that seems unlikely in this context.--Shantavira|feed me 12:29, 18 October 2012 (UTC)
The term is non-specific, and can refer to any type of stone. Could be sandstone, shale, mudstone or even granite or limestone. The only thing you can say for sure is that it sorta kinda looks reddish. As nothing of the sort is visible in any pictures of the monument, it probably refers to the cheaper stone that makes up the bulk of the pedestal, and is sheathed with the more attractive and expensive granite and marble. Dominus Vobisdu(talk) 12:56, 18 October 2012 (UTC)
This color photo of the monument shows that the pedestal has a reddish tint to it.    → Michael J    13:36, 18 October 2012 (UTC)
Most likely because it was taken at sundown or sunrise, with a very red sun. Other photos show that the granite is more gray than pink. Dominus Vobisdu (talk) 13:51, 18 October 2012 (UTC)
I expect you will find the most likely answer at http://www.anr.state.vt.us/dec/geo/redstone.htm, which describes a redstone quarry in Vermont. It states,"the rock is a reddish- purple rock called Monkton Quartzite". Looie496 (talk) 15:45, 18 October 2012 (UTC)
The linked article states; "New Hampshire granite, redstone, and marble." There is a village called Redstone, New Hampshire where there are quarries yielding "coarse constructional stones, all biotite or biotite-hornblende, but varying in colour, pinkish ("red") and dark-yellow greenish-grey ("green") varieties being found remarkably near each other at Redstone, on the east side of the Saco valley. The finer varieties take a high polish and are used for monuments..." Alansplodge (talk) 18:06, 18 October 2012 (UTC)
On a separate note, I think in the Infobox it should distinguish between the material the sculpture is made of and the materials the base is made of.Bus stop (talk) 21:33, 18 October 2012 (UTC)

Matching neurotransmitter and feeling[edit]

Can we quantify in ml and name neurotransmitters responsible for each feeling? For example, happiness -> 0.03 ml serotonine, and such.83.52.248.109 (talk) 14:26, 18 October 2012 (UTC)

Unfortunately not. The closest we can come to matching neurotransmitters with feelings are probably "dopamine ↔ pleasure", "norepinephrine ↔ vigilance", and "oxytocin ↔ love", but those are all oversimplified. The role of serotonin has been incredibly difficult to understand, but"serotonin ↔ satisfaction" captures some aspects of it; happiness really doesn't.
Also, because neurotransmitters are targeted and channeled in a very precise way, quantifying them in terms of concentrations is not meaningful. It may make sense for hormones, which diffuse through the bloodstream, but not for neurotransmitters, which are released only at specific target sites.Looie496 (talk) 15:09, 18 October 2012 (UTC)
The effect of the neurotransmitter depends also on the sensitivity of the receptor and the reuptake of it. OsmanRF34 (talk) 15:40, 18 October 2012 (UTC)
  • You are making the naive materialist mistake of equating a high-level emergent property with a physical substance. Happiness comes about because of the harmonious arrangement of the factors of your life. Are you healthy enough so you are not in a constant state of suffering, including chemical imbalances? Are you free from major worries about food, money, safety, shelter, the well-being of loved ones? Are your priorities in order, so that you are not frustrating your own goals? Do you have pursuits that bring you passion and pleasure? If your life, body and brain are well-organized and properly functioning you will be happy. This includes the proper levels and flux of hormones and neurotransmitters. But they work as lock and key mechanisms. There is nothing inherent in the shape of the neurotransmitter itself that causes happiness--it is whether it fits and stimulates the right keys, and the whole system works together properly to regulate the traffic of your mid that matters. You could genetically engineer the body to replace serotonin entirely with some sort of pseudoserotonin of another chemical makeup entirely. As long as you also replaced the serotonin receptors with pseudoserotonin receptors you'd be perfectly well off. There's nothing inherent in serotonin itself that conveys happiness. μηδείς (talk) 17:32, 19 October 2012 (UTC)
indeed. for instance, from a (tiny) bit of (objective) experience, I'd say the 'pleasure' center of the brain is badly named; it's more of a 'do that again' center; it can be activated without any real emotions or feelings, pleasure or otherwise, on the part of the recipient. Thus, things like tolerance during addiction, where the 'do it again' function becomes very highly activated, but any pleasurable cognitive response is quite absent. Gzuckier (talk) 04:42, 27 October 2012 (UTC)

electrodynamics[edit]

Hello, sorry for being so ignorant, but what is the relation between classical electrodynamics and electronics? The thing is, electronics textbooks, at least the ones I've been reading (hobby-wise), they talk about analyzing circuits, the behavior of the different components and stuff, never about current density, displacement currents, electric flux and things, yet the stuff seems very important, the more so as Maxwell's equations play a role in relativity and stuff, or so I've read or heard. Are those things a higher-level abstraction, of sorts? Can Ohm's law be derived from Maxwell's equations?Asmrulz (talk) 18:01, 18 October 2012 (UTC)

Electrical circuit theory (Kirchhoff's laws and so on) is a special case of electrodynamics in which the electric fields are guided by conducting wires separated by insulators. You can derive these laws from the continuous equations of electrodynamics. Ohm's law and electronics are derived from a combination of electrodynamics and quantum theory, because quantum theory is needed to explain the behaviour of atomic lattices in resistors, charge carriers in semiconductors and electrons in vacuum tubes. --Heron (talk) 18:42, 18 October 2012 (UTC)
Yes. If you look at any introductory electronics engineering course, then (hopefully) the lecturer will start from Maxwell's equations and work from there. Have a search around youtube for some lectures on youtube or similar. IRWolfie- (talk) 20:58, 24 October 2012 (UTC)

Coffee making soda go flat[edit]

I have on occasion mixed a teaspoon of instant coffee with a can of decaffinated cola. It makes the soda foam violently. I figured it was a mechanical interaction. But mixing coffee that's already been made seems also to make the coffee go flat. Any info on what's going on? μηδείς (talk) 19:28, 18 October 2012 (UTC)

Most probably Alzheimers. Ankh.Morpork 19:30, 18 October 2012 (UTC)
Nucleation, possibly with a side order of Diet Coke and Mentos? Certainly for the teaspoon of instant coffee, less sure for the already made. --Tagishsimon (talk) 19:36, 18 October 2012 (UTC)
I am not quite sure I get Pork's point, although I watched my mother's father die with Alzheimers--terrifying my sisters who were too young to understand his behavior before he became bedridden--not something to joke about. As for nucleation, yes, that's what I meant by "mechanical interaction". But I have noticed that even when the coffee is already well dissolved it still will flatten soda. μηδείς (talk) 20:34, 18 October 2012 (UTC)
Pork is just making a bad joke, I suppose. OsmanRF34 (talk) 00:21, 19 October 2012 (UTC)
Does coffee completely dissolve, or is there some element of particulate suspension? If so, that might account for nucleation. If not, then we seem to be left with weird chemistry. --Tagishsimon (talk) 20:50, 18 October 2012 (UTC)
I'm no scientist. However, I wonder whether this might hold a clue? It seems to suggest that caffeine itself has a surfactant effect in the soda/Mentos reaction, although not a hugely significant one compared to some of the other ingredients (see the slide comparing the performance of the normal and caffeine-free versions). A Google search brought up various relevant articles about coffee and bubbles. So if the amount of caffeine normally present in diet soda has a measurable but small effect when nucleation occurs via Mentos, the caffeine in your coffee powder will certainly provide the surfactant effect, more than replacing the caffeine in your decaffeinated soda, while the powder itself provides nucleation sites. Maybe the quantity is sufficient to cause foaming and flatness even if the nucleation sites aren't so obvious -nucleation is still occurring on the surface of the glass and presumably on any residue or impurities from the coffee solids. - Karenjc 21:10, 18 October 2012 (UTC)
I'll have to repeat the experiment with some well-dissolved and filtered coffee to see if it still flattens it. μηδείς (talk) 17:16, 19 October 2012 (UTC)
I brewed, refiltered, and cooled some coffee. It did flatten the soda to a very minor extent. Of course the coffee I added to the soda was well diluted at that point compared to adding a teaspoon of instant grounds directly to the glass of soda. μηδείς (talk) 17:21, 21 October 2012 (UTC)

Periodic table of baryons[edit]

Our articles on baryons are by their nature a bit hard to comprehend... not helping is that we don't have an orderly scheme to present them all in a complete, visual array. List of baryons is a great beginning, but it doesn't give an overall impression of organization. Articles like Eightfold Way (physics) show little pieces of the elephant, but tend to leave a person more confused than ever. Now, nicer images exist - e.g. the pyramid at[1] - but even that is incomplete.

Now it occurs to me that for didactic purposes only (I'm not saying this has any deep physical meaning) we could arrange the bosons by the quark composition, as follows:

Delta                Sigma        Xi      Omega
uuu uud udd ddd | uus uds dds | uss dss | sss  (u,d,s - the [[baryon decuplet]])

                  uuc udc ddc | usc dsc | ssc
                                ucc dcc | scc  (u,d,s,c)
                                        | ccc

                                ucb dcb | scb
                                        | cbb  (u,d,s,b+c)
                                        | ccb

                  uub udb ddb | usb dsb | ssb
                                ubb dbb | sbb  (u,d,s,b)
                                        | bbb

With J=3/2 and J=1/2 states immediately above and below or side by side in a table. (This would ideally be a cute Wikitable format; I just didn't want to code such a thing when I'm just testing the breeze). Question:

  • Is this or some other "periodic table of baryons" actually in use, so it could be sourced and presented as a real concept?
  • Our list of baryons lists a number of "prime" particles which have the same quark composition and angular momentum as others. Are these misfiled -should they be moved to the section for "baryon resonance particles"?
  • Aside from the J=1/2 vs. 3/2 thing, is there a way to organize the resonance particles as part of such a "periodic table", or is there a very large or unknown potential variety of them?

Wnt (talk) 20:07, 18 October 2012 (UTC)

Is it possible to trap a photon in such way that it remains stationary ?[edit]

Hello friends, I need some help to understand photons behavior and I would like to understand the experiments of Nobel prize winners, in physics, in 2012. In everything that I could read about photons behavior, I understood that they move in light speed, they are mediator of electromagnetic forces and they don´t have rest mass because they don´t exist in stationary way. So I read this week in brasilian´s magazins that Nobel prize winners in 2012, have conducted some experiments that keep one single photon stationary ba 10 ms, in a chamber that has 25 cm. Can somebody explain a little bit what actually they did and how this affect our knowledge of photons behavior ? — Preceding unsigned comment added byFuturengineer (talkcontribs) 20:53, 18 October 2012 (UTC)


The Nobel Prize commission, on behalf of the Nobel Foundation and the Royal Swedish Academy of the Sciences, publishes a whole web-page explaining this background for the 2012 Nobel Prize in Physics. There is apress release; a"popular science" introduction to the physics; and anadvanced physics brief for scientists familiar with the topic. These resources explain, in various degrees of detail, the background; the novelty of the physics discovered by the laureates, and the implications to the scientific community. We also have articles on the laureates, Serge Haroche and David J. Wineland (and in Portuguese: pt:Serge Harocheand pt:David Wineland). I believe you may be confusing photons and ions. Have you read through these resources? Any questions still unanswered? Nimur (talk) 00:08, 19 October 2012 (UTC)

Thanks Nimur, I didn´t know this site of Nobel Prize organization. I understood the way that they trapped a photon. Photon is not stationary but reflectin in two surfaces very reflective and close each other. So they send a specail athom and see in the other side if ocurred changes in phase from wave in scuh way that they can detect if therwas a photon or not in cavity. Now my question is regarding decoherence. They mentioned that they can solve problems like Schrodinger paradox and define the way that state superposition goes to just a definitive state. I don´t know how they can determine this, but my question is They can use this to observe double slit experiment and define how/when electron changes from wave to particle ? So their experiment will help to solve this strange phenomenon of quantic phisics ? — Preceding unsigned comment added byFuturengineer (talkcontribs) 02:04, 19 October 2012 (UTC)

Understanding the "live" wire in a home[edit]

Hi all, I have just removed my ceiling fan, and sticking out of the ceiling I have three disconnected wires, a black high-voltage wire, a white neutral and a green ground. With the fuse back on, I have tested the wires with a non-contact voltage sensor. Even though the hot wire is not connected to anything, the sensor still shows a AC current in it. My question: didn't we learn in high school that circuits have to be complete for current to flow (or at least be connected to ground)? Why is there an AC current in this dead-end? And why is it that even with this voltage (which has to be high enough to light up the sensor) would I not be able to light a light bulb with a single wire — I'd need to connect the other end to neutral? Thanks! — Sam24.128.48.26 (talk) 21:54, 18 October 2012 (UTC)

Voltage is not the same thing as current. Voltage is basically a force that is capable of driving a current if you complete the circuit. Your voltage sensor, if it's the usual thing, doesn't show current. Looie496 (talk) 23:23, 18 October 2012 (UTC)
yeah, but he said noncontact current sensor. I'm guessing that, given his description of the setup, that there can't be a real current, so it can't be one of those loop around the wire current sensors that picks up a magnetic field from a real current, so maybe it's one of those now seldom seen neon bulb indicators, that can indicate a hot wire by the current passing through capacitative coupling to the wire and/or ground, usually via your hand, or one of the similarly acting IC operated capacitative sensors you can get now. which does in fact make it a voltage sensor, like you said, despite his calling it a current sensor, and answers his question. no curent, just voltage.Gzuckier (talk) 04:49, 27 October 2012 (UTC)
A lot of people, and a lot of books, and use the term "electromotive force," so Looie's terminology is commonplace, but it's still a little bit tricky: voltage is not a force in the same sense that a stretched spring exerts a force. Voltage is in fact a measurement of potential energy per unit charge. Nimur (talk) 23:27, 18 October 2012 (UTC)
Ok, but if there is no current in the wire than what, at it's most basic level, is causing the sensor to register something. Surly the sensor is measuring a rising and collapsing electromagnetic force, right? I assume a guassmeter would also show an EMF, right? But doesn't there have to be actual movement of electrons to cause this changing EMF? — Sam 24.128.48.26 (talk) 12:27, 19 October 2012 (UTC)
If you're working on the ceiling fan, and you didn't turn off the electric mains (by switching off a circuit-breaker, or disconnecting a fuse at the fuse-box), then you should not be working on that ceiling fan. The electricity in a household wire can be fatal. Leaving aside all other discussion about the fascinating physics associated with electricity, do not work on the wire if you aren't sure it's disconnected from the mains. Call an electrician if you aren't trained in proper procedure. In fact, the danger may arise from the same root-cause as the answer to the question: you may be completing the circuit from high-voltage to ground. If the easiest path for current to flow is through you, and not through the return wire,you can be electrocuted. For the sake of completeness, there are other reasons why your meter might show a signal, but if you aren't certain, why take the risk? Nimur (talk) 23:48, 18 October 2012 (UTC)
Thanks. I guess I figured when I said "with the fuse back on" (though I should have said circuit breaker) it was clear that I had switched the circuit breaker while I was in contact with the wires, and that my usage of the non-contact voltage tester was to be double-certain. The disconnected wires are now nine feet above the ground, so it was safe the turn the circuit breaker back on. — Sam 24.128.48.26 (talk) 12:27, 19 October 2012 (UTC)
Turn off the mains electricity for the whole house. I was working on a ceiling lighting circuit earlier this year, and gave myself a painful electric shock. I thought I had isolated the lighting circuit at the circuit breaker - but clearly there was still a significant potential difference between me and the wire I touched! AlexTiefling (talk) 09:58, 19 October 2012 (UTC)
How did you verify that the power was off? You need to measure the neutral <-> ground voltage (to check for miswiring or ground loops) as well as the hot <-> neutral voltage, and should probably check the hot <-> ground voltage for completeness. If any of these shows an appreciable voltage, there's a malfunction somewhere, and you should probably call an electrician. --Carnildo (talk) 00:24, 20 October 2012 (UTC)
That's just the thing - I didn't double-check that it was off. I just threw the circuit-breaker, checked that the light wouldn't come on, and went to work. Once I'd received the shock, I did indeed call the electrician. AlexTiefling (talk) 07:15, 20 October 2012 (UTC)
My rule of thumb; once you've turned off the presumable circuit breaker, before you grab the wire, ground it to make sure. better a fat spark and trip the breaker for a wrongly labeled circuit that blow yourself across the room, at a minimum. Gzuckier (talk) 04:52, 27 October 2012 (UTC)
With AC, there will be a very small AC current flow in a dead-end live wire due to capacitance. The wire is one end of an air-gap capacitor, with the other end being whatever grounded object happens to be nearest. The capacitor charges and discharges on each cycle of the AC voltage. The capacitance is very small, so the current that flows is small. The capacitance of a dead end wire is sometimes called self-capacitance, and modeled as if it did not depend on any ground being nearby (ground is assumed to be at infinity). In real situations, there will always be a ground closer than infinity. Self-capacitance is simpler to calculate, because the geometry of the grounded conductor is ignored.--Srleffler (talk) 17:42, 19 October 2012 (UTC)
  • I asked a related question before [2] - the bottom line is that atest light can work either by conducting a hopefully regulated amount of current from the live wire through the user, or can conduct the alternating current from the live wire back to itself (delayed by half a cycle) by using capacitance. Wnt (talk) 17:35, 22 October 2012 (UTC)
which brings up the largely ignored second half of the OP's question; while there isn't enough current via capacitance to light an incandescent bulb, there can indeed be enough to light a little NE2 neon bulb if you can still find one, or sometimes an actual fluorescent tube, dimly. Gzuckier (talk) 04:56, 27 October 2012 (UTC)

Radio station reception range[edit]

About how far away could I expect to reliably receive KOKC (AM) from its transmitter location well enough to listen to University of Oklahomafootball games? KOKC is a clear-channel station with technical data found here. With regards to my hometown of Salina, Kansas would I be more likely to receive the game clearly on KOKC or KGSO? I can't seem to find any stations that actually air the OU football games over their online streams, for some reason, so over the air seems to be the only way I can tune in via radio. Thanks,Ks0stm (TCGE) 22:27, 18 October 2012 (UTC)

Clear channel is an amazing thing. I've picked up WSM (AM) west of the Mississippi, as far as Albuquerque, at night-time, using no special equipment other than my Toyota's AM/FM radio. It seems a no-brainer to pick up a 50 kilowatt AM station that's a mere 250 miles distant over flat ground. Nimur (talk) 23:07, 18 October 2012 (UTC)
AM reception is very erratic, because it depends on the state of the ionosphere. Sometimes you can pick up a strong station a thousand miles away; sometimes it is noisy at fifty miles. Quite often a distant station will come through clearly for a little while and then fade out as the layers in the ionosphere shift. Looie496 (talk) 23:17, 18 October 2012 (UTC)
True, but 50 kilowatts is a lot of power; undesirable effects due to skywave multipathing, bad weather, and all that, often fall well under the noise-floor. If you look at the links on our KOKC article, one includes a map of air-checks with reliable reception ranging across most of the central United States. Nimur (talk) 23:21, 18 October 2012 (UTC)
I have to say, though, that map looks really old, and over the last 10 years or so (as long as I can reliably remember) I have noticed that AM stations seem to be becoming harder and harder to receive, even relatively locally. I don't know whether this is due to power line interference or what. I used to have practically no problem receiving KLIO in Salina (back when it was KFDI-AM), but over the years reception has gotten worse to the point where my car radio won't even pick it up reliably. Ks0stm (TCGE) 00:33, 19 October 2012 (UTC)
Well, the laws of physics haven't changed much; and the ionosphere, though it changes daily, has beenclosely monitored using many distinct metrics bythe scientists who worry about such things. The most probable effect is that some of the AM stations you've been tuning to have reduced their transmit power as the economics of broadcast radio have changed. (Electricity isn't free, and advertising dollars on AM radio are drying up). However, KOKC and WSM, and other relics of the AM era, are currently broadcasting in the clear at fifty kilowatts, day and night, so for any specified sky conditions, you should be receiving approximately the same signal strength today as you would in 1948. KLIO, on the other hand, is authorized to broadcast only at 1 kilowatt. Nimur (talk) 00:42, 19 October 2012 (UTC)
What has changed over the years is the design of radios, particularly car radios. Up until the 1960's, radios of any quality, and car radios, were vacuum-tube based. Tube design provides high cross-modulation performance. What that is about is this: Any radio has to a cerain extent the undesirable property of cross-mixing radio signals and noise whith that of the signal/station you have tuned it to. In AM reception, the effect varies from just hearing another station in the background, to what radio people call "monkey chatter" (think of multiple Donald Ducks all taking at once) to something like white noise ie hiss. In the 1960's tube designs were replaced by bipolar transistor designs, and in car radios the tuning was based on permeability tuning - sliding magnetic cores. Bipolar transistors are not as good cross-modulation wise as tubes, but the problem was minimised to a certain extent in car radios by multiple permeability tuning circuits that reduced adjacent channel signal strength before it got to the transistors. However, in the last 10 to 15 years car radios are synthesisor based - tuned by microcircuits and not permeability tuning. This is low cost, but cross-modulation performance is very poor. In a nutshell, radios you buy today are not as good in AM noise performance as radios you used to buy.
What has also changed is the widespread use of computers, TV sets, compact flourescent lights, microwave ovens etc, that incorporate switch-mode power conversion. These devices feed back more radio frequency noise into the power wiring that older products did. An individual computer etc may not produce much interference (except close to it), but all the devices in a street each causing noise, adds up to a blanket of noise that makes AM reception harder.
Ratbone 120.145.50.173 (talk) 07:48, 19 October 2012 (UTC)
Maybe more buildings and structures in the way? During the day, you mainly receive ground waves, because the D layer of the ionosphere absorbs much of the signal. Conductivity of the surface also has an effect, so a lowering of the water table could perhaps play a role. If you noticed worse reception at night, maybe regulations are the reason. see here. Ssscienccce (talk) 21:51, 26 October 2012 (UTC)

Sugar, oil, starch in plants[edit]

Are those different forms that nature found to store energy in plants? Are they equivalent replacements? And can you divide plants according to their capacity of storing sugar, oil or starch? Or can different plants in the same division implement different solutions? OsmanRF34 (talk) 23:47, 18 October 2012 (UTC)

Good question, and a difficult one. For starters, see Starch#Energy_store_of_plants. Basically, starch is necessary for long-term energy storage, but only after sugars are made first. As far as I know, oils are not used to store energy in plants, but I welcome information to the contrary. I think oils are mainly secondary metabolites, that can aid in defense, signaling, etc. SemanticMantis (talk) 19:28, 19 October 2012 (UTC)
If they aren't, then where does vegetable oil come from?!? Lipid#Energy_storage states "Triglycerides, stored in adipose tissue, are a major form of energy storage both in animals and plants". I don't know how it can be plainer than that. --Jayron32 19:34, 19 October 2012 (UTC)
Ah, of course, thanks. I guess I was thinking more of the various volatile/aromatic oils. SemanticMantis (talk) 21:06, 19 October 2012 (UTC)
Oils do also serve other purposes in both plants and animals, besides energy storage, like providing flexibility to exposed surfaces without evaporating too quickly, as a solvent for oil-soluble substances, etc. StuRat (talk) 19:54, 19 October 2012 (UTC)