Wikipedia:Reference desk/Archives/Science/2010 December 28

= December 28 =

What Makes A Human Voice Sound Male Or Female?
I was wondering what qualities a human voice possesses that make it sound male or female. If you listen to a spoken voice, you can usually tell quite easily whether it is a male or a female talking based only on the sound of the voice. But why is this? Obviously pitch has something to do with it; men's voices generally being lower than women's. But if you simply raise the pitch of a man's voice it doesn't sound like a woman's - it sounds like the same man's voice only higher-pitched. Is there some other acoustic property that differentiates male's and females voices? Thanks! Stripey the crab (talk) 03:20, 28 December 2010 (UTC)


 * You may be interested in Voice_therapy_(transgender) and . In addition to the roughly octave difference in fundamental pitch of the sexes that you mention, there are differences in overtone production and other differences in phonation. - Nunh-huh 03:51, 28 December 2010 (UTC)


 * A complex sound, such as a human voice, is not a single frequency (pitch). The sound contains energy across a wide frequency spectrum, including harmonic and non-harmonic tones.  Like a musical instrument, a human voice has a timbre in addition to its pitch.  Usually, human speech has a large "white noise" component, usually described as the "breathy-ness" of the voice; it often has a strong impulse-signal (especially while speaking hard consonants and glottal stops; and it has a harmonic component (the vowels, and other tonal components).  The human larynx is very "nonlinear", so there are also a huge amount of atonal (nonharmonic) components.  Our ears are trained (and biologically predisposed) to detect certain characteristics of sound; the study of this behavior is called Psychoacoustics.  It has been pretty well established that humans detect ratios of frequencies better than they detect actual absolute-frequency values themselves (generally to the discredit of the idea of "perfect pitch" musicians - they really should be called "very sensitive at detecting whether an instrument is in-tune relative to itself" or "perfect relative pitch" musicians) .  In other words, our ears and the brain-center that interprets signals from them are sensitive to timbre - not to pitch.  Now, when you simply speed up the playback of an audio clip, you're multiplying all of the frequencies by a constant value - so the pitch changes, but the ratios (the timbre) is still the same - that's why even a high note on a bass-guitar can never sound like the same note played on flute.  Nimur (talk) 12:56, 28 December 2010 (UTC)
 * Perfect pitch and relative pitch are different things. Relative pitch means you can hear intervals very precisely (this is necessary to sing well, for example). Perfect pitch means you can identify a pitch just by hearing it. Lots of people have good relative pitch, fewer have perfect pitch but some certainly do. --Tango (talk) 16:38, 28 December 2010 (UTC)
 * I've played with a program where you can speed up or slow down a sample without altering the pitch and also alter the pitch without speeding up or slowing down the sample. Increasing the pitch of my male voice would give a very good approximation of a lady's voice, I can't remember now by how much I increased it but I did try with a few other people so it wasn't just me. So I think even thought it might be a bit more complicated then that, the main factor is just pitch. Vespine (talk) 03:53, 29 December 2010 (UTC)
 * Ok i've just had a read of the voice therapy article and it looks like at least some of the research disagrees with me but it is not without dispute. Maybe my small sample wasn't "common" because the people I tried it with were more musical then average and not overly "masculine". But it doesn't completely refute what I observed.. Vespine (talk) 03:58, 29 December 2010 (UTC)

Males and females have different vocal cord tensions, altering pitch, different vocal tract length, altering timbre, and different speech patterns and pronunciations in most dialects. 208.54.5.50 (talk) 14:51, 30 December 2010 (UTC)

Kit fox or coyote?
An anonymous editor recently that File:DesertKitfox.JPG is a photograph of a coyote, not a kit fox. If that claim is true, then the photo should be removed from the Kit Fox article. Can anyone confirm or refute this claim? —Bkell (talk) 05:38, 28 December 2010 (UTC)
 * Looks like a coyote to me. Since we have other useable image, we should switch this disputed one. Rmhermen (talk) 07:22, 28 December 2010 (UTC)

Resistricted Earth fault protection for electrical Power system
=== For High Impedence Resistricted Earth Fault protection, we provide stablizing resistance and metrosil resistors(>3kV).

The question is if the knee point voltage of the current transformer is specified as 300v then is there any chance that the voltage accross the relay terminal would increase greater than the knee point voltage of the CT. If this is not possible then why do we need a metrosil accross the relay if the source(CT) is not capable of supplying a voltage in excess of knee point voltage.???? === — Preceding unsigned comment added by Rajxananoid (talk • contribs) 08:08, 28 December 2010 (UTC)
 * Because the knee point voltage is not the maximum voltage, but mainly in case there was a fault, for example the source current getting coupled to the measuring current. Ariel. (talk) 09:28, 28 December 2010 (UTC)

What exactly is the "Postulate" in Newton's Laws ?


I understand that to formulate a theory to describe the working of the Universe, we need a set of postulates or axiom. We can't just start from nothing, for then it wouldn't be a theory, it would just be a logical truth. Looking at Quantum Mechanics or Lagrangian mechanics, it is clear to me what exactly is "assumed" ie the postulates involved in building the theory. However, looking at Newton's Laws of motion, it's not all that apparent to me. While Newton's first law defines an "inertial system", where the second law can be applied, the second and third lawsdeal with "Force". Now, what exactly is Force ? Is Force defined to be the rate of change of momentum ? It can't be, because that would mean that's a definition and not a postulate. We already know we need a postulate ! The article on Newton's Laws brushes on this issue, but it is still not clear to me. What exactly is the postulate in Newton's Laws ? Or alternatively, what is the definition of Force ?  Rkr 1991  (Wanna chat?) 13:00, 28 December 2010 (UTC)


 * From the cited article, Newton postulated that mass, acceleration, momentum, and (most importantly) force are assumed to be externally defined quantities to which we can today add that his observations of these quantities failed at both sub-molecular scale and relatavistic speed. Cuddlyable3 (talk) 13:25, 28 December 2010 (UTC)


 * I'm sorry, but I don't understand. "Externally defined quantities". What exactly is that definition ?  Rkr 1991  (Wanna chat?) 13:34, 28 December 2010 (UTC)
 * We don't really have a better explanation than "mass is just this thing, y'know?" Mass, like certain other properties, are fundamental characteristics of matter.  It happens that mass is "that property of matter that is susceptible to gravitation," and simultaneously "that property of a body that characterizes quantifies inertia."  Other properties, such as position, are similarly difficult to describe.  But Newton's laws explain the relationship between mass, position, and time - that mass is the constant ratio that multiplies the second-derivative of an object's position with respect to time.  Similarly, we can define "force" - it's just this thing that, if scaled by mass, gives the second derivative of a body's position with respect to time.  From that, we can define more sophisticated concepts about energy (or, we can start with energy as the "axiom" and derive force and position and mass).  It really doesn't matter; the "equals sign" in F = ma has no preferential direction, so "ma = F" is just as good an axiom.  Nimur (talk) 15:37, 28 December 2010 (UTC)


 * If that's the case, how come we have a clear postulate in, say, Lagrangian Mechanics ? There, we have a clearly defined quantity called Action, and a nice axiom about it. Since Lagrangian mechanics is equivalent to Newtonian mechanics, isn't it fair to expect a similar clear postulate in Newtonian Mechanics as well ?  Rkr 1991  (Wanna chat?) 15:59, 28 December 2010 (UTC)
 * Sure, but action is defined in terms of energy; and Lagrangian mechanics pretty much punts on the definition of energy. (It's just this thing, y'know, and here's an equation for it).  Why is T = d/dt(dL/dqdot)?  Just by definition?  The formulation of Lagrangian mechanics merely expresses a relationship between energy and generalized coordinates of position and momentum (which is mathematical equivalent to F = ma); but it never explains why action should be minimized; nor why energy relates to momentum or position according to some particular formula; nor why mass exists.  Those are simply mathematical abstractions of experimentally-observed reality.  Nimur (talk) 18:10, 28 December 2010 (UTC)
 * My understanding is that the "laws" are not a theory in the sense used in the original post. They are simply a description of how the world operates. They are not an explanation of why it operates that way or much of a guess as to the underlying reasons for the behavior. Contrast this with Newton's gravitation, which postulates that there is a force called gravity (G) that, for reasons and by means Newton does not speculate on, has a predictable operation with regards to planets, solar systems, what have you. G is the postulate in that, very clearly so, and for this reason was described as "occult" by Newton's critics (it was to them as if Newton was just inventing something out of nothing without a typically Cartesian explanation of how it supposedly worked or enacted its power). Contrast this again with the kind of work done with Einstein in General Relativity, where G is replaced by the assertion that mass itself warps space. All of this is just to try and make it clear that I don't think Newton's laws are the same thing as the theories at all, which is why they are even today called "laws", which generally are just reserved for expressions of relations between entities (like Boyle's Law, which is also not a theory). The terminology is imprecise, however. --Mr.98 (talk) 16:54, 28 December 2010 (UTC)


 * But Newton did speculate on the means by which gravity works. In "Principia" (1687) Newton criticized the vortex model of gravity promoted by Christiaan Huygens and speculated on Mechanical explanations of gravitation such as it being "a condensation causing a flow of ether with a corresponding thinning of the ether density associated with the increased velocity of flow." but famously capitulated in the 2nd edition of "Principia" 1713 with "I have not as yet been able to discover the reason for these properties of gravity from phenomena, and Hypotheses non fingo (I do not feign hypotheses). Cuddlyable3 (talk) 18:21, 28 December 2010 (UTC)


 * The overall point of Newton's work on gravity though was that his postulation of a gravitational force worked, even though (as you note), he freely acknowledged he had no clue how it worked. (And while he may have speculated on its nature in a letter, it is consequential that in his widely published work, he did not.) --Mr.98 (talk) 23:36, 28 December 2010 (UTC)

@Nimur : Yes, I got your point. But just to make myself clear, I'm not asking "Why" the postulate is made. I'm merely asking "What". I understand that there is no need to answer the question "Why" as this is a postulate". The thing which is unclear to me is what exactly is that postulate.  Rkr 1991  (Wanna chat?) 06:06, 29 December 2010 (UTC)
 * I'm pretty sure the postulate is merely the Hypotheses non fingo; that is the mechanics of motion can be described without determining their root causes. -- Jayron  32  06:15, 29 December 2010 (UTC)

Wouldn't there be an article if they exist already?
The streetlight would give energy to the grid instead of take from it. There will be a battery in the shaft of the streetlight. As a consequence, during the day, it'll be recharged to 100% and the excess gets sold back to the grid.

Because the LED streetlight will be powered by a battery all night, a solar panel will be added to the top of it in order to expedite the daytime battery recharge, and sell its excess to the grid.

While the light faces the road, there will be three wind turbines flanking it, at the height of where the light is. One on the left of the pole, one on the right, and one behind. The solar panel would be like an umbrella covering the light and turbines. (To reduce wind resistance, the panel might have to be made circular.)

Now considering the average dimensions of a streetlight that illuminates a typical boulevard,


 * 1) How big would the three said wind turbines need to be in order to appear the correct proportions to the streetlight?
 * 2) How many blades should it have, and what design should those blades be in order to procure the most energy out of the wind?
 * 3) How big must this circular solar panel be in order to cover the light and turbines like an umbrella?
 * 4) How big/tall would the battery need to be stored inside the shaft in order to provide 168 hours' worth of LED lighting without any charging input whatsoever?
 * 5) How much would the said battery cost?
 * 6) How many watts does a typical LED streetlight use?
 * 7) Per 10% of power recharged to the battery, how much sunlight would the solar panel need?
 * 8) How fast would the winds need to hit the turbines in order to cancel out the watt usage of the LED streetlight?
 * 9) Considering the average weather patterns for the state of Kansas, how long would the said streetlight take to give a net of 1,000 KW to the grid?
 * 10) How many KWs would it give to the grid each month? Therefore, how much money would it generate, assuming 10¢/KWh?
 * 11) How much would a typical LED-lit boulevard streetlight cost?
 * 12) How much would each of those said turbines cost?
 * 13) How much would the said solar panel cost?
 * 14) Putting labor and the cost of all these together, how long would one such streetlight take to pay for itself, assuming typical Kansan weather patterns?
 * 15) What widely-available items can I assemble together to create a fully-working tabletop-scale model of the said power-generating streetlight?
 * 16) How do I pitch the idea to any environmentally-inclined energy companies so that I can win a contract to get it built across many miles of roads nationwide?
 * 17) I would like to see these streetlights light the length of all Interstate highways 5 lights to a mile, on each side. How do I make this plan follow through?
 * 18) In order to close down all coal, other polluting, and nuclear power plants in the United States, how many of these streetlights would the nation need?
 * 19) How many miles of four-or-more-laned roads are there, therefore, how many of these streetlights would I need per mile of these roads, in order to shut down the above-said power plants?
 * 20) MS Paint would be a tad troublesome to draw 3D sketches. Therefore, in what free program can I draw a 3D sketch of this streetlight?
 * 21) If I decided to add a bendable solar panel that wraps around down the full length of the pole, how much extra power could it produce in Kansan weather, how much would that panel cost, and how long would it take to pay for itself?
 * 22) Do you have any questions?

--Let Us Update Dusty Articles 14:25, 28 December 2010 (UTC)

First responses

 * Solar panels on street lights certainly exist (see New Jersey's program to install 200,000 on street lights and power poles) Even solar/wind off-grid ones exist Rmhermen (talk) 14:56, 28 December 2010 (UTC)
 * The big drawback with solar panels is the problem of cleaning the grime off . I wonder how they're going to deal with that. (A fleet of expensive aerial work platforms using lots of energy is my assumption, or perhaps they'll just leave the panels dirty and let them operate at 20% efficiency, or use some combination of the two strategies.) 213.122.19.181 (talk) 15:12, 28 December 2010 (UTC)


 * This hybrid wind and solar powered lamp project was proposed in Shanghai, China. I scanned the proposal briefly; the English language grammar is atrocious, but the numbers seem very reasonable.  They discuss cost and power budgets, and some competing lamp technologies.  You might find it useful.  Nimur (talk) 15:47, 28 December 2010 (UTC)

LUUWDA's first follow-up
RMHermen, there are some problems with that design in your link: There could be three wind turbines mounted on that pole- to the left and right of, as well as behind the light. The panel isn't large enough. One that's placed like an umbrella over all the turbines and light atop the pole would have a larger area and not be impeded by the shadow of the fan.

I suppose that the solar panel can be sloped like a cone in order to let the rainwater rinse off all the grime, therefore preclude the need for AWPs.

If I can design a model of the solar wind hybrid streetlight that will out-generate the one shown in the link, then I will give the nation and the buyers a greater edge in environmental power generation.

I see that New Jersey is already well on its way to being an environmental power producer. Great job for them! (I recommend that they still also mount wind turbines for greater effect.) --Let Us Update Dusty Articles 16:12, 28 December 2010 (UTC)

Second responses

 * So many questions! Anyway, one I can answer is 20 - try SketchUp - it's free + reasonably easy to use. SmartSE (talk) 16:14, 28 December 2010 (UTC)


 * I was going to recommend Blender_(software). It's free and really hard to use, which gives a greater sense of achievement. 213.122.19.181 (talk) 16:20, 28 December 2010 (UTC)


 * One thought: Skip the battery. Batteries are expensive, wear out quickly, and often involve toxic chemicals/materials.  Instead just sell all the energy to the grid during the day (when usage, and hence prices, are higher) and buy it back at night.  One disadvantage to this is that you lose the "battery back-up".  That is, if the grid goes down, so do your streetlights.  However, streetlights aren't absolutely necessary, as cars have headlights, so we could get by without them during an outage. StuRat (talk) 16:32, 28 December 2010 (UTC)


 * The more heavy (and wind-catching) things you stick up the pole, the stronger the pole needs to be, and soon it will become like a pylon and cost a lot, cast a big shadow, and get in the way. Streetlight speaks darkly of metal fatigue and damage from high winds. 213.122.19.181 (talk) 16:48, 28 December 2010 (UTC)


 * Yes, and windmills make noise, have moving parts that require maintenance, can have pieces fall off, say in a hurricane, to create dangerous flying debris, etc. Perhaps just a cylinder of solar cells around the pole might be best (or just on the side facing the Sun).  I wonder if solar cells could be created in a saw tooth fashion like this:

/ |    | \        |  P  | / | O  | \ | L  | / | E  | \ |    |


 * The angled bits would be the solar cells. StuRat (talk) 17:27, 28 December 2010 (UTC)
 * That's a nice design. It could probably get wider lower down, where the extra bulk won't affect stability so much, tapering to a point at the top, although perhaps with a bare section right at the very base, to allow people to walk past it. 213.122.36.99 (talk) 18:38, 28 December 2010 (UTC)

1. 2. 8. See the article Wind turbine for ideas. 4. See the article Rechargeable battery for types and their energy densities. 9. 10 KW is a unit of power that makes no sense in these questions "how long would it take?" KWh is the saleable quantity. 15. One can buy small garden lamps that comprise LED's, a battery and a solar cell for daytime charging. 16. See the article Business case. But first find an "environmentally-inclined energy company" with an oversized PR budget. 17. This is one way. 18. 19. More than a few. 20. See 3D computer graphics software. Cuddlyable3 (talk) 18:58, 28 December 2010 (UTC)


 * For a bit of progress with 18 and 19, there's electricity consumption, which gives 14,378 kWh per person. The 2010 figure for US population is 308,745,538, so that makes 4,439,143,345,364 as a figure pending translation into a number of streetlights. Oh, minus 9.5% that comes from renewable energy already. So only 4017424727554.42 kWh needed. Much easier. 213.122.36.99 (talk) 19:14, 28 December 2010 (UTC)

To StuRat
StuRat, excellent ASCII sketch! I could put that in, along with the turbines and "panel umbrella" (but as long as that "umbrella" doesn't shade the other pole-mounted panel.)

To keep high winds from snapping off the wind turbine blades, they can be kept inside "cages" that surround all sides of the blades with some type of grating, so whenever anything falls off, it stays inside the said grating and does not cause a hazard below. To perform any needed maintenance, the utility worker would just need to unlock the grating with a skeleton key and open it like a door.


 * Thanks. I thought a bit more on it, and decided that a long, flexible spiral would be easiest to apply to existing utility poles, using suitable adhesives.  Here's a revised diagram:

|    | \       / |  P  | | O  | \ / | L  | | E  | \ / |    |


 * StuRat (talk) 06:55, 29 December 2010 (UTC)

To Cuddlyable3
9: Yes, how long would it take for one such solar wind hybrid streetlight to generate 10 KW of energy? If this doesn't make sense to you, would it to anyone else? Could they answer it?

15: Now how about miniature wind turbines? What can I get to make the miniature turbine parts, and where?

18 & 19: Yes, but is anyone able to do the math and get me a numerical approximation?

Thanks for the other tips though.

To 213.122.36.99
Thanks, so how many of these said solar wind hybrid streetlights would need to light our roads to provide 4.02 petawatt-hours of power?

Therefore, if we decided to light even the paved two-lane roads as well as all the roads with more lanes in the United States, how many of these streetlights would we need for every mile of these roads? --Let Us Update Dusty Articles 04:49, 29 December 2010 (UTC)

213.122.18.78's/213.122.36.99's Follow-up

 * The CIA World Factbook [] gives 6,506,204 km of US roads, paved and unpaved. (Not sure if this exactly congruent with "suitable for street lighting", but at least we're not discussing coastline lengths.) So that means ... wait, how much power does each one of your lamps generate? I think I missed that. Anyway 4017424727554 (kWh) / 6506204000 (m) makes about 617.476 kWh that each metre of road has to generate (per year, I assume). This site claims "A rotor diameter of 2 metres might yield about 500 kWh of electricity per year". I'm not sure what that site is, but it seems likely that they want to sell you turbines, and therefore have made optimistic estimates of turbine power based on a turbine on top of a hill. So (assuming no order-of-magnitude errors in my various sums and guesses), if you have two-metre wide rotors spaced one metre apart on every road in the US, I think you will fall somewhat short of generating enough power. (For heartwarming tales of improvised wind turbines, see William Kamkwamba.) 213.122.18.78 (talk) 09:37, 29 December 2010 (UTC)

LUUWDA's response to the IP user
That is for one rotor of wind turbine. Each streetlight in my design has 3, plus a solar panel umbrella atop them all, and as suggested by StuRat, down the shaft of the pole.

That means more than 3 meters apart from one another, but thanks to variables in the availability of wind & solar power, let's just make them 3 meters apart, assuming 500 kWh/year per rotor. (I am unsure how many square feet of solar paneling each streetlight will have, and therefore how many kWh/year they will generate.)

Then two of these streetlights would face each other from their shoulders, so that means we just need these streetlights 6 meters apart from one another.

Also consider the fact that some medians of boulevards and highways are also equipped with lightposts in the center. Since this means two lights have to shine on both sides of the road, there can only be two wind rotors. There will still be the solar panels though.

Once you factor the median lights in, how many streetlights per mile (or kilometer) do we need after all? --Let Us Update Dusty Articles 13:03, 29 December 2010 (UTC)


 * If the three rotors face in different directions, that doesn't mean they'll produce three times the power, since the wind only blows in one direction at a time. Windmills usually turn to face the wind. There's also the nifty vertical-axis option: Wind_turbine. (The Panemone WECS, on the other hand, is slated as "one of the least efficient types of wind turbine", so don't use one of those.) If the three rotors face in the same direction, close together, one behind the next, that configuration won't produce three times the power either. I'm not sure exactly what happens, but the rotor in front is going to disrupt things for the rotors behind. 213.122.0.247 (talk) 18:06, 29 December 2010 (UTC)

Fox barks
What does British fox barking sound like, and how can it be differentiated from dog barks? Thanks 92.29.118.30 (talk) 15:21, 28 December 2010 (UTC)


 * Well they kind of cough and yip, a bit higher and harsher than a dog. Also they're slightly more restrained and won't bark continuously for ages. Some recordings here: I tried the one from Woking, sounds like a fox to me. They also make some very unsettling screaming noises when fighting or mating (which they seem to like to do under my bedroom window in summer). 213.122.19.181 (talk) 15:30, 28 December 2010 (UTC)
 * The recording called "foxesbymoonlight" on the same site is the sound that I associate with winter and vixens calling looking for a mate. Richard Avery (talk) 19:43, 28 December 2010 (UTC)

I ask because I heard something that may or may not have been a male fox - a somewhat high pitched single rather long bark, then quite a long pause, then this single bark followed by a pause being repeated several times. It was in a wooded area in a suburb - I'm not sure if there is a house inside the wood or not. 92.15.14.203 (talk) 20:36, 28 December 2010 (UTC)
 * Another suspect might be the Muntjac which sounds a bit like a dog with a sore throat. They're increasingly common in woodland in the South East and Midlands. Alansplodge (talk) 00:08, 29 December 2010 (UTC)

Very good point, I now recall seeing somewhere else in the past a muntjac that barked while I was watching it, and my hazy memory suggests it was similar, although it did not do the long regular series of barks I heard above, probably because it had been disturbed by me. So I conclude that what I heard was probably a muntjac. 92.29.120.235 (talk) 12:56, 29 December 2010 (UTC)

Using spy satellite film to take pictures on the ground
I recall reading an article, maybe 5 years ago (that's a big approximation, I don't remember when it was), about someone designing a camera that took old film, intended for early spy satellites, and took high resolution pictures from the ground with it. I think I read about it in Discover (magazine), though it might have been Popular Science or something else entirely. I'm pretty sure it was a magazine I read it in, though. I recall that while the camera used film, they converted it to a digital file, rather than just print a huge picture. The example picture that was taken was of a beach scene. I remember that they had blown a section of the picture up, and found a couple of guys taking photos of the women on the beach with telephoto lenses from a bluff overlooking the beach. My Google skills are failing me; does anyone recall this article, or know what I'm talking about? Buddy431 (talk) 15:58, 28 December 2010 (UTC)


 * "The Sharpest Image," Popular Science, November 2005. —Bkell (talk) 16:44, 28 December 2010 (UTC)
 * Thank you so much. Buddy431 (talk) 17:06, 28 December 2010 (UTC)


 * Peripherally related spy-camera note: the BBC is running a documentary this week called Polar Bear: Spy on The Ice - you can see videos of the "spy-cameras" they used to film bears in their habitat in Norway here: 'Spy cams' film polar bears up close and Polar bears get the better of spy cameras. The only difference between a ground- and satellite- spy camera is where it is; satellite cameras might use different lenses (or mirrors), different film formats, or lower ISO film (nowadays, radiation-tolerant CMOS or CCD sensors), in order to facilitate long-range imaging from orbit.  They might have been specially engineered for small form-factor or other flight characteristics.  But otherwise, they need not be any different from a ground-camera.  Nimur (talk) 13:32, 29 December 2010 (UTC)
 * Well found Bkell, that reminds me of gigapan. SmartSE (talk) 14:58, 31 December 2010 (UTC)
 * Except Flint is (or was, it appears that he hasn't done anything recently) taking huge photos with one exposure, while gigapan just stitches together lower resolution photos to make big ones. Buddy431 (talk) 21:38, 31 December 2010 (UTC)

What does this mean?
What does "mildly discoid medial meniscus with accompanying myxoid degeneration" mean? 74.198.151.76 (talk) 18:30, 28 December 2010 (UTC)


 * Here's discoid meniscus, which has a picture labeling the medial meniscus. In my capacity as not a doctor, I think "accompanying myxoid degeneration" means it's gone all slimy. definition of myxoid 213.122.36.99 (talk) 18:50, 28 December 2010 (UTC)
 * Please remember that Wikipedia doesn't do medical advice. Your question should be referred to the medical practitioner who wrote the note in the first place. Tonywalton Talk 00:50, 1 January 2011 (UTC)

Density
So why hasn't the definition of density changed to be more accurate as to what density actually measures? Since the volume of one atom times 1,000,000 will be different than the volume of 1,000,000 atoms in a cluster? —Preceding unsigned comment added by 165.212.189.187 (talk) 20:11, 28 December 2010 (UTC)
 * "density of a material is defined as its mass per unit volume. "  That seems pretty straightforward to me.  As true today as the day it was written.  I don't understand your point about atoms. APL (talk) 20:34, 28 December 2010 (UTC)


 * The unit you are looking for is called the Molar concentration. Ariel. (talk) 20:36, 28 December 2010 (UTC)

No. If there is "free space" among (on the "inside") 1,000,000 atoms in a cluster of a particular substance and we attempt to measure the density (mass/volume) we are incorrectly including the free space between those atoms as part of the volume. Conversely, if we attempt to measure the volume of one of those atoms we would not be including any any of that same free space as there is only one atom. Get it? —Preceding unsigned comment added by 165.212.189.187 (talk) 21:05, 28 December 2010 (UTC)
 * What possible value would such a measurement have?
 * Besides, the fundamental particles seem to be points. In which case your way of measuring volume would just give you a "divide by zero" every time. APL (talk) 21:08, 28 December 2010 (UTC)


 * Volume and density are clearly defined on a macro-scale. On a sub-atomic scale, all space can be viewed as either full or empty, depending on your view.  Volume, mass and density have no meaning at lowest level (where there is no mass, only energy, (depending on your viewpoint) ).    D b f i r s   21:39, 28 December 2010 (UTC)

APL, exactly my point. —Preceding unsigned comment added by 165.212.189.187 (talk) 20:16, 29 December 2010 (UTC)


 * Alternatively, the probability distribution waveform of any particle is distributed throughout all space, so everything would have zero density by this (silly) analysis. There was a discussion a few days ago: Reference_desk/Archives/Science/2010_December_22    D b f i r s   10:34, 30 December 2010 (UTC)
 * ... though if you integrate the product of particle mass and the probability distribution waveform over any conventionally defined volume, and add for all particles conventionally regarded as within the volume, the result will be conventional density to a very high accuracy.   D b f i r s   11:21, 30 December 2010 (UTC)

Dbfirs, What is the density of a sponge wrapped in plastic wrap? is it equal to the density of the plastic wrap PLUS the density of the sponge, or the combination as it exists? I guess it depends on your viewpoint, right? —Preceding unsigned comment added by 165.212.189.187 (talk) 19:03, 30 December 2010 (UTC)
 * No, it just depends on the exact question that you ask. The density of the sponge remains the same whether it is wrapped in plastic or unwrapped.  The density of the package including the sponge inside would be a different question with a different answer.  The density of compressed sponge would be much higher, whether or not it is wrapped.  Perhaps you are thinking of a question such as "what is the density of a (specified) gas?", where the answer, even in the absence of a container, depends on the temperature and pressure.    D b f i r s   20:44, 30 December 2010 (UTC)

Exactly my point: There are different densities for the same "thing" depending on the "way" one measures it. To me that means there is a flaw in the DEFINITION.

rubber cement
how stong is rubber cement compared to liquid nails —Preceding unsigned comment added by 66.66.92.152 (talk) 20:13, 28 December 2010 (UTC)
 * Different glues work best on different materials. A good glue is stronger than the material it's glued to, anything more is pointless, and anything less is not a good glue. (But stress concentration explains why things will often re-fail at the glue point, even if the glue is strong enough.) Ariel. (talk) 20:39, 28 December 2010 (UTC)
 * In my experience "No More Nails" would be very much stronger than rubber cement or "cow gum" as it is also known. The rubber cement is for sticking paper. I stuck some wood to plaster with NMN, and when I prized it off it was the plaster that broke off, not the NMN. I assume "Liquid Nails" is the same as NMN. NMN is not flexible, rubber cement is. 92.15.14.203 (talk) 20:42, 28 December 2010 (UTC)
 * Yes, the problem with "liquid nails", "no more nails" etc is not the strength of the glue but the problem of getting a good bond with both materials. For some surfaces, especially flexible materials, rubber cement will form a stronger bond, so will serve its purpose better even though the glue itself might be weaker.    D b f i r s   21:31, 28 December 2010 (UTC)

Brie cheese
OK, I've been wondering this for a while now. Why does brie cheese smell like semen? THis may sound crass but it is out of genuine curiosity that I ask this, and so I'm looking for a genuine, scientific answer. Thank you. 24.92.70.160 (talk) 20:39, 28 December 2010 (UTC)


 * Smell is a bit subjective, but the odor of Brie (indeed of all cheeses) is due to the particular cheese cultures used to make the cheese. The article Brie covers some of the specifics of manufacture, but the mold used to culture and flavor brie is Penicillium candidum.  -- Jayron  32  21:07, 28 December 2010 (UTC)


 * Amines are well reputed for being malodourous. In spoiling cheese, nitrogen in the form of protein is digested by microorganisms, into the amines that you're smelling. Note, the microorganisms probably got on the cheese from where it was stored, either by yourself or your retailer. If you're interisted: Spermidine --Plasmic Physics (talk) 09:14, 1 January 2011 (UTC)

Saliva
Why does saliva get foamy when you spit? ScienceApe (talk) 21:28, 28 December 2010 (UTC)
 * Proteins in the saliva provide a medium in which to form bubbles. Its the same reason why whipped eggs form foams (soufflé or meringue), or why sea foam forms.  -- Jayron  32  21:37, 28 December 2010 (UTC)

Clover
Why don't humans eat clover? – Athaenara ✉  22:48, 28 December 2010 (UTC)


 * Some humans do eat clover: http://www.associatedcontent.com/article/2851188/cooking_fried_white_clover_blossoms.html?cat=57 (damn spam filter). Search "fried clover" or "eating clover" in your favorite search engine to find many more examples. Buddy431 (talk) 23:10, 28 December 2010 (UTC)


 * Trifolium repens discusses some of the culinary uses of that species; Trifolium pratense points out that this particular species does have estrogen-like compounds which makes it troublesome for some people. General notes seem to be that it is hard to digest raw. --Mr.98 (talk) 23:50, 28 December 2010 (UTC)


 * Which might explain why we eat it indirectly, such as in the form of clover honey. StuRat (talk) 00:45, 29 December 2010 (UTC)


 * Fenugreek (not in the clover genus, Trifolium, but in a related genus, Trigonella) is eaten in various forms in many cultures. --Dr Dima (talk) 00:09, 30 December 2010 (UTC)


 * They don't have any crimson to go with it? --Trovatore (talk) 03:04, 30 December 2010 (UTC)




 * More seriously, I seem to remember that as kids we used to pluck the clover flower, and suck the nectar out from the stem. I don't see any mention of that in any of the articles named above. --Trovatore (talk) 03:11, 30 December 2010 (UTC)
 * Could you be thinking of honeysuckle, Trov? Wiki Dao  &#9775;  (talk)  03:20, 30 December 2010 (UTC)
 * No, I'm pretty sure it was clover. --Trovatore (talk) 03:28, 30 December 2010 (UTC)
 * Because that's a very common thing to do with honeysuckle. I don't see how one could do that with a clover flower.  Wiki Dao  &#9775;  (talk)  03:35, 30 December 2010 (UTC)
 * You just pinch off the flower, put your mouth on the green part, and suck. It isn't complicated.  No guarantees though -- I think the last time I tried this, I might have been four.  --Trovatore (talk) 03:55, 30 December 2010 (UTC)
 * Yes, that is a very young age from which to retain an accurate memory... Wiki Dao  &#9775;  (talk)  04:03, 30 December 2010 (UTC)
 * Nevertheless I believe it was in fact an accurate memory. --Trovatore (talk) 04:04, 30 December 2010 (UTC)
 * Okey-doke. If you say so.  Come spring-time, we'll have to give both a try and see which works. :)  Wiki Dao  &#9775;  (talk)  04:09, 30 December 2010 (UTC)
 * Video on how to eat honeysuckle nectar:
 * Can't seem to find one on how to eat clover nectar (at least, without using a proboscis...). Wiki Dao  &#9775;  (talk)  04:36, 30 December 2010 (UTC)
 * I do not see why you are so skeptical about this. Clover is well-known as a source of nectar.  Why shouldn't it come out the base, if you suck on it?  As for honeysuckle, it has never been common in any place I have ever lived. --Trovatore (talk) 04:40, 30 December 2010 (UTC)
 * I have never, in my experience, sucked nectar from clover, nor ever seen anyone else do so. Sucking the nectar from honeysuckle I have done many times, and seen others do many times, too.  My experience of this is from Virginia to Vermont, and once or twice even somewhere in the midwest.  So at this point, I'd like to see an RS for sucking clover nectar, especially if, as Sluzzelin seems to have thought, doing that might be "hazardous".  Wiki Dao  &#9775;  (talk)  04:50, 30 December 2010 (UTC)
 * Well, the "hazardous" thing is a bit overwrought in my opinion. Someone brought up that clover has phytoestrogens, and in unusual circumstances those can be harmful, but a lot of things have phytoestrogens.  And of course as always, it's hard to know what might have been sprayed on (or peed on, or crapped on) a patch of grass not under your control, but there could be similar issues with honeysuckle.
 * As for a reference, Sluzzelin apparently gave you one (though I haven't yet followed the link). --Trovatore (talk) 05:11, 30 December 2010 (UTC)


 * Yes, sucking the nectar from individual white clover flowers is as well-known in the UK as making daisy chains: it's something children will generally try when lounging on a lawn full of them. You can also do it with the flowers from dead nettles, Adam and Eve plant, and the plant I always forget the name of that is a bit like ivy (to a child) and has purple and white varigated flowers that have a cone at the base and then spread in a flat circle. Anyway, I don't know where you got the idea this only works with honeysuckle: white clover was always the featured flower when children did this in my books, but I had more success with a variety of others. I was often scolded for deflowering an entire plant to suck its nectar ;) 86.164.67.8 (talk) 09:00, 30 December 2010 (UTC)
 * Ok, I yield to the emerging consensus. Always fun to learn something you didn't know before... :)  Wiki Dao  &#9775;  (talk)  16:15, 30 December 2010 (UTC)
 * When I was young, on holiday in the Scottish highlands, I and a friend used to do this with fuschia flowers. (I don't know why fuschias were growing wild in abundance in the Scottish highlands, but there they were.) We would bite the bulging hind part of the flower (just past the green lump), which I guess is the nectary. A burst of delicious nectar would result. Since then I've tried the trick out whenever I see a fuschia, but puzzlingly it's never worked since. I just get a mouthful of dry flower parts. Maybe only those ones growing in the far north are full of nectar. I don't see why that should be. 213.122.8.29 (talk) 16:57, 30 December 2010 (UTC)
 * Maybe bees (and other insects) harvested whatever nectar was available? And in the far north it's too cold for them? (Is that actually true?) Try a fuschia indoors, where there are no bees. Ariel. (talk) 20:14, 30 December 2010 (UTC)

would using and electric welder demagnetise a rare earth magnet
I have a Magneto with rare earth magnets fitted to my classic motorcycle, I have recently welded a compounent to the chassis of the machine but forgot to remove/disconect the Magneto whilst doing the repair.Would this have had an effect on the magnets within the Magneto. (de-magnetised). —Preceding unsigned comment added by 86.11.245.195 (talk) 23:23, 28 December 2010 (UTC)
 * Rare earth magnets have a high resistance to demagnetization, unlike ferrous magnets they shouldn't demagnetize in the presence of other magnetic fields. Rare earth however magnets will still demagnetize if they are heated past a certain point, for common N type magnets this starts at a relatively low temp of about 80 deg C. If you didn't heat the magnets with the welding, but are just worried about the magnetic fields then you should be ok. Of course, this is just my opinion and it could be wrong. If the magnets aren't rare earth, or if they did manage to heat up, also depends on what kind of welding you used, some welding creates much higher magnetic fields then others. In the end, you'll probably still need to test the magneto to see if it is working correctly. Vespine (talk) 01:08, 29 December 2010 (UTC)
 * The easiest way to test it would be to start up the motorcycle. PhGustaf (talk) 03:57, 29 December 2010 (UTC)