The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
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)[reply]
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 timbrein 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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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 ? Rkr1991(Wanna chat?)13:00, 28 December 2010 (UTC)[reply]
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)[reply]
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)[reply]
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 ? Rkr1991(Wanna chat?)15:59, 28 December 2010 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
@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. Rkr1991(Wanna chat?)06:06, 29 December 2010 (UTC)[reply]
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,
How big would the three said wind turbines need to be in order to appear the correct proportions to the streetlight?
How many blades should it have, and what design should those blades be in order to procure the most energy out of the wind?
How big must this circular solar panel be in order to cover the light and turbines like an umbrella?
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?
How much would the said battery cost?
How many watts does a typical LED streetlight use?
Per 10% of power recharged to the battery, how much sunlight would the solar panel need?
How fast would the winds need to hit the turbines in order to cancel out the watt usage of the LED streetlight?
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?
How many KWs would it give to the grid each month? Therefore, how much money would it generate, assuming 10¢/KWh?
How much would a typical LED-lit boulevard streetlight cost?
How much would each of those said turbines cost?
How much would the said solar panel cost?
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?
What widely-available items can I assemble together to create a fully-working tabletop-scale model of the said power-generating streetlight?
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?
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?
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?
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?
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?
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?
Solar panels on street lights certainly exist (see New Jersey's program to install 200,000 on street lights and power poles[2]) Even solar/wind off-grid ones exist [3]Rmhermen (talk) 14:56, 28 December 2010 (UTC)[reply]
The big drawback with solar panels is the problem of cleaning the grime off [4]. 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)[reply]
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)[reply]
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.
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)[reply]
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#Dangers speaks darkly of metal fatigue and damage from high winds. 213.122.19.181 (talk) 16:48, 28 December 2010 (UTC)[reply]
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:
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)[reply]
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#Free packages. Cuddlyable3 (talk) 18:58, 28 December 2010 (UTC)[reply]
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)[reply]
LUUWDA's second follow-up
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:
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?
The CIA World Factbook [[5]] 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 [6] 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)[reply]
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.
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#Vertical_axis_design. (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)[reply]
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: [7] 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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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. TonywaltonTalk00:50, 1 January 2011 (UTC)[reply]
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)[reply]
"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)[reply]
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)[reply]
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)[reply]
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)). Dbfirs21:39, 28 December 2010 (UTC)[reply]
... 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. Dbfirs11:21, 30 December 2010 (UTC)[reply]
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)[reply]
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. Dbfirs20:44, 30 December 2010 (UTC)[reply]
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.
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)[reply]
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)[reply]
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. Dbfirs21:31, 28 December 2010 (UTC)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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[9], doing that might be "hazardous". WikiDao ☯ (talk)04:50, 30 December 2010 (UTC)[reply]
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.
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)[reply]
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)[reply]
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)[reply]
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)[reply]
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)[reply]
p.s. am I also riht that the fork could just as easily have 4, 6, 8, or 12 prongs? In this case, half of the prongs would oscillate one way and half the other??? (inverse frequency) what ensures this?? 87.91.6.33 (talk) 02:11, 29 December 2010 (UTC)[reply]
For the 1st question, my guess is that the "handle" creates a node. This explains why the two prongs oscillate in opposite directions, because they are really one bent prong with a handle in the middle. Not sure about more then 2 forks, I suppose it's possible but would depend on specifically how it is designed. Vespine (talk) 03:34, 29 December 2010 (UTC)[reply]
I think the answer to this is quite simple: the tuning fork starts out in some combination of equal-phase and opposite-phase vibration, but the equal-phase part is quickly damped out by the mechanism described by that Yahoo answerer. You'll always end up with mirror-symmetric oscillation eventually as long as a mirror-symmetric oscillation mode exists and you started out with at least some energy in that mode. I see no reason why it couldn't also work with 3, 5, ... prongs, since those shapes can oscillate symmetrically too. The oddly titled article Odd sympathy discusses this. I'm not sure I understand what happens to the metronomes on the soda cans, but I think it's somewhat different. -- BenRG (talk) 11:32, 29 December 2010 (UTC)[reply]
I once read that when a woman drops something she tends to throw her hands back and step back, as if avoiding anything further to do with the falling object at that moment, while a man will use all his limbs in a seemingly desperate attempt to slow the object in its fall to the floor. Some random original research would seem to support that view, but I have no idea if it's more broadly true. HiLo48 (talk) 05:48, 29 December 2010 (UTC)[reply]
I suspect whoever wrote that was completely making things up, either based on a small selection of people they had known to drop things, or just because it matched how they thought the world worked. It doesn't fit with any of my personal experience or observations, nor does it seem at all consistent with anything I have read on the actual science of gender differences. Did you, perhaps, read it in a fiction book? 86.164.67.8 (talk) 17:41, 29 December 2010 (UTC)[reply]
It may be a counterpart to an impulse a highly developed capacity to grasp. The hands are used to hold onto something, and they do that under a wide variety of circumstances and over extended periods of time. The hands of humans are very well developed in this area and there is probably complex mental functioning supporting the grasping functions of the hands. The realization that there is a failure in that function probably causes complex mental reactions. Somehow, I would guess, that leads to overreaction, or fear. Bus stop (talk) 12:25, 29 December 2010 (UTC)[reply]
The answer to this, I think, is actually quite complex. The mechanism is actually a way of speeding reaction times, but the way we perceive it is shaped by some special brain mechanisms. Some of the factors that come into play are discussed in the article Neuroscience of free will, especially the section relating to reaction times. Looie496 (talk) 16:36, 29 December 2010 (UTC)[reply]
It think it is a VERY good question, I would love to read a study on this, my emotional state when I drop something insignificant is, for 1 or 2 seconds, completely an over-reaction, given the non-gravity of the situation. Maybe Sean or Bus are onto something here. --Lgriot (talk) 14:15, 30 December 2010 (UTC)[reply]
If it is a food item and you are a proto-human you may lose that food item: a fellow of your own species may pick it up and run away. Bus stop (talk) 19:56, 30 December 2010 (UTC)[reply]
Totally OR: Remnant from our tree-dwelling monkey-like ancestors? They evolved a fear of dropping things, because it would very frequently mean you loose it forever, and the only things a tree dwelling creature would we have in their hands is either valuable food, or ideed as mentioned above, a baby. Droping any of of the 2 would have either serious or extremely serious evolutionary consequences? --Lgriot (talk) 09:35, 31 December 2010 (UTC)[reply]
Contrary to popular opinion, humans - homo sapiens - are not the only primates possessing opposable thumbs. Chimpanzees and monkeys can oppose the thumb to the index digit. What makes the human hand unique in the animal kingdom is the ability of the small and ring fingers to rotate across the palm to meet the thumb, owing to a unique flexibility of the carpometacarpal joints of these fingers, down in the middle of the palm. This is referred to as "ulnar opposition" and adds unparalleled grip, grasp, and torque capability to the human hand. This feature developed after the time of Lucy, a direct human ancestor, who lived about 3.2 million years ago.
And from the same source:
About a quarter of the motor cortex in the human brain (the part of the brain which controls all movement in the body) is devoted to the muscles of the hands. This is usually illustrated with a drawing of a human figure draped over the side of the brain, body parts sized proportional to the amount of brain devoted to their movement, referred to as a homunculus - as illustrated in this drawing from Dr. Wilder Penfield's monograph "The Cerebral Cortex of Man." (the illustration is at that source)
Inadvertently dropping something from one's hands requires an immediate response under certain circumstances.
The comment above about men-v-women on this issue reminds of an incident from my own life. A female coworker and I found ourselves in a van with a flat tire. An older Chevy Astro as I recall. I jacked it up and took the flat off. Right as I did that the jack sank suddenly into the soft earth and the van began to tilt and was seemingly going to fall. I grabbed the edge of the wheel well and pulled for all I was worth, and began urging my co worker to retrieve the jack and re-position it. She had already backed up to a safe distance outside the path of the tilting van and laughed at the very suggestion that I could hold this van up while she crawled underneath it and recovered the jack. She was probably right, and I would have hated to crush her skull or spine that day, but it rather shattered my illusion of being Superman. Beeblebrox (talk) 00:01, 2 January 2011 (UTC)[reply]
What kind of holly?
The holly and the icy
What kind of holly is this? I never realised that there were multiple holly species until this evening, when I discovered that there were lots of different categories at Commons for different species of holly. Nyttend (talk) 05:04, 29 December 2010 (UTC)[reply]
I'm not sure we can tell from that one picture. There are literally hundreds of different species and/or hybrids of Holly, and many are likely to be indistinguishable execpt by careful, direct, examination by a knowledgeable botanist. See Holly#Selected_species for an idea of the problem. Browsing through several of these that have pictures in the articles, I can't find much to distinguish them either from each other, or from your picture. --Jayron3205:17, 29 December 2010 (UTC)[reply]
Hello. Is antimatter attracted or repelled by dark energy? Is there anything in the universe which is attracted by dark energy? Thanks in advance.--Leptictidium (mt) 11:32, 29 December 2010 (UTC)[reply]
Dark energy (not dark matter) is basically another way of looking at the metric expansion of space. As such, it's a property of the vacuum, rather than something to do with matter, so normal matter vs. antimatter is irrelevant.
I'd like to add that it is unknown whether or not dark energy is a property of the vacuum. That is a leading theory, but alternative theories (such as quintessence) would allow the repulsive effects of dark energy to be associated with some new type of particle. Since we don't really understand what causes dark energy, it is safe to say that there are lots of possible explanations. Some are more plausible than others. Dragons flight (talk) 18:34, 29 December 2010 (UTC)[reply]
It depends very much on the actual warhead. With a dead weight, maybe around a dozen. With a HE warhead, I'd guess hundreds. In both cases, there would be a very large spread of possible outcomes. If you assume WMD loads, the numbers can become much higher. --Stephan Schulz (talk) 14:02, 29 December 2010 (UTC)[reply]
With due respect, the OP's scenario is worrying about cruise-missile targeting from the vantage point of "concerned citizen," and not from that of a "geopolitical strategist." Most reliable references on the strategic implications of cruise-missiles focus on their cost-benefit analysis; and most rational strategists would opt to target airports and air-bases, not busy city streets. Cruise Missile Proliferation in the 1990s discusses details and specifications some of the various missile capabilities known to exist in various countries. The Cruise Missile Challenge, a policy report published by independent agency CSBA, gives a good overview of cruise missile politics, cost, and even discusses their potential strategic use in the Taiwan Strait conflict. Bear in mind, cruise missiles are really expensive - and Taiwan doesn't have many of them; so strategically, the most significant targets for them would be military airfields (where a single strike could incapacitate hundreds of millions of dollars of enemy aircraft). Airbase vulnerability to conventional cruise-missile and ballistic-missile attacks, published by the infamous RAND Corporation, provides a stunningly (and frighteningly) detailed scenario of potential damage (and vulnerability of) an American air-base to an enemy cruise-missile attack; and it lays out the cost-benefit analysis of strategic and tactical missile strikes. Regarding blast range, collateral damage, casualties, and targeting effectiveness, of course that sort of detail would be highly confidential; but you can easily estimate the power of a 200 kg warhead and the probability of landing on a crowd of any particular density of people-per-square-meter. (But you can see maps, diagrams, and blast-radii in that altogether terrifyingly descriptive RAND book). Ultimately, keep in mind that military use of cruise-missiles against civilian targets is both expensive and geopolitically stupid - the world does not look kindly on the use of powerful technological weaponry against civilian targets. Taiwan would be unwise to expend its very limited stockpile of tactical or strategic missiles against a civilian target; each missile fired at a civilian target would clearly aggravate their adversary; and simultaneously, it would do little to impede the Chinese military capability for retaliation. Nimur (talk) 14:10, 29 December 2010 (UTC)[reply]
Also, deliberately attacking the civilians of your enemy is prohibited by the Fourth Geneva Convention (1949). You can, say, attack the Ministry of War's building, even if doing so will cause civilian casualties, but you can't launch attach that will solely cause civilian deaths. CS Miller (talk) 15:29, 29 December 2010 (UTC)[reply]
When was the last time a world-class business city was attacked by a state's armed forces using big-enough-weapons? The city must be a key player in international business (e.g., NY, London, Tokyo, HK ...). Did it ever happen after WW2? The Chinese civil war (-1949) was not a war between two countries. Berlin was only denied land-based access by the Soviets. Seoul was not an international business city at the time of Korean war. 1950s and 1960s Saigon might have been a large city however Vietnam as a French colony was not very "international". Beirut has always been a regional city. The 9/11 attack was not ordered by any country. Baghdad certainly was not very international. -- Toytoy (talk) 18:12, 29 December 2010 (UTC)[reply]
I can't define it. However, it must have a certain percentage of investments from many major 1st world countries. As a result, if you attack this city, investors could get very angry at you. You not only make the victim country very angry, but you also make many other 1st world countries very very unhappy. Let's say I bombed a small town in Kansas. People around the world may never heard of that town (population 32). They do not get very angry. But if I bombed London or Paris, people all over the world knew the city, many people have money in these cities, they get very very very angry. -- Toytoy (talk) 18:21, 29 December 2010 (UTC)[reply]
I asked because 'When was the last time a world-class business city was attacked by a state's armed forces using big-enough-weapons?' is quite an interesting question that I don't know the answer to....um...Kuwait City, Belgrade...maybe...I'm struggling. Sean.hoyland - talk18:35, 29 December 2010 (UTC)[reply]
The Hsiung Feng IIE's modern 200 kg high explosive payload might be roughly comparable to the WW2-era 980 kg Amatol payload of the German V-2 missile. The worst loss of life in a single V-2 attack was 160 killed and 108 seriously injured and a modern reconstruction (see article) demonstrated that the V2 creates a crater 20 m wide and 8 m deep. Cuddlyable3 (talk) 22:19, 29 December 2010 (UTC)[reply]
Note of course modern Hong Kong in many parts has a much higher population density then pretty much anywhere in wartime England I would guess Nil Einne (talk) 19:55, 30 December 2010 (UTC)[reply]
Elipitical Orbit
I would like to know whether the orbit of a planet/satellite become an elipitical orbit if its tangential velocity is reduced or increased beyond the confines of a circular orbit. References preferable. --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time!12:35, 29 December 2010 (UTC)[reply]
Yes it does (in both cases), at least as long as an increase in velocity is not so large as to make the orbit unbound (i.e. parabolic or hyperbolic). In the spherically symmetric gravitational field of the central body any (bound) orbit is periodic, i.e. the satellite has to return to its original position. If you decrease the velocity, that point will become the apocenter (i.e. the point farthest from the central body) of the elliptical orbit, if you increase the velocity it will become the pericenter. --Wrongfilter (talk) 12:57, 29 December 2010 (UTC)[reply]
Regarding references: I highly recommend the book To Rise From Earth, which provides a straightforward explanation of orbital mechanics that is accessible to any interested reader (even if they don't have a firm background beyond basic algebra). This book is intended to introduce the concepts and basic mathematics of spaceflight without requiring a full-blown degree in astronautics. It is suitable for anyone with at least a junior-high or high-school level of algebra, and claims to use "no equations" to describe orbital mechanics (though I seem to recall a few). There are also plenty of textbooks that study this subject in greater details, if you do have at least some background in basic calculus and physics. And if you are interested in professional grade space navigation, NASA provides DESCANSO, a compendium website of educational and technical resources, including free textbooks, for Deep Space Communications and Navigation systems that will hold nothing back on the "details." (After all, if you want to point your communications antenna at an interplanetary probe, you had better calculate its orbit exactly - no "approximations"). Nimur (talk) 13:41, 29 December 2010 (UTC)[reply]
Radiotherapy and many (but not all) forms of chemotherapy rely on the greater susceptibility of rapidly dividing cells to DNA damage. While the malignant cells targeted by these therapies certainly fit the bill, there are a few other places in the body where normal cells divide rapidly; it is the sensitivity of these tissues that often establishes the maximum tolerable dose for these therapies, and which is responsible for many of the side effects associated with these treatments. Quickly dividing cells in bone marrow, the lining of the gastrointestinal tract, and in hair follicles are all sensitive to DNA-damaging treatments, leading to (respectively) anemia, (some of the) nausea, and hair loss associated with certain types of cancer treatment. With radiation therapy, hair loss will only occur within the areas exposed to ionizing radiation; with systemic chemotherapy hair loss can be widespread. TenOfAllTrades(talk) 19:39, 29 December 2010 (UTC)[reply]
Animal slime?
With regards to the slime secreted by slugs/snails, frogs, fish, eels, etc. - is it all the same basic stuff, regardless of the creature that secreted it (I guess that some animals can add toxins and irritants to it)? If so, is there a an easily writeable chemical formula for this substance? --95.148.109.133 (talk) 18:54, 29 December 2010 (UTC)[reply]
That's kinda like asking "What is the blood type of someone who's asleep". Even ignoring the fact that "intelligence" is a nebulous, unmeasurable quality to begin with. So, insofar as someone has a measurable thing called "intelligence" at all, it shouldn't be different just because they are asleep. Since someone cannot take an intelligence test while asleep (indeed, one cannot take any test while asleep) it seems a silly proposition to begin with. Animal intelligence is even more difficult to assess; we can measure animals on their ability to perform certain tasks (such as run through mazes or pfoint at pictures to get food), but exactly how or why these tasks might indicate "intelligence" is pretty difficult to assess. --Jayron3220:56, 29 December 2010 (UTC)[reply]
You can still respond to stimuli while asleep. You can't take an IQ test, but neither can any animal except a human. Can't they still test your intelligence the same way they test that of an animal? I don't see why intelligence would be the same when you're asleep. People have been known to walk and talk in their sleep, and they certainly don't act as smart as people who are awake. — DanielLC21:23, 29 December 2010 (UTC)[reply]
What particular measure of intelligence do you propose? The WAIS may be difficult to administer to someone who is unconscious. As I stated, the very concept of quantifying intelligence is problematic even for humans. Its hardly a rigourous, scientific thing. This is even moreso for animals; assigning a quantity, which may not have any real meaning, to a subject which cannot even be tested for that quantity, is doubly meaningless. --Jayron3221:29, 29 December 2010 (UTC)[reply]
And you can't test the intelligence of a sleeping animal anyway. Intelligence is not something floating around in your blood. When they talk of animal intelligence, they either talk in very large generalizations regarding the forebrains of an entire species (which you could do about humans, too, but it doesn't tell you anything surprising, asleep or otherwise) or they talk about things like problem solving, which require being awake to measure. --Mr.98 (talk) 22:29, 29 December 2010 (UTC)[reply]
I wouldn't recommend a test designed for humans. How do they compare the intelligences of animals? Can't they also do stuff like use an MRI to see what sections of the brain are being used, an other tests to see what those sections actually do?
Sleep (see article) is clearly a period when the person does not demonstrate their intelligence. For example, the sleeper is oblivious to unexpected dangers and will not converse. However experiments in sleep deprivation show that sleeping has a rejeuvenating effect on memory whose health is essential to intelligence, see the article Sleep and memory. Higher mental activities such as learning and creativity (see articles) can also occur during sleep. A possible answer to the OP is that the sleeper's mind is liberated from its survival needs to be intelligent, conscious and coherent, but that all the mental resources to be so are present in latent form. The Autonomic nervous system continues in sleep to control essential functions such as heart rate, respiration and digestion but these are classed as evolved rather than intelligent functions. Cuddlyable3 (talk) 21:55, 29 December 2010 (UTC)[reply]
Intelligence during sleep can manifest as the creation of dreams which are full of puns, and which relate recent events to meaningful events and themes in one's history. Dreams are often forgotten within seconds of waking, but occasionally I have been able top recall dreams which would be amazing works of creative writing if done during waking hours. Edison (talk) 19:41, 30 December 2010 (UTC)[reply]
I don't see why it needs to be lucid. The only difference between lucid dreaming and the ordinary kind is that you've figured out that you're dreaming. Knowing that fact is not a necessary condition to exercise cognition, nor to be conscious (in the sense of phenomenal consciousness).
In fact I don't think it's necessary even to be dreaming. I'm pretty sure there are times that I am asleep, but both phenomenally conscious and exercising cognition. --Trovatore (talk) 03:59, 31 December 2010 (UTC)[reply]
True, but it's always nice for it to be confirmed by those of us with access to the standard reference sources! Colourless gas that condenses to a pale yellow liquid. Physchim62(talk)15:17, 30 December 2010 (UTC)[reply]
December 30
Wormholes
From what I have heard in the past Hawking said that wormholes cannot exist because if matter gets sucked into the blackhole, it gets destroyed. So one cannot "enter" a blackhole and survive it. So what's the latest theory about it?
Also I have read in a newspaper that all blackholes leads to a new universe. Is that true?
Please explain in layman terms without complex equations.
Total non-expert opinion: The only way we have to test such a thing with our current level of technology is through "thought experiments." It may be decades or even centuries before we can actually know the answer to such a question with any degree of certainty. So, Hawking is probably right, but even he doesn't know for sure. Beeblebrox (talk) 00:32, 30 December 2010 (UTC)[reply]
No, one can not do that because as far as we know they don't exist. There are some thought experiments where they have them, but don't confuse that with actually existing. BTW if you really could convert all matter entering a wormhole to energy that would be tremendously useful, plus you could use them for long distance communication. But in any case the difference between matter and energy is not very clear, so I don't see why a wormhole would allow one and not the other. Ariel. (talk) 01:22, 30 December 2010 (UTC)[reply]
I haven't heard anything like that. But some people define the inside of a black hole as a different universe since it's isolated from its parent. Ariel. (talk) 01:22, 30 December 2010 (UTC)[reply]
Sort of. Its a bit more complex than that. In on definition, the Universe consists of all of the locations which are capable of exchanging information with each other (or places which have overlapping light cones) or something like that. The thing about black holes is that anything which crosses the event horizon is suddenly incapable of exchanging information anymore; such that inside of the event horizon is effectively "outside" of our universe, based on the above definition of The Universe. See cosmic censorship. This does NOT mean that the inside of the event horizon is a universe with galaxies and stars looking like our universe. It just means that, effectively, since it cannot exchange information with anywhere in our universe, it isn't part of our universe. --Jayron3219:50, 30 December 2010 (UTC)[reply]
The wormhole that exists in the Schwarzschild metric (the simplest solution to Einstein's field equations including a black hole) is not an interesting wormhole because a) it disappears when you alter the metric to make it fit reality (for example, making the black hole come into being at a certain time, rather than existing for eternity into the past and future) and b) it doesn't exist for long enough for anything to cross it, even at the speed of light. There are other solutions involving wormholes that would be possible to cross, however they always require exotic matter and there is no evidence that such matter is possible. --Tango (talk) 20:16, 30 December 2010 (UTC)[reply]
I recently watched Subway (Homicide: Life on the Street). As Vincent D'Onofrio's character is dying, one of the last things he says is that the leaves of a sugar maple turn upward before a rain to catch the raindrops. Our article doesn't mention this so I'm wondering if anyone knows if it is true or not. Beeblebrox (talk) 00:26, 30 December 2010 (UTC)[reply]
Speculation: there is often an updraft before a storm – the leaves of many trees will "turn up" in a very distinctive way preceding rain in that case, perhaps sugar maple leaves doing so are particularly distinctive...? WikiDao ☯ (talk)01:20, 30 December 2010 (UTC)[reply]
In the UK there is a common phenomenon during summer whereby the leaves of trees appear to turn up, but in fact are showing there undersides because they are lifted by a southerly or south-westerly wind which often precedes a rain bearing atmospheric depression. Caesar's Daddy (talk) 08:39, 30 December 2010 (UTC)[reply]
Where I live there is a lot of Devils club. Normally they have broad, flat leaves the size of a dinner palte. When it is espescially dry these leaves can be seen to distintcly fold upwards. There must be some reason for this. If not to capture water, what would it be? Beeblebrox (talk) 19:57, 31 December 2010 (UTC)[reply]
An unusual problem with viewing a 3D film.
There is, to my knowledge, a certain percentage of people that cannot see stereographic 3D effects - I am not among them. I am somewhat of a 3D enthusiast, I am a master of stereogram viewing (both parallel and cross-eyed) and enjoy viewing anaglyph images and autostereograms. I have seen many 3D movies in a variety of formats, including IMAX 3D and Fusion Camera system - either of which was apparently used to present the 3D in Tron: Legacy, a movie I saw just 20 minutes ago.
So you can understand why I am utterly confused by the fact that at the moment the movie was supposed to change over to 3D, I saw nothing of the sort - the image was flat. I had gone to see the film with a group of friends, and they all saw the 3D effect fine, and they are not the practical joking type. I switched my glasses with one of them during the credits and she said she saw the 3D clear as day, so it wasn't the glasses. All throughout the film I was stupefied, wondering whether we sat down in the wrong theater. I closed one eye and the other to check if the images for each were different for each eye, but they were identical. I took off the glasses and saw slight blurring like the image was focused "behind" the screen (and in fact I could see a slight 3D effect of the image "behind" the screen when I looked at the edges with the glasses on), but not the characteristic difference of blurring between near and far focused objects.
The biggest mystery was the previews, all of which were in 3D. I saw them in all their glory. The 3D effect in some of them took my breath away. And yet during the movie I saw none of that. I was very disappointed by this development.
I decided half-way through that they put the wrong version on and just enjoyed the movie. But when I told my friends it wasn't 3D they looked at me like I was crazy. I thought about it during the drive home, and I came to the conclusion that what happened to me was impossible, but it happened!
What could have caused me, someone who has never had a problem seeing 3D, to have this happen? This is the most bizarre thing that has ever happened to me, and I want to know what caused it so I can keep my sanity. Thanks in advance. Chris16447 (talk) 07:35, 30 December 2010 (UTC)[reply]
The only explanation I can think of is that your experience with autostereograms caused you to mentally cancel out the 3-D effect. As you will know, 3-D vision is processed entirely within the brain as an interpretation of what is "seen" by the eyes, so there must have been some discrepancy between what you expected to see and what was actually received by your eyes. I'm surprised that this lasted throughout the whole film. If it ever happens again, try closing your eyes for a while, then persuade yourself that the picture is just 2-D, then open your eyes and be pleasantly surprised. Dbfirs10:24, 30 December 2010 (UTC)[reply]
An alternative (speculative) explanation is that you are colorblind and that your eyes cannot be fooled by any 3D system (there is more than one). Quest09 (talk) 13:43, 30 December 2010 (UTC)[reply]
I have not seen the movie, so this doesn't even qualify as good original research, but I was recently told by friends that are big 3D enthusiasts that the 3D effects in the movie were barely noticeable as well. 10draftsdeep (talk) 13:56, 30 December 2010 (UTC)[reply]
Even if they did use the colored 3D glasses, colorblindness wouldn't be an issue. All 3D glasses work by filtering the light that reaches your eyes so that each eye sees an image photographed from a slightly different angle. Whether you perceive those slightly different images in full color or not is irrelevant. —Bkell (talk) 14:42, 30 December 2010 (UTC)[reply]
It is just possible that, if you do not already wear spectacles for which you have been properly and recently sight-tested, and if as is probable the 3D system being used utilises directional polarisation, you have slight undiagnosed astigmatism which happens to make the image stream in one eye sufficiently less focussed as to hamper the 3D effect, especially when it is smaller. The everyday effects of mild astigmatism can be unobvious to the sufferer, whose brain compensates for them unconsciously. It might be worth your while to visit an optometrist. 87.81.230.195 (talk) 17:50, 30 December 2010 (UTC)[reply]
What I don't get is that the OP claims to have seen the previews in 3D just fine, but then couldn't see the movie in 3D. Did you change seats between the previews and the movie, Chris16447? I think the 3D effect gets worse the further from the center of the theater you are (but I'm not sure about that). WikiDao ☯ (talk)18:14, 30 December 2010 (UTC)[reply]
The previews likely had the most extreme 3D effects, while the movie was more restrained. That's because the same level of 3D, which makes you want to see a movie in the preview, would probably make you sick, if you watched it for an hour or two. StuRat (talk) 18:18, 30 December 2010 (UTC)[reply]
They may have even made the effects more extreme in the previews. It might make sense to do so — a preview is a pretty brief encounter, and you'd want it to be eye-popping. But for a multi-hour viewing, eye-popping might turn into eye-strain too easily, at least amongst the non-enthusist population. My understanding is that it is not too hard to adjust the depth of a 3D film at different points in its production; it is not the case that it is simply "filmed in 3D" and that's the depth that it is permanently set to, I don't think. --Mr.98 (talk) 18:20, 30 December 2010 (UTC)[reply]
I think that depends on the type of movie. With a CGI movie, it's relatively simple to adjust the camera angles on an existing scene in the computer. With live-action, though, you're limited by the placement of the original cameras. Picture something behind a pole. The two cameras will hide different parts of the scene behind the pole. By moving the depth you also change what is hidden (from each eye) behind the pole. Hiding part that was visible before could probably be done simply enough with a computer, but creating the portion which was formerly hidden is a bit trickier. Your computer program would have to figure out the pattern on the wallpaper and then recreate it there, for example. To simulate this problem, place a vertical finger right in front o\f your nose, then close one eye while moving the finger forward and back, then repeat with the other eye closed. See how the portion of the room which is hidden (behind the finger) changes, in each eye ? StuRat (talk) 18:32, 30 December 2010 (UTC)[reply]
98 may have a point. If the question-asker was sitting somewhere where the 3d effect was weak (or if his own stereo perception is weak) he still would have noticed the 3d during the previews because they're packed with crazy out-of-screen effects that you'd have to be completely stereo-blind to miss. The film, thankfully, had almost no out-of-screen gimmick shots. APL (talk) 20:17, 30 December 2010 (UTC)[reply]
Some things which can prevent the eyes from working together are:
1) Alcohol, causing the classic double vision.
2) Head injuries.
3) Obscured vision in one eye, due to dirty glasses or contacts, or "slime" on the eye. I often have this problem when I first wake up.
Also, you may just may see 3D effects less than others, so that this movie, with minimal use of 3D, was below the threshold you recognized as being 3D. StuRat (talk) 18:26, 30 December 2010 (UTC)[reply]
Obvious question : You realize that the film was only 3d 'On the grid', right? Real-world scenes were intentionally flat. (But strangely, not quite at the plane of the screen, so you needed the glasses throughout.) APL (talk) 20:17, 30 December 2010 (UTC)[reply]
I saw the movie recently and also particularly at the start and throughout other points in the movie was wondering if I was "getting" the 3d. Vespine (talk) 23:17, 30 December 2010 (UTC)[reply]
At the start there is no 3d to get. The movie is entirely 2d until Flynn enters the computer generated world of 'The Grid'. (Sort of like the color in 'The Wizard of Oz'.) APL (talk) 02:34, 31 December 2010 (UTC)[reply]
I am wondering if it's possible that others will develop this same "immunity" to these new 3D films, and it ultimately will end up being just a fad instead of the new way all movies are made. Personally I would find that hilarious, but I magine a lot of people in Hollywood wouldn't see it that way. Beeblebrox (talk) 20:37, 31 December 2010 (UTC)[reply]
What I think is that perhaps the movie does not contain such "intense" 3d scene as the demo. In fact, most move does not contain sharks popping out of the screen... those are usually issolated to "science" type shows/imax or short demos. Imagine the strain you would feel if the body tries, reflexively, to jerk out of the way of the oncomming animal/item/etc. Plus, I also noticed that 3d cinema films are not 3d intensive as home cinema films. --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time!08:28, 1 January 2011 (UTC)[reply]
You are going to have to know the density of this solution, which because it is strong will deviate significantly from 1. Then from your volume calculate the mass and take 40% if it. Graeme Bartlett (talk) 12:47, 30 December 2010 (UTC)[reply]
Ok, thank you. If we know that Lanthanum chloride has a density of 3.84g/cm^3 and water 0.997g/cm^3 (@ 25 degrees), is there a formula for calculation the density of the solution from these numbers? Abbott75ღ13:24, 30 December 2010 (UTC)[reply]
Unfortunately not; since volumes are not additive in mixing two substances, you cannot simply average the densities. The density of the resulting mixture will depend factors which cannot be directly measured, excepting by measuring the density itself. In other words, you cannot calculate or derive the density of such a mixture, you'd have to measure it directly. --Jayron3214:50, 30 December 2010 (UTC)[reply]
The last two inventions which changed my life are the cell-phone and Internet, and that was long ago. Where is my flying car? My automatic driving car? My maid robot? Quest09 (talk) 13:38, 30 December 2010 (UTC)[reply]
Well, this Roomba is no maid robot. It is expensive, doesn't cook, doesn't clean the bathroom, doesn't make beds... It is a far cry from a maid. Quest09 (talk) 13:49, 30 December 2010 (UTC)[reply]
Follow-up: if we had a very efficient battery, which would weigh just a couple of pounds and hold lots of energy, would a (Blade Runner like) flying car be feasible? Or does the problem lies elsewhere? Quest09 (talk) 14:04, 30 December 2010 (UTC)[reply]
If that was possible, then yes, but I don't think it is, due to inherent limits on how much energy a chemical battery can store. Batteries only store a few extra electrons on atoms, and electrons weigh around 1/1836 of the weight of a proton (a little more for a neutron). So, if you use an ion engine, you propel only a tiny portion of the mass of the battery out the rear of the plane, whereas a jet fuel engine can propel 100% of the mass of the fuel out the back. Plus, the battery powered plane would have the weight of the battery to carry the whole trip, while a conventional jet plane is much lighter when it lands, having much less fuel on board. (I suppose you could arrange for a system where spent batteries are ejected with parachutes, then returned to the base and recharged, but that doesn't sound very practical, either). StuRat (talk) 20:24, 30 December 2010 (UTC)[reply]
The problem is the definition of an "invention." Historians like to say the "printing press" was one invention; but it relied on several abstract concepts (like written language), several constituent technologies (like reflowable lead metallurgy), and several "sub-inventions" (like the hinge on the lever that operated the paper-press). So, you have listed "the internet" as an invention; but in fact that "invention" really depends on many thousands of abstract concepts (like Turing completeness), constituent technologies (like low-noise radio frequency modulation), and specific sub-inventions (like ARP/RARP). Yet, you and many others consider "The Internet" a single "invention" worthy of listing next to "The Transistor" and "Fire." My point is, it's up to historians to decide which abstractions and implementations count as An Invention, and which are merely Contributing Knowledge.
Personally, I consider the Wikipedia to be an important invention. Sure, it didn't pioneer any new physics equations and it suffers from a dismal lack of flashing lightbulbs that blink; but it is an accomplishment of technology. It is a simple synthesis of pre-existing technologies to address an actual social need (the need for free, free information). I would place the accomplishment of "invention of Wiki" on the same tier as "invention of packetized data routing" (another critical technology step towards making free information possible). Futurists have dreamed about a free encyclopedia for nearly a century. Some of the greatest minds of the 20th Century predicted such a device. (H.G. Wells predicted it in 1937, Vannevar Bush predicted it in 1945, Doug Engelbart demonstrated a very simple prototype in 1968). But until very recently, these geniuses lacked several critical pieces of technology necessary to implement their technology: they did not have digital computers; cost-effective display screens; packetized information transfer; and a few specific computer programming languages (in specific, free implementations of HTTP, PHP, and SQL that make it plausible to design a machine that bidirectionally communicates encyclopedic data to and from humans). While the Wikipedia is not a new ASIC technology, nor a new computer algorithm, nor a new energy source or material, it is an invention: it is the synthesis of present technologies to address a need. Other inventions - flying-cars, laser-ignition hydrogen bombs, smart-phones - all do exist; but they fail to address an actual need for the human species. We have finally invented the Wikipedia; at present, it takes the form of an Organization with semi-centralized repositories of huge digital electronic computers that are programmed in PHP and SQL, and relaying their information bidirectionally over wired and wireless electromagnetic signals to billions of small digital computers across the planet. Since the invention of the Printing Press, I am not sure that our species has made such an important contribution toward free, free information. Nimur (talk) 14:51, 30 December 2010 (UTC)[reply]
Nimur, thank you for bringing attention to the lack of flashing lightbulbs that blink on Wikipedia. Hopefully this will help the problem a bit: —Bkell (talk) 15:01, 30 December 2010 (UTC)[reply]
Do you think you could design a wikipedia-bot to make those blink every time vandalism is added to the project? Just monitor the recent-changes RSS feed and filter by evil bit. Nimur (talk) 15:31, 30 December 2010 (UTC)[reply]
Some other inventions in the "change your life" category might be GPS, Virtual Reality, flat screen (and now 3D) TVs, etc. While not all of these technologies are yet fully implemented, at some point we may instantly always know where we are relative to our destination (thanks to GPS) and be able to do many activities (games, shopping, exercise, gatherings with friends & family, business meetings, etc.) without leaving our living rooms (thanks to VR and high tech TVs). StuRat (talk) 18:07, 30 December 2010 (UTC)[reply]
It seems a little counter-productive that half our inventions are about finding your way around outside easier and the other half are designed to keep you from wanting to leave your house. Matt Deres (talk) 19:35, 30 December 2010 (UTC)[reply]
Well, they both seem designed to keep us from getting lost outside. It would have made for a different ending to The Shining, although perhaps Jack never would have gone nuts in the first place, if he had a Wii to play with, instead of talking with ghosts. :-) StuRat (talk) 20:08, 30 December 2010 (UTC)[reply]
Should someone come up with a cheap flying car, I would be first in line to vote to have its use heavily restricted. It's bad enough dealing with the hazards of regular automobiles, even though we've had hundreds of years to develop rules, regulations, and infrastructure to support them. The last thing I want is everyone and everybody flying a plane over my house! --Mr.98 (talk) 18:12, 30 December 2010 (UTC)[reply]
Here are some answers to specific inventions you asked about:
Flying car ? These have been made, but aren't very practical. Cars need to be tough, which means heavy, since we want to be able to survive a fender-bender, and they can't have big wings on them. The wings can be removed, but then must be stored somewhere, which is almost as inconvenient as just storing a whole plane. Thus, this may never be practical.
My automatic driving car ? This is a possibility, and work is being done on this now. The problem is safety, as a car that crashes only 1/1000th of the time would still be completely unacceptable. In the meantime, we could maybe have a car supplement your own driving, like warning you of hazards and pulling off the road and bringing the car to a safe stop if you slump over the wheel.
My maid robot ? This is probably the most practical invention in the short run. If it's small and light enough, and doesn't have sharp parts, it shouldn't be particularly dangerous, so we could handle ones that make occasional mistakes. They likely will be given one task at a time, until eventually they do most of the things a maid would do. We have vacuuming handled by the Roomba, and there are others that can deliver drinks, control the lights and temperature of a house, order food from the grocery store, etc. Whether it's best to leave all these as separate devices or combine them into one is an open question. A big improvement in artificial intelligence is needed to allow for a general purpose robot that you can tell to do something new, like "kill that hairy spider in the tub", so it can figure out all the steps to do it. StuRat (talk) 20:49, 30 December 2010 (UTC)[reply]
Regarding the car, I ask myself if it would crash very often in a specially adapted route. Imagine that you put some sort of sign for the robo-car to orient itself. In a road, it might be easier, mostly, you get a straight line, if something is in front of you, you brake. Quest09 (talk) 21:11, 30 December 2010 (UTC)[reply]
Well, that much is already being done. Cars in the higher price range have systems that, if the car strays too close to the middle line in the road (and the sideline, where applicable), will start shaking the steering wheel and even adjust the course - this is to (to an extent) prevent people from dozing off at the wheel and crashing. And while navigation systems are a far cry from autopilot for cars, you could argue that to an extent they do perform that role - the driver still has to do the actual driving, but now the car or a mounted device in the car takes care of the directions. TomorrowTime (talk) 21:32, 30 December 2010 (UTC)[reply]
The automatic driving car is already reality, it will just need 10 years of technological development and legislation to make it production ready. Both BMW and Audi have demonstrated it. BMW's autonomous 330i did a full-on flying lap of the Top Gear test track (with an extremely frightened Jeremy Clarkson at the wheel just in case he needed to take over the controls). Audi's autonomous TTS did a hill climb at Pike's Peak at a very respectable average speed. The technology is already there: military grade GPS, radar guided cruise control, lane detection systems, automatic road sign recognition, pedestrian and animal recognition, autonomous parking. All it needs is a standardised car-to-car communication protocol (which the manufacturers are already working on). The technology is basically ready, all we need is for it to mature and also for legislation to catch up. Zunaid08:38, 31 December 2010 (UTC)[reply]
We use the chemical called Tetrachloroethylene for dry cleaning . However, this chemical has become very expensive due to its increasing scarcity.Kindly recommend either a more easily available and safe to use alternative chemical or a combination of chemicals with their respective proportions. —Preceding unsigned comment added by 41.205.179.120 (talk) 14:12, 30 December 2010 (UTC)[reply]
If I understand correctly, by measuring the voltage drop across the low-resistance precision resistor I'll get the current drawn by my PC, right? But what about the voltage? How would I measure it? I'm afraid I can't connect my oscilloscope directly into the mains without getting something burnt. --Belchman (talk) 23:21, 30 December 2010 (UTC)[reply]
I think you can just assume the voltage is correct for where you live (110, 115, 120, 210, 220, etc.). If you want, you can measure voltage separately by running it through a very very high resistance precision resistor, then measuring through (NOT across) that resistor. It's A/C though, so the voltage is a bit complicated. If you are willing to assume it's a sine wave, then you can filter it slightly and then apply a correction factor (I don't remember how much). You'll need to do the same correction for the current as well since it's A/C current. Or you can leave it unfiltered and watch the waveform as is (see power factor to learn a bit more about what it will look like). Ariel. (talk) 23:39, 30 December 2010 (UTC)[reply]
This may sound really dumb, but what's the difference between "measuring through" and "across" the resistor? Probably I'm more than familiar with the concept, it's just the wording (I'm not a native speaker of AmE). --Belchman (talk) 23:52, 30 December 2010 (UTC)[reply]
Okay, that's what I thought. Anyway, it's a bit weird to my understanding to be measuring voltage "through" since there's no such thing as "absolute" voltage. I guess the "through" measure is the voltage between that point in your chart and the ground, right? --Belchman (talk) 00:31, 31 December 2010 (UTC)[reply]
In my chart the voltage source and sink is on the left and right (the open lines). When I say "through" it means the voltage passes through the resistor before being measured. Ariel. (talk) 01:25, 31 December 2010 (UTC)[reply]
BTW, I'm answering because you asked. But I'm a bit worried about you building/measuring this without really understanding it. At the very minimum please run all your tests via a GFCI outlet. Ariel. (talk) 23:41, 30 December 2010 (UTC)[reply]
(After Edit Conflict)
I'm not sure than an oscilloscope is the right tool for this job. Scopes are very versatile, so I'm sure some clever person could devise some way of making it work with enough extra components, but wouldn't you be happier with a watt meter like a Kill A Watt? APL (talk) 23:42, 30 December 2010 (UTC)[reply]
I'm an electrical engineering student and I have this cheap oscilloscope. I'm just 'playing' with it a little in order to understand it better. --Belchman (talk) 23:46, 30 December 2010 (UTC)[reply]
"Playing" with mains electricity isn't to be recommended... perhaps you should wait until you are further on in your studies when you'll be able to answer questions like this yourself. Then you should be able to experiment in a safe manner. --Tango (talk) 23:56, 30 December 2010 (UTC)[reply]
I should have said that I'm a graduate student, not an undergrad. And believe me it's surprisingly difficult to gather information about such a simple thing like this one... --Belchman (talk) 00:07, 31 December 2010 (UTC)[reply]
I strongly recommend that you do not attempt any of the suggestions above. Measuring directly at the mains cables is only something to be done if you are sure you know exactly what you are doing. I am fairly convinced that not even the people making the suggestions know what they are doing here. For instance, no one has mentioned that the scope needs to be earth free if the measurement is not to end with a loud bang and tripped breakers. Taking the earth off equipment is something that is done in a controlled lab environment but is in no way suitable for use in a home - especially one with children and pets present. In short - don't do it. SpinningSpark16:32, 31 December 2010 (UTC)[reply]
Not a bad idea. Years ago I had one of these mounted above my workbench, with one side set to plug into the wall, and another with a socket for the device under test. Worked fine, though it was a little slow. No idea how to get one, and no memory of how I got mine. PhGustaf (talk) 01:11, 31 December 2010 (UTC)[reply]
Belchman, why do you think that you, "can't connect my oscilloscope directly into the mains without getting something burnt"? What is the voltage range of your 'scope? Do you have a 10:1 probe? If not, do you know the input impedance of your 'scope, and using that information, can you construct one using some appropriate resistors? Earlier replies told you how to measure the current waveform, so that, with a measurement of voltage, will give your the volt-amps. Are you satisfied with the apparent power or do you want to know the real power dissipated by you appliance? Is your 'scope dual channel, allowing you to measure the phase difference between the current and voltage? -- 119.31.126.66 (talk) 01:56, 31 December 2010 (UTC)[reply]
The current drawn by a PC is far from sinusoidal so a simple phase comparison with the supply voltage is not possible. One would need to measure the voltageXcurrent products at many points on the waveform and integrate. This would be practical only on a dual-channel digital recording oscilloscope. Cuddlyable3 (talk) 03:03, 31 December 2010 (UTC)[reply]
We are not allowed to give medical or legal advice, but dangerous electrical advice is perfectly ok? Apparently. I suggest that the OP buys something like this. Cheaper than an oscilloscope and perfectly safe to use. SpinningSpark15:57, 31 December 2010 (UTC)[reply]
Elevated temperatures makes Molybdenum react with oxygen to make tetraoxide. What is the threashold, in other words, which is the temperature point that makes Molybdenum form Molybdenum Tetraoxide with certainty?199.126.224.245 (talk) 23:51, 30 December 2010 (UTC)[reply]
No, the article says that it forms molybdenum trioxide with oxygen at high temperatures. The molybdenum trioxide article also gives values for standard enthalpy of formation and standard entropy. If you could locate a value for standard free energy of formation, you could get a fairly close answer to your question using the equation ΔG = ΔH - T * ΔS, where ΔG is free energy, ΔH is enthalpy, ΔS is entropy, and T is the temperature you are looking for. --Jayron3200:53, 31 December 2010 (UTC)[reply]
There is a problem with the question. Molybdenum trioxide becomes less stable with increasing temperature, not more stable. The same is true for any metal oxide. If you solve for ΔG = 0 (equilibrium), then ΔH = TΔS at T = 2208 K for MoO3 ⇌ MoO2 + ½O2. But the reaction of oxygen with molybdenum is slow at room temperature, not least because you get a protective oxide layer on the metal surface. If you heat the molybdenum in air, the oxidation becomes faster, especially above 795 °C when the layer of MoO3 on the metal surface melts. Physchim62(talk)11:32, 31 December 2010 (UTC)[reply]
December 31
A question that is about 15 years overdue: What'll it take for beanies to actually fly the wearer?
In my childhood, I remembered reading a lot of Calvin & Hobbes humor comics. Calvin waited 6 weeks for a Beanie to arrive in his mail, after ordering it through a magazine catalog (IIRC.)
While he waited, he dreamed of flying all through the sky with the beanie, while holding it by the handles.
Then one day, it arrived. He put it together and got it to run. However, the motor wasn't giving it enough of a spin to lift him off the ground. Calvin got enraged, smashed it up, and vented to his tiger pal Hobbes about it.
I had wondered what it would take to make a beanie that actually flies the wearer, but back in the mid '90s, there was no Wikipedia (and its Reference Desk), no Answerbag, no AOL Answers, nor any other Q&A sites I was aware of back in the days of crawling through the "Information Superhighway" on 14.4k modems.
(On what online venue could I have asked this question back in '95-'96 anyway?)
For one, bigger blades; I am not sure the standard propeller blades on a beanie could generate enough Lift to actually pick you up off the ground. You'd also need a motor to drive the blades. Furthermore, helocopter blades will tend to twist you out of alignment; so you'd need a counteracting set of blades; either a second set which rotated in the opposite direction, like the this one or a second blade at right angles to the main ones, like the this one. --Jayron3202:25, 31 December 2010 (UTC)[reply]
But a smaller one. My guess based on some googling is that you need approximately 8 foot blades to lift a human. There are some website that give formulas to calculate the lift of a helicopter. You can't increase the lift forever - once you hit the speed of sound you can't do any better. At lower altitudes you can use smaller blades because the air is thicker, so you need to take into account how high you plan to go. Ariel. (talk) 09:18, 31 December 2010 (UTC)[reply]
I never knew that was actually possible in the laws of physics. Of course, it's got support and a seat for the rider. Looking at the actual C&H strips, you can see it's just a hat with a propeller.
My local news just showed a video of a suspected DUI traffic stop in which the driver failed in his attempt to walk a straight line — however, after stumbling and giving up, he proceeded to turn a cartwheel. How is it that alcohol can prevent someone from walking straight but not from maintaining the balance and agility necessary to avoid falling over like I do when I try to turn a cartwheel while sober? Nyttend (talk) 04:09, 31 December 2010 (UTC)[reply]
The issue is that DUI tests are standardized; they need to be to be admissable as evidence in a court of law. Officers perform the same set of standardized tests, and videotape the evidence. Turning cartwheels isn't a part of the standardized set of DUI tests in any state I know of. So the fact that one could do so doesn't make any difference in establishing reasonable suspicion to arrest someone for DUI. If litigated in court, I suppose that the defendent could perhaps use such cartwheel as evidence that he was sober enough to drive; but that wouldn't mean that the officer at the scene would be wrong for arresting the person for DUI if they failed the standardized tests. They may argue to get their license back based on that evidence, but that has no bearing on how the arresting officer should act at the scene. The officer should always do it "by the book": administer the standard tests, and if the standard tests are failed, place them under arrest. Let the courts deal with anything that comes later. --Jayron3204:24, 31 December 2010 (UTC)[reply]
I wasn't trying to question the claim that he was drunk; the rest of his behavior made it obvious that he was very much under the influence. My question asked how he could perform a cartwheel despite being unable to do much simpler things. Nyttend (talk) 05:04, 31 December 2010 (UTC)[reply]
Balance depends heavily on feedback-driven control, which is particularly impaired by alcohol. A cartwheel is a complex motor sequence, but it doesn't depend very heavily on feedback. Looie496 (talk) 04:59, 31 December 2010 (UTC)[reply]
Can you explain what you mean by "feedback"? I've read the "Biology" section of our feedback article; its final paragraph somewhat resembles what I think you mean, but it seems somewhat irrelevant, so I suspect that you mean something different. Nyttend (talk) 05:08, 31 December 2010 (UTC)[reply]
In order to balance, your body needs to get information about where it is now and use that information to maintain that position. So your brain analyzes a whole shitload of information; some from your inner ear, some from the tension on your muscles, some from your vision, to determine where you are in relation to, say, the ground, and then based on that information, it makes minute adjustments to your muscles to keep you standing straight and balanced. Alcohol short-circuits that feedback, so while you may be fully in control of your muscles while drunk, your brain is receiving bad information about your "location" in the world, so it cannot easily autocorrect if you are falling. That's why drunks fall over; not because they don't have muscular control, but rather because their automatic balancing system is receiving fuzzy information. --Jayron3205:15, 31 December 2010 (UTC)[reply]
... and safe driving relies on this "feedback", so the walk test is better than the cartwheel test. Even drunk drivers can make a car cartwheel! Dbfirs10:16, 31 December 2010 (UTC)[reply]
... and turning a cartwheel cannot be performed by anyone able to drive, so it has no value as a test, since a DUI test should be positive for all (or most) drunk drivers and negative for all (or most) non-drunk drivers. However, why put people to walk? In Europe, as far as a I know, they always use a breathalyzer. If you want, you can request an additional, more precise blood testing. Quest09 (talk) 20:51, 31 December 2010 (UTC)[reply]
Not to say any of the above comments are wrong, but to answer the question a bit more directly, the "biology" part of the feedback article doesn't really cover its role in motor control -- the "control theory" section is more relevant. Basically feedback control of a movement means noting errors in the execution and adjusting the movement to reduce them; feedforward control means generating the correct muscle activity before any useful feedback comes in. In a cartwheel, by the time you have noticed that you screwed up, it is too late to do anything about it. (The feedback is however useful for learning -- if you get something wrong, you can try to change it on the next attempt.) Looie496 (talk) 23:47, 31 December 2010 (UTC)[reply]
How can the universe be infinite?
The article Universe says that "The universe is very large and possibly infinite in volume.". However, this seems at odds with logical thinking.
The universe is expanding at a very high speed, but not at an infinite speed. Let's call this speed x
The universe has been expanding for a very long period of time, but not an infinite period of time. Let's call this time t.
Therefore, the current size of the universe should be a direct function of t and x. If neither x nor t are infinite, how can the size of the universe be infinite at any given moment? Thanks. Leptictidium (mt) 07:43, 31 December 2010 (UTC)[reply]
I'm not a cosmologist, but my general understanding is that if the universe is infinite in extent now, then it always has been. It's often claimed that the big bang means that the universe sprang from a single point, but that is not in fact a necessary part of the theory. If you run the equations backwards you get to a moment when the universe was infinitely dense, but it did not necessarily have zero volume. --Trovatore (talk) 07:55, 31 December 2010 (UTC)[reply]
If the infant universe had infinite volume and infinite density, then it must have had infinite mass (since density is a function of mass and volume). However, our present universe does not have infinite density, so where did all the mass go? Leptictidium (mt) 08:17, 31 December 2010 (UTC)[reply]
If it has infinite volume now, and density finite but bounded away from zero (that is, there is some nonzero density such that every part of the universe is at least that dense), then it also has infinite mass now. So why did it have to go anywhere?
For one thing, the big bang wasn't necessarily the whole universe, it could have just been a portion, and there may have been many other big bangs, far away. We wouldn't know about these other big bangs unless one of them expands into ours. StuRat (talk) 08:45, 31 December 2010 (UTC)[reply]
I recently completed a second year cosmology paper, and what I was told is that the universe is not infinite, neither does it have an edge. The best definition of the edge of the universe you can get is halfway between the centre of the universe and itself. In other words, if you had a ridiculously long pole, growing longer at the same rate as which the universe is expanding, you should be able to tap yourself on the shoulder. --Plasmic Physics (talk) 09:10, 31 December 2010 (UTC)[reply]
Well, you can write down models where space is finite in total area without "ending" anywhere. The surface of the Earth is also like that. There's no central point on the surface of the Earth, and any point on the surface could be described as "halfway between the antipodal point and itself", though it's probably better not to describe it that way. There's no evidence favoring those models over other models, but they are at least consistent with the available evidence. -- BenRG (talk) 10:32, 31 December 2010 (UTC)[reply]
What cosmologists mean by the "total size of the universe" and the "expansion of the universe" doesn't exactly match the everyday meaning of the words, in part because in general relativity the distinction between space and time is a bit fuzzy. Shown to the right is the Milne universe, which is basically a simplified (numerically inaccurate) version of standard cosmology that's easier to visualize in a 2D diagram. This model is spatially infinite at all times, in the sense meant by cosmologists. See the previous Ref Desk threads Light from just after the Big Bang and Infinite amount of mass in the universe? where I mention the Milne model, and Speed in space which has a more accurate picture. And also see Ned Wright's cosmology tutorial. -- BenRG (talk) 10:32, 31 December 2010 (UTC)[reply]
@Leptictidium: You asked why we have finite density now if we had infinite density in the past. It is important to realise that this question is actually the wrong way round (no blame - I make that kind of mistake too often myself). We do not know that the density was infinite in the past; what we do know is that now it is finite. The "correct" question would then be why we had infinite density in the past when we have finite density now, and we can answer that one. We also know that the universe is expanding (i.e. mean density is decreasing) and we have a theory for that expansion. Using that theory and our knowledge about the present state of the universe as initial condition, we can determine how the mean density of the universe evolved in the past. Doing that we find that the density increased (going backwards in time) without bound. The point where the density formally diverges (becomes infinite) is called the "Big Bang". The Big Bang is just that: an extrapolation backwards in time. However, we also know that our theory breaks down at some point when the mean density becomes larger than what we can handle with our knowledge of quantum theory and general relativity. Hence, the big bang is a simple extrapolation beyond our secure knowledge of physics. Unfortunately, the big bang is, especially in popular science books and documentaries, often represented as a secure fact and it is way overstressed. The initial question, whether the universe is finite or infinite, is not answered yet. We do have some constraints on the minimum possible size (if it is finite), nothing more. There is a nice book about this topic (the topology of the universe) by Jean-Pierre Luminet, which is available in English, I think. --Wrongfilter (talk) 11:45, 31 December 2010 (UTC)[reply]
The way I see it, if the universe were expanding at the speed of light in all directions, and we are correct that it is impossible to exceed the speed of light, then for all intents and purposes, the universe would be infinite since you can never get to any edge. Googlemeister (talk) 15:07, 31 December 2010 (UTC)[reply]
The universe is not expanding at the speed of light. The rate of increase of distances (which is not a velocity!) is proportional to the distance (suitably defined) and is not limited by the speed of light. --Wrongfilter (talk) 15:35, 31 December 2010 (UTC)[reply]
The connection with the visible universe is not correct. The rate of increase of the distance between two objects (they are not "travelling" - where would they travel to?) is equal to 300000 km/s (the speed of light) when they are at a distance of 4.28 Gpc (for H0=70 km/s/Mpc), that corresponds to a redshift of 1.45 (per Ned Wright's cosmology calculator), nowhere near the horizon. The speed of light has nothing to do with the metric expansion of space. --Wrongfilter (talk) 18:03, 1 January 2011 (UTC)[reply]
Expanding on Wrongfilter's reply: in the Milne universe, shown above, there's no upper limit to the cosmological recession speeds, even though the special relativistic speeds of the very same objects are all less than c. The cosmological recession speed in this case is equivalent to rapidity (times c, since rapidity is usually given as a unitless number). A rapidity of 1 (or c) has no special significance. It's like an angle of 1 radian. -- BenRG (talk) 01:31, 2 January 2011 (UTC)[reply]
If I evaporated a solution of antimony trichloride in a solution of concentrated hydrochloric acid, would the antimony trichloride precipitate as a solid? --Chemicalinterest (talk) 12:47, 31 December 2010 (UTC)[reply]
Most of the chlorides if produced by this way would give the oxide and hydrochloric acid. I have to have a look for the example of antimony trichloride, but I doubt that the compound is stable in water at all.--Stone (talk) 13:34, 31 December 2010 (UTC)[reply]
The group 15 elements form a huge range of oxohalides as well. SbOCl is the simplest example in this system, but there are many others. Also, SbCl3 is described as deliquescent, so you are not going to be able to form a solid by evaporation at ambient temperature and pressure. Raising the temperature or lowering the pressure will drive off HCl before it drives off water, and so promote hydrolysis of the chloride to the oxochloride. In short, no. Physchim62(talk)16:05, 31 December 2010 (UTC)[reply]
Sorry! I have to correct myself. Butter of Antimony [12] is the very old name of the compound. Best produced by dissolving antimonsulfid in conc. hydrochloric acid. When always an excess of hydrochloric acid is present the liquid can be evaporated. You get a white substance of waxy consistence ( therefore called Butter of Antimony). If the solution of Antimony trichloride in water is diluted in water a complicated mixture of oxides is formed which at the end will be antimony oxide.--Stone (talk) 17:16, 31 December 2010 (UTC)[reply]
Best length of radio aerial
I have a small mains-powered transistor radio, which had an aerial wire sticking out of the end. The aerial wire has now broken off and I will need to re-attach it, or bin it. The wire was 970mm long. I mostly use it to listen to a radio channel on about 94Mhz, FM. Where I am, reception is not very good. What would be the best length for the new wire aerial? If 970mm was the best length, would there be any advantage in having the wire a multiple of this length, such as twice, thrice, four times, etc? A particular problem I have is that another more intense signal is right next on the dial to what I want to listen to. I still get some reception without the wire attached, but it is not as good. Please do not suggest buying a DAB radio as the signal is not good enough here, regretably. Thanks 92.24.176.169 (talk) 19:45, 31 December 2010 (UTC)[reply]
Under ideal conditions the best length, a quarter wavelength with some adjustment for end effects, would be about 760 mm. It sounds like your biggest problem is the stronger station, and a longer wire would just make the strong station stronger. If the weak station and the strong station are in different directions, try putting some kind of metal screen in the direction of the strong station. Jc3s5h (talk) 20:00, 31 December 2010 (UTC)[reply]
Odd multiples will match the impedance of the input stage better, an even multiple will have a high impedance. However boosting the input will overload the radio more and increaase the problem due to the interfering station. If you have the space a dipole antenna connected via a balun to the antenna input will get you more control. Match the polarization and rotate to minimise the interfering station. Graeme Bartlett (talk) 22:08, 31 December 2010 (UTC)[reply]
The aerial has only one connection, I would not know where to connect the other half of a dipole. From what I remember of other radios, dipole antennas for VHF are not very big. If the interfereing channel is ignored, would for example a 3/4 wavelength monopole be better than a 1/4 wavelengtn monopole? 92.24.185.151 (talk) 23:23, 31 December 2010 (UTC)[reply]
Please explain why a 1/4 wavelength aeriel will be better than an aerial three times as long as this, I'm sceptical. The longer aeriel will collect three times the signal energy. (And three times the signal energy is nothing compared to the higher signal intensity of someone living nearer the transmitter, so the radio should be easily able to cope with it). The Wikipedia antenna article also says: "The random wire antenna is simply a very long (at least one quarter wavelength) wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. Folding will reduce effectiveness and make theoretical analysis extremely difficult. (The added length helps more than the folding typically hurts.)". That says nothing about a quarter walevlength being best, and the links I've read also say nothing about a quarter wavelength being best, although warning against using a half-wavelength or multiples of that. 92.15.14.57 (talk) 14:46, 1 January 2011 (UTC)[reply]
The thing about a random wire antenna is for cases where a 1/4 wavelength is impossible to string - it's just too long. So instead a wire is placed randomly. If you actually can run the wire to the correct length then do that. Ariel. (talk) 23:50, 1 January 2011 (UTC)[reply]
January 1
When beer is left in an open container for a long time
Carbonation is bad for your teeth, in that it forms carbonic acid, which can etch the surface and allow cavities to form. So, in a sense, flat beer is healthier. StuRat (talk) 06:22, 1 January 2011 (UTC)[reply]
(ec) I don't think it loses much alcohol in moderate time, because there isn't that much to start with. (Whiskey, on the other hand, becomes substantially weaker in a few hours, I think.)
(ec)Not sure what you mean by "better for you". You may be better off with a Soft_drink if you don't like beer, especially if you're driving. What happens to beer depends how long it's left. After a few hours the carbonation will go, as Beeblebrox says. The beer will also warm up to room temperature. Some beers taste better very cold, and are traditionally drunk in this state (US and Australian beers in particular) while others, such as UK "bitter" are more often drunk at room temperature. So some beer will taste nasty, other beer won't. After a few days in an open vessel the sugars in beer will start to grow mould and the sugars will turn to vinegar. How long do you mean by a "long time"? TonywaltonTalk00:40, 1 January 2011 (UTC)[reply]
Agree that before much alcohol has evaporated the quality will be affected. By the way, English bitter should be drunk at cellar temperature, i.e. about 9degC. It isn't heavily carbonated like canned beer. Itsmejudith (talk) 17:07, 1 January 2011 (UTC)[reply]
Maybe Tin(IV) sulfate then? I can't see anything happening to the sulfate itself, and copper compounds are all usually brightly colored. --Jayron3215:30, 1 January 2011 (UTC)[reply]
Which may actually be pretty acidic; copper(ii) is a pretty decent lewis acid, and in solution readily forms copper hydroxide complexes, leaving hydronium behind. --Jayron3218:27, 1 January 2011 (UTC)[reply]
I have just completed some tests on a mixture of the almost colorless solution and the white precipitate. Excess HCl dissolves it to form a light yellow-green solution; dilute hydrogen peroxide has no effect on it; and dilute ammonia solution makes the precipitate somewhat more yellow and precipitates more from the solution part. Hope this helps in some way. --Chemicalinterest (talk) 23:04, 1 January 2011 (UTC)[reply]
Complex/Quadrature Sampling
While reading some web pages on Software Defined Radio, I saw a method to get a high sampling rate by using two ADCs of lesser speed. Contrary to intuition, the two ADCs were operated not 180° out of phase but in quadrature. What is the actual name of this technique, and is there a wikipedia page on it? I'm currently reading an external link from the SDR article, but it seems to talk about QAM modulation techniques rather than sampling techniques. —Preceding unsigned comment added by 59.93.16.208 (talk) 06:12, 1 January 2011 (UTC)[reply]
Depending on the exact arrangement, it might be a phase detector combined with an interpolation algorithm; it might be simply a quadrature sampler; it might be an interferometer (if the Q/I components are compared to a reference signal). There are a wide class of methods that use 90-degree (quadrature) modulation to analyze signals; the exact circuit might help us narrow down the method. Our quadrature article links to some of the numerous uses and applications of 90-degree phase shift for signal analysis; because of the unique properties of fourier analysis, phasing a signal by 90-degrees (in other words, "multiplication of the signal by i) allows additional information to be inserted or extracted from a waveform, because the quadrature signal is orthogonal to the original signal. So many related techniques rely on this quadrature orthogonality property, it's difficult to name a specific one without looking at the exact circuit. Nimur (talk) 08:17, 1 January 2011 (UTC)[reply]
I was reading the GNU Radio site. This is what they have written about the hardware. They have also given an image in which the input from two ADCs are multiplied with Sin and Cos.
The USRP has 4 high-speed analog to digital converters (ADCs), each at 12 bits per sample, 64MSamples/sec. So in principle, we have 4 input and 4 output channels if we use real sampling. However, we can have more flexibility (and bandwidth) if we use complex (IQ) sampling. Then we have to pair them up, so we get 2 complex inputs and 2 complex outputs.
The range of signal frequencies that can be sampled without alias error is said to be limited at half the sampling frequency, called the Nyquist frequency. Alias error here refers to false readings of signal frequencies above the limit. The sketches below demonstrate that phase errors still occur at the Nyquist limit. In the upper sketch the solid samples are at the Nyquist rate and appear to allow an unambiguous reconstruction of the sinewave signal. However with an unfortunate sampling phase relative to the signal, we get the open samples which are all zero. Simply shifting the signal phase by 90 degrees has made it "invisible" to the sampler. In contrast, the lower sketch shows the 0-90-360 degree sampling described by the OP. Here there is no phase ambiguity. Both I and Q (quadrature) components of the signal can be reconstructed. What has been obtained is not an increase in bandwidth but a removal of (amplitudeXphase) ambiguity.
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I have read somewhere that if a fragment of a red giant remains during the explosion, the star collaspes into a black hole. Is this true? Also what causes the super giant to become a black hole and not a Neutron star? What's the deciding factor between these? --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time!08:10, 1 January 2011 (UTC)[reply]
Also, I think you are confused between red giants, which do not explode and is something that happens to smaller/mid-range stars and supernovae, which do explode and is something that happens to larger stars. There is always a remnant after such explosions. SpinningSpark10:20, 1 January 2011 (UTC)[reply]
"Deep snowdrifts have trapped thousands of people in their homes on the Danish island of Bornholm [...] There is so much snow that islanders have started dumping it in the sea - a practice normally forbidden for environmental reasons."
Does anyone have any ideas what these "environmental reasons" could be? Do you think it's just in case the snow is contaminated by oil or something, say from the roads? 86.185.77.168 (talk) 23:00, 1 January 2011 (UTC)[reply]
