Wikipedia:Reference desk/Archives/Science/2007 March 7

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Science desk
< March 6 << Feb | March | Apr >> March 8 >
Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

March 7[edit]

Why do White Castles disagree with so many people?[edit]

Hello. I personally love White Castle, but all I hear from everybody is how they give everybody gas and make everybody feel awful and things like that. I'm asking this cause I've never had a problem with them before, but today I had 8 of them for lunch and I feel absolutely awful. Why does it seem like they cause this reaction more than any other fast food place? NIRVANA2764 02:49, 7 March 2007 (UTC)

I'm not sure (don't have any references to cite about any of this), but they're pretty greasy, aren't they? Some people can't tolerate much grease at all. Others of us, we can usually eat lots of it comfortably, but sometimes, depending on metabolic cycles or mood, or what else there is in the stomach, or whatever, too much grease is definitely gross. —Steve Summit (talk) 04:05, 7 March 2007 (UTC)
Here's the nutrition info for a single White Castle hamburger (I had to go to a third party site, since White Castle's own site has the nutrition info conveniently "under construction"): [1]. I'm assuming you mean you had 8 regular single hamburgers. In this case, you had 56% of your daily calories, 64% of your daily fiber, 88% of your daily fat, 120% of your daily saturated fat, 96% of your daily protein allowance, and 48% of your daily sodium allowance. This is a lot to digest at once, especially the saturated fat. The onions also really do me in. While a hamburger is definitely healthier than a double cheeseburger [2], this benefit disappears when you eat eight of them. What makes the WC hamburger "junk food" is that it doesn't fill you up and you need to eat eight to feel full. You would have to eat about 14 WC hamburgers to get your daily calorie requirements, at which point you would have eaten 210% of your daily saturated fat allowance. And, if you are like many people who eat twice their daily calorie requirements, that would give you 28 WC hamburgers and a whopping 420% of your daily saturated fat allowance. And, despite all that bad fat, you still would be lacking many of the vitamins, minerals, amino acids, etc., your body needs. StuRat 12:27, 7 March 2007 (UTC)

well my wife said she saw how white castle burgers are made. they say they steam them and cook them from one side and dont bother to flip it. let me just say that is very nasty XD as one side remains a bit raw. if you look closly to your burger you will see 4 little imprints on one side only that is where they steam them. the other side is just left to cook that way. one side is well done while the other is not so well done which gives you problems with your stomich =) but i got to admit those little burgers are very tasty!Maverick423 14:24, 7 March 2007 (UTC)

I am pretty sure they don't start out with 'raw' material in the first place, i think those little postage stamps are actually soybeans and sawdust, with some fryer grease mixed in to give it a beefy taste. So in terms of done-ness, I really don't think you have anything to worry about. -- 15:10, 7 March 2007 (UTC)

plasma to electricity[edit]

This phenomenon requires energy, in the form of applied high voltage, to get started, but probably cannot be used as a supply of energy. Nimur

is there a way to turn plasma to electricity or to create plasma in a circuit between 2 electrodes and than mix in a third source energie (plasma ,light or other)?

Not sure what you mean. A plasma is an electrically neutral collection of charged particles. In that sense it is more like a conductor with interesting properties associated with drift and diffusion current and the large difference in velocities between electrons and ions. Inserting an electrode into a plasma will charge it up negatively due the larger amount of electrons that will impact it per second (due to velocity differences). equilibrium will be reached at some voltage that allows for equal impacts. This is very similiar to a diode. --Tbeatty 04:27, 7 March 2007 (UTC)

im not talking about puting an alectrode in the plasma, i mean creating flow of plasma between a positive an a negative electrode put in a closed circut and than mixing another kind of plasma in the flow for it to go trough the electrodes along with the current , if the system is strong enough the idea would be to extract energy from lightning or maybe from sunlight if it is compatible , would this be possible? clockwork fromage

No. --Tbeatty 05:08, 7 March 2007 (UTC)

is it that far fetched?

It looks like some have tried to extract energy from a moving plasma in a magentic field: from magnetohydrodynamics:

MHD power generation fueled by potassium-seeded coal combustion gas showed potential for more efficient energy conversion (the absence of solid moving parts allows operation at higher temperatures), but failed due to cost prohibitive technical difficulties. ref=# ^ [3] GB 05:48, 7 March 2007 (UTC)

so basically it would be possible to capture lightning this way but extremely hard and if magnetic reconnection occurred it would make a huge explosion , correct ?

Fluorescent light or neon light? I still can't decipher exactly what the original questioner means. You cannot extract energy from lightning (electric sparks) that you induce in your device; you have to supply energy to create them. Nimur 07:01, 7 March 2007 (UTC)

lightning from storms not man made , why coudnt that be considered as an alternative energie source ? clean , renewable and great potential clockwork fromage

Lightning is hard to predict and hard to collect. It doesn't offer a constant, predictable, or reliable energy source for mass power generation. -- mattb @ 2007-03-07T15:08Z

its predictable is you use lightning rods and you seed the clouds

Quntam energy compulsion cycle?[edit]

I read in an article that quantam energy compulsion is caused by the diminutive release of the particle decobodification through homosapions and large values of hydrocronic electric plasums but acourding to theoritical quantum sulfur theory almost all mast produced hydrocronic electricity is by far indeginable.Intectuell homospions such as myself find this humerous because of the inditable facts.because of that mistake I knew the rest would be "mumbo jumbo" so thats why I posted my question.Anyway my question is how does the hydrocronic Quantum theory prove that all protons have quantum energy???ALSO I think that Milad is really cool!!! —The preceding unsigned comment was added by (talk) 04:33, 7 March 2007 (UTC).

I believe this will answer all of your questions. --BenBurch 14
07, 7 March 2007 (UTC)
Am I missing something? Capuchin 14:32, 7 March 2007 (UTC)
About 500 mg. ;-) --BenBurch 16:55, 7 March 2007 (UTC)

membranes freely permeable to K+ (Na+?)[edit]

"if a membrane were freely permeable to K+ but impermeable to other positively charged ions, K+ ions..." continue moving until equilibrium potential (K) is reached.

why is there a constraint that it be impermeable to other positive ions? why not also include negatively charged ions?

what about the conditions if the equilibrium potential for Na were desired to be reached? should the membrane be permeable to Na+ only?

note: RMP assumed at -70mV for standard 'excitable cell'

Take a look at Reversal potential. --JWSchmidt 15:38, 7 March 2007 (UTC)
The equilibrium potential (aka reversal potential) of an ion assumes that the membrane is permeable only to that ion, and impermeable to all other ions, not just ions of the same charge. So the constraint would include both positively and negatively charged ions. To reach sodium's equilibrium potential, the membrane must be permeable to sodium only, as you said. --David Iberri (talk) 17:12, 7 March 2007 (UTC)


idea#1:Does the time behave like avector? Moving with aconstant velocity, ds1=vdt1,ds2=vdt2 ds=SQR(ds1^2+ds2^2), vdt=SQR{(vdt1)^2+(vdt2)^2}, hence, dt=SQR(dt1^2+dt2^2). Moving with acceleration and velocity is zero, ds1=gt1dt1,ds1=gt2dt2, dt=SQR[{(t1/t)dt1}^2+{(t2/t)dt2}^2]. it looks like the time behaves lik avector here,but it doesn`t when, ds=ds(v)+ds(g)=vdt+gtdt.the question is why is that?

idea#2:can we use the phenomenon of MIRAGE and LOOMING to explain why the planets of the solar system rotate in one direction while venus rotates in the opposite direction???

See Retrograde_motion#Retrograde_rotation for current theory. StuRat 12:03, 7 March 2007 (UTC)

idea#3:LOGICAL OBSERVATION FUNCTION. i think it is better to redefine th concept of velocity,because v=ds/dt,it means that the derivative of (s)with respect to astraight line which is (t).now, let`s put,

v=[(ds/dt-df/dt)/SQR{1+(df/dt)^2}], f(t)= constant if (s) as avector<0, f(t)=it,i=SQR(-1) if (s) as avector>0, we will call f,the logical observation function. it helps us to understand the relativistic concepts of helps us for instance to understand and solve the twin paradox. 10:15, 7 March 2007 (UTC)ARTHER.

For one analysis see [4]. Edison 14:50, 7 March 2007 (UTC)
Edison brings up an excellent point. Nimur 20:17, 7 March 2007 (UTC)

Burglarizing snot from my nose[edit]

Get that booger outta there!

A while back (about two years), I recall in the news a study about nose-picking. The findings—at least those reported in the news—were that people who pick their noses are more in touch with their bodies than those who do not pick their noses. However, the article on nose-picking only mentions a bunch of risks associated with nose-picking—all of which seem highly improbable.

Getting to the point, I was wondering if anyone else had heard about the study? Was the science behind the study credible? I think this would make a nice addition to such a lovely topic. − Twas Now ( talkcontribse-mail ) 12:39, 7 March 2007 (UTC)

what good is digging for gold if you cant share it with the towns people! but honestly nah i havent heard of such a study. however i did hear that people that masturbate are more intouch with there bodies (gee wonder why) Maverick423 14:31, 7 March 2007 (UTC)

What makes paper sticky when damp?[edit]

At one point or another, I'm sure everyone has received a wet newspaper in the driveway. Or has stepped on a sheet of paper after taking a shower. What makes wet newsprint cling to itself so tightly? And what makes paper stick to damp skin so steadfastly? -- 14:30, 7 March 2007 (UTC)

well paper starts off as a goo or something like that that is dried repeatly. when its a goo it sticks alot however when it drys you can write on it and all that good stuff. that is why people use wet paper to make art works.Maverick423 14:42, 7 March 2007 (UTC)

I think Maverick is on the right track. It starts off as a thick, fibrous and gluey pulp. The addition of water probably makes the paper wet, and bothers the glue, which would make it go back towards the pulp stage of it's development? [Mαc Δαvιs] X (How's my driving?) ❖ 01:15, 8 March 2007 (UTC)

Maybe it's to do with the fact that the hydrogen bonds continue through the fibrous material. Seans Potato Business 20:44, 8 March 2007 (UTC)

Seagulls as game birds?[edit]

Why don't people shoot seagulls for food? They're big, they're fat, there's lots of them but as far as I know, people don't eat them. Considering that people shoot ducks, pheasants, pigeons, etc (all smaller birds), why not the seagulls too? -- 15:55, 7 March 2007 (UTC)

because they live in rural/semi-rural/populated areas, that is the same reason why people cant shoot geese >.< it would be good if we could because all the local fields and parks by me are absolutely covered in goose droppings. -maxx- 15:58, 7 March 2007 (UTC)
Local by-laws in most areas say you can't kill animals without special permits. They're also more likely to have harmful chemicals in their body, more so than birds who live in rural areas or on farms. -- Zanimum 16:27, 7 March 2007 (UTC)
And their leader, User:Kurt Shaped Box, would have them attack and wipe out mankind. StuRat 18:36, 7 March 2007 (UTC)
We actually eat very few carniverous animals in our daily diet - and there is a good reason for that. Biomagnification. Toxins in the environment are taken up at the bottom of the food chain and concentrated at each subsequent link of the chain. Seabirds are towards the top of the marine food chain - we are better off eating fish instead. SteveBaker 19:02, 7 March 2007 (UTC)
My grandmother actually dined on gull stew with her family during WWII. According to her recollections, her father once shot two black-headed gulls and brought them home for the pot (he'd eaten them himself as a child, so I guess he thought "why not?") to supplement the rations. The meat was apparently quite strong-tasting, tough, dark and stringy but it 'wasn't awful'. --Kurt Shaped Box 00:02, 8 March 2007 (UTC)
Seagulls are scavengers: they eat things like garbage and carrion. This means they pick up the flavor of whatever they eat (seagull meat, like most carnivore meat, doesn't taste very good), and they tend to pick up whatever diseases and internal parasites their food had. --Carnildo 20:15, 7 March 2007 (UTC)
Gulls are also generally very scrawny. The bulk you see is mostly feathers. --Kurt Shaped Box 23:27, 7 March 2007 (UTC)

If seaguls, then why not pidgeons, foxes, cats, &c :] HS7 19:20, 8 March 2007 (UTC)

Pigeons are frequently eaten, although they're not the feathered rats we see in urban areas. Corvus cornix 22:29, 8 March 2007 (UTC)

Birds have very little fat on them, with up to half of their weight being made up of muscles, mostly in the wings, and the rest divided roughly equally between feathers and bones :) HS7 19:53, 8 March 2007 (UTC)

AFAIK, most of a bird's muscle mass is in the breast - those muscles are the ones that power flight, not the ones in the wings (take the feathers off the wings themselves and there's not much there). Birds that do a lot of walking/running also have muscular legs (i.e. the 'drumstick'). --Kurt Shaped Box 20:32, 8 March 2007 (UTC)

sorry, that should have been for the wings :( HS7 20:19, 9 March 2007 (UTC)

Oil sands vs. Tar sands[edit]

A reporter has asked why we use tar sands as the title for the article, not oil sands. Based on the talk page, this is what I could guess, and I'd like confirmation.

It seems that they were originally known by scientists, geographers as tar sands. The name oil sands only came about when technology advanced enough to make extraction easy enough for the public to pay attention, and eventually oil corporations started making investments in the projects. As a result, oil sands became the popular name.

Is this interpretation of the discussion correct? -- Zanimum 16:26, 7 March 2007 (UTC)

yes I do belive that it is, as you can get tar from oil and oil from tar but amongst the commonfolks the preferred term is oil sands, just like they say concrete not cement. -maxx- 18:23, 7 March 2007 (UTC)

I imagine the oil companies prefer the term "oil sands" because that doesn't bring to mind all the sludge in "tar sands", which then has to be disposed of. Thus, this euphemism makes it seem like a cleaner energy source than it really is. StuRat 18:34, 7 March 2007 (UTC)

Coefficient of friction between wheel bore and axle[edit]

How might someone determine the coefficient of friction between a wheel bore and axle given a setup like the one pictured here? Given that you know the mass and radius of the wheel, the radius of the wheel bore, the radius of the axle, the width of the wheel/axle contact, the mass of the weight on the string and the time for the weight to fall a given height, what equation(s) would give the coefficient of friction? dryguy 17:37, 7 March 2007 (UTC)

Do you really need to know the coefficient of friction, or do you just need to know which is best out of a series of wheels ? StuRat 18:31, 7 March 2007 (UTC)
I want to be able to compare different lubricants and be able to compare data with others using similar, but possibly not identical setups. The latter requirement gives rise to the desire to be able to compute the coefficient of friction in order to separate out differences in wheel mass, axle/bore diameter, height of drop, etc. dryguy 18:40, 7 March 2007 (UTC)
If the wheel is not slipping, then the only friction is between wheel-bore and axle. You could try to apply a force and measure the acceleration, but I imagine the coefficient-of-friction is so low (close to zero) that you will not be able to practically apply this technique. You might also try spinning the wheel at high rate of speed (perhaps use a power-drill with a known RPM rate), and determine the slow-down time of the wheel. Then you can determine the torque due to friction. I'll see if I can find simple equations to determine "mu-k" (kinetic friction coefficient) from the slow-down time. Nimur 20:22, 7 March 2007 (UTC)
I agree that wheel-bore/axle friction is the only friction. I just meant that the time for the weight to drop a given height will depend on other factors besides the friction, so it will be nice to have a way to ferret out the coefficient of friction in order to compare set-ups that have differences in wheel mass, height, etc.
The drill sounds like a good idea; the main difficulty will be selecting the right rpm to approximate what a car experiences on the track. Thanks for offering looking up the equations - it should be a big help. dryguy 21:13, 7 March 2007 (UTC)

indigestible edible muffins[edit]

Jim said that "they" used to manufacture and sell "edible muffins" that were indigestible. The muffins could be chewed and swallowed like regular food, but the chemical structure prevented the body from metabolizing the nutrients (or it contained no nutrients) resulting in complete elimination from the body with zero calorie absorption.

Is this true? What was this product called and how did it work chemically? Who was "they"? Why was it discontinued? NoClutter 17:49, 7 March 2007 (UTC)

I imagine it would be very rough on your digestive system. Everyone needs some fiber, but 100% non-nutritive fiber in that quantity would be overkill. StuRat 18:28, 7 March 2007 (UTC)
You could certainly bake something like that using artificial sweeteners in place of sugar and Olestra as a cooking oil. That would result in something with almost zero nutrients - yet which would be tasty and not do terrible things to your digestive system. SteveBaker 18:54, 7 March 2007 (UTC)
Tasty is a matter of perspective. Some people can distinguish between natural and artificial ingredients such as {sugar vs. saccharine or sucralose}, or {fat vs. olean}. Nimur 20:33, 7 March 2007 (UTC)
I certainly can, and Olestra causes "anal leakage", so I wouldn't call it free of side effects. If a delicious calorie-free muffin really could be created which had no adverse side effects, it would be a runaway success. If they canceled production, we can be reasonably sure it didn't meet all those requirements. StuRat 21:21, 7 March 2007 (UTC)

Full Moon Madness[edit]

I need help with the following issue. Please do not tell me I need psychological help or meds. I have noticed that everytime there is a full moon, I am anxious, short-tempered and have a general feeling of nervousness/anger. Does anyone experience this? Is there a scientific reason for this? Does anyone know of how I could curb these symptoms?

Are you female? If so, perhaps your monthly period simply happens to coincide with the full moon (give or take a few days)? SteveBaker 20:11, 7 March 2007 (UTC)
Are you a werewolf? If so, perhaps your monthly period simply happens to coincide with the full moon (give or take a few days)? Nimur 20:23, 7 March 2007 (UTC)
(You didn't sign your message - but looking at the edit history, I deduce that you are indeed female). I did some further research. Menstrual cycles typically happen on a 28 day cycle - but anywhere between 21 and 35 days is considered normal. The moon is full every 29.5 days - so it's very possible that your body might happen to be in sync with the full moon just by pure coincidence. It would be surprising if you were so perfectly in sync that this would be the case forever - but over a period of years, I bet you find that the relationship between the phase of the moon and these times of unease gradually drifts out of sync. Your symptoms seem quite believable - we married guys know only too well that we need to keep a low profile at "certain times of the month". Generalized grouchiness/anxiousness is certainly an absolutely typical symptom. You can certainly talk to your doctor (you might not want to start off by claiming to be a lunatic though! See Lunar effect) - I believe there are treatments relating to birth control pills that can tame the worst of the symptoms - but we aren't allowed to offer medical advice here - so "See your doctor" is as far as we can go. SteveBaker 20:29, 7 March 2007 (UTC)
Barring the possibility of some menstrual cycle coincidence, you should be aware that there is absolutely no scientific reason why a full moon should have an effect on anyone's mood. Your problem may just be your own superstition; I would recommend learning more of the real facts about the Moon— and try looking at it through binoculars sometime, and you'll see it's just a beautiful piece of geology.--Pharos 21:03, 7 March 2007 (UTC)

Also, maybe you spend a lot of time at the full moon thinking about the psychological effects of the full moon, which could make you nervous and jittery. -- 22:16, 7 March 2007 (UTC)

Not true i have heard of psychological studies that state that the full moon effects a person by drawing more blood to the head which can cause some of the symptoms that juliet mentioned. i will look for a source for this to back this up give me a bit Maverick423 22:19, 7 March 2007 (UTC)

No need to look it up - let's do the calculation. Let's say the gravitational pull of the full moon could result in blood being "pulled to the head". What is the gravitational pull of the non-full moon? It is the same. The amount of light reflecting from the moon to the earth should not affect the gravitational pull of the moon. --Bmk 22:27, 7 March 2007 (UTC)

heh it appears you are correct i revisited the place i found it on and it states that it does not effect the human body lol i guess i forgot to read that one word Maverick423 22:38, 7 March 2007 (UTC)

I also think women's periods can come to coincide with recurrent events. I forget where I heard this. But that would explain the regularity. 23:37, 7 March 2007 (UTC)

Well, it's a cycle, and it can be easily coordinated with other women. Depending on the intensity of the "problem," the questioner could be recommended to see a doctor to refer her/him to a psychiatrist. It could just be the menstrual cycle or a perceived effect coming from local superstition. [Mαc Δαvιs] X (How's my driving?) ❖ 01:08, 8 March 2007 (UTC)
If the two intervals coincide by chance - which is really likely if at typical human cycle is 28 days and the moon cycles over 29.5 days - there must be a huge percentage of women who's menstrual cycles just happen by pure coincidence to be 29.5 days. Since this feeling lasts several days, and the moon looks full for several days there is maybe a one in ten chance of it happening to coincide with the full moon. There must be literally millions of women who hit this point in their cycle on a full moon. It's not just likely - it's nearly certain that a large slice of the population hit the exact frequency and phase to match the moon. It means nothing - it's just a coincidence. SteveBaker 03:25, 8 March 2007 (UTC)

Stuttering and the neurotransmitter Dopamine[edit]

  • My question is, what is the actual relationship with stuttering and the neurotransmitter dopamine?
Changing dopamine levels can have dramatic side-effects. Levodopa is a drug used to combat everything from schizophrenia to Parkinson's disease by elevating the dopamine levels. Yet, it sometimes has unwanted psychological side-effects worse than the original condition. I am not an expert, but I think there is not a direct one-to-one correlation between dopamine level and correct synapse function, let alone mental health. Nimur 20:27, 7 March 2007 (UTC)

i am trying to think[edit]

what give rise to thought?

what i mean is, if the brain works on the same physical and chemical laws that govern non living things, then thought generation should be an entirely random phenomenon. then how is it that as an individual i am able to think about what i want to think about? 20:53, 7 March 2007 (UTC)

Not knowing anything scientific, logically I would guess that the mind has set things to 'think' that will help keep you alive. This could be awareness of others, memory of past events, automatic responses. Self-awareness and [Consciousness]] are supposed to be two of humanities biggest 'divides us from the animals' characteristics. I suspect this ability to understand/realise ourselves and others gives us the ability to think beyond simplistic survival towards more advanced survival. I risk being 100% wrong here, but that's how I would think of it. How you choose what to think will be sparked by things you see, things you hear, smells, sounds, situations, taste any of the senses really. Great question though - hopefully someone with half a brain gives you an actual answer rather than just, well, drivel like me! ny156uk 22:01, 7 March 2007 (UTC)
Nope, you pretty much nailed it… I think, therefore I am. It's one of the olders questions to confound man, the oldest is "how can I get that girl's attention" ;). Vespine 02:26, 8 March 2007 (UTC)
But what about "we think, therefore we am?" Better instead say "thinking exists, therefore thinker(s) exist. Let me answer your original question with a question: if earlier conditions in an object must entirely determine the later conditions, plus perhaps some random noise, then how can "freedom of choice" exist? When you get right down to it, what is free will? What does it mean to have selective intent, to be able to make decisions? Or in other words, is freedom of choice just an illusion? If not, then it's outside of known physics, since modern physics only includes the pure determinism of Classical Mechanics and the statistical randomness of QM. Where does our apparent freedom to make decisions come into contemporary physics? Perhaps self-awareness isn't the mystery of consciousness, since a purely deterministic computer program could concievably observe its own operation yet remain deterministic. On the other hand, how could a computer program ever have the ability to observe the factors affecting a decision, then choose to ignore them and instead make the wrong decision intentionally, because it wanted to? --Wjbeaty 03:47, 8 March 2007 (UTC)
The questioner contends that physical and chemical laws yield an "entirely random phenomenon." I think this is fundamentally incorrect. If you drop an apple, there is no randomness about the direction it will fall. If you mix vinegar with baking soda there is no randomness as to what will happen. These are structured events governed by physical laws, which scientists can study and uncover. This is quite the opposite of your question. Perhaps you might ask whether our thoughts are entirely deterministic, or if there is enough complexity in the system to yield complicated behavior. Or perhaps you subscribe to the notion that quantum mechanics and its sub-atomic uncertainty propagates up to macroscopic events like chemical reactions (this is a disputable issue, depending on how you interpret the statistics and how you choose to define random). Nimur 17:53, 8 March 2007 (UTC)


Why are some things that need to be aerodynamic not pointy in the front? Wouldn't hand gun bullets travel farther and faster if they were sharp instead of round at the front? Wouldn't airline jets have less drag and be more efficient if they had pointy noses like fighter jets instead of those round bubbly nose cones?
For the first example someone told me they're meant to be that way so they don't pierce right through the victim and hit someone else. Which is just silly because you can still make them aerodynamic and use less gun powder. What about the airplanes example? Is there any harm in making the nose too aerodynamic? —The preceding unsigned comment was added by (talk) 22:24, 7 March 2007 (UTC).

Believe it or not, there is at least one article dedicated to that exact question - you can read all about it at nose cone design, and also some in nose cone. It appears that simply making the nose slimmer is not sufficient - there are more complicated aerodynamic considerations to take into account. And also, don't forget that the sharper the nose cone, the longer it must be to connect to a body of given width, so there is much more metal-air frictional interface. But I know very little about aerodynamics. --User:bmk
I've corrected bmk's links. To summarize, however, a pointy nose is not necessarily aerodynamically ideal. The first article specifically notes that for velocities below Mach 0.8 (such as airliners), blunted nose cones are ideal. — Lomn 22:36, 7 March 2007 (UTC) (after edit conflict)
Also note that bullets from rifles have a spin, so air isn't just moving straight along them. Thus, if you were to add a nose cone, it would need to be more of a corkscrew shape. Also, I believe any point on a bullet would cause the bullet to tumble once the point got slightly off center, and a tumbling bullet is much less aerodynamic. This is a basic stability issue. While passenger planes are designed to be stable, which makes them easy to fly, fighter planes are designed to be aerodynamically unstable, which allows for quicker turns and maneuvers, and a round nose is more aerodynamically stable than a pointy one. StuRat 23:19, 7 March 2007 (UTC)
I've coma across this same question in model rocket circles, those guys know a lot about nose cones. This site has some great info and here is even a piece of software to design nose cones. Vespine 02:23, 8 March 2007 (UTC)
One critical concept involving pointy-fronts on non-supersonic aircraft: if the nose is pointy, and if it hits the air at an angle, then there will be flow-separation on one side and sideways-directed frictional forces which lead to tumbling. Or if a wing has a sharp leading edge, and it hits the air with a positive attack-angle, then there will be major flow-separation above the wing, and major turbulent friction. It's called a "stall." Sharp leading edges cause the air-flow to peel loose from the object's sides. To avoid this situation, eliminate the sharp front parts and make them smoothly rounded. Pointy parts are only good for supersonic objects, and for objects having guide-fins which prevent it from tilting with respect to oncoming air. --Wjbeaty 03:30, 8 March 2007 (UTC)
Bullet noses are only pointed in the case that you want it to go really really far. See .223 for an example of a rifle bullet designed for distance, and 9mm Luger for a handgun bullet designed for stopping power. The idea that you can simply use less powder in a handgun bullet is erroneous, the purpose of the bullet is to hit one target and do as much damage as possible, to do this you need lots of acceleration AND lots of mass. -- 15:01, 8 March 2007 (UTC)

Waking up from a bad dream[edit]

This may seem kind of bizzare--I don't know if anyone else experiencces this. When I have a bad dream, usually I realize it's a dream near the end (just before something realy bad happens to me or someone else, like getting attacked by the beast or what not). The wierd thing is, I'm still terrified and I feel literally stuck in the dream. At this point, I must be consious because I'm trying to "get out" of the dream. Then I try to wake myself up by "jerking" by neck or torso... and the strangest thing is that it always works by the second or third try. A couple of questions: Why on earth don't I ever think "Who cares, it's just a dream, so why don't I try to enjoy it like a horror movie". The second question is, why do I need to physcially shake my body to wake up, why can't I just open my eyes and wake up?
This is not just one incident, it's happened to me so many times. Does this all sound bizzare or does anyone here know what I'm talking about? —The preceding unsigned comment was added by (talk) 22:40, 7 March 2007 (UTC).

What you are describing is so common that it has a name: a hypnic jerk. Take a look at our article on hypnagogia, which basically applies (though strictly speaking, because you're waking up rather than falling asleep, you're in a hypnopompic rather than a hypnagogic state). - Nunh-huh 23:06, 7 March 2007 (UTC)
(1) If you thought this, that is the best possible thing you can do in a dream. See lucid dreaming. It is really cool :) (2) Normally I just take my fingers and pull my eyelids off of contact with my eyes a few times, kind of "popping" them, or just "opening" them past where they would normally physically be able to fold up. If you are lucid, I would recommend trying your best to stay in the dream. The most effective technique for this, is mysteriously, spinning around on your vertical axis. I'm really not sure hypnic jerk has anything at all to do with this, since it is a physical muscle spasm that happens when you are falling into sleep, could that be clarified if I'm missing something? I recommend you do your best to become lucid, and know, accept, and understand that you are in a dream and you can do anything you want. :) What would you like to be able to do in normal life but is often constrained by social or physical limitation? Favorites are flying and sex. You may be on your way to becoming a lucid dreamer! Good luck, hope I helped any. [Mαc Δαvιs] X (How's my driving?) ❖ 01:03, 8 March 2007 (UTC)
If I have a lucid dream I usually have to fight to stay asleep :( Vitriol 01:37, 8 March 2007 (UTC)
Long ago I've had similar eperiences with nightmares, but in order to escape, I used my voice to break out of the dream. If I could use my real-world vocal chords to say "raaaahhh," then I broke out and awakened. (I think I was awakened by the sound.) But after years of nightmares, today I can usually just watch the events without fear. As for being able to enjoy nightmares, I don't think most awake-state skills are available when sleeping. "States of consciousness" are weird things in that all of the skills developed during one state aren't available during another state. Classic example: if you study for an exam while drunk or while very sleepy, then the learned material won't all be available if well rested or sober during the exam! So, recall how scary a horror movie was during your early childhood. Toleration of horror movies is usually a learned skill. Since we learned that skill when awake, it's not necessarily available during sleep. So... we react to nightmares as if we were little kids confronting a horror movie. Learning to enjoy nightmares takes time, and unfortunately it's a *separate* process from learning to enjoy horror movies. For more info search on "state-dependant memory" google search--Wjbeaty 03:18, 8 March 2007 (UTC)
As for "Why on earth don't I ever think "Who cares, it's just a dream, so why don't I try to enjoy it like a horror movie", it's probably a good thing that you don't think that. I've always believed that dreams are not "just dreams". They are messages from the unconscious to the sub-conscious. They mean something. What they mean, or whether any particular dream is significant or not, is not my or anyone else's place to say. Only you can work that out, if it's important enough for you to know. JackofOz 03:53, 8 March 2007 (UTC)
I am a skeptic and I am not sure there is much scientific evidence, if any evidence at all. "Evidence is not the plural of anecdote." In my opinion, it seems logically fallacious since I can completely control any of my dreams. So my unconscious and sub-conscious is taking a break while my conscious takes over driving for a while? It's a personal belief thing. Since we're on the subject, I'd like to ask what compelling evidence there is for an unconscious and sub-conscious? We usually assume a conscious. [Mαc Δαvιs] X (How's my driving?) ❖ 07:55, 8 March 2007 (UTC)
Well, if you remember that your 'conscious' and 'subconscious' are both just you, there isn't really a problem. Have you never sort-of known something that you haven't properly thought about consciously? As in, something bothers you about a situation, then you have a proper think why, and you realise through conscious thought? Subconscious is just a name for the process that is doing that first thinking, but that doesn't mean there are two seperate people in your head. It's all you. It's just useful semantics. Dreams seem to me to be a way of sorting out the thoughts in your head. Since you don't tend to think about everything consciously all the time, while it might be 'at the back of your mind', they can bring up things you didn't realise you were thinking about. You could call this 'messages from your subconscious to your conscious', because that is a convenient way of putting it. An example (although anecdotes are not reliable evidence, it serves to explain what I mean): Every so often, when I'm living away from my family, I get a dream where some natural disaster sweeps in and I'm trying to get them all safely out. I wake up, thinking about the dream, and realise that I'm missing my family and worrying about them, having not seen them for a while. I visit home. It's only my own thoughts, no outside intervention, but it is a useful way of picking up the thoughts and feelings that I don't have time to think about, or don't want to think about, when I'm awake.
On to lucid dreams. In lucid dreams you are aware of dreaming and appear to have conscious control over the dream, yes? However, studies (damn, where are they?) have shown that when questioned shortly after waking, lucid dreamers report not retaining constant lucidity throughout the whole dream. So they have moments when they act as if it is real, or they do/think something that makes no lucid sense. So your actual lucidity may not be as total as you'd think. Another way of looking at it is that you have exchanged one valuable function of sleep for the excitement of lucid dreaming. However, I imagine you end up doing most of the thought-sorting you'd normally do in a dream, just with the impression of more control. If not, I would expect your memory to be shot to pieces :-P
Finally, everyone is in complete control of all their dreams, because dreams are all in the head. Just because it is what we are calling the 'subconscious' doesn't make it any less you, in your brain. Although scans have shown that dreamers usually have sections of their brains less active in such a way as to render them functionally mentally handicapped in the dream. Which explains some of the odd reasoning. (And if you want proof of unconsciousness, let me find you a general anaesthetic.....) (Possibly all this is ranting and should be removed?)
As to the jerking, I get that too sometimes. It seems to be related to the hypnogogic jerk, in me at least. It's like my muscles get hooked back up to my 'dream muscles', so a dream motion causes an actual motion, and that movement is enough to jerk me awake. I used to find realising I was asleep woke me straight up, unless I tricked myself into not fully realising (by pretending it was a film or book I was watching/reading/writing), but in recent years I've had to claw my way awake if I don't like it. I think it's just one of those things. You're not alone :-) Skittle 01:49, 9 March 2007 (UTC)
I guess I'm lucky because all of my dreams are "lucid" dreams (I know I'm dreaming) and I'm fully able to just open my eyes at any time and wake up.. as long as I'm dreaming. --frothT 09:11, 8 March 2007 (UTC)
The "dream producer" can in my experience work amazingly fast. If the phone starts ringing, your mind may try to keep your sleep going by incorporating its sound into the dream, by creating an instantaneous "backstory" which leads up to you hearing the ringing as part of the dream action, like you pressing a doorbell in the dream. Similarly if the clock radio is giving the news, the words of the announcer may be incorporated into the dream. The point of this in the extreme is that your body may be about to give a big movement and the dream creator provides an instant nightmare to "explain" it. We do not provide medical advice, but if this causes problems for you or a bed partner, you might wish to discuss it with your doctor. You might be interested in Sleep , Dream , Sleep paralysis , Lucid Dreaming , Sleep disorder , Night terror , Restless legs syndrome , Sleep paralysis , False awakening , and Polysomnography . Edison 22:54, 8 March 2007 (UTC)

So that time when I had a dream where people decided to start ringing a bell just before my alarmclock started ringing, I made all of that up after I heard the alarm? A bit worrying if I did, messing up my own memory deliberately, and it didn't even work as I still woke up :( HS7 20:15, 9 March 2007 (UTC)

Actually I just realised, it didn't do it deliberately as I was asleep and therefore couldn't deliberate it, so I must have just done it on purpose :] HS7 20:16, 9 March 2007 (UTC)

Homework (but it's only a small part of a question in a series)[edit]

So. AP Physics C. We're working on circuits and we've got this big packet of questions. There are diagrams I can't reproduce, but the question I'm asking is basically theoretical. I've got an idea, and I just want to make sure it's right. So the circuit in question is roughly symmetrical. A wire runs off the positive end, forks into a resistor and a bulb of unknown size, then rejoins and forks again, this time into two bulbs (of unknown size) and two resistors of a different resistivity (if that's the right word) from the first one. The four wires then go back into another fork into a bulb and a resistor, the same as the first two. In other words, to simplify it, the positive and negative charges follow the same path until they meet at those four middle obstacles (2 equal resistors and two questionably equal bulbs). The question is whether, for those two questionably equal-in-size-and-thus-resistivity bulbs, the CURRENT FLOW in one is equal to that in the other regardless of any size difference. My feeling is that since the same net flow flows regardless, the same current will flow over each bulb, just slower (this is clearly the wrong term, but I think the gist comes across) depending on bulb size. In other words, the ratio of flow between the two would be a simple 1:1 regardless of size, and the ratio of that current flow to the flow of current through the battery would be 1:4 because the charge is equally distributed through the four "obstacles" in that equal level of charge, so to speak. Correct? Hopelessly wrong? Thanks for any feedback, 22:36, 7 March 2007 (UTC)

I learned about resistors and stuff like this when i was in highschool however i cannot give you a conclusion unless i see a diagram as that is how i solved all problems like this. as far as the flow you got to realise that you placed resistors in the circit which in turn would reduce the voltage of the power going through your wires. and with out exact resistence stated we cant know how much of that power is taken by the resistors. try to make a diagram or something so i can check it out unless someone else can solve this before you do.Maverick423 22:45, 7 March 2007 (UTC)

also realise that the size of the bulbs dont effect the flow of power unless they too have some sort of resistave material inside them to do so. Maverick423 22:48, 7 March 2007 (UTC)
acctually i think i may have something for you to think of for what you are trying to do. this is my rough diagram ( 120 v source)====B===B===B===B (back to 120 v source) the wires here are connecting in a perallel fashion which means 120v are distributed equally however if they were connected something like this (let me try) (120)==<B}==<B}==<B}==<B}==(120) the power is spread out into the bulbs so 120v becomes 30v per bulb because the power is spread within the bulbs. really this is alot simpler to explain in a diagram but im trying my best to help you with what i got Maverick423 22:57, 7 March 2007 (UTC)

Here's my attempt at a diagram. None of the bulbs are necessarily equal, though I think the top and bottom ones have to be. And the large/small bulb convention is based on bulbs he's had us use in experiments, which do have different resistivities.

   ________________ _______
   |               |       |
   |               |       |
--------         bulb     1.6V resistor 
4V battery         |       |
  ---              |       |
   |        -----------------------      
   |        |      |       |      |
   |      .8V R   bulb    bulb   .8V R
   |        |      |       |      |
   |        -----------------------
   |               |       |
   |             bulb     1.6V R
   |               |       |
   ------------------------- 22:58, 7 March 2007 (UTC)

the energy is reduced each time the power passed a bulb or resistor unless the (hot) wire is perrallel to the neutral one. but since your trying to reduce the volts this would be pretty much wasteful. however the volts if connected from the resistor to the bulb will be reduced and you can still maintain 4.5 v by bypassing the resistor with a parallel wire. ill see if i can make you a diagram

Yeah. I get that. The question is whether the flow of charge through those two middle bulbs is equal regardless of any difference the two might have in resistivity. 23:07, 7 March 2007 (UTC) Oh, and it isn't 4.5. I copied that down wrong and that may have thrown you, cause then the numbers wouldn't have worked.

sorry for the late response i had a emergancy. well according to what you provided it seems that the bulbs assuming they use about 1v each will not be equal. but seeing as how there are 2 diffrent sizes i would assume that the smaller of them is .4v and the bigger about .8v which would mean that both the center bulbs should have more then enough energy to be powered but they wont be equal seeing as how the small bulbs will only use .4v and the resistor next to the small bulb blocks off 1.6v. this is of course assuming that this is the voltage usage of the bulbs either way the bulb next to the resistor will have to use 1.6v to allow both bulbs in the middle to be equal to each other. the .8v resistors will not seem to have a effect since they are not in the direct current of the power source they are well out of the way. Maverick423 02:21, 8 March 2007 (UTC)

What's a bulb? If you mean a traditional Incandescent light bulb, then we need to decide if you have a theoretical bulb or a real bulb. A theoretical bulb has a fixed resistance and no inductance. For this, you can create an equation that describes this circuit exactly as a pure series/parallel resistive circuit: simply assign resistances (B1, B2, B3, and B4) to each bulb and plug them in. Real bulbs are very different, however, for two reasons. First, A real light bulb filament is a coil,and a coil is an inductor. This is means that current cannot change instantaneously. Second, a real bulb has a change in resistance with temperature, and therefore a change of temperature with time*current. This means that when you flip the switch (i.e., when the voltage changes instantaneously from 0 to 4v) you initiate a complicated time-varying set of changes in the current through each bulb. If we characterize each bulb as having a fixed inductance L, a fixed coefficient of resistance/temperature C, and a fixed dissipation of power P, then each bulb is (L,C,P). With four bulbs, you have twelve numbers and a whole lot of calculus. I would speculate that for some valid sets of bulbs, your circuit will exhibit chaotic behavior. -Arch dude 02:38, 8 March 2007 (UTC)
The homework question is somewhat of a "trick question" because it tests you for the "sequential" misconception, the "current sharing" misconception, the "absolute voltages" misconception, etc. Many beginners incorrectly believe that batteries supply a (constant) current which then divides itself as it hits branch points. To avoid all these mistakes, base your reasoning entirely upon Ohm's law: the current through a particular resistance is only determined by the voltage measured between the two resistor terminals, divided by the resistor's ohm value. Ask yourself this: will you ever measure two different voltage values across the terminals of two separate lightbulbs if the two bulbs' wires are connected to each other? Also ask: do you *know* that the ohms value of those two bulbs is equal? --Wjbeaty 02:48, 8 March 2007 (UTC)
Voltage will be the same across parallel elements. BTW, what are those resistors with voltage? Resistors don't directly regulate voltage. Let me read this question over before I answer in more detail. --Wirbelwindヴィルヴェルヴィント (talk) 03:00, 8 March 2007 (UTC)
Ok, you're thinking if the two bulbs parallel to the (magically) 0.8 V resistors have the same resistance, and we're assuming light bulbs to be a resistor and not an RL circuit, then yes, you're correct in thinking that the current through each of those two bulbs will be the same. However, they do not move slower, just that you have less current (amperage). For the other part, current going through each of those middle bulbs are the same through each of the four branches... That part is the wrong assumption, unless the resistors and the bulbs have the exact same value. Then yes, the current through each bulb will be 1/4 of the total. But if it's not: If the 0.8 V resistors have less resistance than the bulbs, then less current will blow through the bulbs than the 2 resistors, and vice versa. I'll draw a diagram right now to show you more clearly. --Wirbelwindヴィルヴェルヴィント (talk) 03:11, 8 March 2007 (UTC)
Ok, I uploaded an image to help demonstrate. Assuming those are not 1.6V resistors and 0.8V resistors, but that there is a voltage drop across them of those values, that means everything parallel to them has the same voltage. That means both Bulb A, Resistor A, Resistor D and Bulb D have the same 1.6V drop. This also means that Bulbs B, C, and Resistors B, and C have the same 0.8V drop. So the question (I think) is, do Bulbs B and C always have the same current. The answer is no, because the current through those is dependent on the resistance of Bulb B and Bulb C, which is given by dividing the voltage by the resistance, or 0.8V divided by the resistance of Bulb B and 0.8V diided by the resistance in Bulb C. So from that, you can see that they will have different current if the resistances vary.
As for the total current through Bulb B + Bulb C + Resistor B + Resistor C, it is the same as the current through Bulb A + Resistor A, which is the same as the current through Bulb D + Resistor D. The actual value is computed by finding the equivalent resistance of all 8 elements, and then dividing 4V by that total resistance. But that only gives you the current through each set of parallel elements. Hope this helps. If not, ask here or you can reach me on my talk page. --Wirbelwindヴィルヴェルヴィント (talk) 03:50, 8 March 2007 (UTC)
. When exact circuits are specified, exact answers can be given. Circuit equivalents can be determined and circuits can often be simplified and solved, using such tools as Ohm's Law, and rules for parallel resistances, series resistances, current divider. "The question is whether, for those two questionably equal-in-size-and-thus-resistivity bulbs, the CURRENT FLOW in one is equal to that in the other regardless of any size difference. My feeling is that since the same net flow flows regardless, the same current will flow over each bulb, just slower" I know of no electrical principle that" the same net flow flows regardless." When you say "the same current will flow over each bulb, just slower" that implies a misunderstanding of what electrical current is compared to what electrical charge is. One might say "the same charge will flow through a circuit element, just slower" which would be less current, but it is quite incorrect to say the same current could flow but more slowly. Re-read in your textbook the difference between charge (coulombs) and current (amperes, or coulombs per second) and abandon attempts to analyze circuits based on motivation of charges to do this or that. Look at an example in your text of circuit reduction, or provide exact circuits to be analyzed. In my sad experience, attempts to analyze complex circuits qualitatively and verbally fail utterly. I agree with Wjbeatty and Wirbelwind. The key question appears to be if the two unknown bulbs identified by Wirbelwind as Bulb B and Bulb C which are connected in parallel will carry the same current. As the question is interpreted, they each have the same voltage applied across them from the nodes shown above and below. As stated, they do not necessarily have the same wattage and thus can have different resistances. What if Bulb B was a 10 watt bulb and Bulb C was a 1 watt bulb? Then Bulb C would have far less current flowing through it. Circuit elements in parallel need not have the same current flowing through them at all, and often have vastly different currents. All the rest of the circuit has no relevance to this question. Edison 16:17, 8 March 2007 (UTC)

Energy / momentum / mass[edit]

The relativistic energy-momentum equation is E² = (mp)² + (mc²)². For a stationary object (p=0), this can be reduced to E = mc². Which of these relations / equations was discovered / derived first? →Ollie (talkcontribs) 23:18, 7 March 2007 (UTC)

Aren't they essentially the same equation? E=mc² is the famous one but it may be because it rolls of the tongue so much nicer ;) Einstein may have gone through the 1st one to arrive at the simpler one but there is no way someone else came up with the 1st for Einstein to just reduce it into his famous equation. Once you have one the other seems arbitrary, chicken or the egg? Vespine 01:06, 8 March 2007 (UTC)

Einstein derived the first equation from the mathematics of Lorentz transformations when he was creating the Special Theory of Relativity. After that, he did what any mathematical physicist would do and set p=0.MisterCDE 06:13, 8 March 2007 (UTC)