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Reference Desk

2006 (UTC)

It's not a typical cell like those that you encounter in bodily tissues. It is a gamete, essentially half a cell. --Russoc4 21:12, 8 November 2006 (UTC)

This is just so weird to think about. So what organelles do gametes have? — BrianSmithson 22:38, 8 November 2006 (UTC)

See Ovum and Sperm for more details. bibliomaniac15 Review? 00:06, 9 November 2006 (UTC)

All of your mitochondria come from your mother's egg. That is true of all vertebrates as far as I know. The sperm's mitochondria do not survive in the zygote. alteripse 01:11, 9 November 2006 (UTC)

Repent! The End Is Nigh!

I was thinking about how the gravitational pull of the moon gives us tides, and how that body of water goes ahead and absorbs energy which I figure must come from the moon's orbit and the moon will have to change it's orbit to accomodate loss of energy. I can't remember whether it will move further or closer but there is a loss of potential energy if it moves closer, so is the moon gonna fall in on earth? --Username132 (talk) 16:15, 8 November 2006 (UTC)

Farther. Good explanation here. JBKramer 16:19, 8 November 2006 (UTC)

Hey Kramer, thanks for the article, but there are a few things I don't understand. Why is this?

it h

when it's in the part of its orbit closest to the Sun, it's closer, but when it's in the part of its orbit farthest from the Sun, it's farther away.

Maybe I am misreadig this, but I interpret this to mean when the moon is in it's orbit around the Earth it is closer to the Earth when it is closer to the Sun, and farther away from the Earth when it is on the side away from the Sun. This is counter-intuitive to me as the Sun should be pulling it away from the Earth when closer to the sun, and pulling it closer to the Earth when on the far side.

Please sign your posts. The article means that the Moon is, when its orbit has grown, even closer to (or farther from) the Sun at those times than before: because its orbit is bigger, its distance to the Sun varies more (and reaches higher maxima and lower minima). --Tardis 19:40, 8 November 2006 (UTC)

This is also confusing.

Tidal friction, caused by the movement of the tidal bulge around the Earth, takes energy out of the Earth and puts it into the Moon's orbit, making the Moon's orbit bigger (but, a bit pardoxically, the Moon actually moves slower!).

The moon should move faster when more energy is added to it's orbit. Now, the angular velocity slows down as it takes longer to make it around the Earth, but the article does not make that distinction.

No, it really goes slower. Look at [[orbital tidal locking, with the Earth always having the same face turned toward the Moon, as well as vice versa; as I said when this came up in the "blowing up the Moon" question just above, I think the resulting "day = month" would be about 40 of our present days. For the Moon to fall for this reason is impossible; that could only happen if the day was longer than the month, so the forces would act the other way. --Anonymous, 05:00 UTC, November 9.

Oh, okay, I understand. So eventually some poor people will be stuck with an eternal eclipse and places would get awfully cold while the sun wasn't shining on them?--Username132 (talk) 10:53, 9 November 2006 (UTC)

I'm not sure where Anonymous above got the some of his/her ideas. First, the idea that angular momentum from the Earth would be transferred to the Moon. Second, that there is only one particular speed is possible for a given orbital radius. Third, the idea that the Moon moving further away from the Earth would contribute to tidal locking (the same face of the Moon always faces the Earth already and tidal locking would cause the same face of the Earth to always face the Sun)
It is possible that the Moon could collide with the Earth, although not before the Sun dies. The Moon (as well as any other body in orbit around any other body, or even any accelerating body) loses energy via gravitational radiation. In the case or orbiting bodies this will cause them to orbit more closely the center of mass of the system. This would, however, take an extremely long time to happen and there are far better things to worry about.

First, because angular momentum is conserved and has to go somewhere. The relevant force is acting between Earth and Moon, so if one loses angular momentum, the other gains it. Second, Kepler's Laws. Third, because tidal locking is the end situation for the process we're talking about. The Earth feels a stronger tide from the Moon than from the Sun (tide varies as m/r³) and would become locked to the Moon, not the Sun. --Anon, writing in a hurry, 02:54 UTC, Nov. 10.

Well orbital velocity depends on the relevant masses of the bodies as well as the distance between them. Ergo not all orbits at the same distance have the same period. Kepler's (third) law (actually formulated to describe motion of planets around the Sun) do hold for systems of bodies of the same masses and ensures conservation of orbital angular momentum - ignoring intrinsic angular momentum. If you move the Moon further from the Earth but decrease its velocity (as per Kepler's law) you will not increase its angular momentum.
It is possible to show how the Moon may move further from the Earth, but it requires a general relativistic treatment.

Buyoancy of wood

I have a piece of driftwood that I want to sink to put in my aquarium. I know it will take a while for the wood to soak enough to no longer float. Is there a way to speed the process?

TrekBarnes 19:39, 8 November 2006 (UTC)

Increased pressure? (That is, put it in some kind of a pressure vessel and apply pressurised water.) (I ASSUME that the heat of a pressure cooker would damage the wood.)

Add some non-toxic ballast, concealled within the driftwood? Rocks? Stainless steel? Embed or cement the driftwood into a rock or concrete base?

Atlant 20:01, 8 November 2006 (UTC)

Aquarium driftwood is supposed to be boiled for a couple of hours before it is placed in the aquarium AFAIK. Reducing buoyancy is not the only reason this is done for. Cooking the driftwood also disinfects it; that is, reduces the tendency of wood to rot and, more importantly, reduces the tendency of fish to die... Also, cooking removes excess resin and sap. The resin, especially of conifer driftwood, is certainly not something the fish would like to swim in. So, just keep your driftwood in boiling water for a couple of hours, weighted down by some iron (I used a pair of weights I exercise with). Beware that boiling the driftwood can be quite messy; the vessel will no longer be suitable for cooking food. Let the driftwood cool completely before placing it into aquarium, and let your filter run for a day or so after you put the driftwood in; only then you can start to populate the aquarium with fish. --Dementios

Oh, and there is still a chance the driftwood would float even though it was boiled. Apparently, boiling removes most of the trapped air, but not all of it. In such a case, weight the driftwood down in the aquarium with a decorative stone piece (also boiled, to disinfect it). Hope this helps. --Dementios

If it's well-weathered driftwood that I gather from the lake, and sunbleached, I just weight it with rock and put it in. You should have some cleaner fish that really like to chew driftwood! --Zeizmic 00:23, 9 November 2006 (UTC)

My guess is the cleaners eat bacteria/fungi growing on that wood not the wood itself! -- 85.179.3.83 11:47, 10 November 2006 (UTC)

Transit of Mercury

Survey: before reading this, did you know that a transit of Mercury is going on right now? Just curious. --Bowlhover 21:43, 8 November 2006 (UTC)

Note: transit will end November 9 00:10 (UTC).  --Lambiam 23:13, 8 November 2006 (UTC)

Yes

• Yup. Melchoir 21:53, 8 November 2006 (UTC)
• I did. --Cody.Pope 22:45, 8 November 2006 (UTC)
• I did, i just saw it through a telescope around 1 hour ago. there is also a rather large sunspot at the moment, it appears bigger than mercury. Xcomradex 23:13, 8 November 2006 (UTC)

Lucky you. I waited to see the transit for more than a year. It was clear for the entire week last week, but it's completely overcast today. (Oh well, at least I saw the 2004 Venus transit by an incredible stroke of luck.)

By the way, which sunspot did you see?? --Bowlhover 23:28, 8 November 2006 (UTC)

my sunspot was roughly where that arrow is, at about the 8 o'clock to 8:30ish (top of the sun being 12:00). at the time, mercury was at about 1:30 position, about 1/4 to 1/3 of a radius in from memory. but from the simulation, i'd say the image was inverted. Xcomradex 00:18, 9 November 2006 (UTC)

it looked a lot like this. Xcomradex 00:35, 9 November 2006 (UTC)

• A'yup, I knew -- but New England has been overcast. 'Darned shame, too -- I got some nice pictures of the transit of Venus not so long ago. -- Atlant 17:19, 9 November 2006 (UTC)

No

• No. But I knew that they could only happen once every ${\displaystyle {\frac {1}{{\frac {1}{88}}-{\frac {1}{365.24}}}}\approx 116}$ days or so. (Not that they do that; the article seems to suggest that about 5% of the potential transits occur due to inclination and such...) --Tardis 22:40, 8 November 2006 (UTC)
• No. As long as Mercury isn't retrograde...  --Lambiam 23:13, 8 November 2006 (UTC)

Animal twins

When mammals get litters or 4 or more offspring, are they from one egg cell (like identical human twins) or an egg cell each (like non-identical twins) or a combination thereof?

• They're certainly not always identical -- look at any litter of puppies or kittens. Are some of them identical? Sometimes, I imagine -- and I'd guess about as frequently as human identical twinning. --jpgordon 23:05, 8 November 2006 (UTC)

• Nine-banded armadillos, however, always have identical quadruplets. StuRat 23:17, 8 November 2006 (UTC)

It's normally non-identical twins. Of course, there're exceptions, as StuRat has pointed out. --`/aksha 11:13, 10 November 2006 (UTC)

Viagra

1) Do you need a prescription to get it in Canada? (Vancouver, BC)

2) Does it increase stamina for men with no rectile problems at all?

3) Is it safe.. side effects?

4) How much does it cost?

Viagra is for erectile dysfunction, not "rectile" (although, the gay partners of men taking Viagra might possibly suffer from rectal problems, as a result). StuRat 23:13, 8 November 2006 (UTC)

Oo! Do you think thats wise?--Light current 23:58, 8 November 2006 (UTC)

1) Dunno.

2) Yes.

3) You can have a heart attack during sex.

4) Check your email.

--Kurt Shaped Box 00:39, 9 November 2006 (UTC)

1) Yes, though my information is 3 years old and there was talk of releasing it non-prescription even then. There may now be a low-dose version that can be obtained off-the-shelf.

2) For men without erectile difficulties, an increase in stamina isn't necessarily a good thing and can cause problems, not to mention discomfort.  freshofftheufoΓΛĿЌ  03:06, 9 November 2006 (UTC)

1) Do you need a prescription to get it in Canada? (Vancouver, BC) - Yes
2) Does it increase stamina for men with no rectile problems at all? - maybe
3) Is it safe.. side effects? - see Viagra#Contraindications and Viagra#Side_effects
4) How much does it cost? - ask your pharmacist
- Cybergoth 22:33, 9 November 2006 (UTC)

Zinc Production in Port Pirie, South Australia

What are the benifits of Port Pirie as the location for a zinc smelter? I believe it has something to do with the deep ocean bay or dock, but I am looking for more specific answers. --203.28.159.168 23:12, 8 November 2006 (UTC)

Possibly the proximity of Broken Hill which had one of the largest Pb-Zn-Ag orebodies in the world. The article on Ore genesis might have more helpful links.---Sluzzelin 23:54, 8 November 2006 (UTC)

Also, have you considered that there was also a town already there before the smelters were built, which is easier than starting from scratch. --Robert Merkel 01:07, 9 November 2006 (UTC)

You also need to consider the proximity of major electicity supplies, Port Pirie is only an hour south of Pt Augusta which has a major power plant because of coal mining at Leigh Creek.

November 9

Skid Marks

Is it possible to determine the amount of rubber removed from a cars tyres by measuring the length of the skid marks? Or does this depend upno the cars weight as well? Also, how do the police tell what speed the vehicle was doing just by the length?--Light current 00:35, 9 November 2006 (UTC)

I doubt the length is enough to tell the amount of rubber removed. Heavier cars with a softer tire would leave more rubber on the ground, I'm fairly sure. However, how much it varies by, I have no idea. The police can estimate how long it takes the vehicle to break by how long the skid mark is, which is related to the speed, but I'm not sure how accurate that is either, but cars generally have stopping distance statistics. --Wirbelwindヴィルヴェルヴィント (talk) 02:11, 9 November 2006 (UTC)

Well, you can estimate how much rubber there is per square centimetre of the skid mark, and then multiply this by the skid mark's area. --Bowlhover 03:17, 9 November 2006 (UTC)

THe problem as with other things is estimating how much rubber has been spread per sq cm of road. Would they have to scrape it off and weigh it. Or could a solvent be used to remove the mark then the liquid be analysed? Actually I dont think tyre rubber is soluble in anything--Light current 13:15, 9 November 2006 (UTC)

The stopping distance depends on the weight of the car in this case. (The stopping distance given by the manufacturer is usually the distance it takes to stop without skidding). Assuming that the driver slammed the brakes, thus causing the skid marks to appear the instant the decceleration started, the speed of the car can be found out quite accurately. Using the formula F=μN (μ is the co-effecient of friction between the road and the tyres. N is the weight of the car), the frictional force is calculated. Knowing the mass and the force, the decceleration can be calculated. Now we know the force that stopped the car, we know the decceleration and we know the distance S at which it stopped (That is the length of the skid marks). v=sqrt(2aS) will give us the velocity of the car just before braking. -- Wikicheng 04:53, 9 November 2006 (UTC)

Yeah I think youll find that the coefficient of friction varies wildly from start to finish of the skid marks--Light current 00:57, 10 November 2006 (UTC)

I don't think so. The coeffecient of friction is a constant for a pair of surfaces -- Wikicheng 10:07, 10 November 2006 (UTC)

You're assuming the two surfaces have no changing properties: As tires heat up the rubber gets softer and more likely to grip on some surfaces but more likely to smear on other surfaces. There is also the question that noone has yet raised of ABS which throws off your calculation of sliding friction because the tire is only sliding for brief periods. --Jmeden2000 15:35, 10 November 2006 (UTC)

Well... you are right regarding the changing properties...:-) -- Wikicheng 17:07, 10 November 2006 (UTC)

I've seen the police doing tests after a deadly accident in which one car was still in good driving condition. They slammed the brakes on the same road at different speeds and measured each time the length of the skid marks. I further heard that NapiSan is effective.  --Lambiam 10:27, 9 November 2006 (UTC)

Joules and Farads and Volts, oh my!

What is the formula that shows how many joules there are based on Volts and Microfarads? I am wondering how many microfarads it will take at 35 or 50 volts to equal one joule. Thank you. Ilikefood 01:51, 9 November 2006 (UTC)

If you look at the page on volts, V = J / C, or J = V * C. --Wirbelwindヴィルヴェルヴィント (talk) 02:15, 9 November 2006 (UTC)

that page is wrong then. I'm not sure what they are getting at. P = VI , Volts * couloumbs/sec. Energy is the integral of Power through time. Therefore, Energy = qV (q is the total charge due to integrating I, electron Volt is also energy makes sense from equation). I = C dV/dt. Therefore, Energy = integral (CV dV) = 1/2 * CV . The Capacitor article seems to have it correct. The volt article looks very confusing. I think they confuse J (current) with Joules (Energy) --Tbeatty 04:40, 9 November 2006 (UTC)

Someone should edit it before I make myself look bad again =D --Wirbelwindヴィルヴェルヴィント (talk) 05:30, 9 November 2006 (UTC)

Volts = Joules per Coulomb. That formula has nothing to do with capacitance -24.84.54.54 05:40, 9 November 2006 (UTC)

Um, right. So the correct answer is Energy (in Joules) = V^2 * F, right? ^^; --Wirbelwindヴィルヴェルヴィント (talk) 05:56, 9 November 2006 (UTC)

That's right. But for convenient units, it's often expressed as kV^2 * uF (kilovolts squared times microFarads).

Atlant 17:22, 9 November 2006 (UTC)

See in Capacitor the section " Stored energy:" The energy stored in Joules is given by:

${\displaystyle E_{\mathrm {stored} }={1 \over 2}CV^{2}}$ where V is the voltage across the capacitor. So solving for capacitance in Farads, ${\displaystyle C_{\ }}$ = ${\displaystyle 2*E_{\mathrm {stored} } \over V^{2}}$

Multiply by 1,000,000 to get microfarads. For example, for 20 volts, 1 Joule would require .005 Farad or 5,000 microfarad. For 100 volts, 1 Joule would require only .0002 F or 200υf. Edison 18:08, 9 November 2006 (UTC)

So you're saying that voltage squared times farads equals joules? Ilikefood 21:40, 9 November 2006 (UTC)

I would go with voltage squared times farads divided by 2. Edison 23:28, 10 November 2006 (UTC)

Absolute minimum density, part II

I'm not sure how to ask this question, exactly. But building on the earlier question that asked about the absolute minimum density of empty space, what part do photons play in the density of space? According to the article Photon, photons have 'invariant mass', but I'm not sure I understand what 'invariant mass' is. Empirically, space appears to be full of photons... observing a distant star, I'm seeing the photons emitted from it in the distant past. If I move a small amount to one side, I still see photons emitted from that star. That tells me no matter where I stand in view of that star, I will see photons emitted from it. So space is full of photons, from that star and every other star. So can space be said to be 'full of photons'? Yet, being massless, photons don't really fill anything up, yes? 192.168.1.1 9:59, 8 November 2006 (PST)

Although a photon viewed as an elementary particle is massless, it has energy E = hν, where h is Planck's constant and ν is the photon's frequency. Therefore it adds to the invariant mass of any system to which it belongs (such as a compartment of space through which it is moving) by the famous equation E = mc, by which m = E/c = hν/c. Since there are unsolved problems with the "energy balance" of the cosmos (see Dark energy), I'm sure physicists have estimated the contribution of photons to the energy density of space, but I don't know the result.  --Lambiam 10:16, 9 November 2006 (UTC)

It might help to know that the energy density associated with a photon gas is ${\displaystyle \sigma T^{4} \over c}$ (someone check my proportionality constant?), which means that, for instance, the cosmic background radiation has an energy density of ${\displaystyle 1.04\times 10^{-14}\mathrm {J/m^{3}} }$, or a density of ${\displaystyle 1.16\times 10^{-31}\mathrm {kg/m^{3}} }$. This is equivalent to one electron per 7.85 cubic meters; very little! Of course, there are stronger light sources: direct sunlight has an energy density of ${\displaystyle 4.50\times 10^{-6}\mathrm {J/m^{3}} }$, or ${\displaystyle 5.01\times 10^{-23}\mathrm {kg/m^{3}} }$. But this is still tiny; the density of water is ${\displaystyle 1000\mathrm {kg/m^{3}} }$, and an entire Earth's volume of that sunlight would mass only ${\displaystyle 5.43\times 10^{-11}\mathrm {kg} }$. Obviously the mean density in a galaxy is somewhere between direct sunlight on earth and the CMB. --Tardis 04:03, 10 November 2006 (UTC)

IC Accelerometer

Ant idea on how the IC ADXL202 measures acceleration? —Preceding unsigned comment added by 210.212.194.210 (talk • contribs)

gooooooooogle Weregerbil 09:57, 9 November 2006 (UTC)

See . A micromachined spring holds surfaces apart. Separation affects capacitance. F=MA. Distance, i.e. capacitance, is a function of acceleration. Edison 17:33, 9 November 2006 (UTC)

Step down Transformers

We use Iron core step down transformers,which suffer from heating and hysterisis loss. Why cant we use capacitors arranged in series instead to step down voltage more efficiently??—Preceding unsigned comment added by 210.212.194.210 (talk • contribs)

Capacitors change the power factor and also as not useful (offer a lot of impedance) at low frequencies, which is a loss. --Wikicheng 10:28, 9 November 2006 (UTC)

Actually its not a loss, its a mismatch. No power is lost in a capacitor.--Light current 13:43, 9 November 2006 (UTC)

Also capacitors do not provide safety isolation from the mains supply. Some completely isolated low power devices do however use 'capacitor droppers'--Light current 13:41, 9 November 2006 (UTC)

Transformers maintain about the same voltage "transformation" ratio for any load within their rated capacity. They also don't care too much about the reactance of the load.

By comparison, it would be hard to design either a purely inductive or purely capacitive voltage divider with the same flexible characteristics (to accommodate a variety of loads). As Light current pointed out, you could do it for a single, constant load though, you'd still have those safety isolation concerns.

More and more, people tend to use off-line switching power supplies that first rectify the mains power, then convert it to high-frequency AC which is then run through a very small, low-loss transformer and possibly converted back to DC. For example, nearly all low-voltage lighting run from mains power now operates this way.

Atlant 17:28, 9 November 2006 (UTC)

It is quite possible to step voltage up or down with capacitors, or with storage batteries. To step down voltage, charge them in series and discharge them in parallel. To step up voltage, charge them in parallel and discharge them in series. Some electric utilities in the late 19th centiry used this method with storage batteries to transmit DC at 1,000 volts to distant substations to back up local low voltage DC generation. A switch was used to change over from series to parallel. A switch could similarly be used with caps, but electronic switching is more efficient for continuous operation. Practical capacitors do contain resistance and have I^2 R losses. The caps in series would divide up DC voltage partly in proportion to their leakage resistance, so some might fail from overvoltage unless resistors were connected across each cap to force equal voltage division. Cost and complexity are likely the reason that transformers are used instead. The LM2798 says it somehow uses a switched capacitor to step down DC voltage, perhaps in a more subtle fashion than I discussed.The LM3351 is a capacitive step up device. Edison 17:47, 9 November 2006 (UTC)

Transformers generally reflect any load impedance to the primary. So reactive load ---> reactive load to primary supply. Not what the utilities want!--Light current 23:36, 10 November 2006 (UTC)

Polarizers

Will the efficiency of polarizers be affected in case a polarizer film is attached to a transperant glass/plastic plate or sandwiched between them?? —Preceding unsigned comment added by 210.212.194.210 (talk • contribs)

Not much.

Atlant 17:32, 9 November 2006 (UTC)

I would think that it would depend on the refraction index of the material, since polarization filters light from certain directions, the glass attached to the exposure side of the film might defract the light hitting the film, and depending on the angle, cause some of that light to be filtered out instead of allowed through. I'm not sure though. --Wirbelwindヴィルヴェルヴィント (talk) 18:41, 9 November 2006 (UTC)

LIVER AS METABOLIC BUFFER

It is said that liver acts as a metabolic buffer/How does it act so......can anybody tell in this detail...its not a home work question...when iam studying metabolism the thing i observed is that each and every metabolic cycle somewher touches liver...so i want to know about this..... --hima 12:06, 9 November 2006 (UTC)

Welcome to Misplaced Pages. You can easily look up this topic yourself. Please see liver. For future questions, try using the search box at the top left of the screen. It's much quicker, and you will probably find a clearer answer. If you still don't understand, add a further question below by clicking the "edit" button to the right of your question title. .--Shantavira 12:54, 9 November 2006 (UTC)

The liver takes up glucose when blood sugar is high, and put sugar into the blood when blood sugar is falling. In other words, in many ways, it can shift its metabolism and what it takes up and puts out in response to fed and fasting states to maintain metabolic homeostasis for the organism. alteripse 13:38, 9 November 2006 (UTC)

BLOOD

Is blood red or blue? As far as i know blood is red only because of the oxygen on the cells and when thats gone you turn blue....so what colour is it?

It is red when oxygenated in arteries and bluish when deoxygenated in veins. alteripse 13:35, 9 November 2006 (UTC)

Is it blue or is it more maroon (purple)? And when they take a blood sample does it matter that its taken from a vein?--Light current 13:39, 9 November 2006 (UTC)

Blood is never blue. Many textbooks have simplified diagrams with red arteries and blue veins, while blood in the real world is either bright red or darker red. --Wjbeaty 02:59, 10 November 2006 (UTC)

I think the taking from a vein matters more in the sense that taking blood from an artery is like trying to have a leisurely sip from a firehose. Confusing Manifestation 14:35, 9 November 2006 (UTC)

We routinely sample blood from arteries - it is not difficult in the least. The reason it is not more widespread is a) good candidates (such as the radial artery) are deeper and hurt more than veins and b) the risk for complications if a clot forms is higher. InvictaHOG 16:56, 9 November 2006 (UTC)

So the body has more veins than arteries and they are more accessible (nearer the surface). Is that right?--Light current 16:59, 9 November 2006 (UTC)

I actually think that there are more veins than arteries, but I don't think that I have ever seen that written anywhere. It's not that arteries are necessarily further from the surface. It's just that the ones you'd feel comfortable sticking are further away (ie the carotid artery is pretty easy to poke but it's kinda important!) InvictaHOG 20:25, 9 November 2006 (UTC)

There certainly are more veins than arteries. The arteries are (just about) always accompanied by at least one vein, but the superficial veins are not accompanied by arteries. 62.16.185.24 22:51, 9 November 2006 (UTC)

There's likely minimal difference in the number of arteries & veins--the closed system requires something close to a 1:1 ratio. But veins are almost always closer to the surface of the body than arteries. Often veins sit right on top of arteries. -- Scientizzle 17:09, 9 November 2006 (UTC)

As the danger from damage to an artery is much higher than from damage to a vein, it is no wonder that natural selection made the arteries lie further inside. To the orginal questioner: I hope you are not misled by the usual pictures in biology books that depict arteries in red and veins in blue. This is only to allow to distinguish them. Of course, the choice of colours is influenced by reality: oxygen-rich blood is bright red, and oxygen-poor blood has a darker, slighly purple-ish red. Simon A. 18:58, 9 November 2006 (UTC)

So why are subdermal bloodclots blue? Such as a black eye, which is really blue, but then also red, yellow and even greenish. Where do those colours come from? DirkvdM 09:55, 10 November 2006 (UTC)

The different colors are due to different decay products choleglobin/verdoglobin (black), biliverdin (green) and bilirubin (yellow/brown), according to the German hematoma entry. -- Rwst 15:15, 10 November 2006 (UTC)

Chemisty Question about lollipops

Why do lollipops turn sugary? You know, they start out as solids and then if you dont eat them, they turn sticky and gooey. Why?

Have you tried reading the answers to the exact same question further up this page? See #Chemistry: lollipops. Confusing Manifestation 14:37, 9 November 2006 (UTC)

optical

Describe the process of prism thinning.

see ]--Light current 15:05, 9 November 2006 (UTC)

Body Sensor

What is one's body sensor? Have been unwell for 2+ weeks with middle ear virus and doctor believes I should have made more of a recovery by now. He is sending me for a scan as he thinks it is my 'body sensor'. What kind of scan will it be? MRI?

J Wheeler

Your balance sensor is located in the inner ear and comprises the system of 3 semicircular canals mounted mutually orthogonally (my favorite word). THese canals are filled with fluid that sloshes about when you move your head and tells your brain which way up your head is . To look at your middle ear it will probably be an MRI scan. Im not sure if that can do it with ultrsonics nowadays.--Light current 16:47, 9 November 2006 (UTC)

Crossing legs and weight

If one cannot cross ones legs comfortably, does that indidcate that one is overweight?--Light current 17:30, 9 November 2006 (UTC)

Male and female pelvis design also affects this.

Atlant 17:34, 9 November 2006 (UTC)

It indicates the person has a narrow waist/pelvis, thats why the position is usually more confortable for women but I guess fat legs doesn't help + guys crush their balls so even less comfy. Keria 18:00, 9 November 2006 (UTC)

Yeah well I didnt want to mention that one. Ouch!--Light current 18:04, 9 November 2006 (UTC)

Ouch? Does it hurt for you when you cross your legs? I don't think "crushing the balls" hurts, unless you crush them hard. --Bowlhover 03:09, 10 November 2006 (UTC)

You are obviously a woman--Light current 07:57, 10 November 2006 (UTC)

Yes, how did you know? Actually, I'm not. I'm a boy who loves to cross my legs. For me, it doesn't hurt at all (does it hurt for you?). --Bowlhover 02:36, 11 November 2006 (UTC)

Guys tend to cross their legs by resting the ankle across the opposite knee, thus avoiding ball/cock-compression. --Kurt Shaped Box 23:59, 9 November 2006 (UTC)

Im afraid Im not allowed to comment! 8-(--Light current 00:04, 10 November 2006 (UTC)

Well, let me then. Right now I sit with my legs crossed knee over knee, as I often do (even more than ankle over knee, I think). Never a problem. Maybe I let my balls hang loose more than others. :) Tight pants might be a problem. I prefer loose clothing. Maybe that's it. DirkvdM 10:02, 10 November 2006 (UTC)

Also I ve noticed small children rearely cross their legs and seem to have difficulty doing so. Is this because of the undeveloped pelvis or the higher propartion of body fat?--Light current 15:43, 10 November 2006 (UTC)

I've noticed they often sit like this (top view of head and legs), which requires a flexibility which most adults lack:

  /\   /\
\/  \ /  \/
     O

StuRat 22:00, 10 November 2006 (UTC)

Looks like the old symbol for a thermistor--Light current 22:03, 10 November 2006 (UTC)

Kids are generally more limber than adults. Robovski 04:46, 11 November 2006 (UTC)

Mammal kidneys

What mammal has kidneys that are at least four times more efficient at retaining water and excreting salt than those of humans?

It is a fairly broad question, but a reasonable place to start looking would be marine mammals or desert dwelling organisms like the kangaroo rat. --TeaDrinker 20:33, 9 November 2006 (UTC)

Camel ? StuRat 00:16, 10 November 2006 (UTC)

Dolphins or whales--Light current 02:00, 10 November 2006 (UTC)

(Sound of klaxon) Dolphins do not drink (according to QI). --Shantavira 08:13, 10 November 2006 (UTC)

Of course, if their food contains a great deal of salt, they must have some means of reducing the amount of salt in their plasma. If I recall correctly, most marine mammals have excretory output which has salinity above that of the surrounding water. Most marine mammals have a blood salt level which is significantly lower than the surrounding water, which indicates a kidney which is fairly efficient at removing salt. (Salt) water uptake by marine mammals is still fairly unknown; it has been demonstrated (again, by my recollection) for some species of seals. The thinking is that the water contains nutrients not found in the food... But this is a bit outside my official research, so a real expert may be able to correct me. (I recall reading that the Kangaroo rat can raise its urine salt content 14-17x the level in its plasma, that's why I included it...) --TeaDrinker 21:11, 10 November 2006 (UTC)

science

where can I go to find out about different subatomic particles and their charges?

Our List of particles might be of use to you. Let us know if we can help you further :-) --HappyCamper 20:32, 9 November 2006 (UTC)

Boiling-point elevation

Why does boiling-point elevation happen? A.Z. 20:34, 9 November 2006 (UTC)

A simple way to think of it is like this: take some liquid, and add heat. It boils if enough energy is put into overcoming the attraction forces between the molecules of the liquid. Now, if you add something that increases this interaction, then naturally, the boiling point will go up. Say, when you put some sugar into water. This is an overly simplified picture though. The mass of the particles, the size, the dipole moment, etc...all come into play. Actually, you might want to look at vapour pressure too. The effect of adding solute to solvent lowers the vapor pressure. Anything else the reference desk can help you with? --HappyCamper 20:42, 9 November 2006 (UTC)

There was an episode entitled "DEAD RECKONING" of "Science Fiction Theatre" first shown September 17, 1955, in which an airplane, maybe a DC-3, had a broken altimeter, and was unpressurized, and the pilot needed to fly above the mountains without going so high he would pass out from hypoxia. Fortunately there was a professor on board who had a hotplate, a pan of water, a thermometer, and a thorough knowledge of Boiling Point Elevation. By boiling the pan of water on the hotplate and observing the temperature of the boiling water, he could accurately determine the altitude, and get the plane safely through. If the plane climbed, the boiling point would decrease immediately; if it descended, the boiling point would immediately increase. Edison 05:50, 10 November 2006 (UTC)

Note that the variation of the boiling point with elevation is not the same as boiling-point elevation, though! --Anonymous, 00:02 UTC, November 11.

Isn´t there a situation in which adding a solute to a solvent will decrease the boiling point? Why should "The mass of the particles, the size, the dipole moment, etc..." of the solute always increase the intermolecular interactons of the compound?A.Z. 17:29, 11 November 2006 (UTC)

Diseases which warrant a Quarantine

I read on another website that there are nine human diseases for which a quarantine can legally be forced; the most common in the United States is Plague. All I ask is a list of the other eight, or if this number is incorrect, the correct list. I just want to know! Thank you very much!

Google is your friend: according to this web page, the diseases are: cholera, diphtheria, infectious tuberculosis, plague, smallpox, yellow fever, viral hemorrhagic fevers, and (since 2003) SARS. Simon A. 22:09, 9 November 2006 (UTC)

Just to clarify, for these diseases, isolation is warranted (but not mandated). Quarantine, which refers to the sequestration of individuals, plants, animals, or items which do not necesserily show symptoms but have been exposed or have a suspected capability to transmit infection etc., is much more broadly used, and in some cases is practiced with little to no explanation (I think with a 20 day limit). Some info (for one state) in the code books at 105 CMR, specifically section 300.200. Tuckerekcut 22:20, 9 November 2006 (UTC)

I should point out...that what can be "legally enforced" varies greatly between countries. Different countries have different laws regarding quarantine. --`/aksha 11:13, 10 November 2006 (UTC)

Capacitors

When you put a capacitor across a battery, it raises the battery's power, but how come when you apply something to that, the electricity doesnt just skip the capacitor? I thought that electricity always took the path of least resistance, so if there's a lightbulb or something connected to both of them, why does electricity still go to the capacitor and raise the voltage? For example:

         +                       -
   ___ /---Capacitor--\____
 /      \----Battery---/       \
 \_______           ___________/
              Light (or anything else)

if the capacitor is taken out, the light is dimmer. I don't understand how the electricity still goes through the cap. so could somebody please tell my whats going on? Thanks Ilikefood 21:47, 9 November 2006 (UTC)

Most, but not all, electricity takes the path of least resistance. StuRat 00:08, 10 November 2006 (UTC)

I don't understand; steady DC current doesn't flow through a capacitor. Melchoir 00:25, 10 November 2006 (UTC)

I think the key is that the voltage from the battery is not constant. The capacitor then acts sort of like a regulator. --HappyCamper 00:35, 10 November 2006 (UTC)

THe battery has a certain internal resistance. THis can be quite high if the battery is nearly discharged. When the capacitor is attached it will charge to the o/c voltage of the capacitor. If a lamp is then connected, the capacitor will supply most of the energy to the lamp until it discharges to the on load voltage of the battery. At this time, the energy will be supplied solely by the battery and since there is a resistance in series with the voltage source, the lamp will be dimmer.--Light current 01:03, 10 November 2006 (UTC)

It is absolutely false that electricity takes the path of least resistance. In fact, electricity takes ALL possible paths, and divides in inverse proportion to the resistance of each path (for DC) or the impedance of each path (for AC). Consider that in your home, the various devices are all connected in parallel, and each operates. If electricity took only the path of least resistance, then only the one lowest resistance device would operate at a time. Instead, the low wattage (high resistance) device draws a little current, while the high wattage (low resistance ) device draws a lot of current. A capacitor across a battery charges up to the battery voltage. When a load is connected across the battery and capacitor combination, the battery AND the capacitor discharge, increasing the initially available current because of the decrease in the internal resistance of the combination. The battery supplies current to the load, and the capacitor supplies current to the load. There is no "skipping." The output voltage of the capacitor will drop as it discharges. The output voltage of the battery will drop as it is discharged and chemical effects such as polarization (hydrogen bubbles etc) limit its output voltage. Edison 06:01, 10 November 2006 (UTC)

Number of Species in Asia

Does anyone know and/or have a source for a rough estimate of the amount of species of the following in Asia:

• Fish
• Mammals
• Birds
• Reptiles
• Amphibians
• Insects

Thank you. --24.247.126.44 23:22, 9 November 2006 (UTC)

List of Asian birds claims to be complete, but that's all I found. Melchoir 00:06, 10 November 2006 (UTC)

Another Curious Question for Anyone and Everyone to Answer

For the human eye in general, is it easier to detect and see a black dot on white, or a white dot on black? Hmm? Which would have less noise or more visibility? Or are they equally seen well? Thanks a bunch.

I remember reading somewhere that it is easier to see white text on black. Maybe this can help answer your question? --HappyCamper 00:37, 10 November 2006 (UTC)

Black on white is certainly easier for me to read. After a page of white on black, I can see after-images and my eyes go a bit squiffy for a few seconds. The absolute worst for me is red text on a dark blue background - the words actually seem to wobble around on the page. --Kurt Shaped Box 00:39, 10 November 2006 (UTC)

I can explain this last bit: red and blue light have sufficiently different wavelengths that the dispersion of your eyes' optics makes it impossible to focus on red and blue objects at the same distance simultaneously. When you have a close mix of red and blue like that, your eyes have a miserable time trying to focus on the page/screen. It's sometimes interesting to look at a mix of red/blue text on black; as you read, you can watch the words of the two colors alternate going in and out of focus. --Tardis 03:11, 10 November 2006 (UTC)

Blue is always difficult to focus on with a black background, regardless of other colors in the field. Colors with smaller wavelengths are not as good at illiciting pupillary constriction (for a variety of reasons), that's (one reason) why blue signs tend to look blurry at night (the backlit kind, that is). This is why not many cars use blue for gauges (not that I don't have the utmost respect for VW...). Blue gauges are both hard to focus on, and also tend to ruin your night-vision because so much light gets in past the wide open pupils. In contrast, orange and red lights constrict the pupil rapidly, preserving the rods and cones (which take longer to recover sensitivity than the pupil takes to dilate). As for the original question, it is easier to see a white dot on black, it is generally easier to detect a spot of signal in a sea of non-signal, in just about any sensory system. Although there are plenty of endogenous additions to the visual system, this still holds true. Really, it is not much different than asking, "is it easier to feel a lump in my mattress, or a clear spot in a field of lumps?" Tuckerekcut 04:39, 10 November 2006 (UTC)

I suppose that it is easier to recognise a white dot on a black surface than the other way round. Black means no light. A spot of light on a no light zone must be easier to spot than a tiny 'no light' zone on an 'all light' (white) zone ? In college physics labs, we are told to take the readings at minimum light rather tham maximum light in polarizastion experiments -- Wikicheng 10:16, 10 November 2006 (UTC)

(after edit conflict)Kurt, don't the after-images indicate that white on black has a greater subjective contrast? So it is really over-effective and grey on black would also do. At least, that makes some sense to me. DirkvdM 10:17, 10 November 2006 (UTC)

The question asks for a threshold of visibility task rather than say what makes for comfortable reading. As a thought experiment: assume that the black surface reflects a total of 1/100 as much light per unit area as the white dot does to the observer's eye. With no white dot, a black surface of a certain area under a certain illumination reflects a total of 1 unit of light to the observer and the scene looks black. Now add a small white dot which by itself reflects 1 unit of light. Now the total light reaching the observer is 2 units. The result is a doubling of the total light, or a 100% increase. Now imagine a white surface which reflects a total of 1000 units of light. A black dot is added and the total brightness decreases by 1/1000 or a .1% change in total brightness. From this, it sounds like in general it would be easier to detect a white dot on black than a black dot on white. Note that in signal detection or threshold measurement experiments, you have to make the task difficult enough the observer is uncertain and there are errors, or the observer would always be correct and the data would be meaningless. So white dot on black should be more detectable than black dot on white. Edison 23:44, 10 November 2006 (UTC)

November 10

make nanorobot

I would like to make nanorobot but i don't know what I should study. Is there a specific field of study for that? Mye89 04:47, 10 November 2006 (UTC)Renaud Miclette Lamarche

What you need to study is nanotechnology. It's an emerging field but more and more institutions are offering it in thier syllabus. What you want under your belt is physics and chemistry, and mathematics won't hurt either. Vespine 05:19, 10 November 2006 (UTC)

Electrical engineering would be a good field of study to prepare for a career in building nanorobots. You might find interesting the Misplaced Pages articles on Robot , Micropower , Integrated circuits , Microelectronics , and Microelectromechanical systems . Edison 06:07, 10 November 2006 (UTC)

Language

1. .If someone sas that a particular language is harsh or ugly,then that's an expresstion of his or her taste.Exlain why please.
2. .Give three(3)reasons to explain why English is currentlythe language of science.
3. .Started as the variety used in South East English,Standard English is now understood and used worldwide.can you explain what is meant by Standard English?
4. .Why is English used widely in India?

Thank you very much!Please be quick!

Please refer to the top of this page where it says to Do your own homework. We really can't stress that enough. Although, we can point you in the right direction. For instance, the article on the English language might have some answers for you. As well as articles linked off of that. Dismas| 07:49, 10 November 2006 (UTC)

This really doesn't seem to be a homework question, just from the question that's being asked. That being said:

1. Maybe the linguistics article has something related to harshness of a language? A quick perusal of related topics brought up descriptive linguistics and phonology as things related to the spoken "quality" of a language, though beauty is of course in the eye of the beholder.

2. Well, one or two centuries ago the primary "scientific" language was French and some German. After that, the English-speaking countries sort of started to dominate scientific discourse, which led to the the adoption of English.

3. See Standard English and Basic English (both of which are linked in the English language article).

4. This is an extension of #2 - English is also one of the primary languages used in international business and diplomacy (another being French), so its presence in India is probably directly related to that. See also lingua franca for a more general discussion.

16:39, 10 November 2006 (UTC)

If it weren't homework, if probably wouldn't say "Give three(3)reasons to explain...". Chickenflicker 03:48, 11 November 2006 (UTC)

Just because I'm paranoid...

Yes, I do suffer from paranoia. No this doesn't mean that someone is not out to get me. I just need someone to put me at rest really as this is nagging at the back of my mind. Would it be possible for someone to 'bug' my home, then monitor me remotely from 100 miles away? I invited someone I know online to stay with me for a couple of days last month and ever since, I have noticed things in our online communications that don't seem 'quite right' - comments suggesting that he knows things that he could only know if he were watching me. Like I say, maybe it's just me being paranoid and seeing things that aren't there. I've read the Covert listening device article and from that, it doesn't *seem* possible (he's had access to two rooms of my house, neither of which contains my computer, so it's not my machine sending out, so it would have to be a small hidden camera or a microphone - he's not had access to my house since to retrieve anything). Anyone able to help, or point me in the right direction to info that can? Thanks. Posting anon because I feel a bit embarassed asking this.

What kind of things are you noticing? What has he been saying? Maybe we could help you think of a more reasonable explanation for his comments. Dismas| 07:47, 10 November 2006 (UTC)

One of the things he said was a reference to me being quite ill at the moment. I've never told him that I've been ill. That's what tripped me off (I do have these episodes) - thanks, but finding reasonable explanations doesn't really help me. If I could be sure of the technical side, I'd know what to be looking for. --81.79.36.167 07:53, 10 November 2006 (UTC)

Unless he uses equipment already in your house (such as the telephone) a bug would need to transmit. A larger range would require a bigger bug or some relay station to amplify the signal. Any transmitter requires power and unless it uses some power source already in your house, the batteries will run out after a wile. Note that this answer is not based on any knowledge of actual existing equipment, just common sense. DirkvdM 10:25, 10 November 2006 (UTC)

Call a good detective agency and ask if they have detection equipment to check your appartment. Or you can set up a fake conversation with a friend where you slag off the spy and see if there is any change in his character next time you chat. Keria 10:40, 10 November 2006 (UTC)

Have you tried using a metal detector? Not really claiming to be an expert in this, but common sense sort of tells me that bugging a house electronically will require things of metal. Also, when this friend was staying at your place...how often were you in contact with him/her? As in, were you almost always around him/her? Or did you sort of just leave the person in your home? If you were with him/her the whole time, except when they were sleeping, then you can probably rule out anything elaborate.

Otherwise, yes...keep a good record of all communications you have with him (so emails, IM logs). If you find any hard evidence of being spied on, contact the police or some expert first, instead of confronting the person.

Alternatively, exactly where did they stay in your home? It may not be that they're spying on you, but simply that the person snooped around your place during their stay. Do you keep a journal or diary or anything that they could have found? If you live with other people, the perhaps that person talked to them, and just found out some stuff about you which you haven't personally revealed. --`/aksha 11:07, 10 November 2006 (UTC)

The longer you think about ther more ways you will imagine how somebody could spy on you, and the you will have to convince yourself for all this possibilities that they are actually not plausible or practible. Now, I feel the urge to apply to your common sense and ask yourself: why should he spy on you? But I imagine that this is harder than it sounds as you are actually suffering from an illness clouding your common-sense reasoning. I hope you have someone to help you through this, a therapist, doctor or at least some good friends that you still trust. However, one thing needs to be pointed out: You say that fact that he knew you are ill tipped you off. Make yourself aware how much "invisible" information the human voice carries. If a friend of mine whom I know well phones me I might be able to guess whether he is well or ill just from the way how he says "hello", before he even went on talking. There is no spying in this -- our brains analyse these hidden clues automatically and subconciously all the time. Simon A. 11:54, 10 November 2006 (UTC)

He could have a small battery-powered bug that sends a weak signal just outside the home. Then, outside, he could have a powerful rebroadcast station that's either plugged into an outside outlet or has powerful batteries. Another option would use the phone. The bug could be in the phone, and could be programmed to record everything in the room, then call him at 3 AM and upload the recording to his computer. Also, I think it's a bad idea to allow people you meet on the Internet to stay at your home normally. But, if you're the paranoid type, it's especially bad, as it will lead to this type of problem. StuRat 16:51, 10 November 2006 (UTC)

Was you paranoid alredy from before this someone stay with you? Is it possible he is enamored of you?

Hevesli 17:09, 10 November 2006 (UTC)

Yes, he absolutely could. Both via conventional monitoring technology (hardware), and thru software. Check out this recent article. Anchoress 17:17, 10 November 2006 (UTC)

Supercharger

If we add an low resistance air filter and then an air pump to compress the intake air of an fuel injected engine, will there be a increase in performance??Or do we need to tweak the ECU settings???

See turbocharger--Light current 14:39, 10 November 2006 (UTC)

Or see supercharger. And yes, I would assume you will want to increase fuel flow to match the increased air flow from the blower, if maximum power is your goal. StuRat 16:35, 10 November 2006 (UTC)

Whats the diff. Is there one?--Light current 16:37, 10 November 2006 (UTC)

Yes, a turbocharger is driven by the engine exhaust, which has the disadvantage of not providing much boost at low speeds, only at high speeds, while a blower is driven off the engine using a belt or chain. StuRat 16:41, 10 November 2006 (UTC)

Super answer! Thanks 8-)--Light current 16:46, 10 November 2006 (UTC)

Thanks (I'm not just blowing hot air, here). :-) StuRat 17:26, 10 November 2006 (UTC)

please tell me about te project (TREFFIC PUMP)

hi, i m nishant srivastava frm (bhopal) india.i m i B.teck final yera student of mechanical engg. i m working on a project TRAFFIC PUMP.. this project is basically use for water lifting.the hollow speed breaker of the material of rubber contain NON RETURN VALVE and this brekar are attached with pipe which also contain the NRV ..when the heavy vehical passes over the brekars then water lift in contineous ..so tell me mor abt that thank u

Based on your description, the pumping action of a traffic pump is pretty much the same as that of a muscle pump in the human body. Go to Google Images and search for "muscle pump" or "skeletal muscle pump" to find illustrations of its action. You had a pretty understandable description of a traffic pump. Is there something specific that you don't understand? --68.238.248.188 14:01, 10 November 2006 (UTC)

I can think of one negative: You can either put the rubber hose on top of the road, in which case it will wear out much more quickly, or imbed it in the road, which will cause the road to flex more, and wear out slightly more quickly. Also, being near the surface, the water would be subject to freezing, but I assume you would only use this system in portions of India where the temperature stays above freezing. StuRat 16:32, 10 November 2006 (UTC)

You need something like they used to use for picking up water by railway engines at high speed: a long trough full of water and a scoop on the engine. Whoosh!--Light current 16:35, 10 November 2006 (UTC)

That would slow down the truck (and pull it off the road, if the scoop was on one side only). I believe the goal is to pump water, say for residential use, for "free" (not costing the trucks anything). StuRat 16:39, 10 November 2006 (UTC)

how much electricity is produced

i would like to know about the amount of electricity that is produced when a peizoelectric material is used that is the relation between amount of elec produced and the dimensions of materials required????/

See piezoelectricity--Light current 14:38, 10 November 2006 (UTC)

Separating Mixtures

I have a beaker full of water, salt, and iron. I want to separate them from each other. The salt has dissolved in the water, and I assume the iron will be at the bottom of the beaker, and that it is finely ground up into a powder. I know that I should boil the mixture and separate the water via distillation, but how should I separate the remaining substances? What can I do to separate the salt and iron? Thanks for any help. --ClockFace 15:01, 10 November 2006 (UTC)

If the iron has already separated at the bottom, just pour off the water (keep it for the boiling stage to isolate the salt). You might then want to add distilled water to the iron, stir, wait for it to settle, then pour it off several more times to remove any remaining salt. If the iron particles were too small to settle, then a centrifuge would be needed. StuRat 16:12, 10 November 2006 (UTC)

A magnet or electromagnet would be able to selectively remove iron particles from the solution in the beaker. Then boil off the water and only the salt is left. I expect that is why the problem specified a ferromagnetic material instead of some other material. Edison 16:26, 10 November 2006 (UTC)

Pouring off the salt water is known as decantation. —Keenan Pepper 16:46, 10 November 2006 (UTC)

Why not use a filter paper to remove the iron particles. The remaining brine can be evaporated to get the water and salt separated. 8-)--Light current 16:30, 10 November 2006 (UTC)

I would like to thank you all for your quick responses. Thanks a bunch! =] --ClockFace 18:50, 10 November 2006 (UTC)

To remove all the iron you are gonna have to increase the pH of the water to facilitate precipitation of iron oxide (some will be colloidal, but it will dry out on the filter eventually). Since the iron oxide will not be ferromagnetic, a filter will be more useful than a magnet to separate iron from the salt water (which may or may not be brine, the poster did not indicate the amount or kind of salt). Distillation is probably the easiest way to then resolve the salt water. Tuckerekcut 18:55, 10 November 2006 (UTC)

Does anyone else think this sounds suspiciously like a homework question? Skittle 21:55, 10 November 2006 (UTC)

To me, it sounded like they wanted help doing a chem lab, in which case, giving them a few pointers is OK, so long as they actually do the lab work themselves. StuRat 22:47, 10 November 2006 (UTC)

Rusting iron in water

Why is there iron oxide in the mix. The OP didnt say there was/. And of course we assume the salt is NaCl--Light current 20:25, 10 November 2006 (UTC)

Maybe your chemistry is a bit rusty, but small iron particles in saltwater would rapidly oxidize. StuRat 21:54, 10 November 2006 (UTC)

Not without an oxidiser!--88.110.36.197 03:46, 11 November 2006 (UTC)

There's always dissolved air in water. StuRat 08:34, 11 November 2006 (UTC)

I think the iron does not have time to oxidise in salt water without access to free O2. I thought the ions in water were OH- and H+ and therefore no source of free oxygen except for the dissolved air. But I could be wrong. 8-? OK lets assume the water had been boiled to remove dissolved oxygen 8-)--Light current 18:32, 11 November 2006 (UTC)

If you boil the water in air, you still end up with some dissolved oxygen in the water. You would need to boil it in some other gas, such as nitrogen, to remove all the dissolved oxygen. StuRat 20:51, 11 November 2006 (UTC)

OK You win I give up 8-)--Light current 21:11, 11 November 2006 (UTC)

See on rusting. Its very interusting 8-)

Cancer

How does cancer kill? It can't be just because there's an extra lump in the body. Or can it?... Jack Daw 15:13, 10 November 2006 (UTC)

In some cases, yes, because the lump puts pressure on some vital organ, like the heart or lungs or a blood vessel, but that's rather rare (and easily remedied with surgery). More commonly, the cancer cells destroy some system (like the immune system, allowing other diseases to run rampant, or the lungs, depriving the body of oxygen). StuRat 16:07, 10 November 2006 (UTC)

How does it destroy the immune system or lungs? Jack Daw 16:51, 10 November 2006 (UTC)

Generally it kills in three ways: displacement, compression, or metabolism. Some cancers, leukemia comes to mind, can become so widespread throughout the body that they actually replace the cell type they are derived from. In some kinds of leukemia, the cancerous bone marrow replaces all of the normal marrow in the bones, leaving no healthy cells left to produce blood cells. Other times a tumor can grow large enough that is pushes other sensitive organs out of the way or occludes important blood vessels. This usually happens with faster growing cancers, and is most prominent withing the head, where there is limited space to begin with. For the most part, though, cancer kills through "overeating". Cancer cells metabolize and grow vey quickly. Much like teenagers, they eat everything in sight and don't actually do much work other than growing. This leaves other cells in the area hungry, and eventually leads to their death. You might note that these things are not mutually exclusive, and also that benign tumors are capable of the compression and overmetabolism too. Tuckerekcut 16:36, 10 November 2006 (UTC)

How can it displace other cells? Won't the healthy cells keep dividing into more, functioning cells as usual, even if there are cancerous cells dividing as well? As for compression, do cancer cells grow too fast to constantly surgically remove them? That is, is the recovery period for brain surgery for cancer removal longer or shorter than the period at which cancer cells (if they re-emerge) might become dangerously large again? As for metabolism, couldn't that problem be solved by giving the patient an extremely hyperglycemic diet, perhaps through TPN? Jack Daw 16:51, 10 November 2006 (UTC)

Great questions. Displacement is usually secondary to the the metabolic outperformance. Often vascularization of the new growth is more extensive (though less organized) than the normal tissues, which allows the cancer cells to grow faster, and which shunts much of the nutrition to the tumor. As a result, the normal cells die off faster and grow slower, and become outnumbered. In fact tumor cells, even the ones that grow exceedingly fast, can be removed if they are detected, and cerainly don't grow faster than a scalpel. This is why benign tumors are so named. However, if the margins of the tumor are very complicated or if they metastisize, either by "blending" into nearby tissue or by travelling through the circulatory or lymph systems, they can be more difficult to remove surgically. Radiation therapy can help kill cancer cells selectively in a situation such as blending where the tumor is in a known area with blurry borders, and chemotherapy can help destroy cancer cells which have metastasized. Unfortunately a hypernutritive diet won't help much because the nutrition deficit is more of a local problem than a body-wide one. Tuckerekcut 18:46, 10 November 2006 (UTC)

Awesome info, and you picked up on my hyperglycemic->hypernutritive mistake, great. Well, thanks! :D 130.243.242.176 22:13, 10 November 2006 (UTC) <- me Jack Daw 22:14, 10 November 2006 (UTC)

These answers have also hit on one of the primary reasons why chemotherapy is effective. The chemical poison kills all cells but becuase the cancer cells abosrb more poison in a shorter time, they receive a lethal does sooner. The idea is that they will die before the non-cancer cells. --Tbeatty 05:13, 11 November 2006 (UTC)

Why so big?

Why has been the dinosors so big? Is it a thing what can be explained from evolution?

Hevesli 17:01, 10 November 2006 (UTC)

There are certain advantages to size, like being able to defend yourself from a smaller predator or, if you are the predator, being able to kill your prey. This would naturally lead to an infinite race to be the largest, unless there were also some advantages to being small, which there are. Food requirements are reduced, the ability to hide is better, etc. However, to explain why land animals used to be much larger than they are now, one of these advantages or disadvantages must have changed from the time of the dinosaurs until now. Note that sea animals, namely whales, are the largest they have ever been right now, so this change apparently does not apply to the sea. One change I'm aware of is that oxygen levels in the air used to be higher, as demonstrated by air bubbles stuck in amber from the time of the dinosaurs. Our current lower oxygen levels would limit the size of animals, as present dinosaur-sized animals would need to move quite slowly or have greatly increased lung capacities relative to the sizes of their bodies. The oxygen level in water is related to that in the air, although sea mammals don't use the oxygen in the water, but rather breathe air. Also note that different calculations come into place, as sea mammals have reduced energy requirements. This is due to more efficient locomotion and thermal control mechanisms. StuRat 17:20, 10 November 2006 (UTC)

Also note that not all dinosaurs were very big. Skittle 21:51, 10 November 2006 (UTC)

How long did it take for dinosaurs to grow so big? The rise of the dinosaurs started 20 million years after the Permian-Triassic extinction event and they had 160 million years to evolve. The Cretaceous-Tertiary extinction event that wiped them out occurred 'only' 65 million years ago. So maybe 'we' just need more time. But also, mammals require much more energy, and thus much more food, per weight because they are warm blooded and need to keep their temperature up all the time. So a viable population will require a much larger area. So given the same habitat size, reptiles can afford to grow larger. Another thing is how large the habitat can be. If a species specialises more, it will have a smaller habitat and can therefore not grow as large. Maybe mammals have a stronger tendency to specialise. Note that I know little about the subject and am just doing some educated guessing. :) DirkvdM 08:21, 11 November 2006 (UTC)

Well, according to this documentary I saw, dinosaurs were warm blooded. Anchoress 08:33, 11 November 2006 (UTC)

How are refusals to participate handled on surveys ?

The surveys I see typically have a 3% margin of error. However, I can't believe that over 97% of the people they ask to participate agree, especially if not compensated. I'm guessing they just assume that the participants are representative of the population, while I most definitely would not. That is, if 10% refused, I would add that to the margin of error to get a 13% margin (12.7%, technically). For example, in the recent US elections, most of those who refused to participate in surveys may well have been conservatives disgusted with the Bush administration and the numerous financial and sexual scandals of Republican Congressmen. Thus, their non-participation would bias the survey. Also note that surveys where participants self-select (say a web site with a link to take a survey) have a much higher rate of non-participation, which is unknown, as the number of people who read the ad and decide whether to participate is unknown. How are these issues handled by statisticians ? StuRat 17:07, 10 November 2006 (UTC)

The question is a good one, and I know the answer only to the seond part. Survey where the participants self-select, such as in your example of the web site, are either totally useless or only an extremely rough indicator. Professionals don't take them seriously as far a I am aware. (Actually: As I am a scientist working for a university I occasionally get request to form out web surveys from within the university. These are, however, usually parts of master theses, typically by students of economy or social sciences, and I always have the feeling that the results will be enough to earn a degree but not to publish a paper. Or, worse, the survey originates from some internal project office within central adminstration and tries to assess some work-place related issues in order to burn some money for pretended actionism.) For properly random-sampled survey, I imagine that the bias problem is the reason why the precentage of refusals are always given. Maybe you are supposed to form your own opinion how this contributes to the error. As far as error figures are concerned: in German newspaper I hardly see them given. Simon A. 20:12, 10 November 2006 (UTC)

I suspect the university has you do the surf\veys so they can imply that they are "scientific surveys". If I were you, I would insist on a big fat disclaimer on all those surveys saying "This is NOT a scientific survey, and is only to be used for entertainment purposes". StuRat 20:57, 10 November 2006 (UTC)

In a related question, how is lying on the survey handled ? Is any margin added to account for the percentage which can be expected to lie ? If niether of these are accounted for, I would expect survey results to be highly inaccurate. In cases where they can actually be checked, like voter surveys, I would expect many election results to fall outside the margin of error. StuRat 21:02, 10 November 2006 (UTC)

The margin of error on a survey, by definition, covers only the error that is likely to take place due to random sampling. If you ask 1000 people out of a much larger population about something, your error due to the fact that you didn't ask the entire group is going to be about 3%. Other possible sources of error are not accounted for in the margin of error, simply because that's how the margin of error is defined. As such, the margin of error of a survey is not necessarily a good measure of how far off the survey is actually likely to be from the true value you would get if you asked everyone, and everyone responded truthfully. Chuck 23:30, 10 November 2006 (UTC)

In that case, the term is thoroughly misused by the public, and those doing amateur surveys, to mean the total maximum error. StuRat 02:32, 11 November 2006 (UTC)

There are lots of corrections and that is why there are lots of polling organizations. The first correction has already been touched on and that is a sample of the real population will always have a margin of error. But as polls develop and they are compared to the actual results, the errors associated with systemic bias are corrected from historical analyses. For example, it is known polls are more likely to garner a response from Democrats than from Republicans. This is true for both phone polls and exit polls. Since pollsters know this, they correct for it. There is also differences based on age, gender, education, region of the country, etc. These are all put into a fudge factor that they use to weight the poll. This is why Zogby and Gallup get different results even though they ask the same question: they have different weighting factors. It is also how exit polls can exceed the margin of error. --Tbeatty 02:54, 11 November 2006 (UTC)

US Congressional Election results vs Voter Surveys

Is there any analysis of how accurate survey results were, in relation to the actual election results ? I'd be interested to know how well they did at predicting the results. StuRat 21:07, 10 November 2006 (UTC)

At you can scroll down to "Rudimentary statistics" and see a nice explanation of statistical sampling theory. The site, although somewhat partisan in philosophy, also presents a nice compilation of all the published scientific polls regarding President Bush's approval rating over time, so you can get an idea of the central tendency and see which polls tend to produce higher and lower approval ratings, and compare his ratings to past 2 term presidents. One key point is adjustment: I will make up illustrative numbers: a polling organization may assume in their population model that the voters are, say 55% Democrat and 45% Republican. In a 3 day phone survey of 1000 respondents, they may have found 70% of those who answered the (random) phone call and completed the survey said they were Democrats and 30% said they were Republicans. A high % of the Republicans say they approve of Bush and a high % of Democrats will say they disapprove. Rather than reporting the actual observed percentages, the pollster is likely to adjust the observed Dem/Rep proportions to the ones espected, before computing the overall approval rating. They will make similar adjustments for black vs white, male vs female, to adjust for the fact that, say Republicans don't do phone surveys, or at work, or only use cel phones, or whatever skewed the sample percentages away from the population percentages. Thus it is an art as well as a science, and is hardly ever a pure exercise of random sampling. One pollster for a party admitted to absolute fraud: if the person hung up, the surveyor just made up responses. Amazingly the daya came out favorably for the party funding the poll. Edison 05:59, 11 November 2006 (UTC)

Mileage equivalent of raising a car.

I was wondering how far an average car might travel using the same fuel burned to get to the top of a 20m car park. Petrol has an energy content of 32MJ/l so assuming 8 miles per litre, 4MJ per mile. 1 Joule is the minimum energy to raise 1kg 10 cm, so assuming a 400kg vehicle, 80,000J would be required. Engine efficeny is 30% so this becomes 240,000 J, if we say 250,000J we get a distance of 1/16 mile which is approximately 100m. This seems silly, implying cars use only five times as much energy to move "up" as to move "along". Have I slipped a decimal point somewhere? Rich Farmbrough, 17:40 10 November 2006 (GMT).

HAve you taken into account the air resistance and rolling friction and other losses in climbing the hill? THe hill probably takes the sum of the two energies you calculated assuming the same speed of travel.--Light current 17:52, 10 November 2006 (UTC)

I've thought about this issue myself, as I used to drive 15 minutes to get to a parking structure, then I would drive another 15 minutes within the structure, waiting in lines and searching for an open space. I'm sure most of my gas was wasted in that damn thing. If there was a way to reclaim the gravitational potential energy, say by regenerative braking, much of this waste could be eliminated. StuRat 18:32, 10 November 2006 (UTC)

Cos is Regenerative braking--Light current 18:35, 10 November 2006 (UTC)

Only five times as much? Ideally, it would be infinitely much more, because when lifting a car, actual work is done in the sense that there is a difference in the energetic state. When moving a car horizontally, that is not the case. So if there would be no resistance to overcome and the acceleration at the start of the trip would be regained during breaking at the end, there would be no consumpton of energy at all. That cars still use one fifth of the energy for horizontal transpor tis an indication of how horribly inefficient they are. Take a very smooth cannon ball. How much energy does it take to lift it to a height of 2 m? And how much energy would it take to make it roll 2 m over a smooth surface? For something closer to home, take a baseball. You'd have to give it a really minor push (with your pinky) to prevent it rolling more than 2 m. And the major reason it will stop at all is that the surfaces aren't smooth enough. DirkvdM 08:50, 11 November 2006 (UTC)

And an idling car uses an infinite amount of energy per distance moved ! StuRat 20:31, 11 November 2006 (UTC)

Yes thats why you should turn off your engine whilst waiting.

Is a solution defined as a mixture in chemistry

Prompted by an earlier question I wonder: Is a solution defined as a mixture or a compound in chemistry?--Light current 18:40, 10 November 2006 (UTC)

Why don't you read the article you linked to, solution. First sentence. Tuckerekcut 18:57, 10 November 2006 (UTC)

I did. It is confusing as it mentions homogenous mixtures.--Light current 19:02, 10 November 2006 (UTC)

Does the first sentence of chemical compound help? Could you prepare salt-water solutions in which you alter the the ratio of the components? DMacks 20:07, 10 November 2006 (UTC)

OK a solution appears to be a mixture . THanks for the solution to this problem 8-)--Light current 20:15, 10 November 2006 (UTC)

"There are three different types of mixtures: homogeneous mixtures (also called solutions), heterogeneous mixtures, and colloidal dispersions." from Mixture --`/aksha 03:04, 11 November 2006 (UTC)

Blindness & Nothingness

One can be fairly sure that it is nearly impossible to imagine nothingness. For when you are thinking of nothingness, you're still thinking of something. But nevertheless, I've tried. Today, I was closing my eyes, meditating, and I was trying to imagine what it would be like to be blind. Here is my question: does the mind of a blind person interpret the lack of vision as a sort 'blackness' - much like I do when I close my eyes - or does the mind of a blind person interpret the lack of vision as a complete absence of anything (i.e. no blackness, just nothing)? - R_Lee_E (talk, contribs) 18:42, 10 November 2006 (UTC)

There is actually a way to imagine nothingness (well my nothingness is actually black). As for being blind IDK--Light current 19:55, 10 November 2006 (UTC)

Don't know either. However, I remember an interesting piece of news. A museum made a completely dark room, where visitors has to use their tactile sense to orient themselves. The idea was to give seeing people an impression of what being blind was like. A spokesman of some German association of blind people commented that he considered the setup a bad idea: after all, a seeing person would feel frightened and disoriented due to the vivid impression of the blackness. From these feelings, the spokesman argued, the visitor would get a way too negative idea of how blind people experience the world, as under normal circumstances they feel as normal (i.e., secure and oriented) as normal people do, and they do not expeience any blackness or lack of sensation as long as their other sense provide usual input. Simon A. 20:20, 10 November 2006 (UTC)

Very interesting. - R_Lee_E (talk, contribs) 21:49, 10 November 2006 (UTC)

I think it depends whether the person has been blind from birth or could once see and has been blinded. See also Eigengrau. —Keenan Pepper 20:30, 10 November 2006 (UTC)

I expect the latter. Consider a curious bat wondering what it's like for people who don't have a sonar-type sense. Do people specifically notice that they don't have this sense? Or consider the similar question a monkey might ask of people without a prehensile tail: do people try to move their tail to grab things only to constantly notice they don't have a tail? Essentially animals (humans included) have a set of inputs and outputs, if you like, that we learn to use at the appropriate times. If you've never had a particular sense or limb, you'll never feel inclined to use it or to even notice it isn't there (obviously the case of a person who has only recently lost their sight is a different matter), I expect. digfarenough (talk) 22:53, 10 November 2006 (UTC)

If they were born blind, they would have never devolved the neurons to interpret vision in the first place. Check out this article Wiesel and Hubel 28 (6): 1029. (1965) --Cody.Pope 23:09, 10 November 2006 (UTC)

A blind person wouldn't be "thinking of nothingness", they'd still build up an 'internal' interpretation of what the world is like based on their other senses.

Trying to "blank" your mind and not have any thoughts at an instant is a completely different thing. Complete clearing of the mind of thoughts is supposed to be a skill learnt by some forms of meditation, and supposedly not easy either. I personally can't imagine how someone could be consicencly awake and not have any thoughts (heck...your mind's thinking and working even when you're not consciencely awake), but some people (like buddist monks and stuff) claim they can completely clear their mind of thoughts during meditation. --`/aksha 03:04, 11 November 2006 (UTC)

YEs its not easy. You let thought come and let them go with out holdnig on to them. Finally thoughts are more rare and eventully stop--88.110.36.197 03:43, 11 November 2006 (UTC)

If you are what you think then to stop thinking would mean to stop existing. Think on that (or not). DirkvdM 18:17, 11 November 2006 (UTC)

I dont think so!--Light current 18:24, 11 November 2006 (UTC)

Plasma

How Hot would it have to get for water to turn into a plasma and if it was hot enough would it actually be Hydrogen and Oxygen gas?67.126.140.134 20:31, 10 November 2006 (UTC)

Yes, it would split into oxygen and hydrogen first. StuRat 20:45, 10 November 2006 (UTC)

And then into a lot of ions?--Light current 20:54, 10 November 2006 (UTC)

Thank You StuRat I thought that,but anyways is there a formula for how much volume, lets say a liter of water, would take up when it is turned into a gas?

Depends on the volume its allowed to expand into. PV/T is a constant. I think plasmas act like a gas.--Light current 21:00, 10 November 2006 (UTC)

Plasmas definitely don't follow the ideal gas laws, but you can use them for back-of-the-envelope calculations. —Keenan Pepper 21:07, 10 November 2006 (UTC)

Im sure my answers will be sufficiently accurate for the purposes of the OP 8-)--Light current 21:09, 10 November 2006 (UTC)

According to my calculations, at atmospheric pressure, water is halfway dissociated into H₂ and O₂ at about 4000 kelvin. —Keenan Pepper 21:18, 10 November 2006 (UTC)

Of course, blood plasma is mostly water. :-) StuRat 21:45, 10 November 2006 (UTC)

...with dissolved oxygen gas! Though as far as hotness...um, I didn't make the cut for the Under The Labcoat 2007 calendar. DMacks 22:03, 10 November 2006 (UTC)

Things to be discover

What do you think are the next more important discoveries to be done? I suggest: cure for AIDS, cheap clean energy, cheap space travel, light computation??Mr.K. 22:32, 10 November 2006 (UTC)

I picture programmable hunter-killer viruses. For example, a patient's cancer cell can be extracted, then a hunter-killer virus is programmed to destroy any cell with that exact DNA sequence. It's placed back into the body of the patient, and infects and destroys any cells with that DNA. After all the cancer cells are dead, the virus loses the ability to reproduce, and dies off, too. StuRat 22:37, 10 November 2006 (UTC)

I like StuRat's idea, but it would be great for conservation. Something like that which could destroy Batrachochytrium dendrobatidis, and save many frog populations of the world. But, something needs to be done about climate change, or it would be all useless. --liquidGhoul 23:12, 10 November 2006 (UTC)

When StuRat mentioned programmable hunter-killer viruses, I thought of a computer virus that targets spammers... Vitriol 23:40, 10 November 2006 (UTC)

Oh, yes, please! DirkvdM 20:42, 11 November 2006 (UTC)

Viruses are one way to change DNA for gene therapy, but the problem is they are unpredictable, cannot be retracted, and are capable of mutation. Right now, it seems like RNAi is the future of gene manipulation. And you'd never believe where it comes from: worms. If you ask me, what scientist need to do next is to determine the exact etiology of disease (pick one...). If we know what goes wrong in the human body, precisely, only then can we hope to fix it. Tuckerekcut 23:48, 10 November 2006 (UTC)

RNAi doesn't come from worms... RNAi was first observed in plants (although it wasn't called RNAi then) and was then (and is now) used rather successfully for gene knockdowns with Caenorhabditis elegans (and is also used for gene silencing in transgenic plants). However we're simply taking advantage of a existing (still poorly understood) mechanism for gene regulation that occurs throughout the eukaryotes. Nil Einne 15:35, 11 November 2006 (UTC)

hunter-killer viruses would be a scary invention considering viruses pnchant for mutation. rechargeable battery technology for cars and other mobile appliances would transform the world. Stored energy with high enough density to enable flight and cars without burning fuel or toxic byproducts (or toxic accidents) would change everything. Climate Change is social problem, not a scientific one, meaning that current environmental goals of political organizaitons such as the UN and other states are geared towards wealth redistribution, not science. Climate change is a function of being on the planet. --Tbeatty 05:55, 11 November 2006 (UTC)

I don't know why cheap space travel is so important. A cure for AIDS is but there are also a lot of other medical related issues which are major problems in developing countries. Malaria, TB and cholera are three that come to mind. Some would argue these don't require inventions others would say they do. Nil Einne 15:35, 11 November 2006 (UTC)

Understanding turbulence would be big, but probably nowhere near 'next'. When Einstein was asked what he would want to ask God, he said "Why turbulence?" (or something thereabouts). DirkvdM 20:42, 11 November 2006 (UTC)

Tbeatty, you say "Climate change is a function of being on the planet". Do you mean by that that it is an inevitable natural occurrence (which is true) or that human induced 'Climate change on steroids' is inevitable (which isn't true)? DirkvdM 20:42, 11 November 2006 (UTC)

The planet's climate change is an inevitable natural occurance. Natural variations far exceed any predictions about the human contribution. --Tbeatty 21:04, 11 November 2006 (UTC)

"impossible Physics"

Can someone begin a "list" of the "impossible Physics" that our astronomers witness within visual space. Im interested in things that physically are "suppossed" to be impossible based off certain standards scientists have created throughout human history.

eg.. Black Holes, timing issues, etc...

Thanks 68.73.81.36 00:05, 11 November 2006 (UTC)

• Sending information faster than the speed on light via quantum tunneling. StuRat 02:28, 11 November 2006 (UTC)

• I don't think they've observed this, have they?--Tbeatty 02:45, 11 November 2006 (UTC)

• I believe that they have sent an audio transmission faster than the speed of light. StuRat 08:29, 11 November 2006 (UTC)

• I would like to see this. The only thing that I have seen that is faster than light is phase information. This isn't real information and can't be used to transfer real information. The other thing is coupled photons (I forget the real name). They are coupled and their existence is actually known before they are created but I think they still obey speed limit rules.--Tbeatty 08:50, 11 November 2006 (UTC)

• Here is the article: and here is the relevant excerpt:

Professor Gunter Nimitz of Cologne claims he has transmitted Mozart across a 14 cm metal barrier at 4.7 times the speed of light. Professor Raymond Chiao of California has also measured transmission at 1.7 times the speed of light. This was reported in the BBC science program "Horizon". According to Einstein, faster than light travel is not possible, if one starts at below light speed; so these results are astounding. They rely on a mechanism called quantum tunneling, where a photon can be in several places at once. Some believe that the photon is really interacting with another one in a parallel universe, hence the weird effects seen when, for example, two photons sent through two separate slits, instead of forming two distinct bright spots, interact with each other, producing many dark and light bands. How one photon can be in so many places at once is for budding geniuses to explain.

StuRat 09:02, 11 November 2006 (UTC)

To clarify this. Prof. Nimtz is considered an annoyance by many of his collegues due to his insistance on this claim. The facts, as the majority of physicists in the field see them, are as follows: There is a well known paradox in quantum mechanics with respect to the phenomenon of quantum tunneling. The description of tunneling by means of the Schrödinger equation says that the time that a particle needs to tunnel through the barrier is independent of the length of the tunnel, and hence, a particle that travels through a very long "tunnel" appears to be travelling faster than light if you take the solution at face value. Nimitz set out to demonstrate this in the lab using the simplest possible realization of quantum tunneling: microwaves propagating through a wave guide (simply a conducting, hollow metal tube; here with square cross section and a few dozens of centimeter long) which is too small to conduct the waves (i.e. the width is (slightly) less then half the wave length). Then, classical electrodynamics say the the wave is exponentially dampened, i.e. only a tiny bit comes out at the other end. The tunneling solution also says that the wave comes out "too early". But how do you measure the time that the wave needs to traverse the waveguide? A wave is not point-like, but has some extension. Nimitz, it seems, looked at the "center of mass" of the wave packet, which indeed moves faster than light. However, the information that the wave packet carries, enters the wave guide already as soon as the leading flank, i.e. the first bit of the wave enters, and the it should be considered as arrived once the leading flank exits. Careful theoretical analysis of the solution of the Schrödinger equation shows that the leading flank, other than the "center of mass", does not travel faster than light, i.e. causality and hence special relativity is not violated. As far as I am aware, Nimtz agrues a minority position by claiming that his experiments are not covered by this theoretical analysis. Simon A. 10:59, 11 November 2006 (UTC)

I've just looked at Google scholar: I was unjust to Nimtz by making him appear stubborn. It seems that in his more recent publications, Nimtz now embraces the claim that "faster-than-light effects" in tunneling cannot violate causality. The debate is hence now no longer whether special relativity and its light-speed barrier is challenged by tunneling experiments (it is not), but rather how to correctly explain why it is not and whether it is proper to call it "faster-than-light" nevertheless. Simon A. 11:56, 11 November 2006 (UTC)

Is this intended to be ammo for a ID vs. Evolution debate? ;) - R_Lee_E (talk, contribs) 03:33, 11 November 2006 (UTC)

November 11

Paper Mache

What is an easy way to create paper mache using newspaper and masking tape? I can't seem to find any methods on Google. The final product will be used to support weight. (It is a chair. The base can only be 200 square centimeters touching the floor.) --Proficient 02:59, 11 November 2006 (UTC)

You can certainly tape a lot of newspaper together to support weight, but that is not what papier mache is at all. StuRat 02:22, 11 November 2006 (UTC)

You don't need tape to create paper mache. Just get a bowl and fill it with glue. Rip up strips of newspaper, and throw them in the bowl. Then, paste these strips of newspaper onto whatever surface you want them on. --Bowlhover 02:33, 11 November 2006 (UTC)

Perhaps I should make my question clearer. I want to make a paper mache like substance only using newspaper and masking tape. (kind of like liquefied masking tape) How can that be done? I cannot use glue. Maybe paper mache is not the correct word to use. How would I go about compressing newspaper then taping it efficiently? Sorry if my question was vague, because I am asking this question on behalf of my sister. Thank you. --Proficient 03:02, 11 November 2006 (UTC)

You could shred and wet the newspaper and compress it into the forms you want, then once they're good and dry you could wrap them in masking tape to fasten them together and help them keep their shape. Anchoress 03:41, 11 November 2006 (UTC)

What is wrong with glue? Note that you are not supposed to use the kind of glue that children or hobbyist use to glue paper together. this stuff is to sticky and dries to fast: you cannot model. For paper maché, you use the old-fashioned kind of glue which one uses to affix wallpaper to walls. It's a dilute liquid stuff which sticks only mildly to your hand, so that you can easily mix a bowl with this glue with paper shreds and start sculpting. (If my dictionary is right, English really lacks proper terms to describe the different traditional kinds of glue, such as the kind of glue, we are talking about here, and which is called de:Kleister in German. The German wikipedia article says it is a mixture of water and either methyl cellulose or starch. Usually, you buy it in DIY stores as a powder and mix it with water.) See also methyl cellulose#glue and binder. Simon A. 11:13, 11 November 2006 (UTC)

From memory, you can make it by cooking cornflour with water. Other flours would probably work as well. Also, I used to call it something and not glue. Possibly gum glue or gum paste or something. You could buy it in a small tub (already made) in Malaysia and this stuff tended to work better (I think) and last longer then homemade stuff (not sure whether it was that different or just had presevatives of some kind). This page may be interesting Nil Einne 15:02, 11 November 2006 (UTC)

Kepler

What is the title of the book that has a clear discription of Kepler's discovery that spherical balls do not fall straight down from the edge of a table? The chapter's discussion points out how Kepler put ink on the balls to determine trajectory distances on a piece of paper he laid out on the floor. The discussion goes on to point out that the notion of trajectory made him ask the question, "what if the ball's trajectory flew past the edge of the earth?" Writer1 02:38, 11 November 2006 (UTC)

A question on the biology of free will.

If the brain is a chemical machine, and all physical objects -- including neurons -- adhere to a system of laws, isn't it possible to predict the future behaviour of a person based on the billions of minute events occurring in the brain? Doesn't this imply that there is no such thing as free will? (I have very little education in psychology or neurology, this is merely something I'm curious about.) —The preceding unsigned comment was added by Pesapluvo (talk • contribs) 03:12, 11 November 2006 (UTC)

Well, you've got some pretty big if's in there, depending on what you mean by "a system of laws". Modern physics, at least in some interpretations, is not completely deterministic -- see interpretations of quantum mechanics. However, even if quantum indeterminacy can show up at the neuronal level, behavior that's unpredictable merely because it's random is not what most metaphysical libertarians would consider to be "free will". For true free will, there does seem to need to be some non-physical part of the story, such as a soul. --Trovatore 03:35, 11 November 2006 (UTC)

No, because so much of human behaviour consists of reactions to outside stimulii. It might be barely possible to predict a particular person's reaction to a particular event. Anchoress 03:43, 11 November 2006 (UTC)

You might as well ask if free will is an illusion cause by imperfect knowledge or ask how can you tell if reality is real - how do you know you aren't really a brain in a jar being fed artificial stimuli of a 'reality' totally different from your actual 'true' reality. You don't have a way of knowing, as there is no testable difference. Robovski 04:37, 11 November 2006 (UTC)

We have a featured article on free will, and it has sections on perspectives of various scientific disciplines on the subject. --Allen 04:41, 11 November 2006 (UTC)

If there is an apparently "random" element, some would suggest that this random element is directed by the "soul" of the individual, thus providing free will. StuRat 06:09, 11 November 2006 (UTC)

Considering random, there is the quantum level, and random events can and do happen there. Perhaps the soul lies in the strings? Robovski 06:16, 11 November 2006 (UTC)

See the articles Determinism and Free will. In thinking about this issue I have always found it an unsurmountable problem to give a working definition of "free will". However, whatever the definition, I don't get why people think that true quantum randomness can save a concept of "freeness" of the will under assault by determinism.  --Lambiam 20:44, 11 November 2006 (UTC)

I don't think that's the claim. The point is not that quantum randomness constitutes freedom, but rather that, since the outcome of a quantum interaction is not determined, there is an opening for an agent-caused outcome without violating any physical laws. For a simple example, imagine a situation in which QM tells you that a neuron may fire, or not fire, with probability 1/2. The agent's choice causes it to fire. Looking at it from the outside, you can't establish that the agent has manipulated physical reality, because it might have fired anyway. --Trovatore 20:56, 11 November 2006 (UTC)

Refractive index of cellulose

What is the refractive index of cellulose? Chickenflicker 03:43, 11 November 2006 (UTC)

You should try a google search. It depends on what exact cellulose polymer, cellulose is 1.5400; Cellulose nitrate is 1.5100; Methyl cellulose is 1.4970; Ethyl Cellulose is at 1.4790. Other polymers rmosler 15:55, 11 November 2006 (UTC)

Supernova

If there was a supernova at the centre of the Milky Way (which is obscured by dust in optical wavelengths), how bright would it appear? Let's say the Pistol Star turns into a supernova. Since all but a billionth of its light is blocked by dust, can we even see it without a telescope? --Bowlhover 06:25, 11 November 2006 (UTC)

Don't know about optical but Super-Kamiokande would certainly see a neutrino shower. Maybe it would also trigger LIGO? -- Rwst 11:43, 11 November 2006 (UTC)

Yes, you would be able to see it without a telescope

How bright (what magnitude) would it be? --Bowlhover 20:24, 11 November 2006 (UTC)

It depends on the type of supernova. If it were a type 1a it would have a magnitude of about -19.6 (they all have very similar magnitudes). Type 2b supernovae vary quite a lot.

Could science achieve this in the future?

As you probably know, your brain stores all the information, knowledge and memories you have acquired since birth.

In the future, would it be possible for scientists to dissect the brains of dead people to uncover the information, knowledge and memories the deceased have acquired during their lifetime?

There would be endless possibilities if this could be achieved. For example, if someone was murdered, scientists could dissect their brain and find the part which stores memories of their murder, and hence find out who was the murderer. If there was a fast food chain with a secret recipe very few people knew, and one who knew the recipe died, scientists could dissect their brain and find out the secret recipe.

Yes, it's possible, some day, but the far more important value would be the ability to reproduce the mind of the dead person in a computer. StuRat 08:26, 11 November 2006 (UTC)

If your mind can be recovered, are you really dead? I don't think memories from dead people will ever be recoverable, however it may be possible for live people to transfer memories electronically at some point. --Tbeatty 08:41, 11 November 2006 (UTC)

I seriously hope it is and will remain science fiction. I also think it will never be possible, as the information in the brain is probably not stored as text and images but instead by complex connections and relations between personal experiences, memories, and emotions. –Mysid☎ 09:04, 11 November 2006 (UTC)

The brain is not a very well-understood organ. We know a lot about it, but there's also so much more about the human brain/mind that we do not know. Questions like this become almost a matter of personal philosophy. I for one, believe that everything you are is in the phyiscal brain, so that there is no spiritual 'mind', 'spirit' or 'soul' aside from what the brain generates. Therefore, i would say the answer to your question is yes. I believe with the rate biology is advancing, there will be a point in the future where we will have the ability to take a phyiscal brain, and in effect 'extract' everything the person whom the brain belonged to knew. To replicate all the connections of a biological brain with technology. I suppose, this ultimately means (for someone with my beliefs at least) that the person isn't really dead, because everything that made him/her who he/she is is in the brain. And then from there, speculation becomes fantasy.

A quote of interest here, which i remember but can't remember were from, went something like this "If our brain was simple enough for us to understand, then we would be too simple to understand it." Perhaps it's true we may never achieve that level of understanding regarding how our own minds work? And i would imagine, advances in technology allowing people to 'extract' knowledge from another person's brain would be highly contraversial, brining to life entire new ethical and moral issues. So i guess it really isn't something we can expect in the near future after all. --`/aksha 10:34, 11 November 2006 (UTC)

• I disagree. No individual human may understand all the workings of a brain, but collectively, and with the aide of computers, we may. A much simpler device, like a car, is understood well enough by all of us collectively to construct, optimize, repair, and use it. However, few individuals likely understand every aspect of everything that happens to make a car operate. Your auto mechanic, for example, probably has no idea about the chemistry and physics behind combustion, he just knows what the proper air-fuel mix is to get the most power out of the engine. And the physicist who does understand all the theory may not know what the acceptable clearances are for the cylinder. StuRat 20:20, 11 November 2006 (UTC)

• To be honest I think the original contention "...your brain stores all the information, knowledge and memories you have acquired since birth" is highly unlikely, and certainly unproven. Thus further discussions are mere speculation. And even if there was some validity to the argument, tracing the neural pathways of specfic thoughts and memories would seem to be extremely difficult, if perhaps not necessarily impossible. I also suspect these would degenerate VERY quickly after death. --jjron 14:01, 11 November 2006 (UTC)

• Decomposition would certainly destroy the memories stored in the brain, and freezing might, as well. But, that would give scientists a few days to work, perhaps enough time with some future technology. And embalming might preserve the memories indefinitely. StuRat 20:13, 11 November 2006 (UTC)

The human liver and the break down of alcohol

How is it that the human liver is capable of breaking down so much alcohol? Where in human evolution did our liver become so effective? I don't see anthing that would cause prehistoric man to become specialzed such as having a high alcohol diet. Alcohol dehydrogenase. Ed Dehm 07:24, 11 November 2006 (UTC)

The article you provided says that the bacteria in the digestive tract produced alcohol which was toxic and needed to be broken down. Even the human liver can't stand a high alcohol diet and will suffer damage, or develop conditions such as cirrhosis. –Mysid☎ 08:15, 11 November 2006 (UTC)

It brings up the question as to why is alcohol intoxicating? It seems that if alcohol were so debilitating, users of it would be selectively removed from the gene pool. I suspect that spoiled grain and fruit were staples of the early diet and that natural alcohols needed to be processed whence the development (or rather selection) of alcohol dehydrogenase. I don't think it was alcohol that was produced by bacteria in the digestive tract as that bacteria would still exist. Does that bacteria exist? Whose water do you have to drink to get it? --Tbeatty 08:38, 11 November 2006 (UTC)

You can look at nearly every non-inert small organic molecule, and it will be toxic in the quantities people fill themselves with. Most chemicals are poison, really. -- Rwst 11:48, 11 November 2006 (UTC)

Why are you so sure humans have a unique ability to breakdown alcohol? Do you have any evidence for this? I suspect you will find chimpanzees and cats probably have similar abilities as ours. Bear in mind a fair number of Asian people have defects in acetaldehyde dehydrogenase affecting their ability to digest (and therefore consume) alcohol (see Alcohol flush reaction) Nil Einne 14:49, 11 November 2006 (UTC)

The question is really good. Consider methanol as a counterexample. AFAIK it is also naturally produced by bacterial decomposition, however, it is significantly more toxic than ethanol. A glass of 40% methanol will probably kill you, a glass of vodka will probably not (unless you drive, but that's a different story). Anyway, what is the biological significance of ethanol? Does it has a signal function of some sort like Nitric oxide, or is it just "serendipity" that ethanol doesn't kill us straight away, while methanol or, say, acetone do? I do not know. Anyone? --Dementios

Alcohol dehydrogenase also breaks down methanol and ethylene glycol to a certian extent, and you do actually produce very small amounts of acetone when your body is in a fasting state, see Ketone bodies, of course acetone is waste product, and it leaves your body the way most waste products do--71.247.105.54 19:55, 11 November 2006 (UTC)

Hospital Information

Is there a free site where I can find information regarding surgical volumes for medical facilities?

Are you talking globally? Nationwide? For some region? Over what period? Anchoress 07:41, 11 November 2006 (UTC)

What's a "surgical volume?" Tbeatty 08:29, 11 November 2006 (UTC)

At a guess, I would think he mean's how many patients for all kinds of surgery there are (i.e. surgical throughput). However the question is in what area and over what period as anchroess said. Nil Einne 15:25, 11 November 2006 (UTC)

Radial Tunnel Syndrome

I was diagnosed with Radial Tunnel Syndrome and all I was given was anti-inflammatories. I was not given or told to wear a brace or do any type of excercise. My next appointment is in 6 weeks. My two questions are: (1) should I be doing some type of treatment during these 6 weeks, such as wearing a brace. (2) What is the full recovery rate percentage, and if everything goes as planned (whether it's surgery or non-surgical treatment), will I be able to do serious heavy lifting again.

The Reference Desk cannot give medical advice. However, by googling I found e.g. Merck and RSI which suggest avoiding rotating the wrist or bending the arm at the elbow. –Mysid☎ 11:47, 11 November 2006 (UTC)

The little black hole that could

Suppose we created a microscopic black hole. Ignore Hawking radiation and assume that the black hole's mass is exactly equal to the mass of material that has passed through its event horizon. We are going to place our black hole on the surface and watch it fall through the Earth's gravity well, eating matter as it goes. It will oscillate through the Earth, falling from one side to the other. Assume also that the earth is a rigid, uniformly dense sphere with infinite structural integrity, so it won't collapse in on itself - the only way to remove matter from the earth is to transfer it into the black hole, and that only happens to matter that crosses its event horizon.

Initially, the black hole has insignificant mass and will just pass through the earth. Over time, however, more of the earth's mass will be transferred into the black hole. What I'm actually interested in is, what would be the behaviour of this system under Newtonian mechanics? We have what is basically a point mass falling through a uniformly dense sphere, and the point's mass grows from zero to one in direct proportion with the sphere's mass shrinking from one to zero. How would the two bodies movements change as the black hole grows? Any other interesting thoughts about this idea are welcome. Maelin (Talk | Contribs) 12:55, 11 November 2006 (UTC)

You cant have little black holes, they have to be of such a mass that when the star that created them collapsed, they were crushed by their own gravity, into a singularity, which is my other point, all black holes are the same size, in that they have no size. They are singularitys. Philc _TC 14:12, 11 November 2006 (UTC)

Of course, you can have little black holes. Every star size BH will shrink to such a size, due to Hawking radiation. As to the original problem, it boils down to the same problem of a second mass in Earth's orbit if the BH is on an orbit that doesn't pass through the earth. If it passes through, deceleration because of side effects like a mini accretion disk and such will lead to it orbiting the mass centre of the Earth within the Earth, with crushing it finally when it has enough mass. -- Rwst 14:58, 11 November 2006 (UTC)

Three points: Microscopic black holes are theoretically possible - and are believed to have existed in the early Universe. The current thinking on Hawking radiation is that it wouldn't actually cause black holes above a certain size to evaporate (the method by which Hawking radiation is generated means the black hole must absorb matter in direct proportion to the radiation they 'emit' (for want of a better word). The second point: Black holes are a feature of GR; there is no Newtonian treatment of black holes. Thirdly: Black holes do have a size. The event horizon of the black hole marks its boundary and has a radius dependent on the mass of the black hole (known as the Swartzchild radius)

May we assume that the black hole is not rotating, and that – as the Earth in this problem has "infinite structural integrity" – the black hole eats out a hollow track with cross section πr, where r is the Schwarzschild radius of the black hole?  --Lambiam 19:46, 11 November 2006 (UTC)

Note that, as the black hole feeds, it's event horizon will expand. (Unlike us, however, it won't need to loosen it's belt.) :-) StuRat 20:06, 11 November 2006 (UTC)

Hard skin

Is there a name for a lump of hard skin just below the surface. I have one and the doctors (including the orthopedic surgeons) dont know what to call it. --Light current 16:04, 11 November 2006 (UTC)

You'll have to be more specific or else provide a picture. If it's a hard lump, it's important to know whether or not it feels like it is attached to the skin or moves separately from the skin. Dermatologic questions are really hard to answer over the internet. InvictaHOG 18:33, 11 November 2006 (UTC)

It seems attached to the outer surface of the skin and can be moved about =/- 5mm horizontally in relation to the underlying flesh. Its a hard lump A bit like a seg but uner the surface. Surgeon says it might be a cyst but wont know till he cuts it out. If its not serious (ie just hard skin) I may not want to have it cut out as it will leave a scar and prevent certain activites that I use my hand for.--Light current 18:49, 11 November 2006 (UTC)

I think that last part was TMI. Are you sure it's not a swollen gland in the hand? --Tbeatty 21:13, 11 November 2006 (UTC)

Laypersons

Why do laypersons think they understand many concepts that no physicists claim they understand? This is particularly prevalent with questions concerning black holes and some aspects of quantum mechanics. (This may apply to other sciences)

• Usually bad Cable Scifi/Cop/CSI shows, writters tend to throw around very bad science as technobabel--71.247.105.54 17:08, 11 November 2006 (UTC)

Becuase theyre looking at it from a different point of view untrammelled by the 'facts'?--Light current 17:14, 11 November 2006 (UTC)

Sort of like this whole page :)? --Tbeatty 21:14, 11 November 2006 (UTC)

While the math requires a physicist, the interpretations do not. For example, the fact that certain "particles" follow a wave probability function doesn't immediately tell you what that says about them. The interpretation, however, is that they really aren't in any particular location, but only have a probability of being there. Also, whether they are passing in and out of parallel universes seems to be a matter of interpretation, depending on what one makes of double-slit experiments. StuRat 19:48, 11 November 2006 (UTC)

• Exactly right, when people draw interpretations without actually understanding the underlying concepts, they usually wind up pulling interpetations out of their asymptotes. But popular mistakes usually take on a life of their own, and before you know it they become "common knowledge" For instance, the difference between a 'Parallel universe' and a Parallel universe, or 'Zero-point energy' and Zero-point energy.--71.247.105.54 20:10, 11 November 2006 (UTC)

Hmmm Shouldnt those pages be 'dab'ed?--Light current 20:41, 11 November 2006 (UTC)

Zero-point_energy#See_also and Parallel universe, one's a see also, the other is already disambiguated--71.247.105.54 20:44, 11 November 2006 (UTC)

While the math requires a physicist, the interpretations do not. This is exactly the point. The maths strongly resists interpretation into non-mathematical language. Added to that, the 'interpretations' are all drawn by physicists who already understand the maths and can very rarely be appreciated by people who don't understand the underlying maths. This is largely what leads to laypeople's mis-understanding of concepts.

Determining molecular structure

How do you determine the structure of a molecule? Jack Daw 17:36, 11 November 2006 (UTC)

Look here -- Dementios.

NMR, mass spec, IR, just to name a few, depends on what the molecule is, and in what state your sample is in--71.247.105.54 19:40, 11 November 2006 (UTC)

Why does nature likes so much to produce things in pairs? (two ears, two eyes, two lungs, two legs, four legs...

So why is it? Are intelligent creationists right?Mr.K. 20:13, 11 November 2006 (UTC)

• See Bilateral Symmetry, Bilateria, and Developmental biology, also Embryology while you're at it --71.247.105.54 20:17, 11 November 2006 (UTC)

Symmetry and redundancy. Anchoress 20:19, 11 November 2006 (UTC)

Symmetry. And Yould have difficulty walking with only one leg.--Light current 20:34, 11 November 2006 (UTC)

If humans had only one foot they would probably have some other mechanism of moving. ("Intelligent creationists"? :-) –Mysid☎ 20:53, 11 November 2006 (UTC)

"intelligent creationist": someone who believes on "intelligent creation", also plainly known as creationist. It sounds logical isn't it?Mr.K. 20:56, 11 November 2006 (UTC)

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