Wikipedia:Reference desk/Archives/Science/2010 November 25

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November 25

light peak

i have some doubts in light peak topic which and what is the use of the micro controller used in it and how the data conversion takes place (electrical to optical) —Preceding unsigned comment added by 117.254.115.64 (talk) 00:30, 25 November 2010 (UTC)

Have you read our article on Light Peak and checked the official Intel Research Light Peak Overview website? Nimur (talk) 00:49, 25 November 2010 (UTC)

The microcontroller probably buffers, handshakes, and maybe adjusts output power. The optical signal comes from infrared lasers. Ginger Conspiracy (talk) 04:12, 27 November 2010 (UTC)

File:Brake shoe metal specimen.JPG

Does phosphorus (P) really look like that? --Chemicalinterest (talk) 00:58, 25 November 2010 (UTC)

The two standard allotropes of phosphorus are white phosphorus and red phosphorus; this could be something like "violet phosphorus" or "black phosphorus", both of which are more stable that white or red phosphorus, but require high temperatures and/or pressures to form. It could also be some form of phosphate. Phosphate minerals and Phosphorite are important sources of phosphorus, often for use in fertilizers. --Jayron32 01:07, 25 November 2010 (UTC)

The only time I recall encountering elemental phosphorus, it looked like white phosphorus. More often, I've encountered calcium phosphate, or various mineral forms like apatite. Nimur (talk) 02:06, 25 November 2010 (UTC)

My money's on that being a phosphate-containing mineral, rather than pure phosphorous. (Similarly, the samples for 'chromium' and 'magnesium' have the look of metal-containing mineral ores rather than the pure metals themselves — though I'm not qualified to say whether or not they're just very badly oxidized.) TenOfAllTrades(talk) 14:48, 25 November 2010 (UTC)

Brachistochrone problem

Can anyone explain the Brachistochrone problem in a more simple way than "The curve connecting two points displaced from each other laterally, along with which a body, acted on only upon by gravity, would fall in the shortest time."? Thanks in advance. Toolssmilezdfgsdffgrdsfrtdfh975243 (talk) 01:20, 25 November 2010 (UTC)

You have two fixed points. How do you connect a wire between them so that a bead moving under gravity gets from the higher bead to the lower bead in the least time? Assume the wire is frictionless. --140.180.14.145 (talk) 01:35, 25 November 2010 (UTC)

I think the word with is unnecessary, and makes the phrase confusing. 81.131.65.104 (talk) 14:17, 25 November 2010 (UTC)

I agree. Ginger Conspiracy (talk) 04:07, 27 November 2010 (UTC)

Corvus

Why were Corvuses so upseting to a ship's balance? Is it because it is a large, heavy mast sticking vertically in the air? If so, couldn't one sail with it lowered? And I can't imagine that it could weigh any more than the ship's mast, or at least not with the leverage the mast would have with such an enormous height. Thanks in advance for the answers. --T H F S W (T · C · E) 02:53, 25 November 2010 (UTC)

The illustration in the linked article seems to show it being much longer than a mast, and it had to be sturdy enough to support a column of rushing troops, so it would have been both heavy (they gave the estimate of 1 ton) and have had a high center of gravity. Lowering it along the deck of the ship, or better yet, into the hold, would certainly help, but it looks from the diagram like the only way it could be lowered was off the side of the ship, which would pull the ship over to that side (if it wasn't supported by another ship at the far end). StuRat (talk) 03:24, 25 November 2010 (UTC)

Well, I wouldn't really consider that diagram as an authority, and the beam supporting it is not a mast. And I think corvuses (or whatever the plural for corvus is) went off the front, rather then the side most of the time. And I think a mast would have to be stronger; I don't think a large group of soldiers would have nearly as much weight as a couple tons of sail. Plus, whereas soldiers rushing across are spread out and and are supported at both ends, a mast has to support the hole sail from the top. --T H F S W (T · C · E) 04:29, 25 November 2010 (UTC)

On a TV show (don't recall which one, but I think it was on the History Channel), they recreated a corvus and found it to be extremely clumsy and dangerous to its deployers. Clarityfiend (talk) 05:02, 25 November 2010 (UTC)

One other factor to consider is that wood is better under compression (like a vertical mast) than it is under a sheering or bending load (like a deployed corvus). Thus, much more wood is needed to support the 2nd case. Although, while the weight of the sails and the mast itself compresses the mast, the force on the sails, from the wind, is a sheering force, so the mast must be strong enough to withstand that, too (up until the point where they pull in the sails in high winds). StuRat (talk) 17:10, 25 November 2010 (UTC)

No. The mast is not taking up most of the sheering force of the sail. That is, instead, transferred via the rigging, in particular the stays, shrouds, and sheets. --Stephan Schulz (talk) 00:16, 26 November 2010 (UTC)

In that case, my point (about the corvus needing to be bulky to support sheering forces not experienced by the mast) is even stronger. StuRat (talk) 04:58, 26 November 2010 (UTC)

Yes. And the corvus was also intentionally made heavy. It was supposed to smash down any defenders, and to securely fix itself into the enemy ship with a spike. It's not very effective if your armored legionaries run over the boarding bridge while it slips off the other ship...swimming with 40 pounds of bronze armor may be borderline possible for a good swimmer, but it is definitely not a battle-winning strategy. --Stephan Schulz (talk) 10:12, 26 November 2010 (UTC)

The reason carrying a corvus in rough seas is problematic is that it raises the ship's center of mass. A stable ship will have a low center of mass. The higher a ship's center of mass, the more likely a slight tilt will cause it to capsize. WikiDao ☯ (talk) 15:29, 26 November 2010 (UTC)

I believe everyone here knows that, the real Q is why it raises the center of mass more than the mast does, which we seemed to have answered fairly well. There is also the point about the center of mass being off center, which has also been addressed. StuRat (talk) 17:58, 26 November 2010 (UTC)

Mast? I had thought the corvus was deployed on oar-ships. Any heavy weight above the water-line, whether in addition to a mast or not, would have made the ship top-heavy, I'm just trying to make that answer clear. WikiDao ☯ (talk) 20:00, 26 November 2010 (UTC)

I thought they had masts for sails and resorted to oars when there wasn't enough wind or it wasn't blowing the right way, but I could be wrong. StuRat (talk) 05:41, 27 November 2010 (UTC)

At the time in question, warships were primarily oared. They used sails to move around if the wind was favorable, but they would actually take down the masts and sails, and even store them on land if possible, before a battle. One detail of the Battle of Actium was that Mark Anthony's forces, contrary to prevailing practice, took their sails and rigging on board, which decreased maneuverability of the ships and may have been bad for morale. --Stephan Schulz (talk) 17:42, 30 November 2010 (UTC)

How does radiometric dating work?

I understand the principle behind radiocarbon dating, namely that the fraction of C-14 in the atmosphere is maintained at a constant level by the flux of cosmic rays activating nitrogen. Since organisms exchange carbon with their surroundings, the fraction of C-14 in an organism also remains constant during its lifetime. When the organism dies, C-14 is no longer in steady-state and its fraction begins to decrease, allowing its use for dating.

My question is about other forms of dating, like uranium-lead dating. As far as I understand, uranium concentrations are not being held in steady-state like C-14 is, so all uranium created from the supernova (or equivalent) that formed the solar system should decay at the same pace. If this is so, how can uranium be used to find the age of a rock, and what exactly does this age correspond to? The Wikipedia article on the subject goes in depth on the calculations involved, but not this background. —Preceding unsigned comment added by 68.40.57.1 (talk) 05:48, 25 November 2010 (UTC)

Quoting from the article you linked to:

Uranium-lead dating is usually performed on the mineral zircon (ZrSiO4), though it can be used on other minerals such as monazite, titanite, and baddeleyite. Zircon incorporates uranium and thorium atoms into its crystalline structure, but strongly rejects lead. Therefore we can assume that the entire lead content of the zircon is radiogenic. Where this is not the case, a correction must be applied. Uranium-lead dating techniques have also been applied to other minerals such as calcite/aragonite and other carbonate minerals. These minerals often produce lower precision ages than igneous and metamorphic minerals traditionally used for age dating, but are more common in the geologic record.

From later parts of the article, it can be more complicated then that as lead can sometimes leach but this seems to be the basics.

Nil Einne (talk) 06:59, 25 November 2010 (UTC)

Sunrise still becoming later after solstice

I wanted to find when sunrise would be in Cincinnati, so I went to sunrisesunset.com, selected Cincinnati at http://www.sunrisesunset.com/custom_srss_calendar.asp, and got a calendar for December. To my surprise, sunrise is latest at the end of the month: yes, it's only three minutes later than at the solstice, but it's still later. Why would sunrise continue to happen later after the solstice? 66.161.250.230 (talk) 12:29, 25 November 2010 (UTC)

I think we've discussed this before so you may find something in the archives. In any case [1] [2] should get you started Nil Einne (talk) 14:07, 25 November 2010 (UTC)

If you look at those data for Cincinnati, you will see that both sunrise and sunset are getting later in late December, and the daylight period is getting longer (as you would expect). The reason is that the moment that the Sun is highest in the sky is not exactly midday, even after accounting for time zones. You can get a better explanation of why in our article on the Equation of Time. Physchim62 (talk) 14:15, 25 November 2010 (UTC)

That happens because earth's orbit is not a perfect circle. It is slightly elongated. Because of that some days are actually slightly longer or slightly shorter than 24 hours. That causes a slight shift in the sunrise time that compounds the shift in sunrise time due to the change o seasons. The final result is that the latest run rise is slightly shifted from the solistice. 76.123.74.93 (talk) 14:13, 25 November 2010 (UTC)

People have known about this for a long time, even the ancients who, lacking the distractions of the modern entertainment industry, filled their time with astronomical observations and careful calculations of recurrant celestial events. The Analemma was devised as a means of calculating deviations in the actual day from the mean solar day. --Jayron32 14:58, 25 November 2010 (UTC)

The earliest sunset is in mid December, the latest sunrise is in early January. http://www.timeanddate.com/worldclock/sunrise.html The shortest day of the year is at the winter solstice. I do hope that the proposed bill coming before parliament in the UK is succesful and we switch to continental-european time so that the evenings are lighter and more enjoyable, particularly in the spring and autumn. 92.28.251.194 (talk) 18:34, 25 November 2010 (UTC)

If it does, you will find, not immediately but over time, that the nominal times of events start getting later and later, until in the end an equilibrium is reached not much different from if you had done nothing. Ultimately, the times people do things are determined by the Sun. Messing around with the clock, as with daylight saving time, works if you change back and forth every six months, because there isn't time for the adjustment to happen. But it's not going to work to make people get up in the dark on a long-term basis. --Trovatore (talk) 19:32, 27 November 2010 (UTC)

I infer that you do not work for a living? Because most people's routines are set by their 9 to 5 working hours. 92.15.11.45 (talk) 19:55, 27 November 2010 (UTC)

Those hours, in the long run, are adjusted to the convenience of the workers (including managers; managers are also workers, and also dislike getting up in the dark). So before too long it'll be 9:30 to 5:30, and then 10 to 6.

This is actually a good example of what I was talking about. When I was a student, doing a summer job for IBM in Tucson, my hours were somewhat flexible, but to match other people I was getting rides with, I went along with the most common schedule, 7 AM to 3:42 PM (the 42-min lunch hour has some historical significance at IBM). It took me a long time to realize why it was so early. Eventually I hit on it: Arizona doesn't observe daylight saving time. So in the summer, people made their own.

That will occur in society at large. --Trovatore (talk) 20:02, 27 November 2010 (UTC)

I've heard that people start work at an early hour in the US, but in the UK I do not believe that will happen. Being further from the equator, the time of sunrise and sunset is much more variable throughout the year than where you are. In mid-winter on a cloudy day it gets dark at 3.30pm for example, with dawn around 9am. In mid-summer it gets light around 3.30am and dark around 10pm or later. 92.15.14.132 (talk) 20:37, 28 November 2010 (UTC)

Fine, sure. I didn't mean that particular schedule. I meant that, in the long run, schedules will be determined by solar time, not by nominal time. If you artificially set your clocks an hour later, schedules will eventually be an hour later by nominal time. Not necessarily exactly — different organizations will respond differently — but that's the best first-order estimate. --Trovatore (talk) 01:14, 29 November 2010 (UTC)

I used to do office work on flexitime: some people arrived and left early, but that was due to wanting to avoid the rush hour crowds; others used to start and leave late. The statistics show that most people do fixed hours. The point of switching to European continental time is the longer-lit evenings allowing more and pleasanter outdoor recreation in the evenings, plus the syncronisation of business hours. 92.24.176.72 (talk) 13:45, 29 November 2010 (UTC)

But even "fixed" hours will change (possibly, to different fixed hours). You can't change people's preferences for when they get up, work, sleep, etc, just by putting a different number to it. The current equilibrium, ultimately, is driven by the hours of sunlight. Put a different number to the same hours, relative to sunrise and sunset, and the hours that people do those things will likewise change. --Trovatore (talk) 20:50, 29 November 2010 (UTC)

Are you not forgetting the effect of electric light on society? The proposed change is an optimisation of that. You should try getting a job in the UK - then you will rapidly drop these fantasy pastoral ideas. If you are an employee and not on Flexitime then you cannot choose. People in the UK are accustomed to getting up or starting work before dawn in winter. Perhaps in the backwoods of the US, where there is little contact with the rest of society, your ideas are true, but not in the typical urban culture. If what you are suggesting is true, then business hours would change with the seasons (particularly in the north where the UK is) but they do not. 92.29.120.7 (talk) 11:09, 30 November 2010 (UTC)

I explained why business hours don't change with the seasons. It's because seasons are too short. Let a season go on long enough, and they would indeed change.

The hour on a clock is just a number. In the long run, the equilibrium is not determined by that, but by sunlight. And no, I'm not forgetting about electric lights. --Trovatore (talk) 19:07, 30 November 2010 (UTC)

Lots of places I have worked in the UK have offered me flexibility of about half an hour, so I could work 8:30-4:30, or 9-5, or maybe even 9:30-5:30. Loads of desk jobs work like this, and times shift depending on many factors. Lots of offices use hours slightly offset from 9-5. If people wanted to start and finish such jobs earlier, they could. People are just as likely to start them later as they adjust. But these are desk jobs. Many, many people in the UK work shift jobs that do not run 9-5: they do not currently experience the light mornings/dark evenings that you and journalists complain of, nor will they win lighter evenings as a result of a change to continental time. Although we could then declare 1am (which would really be midnight) to be the beginning of a new day, solving the illogicallity another user was complaining about :) 86.161.109.130 (talk) 01:19, 29 November 2010 (UTC)

I raised this same question earlier this year and received some excellent answers. See HERE. Dolphin (t) 01:15, 26 November 2010 (UTC)

Special relativity

It's been said that special relativity raises the status of measurement - that the value of a quantity is intimately tied to how it can be measured. But where in special relativity does that become important. I learned SR by first having the Lorentz transformations derived, and (almost) all the results followed from these equations. So where does the elevation of measurement come into effect? 70.52.44.192 (talk) 13:02, 25 November 2010 (UTC)

Are you sure that the statement refers to special relativity, not quantum mechanics? --Wrongfilter (talk) 14:34, 25 November 2010 (UTC)

How did you derive the Lorentz equations? I've certainly seen them derived starting with a discussion about how time and space intervals are measured e.g assuming distances are measured by sending and receiving light signals. As I recall the term "operational definition of measurement" was thrown about. 129.234.53.175 (talk) 18:19, 25 November 2010 (UTC)

The Lorentz equations are so basic that the way you derive them depends a lot on which assumptions you want to use. It's kind of like proving 2+2=4.

I don't think I agree that special relativity changes the nature of measurement, versus Newtonian physics. What I do think, though, is that physicists and mathematicians overlooked special relativity for decades because they weren't thinking carefully about measurement. That was the only real contribution of Einstein's 1905 paper. the Lorentz transformations had been derived already (by Lorentz) but people were still stuck to Newton's idea of absolute mathematical time, which they believed was the thing being measured even if physical clocks were affected in such a way that they measured it wrong. Einstein finally threw that away, and people who read his paper finally realized why the Lorentz transformations made sense. It's interesting that the key to understanding quantum measurement turned out to be the same as the key to understanding special relativity: treating the measurement apparatus as a physical system that follows the same rules as the thing being measured. I have the fond hope that whatever is preventing us from understanding quantum gravity will turn out to be equally fundamental... -- BenRG (talk) 21:35, 25 November 2010 (UTC)

Relative velocity

I think it is more practical saying Lorentz assumed the Lorentz Transformation (LT) and Einstein is the first person trying to derive it. If you look at the time equation of LT, you will wonder how did Lorentz get it? But after you change the spatial equation to x=(x'/γ)+vt, and change the time equation to t=(t'/γ)+(vx/c^2) then put the right part of the equation into t of the previous equation, you will find out that the result is x = γ(x'+vt'). Yes, after you combined equations in LT you get the spatial equation of the inverse LT. Do you know how Lorentz get the time equation? It is so simple that Lorentz just assumed the "hypothesis of ruler contraction" to get x'= γ(x-vt), and the x= γ(x'+vt') for inverse LT, then replaced the x' in the later equation by γ(x-vt); and ha, there is the time equation in LT. Any two of the four equations in LT and inverse LT can derive the other two of them. That means, no matter how people derive LT, the equations of LT and inverse LT will always coexist. Logically speaking, we may assume S' is moving at velovity v and S is rest or we may assume S' is rest and S is moving at velocity -v but to assume both conditions to coexist we should be able to find something very bad in the LT. It is bad, in LT, the v is always zero.Jh17710 (talk) 04:29, 26 November 2010 (UTC)

The phrases "is at rest" and "is moving at velocity v" are meaningless, unless it's clear what movement is being measured relative to. If the x and x' axes point in the same direction, then the statements "S' is moving in the x direction relative to S at speed v" and "S is moving in the x' direction relative to S' at speed –v" mean the same thing. There is no inconsistency there, and no problem with the LT and the inverse LT coexisting in the same problem. Red Act (talk) 19:40, 26 November 2010 (UTC)

It is not easy to see the problem by looking at the four equations only. However, if you add two equations t'=t/γ and t=t'/γ that we could derive within LT and inverse LT, then you will see the problem very clearly. We will have γ=1 and so that v=0. How do we derive t'=t/γ and t=t'/γ within LT and inverse LT? Please refer to http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Archives/Science/2010_November_19 .Jh17710 (talk) 05:28, 27 November 2010 (UTC)

I've updated the page you linked to with explanations of your latest errors. Red Act (talk) 08:09, 27 November 2010 (UTC)

Platinum arsenide

Does anyone here know how to extract platinum metal from platinum arsenide (in my case it is sperrylite) and disposing the arsenic safely? I have search the internet and found no information on this.

Another thing I want to know that when we burn platinum arsenide,does it decompose? I gues it is because platinum is noble metal,and I have done and experiment,when I burn it,it turn to black and somewhat seem shrinked. If it does,it will decompose to platinum metal rather than its oxides?

I heard that platinum arsenide is attacked with oxidizing acid like nitric acid, when it attacked,does it form platinum nitrate and arsenic nitrate or just eat the arsenic away leaving the platinum metal?

Thank you very much! —Preceding unsigned comment added by 124.82.11.255 (talk) 14:08, 25 November 2010 (UTC)

Chemically extracting metals from their ores is actually usually a very dangerous process. Platinum extraction, as you note, produces nasty arsenic compounds. Gold extraction often involves the use of cyanides, see Gold cyanidation. Metal extraction is almost universally poisonous, environmentally destructive, and/or energetically expensive. See tailings and slag for examples of toxic wastes from various stages of metal extraction processes. --Jayron32 15:02, 25 November 2010 (UTC)

aqua regia will convert this to chloroplatinic acid H₂PtCl₆, and nitric acid to Pt(NO₃)₄. Burning the arsenide should remove the arsenic as an oxide vapour, but this could be polluting. Graeme Bartlett (talk) 21:17, 25 November 2010 (UTC)

Will the reaction with nitric acid produce arsenic nitrate?

ECG

Performing ECG on a patient having a metalic pin in his femurKhuloodm (talk) 16:12, 25 November 2010 (UTC)

Dose a metalic pin in a patient's bone affect ECG readingsKhuloodm (talk) 16:22, 25 November 2010 (UTC)

I have no idea, having a look at the Electrocardiography article, I can't deduce any plausible reason why a metal pin should affect ECG readings, but if that's a homework question, maybe it's one of those trick questions that only ECG technicians know the answer to. Vespine (talk) 21:44, 25 November 2010 (UTC)

No, a conductive metal pin would not influence a ECG any more than normal conductive saline fluids. MRI is a different story, but femoral traction pins should be safe at 1.5 Teslas: PMID 19897988; unlike other kinds of implants at higher magnetic strength: PMID 16835741. If this is an for an actual patient, please don't ask the reference desk. If it's for homework, you shouldn't really be asking it here either. Ginger Conspiracy (talk) 02:25, 27 November 2010 (UTC)

Human urine

What does human urine taste like ? Obviously I have no interest in trying it out and I'm not asking you to go do some original research I'm just morbidly curious. I'm more looking for scientific answers in the form: human urine contains these compounds, which are also found in these more commonly ingested substances, so it might taste like this. Thanks. 24.92.78.167 (talk) 17:29, 25 November 2010 (UTC)

Our article on urophagia discusses this a bit - it seems to vary quite a bit based on what the excreter has recently eaten and drunk. Because salts are concentrated in it (per our article), I assume it is usually salty unless something odd is affecting the flavour/odour. Matt Deres (talk) 18:33, 25 November 2010 (UTC)

It's definitely salty. It tastes pretty much how it smells: like urine. Urine is generally sterile, and safe enough to drink in small quantities; there's no reason not to try some (other than the grossness factor, which isn't insignificant). Buddy431 (talk) 00:03, 26 November 2010 (UTC)

Its salty (due to the salts) and has a bitter / ammonia-like taste due to the urea. Beyond that, it very much depends on what else the person has been eating drinking. Rockpocket 00:13, 26 November 2010 (UTC)

In the early days of medicine, physicians would taste the urine of any patient suspected of suffering diabetes. If the urine was slightly sweet due to the presence of sugar this confirmed the diabetes. See History. Dolphin (t) 01:05, 26 November 2010 (UTC)

You're clearly referring to diabetes mellitus, as distinguished from diabetes insipidus (the latter associated with dilute, not sweet, urine). Note that urine contains no sugar until the diabetes mellitus is sufficiently advanced for blood glucose to exceed the renal threshold (about 180 mg/dL or 10 mM), so the "taste test" would not rule out early diabetes mellitus (of course, diabetes mellitus generally isn't symptomatic until the renal threshold of glucose is exceeded, so it was a useful test). -- Scray (talk) 01:44, 26 November 2010 (UTC)

Mellitus means sweet in Greek... that's an intentional correlation. Apparently a number of cultures either tasted the urine themselves or used animals (ants or bees) to determine whether or not a particular individual's urine contained sugar, making it sweet. Shadowjams (talk) 12:25, 26 November 2010 (UTC)

Much of taste comes from smell. 66.108.223.179 (talk) 23:06, 27 November 2010 (UTC)

Actually, much of flavor comes from smell, taste is pretty much specific to the taste buds. Rockpocket 17:34, 28 November 2010 (UTC)

cloning plants

Were scientist cloning plants before Dolly the Sheep? If so, for how long? —Preceding unsigned comment added by 69.247.48.131 (talk) 20:47, 25 November 2010 (UTC)

You don't need to be a scientist to clone plants. Everytime you take a cutting of a house plant, you are cloning it! 86.162.106.18 (talk) 21:07, 25 November 2010 (UTC)

King's Holly Mac Davis (talk) 23:16, 25 November 2010 (UTC)

Banana's are famously propagated by cloning. Bananas have probably been cultivated for the past 7000 years in some areas [3], but it's unclear how long they have been cloned, rather than grown from seed. In any case, grafting has been practiced in the far east for the past 4000 years or so. Buddy431 (talk) 00:12, 26 November 2010 (UTC)

The Navel Orange is my favorite example, since all of the millions and millions consumed over the last 180+ years have been, essentially, the same orange! The Masked Booby (talk) 03:30, 26 November 2010 (UTC)

Along these lines, the same can be said for every commercial apple variety. There's only one granny smith, only one red delicious, etc. The point is that if a certain apple tree makes tasty apples, there is no guarantee that the offspring grown from seed (indicating sexual reproduction) will taste the same. The only way to ensure this is by grafting (cloning) one tree over and over. SemanticMantis (talk) 15:13, 26 November 2010 (UTC)

That's not strictly true: as the Red Delicious article points out, there have been a number of mutations that have occurred over the last hundred years, leading to multiple strands (genetically similar, but not identical), that may truthfully be called Red Delicious apples. In general, though, you are quite correct. Buddy431 (talk) 23:32, 26 November 2010 (UTC)

Thanks for the clarification Buddy431. Wouldn't we expect the same state of affairs for navel oranges and bananas then? Or do you think that the other fruits have not (for some reason) mutated over myriad cycles of cloning? SemanticMantis (talk) 23:13, 29 November 2010 (UTC)

For naval oranges, definitely. See this list of orange types. I count many dozens of varieties. Note that in most cases, the first tree where the mutation occured is identified, from which all trees of that variety were cloned. I'm not sure about the Cavendish banana; it's only been cultivated heavily for the last 60 years or so, leaving less time for mutations than red delicious apples or navel oranges. Still, we'd expect some mutations, but I can't find any list of varieties like you can for red delicious apples or navel oranges. Buddy431 (talk) 03:21, 30 November 2010 (UTC)

Research subject

Is there a way I could get paid to become a psychological/cognitive research subject? I have a lot of strange abilities. I lucid dream every night, I can depersonalize, derealize, and überrealize very easily and at will. Psuedohallucinations are common, and so are false memories, illusions of precognition, and many other little oddities. None of these things have ever bothered me in life. I enjoy them and learning how to manipulate them. I would like to learn to do more of these things, and help humanity's understanding of these mental effects. I am also very interested in being injected with psychoactive drugs during the dream state to see how sensations and perceptions are altered. My dream recall can go very deep, and is easily trained and untrained. I would really like to find a situation where I can spend some time delving into my own mind in waking and dream states while free from the responsibilities of civilization. Any ideas? -- Mac Davis (talk) 23:33, 25 November 2010 (UTC)

Its unlikely anyone is going to inject you with psychoactive drugs, but this site should give you some pointers of how to get involved in dream research. Rockpocket 00:18, 26 November 2010 (UTC)

Hey! That's a really good site. I read a lot of it. I also found a presentation from DEF CON with some scripts and schematics. I also already have somebody reliable to work with. —Preceding unsigned comment added by Mac Davis (talk • contribs) 04:12, 26 November 2010

You can look on the bulletin boards around your local college or university psychology department to see who needs research subjects; they often pay nominal fees for your time. But please don't specifically seek out experiments involving areas in which you think you may be a statistical outlier. To do so will skew the experiments' results. Ginger Conspiracy (talk) 01:37, 27 November 2010 (UTC)

Car turbochargers and torque

What causes turbos to produce so much torque (especially smaller twin turbos)? They smaller twin turbos are always capable of producing so much more torque than horsepower. Why is that? —Preceding unsigned comment added by 76.169.33.234 (talk) 23:38, 25 November 2010 (UTC)

Your statement that some turbos are capable of producing more torque than horsepower is meaningless. Torque and power are two different quantities. Torque is typically measured in Newton.metres and power is measured in Newton.metres.second^-1, Watts, kilowatts or horsepower.

Consider an engine producing a torque of 1000 N.m. If the speed of this engine is 1000 RPM it is producing power of 104.7 kW, but if the speed is 10,000 RPM it is producing 1047 kW.Dolphin (t) 04:58, 26 November 2010 (UTC)

Let me use a specific example to rephrase the question in a way that the OP actually means and would be helpful to follow-up RefDeskers: Why do turbo-charged engines such as that in the SEAT Leon Cupra (2L Turbo, 177kW @ 5,700-6,300rpm, 300Nm @ 2,200-5,500rpm) produce so much more torque so much lower down in the rev range than naturally aspirated engines of the same power e.g. the Honda S2000 (2L NA, 177kW @ 8,300rpm, 208Nm @ 7,500rpm)? The torque curves of turbo charged engines are disproportionately swelled at lower RPMs as compared to NA engines. What makes turbochargers so naturally effective at lower RPMs? Zunaid 10:05, 26 November 2010 (UTC)

Thanks for that clarification. It was perfectly clear to me what was being asked; I don't know if Dolphin really didn't understand or was just being difficult. StuRat (talk) 17:51, 26 November 2010 (UTC)

See:Turbocharger--Aspro (talk) 17:16, 26 November 2010 (UTC)

Does that article actually answer the question ? If so, I must have missed it. StuRat (talk) 17:55, 26 November 2010 (UTC)

Yes. More air drawn into the cylinder on the intake stroke.--Aspro (talk) 18:01, 26 November 2010 (UTC)

And how does that alter the HP to torque ratio ? StuRat (talk) 23:01, 26 November 2010 (UTC)

More oxygen availability causes a faster burn with the same amount of fuel, and possibly more importantly for the low revs case, allows a complete burn with more fuel. Ginger Conspiracy (talk) 02:36, 27 November 2010 (UTC)

Ginger Conspiracy has written More oxygen ... with the same amount of fuel ... If so, that would be a higher air-fuel ratio and I would disagree with that. Use of turbo-charging does not require, or warrant, a change in air-fuel ratio. The primary effect of supercharging and turbo-charging is to significantly increase the volumetric efficiency - more air and fuel per intake stroke, and therefore more heat released during each power stroke; so greater torque and greater power. An increase in volumetric efficiency can cause a 1 litre engine to have the output of a 2 litre engine - greater torque, greater power and greater fuel consumption at the same engine speed. Dolphin (t) 05:26, 27 November 2010 (UTC)

I don't think the above answers explain why one gets more torque at lower RPM than an equivalently powered NA engine. A turbocharged 1L producing the power of a 2L (say 110kW) will more than likely produce the torque of a 2.4L (say 240Nm). The torque boost is always disproportionately greater than the power boost when compared to equivalent NA engines, and always at lower RPM. It seems that turbos boost more effectively at lower RPM. Why? Zunaid 16:22, 27 November 2010 (UTC)

What makes turbochargers so naturally effective at lower RPMs?

That been answered. If you were to ask why turbo's don't show the same proportion of torque at the upper end as NA . The answer would be that if they were allowed to, the stresses imposed upon the components would shorten engine life. --Aspro (talk) 20:40, 27 November 2010 (UTC)

Turbocharged airplane engines, and possibly turbocharged car engines, are equipped with wastegates solely for the purpose of regulating the boost of inlet manifold pressure. The higher the engine speed the more exhaust gas is diverted away from the turbocharger to reduce the effectiveness of the turbocharging and limit the speed of the turbine. If the inlet pressure was not limited by the wastegate the turbine could overspeed itself to destruction, and there would be increasing potential for detonation at higher engine speeds. If turbocharged engines in cars also have wastegates then that explains why the effectiveness of the turbocharging is so significant at low engine speed, but less so at higher engine speeds. Also see Turbocharger#Wastegate. Dolphin (t) 00:31, 28 November 2010 (UTC)