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December 2

Garlic supplements

I take garlic supplements and usually buy whatever's on sale at the grocery store. I happened to notice that brand I bought last time, Sundown Naturals has 75 mgs of garlic. The brand I just bought today, Nature's Bounty has 1000 mgs of garlic. I realize that there's no established RDA for garlic, but I was surprised that the amounts are so wildly different. The lower dosage pill is bigger, too. I'm guessing that one of these companies is playing 'accounting games' with the amount of garlic and that one pill isn't really 13 times more potent than the other, but I don't know that. Can anyone shed some light on what's going on here? Thanks. — Preceding unsigned comment added by A Quest For Knowledge (talk • contribs) 01:26, 2 December 2012

The label for the Sundown product says it contains 400 mg of garlic extract, equivalent to 2000 mg of fresh garlic bulb. Looie496 (talk) 01:39, 2 December 2012 (UTC)

(edit conflict) Herbal supplement#Government regulations should provide some light; basically the entire world of herbal supplements is an impenetrable dark morass of unproven, untested, and unregulated products foisted on the public as "health". It's not harmful (maybe), so there's no reason you shouldn't be taking them, but otherwise, don't actually expect any real consistency or meaningful efficacy from over-the-counter herbal supplements, most of which are about as useful as snake oil. --Jayron32 01:41, 2 December 2012 (UTC)

@Looie496: Oh, that's interesting. The label has apparently changed since I bought it. A Quest For Knowledge (talk) 01:51, 2 December 2012 (UTC)

@Jayron32: I did a bit of research on garlic a couple months ago, and I don't think this was the article I read, but there appears to be some support for garlic and hypertension, Garlic 'remedy for hypertension'. A Quest For Knowledge (talk) 01:51, 2 December 2012 (UTC)

I am in no way doubting that there could be medically useful compounds in garlic. There very well may be. The issue is that the herbal supplement industry is essentially an unregulated industry with no set standards the way that actual medicines have. So yeah, the fact that there are compounds within garlic that reduce hypertension is to me unimportant to the discussion at hand. The question is whether pills in stores by random manufacturers which report some content of "garlic" are useful or consistent. They are different questions. --Jayron32 01:55, 2 December 2012 (UTC)

Plus, with all these vampire shows, like Twilight: Breaking Wind, I assume there's a plague of vampires right now, so having some garlic in your system to ward them off is a good idea. :-) StuRat (talk) 07:17, 2 December 2012 (UTC)

From a culinary point of view, eating garlic is much better than eating garlic pills. 2000mg is two grams, or about one clove - a homeopathic dosis, as far as my cooking is concerned. The natural unit of measurement is the bulb, not the clove ;-). --Stephan Schulz (talk) 08:52, 2 December 2012 (UTC)

There are some of us who hate garlic. And, even for those who love it, do you really want to smell like garlic ? StuRat (talk) 09:12, 2 December 2012 (UTC)

Well, the unenlightened need to become enlightened. And I'm not sure that "smell" is the proper term to use for the heavenly fragrance that garlic and its disciples contribute to the universe. More seriously, I've cooked some meals for people who claim to not like garlic, and they where quite happy with it. It always depends not only on "how much", but also on "how", with garlic added early and sautéed a bit being much easier on the stomach and more discrete on the taste buds than raw garlic. --Stephan Schulz (talk) 09:20, 2 December 2012 (UTC)

Those who love it have no problem with it, by definition. Garlic on the breath of someone who's eaten it in the past few hours is not unpleasant. In fact, it might be a damn sight better than it would otherwise be. It's only a problem on people who haven't showered for a day or more, and the weather is warm. Then, it comes out in their pores and mingles with their sweat and becomes pretty yucky. But a garlic eater who attends to their daily personal hygiene doesn't normally find their smell is a problem for others. -- Jack of Oz ^[Talk] 10:23, 3 December 2012 (UTC)

• Sorry I didn't notice this before. The author is Karin Ried, who has published some articles [1] most recently [2]. "Mean systolic blood pressure was significantly reduced by 11.8±5.4 mm Hg in the garlic-2-capsule group over 12 weeks compared with placebo (P=0.006), and reached borderline significant reduction in the garlic-4-capsule group at 8 weeks (−7.4±4.1 mm Hg, P=0.07)." With an n of 79 split into four groups... hmmmmmm... and the results are not dose dependent ... hmmmm. Not what I'd call a compelling result, but nonetheless, an interesting lead. Other reviews have commented on similar but similarly underpowered research before [3]. Note the best-scoring two capsule group took 480 mg of aged garlic extract and 1.2 mg S-allylcysteine. Wnt (talk) 03:50, 7 December 2012 (UTC)

I want to know some intersest things about how metal found

Any kind of metal — Preceding unsigned comment added by Summeru (talk • contribs) 11:04, 2 December 2012 (UTC)

Iron can fall from the sky in the form of an iron meteorite. It can then be found lying on the ground. You may also be interested in the metal detector. Graeme Bartlett (talk) 12:04, 2 December 2012 (UTC)

In the spirit of providing interesting things about how metal is found, you might enjoy reading some excerpts from Roughing It, a narrative account by Mark Twain about his experiences as a silver miner in Nevada (and other excitement in the old West). Perhaps the author embellishes a little bit, but as far as I can tell, he presents an incredibly interesting (and quite potentially factual) account of ore extraction and processing. Chapter XXIX, Out Prospecting; Chapter XXXVI, A Quartz Mill and Ore Processing; Chapter LX, Pocket Mining, Placer Mining, and Mining Technicalities; and essentially everywhere else in the book, scattered bits of wisdom about silver and gold mining in the mid-nineteenth century. For an encyclopedic overview, we have articles on silver mining. Nimur (talk) 14:02, 2 December 2012 (UTC)

Maybe this is about discovery. (From our article on nickel): "In medieval Germany, a red mineral was found in the Erzgebirge (Ore Mountains) that resembled copper ore. However, when miners were unable to extract any copper from it, they blamed a mischievous sprite of German mythology, Nickel (similar to Old Nick), for besetting the copper. They called this ore Kupfernickel from the German Kupfer for copper. ... In 1751, Baron Axel Fredrik Cronstedt was trying to extract copper from kupfernickel—and instead produced a white metal that he named after the spirit that had given its name to the mineral, nickel."--Fuhghettaboutit (talk) 14:43, 2 December 2012 (UTC)

metal from Lithium and magnesium to cooper and silver and gold had been exist in earth crust and found by man for duration of some thousand years,we dont know clearly about first mining and how could man find minerals,but the usage of minerals and metal goes to age 8-9 thousand years ago. now we have instruments and high technology for mining ,the way of separating of mineral matters on earth crust refers to its molten core and diffraction of layers for duration of its life(4.6 billion years)--Akbarmohammadzade (talk) 15:03, 2 December 2012 (UTC)-

Akbarmohammadzade, I know you are trying to help, but if you want to answer a question in English, please follow some basic rules of the English language and of this page. It is really hard to read otherwise, and therefore not so useful to the original poster of the question.

1. The first word of a sentence should a capital letter. ("Now we have... ", not "now we have...".)

2. Proper nouns should also be capitalise (Earth crust, not earth crust).

3. Don't use automatically translated language, it is so wrong that we can't make sense of it.

4. Questions should end with a question mark.

5. Here we provide references (this is the reference desk), so the idea is that we point the user to specific pages within or outside wikipedia. So if you could link your answer to the relevant wikipedia page (for example did you mean molten core ?). --Lgriot (talk) 14:32, 3 December 2012 (UTC)

As a general rule, if you're going to criticise someone else's writing, you should ensure yours is flawless first. "Proper nouns should also be capitalise" is bad grammar, your last sentence is an incomplete fragment, question marks are not preceded by spaces, and Wikipedia is a proper noun and should begin with a capital letter. Akbar's comment wasn't particularly hard to decipher, in my opinion. – NULL ‹talk›
‹edits› 23:02, 5 December 2012 (UTC)

Fair enough, I was trying to give him/her advice, but if you guys feel I'm only criticising, I'll just keep quiet and won't try to help anyone anymore. --Lgriot (talk) 14:33, 6 December 2012 (UTC)

Muprhys law biatch! 203.112.82.1 (talk) 17:26, 5 February 2013 (UTC)

Photobiolysis

Do we have an article? Is there a missing redirect? Did I make a typo? See [here] for an explanation of what the term means. As of 13:32, 2 December 2012 (UTC), the title of the question is a redlink. Thanks, NorwegianBlue ^talk 13:32, 2 December 2012 (UTC)

Biohydrogen, Photohydrogen, and Biohydrogen reactor all seem to be related. To which, if any, "Photobiolysis" should redirect I'll leave to others more versed in the material. Deor (talk) 17:08, 2 December 2012 (UTC)

Thanks. I came across the word when trying to assist my daughter with homework; it appeared in a chapter about using hydrogen as fuel. It now occurred to me to try search for Biophotolysis instead of Photobiolysis. The term Photolysis is well established, and biophotolysis is a special case, driven by biological processes, so the latter term makes more sense than the former. And indeed, on google scholar, biophotolysis seemed to be the preferred term, and also occurs in our article Hydrogen production, so maybe that would be the best place to redirect biophotolysis. A bit confusing though, if a user gets redirected there, and searches for photobiolysis to locate what he's looking for. NorwegianBlue ^talk 20:56, 2 December 2012 (UTC)

what does burn in nature

we had discussion about matters does burn by fire . they said :only matters made of carbon does burning.what about others? --Akbarmohammadzade (talk) 14:41, 2 December 2012 (UTC)— Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 14:40, 2 December 2012 (UTC)

Many elements burn, including metals and hydrogen gas. Most pyrotechnics do not seem to have carbon. DMacks (talk) 17:02, 2 December 2012 (UTC)

If you can oxidate it, you can burn it. When you "burn" something you simply combine it with oxygen, you oxidize it. Magnesium burns, and it's not organic, for example. OsmanRF34 (talk) 20:11, 2 December 2012 (UTC)

And the oxidizer doesn't even have to be oxygen -- it can be hydrogen peroxide, any of the halogens, any nitrate or perchlorate compounds, etc., etc. In fact, alkali metals spontaneously combust in water, while the aforementioned magnesium burns very well in carbon dioxide... 24.23.196.85 (talk) 00:38, 3 December 2012 (UTC)

Could somebody explain what is meant by "the oxidiser can be a halogen" please? thankyou.124.191.177.160 (talk) 07:23, 3 December 2012 (UTC)

Oxygen's role in burning is to capture electrons from other atoms, to raise their oxidation state (see redox). But oxygen is not the only molecule that can fill this role. Many materials will also burn in a halogen atmosphere, such as chlorine, even when no oxygen is present. Someguy1221 (talk) 07:29, 3 December 2012 (UTC)

And of course I think most people would consider the sun to be "burning", but there's no oxygen anywhere near it, but that's a very different kind of burning then what we would see naturally on earth. Vespine (talk) 21:38, 2 December 2012 (UTC)

Say what? Our Sun article says that it is about 0.77% oxygen by mass. 192.220.135.34 (talk) 00:59, 5 December 2012 (UTC)

Based on our articles on the Earth and the Sun, there's about 8500 times as much oxygen in the sun that in the earth (atmosphere plus crust, etc). Funny. Of course, most of the oxygen (on Earth and Sun) is not molecular oxygen. -- Scray (talk) 01:43, 5 December 2012 (UTC)

Ok, sorry, you are right, there IS oxygen near it, but the vast majority of the "burning" on the sun does not involve the oxygen, it involves hydrogen converting into helium. If there was NO oxygen there, the process would remain the same. Vespine (talk) 22:18, 5 December 2012 (UTC)

Chemical combination with oxygen is known oxidation but burning is fast combination with flam and warming .faster one is exploding. the iron does oxidation but slowly ,Lithium oxidation cause its fast rotating and magnesium burns with bright flame. sulfur and phosphor are burn too. Can we define burning such as this : Chemical combination with flame and high temperature?--78.38.28.3 (talk) 07:57, 4 December 2012 (UTC)(when any meteorite inters to atmosphere it burns , but for high friction)

what do you thinking about this questions?

پرسش از چگونگی اندر کنش گرانش و فضا؟

گراویتون ها(ریزگانهای نامزد ترابری نیروی گرانش ،موجب خمیدگی فضا نمی شوند . حضور میدان در فضا با مبادله ذره تفاوت ماهوی دارد و این را اینشتین به خوبی درک کرده بود. ببینید شما روی صندلی نشسته اید و صندلی برروی سقف قرار دارد و سقف روی ستونها و ستونها روی قشری از پوسته زمین . مثال ساده فوق را اینطور تصور کنید : ذرات گراویتون از زمین (معلوم نیست از کجای زمین)به شما واجسام یادشده گسیل میشود . 1- چه عاملی باعث می شود زمین تشخیص دهد شما اینجائید تا ذره گسیل دارد؟ 2-چرا مواد و اشیا زیر شما بین شما و زمین سایه نمی اندازد؟(مانع برای رسیدن گراویتون) 3- چه چیزی به زمین می گوید شما چقدر جرم دارید تا همان اندازه گراویتون گسیل نماید. 4-گراویتون به هیچ و جه توجیهی برای افزایش شتاب به نسبت عکس مجذور ثانیه و شتاب یافتن ذره در میدان نمی آورد. 5-هیچ مبادله کوانتومی ذره استثنا از قانون پلانک و اصل طرد پائولی نیست. 6-ترازهای انرژی میدان جاذبه از اصل عدم قطعیت هایزنبرگ تبعیت نمی کند. 7-مبادله ذره قوانین کپلر و میدان جاذبه و حرکت در میدان جاذبه را نمی تواند توصیف کند. — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 14:43, 2 December 2012 (UTC)

This is the English Wikipedia and so this question written in Persian is not well suited here. Moreover, from what I can make out from machine translation, this appears to be a homework question, which we will not answer for you because it robs you of the ability to learn yourself. I will post machine translation of this answer into Persian. I hope it's less garbled than the translation I was given of your text.ویکیپدیای انگلیسی است و بنابراین این سوال است از این بخش است که به زبان فارسی نوشته شده است و مناسب اینجا نیست.علاوه بر این، از آنچه که من می توانم از ترجمه ماشینی، این به نظر می رسد یک سوال برای مشق شب، که ما آن را نمی خواهد جواب را برای شما به دلیل آن را به شما محروم می سازد از توانایی خود را یاد بگیرند. من به ترجمه ماشینی از این پاسخ را به زبان فارسی ارسال کنید. من امیدوارم که آن را در کمتر از ترجمه من از متن خود را به او داده شد درهم است.--Fuhghettaboutit (talk) 14:52, 2 December 2012 (UTC)

Gravitons (gravity transport candidate, not the curvature of space. Field presence in space has an inherent difference between the particle and the Einstein exchanged well understood. If you see sitting on the chair and sits on the roof and on the roof of the cortical columns and pillars of the earth's crust. Imagine a super simple way: Graviton particles from the ground (not sure which part of the land) will be sent to you Ballistics above. 1 - You are here to determine what causes the particles are emitted? 2 - Why the materials and objects between you and the ground you would not have a shadow? (Barrier for gravitons) 3 - What is the land mass tells you how you can send the same size gravitons. 4- Graviton anything quite excuse for the acceleration inversely square s and acceleration of particles by the field 5 - No swap Pauli exclusion principle is a quantum particle exception of Planck's law. 6 - Energy balances the gravitational field does not obey the Heisenberg uncertainty principle. 7 - sharing particles of the gravitational field and Kepler's laws of motion in the gravitational field can not describe. is this translation clear enough ? — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 15:12, 2 December 2012 (UTC)

your name is as difficult as my name,i cannot spell it. — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 15:18, 2 December 2012 (UTC) If you want to justify graviton field must first be applied to the total impedance playing field with those particles like photons in space to justify. Each crime should be displaced between Dvtraz energy part of the gravitational energy is emitted. According to Maxwell's equations for the gravitational field Nakarast and radiation or certain wavelengths of emitted gravitational field graviton is not so controversial as the transferor remains Abtr field. The concept of gravity as the curvature of space electrodynamic equations of motion of a particle with space-time with virtual Chharbdy tensor is solved. The extent of the equations Bapkhsh just purely particle radius dependent impedance or density or mass or unresolved issue is resolved--Akbarmohammadzade (talk) 15:46, 2 December 2012 (UTC)

I don't understand what you are trying to say, but you don't seem to have asked a question. You have just made a series of statements. --Tango (talk) 02:06, 3 December 2012 (UTC)

difference between theory and law

we have Faraday or Kepler or thermodynamic laws . so we have several theories about differences between theory and low: A common misconception is that scientific theories are rudimentary ideas that will eventually graduate into scientific laws when enough data and evidence has been accumulated. A theory does not change into a scientific law with the accumulation of new or better evidence. A theory will always remain a theory; a law will always remain a law.

http://en.wikipedia.org/wiki/Scientific_theory

A law differs from a scientific theory in that it does not posit a mechanism or explanation of phenomena: it is merely a distillation of the results of repeated observation. As such, a law is limited in applicability to circumstances resembling those already observed, and is often found to be false when extrapolated.

http://en.wikipedia.org/wiki/Scientific_law--Akbarmohammadzade (talk) 14:49, 2 December 2012 (UTC)

What's your question? --Mr.98 (talk) 15:32, 2 December 2012 (UTC)

something about how we say newton formulas law? — Preceding unsigned comment added by Akbarmohammadzade (talk • contribs) 15:43, 2 December 2012 (UTC)

I don't understand your question. You might like to read Newton's laws of motion and Physical law.--Shantavira|^{feed me} 18:03, 2 December 2012 (UTC)

His question is: Why do we say that Newton's Laws are laws, rather than theories? Good question. My stab at it would be this: We observe through a very large number of observations that they are true. Therefore we take them as basic principles (laws) which can form the starting point of theories. For example, Newton's laws of motion says Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion. So one thing explaining another thing is a theory, while the one thing itself is an assumption (and the assumption is a law if there's a lot of solid evidence for it). My question: If a law is subsequently shown to be not perfectly true, do we say that it remains a law? For example, are Newton's laws considered to be untrue under relativistic conditions? Duoduoduo (talk) 17:15, 3 December 2012 (UTC)

Thanks,the relativistic condition solved newton's laws shortages but all scientific references tell law to newton formulas for their role in classic mechanics.--78.38.28.3 (talk) 05:51, 4 December 2012 (UTC)

Roughly, a law is a simple statement of an important property. A theory is the deductive closure of a number of statements (each of which can be considered a law if you set the barrier of importance low enough). So indeed Newtons laws are the basis of classical mechanics. --Stephan Schulz (talk) 07:36, 4 December 2012 (UTC)

Looking for research on Tetrahydrocannabinoids (THC) use as appetite simulant in cats diagnosed with CHF vs: azotemia (cardiac vs: kidney) problems - common in some cats.

Tried the orexigenic route via Wiki without much success. We are currently using Mirtazapine per vet with mixed results.This guy is a lovable little furry person! — Preceding unsigned comment added by 99.146.148.92 (talk) 15:53, 2 December 2012 (UTC)

I think we probably ought to avoid giving advice here, even if it is for a cat rather than a human. Plus this is such a technical question that nobody except a vet could give useful advice anyway. Looie496 (talk) 16:27, 2 December 2012 (UTC)

Humans, being primates, have large livers meant to metabolize chemicals in plants. Carnivores do not. The popular press has a lot on the toxicity of marijuana to pets. I'd speak to your veterinarian, if I were you. μηδείς (talk) 16:45, 2 December 2012 (UTC)

Cats in particular are reputed to have livers which are not as good as detoxing things; phenols (pinesol, etc.) being a commonly cited example. Gzuckier (talk) 04:06, 3 December 2012 (UTC)

We are proscribed from providing medical advice (human and otherwise) here. This needs to be closed.Dncsky (talk) 17:42, 2 December 2012 (UTC)

Although it's obvious he wants to treat his cat, he has asked for research, which we can provide. μηδείς (talk) 17:56, 2 December 2012 (UTC)

Have you just tried more tempting foods ? I know my cat could never resist the oil from a can of tuna. (You can get the tuna packed in water, too, but that won't have as many calories for your cat.) Also, have you had the cat's mouth and throat checked ? A sore tooth or throat might make it avoid solid foods. StuRat (talk) 18:42, 2 December 2012 (UTC)

That kind of advice is against policy. I should add that Wikipedia assumes zero liability if tempting a cat with azotemia with nitrogen-rich fish causes a worsening of the condition, and anyone who actually has said cat indeed had best ask the vet some questions. However, a request for research is fully appropriate - we should endeavor to assist a scientist or future scientist looking for ideas. Wnt (talk) 02:12, 5 December 2012 (UTC)

Feline stomatitis is a common condition that causes cats not to eat. Both our cats went through it, and eventually recovered after the removal of most of their teeth. --`Trovatore (talk) 02:30, 5 December 2012 (UTC)

To begin with, let's link azotemia. I assume CHF is congestive heart failure? Cannabinoids have been studied in cats a few times, but looking for that and "appetite" gets me one 1972 review article. From a quick skim, it appears that CB1 agonists (substances akin to marijuana) have a favorable effect against development of congestive heart failure in rats. (I was in a hurry, so you should check [4] and make sure that's not a lie) Wnt (talk) 02:23, 5 December 2012 (UTC)

Synchronous belt as serpentine belts

I noticed that for most engines the serpentine belt is a multi-V belt. Is there any engine out there that uses synchronous belts as their serpentine belt? I can't see any reason they are not used other than the higher cost. But if cost is the only concern then some of the luxury and racing companies must've done it already. Google hasn't been helpful due to the synchronous belt/timing belt conflation.

Just to make it clear I'm not asking about timing belts; I'm asking about the belt that's used to transfer power from the crankshaft or camshaft to the various accessories. I'm wondering whether synchronous belts (commonly called "timing belts") have been used for this purpose.Dncsky (talk) 16:21, 2 December 2012 (UTC)

I'm sure some accessories have been driven off the camshaft drive. As an extreme example, Lotus built an Esprit for Mike Kimberley that had its PAS pump driven off the camshaft. I'd also take a punt that somebody has used an ancillary as a timing belt tensioner. Greglocock (talk) 22:18, 2 December 2012 (UTC)

Thanks, I'll look into that Esprit.Dncsky (talk) 22:28, 2 December 2012 (UTC)

Toothed belts offer lower friction power loss than V-belts - so toothed belts tend to be used where the power to be transmitted is higher. Ratbone 124.182.8.228 (talk) 00:06, 3 December 2012 (UTC)

Precisely. So I'm left wondering why doesn't all the high-end automakers use toothed belts instead of the basic V-belts. A thinner toothed belts can do the job of a wider V-belt, so it can help to shave a few grams off.Dncsky (talk) 02:04, 3 December 2012 (UTC)

Not only could you save weight, you could use a sync belt longer and transfer more power. If the belt is uniformly V-shaped (or multi-V for that matter), it seems to be compressed more on its way from the crankshaft and expanded by a greater amount on its way to the crankshaft than a similar sync belt. This does not only imply more physical stress due to the greater amount of expansion, but also due to abrasion if it slips and thermal stress because part of the deformation is converted into heat, which will age the belt.

And now to the really, really bad OR part (I still think it's correct...) All of the above is over-simplified, in that it assumes that a sync belt has uniform stress at "teeth" and "gaps". It's not the pull that counts, but the pull over cross-section, and this is not uniform in a sync belt. The gaps are the weak spots of the sync belt, and more precisely, the transition from teeth to gaps.

ASCII art of a sync belt (the numbers are for reference purposes only)

   ____      ____      ____      ____      ____   
__/    \____/    \____/    \____/    \____/    \__
01234567890123456789012345678901234567890123456789
--------------------------------------------------

The "12" and "78" parts of the belt are more fragile than the rest. If there is only a slight imperfection, it will grow under stress and snap.

On top of that, the teeth per revolution of either shaft must be an integer. Sync belts could still be of use for very large engines, where thermal losses could be an issue, but I think you could go the full nine yards there and use a chain, which is even more efficient.

This is OR too, but I'd guess that the efficiency of a chain would outweigh its weight penalty in these cases. - ¡Ouch! (^{hurt me} / _{more pain}) 07:19, 3 December 2012 (UTC)

Chains are not used for things such as driving the fan, as they would cost a lot more. A chain requires lubrication, which means it need to be enclosed. V-belts give an acceptable life without any lubrication. Ratbone 121.215.26.126 (talk) 08:41, 3 December 2012 (UTC)

Thanks for your input. I'm a little lost on your "must be an integer" point though. It was my impression that vehicle accessories did not need precise timing or speed; they must be able to function over a wide range of RPMs. Dncsky (talk) 14:52, 3 December 2012 (UTC)

You cannot design cogs with, say, 23 degrees spacing. Either 24 (that is, 15 teeth per revolution) or 22.5 (16 per revolution), but nothing in-between. Thus, sync belts would introduce some constraints on the transmission ratios, and there would have to be many different belts for different shafts.

Ratbone: you're right, and these issues are less (in a percentage POV) with huge and/or expensive engines. If the engine is 10 times the weight, the added complexity (e.g. for lubrication) is not 10 times the cost. For small-scale components like the fan (which receives only a tiny percentage of the total mechanical power), it pays off to use a light-weight belt which doesn't rely on lubrication. For the primary power transfer (not "accessories"), the added efficiency of a chain, with the added benefit of lower heat buildup) could be significant. - ¡Ouch! (^{hurt me} / _{more pain}) 15:58, 3 December 2012 (UTC)

Using your example, if 23 degrees is the ideal number, but we're forced to work with 22.5 due to the teeth constrain, then the accessory will be driven 2.2% slower (0.5/22.5). But since the crankshaft goes anywhere from 500 to 5000 rpm, all the accessories must be able to handle a 10x input range as well. In that respect 2.2% is negligible. Dncsky (talk) 03:39, 4 December 2012 (UTC)

Out of curiosity, might it be possible that a little bit of 'slip' in the serpentine belt is seen as a feature, and not a bug? When you turn the air conditioner on and off, for example, you're connecting a pretty substantial load. If the a/c clutch is a bit clunky then you'd be applying a nasty jerk to the rest of the peripherals – and directly to the crankshaft – if there wasn't room for just a little bit of slip on the pulleys. Worse, what if a bearing seizes suddenly on the power steering pump? With a sync belt or chain, that sudden stop is fed back instantly to everything that's connected, with potentially expensive consequences. Could the small efficiency penalty (2-5%) operating the parasitic loads be seen as a reasonable price to save wear and tear, and to protect all the rest of the components from a catastrophic failure of one? TenOfAllTrades(talk) 15:54, 3 December 2012 (UTC)

Fungus ID

I found this fungus after a couple of rainy days, in Southern California. Can anyone identify it? 69.111.189.155 (talk) 17:20, 2 December 2012 (UTC)

Possibly Sparassis crispa, known as the 'Caulifower fungus'? Mikenorton (talk) 17:33, 2 December 2012 (UTC)

Looks like its probably a species within that genus, but I dont think it's that particular species. The species in the picture looks more "curled-up" that S. crispa. I'll ask if someone at wikiproject fungi can have a look for us. douts (talk) 00:08, 3 December 2012 (UTC)

I don't think it's Sparassis crispa, but it might be a different species of Sparassis. I highly recommend posting at Mushroom Observer, there are many California residents who frequent the site and would probably be able to id it for you. Sasata (talk) 00:27, 3 December 2012 (UTC)

Actually, it doesn't look like a fungus at all, but rather like a Slime mold. Morphology of slime molds ranges widely and fantastically, as can be seen here: [[5]]. The specimen in question resembles the sixth picture from the bottom, which is, alas, not identified. Dominus Vobisdu (talk) 00:36, 3 December 2012 (UTC)

Here's a atlas with 18 pages of pictures of identified slime molds: [[6]]. If you click on a picture, and then click on the species name after the word "Title", you end up with a page full of pictures. Dominus Vobisdu (talk) 01:37, 3 December 2012 (UTC)

+1 slime mold. Especially the way it engulfs the blades of grass, rather than pushing them aside. de Bivort 03:14, 3 December 2012 (UTC)

Battery and voltage

Can you construct a battery with any combination of voltage and material? I know that certain materials have different electromagnetic forces when loaded, but you could always 'pile' them to get a higher voltage. And in the way down, you could just put a resistance to deliver a lower voltage than the output. Strangely, I am not seeing a lithium-ion battery in the form of AAA or AA battery on that market, although I would prefer it instead of alkaline AAA/AA batteries. OsmanRF34 (talk) 18:31, 2 December 2012 (UTC)

Googling "lithium-ion AAA" and "lithium-ion AA" gets me plenty of hits. They are certainly out there in the market. You don't see them more often because their voltage is too high. Lithium-ion chemistry provides 3.6V, much higher than the 1.5V expected in standard AAA and AA cells. The higher voltage might even damage the electronics. Your idea of adding a series resistance unfortunately won't work. Consider two loads, one 1MΩ load and a 1Ω load. Whatever series resistance you add to the battery will either make the current too high or too low.Dncsky (talk) 18:42, 2 December 2012 (UTC)

Yes, you are right that google gets you lots of hits, but they are by no means a replacement to the 'normal' AAA. OsmanRF34 (talk) 18:51, 2 December 2012 (UTC)

Like I explained, there's no easy way to step the voltage down. Putting a 3.6V battery in my TV remote will likely ruin it. These 3.6V batteries are for people who design their own electronics for that voltage, RC cars for example. Dncsky (talk) 19:00, 2 December 2012 (UTC)

And what's the point of making it round like an AAA battery? Couldn't they have used a flat cell-phone battery? OsmanRF34 (talk) 19:04, 2 December 2012 (UTC)

Allowing the use of AAA battery holders, I guess? I don't see any advantage in it myself. I would never buy these, since the risk of accidentally putting them in a $200 camera is too high. The vast majority of LiPo batteries are in the flat brick type. Google imaging "lipo pack" gets me the flat rectangular shapes for the first few pages.Dncsky (talk) 19:09, 2 December 2012 (UTC)

It seems as too much trouble just for keeping a minor piece. OsmanRF34 (talk) 19:28, 2 December 2012 (UTC)

They are usable in certain devices like some LED flashlights which can accept both types (although that isn't the primary reason they are made, the market is too small for that). Anyway lithium ion cylidrical cells of various sizes are commonly used in battery packs of various products like laptops, cordless drills, eletric cars, etc. The 18650 is I think the most common size but by no means the only one used. 10440 ('AAA' size) is often used in electronic cigarette. Note that many lithium ion chemistries including the most common lithium cobalt oxide are less flexible in manufacturing then the Lithium polymer battery chemistry so producing flat packs with them isn't so easy. (Anything which looks like a flat pack but has non polymer chemistry most likely just has a bunch of cylindrical cells.) AFAIK cylindrical cells are by far the most common production method for such non polymer chemistries. And when you aren't aiming for excellent packing like in phones, tablets and ultrabooks, the minor amount of wasted space isn't a big enough issue to be of concern. (There are other advantages of lithium polymer cells.) And lithium cobalt oxide still I think predominates among lithium ion chemistries (including polymer). So while lithium polymer batteries are rarely cylidrical, most lithium ion cells produced are likely cylidrical. While you can purchase individual cells included protected ones (with a small protection circuit on top), this is a market which developed for certain specialist hobbyist uses. The cylindrical cells aren't really intended for the end consumer, instead to be used in battery packs for devices or sometimes built in to the device. (And if you are using such lithium ion batteries, putting them in the wrong device and destroying the device should really only be a minor concern compared to the other precautions you have to take.) P.S. Generally speaking, it's best to avoid anyone who sells 'AA' or 'AAA' lithium ion cells. These would generally be called 14500 or 10440 by anyone who you should trust enough to buy such cells from. Nil Einne (talk) 20:18, 2 December 2012 (UTC)

If you want a voltage not available from a standard commercial battery, use a switch mode power converter. This is often done, in order to use an old battery powered device that was designed to use a battery no longer available - e.g., portable scientific instruments, multimeters, and gieger counters that were designed to use 22.5V and 45V batteries designed for 1940's and 1950's hearing aids and portable radios based on tubes instead of transistors. Such instruments were made up until the 1970's when the batteries were still available, and many are still perfectly serviceable. Because modern batteries have a much higher energy density, by using a physically smaller modern battery it is possible to fit both the battery and the switchmode converter in the space provided for the original battery. Keit 58.167.254.96 (talk) 00:02, 3 December 2012 (UTC)

Since nobody else has mentioned it, I'll point out Energizer Lithium-Iron batteries which retain the familiar carbon zinc (are they still made?) sizes, from AAA to 9 volt, I believe. [7]Gzuckier (talk) 07:01, 3 December 2012 (UTC)

As our Zinc–carbon battery article mentions, zinc-carbon batteries are still made and in fact are resonably common in some countries. Lithium-iron primary batteries are mentioned in our Lithium battery article, however the sizing issue isn't the key point. As the above discussion attests, lithium iron (rechargable) batteries are made in the same sizes. However they aren't suitable as replacement in most uses because the devices because the voltage range is quite different from what is provided by most primary cells in those sizes. (They aren't generally sold to consumers for these and other reasons.) Lithium iron batteries have a similar enough voltage range to those in common primary cells that they are generally compatible. Nil Einne (talk) 07:38, 3 December 2012 (UTC)

what are the specific enthalpies of fusion of the chocolate phase transition temperatures?

I think it will be weak compared to water, but I wonder if the phase transition energy can make up for the lack of an precise thermometer when melting chocolate (while preserving the beta crystals) for use in dessert simply by watching where the temperature rise slows down. 128.143.1.238 (talk) 20:15, 2 December 2012 (UTC)

Can you back up and tell us exactly what you're trying to do with chocolate ? If trying to melt it without burning, I recommend a double boiler. If you want a mixture of solid and liquid chocolate, toss some chocolate chips in the dessert, along with the melted chocolate. StuRat (talk) 20:17, 2 December 2012 (UTC)

I'm trying to melt chocolate without melting the beta crystals so I don't have to temper it. 128.143.1.238 (talk) 21:37, 2 December 2012 (UTC)

OK, here's an article that explains the issue: [8]. I'd simply use one of the products sold specifically for this purpose. That is, chocolate with additives so it will properly harden and form a shell, without the precise temperate control needed for 100% chocolate. (Do be sure to avoid trans-fats, though, as those are unhealthy.) One such product is Magic Shell. StuRat (talk) 22:02, 2 December 2012 (UTC)

Goggling on this question, I happened upon an answer: 93 kj/kg given on an engineering forum here. -Modocc (talk) 23:35, 2 December 2012 (UTC)

The birds and the bees

spam
The following discussion has been closed. Please do not modify it.
How is babby formed? Jessqueen99 (talk) 22:01, 2 December 2012 (UTC) See sexual reproduction, gestation, blastocyst, embryo, and fetus. StuRat (talk) 22:04, 2 December 2012 (UTC) There's also fertilization, zygote, implantation and gastrula, as well as several hundred other relevant concepts. μηδείς (talk) 02:10, 3 December 2012 (UTC) Not to mention babby.--Shantavira|feed me 09:13, 3 December 2012 (UTC) This is a popular internet meme, and should be deleted as spam. This is not an honest question, the OP is having a joke by posting this here. OP, don't do this. "How is a Babby Formed?"[[9]] — Preceding unsigned comment added by 217.158.236.14 (talk) 10:11, 3 December 2012 (UTC) Closed per IP 217's explanation. μηδείς (talk) 17:32, 3 December 2012 (UTC)

Placebo overdose

What happens when you overdose a placebo? OsmanRF34 (talk) 23:28, 2 December 2012 (UTC)

That could mean 2 different things:

1) An actual overdose, say of sugar pills. That wouldn't be terrible, unless they have diabetes, but would cause their blood sugar to spike.

2) Tell them they took too many. In this case, they could possibly will themselves into getting sick. StuRat (talk) 23:49, 2 December 2012 (UTC)

I mean 1). Under placebo I mean something without active components (that wouldn't be the case of sugar in people who have diabetes). Why wouldn't it be terrible? Placebo is something without active components, but it, for some mysterious reason, has a real effect in some people. Wouldn't a big dose of that have a bigger effect. OsmanRF34 (talk) 00:20, 3 December 2012 (UTC)

Not really, since a placebo, by definition, has no pharmalogical effect. All that occurs is a psychological effect, in other words, they think themselves into getting better so I wouldn't have thought that a bigger dose would result in a bigger effect. douts (talk) 00:25, 3 December 2012 (UTC)

I don't agree that placebos are just psychological. They have a real effect on your body, although the relationship between believing and physical effect is not well-known. OsmanRF34 (talk) 00:38, 3 December 2012 (UTC)

There have been studies showing that a larger dose of placebo has a greater effect (or, at least, the physical size of the pill does - that's all that is mentioned in our article, and I think my source is QI so that may be all they meant). I think they would need to know it was "an overdose" - obviously there is no such thing if it's just an inert substance, so it can't be a real overdose. If they did know, then a psychosomatic illness (or, more accurately, a somatoform disorder type illness) could easily result. --Tango (talk) 01:10, 3 December 2012 (UTC)

• Are you suggesting the subject has willfully "overdosed" on something he has be prescribed as a placebo? If so, are we to assume he hasn't looked on line to find out how much sucrose (or sawdust) he needs to take to kill himself? Can you be more specific? Thanks. μηδείς (talk) 02:05, 3 December 2012 (UTC)

It is quite possible to be prescribed a drug that has an active ingredient that works as a placebo, as the placebo effect is psychological. See also the nocebo effect. I don't feel it is possible for the lay person to know whether the drug is working because the brain thinks it should work, or whether there is an actual physical effect on the body. So be very careful. --TammyMoet (talk) 10:26, 3 December 2012 (UTC) See this report in the New Scientist which claims that some drugs work by amplifying the placebo effect. --TammyMoet (talk) 10:27, 3 December 2012 (UTC)

The physical size of the placebo matters? Oh no! I've been taking these really small (two millimeter long) placebo pills against catching the cold for a long time. No wonder they didn't work. I'll have to go find larger pills then. – b_jonas 23:11, 4 December 2012 (UTC)

• A beautiful example of placebo effect came up in a test of a drug, sevelamer hydrochloride, for pseudoxanthoma elasticum. [10] The patients receiving the drug experienced significant improvement. More surprisingly, the patients given the placebo did better. It turns out that the pills contained magnesium, and the placebo contained 2.5 times more magnesium than the pills with the drug. And the disease, which is caused by calcium phosphate (apatite) deposition, happens to respond well to administration of magnesium, which helps break up the aggregates and thus to dissolve the deposits. Magnesium overdose is actually possible, though unlikely, with that placebo. Wnt (talk) 02:07, 5 December 2012 (UTC)

December 3

Chromosomes Question

I apologize if this is a stupid question, but are the chromosomes of every human being different? Also, in regards to the chromosomes in cancer cells, these chromosomes are always duplications or alterations of one or more of the (original) chromosomes of the human being where this cancer now resides, correct? Futurist110 (talk) 03:40, 3 December 2012 (UTC)

Since the genes of every human being are different, the chromosomes (the material that contains the DNA within it) must also be different. Wikipedia has a (fairly poor) article titled Genetics of cancer which has a little bit of information for your second question. --Jayron32 04:13, 3 December 2012 (UTC)

The one exception is identical twins, who, theoretically, could have identical DNA. However, even though they may start out identical (or nearly so), there are subtle changes in the DNA which occur throughout our lives, such as telomere shortening (based partly on the environment), causing twins to slowly diverge. In fact, your DNA isn't even completely identical from one cell to the next, due to oxidation damage, etc. StuRat (talk) 06:22, 3 December 2012 (UTC)

BTW, in case there is any confusion on the part of the OP, Genetic recombination in the form of Chromosomal crossover during Prophase I of meiosis means that the each chromosome is different, people do not inherit chromosomes wholesale from their parents. (Chromosome abnormalities as discussed below in some cases arise from problems occuring during crossing over.) Edit: So yes, those genetic differences reflect differences in chromosomes (genes which are close together in a chromosome will not be inherited independently hence genetic linkage). Probably should also mention independent assortment. See also Mendelian inheritance. (End edit.) Even sex chromosomes generally undergo limited crossing over (mentioned in our article on meiosis and discussed in more detail at Pseudoautosomal region). Nil Einne (talk) 18:44, 3 December 2012 (UTC)

Most humans have the same number of chromosomes in most of their somatic cells - 23 pairs, so 46 altogether. What differs from one human to another is the contents of those chromosomes - the genes. A small proportion of humans have a non-standard number of chromosomes, usually due to a chromosome abnormality such as Down Syndrome or Turner syndrome. Chromosome abnormalities such as aneuploidy (having an abnormal number of chromosomes) are also often found in cancer cells, although I am not sure whether they are considered a cause of the cancer or a side-effect. Gandalf61 (talk) 10:39, 3 December 2012 (UTC)

Generally speaking, widespread chromosomal abnormalities – multiple translocations and changes in chromosome number with this sort of ugly karyotype – are a consequence of the overall genomic instability associated with cancer, caused by a combination of loss of cell cycle checkpoints and failure of mechanisms associated with DNA lesion detection and repair. (Of course, this instability increases the heterogeneity of the population of malignant cells, increasing their likelihood of accumulating further harmful mutations and developing drug resistance.)

On the other hand, there are certainly a few specific chromosomal abnormalities that are linked to cancer. The so-called Philadelphia chromosome is probably the canonical example; this translocation of parts of chromosomes 9 and 22 produces an oncogenic fusion protein that is the primary cause of chronic myelogenous leukemia. TenOfAllTrades(talk) 14:31, 4 December 2012 (UTC)

• In theory, with a drop of blood from a crime scene, you should be able to clone segments of DNA (by polymerase chain reaction) from regions of V(D)J recombination, which have undergone said recombination (by choosing a short length, which amplifies better anyway). If you know the blood came from one of two identical twins, you could see if the prevalence of B cells matches one twin better than another, which is likely, since each event is random and which events prevail depend on prior exposure to antigens throughout life. I have no idea if this has ever seen a courtroom; you'd probably be paying someone's salary for three months to get the test done and half the time they can't be bothered to do even a simple DNA match for a case. Wnt (talk) 02:01, 5 December 2012 (UTC)

Are there any blood vessels in the skin? (Skin = Epi, Dermis, Hypo)

thanks. — Preceding unsigned comment added by 109.64.163.33 (talk) 04:06, 3 December 2012 (UTC)

See the Wikipedia article titled skin. --Jayron32 04:11, 3 December 2012 (UTC)

Capillaries, certainly, or you wouldn't bleed when you prick your skin. Unless you have spider veins or varicose veins, you probably don't have much larger blood vessels in your skin. StuRat (talk) 06:18, 3 December 2012 (UTC)

Bicameralism (psychology)

Is this idea accepted as plausible by psychologists, or almost scholars of ancient literature? It seems extraordinary to claim that people were not conscious 3000 years ago, yet I can't find much about how mainstream this idea is. --140.180.249.151 (talk) 06:44, 3 December 2012 (UTC)

"Is this idea accepted"? No. Is it mainstream? No. If it was there'd be more recent discussion of the question. The scholarly consensus is probably that human cognitive abilities have changed little over the last few millennia - but if it has, it may well have deteriorated, for environmental rather than genetic reasons. AndyTheGrump (talk) 07:05, 3 December 2012 (UTC)

Thanks for your answer. I didn't know what the most recent discussion of the question was, being completely unfamiliar with psychology. But I do think human cognitive abilities have improved drastically due to increased education, better living standards, and a more advanced world--this is reflected in the Flynn effect. --140.180.249.151 (talk) 18:22, 3 December 2012 (UTC)

Looks like total BS to me. Very little evolution occurs in 3000 years, certainly not enough to change the core nature of the human mind. StuRat (talk) 07:46, 3 December 2012 (UTC)

To my knowledge, Jaynes did not hypothesize that genetic evolution played any part in the breakdown of bicameralism. Rather, his thesis is more reminiscent of the evolution of memes, which was curiously proposed in the same year as bicameralism. Someguy1221 (talk) 09:52, 3 December 2012 (UTC)

This bicameralism theory is from 1976, the meme theory was popularized by Dawkins in a publication of the same year, but it's much older. OsmanRF34 (talk) 17:53, 3 December 2012 (UTC)

Bicameralism is somewhat akin to the Aquatic Ape Hypothesis in that both are not properly scientific due to being untestable (so far as is known). For that reason alone, beyond whatever anyone actually thinks of these concepts, they're never going to be widely accepted. On the one hand, they are very tempting because they appear to answer so many profound questions at a stroke, while on the other there is frustratingly little rigorous evidence. Matt Deres (talk) 22:42, 4 December 2012 (UTC)

Binary Black Holes

This is a long one.

Let us assume that we have an observer O, a distant star S, and a Black Hole H between S and O. Thus the light going straight towards O will enter H; however, due to H's gravity, light can go around H in an arc. Within a plane, there are two solutions: one arc goes through X, and one goes through Y.

ASCII art:

. S'
.
.
.              X
.
.S             H             O
.
.              Y
.
.
. S"

So there will be two apparent stars S: at locations S' and S". In the 3D case, O will see a ring with H and the true S at its center (although they won't see H or S). S' and S" will be red-shifted equally in that case, and the amount of redshift will depend on the escape velocity of S and the celestial body O is on. Which can even be negative if, say, S is an asymptotic Red Giant and O is on Mercury (planet) deep within the Sun's gravity well. But whatever, S' and S" will have the same spectrum.

So far, so good. Now let us assume that H is not a single, but a binary Black Hole, rotating clockwise within the plane shown above. Both equal mass, centered at H. I'm interested in the spectra in that case.

My friend argued that because the Black Holes emit gravity waves, S" will have a lower redshift; "its" light passes through Y and hits the gravity wave head-on, which will compress the wave. OTOH, the light from S' will pass through X and move in the same direction as the gravity wave; there will be no collision at all, thus the full redshift will be observed.

I suspect that that's wrong, and that the true way of interaction is completely different; that light does not get compressed like some kind of spring. I have the feeling that S" would exhibit the highest redshift, because the gravity wave takes some momentum from the light when it passes through Y. S' would be the other way around; it would gain a comparable amount of momentum, and thus the wavelength will be the shortest.

Bonus question: Is X or Y closer to H? (I'd guess X, because light passing through X gains momentum, which helps escape the gravity well - thus the light which passes X can make the closer pass and still escape at all).

Is the effect significant? From what it looks like, it takes not only a binary Black Hole, but a quite massive pair, lest the orbit size be negligible to the distances H-X and H-Y. So I guess the pairs which do exist are unlikely to exhibit a significant asymmetry. - ¡Ouch! (^{hurt me} / _{more pain}) 10:13, 3 December 2012 (UTC)

You may get an effect from a massive spinning black hole using the Kerr metric. An orbiting pair would have s similar effect. However the light rays will have to pass fairly close. If a binary black hole merges into one a significant fraction of mass is converted to gravitational waves, and as they pass your observer O space can be shifted permanently. I expect that this will cause a temporary red or blue shift. Using gravitational waves observers also hope to see variations in pulsar timings. Graeme Bartlett (talk) 10:42, 3 December 2012 (UTC)

Thanks. Kerr metrics seem to support my point, at least as far as the light paths and the X, Y points are concerned. Particles gain or lose momentum as I predicted, but will that effect red/blueshift light? - ¡Ouch! (^{hurt me} / _{more pain}) 16:06, 3 December 2012 (UTC)

shifting of the frequency could happen if the observer or source are near the black hole(s) so that they are in the gravitational potential well, and then experience gravitational red shift. But it do not see that one side of the gravitational arc would be shifted differently to the other. The gravitational potential for emitter and observer should be roughly constant for the light traveling via different parts of the arc. Graeme Bartlett (talk) 20:22, 3 December 2012 (UTC)

Let's assume that S and O are at the same distance from H. - ¡Ouch! (^{hurt me} / _{more pain}) 08:04, 4 December 2012 (UTC)

Then the gravitational potential due to the black-holes would be the same, no extra gravitational red-shift. Graeme Bartlett (talk) 09:57, 5 December 2012 (UTC)

Origin of Intelligence and Mental Illness Linked to Ancient Genetic Accident

Or so claims this article. The claim is so sweeping I find difficulty in even taking it seriously. What do you think? --Halcatalyst (talk) 12:32, 3 December 2012 (UTC)

It looks like they just reprinetd the University press release [11], which can often be pretty far off the mark. I don't have access to anything other than the abstract of the original paper [12], but that is the place to look for the real (although harder to read) version of the story. 209.131.76.183 (talk) 12:40, 3 December 2012 (UTC)

The role of paleopolyploidy in vertebrate evolution has been known for some time. Most of our genes form a group of up to four different versions that trace back to that event. As a result, double and triple knockout experiments like this are important. This one focused on a single set of genes, Dlg1, Dlg2, Dlg3, Dlg4, and their effects on some touchscreen tests. The university publicity office took that and spun it in a weird way. Note that when the whole genome duplications actually happened, the animals at the time might have seemed bigger or had some other simple differences, but since the genes were all the same these effects would be no more sophisticated than for any other single mutation with pervasive effects. It was not a recipe for instant brilliance. Wnt (talk) 21:16, 5 December 2012 (UTC)

relationship between conductivity and mean free path

This is a very basic formula found in most textbooks, but I don't have my textbook and the absurdity of this simple relationship not being on Wikipedia is aggravating me. Where can I find it? 128.143.1.238 (talk) 13:44, 3 December 2012 (UTC)

Are you referring to thermal conductivity or electrical conductivity? douts (talk) 13:52, 3 December 2012 (UTC) Not sure if it's of any use, but a quick Google search found this paper [[13]] entitled "Calculation of the thermal conductiwity and phonon mean-free path" douts (talk) 13:57, 3 December 2012 (UTC)

Thermodynamics of a microwave

Why is there no heat or work transfer in a microwave heating something or a microwave being used for radiotherapy or sterilising? Thanks. — Preceding unsigned comment added by 138.253.210.27 (talk) 16:32, 3 December 2012 (UTC)

I'm not sure I understand what you're asking here. Heat transfer does occur in a microwave - the water in the food is heated by the microwaves, cooking the food. Microwaves generally aren't used for sterilising objects - normally either gamma rays or temperatures above 200 degrees centigrade are used. If I've mis-understood the question please let me know. douts (talk) 17:03, 3 December 2012 (UTC)

Less than 200 °C is enough, as it's the case of an autoclave. OsmanRF34 (talk) 17:30, 3 December 2012 (UTC)

About 125 °C in a saturated steam environment, a bit more (I've used 160-180ish before) in a dry environment. Fgf10 (talk) 18:37, 3 December 2012 (UTC)

Watertight compartments

• Ship floodability

Watertight bulkhead compartments were written of by the Song Dynasty Chinese author Zhu Yu, in his book Pingzhou Table Talks of 1119 AD (written from 1111 to 1117 AD). Watertight compartments were frequently implemented in Asian ships, and had been implemented in the warships of Kubla Khan.[2][3][4] Chinese sea-going junks often had 14 crosswalls, some of which could be flooded to increase stability or for the carriage of liquids.

Anyone can build wood ships with watertight compartments. However, without watertight doors, the compartments are not very useful. You probably have to install many trapdoors on the deck for each compartment so you can climb up to the deck to go to another trapdoor.

I really don't think it's easy to build watertight doors on a ship made by wood. How did Chinese inventors solve this problem? -- Toytoy (talk) 16:36, 3 December 2012 (UTC)

I don't know about the Chinese but pitch can be produced from plant material and has been used for many watertight application in the past. The introduction of the linked articles talks a little about it. Dauto (talk) 17:07, 3 December 2012 (UTC)

Don't know if this is the case, but could it not be that the space between the keel (if they had one) and the lowest deck was compartmentalised? So as to compartmentalise at least part to the buoyant volume. In that case the habitable decks wouldn't need watertight doors. Lower compartments could easily be sealed with something like pitch, as suggested above. Fgf10 (talk) 18:36, 3 December 2012 (UTC)

Also note that the watertight compartments don't need to be 100% waterproof, from the top. Say the boat is swamped by a rogue wave. You only need to keep it afloat long enough to bail out most of the water. If some water leaks into the watertight compartment in that time, it's OK, so long as the boat doesn't sink before you can bail it out. StuRat (talk) 18:42, 3 December 2012 (UTC)

Yes, with very primitive watertight compartments, you can still buy time to plug the hole and let the sailors bucket brigade the compartment dry. Without compartments, you're dead with the fish.

However, doors made of cheap wood can be very imprecise. They they can absorb moisture. Unless you pay big money for really good woods and treat the parts with tung oil, I don't think it was a good idea to build doors between compartments. -- Toytoy (talk) 04:18, 4 December 2012 (UTC)

Neutron decay and atomic weapons

So I was just watching this video, http://www.youtube.com/watch?v=o_EBqZPCZdw

And the guy in the video (thunderf00t) said that a neutronium bomb would be very destructive but wouldn't release its energy all at once, but rather over the course of 10-14 minutes because that's the time it takes neutrons to decay (10 minute half-life, 14-15 life-time).

Well in a fusion reaction, about 80% of the energy released is in the form of high energy neutrons, and that made me think of the tsar bomb. According to the article, the bomb was tested without a uranium 3rd stage so almost 97% of the energy released in the test came from fusion alone. But yet the explosion came all at once, instead of being spread out, continuously exploding for 10-14 minutes. I thought about this, and I reasoned that it must have been due to the lead tamper they used to absorb the neutrons. So I thought about the neutron bomb. If the tamper were made out of nickel or chromium, allowing the neutrons to escape, would the explosion be spread out over the course of 10-14 minutes like the video suggests would occur? ScienceApe (talk) 17:47, 3 December 2012 (UTC)

All neutrons will quickly lose their energy due to scattering off atomic nuclei in the air/water/soil. Then a significant part of the neutrons will be absorbed by some nuclei. The energy that will be released as by radioactive decay of the remaining neutrons is quite small. Ruslik_Zero 19:28, 3 December 2012 (UTC)

Note that even if neutrons did behave that way — that is, they went until the end of their "life" and then decayed to release their energy — their energy would be incredible diffuse. D-T fusion neutrons travel at a speed of 52,000 km/s; if they survived for 10 minutes they'd be well, well outside the radius of the planet by the time they decayed! It doesn't work that way, obviously. As for the tampers, they do matter with regards to what happens to the neutrons; neutron bombs are just hydrogen bombs where the fusion neutrons are given a direct route outside of the bomb without being use either for fissioning or for just thermal energy. They still all come out in one burst, and still matter for only a fraction of a microsecond. --Mr.98 (talk) 00:25, 4 December 2012 (UTC)

Also note that even if 80% if the energy were in the radioactivity of neutrons (which is false; much of that energy is kinetic), the initial 20% would equal the first ~4 minutes of decay. Even then, the explosion would hardly be a continuous glow.

Also note that enhanced radiation weapons ("neutron bombs") were not designed to be less physically damaging. The physical effects are somewhat less than those of older nukes of that size, but not by an order of magnitude. They were designed to inflict higher overall damage against armored targets, and since those resist physical force quite well, they maxed their neutron radiation rather than their TNT rating.

Don't know for sure about mean free path of neutrons, though. I doubt many would escape Earth. I would think though that most of them would have been captured by one nucleus or the other, within seconds. - ¡Ouch! (^{hurt me} / _{more pain}) 08:01, 4 December 2012 (UTC)

Why issue placebos to control groups for objective treatments?

Reading placebo effect, I saw "The placebo effect is highly variable in its magnitude and reliability and is typically strongest in measures of subjective symptoms (e.g., pain) and typically weak-to-nonexistent in objective measures of health points (e.g., blood pressure, infection clearance)." (Yes, I saw "citation needed", but is the statement really indefensible?). I wonder, if it's an all-but sure bet that sugar pills are *not* really going to be effective against a given cancer, why do testers still do controls with them? It seems about as likely for a control group taking sugar pills to see effective cancer treatment in any of the control group subjects as would be if the control group held water balloons. Is the only purpose in objective (not asking patients how they feel) placebo-using trials to have double-blind studies to keep the doctors honest and from tampering with administration protocols, such as giving more to patients they know are on the real thing so there's a better chance to have success and continued funding? 20.137.2.50 (talk) 18:01, 3 December 2012 (UTC)

The idea is to make the differences between control and test group as small as possible. The placebo effect is a complex thing, for instance, speaking to a doctor will often also have a beneficial effect. By making the control group as close as possible to the test group, you can rule out as much as possible any effects not due to the drug being tested. An other aspect is that without placebos it would be easy to determine for the trial doctors which group is control, and it's then easy to subconsciously treat both groups differently in for instance bed-side manner. It has been shown (bear with me while I hunt for a ref) that a drug given with a positive talk by the doctor will have a better effect than the same drug given with a disparaging talk. Just to rule out effects like that, we do double-blind placebo-controlled trails. Fgf10 (talk) 18:33, 3 December 2012 (UTC)

Blood pressure is something I'd expect to respond to placebos, since just relaxing can change it, and somebody thinking they just took some good meds might be more relaxed. Also note that many meds are approved even though they only have a slight benefit, like in 10% of the patients. So, even a tiny placebo effect could have a major effect on such results. StuRat (talk) 18:37, 3 December 2012 (UTC)

A sugar pill with a smile can rival an alpha blocker with a frown in terms of effectiveness? 20.137.2.50 (talk) 18:53, 3 December 2012 (UTC)

Maybe - but it's certainly possible that a sugar pill given by a guy in a white lab coat with a stethoscope casually draped around his neck who says "This is an absolute wonder-drug - it's the latest thing and it'll fix you up for sure" - is more effective than an alpha blocker handed to you by an intern who says "I'm this probably isn't going to help, but please take it anyway.". In the case of blood pressure - where stress is a known cause - it's quite obvious that making the patient think that they'll be cured will reduce their stress and therefore help their blood pressure to go down. But there are other placebo effects where the link is not at all obvious. It's been shown that weight lifters can lift more weights if given a course of sugar pills that they are told are really steroids...people who are told they are drinking alcohol when they are not will show signs of intoxication. It's a weird set of effects going on here. SteveBaker (talk) 17:57, 4 December 2012 (UTC)

As others have stated, placebos can actually have an effect in patients even in cases of cancer. In fact the American Cancer Society has a long discussion of placebos [14] and while it doesn't mention cancer that much it's a good read if your understanding of the placebo effect is poor. [15] and [16] may discuss the placebo effect and cancer somewhat although I haven't actually checked the articles. As Fgf10 said, there are also other advantages to having a placebo, namely in preventing differences in the interaction between the patient and other people. In other words a placebo or something similar makes it possible to do a double blind which is generally considered the gold standard in medical research. However I would note that not all double blind trials are placebo controlled, as our Blind experiment and Clinical trial mention, it's also common to use existing medicines for the condition being treated. Nil Einne (talk) 20:16, 3 December 2012 (UTC)

I'll look at those sources promptly. But I'm impatiently curious; do those papers even hypothesize what could possibly be going on (in terms of chemistry) in any single case where someone taking a placebo sees a significant improvement in their cancer treatment? 67.163.109.173 (talk) 22:30, 3 December 2012 (UTC)

BTW the Declaration of Helsinki article which is linked from the clinical trial article goes in to a fair amount of detail about the controversy surrounding the usage of placebos when existing treatment exist. Nil Einne (talk) 20:44, 3 December 2012 (UTC)

In a case like that, I'd think using an existing med instead of a placebo would make sense. You would then compare the results to find out if the new med is better than the old med. StuRat (talk) 20:51, 3 December 2012 (UTC)

Yes definitely, when an effective treatment exists for a specific disease, the control group will most likely receive the current treatment, not just a placebo. You aren't necceserily trying to find out if a new treatment is just better then a placebo, you're trying to find out if it's better then the current treatment. Of course "better" might not just be efficacy, it could also be cost, side-effects, how invasive the treatment is, etc... But in most cases where a treatment already exists, it would be considered unetihical to withold it for the purposes of research. Vespine (talk) 21:58, 3 December 2012 (UTC)

As I mentioned in my post I was replying to with references to our articles, that is often done. But as the Helsinki article attests and Vespine mentioned even if it's generally regarded as unethical to withold an alternative existing treatment (although there is some dispute in cases when the consequences and risks aren't high), that doesn't stop it happening particularly in the developing world. (In case there's still some confusion that's the primary reason I brought the Helsinki article in to the mix after already mentioning that it's common to use an existing medication when one exists instead of a placebo.) Nil Einne (talk) 00:43, 4 December 2012 (UTC)

which brings up my nagging question; if we reject a treatment that is no better than placebo, but we don't give patients placbos, aren't we therefore undertreating them? Gzuckier (talk) 18:35, 4 December 2012 (UTC)

Because a measured placebo effect is NOT just 'one' thing. It's not, as most people naively assume, a real physiological change in the patient which improves their condition, or at least it's MOSTLY not that. A placebo is everything except the effect of the substance you are trying to test. That does include things like how the patient reports their condition, but it also includes things like regression towards the mean, statistical bias, reporting bias, experimenter's bias, etc.. Vespine (talk) 02:51, 5 December 2012 (UTC)

good point. Gzuckier (talk) 06:12, 5 December 2012 (UTC)

The placebo effect article raises two other important issues with administering placebos as medicine. One being that it would be pretty much impossible without a degree of deception on the doctor's part, which is problematic; the second being that placebo effect is neither consistent or reliable. Not that any medicine is 100% consistent or reliable, but placebo is, pretty much by definition, the very least consistent and reliable treatment available. Vespine (talk) 21:50, 5 December 2012 (UTC)

Global warming

Is there a way of identifying exactly whether a certain CO2 molecule was created by man or naturally made? Could this identify whether global warming is caused by man or occurring naturally? I've heard that Carbon isotopes can identify CO2 which has been produced by burning fossil fuels but is this an accurate test? Thanks. 138.253.210.27 (talk) 18:01, 3 December 2012 (UTC)

No. A particular CO₂ molecule will contain the carbon-12, carbon-13, or carbon-14 isotope, with the first 2 being stable, and carbon-14 being unstable with a half-life of around 5,730 years. So, if it contains carbon-14, the chances are that it's not a fossil fuel from the age of dinosaurs. However, the molecules containing carbon-12 or carbon-13 aren't necessarily "old", as only 1 in a trillion carbon atoms is carbon-14, even in new CO₂. But, if you look at a large sample, then the ratio of carbon-14 will tell you something about the average age of the carbon molecules.

But now for the complication: carbon-14 is being continually generated in the upper atmosphere: [17]. So, the carbon-14 we find up there might be generated in that way, from carbon from burnt fossil fuels, or it might be from wood somebody burned, or it might be from what a human or other animal exhaled. And, of course, the carbon-14 generated up there doesn't stay aloft, it moves throughout the biosphere. StuRat (talk) 18:19, 3 December 2012 (UTC)

(edit conflict) No, not by individual CO2 molecules. However, that doesn't mean that reliable correlations cannot be drawn to decide if the bulk of CO2 molecules is not from man-made sources. To take an analogy: Imagine you're watching a New York City street and every single person is an exact clone, with the exact clothes. Now, imagine you can only take snapshots of the street, so you don't see people moving, but you can count the number of people at any given time. You don't know where each individual person comes from, but you can correlate the number of people on the street with certain times of day, and you can also correlate other events that occur at those times, so you can say that the increase of people on a specific street at a specific time may be due to a train arriving at a nearby subway stop. You don't need to see the people get off the train to consider that a reasonable conclusion. You don't even need to know which specific people got off the train, the fact that there are more of them at the same time every day, immediately successive to the train arriving, is enough to establish the reasonable conclusion that some of those people got off the train. It's the same thing with CO2 increases. You don't need to know which CO2 molecules came from, say, a volcanic eruptions and which come from burning coal. We know that some increase in CO2 is going to come from burning fossil fuels, because it is patently obvious to anyone with a high school chemistry level knowledge of combustion that burning hydrocarbons makes CO2. We don't need to watch each CO2 molecule individually from the moment it formed and track each one to know that, in the bulk, burning more stuff makes CO2, any more than you need to track every pedestrian to know that the number of people on the street will increase after the train arrives. --Jayron32 18:25, 3 December 2012 (UTC)

• There's another aspect to this. As our article on isotopes of carbon points out, plants take up ¹²C in preference to ¹³C, and that preference carries over to fossil fuels. The main sources of atmospheric carbon are fossil fuel burning, respiration, and volcanoes. Volcano-derived carbon has a different isotope ratio than biologically generated carbon -- this ratio is known as δ¹³C. There is also a smaller difference between carbon derived from fossil fuels and carbon derived from recent respiration, because of differences in the atmosphere when the fossil fuels were created. Looie496 (talk) 18:49, 3 December 2012 (UTC)
• The effect of fossil fuel burning changing the isotopic ratio of carbon in the atmosphere is known as the Suess effect and was first described in 1955, when its influence on radiocarbon dating was noted. That said, we have many additional lines of evidence that the increase of CO₂ is anthropogenic. The simplest is basic chemistry. We (roughly) know how much fossil fuels we burn, and hence how much CO₂ we emit. We also can measure the amount of CO₂ in the atmosphere. The increase in atmospheric carbon dioxide corresponds to roughly half of what we release (much of the rest is absorbed by the oceans). We can also see a corresponding decrease in atmospheric oxygen. Note that the question of where the CO₂ comes from is different from the question of what its effect is. That said, the spectroscopic properties that give rise to the greenhouse effect have also been known for more than 100 years and the effect of adding carbon dioxide was first quantified by Svante Arrhenius around 1900. --Stephan Schulz (talk) 20:41, 3 December 2012 (UTC)

Travelling to star

Scenario: I pick a star 100 million ly away to travel to. And i can get there because i can live forever. the star is on the very ege of a galaxy 200,000 ly across. When i plug the coordinates of the star into my space craft, HAL, will i travel in a straight line and wind up possible 200,000 ly off my mark? or will i have to adjust my course as i get closer? or something else?165.212.189.187 (talk) 18:40, 3 December 2012 (UTC)

No, if you travel in a straight line at a star on the other side of the galaxy, when you get there the star will not be there, because the galaxy is in motion: it is moving relative to where it is now in several ways, it is rotating about an axis, and it is moving in a line away from other galaxies. You would need to aim for where the star will be when you plan to arrive, based on where the star is now and where it will move over the course of your trip. This is not trivial, because a) the star is not now where you see it (because light takes time to travel) and b) the star's location needs to be calculated taking into consideration a) your current motion b) the stars motion and c) the complete motion, including acceleration, deceleration, and top travel speed, of your spaceship. This is all hypothetically possible to calculate, so other than the tricky math, there's nothing wrong with calculating a straight line path that should make you arrive at the same point in spacetime as that star some place in the future. --Jayron32 18:52, 3 December 2012 (UTC)

And this is similar to planning trips within our own solar system, although the other planets are within a few minutes or hours of where they appear to be. If it's a round trip, that makes it even more complex. StuRat (talk) 19:26, 3 December 2012 (UTC)

Or you could just program your ship's computer to adjust your course every (insert period of time here), so that as you get closer, the error factor will be reduced with each course change. douts (talk) 19:03, 3 December 2012 (UTC)

You'll have to compensate continually for the near infinite number of disruptions from gravitational influences along the way. Fgf10 (talk) 19:21, 3 December 2012 (UTC)

Practically yes, but hypothetically, if you could keep track of the entire galaxy in a single computer, and reliably predict the entire gravitational field of the galaxy, as well as changes to that field over time, you could hypothetically have all those corrections made before the trip. That is, any corrections made to your trip would come from incomplete knowledge rather than anything which is physically impossible to know. Any corrections made along the course due to incomplete knowledge could be corrected before the trip if the information had been known ahead of time. --Jayron32 19:24, 3 December 2012 (UTC)

I don't think that's even theoretically possible. That is, storing the location and vector of every atom in the universe would require a computer made of more atoms than the universe. There's a thought experiment along these lines, but I forget the name. Of course, if your margin for error is large enough, like a solar system, no corrections may be needed. If, on the other hand, your goal is to dock with a spaceship in that solar system, then corrections will be required at some point. StuRat (talk) 19:31, 3 December 2012 (UTC)

Well, I suppose yes, you are correct. The question is when the corrections need to be made: constantly along the way, or only at the end. I think the analogy of the airliner is appropriate: Airplane pilots basically aim their plane at the airport and don't adjust much during the length of the trip: autopilot is capable of keeping the plane on the correct course, usually a fairly easy-to-calculate great circle course (the Earth equivalent of a straight line), and the pilots only need to be involved in the take off and landing portions. For most of the trip, the pilots don't do much except monitor the plane to make sure nothing goes wrong. For a properly working plane, 99% of the trip doesn't need any adjustments at all. Hypothetically, traveling to a distant star should involve a similar level of involvement: aim and fire, and then adjust the final destination when you get close. You aren't likely to end up ridiculously off course if the proper calculations are made ahead of time. --Jayron32 19:39, 3 December 2012 (UTC)

Are you sure that autopilot isn't making tiny corrections all along ? StuRat (talk) 19:51, 3 December 2012 (UTC)

At a more practical level, unless the target star has a circular orbit with precisely known velocity, making predictions will depend on the distribution of dark matter in the target galaxy, which we know only at poor resolution. Looie496 (talk) 19:34, 3 December 2012 (UTC)

Add to all this above that your target star maybe doesn't exist anymore or disappear during your journey. OsmanRF34 (talk) 22:02, 3 December 2012 (UTC)

So couldn't the galaxy also be moving not just directly away from us but also some other arbitrary direction? What do you mean "in Aline away from other galaxies" GeeBIGS (talk) 00:44, 4 December 2012 (UTC)

The expansion of the universe causing movement away from distant galaxies should be the dominant factor at that distance, but there would also be a smaller factor in another arbitrary direction. At shorter distances this factor is dominant. See for example Andromeda–Milky Way collision. PrimeHunter (talk) 01:22, 4 December 2012 (UTC)

No, gravitationally bound objects like galaxies do not expand due to metric expansion. -- Finlay McWalterჷTalk 01:32, 4 December 2012 (UTC)

The thought experiment could be expanded. If the person can live forever, they could travel to a star that is 50 billion light years away. Under that scenario metric expansion might come into play. Would that be correct? Would it still be possible to make almost all calculations before setting out on the journey? Bus stop (talk) 01:58, 4 December 2012 (UTC)

I don't think any stars (we know about) are that far away. Plus the star would be unlikely to exist when we got there. StuRat (talk) 02:30, 4 December 2012 (UTC)

[18] Bus stop (talk) 03:04, 4 December 2012 (UTC)

What I'm trying to get at is that in some cases the star is actually closer than the calculations predict because the arbitrary direction could be directly at us. Right?GeeBIGS (talk) 05:17, 4 December 2012 (UTC)

At shorted distances the arbitrary direction becomes dominant = the closer you get the more the arbitrary direction matters? So it seems like any path looks like a really long straight line with a sharp turn towards the end of the trip?GeeBIGS (talk) 05:30, 4 December 2012 (UTC)

How the path looks will depend on the kind of corrections applied.

The computationally least expensive way would be...

1-to fly where you see the star,

2-look for the star and turn towards it,

3-to fly where you see the star then (and so on)...

But that's not only wasteful of time and fuel, it's possible that you lose track of the star and cannot find it because it has changed while you were flying.

A more practical way which does not assume that the star is as unchanging and immortal as the pilot is to keep track of it, and to apply corrections after, say 5% of the distance, then after 5% of the remaining distance, etc.

The former method would look like GeeBIGs assumed, but the latter would be quite close to a least-time intercept course. It would still arc more tightly towards the end but not nearly as much as the first approach. You would be able to account for more and more of the arbitrary components, but quite gradually.

And finally, bright stars don't last for 200 million years. The speed of the ship becomes important, for even a faint star would not last that long if you were going no faster than the Pioneers/Voyagers. But these are probably a moot point, as they would not be fast enough to escape our galaxy... - ¡Ouch! (^{hurt me} / _{more pain}) 08:00, 4 December 2012 (UTC)

What I'm trying to get at is that in some cases the star is actually closer than the calculations predict because the arbitrary direction could be directly at us. Right?GeeBIGS (talk) 05:17, 4 December 2012 (UTC) — Preceding unsigned comment added by 165.212.189.187 (talk)

We can detect if a star is moving towards us or away, and measure the speed, using the blueshift or redshift. That's the Doppler effect applied to light. StuRat (talk) 20:41, 4 December 2012 (UTC)

Then why did others say that the arbitrary direction matters as you get closer? And that it might not be there when you get there? Aren't you only detecting the metric expansion with blue/redshift? It would appear that way but consider a star in some 200,000 ly orbit: we see the light while its at 12 oclock; we travel toward it; when we ge to where it was couldnt it have "come around behind us through 3, 6, 9" ?165.212.189.187 (talk) 21:04, 4 December 2012 (UTC)

Regarding the metric expansion of space: My understanding is that most galaxies are flying away from each other due to the inertia from the Big Bang, so have a redshift. We expected them to be flying away at a decelerating rate, due to gravitational attraction, but found they are actually flying away at an accelerating rate. The explanation for this is the metric expansion of space. StuRat (talk) 21:10, 4 December 2012 (UTC)

Mars Curiosity findings

There are reports of interesting chemicals being found on Mars. However, they caution that it might be contamination from Earth. Why didn't they take care of that possibility before they sent it? They had it in a clean room, why didn't they clean the damn thing to preclude the possibility of what they find being from Earth? Bubba73 ^{You talkin' to me?} 23:48, 3 December 2012 (UTC)

I'm sure they tried, but it's quite difficult to keep it sterile. What if an adjustment needs to be made after it's cleaned ? Do you clean the whole thing again ? And do you store it in a vacuum until launch, to prevent contamination by the air ? StuRat (talk) 23:57, 3 December 2012 (UTC)

This episode of NPR's Science Friday talks about the degree to which a planetary probe is cleaned and sterilised. -- Finlay McWalterჷTalk 00:18, 4 December 2012 (UTC)

Thanks for the info and link. But if they are going to send it off not clean, and they have those doubts about their initial results, will they ever be able to have confidence in them? Bubba73 ^{You talkin' to me?} 00:53, 4 December 2012 (UTC)

I recall reading that initial scoops of Martian soil are discarded because of the possibility that they will be contaminated. If I recall correctly, the operation of the mechanism is designed to clean itself with the first few scoops of soil. After that it is not expected to be able to still contain contamination from Earth. But I am just recalling this from memory (faulty). I think I read it in Scientific American. Bus stop (talk) 02:05, 4 December 2012 (UTC)

Here it is: "But before Curiosity fired up its CheMin (Chemistry and Mineralogy) instrument to analyze the soil, it first had to purify its sample-collection instruments using Martian sand as a cleansing abrasive."[19] Bus stop (talk) 02:21, 4 December 2012 (UTC)

They go for 50ng/g of sample contamination. If anybody here has a clue how clean that is? To get lower than that you have to built a polymere free instrument only using ceramics and metals. No cables with isolation no electronic boards .... This is impossible. The cleanliness they have is amazing.--Stone (talk) 03:21, 4 December 2012 (UTC)

To put 50ng/g in perspective, the standard for the purest form of water calls for less than 100ng/g of solid contaminants.Dncsky (talk) 03:58, 4 December 2012 (UTC)

Bubba: this is how science works. One must always consider alternate explanations for data. It's not that they didn't send the probe off clean, but rather that no matter how clean you think your probe is, if you get striking results that could be explained by contamination, you are going to say that contamination is a possible explanation for the results. Ideally, there will be other tests they can do to rule out the possibility of contamination.--50.196.55.165 (talk) 19:25, 7 December 2012 (UTC)

What i like best is the fact that curiosity find the same stuff Viking found in the 1970s. Klaus Biemann reported that they fond dichloromethne and chloromethane, but they argued that it was contamination from solvents used for cleaning. But now it looks more like the chloromethanes were produced by the reaction of organics wit the chlorine from the perchlorates.--Stone (talk) 03:25, 4 December 2012 (UTC)

Perhaps they were using "Earth contamination" as a catch-all for anything that could invalidate the results. Bubba73 ^{You talkin' to me?} 18:21, 4 December 2012 (UTC)

December 4

How long do water molecules last (live?)

If a snowflake falls on a glacier, (3.5 x 10^19 molecules to a snowflake I read)...and we could follow one molecule when the snow melts, the water runs into a river, then to the ocean, and then at some point evaporates becoming clouds, and pushes onshore to fall as snow again...does that one water molecule exist throughout, changing states from solid to liquid to gas, around and around? Forever? Does something break up an H20 molecule at some point? Does a water molecule have a birth, life, death, or will some of them go around and around for years, ages, eons? How does it work? Thanks if you can help me understand and picture it. — Preceding unsigned comment added by 94.208.75.76 (talk) 03:10, 4 December 2012 (UTC)

Water molecules in liquid and solid change their specific atomic associations over time (exactly which two H are attached to exactly which O). The origin of "neutral water pH is 7" is that some aren't even associated as a 2:1 form at all. See self-ionization of water. DMacks (talk) 03:17, 4 December 2012 (UTC)

I am wondering though, at any point do H2O molecules cease to be H2O molecules? For instance are there any naturally occurring events or processes causing H2O molecules to cease to exist? Do any H2O molecules drift off as hydrogen atoms and oxygen atoms? Or do any hydrogen atoms and oxygen atoms combine with other atoms or molecules to form new substances? Conversely, are there any naturally occurring processes on Earth which create H2O? Bus stop (talk) 04:40, 4 December 2012 (UTC)

There are certainly biological processes which do both. Also, an acid plus a base produces a salt plus water, and that reaction happens in nature both inside and outside of organisms. StuRat (talk) 04:46, 4 December 2012 (UTC)

Also, I'd expect water ice to be more stable than either liquid water or water vapor. On Earth, water ice tends to only last for a few hundred thousand years, in Antarctica, say. However, liquid ice deep inside Pluto or beyond might have formed when the solar system formed, some 4.3 billion years ago, and never melted since (unless tidal forces from Charon (moon) heat it enough to melt the ice). In that case, those molecules should mostly be the same as they were when formed. StuRat (talk) 04:57, 4 December 2012 (UTC)

• In quantum mechanics, particles do not have individual identities that persist over time, and molecules, which are arrays of particles, don't either. When two water molecules come close enough together for their wave functions to overlap, it is impossible even in principle to say which is which afterward. So really the question is meaningless, and some of the responses above are too. Looie496 (talk) 05:50, 4 December 2012 (UTC)

Atoms with individual identities

• • I don't know that you can say that it is impossible to identify individual atoms with individual identities. I mean, this picture does a pretty good job of that. Those bright spots are individual carbon atoms, and the entire structure is a macromolecule known as a carbon nanotube. You can not only resolve the structure as a whole, but individual carbon atoms within it. --Jayron32 07:01, 4 December 2012 (UTC)

If we consider an oxidanyl group to be the core of a water molecule, how long is the average lifespan above sea level an oxidanyl group with nothing else attached, besides more hydrogen? Plasmic Physics (talk) 06:05, 4 December 2012 (UTC)

Certainly we can calculate the rate of the reverse reaction of H2O --> 1/2 O2 + H2. It's vanishingly small, but finite at 300K ==> long but finite lifetime. John Riemann Soong (talk) 06:12, 4 December 2012 (UTC)

Please do. I'd be interested to know if they last thousands, millions, billions, or trillions of years. StuRat (talk) 06:16, 4 December 2012 (UTC)

Such a calculation is not trivial, as this is not a single step, or elementary ("single hump") reaction. It involves in theory an infinite number of component reactions. However, if only high "engineering" accuracy results are required, you can ignore intermediate forms occuring at less than parts per million concentrations - then the species involved will be limitted to:-

H

H₂ (end)

O

O₂ (end)

O₃

OH

HO₂

H₂0 (start)

H₂O₂

A total of 136 competing elementary reactions occur between these 9 species. If anyone wants to know what they are, ask, and I'll post.

There are two approaches to the calculation: 1) use the mathematics of dissociation. This requires knowing the enthlapy of formation of each species (no problem, you can look it up in standard tables), writing the dissocation equation, and solving for the roots of the equation. Therein lies a problem - the calculation converges very very slowly on to the roots - days and days of computer time is required (assuming a typical up to date PC), and it is so darm easy to make a mistake in writing the equation. When you get the answer, you'll find the overall reaction rate is so slow, like one molecule every few hours or something, the result can't be valid on relativistic grounds. 2) use reaction rate data in the modified arrhenious equation for each of the 136 reactions, and solve 136 non-linear simultaneous reactions for the overall rate. That has two problems - a) good data is not readily available for all the reactions, so some devious pondering is required, b) solving 136 non-linear reactions is going to take some serious computer time.

However, if you only want to know roughly, you can ignore O₃ and cut it down to 40 or so reactions.

Ratbone 120.145.182.171 (talk) 07:00, 4 December 2012 (UTC)

I like it rough, so please proceed. StuRat (talk) 07:04, 4 December 2012 (UTC)

Who, me? Or John RS? I accept bribes if they are large enough. But even then, you won't get an answer (even a rough answer) until long after this question has been archived. Ratbone 120.145.182.171 (talk) 07:14, 4 December 2012 (UTC)

OK, never mind then. StuRat (talk) 20:37, 4 December 2012 (UTC)

Hmmmm, I think you're looking for the "hydrogen exchange rate" or perhaps "proton exchange rate", "hydrogen-deuterium exchange rate" etc. Looks like [20][21][22][23] might be useful but I haven't accessed; the first abstract says OH- exchange predominates (for water in organic solvents). There are sites like [24] for proteins and surely water is a simpler case. I haven't found your number yet but the truth is definitely out there. Wnt (talk) 01:51, 5 December 2012 (UTC)

centripetal acceleration and linear acceleration, assuming "constant effort"

Linear plot of the "w1118" genotype

Logarithmic plot of the "fumin" genotype

Following literature concerning velocity and curvature, I decided to explore the power law among my fruit flies by taking their trajectory data and plotting log v against log R for each fly, where R is 1 over the calculated instantaneous curvature at a point. If v = K * R^b, the slope of this plot should be b and the intercept log K. Different genotypes (at least 4 different ones) appear to have per-fly average slopes ranging from 0.465 to 0.499, often with statistically significant differences between the averages: i.e. 95% confidence intervals are on the order of +/- ~0.008 whereas the difference between w1118 and fumin is ~0.03. To the right are two histograms of two genotypes, each a histogram of a collection of 60-75 flies over 4-5 experiments per genotype. One histogram has frequency colored linearly, and the other has frequency colored logarithmically-- I'm doing this to highlight different aspects of my analysis. Despite the differences, the values of the slope imply that b would be almost half, which would be consistent with centripetal acceleration being constant, since if v^2/R = K^2, where K is some constant, then v = K * R^0.5, consistent with the power law. It's the small deviations from this law that are interesting, since I think this is what separates different genotypes from each other.

The Spearman correlation (or even just the plain old Pearson r) is quite decent, on the order ~0.85. However, there is much overlap between the genotypes' distributions, though the means are statistically significantly different probably because of each genotype's sample size being on the order of n = 60-75. I was thinking that part of the spread in the plot could be due to the fact that centripetal acceleration isn't really constant and as linear acceleration will vary too, if we assume that the total "effort" would be nearly constant or fall within a tight range.

I'm actually surprised that my fit is that good, so I'm thinking, how do I get even tighter distributions that can distinguish between genotypes? The thing is, I can't think of what relation would constrain linear acceleration and centripetal acceleration together. I don't think it's really accurate to model linear acceleration + centripetal acceleration = constant, because I think the centripetal acceleration in an arbitrary non-circular path would include portions of linear acceleration. (And centripetal acceleration is a fictitious force and all that, so one might imagine it as a convenient way to talk about linear acceleration in a different reference frame.) Yet I don't think centripetal acceleration = linear acceleration either, even if we model an arbitrary path as the sum of tiny circular paths with ever changing radii (and directions) of curvature. (Ideally, each circular portion is infinitesimal in size, but we sample only at 15 Hz.)

The idea that effort is constant isn't too ridiculous, because the flies' activities are being driven by super-intense blue light (the wavelength they are most sensitive to) and if they rest, they only rest for a brief moment. You can see that to avoid taking the log of 0, and avoid the effects of noise at the same time, I've filtered all the data points where velocity dipped below 0.1 mm/s (that is, all points below log v = -1).

The basic power law relation I'm using predicts that velocity should be infinite for a straight-line path (infinite curvature), and that curvature should be infinite at zero velocity. Some literature offer a correction of R_eff = R / (1 + alpha*R), where infinite R would imply a finite R_eff of 1/alpha, so K*(1/alpha)^b would be the "max velocity". Curiously, I don't appear to have hit the upper limit of this relation, because the straight-line trend without the correction appears to carry to 90 mm/s (log v = ~2, the upper cutoff point, to avoid using data with random tracking errors, which are usually detectable because velocity is some ungodly amount for flies, like 360 mm/s), and using this correction generally makes the overall linear trend worse. In an arbitrary path model, would centripetal acceleration be basically linear acceleration even for seemingly straight line paths? How do I come up with a better "constant effort" model that would also account for the change in intercept (and in the transition zone, slope) at low velocities ? John Riemann Soong (talk) 05:54, 4 December 2012 (UTC)

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One problem with your model is that in an ideal world the fly has to expend no power on a continual basis in order to generate centripetal acceleration whereas to accelerate in a linear fashion requires power. Do you have a model for the L/D ratio of the fly? Do you think the flies perform at their aerobic maximum, or are strength limited? Greglocock (talk) 22:39, 5 December 2012 (UTC)

I'm measuring walking, not flying. The calculated (supposed) centripetal forces are on the order of ~0.02g. Flight muscles are likely to be stronger than leg muscles (are they actually?) but since a fly has to generate at least 1g of lift during flight, probably on the order of several g for rapid ascent, I think the flies are aerobic-limited? How do I modify the equations for general planar motion if there is friction? Or can I use the equations as is? Are you saying that flies should not be using any energy in centripetal acceleration but my model is not reflecting that? My flies are being confined to a 2D planar arena (they are forced to walk), so I'm trying to wonder what a "real walking" model should include.

If there is friction, tighter turns should require more energy and effort, right? John Riemann Soong (talk) 03:17, 6 December 2012 (UTC)

Also, there is an observed 1/3 power law in idealized handwriting and eye saccades, and some other movements-- this is in the presence of friction. Both a "minimum jerk" model (a criterion for smoothness) and the viscoelastic model (reducing strain on a nonpoint body) are suggested as origins of the trend. John Riemann Soong (talk) 03:20, 6 December 2012 (UTC)

Mauser 98

Does the Mauser 98 give any positive indication when the ammo in the magazine runs out? In other words, when the shooter fires off the last cartridge, how does he (she) know that it's time to reload (other than by counting shots)? 24.23.196.85 (talk) 06:51, 4 December 2012 (UTC)

While there may be variations - after all the Mauser 98 action was manufactured for a long time and for a great many customers - my M59F1 (built from an ex-german M98k receiver) has a knob on the magazine follower that will hold the bolt back when the magazine is empty. Only way to close the bolt is to fill the magazine or push the follower down with a finger - it is natural to assume that such a device is common to most or all M98 actions. WegianWarrior (talk) 09:16, 4 December 2012 (UTC)

This article on the The 1896 Swedish Mauser says "After the last round fired and ejected, the follower locks the bolt open for rapid reloading", although this was an earlier design than the M98. However, the Persian vz98/29 Mauser (made in Czechoslovakia for Persia (Iran)) " It’s useful that the magazine platform does not lock the bolt open after the last round has been fired and ejected. As an idiot’s guide it’s probably useful to show some thick squaddy that the gun is empty, but not required for the sort of shooting we do." So it looks a bit variable. Alansplodge (talk) 14:37, 4 December 2012 (UTC)

Thanks! I was asking specifically about the Karabiner 98k version used by the German Wehrmacht during World War 2. 24.23.196.85 (talk) 22:47, 4 December 2012 (UTC)

This page has some downloadable instruction manuals for the 98k. This simplified manual for a late-WWII 98k doesn't mention it. Alansplodge (talk) 17:01, 5 December 2012 (UTC)

Thanks, Alansplodge! I've checked the manual, and it says nothing about the bolt locking back when the magazine is empty. So, I can safely infer that the only way to know for sure is to count your shots -- and if you happened to take the rifle from an enemy who fired it and hadn't reloaded (as my character has done), you're in danger of ending up with an empty mag without knowing it. 24.23.196.85 (talk) 01:41, 6 December 2012 (UTC)

what's the differences between forged steel and wrought steel?

what's the differences between forged steel and wrought steel?thanks a lot. — Preceding unsigned comment added by 121.15.133.68 (talk) 06:54, 4 December 2012 (UTC)

Do you mean how they are made, their properties, appearance, or what ? StuRat (talk) 07:00, 4 December 2012 (UTC)

I've never heard of "wrought steel". There is Wrought iron, which is, I suppose, an ultra low carbon steel. Its properties can be compared to Steel itself, by looking at both of those articles. --Jayron32 07:41, 4 December 2012 (UTC)

This page describes wrought steel as carbon steel that is shaped by rolling rather than casting. Looie496 (talk) 19:12, 4 December 2012 (UTC)

The term "wrought" is a little bit confusing, because it refers to both a process of working metal; and also to a chemical recipe for certain types of metal (usually iron) that are soft enough to be useful for that style of metalwork. In this case, wrought steel is referring to steel that has been worked. See also, wikt:wrought. In fact, ASME (an organization that is generally well-regarded for its expertise in the fields of materials science and engineering) has standards related to wrought iron, wrought copper, wrought steel, ... the list goes on and on. I have never personally worked with anything called "wrought copper," but nonetheless, there's at least one ANSI standard for it, (ANSI/ASME B.16), and in fact there are entire trade organizations centered around it. Nimur (talk) 15:27, 5 December 2012 (UTC)

TEXTABLE LANDLINE TELEPHONES! - Where can I buy one?

If you know the correct article title, you may edit the original dead-end WL to it.

I've been searching high-and-low for landline phones that can send and receive SMS, but even Best Buy has none. Why are they so hard to come by???

If they're not available in the good ol' US of A, then what are some GREAT textable landline phone models that I can order from overseas? (Or if there are some textable landline models sold from some online specialty stores that are physically located in a US warehouse, that's even better due to reduced shipping costs!)

I vow NEVER to get a landline until I find one that sends and receives texting. Why are they so hard to find in America in the first place? Thanks kindly. --70.179.167.78 (talk) 08:29, 4 December 2012 (UTC)

Once you have the phone, then what? Have you evidence that American phone companies have the ability to send text messages to a land line phone? I've never heard anything about that being possible. Which isn't to say it's not but it's not that popular. Dismas|^(talk) 09:08, 4 December 2012 (UTC)

The American landline phone standard, POTS, was designed decades ago and while they have expanded the service options over time, the system generally does not support text messaging (i.e. SMS). Some of the landline alternatives, such as home VoIP through an internet service or digital phone from a cable company, may offer SMS options but they are still rare in my experience. You should verify that the phone service you want to use supports text messaging at all, before worrying about where you can find compatible phones. Dragons flight (talk) 10:54, 4 December 2012 (UTC)

If you can use a landline, you must be in a building. And if you are in a building, you can use a PC to access the internet. And if you can do that, great, because many phone companies offer a website that lets you send an SM to a mobile phone on their network. Nobody can send an SMS to you though. Why not use email? Or just phone them? Ratbone 124.182.41.70 (talk) 11:32, 4 December 2012 (UTC)

The people above are correct - the land line phone system doesn't support SMS. SMS is only possible on mobile phone networks. You can also email texts to cell phones - each carrier has a different format for the address associated with a phone number. You can also send a text message to an email address via SMS on the phone. There are devices that connect to the mobile phone network and let you plug a landline phone into them, but I can't recall what they are called. Perhaps one of those has SMS built in, but you would have to access it from the base, not the landline phone plugged into it. 209.131.76.183 (talk) 13:15, 4 December 2012 (UTC)

actually, IIRC, texting goes via the same path as the caller id; which is at least optionally available on landlines. so in principle, it should be possible? Gzuckier (talk) 18:40, 4 December 2012 (UTC)

No, it's very different. In North America the CID burst is an analog frequency-shift-key encoded sequence (a Bell 202 variant) transmitted in-band (and if the phone is off-hook, preceded by a DTMF-like alert tone); arrangements in different phone systems are similar. SMS is an out-of-band digital message type sent as a Mobile Application Part message on a GSM digital connection. There is no agreed upon standard (at least that I've ever heard of anyone actually implementing) for wrapping SMS in an in-band (FSK, QAM, whatever) burst. ISDN, which does support wrapping additional protocols in messages in a D channel, can support SMS, and some ISDN handsets do (but I don't know how standard and interoperable this really is). -- Finlay McWalterჷTalk 18:55, 4 December 2012 (UTC)

Fax it: send and receive text. --VanBurenen (talk) 19:21, 4 December 2012 (UTC)

May I ask, what about a land-line do you actually want ? The more comfortable headset ? Not having to charge it ? Or something else ? Because, if you have a cell phone already, a land line does seem like an unnecessary expense these days (although I have one, since it's bundled with my Internet). StuRat (talk) 20:35, 4 December 2012 (UTC)

Sound quality is usually better on land lines. --Trovatore (talk) 00:29, 5 December 2012 (UTC)

I asked pretty much the same thing Wikipedia:Reference desk/Archives/Science/2011 December 30#What'll it take to upgrade landline networks to allow texting to and from landline phones? but never received a response from the OP (which doesn't seem uncommon for them). Me and Astronasut made a similar point to Dismas and most other respondents basically touched on similar ideas as to the above discussion but this doesn't seem to have been take on board either. Nil Einne (talk) 23:00, 4 December 2012 (UTC)

It does seem like the companies offering landlines have concluded that their extinction is inevitable, and thus decided to invest the bare minimum to keep them operational until that time. So, any R&D, such as into supporting texting, is off the radar. StuRat (talk) 00:22, 5 December 2012 (UTC)

wandering offtopic here, but the reason i keep the old landline is that it was built to survive nuclear war, so the odd hurricane won't phase it. whereas isdn lines and cell towers are more fragile. of course, eventually, there will be nobody for me to talk to call from my cold and dark house in the disaster area. Gzuckier (talk) 06:05, 5 December 2012 (UTC)

I'll talk to you! I hope landlines don't go away. I like being able to make calls indoors - I see people standing out in their yard so they can get reception. Also, if I dial 911 they know where I am. Also, it is so easy to use: just pick it up to talk, put it back down to hang up - no extra buttons to press. And my cable goes out so often - if I relied in them for the phone it would be out of order a considerable part of the time. And the landline doesn't drop out! And, perhaps most of all, is the sound quality. Cell phones have terrible sound quality. I think it is bad manners to call someone with a cell phone unless there is no alternative. Bubba73 ^{You talkin' to me?} 06:22, 5 December 2012 (UTC)

I don't think any of those are absolute limits of cell phone technology:

1) A cell phone network can be made more reliable than land lines, since, if one tower goes down, it can glom on to the next. If the telephone wire leading to your house is cut, though, that's it, no hope of using it until a repairman is sent out. I just had my land-line go down, but, other than reception problems, have never had a cell phone go dead on me.

2) I actually have better sound quality on my cell phone than land line.

3) Flip phones can be made to answer when you flip them open and hang up when you close them. Clam-shell phones could do the same.

4) Reception can be excellent, if they have enough cell towers.

5) A cell phone with GPS could direct emergency personnel to your location, even if you are cowering up a tree with a grizzly bear below.

There may be one absolute limit of cell phones, though, and that's on comfort. They really can't provide a full-sized headset and still have it be as portable as they want. A compromise might be to place your cell phone in a docking station when home, which could charge it and also tie in to the house phones, and add a bigger antenna, to boot, and maybe a full-sized QWERTY keyboard for texting. StuRat (talk) 06:38, 5 December 2012 (UTC)

Landlines won't go away - they'll just change into something better. The trouble with cellphones and any other sort of radio technology is that it won't scale well. The more users use it for data (internet, video on demand, etc), the more the number of cellphone base stations (towers) and/or the radio bandwith required becomes impossible. More of the current problems with landlines (call quality, reliability, bandwidth) is due to the fact that the Customer Access Network (CAN) ie the copper cable network that connects dwellings and offices to the phone company exchange is old. A lot of cabling is 30 to 50 years old and is just about stuffed - in Australia at any rate. Image the car you might have bought 50 years ago - it would have been reliable back then. But now its rusty and worn out. But they have started rolling out Fibre-To-The-Home (FTTH) to replace the CAN. Because it's new it should be reliable - like a new car. And the communication is via VOIP digital instead of voice frequency analog, so upgrades to what your fixed phone can do will be a lot easier. Ratbone 120.145.196.13 (talk) 06:58, 5 December 2012 (UTC)

I'd argue that land-lines don't scale well, since, if you need to dramatically increase the capacity, at some point you need to lay more wire (or fiber) to every house. That's a lot more work than upgrading the equipment at the cell-towers. StuRat (talk) 16:56, 5 December 2012 (UTC)

I'd avoid bundling like the plague. If your landline is part of the cable service, you have to use the mobile to call for repairs. One less level of redundancy.

Mobile services are generally not very reliable. I've had 4 outages during November, that is one per week (although that's above average) and there was no reception from any secondary tower. Too loose a spacing, I guess. I've never had my landline fail, only my phone.

Mobiles are more prone to failure, too: made in China, and their batteries can fail.

Even if there is a secondary tower, I doubt that the landline would fail more easily than both towers at the same time. I doubt that "more towers" can be extended on demand. The aether can only take so much. That's no problem with landlines; signals will not carry over from a line to the other.

Mobile is susceptible to flooding. A single jammer used by terrorists could take a large chunk out of a mobile service. It's not that easy to kill landlines.

Flooding 2.0 - If too many users are on, the service degrades. At least twice a year (xmas, new year), mobile would go down on me.

Poor sound quality on a landline seems to be an issue related to the phones themselves, not the lines, or the line is already damaged and needs replacement.

"the companies offering landlines have concluded that their extinction is inevitable": Except T-mobile. They extincted their mobile service for half a day.

Phones with GPS, that is actually useful. OTOH, the towers could easily add similarly useful info which would be spoof-proof (tower ID + direction + approximate distance).

Texting vs. faxes: At least faxes have the advantage that you can "print" documents to faxes. No need to type them using a keypad which is no better then your average remote. If you have the time to text, you could as well call and save some time. Even Apple are expected to support phone calls by 2030. - ¡Ouch! (^{hurt me} / _{more pain}) 09:51, 5 December 2012 (UTC)

RE: "the companies offering landlines have concluded that their extinction is inevitable", you seem to have misinterpreted my comment to refer to outages. I mean that they think land-lines will no longer exist at some point. In the US, at least, there's the additional issue that all the taxes go on the land-lines, so you get a minimum of like $30 a month, even if you don't use it. My cell phone, on the other hand, is $7 a month.

As for cell phone networks being overwhelmed by traffic, this has happened on land-lines, too, during holidays. It seems to be less of a problem, lately, though, presumably because cell phones have taken much of this burden off the land-line network. So, this is not an inherent problem with cell phones only.

The advantage of texting, just like an e-mail, is that it doesn't require an immediate response. So, if you're in a meeting, and your significant other wants to ask when you will be home, would you rather have your phone ring, or have a text come in, which you can answer after the meeting ?

The advantage of a full-sized QWERTY keyboard, as in a PC, is that I can touch type, dramatically increasing my speed. Those on a cell phone are just too small to permit this. StuRat (talk) 16:38, 5 December 2012 (UTC)

Where I live I have never experienced a mobile network outage, not even when everything else has gone down. I suspect it's more down to how competitive service providers are in your area. --83.84.137.22 (talk) 16:22, 5 December 2012 (UTC)

Another problem with cell phones is there is a long delay whereas a landline is essentially instantaneous. I often hear myself being echoed back. And on a landline you can talk and listen at the same time, just as in a normal face-to-face conversation. Cell phones don't allow that. Those two things together make talking on a cell phone like the awkward remote TV interviews where there is a delay before the other person starts responding so the interviewer starts talking and at that time the remarks of the first person come back, etc, etc. Bubba73 ^{You talkin' to me?} 16:32, 5 December 2012 (UTC)

I wonder if the 2-way versus 1-way at a time issue is an inherent limitation of cell phones or just a poor implementation. It might be necessary to turn off the speaker when you're talking, to limit echoes, since the speaker and microphone are too close together. I wish they had tri-fold phones which could still be small yet expand out enough so the microphone is actually by your mouth and the speaker is actually by your ear. The increased distance, and sound damping from your head, should make it possible to enable simultaneous 2-way communication without echoes. StuRat (talk) 16:43, 5 December 2012 (UTC)

There are 2 reasons why cell phones do not have two-way simultaneous talking ("duplex working" is the technical term). Firstly, two simultaneous directions requires two radio channels, doubling the bandwidth. Bandwidth is precious and MUST be conserved. Secondly, the transmit power power is up to 1 x 10¹¹ times the recieve level, even though it is only around 200 mW. The tranmist energy overloads the sensitive recieve circuits, even if not on the exact same radio channel. It is readily possibly to fix this problem with what is known as discrete directional filtering, but such filters take up a lot of space, and would take the size and weight of a cellphone back to that of a housebrick, or aborb a lot of power, or both. There is a third, minor, reason: The same computer-like chips in the phone are used to process both transmit and recieve signals. To work in both directions simultaneously, you'd need increased processing grunt, increasing the battery drain. Battery capacity is precious too. Feedback from speaker to microphone is not a problem. The success of the better types of loudspeaking conference phones demostrates the success of the electronic enginner's bag of tricks (hybrids and VOGC's) in that regard. Keit 120.145.164.75 (talk) 01:21, 6 December 2012 (UTC)

Re: "cell phone network can be made more reliable than land lines" back there - I've had a land line for 40 years. I think there have been three times when the service was out. Possibly four times, but I don't think so. So about one outage per 10 years. How many times do I get "no service" on my cell phone? Many. How many times to I call a number and NOTHING happens? Many. How many times are there dropouts on a cell phone? Many. Bubba73 ^{You talkin' to me?} 19:31, 5 December 2012 (UTC)

You're somewhat comparing apples and oranges there if you compare your land-line, used in one location, with a cell phone, used at multiple locations. If you just compare your cell phone, used at home, with your land-line, that's more fair. And, again, just because some cell phone service is crap doesn't mean it always must be, due to limits of the technology. A similar argument could be made on cars, early on: "Those darn horseless carriages break down once a week, but my horse has been reliable for 20 years, so cars will never replace horses". StuRat (talk) 19:38, 5 December 2012 (UTC)

I don't use my cell phone at home because (1) I want to be able to talk indoors, (2) cell phone is too unreliable, (3) sound quality is bad, (4) it is too hard to use. Bubba73 ^{You talkin' to me?} 21:06, 5 December 2012 (UTC)

And another thing - with a landline, you get in the phone book! Very important. Bubba73 ^{You talkin' to me?} 22:22, 5 December 2012 (UTC)

House wall mold sensor?

Is there any substance that can detect mold growth inside walls? such that when mold start to grow it will also grow on a sensor that will alert the house manager? which can then preemptively take action. This is different from measuring the conditions such as temperature an moisture which doesn't indicate actual mold. Electron9 (talk) 13:25, 4 December 2012 (UTC)

In my area, the humidity runs about average and mold grows on moist foods just about anywhere and everywhere you happen to leave it out. I'm fairly sure that the mold spores are widely dispersed from soil and foliage here. Thus, if you taped sterile food or growth medium to a wall or inside it you would quickly grow plenty of mold in a day or two, but that wouldn't indicate anything. I haven't lived in any of the more arid areas of the country though, where the spores might be less of a problem. In addition, the available moisture within the wall will likely differ in different locations. So if you placed dried bread high in the wall, it may remain relatively mold free for a while, until it absorbed enough moisture. But even then, its hygroscopicity will likely differ from the wall materials, such that the moisture conditions differ, especially in areas near window sills, bathrooms and basement walls. Low levels of mold are frequently present anyway, which is why storing clothes in such darkened moist areas is generally not a good idea. Modocc (talk) 14:02, 4 December 2012 (UTC)

Neurasthenia

I was reading this article but I don't exactly understand what it is. Is it a psychological disorder or a physical disorder of the nervous system? Thanks. 82.132.210.65 (talk) 14:48, 4 December 2012 (UTC)

Neurasthenia was a 19th century disease concept. It describes a combination of symptoms used by doctors to make the diagnosis. The main symptom was fatigability so severe that the patient felt unable to engage in normal work and normal family and social obligations. The doctors knew that there were no objective structural abnormalities in the body (i.e., no "pathology"). There were many hypotheses of cause. These days patients with those same symptoms are likely to be diagnosed with chronic fatigue syndrome. Both of these conditions are good examples of attempts to provide a social role and medical response for symptoms that are not at all understood at the organ or tissue or cellular level. alteripse (talk) 15:23, 4 December 2012 (UTC)

December 5

Subjective time

When hiking for four miles in and four miles out in a relatively unfamiliar area, my perception is that a landmark which I remember from "about halfway" on the way in is at little more than 1 mile in on the map; thus invariably when hiking I find that most of the landmarks I've remembered come out in rapid succession "close to" the end of the return trip. I take this to support an idea that subjective time, whether on a short or lifetime scale, depends on novelty (or retroactively from memory?) and runs according to the 1.7 or 1.8th root of clock time (it is relatively easy to derive a square root relation mathematically). Is there any literature on a subjective time formula that is more believable than the IMHO absurd inverse proportion mentioned in the article? Wnt (talk) 01:26, 5 December 2012 (UTC)

Instead of highway hypnosis...hiking hypnosis.GeeBIGS (talk) 02:43, 5 December 2012 (UTC)

I suspect that it's not a fixed formula, but depends on what you encounter on the way. In general, the things you encounter on the first half of a trip will be "newer", so you will notice them more (like the 1st weeping willow tree, perhaps), but notice subsequent appearances of similar objects less. So, it will seem like you encountered more during the first part of the trip than the last. However, if the first half was boring and then you hit some fantastic scenery, that might alter your perception. StuRat (talk) 06:25, 5 December 2012 (UTC)

The memorability of landmarks certainly depends on their novelty which decreases as one penetrates further into the previously unknown area. Since this observation depends so heavily on unpredictable subjective factors and previous experiences, it seems impractical to derive a meaningful mathematical relation to time (or distance) passed. SkylonS (talk) 11:22, 5 December 2012 (UTC)

I have always noticed that the first trip to a new destination always takes longer than the return and the second trip there even less time than that, tending to a constant rate on about the third and later trips. Is this (at least similar to) what you are talking about? μηδείς (talk) 16:46, 5 December 2012 (UTC)

Not really. In this instance worry about deer season had pushed me to a simple, straight path, which I'd already checked on the map before going, along the bottom of a valley with regular distance markers. I didn't even need to note landmarks, and my rate of travel was very nearly constant. Even so, I paid more attention to the distance markings on the way back, and was "predictably surprised" to find the thing I'd thought of as being halfway out not far from the first mile marker. Wnt (talk) 20:48, 5 December 2012 (UTC)

Buttons

Are all silver metal buttons on pants nickel?--Wrk678 (talk) 06:07, 5 December 2012 (UTC)

I doubt it. Some might be painted silver, with steel or some other metal underneath. Some might be copper or nickel-plated. And, for expensive high-fashion clothes, they may actually use silver (solid or plating). There may not be any which are all nickel. StuRat (talk) 06:21, 5 December 2012 (UTC)

I'm wondering because I'm allergic to nickel. Is it usually nickel plated. They are just 30 dollar pants. — Preceding unsigned comment added by Wrk678 (talk • contribs) 06:47, 5 December 2012 (UTC)

I've seen pants with plastic and cloth-covered buttons, but the zipper and any rivets might be a problem. You can get pants without rivets, but the zipper might be a problem. I've seen plastic zippers on coats, but not pants, since they need to be larger. There are button-fly jeans, but I don't know if you can get those in nickel-free buttons. Velcro would be ideal. Have you considered having pants custom made ? StuRat (talk) 07:37, 5 December 2012 (UTC)

Here's a site which sells nickel-free buttons and rivets, so you can have a tailor replace the ones on your pants: [25]. No mention of the zippers, though. They also have a test kit, so you don't have to trust the salesman who claims their pants are nickel-free: [26]. StuRat (talk) 07:42, 5 December 2012 (UTC)

I'm just wondering if most silver metal buttons are nickel plated.--Wrk678 (talk) 08:54, 5 December 2012 (UTC)

Well on [27] I see about one in six of the jeans metal buttons tested contained nickel. You might get away with just coating them with clear nail enamel just in case. Dmcq (talk) 09:45, 5 December 2012 (UTC)

Could you just paint the buttons with something like clear nailpolish? Vespine (talk) 21:33, 5 December 2012 (UTC)

Light traveling to a star

As I understand it, while the universe is 13.7 billion years old, the actual current distance from here to any star (let's talk about red dwarfs, which last a long, long time) that we've ever seen is more like 45 billion lightyears, due to expansion of the universe that has occurred since the light we see was emitted. As I also understand it, there could be some stars that we cannot see because their light could never reach us, and that are unreachable by light that we send out.(Correct me if I've got these things confused.)

Suppose there's a visible star that's x lightyears from us in terms of when it emitted the light that we currently see. Based on what we know now about the past and future history of expansion of the universe, are there stars that we currently see that we could never reach with a beam of light? If so, what is the critical value of visible distance x above which the star is unreachable by light that we currently send? Duoduoduo (talk) 15:55, 5 December 2012 (UTC)

Given that it's impossible for a star to move at the speed of light, if we sent a beam of light to x star, at some point in the future (billions of years perhaps) the light would reach that star (assuming it isn't swallowed up by black hole or distorted in some other way). I've got no idea of the rate the universe is expanding at, but again, assuming that it's less than the speed of light - a beam of light would, in theory, eventually reach the most distant part of the universe. Conversely, if the universe is expanding at the speed of light, then it wouldn't as light cannot travel faster than the speed of light. I may have got that completely wrong, I'm no expert at physics this advanced, so if I have, any astro-boffs feel free to correct me. douts (talk) 16:45, 5 December 2012 (UTC)

I thought it's established that there are stars that cannot communicate with us, and I thought that that was due to the expansion rate of the universe being greater than the speed of light. If so, my question stands. Or is it known that the expansion rate was only greater than the speed of light during the inflationary period, and not now, and never again? I can't tell from the article Metric expansion of space. Moreover, even if a star is moving away from us within space at of course less than light speed, and even if the universe itself is expanding at less than light speed, couldn't the sum of those two exceed the speed of light, making the star unreachable by our emitted light? Duoduoduo (talk) 17:03, 5 December 2012 (UTC)

I dont know is the honest answer, I'm not clued up enough on astrophysics to be able to give you a good answer. My response above is based my very limited physics knowledge. I'm sure there are other users who are much more clued up on this than I am. Sorry I couldn't be of more help. douts (talk) 17:23, 5 December 2012 (UTC)

They think the expansion rate was greater than the speed of light at some time in the past, but is not now. thx1138 (talk) 17:40, 5 December 2012 (UTC)

... but the expansion is speeding up at present, and we can currently observe galaxies with a red-shift greater than 1.5 which we believe are currently "receding" from us at a separation speed greater than the speed of light. (Please note that this doesn't mean that these galaxies are "travelling" faster than light.) Also galaxies at an estimated current distance of about 4,740 megaparsecs (146 million million million million miles) will soon disappear forever from our view because their light will never reach us. Galaxies further away than this (assuming that they exist) can never be observed by us (unless we find "wormholes" or some such trick to move without travelling). I don't have a figure for your "x" distance for light to reach the star from us, but I'm sure there are some experts here who can calculate it. Dbfirs 18:20, 5 December 2012 (UTC)

Galaxies do not disappear from our view. Ruslik_Zero 18:41, 5 December 2012 (UTC)

What makes you think that? The article Future of an expanding universe claims that in another two million million years all galaxies will have become undetectable except for those in our local cluster. Dbfirs 23:56, 5 December 2012 (UTC)

• See observable universe, which discusses these issues. It says some galaxies exist which we can see at early development, greatly redshifted, but light from them from later times will never reach here. How many can we see in their present form? Well, none, of course (unless you use a speed of light frame of reference...) Wnt (talk) 20:56, 5 December 2012 (UTC)

Thanks for the link. Like most people, I struggle to get my brain round the complexities the current understanding of the universe, but I think the answer to the OP's "x" is 16 million million light years (94 thousand million million million miles) as measured now. No doubt someone will correct me if I have misunderstood the symmetry. I'm not a cosmologist! Dbfirs 23:56, 5 December 2012 (UTC)

Variable displacement with open exhaust valves

According to variable displacement, when a cylinder is deactivated all of its valves are closed. The piston then continuously work against the trapped exhaust gases infinitely until that cylinder is reactivated again. Is there any engine out there that keep the exhaust valve open continuously during deactivation? It seems by keeping the exhaust valve open less work will be wasted.Dncsky (talk) 16:25, 5 December 2012 (UTC)

I think I see a problem with that. You would then be pumping exhaust air (from the operational cylinders) in and out of the cylinder, and I bet that would cause deposits to accumulate in the cylinder in question. StuRat (talk) 17:05, 5 December 2012 (UTC)

Doh! How did I not see that before. Thanks for your help.Dncsky (talk) 17:07, 5 December 2012 (UTC)

Resolved

Besides, the work done on the gas trapped in a contained cylinder is conservative (parasitic losses ignored). In this case, the parasitic losses would be... gas escaping by leaking out. So, opening the valve actually is detrimental, as it makes the engine more lossy and less efficient. By keeping the system closed, any energy spent by the engine during compression is recouped in the next phase of the cycle. The problem is then reduced to an engineering technicality, the objective being to smooth out the power variations over a cycle. Nimur (talk) 17:10, 5 December 2012 (UTC)

The heat of compression would be transferred from the gas to the cylinder walls and to the radiator. If the exhaust valves were open there would be no compression and thus no heat loss due to compression.Dncsky (talk) 17:16, 5 December 2012 (UTC)

If the cylinder is perfectly closed, upon decompression the exact same amount of heat would go right back from the cylinder walls and into the gas inside the cylinder. Now, as I said above, we have an engineering practicality to consider: which parasitic loss is worse - the energy lost to turbulent convective air movement, or the energy lost to thermal conduction to the outside world? It seems that the engineers who design engines have carefully considered the problem, and decided to use a closed cylinder. That would seem to indicate that wicking away of thermal energy by the engine block is a less lossy process than turbulent airflow, which makes intuitive sense to me. In your own engine, with its own size, shape, and material properties, your mileage may vary, literally and figuratively. Nimur (talk) 18:10, 5 December 2012 (UTC)

Under full load conditions, the amount of heat lost through the cylinder walls to the coolant, and through the piston into the oil, is of the order 6% of the total combustion heat. Note that the total heat rejected to coolant is much much higher than this, as it includes heat lost in the cylinder head exhaust passages and exhaust valve (around 15% typically) and losses due to piston ring and bearing friction (which ends up as heat in the coolant). See R F Taylor's or Harry Ricardo's classic textbooks on high compression engines for typical figures. The 15% loss in the head will not happen if the exhaust valve does not open. 6% is a low value to start with. However, if the cylinder is not firing, the gas temperature will only be a small fraction of the combustion temperature, lowering the heat conducted to the cylinder wall and piston. Further, this heat flow is aided by gas turbulence within the cylinder. Some turbulence is driven by the shape of the piston top, but a lot is driven by the the gas flow past the intake valve. If the intake valve does not open, turbulence will be less, lowering the heat loss still further. My rough estimate (to complex to set out here) is that when not firing, the cylinder heat loss to coolant will drop to less than 8% of the full throttle value, which was only 6% of combustion heat anyway. Keit 120.145.164.75 (talk) 01:04, 6 December 2012 (UTC)

Using the numbers you provided the other day:

Brake Power Output:........265 kW (39%)

Total Loss to Coolant:....164 kW (24%)

Loss to exhaust:..............233 kW (34%)

Loss from engine surfaces..19 kW ( 3%)

Loss from closed valve variable displacement: 683kW * 6% * 8% = 3.3kW

3.3kW is admittedly negligible, but it's still larger than if the exhaust valves were open. But like Sturat mentioned opening the exhaust valves is unfeasible. Dncsky (talk) 01:50, 6 December 2012 (UTC)

I think you are right - loss with valves open should be less. StuRat was concerned about deposits, but I not sure this is a real concern. The Caterpillar 3516 engine (diesel, 2500 kW max output) with electrically controlled fuel injection turns off cylinders at low speeds and loads (unless this feature is disabled at customer option) by not pulsing the injectors in selected cylinders. The intake and exhaust valves continue to operate normally. Soot will not build up in the "off" cylinders as they are still pumping air through. It also picks different cylinders to turn off each time it decides to do it. In a gasoline engine, soot should not be forming. StuRat also realised that there would be new pumping losses in and out the cylinder. It is hard to accept that these would exceed the loss with valves closed, as you can view it as reducing compression, thus reducing the conversion of mechanical effort into heat to be conducted away. Keit 120.145.164.75 (talk) 03:03, 6 December 2012 (UTC)

But.... if the heat of compression is conducted away, then won't the loss of heat from expansion be refilled from conducting heat in? Gzuckier (talk) 02:00, 6 December 2012 (UTC)

Some of the heat will be conducted back to the gas, some of it won't. The part that doesn't goes into the coolant and then outside the car. Dncsky (talk) 02:45, 6 December 2012 (UTC)

Heat conducted into the gas during the low pressure part of the compression-expansion cycle will be less than the heat conducted out of the gas during the high pressure part of the cycle, with the geometric mean gas temperature equal that of the cylinder walls. This will modulate the piston pressure resulting in a net mechanical loss. Keit 120.145.164.75 (talk) 03:08, 6 December 2012 (UTC)

Antidepressants

How can pharma. cos. and the dr. and scientists they employ to test these drugs be so sure that they "may cause suicidal ideation", yet not also cause homicidal ideation? Logically, presuming that "this may caues you to care less than you currently do about your own life" it would follow that it might also "cause you to care less than you currently do about a random stranger's life"165.212.189.187 (talk) 18:56, 5 December 2012 (UTC)

It is based on monitoring patients who take the drugs. Pharmaceutical companies are required to collect information from patients and doctors about potential adverse effects of all the drugs they sell. Suicidal ideation is observed, but homicidal thoughts are not. 148.177.1.210 (talk) 19:02, 5 December 2012 (UTC)

Suicidal thoughts are a typical symptom of depression. So is a lack of motivation. If an antidepressant helps with motivation when the suicidal thoughts are still there, the risk of suicide goes up. Homicidal behavior is generally not associated with depression, so there are unlikely to be homicide-related effects of antidepressants. 148.177.1.210 (talk) 19:05, 5 December 2012 (UTC)

The premise is wrong. As the word "may" indicates, there is no certainty that these drugs cause suicidal ideation -- there is only some limited evidence to support that possibility. There is also no certainty that they don't cause homicidal ideation -- there just isn't any significant quantity of evidence to support that possibility. Looie496 (talk) 21:57, 5 December 2012 (UTC)

A person may find it less objectionable to admit to having urges to kill oneself than to admit to having urges to kill another person. Bus stop (talk) 22:23, 5 December 2012 (UTC)

Using your reasoning suicide rates and homicide rates must be highly correlated in every country then. Dncsky (talk) 02:00, 6 December 2012 (UTC)

I don't understand your point. Bus stop (talk) 02:21, 6 December 2012 (UTC)

why is it that advantageous for RBCs not to have nuclei?

Wouldn't it be more cost-effective if RBCs could repair themselves? It seems to me that the cost of constantly making RBCs would be more than the benefit of the extra space. Or is the risk of oxidative damage and subsequent cancer so great that all bloodmaking is confined to the marrow? 71.207.151.227 (talk) 20:21, 5 December 2012 (UTC)

The big advantage is that you can pack a lot more hemoglobin into the same space, and the cells are much more flexible and able to squeeze through tight capillaries whike suffering less mechanical damage. That outweighs any benefit you get from self-repair. By the way, mammalian RBCs lack nuclei, whereas those of fish, amphibians, reptiles and birds have nuclei. Dominus Vobisdu (talk) 20:33, 5 December 2012 (UTC)

There is a correlation between nucleated red blood cells and poor prognosis in intensive care [28] though this doesn't speak to the direction of the causality. Our article red blood cell contains the interesting information, which I hadn't known, that enucleation of red blood cells has evolved three times independently in vertebrates. I would be tempted speculate about the increased need for circulation in warm-blooded mammals, except... birds do all that and more. Fundamentally, saying why evolution went a certain way is a rather speculative enterprise. Wnt (talk) 20:40, 5 December 2012 (UTC)

Sometimes speculative, sometimes not. Often, it's pretty easy to determine how an innovation is advantageous. You're quibbling with the word "why", which has two distinct meanings, one teleological, and one purely explanatory, closer in meaning to "how". The former lies outside of the scope of evolutionary science. The latter does not. It's rather easy to explain why (= how) a four-chambered heart is advantageous, or why (= how) enucleated RBCs are an improvement over nucleated ones. The problem starts when you start attaching a teleological sense to the word "why". Dominus Vobisdu (talk) 00:40, 6 December 2012 (UTC)

Enucleated RBCs are smaller, kind of not quite donut shaped rather than fried egg shaped, and it would seem to me can negotiate the tight constriction of the capillaries better. A lousy comparison, but look at the trouble sickle cells have. Even if not directly causing clots, rbcs with a larger cross section would require lower blood velocity, require larger capillaries, or get a lot more wear and tear bashing around the tight turns. "Cold-blooded" critters don't have the same oxygen requirements we do and presumably can deal with reduced blood flow, while birds on the other hand have a more efficient lung design which can presumably provide sufficient oxygen with reduced blood flow from the "oxygen push" side. Plus the raw material of rbcs is largely recycled anyway. (Entirely guessing all this on my part, i should mention) Gzuckier (talk) 02:10, 6 December 2012 (UTC)

• Nuclei are metabolically costly and exist to (1) express proteins, and (2) undergo cell division. But red blood cells basically serve as a substance meant to convey oxygen. They don't need to reproduce since they are produced copiously by the marrow, and they don't need to express proteins because they are already packed full of hemoglobin and do their job best just by transporting oxygen as efficiently as as possible until they wear out and are replaced. μηδείς (talk) 03:21, 6 December 2012 (UTC)

Phylogeny

This is more of a conceptual question about phylogeny. Looking at phylogenies, how do scientists know that ancestral species is still alive or not? What if the species is an marine invertebrate that was only present shortly and that was in an evolutionary arms race and became quickly extinct but its daughter lineages survived because those lineages could adapt to changing times and evade predation? What if we have no traces of the actual ancestor so we erroneously infer the "actual" ancestor as a extant species? How did adaptations evolve? Exaptation may explain how tetrapods may have colonized the land, but did adaptations initially arise spontaneously and by sheer luck those traits were favored than others and underwent adaptive radiation and diversified into many different forms? Were the initial mutants "hopeful monsters" and somehow the "hopeful monsters" were lucky enough to find mates because the mutations were rather common? Sometimes, evolution by natural selection can seem, well, miraculous. It's like "Ding! You got a new adaptive trait that was beneficial to you and you could successfully breed as much as you want!" 75.185.79.52 (talk) 23:14, 5 December 2012 (UTC)

To answer your questions in order:

1. Most phylogenies present an implicit assumption that the ancestor is long gone.
2. It is actually the usual case that there is no archaeological or other direct evidence of the ancestor.
3. "We" don't declare an extant species to be the ancestor, ever. It would more usually be stated something like "Species A is the closest living relative of Species B."
4. Randomly, although some organisms experience mutation faster than others, and some organisms may mutate faster under certain forms of stress.
5. See natural selection. Genetic changes that have no benefit to a species may become common anyway (see genetic drift and founder effect).
6. Generally the initial mutants are not suspected to have been "hopeful monsters". Rather, changes occur that are incrementally beneficial to an organism. See evolution of the eye for an example of how something quite complicated can come into being gradually.
7. It's true that more mutations are harmful than beneficial, and even more are just completely pointless (see silent mutation, for example). But when you have organisms multiplying in great number all over the planet for countless generations, it's OK to be terribly inefficient. If you mutate enough animals, it's simply inevitable that one of them will get some kind of improvement. Someguy1221 (talk) 00:01, 6 December 2012 (UTC)

Good job I checked before I posted my mini-essay of an answer :) Yours is a much more concise answer! lol. douts (talk) 00:15, 6 December 2012 (UTC)

A related matter; debating evolution wih a person of normal intellect who nevertheless was an evolutionary skeptic, it became clear that his position was that in cases where the sequence of speciation is recorded, such as the evolution of the horse from eohippus, that in fact that is a species evolving within itself, rather than new species being created and the parent species becoming extinct. Does it all really depend on our definition of speciation? I mean, we argue that Great Danes are the same species as the ancestral canis familiaris that first ate our garbage, but the possibility that they could interbreed is still speculative, no? Gzuckier (talk) 02:20, 6 December 2012 (UTC)

I'd call it an educated guess with a rather convincing argument. It's the case that most extant breeds to descend from the ancestral Canis lupus familiaris can successfully interbreed, so it stands to reason that most/all of those extant breeds could hypothetically interbreed with that common ancestor. The extant breeds can even mate with familiaris's nearest neighbor, the Grey Wolf, which is rightly considered the same species as the domesticated dog. It would be rather remarkable, nay, paradoxical, if two subspecies could interbreed with one another, but not with an ancestor that post-dates the MRCA. Someguy1221 (talk) 02:34, 6 December 2012 (UTC)

Along those same lines, I am of the opinion that when everyone agrees that three organisms (one ancestral and two extant descendants) are the same species, they are probably correct. Far more difficult than arguing two organisms could interbreed is arguing that they could not. To this day, it's not clear if Neanderthals were actually a distinct species from humans; everyone agrees that reproductive isolation between humans and neanderthals was at least the norm, but that can arise from geographical isolation and selective breeding just as easily as it can arise from actual speciation. Someguy1221 (talk) 02:44, 6 December 2012 (UTC)

December 6

heavy cream in a blender

I blend heavy cream for 1 minute on high on a really good 1000W blender with the top open -- I can see the liquid sloshing around. I stop the blender. When I look inside the jar, the cream is essentially solid. When I try blending the cream again, it no longer sloshes around. What's the mechanism? John Riemann Soong (talk) 01:28, 6 December 2012 (UTC)

Not sure of the chemistry, but we say "the cream has set". StuRat (talk) 01:30, 6 December 2012 (UTC)

It seems that it could not set while it was kept in constant motion. Bus stop (talk) 01:35, 6 December 2012 (UTC)

Agglomeration (sticking together) of the butterfat particles? 24.23.196.85 (talk) 01:48, 6 December 2012 (UTC)

The article on butter (which is essentially what you've made) covers it, as does churning (butter). You've inverted the emulsion from oil-in-water to water-in-oil. Acroterion (talk) 02:43, 6 December 2012 (UTC)

Well, it's not butter, it's still soft. I wonder why it can't set while it's in motion, and why this setting is not reversible. If I constantly blend water at -5C, won't ice eventually form? Or would I create supercooled ice? John Riemann Soong (talk) 03:50, 6 December 2012 (UTC)