Wikipedia:Reference desk/Archives/Science/2010 June 30

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June 30

Are sodium chloride crystals always square?

Recently I've been making homemade potato salad. Never even knew how much I loved it until I made it fresh. Anyway, you put a ton of salt in the water where you boil the potatoes. So I left the salt laden water and went away for two days and when I got back I had salt crystals all over the bottom of the pan, big fat squares and smaller ones, all square crystals. I thought this was pretty neat. I just headed over to the articles and see a picture of a square crystal at the top as well as the structure, which looks conducive to squares, but I'm curious if they're always square like this?--141.155.157.4 (talk) 00:04, 30 June 2010 (UTC)

Like other crystals, salt has preferred cleavage planes. In the case of NaCl, the preferred planes are aligned at 90-degree angles (in all three axes). As such, there is a preference for square and rectangular shapes. In practice, impurities and the mechanics of forming and breaking crystal faces means that there will be imperfections. You can see such imperfections in the many images on our sodium chloride article. The atomic structure means that the alignment of faces will prefer 90-degree angles; it doesn't directly affect the aspect ratio of the crystals that form, so it is equally easy to form rectangles as squares; but because the crystal probably grew homogeneously and isotropically, a cubic structure is very common. Nimur (talk) 00:38, 30 June 2010 (UTC)

Drugs

Why are drugs so costly. I think heroin costs as much as Rs 1 crore (that's 10 million) per kg  Jon Ascton  (talk) 03:16, 30 June 2010 (UTC)

I don't imagine that the heroin industry has a substantial R&D budget. TheGoodLocust (talk) 03:28, 30 June 2010 (UTC)

Heroin is highly addictive, which means people are willing to pay such large amounts for it. The costs and risks involved with smuggling and dealing illegal drugs (if you risk many years in prison, you're only going to want to take that risk if you can expect massive profits - it's the risk/return trade-off that is discussed a few sections above) mean it isn't viable to sell it any cheaper. The combination of those two facts means that it is sold at very high prices. (If the first weren't true, it wouldn't be sold. If the second weren't true, it would be sold much cheaper.) --Tango (talk) 03:54, 30 June 2010 (UTC)

Also, since drug dealing is already illegal, dealers tend to have no qualms about using illegal business practices to get rid of competition and charge monopoly rates. Since it's so hard to quit drugs, they can get away with making these rates very, very high. — DanielLC 05:12, 30 June 2010 (UTC)

Hardly. Drugs are an incredibly competitive market. Certainly they have a low elasticity, but that balances against an incredibly fluid market, unregulated (notwithstanding, of course, the massive resources spent prohibiting them). Insofar as dealers have monopoly rates it's a function of how able they are to repel competitive dealers, which largely requires illegal activity that attracts much more attention than the actual drug selling does. In short, drug prices are high because interdiction and law enforcement efforts make them that way. That doesn't mean though that they're not a competitive market. Shadowjams (talk) 08:04, 30 June 2010 (UTC)

The book Freakonomics has a chapter devoted to the economics of crack. Its pretty good read on the subject. --Jayron32 03:45, 2 July 2010 (UTC)

why does my sink solution turn cloudy when I add baking powder to it?

I mean dissolved sodium bicarbonate should be transparent... right? Or does some of it end up not dissolving? John Riemann Soong (talk) 03:42, 30 June 2010 (UTC)

P.S. I had HUGE chunk of dishwater. Surely that's enough water to dissolve a tablespoon or two of sodium bicarbonate? Would the alkaline conditions precipitate any ions commonly found in food? John Riemann Soong (talk) 03:46, 30 June 2010 (UTC)

Do you live in a hard-water area? If your tap water has a high level of calcium or magnesium ions, then those ions could react with the baking soda to form insoluble carbonates, which could make the water cloudy. FWIW 67.170.215.166 (talk) 09:22, 30 June 2010 (UTC)

(edit conflict)

In ionic solutions, the ions are fully disassociated, i.e. if you dissolve in water the salts sodium chloride and calcium iodide, you also get sodium iodide and calcium chloride. What else was in the water? If there was a soluble calcium salt (say calcium chloride), then the insoluble calcium carbonate will be produced, which will precipitate out of solution. (Calcium bicarbonate decomposes to calcium carbonate). Do you live in a hard water area? Hard water contains calcium salts. CS Miller (talk) 09:43, 30 June 2010 (UTC)

reason of raining

What is the reason of raining ? —Preceding unsigned comment added by 203.194.98.218 (talk) 04:02, 30 June 2010 (UTC)

See rain for an explanation. Looie496 (talk) 04:58, 30 June 2010 (UTC)

V-tails

Why are V-tails so stealthy, since when top of the aircraft faces the radar it forms a right angle or corner reflector? --The High Fin Sperm Whale 05:05, 30 June 2010 (UTC)

Are they terribly stealthy? Anyway, how often do you think the top of an aircraft is going to be facing radar? AFAIK we don't have satellite based radar. TheGoodLocust (talk) 05:38, 30 June 2010 (UTC)

AFAIK V-tails reduce RCS when viewed from the side by avoiding the right-angle reflector formed by the conventional rudder/tailplane combination. BTW, in most V-tailed stealth aircraft (e.g. F-117, F-22, YF-23) the ruddervators are mounted at an angle other than 90 degrees. FWiW 67.170.215.166 (talk) 09:28, 30 June 2010 (UTC)

Yes, the critical point here is that from certain directions, the reflections are attenuated. Designers of these aircraft "estimate" which view angles are most likely during a standard flight / sortie during the high-level system-design, when things like "preferred combat sortie flight altitude," "cruising speed," and "maximum allowable proximity to hostile RADAR" are still subject to re-design. As these parameters solidify, flight profiles emerge that indicate that, for example, the aircraft might always be viewed from the side at an angle of, say, 15 to 45 degrees elevation; then the designers then attempt to make such a viewing angle the most stealthy (attenuated reflection). Pilots and mission planners are instructed to design flight profiles to keep the aircraft within its "best-performance" spec. In practice, because aircraft specs are hard to change once they are built, and combat flight profiles are subject to operational needs, the aircraft may be used during combat in a "sub-optimal" stealth regime; but it's still probably more stealthy than an aircraft that wasn't designed carefully with RADAR reflectivity in mind. What this means, on average, is that combat flight profiles that get the aircraft closer to hostile zones will result in statistically fewer detections; and thus, statistically fewer downed aircraft. Historically, especially after the fall of the USSR, the development of stealth aircraft went hand-in-hand with complete and total air superiority during most combat operations; so these kinds of design considerations are subject to fierce debate in terms of how economically effective they are. But if we were fighting an air-war on the scale of, say, World War II, when anti-aircraft fire could down 10% of the planes on any given mission, we would be fighting tooth-and-nail to improve those statistics. Every fraction of a dB of attenuation corresponds to a few extra moments of non-detection, and thus a few extra moments of tactical advantage. I could ruminate extensively on the futility of these sorts of optimizations with respect to modern warfare, but I won't... Nimur (talk) 17:20, 30 June 2010 (UTC)

Chromosome Location

Which chromosome isresponsible for the DNA that codes for our brain and memory, whether someone is naturally better at Math or better at art? Is it all encoded on one chromosome or is spread out among multiple chromosomes? Also, how is it posible to know which part of a chromosome or the genetic material encoded on say chromosome 6 for example has the DNA for brown eyes, how do scientists know this? —Preceding unsigned comment added by 71.143.241.161 (talk) 07:24, 30 June 2010 (UTC)

No one knows what codes for brain and memory, and they don't know what codes for brown eyes. At best all we can say is that a bunch of people with a similar trait all had this piece of DNA in common. But often you'll have people with that trait that don't have the gene, and sometimes people with the gene still don't have the trait. It's rare to actually be able to "read" the DNA and understand what it does. Usually all you can say is that this piece seems to be common to these traits, without understanding any of the details - and without even understanding what other DNA might have an effect too. Ariel. (talk) 11:54, 30 June 2010 (UTC)

No DNA directly codes for traits, features, aptitudes, or any such things. Bits of DNA (usually called genes) generally code (directly or via the intermediary of RNA) for the production or expression of proteins, which then interact in often extremely complicated ways (including promoting or blocking the actions and/or effects of other DNA or proteins). The end results of all these RNA and protein expressions (including, crucially, their timing) and interactions may usually, often or sometimes (depending on the context of all the other interactions going on) result in the physical manifestation of certain particular traits, features, etc of the human body and brain: saying that "gene x codes for feature y" is a frequently used shorthand expression, but glosses over the complexities and can be misleading.

Sometimes a functioning gene may not be contiguous: that is, it may be split into two (or more?) physically unconnected parts. Sometimes a part of a gene "for x" may also interact with some or all of another gene to result in "y", so the same short stretch of DNA may be expressing two (or more?) different proteins at the same or different times; also, the same protein may do two (or more?) different things at different times, or at the same time in different places, depending on the other proteins present there.

Things like higher mental properties and aptitudes are very difficult to correlate with specific bits, or combinations of bits, of DNA - the concept of emergent properties may be useful to consider in this regard.

Chromosomes are merely a way of packaging all the genes into manageable 'chunks' that are less fragile, less unwieldy, and easier to copy than if they were all in one 'chunk' - a single chromosome, which the earliest life forms with fewer genes presumably started out with. It's possible for a single chromosome to split into two, or two to merge into one, without this preventing successful reproduction by the individual concerned with an 'unmodified' mate. For example, Chimpanzees and Bonobos have 48 chromosomes instead of Humans' 46 because around 1 million years ago (after the split some 4-8 million years ago between the Human and C/B populations) two chromosomes in a human individual joined up to form one larger one which, after spreading through the human population, is now our Chromosome 2. Similarly, a human family has recently been identified in which 2 more chromosomes have merged giving a complement of only 44, though all (or nearly all) of the genes involved are still present, just differently packaged. [Sorry, can't re-find the reference for this. Anyone?] Migration of individual genes from one chromosome to another is, I believe, not at all uncommon, and minor losses (or duplications) of one or several genes in a chromosome are pretty common.

The approximate position or near-exact identity of a particular gene "for" x has in the past been worked out by looking at people with and without x, and with and without various bits of chromosomes, and finding the correlations. Now that gene sequencing has, very recently, become much easier and cheaper and the entire human genome (that is, those of a handful of individual humans) has been sequenced, this field of knowledge is moving more rapidly than laypersons (like myself) can keep up with. 87.81.230.195 (talk) 14:05, 30 June 2010 (UTC)

There are a couple of misconceptions in the original question. First, memory is not encoded in the DNA, it is encoded in the connections (synapses) between neurons within various parts of the brain. The field of neurophysiology is all about the chemical and electrical signals that mediate memory formation. There might be a role for epigenetic mechanisms in memory formation, but this is still an active area of research and not definitive. Formation of the brain itself is an extraordinarily complicated process that is guided by thousands of genes scattered across all chromosomes, acting in different cell types at different times during development. The field of developmental neuroscience aims to understand this process from anatomic, cellular, and molecular points of view. Whether a person is skilled at math or art (or both!) is a result of multifactorial inheritance and cannot be pinned to a single gene, and is equally dependent on complex interactions between their genetic makeup and their environment. See nature versus nurture for a general discussion, although I think this is a false dichotomy -- everything is about genes AND environment. The methods used for identifying genes associated with human characteristics (eye color, disease risk, complex traits) are quite diverse and depend on the specific question being asked. The OP should start with human genetics as a basic introduction to the topic. --- Medical geneticist (talk) 14:53, 30 June 2010 (UTC)

Putting aside environment for a moment, what are some of the methods used now or in the past that scientists and researchers use in order to identify genes associated with human characteristics? Does one of those methods include comparing the genes of people with a similiar characteristic or trait? And also, when they identify those genes are they able to trace them back to where and which chromosome they came from? I ask because, I once read that the location on the chromosome and which specific chromosome determines what that DNA will turn into or become, though I am not sure how true that is? —Preceding unsigned comment added by 71.143.241.161 (talk) 17:29, 30 June 2010 (UTC)

I've tried to answer part of this question below, but I'm having trouble understanding your last question. Can you clarify what you mean by "the location on the chromosome and which specific chromosome determines what the DNA will turn into or become" ? --- Medical geneticist (talk) 19:18, 30 June 2010 (UTC)

Concerning the original question: All of the chromosomes are involved in generating the structure of the brain. There are 23 pairs of chromosomes, each containing several thousand protein-coding genes. The great majority of genes are expressed in the brain, and a large fraction are expressed only in the brain. In quantitative terms, most of the information in our genome is directed toward shaping our brains. (This is not to deny the contribution of experience and environment -- I am only asserting that the contribution of genes is very large, not that other contributions are small.) Looie496 (talk) 17:38, 30 June 2010 (UTC)

As I said above, there are lots of methods that can be used to determine the function of genes. A classic method is called linkage analysis where one basically tries to identify markers that segregate with a particular trait following a particular inheritance pattern in a family. For the study of complex traits, the genome-wide association study or GWAS (unfortunately, that article could be much better) has become the dominant method of identifying genes associated with human characteristics. There have been hundreds or thousands of GWAS studies performed in the last few years, all building on the completion of the human genome and Hap map projects. One way to perform a GWAS is to compare people with a certain characteristic (disease, trait, etc) to people without that characteristic by looking at the presence of single nucleotide polymorphism (SNP) markers, which are genetic differences that are present in the general population at a certain frequency. Using fancy statistics you can determine which markers are more often present in people with the trait versus those without, thus generating an "association" between a marker and the trait of interest. By definition, we know exactly where these markers are located along each chromosome (otherwise they wouldn't be that useful) and what genes are nearby. However, association does not equate to causality and there are lots of challenges to interpreting the biological significance of any given association. --- Medical geneticist (talk) 19:15, 30 June 2010 (UTC)

Even if talents have a genetic basis, I don't think it's possible to determine that any single gene is responsible for what the individual is good at. An example of environmental factors taking precedence over genetic predispositions is music making a child more intelligent, as it has been shown that playing a musical instrument increases can make a person smarter in subjects such as mathematics, while limiting a child's exposure to music has been demostrated to have the opposite effect. ~AH1^(TCU) 21:36, 2 July 2010 (UTC)

Telescope Eyepiece

In old German astronomy texts the ocular is described as : mit 20 Linien Oeffnung ( 20 lines opening) . Is there a possibility to translate this into a unit used today? Thanks.--Stone (talk) 07:28, 30 June 2010 (UTC)

The length unit line (German: Linie) seems to be referenced here. Best see both of these articles. HTH. --Ouro (blah blah) 08:47, 30 June 2010 (UTC)

The line was a unit of length of about 1.9–2.2 mm throughout most of Europe. I've not been able to find a specific reference to the German Linie, but it's a fair assumption that it was about the same length. That makes your occular 38–44 mm: does that sound reasonable? Physchim62 (talk) 09:14, 30 June 2010 (UTC)

Perfect thanks! There was no German line. The French line was in use for most of the technical stuff like telescopes. The best point to look for is the w:de:Pariser_Linie given with 2,256 mm. Paris inch is another place to look for. Why do we have no article on the Paris line? --Stone (talk) 09:22, 30 June 2010 (UTC)

Ligne. Although I think I might merge it into Line (length) along with the other translations. Physchim62 (talk) 09:48, 30 June 2010 (UTC)

Be bold! --Ouro (blah blah) 10:56, 30 June 2010 (UTC)

I understand from the german text, that these two units are similar, but not the same. --Eingangskontrolle (talk) 19:11, 1 July 2010 (UTC)

Make more time

I've been asked at work to make more time for a project, but I'm not sure I have the necessary supplies. What's time made of? 67.188.234.85 (talk) 08:36, 30 June 2010 (UTC)

Rocks and buckets. --TammyMoet (talk) 08:41, 30 June 2010 (UTC)

A song text says: time is made from honey slow and sweet. Worth a try.--Stone (talk) 08:41, 30 June 2010 (UTC)

Yeah, that's what the song says. But only the fools know what it means. --Trovatore (talk) 08:54, 30 June 2010 (UTC)

Next you'll be sent down to the supply depot for a "long weight". CS Miller (talk) 09:47, 30 June 2010 (UTC)

Don't forget to pick up some "elbow grease" while you're there. And don't come back without it! Physchim62 (talk) 12:56, 30 June 2010 (UTC)

Making more time is easy. What you do is you find some midnight oil and ignite it. I suppose that the additional time is a waste product of this process. Googlemeister (talk) 12:59, 30 June 2010 (UTC)

I had some midnight oil, but it solidified when it got cold out. So I burned it at both ends and that worked out just fine. Matt Deres (talk) 13:40, 30 June 2010 (UTC)

If you keep it up, the <small> tag will break sooner or later. --Chemicalinterest (talk) 14:46, 30 June 2010 (UTC)

Did you intend that to be a reply to 67.188? 86.164.57.20 (talk) 15:51, 30 June 2010 (UTC)

Or your face will get stuck that way.... Paul (Stansifer) 17:41, 30 June 2010 (UTC)

Gibberish
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the best way to make more time for a budget is to make the office more like a home. spend about three thousand dollars on office fixtures that make it more like a home. and you will see that everyone on the project has more time to work on it ] Translation. --Chemicalinterest (talk) 19:32, 30 June 2010 (UTC)

In the June 2010 Scientific American article "Is Time an Illusion?", we learn that, "The universe may be timeless, but if you can imagine breaking it into pieces, some of the pieces can serve as clocks for the others." Hopefully that will help. Bus stop (talk) 19:42, 30 June 2010 (UTC)

Simple: you spend less time doing other things!--RampantHomo (talk) 01:17, 1 July 2010 (UTC)

I've also heard that you can spend all your time making money, or you can spend all your money making time. --Trovatore (talk) 01:24, 1 July 2010 (UTC)

Sheesh. Time is made of paper, ink, and staples. What else? --Anonymous, 03:36 UTC, July 1, 2010.

You can extend the time you have using time dilation. Either move slower than everyone else, move further from a gravity well, or some combination thereof. Also, make sure not to spend more than a few milliseconds doing this, or you'll waste more time than you save. — DanielLC 07:56, 2 July 2010 (UTC)

Time may be partially or completely made of Paul Simon. He wrote "Time, time, time, see what's become of me." If there's not enough Paul left (he was getting kind of small the last time I looked), he may be able to suggest other aging musicians who could help. (I don't think Crosby has much to do these days.) Twang (talk) 18:23, 2 July 2010 (UTC)

You don't actually have to make more time (ie. in a schedule, or physically creating time which is impossible) to make it feel like you have more time. See time perception and perception of time. I'm sure there are techniques to make it feel like you had more time than you did considering all the stuff you've gotten done and I've done that, however I don't have the capacity to elucidate them, but compare apathy and flow. ~AH1^(TCU) 18:35, 2 July 2010 (UTC)

Fabry-Perot filter

What's a MEMS-based tunable Fabry-Perot filter? There isn't an article on it. --76.77.139.243 (talk) 13:15, 30 June 2010 (UTC)

There is, it's just called a Fabry–Pérot interferometer! Physchim62 (talk) 13:21, 30 June 2010 (UTC)

And you may want to read up on MEMS as well. "Tunable" suggests that the wavelength that the filter passes can be adjusted, probably because the MEMS is capable of adjusting the spacing of the components on demand. -- Coneslayer (talk) 13:25, 30 June 2010 (UTC)

Why do cars go slower in reverse than they do going forward?

^Topic says it all. 148.168.127.10 (talk) 14:13, 30 June 2010 (UTC)

In general, because it is anticipated that you'll only travel for very short distances in a backwards direction; because visibility is restricted, and because steering works differently, both of which make longer distances a more unlikely proposition. And then because having only a single reverse gear calls for less machinery in the gearbox department, equalling lower cost. --Tagishsimon (talk) 14:17, 30 June 2010 (UTC)

Taking a slightly different tack: as Tagishsimon notes, cars have only a single reverse gear. It's comparable, roughly, to first gear going forward, so a car goes about as fast in reverse as it does going forward in first gear. The car doesn't go faster in reverse because there are no additional gears as there are for driving forwards. Now apply the rest of Tagishsimon's answer -- there are no further reverse gears because of cost, weight, lack of need, safety, etc. But the fundamental mechanical limitation is the single gear ratio. — Lomn 14:49, 30 June 2010 (UTC)

Actually most cars can go pretty fast in reverse gear, much faster than is safe anyway. I've always thought they should have a speed limiter in reverse gear. Maybe they do these days, it's a while since I tried accelerating hard in reverse.--Shantavira|^{feed me} 15:04, 30 June 2010 (UTC)

Yes, you can go quite fast, in the same way that you can go quite fast forwards in 1st gear, but the car doesn't like it! (And neither does your fuel consumption.) --Tango (talk) 16:33, 30 June 2010 (UTC)

Some cars do go as fast in reverse as forwards...the Bond Minicar, for example doesn't have a proper reverse gear - so to drive backwards, you stop the engine - flip a switch that makes the starter motor run backwards and start the engine running in the opposite direction! There is one such family of cars, the DAF Daffodil and it's successors that used an early continuously variable transmission called "Variomatic" - fans of the Daffodil who restore these cars have races where everyone drives in reverse! The Dutch have a regular series of races where everyone drives in reverse - and the Daffodils had to go into a class of their own because they can go 100+ mph backwards! Here is a YouTube video of one race...but I don't think it's the Daffodil class because they typically race at '-60 mph'!

Also, there are indeed cars with speed limiters in reverse. The older BMW MINI ONE's (which also had continuously variable transmissions) have to be speed-limited in reverse in order to avoid shredding their wierd rubber drive belts. It's in the nature of any normally-gearless transmission system that in order to go backwards, you have to have a way to use auxilliary gears to get into reverse (often built into the differential casing) - and that naturally results in a car that goes as fast in reverse as forwards. Since that's obviously dangerous, using a speed limiter is a smart idea.

My (stick-shift) MINI Cooper'S can do close to 45mph in 1st gear - and the 1st and reverse gear ratios are almost identical - so it clearly could go 45mph in reverse. I don't intend to find out though!

SteveBaker (talk) 19:42, 30 June 2010 (UTC)

Steering while driving in reverse at high speed is not nearly as stable as when going forward at the same speed so experimentation as to how fast your car can go in reverse is probably not a fantastic idea. Googlemeister (talk) 20:09, 30 June 2010 (UTC)

See Steering#Rear_wheel_steering. Acroterion _(talk) 20:30, 30 June 2010 (UTC)

I recall seeing an English film in which a couple were out driving in the early days of the automobile and their car did not have sufficient power to make it up a steep hill -- it kept stalling, even in 1st. They switched places and the woman backed it up the hill successfully because the reverse gear was geared lower than 1st gear. Does anyone here know (1) what film that was from and (2) how common it is (or was) to have the reverse gear geared considerable lower than 1st? -- 60.49.38.251 (talk) 11:05, 1 July 2010 (UTC)

In winter it's common to drive a Front-wheel drive car in reverse up a slippery slope to maximise the traction of the engine weight over the front wheels. Cuddlyable3 (talk) 11:24, 1 July 2010 (UTC)

No idea about the film, but lots of old (and newer) cars have reverse gears at higher ratios compared to the rest, resulting in more torque and less top speed for the gear. It only stands to reason, for all the explanations mentioned, that you would want the reverse gear to allow only slow, careful motion. Our own article on gear ratios proclaims this, at least for the 2004 Chevy Corvette. --144.191.148.3 (talk) 19:07, 1 July 2010 (UTC)

Acidity of warm water

since

1. Is warm water more or less acidic than cold water?
2. What happens when a carbonated beverage becomes warm?

--478jjjz (talk) 16:40, 30 June 2010 (UTC)

Pure water is neutral at any temperature, as far as I know (I can't think of any reason for it not to be). A carbonated beverage contains carbonic acid, so is slightly acidic. I don't know what happens to it when it changes temperature, though. --Tango (talk) 16:44, 30 June 2010 (UTC)

In practicality, water will have the same pH, whatever the temperature is. If there is a lot of carbon dioxide (such as you blowing breath through the water), then it will be more acidic when cold since more carbon dioxide dissolves in cold water.

Gases are less soluble in high temperatures than in low temperatures. So the equilibrium below would go toward the gas side. --Chemicalinterest (talk) 18:06, 30 June 2010 (UTC)

A solution is neutral when pH = pOH. This may or may not be 7, depending on the temperature. John Riemann Soong (talk) 19:03, 30 June 2010 (UTC)

I believe the pH of completely neutral boiling liquid water (no carbon dioxide) is 6.15. Now if you turn the pressure up and it boils at a higher temperature, you can increase the self-dissociation constant considerably. John Riemann Soong (talk) 19:14, 30 June 2010 (UTC)

CO₂ (g) + H₂O (l) ⇌ H₂CO₃ (aq)

What is the role of temperature in the above reaction?--478jjjz (talk) 16:49, 30 June 2010 (UTC)

Primarily because of entropy, when you warm a solution, otherwise solid solutes become more soluble, whereas gaseous solutes become less soluble. Warm water can hold less dissolved gasses (such as CO₂) than cold water. When you boil water, this is the origin of the initial bubbles you see when the water is still below the boiling point. It's not the water turning into gas, it's the dissolved gasses coming out of solution as the water warms. -- 140.142.20.229 (talk) 17:16, 30 June 2010 (UTC)

Several things I should add: While absolutely pure water contains equal concentrations of hydronium and hydroxide ions, the absolute concentrations of them varies slightly with temperature (see autoionization constant for water). Also water, even pure water, rapidly picks up a small amount of carbon dioxide from the air, pushing the pH into the acid range. Finally, in addition to the temperature dependence on solubility, there is a temperature dependence on acid dissociation constants. I'm not sure what it is for the carbonic acid <==> bicarbonate transition, but for the bicarbonate <==> carbonate transition, it's enough to cause a 0.1 pH units or so difference per 10 °C change near room temperature. -- 140.142.20.229 (talk) 17:30, 30 June 2010 (UTC)

This one smacks of homework. We won't do homework, as a rule of thumb, unless you're stuck. The second one is an unusual question though, so I'll bite: gases are less soluble at higher temperatures, so the drink will become fizzier as you warm it. This Elmhurst College page has a bit more on it. Brammers (talk/c) 17:42, 30 June 2010 (UTC)

Gases are less soluble in hot liquids, so the equilibrium would go to the gas side. In cold temperatures, it will go away from the gas side. See Le Chatelier's principle for an explanation of equilibrium. --Chemicalinterest (talk) 18:06, 30 June 2010 (UTC)

The above is true, and is true for all gases. It's an entropy effect. Physchim62 (talk) 12:40, 1 July 2010 (UTC)

The pH of water varies with temperature, and this can occasionally have important chemical effects (I personally once spent three months studying one of them, but it never got to the point where it could be published). We say that water is neutral if it has equal concentrations of H⁺ and OH⁻, but these are different chemical species with different chemistry. If you heat pure water, you will increase the concentration of H⁺ (and of OH⁻ at the same time), so you will increase the rate of any reaction which depends on H⁺ for its rate-determining step. Physchim62 (talk) 12:40, 1 July 2010 (UTC)

For a related topic on a larger scale, see ocean acidification. The oceans release more carbon dioxide from carbonic acid and are able to absorb less carbon dioxide from the atmosphere at a warmer temperature, but high atmospheric carbon dioxide concentrations that would likely be responsible for the warming result in more carbon dioxide going to the oceans and therefore more carbonic acid production and increased acidification. ~AH1^(TCU) 18:28, 2 July 2010 (UTC)

I tried to sanitise my potato peeler by sonicating it in acetone

When I dipped it in acetone it seemed fine...then I turned the sonicator on and the solution turned all black! When I removed the peeler from solution half of the lacquer/varnish had been dissolved.

question: is the peeler still safe to use for food? (I brought it from home to peel plant/vegetable tissue for the lab, but still...)

Also, why would acetone do this, as opposed to methanol, ethanol or isopropanol? Or heavy-duty glassware detergent?(Nothing happened with those agents when I used them as sonicating solvents.) John Riemann Soong (talk) 19:21, 30 June 2010 (UTC)

Acetone is a more powerful solvent. I don't think that it is unsafe. Wash away the dissolved residue and let the acetone evaporate. --Chemicalinterest (talk) 19:23, 30 June 2010 (UTC)

Because acetone is a strong solvent for paints and plastics and is used to strip some kinds of paints and lacquers? It's commonly used as nail polish remover and to remove uncured urethane, and to my knowledge, it's not a particularly good disinfectant (or at least not better than), compared to, say, ethanol or isoproanol, and more toxic to people than either, at least until it's all evaporated. Acroterion _(talk) 19:27, 30 June 2010 (UTC)

Actually acetone is not very toxic at all. It's a great solvent, but not a particularly good disinfectant (possibly because it's not very toxic). Ariel. (talk) 05:41, 1 July 2010 (UTC)

Yes, for short-term exposure, even to high concentrations, it's not too bad (and I rather like the odor), but occupational exposure to acetone-based paints and finishes can do harm. Urethane floor finishes once exclusively employed an acetone solvent/carrier, and I was acquainted with a number of floor finishers who were pretty well addled. Acroterion _(talk) 12:22, 1 July 2010 (UTC)

Acetone does it because it lacks OH groups, which means that dissolution of non-OH containing solids such as lacquer is not unfavourable as it is in MeOH , EtOH , water/detergent etc.. but it is polar, which usually helps.

Other non hydrogen bonding solvents will do the same eg DCM, CCl4, MeOAc 83.100.252.42 (talk) 21:37, 30 June 2010 (UTC)

Is carbon tetrachloride isn't polar though....isn't it exceptionally oily? How it dissolve lacquer when hexanes wouldn't?

Also lacquer I think is composed of solvent-like polymers with lots of esters or carbonyl functionalities...do esters and nonprotic carbonyls generally prefer to bond to carbonyl carbons electrostatically rather than through hydrogen bonding? I suppose it's because carbonyl oxygens are weaker hydrogen bond acceptors? John Riemann Soong (talk) 22:02, 30 June 2010 (UTC)

1. CCl4 is much more polarisable. (and a fundamentally bigger molecule that hexane)

2. a. Yes your description of lacquers sounds right.

2. b. No. The idea related to the hydrogen bonds is that MeOH etc can form 2 hydrogen bonds with MeOH, but only one with C=O , that's why hydrogen bonding solvents show reduced dissolving power compared to other polar solvents for molecules that are not hydrogen bond donor/acceptors.

Non-protic polar molecules tend to dissolve ... generally .. the polar factor is usually small compared to the entropy effect. eg acetone and hexane mix. The energy of dipole dipole interactions is going to be fairly limited compared to the thermal energy in a liquid at r.t - any interactions may be frozen out in the solid though. A hydrogen bond to C=O is stronger than a dipole dipole interaction. 83.100.252.42 (talk) 22:35, 30 June 2010 (UTC)

Next time sonicate the peeler in water with detergent! Graeme Bartlett (talk) 12:10, 1 July 2010 (UTC)

Or use a brush.. I remember your question about cleaning a knife with a gas flame.. what next?! . "I used laser ablation to remove grease spots from a tea towel and I'm worried it's affected the fabric..." Sf5xeplus (talk) 12:52, 1 July 2010 (UTC)

Ewwww brushes. I was trying to kill microbes and remove any biofilms, not generate them. 15:50, 1 July 2010 (UTC)

Parasite?

Does anybody happen to be able to identify this (I suppose) parasite? (Sorry for the out-of-focus image.) Some context: several of this white pods appeared, together with whitish spiderweb-like filaments, on a lemon plant kept in a vase on a balcony in an apartment building in Rome (Italy). The largest pod is about 1 centimeter long. Thanks! Goochelaar (talk) 19:44, 30 June 2010 (UTC)

It is a kind of a scale insect, probably Margarodidae family. --Dr Dima (talk) 20:44, 30 June 2010 (UTC)

It really looks like the cottony cushion scale.--Stone (talk) 21:38, 30 June 2010 (UTC)

Thanks to both! It looks like it indeed. My lemon is not happy, but at least I have learnt something today. Goochelaar (talk) 21:55, 30 June 2010 (UTC)

You are welcome. The easy way to deal with those guys is simply to remove them using a cotton ball soaked in vodka or dilute ethanol. Don't soak the cotton ball too much, and don't let the alcohol drip on the soil or roots. You will need to repeat this several times, every other week or so. There are species of scale insects that would color the cotton ball bright red, this is normal (it's not blood, it's carmine). --Dr Dima (talk) 22:51, 30 June 2010 (UTC)

A lemon tree? Carmine? The OP might be able to make a Campari and Lemonade --Frumpo (talk) 08:05, 1 July 2010 (UTC)

how to remove cuticle from a leaf?

Is there any way of removing the cuticle of a leaf while keeping most of the cells underneath it alive? It's okay if some of them are injured. A surfactant + sonication, maybe? John Riemann Soong (talk) 19:50, 30 June 2010 (UTC)

this paper says that the plants they chose allow the leaf epidermis to be easily (?) removed with a dissecting needle and forceps. You will probably need a good stereo microscope and a steady pair of hands :) --Dr Dima (talk) 21:01, 30 June 2010 (UTC)

Interesting..... uhh I'll try it out tomorrow. Maybe there's a way to "weaken" the cuticle? Btw, if I dip the leaves in alcohol or something it won't kill the cells inside, should it? Maybe a few seconds of sonication then attempt to pry off the epidermis? (Btw, I assume the bottom of the leaf is covered with a water-impermeable substance too ... just less waxy...) John Riemann Soong (talk) 21:13, 30 June 2010 (UTC)

The cuticle and the epidermis are different though, this paper used organic solvents - xylene, chloroform, n-butanol, and dichloromethane to remove the cuticle. They also used sandpaper and found that this was better at increasing cuticular conductance than using solvents. Smartse (talk) 21:34, 4 July 2010 (UTC)

Extinct Volcanoes in North America and Asia.

Please give me the names and information about extinct Volcanoes in Canada, Alaska, The United States, Australia, and New Zealand. Also, any other outside Reference sources of Information I can consult. --24.193.198.15 (talk) 20:58, 30 June 2010 (UTC)

You can find the ones we have articles on in Category:Extinct volcanoes 83.100.252.42 (talk) 21:05, 30 June 2010 (UTC)

You may also be interested in Large igneous province, supervolcano and extinct volcano. ~AH1^(TCU) 18:17, 2 July 2010 (UTC)

which type of plant cells (and species) tends to have the biggest / most permissive plasmodesmata

Are onion root cells a good choice, or are there other types I should look at? What are "root tip cells" btw? Could I get them from store-bought onions? John Riemann Soong (talk) 21:11, 30 June 2010 (UTC)

Plasmodesmata are all the same size AFAIK, in c4 plants the number of plasmodesmata are increased to allow a greater flow of substrate so I'd guess that they don't vary much between species and tissues. Sorry for not being able to give a reference but plasmodesmata aren't too well understood. Looking at your previous questions here, you are aware that movement proteins somehow increase the size exclusion limit though. Root tip cells are what they say on the in - cells at the tip of the root - see this, a store-bought onion won't be growing, so there won't be any root tip cells. Smartse (talk) 21:28, 4 July 2010 (UTC)

Do any nonhuman animals possess a conscience?

Or is it impossible to determine with certainty, as with love, mentioned above? --95.148.107.189 (talk) 21:52, 30 June 2010 (UTC)

As with love, how do we define it? There are definitely experiments that show that many other animals understand what we might call "fairness"—getting angry when they don't get equal treatment for other animals they consider their equals. See this story from NPR from a couple years back. Is that a "conscience"? Can we speak with any certainty about human emotions in non-humans? Do we trust Koko when she signs "mad" at the three kittens who have lost their mittens? --Mr.98 (talk) 22:34, 30 June 2010 (UTC)

(ec) You must be more specific in what you ask. Conscience means (1) ability to know good and evil, that is, to tell a moral right from moral wrong; and (2) an ability to feel remorse. AFAIK this is not directly related to the ability to feel affection or love. There exist definitions of conscience, consciousness, sentience, sapience, and self-awareness; knowing them will allow your question to be formulated more precisely (but not necessarily to be answered more fully, as the answers to most questions of that kind are not yet known). Too many a flame war has been fought due to inconsistent terminology on this subject; you would not want to be on the receiving end of most of it. Please restate your question more specifically. --Dr Dima (talk) 22:37, 30 June 2010 (UTC)

I'm not sure any of those terms have "precise definitions". In fact their articles are largely about the endless philosophical debates about what they might mean ("sapience" is the exception, because it foists the definition off onto "wisdom" and "sound judgment"). The plain fact of it is that these terms mean a lot to us as emotional/intellectual beings but applying them in a precise, "scientific" manner seems fairly impossible, because nobody can really agree on what is "precisely" meant by them (and any one "precise" definition ends up excluding other meanings that are seen as important).--Mr.98 (talk) 00:08, 1 July 2010 (UTC)

I said "definitions", I never said "precise definitions". By putting "precise definitions" in quotes you incorrectly cite the previous post. --Dr Dima (talk) 02:13, 1 July 2010 (UTC)

If you are very interested in animal intelligence, can I point you towards the books of Temple Grandin, especially Animals in Translation? They are a delight to read and extremely enlightening. If I can hazard a personal opinion, I think she does a good job of asking the "right" kind of questions about animal intelligence, and avoiding the pointless ones (which are really just proxies for "do animals have souls?" and other metaphysical dead-ends). --Mr.98 (talk) 00:11, 1 July 2010 (UTC)

If animals have any sense of morality, it must be very different from the human sense, and even that has a lot of intervariability. However, we cannot "test" to see if animals have a self-awareness, as brain scans fail to "detect" any material consciousness and humans assume that we (the self) have a consciousness but this delves into the realm of qualia. You might also like to try the thought experiment involving robots, as we cannot currently by definition create a "consciousness" in a robot just as we cannot test for a consciousness in either robots, other humans or animals. ~AH1^(TCU) 18:13, 2 July 2010 (UTC)

Neutron star vs. quark star vs. black hole

1) According to the article neutron star, the star doesn't collapse further because of the Pauli exclusion principle. But the article also clearly indicates that a quark star or black hole will collapse further. Does this mean that the Pauli exclusion principle only applies up to the point at which the strong repulsive force that keeps the nucleus from imploding applies?

2) I'm still miffed by the whole black hole paradox. As person A approaches the black hole, his clock will continue to go slower and slower until it appears to the outside world that it stops (i.e., it's asymptotic). But as person A approaches the black hole, time doesn't stop for person A. What the heck is going on here? Magog the Ogre (talk) 22:31, 30 June 2010 (UTC)

For (1), yes. And for (2), that's just what happens. It's like in special relativity, where a clock moving relative to your frame of reference will go slower than one that is stationary, except that it's caused by the gravitational field rather than the relative motion of reference frames. Confusing Manifestation(Say hi!) 23:44, 30 June 2010 (UTC)

Are we to assume that guy A just gets torn apart right at the event horizon then? Because right at the edge, time will be going infinitely fast. So we're assuming the black hole falls apart via Hawking radiation in person B's time, which would be infinitely quick by person A's time? If so, that means that person A would get ripped apart before falling within the event horizon... I think... Magog the Ogre (talk) 01:11, 1 July 2010 (UTC)

No, the person A (Shall we call her Alice?) does not get torn apart at the horizon (assuming that the black hole is big enough that the horizon is not too close to the center of the black hole where alice will be torn apart by the singularity. See spaghetification). Also even though from the point of view of B (Shall we call him Bob?) Alice does halt to a stop as she approaches the horizon, from the point of view of Alice nothing special happens at the horizon and she does not see Bob spedding up to infinite speed. Dauto (talk) 03:31, 1 July 2010 (UTC)

I think you meant spaghettification. CS Miller (talk) 06:41, 1 July 2010 (UTC)

Yes, indeed. Thank you. Dauto (talk) 17:07, 1 July 2010 (UTC)

Yes, but this is a contradiction. Bob stops seeing Alice move, her time stops. So, um, when she sees Bob, doesn't she see him quicker and quicker? That's what Stephen Hawking maintains anyway. It violates the principle that one person's reality does not conflict with another's (I can't remember the name). Grr, this is the second or third time I've brought this up on here, is there some internet forum where physicists hang out? Magog the Ogre (talk) 00:43, 2 July 2010 (UTC)

You're thinking of Leonard Susskind and his book "The Black Hole War". But it's not really a paradox (even though it seems like one); as long as the two can never get together and "compare clocks", there's no problem. From Alice's point of view, she passes through the event horizon just fine, but gets spaghettified eventually. From Bob's point of view, Alice sits near the Event horizon forever. But Alice can't come back and ask Bob what happens after what happens after (to him) an "infinite" amount of time because she's stuck in the gravity well of a black hole. Bob sees one thing, and Alice sees another, but as paradoxical as it sounds, it ends up being OK. Buddy431 (talk) 02:37, 2 July 2010 (UTC)

Alice and Bob see different things but without contradiction (That's why the theory is called relativity).For instance, from the point of view of Alice there is no Hawking radiation, while from the point of view of Bob there is a surface just above the horizon (called the extended horizon) of incredibaly high temperature from which the Hawking radiation comes from. Which one is right? Both are. To reiterate what I said earlier, Alice doesn't see Bob speeding up to infinite speed. The idea that Bob and Alice have clocks that tick at different rates and that if one sees the other one faster than the latter must see the former slower is too simplistic and plainly wrong. It is wrong even within special relativity where when two observers pass each other both of them observe the other's clock to tick more slowly than their own. Dauto (talk) 04:34, 2 July 2010 (UTC)

A related concept is the Relativity of simultaneity, which is a function of these same "paradoxes" (being paradoxes only in the classical physics or intuitive sense). It is actually impossible to determine which of two events can be said to occur "absolutely" first. For any observable pair of events which are seperated by any arbritrary space, there will always exist some frame of reference where one occurs first, and a different frame of reference where the other occurs first. This is very similar to the idea that from Alice's frame of reference, she passes through the event horizon at a steady rate; and notices no observable change to herself at the event horizon in terms of her motion, but Bob observes her stop moving entirely. That's the core principle of the term "relativity"; there is no universal reference frame from which measurements can be made in an absolute manner. All reference frames are relative to each other. --Jayron32 04:51, 2 July 2010 (UTC)

I think you may all be referring to the cosmic censorship hypothesis as the solution. Magog the Ogre (talk) 23:09, 3 July 2010 (UTC)

I don't think that's relevant. That hypothesis is about the non-existence of naked singularities. We're talking about regular black holes - there is nothing naked about them (other than their lack of hair, I suppose!). --Tango (talk) 23:50, 3 July 2010 (UTC)