Wikipedia:Reference desk/Archives/Science/2013 May 1

= May 1 =

Can Middle-Easterners be of mixed racial heritage?
Besides Middle-eastern are considered white can some be mixed, like East Indian. If not all Middle-eastern are white, where are middle-eastern most likely to be mixed with? Is most North African people whites? Do people live in Egypt and Morocco include white peoples? Is India/East Indian considered as Asian? I always remove East Indians/India from being considered as Asians because they don't look Oriental. Is Southeast Asia like Malaysia, Singaporean, Thailand ethnic diverse. Like some people living in these countries have Chinese, Vietnamese, Filipino, East Indian. I thought people in Thailand are just Thai, I didn't hear they have Vietnamese, although I hear Thialand people ahve some Chinese in their ethnic groups. Because asiannation.org don't present the interracial group with those categories.--69.233.254.115 (talk) 00:08, 1 May 2013 (UTC)
 * I count six questions and three comments there. Could you pick one or two questions from your list?  We can't deal with all that in a useful way. Looie496 (talk) 00:18, 1 May 2013 (UTC)
 * The easiest way to start might be to abandon the notion that there is such a thing as a pure or standard white person in the way that one can define a pure shade of green on the RGB color map. For example, who are whiter, Irishmen? or Poles?  There are racial differences that exist in a multi-dimensional continuum that is much more complex than anything that can be represented on a two-dimensional map.  The best one might do is map phenotypes and say that, by average facial appearances, perhaps, Burmese look intermediate to Thais and Bengalis, while Australians and Icelanders do not.  Whether Greeks or Finns are white depends on how you want to define your terms.  You might enjoy reading Cavalli Sforza and looking at some of his genetic maps.Note both Africa and Europe are green on this one. μηδείς (talk) 01:55, 1 May 2013 (UTC)
 * Additionally, if you just look up our articles on the countries you are interested in, such as Thailand, Malaysia and Singapore, they usually have the info you are after right in the lede, such as About 75% of the population is ethnically Thai, 14% is of Chinese origin, and 3% is ethnically Malay;[1] the rest belong to minority groups including Mons, Khmers and various hill tribes. The country's official language is Thai. The primary religion is Buddhism, which is practiced by around 95% of the population. . If you want more info, those articles will either have a section on demographics, or even their own whole page such as the Demographics_of_Thailand. Vespine (talk) 06:21, 1 May 2013 (UTC)


 * Racial identity and Passing (racial identity) might be of use here. OsmanRF34 (talk) 15:08, 1 May 2013 (UTC)

Corynebacterial porin B
Is Corynebacterial porin B an enzyme? Revolution1221 (talk · email · contributions) 01:01, 1 May 2013 (UTC)


 * Believe it or not, Corynebacterial porin B is an article; it sources to . I didn't see anything obvious in NCBI about porin B having known enzymatic activity or an active site for any identified reaction - as a simple channel it doesn't need to catalyze ATP breakdown - but it is not uncommon for a protein to have an as yet unidentified enzymatic activity. Wnt (talk) 01:28, 1 May 2013 (UTC)

Why does the same temperature feel so much hotter at the beginning of summer than once it's been summer for a while?
I live in Minnesota and within a week recently we went from having snow on the ground to experiencing 73 degree Fahrenheit temperatures. The other night it was only maybe 68F yet it felt absolutely scorching. I know that within a month or two that will feel like a cool temperature. What's going on inside my body that causes me to adjust? Is it blood related? Thank you. NIRVANA2764 (talk) 02:57, 1 May 2013 (UTC)
 * You get used to it. μηδείς (talk) 03:19, 1 May 2013 (UTC)


 * The concept is called Acclimatization. Wikipedia's article isn't that great, but if you want to do serious research into the concept, you'd use that word to help you along. -- Jayron  32  05:16, 1 May 2013 (UTC)


 * Relative humidity is also likely to be a relevant consideration. High temperatures are uncomfortable, but so too is high relative humidity. In many climatic zones it is likely there will be more water vapor in the air in spring than in summer. If this is true for Minnesota it is likely that 73F in spring is accompanied by higher relative humidity than 73F in summer. A day of 73F with high relative humidity could be very uncomfortable whereas 73F with lower relative humidity would not be so uncomfortable. It is this effect that causes us to say that a night where the temperature is 75F is unbearable whereas a day where the temperature is 75F is comfortable. As temperature falls the relative humidity rises, and vice versa. Dolphin  ( t ) 05:42, 1 May 2013 (UTC)
 * Yes, in the NYC and Phila areas, especially more inland, a hot day in muggy June is much worse than an equally hot day in dry August. μηδείς (talk) 16:09, 1 May 2013 (UTC)
 * See "Human Adaptations to heat and cold stress", a nice scientific paper on the subject, produced by the US army: . It covers several physiological responses, and discusses what types of temperature exposure are needed to induce reactions. This and other sources basically uphold the notion that your "comfort zone" is based on what you were exposed to in the past few weeks, and that matches your description as well. SemanticMantis (talk) 13:01, 1 May 2013 (UTC)


 * Its not just perception either. The same heat wave occurring in May (at the start of the season) tends to be much more fatal than one with equivalent conditions occurring in August (late in the season).  The Spatial Synoptic Classification program at Kent State provides heat wave warnings to major cities based estimates of dangerous conditions, and they literally require higher temperatures in order to consider a heat wave dangerous at the end of the season than at the beginning.  Part of this is psychological.  People perceive the heat and make decisions about managing it differently when it follow months of warm temperatures, than when it comes early in the season.  However, there may also be a physiological component involved in adaptation that influences  how much mortality can be expected during a severe heat wave.  Dragons flight (talk) 13:59, 1 May 2013 (UTC)

2-Oxabutan-3-one or ethyl formate
Is the activation barrier for the reaction of ethanol with carbon monoxide small enough for the reaction to be spontaneous? Plasmic Physics (talk) 07:30, 1 May 2013 (UTC)
 * Not without a catalyst. 24.23.196.85 (talk) 23:49, 1 May 2013 (UTC)
 * More specifically, a direct reaction between ethanol and carbon monoxide is a specific case of the Oxo synthesis, which requires a rhodium catalyst and produces (in this case) propionaldehyde:


 * C2H5OH + CO + H2 → C3H6O + H2O


 * which can then be reduced with hydrogen to produce n-propyl alcohol. If you want to produce ethyl formate, though, then Fisher esterification (what, no article?) of ethanol with formic acid will work much better for you. 24.23.196.85 (talk) 05:31, 2 May 2013 (UTC)
 * You mean Fis c her esterification? But I'll add a redirect from an obvious/easy-typo of his name... DMacks (talk) 05:39, 2 May 2013 (UTC)
 * Yep, that's what I meant. Thanks! 24.23.196.85 (talk) 23:54, 2 May 2013 (UTC)


 * I was trying to logically extend hydroxyaldehyde isomerisation, such as exists for saccharides, to higher bond orders. It's doesn't seem to be extendable. I was inspired by the synthesis of 2-oxabutan-3-ol from ethanol and formaldehyde. Plasmic Physics (talk) 05:41, 2 May 2013 (UTC)


 * One important thing to remember about carbon monoxide is that it is technically a carbene, so if you're trying to understand its chemistry it helps to look at it by analogy to other carbenes. That lone pair on the carbon reacts the same way other carbenes do, so you've got all of the same sorts of "singlet" and "triplet" reaction possibilities.  I've not sat down to do work out the reaction you bring up here, but I suspect that useful mechanisms would be those that take carbene-like chemistry into consideration.  -- Jayron  32  13:21, 2 May 2013 (UTC)


 * I was thinking more about a carbonyl insertion reaction. Plasmic Physics (talk) 05:35, 4 May 2013 (UTC)

Isotope enrichment
Concerning the mass spectrometric method: why isn't the element converted into a soluble salt instead of ionising it, to save energy costs? Plasmic Physics (talk) 07:45, 1 May 2013 (UTC)
 * Are you proposing using some method other than mass spec to separate isotopes? Or...well I'm not quite sure how just making something a soluble salt instead of ionizing it (aren't salts ionic?) would help MS? DMacks (talk) 14:52, 1 May 2013 (UTC)


 * It requires more energy to ionise a substance, doesn't it? Salts are ionic, but that is their natural state. Plasmic Physics (talk) 21:21, 1 May 2013 (UTC)
 * By definition, it always requires the same amount of energy to ionize a given atom, but the actual "cost" of it could obviously be different. By "ionising it", I assume you mean transiently, using some sort of electrical discharge, laser, etc.? So right there is another difference: if you enrich a salt, you get a salt; if you enrich a neutral metal (or whatever other elemental form), you get a neutral metal. If you want the neutral compound and you convert it into a soluble salt to enrich it, you then have to convert it back to the neutral form. Process design might be more sensitive to the number of steps and amount of processing than solely to the energy cost. But ultimately, you're on the right track, as our Isotopic_enrichment article notes, that MS separation is not economically practical and is rarely done unless actual cost is not a concern. If I'm still not understanding your question fully, please give us a specific example of a chemical you have in mind. DMacks (talk) 21:55, 1 May 2013 (UTC)


 * Yes, but you only need to convert the isotope to a salt once and back once in a cascade. It should remain in a saline condition between consecutive runs. To be sure that what I'm suggesting could make a significant difference, which part of the MS separation process is the most costly? Is it the transient ionisation?
 * Here is an example: suppose you want to enrich cobalt, take the sample and convert it to a solution of hexaamminecobalt(3+) chloride in liquid ammonia. Plasmic Physics (talk) 00:23, 2 May 2013 (UTC)
 * Yes, I'm aware that the counter-ion will curve in the opposite direction in each run, but certainly there is a way to rectify that at the target? Plasmic Physics (talk) 00:27, 2 May 2013 (UTC)
 * I've thought about this before too. Basically, why can't you construct a hydrocyclone where ionic species are deflected with a magnet? Or even a Zippe-type centrifuge that works in aqueous phase. 202.155.85.18 (talk) 03:00, 3 May 2013 (UTC)


 * A hydroclone is altogether different. How do you intend ficilitate magnetic fields in a hydroclone? I think that, using a liquid phase in a Zippe-type centrifuge will put too much strain on the system, it will make it too heavy to opperate at those high speeds. Plasmic Physics (talk) 13:20, 3 May 2013 (UTC)
 * What if you just had a soluble uranium salt with the natural isotopic ratio in a beaker with a stirrer, and applied a voltage using a cathode in the middle of the vortex and the anode somewhere else? The U-238 should be in lower abundance in the middle of the vortex so with multiple repetitions U-235 should be concentrated on the cathode. Obviously, it doesn't work since every 2 bit dictator isn't doing it, but why not? 202.155.85.18 (talk) 01:21, 6 May 2013 (UTC)


 * That is not a hydroclone, hydroclones filter out solid particulates, not solutes. Both isotopes would be concentrated at the cathode, that setup will achieve no-to-very poor enrichment. Plasmic Physics (talk) 02:42, 6 May 2013 (UTC)
 * Single iterations of Zippe-type centrifuges achieve poor enrichment too. That's why they're run in series again and again. Also, while what I described above is not a hydrocyclone, what you said about hydrocyclones is total non-sense. They don't filter anything and they are applicable to the separation of liquids of different densities, as noted in the lede of wikipedia's article on the topic. 202.155.85.18 (talk) 06:57, 6 May 2013 (UTC)


 * I did say very poor, and how do you suppose collecting the hypothetically enriched isotope. 'Filter' is a loose definition of 'sorting' or 'separation', which is also mentioned in the same lede. Furthermore, the solute in question is not a liquid, so the fact that a hydrocyclone can also sort or separate liquids are of no relevance. Plasmic Physics (talk) 07:40, 6 May 2013 (UTC)

Time period of a pendulum when placed in water
What is the formula (and its derivation) of time period of a pendulum when it is placed in water? Assume that pendulum is able to oscillate to and fro even its motion is being resisted by water. Concepts of Physics (talk) 08:58, 1 May 2013 (UTC)


 * Wouldn't the "period" change as it slows ? And, since the resistance in the water varies with the velocity, we could expect the pendulum to slow more at the bottom of the swing, where the pendulum is going faster, than at the tops of the swing, as well as more when the pendulum is first released. StuRat (talk) 10:00, 1 May 2013 (UTC)
 * Perhaps do it for a superfluid like liquid helium? Dmcq (talk) 10:17, 1 May 2013 (UTC)
 * I think perhaps this is supposed to be a straightforward question where one just considers the weight as opposed by buoyancy. Unfortunately the effective mass isn't such an easy factor. Dmcq (talk) 10:56, 1 May 2013 (UTC)


 * StuRat is back after a short absence (where have you been, Stu?), but he's still posting about things he should check first.
 * Regardless of whther a pendulum is in a vacuum (no friction), in air (a little bit of viscous friction), or in water (a large amount of viscous friction), the basic period is fundamentally the same - being determined by gravity and the pendulum mass-centre length. However at each swing, the peak deflection reached is a little bit less due to the viscous loss.  This means that on the swing out from centre, decelleration is faster than in a vacuum, so it takes less time to reach the peak, and while on the down swing it accelerates a bit less, less energy is lost on the upswing because of the shorter distance.  So the overal time for an upswing and a downswing is less than it would be for a vacuum.
 * We can thus conclude that the greater the viscosity, the shorter the period. It is analogous to an resonating electrical tuned circuit comprising an inductance and capacitance in parallel.  Practical inductors and capacitors have electrical resistance, which, by dissipating a small amount of energy each cycle, causes the resonation to be a slightly higher frequency.
 * It is also analogous to the oscillations of a clock or watch balance wheel. Air viscosity acting on the hairspring and on the wheel cause an energy loss in each swing, as does the bearing oil viscosity.  The result is a reduction in amplitude and a shortening of the oscillation period - the clock runs faster, NOT slower.
 * The physics math in all these cases is the same, only the units change.
 * Ratbone 124.178.42.184 (talk) 10:50, 1 May 2013 (UTC)
 * The Pendulum is dependant only on the pendulum's length, and the local gravitational acceleration. It is not dependant of the mass of the pendulum. CS Miller (talk) 12:42, 1 May 2013 (UTC)
 * Error in my post above corrected. Ratbone 60.228.254.67 (talk) 12:45, 1 May 2013 (UTC)


 * You can find an exact treatment in the case of laminar flow in the book on fluid dynamics by Landau & Lifschitz. The exact solution involves an integro-differential equation, the effective friction force at any time t depends on the trajectory x(t') for t'<t of the pendulum. Count Iblis (talk) 12:43, 1 May 2013 (UTC)

I found this article related to my question, but it explained in a complicated manner. Could someone explain the same in a simple language? Concepts of Physics (talk) 15:15, 1 May 2013 (UTC)
 * He considered that the pendulum is acted on by a notional gravity, this being the Earth's gravity reduced by the displacement of water by the pendulum - this causes an upward force on the pendulum. Because the notional gravity is less than standard gravity, the acceleration of the pendulum is lowered, and the time for one complete swing cycle of the pendulum is longer than normal.  However, measurement showed that the oscillation time was different to what would be calculated by this alone.  He accounted for this difference by taking into account momentum of the water, some of which follows the pendulum in its swing due to viscosity.
 * It would seem that my post above is wrong in part because I forgot about the momentum of the water dragged about. He essentially assumes the container of water is not full and open at the top, so that the water level rises by its displacement by the pendulum.  I assumed that pressure was unchanged, which means the water was not displaced, which is possible in a sealed container but in practice not a likely situation.  Serves me right for slinging off at StuRat, though my comment is still valid.
 * His taking into account the momentum of the water dragged about is reasonable, but I don't accept his calculated result (mass of moving water half the displaced mass - doesn't sound right, and his measured results support that he got it wrong. Consider a pendulum in oil - the displaced mass will be about the same, but the viscosity considerably greater, and more fluid will move.  So the effect on the pendulum will be different.)  Ratbone 60.228.254.67 (talk) 15:40, 1 May 2013 (UTC)

In the last part of the article, he gave a formula. Should I use the same formula to calculate the time period of a pendulum placed in water? Concepts of Physics (talk) 16:01, 1 May 2013 (UTC)
 * Yes, if you accept his reasoning and results. Note the use of the notation m* and g* - these designate the modifified mass and modified "gravity" as determined by formulae given earlier.  You need to do some substitution to actually do the calculation.  As stated above, I don't accept his theory.  His result does not look right, and he has ignored viscous frictional loss.  Do you need further explanation of why?  Ratbone 121.215.62.31 (talk) 00:33, 2 May 2013 (UTC)
 * I agree with the reasoning there, it looks about right to me, the extra momentum of the water is what I meant by it being difficult to calculate the effective mass, kudos to them figuring it out. The surface of the water doesn't matter. Dmcq (talk) 13:26, 5 May 2013 (UTC)

What does "[O]" mean?
In a simple chemical reactions, I saw the use of [O] in the equation. Here, oxygen is lying between large brackets. I want to know what does "[O]" mean? What it is denoting? Concepts of Physics (talk) 09:12, 1 May 2013 (UTC)


 * I assume they mean a single oxygen atom. The reason for the brackets would be that this is not very stable, and will soon form diatomic oxygen (O2), ozone (O3) or some other molecule. StuRat (talk) 09:56, 1 May 2013 (UTC)


 * StuRat should stick to topics he understands or has checked before posting. The normal use of square brackets in chemistry is to indicate concentration.  For instance, the rate of reaction is often of the form:
 * R = [X][Y]k
 * where R is the rate of reaction, [X] is the concentration of a chemical X, [Y] is the concentration of chemical Y, and k is a rate factor that is dependent on temperature, usually assumed to be determined by the modified arrhenious equation. Sometimes the square bracket term is shown in the form [X]2 (or some other power) meaning that the reaction rate is determined by concentration squared (or raised to some other power)
 * Where the chemical is a gas, the square brackets indicate the gas density.
 * Where you see square brackets used in equations in chemistry, they are not chamical equations such as you probably learnt in junior high school, they are equations of or depending on concentration.
 * In standard chemistry notation, single atoms (such as atomic oxygen) are always shown without a subscript, as in O, if the diatomic or polyatomic form is meant, you must show the subscript, as in O2, O3, etc.
 * Ratbone 124.178.42.184 (talk) 10:35, 1 May 2013 (UTC)


 * If [O] is used above a reaction arrow in a chemical equation, it means oxidation or the addition of an unspecified oxidant. Similarly, [H] refers to reduction or to the addition of an unspecified reducing agent.  148.177.1.210 (talk) 11:45, 1 May 2013 (UTC)

Electromagnetic absorption by water
Hi, I was reading this article (http://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water) and came across the vibrational spectrum section. I noticed that the first paragraph was cited as coming from the book Tunable Lasers by F.J. Duarte and wondered if you could tell me which page numbers this came from as I cannot find it in the book of which I have a copy.

Any help would be much appreciated.

Thanks Roan — Preceding unsigned comment added by Vazzy044 (talk • contribs) 11:50, 1 May 2013 (UTC)


 * The citation is only in respect to defining the atmosphere infrared window. But I could not find it in my 2nd Edition either.  Ratbone 60.228.254.67 (talk) 12:57, 1 May 2013 (UTC)

projectile motion
A bullet fired at an angle 30 degrees with the horizontal hit the ground 3km away.By adjusting its angle of projection can one hope to hit   a target 5km away?assume muzzle speed to be fixed and neglect air resistance. — Preceding unsigned comment added by 197.250.192.22 (talk) 14:56, 1 May 2013 (UTC)


 * DMacks (talk) 15:03, 1 May 2013 (UTC)


 * You can use the Vh=Vtsin(a) and Vv=Vtcos(a) to determine the vertical and horizontal components of the trajectory (assuming ballistic, with no air-resistance - in high-school physics these are valid assumptions). s = ut + 0.5 at2  gives the time-of-flight. These can then be manipulated to relate i) initial speed, ii) launch angle and iii) distance travelled, for a given height difference. CS Miller (talk) 15:13, 1 May 2013 (UTC)


 * Note that in a vacuum fired directly from a flat surface, a 45° angle will go the farthest. However, in the real world, air resistance alters the calculations, as does the height of the gun above the ground and the topography of the ground. StuRat (talk) 18:53, 1 May 2013 (UTC)


 * The answer, under the given constraints (which, as some people seem to have missed, explicitly assume negligible air resistance), is obviously "yes" (because you can assume a target that is at a lot lover elevation than the 3km target). --Stephan Schulz (talk) 20:53, 1 May 2013 (UTC)


 * For those who are curious, here's a link to lover elevation. StuRat (talk) 03:42, 2 May 2013 (UTC)
 * Hey, I was hunting a memory leak all day (and half the night). One little spelling mistake is nothing. Found the sucker, too, at 1:30 am (local time)... --Stephan Schulz (talk) 07:01, 2 May 2013 (UTC)
 * Good jab Stu Rat, and good argument by Stephan Schultz, too.
 * This topic is fight! I'gonna try to put a hint here how to attack this kind of gunnery problem without too much pain,as knowledge is half the battle:
 * To OP, this is one of the problems which can be solved using an upper bound. If the angle is very low (say, below 10 degrees), the range is roughly proportional to the angle. If it isn't, it can still serve as a crude upper bound. As you know, 45 degrees is the angle for maximum range. Now, do the math, and you'll get a good result.
 * That's how you can solve that kind of problems (unless the question is more tricky and asks a close enough case to defeat the upper bound).
 * 217.255.147.75 (talk) 05:53, 2 May 2013 (UTC)


 * This is straightforward. The range of a projectile fired at elevation &theta; along level ground (ignoring air resistance, curvature of Earth etc etc) is proportional to sin(2&theta;) - see Projectile motion. You know the range at an elevation of 30 degrees, so you can calculate the range at any elevation - in particular, you can calculate the maximum range, which is achieved at an elevation of 45 degrees. Gandalf61 (talk) 08:23, 2 May 2013 (UTC)
 * To explain Gandalf's point further: for an elevation angel (oops, another case of "unclear fusion") of x, the range is
 * (sin x) (cos x) R,
 * for some length R. One useful trigonometric identity states that (sin x) (cos x) = sin(2x) / 2, which has a well-known maximum. The upper bound method is not really needed as long as no air resistance is involved. And it's a lower bound. The range is less than 0.1km per degree for angles >30°, so a range of 5km cannot be achieved at angles <=50°. Then again, you'd have a negative derivative at 50°, so you'll know that there is no angle >50° with a range of 5km either. Mathematics For The Win.
 * I must be getting old. Some IP user beat me to a "pain" topic. - ¡Ouch! (hurt me / more pain) 06:32, 3 May 2013 (UTC)
 * Oops sorry. It's an upper bound on the range or a lower bound on the angle needed to achieve the range. It can be seen as both. - ¡Ouch! (hurt me / more pain) 06:39, 3 May 2013 (UTC)

Are we made to process decimal numbers?
I mean mentally, can be calculate with them faster? OsmanRF34 (talk) 15:03, 1 May 2013 (UTC)
 * Faster than what? If you are asking whether 10 is the optimal base, the usual explanation of the reason why we use base 10 is that we have 10 fingers. Looie496 (talk) 15:37, 1 May 2013 (UTC)
 * I'am aware that on the physical level having ten fingers makes it appear that's easier to add numbers up to ten using your fingers. But, could something be discovered in our brains? In the same way that our brains are somehow limited to remember smells (dogs have a much bigger area for that). Just imagine we could subitize up to 12, maybe we would use the base 12 then. Maybe the base 10 is not the product of having 10 fingers, but the product of 2x what we can subitize. OsmanRF34 (talk) 16:25, 1 May 2013 (UTC)
 * The question is still: faster than what?  If you compare base 10 to binary, it's clear that base 10 is easier for us, because it allows us to memorize tables (which our brains are pretty good at) rather than having to maintain a representation of long arrays of 1s and 0s.  But if you compare base 10 to, say, base 12 or base 8 or base 16, the answer is far from clear. Looie496 (talk) 16:33, 1 May 2013 (UTC)
 * I mean comparing with another plausible base: 12, 16 or~even 60. OsmanRF34 (talk) 18:24, 1 May 2013 (UTC)
 * Well, it's certainly easier to add .140625 + .048 than to add 9/64 + 6/125. On the other hand, it's easier to multiply 1/32 * 1/64 than .03125 * .015625. Gzuckier (talk) 16:07, 1 May 2013 (UTC)
 * I think the question might be asking about base-10 numers, rather than positional notation. That is, is it easier to mentally calculate something like 145 + 346 or 0x91 + 0x15A. My guess is that it's probably a function of what you've been taught. The Babylonians used base-60, the Aztec and the Mayans used vigesimal (base-20), and I don't think they suffered from it (if you click through the "positional systems by base" list in the info box on those articles, you can see how various cultures used different positional bases). There's also "strange" mixed systems like the yan tan tethera sheep counting systems, although I don't know if any of those were used with arithmetic (e.g. if one group had lezar sheep and the other had borna, would the Teesdale shepard know that there were bumfit sheep in total, or would he have to start counting from yan again). -- 71.35.109.118 (talk) 16:31, 1 May 2013 (UTC)
 * The Babylonian system was based on a base 10 then a base 6 to form each 60, and the vigesimal systems were typically based on 5 then 4, you can see that in the larger numbers in the yan tan tethera system. I think the number systems in use are best for remembering everyday quantities, say up to a couple of hundred, rather than for speed, if we had to frequently contend with larger numbers without writing them down I believe we'd spend time on learning to use a larger number base. People doing memory tricks typically use a base of 100 or even a thousand to chunk numbers up, to a person like that a twelve digit number is only four digits long. Dmcq (talk) 17:14, 1 May 2013 (UTC)


 * I'm am of an era before pocket calculators were invented. Mental arthritic with fractions was quick and easy before the International System of Units came along, because you had so many common denominators. One  could transpose  your head. Yet,  having everything in base 10  brought is own advantages. With big numbers, you sometimes, only have to mental  subtract/add the powers and a little metal arithmetic to get you answer.  On balance therefore, think  the modern way is better. If you're interested in math, it is worth learning all forms of notation. But  I think I know what the OP means... Being able to use factions to come up with the answer before my nephew could switch his calculator on, was not to my mind explaining math but showing off as that as an Uncle  I was a smart ass - (where old age and cunning will always triumph over youth and skill..). But fractions were not part of his curriculum – so he would not let me explain it to him.  Are are modern schools failing us? We where taught by  rote all the common signs and tans (so we could guesstimate without reference to tables), most every day problems.  We now have an education system of “one step forwards and two steps back”. No wonder China is now leading the world.Aspro (talk) 18:48, 1 May 2013 (UTC)


 * In view of those comments, maybe "mental arthritic" wasn't a spell check error after all. Very Freudian; almost Jungian.  --   Jack of Oz   [Talk]  19:14, 1 May 2013 (UTC)


 * Aspro is the typo-spell-champion: "metal arithmetic", "factions", "we where taught". No wonder China is leading the world.OsmanRF34 (talk) 19:29, 1 May 2013 (UTC)


 * Quite. We didn't have spell cheque back then to re-right watt we rote: but...
 * ''I have a spelling checker
 * I disk covered four my PC.
 * It plane lee marks four my revue
 * Miss steaks aye can knot see.
 * Eye ran this poem threw it.
 * Your sure real glad two no.
 * Its very polished in its weigh,
 * My checker tolled me sew.


 * A checker is a blessing.
 * It freeze yew lodes of thyme.
 * It helps me right awl stiles two reed,
 * And aides me when aye rime.


 * Each frays comes posed up on my screen
 * Eye trussed too bee a joule.
 * The checker pours o'er every word
 * To cheque sum spelling rule.


 * Bee fore wee rote with checkers
 * Hour spelling was inn deck line,
 * Butt now when wee dew have a laps,
 * Wee are not maid too wine.


 * And now bee cause my spelling
 * Is checked with such grate flare,
 * There are know faults in awl this peace,
 * Of nun eye am a wear.


 * To rite with care is quite a feet
 * Of witch won should be proud,
 * And wee mussed dew the best wee can,
 * Sew flaws are knot aloud.


 * That's why eye brake in two averse
 * Caws Eye dew want too please.
 * Sow glad eye yam that aye did bye
 * This soft wear four pea seas.''


 * What would have helped me would have been touch typing courses so I could look at what I was typing without looking at the keyboard instead. Like what one does when writing with a fountain pen -a communication tool from long before  your time. BUT as word possessors hadn’t been invented back then; so I am having to cope the best I can with these modern contrivances -that insist on correcting things (like spelling) for you. You too, will one-day be old, and have the piss taken out of you because you came  into the technology late. “Why don't I 'proof read' your  own text before hitting enter”,  I might next hear you say... My typist did that for me, and she  earned about  a third  or fourth  in gross  pay to my take home pay after tax. So why, should I get out of this habit when I contribute to Wikipedia Pro bono ? Anyway,  I already have you to correct things for me now – funny how the world works, isn't it   : ¬ ) Aspro (talk) 21:41, 1 May 2013 (UTC)


 * There are reasons to suppose that base 12 and base 60 have advantages. 10 is only evenly divisible by 5 and 2. 12 is divisible by 2,3,4 and 6 - so division is typically easier in base 12. However, there is a downside.  In base 10, we belabor our kids to memorize the multiplication tables from 1x1 to 10x10 - which is 55 separate multiplications - of which the 1x and 10x tables are trivial - so really, 36 non-trivial facts have to be rote-memorized at a tender age.  If you go to base 12, then you have 54 non-trivial facts to remember.  That said, when I was a kid living in the UK, we were forced to memorize multiplications up to 12x12 because with pre-decimalized base-12 currency, you frequently had to use base 12 calculations in order to do arithmetic with money.  So clearly it's possible for children to master base 12 multiplication tables...but since the number of things you have to memorize is proportional to the square of the number base - it gets unmanageable fast!


 * On that basis, I think we could work a little faster in base 12...but it's commonly believed that we do better in base 10 because we have 10 fingers.


 * But let's push this to the limits:


 * * Base 60 would be even better from a division perspective (you can evenly divide by 2,3,4,5,6,10,12,15,20 and 40) - but memorizing the 60x60 multiplication table would be horrifyingly bad! But if you *could* memorize them, then the number of digits you'd have to multiply for larger numbers would be tiny.  37x41 is an ikky calculation to do in your head - but in base 60, you have that memorized - so it's no harder than 7x8...so doing the base 60 equivalent of 3741x4137 is no harder than 78x87 in base 10.
 * Base 2 means that the multiplication tables would only demand that we remember 1x1=1, 10x1=10 and 10x10=100...which is entirely trivial. But multiplying 100010x10101 is *nasty* to do in your head - and almost every division by a non power of two results in a nasty recurring decimal!


 * So clearly, going to either extreme is bad - a happy medium for mental arithmetic is somewhere between 2 and 60. There is a trade-off between the amount of rote memorization and the reduction in the number of digits and ease of division.  Hence, I very much doubt if we'd do better in bases much smaller than maybe base 8 or in bases much higher than maybe 12...but I think 12 would have a clear benefit over 10...if we had two more fingers!


 * SteveBaker (talk) 20:19, 1 May 2013 (UTC)


 * Incidentally - I think a bigger improvement could be had from having the ten symbols we use represent the numbers -5 to +4 rather than 0 to 9. Suppose we use an apostrophy to indicate the negative symbols: So -5 in our system is 5', -4 is 4' and so on.  Counting up from zero, you count:  0,1,2,3,4,15',14',13',12',11',10,11,12,13,14,25',24',23'...and so on up to 44,15'5',15'4',15'3'...and so forth. This is clearer if you don't use 5',4',3',2',1' - but some other symbol entirely.  Anyway, there are numerous advantages to doing arithmetic like this.  Firstly, negative numbers are no longer "special".  You add them the same way you add positive numbers.  One thing I like is that when you're faced with a long column of numbers, you can go down cancelling out the all of the 4s with the 4's, the 3s with the 3's and so forth - without having to remember how many 10s to carry.  It's a little like the roman numerals system where the number 9 is IX (ten minus 1) and 8 is IIX - just as 9 is 11' and 8 is 12' in this system.  Of course it's horrible to learn once you know regular arithmetic...but that doesn't make it a bad system! SteveBaker (talk) 20:30, 1 May 2013 (UTC)
 * There's more on this in signed-digit representation. TenOfAllTrades(talk) 20:55, 1 May 2013 (UTC)
 * Its a bit like the qwerty keyboard in this respect. If we started from scratch, then this notation would be the way to go. How does it work on big numbers? There does not seem to be any problem with getting computers to out put this instead of base 10 as it is just math.Aspro (talk) 22:04, 1 May 2013 (UTC)
 * Thanks for that link TenOfAllTrades! I think you provided it the last time we talked about this too!  I can never remember the name of the system.
 * And yes, it has the same problem as switching from QWERTY...or fixing the spelling of English words. We're stuck with a path dependence issue here.
 * There are no special problems with large numbers - in the signed digit representation some numbers have an extra digit (9 becomes 11') but you don't need a minus sign (-4 is just 4'). Computers would have no problems with using this format to interact with humans.  The "two's complement" method for doing arithmetic that all modern computers have built into their hardware is, in effect, a base-256 signed-digit representation - so you could reasonably claim that computers already use this trick precisely because it's so much better than our normal notation. SteveBaker (talk) 14:00, 2 May 2013 (UTC)


 * There's some speculation that early numbering systems were base 12, and that they were derived by counting the phalanges on one hand using the thumb of that hand. Three segments for four fingers is 12.  The Wikipedia article on the Duodecimal notes this, indicating that such counting systems still exist today, using the right hand to count to 12, and the left hand to keep track of iterations of 12.  That gives one likely source of the Babylonian Sexagesimal system (12x5=60).  Now, when written in cuneiform, the Babylonian system was written in base-10 (the 60 numbers were six groups of ten rather than five groups of twelve), but the counting system itself is likely centuries older than the writing system, which could explain the difference.  -- Jayron  32  20:31, 1 May 2013 (UTC)

The techniques we use to do mental computations are not what the brain uses to process data. In recent years it has been found that the extraordinary skills of savants are actually present and used by the brains of ordinary people, albeit when processing lower level information. Unlike savants, we normally don't have access to this processing capability (we only experience the results). By supressing the temporal lobe, one can turn ordinary people into savants, see here.

When we do mental arithmetic, you have to compare this to using a computer that only runs a word processor. To run that word processor, the computer of course performs many computations, but you can't access those facilities. Then you can still do calculations in an extremely cumbersome way, by e.g. use the word count facility of the word processor. So, while you may be struggeling to multiply two 3 digit mumbers mentally, your brain routinely does much harder computations at lightning speed all the time. Count Iblis (talk) 00:10, 2 May 2013 (UTC)


 * I agree with everything Steve Baker said, except this statement "but memorizing the 60x60 multiplication table would be horrifyingly bad!". I don't think it would be that hard. I really wish we still used the sexagesimal system. Dauto (talk) 14:44, 3 May 2013 (UTC)
 * You don't even need to memorize it. There are other ways to multiply in sexagesimal with about the same speed as decimal multiplication, e.g. using reciprocal divisors or mixed-radix multiplication. Double sharp (talk) 05:20, 20 November 2013 (UTC)
 * To use that example from above: here's how I would calculate 37×41 mentally in sexagesimal, with the convention that 1'00 means sixty. 37×41 = (40×41) − (3×41) = (2/3 × 41'00) − (3×40 + 3) = 27'20 − 2'03 = 25'17. The key point is to note that sixty has the "axes" of divisors 1-60, 2-30, 3-20, 4-15, 5-12, and 6-10: thus multiplying by 15 can be effected simply by multiplying by 60 (trivial in sexagesimal) and then dividing by 4. When faced with coprimes like 37×41, you can break one of the numbers up to a number with a nice relationship to 60 (here I used 40, which is two thirds). Armed with these relationships, all you really need to remember from the multiplication table are the products less than or equal to 1'00. These are: the 2× row to 2×30, the 3× row to 3×20, the 4× row to 4×15, the 5× row to 5×12, the 6× row to 6×10, and the 7× row to 7×8. The main reason why this becomes a practical method for sexagesimal is that almost all these rows involve just factors and are thus easy to remember, and there aren't that many products left (29+18+12+8+5+2=74, not too far off from the decimal or duodecimal tables). If you have a gap between divisors, this becomes a less practical method to use. The other main beneficiary of this method is base 120; the table is as big as vigesimal's, but substantially easier to memorize. Double sharp (talk) 10:35, 8 March 2015 (UTC)

Disinfectants that don't stink ?
So, I'm happily eating my dinner at a restaurant, when the busboy starts spraying down the adjacent table with an ammonia-based disinfectant. The rest of my dinner now tastes like ammonia. Is there an inexpensive odor-free disinfectant they could use instead ? StuRat (talk) 18:57, 1 May 2013 (UTC)


 * That is when I say "excuse me I'm eating here. please spray the rag instead of the table" One time I had a busboy vigorously wiping the adjacent table so hard that he was literally flinging pieces of food from the rag onto my table gross!165.212.189.187 (talk) 19:18, 1 May 2013 (UTC)


 * That's why they call them busboys. My brother-in-law actually wrote a mock paper on the "laws of busboys". But that was before the internet. μηδείς (talk) 19:24, 1 May 2013 (UTC)


 * They could use something based on a quaternary ammonium compound - very effective and odourless. see: http://www.henryschein.com/us-en/Medical/ResourceCenter/SurfaceDisinfectantsCategories.aspx Richerman ''   (talk) 19:36, 1 May 2013 (UTC)


 * Is it inexpensive ? StuRat (talk) 19:45, 1 May 2013 (UTC)


 * Not that much more expensive, however it does need a longer contact time that products based on, say, bleach - which are cheap but smelly - but not that bad if diluted properly (think about the stuff they sell for sterilising babies' bottles - it's called Milton in the UK). Actually the correct way to disinfect a surface is to clean it first and then use a disinfectant, as organic matter tends to make disinfectants ineffective. This is less of a problem with quats and they can be made into a product that cleans and disinfects. Richerman ''   (talk) 20:10, 1 May 2013 (UTC)


 * I wonder if the management of this restaurant are aware of this practice? In Europe we (and the health authorities) would not stand for such an 'irritant' (which is what ammonia is) being sprayed around. As Richerman above correctly states: organic matter tends to make disinfectants ineffective. Therefore, the busboy should first wipe the crud off the table, then finish off with a 'clean cloth' or wipe. What your  restaurant Management use is up to them (and they most  probably  know  the States Hygiene Guidance inside out). In Europe a lot of   restauranteurs ( ok – before anybody says - “but my mum and dad never used it” were not talking about your mum and dad) use a dilute solution of distilled vinegar (1/2 to a cup to a bowl (UK units)), (which bulk bought form the wholesaler is dirt cheap and does not leave a residue. The advantage, is that it leave tables sparkling and works to the satisfaction of our health authorities. Relying on other detergents doesn't leave such a finnish.  Was this restaurant packed out with people cueing out-side to get in? The management should value your input. If they don't – then there are always other  restaurants  to pig out in (or should that be dine out in?). Whatever! --Aspro (talk) 23:47, 1 May 2013 (UTC)
 * A lot of anti-bacterial sprays for use in commercial kitchens are marked "low taint". Alansplodge (talk) 23:50, 1 May 2013 (UTC)


 * So it only smells a bit like a taint then ? StuRat (talk) 03:38, 2 May 2013 (UTC)


 * According to its data sheet its just cheap (expensive) isopropyl alcohol – so it wouldn’t leave any residue. BUT LOOK AT THE PRICE. £4.00 per litre!   I would not consider a restauranteur to  have control of his cost (and thus the quality of the food) if the table attendant  started spraying that around. That's what, £40 per litre wholesale!!! That's one of a hell of an very expensive plastic spray dispenser if you ask me.--Aspro (talk) 00:24, 2 May 2013 (UTC)
 * Am I missing something? How do you make £4 per litre retail into £40 per litre wholesale? We use very similar stuff at work - a charity - to keep the public health inspector happy. You get an awful lot of squirts out of a litre by the way. Alansplodge (talk) 18:24, 3 May 2013 (UTC)


 * With the greatest respect Al, I do think you are missing something. You highlighted a brand above... Quote:. Data sheet say's it contains  only between 5 and 10%  Isopropyl-Alcohol. Which  is  £4 English pounds per litre. Look at  add water (expensive bottled water if you like) and do the math. I think I have been over generous. I think your charity  are buying ruddy expensive plastic spray bottles with a fancy label. What do you think? Please don't think of me as a smartass, I was a commercial buyer at one time - it was my job.Aspro (talk) 22:56, 3 May 2013 (UTC)


 * Don't you think now, that these spray-things are just for housewives, who husbands just shell out the money to keep them happy? If you are involved with a charity, every £ counts. Inform the charitably committee that  the charity is better off  by following the practices of  commercial organizations. Volunteer   Beatrice et al, might think its the bees knees in their kitchens but are they  paying for the over-cost for its use in  the charities kitchens? Aspro (talk) 23:26, 3 May 2013 (UTC)


 * Speaking of things that stink, your attitude to domestic deities seems somewhat sexist and antiquated. --   Jack of Oz   [Talk]  00:20, 4 May 2013 (UTC)


 * Not at all. Consider this: if your doc told you that your wife, that she was to convalesce in bed for two weeks (– making you the house-husband), meaning  that had to do the weekly shop down  at the Mall. With all the other things you have to do during this time, you would probably only have time to whizz round and grab bottles off the shelf, without a mind to what they contained or their value for money. So doesn't it follow, if your happy getting in the shop, then you are happy with your wife's efforts to run the home. The fact that you probably (I don't know) leave it to  the wife look after the kids ( “ah but I took the kids to the park only last month – Oh was it January -how time flies”), scrub the floors, clean up after you, and do your  washing, (not now dear, I'm editing Wikipedia – tell me about it tomorrow!). I think that comment is  the pot calling the kettle black when it comes to sexism.Aspro (talk) 21:16, 4 May 2013 (UTC)


 * You referred to products that are "just for housewives", as if these are sub-human creatures who are fit only for the worst quality goods imagineable. Welcome to the 21st century.  Also, there are actually households containing more than one adult, who sometimes do naughty things with each other when they're not scrubbing the floors or editing Wikipedia, and there's not a wife or even a woman in sight. --   Jack of Oz   [Talk]  21:56, 4 May 2013 (UTC)
 * Would you have been happier if I said house-people? Think you're just trying to make a mountain out of a mole hill, when the average reader would get my gist. This type of   nitpicking on WP ref desk  reminds my of    Troll_(Internet) and Criticism. Over to you now,  as I'm sure you will want to be true true to form and let off some fireworks. 22:41, 4 May 2013 (UTC)


 * Not at all. I've made my point.  You've reacted.  It's over.  --   Jack of Oz   [Talk]  22:52, 4 May 2013 (UTC)

Does anyone know this mushroom?
It's growing in my backyard, but I've never seen it. (But I guess it must be quite common). Txs! Joepnl (talk) 21:04, 1 May 2013 (UTC)


 * Holy shit, you've got Morels in your yard! --Digrpat (talk) 21:14, 1 May 2013 (UTC)


 * I'm no mycologist, but I've eaten my fair share of Morels, and I concur that these are likely they. I still wouldn't eat these, however, as while Morels are quite tasty, then penalty for being wrong about the kind of mushroom it is could be, um, unpleasant, as Morchella indicates.  -- Jayron  32  21:43, 1 May 2013 (UTC)
 * What or who would be the most reliable source for determining whether a mushroom is toxic or not? ←Baseball Bugs What's up, Doc? carrots→ 04:12, 2 May 2013 (UTC)
 * Well, a mycologist, preferably one with graduate degrees, and with experience foraging and identifying fungi in the local region. You might get some guidance from a university extension, but even the experts are fairly reticent to give formal ID and eating recommendations, especially to people appearing "off the street". Something about ethics and liability. The experts are far more forthcoming if you sign up for a class. Much like our "no homework" policy, they will teach you the mycology you need to make informed decisions, but nobody can do your homework for you. In practice, people also learn from books, clubs, elders, lore masters, etc. The first thing anyone should learn about are the risks involved in eating found mushrooms. SemanticMantis (talk) 04:57, 2 May 2013 (UTC)


 * I recall a computer science problem in college - which was to write a piece of software that would take a list of arbitrary characteristics for some objects within a more general class - and to deduce a set of rules to divide them into two groups - and to provide a 'confidence' level for that decision. So, for example, given a description of a tree, find a rule that determines whether it's deciduous or not given things like the shape of the leaves, the height, the branching ratio, the trunk diameter, the smoothness of the bark, the soil pH it prefers and so on.  Hand the software a new tree description and it'll tell you whether it's deciduous or not - and the confidence level of that decision - and it'll list the rules it uses (eg, if the length to width ratio of the leaves is greater than 10 then it's not deciduous unless adults of the species are less than 5 feet tall...or something like that).


 * One of the dozen or so data sets that we were given to test our software with was a long list of the characteristics of several hundred species of mushroom (size, color, surface patterning, shape, smell, taste, location, etc) - with the goal to deduce which were poisonous and which were not. It turns out that there is famously absolutely no rule or even complicated set of rules to allow you to determine this with any confidence level better than chance.  The only solution is to come up with one unique rule for each type of mushroom.  That fact prevents you from knowing whether a mushroom that you've never seen before is poisonous or not - other than by feeding it to someone and observing whether they drop dead or not!  This was an excellent test of our software!


 * What I learned from that is that the only possible way to be entirely safe is to learn to recognize every species of mushroom that grows in your area - and to do so with perfect accuracy...which backs up what SemanticMantis says.
 * SteveBaker (talk) 13:37, 2 May 2013 (UTC)


 * I think that overstates the problem a bit. People who collect wild mushrooms do learn to recognize a few specific types, and stay away from anything else.  The same thing really applies to wild plants of all sorts.  It's much easier to learn to recognize things when you have a teacher and a variety of genuine examples in front of you.  For example, I can take anybody into our local hill-park and teach them to recognize poison-oak in ten minutes.  Learning to recognize it from pictures and descriptions is quite difficult, though. Looie496 (talk) 14:43, 2 May 2013 (UTC)


 * And is the method to identify poison oak in 10 minutes to apply it to your skin and see if it starts to itch and burn ? (Personally, I would consider choosing such an identification method to be a rash decision.) StuRat (talk) 06:57, 3 May 2013 (UTC)
 * Of course you're joking, but to give a serious answer, one of the big problems with poison oak is that in a person who is not sensitized, it takes several days for the rash to appear (and then you get a month of misery). Even in a person who is sensitized by repeated exposure (like me, unfortunately), it takes a day or so.  So learning to recognize it by experience is nearly impossible. Looie496 (talk) 14:34, 3 May 2013 (UTC)


 * From Morchella I understand that it's hard to grow Morels. I guess we've managed to apply the right amount of neglect to the yard to fool them. Thanks for the info! I won't be eating them btw :). Joepnl (talk) 17:37, 2 May 2013 (UTC)


 * Yes, never eat an unidentified 'shroom...that's the morel of the story. StuRat (talk) 06:57, 3 May 2013 (UTC)
 * I am not sure about the US, but in France all pharmacists have a significant amount of training on recognising edible and dangerous mushrooms (they are required to have that by law), so we always check with the local village pharmacist if we are not sure about some of the muchrooms. (I guess you would usually call them drug store owners, not pharmacists). --Lgriot (talk) 08:14, 3 May 2013 (UTC)


 * There are old mushroom hunters. There are bold mushroom hunters. However, there are no old bold mushroom hunters.196.214.78.114 (talk) 12:17, 3 May 2013 (UTC)