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August 2

No electricity for you!

According to a news article discussing the recent massive blackouts in India, [1], 1/3 of India's 1,200,000,000 never have access to a supply of grid electricity at all, under the best of circumstances, even for part of each day. It's hard to imagine viewing a house for sale in the US or the UK and hearing that there is no electric line close enough to supply it with electricity. How long ago were electric lines extended to more than 2/3 of the population of the US, the UK, France, and Germany ? Was it 100 years ago, 50 years ago, or what? Do the nonelectric 400 million Indians use Kerosene lamps, candles, or what, once the sun goes down? Edison (talk) 01:13, 2 August 2012 (UTC)

This is one of my favorite graphs. The US hit the 2/3 mark a little over 80 years ago, and we hit the 100% mark about 50 years ago. This graph is by households, and I can't rule out that that the average number of household members might be different for wired and unwired homes. Someguy1221 (talk) 01:27, 2 August 2012 (UTC)

A substantial number of that 1/3 don't even have houses. They live in camps, train stations, or wherever they can find a bit of shelter. Looie496 (talk) 01:41, 2 August 2012 (UTC)

But aren't the train stations electrified? 203.27.72.5 (talk) 02:51, 2 August 2012 (UTC)

I suspect in the more rural areas they may not be, and even if they are the lights etc are likely turned off when no train is expected. Nil Einne (talk) 05:22, 2 August 2012 (UTC)

How many homeless in India? Literally no shelter, not even a public shelter, a derelict automobile, or an improvised shack? Sleeping on the ground, in the open? In some countries many people live in hovels, but tap into electric lines and steal current. The key thing would be having mains run somewhere near the house/shack. Edison (talk) 03:03, 2 August 2012 (UTC)

Theft of electricity is a common problem in India (our article appears to be solely on the situation in India), but I think much more among those who already have or could have electricity [2] [3] [4] [5] [6]. For those in situations you mention, they are unlikely to be able to convince corrupt officials to turn a blind eye, plus if someone's shack in the middle of no where has electricity it's a bit of a dead giveaway. Not to mention they may not have the skills or tools to do it, or the equipement to do anything useful with the eletricity. (And if they did have the tools and skill, they'd probably be better of just stealing the wire to sell provided they can avoid vigilantes [7] [8].) Nil Einne (talk) 06:08, 2 August 2012 (UTC)

Agree with Someguy. In the US, the 2/3 mark was reached by about 1927, and electrification was essentially universal by 1952. Can't say about India, but the house I grew up in in Pennsylvania was not electrified until 1972 because of a combination of remoteness and local political bickering (whereas my grandparents' home in the nearby city was electrified from when it was built in 1920). Lighting and refrigeration were powered by propane gas, supplemented with kerosene lamps, with candles for dinner. The level of comfort, though, far exceeded that that you will find in rural India, even in those areas that are electrified. Clotheswashing was probably the only chore that was significantly more time consuming than in a contemporary electrified household. So comparing when the US and India reached the 2/3 mark is like comparing apples and oranges. It does not mean the levels of comfort and convenience were comparable at that point. Dominus Vobisdu (talk) 02:00, 2 August 2012 (UTC)

Another factor you need to take into account is home generation. In Australia, large amounts of the population outside of metropolitan areas of the large cities were not covered by grid electricity until the 1960's. But what people had was gasoline or kerosene - powered home and/or farm generators. So they had all modern electric lihting and appliances, it's just that they were powered from their own generators and not from a power station. In many small rural communities in those days, often a local business such as a gas-station would provide electricity to nearby houses and other buildings in the village centre. I imagine a similar thing happened in rural USA and many other countries with a significant dispersed largely farming based population. And some people had gasoline powered washing machines. Wickwack120.145.176.119 (talk) 03:08, 2 August 2012 (UTC)

I think kerosene lamps are the most popular source of lighting besides electricity in Indai by far [9] [10] [11] [12] [13] [14] [15] for households. (Despite what [16] may lead one to think, propane doesn't seem to be a significantly lighting source.) From the last two results, the percentage of households without lighting is fairly small although given the population of India, still around 1.1-1.2 million households depending on which source you use (not sure what percentage of the population this is). BTW, with reference to some of the answers above, according to the census data at least, the number of houseless households (according to the definition they use) is relatively small, although given the population of India still affecting close to 2 million people as of the 2001 census [17]. I expect the number is an underestimate (the PDF mentions it may be an overestimate but also mentions how they only visited certain areas and how they may have difficulties getting cooperation). Perhaps more importantly, just because you have access to kerosene lighting doesn't mean you use it regularly. In fact some of the other sources also note that just because you are nominally connected to the electric grid doesn't mean you have a reliable or even particularly usable supply, even discounting things like the recent blackouts. Nil Einne (talk) 05:58, 2 August 2012 (UTC)

In the UK, nearly all houses were connected to the "National Grid" by the 1960s. The nearest mains electricity to where I live was five miles away until 1961. A few houses had their own generators, but most of us used paraffin or bottled gas for lighting. One house near where I live was not connected until about ten years ago, and there are still just a few isolated properties in the UK without a connection to the "grid", but they are rare. Dbfirs 07:10, 2 August 2012 (UTC)

It's a technical quibble, mostly, but the national grid and mains electricity aren't the same thing. "Mains" just means you get electricity from a shared community power supply; "national grid" means there's a high-voltage connection between that community power and the UK's overall generating capacity. In the islands of Scotland, plenty of people have mains electricity but aren't on the grid - e.g. people on Orkney are on both, but on Shetland the power grid is isolated from the national grid. Eigg only recently got mains electricity (meaning householders didn't have to generate their own) but still isn't on the grid. -- Finlay McWalterჷTalk 00:26, 3 August 2012 (UTC)

Thanks for the correction. I'd forgotten about some of the Scottish islands. I think all the English and Welsh islands are connected to the National Grid, or at least the ones with significant population. Dbfirs 07:59, 3 August 2012 (UTC)

Why Does the Annual Mortality Rate Rapidly Increase Between Ages 113 and 114?

A 113-year old person has about a 50% chance of surviving to age 114 on his/her 113th birthday, but a 114-year old person has about a 30% chance of surviving to age 115 on his/her 114th birthday. How come? Futurist110 (talk) 02:46, 2 August 2012 (UTC)

I want to point out that the annual mortality rate stays roughly constant at ages 110-113, yet rapidly increases for ages 114 and 115. Look at the Gerontology Research Group's supercentenarian tables and you'll see what I mean. Futurist110 (talk) 02:49, 2 August 2012 (UTC)

From [18]:

Human mortality after age 110 is at at a constant level of λ = 0.7. This implies an annual probability of death of q_x = 0.5. This result confirms the previous analysis by Robine et al. (2005). Correspondingly, life expectancy after age 110 is about 1.4 years. Beyond the age of 114, data become too sparse to allow us to make reliable statements. (emphasis added)

There just aren't enough people who live to 114 in order to get good statistics on their mortality rate. Dragons flight (talk) 03:23, 2 August 2012 (UTC)

We had a similar question a couple months ago. You may be interested in some of the answers to it. Evanh2008 ^{(talk|contribs)} 03:26, 2 August 2012 (UTC)

When researching my answer for that question, I came across a wide variety of sources that gave wildly different estimates for the death-rate-vs-age curve. I recall once finding, although I can't remember where, a review that compared different methods of calculating that curve. Based on which source you went by, you could make the curve come out as a positive, negative, flat, or some exotic non-monotonic function, and the values themselves varied significantly, but all probably in the vicinity of 70% at those ages. The numbers of data points to go on at those ages is really just too small for good statistics, if you want to incorporate years worth of mortality data, you have to keep in mind that the lifespan average is a moving target, complicating things significantly. You can only trust a lifespan histogram for a cohort that is 100% dead. Someguy1221 (talk) 04:58, 2 August 2012 (UTC)

Mortality rates (or at least the ones that I'm using) are all for dead people only. And for the record, it's interesting that as the 115+ year old people ever sample got larger over the last 10 years, the mortality rate at age 114 and 115 actually increased a lot, from about 50-55% in 2000 to about 70% right now. Futurist110 (talk) 05:58, 2 August 2012 (UTC)

There are enormous numbers of different mortality tables created by different people for different purposes based on different populations and datasets. To talk about the mortality rate is meaningless. Please link to the mortality table you are talking about. Normally, mortality tables are pretty much just guesses after around age 90. They use real data until there isn't enough to draw meaningful conclusions (which, depending on your dataset and methodology will be somewhere between about 90 and 110 - definitely well before 113), and then you just pick an arbitrary age as the maximum possible lifespan and pick some smooth curve to get you up to 100% by then. You shouldn't take any mortality figures too seriously after about age 90. They are based on too little data. --Tango (talk) 17:41, 2 August 2012 (UTC)

http://www.grg.org/Adams/B2.HTM - Here is the table that I was talking about. The mortality rates are very easy to calculate from it. Futurist110 (talk) 19:48, 2 August 2012 (UTC)

That's not a useful data set for this kind of work. It is collated from various sources with no way of knowing it if is complete or unbiased. It spans more than 20 years, during which time mortality rates have changed enormously. It spans multiple countries, which have widely varying mortality rates. It is also far too small. Your 30% figure is, with 95% confidence, assuming a simple binomial model, anywhere between 21% and 37%. Your 50% is actually anywhere between 33% and 61%. So, you see, they could actually be exactly the same and it would still be consistent with your data. Your dataset is too small to give enough make the confidence intervals small enough that they don't overlap. That means you can't draw any conclusions. --Tango (talk) 01:14, 3 August 2012 (UTC)

Ah, the miracle of the confidence interval. --TheMaster17 (talk) 08:54, 3 August 2012 (UTC)

Actually, I think that all or almost all of these cases with the exception of the Japanese ones have been verified by the Gerontology Research Group and its correspondents. As for Japan, their koseki system is very efficient, and thus the GRG does not usually consider it necessary to double-check Japanese cases. Thus, we know for a fact that all or almost all of these cases are accurate and reliable. As for what you said about confidence intervals, that is very interesting. Let me look more into that. Futurist110 (talk) 22:00, 3 August 2012 (UTC)

Earthing

What is the simple way to check whether the earth wire of a house electrical circuit is properly grounded? Thank you.175.157.5.252 (talk) 03:17, 2 August 2012 (UTC)

Call a competent electrician and ask them to check it out. Nil Einne (talk) 05:20, 2 August 2012 (UTC)

I tried looking this up online, only to deduce that doing it properly is not simple at all. Someguy1221 (talk) 05:26, 2 August 2012 (UTC)

The OP geolocates to Sri Lanka. I'm not at all certain, but Sri Lanka should be a country that uses the Multiple Earth Neutral System (MEN), or a close variant. In this system, the house earthing system has two main parts: An earth stake buried in the soil, and a connection to the street distribution nuetral wire. The house earth stake is of prescribed length, and it is generally sufficent to make a visual inspection. If the stake has no significant corrosion, and the wire connected to it is sound and the method of connection is sound (ie a pip clamp in good condition), then assuming the original installer did the right thing, that's all that's realy needed. The earth stake at each house does not ON ITS OWN do much - the system relies on all earth stakes at each premises fed from the street distribution having all their earth stakes connected in parallel by the power company's nuetral wire. All the earth stakes in parallel provide a low impedance to sink fualt currents even though an indiviual eartb stake caould not do so. If the neutral connection from the power company's strett wires to the house nuetral is deffective, then the house will have no power. If you know how to use a multimeter, check between your nuetral bar (in meter box) or the nuetral or earth pin of any wall outlet and the earth stake, on the earth stake below where the wire connectes to it. Check first for voltage - there should be well under a volt. If there is no voltage, then check resistance - it should be less than one ohm. These checks do not 100% guarantee everything is fine - beyond that you need a trained electrician. However they cover alll common deficiencies in an MEN system in a reasonably built up area. If you live in a new, undeveloped area or are isolated in a remote location, there's a bit more to it. Kiet121.215.2.150 (talk) 05:55, 2 August 2012 (UTC)

Determining that you have a ground is relatively simple, but determining that it's a proper ground is not. For example, you might currently only have a ground because a puddle of water is making the connection, which obviously isn't a proper ground, as you will no longer be grounded once that puddle disappears. StuRat (talk) 08:27, 2 August 2012 (UTC)

With the MEN system, that isn't generally a factor. A visual inspection, and grasping the stake and attempting to wriggle it is sufficient, assuming the installation was done in accordance with standards, as the electrical resistance to the "great body of earth" of an individual earth stake is unimportant. If an earth stake is so badly corroded that a puddle makes any significant difference, you'll almost always notice it on inspection. The most common defect is the wire is broken or the wire is no longer connected to the earth stake due to accidental damage or a defective clamp - all of which is easily spotted on visual inpection. In unusual situations such as remote area single-wire-earth-return feeds, there's more to it, but I did include a disclaimer. Keit120.145.189.101 (talk) 10:28, 2 August 2012 (UTC)

The suggestion to "wiggle the stake" is utter nonsense except to note that the wire is not connected to the ground rod. Such a practice could result in you holding a wire broken off by the action from the ground rod, with lethal high voltage on it, flowing through your body to ground. A utility I worked for would drive ground rods at transformer sites in 5 foot or so incremental lengths, with each stake screwed into the previously driven one. I would use a "ground megger" to measure the resistance of the new ground to several remote grounds. Sometimes it required 30 feet of ground rod to get to a required low impedance in soil underlaid by sand. A puddle at the surface would have scant effect on the portion 10 or more feet down, Several rods might be driven several meters apart and connected in parallel by large cables. One approach was to drive multiple grounds and use solution of a system of equations to determine ground impedance. Another approach was to use a remote ground. as a reference.Requirements might be less severe at a residence. Local codes will specify how low the impedance must be.and how many amperes of fault current the ground rod or system must sink without melting, possible thousands of amps for some time until fuses or breakers operate. In some US locations, codes might allow a clamped connection to a cold water pipe connected to a municipal water system by sturdy metal pipe, with a suitable jumper bypassing the water meter. It is not a job for the uninformed novice. Electrical shock hazard or structural fire might be the punishment for a mistake. The local ground has as one job the prevention of dangerous high voltage on all the conductors in a building if the transformer has a fault and primary voltage arcs to the low voltage secondary. Edison (talk) 05:14, 3 August 2012 (UTC)

Actually, Edison, it is YOU that wrote utter nonsense. Let's go thru this carefully: Firstly, the OP specifically asked about a HOUSE installation - not a substation, not a power station, not even a street transformer - just a house. My answer above is valid for a house, and is not intended for substations etc. Secondly, he geolocates to Sri Lanka. If he was in UK, Australia, Germany, etc, my answer would have been "go find a qualified electrician." But in Sri Lanka, he could be well off and in a quality city dwelling, or he could be in more third world conditions, and he may need to be both more interested and more resourceful. An lastly, and most importantly:-

I'll say this one more time, in capitals, so read it carefully: IN THE MEN SYSTEM (which these days is most of the World. USA may be different) INDIVIDUAL DWELLING EARTH STAKES INDIVIDUALLY DO NOT DO MUCH. THE SYSTEM OPERATION AND SAFETY COMES FROM A MULTITUDE OF SUCH EARTHS CONNECTED IN PARALLEL by the supply authority's neutral wire. You can (though it is illegal) cut any ONE of them without making any noticable difference. You are NOT at risk of shock if you disloge the wire from the electrode, any more than you would be if you disloged it accidentally, as I have done with a lawnmower. Electrical saftey standards must cover this sort of situation - in fact any system that allowed safety to be compromised by a single point of failure is just not on. You are however, generally expected by the terms of the supply contact you have with the electricity supplier to put any damged or corroded wire and/or elctrode right promptly - otherwise you could end up with most of the earths in the area damaged, and then there would be a problem. Household earths are not normally specified by performance, they are specified in terms of a mandatory stake/electrode length (typically 1.5 meters). A typical house earth may well be several hundred ohms resistance. If there is an appliance fault, the bulk of the fault current DOES NOT go to earth via your own earth stake. It returns to the transformer via the supply authority's nuetral wire, with only small amounts of current entering and leaving earth via individual stakes on the way.

It is thus perfectly ok to check the validity of the clamp that connects the wire to the eath stake by attempting to wriggle it. If it moves it's not up to scratch and needs fixing. It is possible that the buried part of a stake has corroded away. But if you grasp it and try to move it, and you can't then it's fine (resistance is not what makes it legal - only its depth). If you can feel it move at the top , then it needs fixing. Visual inspection and "wriggle" testing is what an electrican will do. An earth megger and similar instruments is not what the OP will have, and it has no relavence, as the requirement is a buried depth, not a specified resistance.

Keit60.230.203.89 (talk) 12:44, 3 August 2012 (UTC)

If you are testing grounds relative to other grounds, how is it determined that the first ground is working? Someguy1221 (talk) 07:54, 3 August 2012 (UTC)

This has absolutely NO relavence to teh OP's question, however: Special instruments are available, for which the internal operation is a bit complex to explain here, at least without diagrams and assuming a sound knowlege of meshed electrical circuit mathematics. Essentially, what they do is use selected earth stakes chosen as potential reference access points, and force a current though the earth stake under test, monitored by a sensing coil clamp around the electrode or its' connecting wire. The instruments do an internal calculation to find the resistance to "great body of earth" of the electrode under test. As long as the resistance of the reference electrodes is less than a certain amount, the resistance of reference electrodes does not affect the result. Earth electrodes near each other and near to other structures (eg metal pipes) share current paths through the soil to the great body of earth - this is manifested in what electrical engineers call "common resistance" - a resistance common to nearby stakes/electodes and added to the unique "component" resistance each electrode. In other words, 2 nearby electrodes form what is equivalent to "Y"-shaped circuit to great body of earth. I hope this is clear, as the subject is actually of some complexity, and the accurate measurement of earth systems is actually something that requires specialist knowlege of engineers. Whole textbooks have been written on this subject alone.

I point out that the words "ground" and "grounded" is USA terminology, but has spread around do to the wide availability of US textbooks and magazines. This is unfortunate, as the meaning of these words depends on context, and can be a source of confusion. The correct terminology for most of the English-speaking world is earth, meaning the great body of earth, earthed, meaning effectively connected to the great body of earth, earth stake or earth electrode, meaning the means of connecting to the great body of earth. Keit120.145.181.139 (talk) 11:15, 3 August 2012 (UTC)

Supplementary question from editor Edison moved to a new question Explain electricity consumer earthing by Keit. I moved it because an answer requires coverage of several related topics and would most likely not help the OP for this question. The OP is of course free to read the new question and its' answer(s). Keit60.230.207.82 (talk) 04:01, 5 August 2012 (UTC)

spina bifida case

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

203.27.72.5 (talk) 08:16, 2 August 2012 (UTC)

Big Bang of nothing

Was the initial condition of the Universe an infinitely tiny bit of totally empty space? Since the initial mass of the Universe would be zero, dividing zero mass by zero volume does not give a singularity.

Then cosmic inflation hits and this empty space is blown up at vast speeds. This is all fine and dandy until a virtual meson pops up. This virtual meson is then torn apart before it can pop out. In order to avoid two bare quarks, each of the quarks gets paired up with another quark, giving a universe of two mesons. Each of these two mesons is then torn up, giving four mesons. Then eight, then sixteen, etc.

Exponential meson production continues until the Universe has enough mass/energy to reach a flat state and this stops inflation. The mesons then decay through the weak force, which applies its bias towards matter over antimatter. Would the result fit the observed Universe? Hcobb (talk) 13:14, 2 August 2012 (UTC)

I'm not an expert cosmologist, but as far as I understand the current theory, the standard models of the big bang start at infinite (or at least very high) densities, not at density zero. Energy already existed during cosmic inflation and was "stretched flat" by it - this explains the largely flat, isotropic and homogeneous appearance of the cosmos. If matter/energy was created during inflation, there is no good reason for this flatness. --Stephan Schulz (talk) 13:25, 2 August 2012 (UTC)

For most of the inflationary epoch, the universe is almost empty except for the scalar field (the inflaton), which is similar to the modern-day dark energy and the Higgs field—it has mass/energy but it's not matter in the conventional sense. Eventually the inflaton field decays, and that's the origin of all of the matter in the present-day universe. Any ordinary matter from before inflation is diluted to the point of irrelevancy. There is interest in looking for magnetic monopoles as relics of the pre-inflationary universe, but there's no theoretical reason to suppose there's even one of them in the present-day observable universe. -- BenRG (talk) 19:45, 2 August 2012 (UTC)

One outstanding question in cosmology is whether the early universe was isotropic and homogeneous. For example, consider reading this section, anisotropy in the observed cosmic microwave background. To the best of my understanding, the universe we see today appears very isotropic and inhomogeneous: it is still unknown if today's universe evolved from a similar isotropic, inhomogeneous initial condition. Nimur (talk) 15:10, 2 August 2012 (UTC)

If you mean the universe of 13.7 billion years ago, there's no question that it was extremely isotropic and homogeneous. The present-day universe is still very much so at large scales (~1 billion light years), but it's neither homogeneous nor isotropic at smaller scales. This is a result of magnification of slight inhomogeneities in the early universe by ordinary gravitational attraction. This process is well understood (though not by me). If you mean the universe before inflation, nobody has any idea. According to the inflationary model, the observed fluctuations in the CMB come from quantum fluctuations during inflation. They have nothing to do with the pre-inflationary universe. -- BenRG (talk) 19:45, 2 August 2012 (UTC)

Stephen Hawking insists that there was nothing prior to the big bang.

If our big bang article is correct, the concensous among scientists currently is to asume that the universe started of as a singularity with very very very high tempretures and pressure. The whole thing is very very complicated (I haven't been able to digest it completely yet) and coupled with the fact that the article provides a lot of info on this I feel that I don't need to repeat all of it here.Aliafroz1901 (talk) 16:10, 2 August 2012 (UTC)

Singularities are maths way of telling you you've made a mistake. I'm not sure any scientists actually think the universe had infinite density at time t=0 - what would that even mean? The singularity just tells us that it doesn't make sense to extrapolate all the way back to t=0 like that. Our understanding of physics starts a tiny fraction of a second after the "Big Bang", at which point the density was extremely high, but finite - we don't know what actually happened before that. It may well be that nothing interesting happened at t=0, it's just the time you happen to get to if you incorrectly extrapolate back. --Tango (talk) 17:51, 2 August 2012 (UTC)

Given the evidence,[19] it's safe to say that it all happened in the Big Inning. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:21, 3 August 2012 (UTC)

The inflaton field does not need to decay. Just mix with virtual particles and Quantum chromodynamics will suck the energy out of the inflation field into a uniform meson soup. It's Hawking radiation on steroids because as soon as any mesons are created they'll exponentially multiply like rabbits. No new physics is needed, just an empty tiny bit of space suffering from a Negative Space Wedgie. Hcobb (talk) 00:37, 3 August 2012 (UTC)

Tango I never said that the universe had infinit pressure, what I said was that it may have had extremely great pressure. And you are correct We don't know what was there at T=0, I know that and I was not presenting unchalengeable facts, only presenting the sciontific concensous on the matter.Aliafroz1901 (talk) 10:46, 3 August 2012 (UTC)

... and, of course, in some models, there never was a time t = 0, as Tango implied above. Dbfirs 11:22, 3 August 2012 (UTC)

"and, of course, in some models, there never was a time t = 0" some models doesn't mene all thereies, and If the above linked big bang article is correct the big bang only tooke a few seconds to complete so most thereies would include a time T=0. — Preceding unsigned comment added by Aliafroz1901 (talk • contribs) 16:32, 3 August 2012 (UTC)

... It all depends on what you think time is! Using conventional modern "time", the earliest we know about is the Planck epoch. Dbfirs 06:13, 4 August 2012 (UTC)

How do antibodies kill antigens/pathogens?

How do antibodies kill antigens and pathogens? Does the antibody kill the pathogen/antigen directly, or does immune cells kill the marked pathogen/antigen, or both, and if the antibodies kill the pathogen/antigen directly, how does that work? — Preceding unsigned comment added by 187.126.186.208 (talk) 14:10, 2 August 2012 (UTC)

See the Wikipedia article titled Antibody which explains all of that, and a lot more. --Jayron32 16:17, 2 August 2012 (UTC)

I found the following in the above article

"An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. Each tip of the "Y" of an antibody contains a paratope (a structure analogous to a lock) that is specific for one particular epitope (similarly analogous to a key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly (for example, by blocking a part of a microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.

Antibodies are produced by a type of white blood cell called a plasma cell. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR). The BCR is only found on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells, or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms."

So the answer to your first questionn seemes to be that both antibodies and immune cells kill antigens. and for the second it semes to be that antibodies kill pathogens via several methods with one of them being blocking an issential part of a microbe.Aliafroz1901 (talk) 16:49, 2 August 2012 (UTC)

Weight increments on a digital scale

I have always been curious and puzzled by this. Can someone please explain this to me? I have consistently noticed that digital weight machines (for weighing the human body) always seem to present the person's weight in increments of 0.2 pounds. So, the person weighing himself might get results of, say, 170.0 or 170.2 or 170.4 pounds, and so forth. But, the scale will never list weights such as 170.1 or 170.3 or 170.5 pounds. Why is this? I assume it has something to do with accuracy, precision, and rounding, etc. But, still, can't the machine (scale) "round" to the 0.1 pound increment, just as easily as its programmers selecting to round it to the 0.2 pound increment? This befuddles me. Any input? Again, I am referring to digital scales that measure the human body (e.g., a person trying to lose weight). I am not referring to the smaller types of scales that might measure fruit or food (in ounces or grams) or such. Thank you! Joseph A. Spadaro (talk) 16:51, 2 August 2012 (UTC)

A digital scale typically has an electronic sensor that converts weight to a voltage. This analog voltage is then converted in an analog to digital convertor (ADC) to a digital number. The ADC outputs a number with a fixed step size, each step representing a voltage difference of, in this case, 0.2 pounds. The ADC has a fixed and limited number of output values, so the scale cannot detect changes smaller than the step size of the ADC. To display these changes, the scale would need a more sensitive, more expensive ADC. It is also possible that manufacturers prefer to use the same ADC in scales that use pounds as they use in metric scales, which have often a step size of 0.1 kg, which is roughly 0.2 pounds. - Lindert (talk) 17:13, 2 August 2012 (UTC)

I've noticed that digital scales also have programming to make it look like you weigh exactly the same thing unless there's some large difference. This keeps it from giving a slightly different weight if you step off and right back on, and thus makes it seem more precise than it really is. I'm surprised they don't randomly sometimes add 0.1 to the weight (and then remember that), to make them look more accurate as well. (Heck, they could evenly randomly add several digits, to really make it look accurate, but that would cost more in display digits.) StuRat (talk) 17:43, 2 August 2012 (UTC)

Never confuse resolution with accuracy. Most digital scales for body weight are designed to weigh to a maximum weight of 130 kg or 300 Lb, with a display resolution of of 0.2 kg or 0.2 Lb. That's a resolution of 0.2/130 => 0.15% (in metric mode) or 0.2/300 => 0.07% (USA mode). The accuracy won't be anywhere near as good as that - 2% accuracy would be a good achievement with standard electronic circuitry. So while the display can resolve to within 0.1 kg or 0.1 Lb in terms of available digits, when weighing a 100 kg (220 Lb) man, you can only trust it to within 2 kg (4.4 Lb).

So why do they display to within 0.2 and not 0.1? ADC's (as mentioned by Lindert above) are made in standard resolutions: 8-bit, 10-bit, 12-bit, 16-bit, and 24-bit. The more bits, the greater the cost. If a scales manufactuer chooses to buy 8-bit ADC's, and decides to set the maximum weight at 300 Lb, the resolution will be 300/2⁸ = 1.17 Lb. That's good enough weighing a 300 Lb man (it exceeds the system accuracy) , but what if Mother wants to weigh her 20 Lb child? The resolution is then 1/20 ~ 5% - not too good. So, most manufacturers wil choose a 10-bit ADC. Then the resolution will be 300 /2¹⁰ = 0.3 Lb. Most electronic engineers, though, know a simple circuit trick to get another bit of resolution without the expense of a 12-bit ADC. So the system resolution is 11 bits i.e., 0.15Lb. Since to display this will require the cost of an extra digit, a quick bit of programming of the internal micro-computer will round it to 0.2. This can also save a few cents on the cost of a transistor etc to drive the display to resolve to 0.1.

The reason for the disply stability mentioned by StuRat is an issue with digital readouts well known to electronic engineers known as "Least significant bit uncertainty". In digital systems fed by an analog (ie continously variable) inputs such as force measuring strain gauges, small random variation in the input value and noise in electronic circuitry can, if the measured vaule is close to toggling the last digit, cause the last digit to rapidly flip between two adjacent values. Electronic engineers are used to this, but it can make non-technical people think the device is faulty or not trustworthy. So what we do is add hysteresis - the weight must increase at least twice the display resolution before the display is updated. Most bathroom scales wait until the weight is stable for a few seconds before settling on a value though.

Keit121.215.24.203 (talk) 23:58, 2 August 2012 (UTC)

I think they go beyond that, though. They don't want anyone to weigh themself twice in a row and get a different reading the second time, so require quite a large change from last time before they will register a change. Ironically, this improves the apparent precision while actually reducing the accuracy. You can trick it into giving you a real 2nd reading by adding a known weight, like 10 lbs, and then subtracting that. StuRat (talk) 04:16, 3 August 2012 (UTC)

That could add more error than you think it's eliminating unless you've ensured that your 10lb weight is exactly 10lbs. I highly doubt it is common practice for digital scale designers to include hysteresis, as consumer goods' sales are unaffected by small differences in post-purchase observed quality, perceived or otherwise. It is possible to see instrumentation report an identical voltage several measurements in a row, and there may even be some hysteresis effected by the circuitry, but to suggest it is intentional is unsubstantiated. BigNate37_(T) 05:27, 3 August 2012 (UTC)

It's definitely the case on my scale. I can eat a big meal, without using the bathroom, and it still reports the same weight as before. They don't want people returning the scales when they see how imprecise they are. With this system, they likely fool the people until after the return period ends. StuRat (talk) 05:32, 3 August 2012 (UTC)

Have you tried weighing yourself, and then reweighing yourself holding some weight that's say something like 5 pounds just to see if the scales still report the same thing? You could also weigh yourself repeatedly and each time increase the weight you're holding until you should be reading quite a substantial amount more. I, for one, doubt that any scales are designed in that way. 101.172.127.247 (talk) 08:13, 3 August 2012 (UTC)

What StuRat is describing is a symptom of possible mechanical binding, or a possible fault in the electronics. As a professional electronics engineer I am very familiar with the use of hysteresis in the manner I described. As I said above, many scales wait until the reading is stable for at least 1 or 2 seconds and then feeze it. It may be that Stu's scales work this way, and are programed to detect a large change as time to unfreeze the display - I have not seen any like that. The various scales I've seen either don't freeze the display, or if they do, they stay frozen until you get off completely. It is sufficient to "cover" +,- 1 digit to solve the least significant bit ambiguity. In pactice a design engineer may choose to make it cover 2 digits in order to ensure that production variation in parts and parts aging in use is not going to be an issue, but I would not expect more than that. I've tested my scales by taking 1 reading with just a large drum of carefully measured water (20 kg), then adding 0.2 kg, and the reading went up as expected, but both readings were about 3% low. Keit120.145.181.139 (talk) 11:32, 3 August 2012 (UTC)

I've heard of fake repeatability, by storing and repeating the last weight if it's close, being a common 'feature' in cheap scales see e.g. [20] [21] [22] [23]. These primarily refer to bathroom scales but I've also heard of it occuring in some kitchen type scales. As mentioned [24] and some of the other links, most scales only seem to store the last value, so rather then doing StuRat's complicated suggestion, just start the scale then add some other weight, allow it to stablise and take it off is usually enough to avoid the (IMO) cheating circuit if you want to determine real repeatibility of the scale or just get a new result from some intentional change. Another form of (IMO) cheater circuit, particularly common in cheap kitcen scales of the brandless made in China variety yet ironically very annoying when you're actually using them for their intended purpose appears to be what you're (Keit) referring to, i.e. drift rejection; where if the weight slowly changes it assumes it's drift and does not change. So if you add stuff too slowly it can seriously reduce the accuracy from what the scale is capable of because it takes a while for the scale to accept it's being changed [25]. (P.S. Whether these are useful features to the consumer or silly cheating obviously depends on one's POV, I've made my views clear but I understand not everyone will agree.) Nil Einne (talk) 20:42, 3 August 2012 (UTC)

Thanks, Nil, I knew I wasn't imagining it. Keit, you're lucky if you've never encountered this "feature" before. My strongest objection to this practice is that you can't tell if a scale uses this method or not, until you buy it. Nothing on the label tells you, and they aren't likely to let you try out the scales first (at the stores where I shop, at any rate). You could try reading online reviews, but those unfamiliar with this deception might say the scale is extremely accurate, since they step off and back on and get the exact same weight. StuRat (talk) 23:32, 3 August 2012 (UTC)

Thanks to all for the valuable insight and input. It does, indeed, make sense now that I have read the above replies. I can now understand why the manufacturers choose the scales to display weight to 0.2 rather than 0.1 pounds. Thanks again. Much appreciated! Joseph A. Spadaro (talk) 22:57, 4 August 2012 (UTC)

Can a singularity spin?

I was watching a video by creationist Kent Hovind and he was bashing the Big Bang Theory, and one of his claims that the BBT is false is his assertion that the singularity was spinning before it "exploded" (I know it didn't explode, but rapidly expanded). He contends that due to the conservation of angular momentum, all of the galaxies must be spinning in the same direction, but he points out that some of them are spinning in opposite directions. Two questions, can a singularity spin, and if so, was the singularity that spawned the universe, spinning before it expanded during the Big Bang? 148.168.40.4 (talk) 17:55, 2 August 2012 (UTC)

The cosmos has no net angular momentum (to within experimental precision). The spins of individual galaxies come from random local perturbations in the highly uniform initial state. They point randomly in all directions.

Singularities don't really have any properties. They exist in theories and are a sign that there's something wrong with the theory (for example, the ultraviolet catastrophe is a singularity in classical physics which was solved by quantum mechanics). The big bang singularity should disappear in a better cosmological theory, perhaps based on cosmic inflation. However, a cosmos with an overall spin is possible in general relativity, so the lack of overall angular momentum does need to be explained. It is a prediction of inflationary cosmology. -- BenRG (talk) 18:35, 2 August 2012 (UTC)

I suspect that Mr. Hovind is confusing the origin of the solar system (which did start with a spinning mass of dust) and the universe. I don't think cosmologists say the early universe was spinning. thx1138 (talk) 19:11, 2 August 2012 (UTC)

It's not even clear to me what "spinning" in respect to the universe would mean. Spinning compared to what? The Universe, which emerged out of the mathematical singularity, is all that is. What would be the frame of reference to say "it was spinning"? --TheMaster17 (talk) 08:51, 3 August 2012 (UTC)

That's a difficult question. Spin is not necessarily dependant on a frame of reference. Consider two masses in deep space connected be a string. If they are spinning, the string will be pulled taut. If they aren't, it won't. Whether the string is taut or not is not a frame dependant observation. --Tango (talk) 11:38, 3 August 2012 (UTC)

Yeah, I was wondering about this frame-independence of rotation, too, after I wrote my comment. But how would this appear from inside the universe? You would need a centripetal force (for example gravity) to hold the spinning "thing" together, wouldn't you? And wouldn't that mean there had to be a "center of rotation" somewhere (and in total, a physical difference between directions: spinward, anti-spinward and perpendicular), for which we have no indication (because the observable universe is isomorphic)? But I admit I'm out of my field with this topic, my lessons regarding relativity are mere distant memories. --TheMaster17 (talk) 12:28, 3 August 2012 (UTC)

It's not really my field, either... I don't think you need a centre of rotation, but you do need an orientation. So the universe could be homogeneous but it couldn't be isotropic. As you say, that isn't consistent with our observations. --Tango (talk) 17:29, 3 August 2012 (UTC)

You can have rotating black holes, so I don't see why the initial universe couldn't also have spin. The evidence suggests it didn't, though. --Tango (talk) 11:38, 3 August 2012 (UTC)

What evidence suggests the universe is not or had not been spinning? μηδείς (talk) 06:33, 4 August 2012 (UTC)

See my short discussion with Tango above. If the universe today would be spinning, not all directions in the universe would be the same. You would expect measurable differences between spinward and anti-spinward, for example. All observations at the moment point to an isotropic universe (meaning all directions are the same). But I'm not sure how exactly spinning would manifest, and in what measurements. We need someone with more physics background to answer this in detail. --TheMaster17 (talk) 08:03, 4 August 2012 (UTC)

Unexplored Areas

Are there unexplored land areas left on earth? Reticuli88 (talk) 18:47, 2 August 2012 (UTC)

I'd imagine that the majority of Antarctica's surface area has never known a human footprint. Though humans may have looked out of the window of a plane at it. --Kurt Shaped Box (talk) 18:54, 2 August 2012 (UTC)

Of course, most of the surface is hidden under ice, and likely won't be explored until we manage to melt off the ice cap. StuRat (talk) 04:18, 3 August 2012 (UTC)

There are almost certainly caves that have never had a person in them either. New land may appear when ice melts off it, or when molten rock solidifies. There are also likely to be some small; islands that humans have never visited. A related question that was here before was: what is the last land to be discovered? Graeme Bartlett (talk) 23:43, 2 August 2012 (UTC)

Thinking back to the last time I remember a somewhat similar question to the OPs being asked here, there was talk of unclimbed mountains - e.g. Gangkhar Puensum. --Kurt Shaped Box (talk) 00:16, 3 August 2012 (UTC)

While the ocean depths are not lands per se, http://xkcd.com/1040/ is relevant here. Bear in mind as a webcomic it takes gratuities liberties with the truth; for instance, David Bowie never walked the Abyssal Plain (though I believe Freddy Mercury has). BigNate37_(T) 05:31, 3 August 2012 (UTC)

Either the author of XKCD needs to write larger or scan at higher res, because I can't read most of that. Can you ? StuRat (talk) 23:37, 3 August 2012 (UTC)

Click the image to be directed to http://xkcd.com/1040/large/, which I am able to read with relative ease. BigNate37_(T) 23:47, 3 August 2012 (UTC)

Thanks. StuRat (talk) 03:40, 4 August 2012 (UTC)

It's "liberties with the truth". Truth needs no tips. Clarityfiend (talk) 19:56, 3 August 2012 (UTC)

Just because I'm wrong doesn't mean you have to tell everyone! BigNate37_(T) 23:47, 3 August 2012 (UTC)

It depends what you mean by unexplored. There are 67 uncontacted tribes in Brazil, and even within 100 miles of Sydney, new discoveries are being made in the dense rainforest.--Shantavira|^{feed me} 07:28, 3 August 2012 (UTC)

North Sentinel Island has not had many visitors. --Daniel 23:41, 3 August 2012 (UTC)

There are vast stretches of southwest Tasmania inaccessible due to horizontal scrub. There are mountain ranges in Canada which have likely not yet been climbed. 207.224.43.139 (talk) 06:22, 4 August 2012 (UTC)

Unconscious mind

Regarding the unconscious mind:

• What evidence is there to prove that it exists?
• Does the evidence point to either nonconscious processes or actual hidden thoughts?
• Is there anyway to access the unconscious mind?

--Melab±1 ☎ 19:10, 2 August 2012 (UTC)

Unfortunately this comes down to definitions. Neither "unconscious" nor "mind" have a specific universally accepted meaning, so the answer to the first question comes down to which definition you prefer. Some people, for example, don't think that the word "mind" should be applied to anything that is not consciously experienced, so to them, "unconscious mind" is an oxymoron. The best thing would be for you to read our article on the unconscious mind and come back with any questions it leaves unanswered. Looie496 (talk) 19:27, 2 August 2012 (UTC)

(edit conflict) It depends on what you mean by these terms, which are not defined the same way by different people. If you mean "are there processes in our nervous system which we are unaware and over which we don't have any conscious control", the answer is absolutely: the Autonomic nervous system governs a range of bodily functions. If you mean the "Freudian" concept of the Unconscious mind or of subconscious, the answer is that it is a lot less likely that such models accurately represent how the mind works. Concepts like "repressed memories" and the like are very controversial and poorly accepted among actual neuroscientists. People that study the "human mind" as a "soft science" (i.e. psyschology/psychiatry etc.) are more likely to work with such models of the human mind, but those that study the actual functions of the nervous system (neurologists/neuroscientists/neurobiologists) don't find them very useful. --Jayron32 19:29, 2 August 2012 (UTC)

I don't know all about that id and ego stuff but it is quite clear to me that thinking goes on without my being aware of it. I've done things like for instance stopping the car and only figuring out why it was the right thing to do a couple of seconds afterwards. Dmcq (talk) 21:50, 2 August 2012 (UTC)

There are things like reflex, training, and instinct which affect behavior, but I'm not sure what is sturcturally different than conscious behavior. Awareness is not the same thing as consciousness. --Jayron32 03:10, 3 August 2012 (UTC)

I don't know all the definitions but I in all probability have accessed the unconscious mind. At times I have walked from my room to the dineing room without realiseing what I am doing. At other acasions I have gone into the bathroom, come out and forgotten all about it then have my parents remind me that I have been to the bathroom, then remember it, then think that it was all a dreem. The latter tipicly takes place when I am half asleep.Aliafroz1901 (talk) 11:27, 3 August 2012 (UTC)

We are rarely consciously aware of what we are going to say, until we say it. If we had to consciously deliberate every word we were going to produce before we produced it, we could only do so by thinking in words about what word we were going to use, leading to an infinite regress. Hence most of what we say spontaneously is produced by the subconscious, with us only becoming conscious of what we are saying when we vocalize it. This is why we have the phenomenon of there being something on the tip of our tongues; a thought of whose struggle to make it into consciousness we are quite aware. μηδείς (talk) 16:55, 3 August 2012 (UTC)

I mainly don't think in words so I don't have that problem :) But yes I don't normally think about the actual words I'm going to say. Dmcq (talk) 18:45, 3 August 2012 (UTC)

It's one of, probably the, main trick to writing. Don't try to edit yourself as you write. Let the words flow. Then go back and consciously edit as a separate second step. If, while doing the first "free-flow" draft, you get stuck, write FIX (or the word you know should be replaced with a better one) in capital letters and keep going. If you try to edit while you write you give your subconscious a complex, and end up with the writer's version of a stutter. This has got to be the number one problem of people whom I teach writing to. μηδείς (talk) 05:28, 4 August 2012 (UTC)

Race and obesity

Why are white and black women more likely to be obese, while obesity is much rarer among women of other races? --108.206.7.65 (talk) 20:35, 2 August 2012 (UTC)

White and black women where? Such a broad statement is unlikely to be true, so your premise is highly flawed. Certain socio-economic groups in certain countries have a gretaer propensity for obesity, so if you define which groups in which countries you seek information on, it would be very helpful. The data is very different if one is looking at Zimbabwe or the U.S. or Australia, for example. --Jayron32 20:45, 2 August 2012 (UTC)

In America. I've noticed that white and black women seem to have much higher rates of obesity than Asians, Indians, etc. --108.206.7.65 (talk) 21:27, 2 August 2012 (UTC)

Obesity is also very high e.g. among Palestinian women (31.5%, [26]), who are neither white nor black, but Arab. I would say obesity is much more correlated with culture (including subculture) and with unemployment than with race. - Lindert (talk) 21:30, 2 August 2012 (UTC)

Palestinians are white, or at least defined as white by the U.S. census bureau. In regards to the original question, I saw a lot of fat Latina women here in the U.S., and I think that nowadays there is generally greater obesity among poorer people. More black and Latino people tend to be poor nowadays, so that is probably why there is a greater % of obesity among them. A lot of white people are also poor, if you go by total numbers. As for why poor people tend to be more obese, it's because they are often unable to afford healthier food or do not have the time to cook it, and thus buy and eat much more cheap fast food than higher-income people do. Futurist110 (talk) 21:42, 2 August 2012 (UTC)

The OP might be interested in our article on Steatopygia as it seems somewhat relevant here. Dismas|^(talk) 22:13, 3 August 2012 (UTC)

A related question

Why is it that black and white women's appearances can range anywhere from very pretty to very ugly, but women from other races are almost always attractive? --108.206.7.65 (talk) 21:29, 2 August 2012 (UTC)

That is purely subjective and varies from person to person. Apperently you are of that opinion, and therefore it is only you who can answer why you feel that way. Noone can answer it for you. - Lindert (talk) 21:34, 2 August 2012 (UTC)

I agree with Lindert on this. I, for instance, have way different tastes than you do. Almost all of the women that I find sexually attractive are white and/or light-skinned. As yourself what qualities you find attractive in women and you'll probably be able to answer your own question afterwards. Futurist110 (talk) 21:39, 2 August 2012 (UTC)

The OP asked a similarly loaded question a few days ago,[27] and being from Missouri, I guess he has to be shown. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 3 August 2012 (UTC)

I think that OP's opinion are right. I have seen more obesity in white people around 45 to 50 years old than caucessian and Asians. GiantBluePanda (talk) 23:51, 3 August 2012 (UTC)

Um, how does your explaination explain why you believe the OP's opinion that 'black and white women's appearances can range anywhere from very pretty to very ugly, but women from other races are almost always attractive' (which is the subtopic you're replying under) is 'right' ? Nil Einne (talk) 17:26, 4 August 2012 (UTC)

Baby bird identification

Can someone identify these birds? The caption is "min egen bild" with a marker identifying it as Swedish; the user has no other uploads, and the filename is not particularly helpful. Nyttend (talk) 22:11, 2 August 2012 (UTC)

Birds are not really my thing, but I get whip-poor-will vibes looking at them, or perhaps some other brand of nightjar. Looie496 (talk) 00:10, 3 August 2012 (UTC)

The WP:BIRDS guys might be the ones to ask about this. They have regular 'birds for identification' discussions on their talk page. I don't think that any of them regularly contribute to the refdesks, but I'm sure that they'd be able to come up with a concrete answer, or at least narrow it down to a genus, if it happens to be one where the young of many species look very similar... --Kurt Shaped Box (talk) 00:25, 3 August 2012 (UTC)

Copied over there. Thanks for the pointer. Nyttend (talk) 01:32, 3 August 2012 (UTC)

Look like baby European Robins. Definitely not nightjars of any sort (though I can see why you'd get those "vibes"), as those species don't build nests; they lay their eggs directly on the ground. MeegsC (talk) 03:21, 3 August 2012 (UTC)

what physically changes between the ages of 18 to 22 -- fourth years look older than first years, but is it senescence?

I look at the photos of my friends (now 22) when they were first years (at 18), and they look so young! I am sad that we have lost our juvenile features and we seem "less cute" than before. But puberty ends between 16-18 doesn't it? What biological processes are occurring specifically? I don't think its the same type of aging that occurs later -- for example, I think our collagen remains taut, we don't develop wrinkles (yet), but what is changing? Nothing gold can stay (talk) 23:33, 2 August 2012 (UTC)

The biggest, most noticeable, effects of puberty tend to finish by around age 18 in boys and 16 in girls, but it doesn't stop completely until quite a bit older, particularly in men. Chest hair, for instance, is often still developing by age 22. --Tango (talk) 01:34, 3 August 2012 (UTC)

It could just be normal mature aging, as noted at senescence above, but some people continue to grow and develop through puberty into their early 20s. One somewhat famous example: David Robinson (basketball) grew three inches between the ages of 18-22, while many people stop growing in height well before then; for example I reached my adult height at 13. There is a lot of variation. There are also significant effects of things like diet and exercise. I went through a lot of changes at that age, crappy college food and a lack of activity added significant weight which had a general effect on my facial features and body shape. --Jayron32 03:07, 3 August 2012 (UTC)edit: spelling error corrected --Jayron32 04:07, 3 August 2012 (UTC)

"Man people" ? :-) StuRat (talk) 04:05, 3 August 2012 (UTC)

I think it depends on sex as well. When I was studying human developmental psychology some 30 years ago, I was told that the male physique continued to develop and mature until the mid-20s, whereas the female body reached maturity some years earlier. There then followed a period of relatively little change until the mid-30s when the ageing process started to have undesirable effects. In the years since, these dates may well have changed (50 is the new 30?) but the general principle still holds good. --TammyMoet (talk) 08:05, 3 August 2012 (UTC)

My female friends definitely seem to "mature" between the age of 18 and 22. My male friends seem to age less, actually. Nothing gold can stay (talk) 15:22, 3 August 2012 (UTC)

I haven't the slightest idea of a relevant article in general, but many things cause aging during that period: taking up alcohol and cigarettes, late nights and lack of sleep, excess sun exposure, poor eating habits, stress, and even sexual activity can affect the freshness of young skin. μηδείς (talk) 16:43, 3 August 2012 (UTC)

August 3

Magnitude 10 earthquake by combination of faults

I heard on a Discovery Channel program that a magnitude 10 earthquake could occur if the Cascadia subduction zone, the San Andreas Fault, and the Aleutian Trench all simultaneously ruptured. Is this possible? If so, how likely?--Jasper Deng (talk) 04:08, 3 August 2012 (UTC)

It's mentioned in the Cascadia article you linked to. 10-14% for magnitude 9 or higher in the next 50 years. Hot Stop 04:14, 3 August 2012 (UTC)

As likely as anything else, which means not likely at all. No earthquake in recorded history has been measured or estimated to have a magnitude greater than 10. 9.5 is the highest I can find at either Lists of earthquakes or Historical earthquakes. Sadly, the Discovery Channel (and other supposedly educational channels like the History Channel and TLC) have gone down the drain over the past decade or so. When they do run a "science" show, which is rare, they tend towards the sensationalistic, like impending asteroid impacts or supervolcanos, or stuff like that. I suppose this is what happens when geologists get really drunk at parties. Could it happen? I suppose. Could it happen this week? I wouldn't hold your breath... --Jayron32 04:14, 3 August 2012 (UTC)

Such a quake could possibly be a once-in-ten-milleniums in frequency/probability; I don't hold my breath for any megathrust earthquakes anyway.

However, it seems logical. If the subduction zones could each generate 9.5 earthquakes, and the San Andreas Fault a 9.1, then this could produce something like 9.8. If it so happened that another adjacent subduction zone like the one off eastern Russia also joined in, this would easily break 10. The chances of this is extremely unlikely, but not impossible.--Jasper Deng (talk) 04:19, 3 August 2012 (UTC)

Basic answer: nobody knows. The general opinion was that the Japanese tsunami quake was extremely unlikely -- until it happened. The dynamics of large earthquakes are still quite poorly understood, and we only have about 100-150 years of good worldwide data on their frequency, so events that occur less often than that could easily be misunderestimated (as GWB might have put it.) Looie496 (talk) 04:27, 3 August 2012 (UTC)

General opinion was spot on. The Japanese tsunami quake was extremely unlikely. Just because it's actually happened, the chances of it recurring haven't suddenly increased (aftershocks from the original quake aside). -- ♬ Jack of Oz ♬ ^{[your turn]} 11:36, 3 August 2012 (UTC)

Indeed. It is a common misconception that unlikely things happening is evidence that they weren't unlikely after all. You can't draw conclusions from a single data point like that. --Tango (talk) 11:42, 3 August 2012 (UTC)

But we have had quite a few earthquakes of magnitude larger than 9 in the last 100 years. Count Iblis (talk) 15:42, 3 August 2012 (UTC)

I've been following the literature on this, and it's pretty clear that many geologists have seen the Japanese quake as a wake-up call indicating that many probability estimates need revision. This overview from Science (available online here at the moment) may be helpful. Looie496 (talk) 16:59, 3 August 2012 (UTC)

* The problem comes with earthquakes with a long recurrence interval, like the Japanese earthquake and the 2004 Indian Ocean earthquake. We do have some idea about the biggest sections of subduction zones that are likely to rupture, which is about 1600 km as I recall, which is the length that ruptured in the 2004 earthquake. Magnitude is just the logarithm of the product of rupture surface area and displacement, so if we know the biggest area and the biggest displacement, we can work out the biggest magnitude possible. Using data from many large earthquakes it is possible to say that a M 10 earthquake would require a rupture of 1 million square kilometres [28]. The width is relatively fixed depending on the dip of the megathrust and the depth of the top and base of the seismically coupled zone, with a likely maximum of 150 km. However, if we take 200 km, we need a fault length of 5000 km, something like the whole Peru-Chile plate boundary rupturing at once, for which there is no evidence at all. Large earthquakes are often made up of sub-events and they may change in type. The 2002 Denali earthquake started on a small thrust fault, before switching to the strike-slip Denali fault and then splitting off that onto the Totschunda fault, yet another strike-slip fault, so it can happen. Note however, that all these faults physically intersect each other, which the Aleutian Trench and the San Andreas Fault do not (unless you throw in the Queen Charlotte Fault as well). Also, all your separate faults have to be in the same part of their seismic cycle and be close to rupture, which becomes increasingly unlikely as more fault segments are involved. Mikenorton (talk) 22:18, 3 August 2012 (UTC)

Deicing equipment / heaters

Is there any disadvantage to running deicing heaters, whether it's the pitot tube or the other deicers, even if it's not needed? I'm talking about onboard systems too, not deicing on the ground. Shadowjams (talk) 06:06, 3 August 2012 (UTC)

1) I imagine it lowers fuel efficiency somewhat, depending on how they generate the electricity to run them.

2) Running that much electricity through wires has to increase the risk of fire, explosion, and electrocution, if the wires are damaged, but this risk should be minimal in a properly maintained airplane.

3) Running them on a hot day while sitting on the ground might actually cause overheating damage. StuRat (talk) 06:13, 3 August 2012 (UTC)

Anybody with cites or definitive knowledge have any ideas? Shadowjams (talk) 06:38, 3 August 2012 (UTC)

I'm about to board an international flight, and I'm seated in the first row. I'll see if I can quickly ask the pilot :) 101.172.127.242 (talk) 09:27, 3 August 2012 (UTC)

OK, the pilot was happy to answer my questions and took about 15 minutes to talk to me about various things. He said that the Airbus A-320 we were flying in was fitted with a deicing unit for the engines, a deicing using for the leading edge of the wing called "wing air" and small electric heating elements on the pitot tubes. The wing air and engine deicing work by taking a bleed of hot pressurised air from the turbines and directing it to the wing surface or the part of the engine that needs heating. Both of these lead to a performance penalty because they take pressure away from the turbines. The engine deicers are disabled by interlocks when not in the air and the wing air causes an extra take off distance equivalent to about 700kg of extra weight if it's activated on the ground. The power used to deice the pitot tubes is negligible, and that unit is activated automatically during the necessary parts of the flight envelope. 112.215.36.173 (talk) 14:06, 3 August 2012 (UTC)

I'm guessing this wasn't in the US, where knocking on the cabin door might get you tackled and arrested by a TSA agent. StuRat (talk) 23:19, 3 August 2012 (UTC)

I didn't know the TSA agents actually get on the plane and fly with the passengers. I actually avoided the awkward scenario of knocking on the door by stopping the pilot as he came out to use the restroom. He was very friendly...to the point it was actually hard to end the conversation and get rid of him once I had my answer. He even invited me to come up to the cockpit to see what the indicators look like when the deicers are running, etc. I've flown this route every other week for over a year now, so the cabin staff remember me and are quite friendly, though I obviously havn't spoken to the staff on the flight deck much before. As you can see from the location of my IPs (origin and destination) this wasn't in the USA. 112.215.36.184 (talk) 03:43, 5 August 2012 (UTC)

Wow, cool. Thank you! I didn't know pilots actually took time to talk to passengers anymore! Shadowjams (talk) 22:57, 3 August 2012 (UTC)

Can we mark this Q resolved ? StuRat (talk) 23:22, 3 August 2012 (UTC)

Resolved

Ask for help to identify the fungus.

See the link attachment for the Image. Thanks. SYSS Mouse (talk) 15:35, 3 August 2012 (UTC)

Location please? Likely to be the young fruiting bodies of any of the bright yellow species of shelf fungi under the genus Laetiporus. If from N. America, likely to be Laetiporus sulphureus.-- OBSIDIAN†SOUL 15:55, 3 August 2012 (UTC)

Oh dear. I think I saw Steve eat that once. (It goes without saying, but don't eat it.) BigNate37_(T) 16:01, 3 August 2012 (UTC)

It was not specified. It is from a forum post (The forum is in Chinese thus not linked) but the user who posted it is from Eastern Canada. EDIT: Also, the same fugus one week later. [29] SYSS Mouse (talk) 16:35, 3 August 2012 (UTC)

Definitely Laetiporus then. They're quite distinctive. See this guide. That said, again, don't eat it! :P We're not exactly mushroom experts here, heh.-- OBSIDIAN†SOUL 17:25, 3 August 2012 (UTC)

Thank You. SYSS Mouse (talk) 03:51, 4 August 2012 (UTC)

Resolved

Nutrition in Human Breast Milk

I'll freely admit that this question is purely inspired by the Song of Ice and Fire series--

A character in said series is about 8 years old and still subsists primarily on his mother's milk. I'm just wondering if the nutritional needs of a human beyond baby-hood (wherever one draws that line, 8 years old is clearly not a baby) can be met purely through breastmilk. Protein/fat I can see--but does the milk contain enough of the vitamins and minerals?

Puh-lease do not respond with "it's just a book" I'm not asking about the book, that's merely the impetus for the question.199.94.68.91 (talk) 18:46, 3 August 2012 (UTC)

Doing a Google search for the phrase "nutrition data human breast milk" turned up this page as the second result (after the Wikipedia article on human breast milk). That page contains all of the data on the nutrient content (including micronutrients such as vitamins and minerals). Finding the recommended daily intake for these nutrients for an 8 year old should also be easy to find. By cross referencing those two data sets, you can see where breast milk is both adequate and inadequate for nutritional needs. --Jayron32 19:00, 3 August 2012 (UTC)

I asked a question a long time back about how babies can get complete nutrition from milk, which seems to be deficient in several key nutrients. The answer, as I recall, is that babies are born with with excesses of those nutrients, and they switch to solid foods before they run out of this stockpile. In your case, you said "primarily", so the supplemental foods they get might supply the missing nutrients. If, however, a child was fed nothing but milk (human or otherwise) for 8 years, then I'd expect severe malnutrition. StuRat (talk) 23:15, 3 August 2012 (UTC)

Add to that the fact that the majority of humans become lactose intolerant at around 2 to 7 years of age. They will have limited to no nutritional benefits from drinking milk after that. Though the very recent evolution and growing dominance of lactase persistence is circumventing this somewhat.-- OBSIDIAN†SOUL 03:26, 4 August 2012 (UTC)

It's very recent by evolutionary standards - it's still about 10,000 years ago. I'm not sure what the overall prevalence of lactase persistence is, but in people of European descent (which I think best describes the character in question, although I haven't actually read the book) it is by far the majority as the article you linked to says. --Tango (talk) 18:04, 4 August 2012 (UTC)

Haven't read the book nor follow the series either. :P So I was assuming the OP meant all humans. -- OBSIDIAN†SOUL 00:55, 5 August 2012 (UTC)

Is there some reason why there is no link here to human breast milk? Or is the OR of various posters supposed to be more relevant on the wikipedia reference desk? μηδείς (talk) 22:16, 4 August 2012 (UTC)

Because it doesn't contain the answer?-- OBSIDIAN†SOUL 00:55, 5 August 2012 (UTC)

Filial Imprinting

Hello. Is filial imprinting related in any way, shape, or form to evolution? If so, how? Thanks in advance. --Mayfare (talk) 19:25, 3 August 2012 (UTC)

Anything that influences survival is related to evolution. Since filial imprinting enhances the survival of the young (by helping them stay protected), it is related to evolution. Of course "related to evolution" is an extremely vague term -- if you have something more specific in mind, please clarify. Looie496 (talk) 20:55, 3 August 2012 (UTC)

Filial imprinting can augment and override evolutionary instincts by allowing offspring to mimic learned behaviors appropriate for specific environmental conditions. 207.224.43.139 (talk) 05:56, 4 August 2012 (UTC)

It is related to evolution in that it is a characteristic that evolved. Was there another relationship you were thinking of? --Tango (talk) 11:17, 5 August 2012 (UTC)

I was thinking along the lines of ethology and maybe natural selection. --Mayfare (talk) 16:11, 6 August 2012 (UTC)

HF solid-liquid transition: densities

Does anyone know if solid HF expands (like regular substances do) or contracts (like does very similar water, both have hydrogen bonds and so) upon melting? Has this been measured (I've done a search, returns nothing)? Are there values?--R8R Gtrs (talk) 19:33, 3 August 2012 (UTC)

What search returns nothing? Googling the obvious keywords suggests this depends on pressure because of different possible crystal structures. 207.224.43.139 (talk) 05:55, 4 August 2012 (UTC)

August 4

Farts

Not trolling—is it possible to fart in your sleep? 71.146.0.138 (talk) 01:26, 4 August 2012 (UTC)

I would assume so based on the various TV shows with characters farting in their sleep. Futurist110 (talk) 01:48, 4 August 2012 (UTC)

Does this count as original research? Yes. I've been told I do it all the time. Mingmingla (talk) 01:50, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

Flatulence is caused by the buildup of gases in your gastrointestinal tract, usually as byproducts of secondary digestion by your gut flora. Their movement down your intestines is also controlled by the peristaltic movement of involuntary smooth muscles, which does not depend on you being conscious. So yes.-- OBSIDIAN†SOUL 03:40, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

The most common thing to wake me on long car trips where I am not driving is the rush of air as the windows are rolled down in panic. My grandmother's favorite story was of the woman from the next county over who, when looking for the pepper at the church kitchen while cooking pierogies on a Sunday, instead of asking, Gde póper déla? with a fixed Polonic penultimate accent asked Gde popér(-)dela? with a free Ukrainian oxytonic accent. μηδείς (talk) 05:13, 4 August 2012 (UTC)

As a non-speaker of Polish or Ukrainian (aplogies for this lamentable deficit) I'd be quite interested in understanding this semantic joke, any chance of a translation? Richard Avery (talk) 06:49, 4 August 2012 (UTC)

Certainly. The past tense of East Slavic verbs is formed by the past participle, which is declined for gender and number, with an implied form of "to be" which is usually deleted. (English retains the archaic perfect forms "Christ is risen" and "The time is come" which are parallel, except that East Slavic drops the "is" as implied. French has Elle est venue, "she is (has) come", with the feminine past participle of venir, "to come") The past participle of delati "to do, to put" for women is delala, shortened by haplology to dela. (One generally adds -la to the verb stem to form the Slavic feminine past participle.) "She put the pepper on the table" is Wona de(la)la poper na stol. The verb perdeti, "to fart", (perd-, following Grimm's Law, is cognate to the English; the root is PIE) like many verbs, takes the prefix po- to imply a single, completed action, as opposed to a continuing action: poperdeti, "to make a fart" whose feminine past participle is popérdela. Hence, the only difference between "Where did she put the pepper?" Gde póper déla and "Where did she fart?" Gde popérdela? in my grandmother's dialect is one of where the stress falls. Her friend's dialect, however, had a different stress pattern, where poper was stressed on the final syllable, as opposed to most of the ladies at the church who pronounced the word póper with initial stress. Hence their humorous reaction to her innocent question. μηδείς (talk) 07:26, 4 August 2012 (UTC)

:-) Thankyou. Richard Avery (talk) 14:10, 4 August 2012 (UTC)

Race and Running Speed?

This is a serious scientific question. I'm not trying to be offensive or racist. I've noticed that there are a lot of black people in professional (such as Olympic) running events. I have two questions:

1. Is the % of black people in professional running events disproportional to their % of the population? 2. If this is disproportional and a favorable proportion to black people, do black people have a genetic ability to run faster?

Thank you. Futurist110 (talk) 01:55, 4 August 2012 (UTC)

East Africans in particular, right? —Tamfang (talk) 02:46, 4 August 2012 (UTC)

Well, skin colour isn't going to make any difference at all. And different groups of people from many parts of the world have black skin. I doubt if the OP was thinking of Australian Aboriginals, Polynesians and south east Asians when he wrote that question. Some groups of people seem to have a higher proportion of members who can sprint faster than many (West Africans), or run longer distances better than others (East Africans), but one has to take social, geographic and economic factors into account too. If you live in a poor country, you're more likely to choose running as a sport than swimming or equestrian. If you live at high altitude, you can have an advantage in endurance sports. HiLo48 (talk) 03:04, 4 August 2012 (UTC)

See Kalenjin_people#Athletic_prowess. Members of the Kalenjin tribe of Kenya win about 40% of marathons world-wide. μηδείς (talk) 04:56, 4 August 2012 (UTC)

By black, I meant the U.S. census definition of black, meaning of Sub-Saharan African descent. Futurist110 (talk) 06:29, 4 August 2012 (UTC)

And HiLo pointed out that having black skin itself is irrelevant to running, it's probably only a chance marker (for US Americans...) for a certain genetic, cultural, geographic and economic background that is relevant. Black skin is as relevant to running as is white skin to building high skyscrapers. The two things simply have nothing to do with each other causally, they are only associated by common economic, cultural and educational traits (that for example favor "white" architects to build many skyscrapers). --TheMaster17 (talk) 07:48, 4 August 2012 (UTC)

So you're saying it has to do more with lifestyle and exercise and that it has nothing to do with race? Gotcha. Futurist110 (talk) 07:56, 4 August 2012 (UTC)

HiLo: Sources please. And scientific ones for this Science desk, not social commentary. Rmhermen (talk) 14:07, 4 August 2012 (UTC)

Sources for what? If we demanded sources for everything posted here this would be a very different place. I'm not trying to deceive anyone. I just can't be bothered hunting down sources right now. Ignore my comments if they don't fit your belief structure. HiLo48 (talk) 18:11, 4 August 2012 (UTC)

There was a BBC Horizon documentary about this issue quite some time ago about the long distance runners from Kenya and Ethiopia. The conclusion was that the most relevant factor here was that these runners have longer legs in relation to the rest of their body (or certain parts of their legs are longer), and that means that for the same effort they will go faster. It is basically the same reason that explains why bipedal motion is more efficient than walking on 4 legs. A human can outrun a horse on the long run, hunter gatherers in Africa run for hours persuing antilopes eventually catching up with them...

For the sprint the type of muscles tissue you have is important, apparantly people of West African ancestory have the right stuff. Social effects can't be of much relevance here, because of the huge gap between the best white 100 meter personal best and the average best season's best time over the last decade. Only one white athlete has ever run faster than 10 seconds and none of the athletes from East Africa or Asia, see 10-second barrier:

"Nearly all the sprinters who have beaten the 10-second barrier are of West African descent. Namibian (formerly South-West Africa) Frankie Fredericks became the first man of non-West African heritage to achieve the feat in 1991 and in 2003 Australia's Patrick Johnson (who has Irish and Indigenous Australian heritage) became the first sub-10-second runner without an African background.[5][6][7][8] Frenchman Christophe Lemaitre became the first white European under ten seconds in 2010 (although Poland's Marian Woronin had unofficially surpassed the barrier with a time of 9.992 seconds in 1984).[9] In 2011, Zimbabwean Ngonidzashe Makusha became the 76th man to break the barrier, yet only the fourth man not of West African descent.[10] No sprinter of predominantly Asian or East African descent has officially achieved this feat."

Count Iblis (talk) 15:46, 4 August 2012 (UTC)

Keep in mind as well that you are talking also about the very bleeding edge of the bell curves, here. The bell curves for all populations in terms of running performance are going to look nearly identical; where they vary are going to be maybe tiny, almost imperceivable shifts in the median, and tiny, tiny differences on the far fringes. The Olympics and whatnot are pitting the far fringe of one country against the far fringe of another. The tiniest of differences in genetics, training, and so forth make the differences in such situations. The lesson here isn't that the population genetics don't matter for these sports — they do seem to — but that you shouldn't read racing performance (or sports in general) as telling you too much about population genetics. It is not likely the case that your average Ethiopian is genetically a better long-distance runner than, say, your average Swede, but over a large population of Ethiopians and Swedes, your handful of gifted Ethiopians will be better at this sport than your handful of gifted Swedes. (It is also obviously the case that the countries that spend more time and more money on searching out talent end up with more of it. There is likely no genetic reason that Americans, Russians, and Chinese dominate gymnastics and Africans do not — finding and cultivating gymnastic talent is just a much bigger deal in the former countries, so they are able to find those who reside at the end of the bell curves and devote enough resources to them that they go to the Olympics as opposed to doing other things with their lives.) --Mr.98 (talk) 17:48, 4 August 2012 (UTC)

In terms of long distance running again certain people from East Africa have a slight advantage - hence the dominance of Ethiopeans, Somalis and Kenyans in these competitions - they tend to have longer heel bones calcaneus than most other people. This difference gives then a slight leverage advantage to the transfer of power frome their achilles tendon's to the ball of the foot - in long distance races this small advantage adds up to result in a disproportionate number of marathon champions. (The same leverage advantage comes into play with Maasai men's traditional jumping dances.) Roger (talk) 18:26, 4 August 2012 (UTC)

I missed where Futurist attributed running speed to skin color. Has anyone ever heard of the Kalenjin people, who win 40% of marathons world wide? I wonder what percentage of the world population the Kalenjin are? Something near 40%? Nothing statistically improbable going on there.... μηδείς (talk) 21:22, 4 August 2012 (UTC)

See second paragraph of first post. HiLo48 (talk) 00:14, 5 August 2012 (UTC)

The user is American, I expect he would have said races with dark skin if he had been referring to Australian Aborigines or other dark skinned races, and given his clarification, I think my expectation was correct. μηδείς (talk) 18:12, 5 August 2012 (UTC)

I guess I missed the part where anyone here claimed that the genetic and social opportunity were equally distributed. Fighting strawmen with strawmen is a waste of everyone's time. --Mr.98 (talk) 21:34, 4 August 2012 (UTC)

So your point is that the Kalenjin are pampered rich brats? This is the wikipedia reference desk. If you think this place is about arguing you are mistaken. Provide links and refs, not ideological OR and ad hominem. μηδείς (talk) 22:19, 4 August 2012 (UTC)

Are you just trolling? Because you don't seem to be addressing anything I — or anyone else here — has actually written. --Mr.98 (talk) 02:03, 5 August 2012 (UTC)

Everything you have provided above is OR, Mr.98. I'd love to see your graph of Inuit vs Kalenjin running ability. Talk about straw men, as for "social opportunity", what are you on about? The 1% and how they monopolize running shoes while the barefoot rest of us can't afford the price of running down the street, perhaps? Who brought that issue up? Was there a paragraph on it I missed in the Kalenjin article? μηδείς (talk) 18:12, 5 August 2012 (UTC)

"Social opportunity" just means the fact that they have folks who search out the talent and put them in there. It's a necessary prerequisite, obviously, to getting to any competition. Again, I don't think you're actually reading anything anyone else writes with the intention of making sense of it — which is a pretty good sign of a troll. What you get out of it, I'm not sure, but feeding you probably isn't going to help much. (My stuff isn't OR, it just isn't cited. I could awash you wish boring academic books about sensible ways for thinking about the biology and sociology of race, including books on sport and race in particular, but why bother? You aren't going to read them; you can't even be bothered to read posts on here that are contrary to your pre-held beliefs.) --Mr.98 (talk) 15:12, 6 August 2012 (UTC)

Body build is also important, for long distance running your BMI has to be very low while you can still eat 5000 Kcal/day or more. Take e.g. Mo Farah, his height is 1.75 m but he only weighs 56 kg. Many people from East Africa have this type of "walking skeleton" body build. Count Iblis (talk) 19:27, 5 August 2012 (UTC)

Usain Bolt says that the Jamaican food that he eats makes him run fast. Count Iblis (talk) 15:23, 6 August 2012 (UTC)

Neurology and music

Is there any neurological basis to the moods associated with different types of musical scales, or is it entirely cultural? --108.206.7.65 (talk) 01:59, 4 August 2012 (UTC)

See Cognitive neuroscience of music.—Wavelength (talk) 02:36, 4 August 2012 (UTC)

That article doesn't discuss my question specifically. --108.206.7.65 (talk) 17:37, 4 August 2012 (UTC)

Can you perhaps elaborate a bit on what prompted the question ? Do you think there are different moods associated with different types of musical scales and if so what are they, for example ? Sean.hoyland - talk 17:51, 4 August 2012 (UTC)

For example, major scales are associated with positive emotions while minor scales are sad. --108.206.7.65 (talk) 17:16, 5 August 2012 (UTC)

This Nature article[30] and it's sources may interest you. And there are these articles about the minor third and sadness in speech (for speakers of American English).[31][32][33] Sean.hoyland - talk 17:49, 5 August 2012 (UTC)

It certainly must have a cultural dimension, as listening to squealing Chinese music must be more pleasant for them, or they would have executing all of the musicians long ago. StuRat (talk) 03:36, 4 August 2012 (UTC)

The short answer is that yes, there are absolutely strong innate underpinnings to the emotional influence of certain tones, chords, prosody, and many other features of music, many of which are universal across cultures (in neurologically healthy individuals, anyway). Though of course culture does have some influence at the same time. If you're interested in exploring this concept in depth, but want something that is (fairly) accessible to a non-cogntive-science-expert, then I can very strongly recommended both Daniel Levitin's This is Your Brain on Music and Oliver Sacks' Musicophilia. If memory serves, Steven Pinker also treats the subject, albeit much more briefly, in his books How the Mind Works and The Blank Slate, which are great reads in any event. If you're looking for something especially light, I stumbled across a documentary sometime back called How Music Works which, from what I saw, seemed to put a good deal of examination into this subject as well, but I did not watch it at length. I believe it was a BBC production, but don't hold me to that. Snow (talk) 03:57, 5 August 2012 (UTC)

Hydrotriiodic acid

Since hydroiodic acid contains the iodide ion, I don't see why combination with elemental iodine should not produce the triiodide ion as with iodide salts.--Jasper Deng (talk) 04:10, 4 August 2012 (UTC)

http://pubs.acs.org/doi/abs/10.1021/j100810a041 207.224.43.139 (talk) 05:48, 4 August 2012 (UTC)

Involuntary Change of Sexuality?

I know the one's sexuality is not a choice, but is it possible in extreme cases for one's sexuality to (somewhat) change over time due to factors out of this individual's control? For instance, could it be possible for a bisexual gay who initially strongly preferred women when it came to sexual attractiveness to strongly prefer men later on? Personally, I was always straight, but the characteristics and types of women that I found attractive have changed over the years. My question is if it is scientifically possible for such a change in one's view of sexual attractiveness to be much more extreme over the years, as in my example above? Futurist110 (talk) 07:35, 4 August 2012 (UTC)

That's a minefield of a topic. See Sexual orientation for a brief and extremely simplified overview; and the Kinsey Reports and the Klein Sexual Orientation Grid for two studies which have attempted to find out. But the answer is yes from the results of the Klein Grid and from personal observation.

The why, however, is problematic. It may be prison sexuality, latent bisexuality (in the traditional sense or the innate bisexuality sense), situational sexual behavior, coming out or finally accepting repressed homosexuality, self-enforced conscious rejection or adoption of an orientation (however ineffective that may be), experimentation, peer pressure, the result of personal trauma, positive or negative reinforcement over long periods, dissonance between gender and very strong emotional attraction (affectional orientation), hormonal, genetic, cultural, etc. Add to that the questions surrounding gender and sexual identity, and the religious and cultural conventions that attempt to control or classify them, and you end up with only one conclusion:

Sex is complicated.-- OBSIDIAN†SOUL 09:51, 4 August 2012 (UTC)

Tom Robinson describes himself as "a gay man, who happens to have fallen in love with a woman". Go figure. --TammyMoet (talk) 12:28, 4 August 2012 (UTC)

I am not sure about the issue of control (who would say their sweet tooth is voluntary?) but I can attest that my polarity, for lack of a better word, has varied over the years. Before I knew what sex was I had crushes on males and females. From puberty to 18 I was primarily homosexual. From 18 to 24 primarily heterosexual in action, and homosexual in dreams. (My boyfriends and girlfriends have always known I was bisexual.) Then the reverse. Then back again after some time. I must say, the most shocking development was when I dreamt of having sex with Britney Spears. (And this was even after the South Park episode.) She is not at all my type physically or musically. But it was a dream, and I don't blame myself for acts of my subconscious. (And it was fun!) I can offer no explanation. But I recommend everyone try both ways lest they never know what they are missing. μηδείς (talk) 21:19, 4 August 2012 (UTC)

The recent scholarly history on this subject has presented an interpretation of sexuality as a largely innate (and to a large degree unalterable) psychological/cognitive feature. This trend, perhaps unsurprisingly, co-evolved with increasing social tolerance for, and understanding of, LGBT drives, and the overturning of the previous reigning paradigm that gay and lesbian desires were almost entirely learned (and thus "correctable". Even more recently, however, some researchers are starting to question whether we may have over-corrected a bit might not be a bit more of a spectrum or "continuum" in which some (though certainly not all) individuals may have the propensity to slide from one category of sexual preference to another over the course of their lives, or under certain circumstances. This view is slowly gaining some traction in terms of research geared specifically towards human neurology, but it's worthwhile to note that this interpretation of sexuality in many social species has been uncontroversial for some time. All of that being said, there is at least some degree of innate preference in the vast majority of individuals and we're starting to understand the developmental mechanisms that go into forming them a bit more. For example, it's now fairly well-established fact that men who were born as the third son or on are markedly more likely to self-identify as gay upon reaching sexual maturity (even adjusting for social home life during upbringing; that is, whether they were raised along side those siblings or not). The popular explanation for this phenomena being that somehow the hormonal influence of past pregnancies somehow influences the development of these males in utero to result in children who (in our past evolutionary context) would have been able to assist their siblings in raising their progeny (who would share at least some of their genes, afterall), without further straining the demand on limited resources with their own offspring or becoming competitors for limited mates. This is just one of many small but convergent facts that point to innate biological mechanisms influencing sexual preference long before the cognitive machinery is up and running to directly make these "choices". But then there are some who, as they mature, will bounce back and forth between these preferences - Medeis' seems to be one such, from his description. Honestly, most modern researchers are not likely to be surprised by this, I would think -- the concept of malleability, but only within certain constraints, is a pretty common refrain in a number of different sub-disciplines of the cognitive sciences these days.

All of this deserves one big caveat though -- while a small proportion of people may change their predilections over the course of their life, all research on the idea of "triggering" such a change suggests that, by and large, it cannot be done; that is to say Conversion therapy and similar methodology for "forcing" a gay person straight (or, theoretically, vice-versa) will have no substantive effect (unless perhaps that person's neurobiology was already swinging them into that new state). Needless to say, many of the findings presented above are highly contentious (and as Obsidian noted, subject to interpretation via context), but I've tried to synthesize and represent the currently most common views by scholarship on the issue. As regards the concept of a sexual orientation spectrum that I opened with, there has been a fair amount of both speculation and research in the last couple of years in particular and I'll see what I can't do about re-locating some of it for you. Snow (talk) 03:42, 5 August 2012 (UTC)

I just want to take clear--the change in sexuality has to occur naturally without a person wanting it. Futurist110 (talk) 07:36, 5 August 2012 (UTC)

That is actually not clear at all. There is a difference between something that is not voluntary, and something that is against one's wishes. μηδείς (talk) 23:33, 5 August 2012 (UTC)

Just see Sexual_orientation#Fluidity_of_sexuality. 112.215.36.172 (talk) 10:09, 5 August 2012 (UTC)

Getting wet

It is raining. The rain is coming at me at 45 deg. I have no raincoat. Will I be dryer when I get home if I run through the rain or if I walk? --89.243.128.176 (talk) 14:04, 4 August 2012 (UTC)

If it's coming towards you, then running will result in less water falling on you. If its hitting your back, walk at the same speed as the rain is moving horizontally.--Gilderien Chat|List of good deeds 14:05, 4 August 2012 (UTC)

I agree with the first part, and in the second part, that strategy will indeed minimize the rain hitting you from the side, but it depends on the vertical velocity of the rain whether that is more important than minimizing the time rain is hitting you from above, which you would get from running as fast as possible. - Lindert (talk) 14:19, 4 August 2012 (UTC)

There was actually a recently released study on this in the European Journal of Physics. (See news coverage [34], [35], and freely available research article [36]). The short answer is that you'll be drier in almost all cases if you run instead of walk, although there are exceptions. -- 71.35.119.233 (talk) 18:14, 4 August 2012 (UTC)

Is it just me or has this all ignored the fact that if you run home, you spend less time in the rain? Yes, you may make complicated alterations to the raindrop-per-second rate and those are interesting deductions. But as long as rain is subject to gravity, you're going to be dryer for having spent less time in it. BigNate37_(T) 18:48, 4 August 2012 (UTC)

Indeed. I expect everyone knows from personal experience that you can avoid getting as wet by running home. If you have to be outside for a fixed period of time, then all of this might make a difference, but if you can get home in half the time, you'll be drier. It's important not to over-think problems! --Tango (talk) 19:09, 4 August 2012 (UTC)

In a first approximation, speed doesn't matter. You have a certain density of raindrops in the air, and if you cover a certain distance, you will sweep out a certain volume (cross section times the distance covered), and that volume contains a certain amount of water. Count Iblis (talk) 19:37, 4 August 2012 (UTC)

We're not ancient Greeks - we don't ignore empirical evidence in favour of pure reason. We've all been caught out in the rain and know what happens. If you run, you don't get as wet. If your reason doesn't fit with the empirical evidence, they your reason is wrong. Now, it is possible that I'm simply wrong as I get just as wet either way - there is a natural human tendency to overestimate the amount of control we have over our lives. The way to find out isn't with maths, though. It's with people running and walking in the rain and seeing what happens. --Tango (talk) 20:38, 4 August 2012 (UTC)

Actually I think Count Iblis's approach is the best way of visualizing this problem, but you need to think of it in the rest frame of the raindrops, not the rest frame of the street. If the raindrops are falling at a 45° angle downward and to the right, then with respect to their rest frame, you, the street, and the shelter you're trying to reach are all moving at a 45° angle upward and to the left:

                  .........._........
                   ........|\.........
                    .........\.........
                     .........\.........
                      ..........#........
                       .........#.........
                        ........#..........

The ### is you, the dots are (stationary) raindrops, and the dotless areas on either side are shelters. You want to sweep the # figure in any upward/sideways direction, minimizing the number of dots you intersect. If you "stand still", you're moving up and to the left and intersecting more and more drops without bound, so that's bad. If you want to reach the shelter on the left, it appears that the most efficient way of doing it is to go directly to the left, which corresponds to running as fast as possible. If you want the reach the shelter on the right, the most efficient way appears to be straight up: since you're 1/3 as wide as you are tall, you intersect about 1/3 as many raindrops that way than if you went horizontally. This corresponds to running at the horizontal speed of the rain. But if the rain were falling more vertically, the shelter edges in this picture would be closer to vertical and going straight up wouldn't look so attractive any more. Once the slope of the sides exceeds 3, you're better off running as fast as possible. This approach still works if you add a third dimension and replace the rectangle with a more accurate human shape. -- BenRG (talk) 21:28, 4 August 2012 (UTC)

I asked a slightly more complicated version of this question here at the math desk: How wet will the windshield get? μηδείς (talk) 18:59, 4 August 2012 (UTC)

It is also important not to underthink the question. A tall skinny person moving at a certain speed with his body inclined at a certain angle will only get the top of his head wet, while at a faster speed he will run into the rain in front of him. The cross section, angle of attack, and relevant speeds all matter. See the link above for the definition of the variables in the formula ρ·s·A·(u·sin(Θ)/v+cos(Θ)) μηδείς (talk) 19:32, 4 August 2012 (UTC)

Time to bring in the Ultimate Authority: Mythbusters. They tested it and found you get wetter by running (at least for the way they set it up).[37] Clarityfiend (talk) 00:34, 5 August 2012 (UTC)

• They seem to have done only one trial per configuration, and there are no error bars.
• The theoretical model predicts that when the rain is vertical the amount you absorb should be very similar whether you walk or run, but when walking a much larger fraction of it falls on your head. Their coveralls had no hoods.
• Running might splash more water from the ground onto your legs.

They seemed to have no theoretical understanding of the thing they were studying, and they made no attempt to isolate possible causes of their surprising result. Yet they pronounced the myth busted. Very poor science. -- BenRG (talk) 02:07, 5 August 2012 (UTC)

Your graphic does seem to be an excellent proof of the fact that standing still in diagonally falling rain will get you infinitely wet. Does anyone have an opinion as to the validity of the formula I reposted? μηδείς (talk) 03:12, 5 August 2012 (UTC)

It looks correct to me. It's not the same problem, though. For an arbitrary rain direction I think it would be $\rho (s/v){\vec {A}}\cdot ({\vec {u}}+v{\hat {x}})$ where ${\vec {A}}$ is the directed area (unit normal times area). For an arbitrary shape (like a human figure) you'd need to replace ${\vec {A}}$ with a function that returned the cross-sectional area. -- BenRG (talk) 04:40, 5 August 2012 (UTC)

Having seen parts of episodes of Mythbusters before, I'm not exactly surprised. I'm sure they've done some okay stuff, but whenever I've seen they often seem to be pronouncing some myth busted or confirmed on the flimisiest of evidence. The lack of repetion or real theoretical understanding of what they're doing seems to be a common problem. This shouldn't exactly be surprising, it's a TV show and a lot of the nitty-gritty of real science isn't exactly exciting. It does seem to me people give way to much credence to them, particularly in complicated cases where things could easily have gone wrong. Nil Einne (talk) 05:34, 5 August 2012 (UTC))

That's disappointing even for Mythbusters. They specifically said in their intro that walking gets you head wetter and running gets your front wetter and then they only measured the water on their front. Of course they concluded the running gets you wetter... The show is obviously intended to be entertaining rather than rigorous, but it is usually a little better than that. --Tango (talk) 11:25, 5 August 2012 (UTC)

Well at least they didn't just fake the results when the actual results weren't cool enough I guess [38] Nil Einne (talk) 19:05, 5 August 2012 (UTC)

If we're using Brainiac as our point of reference, then Mythbusters deservers a Nobel Prize! That show was ridiculous. --Tango (talk) 23:51, 5 August 2012 (UTC)

Count Iblis' approach only works if you're running at least as fast as the downward velocity of the raindrops (or even faster?) (i.e. never). When running slower, the raindrops you sweep out will be replaced by additional raindrops falling on you before you get out from underneath them.

Another consideration is how much more you will sweat when running than when walking and whether you would rather be drenched in sweat than in rain.--Wikimedes (talk) 06:50, 6 August 2012 (UTC)

How many strings make up a quark?

I don't know if this question has a meaningful answer, but I'll throw it out there anyway. ScienceApe (talk) 16:21, 4 August 2012 (UTC)

String theory was originally a theory of strongly interacting quarks, in which a quark was the end of a string (thus explaining why single quarks never appear in isolation).

In superstring theory as a theory of quantum gravity, I think a quark would be "one string". Quarks are complicated even in the standard model, though, so take this with a grain of salt. -- BenRG (talk) 16:30, 4 August 2012 (UTC)

August 5

botox and spoiled food

okay, let's say i a come across some improperly stored food that has become contaminated by botulism toxin. can i harvest it from the can of food and use it to reduce the appearance of wrinkles in my face.

note that the question is not SHOULD i do that but can i, in theory, do that? or is the kind you put in your face a *different* type of botulism. — Preceding unsigned comment added by 24.228.83.134 (talk) 01:36, 5 August 2012 (UTC)

There are seven different types of botulinum toxin, and the one used to reduce wrinkles (along with treating many conditions) is naturally found in improperly canned food. Someguy1221 (talk) 01:51, 5 August 2012 (UTC)

But as far as harvesting the toxin, the preparation you find in a cosmetic surgeon's office was purified from a bacterial culture, and not from spoiled food. Purifying it out of food would likely be extremely difficult, and purification is necessary to prevent allergic reactions that would result from injecting random crap under your skin. Someguy1221 (talk) 01:56, 5 August 2012 (UTC)

Organic group abbreviations

I can't seem to find any information (on WP nor on the wider Internet) about abbreviations for organic groups. Our article methyl group mentions that that group is often abbreviated as "Me". I see other abbreviations from time to time (for example, "Pr" for the propyl group). Is there any commonly-accepted list of these abbreviations, or are they simply ad-hoc shortenings? — This, that, and the other (talk) 03:11, 5 August 2012 (UTC)

We have a (probably incomplete) list at Symbol_(chemical_element)#Other_symbols_that_look_like_element_symbols. That list is sadly unreferenced, so I'm left with no clue as to whether there is an accepted standard or if people just make them up as desired. Someguy1221 (talk) 04:01, 5 August 2012 (UTC)

Thanks :) — This, that, and the other (talk) 05:40, 5 August 2012 (UTC)

Here is a list of commonly used abreviations. I don't know who the authority is on this though. IUPAC doesn't seem to have much to say on the topic. 112.215.36.172 (talk) 10:18, 5 August 2012 (UTC)

Please explain electricity consumer earthing

In the multiple earth neutral system Keit described in response to an earlier question, how many of these household ground rods with "several hundreds of ohms" resistance each are typically combined in parallel? Is it only to the neutral from the local transformer, or are the secondary neutrals of multiple transformers connected? Are metal cold water pipes not also used as grounds (granted some places use nonmetallic pipe, and the US lately seems to require a driven ground rod in addition to and water pipe ground))? Is a secondary neutral carried all the way back to the substation? Ive seen lots of installations (US) where there is a ground rod at the transformer and one at each house served by the transformer, without a "lighting secondary main" of phases and a neutral connected to other transformers along the line. It is all too common for there to be a fault in the transformer or external to it from the primary to a secondary conductor. If such a fault from the primary to secondary occurred and there were tenor 20 houses with 200 ohms ground resistance each, all the wiring in the houses would be elevated to quite a high voltage, until the primary fuse blew. Recent US code called for a supplemental ground if the first driven ground has over 25 ohms resistance. Common US practice is to bury the rod and the connection of the wire to it, making the "wiggle test" difficult. Also it is common for the connectors in the neutral line to develop a loose or high impedance condition, with normal load current having to flow to earth through the ground rod or water pipe at the house, until the problem is fixed. In a loose neutral condition, the remote grounds would not help much. Edison (talk) 20:17, 4 August 2012 (UTC).

As Edison's question requires an answer that covers several related topics that will be off-tack for the OP of the earlier question, I have moved his query to here - I hope Edison and everbody else does not mind. Edison has asked so many questions in his lengthy paragraph above that an answer must also be pretty long. So I intend to answer it all, but different parts of the answer will come over the next day or so - I do have lots of other commitments. As it appears that Edison has some misconceptions about what house/dwelling earth stakes/electrodes are supposed to do, and what they are not intended to do, I shall include an explanation on that, as well as answering Edison's specific questions & comments. I suggest that Edison and everyone hold follow up comments or queries until I complete it. Keit60.230.207.82 (talk) 04:11, 5 August 2012 (UTC)

I applaud your moving my questions to a separate topic and welcome your enlightenment on the topic of earthing practices. Grounding/earthing problems are a frequent root cause of power quality complaints. Edison (talk) 00:38, 6 August 2012 (UTC)

• In the multiple earth neutral (MEN) system, how many of these household ground rods are typically combined in parallel?

It varies considerably.

In accordance with standards enforced by the Authority, each property that has a consumer's meter (for electricity charging) must have ONE earth electrode. The electrode must provide a standard buried depth (which is not varied, regardless of soil conductivity or any other factor). The electrode is connected by a wire (known as the earthing conductor) to the meter box neutral bar (a copper bar to which all the house wiring neutrals are connected). The neutral bar has the neutral wire from the supply authority's street distribution connected to it. The supply authority/power company's neutral condutor running down the street thus connects all the house/consumer earth electrodes in parallel. The number connected in parallel in the MEN system may range up to several hundred or more.

The supply authority MUST ensure that the system is safe in all cicumstances. In a well developed street with a hundred or more consumer earths paralleled, there is no problem. However, in a new land development, the first house completed may, for a while, be the only house completed. There are some mitigating factors, but with only one functioning comsumer earth, the supply authority must install a good enough earth electrode system at the distribution feed point (transformer, transformer & ring main unit, or whatever), and may, if soil conditions are not favorable, install additional spaced earth electrodes, AND/OR, interconnect the neutral with that of an adjacent distribution area with a good number of installed consumer earths i.e., implement a CMEN. What is a "good enough" earth system? That is a complex issue of its' own. It is clear that Edison has some misconceptions. If you want to know more about this sub-topic, post a new question.

• Is a MEN only to the neutral from the local transformer, or are the secondary neutrals of multiple transformers connected?

Often, the neutral, and thus the earthing system, for a distribution (240V supply for a street or small area) is isolated from the neutral & earths of other areas. However, the supply authority/power company may elect to electrically tie the neutrals of two or more distribution areas together, either directly, or via the high voltage (6.6 kV and higher) neutral and earthing system. This is known as the CMEN system (Commoned Multiple Earth Neutral). Again, the reasons for tieing MEN systems together or not tieing them together are a complex subject on its own, but reasons for a CMEN may include: a) insuficient consumer earths in a particular MEN area, b) poor soil conductivity, c) high voltage system configuration, to name a few. There are both pros and cons, depending on circumstances, regarding implementing a CMEN or just having seperate MEN runs.

Keit60.230.207.82 (talk) 04:43, 5 August 2012 (UTC)

• Are metal cold water pipes not also used as grounds?

The basic answer is "No, but...". They have been used in the distant past, and it is possible that one could find an old house that still has as its consumer earth as metal water pipe.

Regardless of the presence of any "in ground" metal, an earth electrode of prescibed length MUST be provided. However, the principle is that the house earthing system must present the people in and around it with the lowest available voltage (i.e., closest to the potential of "great body of earth"). If fortuitously earthed metalwork is available, e.g., metal water pipe, gas pipe, the steel of a steel framed building etc, and due to high local soil resistivity such metal work could be a "better earth" than the prescibed length stake, and as such offer a lower voltage, then the house earth shall be electrically connected to this metal work. Rules on connecting to water pipes vary regionally, as it has some definite disadvantages - it can present a risk to plumbers and can "export" voltage to other properties/consumers - but in no case shall metal work be relied upon for electrical earthing. If a building is multi-storey or surmounts a hill top, it may be subject to lightning strikes as defined by relavent standards. In such cases, there will be lightning ariels (pointy rods on the roof that provide the most attractive place for a strike), down-conductors, and a lightning drain earth system. Lightning drain earthing systems will gnerally comprise multiple deep electrode systems to provide a specified low electrical impedance to "great body of earth" and as such far outperform any earth stake provided as part of the building electricity system. Again, you still have to provide the regulation prescribed short length electricity consumer earth electrode, and the lightning drain earth is connected to it (at one point only), and both earth systems must be clearly labelled as to which one they are. Keit121.215.143.169 (talk) 10:06, 5 August 2012 (UTC)

• Is a secondary neutral carried all the way back to the substation?

Essentially, No. There is only one neutral in principle. In open wire street distribution (i.e., unisulated wires strung on poles), there are four conductors comming from the transformer - one for each of the three phases, and the neutral wire. However, in underground distribution, or bundled aerial cable, the cable may be screened, and may be steel wire armoured. Some power authorities earth the armouring at one end only (this avoids heting due to current in the armour and thus maximises the current carrying capacity of the phase conductors. Others earth the armour at all connection points - experience has shown this to minimise lightning-caused faults and is becoming standard practice with all administrations.

In high voltage transmission lines, there is normally no neutral wire at all, but there will be an earth conductor of some sort. In open wire practice, there is normally an earthed wire above the phase wires to provide a more advantaguous place for lightning to strike, and for power cordination purposes. In HV underground transmission, each phase conductor will be surrounded by a coaxial copper screen, and the whole surrounded by steel wire armour. The screens and armour will be earthed at both ends, and thus will provide a return path for current. Mutual inductance between the phase conductors and the screens and armour will force most of the return current to go in the screens and armour and not the great body of earth, regardless of the relative impedances.

See discussion on CMEN above.

Keit121.215.143.169 (talk) 10:39, 5 August 2012 (UTC)

• It is all too common for there to be a fault in the transformer or external to it from the primary to a secondary conductor. If such a fault from the primary to secondary occurred and there were ten or 20 houses with 200 ohms ground resistance each, would not all the wiring in the houses be elevated to quite a high voltage, until the primary fuse blew?

Such primary to secondary faults certainly do occur. However, in a correctly implemented MEN (or CMEN) system there is no dangerous rise in voltage in the houses etc. The MEN consumer earth system is not intended to deal with such faults and quite normally will not be capable of sinking the current. It would be prohibitive in cost to make consumer's earths capable of sinking HV-sourced fault current - especially in many areas of Australia, where the ground is essentially dry sand and/or rock to great depths and the electrical resistivity very high. Power authorities/companies provide other means for managing and sinking fault currents originating in the primary/HV side. I will explain this in another paragraph or 2, or 3.

Keit121.215.143.169 (talk) 11:20, 5 August 2012 (UTC)

• Common US practice is to bury the rod and the connection of the wire to it, making the "wiggle test" difficult.

In my answer to the OP in Ref Desk http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Earthing, I intentionally omitted some factors he didn't need to know.

At one time in Australia, for instance, it was sufficient, in terms of regulations, to drive the house earth stake into the ground near the meter box, and attach a green earth wire of the prescribed gauge, one end to the neutral bar in tehg meter box, and the other end to the earth stake with a clamp. As part of their electricity supply contract with the power company, consumers/householders were required to maintain the wire, clamp and stake in good order and condition (not actually themselves - they should hire an electrician when required). Installing electricians commonly left some excess lenghth in the wire, coiled up, to facilitate re-terminating should it become necessary. However, because the wires were exposed, they tended to occaisonally get damaged. I myself once stripped one such earth wire right off accidentally while operating a large lawnmower. Most folk would eventually notice damage and call an electrician, but some might not. Current regulations require the wire and its attachment to be "protected against damage from reasonably expected events" - this means running the entire wire length in conduit. Commonly, nowadays, the entire setup is buried, but in this case there must be a small pit housing the top of the stake and its' connection, so that it can be easily located and checked. In such cases, the wrigle test is still possible. The lids of the pits are inscribed "MAIN EARTH". Any other earth present, such as a lightning drain earth, ham radio earth, etc must NOT be labelled "MAIN EARTH". Completely hiding it by burying it in soil without a pit is very bad practice and not acceptable. It must be possible to visually inspect it. Keit124.182.149.216 (talk) 12:23, 5 August 2012 (UTC)

• It is common for the connectors in the neutral line to develop a loose or high impedance condition, with normal load current having to flow to earth through the ground rod or water pipe at the house, until the problem is fixed.

Edison's claim that this is common is very surprising - it would only be common if installation practices are very poor and/or the installing electricians incompetent. Never the less, such a fault is obviously possible.

However, perhaps conter-intuitively, a relatively high house earth is actually safer. Remember that the purpose of a house earth (consumer's earth) is to ensure that appliance metal work is at the lowest available voltage, and NOT to ensure the actual voltage is minimal. It matters not a whit if the appliance user, touching exposed metal of the appliance, is at (say) 100 V above true earth, so long as he can't touch anything at a lower voltage. See other paragraphs on this. However, if the house earth, and therefore the house neutral, is, say, 50V above true earth due to high earth system resistance, then that is 50V less to run the appliances. Lamps will be very dim and flicker badly, and power appliances and electronics will not work properly, if at all. This will make the householder immediately contact an electrician to get it fixed. If a house earth was good enough to sink the load current and keep the neutral voltage low, then lamps and appliances will still work ok - so the householder in ignorance will not call an electrician. The open or high impedance neutral connection to the street wiring/cabling may become a residual fire risk. Keit120.145.32.129 (talk) 14:16, 5 August 2012 (UTC)

. Please note that the correct spelling is "neutral" not "nuetral." In the US, at least, overhead or underground connections from a transformer or a lighting secondary main are typically made by crimped connections, which can develop a higher than desired resistance over time. This may be in a phase or a neutral. A "loose neutral" has undesired effects, such as the side of 120/240 distribution with a high load having a low voltage while the other side has a high voltage. It is painfully common. Edison (talk) 00:36, 6 August 2012 (UTC)

I have corrected the spelling. Crimped connections are used here in Australia too. However, connection trouble is very rare. I have been in the electronics and electrical game for many years and have never experienced it, only heard about it. Of course, as we use double the voltage, the effect of any connection resistance will be a lot less. For instance, a 1 ohm resistance in a circuit feeding a 240 V 1 kW resistive load will drop the load voltage by 2% - hardly noticeable. In a 120 V 1 kW circuit, the load voltage will drop 9.4%. Even so, I think you must be mis-informed, either that or crimping practices in your area are poor. The practice of splitting a phase into two, with 120 V (one side earthed) used for lighting and domestic appliances, and 240 V (balanced to earth) for heavy draw items and industrial equipment is pecular to the USA and certain other "110/120 V" countries. We use 240V (single phase) and 415 V (3 phase) for all consumer equipment. However a dropped neutral will still result in a similar problem at reduced degree - a heavy load on one phase will increase the voltage on the other 2 phases. Keit58.169.250.192 (talk) 02:12, 6 August 2012 (UTC)

What the consumer earths in an MEN (or CMEN) system are intended to do:

The consumer earths are principally there to ensure that a person who is holding or touching exposed metal-work of an appliance, and thereby has his body at the neutral voltage, is at a voltage low enough in comparison to any other conductive thing (water tap, damp floor, gas stove, or whatever) he/she could simulataneously touch, that he/she will not percieve an electric shock and is not at risk of electrocution.

An example should make this clear:- Let us say that, due to a certain resistance in the supply authorities earthing system, together with the load current on the street distribution or fault condition existing in the absence of consumer earths, an appliance metal work is at 35 V with respect to the great body of earth. If the consumer (in bare feet perhaps) is standing on a bare damp concrete floor, or is simultaneously touching a gas-main fed oven, then he will get a shock, as the floor or oven will be at zero potential. There is in this case 35 V potential difference across him.

Now, assume each house has its earth stake. If the soil in the area is low in resistivity, small currents will flow to great body of earth via these stakes, thereby forcing the neutral voltage down - making it safe.

Let's now say the area is like many areas in Australia, essentially a thin layer of top soil, and under that dry sand to a depth of 30 m or more, overlaying bedrock. In such a case, the geology is high resistivity and even many parallled consumer earths won't do a terrific job of bringing down the neutral voltage. The consumers, though, are still safe - why? Because everything conductive they can touch is either fully insulated, or is in contact with topsoil, which has all these earth stakes poked into it. If the nuetral is 35 V above true earth, then everything else is nearly the same. If everything the consumer can touch is at the same 35 V, 100V, or even an impossible 350 V, it doesn't matter. There is no potential diffrence across him and he can't get a shock.

Keit58.169.250.192 (talk) 02:59, 6 August 2012 (UTC)

What the consumer earths in an MEN (or CMEN) system are NOT intended to do:

1. Consumer earths are not intended to carry significant current. For both normal loads and fault conditions in street distribution, house wiring, and appliances, the current in the earth stakes is very low. The bulk of load and fault currents is carried back to the transformer in the supply authority/power company's neutral wire. This is only partially dependent on the electrical resistance of stakes to great body of earth vis-a-vis the lower resistance of the neutral. The return current is largely forced into the neutral by mutual inductance between the active (phase) conductors and the neutral. Essentially, this means that the active wire, being very close to and physically in parallel with the neutral, forms a transformer with the neutral, so that whatever current flows in the active wire causes a more or less equal return current in the neutral. In general, a current of more than a few milliamps in the earth stake is an indicator of incorrect or faulty installation.

2. Consumer earths are not intended to sink current due to faults to the High Voltage side of the transformer. Such fault currents are up to 3000 Amps, and to expect any consumer to pay for an earth to handle that would be utterly prohibitive. The power company must provide other means to manage and sink HV fault currents - this will be described below. In practice, the paralleled consumer earths in a well developed MEN or CMEN area can assist in sinking fault currents arising from HV to LV breakdown.

3. Consumer earths are not intended to sink significant load current should the supply neutral be high resistance or broken/open circuit. To provide consumer earths do so would in many, if not most, areas would be expensive, and would mask a neutral fault. With the prescribed single short earth stake, failure of the supply neutral will result in lights and appliances not working properly, and, usually, not working at all, resulting in the consumer/householder urgently seeking an electrician, as mentioned elsewhere. Keit60.230.199.55 (talk) 05:35, 6 August 2012 (UTC)

Principal risk in fault currents from High Voltage transmission lines & feeders - Earth Potential Rise

Each MEN area providing low voltage (115/120/230/240 V) to consumers is feed via a step down transformer from a high voltage (between 6 kV and 132 kV) line or feeder. The principal interest here with faults on HV lines or faults in substations/RMU's/transformers fed from HV is what is called "Step and Touch hazard". When there is a HV fault causing a current to flow to earth via the substation/RMU/transformer earth electrodes, the current leaves the electrode(s), passing through the soil, locally radiating out in all directions, prior to finally heading downwards into the great body of earth. The soil has an electrical resistance - this means that the soil current causes the earth electrode(s) to raise in voltage above the deep earth level. As the current leaves the electrode(s) and spreads out to lower and lower current density, on the surface of the ground there is a contour of decreasing voltage.

A given electrode might (say) be raised to 1200 V above deep earth level, and at 1 meter away the soil surface be at 1000V, at 2 m away 500 V, and so on, until at a large distance the voltage is negligible. This is called Earth Potential Rise. Due to the high voltage available on HV lines, the current into earth electrodes can be substantial, and so Earth Potential Rise can be substantial.

In my example just given, a person standing with one foot 2 m from the electrode, and the other foot 1 m away from the electrode, would have a voltage difference between his feet of 1000 - 500 ie 500 V. Unless he has dry shoes with very good insulation properties, that 500 V difference, known as the step voltage, will result in hazardous current to flow thru his body and may very well kill him.

In my example above, let's say the substation has a metal/wire fence around it, or a brick or concrete wall around it. Brick and concrete must be regardled as conductive. Due to the voltage contour on the ground/soil surface, if a person touches the fence or wall, his hand will be at a higher voltage with respect to his feet - this is known as "Touch Voltage". Touch voltage can be more dangerous than an equal step voltage.

When Engineers design a substation, RMU, or transformer installation, they calculate the gound surface contour of voltage, and calculate the step and touch voltages, and then take action to ensure the step and touch voltages are within safe limits (which assume a 2m high human) regardles of worst case fault conditions.

For any given substation/RMU/transformer. one can draw a more or less circular line, on the ground surface, around the substation/RMU/transformer which is the closest distance a human can safely stand. For a small street trnansformer of RMU, the safe distance can be zero. For a major substation fed from a major HV or EHV transmission line, it can be 50 m or more.

Earth potential rise in LV (120/240 V) distribution due to faults to an LV conductor are a non-issue as the available voltage is not high enough to hurt anyone before a circuit breaker or other protection trips.

Keit124.182.38.215 (talk) 11:34, 6 August 2012 (UTC)

What power companies do in order to reduce Earth Potential Rise & hazardous Step & Touch voltages

There are a multitude of methods, all with their own pros & cons, but the main methods are:-

(a) Reducing the HV fault current by inserting an impedance in the earth connection at the source end of the HV line/feeder - either a resistance or inductance.

(b) In underground HV cabling, utilising the screens and steel wire armouring to carry the return current. As stated elsewhere, mutual inductance between the phase conductors and their screens and steel wire armour forces most fault current to return via the screens and steel wire armour. The ferromagnetic properties of the steel wire armour usefully enhances the mutual inductance effect. Open wire (ie wires slung on poles or towers) trasnmission can use the lighning protection conductor or power coordination conductor for this purpose.

(c) Install an effective earth electrode system at the substation/RMU/transformer to sink the fault current not returned in the screens & armouring. This "left over" current can be hundreds of amps or more, requiring a resistance to earth as low as an ohm or even less. so such earth systems can be very substantial, comprising multiple deep driven electrodes. I have acted as consulting Engineer on projects where substation earthing has cost over $1 million - much more than the substation hardware.

(d) Install a fence or wall at a safe distance, so that humans cannot approach within a Step & Touch hazardous area.

Common industry practice when planning a new HV route is to calculate the phase conductor current under worst case fault conditions (a Phase to neutral short in the substation/RMU/transformer). If it is 3000 Amps or less, fine. If over 3000 A, take action to reduce it to 3000 A, such as Method (a) above. Then, calculate what portion of that 3000 A or whatever it may be, will flow into the substation earth system, worst case. Then, use a suitable (ie, is economic, fits on the site, etc) combination of methods (b), (c), and (d) to get Step and Touch safety.

Yep, even still more of my answer to come! Nearly there. Keit120.145.61.75 (talk) 02:42, 7 August 2012 (UTC)

science/physics

Q1)an object of mass 1kg is tied with a 2m thread and it is rotated by velocity 5 m/s.calculate the centripetal force?

Q2)an object is having velocity 5m/s in east direction,now it turns to the north direction with a same speed and it takes 10sec.calculate the centripetal acceleration?

Q3)a rocket launcher launches a rocket of mass point 325 ton with velocity 50m/s and the launcher experiences a instant velocity of 3.25m/s.derive the mass of the launcher?

Q4)a bullet and a gun having velocity after shooting 500m/s and 8m/s respectively.derive the ratios of the masses?

Q5)two object of same mass,the ratio of there velocity is 1:3and ratioof there rotating radius is 3:1.derive the ratio of centripetal force? — Preceding unsigned comment added by Ekknoorkaur (talk • contribs) 04:37, 5 August 2012 (UTC)

Q6)Will we do your homework for you? I'll answer Q6. No. Looie496 (talk) 04:56, 5 August 2012 (UTC)

Genetically Modified Corn Cell

Ok so, the process of gene splicing has been used to create a recombinant plasmid. Then, this recombinant plasmid has been successfully inserted into a corn cell via a transformation method. From there, how does this genetically modified cell affect or create an entirely new crop, to carry out the newly desired functions? Any help would be GREATLY appreciated!! 220.233.20.37 (talk) 07:13, 5 August 2012 (UTC)

Presumably they don't just put it into any old corn cell, but into a reproductive cell. The corn plants produced from this reproductive cell would then contain that gene, and they would then pass it on to at least some of their offspring. As to how a gene changes the cell function, it's often accomplished by coding proteins, which then do the actual work. StuRat (talk) 07:51, 5 August 2012 (UTC)

Looking at [39], the popular methods seem to involve carrying out any of several transformation protocols on entire suspended embryos, at a very young stage. Someguy1221 (talk) 09:17, 5 August 2012 (UTC)

In theory, one can use any plant tissue [40] as plant cells can regress to regain their totipotentcy and from there can form a callus than roots and shoots and so on. That you don't need an embryo to genetically engineer in important as many crops produce worthless seed, ex Granny Smith apple trees are all descendant from a single branch through cuttings as their genetics are so heterozygous that any sexually derived offspring would be quite different from the parents. 65.95.22.16 (talk) 13:32, 5 August 2012 (UTC)

Grains like commercial wheat and corn seed are created differently from apples, though. There are intentionally out-bred. See hybrid vigor and Hybrid_(biology)#Hybrid_plants. (although neither is a very good explanation). Rmhermen (talk) 17:01, 5 August 2012 (UTC)

As 65.95.22.16 indicates, the transformation isn't usually done on reproductive cells, but rather on vegetative tissue or plant tissue culture callus. You then typically propagate the cells in cell culture (usually under selection so that only the transformed cells grow). At a certain point you can treat the callus with hormones which causes it to sprout roots and leaves, at which point you can transfer it to soil, grow it up, pollinate and collect seeds like a regular plant. This is for most plants. Occasionally you'll find other techniques, e.g. for the model organism Arabidopsis thaliana the easiest transformation method is in planta Agrobacterium transformation, where you basically dunk the whole flowering plants in the transformation solution and some of the seeds they then produce are transgenic. -- 71.35.119.233 (talk) 17:33, 5 August 2012 (UTC)

Priority of Köppen classification

My question is about the Köppen climate classification system. I am trying to determine the priority of calculation. For example, if an area is very dry and also very warm, it may well satisfy the conditions of being in Group A and Group B. The Sahara is mostly classified as Group B, hence B > A. Places in Antarctica, though, could be dry enough to satisfy Group B, but are classified Group E, hence E > B > A. Is this true? And where do C and D fit in? Thelb4^(talk) 16:23, 5 August 2012 (UTC)

It's not a question of priority. The groups are, at least in principle, non-overlapping. An area that is very dry (for the whole year) can't be in group A. It can be extremely dry for part of the year, as with savanna, but then it would have to be wet for another part of the year. Generally speaking A is hot and wet; B is dry all year and not too cold; C is temperate and not too dry; D is cold; E is polar. Looie496 (talk) 17:40, 5 August 2012 (UTC)

Because this will be archived, let me recalibrate that a bit. The basic point is valid, but here is a better description of the categories: A is hot and humid; B is dry (whether hot or cold); C is humid temperate; D is cold and humid; E is polar. Looie496 (talk) 15:36, 6 August 2012 (UTC)

HERBS in lab

hello Can you please explain the difference between oil and extract? Is oil a kind of extract? which one is the ethanolic yield from the seed? Thanks Simagoulou (talk) 18:43, 5 August 2012 (UTC)

An oil is usually taken to mean a lipid that is in the liquid phase, or more broadly any hydrophobic liquid. An extract is, IIRC, an alcohol soluble scent or flavoring element from a food product. Many extracts contain what are called essential oils, which are usually the primary aroma components. To state it another way, the "extract" is all of the stuff you get when you soak the plant in alcohol. The "essential oils" are specific compounds which provide the scents for a foodstuff. Most extracts contain a mixture of essential oils, as many plants contain more than one specific essential oil. For example, many mint plants contain menthol, but they also contain other essential oils that give each a distinct flavor, which is why peppermint is not identical in flavor to spearmint, and thus while both extracts will contain a lot of menthol, they will also contain different things as well. --Jayron32 18:55, 5 August 2012 (UTC)

Are all extracts obtained by soaking in alcohol ? If so, I'd expect the result to be mostly alcohol. Do they then remove the alcohol in some way ? StuRat (talk) 19:12, 5 August 2012 (UTC)

Our article about Extracts mentions that some are used as the alcohol (or similar-solvent) solution whereas others are produced by other processes or somehow lead to the "pure" essence rather than a solution. Some of the terminology in this field is a bit convoluted (or not quite matching the standard modern scientific meanings) because the terms were used in this field well before there was a more specific understanding of the chemistry involved. DMacks (talk) 19:25, 5 August 2012 (UTC)

As DMacks notes, the terminology is a bit fuzzy, but usually when you buy something at the grocery store called "XXX extract" whether it is vanilla extract, peppermint extract, almond extract, etc. it is an alcohol extract, and yes it is more alcohol than essential oils. You can make water-based extracts as well, I suppose; Tabasco Sauce is basically a water extract of chili peppers. However, essential oils are strong juju; pure essential oils are rediculously pungent to the point of being unusable in pure form (from the pepper example, capsaicin, the essential oil of chili peppers, will blister your skin in pure form). Things get whacky when you start dealing with extracts and essential oils in pseudoscientific "new age medicine" bullshit like aeromatherapy and stuff like that; since they're just making it up as they go along the terminology gets contaminated from those fields. --Jayron32 19:34, 5 August 2012 (UTC)

The methods of extraction of essential oils from plant matter vary: steam distillation, or solvent extraction (where the solvent is removed prior to use), or use of carbon dioxide to extract the oils from the plant matter. Jayron, if you don't think essential oils work, then please don't use menthol or Olbas oil next time you have a cold: or peppermint oil if you have an acid stomach (Colpermin to give it its OTC name): or Friar's Balsam for a bad chest. Obviously none of these remedies work because, well, it's all pseudoscience isn't it. Actually the scientific study of essential oils is growing year by year. --TammyMoet (talk) 20:11, 5 August 2012 (UTC)

The issue is not with compounds that have medically verified theraputic effects. I am quite sure that many compounds which are essential oils also have theraputic effects. The issue is that, in the popular media, the real science is contaminated with bullshit. I'm all for double-blind placebo-controlled medical studies which show theraputic effects of any compound. That's fine. I use many compounds which are extracted from plants, and remedies which have a basis in such compounds. But the fact that there is good science sadly doesn't make the bullshit disappear. After all, my local pharmacy carries homeopathic remedies on the same shelves as the actual medicine. As long as that bullshit continues then we haven't won the war... --Jayron32 04:34, 6 August 2012 (UTC)

The usual result of pseudoscience is a core of products which actually work (mints are proven to have anesthetic properties, for example), accompanied by unsubstantiated claims far what can be proven. StuRat (talk) 20:17, 5 August 2012 (UTC)

Austrian window-box plant; ID, please

Could someone ID this plant, please: http://twitpic.com/afxhtc It was seen in many window-boxes in the Salzburg area of Austria in the last couple of weeks. The flowers are about half/ three-quarters of an inch in diameter. Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:04, 5 August 2012 (UTC)

Perhaps a Sanvitalia? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:34, 5 August 2012 (UTC)

Or a Doronicum? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:48, 5 August 2012 (UTC)

Sanvitalia seems correct. Likely Sanvitalia procumbens, which is widely cultivated and seems to have dozens of cultivars.-- OBSIDIAN†SOUL 09:45, 6 August 2012 (UTC)

Can mosquitos breed indoors ?

I have a spare bathroom I only use for the shower, and it tends to stay humid in there. Over the course of a week I killed a dozen mosquitoes in the bathroom, and only a couple in the rest of the house. Could they be breeding down the (rarely used) sink drain or in the toilet bowl ? I wouldn't think there would be any food for the larva there, but I might have rinsed out a bowl in there and left some food residue in the drain. I flushed the toilet several times, and ran the water in the sink for a bit, then poured bleach in both, and haven't had the problem since. Any thoughts ? StuRat (talk) 23:49, 5 August 2012 (UTC)

Googling suggests mosquito larvae in unused toilet bowls is a relatively common problem. E.g. Scrub all the fixtures with bleach. 70.59.11.32 (talk) 00:07, 6 August 2012 (UTC)

It doesn't take much. Mosquito larvae can make do on nutritionally weak food sources and, in some species, subsist entirely on algae. I wouldn't be surprised if the scummy water left in a drain might harbor enough bacteria to bring a handful of larvae to adulthood. Someguy1221 (talk) 05:13, 6 August 2012 (UTC)

Thanks. I was wondering how else they could all have gotten in. StuRat (talk) 19:17, 6 August 2012 (UTC)

Resolved

August 6

Question about the plutonium in the curiosity rover

On the talk page for the Mars Science Laboratory, I posted a question about the plutonium generator in the Curiosity rover. Please take a look, thanks. 67.182.25.41 (talk) 08:03, 6 August 2012 (UTC)

It was an easy mistake to make. The figure given for the beginning of the mission is the total thermal energy produced by the fuel, whereas the figure given for the end of the mission specifically refers to the electrical output. It should also be noted that the relationship between remaining fuel and electrical output is not linear but is defined by the Seebeck effect, which is itself dependent on the temperature of the two nodes of the thermocouples used. So you actually expect a greater-than-exponential loss of power as the mission goes on. But anyway, the actual figures are 125 watts at the start of the mission, and 100 at the end. Although the RTG is actually designed to output 285. Someguy1221 (talk) 08:27, 6 August 2012 (UTC)

Oh, I take that back. I see simply read the passage too fast, and the distinction is made clear. Someguy1221 (talk) 08:28, 6 August 2012 (UTC)

Landing on Mars and coming back

Did some rover, or anything similar, ever landed on Mars and came back? Or is the Curiosity rover and its predecessors just meant to land, perform their work there and report the data to Earth? — Preceding unsigned comment added by 79.155.237.76 (talk) 11:34, 6 August 2012 (UTC)

No, no spacecraft has yet landed on Mars and returned, but there are plans for such a mission, see Mars sample return mission. - Lindert (talk) 12:08, 6 August 2012 (UTC)

I'm surprised they would even consider a return mission. For much less extra fuel and rocket size I'd expect they would be able to just include more analysis equipment. The one advantage I could see is that it might be preparation for a human mission, in which case they should send an exact replica of the human capsule, with either empty seats or maybe a monkey or two (hopefully trained to use the toilet facilities). StuRat (talk) 19:15, 6 August 2012 (UTC)

And why wasn't it done yet? Why is it easier to transport the scientific equipment to Mars than to enhance the rover with a return device? 79.155.237.76 (talk) 12:31, 6 August 2012 (UTC)

Seems pretty obvious, doesn't it? A two-way trip would mean equipping the rover to somehow blast off of Mars. That means shipping a lot of fuel, an extra rocket, etc. Make no mistake: sending something on a rocket to Mars from Earth is hard. Sending something to Earth from Mars is no easier. --Mr.98 (talk) 13:05, 6 August 2012 (UTC)

But, the escape velocity of Mars is smaller than of the Earth, and the way Earth-Mars-Earth is almost for 'free' (I believe).

It's still obviously a lot more work to make a lander that can autonomously blast off again than it is to make one that just stays there. --Mr.98 (talk) 15:05, 6 August 2012 (UTC)

The escape velocity of Mars is indeed lower, but the latter bit is entirely wrong -- you don't subtract the energy load when making the return trip; rather, you add further requirements. And while comparatively less fuel is needed for Mars -> Earth than Earth -> Mars, you have to use a lot more fuel on the (less efficient) Earth -> Mars leg to get your return rocket to Mars in the first place. Also consider: Curiosity (mass approx 1000 kg) was delivered to Mars by an Atlas V rocket, and we'll assume that 1000 kg is functionally the most mass that could have been so delivered by that platform. 1000 kg probably isn't enough to return anything from Mars to Earth. The Atlas itself weighs 340000 kg, so that's a 340:1 mass-to-payload ratio for the Earth -> Mars trip. You'd have (even granting the lesser escape velocity from Mars) less than 10 kg of total science package plus Earth-return package plus payload to play with, and that has to include all the stuff you need to survive re-entry at Earth. So why not use a bigger rocket? Because the Atlas is functionally the heaviest operational rocket available currently (+/- 10% or so). — Lomn 15:06, 6 August 2012 (UTC)

On the other hand, there was also the (failed) Russian Phobos-grunt probe, which would have attempted to return about 200 g of soil from Mars' moon Phobos. You get around the problem of getting off Mars, though the fuel then required for the return trip is similar. It was launched on a Zenit-2M, a somewhat less-powerful rocket than the Atlas 541 that launched the MSL. It's unclear how big the actual return-rocket of the Phobos-grunt probe was. Buddy431 (talk) 18:22, 6 August 2012 (UTC)

Updates To Darwin's Theory of Evolution by Natural Selection

Sorry if this is a somewhat common question; when you search the web and the reference desk archives, there's a lot of junk to filter through.

Does anyone know of a reasonably comprehensive list (for the layman) of modifications which have been made to Darwin's theory since he first proposed it? By this, I don't mean updated knowledge of the details of the events that occurred or the underlying chemical processes; I only mean modifications in the understanding of the principle. I'm no biologist, and the only example of an update that I'm familiar with is the selfish gene theory, but I'm sure there are many others.

Thanks. --75.102.79.215 (talk) 16:47, 6 August 2012 (UTC)

Have you seen the modern evolutionary synthesis article ? There's the history of evolutionary thought article too. Sean.hoyland - talk 17:05, 6 August 2012 (UTC)

History of evolutionary thought#Alternatives to natural selection onwards gives an overview with links to more detailed articles, if you want a book then Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). University of California Press. ISBN 0-520-23693-9. {{cite book}}: Invalid |ref=harv (help) (or the more recent edition) gives pretty good coverage. . `dave souza, talk

The most significant modification seems to be that evolution doesn't happen at a slow, steady pace, but in jumps and starts, like growth spurts in a teenager. The causes are complex, such as a changing environment (or introduction to a new one), or the addition, loss or change of an interacting species (a predator, prey/food, competitor, or symbiont). We have also discovered the mechanisms of inheritance (DNA) and mutation, but that doesn't modify Darwin so much as add detail. StuRat (talk) 19:03, 6 August 2012 (UTC)

See Punctuated equilibrium. I think your explaination is misleading. Both the PE and Phyletic gradualism models appear to be legitimate models for understanding historic evolutionary patterns [41]. The question of the frequency of each model is an unresolved issue and besides, looking at it as a dichotomy is usually seen as flawed anyway. I also suspect you will find that many evolutionary biologists do not agree with your view that it's the most significant modification, in fact I think many would even question whether it's really a significant modification at all, see our article or [42] [43] [44] [45]. Nil Einne (talk) 21:16, 6 August 2012 (UTC)

I am a fan of Gould's but Nil is correct here. μηδείς (talk) 23:16, 6 August 2012 (UTC)

And he's entirely wrong that the mechanisms of inheritance don't modify Darwin — they have profound effects on making sense of evolution. --Mr.98 (talk) 22:31, 6 August 2012 (UTC)

No, if it modified Darwin it would prove that something he said was wrong. It just adds detail. StuRat (talk) 22:58, 6 August 2012 (UTC)

The most important modification is known as the modern evolutionary synthesis. Basically what this means, in lay terms, is the merging of Darwinian natural selection with modern understandings of population genetics. This took a lot of work and happened relatively recently (the 1930s or so) — before then was a sea of competing theories torn between the neo-Darwinians (like August Weismann) and the biometricians (like Karl Pearson). (It is amazing to many in retrospect that Darwin was not seen as particularly correct in the period between his death and the creation of the MES.) The MES is basically a version of evolutionary theory that takes the best of both of those worlds and makes them into one coherent theory. Aspects of it would be recognizable to Darwin but much would be new to him, as he had by modern standards a quite poor understanding of how heredity worked and that has big implications for making sense of the theory. As for other sub-theories (like selfish gene), there are tons... Category:Selection is a nice place to start for much "smaller" topics. --Mr.98 (talk) 22:31, 6 August 2012 (UTC)

The answer, given twice above, is the modern evolutionary synthesis. Part of that, and the most important, is Mendelian genetics followed by the elucidation of the nature and function of DNA by Watson and Crick. There is also the mathematicalization of population genetics by Dobzhansky, et al., and the biological species concept of Ernst Mayr. Most importantly, these are all elucidations. Nothing contradicts Darwin's theory of evolution by natural and sexual selection. μηδείς (talk) 23:14, 6 August 2012 (UTC)

Thomson jumping ring

In a Thomson jumping ring experiment, how do you derive the relationship between the mass/current/temperature of the ring and its jump height?--150.203.114.14 (talk) 17:44, 6 August 2012 (UTC)

It is worked out in an article from The Physics Teacher, available at http://physicsed.buffalostate.edu/wnypta/meetings/2004-05/02-05-05/Hall1997TPT35p80-83.pdf. Looie496 (talk) 18:30, 6 August 2012 (UTC)

Sci Fi Movie Another Earth

In the movie Another Earth, a second Earth appears in our horizon, which looks as far away as our moon. Due to it's proxmity, what would be the physical consequences of earth in the movie Another Earth? Reticuli88 (talk) 18:09, 6 August 2012 (UTC)

Greater magnitude of (due to more mass in close proximity) and variability of (due to varying orbital periods) tidal effects, nighttime reflected sunlight, and solar eclipses. — Lomn 18:28, 6 August 2012 (UTC)

Specifically, I ballpark the tidal influence of Earth2 as being about 5 times that of the moon: Earth2 sits at 4x lunar orbital radius (as Earth is about 4x the radius of the moon), and is 81 times as massive. 81/4² = 5. — Lomn 18:33, 6 August 2012 (UTC)

More importantly, if I recall correctly that's an unstable configuration. In a short period of time the moon would either hit one of the planets or (more likely) be ejected from the system. The two planets would then either drift together or drift apart. Looie496 (talk) 18:37, 6 August 2012 (UTC)

Tide is proportional to the inverse cube of distance; 81/4³≈5/4 —Tamfang (talk) 20:05, 6 August 2012 (UTC)

The second Earth doesn't looks as far as the moon. It looks as big as out moon. Since the earth is bigger, it would be much far away than the moon. Comploose (talk) 18:52, 6 August 2012 (UTC)

I based my numbers on "Earth2 has the same angular size (looks as big) as the moon". However, looking at the pictures in our article, Earth2 is in fact pictured by the film as being far closer than the moon's orbit, which would easily result in immediately catastrophic consequences. — Lomn 19:16, 6 August 2012 (UTC)

In the productions notes in the wiki article:

"The DVD/Blu-ray deleted scenes feature reveals that the filmmakers did intend to illustrate some of the consequences to gravity by filming a scene in which Rhoda encounters flowers floating in mid-air, but the scene was cut from the final film."

...would floating flowers really be possible? What other things would we observe happening if such a thing occured? Reticuli88 (talk) 19:42, 6 August 2012 (UTC)

No. The change in gravity even on the near-Earth2 side of the Earth would be undetectable over small scales. Someguy1221 (talk) 20:05, 6 August 2012 (UTC)

Changes of gravity don't only affect light things. Consider that gravity, besides holding flowers down, holds the ground down. —Tamfang (talk) 20:08, 6 August 2012 (UTC)

Yeah that would have been a terrible gaff. Vespine (talk) 22:21, 6 August 2012 (UTC)

Silviring Analogues for other Metals

I know that you can coat something with a thin layer of silver just by putting it in a hot mixture of Tollens' reagent and sugar, but are there other similar reactions that can be used on non-metallic surfaces but using other metals? I am specifically thinking about possible use for coating something to make it conductive enough to electroplate, so the metal doesn't matter as long as it is cheaper than silver. Bakmoon (talk) 22:21, 6 August 2012 (UTC)

In the electronics industry, there is a need for ceap arbitarily or odd shaped "shield boxes", Over the years, a number of processes for giving molded plastic boxes a conductive surfacehave been developed. A common one is the Pearlstein process: First, "sensitising" is done with a bath of SnCl₂ solution. Next, it is "activated" in a bath of PdCl₂ solution. The result is a reliable but thin conductive surface that can be built up by electroplating. Electonic parts are mounted in printed circuit boards. These boards comprise an insulator substrate, eg fibreglas or phenolic, about 1.6 mm thick, on which copper tracks are manufactured. Often, tracks are on both sides, and plated through holes (PTH) connect from one side to the other, and provide places where the wire end of the parts are soldered. At first the Pearstein process was used to make PTH's conductive after drilling the substrate. Since then better methods have been developed - you might like to research the Atkinson & Wein process and CU-EDTA. You could do a patent search on PTH. You could also consider "aquadag", which is a "paint" comprising fine carbon particles mixed in a water soluble binder. Once somthing has been "dagged" it can be electroplated. This may be acceptable for hobby use or one off's - it is a bit too slow and fussy for production use. Keit121.221.208.142 (talk) 23:05, 6 August 2012 (UTC)

One can chrome plate plastics. There are many ways to make a mirror on various non-metallic substrates, for example using elemental mercury (not sure the process for depositing it) or aluminium (vacuum deposition probably the most common). I've made some really cool-looking metal-film mirrors on various glass objects by precipitation of metallic lithium or sodium, but obviously those are a bit hard to handle (and probably not suitable for most electrochemical cells). DMacks (talk) 23:10, 6 August 2012 (UTC)

Such methods are either difficult, or use hazardous materials though. The advantage of electronics industry methods such as Pearlstein, Cu-EDTA, and aquadag is that they don't require exotic methods, are easy to use (though cleanliness is key) and the chemicals are not particularly hazardous. Keit120.145.61.75 (talk) 02:06, 7 August 2012 (UTC)

What makes Curiosity so special?

Hi all, What makes the Curiosity rover so special compared to previous Mars rovers? There seems to be more excitement over this one than previous landings (if I recall correctly). - Akamad (talk) 22:45, 6 August 2012 (UTC)

It's the most advanced to date. Shadowjams (talk) 22:51, 6 August 2012 (UTC)

The Curiosity rover has an incredibly complex landing system, so people might just be amazed that anything that complex can actually work. StuRat (talk) 22:54, 6 August 2012 (UTC)

It's a tremendous boost for ailurophobes. Clarityfiend (talk) 23:03, 6 August 2012 (UTC)

Thanks. I also ended up finding some information here. - Akamad (talk) 23:05, 6 August 2012 (UTC)

I'll also add that the previous rovers were pretty much limited to looking at things, although in addition to regular cameras they could look with spectrometers, microscopes, X-rays, and even the result of blasting a rock with gamma rays. But the Curiosity can do real chemistry on Martian rocks and soil, and let us learn a lot more than we could in the past. Someguy1221 (talk) 23:10, 6 August 2012 (UTC)

How close would an alien species have to be to detect us if they had our current level of technology?

If an alien species had our current level of technology and they were to focus detection efforts on our portion of their celestial view looking for alien (to them) signals, how close would they need to be to detect us given our output of signals--light, television, radio—whatever we broadcast that they might detect)? One premise: let's ignore time delay. What I mean is that a species forty light years away, if they could detect our electromagnetic output, would only be able to detect what was put out forty years ago. I don't want to limit it in this way. So at any time. Signals spread out and get weaker over distance so I assume it's pretty limited. To state it backwards, if there were aliens on a planet orbiting proxima centauri with our current level of technology, would they be able to detect us given what we output? Barnard's star? and so on, growing more distant.--108.54.25.10 (talk) 23:12, 6 August 2012 (UTC)

I suspect that the answer very much depends on directional transmissions and receivers. If we put all our technology to work to send a powerful signal to a specific planet, and they happened to have put all their technology to aiming a powerful directional telescope right at Earth (or where Earth was) when the signal comes in, then they could be far more distant than if they just try to detect signals when only random radio and TV signals arrive. In the later case, I'd think they would need to be within our own solar system. Of course, the aliens would also need to avoid looking toward Earth when we are behind the Sun or in front of it, as interference from the Sun would make our signals hard to pick out. So, the answer might come down to how close they would need to be to detect Earth, since that's a prereq for them to point a powerful antenna at Earth. StuRat (talk) 23:23, 6 August 2012 (UTC)

This is discussed on our article on the Fermi paradox. Dominus Vobisdu (talk) 23:27, 6 August 2012 (UTC)

I'm just gonna copy my comment from last time this was asked, since I was the only one to respond:

In the best case scenario, the Arecibo message is received at another planet while that planet has its own Arecibo-sized dish pointed directly at Earth. In this case, even a pessimistic estimate gives the Arecibo a detectable range of 10,000 light years [46]. In that same page, it is noted that Frank Drake claims the technology exists to boost this range ten-fold. It's hard to imagine, however, that we'd manage to land the message right on an equivalent detector. I recall seeing a calculation (but I can't recall where), that a modern radio receiver without a directional dish like Arecibo would detect the message from ~400 light years at most. A non-directional emitter and a non-directional detector would have a drastically reduced range, and with modern equipment (I'm told), you may have trouble communicating with Alpha Centauri. Someguy1221 (talk) 04:09, 19 March 2012 (UTC)

If Aliens were pointing their version of the Arecibo Observatory at us, they should be able to detect us easily from a few hundred light years away. All of this is answering based on what has already been built. We have the technology to build, if we so desired but it would be very expensive, intergalactic radio transmitters. Not that we would get any use out of them in our lifetime. But as mentioned in the article linked by Dominus, if the aliens aren't listening to the stars, they won't hear us, unless we happen to nail them directly with Arecibo, and from relatively nearby. Someguy1221 (talk) 23:33, 6 August 2012 (UTC)

• Given that the speed of light is a limitation, they'd have to be no more than about a light century away to detect our radio broadcasts, likely much closer. The fact that we have an oxygen-rich atmosphere almost mandates the presence of photosynthetic, if not intelligent life. Detecting oxygen from other planets' atmospheres is at just about our level of skill now; although we have not done it yet, we do know how. μηδείς (talk) 23:41, 6 August 2012 (UTC)

• The OP specifically asked us to ignore the speed of light delay. StuRat (talk) 23:45, 6 August 2012 (UTC)

In that case my points are false. μηδείς (talk) 02:46, 7 August 2012 (UTC)

If you mean our technological ability, we could build space VLBI telescopes which could detect city lights and radar signals tens of thousands of light years away, and campfires on an Earth-like planet hundreds of light years away, given the necessary budget and clearances. However, only the military uses the formation flight technology enabling large synthetic apertures, and they keep it secret and actively dissuade astronomers from using it. So our actual passive detection capabilities of city lights are presently limited to the few earth like planets within a few dozen light years. Write your congresspeople. 70.59.11.32 (talk) 03:07, 7 August 2012 (UTC)

August 7

Scientific article self-criticism

Hello. I was wondering what the standard procedure is for including a discussion of the limitations or possible flaws of a scientific study (in chemistry in this case, though I doubt it matters) within the paper itself. DOes one generally put an independent section at the end, or what? thank you 134.48.233.92 (talk) 01:50, 7 August 2012 (UTC)

The standard structure of a scientific paper is Introduction-Methods-Results-Discussion, and that would be part of the Discussion section. Looie496 (talk) 02:28, 7 August 2012 (UTC)

Sodium triphosphate alkalinity?

How can I convert sodium triphosphate solution molarity into pH? Ideally I'd like a general formula, not just a pH of specific molarities. 70.59.11.32 (talk) 02:56, 7 August 2012 (UTC)

You'll need the 5 K_a values for triphosphoric acid. From those you can calculate [H⁺] and thus the pH.--Jasper Deng (talk) 03:08, 7 August 2012 (UTC)