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April 5

What kind of psychometric test is this?

I’ve taken this exam as a requirement for a job. Unfortunately, I forgot what the exam was called. All I can remember is that the exam has 100 items grouped into five or four. Each group of five or four questions contains numerical, logical, and vocabulary questions. The questions look something like this:

Something that you use when raining --- U, S, G, C, M (Umbrella)

A small explosive thrown by hand --- G, C, W, J, Z (Grenade)

An apple costs $2.50. If you have $10, how many can you buy? --- 4, 5, 6, 4.5, 5.5

Complete the series: 1, 2, 4, 7, 11, 16, ? --- 22, 21, 20, 23, 24

What kind of psychometric test is this?49.144.142.130 (talk) 02:18, 5 April 2015 (UTC)

It reminds me of the IPATO, which was a special proprietary example of an aptitude test (more specifically - an intelligence quotient test), although the IPATO typically presented its answers in two-dimensional format just to slow certain thought-processes (and to favor people who were really good at linear algebra). Were these questions timed?

Proper administration of an intelligence test (like a Wechsler Adult Intelligence Scale test) typically costs a few hundred dollars. Fees cover the cost of the psychologists and professionals who design the test, as well as the intellectual property licenses for the questions and the scoring matrix - not to mention overhead costs to ensure sterile testing conditions. Many similar IQ tests like the Scholastic Aptitude Test and the Graduate Record Examination are administered by private-sector companies and also generally cost over a few hundred dollars. There are hundreds of alternative psychometric tests of similar caliber, vetted by individual contract companies or even built up by specialized in-house HR departments at large companies, that can be administered at much lower total cost. Perhaps your test was one such proprietary company test. Generally, such tests are not called "IQ" tests, for reasons of political correctness and avoiding liability, avoiding licensing, and avoiding strong emotional responses. Without exception, such tests are named "Incoming Applicant Aptitude Scoring System" or some similarly verbose description; this serves to obfuscate intent, but only for the subliterate.

Nimur (talk) 03:36, 5 April 2015 (UTC)

For that first question, shelter, coat, gaiters, and a mackintosh are also valid answers MChesterMC (talk) — Preceding undated comment added 08:44, 7 April 2015 (UTC)

Air Pollution Maps

Are there any other detailed air pollution level maps like http://aqicn.org? I don't need real-time information like aqicn.org (though it would be nice), but I'm looking for one with the most data points. Aqicn.org only has a few per city unfortunately. WinterWall (talk) 09:18, 5 April 2015 (UTC)

No, there is no denser resource. There is satellite data but most of that is lower resolution and limited to long-term averages (plus it has large calibration issues). There is also model data, but again lower resolution. That said, why do you want more data points? Most particulate pollution (the primary health concern) has a atmospheric lifetime of days and quickly becomes mixed on a regional scale (50-100 km). Local effects, such as being next to a factory or highway tend to provide only moderate perturbations. And, of course, some of the apparent detail is related to noisy or poorly calibrated instruments. More important than where you live in the city, is where the air you were breathing came from over the last several days. Air that is imported from industrial areas will usually be dirtier than that which can from agricultural or natural areas. And that depends strongly on day-to-day (and even hour-to-hour) wind patterns. Dragons flight (talk) 20:34, 5 April 2015 (UTC)

trees

Do trees grow as far down as they grow up? if you turned it upside down would it look the same? — Preceding unsigned comment added by Kelticone (talk • contribs) 11:53, 5 April 2015 (UTC)

It depends on the species of the tree, the distribution of water and minerals in soils (roots will grown towards them), and the wind load (wind encourages deeper roots). It is said of oak trees that the roots are about the same shape as the crown, but this http://gardening.stackexchange.com/questions/1555/how-far-on-average-do-tree-roots-extend-out-from-the-base-of-the-tree indicates otherwise. LongHairedFop (talk) 12:51, 5 April 2015 (UTC)

Oaks appear to oscillate. Roots gow, then stop, leaves and so on grow, then stop and go on with roots again. --Hans Haase (有问题吗) 15:58, 5 April 2015 (UTC)

Most tree roots do not grow anywhere near as far down as the branches twigs and leaves grow up. The roots tend to spread out, often surprisingly shallowly in the case of conifers. There are a few exceptions in species that are adapted to seeking deep water tables, but generally, for most species and most soils, the root pattern is wide but not very deep. A Google search gives some patterns for different species. Dbfirs 16:23, 5 April 2015 (UTC)

Yes, if you've ever seen a toppled tree, the roots tend to cover a circular area perhaps as wide as the crown, but nowhere near as deep. μηδείς (talk) 20:54, 5 April 2015 (UTC)

When looking at the Virginia department of Forestry you see that trees roots grow to the length the widest branch tips. From this we can see that the trees roots do not grow nearly the same length as the actual tree. You also see in they looked at the depth of roots for several different types of trees. By doing this they compared several different research papers to debunk a common myth about tree roots. They found that the deeper the roots the more drought resistant a tree is. And they only grow the length of the branch tips as well. For a final source I found that Jim Urban, FASLA, a noted tree and soil expert. He found that. “Roots require three things: water, oxygen, and soil compaction levels low enough (or with void spaces sufficiently large enough) to allow root penetration. If all these conditions are met, roots can grow to great depths. Under ideal soil and moisture conditions, roots have been observed to grow to more than 20 feet (6 meters) deep. From this we see that they have to have these for the tree to grow.” (Urban) Lami229 (talk) 21:40, 5 April 2015 (UTC)LaurenAlexis

References

Female sexuality

Are lesbian women more or less likely, statistically speaking, to be virgins after the age of 30 than their straight counterparts? Please provide citations to back up your data

Eyebubummerglue (talk) 18:05, 5 April 2015 (UTC)

Not an answer to the question, but as noted at virginity, not everyone used the same definition. Many heterosexual couples consider the loss of virginity to only occur when a penis penetrates a vagina, while homosexual couples often include oral sex, mutual masturbation, and other acts as a loss of virginity. If one uses a definition that is tied to heterosexual acts, then it seems almost certain that many people who identify as homosexual are technically "virgins". On the other hand, if you include a variety of other sex acts, then many people who have been "saving themselves" and self-identify as "virgins" would probably lose that status under an expanded definition. Without a precise definition of which sex acts you mean, I doubt one could even begin to meaningfully answer the question. Dragons flight (talk) 19:37, 5 April 2015 (UTC)

These two journal articles discuss the subjective nature of "virginity", and discuss some data that includes lesbian participants [3] [4]. SemanticMantis (talk) 19:31, 6 April 2015 (UTC)

Jet aerodynamics of sound

Jet aerodynamics of sound is it been save on the speed of light?--83.237.214.60 (talk) 20:26, 5 April 2015 (UTC)

I'm sorry, but this question is not understandable. Some of us can read languages other than English. Therefore you may get a more useful response if you post your question in your native language. Short Brigade Harvester Boris (talk) 20:29, 5 April 2015 (UTC)

kettles in the bath

How many 1.5L kettles of boiling water would be needed to make a 80L bath of cold water the right temperature for bathing? — Preceding unsigned comment added by 108.192.136.193 (talk) 23:28, 5 April 2015 (UTC)

Anywhere from zero to many, depending on the temperature of the "cold" water and one's personal preference as to the right temperature for bathing. Short Brigade Harvester Boris (talk) 23:47, 5 April 2015 (UTC)

Many people use a bathing temperature of roughly 40 °C, so going with that if the cold water is 20 °C, the cold and boiling water should approximately be mixed in a 3:1 ratio. For a 80 liter bath this means 60 l of cold water with 20 l of boiling water (i.e. 13.33 kettles). Of course this is just an example of a typical situation; like the comment above points out, the answer can be quite different depending on the situation. - Lindert (talk) 00:09, 6 April 2015 (UTC)

(OR Alert) Having actually performed this experiment multiple times (after my gas-fired hot water system broke down), I can advise that in practice it takes rather more boiled kettles than the theoretical calculations indicate.

The problems are that (a) one has to boil the n kettles sequentially, not all at once, and (b) it takes several minutes for each kettle to boil, and all this time the hot water already added to the bath is cooling down. I started with a quantity of cold water already in the bath (to minimise the differential heat loss effect) and boiled two kettles in relay, switching on the next filled one before even pouring the previous one into the bath. To achieve a minimally useful depth of acceptably warm bath water took 30-40 minutes of this quite physically energetic process (depending on ambient temperature – it was winter). It also proved very expensive in terms of electricity bills – I ran up a deficit of several hundred pounds (sterling) which took me over a year to pay off.

If the OP is in a similar actual situation, I can advise a much easier and cheaper method which occurred to me eventually (being a dumb First-Worlder ). Boil one kettle of water and pour half of it into a basin by the bath (my handbasin actually overhangs my bath, which is ideal). Diluted with cold water to a comfortable temperature, this is ample to wet oneself down with a flannel while standing in the bath, soap and scrub, and perform one rinse. The second half, similarly cooled, then suffices for a second and definitive rinse.

One kettle's worth also proves ample for hair washing and rinsing with the aid of a pan while bent over the bath. I actually find this preferable to and more thorough than just lying in a bathful of water, though I admit the latter also has its attractions. It also steams up the bathroom much less, reducing any problems arising from condensation, like mould

In case anyone wants to raise the point: yes, installing a shower is in my long term plans. {The poster formerly known as 87.81.230.195) 2.218.13.204 (talk) 15:57, 6 April 2015 (UTC)

• In the big drought of 1976 we where advised to "Save Water, Bath With A Friend" If your friend don't like cold water and has a job – problem solved. You might even get a free back scrub. --Aspro (talk) 21:30, 6 April 2015 (UTC)

• The answer is that you need 80L of boiling water, then you let it cool to the temperature you like. I believe Lindert's equation might be wrong; I think you have to convert to Kelvin first. μηδείς (talk) 02:07, 7 April 2015 (UTC)

• No, it's the temperature differences that matter, not the absolute temperatures, so any units can be used, as long as they are used consistently. StuRat (talk) 02:25, 7 April 2015 (UTC)

Some points:

1) If you have a helper, they can add kettles of hot water while you bathe. You can start bathing with a small amount of water, and continue bathing as that water cools and more hot water is added. Of course, the helper has to be careful to add the water on the far end of the tub so as not to burn you.

2) Bubble bath seems to help to keep the water warm, by providing an insulating blanket of foam.

3) The room temperature also matters, both because the bathwater will cool faster in a cold room, and because it will feel colder, even the water is the same temperature. StuRat (talk) 02:30, 7 April 2015 (UTC)

April 6

Electric bath warmer

Would warming a bath with this product actually work and would it be safe? How long might it take to warm an 80L bath to 40c? 108.192.136.193 (talk) 00:34, 6 April 2015 (UTC)

Note: The image linked shows an immersion heater. -- ToE 09:32, 6 April 2015 (UTC)

We are in no position to answer questions regarding electrical safety based on nothing but a photograph - though I very much doubt that such a device would be compatible with electrical safety regulations in most countries if used in such manner. Even ignoring the obvious risks of electrocution, anything that small capable of heating a bath full of water is going to present a significant risk of burns. In short, we can't answer your question, and even if we could, the only answer we could legitimately give is "don't even think about trying it". AndyTheGrump (talk) 03:41, 6 April 2015 (UTC)

With the caveats mentioned by AndyTheGrump above, my guess would be that, in a cold room, the bath of water would lose heat faster than that device could add it, so it would never reach 40C. In the distant past, I have heated a bath with a higher power immersion heater, and it worked, but it was a very dangerous thing to do and I now have more sense (I think). Dbfirs 07:20, 6 April 2015 (UTC)

Those are designed for heating a cup of cold water to about 80-90°C (175-195°F) for coffee/tea etc. Assuming no losses for all these calculations, we get: To heat 300 millilitres (10 US fl oz) from 10°C to 90°C requires about 100kJ of energy, to do so in 1 minute requires 1.7kW of power. To heat 50litres (about half a bathfull, before you get in( of water by 30°C (from 10°C to 40°C) requires 6,300kJ. At 1.7kW, that's just over 1 hour, so even without any losses to the air, it's impracticable. LongHairedFop (talk) 08:32, 6 April 2015 (UTC)

I doubt it's actually as high as 1.7kW. This one, for example, is just 300W.--Phil Holmes (talk) 12:06, 6 April 2015 (UTC)

Yes, 1 minute sounds very fast to boil a cup of water, I believe a powerful microwave can do it in about a minute, but I wouldn't be surprised if one of those old immersion heaters took 3 or 4 miunutes to boil a cup.Vespine (talk) 00:19, 7 April 2015 (UTC)

I've never used one, so the time of 1 minute was picked at semi-random. The one in Electric_heating#Immersion_heater is indicated at 500W. Anyway, a 300W unit will take about 3hrs to heat a bath, assuming no losses. — Preceding unsigned comment added by 62.56.48.4 (talk) 09:31, 7 April 2015 (UTC)

regrowing fingers

How come my skin regrows when it gets cut and my bones regrow when they break, but my chopped off finger won't grow back? — Preceding unsigned comment added by 219.137.229.2 (talk) 00:56, 6 April 2015 (UTC)

Wikipedia has an article titled Regeneration in humans. I suggest you read that article, and then read any bluelinks from that article, to see where it takes you in your research. --Jayron32 01:00, 6 April 2015 (UTC)

That's a bit beyond my mental abilities. Can you just tell me? Thanks! — Preceding unsigned comment added by 219.137.229.2 (talk) 01:06, 6 April 2015 (UTC)

Healing vs. regeneration. Different processes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:46, 6 April 2015 (UTC)

From what I found it appears that there really is not an answer to this question as of yet. There have actually been documented cases in an article from nature.com it is documented that some children have been known to regrow fingertips and some adults have even grown back parts of their liver. We have the ability when we are in the womb, humans are built piece by piece simply because we have stem cells by the time we are born our cells turn into adult somatic cells. Other animals still have stem cells even in adulthood . According to NUI-Galway’s Frank's research there may be two main reasons of human's lack of regenerative abilities. First if an amphibian loses a limb it can hide and regenerate without the need for food, this is simply not an option for a mammal with a fast metabolism that must eat, thus a mammal must regenerate "quick, and dirtily" . Professor Galway states “Because these (embryonic-like stem) cells are so versatile, it is difficult to keep them under control,” Frank explains. “They are more likely to ‘misbehave' or form tumors than differentiated cells. We hypothesize that only animals that have very simple body plans, like Hydractinia, can manage this problem because they have less complex organs and 'misbehaving' cells are less of a problem. But complex animals, like humans, need better control of their cells to maintain their highly complex organs. They have to get rid of them during early development before they become too complex.”) Lriverauk22 (talk) 03:40, 6 April 2015 (UTC)

References

Note that an injury can be completely healed if the wound is small. That is, new skin or bone can be grown. However, if the injury is larger, then you get scar tissue instead, which isn't as good (less flexible, for one thing), but seems to be necessary to plug the wound quickly, to avoid infection in the case of skin, or allow the use of the leg in the case of a broken femur, etc. In the womb there's little risk of infection and the bones don't need to be used, so there's plenty of time to grow new body parts. Not so on the outside. (The obvious solution would be to use scar tissue to quickly plug the wound, then slowly replace the scar tissue with new skin, bone, etc., but evolution doesn't seem to have figured out how to do that yet.) StuRat (talk) 06:19, 6 April 2015 (UTC)

That sort of language is very misleading - evolution doesn't "figure anything out". It is a simple process of selection where random changes that confer an advantage for survival are passed on and those that don't confer an advantage tend to die out. Richerman (talk) 09:47, 6 April 2015 (UTC)

Yes, I was obviously anthropomorphising it, for comic effect. StuRat (talk) 20:50, 6 April 2015 (UTC)

Evolution does "figure things out" in a way. It's just that it's via non-conscious trial and error. Or as the saying goes, "Nature finds a way." ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:09, 6 April 2015 (UTC)

Turning into a skeleton

After a person is buried in a coffin how long does it take for them to turn into a skeleton? 212.47.240.157 (talk) 03:18, 6 April 2015 (UTC)

After being buried 6 feet underground it takes about 10-15 years according to two of three sources I found with one source saying it could take up to 50 years but that is an extreme outlier and it highly depends on what the coffin is made out of. The 50 year process is common in those that are made out of solid oak.

Here are links to sourcing for this answer. http://www.enkicharity.com/how-long-does-it-take-for-a-body-to-decompose.html http://www.theguardian.com/lifeandstyle/2008/feb/16/healthandwellbeing.weekend2 http://www.memorialpages.co.uk/articles/decomposition.php — Preceding unsigned comment added by Trivle (talk • contribs) 03:47, 6 April 2015 (UTC) Trivle (talk) 03:53, 6 April 2015 (UTC)

Depends on the pH of the soil that the coffin is buried in. Sarcophagus means "flesh-eating"'. Being alkali, the flesh decomposes very quickly. In acid conditions (such as Bog Bodies) the flesh can last millennia. My mother-in-law has pickled herself in gin and tonic and martinis so still looks 21 (cough, cough)--Aspro (talk) 21:48, 6 April 2015 (UTC)

I wish I could tell you how old that joke is. :) Now, these questions are about below-ground burials. Wouldn't the concrete vault stave off that process? Also, wouldn't an above-ground crypt also stave off that process? I recall they disinterred Zach Taylor's body a few years back, and even after 100 years they were able to do something resembling an autopsy. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:07, 6 April 2015 (UTC)

• You need to ask that as a separate question. I.e., other forms of interment as opposed to ground burials as the OP asks about. --Aspro (talk) 22:39, 6 April 2015 (UTC)

• Does the OP's question include underground burial vaults, which are standard in the US? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:42, 6 April 2015 (UTC)

Only the OP knows this but I take his question as to being buried in soil rather than being interned in a crypt or catacomb etc., were other conditions can exist, such as humidity/temperature and lead-lined/butyl rubber lined/wooden/stone/steel, etc., coffins maybe used. --Aspro (talk) 14:26, 7 April 2015 (UTC)

Our article about Incorruptibility may be of interest. Richerman (talk) 23:57, 6 April 2015 (UTC)

I realise that this is several days old but more than 134 years in the case of John Torrington. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 12:57, 8 April 2015 (UTC)

• The OP has been blocked. But in any case, people don't "turn into" skeletons. μηδείς (talk) 18:20, 8 April 2015 (UTC)

"Physicist's guide to life" book?

I'm trying to recall a very good book I read a few years ago by a physicist who seemed to have a very good head on his or her shoulders and a great sense of humour. There were chapters on different themes; I think one might have been about nuclear power and another was definitely about nutrition. Some advice I remember in the nutrition chapter was something like "the best physical exercise for losing weight is pushing food away from yourself at the table". Please, what was this book? I hope somebody recognizes it. Hayttom 04:26, 6 April 2015 (UTC) — Preceding unsigned comment added by Hayttom (talk • contribs)

Did I do something wrong? My question seems to have landed in the middle of the previous answer. Hayttom 04:30, 6 April 2015 (UTC) — Preceding unsigned comment added by Hayttom (talk • contribs)

• The error wasn't yours, it was Lriverauk22's when responding to the #regrowing fingers question. Auk added a number of references using <ref> tags, the same way they might do in an article. But by itself this would produce reference footnotes at the bottom of the whole page (I believe the RD pages are set up to do that; otherwise the footnotes might go nowhere). So each time a new question section was added (including yours), the references got separated farther and farther from the section they belonged to. On the RD and similar talk pages, if you use <ref>, you also need to add {{reflist-talk}} (or {{reflist}}, for a different format) below your contribution, so the reference footnotes stay inside the section. See Template:reflist-talk. It was Dismas who saw what had happened and added the missing template, moving the footnotes up where they belong. Thanks, Dismas. --65.95.176.148 (talk) 18:19, 6 April 2015 (UTC)

Do any of these ring a bell [5]? I believe Physics for Future Presidents includes both nuclear power and dieting, though I don't know if it matches your themes exactly. Dragons flight (talk) 05:58, 6 April 2015 (UTC)

That was quick ... yes, thanks, it was "Physics for Future Presidents: The Science Behind the Headlines". Hayttom 11:30, 6 April 2015 (UTC)

Our links: Physics for Future Presidents by Richard A. Muller -- ToE 18:40, 6 April 2015 (UTC)

Maybe something by Richard Feynman. Richard Avery (talk) 07:07, 6 April 2015 (UTC)

Resolved

sleep deprivation

It is stated that sleep deprivation leads to madness and eventually death. However coma patients survive sometimes years in the coma but not sleeping. Can you explain? — Preceding unsigned comment added by KrikvsPicard1969 (talk • contribs) 11:34, 6 April 2015 (UTC)

Have you read Coma? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:59, 6 April 2015 (UTC)

Are you saying that sleeping and comas are basically the same thing except that coma patients don't wake up in the morning? KrikvsPicard1969 (talk) 12:03, 6 April 2015 (UTC)

It's a different type of sleep, as noted in the article. What you're thinking about is being forced to stay awake, as a form of torture; or in the extreme case, the inability to fall asleep at all, which is called familial fatal insomnia. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:19, 6 April 2015 (UTC)

• Let me summarize -- the following information is in the coma article but might be hard to extract. The word "coma" is widely misused in the popular literature to encompass two distinct states, which doctors call (1) true coma, and (2) persistent vegetative states. Patients never survive for years in a state of true coma -- rarely longer than a few weeks, after which the patient either deteriorates or else progresses to a vegetative state. A patient in a vegetative state can survive for years. In true coma there is no genuine sleep, but in a vegetative state sleep-wake cycles are usually present. Bottom line: those patients who survive for years are not in a coma, they are in a vegetative state, and they do generally have sleep cycles. Looie496 (talk) 18:04, 6 April 2015 (UTC)

• It's worth noting that insomnia does not, in itself, usually result in death, outside of a handful of isolated and poorly-understood cases concerning the condition which bugs linked to. That's not to say that persistent insomnia is in any way pleasant; after even a single day without sleep, cognitive function takes a dive and after a few days you're looking at serious neurological impairment affecting everything from hormone balance to social capability. Before a week, the physical and cognitive state is not far removed from catatonia. But even at its worst, insomnia is unlikely to result in death, unless it compounds upon another issue (say hypertension or heart disease). Those who are said (in the relevant scientific literature) to have died from insomnia belong to just a handful of families who have been afflicted with the (and the wording is ironic but appropriate) nightmarish genetic condition FFI, and have had little or no sleep for years on end before their bodies finally collapse under the strain. This documentary may be of interest to you. Snow ^{let's rap} 23:41, 6 April 2015 (UTC)

Losing weight

If a person eats less and then feels hungry, is that the optimum time to begin exercise as the body is forced to draw upon fat stores rather than food in the belly? — Preceding unsigned comment added by 212.231.208.217 (talk) 17:01, 6 April 2015 (UTC)

Not necessarily. The truth is, you're likely to get a huge variety of answers to this inquiry, as this has long been an area of some controversy in the areas of nutrition and exercise physiology, with perspectives all over the place. While it's true that the exerciser's body will need to secure that energy from somewhere in its metabolic stores, it will not necessarily tap adipose tissue in order to do so, so the net effect upon both overall weight and the maintenance of muscle tissue (which might otherwise itself help keep down weight) could be poor. Again, advice is all over the place on this issue, but the most common perspective is to eat a typical meal about an hour before exercise and then a light snack shortly after; if one is looking to maintain their current weight the amount eaten should be roughly equivalent to that burned; if weight loss is the goal, slightly less should be eaten, but one should typically not go hungry into an intensive workout routine. Needless to say, if you personally are considering a new nutritional/exercise regimen, a consult with a physician is invaluable and (if you're inclined) they can always direct you towards a dietician or other nutritional expert. ([6], [7], [8], [9], [10], [11]) Snow ^{let's rap} 00:04, 7 April 2015 (UTC)

Weight = energy in vs energy out, it's actually not much more complex than that, despite the million self help and diet books that will try to convince you otherwise. The food in your stomach didn't magically 'disappear' becuase you didn't burn it up with exercise at the time. Put another way, if you exercise with food in your stomach, you won't be using up some portion of energy that you would otherwise 'poo' out or something if you didn't "use" it. The enegy from the food you ate will get used, whether you exercise or not, if you exercise you might burn more of it up, if you don't you'll store it, then you'll burn it later. Having said that, I do believe the general recommendation is to eat after exercise not before, but that's as much a practical consideration: exercising on a full stomach is not so comfortable and exercising does make you hungry so it makes sense to eat afterwards. Vespine (talk) 00:13, 7 April 2015 (UTC)

Of course, all of this is relative to general context. Obviously performance athletes and their support teams approach bio-energetics in a much more structured fashion, timing for exact amounts of macronutrients for very specific times, relative to exercise (and correspondingly, exercise timed relative to the metabolic cycle). Snow ^{let's rap} 02:26, 7 April 2015 (UTC)

The "energy in minus energy out = weight gain" is only going to be useful when you are way too heavy, say you weigh 110 kg while you should weight 75 kg. In that case, you should practice calorie restriction. Some exercise is then also recommended, but if you are that obese you are not physically fit enough to do strenous exercise. Exercise when you are not physically fit isn't going to burn a lot of calories, but being active like walking around will contribute quite a lot as you can keep that up for many hours. Simply walking around will burn 60 Kcal per hour more compared to sitting. So, if you do that for ten hours per day (take a standing desk instead of a normal one) you'll burn 600 Kcal more which is quite significant.

It's a totally different story if you your problem is that you weigh, say 82 kg while you want to weigh 75 kg and you notice that you do lose weight when you diet but when you are at your desired weight you tend to gain weight. In that case, the emphasis should not be on the diet but on physical fitness. You should gradually increase the exercise intensity, duration and frequency which will have the effect of increasing your basal metabolic rate. And this means that you should actually increase your calorie intake as you become fitter and are exercising harder. You must then make sure that your diet only contains healthy foods. If you were to diet and restrict calories then that would make it more difficult for your muscles to grow larger. The goal now is to have a steady state situation where you burn more calories at the same weight, which means that you must also eat more calories. You should do a combination of cardio and strength training, you could follow a program like this one. Count Iblis (talk) 05:29, 7 April 2015 (UTC)

The "energy in minus energy out = weight gain" is only going to be useful when you are way too heavy. I disagree, I don't see any reason why that would be the case. It's simply conservation of mass. One thing many people find surprising is that when you "lose weight" you aren't "converting fat into enerty", or digesting it and pooping it out, you are actually EXHALING it. The majority of weight is lost out of your front hole via carbon dioxide, not your back hole :). When you eat, energy goes in, when you exercise energy comes out: if more energy goes in you will gain weight, if more energy comes out you will lose weight, if they are roughly equal you will stay the same weight. It's really NOT much more complicated than that. Vespine (talk) 23:56, 7 April 2015 (UTC)

Agreed. Conservation of mass / energy is basically the only factor ultimately affecting weight. However, it isn't the only factor affecting overall health. Compared to a sedentary lifestyle, regular exercise will generally improve fitness and overall health regardless of weight. That's one reason to prefer a combination of diet and exercise in most recommendations for improving overall health. Dragons flight (talk) 00:29, 8 April 2015 (UTC)

Thing is that the basal metabolic rate is regulated by hormones. The precise mechanisms are not fully understood, but what should be clear is that evolution over hundreds of millions of years is unlikely to have led to a system with obvious flaws. Suppose an animal would need to expend a bit more energy to get to its food source and that food source would yield just a little less energy. If that negative energy balance, however small, would not be neutralized, that animal would eventually starve to death. E.g. if you eat one dry sandwich of, say, 80 Kcal less per day, and your body would not compensate for that, then this would become a deficit of 8000 Kcal in 100 days which would yield 1 kg weight loss. This means that you would lose 100 kg of weight in 27 years time. Obviously the metabolic rate will simply be adjusted to prevent this from happening. But this then also means that you shouldn't gain weight if you eat a bit more.

What goes wrong in people who need to diet to keep their weight from increasing is that they operate their bodies so far out of its design parameters that the feedback mechanisms that would normally keep the weight constant don't work well enough. If you exercise hard enough then the body will take care of its own weight. Count Iblis (talk) 03:06, 8 April 2015 (UTC)

. Your theory, as I understand it, is if you take someone who is in energy balance, i.e. Calories consumed = Calories expended, and increase or decrease their intake by a small amount then their weight won't change. Your explanation is that the body will simply know if they are eating more (or less) and adjust their BMR to compensate. That's an experiment that could very well be done. Certainly it could be done in animals, and probably even in humans if they would consent to being monitored closely enough. My guess though is that your theory just isn't true. I find it more likely that cause and effect is the following: small food imbalance -> small change in weight -> small change in BMR until stable again. Keep in mind that BMR is directly dependent on weight. Heavier people use more energy for the same activities. In humans, this translates to roughly 12 kcal / day / kg of weight. In your hypothetical example of a person who was 80 kcal out of balance, the natural response would seem to be to lose 6.5 kg. At that point the same activities would require roughly 80 kcal less energy than they did before, and the person would again be in balance. Rather than BMR magically changing in order to maintain a specific weight, I believe that their BMR would change primarily in direct response to weight gain / loss. Such changes would already provide the stabilizing effect that limits the weight impact of small dietary imbalances, without needing to assume the body automatically knows if you are slightly out of balance. Dragons flight (talk) 16:31, 8 April 2015 (UTC)

There is some evidence for it, see here: "There is evidence that the hypothalamic-pituitary-thyroidal axis is regulated, at least in part, by leptin. This provides an important interface between adiposity, regulated by leptin, and metabolic rate, regulated by thyroid hormones. The mechanisms underlying the connection between adipose signals and energy expenditure include the regulation of the synthesis and secretion of TRH (thyrotropin releasing hormone) by leptin, through the mediation of input from the arcuate nucleus to the TRH neurons in the paraventricular nucleus (PVN) [1]. In addition, the thyroid axis is also indirectly regulated by leptin's actions on the melanocortin pathway, as alpha-MSH (melanocyte stimulating hormone) stimulates and AgRP (agouti-related protein) blocks TRH release [2]. Furthermore, leptin has direct effects on TRH neurons, regulating its synthesis not only by up-regulating the expression of the proTRH gene in the PVN [3] and by influencing the feedback regulation of the TRH-secreting neurons by thyroid hormones, but also by increasing promoter activities of the prohormone convertases PC1/3 and PC2, essential for the activation of TRH from proTRH [4]."

Thing is, as you point out, if all of the feedback were due to the weight, then the 80 Kcal energy imbalance would require a 6.5 kg change in weight, but that's huge! If I were to eat just one sandwich less per day, 15 instead of 16, then my current weight of 55 kg would become less than 48.5 kg (the dry sandwich alone is 80 kg, but of course, I don't eat dry bread). Or if I were to eat just one piece of sandwich more, my weight would increase to more than 61.5, which is a huge gain in weight. Or you could lose weight by wearing heavier clothes, you would lose exactly the extra weight you would start to wear. Count Iblis (talk) 02:43, 9 April 2015 (UTC)

Addiction

How do people get addicted to non-addictive things like gardening, knuckle cracking, or watching porn? Obviously I understand how people get addicted to marijuana and other substances because it is a drug. — Preceding unsigned comment added by Arduino12345 (talk • contribs) 19:53, 6 April 2015 (UTC)

"The term addiction is also sometimes applied to compulsions that are not substance-related," - Addiction#Behavioral_addiction, we have articles on Behavioral_addiction and Addictive_behavior. The term "addiction" is also often used sloppily, see e.g. Addictive_behavior#Compulsion_vs_addiction and compulsion for some related things. SemanticMantis (talk) 20:18, 6 April 2015 (UTC)

With things like gardening, knuckle cracking, or watching porn, people grow a need to do these things because it provides them some sort of pleasure. This is because when one uses drugs or do activities they enjoy, it elevates the levels of dopamine in the brain increasing the level of pleasure you receive from the action. This even happens when you get good grades, so because those activities you mentioned would bring pleasure to the people doing them they are more likely to continue doing those activities because it provides a euphoric feeling to them.

Here are some sources with information on this topic: http://content.time.com/time/magazine/article/0,9171,986282,00.html http://www.helpguide.org/harvard/how-addiction-hijacks-the-brain.htm http://www.peele.net/lib/diseasing6.html BHope95 (talk) 20:39, 6 April 2015 (UTC)

I suffer from Trichotillomania and can tell you there is no "pleasure" involved, it's very annoying.. Vespine (talk) 00:04, 7 April 2015 (UTC)

Have you tried shaving your head? ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:03, 7 April 2015 (UTC)

Come on, Bugs, seriously, what's the point of this? Vespine presumably shared their condition in order to illustrate an important distinction between different types of compulsion, not to invite obvious lifestyle suggestions made as if they were a complete simpleton. Seriously, what kind of response were you expecting here? "Shay-veeng? What is this Shay-veeng you speak of"? I'm half surprised you didn't wikilink shaving. Snow ^{let's rap} 04:24, 7 April 2015 (UTC)

Very prescient of you Snow. For the record, 1) It's not on my head, it's actually my beard and 2) shaving does not help; You can't shave off every single ingrown, stubble, bump, pimple and even if you could by the afternoon there would be more than anough to continue. There's never a shortage of something on my face or neck to inadvertently pick at. It started about 8 years ago when I quit smoking, and now I'm pushing 40, so I do not fit the typical trich profile. It's not quite so bad that I need medication for it, but I have seen a few doctors who have suggested a few things that have so far not worked. I have not yet tried hypno or "proper" behavioral therapy. I did not intend to hijack this thread, I'm thinking that maybe admitting and "confessing" my problem might help with my continuing struggle to stop doing it, I suspect at least it won't hurt.. :) Vespine (talk) 04:58, 7 April 2015 (UTC)

My question was sincere, and I see from what you're saying that someone with that compulsion will find a way. It's often said that when you stop one addiction you substitute another. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:46, 7 April 2015 (UTC)

Not to put too fine a point on it, but not all habits are addictions. I have a habit of drumming my fingers (and, over the course of a lifetime, I've become quite adept at producing very complex and rapid rhythms using only the five fingers of one hand). It's a nervous habit which would be very difficult to stop, but I don't think any professional would call it an addiction. I think the same applies to knuckle-cracking. ―Mandruss ☎ 05:59, 7 April 2015 (UTC)

Well, except that there is some (disputed) evidence that popping of the joints can cause long-term degradation of musculo-skeletal strength. And as the distinction that you seem to be making is based on genuine harm done, that is minimally relevant. [12] Snow ^{let's rap} 06:09, 7 April 2015 (UTC)

Yes, my lay person test for addiction (and one that at least approximates that used by a large number of professionals) goes as follows. Is it causing significant harm to your life or the lives of others? Is it impossible to stop without being forced to, despite knowing that? If both are yes, it's an addiction. ―Mandruss ☎ 06:16, 7 April 2015 (UTC)

Can an animal genetically engineer itself?

I've been reading about some of the techniques used in genetic engineering, such as Electroporation, Sonoporation, and Vector (molecular biology); and I was wondering whether it would be possible for an animal to use any or these or other methods to introduce it's own DNA into foreign cells that are within it's body. The article for electroporation says hundreds of volts are normally used to introduce new DNA into cells a few millimeters away; however electric eels produce 600 volts of electricity [13]. The Emerald sea slug has genes from an algae that it passes on to it's descendants [14]. Bullets and Bracelets (talk) 21:35, 6 April 2015 (UTC)

Yes, in fact it happens all the time, it's called Horizontal gene transfer. Vespine (talk) 23:01, 6 April 2015 (UTC)

Remember, eels aren't designed to shock themselves, especially internally. They're relatively shock resistant, ensuring electricity will take the easiest path, so even if they wanted to electroporate, I don't think they could. A lot goes into the process beside voltage. I doubt an eel has the brainpower to even begin wanting to actively try.

If the right lightning bolt hit the right river at the right time, maybe something would accidentally fuse, but I'm no expert. InedibleHulk (talk) 23:54, April 6, 2015 (UTC)

Tardigrades are supposed to be pretty good at repairing genetic damage to themselves, if that counts. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:25, 7 April 2015 (UTC)

Part moss, part piglet. Not bad! InedibleHulk (talk) 18:33, April 7, 2015 (UTC)

April 7

microwave

If you push your face against the door of a microwave to watch the food going around inside, how much dose of radiation do you get? — Preceding unsigned comment added by Coosquirt3 (talk • contribs) 00:53, 7 April 2015 (UTC)

Literally nothing, if you mean ionizing radiation, which is the stuff that causes real issues. Microwave ovens do not produce ionizing radiation, which is what causes cancer and radiation sickness and stuff like that. Microwaves emit a high-energy form of radio waves, not much different from the signal that is picked up by your TV set if you receive an over-the-air broadcast. According to this, the average microwave oven "leaks" about 2 milliwatts per square centimeter at a distance of 2 inches from the glass over the whole lifetime of the microwave total. Assuming a microwave lasts ten years, 2 milliwatts per square centimeter per decade is basically next to nothing. --Jayron32 01:09, 7 April 2015 (UTC)

Your response is susceptible to a misunderstanding. Milliwatts are units of energy flux, not total energy. The meaning of the FDA standard is that the flux (i.e., rate of energy leakage) can't increase beyond a certain limit (5 mW /cm2) as the oven gets older. This is not necessarily related to the accumulated flux over time, which would be measured in joules per unit area. Short Brigade Harvester Boris (talk) 01:31, 7 April 2015 (UTC)

Yes, microwaves are designed to be safe. The glass door has a mesh that prevents leakage of sufficient microwave radiation to cook your eyeballs, but I wouldn't recommend spending many minutes with your eyes pressed against the glass, just in case ... Dbfirs 09:15, 7 April 2015 (UTC)

I suppose that in cases of microwaves all been depended on by ionizer (radiator) of microwaves.--85.141.239.195 (talk) 15:47, 7 April 2015 (UTC)

No. Again, ten times no. Microwaves do not ionize anything. Microwaves are not ionizing radiation. Microwaves do not do to your cells what things like X-rays and gamma rays do. --Jayron32 16:45, 7 April 2015 (UTC)

Thanks. I’m thought, that a configurations of ionizer (radiator) of microwaves are been determine.--83.237.194.163 (talk) 17:39, 7 April 2015 (UTC)

Are not been. But when you press your eyeballs against the glass, you really see light waves that aren't really there. No harm staring at water to see what are been later, but if microwaved first, you be not seen again. Like been atomic and hydrogen bomb, but not really leave shadows that aren't really there. InedibleHulk (talk) 18:21, April 7, 2015 (UTC)

Sitting in front of old TVs can also burn shadows, but only on TV. InedibleHulk (talk) 18:27, April 7, 2015 (UTC)

Did geometry is been determine too?--83.237.197.142 (talk) 18:57, 7 April 2015 (UTC)

Of course. If trajectory is been known, you drop rectangle at bisection point. If rectangle area is been greater than or equal to face and volume is been beating ballistic limit, harm is been undone. If not, face melt. InedibleHulk (talk) 19:26, April 7, 2015 (UTC)

Agree, that a radiator of microwaves is been a radio antenna of high microwave ionization.--83.237.214.220 (talk) 16:30, 8 April 2015 (UTC)

Still no. InedibleHulk (talk) 18:59, April 8, 2015 (UTC)

Thank you. I think that magnetical action is been a ionization.--83.237.203.56 (talk) 19:29, 8 April 2015 (UTC)

As for me, the question is in that, could magnetism change a structure of substances or not it didn’t.--83.237.202.245 (talk) 21:42, 8 April 2015 (UTC)

How long do LED, CFL, etc bulbs stay "on"?

lamp 1

lamp 1

lamp 2

lamp 2

lamp 3

lamp 3

LED and CFL bulbs cut on and off 60 times per second right (on US A/C). How long do they stay on in each cycle?

Yesterday I took three photos that included a street lamp. The exposure time was 1/400 second. In two of the photos, the street lamp was very dim but in the third it was brighter than I remember it being.

So how does the light output of modern bulbs vary across one cycle of A/C? Bubba73 ^{You talkin' to me?} 03:20, 7 April 2015 (UTC)

I don't know, but I do know that "60 times per second" is wrong unless the light is only on when the AC current is flowing one way and not the other way. Any such flicker should normally be at 120 times per second. --65.95.176.148 (talk) 03:27, 7 April 2015 (UTC)

You are right - if it flickers, it should be 120 times per second (US A/C). Bubba73 ^{You talkin' to me?} 03:51, 7 April 2015 (UTC)

An LED may not flicker in both directions. Current tends to only easily flow in one direction through a diode. I'd think that'd keep them at 60 Hz. --OuroborosCobra (talk) 03:57, 7 April 2015 (UTC)

Ah, that D does stand for "diode", doesn't it? Good point. (But see Z-man's response just below.)--65.95.176.148 (talk) 18:27, 7 April 2015 (UTC)

Most modern fluorescent lights use an electronic ballast that changes the frequency to to something on the order of tens of kHz. LED bulbs don't turn off and on at all. They use a rectifier to supply the actual LED with DC. Any flicker is just a result of the driver circuitry not smoothing the output very well. Mr.Z-man 04:07, 7 April 2015 (UTC)

Bet me to it, even cheap LED bulbs will have a rectifier circuit in them, I have actually used them as a cheap source of 12v rectifiers for other projects. Vespine (talk) 04:22, 7 April 2015 (UTC)

I've added cropped versions of three photos that I took the other day within seconds of each other. I didn't notice any change in brightness. They were all taken in aperture priority, ISO 100, f/8. (the first one was at a focal length of 60mm, the next two were at 70mm.) The camera exposed the first and third for 1/320 second and the second one for 1/400 second. Yet, the second one is brighter, even though its exposure was shorter. Why? Bubba73 ^{You talkin' to me?} 05:14, 7 April 2015 (UTC)

The lamp in question could very well be flickering, that would explain the different brightness. We're making a lot of assumptions. MY guess is that it isn't an LED lamp, but have no good guess as to what it is. I suppose some sort of fluro makes the most sense. Could you take some more photos, maybe manually set the exposure to 1000th and see what it looks like? also take some photos of OTHER lamps in the area, in case the one you picked just happened to have a faulty driver perhaps flickering because it's "on the way out"? That's probably unlikely, but might be worth eliminating as a factor. Vespine (talk) 06:51, 7 April 2015 (UTC)

New photos, see the link below. Bubba73 ^{You talkin' to me?} 03:04, 9 April 2015 (UTC)

Flickering fluorescent lights are a fairly well known problem in photography. See here for example. Modern DSLRs can include anti-flicker circuitry. Check out the review of the Canon 7d Mk II at the same site for a description of it in action.--Phil Holmes (talk) 10:05, 7 April 2015 (UTC)

My camera (Nikon D7100) as the anti-flicker and I have it on. However, the lamp is only a small portion of the entire photograph, so it may not have picked it up. Bubba73 ^{You talkin' to me?} 15:24, 7 April 2015 (UTC)

I would like more info on this. The OP asks about LED, CFL, etc. These photos look like one of the 'etc' bulbs. I.e., common incandescent. What color balance did you use (AWB?)(and there are sky clouds clearly visible behind so me thinks AWB) ... its reddish, so not a LED nor fluorescent. Its light flux is just varying 120 times per second. --Aspro (talk) 15:12, 7 April 2015 (UTC)

Yes, I did have auto white balance on, and it was set to normal. Bubba73 ^{You talkin' to me?} 15:24, 7 April 2015 (UTC)

In my WP:OR, it is rather hard to get two identical photos, even with a tripod, with a modern digital camera on "auto/normal" modes. The white balance, autofocus, and lots of other factors conspire such that even in controlled situations where you know the subject and light haven't changed, the photos can still look rather different. SemanticMantis (talk) 15:42, 7 April 2015 (UTC)

It wasn't in auto/normal mode. Bubba73 ^{You talkin' to me?} 17:55, 7 April 2015 (UTC)

Forgetting the specific terminology of your camera, I just meant this - "Yes, I did have auto white balance on, and it was set to normal" - that means the camera was making at least a few choices on your behalf, that may well change the apparent brightness in the photograph. SemanticMantis (talk) 18:06, 7 April 2015 (UTC)

Yellowish, street light? I would guess sodium-vapor lamp. I think these can flicker with the power cycle, though I'm not entirely sure. Dragons flight (talk) 17:42, 7 April 2015 (UTC)

I think sodium-vapor is most likely. Bubba73 ^{You talkin' to me?} 17:58, 7 April 2015 (UTC)

Sodium-vapor lights can flicker: flicker. Bubba73 ^{You talkin' to me?} 18:06, 7 April 2015 (UTC)

Here are 32 shots of the same lamp taken over the period of less than 1 minute. This was done in manual mode, 1/1000 second, f/2.8, so the camera isn't doing any fiddling with the exposure. They show that there are times when it is bright and times when it is dim. Bubba73 ^{You talkin' to me?} 01:26, 9 April 2015 (UTC)

CCFL use an inverter. LED a current regulated buck converter which is supplied by rectified and filtered AC input. The unfiltered 120 Hz would be a visible stroboscope, but some converters pulse a higher frequency instead of regulated current. --Hans Haase (有问题吗) 18:46, 9 April 2015 (UTC)

Modern medicine / human evolution

To what extent does modern medicine undermine natural selection in humans, thereby hindering human evolution? ―Mandruss ☎ 11:48, 7 April 2015 (UTC)

This is a hard question. We can't really do controlled experiments, and there's no generally applicable method of quantifying the "strength" or "speed" of evolution. Here's an article that discusses the problems with studying human evolution, and points to newer methods in genome studies and haplotype structure as a way forward [15], and here's a more recent article by some of the same authors: [16]. The point is, these are relatively recent papers in Science and Nature, and we are a long way from having robust and widely accepted methods and results. A few things to keep in mind: Selective pressure will usually act the fastest when it acts at a life stage prior to sexual maturity. Now, some medical treatments save children that would have otherwise died without, but many medical treatments are applied to people who have already reproduced, or may never, and these don't have as strong of an effect. Here's an article that briefly mentions human impacts on human evolution, but it's mostly about human impacts on evolution in general [17]. Now, there are some ways that pressures after reproductive age can influence evolution - notably kin selection and group selection. This recent work on orcas [18] points out some similarities with humans - we are some of the few species where females survive and hang around after menopause. Now, humans did that before modern medicine, but it hints at how culture and sociology can influence evolution via mechanisms different from classical Darwinian selection. Finally, this book [19] seems to have some discussion closely related to your question, but I have not read it. So - no real answers here, but lots of refs. SemanticMantis (talk) 15:02, 7 April 2015 (UTC)

There's also the false dichotomy between the natural and unnatural. Environmental pressures effects evolution. Period. Modern medicine is an environmental pressure which effects human evolution. Nothing else needs to be understood by introducing spurious ideas like "natural" and "unnatural". The question makes more sense if you merely asked "What sorts of evolutionary pressure is introduced to the human species by modern medicine?" --Jayron32 16:42, 7 April 2015 (UTC)

I agree with Jay. Selection pressures are changing, but they are not going away. So evolution will continue to do its thing. Consider moles - by digging underground they stop being preyed on by birds of prey - that means that that evolutionary pressure is reduced, but others come into play (less vision, better sense of smell, better sensing of vibrations, better burrowing). It's similar with humans - we can now treat some conditions that would previously be deadly, but that does not mean that all people have the same reproductive success. It's hard to tell which features currently are selected for, but that does not mean that none are. Richard Dawkins's The Extended Phenotype has some interesting ideas on the interaction of populations and how they modify and interact with their environment. --Stephan Schulz (talk) 16:54, 7 April 2015 (UTC)

• For a species with generation length as long as humans, selection pressure has to be sustained for thousands of years to have a significant impact. In far less time than that we will be able to engineer the human genome from top to bottom. So it really doesn't matter at all. Looie496 (talk) 17:21, 7 April 2015 (UTC)

I believe a better question would be: Is there any form of selection pressure in humans? Selection pressure would increase the likelihood that one set of humans would produce offspring while reducing the likelihood that another set of humans would produce offspring. Other than young death, I've only seen respectable studies linking lack of education and poverty to an increase in the number of offspring, but not to the likelihood of producing offspring. 209.149.113.89 (talk) 19:04, 7 April 2015 (UTC)

Sexual selection is a mechanism that evolved over hundreds of millions of years to keep evolution from going off the rails when for prolonged periods important selection mechanisms are absent. E.g. if prey animals live for many generations in an area where predators are absent, sexual attraction will still lead the fitter animals to contribute to the gene pool. Count Iblis (talk) 20:04, 7 April 2015 (UTC)

Sexual selection is of course a real thing, but for the rest of your claims, please. SemanticMantis (talk) 20:12, 7 April 2015 (UTC)

Well, it just seems logical to me that sexual attraction will, in general, have evolved to enhance the survival of the next generation. The article on sexual selection is a bit misleading because the evidence for sexual selection is most apparant in the rare cases where sexual preference leads to offspring with features that are of no benefit. This then leads to the evidence that sexual selection is a factor these cases, but of course, this is not how it works in general. Count Iblis (talk) 21:06, 7 April 2015 (UTC)

Sort of. But come on, you have some science training, right? You should know that your notion of logic applied to an area that you are not specifically trained in is not a reference. Sexual selection is in no way something that generally increases fitness in the absence of other pressures. Many aspects of sexual selection, and the interaction with other selective pressures are still very poorly understood, and very active areas of research, please don't fall in to this trap [20] :) SemanticMantis (talk) 15:58, 8 April 2015 (UTC)

• Infectious disease is believed to be the greatest evolutionary force in humans, from sickle-cell anemia to smallpox, to cholera causing the evolution of multiple sclerosis. It has also been suggested that shortsightedness among the Chinese is linked to their long history of agriculture (where one need not spot and sneak up on the prey from a distance) and modern medicine has removed much of the burden of things like type-I diabetes and problematic childbirth, which will lead to people who otherwise wouldn't have survived to reproduce passing on problematic genes. μηδείς (talk) 20:21, 7 April 2015 (UTC)

My question was prompted by an earlier thread at WP:RDM, in which the issue of infant cranial size vs birth canal size was mentioned. I don't think there's any disputing that this problem has resulted in the deaths of many mothers (and infant girls), but far fewer after the development of relatively safe C-sections and other things. It seems intuitive that, without the interference of modern medicine, the problem would eventually correct itself. Aside from Looie496's point, which would render this purely academic, is there any validity to this? Is the idea that with modern medicine this should cease to be viewed as a "problem"? ―Mandruss ☎ 02:20, 8 April 2015 (UTC)

@Mandruss: I don't know, I don't think there's a simple answer. But you may enjoy reading Obstetrical_dilemma, and this nice blog post explaining some of the problems with that perspective, written by a physical anthropologist [21]. SemanticMantis (talk) 19:50, 8 April 2015 (UTC)

Also recall that C-sections are not readily available to all. I have no idea what the access rates are, but I suspect rather low outside rich countries, and most of the human population is part of the global poor e.g. [22] SemanticMantis (talk) 19:52, 8 April 2015 (UTC)

Engineering and design - constructional systems of the USSR

Are engineering and design - constructional systems of the USSR, including the civil and military army systems of the USSR being promising advanced (perfected) systems? I saw, many people told that engineering and design - constructional systems of the USSR, including the civil and military army systems of the USSR are not being perfected, because the USSR had not a advanced (perfected) computer.--85.141.239.195 (talk) 15:25, 7 April 2015 (UTC)

Every one of those words is English, and yet I can't understand what you say. Perhaps if you asked the question at the Wikipedia of your native language, you could be better understood? Just about every Wikipedia of any size has a place like the reference desk. If you tell us your native language, we can direct you better to a place where you can be understood by those trying to help you. --Jayron32 16:39, 7 April 2015 (UTC)

The USSR was losing in the Cold (nuclear) War, because the USSR had not a basis of applied programming. I’m sorry, but I had not got an education in applied programming, what’s why I was asking this question.--83.237.197.142 (talk) 18:19, 7 April 2015 (UTC)

Asking questions at a website where they understand your native language is more likely to get meaningful answers. AndyTheGrump (talk) 18:21, 7 April 2015 (UTC)

Thanks. I suppose that to become a winner in Cold (nuclear) War always must be had scientific skills, but not a finances or political reasons as biography of politics.--83.237.197.142 (talk) 18:53, 7 April 2015 (UTC)

I should edit, that I’m understood that Cold War was win the program linguistics of assembler, but what kind of symbiosis of assembler program linguistics did win, I’m don’t know.--83.237.197.142 (talk) 19:37, 7 April 2015 (UTC)

Is been lost USSR from dangerous ovens Cold (microwave) War? μηδείς (talk) 20:00, 7 April 2015 (UTC)

Nothing is ever perfected, I'd say; there are always compromises – between different requirements, or with the time available for the engineers to complete their task. The USSR had good computers, I believe, but they might not have been available to engineers on low-priority projects. —Tamfang (talk) 22:39, 7 April 2015 (UTC)

The new program linguistics are been mainfull.--83.237.207.57 (talk) 10:08, 8 April 2015 (UTC)

I wish to edit that, as I'm know, the USSR always been used the most simplest program linguistics of low levels program math languages.--85.141.232.244 (talk) 12:48, 8 April 2015 (UTC)

I was said to this, that the USSR had not got a complex mathematicals, because the USSR always been used the most simplest program linguistics of low levels program math languages. Of course, the USSR had not got a perfected control systems, because the mathematics of the USSR always been simplest.--83.237.203.56 (talk) 19:15, 8 April 2015 (UTC)

The USSR always had got a simplest mathematics which was free from applying new science methods, so the USSR always been used simplest math Basic and math Fortran.--83.237.203.56 (talk) 20:38, 8 April 2015 (UTC)

I can sort of see the point in talking like that, but the way you reply to yourself to end your sections doesn't do anything for anyone, on any level. Scale it down or go home. InedibleHulk (talk) 20:48, April 8, 2015 (UTC)

Thanks. I understood your massage attention, but I wish to say that the position of mathematics is always been the same for position of linguistics.--83.237.202.245 (talk) 21:58, 8 April 2015 (UTC)

I’m very sorry for myself replying discussion, but I must to said, that using low levels program math languages makes do it impossible to do complex calculations in mathematics and other sciences, because the math logic of this program linguistics is very (basically) simplest, that’s why the USSR had not got to do complex calculations and perfected computer. That's why always win a symbiosis program languages.--83.237.218.62 (talk) 08:51, 9 April 2015 (UTC)

Unless there is someone with a literal gun to your head forcing you to type on Wikipedia, you do not "must to said" anything. Your replies are going nowhere and you are not asking any questions nor listening to any answers or responses. --OuroborosCobra (talk) 10:48, 9 April 2015 (UTC)

I'm sorry!--83.237.207.119 (talk) 12:28, 9 April 2015 (UTC)

Flat loudspeakers

I would like to know something more about a series of big, flat loudspeakers manufactured by YamahaMatsushita some twenty years ago. They were blue with a black frame and marketed as "digital" (whatever they mean with that word). Designed mainly for theatres and similar places.--Carnby (talk) 16:58, 7 April 2015 (UTC)

If you would like to know about how these planar speakers work we have two articles: Magnetostatic loudspeaker & Electrostatic loudspeaker.--Aspro (talk) 21:57, 7 April 2015 (UTC)

Thank you, I also discovered that they weren't made by Yamaha. The were manufactured by Matsushita and sold as Technics AFP series. I found this page with some techncal specs, but it's all in Japanese.--Carnby (talk) 11:56, 8 April 2015 (UTC)

Copy and paste it into Google Translate. It translates Japanese very well. 209.149.113.89 (talk) 12:11, 8 April 2015 (UTC)

Or. Abecedare (talk) 22:11, 8 April 2015 (UTC)

I tried to translate Japanese text; they seem to be big-sized conventional speakers rather than magnetostatic or electrostatic ones.--Carnby (talk) 22:27, 8 April 2015 (UTC)

Squeezing a very round head inside an oval helmet?

Is it safe to squeeze a very round head inside an oval helmet? Given an oval helmet on a very round head, will that protect the round-headed bicyclist from accidents? 140.254.136.149 (talk) 17:19, 7 April 2015 (UTC)

We have a pretty long article on Bicycle_helmets. I'm not sure what you are asking. There are a few different shapes and styles, but many of them are indeed just and oval shell that rides on top of the head. A good fit is important for a helmet to properly protect, see e.g. here [23]. There shouldn't be any squeezing of heads required to wear a helmet. SemanticMantis (talk) 17:59, 7 April 2015 (UTC)

Some cyclists wear skateboard helmets like these [24], to give better protection to the sides of the head. But they are hotter and heavier, so each rider makes their own choices. Here are a few scientific studies on the effectiveness of using bicycle helmets to prevent injuries in crashes [25] [26]. From the first article " Risk of head injury in helmeted vs unhelmeted cyclists adjusted for age and motor vehicle involvement indicate a protective effect of 69% to 74%" -- short answer: helmets do help protect against head injuries. SemanticMantis (talk) 18:02, 7 April 2015 (UTC)

There was a recent ESPN Outside the Lines about hockey helmets and such. Helmets largely protect against skull fracture. They are much less reliable for protecting against concussions. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:22, 7 April 2015 (UTC)

Please be aware that for a cyclist that knows what they are doing, and is just commuting and not racing, a helmet is completely unnecessary (cf the Netherlands and Denmark), and will only put people of cycling. 82.21.7.184 (talk) 20:19, 7 April 2015 (UTC)

Yes, the Danish and the Dutch have it great, with their protected cycle superhighways, [27], and all sorts of other cycling-friendly infrastructure. In the USA however, cyclists " face a higher risk of crash-related injury and deaths than occupants of motor vehicles do" [28]. WP:OR: Last weekend I saw a car intentionally knock down some cyclists in TX. Even in non-race situations, skilled cyclists can crash and get severely injured. I would probably not wear a helmet if I cycled in the Netherlands :) SemanticMantis (talk) 20:51, 7 April 2015 (UTC)

"Knowing what you're doing" is insufficient. Wearing a helmet is essential. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:11, 7 April 2015 (UTC)

Nope, have cycled in the very aggressive British traffic for all my life, had several crashes, never worn a helmet, and never had any head injury (or any other major injury for that matter). As long as you know how to cycle and how to fall, there's no need for a helmet at all. Most cyclists are far too meek, they need to be far more aggressive to be safe. 82.21.7.184 (talk) 07:21, 8 April 2015 (UTC)

You've just been lucky so far. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:57, 8 April 2015 (UTC)

Citation needed. Also, it would be good if you could refrain from personal attacks on the cycling abilities of posters. I agree with the poster above, cycle helmets are entirely pointless if the cyclist knows what they're doing. 131.251.254.154 (talk) 13:45, 8 April 2015 (UTC)

Nope, not lucky, skilled. Big difference. 82.21.7.184 (talk) 16:19, 8 April 2015 (UTC)

That's why the Tour de France guys don't wear helmets, eh? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:08, 9 April 2015 (UTC)

Everyone who is still alive has been "lucky so far". The question is whether the benefits of wearing a cycle helmet outweigh the disadvantages, and there is little, if any, evidence that they do. See here for example. AndrewWTaylor (talk) 13:23, 8 April 2015 (UTC)

The far better solution is to avoid the need for helmets altogether by proper behaviour on the bike. 131.251.254.154 (talk) 13:45, 8 April 2015 (UTC)

I think you mean [29] Nil Einne (talk) 15:28, 8 April 2015 (UTC)

Purely original research, but the VW Golf that overtook me, pulled in front and then performed an emergency stop, ended up with a helmet-shaped dent in his boot. I suspect that I wouldn't be writing this had it been head-shaped. Alansplodge (talk) 18:37, 8 April 2015 (UTC)

The IPs here have provided no references. This is not a forum. It should be obvious that in any operation of a vehicle, there are factors outside the operator's control. Even a perfectly trained and well-behaved cyclist can get hit by a drunk driver [30] [31] [32] [33]. So, do what you want, IP users, we can't give you medical advice, or require you to wear a helmet. But please do not fill this space with un-scourced claims that helmets are useless or unnecessary. Note that in the USA, many states require the use of helmets under some conditions [34] SemanticMantis (talk) 15:53, 8 April 2015 (UTC)

The vast majority of car-bike accidents are through ignorance or stupidity of the cyclist and are very much avoidable. For the tiny minority of the rest, meh, karma. I'd rather actually be comfortable and safe on my bike than to obsessively worry and thus be unsafe. 82.21.7.184 (talk) 16:19, 8 April 2015 (UTC)

Um... - until I see evidence to the contrary, your claim is just your own opinion, and not very helpful on a reference desk. SemanticMantis (talk) 19:46, 8 April 2015 (UTC)

Well, let's get some facts straight here shall we, rather than slagging off 'some IPs', just because they are right. 1) Helmets offer some protection in certain crashes, but their effectiveness has been grossly overstated, mostly for commercial purposes. 2) The more skilled a cyclist is, the safer they are. 3) The best way to avoid head injuries is to avoid crashes and accidents altogether 4) The vast majority of accidents are avoidable by the cyclists, through assertive cycling, assuming all drivers are out to kill them (not that far from the truth), and making sure both you and your bike are up to scratch. 5) Some accidents are unavoidable, and some of those will be fatal. Deal with it. An asteroid could hit you in the head tomorrow. Now, having said that, I still maintain that making cyclists 'special' by making them wear helmets, high-vis, lycra and more such nonsense creates an illusion that cycling is weird and not normal, therefore creating a us-vs-them mentality on the roads and decreasing safety. Disclaimer: I grew up in the Netherlands, and have since emigrated and have been cycling British roads for many years now. Fgf10 (talk) 16:28, 8 April 2015 (UTC)

Fairly sure the risk of unavoidable accidents to even the most skilled cyclist is a few orders magnitudes higher than the risk of being hit in the head by an asteroid tomorrow. Anyway let's not forget the OP's question was whether a helmet would offer protection if their head was too round. The question of whether helments offer protection at all is relevant. The question of how much protection is relevant. While technically not relevant, we can perhaps accept some minor diversion in to whether or not the OP would be better served by improving their cycling skills, whether or not they choose to wear a helmet, but that would seem to be about the limit and even that seems to have a fair chance of being irrelevant to the OP. The question of whether or not mandatory helmet laws exists, or should exist, or do more harm than good, or whatever is not relevant. The question of whether the OP is worrying too much about something which is too low risk is not relevant. I'm not sure what the IP meant above about karma, but whether they meant when someone is injured or killed in an unavoidable accident they shouldn't bemoan it because they obviously did bad in their life, of whether they meant perhaps the person who injured or killed the cyclist will hopefully receive payback some time (which doesn't actually help the injured or dead cyclist, and also ignores the possibility that no one is really at fault in an accident) is most definitely not relevant. People are entitled to their person views about whether or not it's wearing a helmet is a good idea (and all the other stuff), but the RD, and in particular this question is not the place for them. Nil Einne (talk) 17:05, 8 April 2015 (UTC)

I'm not "slagging" anyone, and I don't care if they are IPs or registered like you. I mean to imply that assertions here should be supported by references. You also have provided no references to support your claims. I'd be happy to read any references you have, especially that support points 1) and 4). I'm not unsympathetic to your points, in fact I agree with many of them. Indeed, I don't wear a helmet often, even though I cycle every day in a big city. However, I still believe helmets are useful at preventing injury, and that I am taking a calculated and informed risk. Really, we should just ban all non-commercial autos, and then we'd all be much safer :) SemanticMantis (talk) 19:44, 8 April 2015 (UTC)

colleges for message therapy

Is there any colleges have message therapy courses ? — Preceding unsigned comment added by 106.76.24.162 (talk) 17:40, 7 April 2015 (UTC)

I think you mean "massage therapy". There is a type of vocational school called "massage therapy school", where people come out as licensed/certified massage therapists. Legal massage therapists abide by the laws of the jurisdiction, which may or may not charge illegal services like erotic massages and prostitution. You may be interested in seeking a massage therapy school in your district. 140.254.136.149 (talk) 17:48, 7 April 2015 (UTC)

If you actually mean "message therapy", a course in business writing would be a good option. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:20, 7 April 2015 (UTC)

Discovering an asteroid

A century ago, how was it decided that one had discovered an asteroid? For example, when 284 Amalia was discovered, how did the discoverer know that it wasn't just another asteroid that had already been discovered by someone else? I understand that astronomical tables have been developed for planets and bigger objects, with precise orbits calculated and future locations accurately predicted, but was this routinely done for minor asteroids? Nyttend (talk) 17:59, 7 April 2015 (UTC)

The short answer is that yes they did plot the orbits of all the asteroids. The somewhat longer answer is that sometimes asteroids did get lost and rediscovered later. See: Lost asteroids. In general, if you know the orbit, you can calculate where something would have been in the past and then match early observations with modern ones, so sometimes people do rediscover previously lost asteroids. Dragons flight (talk) 18:08, 7 April 2015 (UTC)

Also, an orbit is characterized by its orbital elements. These are just a set of numbers and are easily compared to confirm that two bodies are in different orbits, provided that there's enough data for the orbital elements to be well established. (Different computations of the orbit for the same body may not produce exactly identical numbers, due to things like perturbations and minor observational errors, but the elements will be close enough to suggest when further investigation is required. That'd be the only case where you'd actually have to compute where the thing was at some particular time.) --65.95.176.148 (talk) 18:38, 7 April 2015 (UTC)

You can probably find the original paper on the topic, this search for [35] Auguste_Charlois between the years of 1888 and 1905 gets plenty of hits. The articles are even freely available. But they do seem to be in French... This address titled "Asteroids past present and future" [36] may also shed some light. SemanticMantis (talk) 18:16, 7 April 2015 (UTC)

Who realised that whales and dolphins are not fish?

See title. It doesn't seem very obvious. --82.45.61.67 (talk) 18:31, 7 April 2015 (UTC)

Aristotle said so in the 4th century BC, according to this book preface (7th page of the PDF). --65.95.176.148 (talk) 18:45, 7 April 2015 (UTC)

It is sort of obvious, when you consider pre-scuba people typically only saw whales coming up for air. Fish don't do that. The first time they killed one and realized it was filled with blubber would've also been a hint. InedibleHulk (talk) 18:49, April 7, 2015 (UTC)

Aristotle had it right, but not necessarily for the right reasons. Moby Dick contains a long passage on the subject, and concludes that dolphins must be fish. Here is what you should read: When Whales Became Mammals: The Scientific Journey of Cetaceans From Fish to Mammals in the History of Science [37] -- it is a nice historical overview of cetacean taxonomy from a historical perspective: it starts with Aristotle, and continues through antiquity, Renaissance, and up to the modern day, detailing each new them in taxonomy and some of the morphological work that supports the claims. SemanticMantis (talk) 20:10, 7 April 2015 (UTC)

Amusingly, Wikipedia has an entire article on the cetology of Moby-Dick. Ishmael/Melville wasn't saying anything about cetacean biology when he said they ought to be fish. He was merely complaining about the over-narrow modern definition of "fish". -- BenRG (talk) 23:05, 7 April 2015 (UTC)

It seems obvious now, but not so much before animal anatomy became widely studied and known. In addition to needing to come up to breathe, whales and other marine mammals have flat tail "fins", which are really highly adapted feet. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:37, 8 April 2015 (UTC)

And their babies stick around nursing for about a year, depending on the species. Some kids drink 500 litres a day. Hard to imagine an early hunter cutting up a mother and not noticing that much milk, even if they'd missed the suckler. They wouldn't have called it a mammal yet, but must've thought it more cow than fish. InedibleHulk (talk) 19:19, April 8, 2015 (UTC)

Can a human body creates toxins by itself?

Can a human body cell creates toxin by itself, or it must be done by bacteria and other foreign things? by the way, CO2 can be called "toxin"? Thanks. 5.28.178.16 (talk) 18:37, 7 April 2015 (UTC)

The human body produces many toxic waste products through natural metabolic processes. These need to be filtered out by the kidneys and then excreted. When the kidneys are not functioning properly, there can be serious health problems that result. Deli nk (talk) 18:41, 7 April 2015 (UTC)

"Methanol (wood alcohol), for instance, is oxidized to formaldehyde and then to the poisonous formic acid in the liver by alcohol dehydrogenase and formaldehyde dehydrogenase enzymes, respectively; accumulation of formic acid can lead to blindness or death." (See Alcohol#Toxicity). StuRat (talk) 18:57, 7 April 2015 (UTC)

For a simple example, see creatinine. This is produced in muscle cells and has to be excreted from the body. It is a very common toxin to be checked to see if the liver and kidneys are functioning well because the rate of creatinine production is fairly consistent throughout the day. 209.149.113.89 (talk) 18:56, 7 April 2015 (UTC)

Whether CO2 is toxic depends on its concentration. It is present in in small quantities in ordinary air and that doesn't injure anyone. But in high concentrations it is a dangerous toxin (not just an asphyxiant). See this page from the CDC and this PDF appendix from a US BLM document produced under their National Environmental Policy Act. --65.95.176.148 (talk) 18:57, 7 April 2015 (UTC)

• Relevant here is the adage the dose makes the poison. The idea is that almost anything is toxic (and almost anything is safe) depending on the amount present. While not 100% true (there's probably some substances toxic in any measurable amount), as noted with something like CO2, it absolutely depends on the dose. Also relevant is the quote The amount of times someone uses the word "Toxin" is inversely proportional to their actual knowledge of chemistry. The word "toxin" is a marketing term created by charlatans who want to sell you magic crystals and other new-age hokum. It really is a marker of a lack of science knowledge to use the term. --Jayron32 19:29, 7 April 2015 (UTC)

• I'm afraid it's Jay's lack of knowledge that's showing. If you consult the OED, you will find four citations of the word "toxin" being used, all of them in genuine scientific writing. (They are all from the period 1890–1905; that part of the dictionary was originally written in 1913 and hasn't been fully updated yet.) Jay is right that the word is often used in pseudo-scientific marketing, but it isn't by any means exclusive to that.

Having said that, the OED's definition of "toxin" is "A specific poison, usually of an albuminous nature, esp. one produced by a microbe, which causes a particular disease when present in the system of a human or animal body", and clearly CO2 does not fit either the "usually" or the "especially" part. But it is a "specific poison" in sufficient concentrations. --65.95.176.148 (talk) 09:56, 8 April 2015 (UTC)

See etymological fallacy; that the word was once used in a scientific context doesn't mean that is how it is being used. It would have perhaps been better to say that it has been hijacked by charlatans. It has become a shiboleth for the scientifically illiterate, and as such, even if it once had a legitimately scientific reason, has become marked and isn't used much in that way anymore. --Jayron32 12:37, 8 April 2015 (UTC)

That's better, thanks. Now, for evidence that the word is in fact still in scientific usage, try this Google search. --65.95.176.148 (talk) 16:35, 8 April 2015 (UTC)

The human body is not merely capable of "creating toxins" is is essential that it does, otherwise it would be a dead body. Roger (Dodger67) (talk) 07:45, 8 April 2015 (UTC)

April 8

Material for heaviest bat possible

If I wanted to make the heaviest and most sturdy bat/club possible, what material or element should I use? (Even if it's not easily workable, though hopefully not too radioactive). CesarFelipe (talk) 02:52, 8 April 2015 (UTC)

Short answer, heavy does does not equal sturdy, so you would have to specify which you want. Others will be along with longer answers. ―Mandruss ☎ 03:00, 8 April 2015 (UTC)

Well, by "heaviest" I mean densest, and by "sturdiest" I mean "resistant to damage/breaking, i.e. not brittle". I've looked up a few materials that are very dense yet brittle, so I don't know if they would work for making a functional bat or not. CesarFelipe (talk) 03:07, 8 April 2015 (UTC)

Yeah, dense doesn't equal sturdy, either, so you still need to specify which you want. You can't be both densest and sturdiest in the same material. ―Mandruss ☎ 03:14, 8 April 2015 (UTC)

Anything that's really dense probably wouldn't make a functional bat, because you'd barely be able to lift it. Platinum is pretty dense and not brittle. An MLB-sized bat made out of it would be around 32 kg (and cost over a million dollars). Mr.Z-man 03:40, 8 April 2015 (UTC)

The usual solution to this dilemma is to make the end heavy, but the shaft lighter (as in a mace (club)). Thus you can get a bat with a lot of inertia, yet still light enough to lift. A standard baseball bat is also tapered to get the same effect. StuRat (talk) 06:17, 8 April 2015 (UTC)

If you are looking for a combination of heavy and strong, you are probably looking for the answer "tungsten".

GilHamiltonTheArm (talk) 07:34, 8 April 2015 (UTC)

Uranium -- Roger (Dodger67) (talk) 07:41, 8 April 2015 (UTC)

If you read this by use (an object to be swung to hit something), then "heavy" refers to energy stored in the bat that may be transferred to what it is being hit. Heavy normally refers to the force pulling down on something by gravity, but in this case, it refers to the force being transmitted. That makes me think of tractor trailers. Lateral force is important there. If you are carting around crates of uranium, it isn't a big deal. It just takes more gas to get moving and a longer braking distance to stop. If you are carting around eggs, you have a problem. The liquid makes them harder to move. Similarly, driving a milk truck is hard because the liquid sloshes around. So, imagine a liquid-filled bat. When you strike the ball, the casing of the bat will want to bounce back from the collision. However, the liquid will continue pushing forward. This will create a very heavy feel to the bat. Can this be done? Yes. I already did it in a school experiment years ago with a water-filled wiffle ball bat. We tried water, cooking oil, and spray foam. Cooking oil felt the heaviest when hitting a ball (and we went through a lot of bats and had a large mess because plastic casing is not very effective). I believe that mercury will be the best liquid for this usage. It is very heavy and remains liquid at room temperature. Is there a heavier naturally occurring liquid? I don't know. Next, the casing. Plastic won't work. Wood won't work. You need something that won't dent, won't crack, won't break... I'd begin with a carbon-fiber casing. How about kevlar? I have feeling that will dent. So, I'm stuck on this point. This is where the sturdiness comes in. Once you are swinging a massively heavy mercury filled bat, what kind of case won't dent or crack? 209.149.113.89 (talk) 12:08, 8 April 2015 (UTC)

Too much sturdiness could work against you. If you see a super-slow-mo of a batter making solid contact, you will see the bat flex slightly. Bats made of ash or hickory are hard but can flex. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:35, 8 April 2015 (UTC)

Indeed, what you want is efficient energy transfer, there are lots of factors that go into that, not just heaviness and sturdiness. --Jayron32 12:48, 8 April 2015 (UTC)

Nothing could ever surpass the might of clicky-ba. --Dweller (talk) 15:19, 8 April 2015 (UTC)

Okay... so what material would I want for a bat to hit the hardest and not break or dent? Let's just assume that my strength is not a concern, and neither is cost. It's hard to tell if tungsten would work because certain configurations are sometimes stronger and sometimes brittle. Depleted uranium would sound good if it weren't for the fact that it's still 60% radioactive. Platinum also sounds interesting but again I can't tell whether it's durable enough for a bat because it's not regularly used for making heavy objects (unlike tungsten and uranium which are used for heavy ammunitions). Are there other alloys that would work better? CesarFelipe (talk) 15:47, 8 April 2015 (UTC)

• A bat with a titanium skin and a core of U-238, osmium, or lead would make sense. Osmium is the densest naturally-occurring element, but it is toxic, and hugely expensive. The lead core would be the cheapest and safest. But I think you'd have to see baseball players becoming over-muscled weightlifters, a huge spike in injuries to batters, and a few deaths a season due to flying bats. μηδείς (talk) 18:11, 8 April 2015 (UTC)

You are assuming that the questioner wants to hit a ball with the bat. He hasn't explained what he wants to do. A bat used to punch a hole in a brick wall is much different than a bat used to hit a baseball. What if he wants to hit a ping-pong ball? Again, a very different bat. If you make the heaviest bat possible and it does nothing more than crush and flatten the baseball, that is pointless if the question is actually about hitting a baseball as far as possible. 209.149.113.89 (talk) 18:28, 8 April 2015 (UTC)

Speculative ref desk questions; a dime a dozen. "You are assuming that the questioner wants to hit a ball with the bat"; priceless. μηδείς (talk) 00:28, 9 April 2015 (UTC)

Well, if I have to be specific, let's say I want to use the bat as a blunt weapon, so I would want it to be able to hit different kinds of surfaces with force, not just a spot as small as a ball. (And again, let's assume strength and cost are not an issue). CesarFelipe (talk) 19:34, 8 April 2015 (UTC)

If you're looking for density, you can't beat Quark-gluon plasma ;). On a serious note, I think Tungsten could be a contender. I know you say "price is not a factor" but all things considered, it's only slightly less dense than platinum (19.25 g/cm3 vs 21.09g/cm3) but it's relatively common and cheap, one site I found shows 99.9% tungsten bars cost about $50 per kg, platinum costs over $1000 an ounce. Vespine (talk) 23:09, 8 April 2015 (UTC)

Women's buttocks and handicap principle

Since there is sexual selection in both genders, I wonder why handicap principle, or maybe rather the sources that are used in that article, gave no examples(that I noticed anyway) of animals from the female sex advertising their fitness through "costly signalling," although certainly signalling exists, whether costly or not. Now buttocks are a sexual signal. But there have been recent articles in the popular media that for some women that have prominent buttocks, it's not only buttock size, but spinal curvature. But spinal curvature seems more definitely costly than buttock size, so it seems that it could be a genuine example, although the popular media doesn't spell that out. The other possibility that comes to mind is large breasts, which can lead to back pain. Of course, one could argue that almost every signal has a cost, but the wikipedia article says it has to be a large enough cost to prove fitness.2601:7:6580:5E3:BD26:AB2F:7045:3132 (talk) 14:48, 8 April 2015 (UTC)

It's hard to spot a question in there, but I suggest if you want to debate the content of our article, posting at Talk:Handicap principle would be your best option. Of course, if you just want a debate, then you'll need to find another website. --Dweller (talk) 15:13, 8 April 2015 (UTC)

• Hmm, it should be easy for someone like you to spot a question in there, even without a question mark. I would denote your reply as intentionally not to the point. Here's a question for you-you describe yourself as former bigshot on a wikipedia board, so do you miss the joy of stifling discussion?2601:7:6580:5E3:944E:5E28:28FE:2E0 (talk) 18:57, 8 April 2015 (UTC)

A term that biologists use is female ornamentation. Here is a list of recent scientific articles on the topic [38] [39] [40] [41]. As for your claims: buttocks may indeed be a sexual signal (for both human males and females), but they also serve many other purposes. Have a look at an image search for say the 100m dash - those muscles help us run. If you look at a google scholar search for /costly signaling human/ [42], you'll see that almost all the scientific work is about cultural signaling, not morphological signaling. SemanticMantis (talk) 15:42, 8 April 2015 (UTC)

I was under the impression that what you're really seeing is larger hips - which correlates directly with the ability to successfully give birth - which would be an obvious indicator of reproductive success what will be selected for. It's easy to imagine spinal curvature being a part of that too. SteveBaker (talk) 17:27, 8 April 2015 (UTC)

• It's called sexual selection. Men who mated with unhealthy females who consumed their fat reserves and had small behinds would be less likely to conceive, and more likey to loose a child due to malnutrition. Hence a gene that makes men prefer curvaceous women would make sense, even if otherwise, large behinds might be a handicap in running to escape a predator. That prerence would result in women's buttocks becoming larger, as the larger the butt, the more eager suitor and healthy babies. μηδείς (talk) 00:18, 9 April 2015 (UTC)

calorific value of carbon monoxide

I am performing an experiment that needs the calorific value of gases produced from combustion of 1kg of coconut shell.I tried to google it but could not find any useful detail.Atleast ,a simplistic approach to estimate the required value is cordially welcome.115.241.9.191 (talk) 17:06, 8 April 2015 (UTC)

I don't know what coconut shell is made of precisely, or why it would produce carbon monoxide during combustion, but maybe Standard enthalpy of formation is helpful. From the table in that article one can see that the energy of 1 mol CO is 110.5 kJ lower than the combined energy of1 mol of elementary carbon and 1 mol of elementary oxygen (i.e. 0.5 moles of O₂), meaning that converting these into 1 mol CO will produce 110.5 kJ in heat. - Lindert (talk) 17:19, 8 April 2015 (UTC)

http://nvlpubs.nist.gov/nistpubs/jres/6/jresv6n1p37_A2b.pdf says 283 kJ/mole at 30 degC. SteveBaker (talk) 17:22, 8 April 2015 (UTC)

And just to be clear, that is the heat produced by converting 1 mol of CO into CO₂, according to CO + 1/2₂ -> CO₂, so it's the difference between the standard enthalpies of CO and CO₂. - Lindert (talk) 18:26, 8 April 2015 (UTC)

Orgasm

Do men and women experience the same overall feelings/sensations when they orgasm? — Preceding unsigned comment added by 117.167.237.194 (talk) 23:43, 8 April 2015 (UTC)

Wikipedia has an article titled Orgasm which has links to further articles that will help you in your research. Feel free to read that article, and follow links from there and see where it leads you. --Jayron32 23:55, 8 April 2015 (UTC)

Per that article, pretty much the same. A bit longer for the ladies, generally, and more of a comedown for the gentlemen. InedibleHulk (talk) 00:00, April 9, 2015 (UTC)

We have no current way of directly measuring qualia, subjective conscious experience. Consider, how do we know that what I see and name as red is not experienced by another person as what I would name green? The color spaces in our heads might be flipped, so that white is black and blue is yellow. As long as we agree to call the same things by the same names, consistently, there would be no way to know that our subjective experiences were reversed.

We do know that people with color blindness have a different experience fro that of trichromats, but only because we notice that the words we use conflict, or the distinction is lost on the dichromat. Even then, we don't know if dichromats view both red and green as red, or as green, or as violet, for that matter.

Assumptions based on physiology say that since the neurotransmitters are the same, the experience must be similar, but we have no idea at what level of processing qualia arise; molecular, cellular or at the level of one or more parts of the brain.

We do know that gene therapy for color blindness has worked in animals, but it has not yet been tried in humans. We will learn a lot if they report that everything appeared red, or green, or brown before, but now I still see red, but I also see a new color, the one people were always calling green. μηδείς (talk) 00:12, 9 April 2015 (UTC)

For the classical answer, see "Of ten parts a man enjoys one only." -- ToE 00:28, 9 April 2015 (UTC)

April 9

Gravity in conditions of the planet Earth

Did in conditions of the planet Earth the gravity been different mathematical values in different physical environments?--83.237.207.119 (talk) 12:20, 9 April 2015 (UTC)

If you are asking about variation of gravity on earth, I suggest you read Gravity of Earth.--Shantavira|^{feed me} 12:58, 9 April 2015 (UTC)

Suggesting a gravity in water.--85.141.232.245 (talk) 14:20, 9 April 2015 (UTC)

Capacitor

An AC circuit contains a 0.01 microfarad capacitor and 0.06 micro farad capacitor that are connected in series. What is the total capacitance of this circuit — Preceding unsigned comment added by 64.56.106.62 (talk) 12:47, 9 April 2015 (UTC)

You might be interested to read Capacitors in series.--Shantavira|^{feed me} 13:00, 9 April 2015 (UTC)

Prototypes of computer

Did the code-making machine Enigma been prototype of computer?--85.141.232.245 (talk) 14:15, 9 April 2015 (UTC)

See the Wikipedia article titled History of computing hardware. --Jayron32 14:23, 9 April 2015 (UTC)

I did not understand, did a binary calculation system machines been a prototypes of computer – the machines of program binary codes?--85.141.232.245 (talk) 15:22, 9 April 2015 (UTC)

No. Dmcq (talk) 16:06, 9 April 2015 (UTC)

So, it to become me to avow that the USSR did not invented a program language and computer, I’m suppose that the USSR had got to invented a binary calculation system machine which was been one of much from word, of course it did been electromechanical (radiotechnical) and electronical versions, but not microelectronical version, so the USSR did it more simplest than over members, because the economy of the USSR was been progressing for win. I don’t know, how binary calculation system was been relating with binary programming?--83.237.200.102 (talk) 17:30, 9 April 2015 (UTC)

The Enigma machine was not a prototype of the computer as we now use the word. As for your other comments, you may find it useful to learn the term popovism. Finally, you are strongly encouraged to ask questions in the Wikipedia of your native language. (If you have already tried that, and they have sent you here, you are encouraged to take your questions to another Wikipedia that may be able to understand you.) RomanSpa (talk) 18:09, 9 April 2015 (UTC)

Much thanks for you explanation. I’m should interesting, did been a different between calculation and programming?--83.237.200.102 (talk) 19:30, 9 April 2015 (UTC)

Pressure reducing valve question

I have a vented immersion heater connected to a 90 gallon water tank in the loft. The tank supplies 0.5 bar of water pressure. There is a vent pipe from the immersion heater that allows any expansion of water to release safely outside. Obviously if I connected the immersion heater directly to the 3 bar mains water supply the water would overflow out of the vent pipe continuously.

However, could I hypothetically replace the loft tank with a pressure reducing valve set to 0.5 bar and connected directly to the mains? From the perspective of the immersion heater it would still receiving 0.5 bar of water pressure, so it shouldn't make any difference as far as I can see. Am I correct in that assumption or have I missed something vital?

Note; this is merely a hypothetical question and I will not be undertaking any work of this nature. I'm just curious if it would actually work. Pressure reducing valve (talk) 17:15, 9 April 2015 (UTC)

Yes, your talking about what is referred to as a unvented hot water system. However, you will also need some other bits -- all explained here: [43]--Aspro (talk) 18:46, 9 April 2015 (UTC)

No that's not right at all.

It would still be a vented system and work at low pressure, the only thing that would change is that the low pressure 0.5 bar of supply water to it comes via a "pressure reducing valve" instead of a loft head tank. If too much pressure builds up inside the immersion heater it would still overflow out the vent pipe.

Unvented systems are entirely different and typically deal with high pressure. I'm not asking about converting a vented system into an unvented system (which is not possible without replacing the entire immersion heater and boiler system) I am asking about changing only the method of water supply to a vented system while keeping everything else the same.

Generic answers won't help here because the system I am proposing is a complete bodge and probably doesn't even have a name. It's an exercise in inventive thinking. Pressure reducing valve (talk) 19:28, 9 April 2015 (UTC)

Reservoir storage

What information is needed to calculate storage volume of a reservoir. I have inflow, outflow and a value for 2s/dt-Q but I don't know what dt is so this is useless. I also have a value for max capacity of river downstream and my guess is this is what I need to use. I also have a storm hydrograph but as I'm only considering baseflow storage volume, I've ignored this. But now I'm not sure what to do. 90.201.190.183 (talk) 18:55, 9 April 2015 (UTC)

Building our own water-mill or hydro power station are we? Think you'll find that dt just means Δ T or in other words the difference in temperature in kelvins or centigrade. The density (mass per cubic volume) changes with temperature.--Aspro (talk) 19:08, 9 April 2015 (UTC)

I should think the expansion of the water due to temperature is small enough that it could be ignored (and it's not linear, anyway, so would require a look-up table to calculate accurately). Just taking the initial volume of water, then adding in the elapsed time since then, multiplied by the net flow (inflow-outflow) would seem to get the job done:

Vcurrent = Vinitial + (Vin - Vout)t

If that volume is less than zero, then the reservoir is empty (except for the small amount currently flowing through it). If that volume exceeds the max capacity, then the reservoir will be at max capacity (possibly with the surrounding area flooded). Evaporation (and precipitation) might be significant on an open reservoir, however, and that depends on not only temperature, but also humidity, wind, and sunlight. As a practical matter, you might just add a fudge factor to V_out, which would vary by season, to account for evaporation and precipitation. StuRat (talk) 19:18, 9 April 2015 (UTC)