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May 14

Is Faraday's law of inductance properly applied to Wiki's article on LC circuits?

The article uses Faraday's law, to explain why a decrease in magnetic field causes and increase in EMF.

"... Eventually all the charge on the capacitor will be gone and the voltage across it will reach zero. However, the current will continue, because inductors resist changes in current. The current will begin to charge the capacitor with a voltage of opposite polarity to its original charge. Due to Faraday's law, the EMF which drives the current is caused by a decrease in the magnetic field, thus the energy required to charge the capacitor is extracted from the magnetic field." LC circuit

The correct way of dealing with floating references is to use the template {{Reflist-talk}}. This puts the refs in a neat box and keeps them with the original posting. For example, DrChrissy ^(talk) 15:19, 14 May 2017 (UTC)

DrChrissy, You just placed "This is a bogus ref to illustrate the template that prevents floating refs" at the bottom of this page, in the wrong section. Was that your intent? --Guy Macon (talk) 16:52, 15 May 2017 (UTC)

@Guy Macon: Hi. Another editor has already raised this on my Talk page - I suggest you read that thread to put this into perspective. DrChrissy ^(talk) 16:59, 15 May 2017 (UTC)

Correct way to deal with floating refs on Talk pages
Floating references The correct way of dealing with floating references is to use the template {{Reflist-talk}}. This puts the refs in a neat box and keeps them with the original posting. For example, This posting contains 3 bogus refs to illustrate the use. References References

Faraday's law of induction applies to magnetic INDUCTION. Magnetic induction occurs when a magnetic FIELD produces magnetic energy within a superconductor, or both magnetic energy and EMF within a non-superconductor.

In an LC circuit, the capacitor does not contain a magnetic field. The capacitor gains its EMF when magnetic energy directly converts into electrostatic energy.

Note: The article uses an inductor's resistance to change in current to explain why current begins to flow to a capacitor after a polarity change.

However, the inductor does not resist a polarity change. Current INSTANTLY reverses direction during the two polarity changes that occur within each cycle.

In my opinion, a better explanation of current flow to the capacitor after a polarity change is the fact that:

WITHIN AN LC CIRCUIT, RELATIVE POLARITY DETERMINES THE DIRECTION OF CONVERSION OF ENERGY.

For example, electrostatic energy cannot convert into magnetic energy without proper magnetic versus electrostatic polarity. Exhaustion of electrostatic energy results in the instability of having an inductor with the entire circuit's stored energy. A polarity reversal makes it possible for magnetic energy to convert into electrostatic energy.

Overall, relative polarity drives the direction of energy conversions. Capacitance and inductance determine the rate of energy conversion. Current and volts are the result of the energy conversions within an LC circuit. Vze2wgsm1 (talk) 01:15, 14 May 2017 (UTC)

You're referring to the article LC circuit. You linked to it in an obscure way, so I hope this helps. Akld guy (talk) 02:06, 14 May 2017 (UTC)

You state that the inductor does not resist a polarity change, and you refer to "the two polarity changes that occur within each cycle". The only way to read that is that you're referring to an LC circuit connected to an external signal source, but the part of the article that you're dissatisfied with is discussing only a capacitor and inductor connected together and to nothing else. It explains what happens when the capacitor, which is charged, begins discharging through the inductor. There is no signal from an external source involved at this part of the article. Akld guy (talk) 02:44, 14 May 2017 (UTC)

An example of capacitor charge and discharge without polarity reversal within a capacitor is when a discharging battery adds electrostatic energy to a capacitor. Afterwards, (after adding extra charge) the capacitor could charge the battery, without changing the polarity of the battery or the capacitor.

Let a battery substitute for a capacitor within an LC circuit. After the battery completely discharges into the inductor, the energy within the inductor would begin trying to charge the discharged battery, in a direction that would make the anode negative, and the cathode positive.

The inductor's attempt to reverse the polarity of the battery requires a reversal of polarity of the energy within the inductor.

Vze2wgsm1 (talk) 22:50, 14 May 2017 (UTC)

• @Vze2wgsm1: Just a sidenote, "Wiki" is not a correct way to refer to Wikipedia.--Jasper Deng (talk) 22:58, 14 May 2017 (UTC)

ceramic capacitor vs tantalum capacitor

Between a ceramic capacitor and a tantalum capacitor of the identical capacitance and rated voltage, let's say 100 µF and 10 V, which one would have a smaller leakage current? ECS LIVA Z (talk) 03:06, 14 May 2017 (UTC)

The leakage of the ceramic is typically a thousand times lower. Typical leakage for a 100 uF, 6.3 VDC rated tantalum-polymer capacitor is 60 uA. A ceramic capacitor of the same capacitance and voltage would have an equivalent leakage of 6.0 nA. Source: Technical Update – Comparison of Ceramic and Tantalum Capacitors --Guy Macon (talk) 03:54, 14 May 2017 (UTC)

Holy crap that's a big difference. Thanks a lot! ECS LIVA Z (talk) 04:08, 14 May 2017 (UTC)

It's an unrealistic comparison though. Tantalums are electrolytics, where many drawbacks (polarisation, leakage, low voltage rating, sometimes accuracy of their value) are sacrificed in order to achieve a high capacity or a small physical size. 100μF is a typical value for tantalum, but would be exceptional for a ceramic. 0.1μF is a more practical upper limit for an off-the-shelf commodity disc ceramic capacitor, 1μF for newer MLCC devices. You can go higher with recent devices (my usual suppliers peak at 22μF] in similar packages to tantalum but the price gets steep (although the voltage rating is high enough to be board-design limited).

Specialist HV ceramics have always been around in large capacities, but those get expensive and obscure. They're more usually made these days from polypropylene capacitors (look at the Tesla coil people and 'MMC' banks). This highlights another issue - at higher frequencies it might not be a simple leakage current that is the problem, but losses within the dielectric. Andy Dingley (talk) 12:22, 14 May 2017 (UTC)

On Digikey I'm finding ceramic capacitors significantly cheaper than tantalums at 0.1 μF, 1 μF, and even 10 μF. The two only reach price parity (with tantalum still trailing badly in performance) at 100 μF, but I don't use anything that big (nor do most hand-held consumer electronics). Seems like the latest technology advances and price drops in MLCC have made tantalum virtually obsolete.ECS LIVA Z (talk) 21:10, 14 May 2017 (UTC)

Here's a ceramic capacitor at 100 μF[1] that's actually cost-competitive against the tantalum equivalent. ECS LIVA Z (talk) 21:18, 14 May 2017 (UTC)

Thanks, those haven't reached my end of the workshop yet. Note the low voltage ratings, which are characteristic of MLCC and indicative of the thin layer trick that allows them to get such a high capacity into a small package. Andy Dingley (talk) 08:45, 15 May 2017 (UTC)

Capacitors can be wired in parallel to increase the total. For example, three ceramic 10 μF units in parallel result in 30 μF, with the same voltage rating as the lowest rated one. Akld guy (talk) 02:33, 15 May 2017 (UTC)

Resolved

Data and maths of man-made climate warming

If a non-climate scientist got basic climate and weather data (like temperature, CO2 concentrations, floods and hurricanes) and he wanted to know whether it's man-made or not, what maths would he need? What steps would he need to take? That is, without appealing to authorities or experts, how could he come to this conclusion? --Clipname (talk) 11:50, 14 May 2017 (UTC)

From an inhuman point of view, the best test would be to get rid of all the men (inclusive) and observe subsequent weather data. Apologies for that answer. Dbfirs 11:56, 14 May 2017 (UTC)

• Attribution of recent climate change and the sources therein may help. Loraof (talk) 14:03, 14 May 2017 (UTC)

First you need to determine whether the CO2 increase was man made. There are multiple lines of evidence that show this is indeed the case, but perhaps the most straightforward is the change in relative concentrations of carbon isotopes in atmospheric CO2. See Seuss effect.

From this point onward you can choose between approaches that run from the simple to the very complex. Possibly the easiest would be to use one of the simplified formulas for radiative forcing as a function of CO2 concentrations. You could then take this answer and use a reasonable value for climate sensitivity to get the resulting temperature change. For this calculation it would be more appropriate to use a value for transient climate response rather than equilibrium climate sensitivity.

You have to also keep in mind that the observed warming is not solely due to CO2. Radiative forcing due to methane is also substantial (a bit more than half as large as the forcing due to CO2).

There's a whole range of approaches beyond this, from fairly simple radiative-convective equilibrium models to full-blown climate system models such as the CCSM. Shock Brigade Harvester Boris (talk) 15:17, 14 May 2017 (UTC)

The thing is, while quantifying the exact amount of past and future global warming takes a lot of effort and calculation, the simple fact that manmade greenhouse gases are warming the planet really doesn't. The greenhouse effect of gases like CO₂ and methane can be demonstrated in a laboratory. We know human activities like intensive agriculture and burning fossil fuels releases these gases into the atmosphere (again, demonstrable in a laboratory). So either the planet should be warming, because we're dumping these greenhouse gases into the atmosphere, or some unknown process is precisely compensating for these manmade alterations to the atmosphere. Occam's razor suggests the former. --47.138.161.183 (talk) 07:43, 15 May 2017 (UTC)

That is a poor argument. If the effect is small, say 1 deg C per doubling (about what you get in the lab) then it will be hundreds of years before we see another 1 deg C, other than short term spikes due to El Nino etc. Who knows what will happen in several centuries? Maybe some actual science as opposed to guessing games and alarmism. Greglocock (talk) 12:10, 15 May 2017 (UTC)

If you mean 1 deg C per doubling of CO2 it won't take centuries to happen. Since the 50s it has not only doubled, but went up by a factors of 8. And that's discounting other greenhouse gases, a chain effect (more heat -> more water vapor in the atmosphere -> even more heat) and other side effects like increased acidity of oceans, disturbing ocean currents, triggering the release of methane crystals. Hofhof (talk) 13:12, 15 May 2017 (UTC)

What has gone up by a factor of 8 since 1950? Not CO2 concentration. On another note, Greglocock's value of 1 deg C per doubling is roughly the effect solely of CO2 in an isolated, static system; it is not plausible to apply such a value to the Earth. Shock Brigade Harvester Boris (talk) 13:47, 15 May 2017 (UTC)

I meant the emissions of CO2. A part of it is absorbed, mainly by the oceans. And it's somehow below 8, but not much. Hofhof (talk) 19:32, 15 May 2017 (UTC)

Exactly. Technology seems to find ways to do things like increase the depth of rock or water fossil fuels can be economically extracted at to amounts that would've been Jules Verne-like fantasy only generations before. Wait, we've done that only a few generations after too (walk on the Moon) Sagittarian Milky Way (talk) 19:45, 15 May 2017 (UTC)

Since 1880 CO2 has increased from 280 ppm to about 400 ppm. So in logarithmic terms that is log(400/280)/log(2), or about 0.5. That is, roughly half a doubling. In the same timeframe global temps have increased by perhaps 0.8 deg C, so a simple estimate of CO2 sensitivity is 0.8/0.5, ie 1.6 deg C per doubling of CO2. That is at the lower end of IPCC estimates, and somewhat more than the direct effect measurable in the lab. The latter is confounded by positive and negative feedbacks when translated to the real world, the sizes and balance of which are very much up in the air. I don't know where any factor of 8 appears in the above numbers, looks like hysterical exaggeration to me. Greglocock (talk) 12:19, 16 May 2017 (UTC)

In your analysis of temperature change you've compared the observed change to equilibrium climate sensitivity, which includes "slow" feedbacks that continue to unfold for a few centuries after CO2 doubling. A better comparison would be to transient climate response, which is the temperature change at the time of CO2 doubling (i.e., before the slow feedbacks have evolved). The ratio of TCR to equilibrium climate sensitivity is around 0.5-0.6. Applying the inverse of this ratio to your computed value of TCR gives us an equilibrium climate sensitivity of 2.7 to 3.2 for a doubling of CO2. That's squarely within the middle of the accepted range from both models and paleoclimate estimates. So, your analysis shows that the models correspond rather well with current observations.

Also, as Hofhof clarified just above, the factor of 8 applies to CO2 emissions. Data from CDIAC show that CO2 emissions from fossil fuels and cement production increased from 5977 million metric tons in 1950 to 35,849 million metric tons in 2013. That's a factor of 6 than a factor of 8. (Note these figures do not include non-fossil fuel based CO2 emissions such as biomass burning.) Whether 6 versus 8 is a "hysterical exaggeration" as you say or "below 8, but not much" as Hofhof says is up to the reader's judgment. Shock Brigade Harvester Boris (talk) 14:08, 16 May 2017 (UTC)

Not a proof, but the "hockey stick curve" is dramatic enough that, if you see it graphed out, you don't have to be an expert to see that something unusual has happened to our weather in the last century. (example)

The caveat there is that all the temperature data older than the late 1600s is based on pretty intense research that could only be done by experts.

... but that's going to be true no matter what. There's no way something as big as this could be deduced entirely from personal knowledge and personal calculations. At some point, you're going to have to use someone else's data. It's just a question of which data you use or don't. ApLundell (talk) 13:51, 15 May 2017 (UTC)

There's also the problem that science is collaborative and cumulative. Scientists are not hermits collecting data and creating theories from it in isolation. There are literally thousands of climatologists around the world that have been working together on this subject, and one person is unlikely to have the time or resources to recreate it all on their own from scratch. --Jayron32 14:43, 15 May 2017 (UTC)

Agreed. Even very basic science is difficult to work out from first principals all by yourself.

Something as basic as personally proving that the world is spherical would involve quite a bit of travel and careful observation of the sun and stars.

It's just not reasonable to expect to be able to personally work out something as complex as global climatology. It'd be like trying to build a battleship all by yourself. ApLundell (talk) 15:19, 16 May 2017 (UTC)

• I will just leave this here --Guy Macon (talk) 17:03, 15 May 2017 (UTC)

I didn't know the Dilbert cartoonist was denialish. Sagittarian Milky Way (talk) 18:54, 15 May 2017 (UTC)

I believe he's also wrong about climate scientists using economic models that have never been right. Economy has used/tried to use physical models to transform their discipline into a real science, but not the other way round (AFAIK). Hofhof (talk) 19:36, 15 May 2017 (UTC)

He does NOT use economic models to address the scientific question. He separates the issue into the scientific questions and then the economic theories behind certain proposed responses to assumed scientific results. He harps on this theme so often its impossible to miss; I've only been looking at his blog since February. μηδείς (talk) 00:19, 16 May 2017 (UTC)

Thanks μηδείς. Now I notice that my answer was poorly formulated. Yes, I meant he bashes climate scientist for supposedly using economic models, which they don't.

I have never read his blog, but in the cartoons, which I read often, this is the first time I see something about his denialism.Hofhof (talk) 00:46, 16 May 2017 (UTC)

Adams is an interesting fellow. Shock Brigade Harvester Boris (talk) 01:17, 16 May 2017 (UTC)

In my personal opinion, Adams is more of a provocateur and self-promoter than anything else. I started reading his cartoons on line in January, then started reading his blogs. His basic premise is Skepticism, and that people are easily manipulated. Whether he applies those premises to his own theories is an open question. μηδείς (talk) 00:48, 17 May 2017 (UTC)

• Bloomberg published a really great graphic that shows the relative contributions of various warming factors since 1880. Answer: it's CO₂. the really scary part is not emphasized in the text, but is very clear from the chart: Warming would be much worse if not for aerosols caused by man-made sulfur dioxide emissions. But these emissions fall out of the atmosphere in 20 years, while the CO₂ does not. This means that we will see an abrupt temperature increase when the Chinese quit burning high-sulfur coal. -Arch dude (talk) 05:20, 16 May 2017 (UTC)

@Arch dude: Their plot for aerosols shows a strong decline, actually. And I'm not sure how they defined "aerosols". And I'm skeptical that sulfur dioxide would affect climate that long - I remember Mount Pinatubo caused colder temperatures, but the next year was pretty OK (according to a greenhouse-acclimated baseline). The article I trot out in this context is this one -- it shows that the infamous "chemtrails" or "geoengineering" conspiracy theory is true, and the conspiracy was killing 1000-4000 people yearly; however, contrary to various disinformation, the source of the chemicals is, of course, the airplane's fuel tank, and the geoengineering occurs in the context of executives trying to talk the government out of raising their fuel costs in the name of safety. Anyway, that was said to hold back global warming by six months, and there are other sources of SO2, so you're not tremendously off, but I think by an order of magnitude or so. Wnt (talk) 14:01, 16 May 2017 (UTC)

"Aerosols" in this context refers to tropospheric aerosols, not stratospheric aerosols from volcanoes. The Bloomberg graphic has a separate line "Volcanic" (which indeed shows a sharp but short-lived cooling effect from Pinatubo). Shock Brigade Harvester Boris (talk) 14:13, 16 May 2017 (UTC)

Yes, the aerosols are currently contributing a strong net cooling, which somewhat offsets the CO₂ warming. That was my point. When China quits burning high-sulfur coal, there will be a sharp increase in temperature. But if they continue to burn coal, with or without sulfur, warming will continue anyway. The sulfur just lagged the effect of the previous decade's CO₂, which will still be there when the sulfur precipitates out. -Arch dude (talk) 15:13, 16 May 2017 (UTC)

@Wnt: Yes, I was imprecise about the atmospheric lifetime of SO₂. Your figure may be correct. I knew it was short but not that short. The increase in net aerosol cooling in the chart comes from increases in net annual generation, which keeps the total up even though it drops out in a few years. But the very same coal plants that add that SO₂ are also adding CO₂, which will keep warming the earth long after we are all dead. -Arch dude (talk) 15:24, 16 May 2017 (UTC)

• Let me just give a pointer to a Scientific American guest blog I wrote on this general issue: https://blogs.scientificamerican.com/guest-blog/global-warming-the-folly-of-certainty/. — Preceding unsigned comment added by Looie496 (talk • contribs)

Thanks for the OR self plug. Given there is a non-zero probability that one of the aliens from Signs is hiding in your house, do you hose it down before bed every night? μηδείς (talk) 19:43, 16 May 2017 (UTC)

Come on Medeis, I've seen you around and know that you're smarter than this. There's a huge space between "non-zero probability" and absolute certainty. The issue is where any specific risk lies along that continuum, together with the costs involved with that risk. Shock Brigade Harvester Boris (talk) 00:22, 17 May 2017 (UTC)

Obviously I am using an extreme example for rhetorical effect, kind of like Al Gore having a dam opened so he can film a clip about water conservation. But there is no such thing as absolute risk, only comparative risk. One really can't argue from "humans burn hydrocarbons" to "Al Gore needs 17 trillion dollars" without a whole lot of assumptions in between. Climate alarmism is really no different from new-Earth creationism when you look at it. It ignores almost the entirety of the planet's history, all the scientific evidence for solar variation, interstellar clouds, orbital fluctuations, volcanism, etc., and rushes to passing the collection plate. The bridge out analogy may be more realistic than the Signs aliens analogy, but it's not much more sophisticated. μηδείς (talk) 00:41, 17 May 2017 (UTC)

Yeah, as someone who studies this stuff I sometimes think the "alarmists" may do even more damage than the "skeptics." I cringe whenever I read things like global warming will mean the end of humanity within a decade. As for the phenomena you mention we know and account for all that, except maybe interstellar clouds (by which I assume you mean things like this) which are on a time scale way too long to be relevant to recent climate change. Shock Brigade Harvester Boris (talk) 13:46, 17 May 2017 (UTC)

This has been done, see this article. So, you can consider only the climate data and analyze the data in a way that doesn't invoke any detailed atmospheric physics and that's then enough to verify that human CO2 and aerosol emissions are the main driving force of climate change. Count Iblis (talk) 20:39, 16 May 2017 (UTC)

My point is not that interstellar gas clouds will be here tomorrow, but that on the long scale they and innumerable other factors affect the climate, but are not taken into account on climate models. Sea levels have been hundreds of feet lower than they are now in the past, and hundreds of feet higher. We have nothing at all like a comprehensive controlled and uniform surface temperature database now; most areas of the earth are not measured with the accuracy at Greenwich, and that record doesn't go back before the 1800's.

We simply haven't got the knowledge or the data to predict anything with the often quoted 97% consensus. (In the 70's, the consensus was that SO2 was driving a new ice age, and acid rain that would ruin the world's ecosystems. That should be the prologue to any climate discussion.) And if we did, simply fertilizing the pacific with iron might cause sufficient algae blooms to address any real problem.

For an unbiased approach on climate change, I recommend Canadian scientist E. M. Pielou's After the Ice Age. She argues that we have actually entered the next cooling phase, although since it is still warmer now than it was during the last ice age, some local warming can make us think the trend is toward warming. μηδείς (talk) 15:27, 17 May 2017 (UTC)

A scientific consensus of a global cooling in the 70s? No. --Modocc (talk) 04:54, 18 May 2017 (UTC)

That is a subscription article, plus time series based articles are at best just for checking that things are okay with the calculations rather than really showing the basics. Plus people can delude themselves by sticking in all sorts of cycles into time series and prove to themselves the opposite of what is evident, that is a common problem with climate change skeptics. I think it would be nice if there was a good illustrated model which showed the main effects for people, one can't expect the general public to trudge through the figures. It is after all a complex second order effect as far as the change in absolute temperature of the earth from about 290 Kelvin is concerned, where the first order effect of the atmosphere has already heated the earth up by about 35K. Sticking in extra CO2 should obviously heat it up more but a good interactive illustration would help elucidate the main actors in the process and their effects and possible future problems like increased methane emissions or the effects of possible mitigations. After all it isn't immediately obvious to people who haven't looked into it why increased CO2 might lead to a cooler stratosphere or why the melting of Antarctica leads to there being more sea ice there.

The talk about climate alarmism and comparing to creatonism is just silly though. It assumes thousands of climate scientists are in some conspiracy. Ignoring scientists is like ignoring a doctor who tells you that you have a tumor, yes they are sometimes wrong but I think a person going and chanting some healing chant instead of going to a medical specialist shows more sense than these 'skeptics'. If they want to do nothing let them dispute any action on economic grounds. Dmcq (talk) 08:32, 17 May 2017 (UTC)

---

This being Wikipedia, I think it only fair to point out Scott Adam's actual views on climate science do not match what some here claim his views are.

Besides the cartoon at http://assets.amuniversal.com/97ed9410fd89013486fb005056a9545d we have his blog post at http://blog.dilbert.com/post/158778029326/how-to-change-my-biases-on-climate-science

I am not saying that I agree or disagree with him, but at least we should have the decency to address his actual, views instead of a straw man. --Guy Macon (talk) 09:27, 18 May 2017 (UTC)

How is a workplace humor comic strip relevant anyway? I learn all my science from cartoonists. Roadrunner cartoons taught me that you can fall off a cliff and it's no big deal. A cartoon showed it so it's reality by definition. Sagittarian Milky Way (talk) 13:28, 18 May 2017 (UTC)

Might I provide another Dilbert cartoon to show what I think of Scott Adam's views and abilities in this mattter [2]. Dmcq (talk) 13:49, 18 May 2017 (UTC)

May 15

Meaning of "above" in geology

I know by the law of superposition in geology that generally younger rocks lie above older ones. Reading Moine Supergroup I see the phrase "tectonically above" used twice and, although I can't find anywhere a definition, I suspect this means that the rocks physically above have been forced there and are, in fact, older. Am I understanding this properly? Would you ever say "tectonically above" if the higher strata were younger – both situations occur in the area of the Moine Thrust Belt? In the article "structurally above" is used twice and I think I can infer from the article that this phrase has the same meaning as "tectonically above". Is this right? When the word "above" is used without qualification in a geological context does it have a definite meaning to a geologist? I'm wondering whether "above" is ever used to mean "younger". Thincat (talk) 08:29, 15 May 2017 (UTC)

You're correct in your assumption - this is tectonic stratigraphy. Thrust faulting has the general effect of placing older rocks on younger rocks. We would use the term tectonically or structurally above (they are synonyms) when the upper sequence lies physically above a lower sequence with a tectonic (faulted) contact, rather than a normal stratigraphic contact. Mikenorton (talk) 10:55, 15 May 2017 (UTC)

Good, thank you. That seems clear now. Thincat (talk) 12:45, 15 May 2017 (UTC)

Induction and Convention of thermoelement

Does induction and convention of thermoelements are depends on their geometry? What geometry of thermoelements is more profitable, it is a complex geometry or simple geometry?--109.252.29.219 (talk) 15:30, 15 May 2017 (UTC)

We have articles about conduction and Convection which are two major types of Heat transfer. Both depend on the geometry of the body and its surroundings. Conduction can be calculated using the Thermal conductivity of material(s) in the path of heat flow. Convection is much harder to calculate since it involves movement of air whose flow may be laminar or turbulent. You may be interested in reading about the Heating element used in an electric heater. Blooteuth (talk) 14:06, 16 May 2017 (UTC)

Generally agree, but note that convection requires the movement of any fluid (usually a gas, liquid, or plasma), due to a thermal gradient, not necessarily air. Also note that the third major form of heat transfer, radiation, is also dependent on the shapes of the radiating and receiving bodies. StuRat (talk) 20:16, 16 May 2017 (UTC)

Is possible induction and convection cooling?--109.252.29.219 (talk) 09:34, 18 May 2017 (UTC)

It can be an absolute cyclone?--109.252.29.219 (talk) 12:20, 18 May 2017 (UTC)

Autopsies in the absence of a coroner's investigation

Back in this question about the death of Margaret Thatcher, I noted that as I saw it, there would be no reason for an autopsy in the absence of a coroner's investigation. I further noted that any such autopsy would require the consent of the next-of-kin; only a coroner can order an autopsy without their consent. user:Nunh-huh, whilst agreeing to my second point (autopsies, unless ordered by a coroner, require consent from the next of kin), said that "autopsies are certainly not reserved for the edification of coroners".

My question is: take, for random example, the United Kingdom. Half a million people die there every year. Obviously, if the death warrants a coroner's investigation (it's somehow possibly unnatural or untimely), an autopsy makes logical sense.

But in which of these half a million cases which do not involve the coroner, would an autopsy still be considered? Obviously, the next of kin would need to consent. But who would be making the request to perform the autopsy? And what criteria would they be using to decide which of those half a million bodies they should be dissecting?

(My question is a general one, in no way particular to Thatcher; it's simply that the debate happened in the discussion of Thatcher's death). Eliyohub (talk) 17:23, 15 May 2017 (UTC)

Just as an example: 80 year old dies at home, coroner releases the body, attending physician has no basis on which to conclude cause of death, or suspects an undiagnosed hereditary illness that may affect living grandchildren and advises an autopsy. Or a patient on a drug study dies and the cause of death is not certain. Or the lawyers want to sue for malpractice and want evidence. Anyone with an interest in knowing what killed someone might suggest an autopsy. Is this somehow mysterious? - Nunh-huh 18:53, 15 May 2017 (UTC)

Have a look here. Summary: Before the coroner is considered, the attending doctor has to decide whether they can certify cause of death and release the body. If the circumstances demand, they must inform the coroner (so you have these steps back to front). The coroner can decide whether the cause of death is obvious, and if it isn't can order a post-mortem.Phil Holmes (talk) 08:02, 16 May 2017 (UTC)

The original post on this subject was at the Humanities Ref. Desk which is more suitable for this continuation than the Science Ref. Desk. Blooteuth (talk) 14:11, 16 May 2017 (UTC)]

From my readings in the medical literature (a medical writer reads a lot of "the literature" as his physician clients do in order to document things clearly in light of existing knowledge about a condition), I can say autopsies are indeed performed in the United Kingdom outside of coroners' inquests, to increase knowledge of conditions where more knowledge of their direct effects on the body is useful in the treatment of the living. They are also sometimes (not always) done after a patient has died while receiving a new or investigational drug or other investigational therapy. Drug regulatory agencies require that in some cases. loupgarous (talk) 23:01, 17 May 2017 (UTC)

Feynman Lectures. Exercises PDF. Exercise 4-2 JPG.

I have tried to solve as Feynman suggested: png. But when I use another virtual displacement png, I get wrong answer. Why? For x and y weights we can put the pulleys as far as needed to make displacements infinitesimal.

Username160611000000 (talk) 19:12, 15 May 2017 (UTC)

And 2nd question: As I see, virtual work method doesn't show the direction of the forces, in contrast to force component method. Is it correct?

Username160611000000 (talk) 19:50, 15 May 2017 (UTC)

If one eats fruits and veggies without washing them or cooking them, then what is the likelihood of dying by acute illnesses and plant toxicity?

Or is that an easy way to commit suicide? Is getting an Entamoeba histolytica or Giardia intestinalis infection still possible in a relatively wealthy, developed country? 50.4.236.254 (talk) 23:44, 15 May 2017 (UTC)

E. coli exposure is essentially ubiquitous in manure-fertilized vegetables [3], but not all strains of E. coli are deadly, and some don't cause illness at all. Further, most infections resolve spontaneously, and the death rate is under 5%[4]. I imagine it would probably be higher if you refused treatment, but then many of the deaths are in vulnerable populations to begin with (children, the elderly). But good luck knowing what kind of fertilizer your food was grown on, and even then, it seems you're more likely to get an upset tummy than die. Entamoeba histolytica seems like a damn hard one to get infected with in a first-world country. Most people in developed countries that carry it got infected while traveling in a developing country [5]. The same is true of Giardia intestinalis, but new infections do occur in developed nations from person-to-person transmission [6]. Someguy1221 (talk) 00:01, 16 May 2017 (UTC)

• This is far to broad to be worth cognitive effort. Please stop posting every thought you have, and narrow your questions down to specifically answerable ones. Do you seriously expect us to list ever plant toxin and food-born pathogen? μηδείς (talk) 00:15, 16 May 2017 (UTC)

• Seconded. --Jayron32 01:42, 16 May 2017 (UTC)

Hmmm... Someguy1221 seems to have provided a sufficient answer. 50.4.236.254 (talk) 01:56, 16 May 2017 (UTC)

Someguy's mentioned not a single plant toxin, and three pathogens spread by fecal contamination that have nothing to do with plants per se. But if you are satisfied, mark it resolved. μηδείς (talk) 00:09, 17 May 2017 (UTC)

It seems more like a half-answer to me. At least I know that acute illnesses are more salient than plant toxicity. 50.4.236.254 (talk) 01:24, 17 May 2017 (UTC)

I somehow don't doubt that permanently dying by cyanide poisoning from improperly prepared cassava is worse than diarrhea. μηδείς (talk) 12:53, 17 May 2017 (UTC)

"Worse" is subjective. If one's intention is to die through mental disorientation than to die by upset stomach on top of mental disorientation, then death by cyanide poisoning (from eating cassava, cherry pits, apple seeds) may be the better option. 50.4.236.254 (talk) 23:29, 17 May 2017 (UTC)

Outbreaks of Giardia lamblia have occurred in Sydney, Australia, Oslo and Bergen, Norway through the water supply, so washing the veg during those brief outbreaks could have raised your chances of getting a nice dose of Giardia. Just sayin'. loupgarous (talk) 10:40, 16 May 2017 (UTC)

There are several peer-reviewed reports in the medical literature of chlorine-resistant cryptosporidium spread through water supplies in the industrialized world, several in the United States (Oregon, Milwaukee, and Arizona, among other places). Then again, crypto exposure was traced in at least one case (the Baker City, Oregon outbreak) to run-off from cattle pastures (stools from humans infected were positive for a subtype of Cryptosporidium parvum common in cattle, according to CDC researchers), which raises the specter of "organic" produce from acreage fertilized by cow manure possibly bringing a little crypto along for the ride to your market. As far as "easy ways to commit suicide", only if you're immunocompromised, and even then it's a crapshoot (no pun intended this close to a mention of cryptosporidium). loupgarous (talk) 22:26, 17 May 2017 (UTC)

See also Ergotism. Count Iblis (talk) 04:33, 18 May 2017 (UTC)

May 16

Death by Medicine

Is this a legitimate peer-reviewed article[7]?

I have my doubts because the site it's hosted on is fishy, and the figures in the article sound way too high. ECS LIVA Z (talk) 00:22, 16 May 2017 (UTC)

It is NOT a legitimate peer-reviewed article. see here 64.170.21.194 (talk) 00:59, 16 May 2017 (UTC)

Just read up on Gary Null. Basically, he's a quack (or at least a promoter and defender of quackery). --jpgordon^{𝄢𝄆 𝄐𝄇} 01:10, 16 May 2017 (UTC)

(edit conflict) See also our article on Mercola.com's head quack. It is not merely "fishy," it is absolutely untrustworthy and so is anything on there. If Mercola.com says the sky is blue, get your vision checked. Ian.thomson (talk) 01:11, 16 May 2017 (UTC)

Thanks, guys. ECS LIVA Z (talk) 01:27, 16 May 2017 (UTC)

While I agree that Gary Null is a quack, iatrogenesis is a serious concern. StuRat (talk) 20:09, 16 May 2017 (UTC)

Resolved

Skin-mole color relation

Does the color of the skin influence the color of the moles appearing on it as I just started to believe? Imagine if the person's skin color is cyan, would the moles on it tend to be in darker shades of blue? If it is true, melanin is a black pigment that produce brown marks on the peach skin but blue marks on cyan skin because the colors blend like mixing paint of different colors. PlanetStar 03:40, 16 May 2017 (UTC)

As you can read from that article, there are dozens of different kinds of moles, and each of them has a different mechanism; the color of one type of mole is different than, and may be controlled by different factors than, any of the other types. I'm not sure your question can be answered with any universal certitude. --Jayron32 12:22, 16 May 2017 (UTC)

I believe you have a mistaken assumption that melanin makes skin more of whatever color it is. Melanin (specifically eumelanin) is a brown or black pigment, never blue. There are other effects on skin color, though, such as carotene, which can turn the skin orange, or excess silver consumption, which can turn it blue-grayish. Blood shows through lighter skin, too, making it more red when flushed with oxygenated blood, or more blue when lacking oxygenated blood. StuRat (talk) 20:03, 16 May 2017 (UTC)

Spiked bulletproof surface

Does a spiked (or with multiple protrusions) surface better protect from bullets than the flat surface of bulletproof vests and the like? My understanding is that a bulletproof material with several tens or hundreds spikes from the same material (each several cm long) better dissipates the bullet energy, while the flat surface receives the bulk of it. 212.180.235.46 (talk) 12:54, 16 May 2017 (UTC)

Whether or not it is the case, how cumbersome would a bulletproof vest be if it was covered with "several tens or hundreds spikes . . . each several cm long"? Also, intuitively it would seem to me that the spikes might well disperse the force of an oblique impact, but an orthogonal impact would likely pass between them and strike the base material directly. {The poster formerly known as 87.81.230.195} 2.122.60.183 (talk) 13:12, 16 May 2017 (UTC)

The article Armour describes the improvements made to armour over history. The effectiveness of passive armour in any given material is increased when the length of the path for deceleration of a penetrating projectile is increased. This may be achieved by increasing the armour thickness or, notably in the design of military Tanks, slanting exposed surfaces which increases effective penetration depth by secant(a) where a = tilt angle to normal to the projectile's trajectory. A layer of spikes each several cm long can be a lightweight way to add thickness to armour but it is not necessarily more effective than using the same weight of material in a solid layer in which energy from a point impact spreads out. The most advanced form of armour suitable for fighting vehicles is Reactive armour. Blooteuth (talk) 13:45, 16 May 2017 (UTC)

Probably spaced armour is closest to what you intend. If I was going to use spikes I'd have them with the wide part outermost and working like a shaped charge - that might form an effective form of reactive armour but that's just my thoughts. Dmcq (talk) 08:58, 17 May 2017 (UTC)

project engineering, project management, project management office, construction management, commercial management, design engineer

I've read all the above articles but so confused. Can someone in simple Laymans terms explain briefly the difference between project management, project engineering, project management office, design engineering, commercial management and construction management? Are there explicit boundaries between them academically or does it just depend on the project? 82.132.221.211 (talk) 18:30, 16 May 2017 (UTC)

Many of these terms are used interchangeably and will have different roles, educational requirements and responsibilities depending on the size and scope of the project. While some universities have programs in project management or construction management that is not always the case. During a career an engineer or project manager may often do a number of these jobs. Here's my opinion on, in general, what each of these titles mean, but remember that there are no clear, universal delimitation.

Project Engineering-An engineer who leads a project. They would have some responsibility for schedules and budgets, but would also spend some time working on technical problems for the project. They would lead/help lead the engineering team if there is one.

Project Management-The project administrator. They handle or lead teams that handle schedules, budgets, ordering, coordination between departments, etc. Basically they make sure the project comes in on time and under budget. They are a main point of contact between the project team and the customer.

Project management office-Group or person who standardizes how a company runs projects. They decide what software will be used for schedules, budgets, ordering etc. This saves time and expense. They make sure records are kept so that if a new project is similar to an older one, you can reuse relevant forms, studies, maps or even vendor phone numbers for the new project. They should prevent reinventing the wheel.

Construction management-A project manager who specializes in construction projects, rather than a general PM who might oversee software development, a new car design, designing a building. A Construction Manager will often be on-site day to day at a construction site.

Commercial management-A person who finds projects for the other jobs in this list. They might also be called sales, business development, etc. They find new customers, identify projects to bid on and help develop the bid or proposal. They identify sub-contractors needed for the project or bid.

Design engineer-Any type of engineer who works on developing, prototyping or improving a new product. Some may jump from concept design to concept design, while others may develop a concept, prototype it and then support it once it's in production.Tobyc75 (talk) 20:36, 17 May 2017 (UTC)

Explosive Reactive Armour

I've heard stories where an occupying army (I think it was Soviet/Russia in this case) were patrolling urban areas with main battle tanks and infantry columns. The tanks were equipped with Explosive Reactive Armour. The resistance forces figured out that they could drop rocks from the top of buildings onto the tank and it would trigger the ERA and kill any near-by infantry. The Soviet/Russia forces were forced to remove all their ERA armor, in which case the tanks became easy pickings for RPGs due to their thin side and back armor.

Is there any truth to this story? Scala Cats (talk) 19:37, 16 May 2017 (UTC)

I am skeptical. Let's look at the components of the claim:

1) Soviet tanks use ERA. This is true. See Reactive_armour#Explosive_reactive_armour.

2) Dropping rocks from buildings sets it off. I'm doubtful that this would supply the required energy, unless it's more like a boulder and/or a rather high building.

3) The ERA detonation can harm nearby infantry. This is true, per our article. However, knowing this, it would be odd to deploy infantry alongside an ERA-equipped tank.

4) Removing ERA leaves only a thin layer of armor. This contradicts our article, which states: "Their use requires that a vehicle be fairly heavily armoured to protect itself and its crew from the exploding ERA." Of course, the elimination of the ERA will make it somewhat more vulnerable to anti-tank weapons.

Note also that there are other forms of reactive armor which solve this potential issue. StuRat (talk) 19:50, 16 May 2017 (UTC)

For point 3, I think this was back in the Soviet-era when ERA was still brand new technology, so it's plausible that they just didn't know any better. Presumably the Soviet commanders learned their lesson the first few times and would no longer deploy infantry around ERA-equipped tanks. Scala Cats (talk) 20:16, 16 May 2017 (UTC)

Those who tested it certainly would have known, but I can see this info not getting down to the infantry commander who tells his troops to shadow a tank for protection from small arms fire. The infantry commander may not even know the tank was so equipped. However, once they figured it out, removing the ERA seems like an odd choice ("Throwing out the baby with the bathwater"). Bringing in armored personnel carriers would make far more sense. StuRat (talk) 20:20, 16 May 2017 (UTC)

Concurring with StuRat But there seems to be a contradiction there or at least unexplained point. Why did the Soviets remove the ERA from their tanks? Your initial scenario seemed to suggest this was due to injury to infantry deployed near the tanks, but if the better solution was simply to be more careful with the deployment of infantry it would seem this would be something the Soviet commanders would realise before removing all their armour, even if they didn't appreciate it during initial deployment. Nil Einne (talk) 05:49, 17 May 2017 (UTC) Edit: 01:41, 18 May 2017 (UTC)

Understanding ammonia

Why is ammonia written with the more electronegative element first, unlike most binary compounds?? Georgia guy (talk) 20:50, 16 May 2017 (UTC)

Carbon hydride is written that way too (CH4) Sagittarian Milky Way (talk) 22:07, 16 May 2017 (UTC)

I thought CH₄ is methane (gas at room temperature). 50.4.236.254 (talk) 23:12, 16 May 2017 (UTC)

According to IUPAC, ordering by increasing relative electronegativity is just as acceptable as ordering alphabetically, although some specific compounds, especially binary compounds, tend to only be written one way. Someguy1221 (talk) 23:21, 16 May 2017 (UTC)

It's important to at least be consistent, or know the context for a chemical, or at least know the scope and audience of the situation. NaH and HNa both exist as distinct and very different chemicals, depending which atom is cationin vs anionic. DMacks (talk) 21:53, 18 May 2017 (UTC)

Methane would be the special name for "carbon hydride", as ammonia for "nitrogen hydride". These two are the only exceptions I could think of looking at electronegativity on the right side of the table -- note that water and hydrogen sulfide and hydrogen selenide are H2O and H2S and H2Se. But an exception also exists at least in the first document I looked at for tungsten hydride [8] -- note that its electronegativity in our table is slightly greater than hydrogen! -- and also gold hydride [9] -- gold has even higher electronegativity. (But only in the Pauling scale, not the Allen scale)

If I were to take an absolutely wild guess, I would speculate that at some point people gave in to the temptation to keep the formulas the same going up and down a row of the periodic table, and made some compromises against the actual electronegativity numbers. Or maybe those were just wrong long ago and the formula became too ingrained to change -- I don't know. This is a historical question really. Wnt (talk) 23:24, 16 May 2017 (UTC)

Indeed the group similarities are important here, and honestly the precise order is not so important. "Electronegativity" as construed here is not actual electronegativity (then where would He, Ne, Ar, and the superheavy elements be?); rather it is a sort of idealised order starting at group 17 and going down to group 0. The order goes down each group with H inserted between groups 16 and 15; the lanthanides follow after La and the actinides after Ac in atomic-number order breaking up group 3, so the "idealised electronegativity order" for labelling compounds according to IUPAC is F, Cl, Br, I, At, Ts; O, S, Se, Te, Po, Lv; H; N, P, As, Sb, Bi, Mc; ...; Li, Na, K, Rb, Cs, Fr; He, Ne, Ar, Kr, Xe, Rn, Og. Mind you, it is quite common to break these when making a point about trends, to talk about "PoH₂" or "F₂O". Double sharp (talk) 00:06, 17 May 2017 (UTC)

I tried to source this ... your phrase above got me better results. I came across this which points me to the Hill system (which is not used/relevant here), and this about the pseudo-electronegativity order. So it can indeed be blamed on IUPAC. Wnt (talk) 14:48, 17 May 2017 (UTC)

• The convention at work with hydrogens works a bit different. Usually (but not always; there are exceptions) acid hydrogens are commonly written first in a formula, while strongly bound hydrogens are written later in the formula. Since neither CH4 nor NH3 has any acid hydrogens, their hydrogen atoms are written later. Examples like acetic acid (H2C2H3O2) and water vs. hydroxide (H2O vs. OH-) are instructive here as well. --Jayron32 11:19, 17 May 2017 (UTC)

And "acidic hydrogen first" is in keeping with the idea that the less-electronegative atom in a simple ionic formula would likely be the cation vs the other part the anion. Jayron32, that acetic acid formula looks incorrect...regardless of order, you're missing one hydrogen atom overall. DMacks (talk) 21:49, 18 May 2017 (UTC)

May 17

WW2 bomb disposal

Resolved

A WW2 bomb was dealt with in Birmingham this week. Any idea what the device is that they've attached to bomb in this picture? http://i2.birminghammail.co.uk/incoming/article13042590.ece/ALTERNATES/s615b/bomb.jpg

Thanks! --TrogWoolley (talk) 09:54, 17 May 2017 (UTC)

An article says it is a clockstopper. The idea is to create a magnetic field that makes the gears of a detonation timer tilt and twist so the clock stops ticking. Search the web for "magnetic clockstopper", "bomb disposal clockstopper" and such. 91.155.195.247 (talk) 10:47, 17 May 2017 (UTC)

Thanks! I might not have read that article - there have been quite a few and keeping up with them has been difficult. --TrogWoolley (talk) 12:48, 17 May 2017 (UTC)

Hmm. Anyone want to add something about this device to the bomb disposal article? --76.71.6.254 (talk) 21:51, 17 May 2017 (UTC)

Lathe coolant

What is the composition of lathe coolant? If it gets on clothes, do they have to be dry-cleaned, or will ordinary washing get it out? 2601:646:8E01:7E0B:81C2:C457:D19E:177C (talk) 11:49, 17 May 2017 (UTC)

• They're oil emulsions, in water. So they're fairly easy to launder.

The HSE guidance is always good, but they are thinking mostly of industrial scales. http://www.hse.gov.uk/pubns/indg365.pdf Andy Dingley (talk) 12:21, 17 May 2017 (UTC)

Here is an MSDS for "machine coolant". It lists ingredients and known hazards. --Jayron32 12:29, 17 May 2017 (UTC)

• The MSDS doesn't really tell the story with machining coolants. There are several hazards, mostly chronic. It's a classic case study for occupational health workers.

Apart from the hazards listed on their linked page [10], of *amines and (very rare) cobalt, the worst hazard used to be mineral oils, and nowadays the worst acute hazard is bacterial. That MSDS doesn't mention either.

Mineral oils are a problem for skin absorption. They can cause skin dermatitis, they also manifest as bladder or scrotal cancer. Classic chronic exposure symptoms, these are due to long exposure and where the toxins remain concentrated for longest. This is largely avoided by regular laundry and provision of clean overalls (a requirement in factories), also plentiful drinking water and easy access to toilet breaks. Bladder cancers have been noted as worse in some sites, simply because toilets were a long way from the production floor, thus discouraging either their use or adequate drinking. Also mineral oils are mostly gone from today's cutting fluids.

Mineral oil in cutting fluid these days is mostly a contaminant, leaked in from lubricating oil.

The worst hazard, and the acute one, is bacterial contamination of the cutting fluid tank. This can show symptoms in a couple of days, if bad, especially for new workers who aren't inured to it. Keep the tanks clean and covered, use a bactericide (or UV light), check for contamination (oil too) and clean thoroughly if found. Andy Dingley (talk) 12:42, 17 May 2017 (UTC)

Do you have some references for that so we can all read about it? --Jayron32 13:03, 17 May 2017 (UTC)

• There's tons of this stuff out there - just search on whatever your particular specialisation might be. It's also enshrined (the provision of laundered overalls) in most industrial Occup Health legislation for developed countries. Here's one of the classic papers that established legislation in the UK, just because I happened to have this one handy. As well as machine tool operators, some textile trades had a similar problem with mineral oil aerosols.

Carcinoma of the Skin in Machine Tool Setters J. G. Fife British Journal of Industrial Medicine Vol. 19, No. 2 (Apr., 1962), pp. 123-125 http://www.jstor.org/stable/27721729

Andy Dingley (talk) 13:13, 17 May 2017 (UTC)

• The toilet stuff is from some of the British shadow factories during WWII. These were new factories, built with the latest modern conveniences and efficiencies (even though some were hidden underground). Workers, often newly recruited youngsters, worked on identical machines doing identical tasks, but in different factories. When investigated decades later (and the bladder cancer link was recognised), it was found that the only differences could be as small as better toilet facilities. Andy Dingley (talk) 13:20, 17 May 2017 (UTC)

Thanks, all! So, the bottom line is, I won't need to have my Levis dry-cleaned after all? 2601:646:8E01:7E0B:FCD4:1102:5887:1AF8 (talk) 09:17, 18 May 2017 (UTC)

Ordinary washing will solve this like any other dirt. 95% will be washed out and the remaining 5% will be evenly spread over all textiles in the washingmachine. To add the illusion of tidy cleanness some chemicals for bleaching and for perfume are evenly spread over all textiles aswell. --Kharon (talk) 15:38, 18 May 2017 (UTC)

You should get far more than 95% removed. Andy Dingley (talk) 17:30, 18 May 2017 (UTC)

May 18

End mill

Can End mill be used to drill holes? The article says "milling bit can generally cut in all directions", so presumably the answer is yes, but I just want to double-check.

(The second half of that quote is "though some cannot cut axially", so it's clear that not all end mill can drill. I'm wondering if any end mills can drill at all.) Scala Cats (talk) 02:13, 18 May 2017 (UTC)

With huge limitations if they have one of their frontal cutting teeth extend over the middle/rotary center of that tool (as you can see on the picture of the article). They are meant to slowly dive into material for just a few millimeters so they can start cutting a Groove, a pocket or alike inner forms without the need for more complicated, timely methodes like milling a path "down" with a slope. --Kharon (talk) 08:32, 18 May 2017 (UTC)

• What are "holes"? Do you need them accurately to size? Good surface finish? Deep and narrow?

An end mill has three obvious shortcomings over a drill bit: it has no ability to centre or guide itself, it has limited swarf clearance upwards and it may not remove any metal from the centre of the bit, when used axially (so can't simply be plunged).

End mills are used for holes, but usually by milling them. An end mill smaller than the finished hole is moved in a circular path, milling a progressively deeper hole as a pocket. Compared to the forces involved with a twist drill, you need a more rigid machine to gain a similar rigidity in the tool (drill forces are largely balanced). Also the "drilling" speed will be much slower. But it does work, and if you're CNC milling on a machine that doesn't have rapid or automatic tool changing, it's done a lot. Andy Dingley (talk) 17:35, 18 May 2017 (UTC)

What happened in AHA guideline in 2015 regarding to the definition of children age?

Till 2015 the definition of child for CPR, was 1-8 year, but in the end of 2015, AHA published updates and there (see p.11) it redefined it as "Children- Age 1 Year to Puberty "). The thing that interesting is that for all updates there are explanations except of that significant update (it may be a difference of 4 and more years...) that doesn't have explanation. Do you know what is the explanation behind this new definition? 93.126.88.30 (talk) 05:40, 18 May 2017 (UTC)

One of my trainers said it was because it's easier to assess. Not so much that it is important to get the "right" details for someone who is 10 depending on how developmentally mature they are, but that is more efficient to gauge a victim by appearance than to ask the age and saving time in this situation is an actual benefit. DMacks (talk) 21:43, 18 May 2017 (UTC)

Homogenous packaged, pre-cooked food

Dogs and cats are usually served homogenous packaged, pre-cooked food, and they get all their nutrition from that. Meanwhile, humans, afaik, have to eat various foods in order to have complete nutrition. Is there a homogenous, packaged, pre-cooked, nutritionally complete, safe (as in not inducing acute illnesses) food product for humans who don't mind eating the sane thing every day? Can humans eat dry kibbles? Or should they eat something like wet dog food with more vegetables? 140.254.70.33 (talk) 13:19, 18 May 2017 (UTC)

There isn't - because pretty well all humans do mind eating the same thing every day. The nearest you would find would be some of the emergency rations issued to the military, or used in famine relief - but even those have some variety to them. There would be no particular problem producing something containing everything needed by the human body - but I can't see anyone actually doing it as there wouldn't be a market for it. Wymspen (talk) 13:27, 18 May 2017 (UTC)

Actually, the product does exist — nutraloaf — and there is a market for it — prisons. But the above is correct that it's not likely to be viable or available as a product in a standard grocery store. See also the humanitarian daily ration. — Lomn 14:11, 18 May 2017 (UTC)

Soylent_(meal_replacement), is probably the closest to what you're looking for. Their marketing tries very hard to imply that you could use it as a 100% substitute for all food. They don't actually make that claim, though. (And I'm personally very dubious about that company's safety record.)

Some emergency rations also claim to be nutritionally complete, so I suppose instead of stocking them in your bomb shelter or lifeboat, you could just eat them regularly. I doubt your doctor would recommend it, though.

ApLundell (talk) 14:19, 18 May 2017 (UTC)

Oh, of course Soylent did not invent the concept of a Meal_replacement, there are other brands. They're just not as aggressive in their marketing so far as implying that you could give up real food forever. ApLundell (talk) 14:27, 18 May 2017 (UTC)

(EC) I actually regularly give my mum a meal replacement drink (in addition to normal food, she has had low weight issues in the past and for various reasons can be quite slow at eating), and it specifically says it's not intended as a total diet replacement. Actually two different brands of pretty much the same thing say that. Our article also notes that in the EU there's actually a regulated difference although this is only for weight control products and they have to say they can't be used for more than 3 weeks without medical advice. So it actually quite a different marketing strategy. However I don't believe Soylent is the only one with such a strategy, maybe just the first. There seems to have been a wave of them recently perhaps inspired by Soylent, e.g. Huel, Mana (drink). I'm not even sure if Soylent is universally the most popular, considering the possible problems of shipping food from the US. See also [11]. I believe there are also some products which predate these, which may be used with feeding tubes or people on a Liquid diet but these are generally very expensive (I've seen commentary from people comparing the price of Soylent etc to the price of these products) and aren't aren't marketed to the general public. They also aren't necessarily recommended long term (especially very long term). Nil Einne (talk) 14:57, 18 May 2017 (UTC)

I think I encountered "Ensure" a long time ago (one of the ones on that list) and didn't find it unpalatable at the time, though its goal of providing calories was not really useful to those of my particular shape. But ever since Guantanamo officials became famous for delivering it rectally (recap) I'm afraid I would look at it like drinking an enema. Their former habit of running commercials with a pseudo-military cartoon character talking about "nutrition in charge" did NOT help with this. Thanks to Gitmo their brand is pretty much irredeemably tarred, even if not by any fault of their own... Wnt (talk) 16:14, 18 May 2017 (UTC)

Since no one has mentioned it so far, the other area that one gets meal replacements is in the care of persons who have difficulty eating normally. For example, cancer patients undergoing chemotherapy often have digestive problems that limit what they can practically consume. A number of brands exist to sell liquid meals (e.g. shakes) to ill people who have trouble eating and/or digesting solid food (e.g. Prosure, Fresubin, etc.). They aren't generally marketed as a permanent solution, but they do aim to provide complete nutrition for a while. Dragons flight (talk) 14:46, 18 May 2017 (UTC)

Huel, which was mentioned above, say on their site that a tiny percentage go 100% (i.e. no other food). Henry^Flower 19:04, 18 May 2017 (UTC)

I had a tracheotomy a while back and I was on liquid glurge (technical term) for several weeks in the aftermath of that, initially by tube and then when the trachy came out that was all I could 'eat'. I think the deal was I was supposed to drink 6 small cartons a day, in practice I couldn't manage half that. Greglocock (talk) 19:53, 18 May 2017 (UTC)

Do any wild/feral animals know what traffic lights or walk signals mean?

Because they know what they know what the light means and not because they just follow the people or learned that when cars stop on busy streets they don't start again for awhile or detect the light changing mechanism's ultrasound or magnetic fields or something like that. Sagittarian Milky Way (talk) 14:33, 18 May 2017 (UTC)

Not as a rule, but on Jamaica I was told that some wild goats did not even observe the traffic signals, but had even learned to request a green light at on-demand traffic crossings. --Stephan Schulz (talk) 14:47, 18 May 2017 (UTC)

That's pretty cool. Sagittarian Milky Way (talk) 17:53, 18 May 2017 (UTC)

Looks to me like he asked an interesting question and got an interesting answer. Take any meta stuff to the talk page or wherever
The following discussion has been closed. Please do not modify it.
At what point, SMW, are you going to stop using the desks for validation of every random thought that enters your head? --Jayron32 14:49, 18 May 2017 (UTC) Hatting this. Wnt (talk) 16:17, 18 May 2017 (UTC) I am sorry Jayron, I did not intend to imply that I want people to tell me they know what traffic signals mean to validate my random thought. I don't know if any such smart animals exist or not and would not be reduced to tears if no one could find any evidence. I am aware that unless it's very conditioned an animal wouldn't give a fuck what the traffic laws are if it thinks the traffic is light enough it can cross without too much trouble. I have made this clearer in the question. Sagittarian Milky Way (talk) 17:53, 18 May 2017 (UTC)

Who would notice? People do however notice cats that ride buses. [12], [13], [14]. Also ditto Jayron. Aspro (talk) 15:06, 18 May 2017 (UTC)

I've seen a pigeon ride a train. And get off the next stop. Sagittarian Milky Way (talk) 17:53, 18 May 2017 (UTC)

the reason that pigeons ride on trains as as passengers, may be due to them beginning to fill the niche left by the extinction of the Passenger pigeon Aspro (talk) 21:36, 18 May 2017 (UTC)

Obey is maybe not the right word, but ravens certainly know how traffic lights work. Cheers ✦ _hugarheimur 15:30, 18 May 2017 (UTC)

I agree. Know that they'll likely get harassed by traffic if they cross on red, not obey. (or whatever color a stop light looks like to their eyes) Sagittarian Milky Way (talk) 17:53, 18 May 2017 (UTC)

There are plenty of humans who don't obey traffic signals either. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:37, 18 May 2017 (UTC)

Original research, a couple of weeks ago in London, but I saw an urban red fox cross a busy road at some pedestrian traffic lights. He didn't wait for the little green man though. Alansplodge (talk) 17:15, 18 May 2017 (UTC)

Some years ago, before the great Bristol urban fox die-off (a distemper outbreak), there was a particular junction (Zetland / Gloucester Road) where foxes could often be observed crossing. They also showed regular behaviour of waiting for the pedestrian light before crossing. There's no indication that they had any relation to the signals, but they obviously recognised stationary traffic on this busy road (even late at night) as being regular and worth waiting for. If you were lucky, you could even wait alongside one - they were very urban foxes. Some of the local students were quite feral though. Andy Dingley (talk) 17:40, 18 May 2017 (UTC)

In general, there are two types of animals which cross roadways: (1) the quick; and (2) the dead. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:58, 18 May 2017 (UTC)

I am getting increasingly frustrated by people leaving answers to ethology-based questions when they apparently have little grasp of the way such studies should correctly analysed and interpreted. Please make yourselves familiar with Morgan's Canon and Occam's razor as a starting point.

In answering the OP question, I would want to see a video/study in which the animal is proven to be watching the lights. In all the studies I have seen, the animal (mainly ravens) are observing the consequences of the lights changing (traffic moving, pedestrians walking) rather than watching the lights. It would also be interesting to know whether the animals can actually perceive the wavelengths emitted by the lights - see Trichromacy.

As stated in the goat example, the goats do not observe the lights themselves. The have probably learnt to press a button by stimulus enhancement from other goats or humans. DrChrissy ^(talk) 23:33, 18 May 2017 (UTC)

condensed climate chart

I love reading about various locales on Wikipedia and checking out their climate charts, but the full spectrum of information available in a climate chart is a little too much to digest. I mostly just focus four items: average high, average low, average precipitation, percent possible sunshine.

Is there a some kind of metric/formula that condenses the monthly climate data of a given location into a single number? As in, a single number that measures how "comfortable" the place is for people? Not too hot, not too cold, minimal precipitation, maximum sunshine, etc.

Is there a website that I can easily look up this metric on a map, say for vacation planning purposes? Scala Cats (talk) 19:57, 18 May 2017 (UTC)

See Degree day#United States. This measure used to be used, and I assume is still used, by Places Rated Almanac. Loraof (talk) 21:48, 18 May 2017 (UTC)