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April 25

Matching a light source to a solar panel

I'm hoping someone can help me. I'm trying to make up a simple set-up to recharge a lot of solar powered decorative strings of lights. They each have a solar panel about 60 mm by 60 mm charging two AAA batteries. I'd thought that just putting them all under a light bulb would work, but now I realize that I might have to use a special kind of bulb that puts out the same light spectrum that the solar panels use. I can't find out much about what type of light these panels work best in. I'd appreciate any links or information anyone can give me. Thanks in advance 49.197.192.93 (talk) 03:26, 25 April 2018 (UTC)

From a little searching, it looks like anything that puts out visible light should work well enough. Sure, you might be able to increase efficiency a bit with very finely tuned light sources, but it sounds like that wouldn't be worth the time or money given what you're doing. Sure it's not better to just remove the batteries and charge them with a charger? You can find battery chargers that take lots of batteries at once. Or are the batteries not removable? Another suggestion is that, if this is something you do often, it might be worth it to wire charging plugs into the strings. Since they're battery-powered, this is low-voltage wiring: just add in DC plugs and get a suitable power supply to plug them into. --47.146.63.87 (talk) 04:24, 25 April 2018 (UTC)

(OP) Thanks for those thoughts. Taking the batteries out involves undoing 4 tiny screws, and we usually have 9 different strings on display in a market stall then need them recharged for next day. I hadn't thought of putting a charging plug into each one, that might well be the answer. I'll wire an ammeter into one of them and do some tests under an ordinary light bulb first.49.197.115.7 (talk) 06:44, 25 April 2018 (UTC)

An alternative would be to forget the batteries and solar chargers, and just wire the lights to a low voltage DC supply (probably 3v if the units use two 1.5v batteries). I've done this successfully with some of my solar lights. One good DC supply should run them all because the current will be small. It doesn't have to be smoothed, so a cheap mains transformer with a single diode on the output might suffice, though full-wave rectification might be better. Dbfirs 07:07, 25 April 2018 (UTC)

(OP) I've just hooked an ammeter into the battery circuit, and the lights use about 30mA when running. Late afternoon sun square on to the panel puts in 35mA, and putting the panel up very close to a selection of light bulbs gives 10mA at most. (So close that the solar panel gets quite hot very quickly). I need to display them pretty well exactly as a customer might buy them, so the charging socket idea seems the best one yet. 49.197.119.149 (talk) 06:45, 26 April 2018 (UTC)

What animals eat feces as a normal behavior?

I've read the following paragraph on educalingo site: "Coprophagia /kɒp.rə.ˈfeɪ.dʒi.ə/ or coprophagy is the consumption of feces. The word is derived from the Greek κόπρος copros, "feces" and φαγεῖν phagein, "to eat". Many animal species eat feces as a normal behavior; other species may not normally consume feces but do so under unusual conditions. Coprophagy refers to many kinds of feces eating including eating feces of other species, of other individuals, or its own, those once deposited or taken directly from the anus.". I'd like to know what animals most familiar with this phenomenon. I've heard about pigs something like that but I'm not sure. 93.126.116.89 (talk) 04:07, 25 April 2018 (UTC)

Have you read our Coprophagia article? Note that you're posting on Wikipedia, not Educalingo. That article gives many examples of animals that do so. What do you feel is not adequately discussed in that article? --47.146.63.87 (talk) 04:12, 25 April 2018 (UTC)

What is a "det. officer?"

(Moved to the Humanities Desk as per the original poster's intent. It's been answered, but it might as well be archived in the right place. --69.159.62.113 (talk) 00:31, 26 April 2018 (UTC))

Does Beano raise the effective glycemic index of beans?

I assume most people know that Beano is a product intended to allow you to eat beans (and some other foods) without experiencing certain inconveniences, or at least reducing them. According to our article, it works by breaking down oligosaccharides into simple sugars.

So does this raise the effective glycemic index of those foods, and if so how much? Is it a situation of "you thought you were being virtuous by eating beans, but to your pancreas, they look like ice cream"? --Trovatore (talk) 20:51, 25 April 2018 (UTC)

As you no doubt suspect, it will increase the digestibility of certain foods. This will possibly raise the glycemic index by losing fewer carbohydrate molecules to farts. Abductive (reasoning) 06:19, 26 April 2018 (UTC)

Thanks for responding, but I was hoping for something more substantive than "possibly", which I could figure out for myself. Any actual data or studies? --Trovatore (talk) 07:14, 26 April 2018 (UTC)

I once read a study of the calories lost to flatus (generally), but have been unable to find it again. Google is probably accidentally censoring it. Sorry. Abductive (reasoning) 23:19, 26 April 2018 (UTC)

I doubt "calories lost" is the key issue here. The point is that the oligosaccharides would be taken up more slowly than the simple sugars the enzyme breaks them down into. So the prompt response in blood sugar (and insulin) might be greater if you have the Beano, even if total calories eventually absorbed are about the same. That's the effect I was trying to find out about. --Trovatore (talk) 23:46, 26 April 2018 (UTC)

You are one of the top ten experts in this field, if one measures by characters typed. Abductive (reasoning) 03:44, 27 April 2018 (UTC)

????? I see plenty of discussions/speculation on this and related issue elsewhere [1] [2] [3] [4] [5]. Beano themselves while not really dealing with the glycemic index issue mention "As a result, it has been estimated that the use of beano® will produce an additional two to six grams of carbohydrates for every 100 grams of food treated by beano®." There is also the paper I highlighted below. I see zero reason to think the minor comments here somehow make them "one of the top ten experts in this field, if one measures by characters typed." Nil Einne (talk) 10:04, 27 April 2018 (UTC)

One assumes that people have already searched for sources before posting their question. And reading those sources only confirms my suspicion that this discussion is as advanced as any held anywhere in the world, ever. Abductive (reasoning) 21:01, 28 April 2018 (UTC)

Your reply makes absolutely zero sense. Of course a good OP would have searched before asking. They also failed to find something that's why they're asking. And your comment makes zero sense. I did not claim these are even close to the best discussion held. There is zero reason to think they are. For starters, they completely missed the first RS I found below. Second, discussions held in forums are rarely great sources. When searching for answers, I frequently comes across crappy discussion threads. Sometime they are similar to those here. Rarely they are better than those here. How I often also find decent RS which have been completely missed by many of the discussions. The presence of a bunch of not very good discussions is no reason to think that they are the best. (And IIRC some of those sources considered stuff not yet mentioned in this thread anyway.) I guess you're new to the internet, but that's simply not how the internet works. A lot of the internet is full of terrible quality discussions. Sorting the wheat from the chaff is one of the key reasons why the RD exists. Another reason is to provide quality sources, often reliable sources which internet discussions aren't. Reliable sources were specifically requested in this thread, so I did not spend a great time trying to find quality discussions other than to look for RS. I didn't spend a great time looking for RS either since I'm only mildly interested in this. This is clearly something that people have considered before, enough so that someone actually did a placebo controlled examination of the effect of beano on postprandial glucose concentration. There is no reason to think anyone in this thread, is anything close to an expert or has considered this at anything close to the level considered before. I mean I'm guessing no one in this thread knew of the source below until I found it either and while it doesn't directly deal with glycemic index, it's fairly related. Nil Einne (talk) 22:36, 28 April 2018 (UTC)

I remember now that the beano FAQ response is one thing that was mentioned in one of the discussions. While true it's only of limited relevance to the question, I wouldn't say it's completely irrelevant and I also wouldn't be surprised if no one here knew of if until I brought it up. Many of the discussions I linked to are both highly flawed (I think one of them possibly even conflated alpha-galactosidase that beano provides and alpha-glucosidase that acarbose inhibits), and yet contain limited new info, as is common with such things including in cases where we can be sure there have almost definitely been informed discussions somewhere. To be clear, I'm not trying to blow my trumpet here. My sole point is that with my tiny about of research, I've uncovered stuff that probably wasn't know to anyone in particular the OP. It also fairly likely that someone who is an actual expert in related areas is likely to be able to come up with a far more informed discussion. (With no disrespect intended to the OP, their background makes me thing they are quite far from an expert in areas for which experts obviously do exist and who would likely to be able to understand this issue far better without having specifically studied it.) Especially if multiple experts in different areas collaborate. Whether this has happened I have no idea, but I also know it can't be ruled it. (By collaborate here I'm mostly not thinking of some sort of scientific collaboration. It could be some people worked together to write answer a question in some newspaper column. It could be it came up over dinner for some reason and they talked about it.) Ultimate point being the idea the OP was an expert in this particular issue, or this discussion was somehow highly informed on the issue compared to discussions that may have taken place all over the world (some of which could be documented no where) is unsupported, and very unlikely Nil Einne (talk) 23:20, 28 April 2018 (UTC)

I completely agree. I am no sort of expert on this question. However, if you don't mind, I am in fact a singular individual, and therefore prefer not to be referred to in the plural. --Trovatore (talk) 05:57, 1 May 2018 (UTC)

But wouldn't someone who has so much gas complaints that he/she wants to use this have slower absorption of these sugars to begin with compared to normal people? Count Iblis (talk) 02:14, 27 April 2018 (UTC)

I came across this small placebo controlled study [6]. It didn't deal with the glycemic index but did look at the effect on postprandial glucose concentration (as well as appetite). The interaction between beano and acarbose may also be of minor interest [7]. Nil Einne (talk) 10:04, 27 April 2018 (UTC)

My indenting was totally fucked up by another editor here [8]. I've fixed it. Hopefully no one was confused in the mean time. Nil Einne (talk) 22:36, 28 April 2018 (UTC)

BTW, although you can get this even from the abstract or heck even the title ('Not Their Glycemic Response'), for the benefit of the RD I might mention the study found beano (called α-Galactosidase but the details mention they used some form of beano) had no statistically significant effect on postprandial glucose concentration for any of the meals tested, suggesting it possibly does not effect glycemic index. Of course far from proving it, especially given the tiny sample size of 12 people. (Admittedly this isn't the kind of thing you're likely to get the kind of funding to do a decent sample size test.) And this also contradicts the findings of the acarbose study. However we don't know the reason for that result. E.g. was it some sort of interaction between the activities of the two? Could it be it's something that only occurs in diabetics? Nil Einne (talk) 23:20, 28 April 2018 (UTC)

Realised I forgot to mention probably the most significant reason namely it was simply a statistical fluke. Nil Einne (talk) 15:14, 29 April 2018 (UTC)

Thanks, Nil, for an interesting link. --Trovatore (talk) 01:01, 1 May 2018 (UTC)

Statics: Which zero-force member can be removed without reducing structural strength?

I find it difficult to figure out this kind of problems. Can you name some simple rules? 161.185.160.21 (talk) 21:20, 25 April 2018 (UTC)

Our article is at Zero force member. Perhaps all of them can be removed. However if the loading is changed they would not be a zero force member any more. Graeme Bartlett (talk) 21:58, 25 April 2018 (UTC)

April 26

Mass of entropy, and so on

Entropy is a genuine source of energy. For example, the proton gradient in the mitochondria really does power the cell and keep us alive. But at a simple level, it seems very mysterious...

• Suppose I have two tiny evacuated chambers, linked by a pore, that contain a total of three helium atoms. There is only one way for all three to be on the left, but there are three ways for one to be on the right and two on the left. So there is an entropy of k_B T ln 1 in the first case = 0 and an entropy of k_B T ln 3 in the second case = (0.0000862 eV/K)(300K)(1.10) = 0.0284 eV at 300 K. By analogy with a mitochondrion, this gradient could be tapped at a gate in the pore to transfer that energy to some chemical reaction or mechanical process.

• I think the entropy there relates to Landauer's principle in that one bit of information has a negative energy value of k_B T ln 2 = 0.0179 eV. Putting one of the three atoms on the far side can be done three ways, generating, it would seem, (k_B T ln 3)/(k_B T ln 2) bits of information. I'll admit, I would have thought the choice of 1-in-3 would be 1.5 bits (1 bit if you choose A, 2 bits if you choose B-or-C, then B or C) but this works out to 1.59 bits, not sure why. It would appear that generating information creates energy out of thin air, though I would assume the total mass of the entire set of evacuated chambers and contents never varies.

• A basic Carnot heat engine would appear to work by equilibrating the lone helium atom at T_H, which then crosses the pore to generate usable energy of k_B T_H ln 3; it then is cooled to T_L before it crosses back to consume usable energy of k_B T_L ln 3. Heating and cooling the actual atom will transfer 3/2 k_B (T_H - T_L) of heat energy. The efficiency, therefore, is ... erm, well, I'm getting (2 ln 3)/3, which surely isn't right. That calculation seems maddeningly close to making sense.

• But if we have no gate in the pore, where does the energy go? The atoms will be on the same side 25% of the time, and opposite sides 75% of the time. Being at 300 K, each atom on average has 1/2 kT = 0.0129 eV of energy per degree of freedom, so I take it they have 0.0388 eV of total kinetic energy on average. If the entropy of being on opposite sides adds to the kinetic energy of the atoms, that would imply that they are moving much faster whenever they are apart. Does that make sense? Is there some force that can be described as?

• But how small does the pore have to be? Could the three atoms be in a simple spherical chamber where you might simply measure which side each is closest to? Do they still have higher energy when they happen not to be on the same side? Can you do that dividing top-vs-bottom, left-vs-right, front-vs-rear??? Since the energy depends on information I suppose it depends on which way(s) you are actually measuring the atoms, and this necessarily perturbs them?

• Now the amount of entropy from a single bit of information at 300 K is a whopping 0.0179 eV, which may seem small, but is huge compared to the possible masses of neutrinos at 10-4 eV or less. Simply knowing a neutrino exists, therefore, should create a bit of information. Is that factored into the neutrino's mass already? Does learning of the existence of a neutrino add to its momentum like those helium atoms above, causing it to massively accelerate? Can you do this with, say, an entangled neutrino by learning about the other particle created by a reaction? Is the "temperature" for this entropy determination going to be determined solely by the neutrino's KE, or something else, i.e. is there a way to erase information about a stationary neutrino and leave it with a negative overall KE?

Any low-level example of this sort you might care to raise should be useful for understanding... Wnt (talk) 07:04, 26 April 2018 (UTC)

I think the important point to make is that information is not a substance, any more than caloric is. Reducing the disorder of a system can be described as "cooling" or "adding information", but in neither case is anything physically added or removed from the system - only the energy distribution of the system's components is changed. See Gibbs free energy as a starting point for the actual calculations required in these cases. Tevildo (talk) 07:50, 26 April 2018 (UTC)

That's what I was doing above - taking T delta S to figure the delta H. Caveat being that at the individual particle level "T" is the energy in each degree of freedom of one particle, and "H" is energy that could be extracted at a gate, if one existed. (True, I was simply dumping that work back into the particle as heat in the 4th point above) Wnt (talk) 11:44, 26 April 2018 (UTC)

• Sorry, but all that is not even wrong. A careful reading of our article entropy might or might not clear what confusions you may have (that is one of our best articles in the topic, but it is still quite a hard read).

Pay attention in particular to the fact that temperature and entropy are statistical concepts: they apply only to systems with a large number of atoms. You can compute an "entropy by atom" or similar by dividing the system entropy by the number of atoms but it does not mean that that entropy is held by a single atom in any meaningful sense. Tigraan^{Click here to contact me} 12:18, 26 April 2018 (UTC)

Per Tigraan, entropy is an emergent property of a system; the entropy of a system of atoms divided by the number of atoms does give you a number, but that value is different than the entropy of a single atom in isolation. The number of distinct states of a system depends on the relationships of particles in that system. Similarly, the temperature of 1 atom is a meaningless concept. Temperature is a mass property of a system of a large number of particles. A single particle has no meaningful temperature. Also, the OP is confusing thermodymic entropy with information theory entropy. Entropy in thermodynamics and information theory discusses the difference, at a very abstract level, the limit of informational entropy is thermodynamic entropy, but to say that the information about a particle adds mass to it is beyond silly. It is broadly true that information-as-negative-entropy has some thermodynamic meaning in that somewhere, there must be some system that you remove entropy from to store information, with the caveat that information is not stored in the same system as the system it is describing (that is, information about a neutrino is not stored in a neutrino!) Also, entropy mass, as such, is just the mass of heat energy; that is the energy a system has from its random thermal motions, if you cool a system down it loses mass; that lost mass is the "mass of entropy". --Jayron32 12:42, 26 April 2018 (UTC)

@Jayron32: I'm sorry, but what I take from Entropy in thermodynamics and information theory seems almost directly opposite to what you say. There is an ln 2 conversion factor between the Shannon entropy h and the physical entropy S, but that's in the formulae I use above. They give an example there of a single particle in a box with partition being used to provide work to two pistons, which therefore must acquire relativistic mass.

I will admit that there is something to this "emergent property" bit that I don't necessarily understand, which is the meaning of the temperature of a system. If I have three particles at a given temperature, does that mean that the average energy per degree of freedom works out to yield that temperature by the Boltzmann constant, or does it mean that they are in equilibrium with that distribution of energies so that their summed KE's are necessarily not conserved? I'm not sure I can have information about an isolated system, because if information is energy, my knowledge of it means the system is not isolated???? Wnt (talk) 14:24, 26 April 2018 (UTC)

I found a paper on a single-particle Carnot cycle at [9]. But it is ... formidable. I am not sure how much of the complexity is truly essential to understanding, as I certainly do not at this point. I note very superficially that it has a graph of temperature for anywhere from 0 to 1000 particles in a simulated system. Wnt (talk) 14:40, 26 April 2018 (UTC)

There are two very different types of questions that need to be answered here, and I feel we're at cross purposes. The two questions are 1) Can you calculate X and 2) Does X have any useful meaning? Clearly, you already know the answer to 1) You've made calculations and gotten numbers. What Tigraan and I are trying to tell you is that 2) is more important here. Any of these values can trivially be reduced to 1 particle systems. But what does a temperature of a 1 particle system tell you about that system? What real, physical, actual thing is such a system supposed to model, or what application do I have for it? That's what Tigraan meant above when he noted "You can compute an "entropy by atom" or similar by dividing the system entropy by the number of atoms but it does not mean that that entropy is held by a single atom in any meaningful sense." The entire system of thermodynamics breaks down when you try to consider 1-particle systems. A 1-particle system isn't a thermodynamics problem, it's a dynamics, problem. That is, we've reduced our system to where we can analyze it's behavior as we can with any other single object (or small number of objects) which are colliding and interacting. The whole point of thermodynamics is that large systems of interacting objects produce behaviors which are predictable and modelable without reference to the individual motions of the particles, and that one can understand how the system works without ever needing to understand how any one particle works. Once you've gotten down to looking at the one-particle situation, sure, you can trivially do thermodynamic calculations on it, and its a fun academic exercise, but so what. --Jayron32 14:58, 26 April 2018 (UTC)

This is a learning exercise. I don't understand entropy well enough, so I was thinking if I can work out a direct correspondence, I'll get a better knowledge of what it means. I still don't understand where the energy would come from if splitting up the three particles on one side of a chamber actually does release it due to entropy. I still don't understand whether creating a lot of new information can create mass-energy from nothing like some new variant of steady state theory, or whether it is conceivable to move information from some high-temperature source into a very light structure that would have negative mass and so on. So if this is a "trivial" exercise, please, by all means lead on! Wnt (talk) 23:50, 26 April 2018 (UTC)

If you're trying to understand entropy in a general sense, take the numbers out for a minute. Just look at it qualitatively: consider that you have 2 particles and are trying to use the 2 particles to move a 3rd particle to the right. Moving an object in physics is what is called work (physics). Now, imagine the 2 particles are moving at the third from the same side, and both hit it to the right. Now, that third particle will start moving in that direction. Your two particles have done work on the third. HOWEVER, in order to do that, you need to assure that the striking particles are always hitting the target from the same side. If the two particles are moving about randomly, in all sorts of directions, with no overall motion in any one direction, the sum total of all of their hits will result in no net motion of the target particle. The total energy of the system (that is the energy of all of the particles) is the same in situation 1 (concerted motion produces work) as in situatiomn 2 (random motion does not produce work). The difference between 1 and 2 is called "entropy". All entropy is is the difference between the total energy of a system and the actual energy used to do work. Of course, being energy that energy has an associated mass, but entropy is inherent to the system and because of that, you can't take the entropy out to find its mass effect on the system; you can calculate that number, but it has no physical meaning. The mass of the total energy in situation 1 is still the same as in situation 2. Entropy is not contained in any of the particles, and cannot be parted out physically, it is just a way to represent the notion that there can be energy in a system which is unavailable to do work. --Jayron32 14:24, 27 April 2018 (UTC)

@Wnt: Be sure to read Jayron32's post above, as that is a concise yet almost accurate of what entropy represents. I have a small nitpick about it (hence the "almost"), but be sure to understand the post before reading the nitpick.

Ok, here we go. The problem is that the sum total of all of their hits will result in no net motion of the target particle is only true in an average sense. Statistical physics only apply to large number of particles; in a three-particle system, entropy (as defined by information theory formulas) can increase by random deviations and you can extract work from a single-temperature source cycle (the average over many cycles will have nonpositive work, but you will see single-cycles where work is positive); however, the probability of such random deviations decreases exponentially with the number of particles involved. The second principle is basically the assumption that we never see improbable deviations in many-particle systems (under certain tedious hypotheses that are not worth mentioning here). Tigraan^{Click here to contact me} 15:11, 27 April 2018 (UTC)

Yes, I knew that inaccuracy, but was trying to contruct a simple, visual model to display entropy. Thanks for expanding on it with the corrections! --Jayron32 16:36, 27 April 2018 (UTC)

You should take serious what Jayron and Tigraan are saying here about how thermodynamics arises. If you are very careful about deriving the thermodynamic formulas of entropy of simple systems, see e.g. the book by F. Reif, you'll see that it depends on the level of coarse graining that you need to introduce. For an isolated system we introduce a function $\Omega (E)$ which counts the number of energy eigenstates between energies $E$ and $E+\Delta E$. Then $\Omega (E)$ will be proportional to the parameter $\Delta E$, but entropy needs to be defined as being proportional to $\log \left(\Omega (E)\right)$. In the thermodynamic limit where we consider the limit of infinitely large systems and consider the specific entropy, the choice of $\Delta E$ doesn't affect the result.

But for finite systems, the entropy will get a contribution proportional to $\log \left(\Delta E\right)$, which is still utterly negligible in practice, of course. This term that arises as a result of having to choose a coarse graining scale to define the entropy will make increasing negative contributions the more fine grained view of the system you take. In the limit where you can resolve the exact physical state, this term will exactly cancel out the ordinary entropy of the system. When you know the exact physical state, $\log \left(\Omega (E)\right)=0$, and therefore the entropy is zero. If you work at this fine grained level where the entropy is zero, then the laws of physics will ensure that it stays zero as they forbid erasure of information. If you work at a coarse grained level, then systems will tend to lose information that's visible at the coarse grained level to a more fine grained level (due to statistics). This is how the second law that says that entropy can only increase, arises. Count Iblis (talk) 02:43, 27 April 2018 (UTC)

Silkie chickens

Why do Silkie chickens have 5 toes on each foot instead of the usual 4?? Georgia guy (talk) 15:18, 26 April 2018 (UTC)

As described in our article on polydactyly § other animals, this is a genetic mutation that is now standardized and encouraged by the humans who breed this type of chicken.

I searched the online database of the Poultry Science library at North Carolina State University, and found this paper: Genomic Regions Associated with Dermal Hyperpigmentation, Polydactyly and Other Morphological Traits in the Silkie Chicken (2010). If you're interested in more technical reasoning for the multiple toes: "A single SNP in a highly conserved cis-regulatory region of Sonic Hedgehog was significantly associated with polydactyly..." which is biology-ese that means the multiple toes are caused by a single mutation, with lots of technicalities.

Nimur (talk) 15:41, 26 April 2018 (UTC)

April 27

Why aren't 3/8 inch and 1/4 inch common calibers?

But .38, .357 and c. .22 are. Decimal inches are less common than fractions of inches in most non-gun fields so why not? Sagittarian Milky Way (talk) 01:46, 27 April 2018 (UTC)

Although the article Caliber and especially the article .357 Magnum don't quite come out and say it explicitly, it seems like specific calibers were derived experimentally, for specific usages. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:36, 27 April 2018 (UTC)

.25 ACP 251/1000" was introduced in 1906 (patented 1905). .25 NAA 251/1000" was introduced in 2002. .380 Revolver Short and .380 Revolver Long 3/8" were introduced in 1860s. .375 Winchester 3/8" was introduced in 1978.
Sleigh (talk) 12:26, 27 April 2018 (UTC)

It is instructive to think about how these items are manufactured - and how they were historically manufactured. Firearms, and their ammunition, are one of the oldest artifacts that were built using machine tools and their manufacture was intricately linked to other developments of the industrial revolution. Modern commercial ecosystems carry a lot of the historical "inertia" - so even though today we may use CNC mills and robotic metal machines, we have a lot of backward compatibility to consider. (Vis: 2017 Annual Statistical Update from the ATF).

If we're building barrels using a CNC router - or if we're using computer simulations to study ballistic physics - then typing in a simple fraction or a simple decimal makes that part of the work easier.

But if it's 1855 and we're using a metal gauge to control the mill, it makes no difference whatsoever if the gauge is a nice rational number, or some part-of-an-inch or part-of-a-furlong-whose-value-cannot-be-expressible-using-conventional-algebras. Your manufacturer would just slide the metalworking tool down to the gauge and mill that much. The result is a perfect, reproducible, accurate, standardized metal piece, whose precise dimensions expressed in inches are irrelevant for many purposes.

If you spend two hundred years building armament in that fashion, then by the time you invent the precision CNC mill, you have to type in whatever inconvenient number is compatible with the billions and billions of bullets that are already on the marketplace, and your product has to be compatible with the stuff built by hundreds of thousands of other people who are building ammunition. Millions of people aren't going to change their way of life just because it'd be great if everyone wised up about simple facts!

Many times before, I have cited James Burke's excellent and very old history documentary series, Connections (1978). In several episodes - particularly, Episode 5 (40 minutes in), there is a great analysis of the interplay between proto-industrial manufacturing and tooling, and the embodiment of those historical technological conventions into the shape of modern artifacts. Half of that episode is about the significant transition from musket to rifle, and why this minor detail of technology is so significant to the culture and history of the United States. (To wit: the Rifleman's Creed is not a general confession of adoration for firearms at large, but of rifles in specific; the first shots of the war that founded our nation are conventionally attributed to precision home-made rifles, rather than muskets - though historians naturally quibble about the important details; and of course, the Americans were the first to prove that rifles could kill other Americans really effectively). In fact, historians call this transition of technologies, which irreversibly guided the course of the Industrial Revolution, the "American system of manufacturing" - in true form, largely guided by American innovation and our desire to build lots and lots and lots of guns.

The point - if there is any - is that precision in manufacturing does not specifically require a convenient numerical representation; and, if history gives us any wisdom, we can predict that people are going to keep doing the same old thing, for many more years.

Nimur (talk) 17:12, 27 April 2018 (UTC)

Very informative, I learned a lot from that. Maybe if the sweet spot for rayguns turns out to be 1.007cm +/-14% the 11.43mm rayguns will outsell the 1 centimeters for decades after the boxes only say metric.. Sagittarian Milky Way (talk) 03:58, 30 April 2018 (UTC)

Agree with User:Nimur, but the British Brown Bess musket had a internal barrel diameter of 0.75 (¾) inch, which required a ball diameter of 0.69 inch to stop it getting stuck inside. From there, we went to the 0.45 inch Martini–Henry rifle. So it seems that there has been a move away from nice round figures, perhaps because of the increasing complexity of the variables. Alansplodge (talk) 11:27, 28 April 2018 (UTC)

Has the 75% loss of flying insect mass been observed outside of Germany?

Ref.: [10] 174.16.98.178 (talk) 20:00, 27 April 2018 (UTC)

It was observed in England. Ruslik_Zero 08:02, 28 April 2018 (UTC)

Citation needed User:Ruslik0? The 75% figure was from a study of nature reserves in Germany. A study by Rothamsted Research comparing insect traps in England between 1970 and 2000 found no decrease in weight of insects in some areas, but a 60% reduction in Herefordshire. [11] Alansplodge (talk) 16:23, 28 April 2018 (UTC)

Insects are gone, the birds that eat them are gone also, fruit plants are not pollinated. A wonderful consequence of progress and development. AboutFace 22 (talk) 21:07, 28 April 2018 (UTC)

April 28

Deaths from opioid withdrawal

How often do people die due to complications of opioid WITHDRAWAL?

I'm hoping for a good reference that says it's rare, as a coworker has claimed that it is a common occurrence in the United States today. Thank you any help you can provide, and have a nice day. :) — Preceding unsigned comment added by 2600:100E:B010:D644:B13E:8816:6408:E067 (talk) 14:50, 28 April 2018 (UTC)

Yes, people can die from opiate withdrawal: "Death is an uncommon, but catastrophic, outcome of opioid withdrawal. The complications of the clinical management of withdrawal are often underestimated..."

Mortality risk during and after opioid substitution treatment: systematic review and meta-analysis of cohort studies.

Alansplodge (talk) 16:33, 28 April 2018 (UTC)

Thank you!

From the first link: "How could someone die during opiate withdrawal? The answer lies in the final two clinical signs presented above, vomiting and diarrhoea. Persistent vomiting and diarrhoea may result, if untreated, in dehydration, hypernatraemia (elevated blood sodium level) and resultant heart failure."

That strongly supports my belief that it is almost impossible to be picked up by an ambulance and die on the way to the hospital from opioid WITHDRAWAL. Which is what my coworker claims happens frequently in the US.

The latter link is a study of the mortality of patients on opioid replacement therapy, so there does not seem to be much mention of death from withdrawal, since anyone in the study experiencing withdrawal would presumably be having those symptoms under medical supervision where, again, they are extremely unlikely to die suddenly of dehydration.

2600:100E:B010:D644:1415:E13:2FA1:9E59 (talk) 19:07, 28 April 2018 (UTC)

That scenario is certainly not impossible. Rehydrating someone who is nearly dead of dehydration is not as simple as giving him a glass of water, and people attending might be afraid to call the ambulance until it's too late to save the person. Death by dehydration is also not a very painful way to go nor does it generally have quick onset and sudden symptoms like heroin overdose, so it might appear a less acute problem to untrained people. 78.0.233.56 (talk) 22:31, 28 April 2018 (UTC)

In adults, opiate withdrawal is uncomfortable but not inherently dangerous, which is why there are several trials that have used naltrexone to induce sudden long-lasting withdrawal in people addicted to heroin or methadone. On the other hand, neonatal withdrawal has a high mortality rate. Klbrain (talk) 23:39, 28 April 2018 (UTC)

It sounds to me like your coworker is mixing up some things. Someone calls an ambulance if they fear someone has overdosed on opioids. In an overdose, death is generally from respiratory arrest, as opioids depress breathing. The initial treatment is immediate administration of naloxone. This reverses the effect of opioids. This can be unpleasant for the person, and there have been instances of people brought out of overdose by emergency personnel and then attacking them. However, EMTs would have to be exceedingly incompetent to let someone die from dehydration or hyponatremia on the way to a hospital. EMTs will be familiar with these, as they're reasonably common in emergency settings, and will commence treatment, such as intravenous fluids, if they suspect it. --47.146.63.87 (talk) 07:23, 29 April 2018 (UTC)

According to [12] and [13] [14], other than the aforementioned risk of combativeness from the patient one of the other issues is that after administration of naloxone the patient may simply refuse to go to hospital due to some combination of fear of prosecution and having no desire to try and overcome their addiction.

The second source also mentions that the there is a risk of aspiration of vomit especially if too much naloxone is given or it's given too fast. Paramedics would likely have sufficient training to avoid this, but naloxone may also be given by other first responders like the police or even bystanders who may have less training. I doubt that deaths are common once paramedics are there or if they are taken to hospital, but it would complicate management.

This guidance on prehospital treatment of opioid related emergencies [15] may be of interest. It mentions for example that many cases involve comorbidities such as multiple drugs so need to be handled accordingly. (It does mention the role of lay responders including them administering naloxone. It also mentions that despite common concerns, it is unlikely limited naloxone administration will lead to severe withdrawal symptoms.)

Refusing follow up treatment leads to obvious concerns over whether the patient may overdose perhaps even on what's already in the system (since the effect of the opioids often outlasts naloxone) or by taking more perhaps due to their lost high. An older study found no evidence for this [16].

But a more recent albeit I think unpublished (only presented in a conference) mentioned in this abstract [17] and in this blog found that while 80% of these patients survived a year, over 6.5% died within the day, and 9.3% within the year. Of the 10% of so who died within a year excluding those who died the same day, around 50% died within a month. All these taken together seem to suggest many of those who receive naloxone are at a critical stage were follow up treatment is desirable including both short term to ensure no further problems in a hospital or similar and longer term in whatever environment to help manage the addiction and whatever other problems they face that may be contributing (e.g. mental illness). Somewhat mentioned by the sources, beyond getting them to a hospital which may be a way to try and get them into such long term treatment, it also needs to be available and you need to come up with strategies to maximise chances of convincing them into follow up treatment. E.g. [18] (This source also mentions another issue, even if they get to hospital they may soon leave, so it's helpful if these efforts come as soon as possible.)

BTW, of some limited (since we're talking about people who have received naloxone not people going through normal withdrawal) relevance to the original question: The author of the study on deaths after refusing treatment also did this published study that only identified 2 deaths that occurred near the time of transport out of 105 patients [19]. (If I understand what they are saying correctly, one died in hospital, one died after treatment.) Although it's possible their methodology would have missed deaths in the ambulance, if these people were dead on arrival and never admitted. (And I guess they would have been missed by the other study on those refusing treatment. Still if this really were happening a lot I strongly suspect there would have been enough knowledge of it that it would have been looked at.)

Even more minor relevance to the original question, some of the earlier sources and [20] mention another issue namely mention that some paramedics or other first responders may refuse to perform CPR and take great care to protect themselves due to concern over hazards at the scene especially fentanyl which a potent opiod which can have an effect simply from skin contact. (These are more likely to be an issue before the patient is in the ambulance.)

Some have express concern over the cost or moral hazard or risks to responders from naloxone treatment and are suggesting usage should be reduced or restricted [21] [22] [23] [24] [25]. The cost issue is well recognised even outside such discussions [26] [27]. I'm sure if you'll look you'll also find discussions on how while a lot of money be spent on treating opioid related emergencies, a lot less is spent on treatment for addicts including related issues which may be contributing to their addiction. And it isn't just because people are refusing treatment.

15:05, 29 April 2018 (UTC)

While I don't think deaths in am ambulance are likely, I don't think you can assume people with withdrawal will be doing it under medical supervision. Treatment centres are often very stretched when there is a addiction epidemic. Of course many people are going to quickly fail and so will have limited withdrawal if they attempt to beat it with limited support but if you have a lot of cases it's likely you'll still have a fair few who don't have medical supervision and are trying to overcome their addiction. In addition, withdrawal may not always be entirely by choice if someone with a problem has trouble getting another 'hit'. Note I'm also not saying that this means there is any significant chance of them dying from withdrawal even outside an ambulance. Nil Einne (talk) 15:12, 29 April 2018 (UTC)

References

April 29

Feynman Lectures. Exercises. Exercise 21-8 PNG

...

21-8. The gravitational force felt by a particle embedded in a solid uniform sphere, due to the mass of the sphere only, is directly proportional to the distance of the particle from the center of the sphere. If the earth were such a sphere, with a narrow hole drilled through it along a polar diameter, how long would it take a body dropped in the hole to reach the surface at the opposite side of the earth?

—  R. B. Leighton , Feynman Lectures on Physics. Exercises

I want to prove the statement that the force is proportional to radius inside the uniform sphere.
Consider a spherical shell 1-2 PNG.
The potential in point 1 is:
$\Psi _{1}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}+\Psi _{\text{1-2,at 1}}$
$\textstyle \Psi _{1}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}+\int _{R_{1}}^{R_{2}}-{\tfrac {Gdm}{x}}$
$\textstyle \Psi _{1}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}+\int _{R_{1}}^{R_{2}}-{\tfrac {G4\pi x^{2}dx\rho }{x}}$
$\Psi _{1}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}-G2\pi \rho (R_{2}^{2}-R_{1}^{2})$
The potential in point 2 is:
$\Psi _{2}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}+\Psi _{\text{1-2,at 2}}$
$\Psi _{2}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}-{\tfrac {G(M_{2}-M_{1})}{R_{2}}}$
$\Psi _{2}=\Psi _{\text{0-1}}+\Psi _{\text{2-3}}-G{\tfrac {4}{3}}\pi \rho (R_{2}^{2}-{\tfrac {R_{1}^{3}}{R_{2}}})$
Difference in potential:
$\Delta \Psi =\Psi _{2}-\Psi _{1}=-G{\tfrac {4}{3}}\pi \rho (R_{2}^{2}-{\tfrac {R_{1}^{3}}{R_{2}}})+G2\pi \rho (R_{2}^{2}-R_{1}^{2})=G\pi \rho [{\tfrac {2}{3}}{R_{2}}^{2}-{R_{1}}^{2}(2-{\tfrac {4R_{1}}{3R_{2}}})]$
If $R_{1}=R$,
$R_{2}=R+dR$
then:
$d\Psi =G\pi \rho [{\tfrac {2}{3}}{R_{2}}^{2}-{R_{1}}^{2}(2-{\tfrac {4}{3}})]=G\pi \rho {\tfrac {2}{3}}[{R_{2}}^{2}-{R_{1}}^{2}]=G\pi \rho {\tfrac {2}{3}}(R_{2}-R_{1})(R_{2}+R_{1})=G\pi \rho {\tfrac {2}{3}}dR(2R)=G\pi \rho {\tfrac {4}{3}}RdR$

$\textstyle ({\textbf {field}})=-{\tfrac {d\Psi }{dR}}=-G\pi \rho {\tfrac {4}{3}}R$

Is it correct? Username160611000000 (talk) 06:36, 29 April 2018 (UTC)

Your equations assume gravitational force is proportional to the product of the two masses (the Earth and m), and is inversely proportional to the square of the distance between their centers. This confirms Ab initio Newton's law of universal gravitation, see particularly Newton's_law_of_universal_gravitation#Gravitational_field. DroneB (talk) 11:45, 29 April 2018 (UTC)

It is correct for spherical object from outside. But it must be proven for a particle inside a solid sphere. Username160611000000 (talk) 12:36, 29 April 2018 (UTC)

To answer what Feynman actually asks you will use these values:

Polar radius: 6356.8 km

Mass: 5.97237×1024 kg

Surface gravity:9.807 m/s²

See Earth. Defending use of Center of mass as the particle equivalent of an object in Newton's laws of motion is not the exercise. DroneB (talk) 13:27, 29 April 2018 (UTC)

The solutions is not a question. Accepting on faith the proposition that the force is proportional to the distance I can write $g(R)=-{\tfrac {g_{\text{surface}}}{R_{\text{earth}}}}R$. The equation of motion is then ${\tfrac {d^{2}}{dt^{2}}}x=-{\tfrac {g_{\text{surface}}}{R_{\text{earth}}}}x$. It's the harmonic oscillator and the answer is half of the period.

But I want to prove that the force is proportional to the distance.

Username160611000000 (talk) 15:28, 29 April 2018 (UTC)

The first thing is to prove or accept the shell theorem. Once you have that, you know that the gravitational force is equal to the force exerted by all the shells below the falling object only, while those above have no effect. If the falling object is a distance D away from the center and a shell has radius r, each shell exerts a force G*rho*4pi*r^2/D^2, where rho is the density of the shell (the force is proportional to the area, in other words, and they all are concentric). So we integrate r=0 to r=D and get the sum of the forces is (G/3)*rho*4pi*D^3/D^2 - 0 = 4pi*G*rho*D/3, which agrees with your calculation. Wnt (talk) 15:08, 29 April 2018 (UTC)

• • I have checked and found that $[{\tfrac {2}{3}}{R_{2}}^{2}-{R_{1}}^{2}(2-{\tfrac {4R_{1}}{3R_{2}}})]\neq {\tfrac {2}{3}}[{R_{2}}^{2}-{R_{1}}^{2}]$ for $R_{2}=R_{1}+0.000...01$. So my derivation is not good. More careful calculation gives $[{\tfrac {2}{3}}{R_{2}}^{2}-{R_{1}}^{2}(2-{\tfrac {4R_{1}}{3R_{2}}})]={\tfrac {2(R_{1}-R_{2})^{2}(2R_{1}+R_{2})}{3R_{2}}}$.
    So ${\tfrac {d\Psi }{dR}}\sim {\tfrac {2(R_{2}-R_{1})(2R_{1}+R_{2})}{3R_{2}}}\to 0{\text{ when }}(R_{2}-R_{1})\to 0$ .
  • When an object penetrates a solid sphere some shells appear above the object . But these shells generate the potential. Inside one shell the potential is constant, but it is not when number of shells changes.
    Username160611000000 (talk) 15:35, 29 April 2018 (UTC)
  • I presume that mistake is that $\Psi _{\text{0-1}}\neq const$ for point 1 and 2. Username160611000000 (talk) 17:42, 29 April 2018 (UTC)
  • $\Psi _{1}=\Psi _{23}+\underbrace {\Psi _{12,1}} _{-G2\pi \rho ({R_{2}}^{2}-{R_{1}}^{2})}+\underbrace {\Psi _{01}} _{-{\tfrac {GM_{01}}{R_{1}}}}$
    $\Psi _{2}=\Psi _{23}+\underbrace {\Psi _{12,2}+\Psi _{01}} _{-{\tfrac {GM_{02}}{R_{2}}}}$
    $\Psi _{2}-\Psi _{1}=-{\tfrac {GM_{02}}{R_{2}}}+G2\pi \rho ({R_{2}}^{2}-{R_{1}}^{2})+{\tfrac {GM_{01}}{R_{1}}}=-{\tfrac {G(4/3)\pi \rho {R_{2}}^{3}}{R_{2}}}+G2\pi \rho ({R_{2}}^{2}-{R_{1}}^{2})+{\tfrac {G(4/3)\pi \rho {R_{1}}^{3}}{R_{1}}}$
    $=-G(4/3)\pi \rho {R_{2}}^{2}+G2\pi \rho ({R_{2}}^{2}-{R_{1}}^{2})+G(4/3)\pi \rho {R_{1}}^{2}=G(2/3)\pi \rho ({R_{2}}^{2}-{R_{1}}^{2})$
    Username160611000000 (talk) 18:10, 29 April 2018 (UTC)

April 30

why we have so long hair?

چه عامل ژنتیکی و انتخاب طبیعی باعث شده برخلاف همرده های انسان ، موی سر تا این حد رشد کند؟ the man differed from his ancient grand parents when he went cave and started to hunting. in such condition : our tail have been fallen. our foot changed shape , because of no need to go up from trees .(from Y shape) our buttocks changed shape , for long duration sitting our body hair had been lost our head hair start to grow long--for which reason? males face start to have long hair (beard)--for which reason? our face deformed; normally we became meet eating animals; too we are still eating fruits. what is the basement reason of our hair length .too our eyebrow hair growth --Akbarmohammadzade (talk) 07:21, 30 April 2018 (UTC)

This site has some likely sounding answers: Why does human facial and head hair continue to grow?. -- Q Chris (talk) 11:57, 30 April 2018 (UTC)

See also this recent RefDesk discussion. One reference from that is What is the latest theory of why humans lost their body hair? Why are we the only hairless primate? from Scientific American. Alansplodge (talk) 19:14, 30 April 2018 (UTC)

how human lost his tail?

Not sure who is asking this, but you should know it happened long before humans. All apes are tail-less. --Lgriot (talk) 12:52, 30 April 2018 (UTC)

See also Human vestigiality#Coccyx. All humans had a tail at a point in early life. Graeme Bartlett (talk) 12:53, 30 April 2018 (UTC)

Indeed, see Prenatal development, which has several pictures of embroys before they lose their vestigal tails. --Jayron32 16:00, 30 April 2018 (UTC)

How often are all 8 planets on the same side of the sun?

How often are all 8 planets on the same side of the sun (i.e. in a 180 degree arc), when was the last time/will be the next time and are there any resonances among the planets that make it more/less likely than if there were no resonances. If things were completely independent, I believe that the answer would be 1/128th of the time (without loss of generality, assume that Mercury is the most counterclockwise in the arc, and then each of the other 7 have a 50/50 chance of being within 180 degrees clockwise of Mercury, so 1/(2^7).Naraht (talk) 14:17, 30 April 2018 (UTC)

Long-term predictions of the positions of the planets are not all that simple to work out; given the intricacies of an n-body problem with that many interacting bodies. As noted at the Stability of the Solar System, the movement of the planets is chaotic in the long term, as noted at Lyapunov time, the Solar System loses its useful predictability after 5 million years. --Jayron32 15:10, 30 April 2018 (UTC)

Okay, but I think Naraht is asking for a simple and approximate answer, for which the effects you note are of secondary concern. Attic Salt (talk) 15:18, 30 April 2018 (UTC)

Not really. Let's say (I don't have the numbers at hand, but let's make some up), that the type of orientation Naraht is talking about only happens once every 10,000,000 years by some overly simplistic calculation. If that were the case, then such a calculation would beyond meaningless since the Solar System is chaotic on any scale larger than 5,000,000 years. It may not be on that scale; if it's every 1000 years or so, then we could work that out. I'm just noting the complexities of the problem. --Jayron32 15:23, 30 April 2018 (UTC)

Well, I'm happy to learn, but 1/128th of the time is pretty often. Is there something wrong with his/her calculation? Attic Salt (talk) 15:27, 30 April 2018 (UTC)

1/128th of what time? They aren't all moving at the same speed... --Jayron32 15:50, 30 April 2018 (UTC)

Regardless, it's a pointless academic discussion anyways, and I seem to have lead you all astray; it seems to happen on order of once every millenium or so; according to this the next time will be in CE 2492. --Jayron32 15:53, 30 April 2018 (UTC)

I don't see anything in that linked article that mentions "millenium or so". Perhaps we might be confused by what is meant by "how often". I suppose the calculation by Naraht is about answering what "fraction of the time" are the planets all on the same side of the Sun. That the next time this happens is what I would call a "deterministic question". Assuming the source you cit is right, and the next time it happens is in year 2492, that would, indeed, be about millennium away from now, but the alignment would then persist for a duration of time. In other words, I don't think that having to wait a while is inconsistent with the possibility that the "fraction of the time" the planets are aligned is 1/128th of the time. Attic Salt (talk) 16:28, 30 April 2018 (UTC)

Presumably, the longest period of time at once that could be true would be 1/2 of a Mercurial year of 87 days, which would be 43ish days. Hypothetically, if both Mercury and Venus were aligned when the entered the same side of the sun as the other 6 planets, they would be able to squeeze in such 43 day windows 2 more times before Venus passed out of alignment. --Jayron32 16:37, 30 April 2018 (UTC)

Okay, but I don't see anything wrong with Naraht's calculation regarding what fraction of the time the planets are on the same side of the Sun. Do you? Attic Salt (talk) 17:11, 30 April 2018 (UTC)

1/128th of what time period, though? It would be 1/128th of the time it takes for all 8 plants to "reset" to the same position; we'd have to do that calculation to figure out the amount of time we're talking about. I mean, if we mean 1/128th of a year, that's every 4 months. It doesn't happen that often. --Jayron32 17:22, 30 April 2018 (UTC)

Well, clearly, over timescales much longer than the longest orbital period (Neptune), but shorter than the timescales over which the orbital parameters change. Attic Salt (talk) 18:33, 30 April 2018 (UTC)

I thought the OP's analysis was rather clever, if not entirely helpful. The duration of any one event is 44 days (half the orbital period of Mercury). I started to write a very boring orrery program to work out an approximate answer. But it was so tedious I gave up. Greglocock (talk) 10:30, 1 May 2018 (UTC)

Fun fact: this is called syzygy. There's a good Scrabble word. Note as stated in the article, sometimes this is used to mean an exact straight-line alignment of bodies (such as occurs in an eclipse), but it can also be used more generally to mean when all the planets in the Solar System are on the same side of the Sun. --47.146.63.87 (talk) 22:34, 30 April 2018 (UTC)

Unfortunately, a standard English Scrabble set contains only two y's. Deor (talk) 16:34, 1 May 2018 (UTC)

And two blanks, which make it possibly to spell "syzygy", using one of the blanks for one of the ys --Jayron32 16:38, 1 May 2018 (UTC)

A word like aqueous seems rather more useful. Wnt (talk) 01:43, 2 May 2018 (UTC)

I like Naraht's idea of estimating the proportion of time that this condition holds, but I think that that's an underestimate because having Mercury most counter-clockwise doesn't include all possible combinations. Imagine an arc defined by ±90^o around bisector of the (smaller) angle Mecury-Sun-Venus. This 180^oC arc always includes both Mercury and Venus, then has a 1/(2^6)=1/64 chance of also including the other 6 planets. I think that even this is an underestimate of the proportion of time the 180^o condition holds. As others have noted this doesn't help to determine the next time it will happen, but it's an interesting question by itself. Klbrain (talk) 23:27, 1 May 2018 (UTC)

Your probability is missing a factor 8. For each planet x, the chance that all the other 7 planets are within 180 degrees clockwise of x is 1/2⁷ = 1/128. The 8 cases are mutually exclusive so the chance that at least one of them is happening at a given time is 8 × 1/128 = 1/16. A Monte Carlo simulation with 10⁸ random constellations gave me 1/16.002. The longest possible duration of such an event is slightly longer than a Mercury orbit of 87.97 days. The planets rotate in the same direction. If all 8 planets are lined up exactly at some time then they are within 180 degrees from around 44 days earlier to around 44 days later. PrimeHunter (talk) 23:29, 1 May 2018 (UTC)

I think that I am, the Mercury is the farthest Counterclockwise is a case, but not all...Naraht (talk) 09:01, 2 May 2018 (UTC)

Last time was 07/14/10 to 09/09/10 (57 days). Last time before that was pre-2003 since the configuration of the gas planets made "everything on the same side" impossible from 12/31/2002 to 09/02/2009 (also 2/22/11 to 7/11/17). Next time is July 3 to August 30 this year (Counting Pluto doesn't change anything for as far as I checked (20/02/2002 20:02:20.02200220022002 to 2020)). Considering only Uranus and Neptune, 1993.3 is when they lapped each other essentially removing 1 planet from the odds, 87 years later in 2080.1x is the next time they're on opposite sides of the Sun making it 1/64tb of the time instead of 7/64th of the time. From 7/11/17 to 9/24/28 the gas planets allow, if it's not all on same side for 4,093 uninterrupted days it's the rock planets' fault. Also all gas planets will fit within 72.2 degrees in 2024 — the smallest in 164 years (1997 to 2161). These things will probably make the next decade a fairly good time for "all planets on the same side of the Sun." Sagittarian Milky Way (talk) 08:17, 2 May 2018 (UTC)

Great data! What software are you using for this?Naraht (talk) 09:01, 2 May 2018 (UTC)

Astrology software. Their positions are extremely good the times I've compared them with the official Jet Propulsion Laboratory (U.S. spaceprobes) ones so I think they're accurate. The version that makes it so easy to find these costs money, I don't know if I want to give free advertising. Sagittarian Milky Way (talk) 16:19, 2 May 2018 (UTC)

Artificially circulating blood without a heart

What makes it so difficult to circulate blood with pumps (even external to the patient) and without a heart at all? Blood pump is about something else, but recently a man in Prague survived 6 months with mechanical blood pumps. Wouldn't that be useful for some extremely ill patients? --Doroletho (talk) 15:45, 30 April 2018 (UTC)

Does the article artificial heart answer any of your questions? --Jayron32 15:47, 30 April 2018 (UTC)

The article could benefit from some expansion around the difficulties of it. It recognizes that "A synthetic replacement for the heart remains a long-sought "holy grail" of modern medicine. " but "embodies subtleties that defy straightforward emulation" is rather a short explanation. I imagine this "subtleties" are maybe reaction to hormones and a two-way neuronal connection to the brain. --Doroletho (talk) 16:03, 30 April 2018 (UTC)

For any given definition of "success" there have been some successful such transplants, the AbioCor never made it out of clinical trials, but a few patients lived over a year with it. Others mentioned in the article are in various states of development and trials. --Jayron32 16:26, 30 April 2018 (UTC)

Also, the heart does not really communicate with the brain to pump. The Cardiac cycle is controlled by the heart itself, with no input from the brain, via the Cardiac pacemaker, a bundle of nerves that is part of the Electrical conduction system of the heart, which can run more-or-less independently from the central nervous system, though of course there are some feedback loops involving the Vagus nerve and the like that control things like heart rate. --Jayron32 16:32, 30 April 2018 (UTC)

I don't think that the autonomic issues is a real problem (feedback systems are fairly straighforward to implement with a pressure sensor). Rather, its damage to the blood cells as they pass through an un-natural pump undergoing un-natural motion, leading to ""pump thrombosis, and hemolysis". To reduce the thombosis, anticoagulants can be given, but they increase the risk of bleeding. Klbrain (talk) 23:42, 1 May 2018 (UTC)

References

Eastern wolf

Hello everybody! What exactly does the term lycaon in the scientific name derive from?--Neufund (talk) 18:45, 30 April 2018 (UTC)

The article titled Lycaon (Arcadia) may grant you some insight. Besides being the specific name of the Eastern Wolf, it is also the generic name of the African wild dog. --Jayron32 18:48, 30 April 2018 (UTC)

May 1

Abortion pill, surgical abortion, and natural abortifacients

While there is an ongoing debate about the abortion pill and surgical abortion, I wonder whether people have considered natural abortifacients to be just as dangerous. "Brewer's yeast, vitamin C, bitter melon, wild carrot, blue cohosh, pennyroyal, nutmeg, mugwort, papaya, vervain, common rue, ergot, saffron and tansy. Animal studies have shown that pomegranate may be an effective abortifacient." Some of them seem to be common household ingredients that can be purchased at the grocery store, and there aren't bans on those things. Anyone can go out and buy yeast, vitamin C tablets, bitter melon, nutmeg, papaya, and pomegranate at a supermarket. Does this mean that a pregnant woman who want a pregnancy have to watch out for those ingredients to make sure that they don't accidentally abort a fetus? SSS (talk) 03:51, 1 May 2018 (UTC)

No. Basically, once you cut out anecdotal evidence (both modern and ancient), "natural health" websites that are only pretending to present science, and studies of feeding rodents simply infeasible amounts of concentrated food extracts, there is no evidence that any of that crap works. Someguy1221 (talk) 04:31, 1 May 2018 (UTC)

There certainly are effective plant-based abortifacients. There is any active disinformation campaign by religious loons to sow doubt and confusion about them. It seems that you are either one of them, or have been fooled by them. Abductive (reasoning) 07:17, 1 May 2018 (UTC)

I have never heard of this "disinformation campaign"; perhaps you have a source to share? I think not just people religiously opposed to abortion, but also mainstream physicians, will advise against self-administering "plant-based" abortifacients. A number of deaths have been attributed in particular to pennyroyal (Mentha pulegium), which may well "work", but only in doses that are dangerous to the woman as well. --Trovatore (talk) 07:40, 1 May 2018 (UTC)

A lot of things can likely cause abortion if ingested in sufficient quantities. Unfortunately they tend to kill or sicken the mother as well. --47.146.63.87 (talk) 04:58, 1 May 2018 (UTC)

A little, maybe, but many of those things only have an abortifacient effect in very high amounts, more than anyone would likely ingest normally. It's probably a good idea to stay away from loosely regulated things like herbal supplements, especially those with ingredients that lack much quality research. Approved abortifacient drugs are reasonably safe, and certainly much safer than attempting an abortion with untested and dangerous methods. (Of course, I recognize many women are driven to the latter by desperation if they can't access medical abortion.) Let's not forget that pregnancy is fairly risky in itself. A lot of overblown claims about these drugs' dangers come from anti-abortion activists who want to scare women away from considering an abortion. --47.146.63.87 (talk) 04:58, 1 May 2018 (UTC)

A significant percentage of pregnancies result in Miscarriages anyway. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:00, 1 May 2018 (UTC)

"nutmeg"

Its effectiveness as an abortifacient is rather questionable, but nutmeg may cause poisoning and has psychoactive effects:

• "In the 19th century, nutmeg was thought to be an abortifacient, which led to numerous recorded cases of nutmeg poisoning. Although used as a folk treatment for other ailments, nutmeg has no proven medicinal value."
• "In low doses, nutmeg produces no noticeable physiological or neurological response, but in large doses, raw nutmeg has psychoactive effects deriving from anticholinergic-like hallucinogenic mechanisms attributed to myristicin and elemicin. Myristicin, a monoamine oxidase inhibitor and psychoactive substance, can induce convulsions, palpitations, nausea, eventual dehydration, and generalized body pain. For these reasons in some countries, whole or ground nutmeg may have import restrictions except in spice mixtures containing less than 20 percent nutmeg."
• "Nutmeg poisonings occur by accidental consumption in children and by intentional abuse with other drugs in teenagers. Fatal myristicin poisonings in humans are rare, but three have been reported, including one in an 8-year-old child and another in a 55-year-old adult, with the latter case attributed to a combination with flunitrazepam."
• "Nutmeg intoxication can vary greatly from person to person, but is often associated with side effects such as excitedness, anxiety, confusion, headaches, nausea, dizziness, dry mouth, redness in eyes, and amnesia. Nutmeg poisoning is also reported to induce hallucinogenic effects, such as visual distortions and paranoia. Although rarely reported, nutmeg overdose can result in death, especially if combined with other drugs. Intoxication takes several hours before maximum effect is experienced. The effects of nutmeg intoxication may last for several days."
• "Nutmeg was once considered an abortifacient, but may be safe for culinary use during pregnancy. However, it inhibits prostaglandin production and contains hallucinogens that may affect the fetus if consumed in large quantities."*
• "While the spicy scent of nutmeg may be attractive to pets, there is potential for toxicity if large amounts are consumed."

Due to my interest in causes of death, (in and out of Wikipedia), I have come across a few cases of nutmeg poisoning. See also this article in a minor American newspaper, The New York Times, concerning nutmeg poisoning cases in Illinois (32 cases) and California (119 cases). Dimadick (talk) 08:47, 1 May 2018 (UTC)

Information about abortifacient herbs in the U.S. has been corrupted by the effects of the blatantly unconstitutional but highly successful Comstock Law, and likely others abroad. (This was resisted by revered American anarchist Lysander Spooner, whose delivery service was put down for political reasons but made it possible for a more primly Mormon outfit like UPS to fight its way to legality) Attempts to recover lost witchcraft and folk traditions are ongoing, but it appears that abortion by herbs was probably not very safe or very sure ([28][29][30], from a PubMed search for pennyroyal abortion). But competence is the first casualty of censorship, which often stops the best aspects but never the worst of what it complains about. Wnt (talk) 12:18, 1 May 2018 (UTC)

Remember folks, laws only stop beneficial things, and if its been regulated by the government, that's because its the best thing ever, and if the government only didn't regulate it, the entire world would be healthier, happier, and would never get sick or hurt ever again! --Jayron32 16:21, 1 May 2018 (UTC)

@Jayron32: Anyone interested can read Comstock Law and decide for himself. Although the stock value of freedom is plummeting fast, and would be given a Sell rating by any competent broker, I don't think the world has fallen quite so far so fast that many others would stick up for this yet. Wnt (talk) 01:39, 2 May 2018 (UTC)

OK. --Jayron32 01:45, 2 May 2018 (UTC)

Sunlight amplification by glasses

Do corrective lenses amplify the sunlight (particularly in summer), akin to burning glass, thus somewhat hurting the eyes? Not seeking a medical advice. Thanks. 212.180.235.46 (talk) 10:08, 1 May 2018 (UTC)

If the lens is convex, it will focus light toward the centre, but the eye or face will be too close for the focus to a small area. Looking at the Sun is not a good idea in any case. For concave lenses the light is spread out, but then the skin just outside the shadow of the glasses will then get a double done, direct sunlight and light spread by the lens, and then get more solar damage. Graeme Bartlett (talk) 10:42, 1 May 2018 (UTC)

• They don't "amplify" it, as that would need some additional source of energy to be added (see laser).

They can concentrate or focus it though. This is a recognised source of potential fire risk, often when people leave their reading glasses on a sunlit desk, or on a car dashboard. Corrective glasses are of broadly two types: to correct short sight (myopia) or for long sight (hyperopia). These require a change in the focussing power of the lens, so can have this focussing effect. Glasses for short sight are concave and so have a divergent effect - they will not focus light and act as a burning glass. It's glasses for long sight (or reading glasses) which are convex and so can act as a burning glass.

As far as staring at the Sun goes, they make it no worse than it would be for a perfect non shortsighted eye would be. Yet that's not itself a good thing, as the eye naturally focusses on the retina.

There's a famous blooper in the novel Lord of the Flies wherein a group of shipwrecked schoolboys includes "Piggy", a sterotypical fat, nerdy kid, who wears glasses. These glasses are part of a power struggle on the island, as their means of starting a fire. Yet Piggy is short-sighted, so his glasses would have been no use for this. Andy Dingley (talk) 10:52, 1 May 2018 (UTC)

I remember trying to convince my English teacher of that error, being a shortsighted thin nerdy kid, but had to wait for a sunny day to prove my point. Alansplodge (talk) 12:07, 1 May 2018 (UTC)

• Corrective lenses merely cause the incoming light to be focused on the retina as accurately as the natural lens of the eye focuses light for a person that has perfect vision. Thus, the corrective lenses may increase damage, not not beyond the damage a person who does not need them would get. The glasses will in fact also filter out some of the UV, reducing total damage. -Arch dude (talk) 19:17, 1 May 2018 (UTC)

Dinosaur skeletons

On many dinosaur reference pages, photographs of the "dinosaur skeleton" are labeled as "reconstructed skeleton." This is inaccurate! A real "reconstructed skeleton" would contain all real, fossilized parts. Most skeletons in dinosaur displays around the world (and pictured in Wikipedia) are man-made materials with very few original fossilized bones included (maybe a leg bone or two, and a vertebra or so). In fact, many of them are only scientific guesses at what these creatures looked like! I believe it would be more appropriate to refer to these as "Concept skeleton including fossilized components." Does anyone else agree?Palw49 (talk) 16:08, 1 May 2018 (UTC)

I'm afraid this isn't the right venue to seek help with this issue. The correct place to ask would be at Wikipedia talk:WikiProject Dinosaurs, which is where you will find editors interested in Dinosaurs who can respond to your question. I would just ask the question there rather than here. --Jayron32 16:19, 1 May 2018 (UTC)

[Edit conflict] You are incorrectly restricting the word "reconstructed" to only one of its accepted meanings. For example, it is common to refer to crime reconstruction, which does not require either every single fact about the crime (which if available would make the exercise unnecessary), or recommitting the crime in question! {The poster formerly known as 87.81.230.195} 2.218.14.51 (talk) 22:10, 1 May 2018 (UTC)

Yep. Palw49's complaint would go likely nowhere, since a quick perusal of the paleontological literature shows that "reconstruction" is used in a much broader way than Palw49 would like it to be. Wikipedia matches the vocabulary used by subject-matter experts, even it it offend's one reader/writer's preferred definitions. Someguy1221 (talk) 22:08, 1 May 2018 (UTC)

Anti-anthropogenic return to our natural greenhouse

If earth's human society catastrophically (or miraculously) instantly stopped emmitting greenhouse gasses into the atmosphere, how long would the earth take to resume normal (pre-human intervention) atmospheric insolation (Is that the right word? It might not be.) conditions? I'm not asking about a return to normal climate because things like ice caps, which effect climate would take ages to recover. (I imagine the recovery would take as long as the damage took - perhaps centuries?)

Posed differently, what if a social or biological or economic upheaval relatively instantly interrupted all or, let's say, all significant anthropogenic greenhouse gass emmisions, what would happen to the atmosphere then and how quickly?

I think I remember a geography professor once telling me that the correct answer could be measured in weeks.

Order of magnutude answers gratefully accepted.Hayttom (talk) 17:30, 1 May 2018 (UTC)

Read this. --Jayron32 17:43, 1 May 2018 (UTC)

I nearly wish I hadn't: "If we stop our emissions today, we won’t go back to the past. The Earth will warm. And since the response to warming is more warming through feedbacks associated with melting ice and increased atmospheric water vapor, our job becomes one of limiting the warming. If greenhouse gas emissions are eliminated quickly enough, within a small number of decades, it will keep the warming manageable and the Paris Agreement goals could be met. It will slow the change – and allow us to adapt. Rather than trying to recover the past, we need to be thinking about best possible futures.". Ack! Hayttom (talk) 17:59, 1 May 2018 (UTC)

Some of the CO2 will last forever on the scale of human history, but it's a relative blink of an eye in terms of Earth's history. Half the excess CO2 will be removed in 30 years, and another 30% within a few centuries. The rest will linger for thousands of years[31]. Someguy1221 (talk) 19:18, 1 May 2018 (UTC)

• Because CO₂ stays in the atmosphere a long time, warming will continue but stay in the arbitrarily-defined "acceptable" range if we stop emitting it now. To get back to pre-human levels of CO₂, we would need to actively remove it from the atmosphere, via Carbon sequestration of some sort. Note that "pre-human" is lower that "pre-imdustrial", since humans have been adding CO₂ via deforestation for a long time. -Arch dude (talk) 19:10, 1 May 2018 (UTC)

Also, the word you're looking for is naturogenic. Someguy1221 (talk) 19:20, 1 May 2018 (UTC)

May 2

In what stage the muscle cell should get the stimulus?

I came across this presentation in which they write that there are 4 steps in muscle contraction: "1. Excitation = nerve impulse, neurotransmitter & excitation of myofiber 2. Coupling = ATP & calcium ions 3. Contraction = muscle cells shorten 4. Relaxation = muscle cell resume normal resting length (ATP)". My question is why the 1st steps isn't considered as relaxation? (I understand that the impulse should not come in the period of relaxation). Based on the reading here on Wikipedia it seems here that the time that the muscle should normally get the stimulus is the latent period. Isn't it? 93.126.116.89 (talk) 00:28, 2 May 2018 (UTC)

The relaxation period is the time during which the muscle fibers are changing from a contracted state to a resting state. Once the fibers stop changing, the relaxation period is over. Stimuli that arrive during the relaxation period will usually not be fully effective. Is that clear enough? Looie496 (talk) 13:44, 2 May 2018 (UTC)

Is the Lepton Number of the Universe a large negative value?

Assuming the Universe's Lepton number started at zero, the electron surplus was balanced by anti-neutrinos and Lepton number was conserved (or at least randomly even) thereafter, then shouldn't the Lepton number of the Universe today be a large negative value?

The problem is the No-hair theorem. Every black hole has a lepton number of zero, no matter how many electrons it eats. Since electrons tend to cluster in galaxies where black holes lurk while neutrinos are spread more evenly the overall balance favors anti-leptons over leptons.

If so, what's the current deficit? Around 1% of the total number of electrons, more or less?

Hcobb (talk) 02:35, 2 May 2018 (UTC)

Unless I'm missing something, the no-hair theorem the no-hair theorem doesn't say that the black hole can't have a lepton number, just that the lepton number of the black hole can't affect the externally observed parameters (i.e. gravitational and EM properties). Given that there's no way any of the decays which the lepton number is used to explain could occur within a black hole and have an effect outside it, and no limit on the total lepton number for the black hole, I can't see how a contradiction would arise. (of course, whether it's more meaningful to consider a universe with 0 total lepton number but a load of high lepton number black holes, or a universe with a steadily decreasing total lepton number is likely a pretty arbitrary distinction). MChesterMC (talk) 10:58, 2 May 2018 (UTC)

Air changes per hour

What is the air changes per hour of a house that is insulated well and has energy efficient double pane windows? I know someone who says that if I cook something with onions and can smell onions the next day that means that the same air from the day before is still there and has not exchanged with outside air. Is that true or false?--User777123 (talk) 04:32, 2 May 2018 (UTC)

Anecdote is not data, but I agree with /someone/. In our modern energy efficient house I can smell the curry that was cooked the previous day. In my non energy efficient house it clears within a couple of hours. Funnily enough when I asked the builder for the first house to vent the extractor fans to the air rather than the attic he said no. Greglocock (talk) 07:33, 2 May 2018 (UTC)

Does air changes per hour point you in the right direction? As to the second query, this can be trivially falsified: chemicals from cooking can settle on surfaces. Also, some, but not all of the air may linger. --47.146.63.87 (talk) 07:36, 2 May 2018 (UTC)

Yes, agreed; this sounds like a "technically true, but practically not so much" kind of thing. Okay, so you fried up some onions yesterday. Assuming the food was eaten, was the pan washed thoroughly? Was the splatter from the oil all wiped up, including the tiny amounts that travel all over, such as the floor? Has the cook themselves washed? Odoriferous compounds could be lurking in many, many places around the kitchen, re-odorizing even perfectly fresh clean air. Matt Deres (talk) 14:27, 2 May 2018 (UTC)

Onion is particularly hard to clean up odors from; the odiferous compounds are a class of sulfur-containing compounds called thioketones which cling to just about any non-polar hydrocarbon out there, which includes oils (such as are found in skin) and plastics, and such compounds are fantastically resistant to soap as well. There's some reports out there that the smell can be removed by rubbing with a metal object, but this feels (speaking as a chemist) likely hokum; in my experience the only things that work are vinegar or bleach. --Jayron32 15:53, 2 May 2018 (UTC)