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October 15

Would the world be in a worse state if we still relied on horse and cart?

Economically, environmentally etcetera? JoshMuirWikipedia (talk) 02:39, 15 October 2016 (UTC)

The use of cars is not allowed by any Old and New Order Amish who consider the rules of their church, particularly regarding rural life, manual labor and humility, to be consonant with a better world obedient to God's will. AllBestFaith (talk) 15:13, 15 October 2016 (UTC)

Sort of a general theme of economics is that making it cheaper for people to do something they already want to do allows them to spend more money on other things. This spurs demand, which spurs hiring, which increases the money available to buy things, which... so on and so forth. It's hard to say precisely how much economic damage would be caused by such a drastic change, but you could imagine a massive collapse of various businesses (caused by the vastly increased cost of travel) would cost jobs, incomes, tax revenues, charitable contributions, and government expenditures on lots of worthwhile things. So, potentially huge. As for environmental issues, horses are pretty awful for the environment, despite being "all natural" (well, so is oil). See for instance the great horse manure crisis of 1894. Someguy1221 (talk) 02:54, 15 October 2016 (UTC)

(edit conflict) Read this and this and this for some background on the environmental question. We of course cannot answer questions of opinion such as "better" or "worse". But those articles should help you become more informed so as to reach your own conclusions. Also consider that the transportation of people and goods by horses is of a smaller scale than other transportation methods, such as rail, air, and road vehicles. This article covers the amount of goods moved through one country (the United States) by road transport. One can drive across the U.S. in 3-4 days by automobile. According to this a horse can travel only about 100 miles in 24 hours under optimal conditions; it would take well over a month to cross the U.S. like that. Also according to This a horse can at best carry 300-400 pounds for at most 8 hours per day. You can extrapolate from these calculations what it would take to move goods around the U.S. solely by horse. Again, "worse" is for you to decide without us telling you. But I've probably given you enough references to make your own comparisons regarding economic differences between using horses vs. trucks for transporting goods; this also ignores rail and air contributions as well.--Jayron32 02:56, 15 October 2016 (UTC)

(edit conflict)I take that to mean you're excluding steam engines. Checking Google maps, it's roughly 1400 miles (2250 km) from Florida to Wisconsin. A horse and buggy gets maybe 6 miles/9.5 km per hour. A single horse with a rider might be able to travel 60-100 km (or 37-62 miles) during a maybe 12 hour period. Horses have to eat, sleep, and even get additional rest even when not sleeping; cars and trucks just need to refuel. It's not unreasonable to assume that a horse pulling a cart with cargo might only be able to safely travel six hours. Even if you had stations for switching off horses and drivers every six hours (and had the swap down to a science), it'd still take about five days to ship oranges from Florida to Wisconsin. That would be too expensive for (at most) a couple dozen crates of oranges though. So, most non-canned, non-pickled foods would have to be grown locally, which would increase malnutrition (if not outright starvation).

The Mississippi river flows about 1.2 miles per hour, and north to south, so it wouldn't help with oranges. Indeed, it would be useless for anything that can't wait a couple of months (assuming you're sailing and rowing as much as possible). An enterprising Wisconsin cheese manufacturer might use the ride to age his wax-sealed cheese, cutting down on production time. Otherwise, the river is useless without steam engines.

And it's about 1850 km (or about 1150 miles) from Valencia to London, which includes at least 33.3 km (20.7 mi) of sailing. It took about a week to sail from Tunis to Genoa, which (per Google maps) is just under 900 km (roughly 550 miles). So, premodern sailors could get about 125 km/75 miles per day on a good day. If the crew rotates shifts and the weather is good, they should be able to pull 5 km/3 miles per hour, making the English Channel a six or seven hour crossing at best (two days at worst). Again, assuming you have stations to switch horses and drivers every six hours, have the sailing crew rotate, and everything's down to a science, it's still just over a week to get a crate of oranges from Valencia to England.

Since uncut oranges can last just over a fortnight, the 1975 series Survivors might have been exaggerating when one of the characters surmised that none of their children would ever taste an orange; but it would certainly be an exotic, decadent, foreign luxury.

And those are the best case scenarios. Realistically, the land travel would probably take two to four times as long. Ian.thomson (talk) 03:55, 15 October 2016 (UTC)

No need for malnutrition. If you can't get your vitamin C from oranges, just eat apples instead. Vitamin pills might be a good idea, too. StuRat (talk) 17:20, 15 October 2016 (UTC)

We know how to travel upriver without steam power. It is slower than downstream but not impossible. Just ask any voyageur. Rmhermen (talk) 04:04, 15 October 2016 (UTC)

I knew about rowing, but figured that it'd be unfeasible over the couple thousand miles involved except for very light travelers (like Huck and Jim). The voyageur article's description of the dangers would (under modern legal conditions) render land travel preferable to that. That said, there were indeed trading posts up the Mississippi, though I expect they'd still have to restrict the goods to something more portable than crates of oranges. Though there does appear to have been plans for (if not actual use of) animal-driven paddle boats after all, so maybe not. No idea what the speed would be. Ian.thomson (talk) 05:20, 15 October 2016 (UTC)

If there were real canals, then animals could pull heavy boats. This used to happen in the Netherlands. Rivers would be too shallow on the edge and not have a track on the side for the horse/ox. One person would be needed to steer the boat, and another to make the animal pull. Graeme Bartlett (talk) 11:36, 15 October 2016 (UTC)

Without getting into stuff like canals and towpaths, riverine commerce was carried out by hybrid sailing/rowing ships for millennia before the invention of the paddle steamer. -165.234.252.11 (talk) 19:33, 17 October 2016 (UTC)

You might find this account of the 1894 great horse manure crisis in London of some interest - http://www.historic-uk.com/HistoryUK/HistoryofBritain/Great-Horse-Manure-Crisis-of-1894/ Wymspen (talk) 11:39, 15 October 2016 (UTC)

Bubbles on puddles

Why is it that when bubbles form on the surface of puddles during rain, this is considered a sign that the rain will continue? My personal hypothesis is that this indicates that dissolved air is coming out of the water, which is a sign that barometric pressure is still falling (and therefore that the low-pressure system bringing the rain is still on the way in) -- am I on to something here? 2601:646:8E01:7E0B:ADC2:429C:883B:48A1 (talk) 10:11, 15 October 2016 (UTC)

What is the basis of your first sentence? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:38, 15 October 2016 (UTC)

Yes, without commenting on the factuality either way, I can't say I've ever heard the expression. During a rainfall you're unlikely to see many bubbles just because the water in the puddles would be in constant motion. Or are you talking about during gaps in the rainfall? There are a number of factors that would influence the presence of bubbles, including pockets of air in the soil itself. Matt Deres (talk) 13:04, 15 October 2016 (UTC)

I think surface tension traps air under a canopy of water until the bubble bursts due to its own inherent instability. I think the formation of the bubble results from the impact of the raindrop on the surface of the puddle, displacing some water and momentarily trapping some air. Bus stop (talk) 15:32, 15 October 2016 (UTC)

Searching for bubbles puddles rain I find half a dozen totally non-reliable sources saying this is a genuine old wives' tale, right up there with the thing about red sky in the morning. As such, well, it has a fair chance of being true. Wnt (talk) 18:08, 15 October 2016 (UTC)

Feynman Lectures. Lecture 31. Sec. 31–2 The field due to the material [1]

I have understood everything except one phrase: "the driven motion of the electrons produced an extra wave which travels to the right (that is what the factor e^iω(t−z/c) says)"

I don't understand why does factor e^iω(t−z/c) say the wave travels to the right. Why not to the left (as we know that waves are source-symmetrical)? In the case of Sec. 31-2 the position z=0 is the glass plate (not the source S). So to use the shifts of the graphs E(t) and E(r) as proof we should assume where source is situated and in what direction the wave goes. But direction is what we have to prove. Besides it is written in Table 31–1 that z is perpendicular distance from the plate (so positive no matter in what point field is measured: to the left or to the right of the plate).

I understand that if the graph of E(t) is like this, then the graph of E(z) is like this in accordance with Fig. 29–2 and Fig. 29–3 and in accordance with rules of graph transformation (like with y=f(x) and y=f(-x)).

Can somebody explain how does factor e^iω(t−z/c) (or Cos[ω(t−z/c)]) prove that direction of wave is rightward? I feel the answer must be simple, but I reached a deadlock. Username160611000000 (talk) 11:51, 15 October 2016 (UTC)

• If the wave from accelerated electrons of the plate would be moving to the left then the factor would become e^iω(t+z/c). Is it correct? Username160611000000 (talk) 15:59, 15 October 2016 (UTC)

You're right that "waves are source-symmetrical" in that the general solution to the wave equation is symmetric. Particular solutions need not be; $e^{i\omega (t-z/c)}$ describes a right-moving wave because its surfaces of constant phase are $t-z/c=a$ for arbitrary a, or $z=c(t-a)=z_{0}+ct$ with a rephrased $z_{0}=-ca$. --Tardis (talk) 15:00, 16 October 2016 (UTC)

Magnesium sulphate and mineral water

Our article on Magnesium sulphate says "It is naturally present in some mineral waters" with a citation needed tag. Is it possible to state this? I know that magnesium ions and sulphate ions could be present in some mineral waters (those in the town of Bath, for example) - but it seems to me that, unless those are the only salt ions present, then the compound itself can't be said to be present. Is this correct?--Phil Holmes (talk) 12:05, 15 October 2016 (UTC)

IUPAC changed the spelling of sulphur/sulphate to sulfur/sulfate in 1980.
Sleigh (talk) 12:13, 15 October 2016 (UTC)

IUPAC has no authority whatsoever over the English language. (Given that they prefer the atrocious "aluminium", it's a good thing they don't.) --Trovatore (talk) 21:57, 15 October 2016 (UTC)

My English dictionary still says sulphur, so that's good enough for me. But can you answer my question?--Phil Holmes (talk) 12:41, 15 October 2016 (UTC)

@Sleigh: it was actually 1990[2]. DMacks (talk) 21:27, 15 October 2016 (UTC)

There are certainly quite a few Br⁻ anions in the sea, but we don't have much of a problem saying that there is common salt (NaCl) in it, right? Same principle. Double sharp (talk) 12:51, 15 October 2016 (UTC)

By extension, if the water has unusually high levels of both magnesium and sulfate but not of other ions, one could say "it has high levels of magnesium sulfate" because there's not any other obvious way it could have only these two being high. And likewise if there are lots of ions but those two are present in a 1:1 ratio and no other ion levels provide the correct ratio for this substance one could deconvolute the components. But you're right, that if you toss certain amounts of MgSO₄ into certain amounts of ocean water, you can't tell after the fact whether you added MgSO₄ to water containing NaCl vs adding MgCl₂ into water containing Na₂SO₄. DMacks (talk) 21:21, 15 October 2016 (UTC)

Mission to Europa

In April 2016 issue of Astronomy, a popular magazine, there is a feature article: "FINALLY. The historic journey to Europa." Europa is a Jupiter satellite of course. They say on page 25 that it will be a flyby mission with 45 revolutions around the moon only because the craft will eventually be destroyed by a powerful electron wind emanating from Jupiter. My questions are: (1) If there is a stable wind of electrons that means that Jupiter must be strongly positively charged and that charge must keep increasing. Is it what's happening? The second question is: (2) "What is the origin of those electrons? Thanks, --AboutFace 22 (talk) 16:32, 15 October 2016 (UTC)

We have an article about the mission at Europa Multiple-Flyby Mission (not sure it needs italicizing, but it is in the article) which leads to Magnetosphere of Jupiter, a featured article all about the topic of your question. Give those a look and come on back if there's anything that's still unclear. Matt Deres (talk) 16:36, 15 October 2016 (UTC)

I've put a note on the article talk page about the italics. The name is apparently rather controversial. Tevildo (talk) 14:16, 16 October 2016 (UTC)

(ec)Could it be that electrons move away from Jupiter at that location, but move towards Jupiter at other locations, in an equal amount, guiding by the Jovian magnetic field ? The other possibility is that the electron wind is in orbit, neither leaving nor hitting the planet. The actual answer may be a bit of both. (Hopefully Matt's links answer these follow-up Q's.) StuRat (talk) 16:42, 15 October 2016 (UTC)

The electrons are trapped in the same way as they trapped in Earth's radiation belts: they gyrate around the magnetic field lines while cyclically moving along the lines up and down out the equatorial plane. The word "wind" is a misnomer. Ruslik_Zero 18:55, 15 October 2016 (UTC)

Loudspeaker's size and weigh

Does a good loudspeaker, one that has deep basses and precise high frequencies, have to be heavy and bulky?--Llaanngg (talk) 17:00, 15 October 2016 (UTC)

As far as the bass goes, yes. To reproduce the lowest bass frequencies at a reasonable volume you have to move a lot of air, which means a cone with a large diameter and a long excursion, and the box itself has to be large and rigid. You can lighten it a bit with neodymium magnets and using plywood instead of heavier particle board, but that only helps some.

One good way around this is to use high-quality headphones. I highly recommend the Audio-technica ATH-M50. --Guy Macon (talk) 17:21, 15 October 2016 (UTC)

There are expensive systems that have good bass and small size, such as this one from Bose: [3]. But, there are limits, which is why built-in speakers on even high-end flat-screen TVs often sound horrid. The solution, if you don't need much volume, is a good 2.1 plug-in speaker system (right, left, and subwoofer speakers), which can give you decent bass for like $30. StuRat (talk) 17:24, 15 October 2016 (UTC)

• No, but it has to be stiff. Unless you have a supply of unobtainium, the necessary stiffness has usually been achieved (as this is the cheapest way) by using materials that are heavy and bulky. In a few cases, esoteric materials (mostly carbon fibre composites) have been used to produce lightweight bass speakers - often as horns (although most horns are used as mid-range drivers, large horns can handle bass). Bose speaker systems have tried this, using cheap injection moulded plastics and marketing. WP used to have a lot more on Bose, but it was deleted during one of the religious wars. So it goes.

A bass speaker will still have to be large though.

Headphones are a little different. The frequency response of eardrums are themselves limited, so much of the low frequency comes from bone conduction. This allows headphones to achieve a useful bass performance, despite the limits of their small drivers. Andy Dingley (talk) 19:15, 15 October 2016 (UTC)

Wait, unobtainium is a term? I routinely use (the French version of) unfoundablium, and thought I was pretty witty to be the first to come up with the term. Tigraan^{Click here to contact me} 17:48, 16 October 2016 (UTC)

It was the goal in the sci-fi Avatar (2009 film). StuRat (talk) 22:51, 16 October 2016 (UTC)

"Unobtainium, n. A substance having the exact high test properties required for a piece of hardware or other item of use, but not obtainable either because it theoretically cannot exist or because technology is insufficiently advanced to produce it. Humorous or ironical." -- Interim Glossary, Aero-Space Terms, 1958, Air University of the US Air Force. --Guy Macon (talk) 00:32, 17 October 2016 (UTC)

Blood tests

When you look at your blood test results, which is the specific blood test that would indicate concerns for high cholesterol? Which is the specific blood test that would indicate concerns for diabetes? And are these specific tests usually included in the CBC (Complete Blood Count)? Or are they ordered specially and individually? Thanks. Joseph A. Spadaro (talk) 19:19, 15 October 2016 (UTC)

Cholesterol is tested using a Lipid profile. Diabetes is tested for by using Glycated hemoglobin levels. Neither is included in a Complete blood count, and will be requested specifically. Of course, to discuss the results of a particular blood test, or if you're worried about your health, you should consult an appropriate professional. Tevildo (talk) 19:49, 15 October 2016 (UTC)

At least in the U.S., they generally only order a glycated hemoglobin test if you have elevated glucose levels. Glucose level is part of the basic metabolic panel, which in turn seems to be part of the standard tests most doctors order. To the original poster, if you are having tests ordered for yourself, your doctor or other practitioner will probably answer any questions you might have. --47.138.165.200 (talk) 03:52, 16 October 2016 (UTC)

Thanks. I have had many CBC's in the past. I wanted to know if I would find anything in there. I guess the answer is "no", then? Joseph A. Spadaro (talk) 15:04, 16 October 2016 (UTC)

We do have an article on the complete blood count. The CBC contains tests about hematologic parameters—the cells in the blood, including red blood cells, white blood cells, and platelets, and reveals information about their number and morphology. It doesn't include tests of blood chemistry, like glucose or cholesterol.

It's fairly standard screening in the U.S. for an initial evaluation of a patient to include both a CBC and tests of blood chemistry. Though they are thus often ordered at the same time (under the theory of "we have to draw his blood anyway, why not get two tubes in one stick instead of doing them separately") they test different things. - Nunh-huh 20:31, 16 October 2016 (UTC)

Yes, thanks. I had assumed that a CBC was more encompassing than it apparently is. In my mind, the term "Complete Blood Count" always translated as "the generic blood tests that a doctor always orders about the most basic items". I guess I was wrong about that. Joseph A. Spadaro (talk) 03:14, 17 October 2016 (UTC)

How do you *spill* methyl mercaptan?

The L.A. Times just published an enraging story about a community (Eight Mile, Alabama) reported to have endured 8 years of stench affecting 1300 people from 500 gallons of spilled methyl mercaptan.

What's confusing me is that methyl mercaptan is a gas sold in pressurized cylinders. How do you spill it, and why didn't it rapidly volatilize?

This is somewhat interesting since I see that a cylinder of methyl mercaptan seems to go for $200-$300 [4], so for $10,000 a person could have fifty of them and (perhaps) build a "dirty bomb" that apparently can leave an entire community seeking long term evacuation. Wnt (talk) 20:31, 15 October 2016 (UTC)

Under pressure higher boiling point gases will liquefy. When spilt as a liquid, it would boil and cool down more. Perhaps there are also traces of less volatile mercaptans contaminating the original gas. These could stay around longer. Also methyl mercaptan could have reacted with ambient substances to make other longer lasting smelly sulfur compounds. One cylinder would disrupt a shopping centre but we don't want too many WP:BEANS.Graeme Bartlett (talk) 20:51, 15 October 2016 (UTC)

Also after reading the article, it claims to be in ground water. It could be stored underground for quite a while. Bacteria should be able to dispose of it if they can get oxygen. Face masks as seen in the protest will do nothing to stop the odor. Graeme Bartlett (talk) 21:00, 15 October 2016 (UTC)

From the article Wnt linked, I found Mobile Gas' FAQ website, explaining that their investigation discovered a line used to carry odorant was damaged by lightning. So there was a continuous source of new chemical flowing through that line - and leaking - over a potentially long period of time. The facts about total quantity and duration, it seems, are subject to some dispute - hence the scandalous story as reported by the Los Angeles Times' reporters.

The website of Mobile Gas links to the State of Alabama's document archive, which contains even more information on the history and facts of the incident as they are known to the state government.

To follow up on Wnt's other concerns: most sources conclude that methyl mercaptan isn't harmful in the very low doses that one normally expects to encounter - but this material safety data sheet published by Chevron Phillips does list toxicity hazards as part of the full safety information for the chemical. In sufficient quantities, this chemical - like almost any other - transgresses beyond nuisance to become a real hazard. Once again, because there is some dispute about quantities and durations of exposure, the community and the company seem to disagree about whether the case in Eight Mile, Alabama, was a mere nuisance or a true health-hazard.

But the same is true of many hazards: if a malicious group wanted to create nuisance or hazard, they could do so with many hazardous items that are freely available in the United States. On the spectrum of things to worry about, I'd say methyl mercaptan "dirty bombs" are low on the priorities list. Emergency responders would probably be able to handle such an event by following "normal" HAZMAT emergency procedures. I'm inclined to link again to caltrops - if an anarchic and malicious person wanted to harm a community, they could do tremendous damage using only a few dollars of parts and no special skills; this doesn't diminish the threat of "unique" chemical attacks, but it does demonstrate that difficulty-of-execution is not the primary barrier that prevents such antisocial behavior.

Nimur (talk) 20:54, 15 October 2016 (UTC)

Thanks for pointing out that link! I should feel guilty for not checking that link when I read the article, but I think the author should feel more guilty for not checking it when she wrote the article. It says "Mobile Gas purchases its mercaptan from a vendor whose product contains a combination of tert-Butyl mercaptan and Methyl ethyl sulfide." I still have to look these up, but tert-butyl sounds heavy and more liquid and stickier.... yeah, we have an article! The methyl boils at 6 C, but the tert-butyl boils at 62-65 C. So indeed it can be spilled as a liquid and can take much longer to evaporate. I see prices as low as allegedly $600 a metric ton, if I believe Alibaba -- then again, I'm not sure I believe anyone here. I mean, the simplest answer to the riddle of the stench is that somebody is lying about how much was leaked out of that line by several orders of magnitude... Wnt (talk) 03:21, 16 October 2016 (UTC)

The same way you spill helium: Really fast. Sagittarian Milky Way (talk) 03:43, 16 October 2016 (UTC)

To support Nimur's point [5] mentions cleanup of an accidental spill using soapy potassium permanganate soloution. It doesn't mention it lasting long term after that. Of course intentional contamination over a wide area may be more difficult. Still I'm not sure if the Eight Mile case is a good example since it sounds like there has been a lot of controversy over precisely what has happened and what's been done [6]. Note also that our Stink bomb article mentions US and Israeli law enforcement agencies and militaries developing devices for riot control and area denial weapons. It seems unlikely that they don't have a fair idea of the capabilities of weapons using these and far more hard to obtain chemicals. Perhaps Butyl isocyanide (admittedly also a fairly toxic compound) which is available here [7] but only in lab quantities. (But I haven't looked at industrial chemical suppliers.) The first source quotes a 1937 experience:

Butyl isocyanide proved to be so disagreeable to manipulate that none of its physical constants except boiling point were determined. Even when a hood with an extra forced draft was used, the odor pervaded the laboratory and adjoining rooms, deadening the sense of smell and producing in the operator, and in others, severe headaches and nausea which usually persisted for several days.

Nil Einne (talk) 07:05, 16 October 2016 (UTC)

Selenium and tellurium compounds might give these a run for the money, taking advantage of the periodically increasing stink down group VIB. Double sharp (talk) 07:41, 16 October 2016 (UTC)

A chemist of my acquaintance was contracted to make the flavouring for spring onion flavour crisps (scallion flavor potato chips). After making a batch he reported to his boss that it was a simple enough synthesis, and would generally have been worthwhile as a product. However the risk wasn't worth it - the chemical is such a powerful smell (like mercaptans) that if they'd ever spilled any, the clean-up would have been so difficult that it would have overwhelmed any profit they might ever have made from it. Andy Dingley (talk) 09:03, 16 October 2016 (UTC)

October 16

Radioactivity sucker

Is there such a device that can suck all the radioactivity out of something radio active. I just saw it on a science film?--86.187.171.5 (talk) 01:25, 16 October 2016 (UTC)

What was the name of the film? Ian.thomson (talk) 01:27, 16 October 2016 (UTC)

Usually you would have to do something like isotope separation. The time when you might be able to "suck" is when you remove radon, which is a gas. See radon mitigation. Nuclear reprocessing can be used if the radioactive substance is a different chemical element. Graeme Bartlett (talk) 02:01, 16 October 2016 (UTC)

Are you by any chance talking about X the Unknown, the article of which you edited prior to posting this question? If so, well, it's a science fiction film. There's a reason it's called that. --47.138.165.200 (talk) 03:58, 16 October 2016 (UTC)

Please keep in mind that not everything in a work of science-fiction is necessarily fiction, so it's legitimate to ask the question. However, I think Graeme has answered it already: basically, no, there isn't. --69.159.61.230 (talk) 06:47, 16 October 2016 (UTC)

• No. But most bulky things aren't themselves radioactive, they're contaminated with particles of something else that is. For soil around large nuclear accidents in particular, there has been success with methods as simple as cabbage growing. These absorb the contaminant metals and grow radioactive brassicas, which contain more of the contaminant (as a ratio) than the soil did, thus help to reduce the contamination in the soil. The vegetables can be picked and disposed of in one place.

If the base material is a liquid, with a contaminant dispersed in it, then separation techniques like chelation can help in a similar way. Andy Dingley (talk) 08:58, 16 October 2016 (UTC)

The sizes of hot particles encountered will vary by means of distribution (and with distance from the source). Particles from a fire, such as that at Chernobyl, entering the global environment, are of the order of 1 μm (ref), which is the same range as ordinary combustion-product contaminants (see the chart in the particulates article). Concomitantly the number of such particles will be in the billions, and only some wholesale process like Andy's brassicas (yay, another reason not to eat cauliflower) will address the issue. But where the particles are large (and distributed by a means like water, or just being ejected by an event like an explosion) there may be few enough (and each particle large enough) to make individual detection and removal practical. This is the case for the effluent from the Dounreay facility in Scotland. It may have shed 5,000 particles, each the size of a grain of sand, into the local marine environment(ref). Those particles, hundreds of times bigger than the aerosolised contaminants from Chernobyl or Fukushima, seem to be staying mostly in the environs of the Dounreay plant. SEPA routinely searches the local beaches for particles, and if it finds one it individually removes it - they've done this about 200 times so far. I imagine (but I can't find sources) that the areas around major disasters like Chernobyl will have a ring of such particles - outside the visible debris area, but with larger (and thus much more dangerous) particles than the airborne ones - and presumably watercourses will have carried these kind of particles away, better than the wind could have done. -- Finlay McWalter··–·Talk 12:55, 16 October 2016 (UTC)

Radioactivity is the continuous process of atoms emitting particles and energy as they decay, see Radioactive decay. It is impossible to predict when a particular atom will decay. One can only characterize a material by its Half-life which is the time for 50% of any large number of its atoms to decay. Materials are known with half-lives ranging from years to fractions of a second for unstable isotopes made in the laboratory, but there is no device that can change the half-life of a given material. An important use of a known half-life is in dating once-living carbon-containing remains by their relative content of carbon-14 whose half-life is 5,730 years. The answer to the OP is that there is no such device for a given material, but there are many ways and devices to carry out Decontamination which includes the physical removal of radioactive substance(s) by methods and devices as basic as a Vacuum cleaner. AllBestFaith (talk) 13:25, 16 October 2016 (UTC)

Isn't it possible to increase the radioactivity of a given sample of radioactive material e.g. by subjecting it to a neutron source or, with some materials, a Neutron moderator? Fission rate is controlled and adjusted in nuclear power plants and bombs. Could an object be made less radioactive in the future by encouraging fission in it now? Preferably so we don't create transuranics or other nastiness.

There is a fictional thing called nuclear damper but that is science fiction. 91.155.195.247 (talk) 14:27, 16 October 2016 (UTC)

See Nuclear_transmutation#Artificial_transmutation_of_nuclear_waste. Fgf10 (talk) 16:22, 16 October 2016 (UTC)

Hmmm, this gives me an idea... Wnt (talk) 14:54, 19 October 2016 (UTC)

With Po-210, even the meekest guy can be an alpha male. DMacks (talk) 15:07, 19 October 2016 (UTC)

Join the UPPU Club today! (See p. 126). Double sharp (talk) 15:34, 19 October 2016 (UTC)

I see this bird in Catford

| Does anyone know what species this bird is? Sorry if it's grainy, but hopefully you can identify it as that's the only photo of that bird I have on my computer._ CyanoTex (talk) 12:02, 16 October 2016 (UTC)

RSPB bird identifier suggests (with me guessing some of the info) a Wryneck [8], but with other possibilities including a starling. -- Finlay McWalter··–·Talk 12:28, 16 October 2016 (UTC)

*| Hmm. I'll see if I can get a more polished picture when the weekend's over. Description: Small bird when next to a pigeon. Black and yellow (more like a golden shade) color scheme. Beak looks more or less medium sized and perhaps of medium thickness._ CyanoTex (talk) 13:35, 16 October 2016 (UTC)

Almost certainly a Common starling (the wryneck is much smaller than a pigeon). See, in particular File:Sturnus vulgaris no.JPG. Tevildo (talk) 14:09, 16 October 2016 (UTC)

I do a bit of bird watching here in the UK. I think it is either a Song thrush or a Mistle thrush. Note the breast patterning. DrChrissy ^(talk) 15:18, 16 October 2016 (UTC)

I still think a starling is more likely - the thrush has a pale breast with dark spots, while a starling (and the OP's bird) has a dark breast with pale spots. A photo of the bird's head would probably be decisive. Tevildo (talk) 15:47, 16 October 2016 (UTC)

The OP describes it as "black and yellow" - that would be a very unusual starling as they are black, sometimes with spots (hence the name "starling"). DrChrissy ^(talk) 16:08, 16 October 2016 (UTC)

I concur that a Common starling is quite likely. At this time of year they are moulting (I was greatly puzzled when I first saw one close up in this state), and additionally the juveniles look somewhat different to the adults – see the first photo in the Description section of the article (already linked above), bearing in mind that there can be some individual variation. {the poster formerly known as 87.81.230.195} 90.197.27.88 (talk) 17:10, 16 October 2016 (UTC)

I doubt it is a wryneck - according to our article, their toes are in the manner of woodpeckers', with two pointing backwards. Common starling is possible, but most are darker and shinier than that. Matt Deres (talk) 13:21, 16 October 2016 (UTC) (restoring comment deleted by CyanoTex). Matt Deres (talk) 19:13, 16 October 2016 (UTC)

* | It is a common starling! Huh. Thanks, Reference Desk._ CyanoTex (talk) 20:51, 16 October 2016 (UTC)

• In October? It's a starling. Andy Dingley (talk) 02:35, 17 October 2016 (UTC)

I'd like to see a bit of explanation there. I mean, I think of starlings as glossy, scruffy, purplish or greenish even, while this seems softer. Its underside is practically a zebra stripe, as much white as black, and it even seems like there's a sort of a whitish band across the back. I understand an immature starling is browner, but usually very visibly speckled white on black though yes some are lighter. Can people comment on subspecies or point to some similar images for reference? Wnt (talk) 11:08, 17 October 2016 (UTC)

Cf. this one. N.b. the brown-edged, black secondaries. "There is more genetic variation between common starling populations than between nominate common starling and spotless starling". As explained at common starling, there is *tons* of genetic variation here, and subspecies are far from being unequivocally defined. Keep in mind we're not only talking juvenile/mature changes and subspecies changes in plumage, we're also right in the middle of molting time, and that creates a lot of varied looks too. Sure, it could in principle perhaps be a funny-looking example of some other bird. But OP shows us a photo that looks much like one of the most common urban birds in the world, and it's probably that. SemanticMantis (talk) 15:12, 17 October 2016 (UTC)

Perhaps it is a leucistic individual. That could explain the white band on the neck. DrChrissy ^(talk) 17:29, 17 October 2016 (UTC)

The image is blurry, but from what I can make out, there appears simply to be three exposed white feathers, with black ones underneath these, because this bird's head feathers are raised on account of it preening feathers on its chest. --Modocc (talk) 17:50, 17 October 2016 (UTC)

What are the grid fins on Shenzhou for?

Soyuz, with grid fins for the launch abort system
(Photo from the grid fin article)

These photos: https://twitter.com/AJ_FI/status/787725451238207488

seem to show Grid fin not covered in the Shenzhou (spacecraft) articles.

What are they for? Hcobb (talk) 19:15, 16 October 2016 (UTC)

They've been a feature of Soyuz since the 1960s(?), although were covered by fairings until the mid 1970s (removed to lose unnecessary weight). They're part of the launch abort system. Andy Dingley (talk) 19:54, 16 October 2016 (UTC)

Are there more species which go on two legs permanently like human being?

I'm not talking about kenguru which is not really goes on two legs only as human being does. The same thing about bears. 93.126.88.30 (talk) 19:38, 16 October 2016 (UTC)

See our article on bipedalism. ---Sluzzelin talk 19:42, 16 October 2016 (UTC)

E/c Birds. We have an article on Bipedalism. DrChrissy ^(talk) 19:43, 16 October 2016 (UTC)

Sasquatch--Aspro (talk) 20:05, 16 October 2016 (UTC)

I'd like to know from the OP why they think Kangaroos do not move on two legs are you talking about the gait, i.e kangaroos hop whereas humans walk? DrChrissy ^(talk) 20:17, 16 October 2016 (UTC)

ok, actually I meant to ask about mammals rather than birds. Kengero use a lot in their frontal legs. 176.100.5.242 (talk) 21:09, 16 October 2016 (UTC)

If you look at articles on kangaroos, they almost all classify them as bipedal. Don't forget, humans sometimes crawl using our front limbs, especially as children. DrChrissy ^(talk) 21:13, 16 October 2016 (UTC)

I believe the general view is that kangaroos are bipedal while moving fast (by hopping), but pentapedal when grazing or moving slow. See our articles (including Macropodidae and Tripod stance) and [9] Nil Einne (talk) 01:55, 17 October 2016 (UTC)

unrelated content

That's got me thinking (and yes, before anybody else says it – I know I should refrain from this bad habit). Apollo lunanoughts could put on foot in front of the other when walking slow but to move quickly, they found hopping was better -due to the inflexibility of an inflated space suit. Now: although they weighed only 1/6 of what they would have done on Earth, their 'mass' was the same and so was the mass of the very heavy life-support system which was on their backs. Look at the mass distribution on a 'roo and compare it with a lunanought. Looks to me about the same. Harrison Schmitt seemed to spend a lot of his time quadrupedal ( I am of that certain age when I was able to watch hours of telecasts live from de moon) Apollo 17 EVAs 10 (Schmitt falls again) . His actions are more like a slow motion rendition, of a holiday-maker in Cornwall, with a heavy backpack of tent and camping gear, looking for where he dropped his spectacles after drinking too much scrumpy. --Aspro (talk) 18:03, 17 October 2016 (UTC) Hopping in low gravity gets around the problem of low friction between the bottom of the foot and the ground. It isn't simply due to the heavy and/or inflexible suit. You can think of walking in low gravity to be similar to walking on ice. Because you fall slowly, it is easier to hop, avoiding a slip, and then quickly adjust your stance when you land. I doubt that Kangaroos have any issues with ground friction. 209.149.113.4 (talk) 18:10, 17 October 2016 (UTC) @ 209.149.113.4. I lived that era so don't try to kid me or anybody else. However, contrary to popular belief, the astronauts employed this form of movement not because of low lunar gravity, but because spacesuits of the era were not designed for walking. Moonwalking Astronauts Can Move Surprisingly Fast --Aspro (talk) 19:11, 17 October 2016 (UTC) Living in that era, you would have known about spacesuit design. You likely read "Have Spacesuit, Will Travel." Then, you would have knowledge that you did state above: the spacesuit weight is reduced, but the mass is not. Therefore, inertia is unchanged. The "heavy" suit is just as hard to start into motion as it is on Earth and just as hard to stop as it is on Earth. But, in less gravity, less weight, there is less friction on the ground. By pushing nearly directly down, friction is not an issue in starting momentum. By landing nearly directly down, friction is not an issue with stopping. The astronauts *did* try walking. They even tried running. It wasn't effective. Their feet simply slid out from beneath them. See Apollo 17 Jack Schmitt as he tries to pick up a sample bag. He steps to the side and leans. The foot with less weight on it slide out from under him and he falls down. Alan Bean became a lecturer and explained that you had to use your whole body to hop because you couldn't depend solely on the connection between your feet and the ground. It tended to slip. So, you had to use your arms to help direct your momentum upwards. While there are falls on record that clearly show that the astronaut lost balance, you can also find many falls on Youtube that clearly show the astronaut taking step and the slipping and falling. See this Youtube collection. The first one leans over, but as he tries to get upright you can see his feet slipping on the ground. Then, one falls over while hopping. You can see him try to push with one leg, but it just slides on the ground. Again, another foot slip. Then, one appears to be standing upright and his feet slide right out from underneath him. I believe that this is more than enough to back the statement that hopping is not used SOLELY because the space suits were bulky. It was also used to overcome the lack of ground friction. 209.149.113.4 (talk) 20:08, 17 October 2016 (UTC)

October 17

Medical, hydrocell

Hydrocell,its origin and treatment — Preceding unsigned comment added by 116.68.82.248 (talk) 07:03, 17 October 2016 (UTC)

Do you mean hydrocele? If so, please read that article and let us know if you have specific questions. Rojomoke (talk) 07:27, 17 October 2016 (UTC)

October 18

In a li-ion battery, does the chip distribute the tear and wear?

In common mainstream li-ion batteries, does the controller distribute the use across all cells all the time? Or could it be that one cell gets weared out sooner than the others? That is, could a used battery have some cells that are still good, even if the battery has lost 30-40% of its capacity? --Llaanngg (talk) 17:56, 18 October 2016 (UTC)

Here's an excellent web resource: This Week in Batteries, an informal blog maintained by the fine folks who run the Chemical Engineering 198 class, Battery Technologies and Markets, at Berkeley.

They have a lot of great resources to help you understand modern battery management systems - the engineered devices around the electrochemical cell that make sure the cells are operating correctly.

It would be irresponsible to categorize all lithium-ion battery systems into the same bucket - there are immensely variable configurations in modern systems. Some battery management and power-supply systems certainly perform load balancing.

One of the easiest, simplest, most straightforward ways to do load-balancing is to connect the cells in series. There is a good reason, based on solid fundamental science, to explain why this works so surprisingly well - but it has alarming shortcomings and serious impact to total system performance.

Nimur (talk) 18:27, 18 October 2016 (UTC)

From the publication list hosted at National Renewable Energy Laboratory, here is Modular approach for continuous cell-level balancing to improve performance of large battery packs (2014), available at no cost from IEEE. NREL actively investigates and sponsors research in battery control algorithms, including active cell balancing technology. Nimur (talk) 00:19, 19 October 2016 (UTC)

The OP's question is a concern common to the thousands of owners of the ageing but popular Toyota Prius hybrid electric cars. Individual cells of the series-connected Li-Ion traction battery do indeed wear out (lose capacity) prematurely. The on-board diagnostic program gives an error code when it detects imbalance. There are video guides[10] [11] [12] on line about how to rejeuvenate the battery by replacing individual cells but it must be warned that this requires working in a high voltage circuit that is dangerous for an amateur without full knowledge and precautions. The manufacturer's battery warranty will not cover an unauthorized repair. AllBestFaith (talk) 12:59, 19 October 2016 (UTC)

The BMW i3 has an active cell balancing mechanism to ensure that all cells are correctly managed. See https://issuu.com/brycheinsltd/docs/evs_and_i3 for details.--Phil Holmes (talk) 14:36, 19 October 2016 (UTC)

October 19

Feynman Lectures. Lecture 32. Sec. 32–5 Scattering of light [13]

Quote: Now we can make an experiment that demonstrates this. We can make particles that are very small at first, and then gradually grow in size. We use a solution of sodium thiosulfate (hypo) with sulfuric acid, which precipitates very fine grains of sulfur. As the sulfur precipitates, the grains first start very small, and the scattering is a little bluish. As it precipitates more it gets more intense, and then it will get whitish as the particles get bigger. In addition, the light which goes straight through will have the blue taken out. That is why the sunset is red, of course, because the light that comes through a lot of air, to the eye has had a lot of blue light scattered out, so it is yellow-red. Unquote.

I need advice to check have I correctly understood. The light when is going through the atmosphere is absorbed and re-emitted (scattered ) by atoms' electrons. There is the formula

$\sigma _{s}={\frac {8\pi r_{0}^{2}}{3}}\cdot {\frac {\omega ^{4}}{(\omega ^{2}-\omega _{0}^{2})^{2}}}$

According to it blue light takes 16 times more scattered energy than red light, as the blue has 2 times higher frequency. But frequency ω that enters into the formula is the frequency of scattered light. So (1): where is blue light from incident beam? I've found several demonstrations on youtube (e.g. youtube.com/embed/LSf7iRD5Jws ). And it looks like the light from a lamp loses blue. And (2): even if blue light re-emitted more intensively, last layer of atoms before eye must absorb red light and re-emit white light. So we have the statement that light keeps its frequency and ω_incident = ω_scattered . (3) When a wave goes through an atom, electrons begin to oscillate and emit: https://s.sender.mobi/u/image/2016/10/19/wl-chKHAa/-.PNG . Electrons emit in all directions in sheet plane whole absorbed energy, but 16/17 of it is blue and 1/17 of it is red light. Then the light from a lamp (which goes form right to left) must lose same amount of blue light as was emitted by electron.

Is it correct?

Username160611000000 (talk) 04:07, 19 October 2016 (UTC)

Yes, the light loses mainly blue frequencies as it passes through a scattering medium and becomes redder. Ruslik_Zero 19:54, 19 October 2016 (UTC)

Is that true that for increasing testosterone it's good to eat a lot of fats?

Is that true that for increasing testosterone hormone it's good to eat a lot of fats (or food which rich with fats)? I saw a youtuber which said it but I don't believe anything without scientific evidence. I would like to ensure or deny it. thank you 93.126.88.30 (talk) 19:34, 19 October 2016 (UTC)

Looking into a general google search for "Dietary effects on testosterone" leads to a lot of sketchy weight building sites with not a lot of hard science. However, using Google Scholar, I was able to find a few interesting published studies. This one is from an older study (1979) but otherwise looks solid, stating "A lower nocturnal release of prolactin and testosterone occurred in men fed a vegetarian diet" while this one from 2008 states "high-fat fed rats showed significantly lower total values of plasma TSH and testosterone" which would seem to indicate the opposite of what your random YouTuber claimed. This article from 1987 seems to indicate the controlling factor is not fat at all, but protein/carbohydrate ratios in the diet. Just some places to research your question. --Jayron32 19:53, 19 October 2016 (UTC)

More to the point, why should anyone care? If you have actual androgen deficiency, consult a medical professional. Otherwise, there's no real reason to care about your testosterone level. There are loads of "broscience" passed around in the world of bodybuilding, etc. which is pretty much all bullshit. If you want to maintain good health, eat a well-balanced diet and get regular exercise. --47.138.165.200 (talk) 01:47, 20 October 2016 (UTC)

may dead bodies infect life bodies with hepatitis or HIV?

may dead bodies infect life bodies with hepatitis or HIV? I'm asking it because I have a doubt if this viruses need nutrition or oxygen etc. in order to exist. 19:37, 19 October 2016 (UTC) — Preceding unsigned comment added by 93.126.88.30 (talk)

This forum discussion has some excellent references to research on the matter. Here is a more general overview form the World Health Organization, and Here is another source specifically for HIV. Wikipedia also has an article titled Health risks from dead bodies which has some brief statements to this effect, but also leads to more reading if you follow the references. --Jayron32 19:45, 19 October 2016 (UTC)

Just a little grammatical aside — you mean "can dead bodies infect....". I know the can/may distinction is a little tricky for some non-native speakers, as not every language has it (not sure about Ukranian). Anyway, you should use may for permission or moral or legal acceptability, can for physical possibility or practical feasibility. --Trovatore (talk) 19:52, 19 October 2016 (UTC)

Are there any reports (preferably scientific reports) which talk about the amount of pain that a person with prosthetic balls suffers when he gets kicked in the balls?

Apologies if this is a stupid question; however, I am genuinely curious as to whether or not people with prosthetic balls experience as much pain as people with natural/biological balls experience when they get kicked in the balls.

Anyway, does anyone here have any thoughts and/or data in regards to this? 128.195.178.33 (talk) 22:13, 19 October 2016 (UTC)

Here is a discussion forum on prosthetic testicular pain. --Jayron32 22:36, 19 October 2016 (UTC)