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February 13

under what conditions will a Grignard or sodium hydroxide polymerize an epoxide

Nucleophiles like Grignards and organolithium reagents open up the epoxy ring, and so do alkoxides. But when the epoxy ring opens, a new alkoxide is generated, which can then open another epoxy ring ... I'm aware epoxides are used as plastics but apparently this is done under conditions of "curing" and isn't as simple as adding base. Which makes me wonder -- what prevents the newly-formed alkoxy species (especially in aprotic solvent) from attacking another epoxide, which then will create a new alkoxy species to attack yet another epoxide? For example, if my intent is to react ethylene oxide with n-butyllithium, what's to prevent polyethylene glycol polymerization as a side reaction? Yanping Nora Soong (talk) 02:20, 13 February 2016 (UTC)

Anionic polymerization of epoxides to make -CH2CH2O- polyether chains (with various substituents in place of the various H) is well known. One can consider concentration, reactant-ratio, competing nucleophilicity, and counterion effects. DMacks (talk) 22:04, 13 February 2016 (UTC)

Are PUFAs in cooking oils harmful?

Is the consumption of too much PUFAs harmful for health? The Wikipedia article polyunsaturated fat has no mention of any negative health effects. But I found some references, none of them reputed journals, which say too much PUFA is harmful. According to this article, PUFAs can cause free radical damage, excessive skin pigmentation, can damage pancreas cells, can impair protein digestion, can cause live damage. --IEditEncyclopedia (talk) 03:08, 13 February 2016 (UTC)

Too much of anything is harmful for health. The source you cite is only the tiniest step up from NaturalNews -- notice the author's list of recommended health books is a a head-spinning catalogue of woo. Shock Brigade Harvester Boris (talk) 03:19, 13 February 2016 (UTC)

There are 14 reviews and meta-analyses of the effects of PUFA on human health published in mainstream journals, some of which are free to read online. None of them find any dangers to PUFA consumption, even in babies. Now as Boris said, the poison is in the dose. Eat enough of anything and you'll probably get sick. And I'll note that the author of that article you linked got all of his information from the Weston A. Price Foundation, which is well known to advocate dietary advice that is completely divorced from science. Someguy1221 (talk) 05:43, 13 February 2016 (UTC)

cabin pressure for private jets

In airliners the cabin pressure is slightly lower than the normal ground pressure for cost saving reason. This causes a barely noticeable discomfort for passenger.

Is the same thing done for private jets? In this case, the passengers are presumably rich enough for pay for the comfort of 100% ground pressure.

The same question also applies for the humidity as well. [Airliner]] cabin air are pretty dry due to, again, cost-cutting measures. What about private jets? Johnson&Johnson&Son (talk) 06:18, 13 February 2016 (UTC)

According to [1], cabin pressure on private jets can be kept much closer to sea level than is typically done on commercial jets. However, maintaining standard atmospheric pressure is not always possible, as cabin pressure is fundamentally limited by the power output of the plane's engines. Someguy1221 (talk) 06:58, 13 February 2016 (UTC)

I didn't realize that maintaining the cabin pressure, whether for airliner or ultra comfy private jets, took that much engine power. I thought that aircraft cabins were pressure vessel so maintaining a particular pressure (that's within design limits) is "free" in the energy sense? Johnson&Johnson&Son (talk) 07:08, 13 February 2016 (UTC)

(I realise it's not "free" in the financial sense since stronger pressure vessel => more weight => more lift required => larger wings and/or bigger engines => higher costs.) Johnson&Johnson&Son (talk) 07:10, 13 February 2016 (UTC)

maintaining standard atmospheric pressure is not always possible, as cabin pressure is fundamentally limited by the power output of the plane's engines. ' absolute bollocks in context. The power to pressurise the cabin is small compared with the power output of the engines. Greglocock (talk) 11:36, 13 February 2016 (UTC)

If you're an expert, provide a better context or a better source. Someguy1221 (talk) 22:34, 13 February 2016 (UTC)

Actually, let me clarify this myself, given that it was given in poor context. The cabin pressure is fundamentally limited by the electrical power outputted by the planes engines, and the efficiency of the cabin pressurization system, and the air-tightness of the cabin, and the ability of the fuselage to withstand the stress of pressure differentials. Someguy1221 (talk) 08:50, 14 February 2016 (UTC)

The cabin is pressurized using bleed air from the engines, that means the same engines that push air backwards to go forward are quite literally shoving air into the cabin as well (via A/C packs to cool it down, compressing air makes it *hot*), not merely generating electricity for some electrical pump. 85.212.111.153 (talk) 08:00, 16 February 2016 (UTC)

(edit conflict) Stress is a big part of it - reducing pressure relaxes stress on the fuselage. See Cabin pressurization. Our article on bleed air (the air pumped out of the engines to power other systems) says that running cabin pressurization from the engines reduced their efficiency (although it doesn't say how much) but that many modern aircraft use electric pumps instead (which of course still need to get their power from the engine, but apparently this air is easier treat (i.e. to get to the right temperature and pressure). Smurrayinchester 11:46, 13 February 2016 (UTC)

Why not have a look at some promotional literature for several common types of small jet?

The Gulfstream 650ER is arguably the best that money can buy, (unless you're a serious super-billionaire who can afford a private Boeing). "At a cruise altitude of 45,000 feet/13,716 meters, a G650ER cabin is pressurized to an altitude of 4,060 feet/1,237 meters. That cabin altitude is almost two times lower than commercial airlines and significantly better than any non-Gulfstream aircraft in the large-cabin class." Forbes Magazine believes the sale price of this aircraft to be around $65,000,000, although as a general rule, if you want to get an accurate figure, you'd have to fly to the sales office, presumably in a credible aircraft.

Somewhere down the line is the Cessna Citation CJ4. "The CJ4 features separate temperature-control zones for the cockpit and cabin, and digitally managed pressurization that maintains a sea-level cabin up to an altitude of 21,067 feet."

A very nice, slightly more affordable aircraft is the Learjet 75. "The aircraft’s pressurization system provides a sea-level cabin up to 25,700 feet (7,833 m) and a maximum 8,000-foot (2,438-m) cabin altitude at 51,000 feet (15,545 m)."

The KingAir is not a "jet," but is a turboprop and uses Jet-A; pilots of the KingAir can log turbine time. Textron includes this helpful documentary, Transitioning from Piston to Jet on their sales page. The KingAir cabin pressurization controls are a little different than the more expensive jets: this article from Flying magazine explains: "One reason is that with five psi maximum cabin pressure, the cabin altitude is near 12,500 feet when flying at 30,000 feet. That's legal, but not comfortable for every pilot."

About the smallest pressurized cabin you can buy is a Mooney. An M20R is decidedly not a jet, but it will set you back a bit more than half a million dollars, brand new. I found a very nice 1969 Mustang for sale on Trade-A-Plane - N7727M, $135,000 - that has a pressurization switch and an automatic isobaric valve to keep your plane from exploding if you try to pressurize above 5psig (roughly 7,500 cabin pressure altitude at the aircraft's service ceiling). It is incredible what a little money can buy.

Nimur (talk) 16:38, 13 February 2016 (UTC)

Gulfstream's marketing appears to be outdated or misleading. The Boeing 787 Dreamliner is capable of 6,000 feet/1,830 m at 43,000 feet/13,006 m (service ceiling) [2] [3] [4]. I'm not sure what it would be at 45,000 feet but it's not likely to be almost two times 1,237 m. The 787 is definitely a commercial airline now and the ref didn't say anything about most. The Airbus A350 XWB is similar [5] although there are fewer in commercial service at the moment. Interesting enough, Cabin pressurisation suggestions the median pressurisation of both the 747 and A380 is actually below the 6000 feet level that Boeing claims is sufficient (as higher gives diminishing returns), although that probably means a fair few were higher at least for the A380. Some sources like [6] claim 5,000 feet for the A380, but that is contradicted by the study and I can't find any advertising from Airbus about it which suggests to me it's probably wrong. One interesting thing that the source does mention is the SyberJet SJ30 which is supposed to have a sea level cabin to 41,000 feet/12497m, although I'm not sure how easy it is to buy one (well unless you trust that they will deliver the new ones). I guess you could become friends with Morgan Freeman [7] [8] [9]. BTW some of those sources and [10] do discuss how passenger comfort is complicated and you shouldn't just focus on pressurisation. (The sources also discuss pressurisation levels for various airplanes but you may want to check this info, per earlier.) Nil Einne (talk) 19:35, 13 February 2016 (UTC)

Indeed, fair points all around, Nil Einne. One hopes that the buyers of expensive jet aircraft will do a little independent research with multiple sources, and fact-check all the advertisement claims. It is very true that new airliners like the Boeing 787 and the Airbus A380 do provide higher cabin pressurization; this was a major marketing advantage for these new aircrafts. Here are some details: Boeing 787 from the ground up, and the 787 No-Bleed System Architecture, both articles from Boeing's corporate communications magazine. Here's an article from airline Lufthansa: Cabin Air Circulation. I can't emphasize enough that the 787 is only a few hundred million dollars more expensive than the G650-series; so it's bound to have a few enhanced systems. My point, really, is to express that aircraft passenger comfort systems have an incredible range from the very low-end to very high-end. In principle, nothing prevents you from operating an A380 or a 787 or similar large passenger airliner as a private jet; well, it helps if you're some kind of Amir. A handful of the most extravagant movie stars and business-people might fall onto that price-point, too. Most ordinary billionaires would find a smaller jet suitable for their needs, and a lot cheaper to operate. I suspect Gulfstream isn't expecting its clientele to be comparing their aircraft against performance specifications of a wide-body superjumbo. Nimur (talk) 22:08, 13 February 2016 (UTC)

If you think the discomfort from the change in air pressure is "barely noticeable", try sitting near a screaming baby when its ears are popping due to the pressure change. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:22, 13 February 2016 (UTC)

On that topic - there is a great deal of misinformation regarding the required use of a safety restraint or seatbelt for a child when flying on a "private jet" - rather, when the child is a passenger on a flight conducted under Part 91 (or Part 135). Subsequent to one particularly severe fatal accident in 2009, FAA has clarified their seat belt guidance. This is a frequently-asked question in general aviation discussions. 14 C.F.R. §91.107 was amended in 2014; this is a good reminder to always check a current copy of the FARs, especially if you are going to be operating a private jet with small babies on board. Small children under two, like sport parachutists, are among the very few individuals who are especially called out as special exceptions to the normal rules for safety restraint; these individuals aren't impervious to accident, but federal regulations are a little bit more lenient regarding what safety equipment they require.

If the small babies are also sport parachutists, they may use the floor of the aircraft as a seat. In such a case, the operator of the aircraft would be wise to consult an aviation attorney for a professional opinion clarifying the applicable rules, among other reasons.

Nimur (talk) 17:59, 13 February 2016 (UTC)

It's not my fault that you can only afford shitty economy seats.Johnson&Johnson&Son (talk) 02:07, 14 February 2016 (UTC)

Heavens. Please review this flow chart. ericg ✈ 00:49, 17 February 2016 (UTC)

See also the thread Can an airliner provide ground level cabin pressure, temperature, humidity etc? on Aviation SE. – b_jonas 16:26, 15 February 2016 (UTC)

Dissolving Low-density polyethylene

So I have a project. I am making a tea infuser out of polyethylene (LDPE to be exact). I’ve made the overall shape, and now I want to give it a matte finish. The model is too complex to be sanded efficiently, so I am looking for an alternative way I could make it less glossy. I think it might be possible apply some chemicals that will dissolve the top glossy layer of plastic and thus make it matte. Unfortunately I have no Idea what those chemicals might be. So I am stuck with 2 questions:

Firstly I would like to know if you think it is even possible to give a matte finish to a polyethylene part by rubbing/dipping it into some chemicals? What chemicals could that be? Maybe a strong acids or even paint thinner(possibly heated)?

The second question is if my tea infuser would still be foodsafe after I apply said chemicals? If I understand correctly, to dissolve polyethylene I have to subject it to a chemical reaction. Does this mean I will end up having a part made of something other than pure LDPE? Can all the leftover chemicals be washed off after I got the desired finish? 46.138.235.28 (talk) 11:32, 13 February 2016 (UTC)

LDPE is pretty tough, and most solvents won't have an effect on it. That said, my experience (with vapour smoothing 3D printed parts, which means PLA and ABS) is that using solvents makes plastic look glossier, not matte. Rough sanding makes things go cloudy because it's a very random process - some parts get rubbed by the grains, some don't, so there isn't a flat surface to reflect light. Using solvents dissolves the surface evenly (and makes it flow a bit) so you get a glassy finish. Smurrayinchester 11:59, 13 February 2016 (UTC)

Another way to think of how that works (and a kind of spherical cow idealization) is to imagine a surface that's already perfectly flat and smooth with tiny little cube-shaped bumps on it. Let's mentally divide the surface into a grid that's the same size as the little cubical 'bumps'. (If you ever played Minecraft, you should have a mental model for what I'm saying.) If a chemical that dissolves the surface is applied, then the grid cells that are already flat will get dissolved away at the exact same rate everywhere - so the surface will stay flat. But a grid cell containing a bump will be dissolved away simultaneously on all five exposed faces of the cube. So the material in that cell is removed five times faster than for the already smoothed cells...and that results in bumps flattening out much faster than the general surface is eaten away. The net result is that the surface ends up smoother.

Now suppose that there cube-shaped holes in the material. The base of the hole only get lowered slightly - but the four adjacent grid cells get attacked from above and the side - so they dissolve away faster than the surrounding area - and that abrupt hole gets smoothed out laterally...and again, the surface ends up smoother.

So where the surface is initially smooth, it stays smooth - but where there are abrupt changes in surface shape, a uniform erosion process will tend to make them flatter.

A uniform erosion process clearly doesn't make the surface rougher - so rapidly heating the surface until it flows would have much the same effect. You need some source of randomness - which is what sanding or sand blasting does. I wonder if, in your case, applying an active chemical, mixed into a paste with some inert material (like sand) would produce the desired degree of randomness? SteveBaker (talk) 17:03, 13 February 2016 (UTC)

A tea infuser is placed in a cup of boiling water. Water boils at 100 °C. LDPE withstands temperatures of 80 °C continuously and 95 °C for a short time. Making a tea infuser out of LDPE is courting disaster. AllBestFaith (talk) 18:16, 13 February 2016 (UTC)

Indeed, I would avoid putting LDPE in contact with boiling water. Although I can find a few sources that say LDPE withstands boiling water, WP:OR - it will rapidly deform and/or melt when exposed to even these moderate temperatures near 100°C. Here is a source, Sterling Plastics of Minnesota, that cites several standard metrics, including a Heat deflection temperature of 120°F - much lower than boiling water or even warm tea. The plastic will melt at just above the boiling point of water. However, the thing about plastics is that their quality and material properties vary widely - you can't be "very very" certain that your material is guaranteed not to melt at 212°F - or even 180°F. This Material Safety Data Sheet for ExxonMobil's formulation of LDPE resin, hosted by SUNY Stony Brook, says it's insoluble in water and not particularly toxic... but I still wouldn't want to drink tea that "might" have some melted LDPE residue in it. The key takeaway is that you can't be sure exactly what goop your plastic sample contains, and you can't be sure what is going to dissolve in your hot water. Nimur (talk) 18:34, 13 February 2016 (UTC)

If the solvent dissolves the LDPE, then the LDPE dissolves the solvent. So only use a solvent you feel comfortable drinking with your tea. I didn't get to the bottom of the question of what plasticizers are there already and what effect they have - [11] makes LDPE sound like a safe alternative, but [12] says that estrogenic activity can be detected when LDPE is "stressed". I suspect melting, dissolving, and near-destroying over boiling water count as stress. Wnt (talk) 20:34, 13 February 2016 (UTC)

Two careers ago I was developing manufacturing processes for bonding or glueing plastics. There are a variety of solvents available and they are almost without exception stupid things to drink. I recommend sand blasting with sugar. Greglocock (talk) 20:59, 13 February 2016 (UTC)

Though I doubted as much, it occurs to me that there are environmentally friendly options like supercritical CO2 - looking this up, I find some articles like [13] that seem to suggest it dissolves LDPE, though almost without exception they're locked behind paywalls in obscure journals; this is one of those topics that We're Just Not Allow To Know About. But of course, it's essentially impossible for a hobbyist project to use CO2 for this anyway, so the grapes were sour anyway. Wnt (talk) 13:42, 14 February 2016 (UTC)

Damaging effects of gravitational waves

It seemed to me, though I don't really know anything about the subject, that if gravitational waves actually stretch space itself, then even intense waves would not cause any damage to physical objects as they passed through. However, at [14], it says that sufficiently strong waves would "rip you apart". Is that actually correct? 81.132.196.131 (talk) 20:34, 13 February 2016 (UTC)

Spaghettification, due to a non-homogeneous gravitational field near a black hole, may be relevant. StuRat (talk) 20:41, 13 February 2016 (UTC)

If the frequency of the wave is low, then your physical size will be preserved by the same forces that usually preserve it (electromagnetism and electron degeneracy pressure), but if the frequency and amplitude are high enough that they can't react in time, then you will rip/squish instead. Analogy: a boat can survive an ocean wave of any amplitude if the frequency is low enough (because any ocean height is equivalent to any other for floating purposes), but higher frequencies will damage it. -- BenRG (talk) 22:47, 13 February 2016 (UTC)

Its a big theme in Star Trek: Enterprise (season 3) and Star Trek: Enterprise (season 4) but, as many ideas in scifi are, real physicians would discribe this as preposterous imagination contradicting the laws of their science. Additionally you could aproach such an imagination from logic. If that was real, why isnt the hole universe already ripped apart into dust, given these waves would be frequent, atleast in astronomic timescale, by all these waves that must have already occured in the past? --Kharon (talk) 07:29, 14 February 2016 (UTC)

Nutrients needed by cuttings in water, specifically Geraniums

pink and red American Begonias

I've been growing |BegoniaGeraniums from cuttings for a few years. Last year I took some leggy cuttings, from a red and pink plants, rooted them in water, and potted them in the early spring. They look just like the plant to the left, although that is not of my plants nor my upload.

This year I decided to trim the longest stems from the potting that looks like the one at right, and to root them in a clear vase. Given the temperature is 6F right now, I have taken my plants out of the window. These cuttings are doing well, about 6-8 inches long, with 2-3 inch roots. But I don't want to pot them until mid-April. when it will be warm enough for them to stay out all night.

My question is, other than three (smaller-than-peppercorn) balls of NPK fertilizer, do I need to add any other nutrients? Thanks. μηδείς (talk) 20:53, 13 February 2016 (UTC)

Just wondering, how do you deal with the water going bad ? I would think you would need to frequently toss out the smelly water and replace it (hopefully with rainwater or melted snow or at least tap water that's been left out long enough to lose the chlorine compounds). But then that means you would lose the fertilizer every time you replace the water. StuRat (talk) 21:03, 13 February 2016 (UTC)

My wife does a large amount of growing plants like this, and her recommendation is to simply pot them on into compost, but keep the plants indoors until it's safe to put them out.--Phil Holmes (talk) 10:35, 14 February 2016 (UTC)

Why are do you call them American begonias when they are pelargoniums? Richard Avery (talk) 13:44, 14 February 2016 (UTC)

• Thanks, all. Answering the above, first, I have almost no sense of smell, due to nasal-polyp surgery, so I just don't worry about the smell. (I do pour out the water and refresh it when it gets low, but I have only had to do this twice since I took the cuttings at Thanksgiving--the second time the day I posted this question) It's my apartment, and, well....

Second, I don't want to pot them in soil yet, because I am keeping them under the desk lamp next to my computer. They aren't blooming yet, but they are very luxuriant, and they will go in a much larger pot when I do plant them, at which point they'll probably go to a friend or relative with more space than I, as a gift.

Third, [Ack--I said Begonia, meaning Geranium--I do the same with Hydrangea] I call them "Geraniums", because that is the US common name for the plants I pictured above. That's what my mom called them when I helped her plant a bed of them in 1973. I have never heard anyone ever call them Pelargonia, and only became aware of this in the last two years, since I first looked up the Pelargonium × hortorum article. μηδείς (talk) 01:22, 15 February 2016 (UTC)

• I am still interested in the original question. If I don't intend to pot my cuttings for 6-8 weeks from now, is there anything I should add besides NKP to the water in which they have rooted? Thanks. μηδείς (talk) 01:40, 16 February 2016 (UTC)

@Medeis: No, they are fine, don't add anything. Recall that something like 95% percent of their dry weight comes from CO2 in the air. And so ~99.99% of their wet weight is not even NPK, let alone any other trace nutrients. Plants get very little relative mass from soil nutrients, and you mostly likely didn't need to add anything, though the fertilizer probably won't hurt. I might have considered putting in a bit of rooting hormone at the start, but since you have roots already there's no need for that. FYI a fun trick for propagating from cuttings in water: any species of willow will root easily, and exude the goodies (auxin, salycylic acid, etc) into the water as it does so, so most plants will root better in water if you start them along with a pencil-sized willow branch, and you can start other things that would not be possible without some hormonal assistance. SemanticMantis (talk) 05:32, 16 February 2016 (UTC)

Thanks, The main issue is that this is the first time I have rooted a cutting that I did not mean to pot or plant it immediately once the roots were sufficient. I have been pretty successful with either rooting the shoots of, or germinating seeds from the wild, but oddly enough, never heard of the willow trick, even though we used auxin in high school, and I have a jar of rootone (of course). I'll have to go get some willow withies ASAP. μηδείς (talk) 21:58, 16 February 2016 (UTC)

PDF Beiträge zur Araneologie (Beitr. Araneol.), vol. 2: Fossil spiders in Dominican amber?

Is there a PDF of Jörg Wunderlich's book Beiträge zur Araneologie (Beitr. Araneol.), vol. 2: Fossil spiders in Dominican amber? If so how can I download it? Very short question, so sorry, but it would be greatly appreciated if you could. Thanks, Megaraptor12345 (talk) 22:21, 13 February 2016 (UTC)

I don't remember seeing it, although I might have; I'd have to use a search engine. Maybe you could try yourself? Search engines use something called a "web spider", something you seem to have an interest it. Try https://duckduckgo.com GangofOne (talk) 23:03, 13 February 2016 (UTC)

Thanks guys, I found it. Megaraptor12345 (talk) 10:28, 14 February 2016 (UTC)

What about respecting the copyright and buying the book? --Scicurious (talk) 00:49, 14 February 2016 (UTC)

February 14

Teaspoons vs mL

Nothing vitally important here - just a weirdness that I can't get out of my head:

My wife and I have both been sick for a while - we went to the doctor together, he examined us together and prescribed the exact same two medicines for each of us. We walked out of the office with four printed prescription forms, my wife turned them in at a local CVS pharmacy counter - and brought back matching pairs of identical quantities of identical drugs.

Later that day, it's time take one of them (which is in liquid form and comes with a syringe to measure out the quantity) - so I look on the label of the bottle labelled for me and it says "Take 5 or 10ml twice per day"...OK...so I ask my wife whether she's going to take 5 or 10ml - an she points out that on the label of her bottle, it says "Take 1 or 2 teaspoons twice per day". Eh? Google helpfully tells me that 1 teaspoon is 4.92892159 mL - so we both have the same dosage range. The syringes we got with the medication are identical - and both have scales in teaspoons and mL.

Sadly, we don't have the original printed prescriptions to hand - so I can't tell whether this happened at the doctors' office or at the pharmacy.

Why on earth did two prescriptions typed by the same doctor on the same day, issued by the same pharmacist using the same software to print the labels out - within 30 seconds of one another - wind up with different units?!

The only kinda/sorta possibility is that I have a distinct English accent and my wife is American - could it be that the doctor concluded that I'd better understand SI units? Maybe women are expected to understand cookery instructions and in some horrific act of gender discrimination can't be expected to understand milliliters?

Neither of those seems likely - does anyone have enough understanding of how medicine quantities get labelled to shed light on this weirdness? SteveBaker (talk) 04:37, 14 February 2016 (UTC)

Why don't you just ask the pharmacist or the doctor? ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:45, 14 February 2016 (UTC)

Specifically, ask the pharmacist first. They should have the original prescriptions on record. If they're different, then you can ask the doctor when you see him again. --69.159.9.222 (talk) 05:44, 14 February 2016 (UTC)

Because of the medical-advice prohibition I'm not going to speculate about what your doctor or pharmacist intended, but I will point out that there are two different teaspoon sizes in the US, one of ≈4.93 mL and the other of exactly 5 mL: see United States customary units#Cooking measures. The latter is mandated by the FDA for nutrition labels, but I can't find any comparable requirement for drug dosages.

My non-medical advice is to lodge a written complaint about this. Mixing unit systems is a disaster waiting to happen, and teaspoons are especially bad because they're easy to confuse with tablespoons, and a lot of household "teaspoons" hold nothing near 5 mL. Not that you would make those mistakes but the sort of people they're trying to help by using teaspoons probably will. -- BenRG (talk) 06:35, 14 February 2016 (UTC)

Interesting! So in fact, the dosages were intended to be absolutely identical rather than identical to within ~1%. That's really not critical in this case because the doctor specified a 5mL..10mL range (he said something like "start with 5mL - but you can take up to 10mL if it doesn't seem to be doing much good"). Each bottle did come with a syringe marked in both mL and teaspoons - so it would take an unusually stupid person to screw up - but I agree that using teaspoons is a disaster waiting to happen...I'm shocked when I see it in cooking recepies let alone in drug prescriptions! SteveBaker (talk) 15:39, 14 February 2016 (UTC)

You're British, aren't you? I think it's pretty well known in North American kitchens that a teaspoon is a specific unit of measure that you should use a measuring spoon for, rather than an actual teaspoon. Likewise it's probably reasonably well known that it's equal to 1/6 of a fluid ounce. (Less well known is that "fluid ounce" has different meanings in US and Imperial measure! But they only differ by about 4%, not enough to matter for culinary purposes. As noted already, the medical usage that it means 5 ml is different again, but again only by a few percent.) --69.159.9.222 (talk) 18:47, 14 February 2016 (UTC)

According to an information sheet from the U.S. Food and Drug Administration, that agency and several professional pharmaceutical organizations recommend against prescribing liquid medications in teaspoon dosages. The chances of confusion with tablespoons is too high, as are errors caused by using inaccurate household kitchen spoons. In my experience, CVS is a company that tries to do the right thing, so an effort to bring this to their attention at the corporate level may be worthwhile. Cullen³²⁸ Let's discuss it 07:19, 14 February 2016 (UTC)

Again, they provided each of us with a syringe to do the measurement...so they did try. SteveBaker (talk) 15:39, 14 February 2016 (UTC)

Maybe the prescription was filled by two different pharmacists? Maybe when they fill it they have to click a checkbox on the computer on what to print, and just randomly picked a different one? Ariel. (talk) 07:28, 14 February 2016 (UTC)

I kinda doubt that...but I guess it's not impossible - but all four sheets of paper were handed to one person who disappeared off to prepare them. I doubt they would have split the task across two people. SteveBaker (talk) 15:39, 14 February 2016 (UTC)

There's a fair amount of paperwork involved in preparing a prescription, so if there was a spare pharmacist they may well have split the forms between them to save time. MChesterMC (talk) 09:20, 15 February 2016 (UTC)

It seems very unlikely that the pharmacy's software would print labels with different units. It is much more likely that the manufacturers' own labels could differ, if you have been given bottles from different batches which may originally have been intended for export to different countries. Something intended for sale in countries which only use the metric system would not have been labelled with doses in teaspoons, while medicines intended for sale in the US or the UK might well. — Preceding unsigned comment added by 81.131.178.47 (talk) 11:37, 14 February 2016 (UTC)

I don't think that's the case. The manufacturer isn't directly involved. The doctor sets the dosage level on the prescription form and the pharmacist transfers that information onto the label, which is printed along with the patient's name and the phone number of the doctors' office. I don't see how the manufacturer had much to do with it. I suppose it's remotely possible that they are from a different batch but they look absolutely identical apart from the label that the pharmacist printed. Usually, we can tell our doctor where we'll be getting the prescription filled - and he sends the prescription to the pharmacist directly so the medication is ready to pick up...but one of the two medications contained Codeine - and evidently that's a controlled substance, so the forms had to be printed out at his office. I have no clue why a hard copy printout is considered more secure. I really wish I had looked at those forms because then we'd know whether this discrepancy happened at the doctor's office or at the pharmacy. SteveBaker (talk) 15:39, 14 February 2016 (UTC)

I did call CVS this morning - but had a hard time getting my question understood. All I could get out of the person on the phone was variations on the theme of: "Don't worry - 5ml is the same amount as a teaspoon - just take the amount it says." - but I think I was having a hard time getting my point across, and they (quite reasonably) assumed I was confused about the dosage rather than curious about the difference. SteveBaker (talk) 15:39, 14 February 2016 (UTC)

Maybe call them again and say, "I'm just curious why one said teaspoon and the other said milliliters. Which would you normally use?" And go on from there. Anecdotally, the only medications I take are in pill form, and they are always expressed in milligrams, as opposed to "grains" or whatever it would be. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:25, 14 February 2016 (UTC)

Yeah, but that's not the same thing. The standard measurement that you get for pills is "X pills, Y times per day" - the unit is "pills" - not grams or grains. The doctor and pharmacist need to care about how much drug is in each pill - but the consumer doesn't need to get involved in the units they use. SteveBaker (talk) 22:34, 14 February 2016 (UTC)

No, it's not "X pills, Y times per day", it's "X nnnMG pills, Y times per day." ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:25, 15 February 2016 (UTC)

OK, please - no mega-gram pills - the ones we have are hard enough to swallow! But no, that's not what is printed on the pill bottles the pharmacist hands over to the patient. Sure, the message from the doctor to the pharmacist probably specifies the dosage in mg/day or mg q.i.d or some such. But that's not what the pharmacist tells the patient. SteveBaker (talk) 16:19, 15 February 2016 (UTC)

• I take an elixir containing a controlled substance which is alternatively prescribed as 5ml t.i.d. or one teaspoon three times a day. I asked the CVS pharmacist about this, and she says that the label reflects what the doctor wrote, but that the pharmacy fills it in milliliters, and according to the US FDA they are considered equivalent. (BTW, always ask for the pharmacist for actual science questions, or you're liable to get a clerk.) I suppose that means I'm technically being cheated, but I never use a full month's worth (it's as needed, for bellyaches, see the talk page) so it don't befront me. μηδείς (talk) 01:04, 15 February 2016 (UTC)

  So your feeling is that this discrepancy must have happened at the doctors' office? Evidently, your doctors' office (like ours) randomly chooses whether to use 5mL increments or teaspoons. Do you think that in your case, you're getting different doctors writing the prescription each time? In our case, if it was the doctor - it was the very same guy, changing his mind not 60 seconds apart! SteveBaker (talk) 16:19, 15 February 2016 (UTC)

I'm not saying there is a discrepancy as such, it was simply assumed by both parties that any prescription written in teaspoons or milliliters would be filled in milliliters, although the large-print instructions to the patient on the label might say "take one teaspoon three times daily", while the volume of the medicine in the bottle would be in milliliters in small print. The issue originally came up with me because while I had been getting instructions in English, they started coming in French. μηδείς (talk) 19:46, 17 February 2016 (UTC)

Fuel vs oxidizer on Falcon 9

Which weights more on the Falcon 9 first stage, the fuel or the liquid oxygen? Johnson&Johnson&Son (talk) 06:51, 14 February 2016 (UTC)

Falcon 9 burns RP-1 and LOX, which is basically kerosene and liquid oxygen. RP-1 is a mixture of alkanes with about twice as many hydrogen atoms as carbon atoms. To burn this one needs three oxygen atoms for every CH₂ in the fuel to get water vapour and carbon dioxide. Given the atomic weights of these elements, the mass ratio of fuel:oxidizer is about 1:3.4. Most rocket engines (American ones at least) run slightly fuel rich to prevent engine damage, but still the liquid oxygen will far outweigh the fuel. PiusImpavidus (talk) 11:25, 14 February 2016 (UTC)

Killing yourself on valentines day

Is there a statistically significant increase in male suicides on valentines day? DonaldsTroosers8888 (talk) 12:49, 14 February 2016 (UTC)

I suppose there is no effect of holidays on suicide rate. The link between Christmas and suicide has been debunked by many sources. I don't find sources about the link between Valentine's and suicide being criticized too, but there are also not so many people claiming there is a link between the two.

Although suicides are not equally distributed along the year (see seasonal effects on suicide rates), the same article also highlights the facts that seasons play a role in suicide frequency, but not necessarily towards the winter months.

Suicides have several interrelated aspects. These aspects are so complex that there's even a branch of science, Suicidology, to study them. It will be difficult to find a single factor (like holidays) that tips the number of suicides into one direction or the other. --Scicurious (talk) 13:37, 14 February 2016 (UTC)

(E/C) I'm having a hard time finding anything reliable. There's this, but I was really thinking a site like this would have something spelled out - but they don't seem to (although the stats are broken down in almost every other way, so I might have simply missed it). We have a related article at Seasonal effects on suicide rates, but it also doesn't answer your question, though it does support the point that springtime in generally the time of the year with the highest rate. Closest thing I can find is the chart on Epidemiology of suicide that shows the changes month by month, but I don't know if it's fine grained enough to account for blips on a particular day. File is here. Matt Deres (talk) 13:46, 14 February 2016 (UTC)

(EC) [15] in some places (in particular Birmingham in the UK) there appeared to be a statisically increase in edit: attempted suicides parasuicides. This probably includes male edit: attempted suicides (particularly since male suicide rates tend to be higher) parasuicides but I'm not sure as they only look at age (adolescents seemed to be the worst affected) not gender. In other places (in particular the US) [16] this wasn't detected there was no significant increase in completed suicides (nor in homocides). However this was before 1990. Also it will likely depend on what you're comparing it to since suicide rates do vary depending on time of the year and even I think day. It sounds like February is a particularly bad time in the US (possibly in most of the Anglophone Northern hemisphere?).

Anecdotally Valentine's Day does lead to a spike in calls to helplines in a number of places although again most of these didn't specify the gender of the caller and I'm assuming it's not always known [17] [18] [19] [20] [21] [22] (n.b. a number of these sources are actually just repeating what one of the other source said but I've included them in case there was a source I missed). A spike in calls to help lines doesn't definitely mean there will be a spike in suicides. Edit: Likewise a spike in parasuicides (or attempted suicides in general) doesn't definitely mean there will be a spike in completed suicides.

Nil Einne (talk) 13:59, 14 February 2016 (UTC)

You could probably repeat the analysis for the US with more recent stats using a similar methodology. The most recent stats I found are here [23] and include 2007 and earlier. From a very quick look, it didn't look like there was a statistically significant increase. You could go further and compare rates for different age groups using data from here I think [24]. I didn't however see data which would allow a simple analysis for rates based on gender. Nil Einne (talk) 14:12, 14 February 2016 (UTC)

One thing to additionally keep in mind is that you need to correct for the fact that Valentine's Day is not universal. Even assuming perfect statistics (unlikely!), worldwide the rate probably would show no change simply because Valentine's Day doesn't exist for huge portions of the population. So, specifying a country may be necessary. Matt Deres (talk) 13:53, 14 February 2016 (UTC)

Also, our OP should consider the possibility, that while a few men feel suicidal when gilted by their one true love - a number who were already feeling suicidal for some other reason may be convinced not to act on that feeling following a gesture from someone who loves them on Valentines' day. Given that, there is no particular reason to assume an increase in the male suicide rate - it could be a decrease - or the two effects I describe might neatly cancel out.

Another issue is whether the effect would be immediate enough to be detectable. Suppose there is indeed some disappointment on the actual day - it might take days or weeks for that to turn into actual action - so the statistics might become blurred over so much time as to be undetectable against the background suicide rate.

SteveBaker (talk) 15:46, 14 February 2016 (UTC)

If I died after being gilted, it would be a murder not suicide. Matt Deres (talk) 22:54, 14 February 2016 (UTC)

I'd have cited Goldfinger. —Tamfang (talk) 00:59, 15 February 2016 (UTC)

Urine processing in the ISS

How does the recycling of pee work in the ISS? Do all astronauts pee into a common container and drink out of it (after processing, obviously)? Or does each astronaut have his own pee container and drinks only the water extracted from his own pee? --Scicurious (talk) 13:39, 14 February 2016 (UTC)

Our article on the International Space Station says that "Liquid waste is evacuated by a hose connected to the front of the toilet, with anatomically correct "urine funnel adapters" attached to the tube so both men and women can use the same toilet. Waste is collected and transferred to the Water Recovery System, where it is recycled back into drinking water." So, they pee into a collective container. It has a reference, but the link is broken. Matt Deres (talk) 13:50, 14 February 2016 (UTC)

It looks like they all drink each others, but not until it's all been distilled and filtered and whatever. You may find this interesting, good old Chris Hadfield, the go to guy for any ISS questions. Richard Avery (talk) 13:54, 14 February 2016 (UTC)

A better WP article is at ISS ECLSS (International Space Station Environmental Control and Life Support System). Matt Deres (talk) 13:56, 14 February 2016 (UTC)

It's worth mentioning that it doesn't only recycle pee - also sweat and water used in washing and left over from cooking, etc. Also, because it recovers about 97% of what you put into it, your pee gets recycled and re-pee'd about 30 times! It's interesting that it works by boiling the water and condensing the resulting steam - but because there is no gravity, they have to spin the thing like a centrifuge to get the steam out of the boiling water. SteveBaker (talk) 15:58, 14 February 2016 (UTC)

Water is water. And if anyone is squeamish about it, it's well to keep in mind that all or most of the water molecules we consume have probably spent time in countless bladders of other creatures over millions and millions of years. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:21, 14 February 2016 (UTC)

Indeed water is just water. But it's interesting to look at that old idea that there are at least a few molecules of water from any historical figure you care to name inside your body. There are roughly 10²⁸ water molecules in a human being, and since we each hold (very roughly) 50kg of water in our bodies but drink (and pee) 2kg per day - we probably cycle through all of it every 25 days = but let's keep it simple and say: "around 15 times a year", so over a 70 year lifespan, we get through maybe 10³¹ molecules. There are 4x10⁴⁷ in all of the oceans, lakes and rivers of the world - so it's pretty clear that even with perfect mixing, there is only a one in 10¹⁶ chance that any particular water molecule came from Napoleon Bonepart - but with 10²⁸ molecules in your body right now - there could easily be 10¹² molecules that he peed out coursing through your veins right now. Of course from the point of view of people spending 6 months in the ISS. all of their body water will have gone through the recycler 7 or 8 or so times during their stay - and will have been well mixed with that of all of the other astronauts many times over.

Of course the idea of perfect mixing is untrue - and doubtless there are water molecules in our bodies that don't get flushed out and replaced continually...and perfect mixing of the oceans is far from true (there is relatively little mixing between the deep waters of the world and the surface). But a back-of-envelope calculation definitely makes it clear that we have nothing to be squeamish about when it comes to water recycling. SteveBaker (talk) 22:31, 14 February 2016 (UTC)

How was the distance to the source of gravitational waves measured?

If such a question has already been asked, please delete. I wonder how did they measure the distance to the two black holes (1.3Bn light years, I don't think triangulation is possible in this case), their respective sizes (30 solar masses for each one) and the energy released. One paper (either the WSJ or Financial Times) said that the amount of energy released was larger than the energy output of all the stars in the Universe! That sounds fishy to say the least. Thanks. --AboutFace 22 (talk) 16:55, 14 February 2016 (UTC)

I don't know in this specific case, but one common method is to compare absolute magnitude (real brightness) with apparent magnitude (observed brightness). (Note that "brightness" isn't necessarily visible light, it can be any EM radiation or even gravity waves.) That is, if you know how bright something really is, you can tell how far away it is by how bright it appears to be at your location. StuRat (talk) 17:30, 14 February 2016 (UTC)

Here is the press release from Caltech, and here is the paper in Physical Review Letters: Observation of Gravitational Waves from a Binary Black Hole Merger. These are the authoritative primary sources of information on the event. Paraphrasing the paper, the distance to the source is estimated by comparing the measured data against numerical models of the proposed source event. Our article, numerical relativity, introduces this methodology from a very high level. From these models, we can parameterize the luminosity distance and the redshift - both of which are measures of the "distance" from the event to the Earth. The distance is determined and validated using a variety of standard statistical data-fitting algorithms, and the authors place confidence in this method above 5σ. Nimur (talk) 17:47, 14 February 2016 (UTC)

I wouldn't think red-shift would be as accurate, since it's not only due to the expansion of the universe, but also due to relative local motion, which may be unknown. StuRat (talk) 17:51, 14 February 2016 (UTC)

The authors published their detailed calculations on arXiv as Properties of the binary black hole merger GW150914, cited from their main paper. In case you wish to follow some twenty pages of their horrible equations, they present the calculations that lead to confidence in this specific luminosity distance D_L by way of a data fit, around page 7.

I won't pretend to follow their work - nor to second-guess it - without spending at least a few hours to study it; but take a look at the extensive author-listing, spanning many many pages, to see how thoroughly this publication has been peer reviewed. The authors explicitly publish the error bounds on all of their model-parameters.

Nimur (talk) 17:56, 14 February 2016 (UTC)

The uncertainty on distance was ~40%. I don't think local motion was the biggest problem there. Dragons flight (talk) 17:58, 14 February 2016 (UTC)

There are many places where the paper appeals to "standard cosmology" parameters when making some conversion; and cites, e.g., additional detailed publication of cosmological parameters specifically when converting from luminosity into redshift. These astrophysicists are professionals! They absolutely did think of all these difficult problems, and published extensive answers in the form of many many hundreds of supplemental papers. Nimur (talk) 18:03, 14 February 2016 (UTC)

Quite the appeal to authority there. Yes, they are professionals, but professionals also make mistakes, like the ship that crashed due to a lack on conversion to metric units. (See Mars Climate Orbiter#Cause of failure.) However, I have no reason to think they made any mistakes here, as the error I mentioned likely falls well within the 40% error mentioned by Dragon's Flight. StuRat (talk) 23:08, 14 February 2016 (UTC)

It is very interesting. Thank you for references and the posts. Any estimate of potential frequency of such events in the future? --AboutFace 22 (talk) 21:12, 14 February 2016 (UTC)

Indeed there is such an estimate, from the original paper, measured in the incredible units of events per cubic gigaparsec: "These observational results constrain the rate of stellar- mass binary black hole mergers in the local universe. Using several different models of the underlying binary black hole mass distribution, we obtain rate estimates ranging from 2–400 Gpc⁻³yr^-1in the comoving frame." Additional details in three more papers cited: [25], [26], [27]. Nimur (talk) 03:12, 15 February 2016 (UTC)

Numerical Recipes and Numerical Models of General Relativity

I've also found by chance that Dr. Saul A. Teukolsky from Cornell has been involved in modeling black holes but his name is not among the authors of the paper in Physical Review Letters. --AboutFace 22 (talk) 21:29, 14 February 2016 (UTC)

• He must be the only person who isn't, then. :-) See pages 11–13 for the list. --69.159.9.222 (talk) 06:34, 15 February 2016 (UTC)

Indeed; it appears he was not specifically one of the collaborators who are listed as co-authors of the big discovery; but undoubtedly, he has contributed immensely to the field. If you're interested in following up, here's a news snippet from Cornell: Cornell theorists affirm gravitational wave detection; here's his faculty website; and here's the website of his research collaboration, SXS (Simulating eXtreme Spacetimes) - GW150914: LIGO Detects Gravitational Waves. For the uninitiated, this researcher is also the co-author of Numerical Recipes, one of the most important books on modern methods for computational physics; this is a book with impact and utility far beyond general relativity or astrophysics. It is well worth the time to read at least some of his work. Nimur (talk) 06:11, 15 February 2016 (UTC)

@Nimur, this is exactly how I came across Prof. Teukolsky's name. I am involved in numerical simulations but in a totally different area rather than black holes. I was writing a program in Fortran 90 (StuRat was the one who gave me the initial push, actually, he probably does not even remember:-) and I needed controlling routines, so I stumbled on Numerical Recipes (would have been difficult to miss this book, actually). I copied and pasted a few routines and tried to compile them. None did. I then found his email address and sent him a message saying your routines do not work. He answered to me saying that the mistakes most likely were due to incorrect typing. I responded saying that I did not type anything, it would have taken me weeks. I copied them from the online publication. If you analyze the code you can see the spaghetti nature of it. A routine would not work without a subroutine which is pages away, or it depends on a Common block which is located next to a "black hole" somewhere hundreds pages down. It was a nightmare. I could not resolve dependencies. Now I do everything in C++. I wished him good luck in black holes simulation business in my final email. Looking at his picture in the link you provided I was surprised he is so young! Thanks, ---AboutFace 22 (talk) 15:44, 15 February 2016 (UTC)

We are dramatically off-topic from the original question at this point...

Numerical Recipes isn't perfect; but it is often the best resource for difficult algorithms. Last week, for example, a user asked to accelerate the cube-root; every educated mathematical programmer ought to spout some variant of Newton's method from memory, but how many can remember how to speed it up even faster without a little prompting from a good textbook?

Here is a listing of informed criticisms of Numerical Recipes, collected by a former JPL researcher and hosted at University of Wyoming: Why not use NR? Here is one critical USENET post from 1991: "Your posts in sci.physics about Numerical Recipes match my experience. I've found that Numerical Recipes provide just enough information for a person to get himself into trouble, because after reading NR, one thinks that one understands what's going on. The one saving grace of NR is that it usually provides references; after one has been burned enough times, one learns to go straight to the references :-)."

If that doesn't summarize my philosophy in general - and your experience in specific - I don't know what will! Numerical algorithms are difficult, so I am not at all surprised that you might have difficulty borrowing code from even a great resource. The point is, without a reference book, you would have to reinvent everything. Or, letting the creators defend their own work: "Our best rebuttal is simply to point to the hundreds of thousands of happy Numerical Recipes users (there are about a quarter-million copies of Numerical Recipes in print)." Nimur (talk) 16:20, 15 February 2016 (UTC)

You, Nimur, are a walking encyclopedia of contemporary knowledge! It is educational to read your posts. I wish I had all this criticism at my disposal when I tried to compile their code. I actually wrote all the routines I needed but wanted to have controls and those failed. --AboutFace 22 (talk) 17:15, 15 February 2016 (UTC)

Ingredients in drugs

Why do some medications contain lye and sulphuric acid? Example migraine drug.

Each unit dose spray contains sumatriptan (base) as the hemisulfate salt 5 mg in an aqueous buffered solution. Nonmedicinal ingredients: anhydrous dibasic sodium phosphate, monobasic potassium phosphate, purified water, sodium hydroxide, and sulfuric acid.

Th4n3r (talk) 18:31, 14 February 2016 (UTC)

Since those are a strong alkali and acid, I would assume it's to neutralize an active ingredient which is itself the opposite. Note that while either would be harmful in higher doses, hopefully the tiny amount they include isn't enough to do so. StuRat (talk) 18:35, 14 February 2016 (UTC)

Those are the last-minute adjustments to make the desired pH for the product. As it says, it's a buffer solution, so the chemicals aren't actually making a result with an extreme acidity or basicity. As StuRat says, it's to bring it back to neutral (and the buffer to help keep it there). DMacks (talk) 21:24, 14 February 2016 (UTC)

Did people in the dark ages know that the world had gone to shit?

Did people in the dark ages know that the world had gone to shit or were they blissfully unaware? Could we be in a dark age right now in 2016 and not know it? BrustyOlfIrl (talk) 18:40, 14 February 2016 (UTC)

The dark ages were characterized by localization and loss of information. Currently it's the opposite: global connectivity and global sharing of information. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:59, 14 February 2016 (UTC)

On the other hand, there's the worry that many of our records will be lost because digital media are (probably) less durable than paper and because their standards keep changing. —Tamfang (talk) 00:53, 15 February 2016 (UTC)

Another way to look at it was movement away from the science of the Greeks towards explaining everything as the direct action of God. In that context, the US does seem to be sliding back into the dark ages, at least in some places.

And, from the POV of the people in those situations, they think they are right and their predecessors were wrong. In the case of the Middle Ages, the commoners, if they knew the ancient Greeks had calculated the diameter of the Earth, would have thought they were idiots since obviously the Earth is flat. In the case of conservative US regions, they would think that all those "scientists" who say the Earth is over 4 billion years old are all just some weird liberal cult, since obviously the Earth is only a few thousand years old. StuRat (talk) 19:01, 14 February 2016 (UTC)

There is always a risk of backsliding. Although it's useful to keep in mind this quote from historical satirist Will Cuppy: "It was called the dark ages because people then weren't very bright. They've been getting brighter and brighter ever since, until they're like they are now." ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:11, 14 February 2016 (UTC)

It's not true that the world "went to shit" in the Dark ages - read our article and you will find that historians don't really believe that any more. It's more that there is a lack of written information about what was happening. You may also be interested in the following newspaper story from the UK - Church of England primary school headteacher sparks online ridicule after claiming evolution is only a theory Richerman (talk) 20:03, 14 February 2016 (UTC)

That's an interesting choice of example. In the UK, the teaching of religion in schools is not only permitted - it's on the curriculum in state-run education. When one lone teacher proclaims Darwin's theory isn't fact - everyone is outraged and it makes headline news. But in the US, where the teaching of religion in public schools is not only illegal, but unconstitutional, entire states are able to pass laws making it a requirement to teach that Darwin's theory isn't fact - and only a small minority of people are outraged. I'm not sure what this says about a slide into the dark ages - but if it is the case that there is a slide back into ignorance and superstition, it's not happening universally. SteveBaker (talk) 21:54, 14 February 2016 (UTC)

In continental Europe possibly not everything "went to shit", but in the UK it definitely did.

See, for example, the end of chapter 1 and then chapter 2 "Life among the Ruins" of Robin Fleming's Britain after Rome (2010) for a pretty thorough summation of the material evidence as we currently have it from archaeology. By the late 300s -- even before the Romans had left -- the economy in Britain was already in terminal decline, even before the final complete collapse of the monetary economy which followed when the Romans stopped providing low-value bronze token coinage. By the middle of the 4th century iron production in Kent had already fallen to a mere 25% of its former level; by the year 410 it had completely ceased. At this same time -- mid 300s -- smaller villas begin to fail. Initially there is a wealth concentration, and some lavish building by the very richest both in the country and the towns. But soon by the 360s and 370s even the grandest villas are starting to fail. Damage is not repaired, principal rooms are converted into barns for animals and stores for corn. As the economy fails, so do manufacturing and craft skills -- airtight pottery, glass, iron nails, etc, etc all become unavailable. As Fleming puts it (p.20) "Nails, for example, seem such trivial things, but once they were gone Britain became a harder place. They grew scarce in the 370s, and by the 390s nails for coffins and hobnailed boots [previously very widespread] were simply no longer available, so the British slipped in the mud and buried the people they loved directly in the cold, hard ground". It is 200 years before the knowledge to make mortar and build buildings out of stone are reintroduced from Europe.

The suburbs around towns start to become depopulated from the mid 300s onwards; after about 370 "both coin finds and pottery sherds almost disappear from these areas". This is where much craft manufacturing had been based. Towns became less and less well maintained. (p. 28) "Nevertheless, urban life persisted to the end of the century in most places and in some for a decade or two longer." However, "at some point in the early fifth century, though, urban life died completely, and all of Britain's towns, public and small, simply ceased to exist" ... "York, for example, reverted back to a marshland" ... (p. 29) "By 420 Britain's villas had been abandoned. Its towns were mostly empty, its organized industries dead, its connections with the larger Roman world severed: and all with hardly an Angle or a Saxon in sight."

(p. 31) "There were no longer organized and interlinked markets. There was no tax, no money economy, no mass production of goods. [Production] surpluses ... had fewer uses and became increasingly difficult both to create and to store." ... (p.32) "Roman sites, particularly those of the fourth century, are littered with the remains of substantial buildings, coins, and broken and discarded manufactured goods, and excavators find scatters of everyday objects lying in broad swaths around every farmstead and villa. Fifth-century settlements, on the other hand, are practically invisible, so rare had ceramics and metalwork become, and so inconsequential their buildings."

In parts of the West Country, some degree of organised administration did evidently continue, centred on reoccupied iron-age hillforts. (p.33) "But compared to fourth-century settlements in the neighbourhood, the first fifth-century inhabitants of Cadbury Congresbury had little. Most of the pots, the glass and the dressed stone were being used there in the second half of the fifth century, but they had been produced fifty or even a hundred years earlier. Some things unearthed at the hillfort -- the glass and some of the brooches for example -- may have been cherished family heirlooms or prized personal possessions, their longevity guaranteed by sentiment. But other objects look as if they had been looted from abandoned sites... the ruins of local villas." ... "Some of the pottery at Cadbury Congresbury, however, came from another source: it was probably salvaged from nearby third-century cemeteries, places where cremation burials lay, and where pots could be dug up, emptied of their human ash and then used for cooking or boiling water. The presence of such material at Cadbury Congresbury and other resettled hillforts points to people clinging to the material culture of the forebears no matter how grim the undertaking, no matter how great the humiliations of scavenging". (The site did subsequently pick itself up a bit, to what passed for an early medieval elite site; but most of the Roman material comforts were lost for good). Jheald (talk) 21:45, 14 February 2016 (UTC)

(Added) The main thesis of Bryan Ward-Perkins (2005) The Fall of Rome: And the End of Civilization is to set out how much was lost, in terms of material well-being and material culture, across a wider swathe of Western Europe. The book has its lovers and its critics; but it's probably a useful corrective, if anyone thinks what happened was just a change of priorities. Jheald (talk) 11:24, 16 February 2016 (UTC)

• Indeed, the Dark Ages is a fairly Euro-centric, and Anglo-centric, historiographical term. The same time period featured the Islamic Golden Age, the almost complete revival of the Mediterranean-encompassing Roman Empire under Justinian I, the Carolingian Renaissance, the Tang Dynasty, which may have been the height of Chinese civilization (see Pax Sinica), the Kamakura period in Japan, etc. Economically, even the late Middle ages were arguably worse for Europe than the so-called Dark Ages, what with the twin problems of the Mongol invasion of Europe, the Black Death, etc. --Jayron32 00:29, 15 February 2016 (UTC)

• No, it's not just Anglocentric. Although some reject it, the concept of a "Byzantine Dark Ages" is commonly held; see a short discussion of it on pages 265-266 of Greek Rhetoric Under Christian Emperors, which relies on George Ostrogorsky's influential History of the Byzantine State in noting the widespread decline of cities, general population declines, and barbarian conquests. See also "The Disappearance and Revival of Cities" chapter in Cyril Mango's Byzantium, the Empire of New Rome, which uses the term in examining the widespread regression of culture and economy in the seventh and eighth centuries (the period of Justinian II, for example), with the decline beginning as early as the sixth century, and continuing until the ascension of the Macedonians in the third quarter of the ninth century. Nyttend (talk) 00:58, 15 February 2016 (UTC)

I think you'll need to define "Dark Ages" for a start. Originally, it was used to mean the whole of the Middle Ages. In Britain, it tends to be used (at least in non-academic use) to mean roughly the Early Middle Ages (specifically, from the end of Roman rule to the Norman Conquest), and in archaeologically, I think its used more to mean Sub-Roman Britain (the part of history that really is dark, because there are little/no surviving records). The Migration Period, which began before the "Dark Ages" but continued through most of the Early Middle Ages featured a lot of "barbarians" invading or raiding the old Roman realms. (And then after the Migration Period proper ended, the Vikings and Magyars started doing their thing too). The people on the receiving end of all that would presumably have considered that the world had gone to shit. Iapetus (talk) 09:54, 15 February 2016 (UTC)

In Ireland what is known as the Dark Ages elsewhere in Europe is known as the Golden Age of Saints and Scholars. Dmcq (talk) 12:33, 15 February 2016 (UTC)

• The difficulty with this question is that throughout history there have always been a substantial fraction of people who think the world has gone to shit; so it's really a quantitative question. In the period 550-600 A.D. there is no question that most of Europe was plunged into despair, but there were also periods of deep gloom earlier and later, such as the Fourteenth Century as described in Barbara Tuchman's book A Distant Mirror. Looie496 (talk) 16:03, 15 February 2016 (UTC)

Or more recent and silly, Mal du siècle. Anyway, people have been saying all my life that the age of glory and greatness is gone; now we're merely sinking deeper into the pit of depravity and destruction. Fifty years ago I believed them, but today's gloomy Gusses are identifying those days as the lost age of greatness. Phooey; the best is yet to come. Only good thing about the good old days was me. Strong, lively, and physically and mentally flexible. Now, stiff, feeble, and, umm, what was I saying? I forget. Jim.henderson (talk) 02:47, 16 February 2016 (UTC)

The Ruin (8th century?) is a classic Anglo-Saxon poem contemplating what had been before. As to the question of whether scholars of that time were aware of how much knowledge had been lost (or, at least, was no longer circulating in sources accessible to them), probably there are some particularly well-known cites that could be made; on the other hand, after the initial collapse fell out of living memory, perhaps people focussed more on making the most of what they had? Jheald (talk) 11:05, 16 February 2016 (UTC)

Spectral response of cones and rods

I am doing some research on the spectral response of cones and rods for a law enforcement client who wants to know how badly night vision is impaired by LED vs incandescent/filtered red/blue lights on police cars.

I find that I can get exact emission curves for the lights, but when I try to figure out the response of the human eye, different websites and scientific papers give me somewhat different curves.[28][29][30][31][32][33][34]

I then found the following on Wikipedia:

Besides the obvious differences in the curves, are spectral absorption curves different from spectral response curves? If so, I think the pages that use the spectral absorption curves should use spectral response curves instead. --Guy Macon (talk) 19:57, 14 February 2016 (UTC

Guy, this is not really my area, but I wonder if the difference is that the first (top) graph uses normalised data for the Y-axis whereas the other 2 do not. The way the absorbances do not drop off to zero in the top graph looks a little strange and I am wondering whether this is an artifact of attempting to normalise the data. Just a thought.DrChrissy ^(talk) 20:27, 14 February 2016 (UTC)

The first diagram is from direct measurements of retinal cells in vitro, the other two are from experiments on living subjects. I think the difference is largely from absorption of (ultra)violet light in the lens. You can find raw data for those diagrams here. -- BenRG (talk) 21:25, 14 February 2016 (UTC)

So is the peak of the blue 420 (top figure) or or 435 (bottom figure)? Or is it 445?(1) And why does (2), which appears to be a reliable source, have the height of the blue so much lower? Why does (3) show it to be so much higher? Why do (4) (page 17) and (5) show such different curves than the other sources? That cvrl.org ref has some intriguing hints suggesting that the answer that the police department asked me to look into needs to be based on dark-adapted curves, which appear to be quite different from light-adapted curves. If I can get good sourcing, that difference would be really good information for me to add to one of our vision articles. --Guy Macon (talk) 05:17, 15 February 2016 (UTC)

There's a significant slope in the absorption curve of the lens near the blue peak, which will shift the location of the peak somewhat, so a disagreement between the peaks of in-vitro and real-world curves is normal. The lens also gets yellower with age. Images (1) and (5) look hand-drawn and probably aren't accurate. (3) may also be hand-drawn. (2) and (3) are normalized differently for some reason. All of the diagrams are normalized. Adaptation later in the visual system probably makes unnormalized curves meaningless (I'm guessing). (4) looks different because the vertical scale is logarithmic.

I suspect the visual system is complicated enough that you won't answer your question this way. Someone must have studied the effect of various lights on night vision since it's obviously important. I'd search medical databases for that instead of worrying about retinal response curves. -- BenRG (talk) 18:57, 15 February 2016 (UTC)

Identification of a spider from Sydney

Hello, everyone! I remember in 2007 I was living in Australia, Sydney, and I was in a park, when I noticed a Eucalyptus tree. I stopped to examine the bark, when I noticed a large Spider staring back at me from lower down the tree. At the time I had been told it was best to avoid spiders as some in Australia were dangerous, so I beat a hasty retreat.

A braver friend of mine, who was with me, took a stick and gently touched the spider with it. Immediately, the spider raced up the tree at a very fast pace. It stopped further up. I obviously took no pictures, but it was, from head to abdomen, about 9cm long. It was mygalomorphid and was a little hairy, the overall colour being a silvery-brown. Any ideas what it might be? Just the family will do but if you have any other details it would be very much appreciated. And remember, I do not want a very definite answer, so just give me a common species that is commonly arboreal and is found in the New south wales region. Megaraptor12345 (talk) 20:36, 14 February 2016 (UTC)

You're pretty confident on the mygalomorph bit? The funnel webs and tarantulas aren't very arboreal to my knowledge. The Huntsman_spider is not a mygalomorph, but they are big, a little hairy, and do the thing where they freeze until jostled, then bolt away at high speeds. They also hunt amongst the flaking bark of eucalypts. SemanticMantis (talk) 15:00, 15 February 2016 (UTC)

As it turns out, no I am not! I am actually quite certain your right. You see, I was so frightened of spiders at the time, I just assumed ever large spider was a Mygalomorph. Thanks, Megaraptor12345 (talk) 17:12, 15 February 2016 (UTC)

Did it occur to you that your friend who poked it might have scared the living daylights out of that little creature? ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:57, 15 February 2016 (UTC)

February 15

Nothing after 'clay effect' ? or we found the world's limit?

OP says "not waiting for an answer," then just posts speculation. Not an actual question. Ian.thomson (talk) 04:38, 15 February 2016 (UTC)
The following discussion has been closed. Please do not modify it.
(I am not waiting for answer) 49.135.2.215 (talk) 01:45, 15 February 2016 (UTC)Like sushi I think prediction for and from what we have seen is faulty 49.135.2.215 (talk) 01:47, 15 February 2016 (UTC)Like sushi Observation by 'inflaton' may be possible? I think graviton is a special case of graviton.... 49.135.2.215 (talk) 01:52, 15 February 2016 (UTC)Like sushi

I am baffled by your Q. Clay effect is a red link, and I have absolutely no idea what you are asking. Something to do with cosmic inflation and gravitons ? StuRat (talk) 04:30, 15 February 2016 (UTC)

Pretty sure it's just someone trying to use the site as a forum. Ian.thomson (talk) 04:38, 15 February 2016 (UTC)

Mud in San Francisco Bay

What's all that "muddy" looking stuff in the San Francisco Bay[35] and where is it coming from? I don't see any major river discharging into it, and there's not much agricultural run-off or pollution heavy industries in SF. Johnson&Johnson&Son (talk) 02:10, 15 February 2016 (UTC)

San_Francisco_Bay#Bay_fill_and_depth_profile may help. I think it's the bay floor. --Tagishsimon (talk) 02:21, 15 February 2016 (UTC)

I agree, although it looks more like sand than mud, to me. Note how the river carves a channel through it, where presumably the depth is greater, so you don't see the sand at the bottom. Also, by the dock on the north side of the bay, you don't see sand there, presumably because it has been dredged. The same is true under the bridge by the ocean. StuRat (talk) 04:24, 15 February 2016 (UTC)

The Sacramento River and San Joaquin River flow into the Bay and are the 1st and 2nd longest rivers in California.[36] Rmhermen (talk) 04:25, 15 February 2016 (UTC)

Yep, but the rivers look clear compared with the bay. StuRat (talk) 04:28, 15 February 2016 (UTC)

There are large agrigcultural fields right on the bay in that photo. The Central_Valley_(California) is one of the most productive and intensively farmed bits of land in the world! Here's some technical data on unimpeded flow in CA [37], here's a simple discussion of agricultural runoff and pollution of the bay [38]. Sometimes the sewers also overflow [39]. So while I can't say for sure what you're seeing, I can say that there are indeed both major rivers and major agriculture running into San Francisco Bay. SemanticMantis (talk) 15:09, 15 February 2016 (UTC)

You may also be seeing the colorful salt ponds of Leslie Salt, which are very brightly colored flat areas in the south bay centered near Fremont. Nimur (talk) 15:21, 15 February 2016 (UTC)

• It is indeed the bay floor. The south part of the bay is extremely shallow -- just a few feet deep in most spots; there are lots of other shallow spots as well. Looie496 (talk) 15:52, 15 February 2016 (UTC)

San_Francisco_Bay#Bay_fill_and_depth_profile says "The bay was navigable as far south as San Jose until the 1850s, when hydraulic mining released massive amounts of sediment from the rivers that settled in those parts of the bay that had little or no current...." Major ecological destruction. GangofOne (talk) 05:46, 17 February 2016 (UTC)

Number of people killed in Dresden

OP (now blocked) not really interested in learning, just framing arguments as questions.
The following discussion has been closed. Please do not modify it.
How many people were killed during the firebombing of Dresden?Nothing but dry cereal (talk) 04:40, 15 February 2016 (UTC) If only there were an online encyclopedia with an article on the topic... ;-) Shock Brigade Harvester Boris (talk) 04:43, 15 February 2016 (UTC) I thought i remember reading somewhere that it was 300 000 GermansNothing but dry cereal (talk) 04:45, 15 February 2016 (UTC) That would be a falsified figure made up by the Nazis. Ian.thomson (talk) 04:48, 15 February 2016 (UTC) But isn't it the case that the victors are the ones who write history? In this case the victors were the allies.Nothing but dry cereal (talk) 04:51, 15 February 2016 (UTC) We have an article that summarizes reliable sources on the topic. If you wish to debate the conclusions, you'll have to argue with mainstream academia on their grounds, not here. Ian.thomson (talk) 04:54, 15 February 2016 (UTC) Even David Irving has since acknowledged that numbers of 200000 (or very rarely higher) are based on Nazi forgeries. --Stephan Schulz (talk) 05:06, 15 February 2016 (UTC) How do we know that the number of people killed in the holocaust wasn't falsified by the allies? People now claim that the nazi reports are false, so I don't see why not. Nothing but dry cereal (talk) 05:13, 15 February 2016 (UTC)

Sine, sine, everywhere a sine

The sine function is defined in trig, but it pops up in waves of all types, including electromagnetic. This seems to indicate to me that it's more "fundamental" in some sense. Has anybody discussed this anywhere? Clarityfiend (talk) 05:58, 15 February 2016 (UTC)

Quite. This has been discussed at enormous length by a great number of great thinkers. Perhaps the best place to start reading: consider that the sine function is generalized using Euler's formula. This is named for Leonhard Euler, who wrote Mechanica (1736). Our article links to an English-language translation. (For the Latin-literate: Per statum non liberum hic intelligo, quando corpora impediuntur, quo minus in ea directione progrediantur, qua conantur; cuiusmodi est motus corporum pendulorum, quae, quia non possunt directe, uti conantur, descendere, oscillationes efficiunt.)

The more you study mathematical physics, the more different ways you learn to express the same thing. The magical bit about the sinusoidal functions is that they are equal to their own second derivative (well, with a bit of a constant multiplication factor). The reason this is very important is that second order differential equations appear to be a very simple, pure, and pretty accurate model-representation for most of the interesting fundamental effects in physics. (For example, elementary kinematics are defined by one of the laws of motion formalized by Isaac Newton: namely, that it is the second derivative, with respect to time, of an object's position that is proportional to the net force applied to that object - this is a more exact way to define "force" and "acceleration", and it is in fact how Isaac Newton describes those terms in the Principia). Sinusoids just happen to be the most parsimonious solution to many such equations - particularly, as Euler remarks, when the object's motion is impeded.

You can read our article on the simple harmonic oscillator to get a more thorough introduction to this concept.

In any event, the mathematical and the philosophical implications of oscillating functions have been studied and re-studied in very great depth for hundreds of years; so if you seek a "discussion" of this phenomenon by "anybody, anywhere,"... it really might help if you specify at least which century you hope to read from.

As pertains to electrodynamics: well, the core concept is the very same: oscillation is a natural consequence because the phenomena of electromagnetic fields are governed by a set of second-order equations, to which sinusoids are one possible solution. If you observe Maxwell's equations, you see that they are, in fact, four separate first-order differential equations that each express one simple experimentally-observed physical relation. But if you do some fancy mathematical mumbo-jumbo, you will see that it is possible to transform that set of four coupled first-order equations into an equivalent set of coupled second-order equations; once again, we can use a couple of sinusoids as a solution to those equations. This is difficult math; it is usually taught as part of a physics class, and the modern form follows work by Oliver Heaviside and some other very smart individuals, rather than the math James Maxwell used. Once accomplished, you have demonstrated that the "spring-constant", or stiffness of the fields, defines the speed of light; and if you're willing to assume that the spring constant is identical in all reference frames, then you have derived the theory of special relativity. A few hundred years of physics are thus reduced to about one page of difficult algebra and two or three lines of calculus. If you would like a text to help walk you through that effort, Griffiths' Introduction to Electrodynamics does the work for you. So, we could probably say that this is some pretty fundamental physics.

Nimur (talk) 07:00, 15 February 2016 (UTC)

Everything Nimur said. On a slightly deeper philosophical level, also see The Unreasonable Effectiveness of Mathematics in the Natural Sciences. --Stephan Schulz (talk) 07:02, 15 February 2016 (UTC)

At the risk of sounding hyperbolic, let me say that there are trillions of examples in the functions of nature, any one of which might periodically triggered such a Q. It's no sin to sec the answer, and I hope you cot a good one above, and won't tan my hide if I reply: "It's just cos that's the way it is". StuRat (talk) 07:23, 15 February 2016 (UTC)

• I'm not going to try to explain why -- and I'm not contradicting the statements above -- but the crucial fact is that the ubiquity of sine waves is a consequence of the law of conservation of energy. Looie496 (talk) 15:46, 15 February 2016 (UTC)

Proving the general solution to the differential equation y ' ' = -ky

In the article simple harmonic motion, the article says "solving the differential equation above produces a solution that is a sinusoidal function." However, I have never seen this proven anywhere in my classes. It is always kind of derived with lots of hand-waving. It is of course, easy to work backwards and see that the second derivative of sin(x) is -sin(x), but is there an article on Wikipedia which details the proof in the forward direction? Like how do we know that sinusoidal functions (expressed or not in Euler form) are the only solutions? Yanping Nora Soong (talk) 16:01, 15 February 2016 (UTC)

Try doing differentials on (e to the i theta) where the term is the same as (cos theta + i sin theta) also called (cis theta). (first differential is (i e to the i theta) and so on) Collect (talk) 16:09, 15 February 2016 (UTC)

That is simply a proof that this class of solution is a valid solution to the differential equation y ' ' = -ky, not the *only* solution. We can all see that sinusoidal functions fulfill the second derivative requirement, but how does one produce this solution in the first place? Yanping Nora Soong (talk) 16:15, 15 February 2016 (UTC)

The analytic method to find the solution is called separation of variables. Many treatments will use the easier- and faster- ansatz method, also known as "guess the answer and check if it is valid," which is what our OP seems to be complaining about. As it turns out, both methods are equally sound, even if you find trial-and-error to be philosophically unsatisfying. From a pure mathematical perspective, we can demonstrate the solution is guaranteed unique and complete, using the concepts of linear independence to show that the solution spans the entire solution-space. This method is taught in most good integral calculus books. Would you like help finding such a book, or would you like help finding chapters that work this solution in any specific book?

For example, Stewart (whose book is used in almost all colleges and universities in the United States) runs this method in Chapter 7.3 for several trivial and nontrivial equations.

Marion & Thornton work the separation of variables for the wave equation, using notation familiar to physicists ($\Psi (x,t)=\psi (x)\chi (t)$!) It's an equally robust treatment, and adds the complexity of partial differential equations in multiple space variables; but if you're unfamiliar with the notation, read through at least the first two chapters of the book. x is usually a vector, not a scalar, in this book; and the transition from x to x is a notation convention that can easily confuse the uninitiated.

Nimur (talk) 16:30, 15 February 2016 (UTC)

I think you're conflating proof with construction. So sure, anyone with a little calc can tell you that two derivatives of a sine gets you back to where you started. Is that proof? Well, no, but we can prove that the derivatives are correct via Taylor series definitions, limit definitions of derivative, etc. So in principle proving that the proposed solution is correct is easy, and that is usually done in classes that cover ODE. In short, guess and check satisfies the rigor demanded by most undergraduates who mainly need to know how to do things like simple engineering or chemistry problems. However, in classes designed for math majors, a little more time is spent on proofs regarding existence and uniqueness of various flavors of ODE. For the first order sort, we have the Picard–Lindelöf_theorem, and also more general things like Carathéodory's_existence_theorem. For second order, here's a statement [40] without much in the way of proof, here's a bit more detail [41], and here is a rather detailed analysis of classes of extant solutions for second-order ODE [42].

Suffice it to say that when someone has proven existence and uniqueness of solutions for the class of problem (which they have, as per above), then there is no lack of rigor in guessing and checking. We know that there is exactly one solution to the initial value problem, and we know that our candidate satisfies the requirements, so we conclude that we have indeed produced the single correct solution, and it happens to be named "sine". Now, constructive proofs are also useful, an can often help in some areas where existential proofs do not. But even if you wanted to pretend you didn't know the answer, and say construct a solution via an iterative method (e.g. something similar to these [43] [44]), then at the end you'd just end up saying "Gee, that's just another way of specifying a sine function" at the end :) (Note that our article on Picard iteration is on a different thing, but that the Picard iterative method I linked above for solving first-order ODE comes from the the constructive method used for proving existence and uniqueness. (As I recall, you can probably get better answers on the math desk)) SemanticMantis (talk) 16:40, 15 February 2016 (UTC)

(edit conflict) See the above comments; any linear second order differential equation has at most one solution, given certain boundary conditions. See here for a proof of this uniqueness theorem. - Lindert (talk) 16:44, 15 February 2016 (UTC)

Like historically, how was the solution derived or found first? Through guess and check? I just don't get why the history of its derivation is constantly omitted from most treatments of simple harmonic oscillators. After all, we have much more fleshed out derivations for many other things in physics (or chemistry). Yanping Nora Soong (talk) 17:07, 15 February 2016 (UTC)

It's difficult to say with certainty how the problem was first solved; I suspect that the solution took its modern form when Euler did it in the 1730s.

Many students learn math only to provide context for other pursuits; in the rush to cover more topics faster, a lot of material is necessarily omitted. This is why I always recommend students study more math. When you think you have studied enough math to mete your ends, study a little more math with greater intensity for at least a few more years.

The history of mathematics is frequently taught in more advanced math courses; but it is a difficult topic and the audience is generally pretty niche. You often must learn obscure ancient languages like French or German or Latin (not to mention Chinese, Arabic, and the countless other cultures who developed mathematics elsewhere!); you must be fluid enough in your comprehension of the subject matter to understand difficult math when it is expressed in unusual formats; and at the end, you have only learned a more difficult way to do something that most people never need. If you study advanced math and physics, you will eventually solve the simple harmonic oscillator so many times, in so many ways, that a little bit of the spirit of Euler and Leibnitz and Laplace and Fourier (and Al Gorithm!) will eventually diffuse into your mind, and things become a bit clearer - but this takes lots of time and a lot of iteration. Nimur (talk) 17:55, 15 February 2016 (UTC)

Actually my interest in the constructive solution arises because I am interested in studying the molecular Circadian clock, and also signals mediated by G-protein coupled receptors and other second messenger systems, especially in the brain, which I suspect are coupled oscillators capable of constructive and destructive interference. The systems for these oscillators are much more complex, so I wanted to extend technique used to construct the solution for simple harmonic motion to a much broader class of oscillators, one in which the oscillators have multiple feedback pathways and multiple converging and diverging outputs, where the "periods" of oscillation depend on things like rate of monoamine reuptake (affected by the activity of transporters like SERT) and the enzymatic activities of such proteins like phospholipase C, protein kinase A, and the forward and reverse binding constants of GPCRs to downstream second messengers. Obviously "guess and check" isn't a viable technique in this case. Yanping Nora Soong (talk) 18:50, 15 February 2016 (UTC)

The oscillators involved in biological rhythms, including circadian rhythms, are almost never harmonic in character. They are almost always limit cycle oscillators, which have very different properties. In particular harmonic oscillators have a fixed frequency and variable amplitude; limit cycle oscillators usually have a (nearly) fixed amplitude and variable frequency. Looie496 (talk) 18:59, 15 February 2016 (UTC)

See below. I am of course aware that biological oscillators can't be modeled as simple harmonic oscillators, or even coupled ones, for one because the feedback mechanisms are not second-order (at least third to fourth), and also because there are multiple converging and diverging routes of feedback, both positive and negative. Still, they can be used as a starting point, which is why non-constructive solutions are not helpful. Also, the idea of that limit cycle oscillators are supposed to have nearly-fixed amplitude is interesting, because it would seem possible that relaxations on constraints on signal amplitude (whether expressed as changes in neurotransmitter concentration or translated into frequency of action potentials) could form possible explanations for bipolar mania and epilepsy. Yanping Nora Soong (talk) 19:09, 15 February 2016 (UTC)

For example, it occurs to me that the serotonin GPCRs (i.e. all 5-HT receptors except 5-HT3 receptor which is an ion channel), have such a wide variety of subclasses because they respond to (and generate) signals that differ in phase and frequency with respect to each other. The period of a GPCR signal tends to be quite long -- for example, it takes about ten minutes from the peak ligand activation of the M1 receptor in petri-dish cells to the (in-vitro) peak of protein kinase A activity as assayed by a fluorescent reporter (I have to find this paper -- it's in my bookmarks somewhere), after which a whole range of downstream effects occur, including transcriptional changes and negative feedback to shutoff the original GPCRs (activation of GTPase chaperones) and following the onset of GTPase activity, there is a phase delay before the downstream messengers are degraded. Thus it seems obvious to me that GPCRs have a very large potential for oscillator behavior, which can be amplified or propagated around a network when coupled to each other, but the signal periodicity of simple GPCR networks would be ill-studied because their periods would be sooo long. (On the order of tens of minutes to hours to days, which is of interest to me as someone with rapid-cycling bipolar disorder.) I am interested in the constructive solution for the simple harmonic oscillator because I could rely on it when constructing a model for the oscillatory behavior of GPCRs (in a simple spherical cow network). Thus handwaving in which textbooks discuss the solution for simple harmonic motion is very very annoying. Yanping Nora Soong (talk) 19:03, 15 February 2016 (UTC)

Well, you won't help yourself by doing a disservice to the textbooks. There is nothing handwaving about using intuition to pick a sine-based solution, then verifying that the candidate solution satisfies all requirements. It is fair to say that modern textbooks don't usually teach iterative methods for constructing analytic solutions to second-order ODE that do not in anyway depend on knowing the properties of sine. If you want to learn more about constructive approaches to solving ODE, that's fine, but that's a pretty niche topic, and you'll have to find more specialized textbooks, this just isn't something that can be covered in most ODE courses.

If you want to read about biological oscillators, and see how other smart people have tried to understand them, you might enjoy reading about the history of the krebs cycle, and its influence on the Belousov–Zhabotinsky_reaction. It is perhaps telling that many chemists and physicists of the time disbelieved this type of fluctuation was thermodynamically possible. Anyway, it took quite a while to establish a good model for BZ dynamics, see e.g. the Brusselator for a very phenomenological approach, and the Oregonator for a slightly more chemically faithful approach. This development in some ways parallels the development of neural models, e.g. FitzHugh–Nagumo_model. The thing is, these things do not have analytic, closed form solutions, in almost all cases! This is why we lean heavily on existence and uniqueness of solutions to ODE, then do numerical integration, or pass off to mathematical machinery that can tell us about the nature of solutions without knowing their analytic form. We can help you find methods and analyses for dealing with nonlinear systems in biology, but I don't think it's really fair to think that lack of constructivist exposition on linear oscillators is even a small part of the challenge. SemanticMantis (talk) 20:20, 15 February 2016 (UTC)

One interesting clue to the molecular biology of Circadian rhythms is that fruit flies which are fed heavy water to the extent that the deuterium in it displaces a significant part of the organism's regular hydrogen get longer Circadian cycles. Colin S. Pittendrigh, Patricia C. Caldarola, and Elizabeth S. Cosbey, "A Differential Effect of Heavy Water on Temperature-Dependent and Temperature-Compensated Aspects of the Circadian System of Drosophila pseudoobscura" quoted in our article Heavy Water, which has a general discussion of why this is thought to be the case - differences in the strength of the deuterium-oxygen bond compared to the hydrogen-oxygen bond may have an effect on most organisms comparable to lowered temperature (although at 50-90% deuteration, the effect is widespread cellular toxicity and death). loupgarous (talk) 11:46, 16 February 2016 (UTC)

A You linked to music and ask about physics, the FFT shows, a sine has no overtones. The more overtones and noise it gets, the more different it is to a sine. --Hans Haase (有问题吗) 16:33, 16 February 2016 (UTC)

Earth science

1. How long would it take for Earth's core and mantle to solidify completely? Assuming that we move Earth out over billions of years with technology so that the crust doesn't melt again.

2. I don't believe the site is unusually geothermal but how much lower than -128.6°F would the record low temperature be without geothermal heat?

3. How long does it take for the strongest possible earthquake to repeat? There should be a minimum distance the plates have to move before a Big Big One can be repeated but it might take much longer than that as the smaller earthquakes keep removing parts of the plate stuckness.

4. Is earthquake risk decreasing or increasing on the timescale of multiple strongest possible earthquakes? (so it doesn't depend on how long it's been since the last Big One) Or does it depend on where in the world? Sagittarian Milky Way (talk) 06:20, 15 February 2016 (UTC)

1) I don't think it would ever solidify under current conditions, where heat seeps in from the Sun (obviously not enough to keep it molten alone), plus radioactive decay and the tidal heating from the Moon and Sun. Eventually the Moon will fly off into space and everything radioactive will have decayed, but that will happen after the Sun goes nova, and then what's left of the Earth will be very different. So, I think you have to radically change the nature of the solar system to get the Earth's core to solidify at all. StuRat (talk) 06:59, 15 February 2016 (UTC)

First, the sun is never going to go nova, it will eventually expand into a red giant and then lose its outer atmosphere leaving a white dwarf, but there will be no nova explosion. Second, the moon will never "fly off into space"; its orbit will continue to expand and in doing so rob angular momentum from the earth until the (earth's) day and month are equal, at which point the situation is stable and no further orbital changes will occur, nor will there be any tides or tidal heating after that point. (This ignores the effect of the expanding solar atmosphere on the moon's orbit, which will probably produce enough friction to cause the moon to actually start getting closer to the earth, possibly reaching the Roche limit in which case it will break up and produce a ring system.) Mnudelman (talk) 18:20, 15 February 2016 (UTC)

For your first claim, we have some coverage of this at Future_of_the_Earth#Red_giant_stage. See also here [45] and Formation_and_evolution_of_the_Solar_System#The_Sun_and_planetary_environments. SemanticMantis (talk) 21:24, 15 February 2016 (UTC)

Thanks for that. Your first citation also addresses my third claim, that the expanded solar atmosphere may slow down the moon until it crosses the Roche limit and breaks up. My second claim, that neglecting the sun's atmosphere the moon's orbit will expand and the Earth's rotation will slow down until the Earth's day and month are equal, is supported by Orbit_of_the_Moon#Tidal evolution, although it also suggests that other factors like the evaporation of the oceans may also mean that it never reaches that point. Mnudelman (talk) 23:54, 15 February 2016 (UTC)

According to Hill sphere the Moon may be too loosely bound to stay with the Earth for long after only 1.3 to 1.95 times its current distance. Will it really be bound until the day is over 27.3 days if magic keeps the Sun from expanding and makes the oceans stay? And the month would also get longer making it take even longer (50 billion years I think). Sagittarian Milky Way (talk) 02:31, 16 February 2016 (UTC)

2) I wouldn't think geothermal heat would much affect the low temps. What does affect it is the atmosphere and oceans circulating heat from the side of the Earth in the sunlight to the dark side. Without that, the poles would get extremely cold during their 6 months of darkness in winter. StuRat (talk) 07:04, 15 February 2016 (UTC)

Do you think it's less than measurement error? Sagittarian Milky Way (talk) 13:41, 15 February 2016 (UTC)

3+4)Knownledge in Seismology is not developed enough to tell. Science still isnt even able to predict vulcanic erruptions right befor they happen. Worse, even "simple" animals seem to know or feel and thus predict such danger in advance while at same time scientists can still only guess what some changes or patterns, they can see with their sensors, mean. Also historic data is very limited because Science can for example calculate fairly well how much ash some vulcano must have errupted 4000 years ago but they can at best roughly estimat the strength of its seismic schocks. --Kharon (talk) 08:53, 15 February 2016 (UTC)

Paleoseismology can tell us a great deal about past earthquakes, such as looking for tsunami deposits. Mikenorton (talk) 10:41, 15 February 2016 (UTC)

1) The mantle is a solid and for the outer core, see Future_of_the_Earth#Solidification_of_the_outer_core.

There is mantle convection so it's not solid all the way through. Otherwise there would be no need to differentiate between lithosphere which includes mantle that has frozen in the intervening 4 billion years and crust which does not. And even when the convecting part of the mantle stops convecting there would still be sections that would be lava-like if a piece were teleported out and depressurized right? (depressurized slowly enough that it stays in one piece and kept at it's original temperature) Sagittarian Milky Way (talk) 13:41, 15 February 2016 (UTC)

It really is a solid, otherwise it would not be able to transmit s-waves. It is perhaps better described as a rheid, capable of flowing over long timescales. The only difference between the lithospheric mantle and the asthenosphere is temperature and the effect that it has on the plastic deformation of the mineral olivine. If you could teleport it out at the same temperature (>1300 °C), it would not flow visibly, you would have to wait a few hundred years to see any changes. Mikenorton (talk) 15:30, 15 February 2016 (UTC)

Then why is lava liquid? (always much more viscous than water but still) From the temperatures I always thought that mantle/core substance would be at least as unviscuous as lava/steel mills if you could teleport, then depressurize without cooling or exploding. And that the lithospheric mantle is the same composition as what's below is kind of the point. That layer should be thicker billions of years from now as the Earth cools, right? After eons upon eons of years shouldn't it be all lithosphere? (the rising solar constant might eventually complicate things by melting/destroying Earth but I'm wondering when the mantle would become 100% lithosphere if "magic orbit adjustments" keep the world habitable till the Sun dies) Sagittarian Milky Way (talk) 17:36, 15 February 2016 (UTC)

Lava happens due to a combination of high temperature and low pressure. As such it only exists in relatively small number of regions near the surface. At greater depths, the rocks remain solid due to the high pressure. The analogy to have in mind is something like silly putty or a firm cheese. It is solid and holds its shape, but if you press on it hard enough then it will deform and move. Glaciers are another example of a mostly solid object that moves and deforms. By contrast, lava won't hold its shape and would simply collapse into a puddle unless cooled. Dragons flight (talk) 18:00, 15 February 2016 (UTC)

3) The repeat period for the strongest earthquake known, the 1960 Valdivia earthquake is thought to be greater than 500 years - the previous great earthquake at that location was the 1575 Valdivia earthquake and that is thought to have been only magnitude 8.5. The predecessor for the 2011 Tohoku earthquake was the 869 Sanriku earthquake and there is evidence of earthquakes similar to the 2004 Indian Ocean earthquake back in 1290–1400 and 780–990 [46].

4) As to future seismic hazard, location matters, as being next to an area that has recently had a major earthquake often increases the risk - see coulomb stress transfer. Mikenorton (talk) 10:38, 15 February 2016 (UTC)

But if you're comparing an average cycle between worst possible earthquakes at a site (and including one of them obviously) with the next such period is seismic risk increasing or decreasing? (ignoring changes in population, wealth or building technique which could make the exact same earthquake more (or less) damaging) Sagittarian Milky Way (talk) 13:41, 15 February 2016 (UTC)

• The predominant sources of heat are the radioactive decay of uranium-238, thorium-232, and potassium-40, which have half-lives of 4.5 billion, 14 billion, and 1.25 billion years respectively. So the Earth still has half of its original U238, most of its original Th232, but only a fraction of its original K40 -- in any case enough in total to keep it molten for billions more years, most likely. However the estimated heat generated by these sources is only about half of the Earth's estimated total heat flux, so there are still some large uncertainties in these calculations. Looie496 (talk) 15:39, 15 February 2016 (UTC)

Radio on smartphones

Some smartphones have FM radio using the headphones as antenna. Could they also have AM (at least partially), MW, or SW with the same "antenna"? Could these radio broadcasts work with other types of antennas connected to the headphones plug? Can independent app developers access the antenna or radio chip at all? --Scicurious (talk) 12:07, 15 February 2016 (UTC)

An antenna of the right length is best, but a wrong length can also pick up a strong signal. Half a century ago in a New York suburb I was getting voices from Egypt on an antenna a little longer than my arm, so physics is not the problem. The problem is the tuner. Most Android chipsets include a FM broadcast tuner on the chip but most phone makers disable it in ROM so no app can reach it. They also don't connect the antenna lead.

I shopped specifically for one that works. As I type this I'm listening to FM music on my HTC Desire 816 connected to an old computer speaker. And yes, the speaker wire is the wrong shape and length but the urban signal is strong. No chip maker, far as I know, includes a receiver for other broadcast signals. Not enough millions of users care. Jim.henderson (talk) 19:14, 15 February 2016 (UTC)

What's the point of including something that normally will get disabled? Couldn't they just remove the FM tuner and make the chipset cheaper and simpler? --Scicurious (talk) 19:45, 15 February 2016 (UTC)

The main cost of making a chip is usually in the design, prototype and setup of the production line, not in the actual printing of the individual chips. The extra FM component on each chip probably costs less then a few cents on each chip, but to design and setup the production of a chip without it would cost a lot more, even if the production line is printing millions of chips. So in a lot of cases it's cheaper and simpler to set up one production line to make one chip, and then disable what you don't need. It's quite common to see devices that have "versions" use the same main boards or components, just with bits not plugged in or otherwise disabled. It's a boon to the hacker to discover the "cheap version" of something can be easily hacked into the expensive version just by plugging some extra stuff in or making some modifications with a soldering iron. Vespine (talk) 22:02, 15 February 2016 (UTC)

(EC) Many chips have features which only some customers use since removing that feature may save hardly anything but having it there helps with some customers, and having 2 chips would cost more. Having the FM radio disabled seems to be at least partially a US or developed world thing and perhaps also with higher end phones [47] [48] [49] [50] [51] [52] [53] [54]. In some developing countries, having a working FM radio on the phone seems to be fairly common perhaps even expected for most lower end phones and not just smart phones [55] [56] [57] [58]. (Actually I'm pretty sure this predated smartphones.) Probably not enabling that FM radio despite the chipset support is at least partially about simplicity and saving costs and may be even security. I can say both my previous phones as well as most of the phones of relatives did have working FM radio, and this wasn't a consideration during purchase. Nil Einne (talk) 22:03, 15 February 2016 (UTC)

One justification for providing FM reception might be that in the event of a large-scale long-duration disaster, the cellphone user would listen to FM news bulletins rather than overloading networks with calls and texts to find out what's going on. Networks might see FM reception as a worthwhile feature on that basis. Going a step further, their reasoning might be that FM antenna towers might be more likely to survive an earthquake, whereas the much larger masts of AM stations might be more likely to collapse. Akld guy (talk) 06:00, 16 February 2016 (UTC)

As far as I know, AM reception isn't provided on any phone I've ever heard of. (If ever I hear of one, I'll buy it because I have difficulty getting an FM signal, and "digital" is a joke where I live in Cumbria, UK.) It's possibly because the mobile signal generates strong interference for AM reception (especially Long Wave). I don't know the technicalities, or whether the problem could be overcome, but I suspect that the interference would be very difficult to suppress. Dbfirs 10:36, 16 February 2016 (UTC)

Don't the components needed for AM reception tend to be larger and heavier than for FM? Shock Brigade Harvester Boris (talk) 02:48, 17 February 2016 (UTC)

In dinosaur days when I grew up, yes. Nowadays plenty of chips like this are on the market. Jim.henderson (talk) 03:22, 17 February 2016 (UTC)

Densitometry: how to determine the base of curves (e.g. in ImageJ)

I’m trying to quantify the bands of DNA on an agarose gel. According to Chapter 15 of a book called [METHODS IN MOLECULAR BIOLOGY] and a book I received from Sigma Aldrich, the following is an appropriate way to isolate the areas under the curves but I disagree and would like to understand the reasoning for the recommendation by Sigma and others. [Figure 1] Sigma et al. says to draw a line under all of the curves to determine the total amount of DNA loaded in the lane. The quantity of cleaved DNA is then determined from the smaller peaks (fig 1). [Figure 2] [Figure 3] The approach in fig 1 seems “unfair”. I think either both total DNA and the digested DNA should be measured to the bottom of the background (fig 2) or neither should (fig 3). --129.215.47.59 (talk) 12:27, 15 February 2016 (UTC)

The smearing in Sigma's example seems to come from the endonuclease activity of CelI/Surveyor nuclease and isn't really background. It's not even an issue with T7E1 so my query doesn't really matter. 129.215.47.59 (talk) 13:09, 16 February 2016 (UTC)

Gravitational waves

Regarding the recent announcement from LIGO, does this mean that, for lack of a better phrase, the effects of gravity would be different at different points in the wave? Would a person feel heavier at the crest vs. the depression of a wave? Dismas|^(talk) 13:38, 15 February 2016 (UTC)

It does affect gravity, but doesn't make you heavier. The effect of a gravitational wave on a solid body is that of a tidal force. It's a periodic variation in the space-dependency of the gravitational acceleration.

Suppose you stand on the Earth. The gravitational acceleration is about 9.8 m/s², so that's how hard you feel gravity pull on you and how fast you accelerate when you're in free fall. But that acceleration isn't constant in place. The tidal field on the Earth's surface is about 3·10^-6 s^-2, so gravity is about 6 µm/s² stronger at your feet than at your head. If you're in free fall, the tidal field tries to stretch you. The effect is tiny, but if you put a long bottle with liquid for viscous damping in Earth orbit, this tidal field will orient the bottle vertically.

The amplitude of the tidal field belonging to a gravitational wave is the second time derivative of it, so that's da/dr=ω²A=4π²f²A, so that's about 2·10^-15 s^-2 for this wave, alternatingly stretching and compressing you, while compressing and stretching you in the perpendicular direction. The effect is perpendicular to the direction the wave travels and depends on its polarisation, which is either + or ×, or a superposition of those, like left or right circular polarisation. PiusImpavidus (talk) 15:50, 15 February 2016 (UTC)

I agree with all that, but if the wave was strong enough you would feel yourself getting heavier and lighter, because the force acting on the Earth would be different from the force acting on you. But the gravitational waves would have to be incredibly strong for the effect to be noticeable. Looie496 (talk) 18:53, 15 February 2016 (UTC)

The sensation of weight is really a sensation of being pushed upward by the floor, which compresses your body's support framework vertically, and probably stretches it horizontally, and stretches or shears body parts that hang down (like arms and a lot of soft tissue). A gravitational wave would effectively alter the stress tensor uniformly across your body, which would reduce stretching and increase compression, or vice versa, along any particular axis. So maybe it would feel like parts of your body were getting heavier and others lighter at the same time. Or maybe it would just feel weird. -- BenRG (talk) 23:40, 15 February 2016 (UTC)

It isn't your body that matters, it is the Earth. Because the Earth is nearly incompressible, the difference in acceleration between the center of the Earth and the location of your body will manifest itself as a force that the Earth exerts against your feet. Looie496 (talk) 16:41, 16 February 2016 (UTC)

You're right that there will be an oscillating pressure on your feet in general because of different material properties. I forgot to think about that. But the relevant part of the ground is only the nearest (speed of sound in ground / frequency of gravitational wave) or so, not the whole earth, and bone is nearly incompressible too, so I think the effect wouldn't be as large as you suggest. The effect could be zero if there was some sort of impedance matching between you and the ground, but I'm not sure what would need to match (possibly the speed of sound); at any rate if you're made of the same stuff that you're standing on then there should be no effect, even though you're much smaller than the earth. -- BenRG (talk) 02:43, 17 February 2016 (UTC)

Related question:

If gravity is a wave, wouldn't it necessarily have a frequency? Is that frequency known? -- Eric, aka:2600:1004:B055:454E:1DDE:1660:247:6303 (talk) 08:29, 16 February 2016 (UTC)

Gravitational waves are ripples in spacetime transmitted via gravity, but one wouldn't say that "gravity is a wave" any more than "water is a wave" just because waves can travel on water. As far as frequencies, more or less any frequency is possible. The first observation of gravitational waves saw a signal rising in frequency from 35 Hz to 150 Hz. Dragons flight (talk) 08:38, 16 February 2016 (UTC)

Okay, that makes sense; I was thinking more along the line of EMR "waves" and such. -- E:2600:1004:B055:454E:1DDE:1660:247:6303 (talk) 08:45, 16 February 2016 (UTC)

In specific, the recently-detected signal was a transient response - sort of a packet-like impulse - caused by a collision event very far away. This specific type of waveform was sought out by researchers because it has a well-defined character that is easier to separate from background noise than a steady-state gravitational wave. It is expected that lots of other gravitational waves exist and propagate: as Jupiter orbits our Sun, it creates a propagating gravitational wave, with periodicity equal to its orbital period. When you wave your arms or move around, you emit gravitational waves caused by the movement of your mass. Both of these cases - the movement of a large planet or a small mammal - create gravitational disturbances that are so weak, we cannot measure them. Scientists specifically sought a particularly energetic and massive event - a collision between black holes - specifically because they knew that would be the most detectable signal. Even though that event is rare and distant, its gravitational signature was more detectable than any closer steady-state source we could look for. Specifically: this waveform detected from the GW150914 event had a large amplitude and a characteristic chirp, which is a very well-understood scenario for signal-processing. Nimur (talk) 16:05, 16 February 2016 (UTC)

In slightly more detail: from our article on the subject Gravitational_wave#Sources: "An isolated non-spinning solid object moving at a constant velocity will not radiate. This can be regarded as a consequence of the principle of conservation of linear momentum." So mass movement is necessary but not sufficient to produce energetic propagation. Thus with the detection of these waves, gravity is demonstrably not action-at-a-distance (which Newton thought was untenable) but entails time-retarded propagation. --Modocc (talk) 20:04, 16 February 2016 (UTC)

This seems to be somewhat counter-intuitive. (Note that our articles: Retarded time & Retarded potential do not mention gravitational waves; is there some other article that I am missing, or should those articles be updated?) -- E:2600:1004:B059:FEE3:50C5:5450:8626:1630 (talk) 01:48, 17 February 2016 (UTC)

I added a short section to retarded potential. -- BenRG (talk) 04:30, 17 February 2016 (UTC)

February 16

Lipophilic substances

Are there any substances or objects I could buy that absorb or absorb oil like a sponge? Preferably one that works on butter, too? If it's a powder like activated charcoal it would have to not damage vacuum cleaners.

I'm tired of having to press down on the floor very hard with paper towels and rub very fast and it still takes forever to get the last few microns or nanometers off (or however little c is needed to make it stop being reflective at glancing angles). It takes far less time to soak up hydrophilic things like diet soda completely. Sagittarian Milky Way (talk) 02:16, 16 February 2016 (UTC)

I believe the usual technique for cleaning up oily spills is first to remove all you can mechanically (with a paper towel, for example, or by mixing with saw dust and shoveling large spills), then to use a detergent and some water to dissolve the rest. At that point it can be sucked up by a sponge just like water alone. StuRat (talk) 03:16, 16 February 2016 (UTC)

I hadn't thought of that because I don't use sponges. They seem disgusting. It seems less painful than trying to get soap off your floor without a sponge, though. I wonder if a wet/dry shop vacuum can be powerful enough to remove oil sheens? (but probably only worth buying one if you're going to be doing a lot of carpentry or ostrich egg juggling) Sagittarian Milky Way (talk) 04:40, 16 February 2016 (UTC)

Nope, a vacuum cleaner won't remove an oil sheen from the floor. StuRat (talk) 02:32, 17 February 2016 (UTC)

In a garage, use ash or sawdust to shovel it. Aware of fire, explosive gas mixtures and damage to the floor to use brake cleaner. Some kitchen cleaner can help as well and less dangerous and hazardous. Operating vacuum cleaners ignites explosive mixures immediately with the motor brushes and power switches! Industrial vacuum cleaners are not protected by default. Oil can thighten the filter of the vacuum cleaner and cause a problem on the motor brushes. Some kitchen cleaner are based on acid, useful for some substances, some use tensides. --Hans Haase (有问题吗) 16:22, 16 February 2016 (UTC)

Oil-absorbent mat are available in motor factors, hardware shops, etc. LongHairedFop (talk) 20:04, 17 February 2016 (UTC)

People shutting down ("dying") and then starting up again ("coming back to life")

Computers that are being restarted usually shut down and then start up again. There is evidence of people doing this too. There have been several incidents where people shut down (or should I say "death") but then start up again (or should I say "come back to life"), which means that people have that capability (if they didn't have this capability, then we wouldn't have these incidents, but we do have them). For example, there was a "dead" baby boy who was put in the morgue freezer, but he was found to be crying when he was taken out of the freezer the next day for cremation. If people can start up again, why has about 99% (I think) of every human who has "died" not "come back to life"? I mean, that baby boy and several other people did, and they're human too. Why is this? VRtrooper (talk) 08:02, 16 February 2016 (UTC)

Occam's razor would dictate that those people only appeared to be dead (we don't have to imagine that people can mistakenly think someone is dead), rather than there being some mysterious force that keeps people dead. Ian.thomson (talk) 08:17, 16 February 2016 (UTC)

Not just Occam's razor, simple fact. They weren't dead. People don't come back from the dead. Fgf10 (talk) 11:40, 16 February 2016 (UTC)

Several religions seem to have different opinions ;-). But more seriously, there are different definitions of death. People do recover from clinical death, though I'm not aware of any case where that has happened without outside (and usually very qualified medical) intervention. And on the other hand, even braindead bodies can be kept "clinically alive" for a while, e.g. to enable organ transplants. BYW, I was quite blown away by Shelly Kagan's Philosophy 176 Open Yale Course. --Stephan Schulz (talk) 12:01, 16 February 2016 (UTC)

Real death is brain death. As long as the brain is recoverable, it's not death. But I do agree with your point, and this is frequently the cause for media confusion. As far as what religions believe, I couldn't care less, and it is not relevant here. Fgf10 (talk) 12:41, 16 February 2016 (UTC)

"Real death is brain death" - a bit of No true Scotsman, eh? Also I think you're probably right but I don't see any way that I can verify your claims. I don't suppose you have any references to share on the reference desk? SemanticMantis (talk) 14:27, 16 February 2016 (UTC)

It's a self-evident fact. I don't see how it can't be true? Fgf10 (talk) 14:31, 16 February 2016 (UTC)

I'm sorry, but a reference desk is no place for "self-evident fact". We are here to provide references. Or at least I am, I'm not sure what you're on about ;)

Nomenclature is an important area of science after all, see e.g. scientific nomenclature. I suspect somebody has written WP:RS on the matter of what is and isn't "true" death, and perhaps we could be enlightened if you could share some sources. Below, I have included a selection of WP links that might help the OP. and illustrate some of the terminological challenges associated with death and revival. As for you and your opinions, I suggest you read up on begging the question, and consider that you may have been logically affirming the consequent.SemanticMantis (talk) 14:27, 16 February 2016 (UTC)

A person is defined by their consciousness, memories and personality. These reside in the brain. As long as the brain is intact and functioning, the person is alive. When it is not, the person ceases to exist. Easy as. Rhetorical devices or logical fallacies are irrelevant. Finding sources is difficult, as they are very frequently tainted by religious thought, as evidenced in your links below. The medical definition of death one is particularly problematic, as a) it just talks about the US, where these sorts of things are treated rather backwardly, and b) is largely about legal and ethical definitions, which are frequently only loosely based on reality. Fgf10 (talk) 15:22, 16 February 2016 (UTC)

Aye, so an unconscious person is not a person? Or perhaps a person in a Persistent_vegetative_state is actually dead, if their brain is not functioning properly, and they have no personality any more? Look, this is all very interesting stuff, and I appreciate the scientific approach. But please don't act like there's no debate on these issues, even among the most atheist of scientists. An easy way to see why there might be some serious scientific debate surrounding death is that there is also debate surrounding Life#Definitions. The fact of the matter is, sometimes ethics and philosophy creep in to science, no matter how much we may wish they were separate :) SemanticMantis (talk) 15:58, 16 February 2016 (UTC)

Don't be obtuse, there is no way that makes sense. Do you seriously think that if you hook up an unconscious person to an EEG, you won't see any activity? Indeed, vegetative state, if no EEG is measurable, is brain death. Vegetative state is mostly a legal construct for countries that don't have provisions for euthanasia. Don't confuse religious and legal mumbo jumbo with scientific debate. I guess most people are too sentimental to actually define death, but this is the science desk, it's just about the facts. Fgf10 (talk) 19:56, 16 February 2016 (UTC)

Here is the encyclopedia entry on death from Plato, the Stanford Encyclopedia of Philosophy. It would be irresponsible to leave the term undefined; it is perhaps equally irresponsible to assert that all scientists agree on its definition. We could make a strong claim that biologists have the best set of definitions, but two problems arise: first, many biologists disagree on the definition - see our extensive and well-cited treatment at our article, life § definitions, and death § problems of definition; and second, biologists do not own the monopoly on our understanding of complex topics.

At the very least, use caution with any overly-broad definition; SemanticMantis has already pointed out a problem with the assertion that one is dead when one is unconscious: most humans sleep, and few of us consider that to be a state of death (but some cultures, and some particularly cloying philosophers, do!)

The original question can only be meaningfully and methodically answered if we are very careful with our terminology; and even then, we should at least keep an open mind about the very difficult, very well-studied philosophical problems that are associated with any carefully-crafted definitions. A very large number of philosophical paradoxes and conundrums famously arise when we scrutinize the mind-body problem very closely.

Nimur (talk) 16:26, 16 February 2016 (UTC)

We have articles on near death experience, medical definition of death, and even general death, note the "problems with definition" section in the last one. You might also be interested in Resuscitation, advanced life support, or even a bit of cryopreservation. SemanticMantis (talk) 14:37, 16 February 2016 (UTC)

The philosophical error in this question is thinking of death as an event, in some way similar to hitting the computer's off switch. Think of death as a process, which can sometimes be stopped part way and even reversed. Our understanding of that process is still imperfect, which is why at times someone who has been considered dead terns out not to be. — Preceding unsigned comment added by 81.131.178.47 (talk) 14:37, 16 February 2016 (UTC)

I question the OP's analogy. When a computer is shut down, do all the components shut down immediately? Or might there be capacitors and other entities which are still "alive" for a while after shutdown? And the data in disk drives and firmware remains "alive". The machine is not really "dead", it's effectively "dormant". ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:45, 16 February 2016 (UTC)

That's a pretty good point. There's a reason why you're supposed to power off your cable modem for 30 seconds before rebooting it -- to make sure you've really "killed it"/shut it down fully. SemanticMantis (talk) 16:00, 16 February 2016 (UTC)

I agree that it's not a good analogy. When a computer "shuts down", you are just removing electrical power. The hardware remains entirely intact, and any data on disk or in nonvolatile memory also remains intact. But when a person dies, metabolic processes cease and decomposition begins almost immediately, destroying the cellular machinery that makes life possible. Unlike removing power from a computer, it is an irreversible change. Various conditions can mimic death to an untrained, or even trained, observer, but after significant decomposition occurs, life cannot be resumed. Mnudelman (talk) 19:20, 16 February 2016 (UTC)

see also Sam Parnia and references there. Also old Coursera course on Resusitation Science. GangofOne (talk) 20:09, 16 February 2016 (UTC)

• Mnudelman has mentioned the relevant issue above, metabolism. As long as this continues, there is life. There are animals, like water bears, or some plant seeds, which show no obvious signs of life, yet which maintain a metabolic trajectory. Basically, life has to be defined at the cellular level. Once a cell has stopped metabolizing, it is dead. When a body has gotten to the point where its functions cannot sustain the metabolic functions of the cells of its essential tissues, it will die. Things like declaring "arrhythmia" or "brain death" the point of death, itselfare legal ones, not biological ones. μηδείς (talk) 22:33, 16 February 2016 (UTC)

There is quite a bit of room for interesting variation here. Cryptobiosis like in tardigrades for example, which is frequently aided by trehalose (I will admit I still don't understand what makes one kind of sugar so much better for being dehydrated/frozen/etc. than another). More relevant for our purposes, clinical factors like hypothermia and xenon (for the latter see [59]; it's neuroprotective). It isn't always obvious why. There is ample room for suspicion that if, somehow, we could send cells just the right kind of signals to make them fight back against dying, it might be possible to revive people we're "sure" are dead. But of course, if we knew that, they wouldn't be considered dead any more, but in a critical condition... Wnt (talk) 01:14, 17 February 2016 (UTC)

Oh oh, there's also the bdelloid rotifers! They dehydrate so severely that their DNA breaks apart. Since they are obligate parthenogens, there are only females, and no meiosis is thought to have occurred in a really long time. But they still can reanimate, and in the process they are able to incorporate the DNA of their sisters through a from of horizontal gene transfer [60], leading to charming titles like Lesbian Necrophiliac Bdelloid Rotifers [61]. 14:38, 17 February 2016 (UTC)

What matters to animals like rotifers and water bears is that they still have enough potential energy so that when conditions are right they can come back on again. They are not being resurrected from the dead, they are simply resuming activity. μηδείς (talk) 19:36, 17 February 2016 (UTC)

Quantitative analysis of gases producing odors in feces of humans, animals and birds

The chemical composition of feces of humans, animals and birds could vary as a result of, (for example), changes in diet. The gases which produce the odors in such feces comprise a number of sulfides, skatole and indole. My question concerns a quantitative analysis of the proportion of each of these sulfides, skatole and indole in the gases causing the odor in the feces. Would the results of such a quantitative analysis vary with the differing chemical compositions of faces caused by, (for example), changes in diet, or would it be independent of the chemical composition of the feces? Simonschaim (talk) 12:21, 16 February 2016 (UTC)

That's careful way of asking why, how, and to what extent shit stinks, right? Very interesting stuff, and relevant to a variety of medical, social, and public safety concerns. I found a large assortment of articles via google scholar, searching various things like / [skatole/indole] fecal analysis quantitative/. I think it's fairly obvious that the quantity of gasses changes based on fecal composition. Other factors include the metabolome and gut bacteria populations. Anyway, here's a selection of freely-accessible studies that will give you some of the information that you seek, using mass spectrometry, gas chromatography, and other quantitative methods, for humans and pigs: [62] [63] [64] [65]. The last one in particular is probably a good place to start. SemanticMantis (talk) 15:52, 16 February 2016 (UTC)

Thank you SemanticMantis for you dtailed answer for which I am most grateful. Although the TOTAL concentration of the gaseous mixture which causes the odor in feces is dependent on the chemical composition of the feces, the point I am interested in is, whether the RELATIVE percentages of the various sulfides, skatole and indole in the gaseous mixture causing the odor depends on the chemical composition of the feces, or is it a CONSTANT irrespective of the chemical composition of the feces — Preceding unsigned comment added by Simonschaim (talk • contribs) 09:00, 17 February 2016 (UTC)

You're welcome. As for your follow up, here's one more article that has data [66] showing that changes in diet change the amount of at least one gas. It seems WP:OR to me that the relative concentrations must change in general -- what mechanisms would keep them constant? A good way to look in to this would be to use google scholar's "cited by" links. For example my last link above on "Malodorous Volatile Substances" has been cited 41 times, and many of those papers will have data related to your interests. SemanticMantis (talk) 14:44, 17 February 2016 (UTC)

STI Testing

Given that there are so many lab tests that can test for pathogens from normal body flora, and there are many different types of pathogens, how do STI clinics track down the right species for treatment? And how long do patients have to wait for the treatment (because these bugs take time to grow) and how much are they charged for lab testing? Is it possible to just look at the outward signs and treat the diseases on the first meeting? 140.254.70.33 (talk) 14:36, 16 February 2016 (UTC)

The article Sexually transmitted infection (STI) has sections about screening and diagnosis that are carried out at a Sexual health clinic. No procedure tests for all infectious agents and separate tests are done for STIs such as syphilis, trichomonas, gonorrhea, chlamydia, herpes, hepatitis and HIV. Public governmental and non-profit clinics often provide services for free or adjust the fee based on a patient's ability to pay. AllBestFaith (talk) 18:40, 16 February 2016 (UTC)

But what about sexually transmitted infections from endemic areas that are acquired by international travel and licentious sex? Not all STIs are global. 140.254.77.141 (talk) 19:12, 16 February 2016 (UTC)

Also, you still haven't answered about the time it takes to do the lab tests or whether they actually do the tests to ascertain the identity of a germ. 140.254.77.141 (talk) 19:16, 16 February 2016 (UTC)

The answers to your questions may differ from pathogen to pathogen. HIV testing, in some cases, can be done in home kits that you buy at a pharmacy, with results available in as little as 20 mintues [67]. Chlamydia, on the other hand, requires cell culturing (which can take several days) or complex PCR techniques (which are expensive, and I am not sure about the time) [68]. Price, when testing can be performed, etc., will therefore also differ. --OuroborosCobra (talk) 19:39, 16 February 2016 (UTC)

The World Health Organization provides a comprehensive fact sheet on STIs and estimates that 357 million new infections occur every year with one of 4 STIs: chlamydia, gonorrhoea, syphilis and trichomoniasis. A WHO report notes that antimicrobial resistance of Neisseria gonorrhoeae is an important public health problem. AllBestFaith (talk) 22:03, 16 February 2016 (UTC)

What sciences fields, besides psychiatry, have an "anti-" version of it?

Is the field of psychiatry all alone with its anti-psychiatric version? --Scicurious (talk) 23:36, 16 February 2016 (UTC)

Psychiatry is not a science. The science, to the extent there is one, is psychology. Psychiatry is a medical discipline. --Trovatore (talk) 23:36, 16 February 2016 (UTC)

Psychiatry might not be an independent science, but what science is truly independent? And I would not say that the science that studies the brain is psychology, which, actually studies the mind. --Scicurious (talk) 23:41, 16 February 2016 (UTC)

The science that studies the brain is neuroscience, not psychiatry. --Trovatore (talk) 23:43, 16 February 2016 (UTC)

Neurology studies the nervous system as a tissue. It's internal medicine for the brain. Psychiatry cares about how the brain generates the mind (or fails to do that).--Scicurious (talk) 23:50, 16 February 2016 (UTC)

Your comments seem to reflect a notion of psychiatry that is completely at cross-purposes with your question. Psychiatry per se does not "care about how the brain generates the mind", though certainly individual psychiatrists may do that.

Psychiatry per se is not a science, and the anti-psychiatry movement is not necessarily against the scientific study of the concerns of psychiatry. Psychiatry is a medical discipline, aimed at treating mental illness. The anti-psychiatry movement generally rejects the "illness" model for mental states. That disagreement is not one over science at all. --Trovatore (talk) 00:05, 17 February 2016 (UTC)

OK, I have rewritten the question to make all pedants happy.Scicurious (talk) 00:50, 17 February 2016 (UTC)

Well, there is anti-politics, for example. Also anti-clericalism. These are more parallel to anti-psychiatry than would be the case if psychiatry were actually a science.

I guess I find your question somewhat hostile to anti-psychiatry, which you certainly have the right to be, but I'm not sure your hostility is based on a correct understanding of what anti-psychiatry actually is. Anti-psychiatry is not in and of itself anti-scientific. It opposes the practice of psychiatry, as it is currently practiced. --Trovatore (talk) 00:56, 17 February 2016 (UTC)

I did not intend to be hostile towards anti-psychiatry. But it seems as a misnomer then. They could have called their criticism "alternative psychiatry" or "neo psychiatry."Scicurious (talk) 01:02, 17 February 2016 (UTC)

Well, their position, as I understand it, is that psychiatry as it is currently practiced does more harm than good. That does not imply that they know an alternative that does more good than harm. If I see you trying to put out a fire with gasoline, and I advise you that that's probably not a good thing to do, that doesn't necessarily mean I know a way to put out the fire, but nevertheless, you really ought to not use the gasoline. --Trovatore (talk) 01:04, 17 February 2016 (UTC)

Speaking as a cognitive scientist myself, I find it to be not in any slight way to be controversial, counter-intuitive, or atypical to classify and accord the status of a scientific discipline to psychiatry, in the same way that medicine itself is undoubtedly a science (or at the least contains an aspect we call "medical science"). It's not that psychiatry isn't a science and psychology is. Rather psychiatry is just not the same science as psychology; it is probably best described as a sub-discipline of psychology (as well as of medicine). There's a lot of different ways to chop up the block (you might just as well draw epistemological hierarchies classifying it as an offshoot or co-branch of biopscychology or neurology) but one thing I feel very confident in affirming is that there is such a thing as psychiatric science.

The above logic would exclude many disciplines, from applied mathematics to medicine, from being sciences simply because they prioritize pragmatics over theory. That's a way to divide the sciences, conceptually, but it's not an argument I typically hear from scientists for discounting fields from qualifying as science whatsoever. Those distinctions generally come down to whether the empirical/scientific process is applied in the field and in what manner -- not what the practical outcomes are. Mind you, I wouldn't necessarily object to the claim that a greater volume of empirically rigorous "hard science" research is done under the umbrella of psychology than psychiatry (at least when you are talking about direct testing of discreet phenomena rather than generalized findings drawn from large datasets of self-reports and other questionable measures), but that also is not exclusionary in itself. Snow ^{let's rap} 04:50, 17 February 2016 (UTC)

I don't ordinarily consider medicine a science, either. It's more like engineering.

But in any case, the question came up in the context of anti-psychiatry, in a way that suggested that anti-psychiatry was opposition to a science. I don't think that's accurate. Anti-psychiatry holds one or more of the propositions: (i) that the practice of psychiatry is harmful, (ii) that its foundational idea of considering certain patterns of thought to be a form of illness parallel to physical illness is misconceived, (iii) that its goals are dishonest and authoritarian. None of those things is an objection to psychiatry as a science. --Trovatore (talk) 05:02, 17 February 2016 (UTC)

Well, while I'd tend to agree that antipsychiatry isn't per se anti-scientific, the movement has traditionally had a great degree of cross-over with anti-scientific or pesudo-scientific hoopla. Further, to the extent that a person embraces the position of antipsychiatry to the broadest and most inclusive extent--that is to say, that the entire discipline of psychiatry is a fundamentally mistaken approach to the human mind--then you can certainly argue that they are rejecting a huge body of scientific research. It's like arguing that a flat earth proponent can still be technically consider themselves a student of the physical sciences if they believe in the concept of scientific proof but just disagree about the evidence relating the the physics of the world around them. I mean, yeah, in the strictest, most abstract sense, we might concede the matter, but at that point do we really have much faith that they really understand even the simpler concepts involved such that we wouldn't feel comfortable calling their ideas non-scientific. I'm not saying that anipsychiatry rises to that level, but it's definitely a field that has been piggybacked upon by those who want to attack the empirical basis of psychiatry en route to developing a much more questionable model of the mind as it applies to human health and suffering, often with a bizarre and/or spiritualist flavor. Snow ^{let's rap} 05:27, 17 February 2016 (UTC)

I think what they see as a "fundamentally mistaken approach to the human mind" is mostly about the concept of "mental illness". The notion that cognitive patterns are "illnesses" does not really have any empirical content. It's more of a social construct, or a metaphor. You can certainly take the position that it's a useful metaphor, but that's not a claim on which science has any real opinion. --Trovatore (talk) 06:06, 17 February 2016 (UTC)

Mental disease is classified as disease for the same reason that a pathogen or physical pathology is; if it affects the fitness of the organism such as to compromise the odds of survival (or, as we sometimes stray with regard to humans, if it interferes with our ability to thrive and derive enjoyment from life). What's more, insofar as the mind is a product of the brain (and other parts of our physiological make-up), it is at least susceptible to the consequences of well understood pathologies of that organ. To try to reject that is to embrace a kind of primitive dualism under the mistaken presumption that it represents some kind of open question of epistemology. sure, mental disease is a "concept" and a "matter of perspective", but only to the same extent physical disease, as a biological process, is, and that's not how most of us use the term. Mental aberrations, be they difficult to describe in the hard question sense, nonetheless have a basis in physical matter and are subject to empirical observation and testing, be it often by indirect measures. Snow ^{let's rap} 07:13, 17 February 2016 (UTC)

OK, first of all, let me come out of the closet here — yes, I am a dualist. I do not think the hard problem of consciousness will ever be answered in physicalist terms. As far as I can see, any potential such answers are simple category errors. The only real physicalist response is Dennett's; he claims it just isn't a problem. But that's self-evidently false.

However. It isn't necessary to reach that question to see the point here. Just look at the central text of psychiatry, the DSM. Every time it comes out, they have to argue for political reasons about what is and what is not a mental disorder. I don't see a lot of that happening with physical illness. Some maybe, but not nearly as much.

Then they define the conditions in a "check off five of nine" kind of paradigm, from a list of symptoms.

I'm not saying the DSM is all nonsense. Could be that it's even "correct", whatever that means. But whatever it is, I'm pretty sure it's not science. --Trovatore (talk) 07:26, 17 February 2016 (UTC)

Fair enough; other than saying that it is basically universally rejected by most scientists who in any direct way study the mind, I don't know how to address the issue of dualism here without completely hijacking the thread into another topic area (which, in any event, we may have already accomplished between us :). But as to you're other points, I think it's worth bearing in mind that you can't judge the empirical validity of an entire scientific domain based on its most problematic researchers, methodologies, sub-disciplines, and issues. Just because one accepts some "fuzzy" initial conclusions in a given area as a place-holder until those mechanics are better worked-out doesn't mean that one is not applying an evidence-based/testable/falsifiable approach to understanding those phenomena; that's just how science works. Most of us do not have the luxury of working solely in the "pure" science of mathematics alone; most scientists, even in the hard sciences, must use conceptual work-arounds to break phenomena down to workable units. Snow ^{let's rap} 12:23, 17 February 2016 (UTC)

You're a dualist? But here you are writing about conscious experience. That's a physical effect of conscious experience. On the flip side, conscious experience is an effect of physical stimuli. What does it even mean to say that it's not physical, given that?

"Diseases" are things we try to "cure", and what we try to cure is a matter of public policy. I don't see how it could be otherwise. Some people might argue that plasmodia ought to have a right to life, or that cancers are miniature John Galts freeing themselves from the shackles of the cellular colony that oppressed them. Those attitudes simply haven't prevailed in society at large. -- BenRG (talk) 19:04, 17 February 2016 (UTC)

Hmm? I didn't say that the physical and the mental were causally disconnected.

I see medicine as primarily as a service contracted by the patient. I don't see that as a "matter of public policy". --Trovatore (talk) 20:15, 17 February 2016 (UTC)

Perhaps a parallel situation occurred around the time that Ignaz Semmelweiss looked into childbed fever. I think it was reasonably well known by women that going to hospitals to deliver their babies was unsafe, but conventional wisdom of the time failed to recognize the spread of the disease by doctors. Once inculcated, these attitudes proved quite resilient, and to this day some women prefer midwife delivery, natural childbirth etc. over conventional hospital delivery. Wnt (talk) 01:06, 17 February 2016 (UTC)

Antirelativity. List of organizations opposing mainstream science -- GangofOne (talk) 08:24, 17 February 2016 (UTC)

• As others have said above, psychiatry is not a science, it is a science-based technology. There are "anti" movements for many other science-based technologies, for example anti-vaccination, anti-abortion, anti-gmo, anti-nuclear, and more broadly, anti-medicine, as in Christian Science. Looie496 (talk) 15:10, 17 February 2016 (UTC)

Being anti-abortion is a completely different animal. Anti-abortion activists do not claim they have a better approach towards abortion. They are just against it.Llaanngg (talk) 15:29, 17 February 2016 (UTC)

Anti-relativity is a thing. It was more prominent when relativity was newer and less-accepted—and in interwar Germany there was a racial/nationalist movement to reject relativity and other "Jewish physics"—but it's still around. Pretty much any physics professor will tell you about the e-mails/letters/etc. they get from cranks about their Theories of Everything that supposedly disprove that moron Einstein's nonsense. And young earth creationism is basically anti-all-science, since YEC beliefs contradict most modern scientific theories. --71.119.131.184 (talk) 23:15, 17 February 2016 (UTC)

February 17

Organ donor transport

After organs are harvested for transplantation, how much time is there to transplant them before they start to decay? (Question inspired partly by Mission 2 in the Rescue Pilot mission pack for Flight Simulator X, "Organ Donor Transport", and several similar FSX missions.) 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 06:10, 17 February 2016 (UTC)

It depends on the type of organ, but from 4 to 24 hours without a perfusion pump. Sjö (talk) 07:29, 17 February 2016 (UTC)

Thanks! Which means that unless the recipient happens to be in the same town where the donor died, air transportation is very much required, right? 2601:646:8E01:9089:F88D:DE34:7772:8E5B (talk) 10:09, 17 February 2016 (UTC)

Well, in cases of brain death the body of the deceased can be kept functioning for a while. Both for ethical and medical reasons usually not much more than a day or so, but it can still give the recipient time to travel to the transplant centre. If the distance from the place where the donor died isn't too big a car transport of the organ(s) will do. But in many cases air transport is necessary, especially since the waiting lists are common for a large number of hospitals, even from different countries, which makes for long transports. Sjö (talk) 11:31, 17 February 2016 (UTC)

Difference between the labor and technology

In what are the difference between the labor and technology, if labor and technology was been started at once in early human times?--83.237.202.6 (talk) 08:51, 17 February 2016 (UTC)

Did Karl Marx been described the labor as technologies in his theory Capital or not?--83.237.202.6 (talk) 10:01, 17 February 2016 (UTC)

I don't understand your question. I don't think it has anything to do with Science. Perhaps the Humanities desk would be better. Dmcq (talk) 10:54, 17 February 2016 (UTC)

If it's about Marx, it definitely belongs in the Humanities. I think he may be getting the physics concept of labor confused with Marx's concept. Ian.thomson (talk) 11:35, 17 February 2016 (UTC)

Agree, that any modern labor is always been a technology, so in what the labor against to technology?--85.141.233.142 (talk) 13:12, 17 February 2016 (UTC)

The payment for human work is always been a payment only for used labor or it is always been a payment for used technology too?--85.141.233.142 (talk) 14:46, 17 February 2016 (UTC)

Yes, Marx belongs on the Humanities desk. However, OP does not have the power to post this question there right now, so we either deal with it here or not. Or I suppose I could move the whole thing there, but then OP couldn't respond to clarify what he's interested in. My point is that criticizing the location of a question isn't very helpful when the more proper place is not accessible. SemanticMantis (talk) 15:24, 17 February 2016 (UTC)

Why did the term labor is always been against to the term technology in it's meaning?--85.141.233.142 (talk) 16:15, 17 February 2016 (UTC)

Since a cost of technology is always been much than a cost of labor, so that technologies are always been a main producing force and basic tool of economic reproduction in economy.--85.141.237.154 (talk) 21:31, 17 February 2016 (UTC)

Is the labor always been only a physical and mental (mindly) human work and nothing more?--83.237.202.6 (talk) 11:27, 17 February 2016 (UTC)

"Physical and mental" covers pretty much anything to do with life on earth, that does not make the question any clearer. Ian.thomson (talk) 11:35, 17 February 2016 (UTC)

I did not understanding had be a professionalism to any labor or not?--83.237.202.6 (talk) 11:44, 17 February 2016 (UTC)

I'm guessing that you're using translation software? Sorry, but the questions are still very unclear. Ian.thomson (talk) 11:52, 17 February 2016 (UTC)

I thinking if any labor had a knowledge (science) base it always been professional, is it right?--83.237.202.6 (talk) 12:10, 17 February 2016 (UTC)

That depends on how one defines a profession. Farming and stonemasonry require scientific knowledge. Ian.thomson (talk) 12:14, 17 February 2016 (UTC)

So why in early human times the labor of first human did not be a technology, so did not be a professionally labor?--83.237.202.6 (talk) 12:23, 17 February 2016 (UTC)

Our relevant articles are Primitive communism and The Origin of the Family (Engels). This would probably be better on RD/H, as others have mentioned. Tevildo (talk) 13:10, 17 February 2016 (UTC)

Also perhaps the larger concepts of labor and technology. We do commonly think of them as fairly different today, but I suspect the distinction hasn't always been so clear. "$\tau \epsilon \chi \nu \eta$" meant skill or cunning of hand, and could have been applied to a stonemason. SemanticMantis (talk) 14:51, 17 February 2016 (UTC)

So about the gathering of first human in early human times, it is be a labor or it is be a technology?--85.141.233.142 (talk) 15:56, 17 February 2016 (UTC)

Hi. I'm sorry for my logical mistake, so about the picking of first human in early human times, it is be a labor or it is be a technology?--85.141.233.142 (talk) 17:02, 17 February 2016 (UTC)

I see that may be the picking of first human in early human times is a labor without technology in what I been not agreed sure.--83.237.216.141 (talk) 19:55, 17 February 2016 (UTC)

At any case, if been used a tool it is always been a technology, so of course the picking of first human in early human times which been used a tool is always been a technology.--83.237.216.141 (talk) 20:23, 17 February 2016 (UTC)

The OP who uses IP 83.237.202.6 and correspondent IP users 85.141.233.142, 83.237.202.6 and 83.237.216.141 all geolocate to Moscow, Russia and they assert unclear but similar question(s) in broken English. Two different word definitions apply: LABOR n. exertion of the body, TECHNOLOGY n. the practical application of science to commerce or industry. The two links give a variety of alternative dictionary definitions. The Science Reference Desk will not engage in a political debate about human ownership rights. AllBestFaith (talk) 22:01, 17 February 2016 (UTC)

Drainage

What are the benefits of prostate drainage?--178.110.105.135 (talk) 15:45, 17 February 2016 (UTC)

There are no scientifically proven benefits and vigorous massage can dangerous and even be fatal see: http://www.chronicprostatitis.com/prostate-massage/ Richerman (talk) 16:41, 17 February 2016 (UTC)

Benign prostatic hyperplasia (BPH) is one of the ten most prominent diseases in men older than 50 years. Surgical intervention such as TURP to relieve this painful condition is itself so costly and daunting that an industry of alternative treatments has arisen. Prostate milking is not sanctioned in western medicine for the treatment of any medical disorder, it risks serious injury but it is also a profitable theme in Internet pornography (Warning: NSFW links abound]) and for marketers of pseudo-medical devices e.g.Wise-Andersen Protocol Wand and alleged cures. AllBestFaith (talk) 22:58, 17 February 2016 (UTC)

I suppose it depends on what exactly you mean by "prostate drainage". There is some tentative evidence that regular ejaculation may decrease a man's risk of developing prostate cancer. --71.119.131.184 (talk) 23:06, 17 February 2016 (UTC)

Series

So if I want 6v and I have two 3v batteries, I can put them in series and get 6v. How do I get 6v with two 3v AC adapters? I tried them in series and it didn't work. Help me, mate. Thanks — Preceding unsigned comment added by 109.207.58.2 (talk) 18:31, 17 February 2016 (UTC)

Assuming they produce AC and contain no rectifying circuitry to produce DC, it should be possible to connect them in series as you have done. You may have inadvertently connected them in opposing phase, causing the voltages to cancel. You had a 50:50 chance of getting it right. Try reversing the output of one adapter. Akld guy (talk) 19:22, 17 February 2016 (UTC)

That also assumes both output leads are floating compared to the input (for example, the secondary of a transformer that is isolated from the primary, rather than a switch-mode or other configuration with a common neutral). If you have a neutral from the plug connect to the neutral of the 3V output, then if you connect them "in-phase", you are merely shorting out one of them and the overall output is just the non-shorted one:) DMacks (talk) 20:28, 17 February 2016 (UTC)

It would be very unusual to connect neutral to the low voltage output. There are too many outlets with hot and neutral reversed. --Guy Macon (talk) 20:48, 17 February 2016 (UTC)

The OP links to the article AC adapter which primarily describes units that contain a rectifying circuit to produce DC and have a two-pole mains plug. Absence of an earth pole indicates the DC output is floating; if this is true then the outputs of two adapters can be connected in series the same way as batteries. However an adapter with the proper output voltage, current capability and connector for a given application is probably available inexpensively and should be preferred. AllBestFaith (talk) 22:32, 17 February 2016 (UTC)