Wikipedia:Reference desk/Archives/Science/2016 February 14

= 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. 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&#38;Johnson&#38;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) 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)  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       (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 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 . 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 DL 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.)  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:, , .  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. -- Jayron 32 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)
 * Boethius's The Consolation of Philosophy was the best seller of the middle ages. It could not be called blissfully unaware.John Z (talk) 23:35, 17 February 2016 (UTC)
 * What percentage of the serfs could read? ←Baseball Bugs What's up, Doc? carrots→ 00:56, 18 February 2016 (UTC)


 * Scholars in the middle ages were all too aware that there had been a vast decline from the might of Rome, and the classical beauty and wisdom of Greece. There are many references to the ruins of such periods which continued to show just how advanced these earlier civilizations had been, and of course, the sublime statues of Greece which could not be copied until the Renaissance. Academics and theologians compared these times to their present, complete with all kinds of plagues. Until very recent times, prob middle 20th century, there has been almost ubiquitous veneration of the classical period, to which the modern era is compared unfavourably. Umberto Eco provides a superb panorama of such times (Name of the Rose), in which scholars worship Aristotle to the point where contemporary discoveries are declared to be refuted if they are inconsistent with the Greek philosophers. Today, I suppose it must feel the same to modern Egyptians, who can look upon the ruins of Ancient Egypt, as they trudge thru their ubiquitous slums unable to even house priceless antiquities properly, heading to their prayers. And of course, orthodox Islam forbids veneration of non-Islamic culture. The ancient Egyptians made the famous death masks for the Pharoahs. Just recently, the contemporary "museum" workers tried to glue a beard back onto one of these after it had fallen off. They failed in the attempt. It must be very humbling to watch the ruins of Great Egypt as you plod about in the slums of Cairo, and bands of archeologists continue to excavate ancient sites all around you. Myles325a (talk) 03:39, 18 February 2016 (UTC)


 * Modern Egypt has all sorts of technology well beyond ancient Egypt. Not so for the Dark Ages. StuRat (talk) 03:49, 18 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.

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)