Wikipedia:Reference desk/Archives/Science/2016 April 28

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April 28

Is it posssible to push in and pull out a hoop in womb, so that liquid can cover an object demi-spherically?

49.135.2.215 (talk) 01:31, 28 April 2016 (UTC)Like sushi

Inserting foreign objects into one's womb is contraindicated. --Jayron32 15:17, 28 April 2016 (UTC)

Theological objectors to its use may be calmed by information that the Intrauterine device is not an abortificant. Its mechanism of action is production of an intrauterine environment that is spermicidal. See Speroff, Leon; Darney, Philip D. (2011). "Intrauterine contraception". A clinical guide for contraception. AllBestFaith (talk) 15:52, 28 April 2016 (UTC)

Is it possible to make chemical reaction, so that equal amount of material can make one-to-one-to-one correspondence?

(technically, I can not surely be back)

49.135.2.215 (talk) 01:34, 28 April 2016 (UTC)Like sushi

Not quite sure what you are asking, but maybe this is such a reaction ?

H + H =  H2

StuRat (talk) 01:49, 28 April 2016 (UTC)

Would the H₂ weigh the same as the 2H? Isn't there some mass change due to binding energy or some such? Edison (talk) 00:03, 29 April 2016 (UTC)

An extremely tiny mass change perhaps, but would it be enough to be detectable with the equipment in your average chemistry lab ? StuRat (talk) 16:16, 29 April 2016 (UTC)

A mass change due to binding energy would accompany a nuclear process, but not a chemical change like this. Certainly no mass change detectable in a typical lab would occur, but then generating free hydrogen atoms is not something for a typical lab either. Note that the Law of Conservation of Mass is relevant to this discussion. EdChem (talk) 16:23, 29 April 2016 (UTC)

There is a calculable mass change. There would not be a measurable mass change, at least for any normal amount of material or any actual working scale. Using my handy-dandy appendix C of my 7th edition of Brown, LeMay, Bursten, I can calculate the enthalpy change for the reaction above, from the enthalpy of formation for H (g)(217.94 kJ/mol) and H₂ (g) (0 kJ/mol) at standard conditions (25 C, 1 atm) and find the reaction above to give me ΔH = -435.88 kJ/mol. So producing 1 mole of H₂ gas from lone H atoms releases 435.88 kJ of energy. The molecules thus have lower internal energy than before, exactly 435.88 kJ of it (the first law of thermodynamics is a mean bitch that way) and thus by the famous equation E = mc², their rest mass is now exactly 435.88/(3.00 x 10⁸)² or 4.84 x 10^-15 kilograms lighter. That's, of course, not measurable on any scale you or I will ever handle, but it is literally lighter. Mass = energy IN ALL WAYS, not just nuclear reactions, and that includes bond energy between atoms. --Jayron32 16:33, 29 April 2016 (UTC)

Locust

on this page Plagues of Egypt#Natural explanations it says 1 ton of locusts can eat as much as 2500 humans. if the average human weight is 70kg then thats 17500kg = 17.5 tons of humans, so 1 ton of locust eat more than 17.5 tons of human. is this a joke or real? — Preceding unsigned comment added by Money is tight (talk • contribs) 02:53, 28 April 2016 (UTC)

That means that it takes as much food to feed a ton of locusts as it does to feed 2500 humans, not that one ton of locusts could eat 2500 humans. Ian.thomson (talk) 02:55, 28 April 2016 (UTC)

Yes, it means they can eat as much as 2500 humans can eat. The second "can eat" is implied. Akld guy (talk) 04:17, 28 April 2016 (UTC)

Maybe it does mean they could eat 2500 humans, I'm sure I saw them eating a human in a film once ;-) Dmcq (talk) 09:16, 28 April 2016 (UTC)

I am happy to confirm that locusts are totally herbivorous. 81.132.106.10 (talk) 11:27, 28 April 2016 (UTC)

I have amended the statement in the article to read: "a one-ton horde of locusts can eat the same amount of food in one day as 2,500 humans can", which hopefully avoids any further confusion. Alansplodge (talk) 11:36, 28 April 2016 (UTC)

The OP has a point - he's arguing that locusts are eating, per pound of locust, much more than humans eat, per pound of human. The source here isn't exactly spectacular: Atlantic's TheWire says "When they get hungry, a one-ton hoard of locusts can eat the same amount of food in one day as 2,500 humans, according to the UN." [1] I mean, I'm sorry, I know it's all the rage to replace humans with machines no matter what, but any article that leaves "hoard" unchanged since 2013 just because it passed the spell checker is not exactly romancing me. Nonetheless, I see the same claim here, which identifies Schistocerca gregaria explicitly for the 2013 outbreak. That source also says that the individual locust can eat its own body weight in a day, which would mean that a ton of locusts can eat no more than a ton of food in a day. short ton, long ton, tonne, metric ton, I'm getting a headache already, but to be charitable, they're implying that 2500 humans can only eat 2200 pounds of food (in day, even!) which gives me serious reason to doubt we have met. Still, I can't eat my own weight in a day (at least, not without going on a heck of diet first), so the locusts do have something on me biologically. Wnt (talk) 16:59, 28 April 2016 (UTC)

Dowsing

Dear sir/Mam,

I want know science behind finding out underground water resources using coconut. I really surprised when I experience this myself, I kept coconut horizontally on my palm straight and walk through land and at specific position coconut tail moves upward and remain straight vertically. This technique called water dowsing, when I searched on Google but could not find satisfactory answer for this one. Please tell me what exactly happened and how it happens....

Regards, Ganesh Gaikwad Mumbai, India — Preceding unsigned comment added by Gangaikwad (talk • contribs) 11:29, 28 April 2016 (UTC)

See Dowsing for our article on the subject. Tevildo (talk) 11:55, 28 April 2016 (UTC)

Since there is water underground just about everywhere, and it's just a question of how deep you have to dig to find it, that makes dowsing impossible to disprove. That is, wherever the dowser claims there is water underground, he is sure to be correct. StuRat (talk) 12:53, 28 April 2016 (UTC)

Under the rocks and stones … —Tamfang (talk) 06:33, 29 April 2016 (UTC)

When the expert well-drillers can't find water but the dowsers can, it indicates that there's something to it. One theory is the dowser is sensitive to the movement of ground water, and unconsciously moves the rod or rods. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:46, 28 April 2016 (UTC)

Evidence, Please.[2] --Guy Macon (talk) 14:16, 28 April 2016 (UTC)

Here's one example:[3] ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:24, 28 April 2016 (UTC)

Yes, sometimes dowsing does work, in that what was indicated by the dowser turns out to be a good place to get water. There is no scientific support for the efficacy, that is outlined in our article. However, there is a good reason why it sometimes works when other methods fail- random chance, and the Texas_sharpshooter_fallacy. Another way of putting it: even a blind squirrel occasionally finds a nut. See also Post hoc ergo propter hoc. SemanticMantis (talk) 14:51, 28 April 2016 (UTC)

Especially if the blind squirrel is male. StuRat (talk) 14:54, 28 April 2016 (UTC)

Whilst not commenting on any scientific basis for this (if there is any), didn't Uri Geller make millions out of dowsing for minerals and oil? Were all these companies simply hood-winked, or did they employ him on the basis of previous results? DrChrissy ^(talk) 15:10, 28 April 2016 (UTC)

Probably "a subset of previous results". That is, he advertised those cases where he was successful and not those where he failed. Infomercials for weight loss products do this all the time, with testimonials from the lucky few who actually managed to lose weight in spite of the crazy diet, and maybe some who just lied to get paid, with a tiny disclaimer below that says "results not typical". StuRat (talk) 16:53, 28 April 2016 (UTC)

Whether scientific or not, there are plenty of people who drill wildcat wells looking for water, hydrocarbons, or anything else. It would be fascinating to find a scientific survey on the statistical success-rate to determine whether the method is, well, methodical. One problem is that of confirmation bias; and with the trouble of any Poisson distribution. If an experimenter will retry a random event until successful, they have a near-100% chance of success... but that's not a methodical way to identify whether their system works, nor if it has any advantage over other methodical approaches.

Regarding Uri Geller: that character didn't exactly "make millions," but he did get a lot of publicity and was seen on TV - and if we're looking for statistically-valid indicators, "as seen on TV" is a sure sign of a scam! Geller's "unique abilities" were scientifically studied at SRI - and you can read what a couple scientists thought - they were published in Nature, (1974). At least a few scientists were convinced that his methods were "better than random chance," but most other scientists disagree with the authors' credentials (they were physicists, not psychologists or statisticians); and there has been immense criticism of their study methods, the statistics, and the conclusions.

Nimur (talk) 15:27, 28 April 2016 (UTC)

The article well summarizes a great deal of evidence for pseudoscience. It should be clear, in any case, that most persons who do dowsing have simply found a paying racket, which in our society is the very definition of success. That said, I reserve a sliver of skepticism of the skeptics because those tests were not conducted with the model of precognition in mind, i.e. it might be easier for a dowser to remember a unique feature in advance, and to remember seeing someone strike water straightaway but have no chance to foresee a hidden mark on an experimenter's paper. Wnt (talk) 17:11, 28 April 2016 (UTC)

Well, let's look at the science. THIS is a careful description of the two-year long "Munich experiment" on dowsing. It started with 500 dowsers, then reducing to the numbers to 46 with the best results. They did more more detailed analysis for the 6 people who performed the best. At each stage, the dowsers agreed with the experimenters that the protocols being used were entirely acceptable - and even when they changed their minds, the scientists would agree to change the experimental setup. So the dowsers have no excuses for any failures.

The original experimenters messed up the statistics and claimed that those 6 people were highly talented - although the other 494 of them were not.

But with more robust statistical treatment, even those six performed marginally worse than chance alone would suggest.

I'd also point out that there is that One Million Dollar Paranormal Challenge - a million dollars sitting in trust at the Randi institute for anyone who can pass their dowsing test. So far four people have been tests - but not one has come REMOTELY close to passing the test. Read: One_Million_Dollar_Paranormal_Challenge#Example_of_a_test_.28dowsing.29) for more details.

CONCLUSION: Dowsing doesn't work - not at all, not even slightly - it's a total and utter bust. Any positive results claimed here therefore anecdotal, flooks, observer bias, rigged tests or flat out lies and deceit. Note that this doesn't stop Amazon from selling you two pieces of bent copper wire (with a sheet of photocopied instructions) for $15.00 (plus $5 shipping).

SteveBaker (talk) 17:33, 28 April 2016 (UTC)

Well, what I meant is that the "no feedback about success or failure" built into the design would frustrate a precognitive model. Even a perfect precognitive would need not merely to learn whether there was success or failure, but to have success be more memorable than failure. Wnt (talk) 18:20, 28 April 2016 (UTC)

I'm a student of the critical thinking arts and "Dowsing" is one of a handful of subjects that has an almost "religious" following. People who know it works can not be convinced by any amount of evidence that it's just not real. It is extremely ingrained in popular culture, The Water Diviner is a recent example, i suspect a very high percentage of the general population believe in it entirely or at least think there's "something to it" that science does not know about, "There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy" is a very popular quote among the peddlers and believers of pseudoscience. . . Vespine (talk) 05:19, 29 April 2016 (UTC)

Regression toward the mean is relevant to the example of the 500 dowsers. Those that were "best" simply were lucky that the random variations went their way in the first tests. As you test again and again the laws of probability will reduce their success rate. The same goes for all other tests of the paranormal where initially some test subjects look successful, but their results drop with time. Sjö (talk) 05:43, 29 April 2016 (UTC)

Remembering numbers

Why is it very much difficult to remember numbers for a long period of time? I am a secondary level student and we have to remember many facts and figures in numbers, so can someone please tell me about it and some ways to improve it? — Preceding unsigned comment added by Sahil shrestha (talk • contribs) 13:01, 28 April 2016 (UTC)

There's a limit to human processing which was first explored by the landmark paper "The Magical Number Seven, Plus or Minus Two"; humans have a difficult time remembering things for a few reasons; but the two most important relevant to numbers are context and size. Very large numbers are hard to remember because the human brain has trouble remembering large sequences of digits, basically about 7 ± 2 is the limit. To get around that, the method known as Chunking is used to get around it. That's why phone numbers are often broken up. In the U.S., the typical phone number has 10 digits. 9195557321 is hard to parse, because it's too many random digits, but 919-555-7321 is more memorable because it is "chunked" into smaller pieces to make it easier to process. The other issue is with context. Numbers devoid of context tend not to stick in one's memory; to make something more "sticky", some random fact needs more facts your brain can connect it to. So, we have various mnemonic devices to do so. Rhymes or poems can work "In fourteen hundred and ninety two, Columbus sailed the ocean blue." makes the number 1492 memorable. One of the most common mnemonic devices to remember many numbers is the Method of loci, where numbers are connected to specific objects in a "memory palace", and as one walks through one's "memory palace", one remembers the numbers by remembering the trip through the palace. --Jayron32 15:59, 28 April 2016 (UTC)

Indeed, it makes the number 28736386354 memorable. Wnt (talk) 17:12, 28 April 2016 (UTC)

Sure, if you chunk it as 287-363-863-54 or some other similar way. --Jayron32 18:12, 28 April 2016 (UTC)

"In fourteen hundred/ And Ninety Two / Columbus sailed the / Ocean Blue? I think you have the wrong meter. :) Wnt (talk) 18:14, 28 April 2016 (UTC)

Sorry. The original poem has no "and".: [4] --Jayron32 18:22, 28 April 2016 (UTC)

Ah, but is that a reliable source? If you search in Google Books you will find many instances of it being quoted both ways, with most of the top hits showing the "and". One of the first hits—with the "and"—is in an article titled Reading for Indian Resistance by Bethany Ridgway Schneider, found in the book A Companion to the Literatures of Colonial America edited by Susan Castillo (this one?) and Ivy Schweitzer; Schneider says the two lines are anonymous, and if that's correct then it'd be hard to know which version is the original. On the other hand, Wikipedia says the lines (without "and") are part of a poem by Winifred Sackville Stoner Jr.; but even if this is correct, Stoner could have incorporated the existing couplet into her verse. I do note that to fit into an iambic meter there should not be an "and". --69.159.61.172 (talk) 21:50, 28 April 2016 (UTC)

Unless you elide the "and" sound into the beginning "n" of "Ninety", then it fits nicely. --Jayron32 00:05, 29 April 2016 (UTC)

2876386354 then. Wnt (talk) 19:05, 28 April 2016 (UTC)

I suggest flashcards. StuRat (talk) 16:58, 28 April 2016 (UTC)

Acne faces

Why do some people get severe acne and the scars to go with them? What causes the severe development of acne? Some kind of gene? Habit? Oily skin? Hypersensitivity? I hardly get any acne. 140.254.77.195 (talk) 14:59, 28 April 2016 (UTC)

Wikipedia has an article titled Acne vulgaris (the full medical name of what is commonly called "acne")> There's an entire section on causes. --Jayron32 15:14, 28 April 2016 (UTC)

OR here, but for me there's a 100% correlation with consumption of trans fats. That is, if I consume trans fats, I get acne. If I don't consume them, my skin is clear. Therefore, I avoid them. StuRat (talk) 16:59, 28 April 2016 (UTC)

I did not know this, but indeed, it is confirmed: [5] I dare say even that awful MEDRS guideline won't leave any room for bitching if we put this one in the article. Fake fat, cooked up over a platinum catalyst... what could possibly go wrong? Olives were invented by Athena... partially hydrogenated oils by Proctor & Gamble. Wnt (talk) 17:17, 28 April 2016 (UTC)

WP:OR In my own case, I've noticed that I would often get an acne outbreak after a cold or another infection -- I wonder why that's the case. 2601:646:8E01:515D:E002:2F3A:1AC5:46BF (talk) 23:53, 28 April 2016 (UTC)

Ayrton fan

How did the Ayerton fan work? And did it work at all, since usually the poison gas was all around? 2601:646:8E01:515D:E002:2F3A:1AC5:46BF (talk) 22:02, 28 April 2016 (UTC)

Well I know next to nothing about this topic, except that trenches were particularly susceptible to gas attack specifically because the gas could accumulate in the trenches, unlike on flat land where it would simply get carried away with any breeze. I'm guessing the fan would provide some level of mechanical ventilation which would carry the poison gas away and out of the trenches much faster and more effectively than just letting natural air currents do it, which if the gas was heavier than air, might take quite a long time. Vespine (talk) 23:13, 28 April 2016 (UTC)

Our Chemical weapons in World War I article has a lot of relevant information, however I could not find anything specifically related to the Ayrton fan, even in the countermeasures section. Vespine (talk) 00:21, 29 April 2016 (UTC)

There were a number of chemical weapons used in WWI, with different properties. Chlorine gas, one of the most widely used, is heavier than air, which is probably what you're thinking of with gas accumulating in the trenches. I think fans might work to blow chlorine gas away from you. I've read some books about WWI, and I've read chlorine attacks had to be carefully managed to make use of favorable winds. Sometimes things went awry and the wind blew the chlorine back towards the side that released it. --71.110.8.102 (talk) 00:57, 29 April 2016 (UTC)

A quick web search turns up [6]:

I did not see the experiments until they had developed, and model "dug-outs" and "pill-boxes" had been built. These could be cleared of smoke with a few flaps of a tiny square paddle or fan. The fan with a flexible blade rather more than a square foot in size was mounted on a T-shaped handle. When smacked on the ground facing the on-coming gas, the cross bar of the handle hit the ground first, the blade flattened out, and sent a puff of air. The friction of the ground retarded the lower part of the puff, which became a vortex cylinder. When smoke rings are formed at the end of a gun, or the funnel of a locomotive, or the lips of a smoker, the central part of the puff advances faster than the edges, and so a ring is formed revolving on itself. Discussing this with Mrs. Ayrton, I asked where the ends of the vortex cylinder were, for I had the impression that a vortex ring must be continuous and cannot be cut. I cannot remember her reply, but it may have been that the under surface of the blade retards the air, and forms an upper vortex cylinder rotating in the opposite direction. But whether the two join to form a ring, I cannot say. An ordinary smoke ring increases in size as it travels, and induces a blast of air to pass through it. It was this that drove the gas back. Of Mrs. Ayrton's originality, perseverance and enthusiasm I was aware, but I found her greatly depressed, and showing a sensitiveness of disposition that was new to me. She could stand up to academical mathematicians, but now she was up against officialism. I must confess that the toy-like models in her laboratory-drawing room seemed a long way from the battlefield. So far as experiments went they were convincing when she showed them to me, and many who saw them, including intelligent soldiers, were impressed. But those who did not or would not come, and those who refused to give the invention a trial...

In spite of the disheartening opposition commonly shown to inventors at this time, several supplies of gas-repelling fans were sent to the front. These were not intended to be merely waved about, and perhaps the name "fan" was unfortunate. The inventor almost accidentally, perhaps intuitively, acquired the knack of using it in the best way, and this needed instruction. One of her assistants from the Central College went out and demonstrated the proper use of the fans, and a few officers were convinced of their value...

Wnt (talk) 01:05, 29 April 2016 (UTC)

Mrs. Ayrton's fan made of waterproof canvas stiffened with cane, with a wooden handle is displayed here but "'The fan was found to have no appreciable effect whatever on the gas cloud: in fact, it was actually worse than useless...' (see C. H. Foulkes, 'Gas!': the story of the Special Brigade (Edinburgh: William Blackwood, 1934), pp. 101-102. AllBestFaith (talk) 07:49, 29 April 2016 (UTC)

It is unfortunate for the troops, but very fortunate for the residential neighbors of the 1920s, 30s, and 40s, that she invented a fan instead of the leaf blower. But is there any actual technological reason she could not have invented the latter, had she thought of it and had the needed resources? Wnt (talk) 11:03, 29 April 2016 (UTC)