Wikipedia:Reference desk/Archives/Science/2014 June 23

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June 23

Gold powder to mix into epoxy for repairing crockery

You can buy a kit containing epoxy and a gold powder which are mixed and used to cheaply mimic kintsugi for repairing broken crockery. The kit is somewhat expensive so I was hoping to find out what gold powder I could buy separately for this. Has anyone a suggestion as to what sort of powder would produce a homogenous gold effect? ----Seans Potato Business 01:35, 23 June 2014 (UTC)

Powdered brass looks like gold, but has a tendency to tarnish over time -- so regular polishing will be essential. 24.5.122.13 (talk) 02:51, 23 June 2014 (UTC)

I wonder if iron pyrite, known as "fool's gold" would work. StuRat (talk) 04:09, 23 June 2014 (UTC)

Pyrite does look like gold, but it oxidizes in air, thus decomposing to iron oxide and sulfuric acid -- this reaction irreversibly discolors the repair, and the sulfuric acid may go on to damage the article. 24.5.122.13 (talk) 06:19, 23 June 2014 (UTC)

I'm picturing the pyrite being protected from oxidation by a clear layer of epoxy. As long as it's stored in a manner to avoid oxidation (packed in oil ?) and doesn't oxidize in the time it takes to make the repair, that is. StuRat (talk) 22:45, 23 June 2014 (UTC)

I think it's a cool idea, but to me, the gold color is not necessary to achieve an artful wabi sabi effect. I'd consider silver as a cheaper alternative, though it also tarnishes when exposed to air. But, this isn't exactly exposed, it's part of the matrix of binder, so that might prevent tarnishing. Have you sourced an appropriate lacquer or resin binder? Depending on the properties, mixing in gold-colored mica flakes might give you a gold sparkle on the finished product. Also, have you come across a "recipe"? it might be the case that it calls for less gold powder per mass of lacquer than you're expecting. SemanticMantis (talk) 16:04, 23 June 2014 (UTC)

Yes, mica is a great choice -- it can look like gold, and it doesn't tarnish or break down. 24.5.122.13 (talk) 00:17, 24 June 2014 (UTC)

Gold leaf (an incredibly thin foil) is extremely cheap (Amazon has it on sale for about $2 for a 3"x3" sheet. Couldn't you fill the crack with epoxy and then rub the gold leaf into it as it sets? SteveBaker (talk) 04:09, 25 June 2014 (UTC)

Space casting

I've recently re-read the Strugatsky Brothers (what, no article?!) novel The Land of Crimson Clouds (which is about an expedition to Venus for mining of transuranics), and in that novel they make a reference to casting rocket parts from molten metal in space (this is how the Khius, the expedition's photon rocket, is made). Now, I'm very familiar with spacecraft assembly in space (this is how the MIR and ISS space stations were built), but I'm not sure that casting is a suitable technique for this -- in the absence of gravity, the metal won't flow unless pressure casting or centrifugal casting is resorted to. Does anyone know whether casting in space would be possible? 24.5.122.13 (talk) 03:03, 23 June 2014 (UTC)

Not an answer, but the authors' article is Arkady and Boris Strugatsky. Rojomoke (talk) 03:55, 23 June 2014 (UTC)

Using a vacuum to draw the metal in is a standard process for intricate shapes. There's lots of vacuum in space :) Dmcq (talk) 08:58, 23 June 2014 (UTC)

But with the same vacuum outside the mold as inside it, how can it work??? 24.5.122.13 (talk) 00:16, 24 June 2014 (UTC)

Pressure casting and centrifugal casting should work. Spherical objects would likely be easier to make in zero-g than on earth (see shot tower). Growing crystals in zero-g is likely to produce materials with useful properties [1], [2]. The space manufacturing article is largely unsourced, but the Environment section lists some possible advantages.--Wikimedes (talk) 06:01, 24 June 2014 (UTC)

The point of using a vacuum is to avoid having any air in the cast so the metal can go everywhere cleanly, you don't have to have channels for the air to come out of and you don't need to worry so much about forming bubbles inadvertently. Sorry I should not have said 'draw in', what actually happens is one has a higher pressure on the surface of the metal so it is pushed up through a tube into the mould but in fact even that is often quite a bit less than normal atmospheric pressure. See Vacuum_permanent_mold_casting#Vacuum for this sort of thing. Dmcq (talk) 06:54, 24 June 2014 (UTC)

So the sum total is, pressure, centrifugal, and vacuum casting are practical technologies for space manufacturing, right? 24.5.122.13 (talk) 07:38, 24 June 2014 (UTC)

Certainly there is no obvious reason why not. Of course there may be many subtle technical issues in practice. A lot depends on what metals you need to cast and how many of each item you need to make. Techniques like lost-wax and sand casting are fine for one-off manufacturing, but are horrendously slow if you want 100 or 1000 of something. SteveBaker (talk) 04:05, 25 June 2014 (UTC)

FYI, centrifugal casting is useful even here on earth. I have a friend who makes miniature figurines for tabletop gamers - he has a machine called a "spin-caster" that uses centrifugal force to fill the molds more effectively than gravity alone. I don't know how many g's it produces, but I'm sure it's a lot more than one...which means that it ought to work OK in zero-g. For making spacecraft replacement parts, 3D printing (which can make metal parts via laser sintering) makes more sense because you don't need to make molds, and you can make parts who's shape is too complex for casting. SteveBaker (talk) 04:05, 25 June 2014 (UTC)

Where is the Phononic Computing article?

I can't seem to find the WP article for Phononic Computing.

That's using Phonons, not Photons.

c.f.: http://www.technologyreview.com/view/428844/how-to-build-a-phononic-computer/

Hcobb (talk) 05:36, 23 June 2014 (UTC)

Phonons are found in any solid state description of crystalline solids. From superconductors to silicon, phonons are prevalent constructs. Until someone actually does something novel and physical, it will most likely remain a subarticle. --DHeyward (talk) 05:47, 23 June 2014 (UTC)

So I herd u liek axolotlz...

When is GFP not GFP? When you hack it for pleasure...

According to an article in a certain other less-reputable wiki (link blocked by spam filter), scientists are attempting to breed or genetically modify axolotls to have ectopic dorsal fins atop the head, like Mudkip (seen at right). Is that right? Has anyone even produced an axolotl with blue coloring, rather than the green that GFP alone would produce (contrary to the aforelinked article's reference to a "GFP-546 axololtl"? NeonMerlin 11:47, 23 June 2014 (UTC)

Googling "genetically modified axolotl" there seem to be plenty of entries. By "right" do you mean "factually correct" or "morally right"? ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:56, 23 June 2014 (UTC)

• • "Factually correct." I'm not one of those who'd consider it "right" not to test the limits of science. Muahahahahahahahahaha! }:-D> NeonMerlin 11:58, 23 June 2014 (UTC)

There's some limited data published ( [3] ) but I'm not seeing a large list of accomplishments. To be clear, as described at EGFP, you can make any color derivative. Though an animal that fluoresces a certain color isn't really the same as being that color, and we should expect better from amphibians which can be blue. I'm seeing reports of blue axolotls online, together with accusations they were merely dyed, and I certainly haven't dug enough to strike truth on the matter. The fin should be achievable by embryonic manipulation, by a skilled hand (amphibian embryos are pretty accessible). There's also some data that a Frizzled receptor is needed to induce dorsal fin, which is a combination of neural crest and somite cells. [4] I would not be at all surprised if a thorough scrape of conference abstracts turned up at least someone with a morphogen bead system to induce a dorsal fin, if it isn't outright published already - I really haven't searched well enough - but I think we'd have an easier time finding a reference for an existing transgenic that actually looks like a "mudkip" :) Wnt (talk) 01:00, 27 June 2014 (UTC)

Children's taste preferences and broccoli and spinach and brussel sprouts

In commericals, movies, and on TV, children are often portrayed as having a strange dislike of eating broccoli, spinach, and brussel sprouts. When I was a child, I loved those vegetables. Could it be those kids are sensitive to some flavor in those vegetables and they happen to think the flavor is bitter? Could it be the preparation of the food, which might be bland? Could it be just me? What's going on here? 140.254.226.182 (talk) 14:43, 23 June 2014 (UTC)

I'm sure preparation plays a part in it; I find those vegetables to be routinely over-cooked to the point of sogginess. In the book Why We Get Sick, the authors posit that kids' finickiness towards vegetables may make solid evolutionary sense: many plants, including several that we routinely consume, are poisonous in some way. Besides obvious stuff like the non-fruit parts of the tomato, many strong tasting plants acquire their flavour to reduce predation - the strong tastes of onions, mint, peppers, and so on, are there to stop pests from eating them. Thus, kids (who are also more sensitive to poisons) have more sensitive tastes than adults as a kind of early warning system to prevent poisoning. A kid who turns up his nose at leafy greens will live for another day, but one that munches on the wrong leafy green could easily end up dead. That kind of natural selection process is just the kind of thing that gets hard-coded pretty easily. Matt Deres (talk) 16:30, 23 June 2014 (UTC)

See some related issues at food neophobia and Selective_eating_disorder. Not that a kid who doesn't like broccoli is a clinical case, but these things occur on a spectrum. I can't easily find a link at present, but a few weeks ago on NPR they had a dietician claiming that kid's eating habits are getting worse, in part because there's so much sugar in some diets, that even sweet fruits like an apple are considered "bland". Also keep in mind so much of our diets are subconsciously enculturated at a young age. I too have always like broccoli and spinach, but I was exposed to them early as a delicious food, not some distasteful green thing that had to be eaten. If you google things like /get kids to eat veggies/, you'll find all sorts of advice blogs like this [5]. In some cases, picky eating can be a bit of a self-fulfilling prophecy, in that the kid picks up on parent's assumptions that certain foods will not be liked.

Now, if you want real science, you'll have to read real scientific publications. This is a large area of research, especially in light of the obesity epidemic in USA and some other countries. Here's two that jumped out "Food neophobia and ‘picky/fussy’ eating in children: A review" [6], and "Parental pressure, dietary patterns, and weight status among girls who are “picky eaters" [7]. Key conclusion from the latter

“ Mothers influenced daughters’ fruit and vegetable intake via their own patterns of fruit and vegetable intake and by influencing their daughters’ tendencies to be picky eaters. ”

As usual, you can ask at WP:REX if you can't get access to the articles through a library or other means. SemanticMantis (talk) 16:27, 23 June 2014 (UTC)

What the Mantis said. Not entirely germane to the question, but there has also been a link established between the severe manifestations of food pickiness and autism. Evan ^{(talk|contribs)} 16:47, 23 June 2014 (UTC)

There is the concept of supertasters, where people have a stronger response to certain taste compounds than others (including bitter compounds in things like brussel sprouts). There's also a number of genetically-related taste differences know, including sensitivity to phenylthiocarbamide (incredibly bitter or tasteless, depending on genetics - PTC overlaps somewhat with supertasting in ways that aren't entirely clear), sensitivity to cilantro/coriander (being either pleasant or soapy depending on genetics), and possibly even raw tomatoes [8] (that last link has a good overview of the genetic components). Note that even if genetics play a role, they're unlikely to be the whole story on picky eating by children. -- 160.129.138.186 (talk) 17:25, 23 June 2014 (UTC)

Encoding information in radioactivity

As an interesting thought experiment, I've been trying to come up with a practicable way of using radiation as a method of storing information, and I'm wondering what other sources may have delved deeper into the idea than I am intellectually capable of doing. There would be very few benefits to such an arrangement, but you would at least have something that is more resistant to damage than, say, a hard drive or data tape, and it could particularly be an interesting sci-fi device (say, embedded on the Moon by an ancient civilization a la 2001). You could also have a very good shot at projecting the decay of the data linearly, based on the half-life of whatever radioactive material you choose to use.

So far I've concluded that you could probably construct something like a hard drive that would use radioactive rather than magnetized materials to store information, assuming you could come up with a scanning device analogous to a read-head that could deal with the radiation involved. That shouldn't be too much of a problem, and the same principle would apply to tape storage as well. My idea, though, is something more akin to a short-range "broadcast"—i.e., to embed information long-term in a time capsule, say, a chunk of rock, with the intention of that information being accessible a thousand years or more down the road. The problem would be that, in such a system, you would be "winding up" the radioactivity and stepping back while it runs its course, so there's no real way of modulating a "broadcast" signal to communicate any meaningful data.

A long shot, maybe, but any references on that? Evan ^{(talk|contribs)} 15:59, 23 June 2014 (UTC)

Not radiation, but in the vein of long-term data storage, there are people working on using lasers to etch quartz glass as an effective storage medium. They claim one of these discs could last "hundreds of millions of years" [9]. SemanticMantis (talk) 21:18, 23 June 2014 (UTC)

Radioactive decay according to current theory happens completely at random, so there's no way to encode data in it the way I think you're imagining. There's a process for etching data into nickel discs that is supposed to be very durable: see Rosetta Project for a well known user of it. 04:15, 24 June 2014 (UTC) — Preceding unsigned comment added by 173.228.123.145 (talk)

Well, it's certainly possible - as a thought experiment, imagine a 10' diameter disk with bits of plutonium or lead stuck to it. You spin the disk under a radiation counter and you get a stream of radioactive/not-radioactive outputs - which you can use as 0's and 1's. The question isn't whether it's possible. The real issues are:

1. Density. How close can you pack your bits of radioactive (or not) material and still have the detector "see" just one bit at a time? (I suspect this is the problem here).
2. Can you write to is as well as read from it? If not, then you have something like a CD-ROM that you can read but not write. In that case, how would you manufacture these things?
3. Safety. How are these things to be used and regulated? There is no amount of radiation that's truly "safe".

SteveBaker (talk) 06:16, 24 June 2014 (UTC)

(To Steve Baker) That kind of platter, consisting of lead and plutonium, would obviously be one dense mother.

(To Evanh2008) That made me think of a breeder reactor of some kind; maybe a type that's both extremly slow and predictable. Maybe we could bury one on the Moon, set to assemble a critical mass exactly 100,000 years from now.

The year 102,101. War was beginning.

Moon: *BOOM*

H.s.superior #1: What happen???

H.s.superior #2: Somebody set up us teh time capsule.

No, there wouldn't be an explosion, but the critical mass would emit a lot of heat, creating a literal "hot" spot on the Moon. A pattern of sources, i.e. several breeders forming a regular shape, would be possible. For example, the pattern could be a series of dots around the lunar equator, set to "light up" in a regular sequence.

Moon: xx..x..x....xxxxxx

Other data storage methods look favorable. A simple punched card made of sheet metal should last billions of years on the Moon — and that's about how long the Moon itself will be there. It doesn't come with a nice "look here!" feature, though. - ¡Ouch! (^{hurt me} / _{more pain}) 07:35, 24 June 2014 (UTC) Bonus points for decoding the "Moon message" above.

Since radioactivity is a stochastic phenomenon, only some sorts of information can be conveyed by it - enough measurements of the time between radioactive decay events, over time, give us a "half-life" that can be quoted with confidence; a language of isotopes with differing easily measurable gamma-ray spectra or particule energies could be made. However, there's no real advantage to doing that, as radiation spectrometers would have to be used to determine the content of a message encoded in that way. While there are now small and relatively cheap (flashlight-sized) gamma-ray spectrometers that can distinguish between these isotopes, the radiation emitted by the isotopes isn't nearly directional enough or confinable to a single "cell" on a storage medium to be rapidly read in a dense enough array to compete with optical drives or static RAM.

Even if such complex encoding were advantageous, it could be done so much better biologically - using DNA and RNA. The equipment for that, since the efforts of Craig Vetter, still costs much more than modern gamma-ray spectrometers, but such encoding can be done with much less hazardous laboratory equipment (E.coli cultures which are bred to be very delicate everywhere but the laboratory, mostly).

Wired magazine described how the "traveling salesman" problem, an intractable and difficult to solve mathematical puzzle, was solved using DNA and RNA analogs to combinatorial mathematical symbols - it took a week in which the DNA codons were arranged to stand for elements of a "Hamiltonian path" statement of the travelling salesmen problem, the tailored bacteria allowed to reproduce, and the resulting recombinations of DNA sequenced out of the bacterial soup and the sequences interpreted for the solution of the problem.[10]

That's an example of the high-end power of recombinant DNA encoding; to do what you're talking about's much simpler (relatively speaking, I sure couldn't do it, even if they turned me loose in a molecular biology lab for a week). You just choose base-pair sequences of "junk DNA" in some organism to stand for the information you want to encode and save, being sure to choose an organism with highly conservative genetic reproduction, and the odds are that you can simply refrigerate the bacterium you use as an encoding mechanism and store those data indefinitely.

Rhodopsin, the protein which is "bleached" in the retina of the eye, has been investigated as an optical storage medium. A bacterial version of this protein can be used to store data much more permanently than magnetic media with the added advantage of being able owing to its molecular structure of being able to encode holographic information, including "interferometric movies," or holograms which encode moving images.[11]

While it's good to think outside the box as you've done to ask why and how one could use radioactivity as a data storage medium, its prime drawback compared to, say, rhodopsin, is read times can go into seconds, while rhodopsin-encoded data can be erased in picoseconds and reset in milliseconds - still sluggish compared to silicon and metal optical data storage, but with the advantages mentioned above. I can't think of a compelling advantage possessed by storage of data in radioactive media. Its very nature is random (within a general stochastic framework), so that the "bits" of data take seconds to read, not microseconds as with current static RAM devices like thumbdrives. But that's not to say that in the future such data encoding strategies couldn't pay off.

Radioactive encoding might be a plausible way to encode data sent (as in the Voyager spacecraft) outside the solar system in the hopes that nonhuman intelligences would detect them and reason out how to decode the messages we sent. Isotopes with moderately long half-lives (months) might be deposited in quantities high enough to survive many decades of travel through space and remain active enough to be detected by a sufficiently advanced spacefaring race. loupgarous (talk) 05:56, 26 June 2014 (UTC)

I suppose the radioactivity could serve as a widely spreadable mini transmitter for conveying a message whose meaning otherwise becomes clear. I'd think that spreading a nuclear isomer with a specific gamma frequency emission would make it possible to detect, from considerable distance, a set of territories it had been spread on (for example, minefields, sanctioned worlds, or asteroids claimed by a particular monopoly), particularly to amplify a terrorist threat from a small number of effectors to a much larger definition of political ownership. Wnt (talk) 00:22, 27 June 2014 (UTC)

From Loupgarous: "Isotopes with moderately long half-lives (months) might be deposited in quantities high enough to survive many decades"

That's another one underestimating the power of exponential decay. (Or maybe I got you completely wrong.)

Let's say "months" are 11 months, and "many" decades can mean as few as five. Then, we have 50 years = 600 months = 54.5 half-lives. That would mean we could start with truly enormous quantities (say, 1000,000 tons) and by the 6th decade, there wouldn't be hardly anything left. After 11 years, we'd be down to 1/4096 of our initial mass (244tons), 60kg after 22 years, 14.6g after 33, 3.6mg after 44, and less than 0.1mg after 50. That's detectable, but is it from a distance, and through all the "noise" the other isotopes down the decay chain emit?

I'd propose a much longer half-life. That would mean lower initial radioativity, but much slower decay, too. If the half-life is much longer than the estimated travel time, the decay is close to negligible but the initial intensity is low. If the half-life is much shorter, the exponential decay reduces the (high) initial activity over time to a tiny fraction. The projected travel time and the half-life should probably agree (at least in order of magnitude), to get the best possible signature at encounter. - ¡Ouch! (^{hurt me} / _{more pain}) 07:40, 27 June 2014 (UTC)

explain this quote about science progress

What this quote means ?

I mean, progress is great, but you have to understand: I worked at MIT simulating nuclear explosions on a 1 MHz 6510. Fifty years ago, Feynman and von Neumann were simulating nuclear explosions on schoolhouses full of coeds with slide rules. Now I'm running a Dual Celeron at 400 MHz, so I feel like I should be having eight hundred times as much fun now, but I'm not. Some days I'd much rather have the slide rule girls. 198.86.53.67 (talk) 16:07, 23 June 2014 (UTC)

Where's it from? As I see it, the speaker seems to be arguing that "faster computers" (in terms of clock speed) should lead to more "fun" in science. But, that is a silly assumption, and the speaker then seems to refute it, by saying that some days s/he would rather have slide rules than fast computers. I guess if there's any good point to the quote, it is that, while computational power can make some aspects of science possible/easier, there are still many fields of inquiry that don't depend much on processing power. Many fields of pure mathematics for instance don't need much of any computing power.

For another more sciency example, my old office neighbor was a young professor and a rising star in her field. She did some amazing work showing fast evolution of certain lizard species in response to fire ant invasion. When she was asked what she was going to do with her funds for computational infrastructure, she said "I don't know. The most advanced technology I used for my Science paper was a bucket and a stick!" SemanticMantis (talk) 16:15, 23 June 2014 (UTC)

Mmm. A bit hard to figure out, yeah, though I'm not sure science per se is really the point. For example, it's not the slide rules the speaker expresses a desire for, but those "slide rule girls"—the "coeds" with the slide rules that Feynman and von Neumann were vaporizing (which is weird, since they were mannequins rather than actual women). It's more libidinous that genuinely scientific, I think. Evan ^{(talk|contribs)} 16:23, 23 June 2014 (UTC)

I think perhaps you read the quote incorrectly; they're talking about simulating nuclear explosions using math - nobody is getting vaporized. Matt Deres (talk) 16:34, 23 June 2014 (UTC)

Feynman and von Neumann both worked on the Manhattan Project, though, so they were literally vaporizing things. How would you factor "coeds with slide rules" into a mathematical simulation? I suspect the speaker (and I really would like to see the quote in its full context) is using "simulating" in a tongue-in-cheek way, at least for the Feynman and von Neumann mention. Evan ^{(talk|contribs)} 16:38, 23 June 2014 (UTC)

I'm pretty sure in Surely you're joking Mr. Feynman, he talks about using rooms full of people to run simulations at one of the national labs. Recall computer used to mean a person! Basically, a smart guy like Feynman can break down the complicated math into an algorithm that only requires each person to make a few short calculations, and hand the result to the right. Bletchley park had a lot of women manning computers and punching cards, I'd not be surprised if Oak Ridge National Laboratory and other fed research sites had teams of talented young women working slide rules to perform detailed calculations/simulations. So, they were "simulating ...on" a schoolhouses full of coeds "- much like we can do "simulating... on a cluster". (But I did misread "slide rule girls " -- maybe the speaker is just a sexist cad :-/ )SemanticMantis (talk) 17:04, 23 June 2014 (UTC)

Yes, I think that's a plausible interpretation of the "simulating" bit, and certainly simpler than mine. So, to paraphrase: "I used to simulate nuclear explosions on a 1 MHz chip, but even before that, Feynman and von Neumann were doing it on paper with young, attractive female assistants. Now I'm running a 400 MHz dual chip—Eight hundred times the processing power, but not eight hundred times as fun. Maybe things were more fun even before I was using a computer—maybe I'd rather have the slide rule girls." Sexist cad... yes, I would agree with that. Evan ^{(talk|contribs)} 18:14, 23 June 2014 (UTC)

To refer to young women as girls was not considered derogatory in the 1940s. The young people doing the calculations were young women because the young men were in the Armed Forces. Since young women were available to do the calculation, they didn't need to assign the young men to non-combat roles at the Manhattan Project that could be done by young women. Robert McClenon (talk) 18:19, 23 June 2014 (UTC)

The young people doing the calculations were young women for the same reason they continued to be young women before and after the war: because women were considered well-suited to being calculators, and could be paid less for the same work. The same reason why there were so many women involved in early computing in general. 86.129.13.205 (talk) 20:09, 23 June 2014 (UTC)

As with the All-American Girls Professional Baseball League, for example. Even now, women like to call each other "girls", because "'women' are old". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:26, 23 June 2014 (UTC)

In what part of the world is the word girl derogatory? It's used all the time here in Ireland. I said good bye girls to my late-30s aged female colleagues (I'm a male in my 20s) when I was leaving work this afternoon, and received a good bye in return.--95.83.253.54 (talk) 19:41, 23 June 2014 (UTC)

My interpretation is that the "fun" and "girls" parts are just added to make the quote more entertaining, and what he's really talking about is that having an 800 times faster computer does not allow him to get 800 times as much work done, or get the same amount of work done in 1/800th the time. I've certainly noticed that despite supposedly much faster computers, I still have to wait just about as long as ever for each web page to load. No doubt this is because a "web page" back when I stated on the Internet was a Gopher ASCII text page, and now it's a full web page with a dozen animated ads. Although, surprisingly, even when I do reload a text only page, there's still a noticeable delay. By now I would expect it to update the page in literally the blink of an eye. StuRat (talk) 19:21, 23 June 2014 (UTC)

• To clarify my comment above, I don't think it's (necessarily) sexist to refer to young women as "girls". The term can be used in horrible and sexist ways. Consider when a 40 yr old woman scientist gives a public lecture, and afterword a male dean who missed the talks says to her "be a nice girl and get us a cup of coffee." -- but it can also be used in neutral or positive tones. But the simple use of the word "girl" isn't really the issue at hand.

I do think it's sexist for someone (presumed male) to imply that science is just so much more fun and entertaining when there's a bunch of young women around at the scientist's beck and call. That is, the implication that the speaker would rather have a room full of young women than a powerful computer seems sexist. Even if it is done in the spirit of joking or entertaining, it just feels like boy's club winking and nodding. And you know what? I'm sick of that in science. Some fields in science have lots of women represented, but some are still basically patriarchy. Computer science and physics seem to get the worst rap on that score. My last lab and current lab actually have a majority of women, and believe me when I say they all have stories about receiving sexist comments and discrimination in the scientific workplace. And this is not ancient history, see Women_in_science#Recent_controversies for some more documented examples. So, I'll withhold judgment until I know who said it or what's going on. And I even cut Feynman some slack for being the product of a different era (he does often speak about women in a cringe-inducing manner). But this is exactly the kind of thing that can keep young women out of science, so I will call out potential sexism when I see it. SemanticMantis (talk) 19:47, 23 June 2014 (UTC)

I think your way of going around things is counter productive. Yes the workplace needs to be policed for stop neanderthal behaviour. However what was stated there was a feeling showing a major problem and you are attacking the messenger. Workplaces are healthier and work better if they aren't too predominantly all one sex. Saying that the people in it should work just as well irrespective of facts is ignoring reality and it is only be acknowledging reality rather than ones wishes about how things aught to be that things are properly fixed Dmcq (talk) 10:34, 24 June 2014 (UTC)

Sorry, I have no idea what you're talking about. "Saying that the people in it [what it?] should work just as well irrespective of facts [what facts?] " --? I didn't say any people in any thing should work in any manner irrespective of any facts. I was merely trying to explain myself, since others seemed to think I was calling the quote sexist because of the word "girl", which was not the case. I absolutely think that a science desk is an appropriate place to talk about sexism and general discrimination/equality issues in science. My reality is that I've witnessed sexist comments from older men, directed at young women, in a science lab, under the pretext of joking. I agree with you that acknowledging this problem is a useful step in correcting it. Without context or provenance, this quote seemed that it could be offensive and sexist to women people. But the scientific question below is probably more interesting and a more fruitful use of our time. SemanticMantis (talk) 16:41, 24 June 2014 (UTC)

I googled this quote. The only hits are for web repositories of the old Usenet group alt.sex.stories. So I'm not sure this necessarily has anything to tell us about Feynmann (who's not responsible for the particular form of this anecdote, however sexist he may have been in his own time), or von Neumann, or anything else. Relatedly: why is 'coeds' interpreted to mean '(very) young women' in US slang, when it is the defining characteristic of coed establishments to be mixed-sex? I ask as a Brit, who only recently encountered this slang for the first time. AlexTiefling (talk) 10:40, 24 June 2014 (UTC)

Well, in the US, the expression "coed" originally referred to a young woman at a university that had recently become coeducational, then to an educated young woman in general. Robert McClenon (talk) 14:53, 24 June 2014 (UTC)

I think of it as a very dated term. A "coed", rightfully speaking, should only refer to women who have appeared in a place recently enough to stand out from the previous status quo. Still, so long as all-female dorms and all-female floors exist to protect women from what are seen as essentially "male" institutions, I suppose some case can be made for continuing with it. Wnt (talk) 23:59, 26 June 2014 (UTC)

Computing power follow-up

The underlying point may be that there are limits to the extent to which advances in computing technology result in substantial improvements in the quality of science. The equivalent of the law of diminishing returns in economics applies. In the 1950s and 1960s, it was commonly thought that weather prediction would become much more reliable by the use of supercomputers. In fact, the use of increasingly powerful computers resulted only in marginally better forecasts. In the 1980s, the quality of weather prediction actually did improve significantly, not because of more powerful computers, but because of the use of more data in computing, both historical weather data for comparison, and the use of weather data from more stations in a given area. Robert McClenon (talk) There are a few cases where the availability of computers actually has transformed a science. The use of computers in the 1960s and 1970s in chemistry made the numerical solution of orbital wave functions (which cannot be solved analytically) feasible, and so took orbital wave functions from abstract theory into being a tool for the analysis of chemical behavior. However, in many cases, such as weather forecasting, the law of diminishing returns applied to the benefit of supercomputing. Robert McClenon (talk) 23:52, 23 June 2014 (UTC)

I agree. I think if we ignore anything about coeds and girls in the quote, and focus on slide rules vs. CPUs, then you have the gist of it. There are some fields that have benefited from cheap and ubiquitous high-powered computation, but computational power alone is no guaranteed progress towards scientific breakthroughs. Processing power can help with e.g. certain areas of fluid dynamics, economics or population biology, but it gives no way out from the chaotic dynamics inherent in weather and other physical systems. It's a shame that an otherwise decent point might get mired in sexism. SemanticMantis (talk) 01:55, 24 June 2014 (UTC)

I think historically, nobody did serious calculations with slide rules. They were for rough estimates. If you needed accuracy you'd drag out the logarithm tables. My school library had a set of them (long obsolete by the time I got there) in something like ten printed volumes. WW2-era calculations were done on electromechanical Marchant Calculators and later on punch-card tabulation equipment. Surely You're Joking, Mr. Feynman's chapter about Los Alamos has some anecdotes about that. 173.228.123.145 (talk) 07:45, 24 June 2014 (UTC)

Agreed as to not doing serious calculations with slide rules, but using them for rough estimates, and then either bringing out the logarithm tables or using the Marchant machine. The logarithm table had been developed with long tedious pencil-and-paper calculation using a Taylor series (which is how logarithm calculation is done under the hood today on a PC or file server). As SemanticMantis says, only in a few areas is processing power alone enough to achieve a scientific breakthrough. Fluid dynamics and orbital mechanics are examples. In the case of weather, the law of diminishing returns applies in a non-economic sense, in which computational power is equivalent to labor. It was only later realized that data was equivalent to capital, and that any non-trivial increase in productivity required multiple factors of production. Robert McClenon (talk) 14:59, 24 June 2014 (UTC)

Slide rule seen here at amazon was a standard calculating tool until the advent of computer and electronic calculators. All it did was to perform multiplications. You of course could get logarithms and square roots. If you had a major project you had to write interim result because the additions had to be made by hand on a piece of paper. Only an engineer intimately familiar with the whole project could use such tools. The idea that you could delegate this work to a bunch of girls is bizarre. The author simply tried to be poetical or whatnot. If you look carefully at Apollo project engineers in documentaries you can see then handling those rulers sometimes, I believe, if my memory is not faulty. --AboutFace 22 (talk) 21:24, 24 June 2014 (UTC)

I think you're misunderstanding something about how algorithms work. From Surely You're Joking Mr. Feynman, which I cited near the top:

“ Everything we did, we tried to do as quickly as possible. In this particular case, we worked out all the numerical steps that the machines were supposed to do - multiply this, and then do this, and subtract that. Then we worked out the program, but we didn't have any machine to test it on. So we set up this room with girls in it. Each one had a Marchant. But she was the multiplier, and she was the adder, and this one cubed, and we had index cards, and all she did was cube this number and send it to the next one.

We went through our cycle this way until we got all the bugs out. Well, it turned out that the speed at which we were able to do it was a hell of a lot faster than the other way, where every single person did all the steps. We got speed with this system that was the predicted speed for the IBM machine. The only difference is that the IBM machines didn't get tired and could work three shifts. But the girls got tired after a while.

”

Now, he does mention they were using Marchant_Calculators. So both myself and the anonymous quote above were a bit mistaken about the slide rules. Slide rules would be almost as quick, but probably not precise and accurate enough, as someone pointed out above. But Feynman absolutely delegated these computations to a "room with girls in it", and ended up using many people as a computational system for running an algorithm. None of them had to have any full knowledge of what was being done, they only had to know how to perform simple computations on an input, and pass the output to the right person. Full text of that chapter (Los Alamos From Below) is available here [12] SemanticMantis (talk) 21:46, 24 June 2014 (UTC)

The slide rule bit looks like a confusion with Feynman's anecdote (in a different chapter) about how he, Fermi and von Neumann would check each other's work by working in parallel - Feynman on a mechanical calculator, Fermi on a slide rule, and von Neumann working in his head. The speed of the three methods was supposedly about equal. AlexTiefling (talk) 16:00, 25 June 2014 (UTC)

As someone who was (during my nocturnal exploration of the power of progressively more powerful collection of microprocessor-based computers, starting with my 4.77 MHz Z80A-based Timex/Sinclair TS1000) accused by my wife of being willing to commit adultery with these machines if they only possessed slots large enough, I got the comparison with a schoolhouse full of young ladies operating Marchand adding machines immediately. Taking the ladies themselves as symbolizing perhaps a byte-wide array of logical gates each - reduced to the role of feeding data into an arithmetic processor which worked by means of electrically-driven cogs instead of using their incomparably more powerful brains for analysis, my Sinclair computer had them beat on computational power, didn't generate NEARLY as much heat (each of the ladies could conservatively be counted on for 300 watts of waste thermal heat, or an IBM PC-XT power supply's worth) but just ONE of those byte-wide computational arrays would have really given my wife something to gripe about, given mutual interest, about two hours and a comfortable place to interact. :-) loupgarous (talk) 06:17, 26 June 2014 (UTC)

Are these the real power figures?

I always got the impression that old computers used to have much lower power requirement than today's machines, just not on the scale of computing abilities (i.e. they were 100s if not 1000s of times slower). The human figures, well, these we can check: 1800 Calories per day = 1,800,000 calories per 86,400 seconds (note case difference) = 21 calories per second = ~90 watts.

I guess the girls were not quite as hot as you thought. *SCNR* - ¡Ouch! (^{hurt me} / _{more pain}) 08:03, 27 June 2014 (UTC)

From Power_supply_unit_(computer)#Original_IBM_PC.2C_XT_and_AT_standard, "The first IBM PC power supply unit (PSU) supplied two main voltages: +5 V and +12 V. It supplied two other voltages, −5 V and −12 V, but with limited amounts of power. Most microchips of the time operated on 5 V power. Of the 63.5 watts these PSUs could deliver, most of it was on this +5 V rail." (emphasis not in original) - ¡Ouch! (^{hurt me} / _{more pain}) 08:08, 27 June 2014 (UTC)

Longitude and latitude

I saw this question on a game show the other day, and it had me confused. So, to clear up my confusion, I will just ask it here. What are the longitude and latitude coordinates for: (A) the North Pole; (B) the South Pole; and (C) the equator? Thanks. Joseph A. Spadaro (talk) 16:27, 23 June 2014 (UTC)

Dredging up some of my geographical knowledge, the North Pole would (I think) be 90° N, 0° E (or W—it doesn't really matter, but you do need to choose one for the sake of notation). The South Pole would be the same with "N" changed to "S". The equator is a circle of latitude (0°) rather than a point or a location, so strictly speaking it doesn't have a is a coordinate. Evan ^{(talk|contribs)} 16:32, 23 June 2014 (UTC)

The equator does have a latitude coordinate, 0, and its longitude coordinates go from 0 to 180E/180W. The North Pole and the South Pole each have a latitude coordinate, 90N or 90S, and a meaningless longitude coordinate. Robert McClenon (talk) 17:01, 23 June 2014 (UTC)

I would say the exact geographic poles have no longitude. Otherwise, it would be misleading to say you moved from 45°N, 45°E to 90°N, 0°E, as that implies that your longitude changed, when it did not. StuRat (talk) 22:32, 23 June 2014 (UTC)

Is that the reason why the poles are walled off in Microsoft Flight Simulator -- to prevent the app from crashing when the plane's longitude becomes undefined? 24.5.122.13 (talk) 00:24, 24 June 2014 (UTC)

I am not sure, but probably. A geographic pole is a mathematical singularity with respect to a lat-lon coordinate system. (Mathematical singularities are sometimes also referred to as poles, so a geographic pole really is a mathematical pole.) I know that some navigation systems and related systems (such as submarine tracking systems and military mapping) have to use special logic, such as a different coordinate system, in the vicinity of the geographic poles to avoid mathematical problems that could otherwise result in a divide-by-zero or similar problems. Robert McClenon (talk) 01:47, 24 June 2014 (UTC)

Pretty much every calculation needs a coordinate conversion from lat-long to XYZ. Depending on the accuracy you need, you can sometimes get away with a sphere, but some calculations need progressively finer approximations to the shape of our planet. A "fat" ellipsoid will usually work fine, but for some applications, even that is too coarse.

The spherical-to-XYZ conversion is quite easy; it is

Q = R cos(lat),   X = Q sin(long),   Y = Q cos(long),   Z = R sin(lat).

Qu Sin Long — does that sound Korean to you, too?

I think the Flight Sim issue is to keep user confusion at a minimum; at Tech Support, you get crazy requests like "My VCR goes forward when I press Rewind", but actually, the numbers were negative, and the user described rewinding from negative 0:30 to negative 0:50 as "going forward." Thus they changed the display from "-0:50" to "9:10". Sudden longidude jumps could cause similar cases of user panic. - ¡Ouch! (^{hurt me} / _{more pain}) 08:05, 24 June 2014 (UTC) "longidude" — really? - ¡Ouch! (^{hurt me} / _{more pain}) 08:08, 24 June 2014 (UTC)

In your example, where does the value of 9:10 come from (to represent negative 0:50)? Thanks. Joseph A. Spadaro (talk) 16:57, 24 June 2014 (UTC)

Ten hours plus negative 0:50. They actually emulate the old analog odometer (shown at Odometer#Trip meters). - ¡Ouch! (^{hurt me} / _{more pain}) 06:24, 25 June 2014 (UTC) You're welcome.

Thanks, all. Joseph A. Spadaro (talk) 16:52, 27 June 2014 (UTC)

relative velocity

If two wheels A and B are rotating on a fix position with speed 60km per hour and 70km per hour respectively. Then what is the relative speed of A w.r.t. B and of B w.r.t. A ? — Preceding unsigned comment added by 182.66.61.206 (talk) 16:53, 23 June 2014 (UTC)

If they're in fixed positions, the answer is 0. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:05, 23 June 2014 (UTC)

There seems to be missing info. That is a linear speed, not a rotational speed, but you could specify a linear speed at the outer edge (or any point other than the center), by taking the radius at that point into account. Now, as for the relative speeds, different parts of the wheels will move at different relative speeds to each other. If those speeds you gave are for the outer edges of the wheels, and that's what we are comparing to find the relative velocities, then, depending on how they are located, the relative velocity could be anywhere from A-B, to B-A, to A+B. So, anywhere from -10kph, or +10kph, to 130kph. StuRat (talk) 22:39, 23 June 2014 (UTC)

Rotation itself is not measured in "speed" (km/h) but in frequency! The angular velocities you gave dont referes to "the wheel" but to an point of the wheel out of its axis. The relative speed between to points on 2 wheels depend on the wheels axis orientation, the axis places, the wheels rotation and the rotational direction. This can get very easy and alike very difficult to calculate. In most cases there is not even one unique result because the relational speed changes - maybe even stops at some points to change direction. --Kharon (talk) 18:26, 27 June 2014 (UTC)

Analysis of conversion narratives?

I am wondering if people have written about or analyzed conversion narratives, especially Christian conversion narratives, as a study in the psychology of religion. Is it me, or are Christian conversion narratives similar in a way that the Christian converts would see themselves as having the worst life imaginable (unrepentent sinner, falling away from God, whatever) prior to conversion and then, once converted, they start seeing their lives positively? How would conversion narratives vary in different Christian traditions (Catholic, Protestant, Orthodox, and Christian minority groups)? 140.254.136.160 (talk) 19:26, 23 June 2014 (UTC)

Try Wikipedia:Reference desk/Humanities. Robert McClenon (talk) 23:35, 23 June 2014 (UTC)

This isn't necessarily the wrong reference desk if you're looking for a scientific analysis of religious experiences, though. I'm not familiar with the content, but noted psychologist William James wrote The Varieties of Religious Experience from a pretty scientific perspective.198.86.53.67 (talk) 14:39, 24 June 2014 (UTC)

James was as much a philosopher as a psychologist, though, so I think that book falls under Humanities. That said, there's been plenty of research into neurological aspects of religious experience, such as the (apparently erroneous) hubbub about a so-called "God spot" in the human brain. I'm unaware of specific scientific studies on the famous "come to Jesus" moments, though. Evan ^{(talk|contribs)} 14:48, 24 June 2014 (UTC)

I didn't mean that this was the "wrong" reference desk, but that the original poster was more likely to get an answer from the Humanities Desk regulars than from the Science Desk regulars. Also, psychology is a social science rather than a natural science, and so is sort of a hybrid discipline. Robert McClenon (talk) 16:54, 24 June 2014 (UTC)

The claim that psychology is a social science rather than (or even that it is simply more of a social science than) a natural one is not really reflective of the field as a modern discipline. Behaviorism gave way to more empirical and biological approaches quite some time ago. Even prior to this, many aspects of the study of the mind had nothing to do with social phenomenon at all. Psychology certainly retains some of its softer branches and approaches, but increasingly its methodology puts the brain and its physical mechanisms center stage and areas such cognition and perception, once regarded as inaccessible and composed of non-quantifiable phenomena are the subject of intense inquiry while the old guard approach of generating abstract models of the organization of the mind and mental phenomena based on behaviour alone is increasingly regarded as limited and problematic. Anyway, the issue is a bit of a red herring anyway, since the OP is really seeking information more likely to be formulated by historical or sociological researchers than psychologists, though clearly there is some overlap. All of that not withstanding, I think your original point that the question would probably receive better treatment at the humanities desk is on the mark. Snow talk 00:34, 26 June 2014 (UTC)