Wikipedia:Reference desk/Archives/Science/2010 March 26

= March 26 =

Biology (Incompatible bloods?)
a father has negative blood and a mother has positive blood, what is some problemsDeanna574839 (talk) 01:10, 26 March 2010 (UTC)


 * I assume we are talking about Rh factor ? If so, then the only potential problem is when the mother and baby don't match (which can happen if the parents don't match).  See Rh_blood_group_system. StuRat (talk) 01:13, 26 March 2010 (UTC)


 * It's not when the mother and baby don't match, it's when the mother is Rh negative, has been previously sensitized to the Rh antigen, and the baby is Rh positive. The reverse situation (mother Rh positive, baby Rh negative) is not a problem. Or, simplifying and applying it to the original question: when the mother is Rh positive, no problems are anticipated, regardless of the Rh status of the father or the baby. - Nunh-huh 01:41, 26 March 2010 (UTC)


 * That's why I said "potential" problem and directed them to the article for details. StuRat (talk) 01:46, 26 March 2010 (UTC)


 * Well, yes, that's my point, and why I felt compelled to clarify your answer. In the question asked, there are no "potential" problems. An answer that suggests that there are is potentially misinformative. - Nunh-huh 02:32, 26 March 2010 (UTC)


 * If a disease condition cannot be predicted with certainty then StuRat is right to characterise it as potential. There are a wide variety of potential causes of the hemolytic disease problem. The OP can refer to the article Rh blood group system which clarifies the concepts Rh positive and Rh negative, and links to the article about potential problems with newborn that are commonest when the mother has D negative blood. I changed the question title for easier reference. Cuddlyable3 (talk) 12:03, 26 March 2010 (UTC)


 * There's no uncertainty at all that Rh incompatibility does not result when the mother is Rh positive - which is the question asked. - Nunh-huh 14:31, 26 March 2010 (UTC)


 * Ok, I (and probably Cuddlyable3) didn't understood what you were trying to say, until just now. Thanks, for the clarification. StuRat (talk) 17:05, 26 March 2010 (UTC)


 * I agree that your title is better, but I also tried to keep the original title, in case it's used as a search term by the Original Poster to find their Q.StuRat (talk) 12:31, 26 March 2010 (UTC)

My wife is RH- and has to have the injection before giving birth and after, the reason given is as follows - the mothers immune system would atk the feotus - Thas what the doctors said to me and my wife when i asked why it is neededChromagnum (talk) 08:11, 30 March 2010 (UTC)

Cityscape and skyline
What is the difference between a cityscape and a skyline? --Extra999 (Contact me + contribs) 06:44, 26 March 2010 (UTC)
 * A cityscape is the profile of a city skyline, a skyline can be the view of any notable horizon, e.g. buildings, mountains or whatever. —Preceding unsigned comment added by 86.4.186.107 (talk) 07:02, 26 March 2010 (UTC)


 * See cityscape and skyline.--Shantavira|feed me 07:48, 26 March 2010 (UTC)


 * Don't confuse a city's skyline with a Nissan Skyline. ~ A H  1 (TCU) 00:17, 27 March 2010 (UTC)

G-23 paxilon hydrochlorate (PAX)
My inner geekdom asks: hypothetically if "paxilon" here refers to a synonym for the herbicide methazole (C9H6Cl2N2O3), is "PAX" a plausible chemical and what might be its formula based on the name "paxilon hydrochlorate"? How would "G-23" be a realistic part of its nomenclature?

If you wonder where this comes from, check out Serenity. --Kvasir (talk) 16:40, 26 March 2010 (UTC)


 * Do you think the novelist thought about it that deeply?
 * Remember the number 42
 * Douglas Adams was asked many times during his career why he chose the number 42. Many theories were proposed,[7] but he rejected them all. On November 3, 1993, he gave an answer[8] on alt.fan.douglas-adams:
 * “The answer to this is very simple. It was a joke. It had to be a number, an ordinary, smallish number, and I chose that one. Binary representations, base thirteen, Tibetan monks are all complete nonsense. I sat at my desk, stared into the garden and thought '42 will do.' I typed it out. End of story. --Aspro (talk) 18:16, 26 March 2010 (UTC)
 * Of course not, I just thought it would be interesting to "reverse-engineer" this chemical from the mere name, but first we need to know what might the formula. --Kvasir (talk) 18:37, 26 March 2010 (UTC)

Moon crashes into the Earth
The Moon currently orbits the Earth and so it doesn't crash into the Earth (at least, in our lifetime). For this thought experiment, assume that the Flying Spaghetti Monster suddenly sticks out his noodly appendage and brakes the moon to a halt (we'll use the Earth as our reference frame just for convenience - from the point of view of an observer on Earth, the Moon is now at "absolute rest"). Now, instead of an orbiting moon, we have a moon that is in free fall and on a collision course with the nearest large body (aka Earth). My question is, how long will it take for the moon to collide with the surface of the earth? Assume that the only bodies that have significant gravity are the moon and the earth, the gravitational constant G is 6.67 x 10&minus;11 kg&minus;1 m3 s&minus;2, the mass of the earth is 5.9742 x 1024 kg, the mass of the moon (maybe not important, but here just for reference) is 7.349 x 1022 kg, initial distance between earth and moon (center to center) is 384403000 m, and the radii of earth and moon are 6378100 and 1737400 m, respectively.

It looks to me as though solving the problem involves a differential equation, which I don't know how to use. So instead I approximated a solution using Excel. According to my estimate, it would take 4.85 days for the two objects to collide. Is this close to the correct answer? 66.178.138.144 (talk) 18:02, 26 March 2010 (UTC)


 * Also please assume that gravity is the only force (no friction/aerodynamic drag) and the rotation of the earth is insignificant for this problem. 66.178.138.144 (talk) 18:05, 26 March 2010 (UTC)


 * Well, even without full diff-eq (which I'm not an expert at; I'm more of a number theory guy), an iterative solution should get you fairly close. Just use Newton's law of universal gravitation with your initial conditions to find the instantaneous acceleration involved. Then assume that acceleration applies for, say, an hour, and use basic calc to find the distance traveled.. Then recalculate the acceleration for the reduced distance. Repeat until the distance from the center of the Earth to the center of the Moon is less than their combined radii. It will actually happen a little more quickly than that (since it spends most of each hour accelerating more rapidly than it did at the very beginning), but it should be close enough. &mdash;ShadowRanger (talk 18:09, 26 March 2010 (UTC)


 * The Moon was in free fall even before the noodly FSM meddled with it. Hopefully he/she/it will allow the "textbook" equation for vertical motion of a falling object ignoring air resistance to give an approximate answer. Taking the OPs figures:

 Distance to fall y = 384 403 000 - 6 378 100 - 1 737 400 = 375 287 500 m Free fall acceleration g = 9.81 m/s²

0.5 Then time to fall t = (2 y / g )

= 8747 s                   ~ 2 hours 26 min 
 * Cuddlyable3 (talk) 18:41, 26 March 2010 (UTC)


 * Sorry, but wrong. That 9.81 m/s2 equation is for objects of relatively negligible mass relatively close to sea level on Earth. You need to use Newton's law of universal gravitation to calculate the acceleration when dealing with two objects, both of non-trivial mass, at a significant distance. &mdash;ShadowRanger (talk 18:47, 26 March 2010 (UTC)
 * Also, while in normal gravitational calculations on Earth (where the object attracted to the Earth has trivial mass), the force exerted by the object on the Earth can be ignored. In this case, the mutual gravitational attraction between the Earth and the Moon would rapidly become non-trivial, so you'd need to keep track of the acceleration of the Earth as well, assuming you want a really precise answer. &mdash;ShadowRanger (talk 18:50, 26 March 2010 (UTC)


 * In other words, the gravitational attraction from the Earth is far less than 9.81 m/s^2 at the distance of the Moon (which would make it take longer) and the Earth falling toward the Moon must also be considered (which would make it shorter). I believe the former has more effect than the latter, so it ends up longer. StuRat (talk) 18:52, 26 March 2010 (UTC)
 * Nice summation, and I agree with your intuition. I do wish I'd done some diff-eq though. Now *I* want to know the precise answer! &mdash;ShadowRanger (talk 18:56, 26 March 2010 (UTC)
 * Mr. Scots-Irish Jewish atheist it is you who must show the superiority of your method while I am content to put my faith in the Holy IPU. Cuddlyable3 (talk) 19:03, 26 March 2010 (UTC)
 * I'm aware it's a weird ethnic background. My dad was Eastern European Ashkenazi, my mother was a mix of Irish and Scots-Irish who converted. I was raised Jewish, but only the cultural aspects took. That said, I'm fairly sure neither the Invisible Pink Unicorn nor the Flying Spaghetti Monster nor the Abrahamic God is likely to post on this reference desk and give us the answer. :-) &mdash;ShadowRanger (talk 19:10, 26 March 2010 (UTC)
 * My kids will be even more confusing if someone tries to categorize them, as I'm engaged to an ethnically Chinese woman, born in Indonesia, but raised in the States. They'll get to check *at least* half the boxes on the Census form! &mdash;ShadowRanger (talk 19:16, 26 March 2010 (UTC)


 * If we make a boundary for 9.8>g>0.163 m/s2, then one can verify at least that the time must be between 2.5 and 19 hours. I don't think it will take days when solving the differential equations (neglect air friction).--Email4mobile (talk) 20:44, 26 March 2010 (UTC)
 * Oops, that's my mistake, 9.8> g > 0.0266 m/s2 will lead to 6 > t > 0.1 days.--Email4mobile (talk) 21:16, 26 March 2010 (UTC)

Like all gravitational problems, your falling moon will obey Kepler's Laws so:
 * $$\text{Time} \approx {1 \over 4} 2\pi\sqrt{(\text{orbit distance})^3\over{G(M_{Earth} + M_{Moon})}}$$

Which gives 6.82 days. Dragons flight (talk) 22:50, 26 March 2010 (UTC)


 * Hi, OP here. Are you sure that this is the correct equation, Dragons flight? 6.82 days would be an average acceleration of 0.00221 m/s2, which is smaller than the initial acceleration of 0.00270 m/s2! I would expect acceleration to increase in magnitude as the moon and earth get closer together.


 * Thanks everyone for the answers you've given so far; they've been helpful. I was assuming that the mass of the moon was negligible (as implied by my original question) but I tried my Excel "iterative solution" again with the mass of the moon factored in and it didn't make a significant difference. This is understandable - the moon is two orders of magnitude less massive than the earth. If someone knows how to do the diff-eq, I would appreciate them chiming in. :) Oh yes, I found this: archived version of  which is currently down. They say it takes "about five days" so that tells me I'm in the right ballpark according to them. I'd still appreciate more confirmation. 66.178.138.206 (talk) 23:15, 26 March 2010 (UTC)


 * Dragons flight's formula is almost right. The correct one is
 * $$\text{Time} \approx \frac{2\pi}{4\sqrt2} \sqrt{(\text{orbit distance})^3\over{G(M_{Earth} + M_{Moon})}}$$
 * The extra square root of two that was missing changes the final answer to 4.82 days which is pretty close to the answer from the spread sheet. Dauto (talk) 02:05, 27 March 2010 (UTC)


 * What's a factor of 2 between friends. :-).  Dragons flight (talk) 04:47, 27 March 2010 (UTC)

The question is based on the moon suddenly accelerating towards the earth. To achieve this, the questioner suggested the Flying Spaghetti Monster has brought the moon to a sudden and complete stop. In fact, this is unnecessary because the moon is already accelerating towards the Earth. Whether the moon is travelling at its current speed, or has been brought to a stop by a Spaghetti Monster, is irrelevant because the acceleration towards the Earth will be the same in both cases.

The moon orbits the Earth about once every 28 days. Falling all the way from its current orbit to the level of the center of the Earth is nearly the same as completing one quarter of an orbit. One quarter of 28 days is 7 days, but of course that is based on the acceleration due to Earth's gravity at the radius of the moon's orbit. If the moon were falling directly towards the Earth it would progressively be subjected to increasing gravitational attraction and that would hasten the fall. Is this progressive increase in gravitational attraction sufficient to explain the difference between about 7 days and 4.82 days? Dolphin51 (talk) 05:17, 27 March 2010 (UTC)


 * The moon's orbital period is about 27.3 days and a quarter of that is about 6.82 which is what Dragons flight calculated above, but that misses a factor of square root of two. Dauto (talk) 14:52, 27 March 2010 (UTC)
 * I've read through the answers to the OP's question and I can't tell which estimate or range of estimates is most likely correct. Could someone sum up? 63.17.63.71 (talk) 00:13, 28 March 2010 (UTC)


 * Ok here are the highlights
 * The OP uses a numerical solution and finds T = 4.85 days which is essentially correct but he want an analytical solution
 * Cuddlyable3 uses a constant acceleration g = 9.8 but that will only give a lower bound since Earth's gravity decreases with distance: T > 2 hours and 26 min
 * Email4mobile uses the bounds 9.8> g > 0.0266 m/s2 and finds 6 > T > 0.1 days
 * Dragons flight points out that this problem can be solved using Kepler's laws and solutions but makes a couple of mistakes in the application of the formula. He uses the wrong value for the semi-major axis which actually is half of the moon-earth's distance and devides the result by four instead of two which is the correct way to do it.
 * Finally I point out those mistakes and find then result T = 4.83 days which is pretty close to the OP's original value.
 * Dauto (talk) 03:39, 28 March 2010 (UTC)

TLDNR, but have you taken into account which side of the Earth the moon is stopped on? Ie, is the moon in front of Earth, or behind it? Aaadddaaammm (talk) 19:19, 28 March 2010 (UTC)


 * That makes no difference since we assume the moon's stopped with respect to the earth. It makes some difference if the moon stops at apogee or perigee but we've been neglecting that. Dauto (talk) 19:53, 28 March 2010 (UTC)


 * If TLDNR means Too Long Did Not Read, that is an impolite comment. Cuddlyable3 (talk) 14:14, 29 March 2010 (UTC)

black and white
Has anyone produced a black and white only digital slr? The sensors aren't wavelength-sensitive, so in order for them to differentiate wavelength, they need a filter in front of them of the right colour. However, if you remove the filters, you could squeeze in more pixels per square inch of the sensor, but they'd only sense light and dark. I would imageine it would have a highly specialist use in high iso, high shutter speed, low light photography. But has anyone built one? —Preceding unsigned comment added by 81.147.56.162 (talk) 18:23, 26 March 2010 (UTC)


 * The digital output of the camera doesn't "know" about the colour filters so the full pixel resolution is there already (before jpeg compression). Removing the filters would gain some sensitivity. Since they are added last to the CCD chip it might be possible to bleach them out. Cuddlyable3 (talk) 18:49, 26 March 2010 (UTC)


 * If nobody has done this, it sounds like a good idea to me. It would be good for pics of color subjects where black and white is used for artistic reasons, and also for subjects which lack color. StuRat (talk) 19:01, 26 March 2010 (UTC)
 * For subjects that lack colour the individual pixels are immediately available in the BMP image format and only need relative weighting of Red/Green/Blue. Cuddlyable3 (talk) 19:39, 26 March 2010 (UTC)


 * It's not a new idea (not necessarily in a DSLR; possibly a digital back for medium or large format cameras, or a rangefinder). I don't think any such camera has gone into production, though, presumably because of the relatively small market.  -- Coneslayer (talk) 19:52, 26 March 2010 (UTC)


 * I know that some microscope cameras are monochrome only. Over the past couple of months I have been using a Leica fluorescence stereomicroscope as part of a research project (if you are particularly interested I was using this one ) in conjunction with a digital camera (this one ). It doesn't need to be full colour since it is being used for fluorescence microscopy - so the only colour it will see is the fluorescence emission wavelength coming through the emission filter of the selected filter set. If I needed multiple fluoresence channels I took individual images with different filter sets, false coloured them and overlayed them in photoshop. Sensitivity is very important here, which is another reason to use monochrome. It's also interesting to note that the camera was only 2 megapixels, since minimising noise is far more important in this application than maximising resoultion (If you need to enlarge something you use a higher magnification lens, whereas if there is too much noise to precisely interpret/measure fine details in the image you're stuck). Equisetum (talk) 19:53, 26 March 2010 (UTC)
 * Sorry, I should really take more time to read the question - I missed the "SLR" bit Equisetum (talk) 21:05, 26 March 2010 (UTC)


 * Yes. Several models in the Kodak/Nikon Pro DCS line were available in three chip styles, Color, Infra-Red, and Black And White. I see that it's not mentioned in our article, but see here.
 * I'd be surprised if there weren't more modern pro cameras offered with similar options. APL (talk) 21:25, 26 March 2010 (UTC)


 * All astronomical CCD's are monochrome (see http://en.wikipedia.org/wiki/Charge-coupled_device#Usage_in_astronomy) in the sense that they don't have any filters. However, to collect any useful data, 1 filter, allowing in a certain range of wavelengths, must be put in front of the CCD.  —Preceding unsigned comment added by 216.16.224.186 (talk) 21:42, 26 March 2010 (UTC)


 * The deal is that a color digital camera has groups of (typically) four sensors grouped into a single "pixel" - one red, two green and one blue. But a slightly different part of the image lands on the red, green and blue sensors.  Hence, if you can get the "RAW" image (not JPEG or whatever) and if you know the physical layout of those four sensors, then with the right software you can get a good monochrome image at somewhat higher resolution than you'd get a color image from the exact same camera.  Since monochrome digital cameras are not in high demand, they'd be costly specialist items.  So you'd be better off using a color camera that saves "RAW" format images - and use some really good image processing software to make your final monochrome image. SteveBaker (talk) 23:06, 26 March 2010 (UTC)
 * From some more searching, it looks like the Kodak DCS cameras mentioned above may have been some of the last SLR cameras to offer monochrome chips as a standard option. (In certain forums they seem to be fondly remembered for this reason.) It looks like a monochrome conversion may be possible. (ie: They remove the colored filters from the chips.) Check it out.
 * Whatever they were in the 90s, now it looks like Steve is right : They're specialty items. APL (talk) 03:06, 27 March 2010 (UTC)

Ethanol
Within the context of talking about food safety, would it be correct to call ethyl alcohol a "toxin"? Our article does not say so, and neither do the other articles I've looked at it, but it would seem to (loosely) meet the definition. Created by a living thing, harmful if swallowed, etc. Our articles treat it within the context of it being a "drug", which it certainly also is, but I wonder if the term "toxin" would also make sense. Matt Deres (talk) 18:37, 26 March 2010 (UTC)


 * It has a Median lethal dose (LD50) so yes, I suppose it is very much a toxin that is dependant on the dose.--Aspro (talk) 18:45, 26 March 2010 (UTC)


 * More importantly, it has an LD50 that can be achieved without exceeding the ability of the human in question to consume it. There are toxins with theoretical LD50s that, practically speaking, are never hit, because they must be consumed and the amount required to kill you is so great that it can't all fit into a normal human before the excretion processes end up removing it. &mdash;ShadowRanger (talk 18:55, 26 March 2010 (UTC)


 * But there must be all sorts of things that we could use to kill ourselves by eating too much, does that make them all toxins ? StuRat (talk) 18:57, 26 March 2010 (UTC)


 * Yeah, I'm not real sure on that definition. Water can kill you by drinking too much of it (no need to drown), though usually only if you are drinking truly absurd amounts and not peeing or sweating out an appreciable amount, and/or you keep it up long enough that you manage to disrupt the electrolyte balance in your body. That said, alcohol is clearly a toxin; it can kill you by the direct metabolic effects of the alcohol, not just by displacing or disrupting the balance of various chemicals in your body. &mdash;ShadowRanger (talk 19:02, 26 March 2010 (UTC)


 * Perhaps the word 'acute' should have gone before 'dose' and 'low' before 'median'. And of course, semantics  can make these things confusing. This may account for the habit of clinicians to say 'poisoning' for when it is life threatening.--Aspro (talk) 19:31, 26 March 2010 (UTC)

No, ethanol is not a toxin. Toxins and poisons are two different things. Ethanol can be a poison in some doses but is never a toxin. alteripse (talk) 19:43, 26 March 2010 (UTC)
 * Can you explain why? Our article says that "a toxin is a poisonous substance produced by living cells or organisms". Ethanol can be produced by fermentation with yeast. This would seem to fit that definition - why doesn't it? 94.168.184.16 (talk) 20:06, 26 March 2010 (UTC)


 * I just wrote you a long answer that was completely lost when Stu answered the next question. Here are 6 more definitions of toxin: . If you define toxin so broadly that it refers to any substance produced by an organism that can cause harm, then you must consider water, oxygen, carbon dioxide, chalk, and glucose to be toxins because they are all substances produced by organisms that can cause harm in sufficient quantities, rendering that usage pretty meaningless. alteripse (talk) 20:26, 26 March 2010 (UTC)


 * Yes, you've discovered my master plan to train everyone to be concise by destroying any responses which fail the test. :-) StuRat (talk) 03:29, 27 March 2010 (UTC)


 * Where did it disappear to? When you get an Edit_conflict, just save your text (e.g., to the clipboard), cancel out, then try again.--Aspro (talk) 21:16, 26 March 2010 (UTC)


 * Yea, with any modern web-browser you should be able to simply hit the [BACK] button and retrieve what you have written. Admittedly, this isn't immediately obvious. APL (talk) 21:27, 26 March 2010 (UTC)


 * “rendering that usage pretty meaningless”
 * To whom? Without identifying  a cohort that statement may apply to, don't you think that statement  is,  err . . . pretty meaningless. Are not clinicians in The Royal Navy, oil recovery industries etc. familiar with Oxygen toxicity?. Maybe I should have said "And of course, some people use semantics to make these things confusing"--Aspro (talk) 23:48, 26 March 2010 (UTC)
 * If you wish to use terms imprecisely, go ahead, but I cannot think of any scientific fact that would justify putting ethanol in different "toxin" category than other simple substances produced as part of normal metabolism by many organisms. I think you are confusing a cultural classification with a scientific one (i.e. "clean" and "unclean" vs healthy or harmful)--- and yes I acknowledge that all semantic distinctions can be considered "cultural". alteripse (talk) 11:23, 27 March 2010 (UTC)
 * Ethanol is considered toxic because even consuming it in small amounts kills some brain cells, starts some cirrhosis, etc. Other substances, like water or glucose, are necessary for life and are not toxic in normal amounts.--Cheminterest (talk) 20:59, 26 March 2010 (UTC)
 * Nonsense. alteripse (talk) 11:23, 27 March 2010 (UTC)
 * There's a lack of evidence that alcohol kills brain cells. Vimescarrot (talk) 21:42, 26 March 2010 (UTC)


 * Alteripse has a good point when he linked to those other definitions of toxin; the term seems to be commonly applied only to proteins, in which case ethanol is definitely not a toxin. But again, it's largely a matter of semantics.  The ill effects of alcohol are widely studied and well known, so there's no real need to group it into a vague category like "toxin" that can have multiple meanings and be applied to substances with widely varying mechanisms and magnitudes of harm. Buddy431 (talk) 03:52, 27 March 2010 (UTC)


 * Abstract for Ethanol Toxicity Paper Ethanol exposure during development is teratogenic. The central nervous system (CNS) is particularly susceptible to ethanol toxicity. In fact, heavy gestational ethanol consumption is one of the leading known causes of mental retardation in the Western world. Ethanol exposure disrupts the proliferation of glia and neuronal precursors in the developing CNS. Depending upon cell population and blood ethanol concentration, ethanol can either inhibit or stimulate cell proliferation. Two features of cell proliferation that are affected by ethanol exposure are the growth fraction (the proportion of cells that is actively cycling) and the cell cycle kinetics, particularly in the length of the G1 phase of the cell cycle. Cell proliferation in the developing CNS reflects the action of positive (mitogenic growth factors) and negative (anti-proliferative factors) regulators. Increasing evidence shows that ethanol interferes with the action of growth factors. In vitro systems are a good model to investigate ethanol neurotoxicity, since the effects of ethanol on cultured cells parallel the effects of ethanol in the developing CNS. The inhibitory effects of ethanol on cell proliferation may result from interference with mitogenic growth factors (e.g., bFGF, EGF, PDGF, IGF-I). Conversely, the stimulatory effects of ethanol may result from the interference with growth inhibiting factors (e.g., TGFβ1). Interestingly, both in vivo and in vitro studies show that proliferating neural cells display differential sensitivity to ethanol. This differential sensitivity correlates with their response to mitogenic growth factors; that is, cells that are actively regulated by mitogenic growth factors are much more susceptible to ethanol than cells that are less or unresponsive to such factors. Ethanol interference with growth factor action could occur at three levels: ligand production, receptor expression, and/or signal transduction. Thus, ethanol-induced alterations in the developing CNS that characterize fetal alcohol syndrome apparently result from alterations in the regulatory action of growth factors.--Cheminterest (talk) 20:32, 29 March 2010 (UTC)

Rusted hammer
Someone borrowed my hammer and now the head is all rusted. It's got a fiberglass handle (no wood) so I was wondering if there's anything I can do (soak it in something, perhaps) that will de-rust it?  DRosenbach  ( Talk 20:11, 26 March 2010 (UTC)


 * WD40 and 0000 steel wool, or superfine wet-and-dry paper. DuncanHill (talk) 20:17, 26 March 2010 (UTC)


 * If it's a Craftsman (Sears) hammer, you can return it for a replacement, they are quite generous with their terms. Otherwise, I'd just sand off the rusted spots.  But beware if the head is now loose in the jacket, as it could fly out during use.  And you could always tell whoever borrowed it that they owe you a new hammer; I would. StuRat (talk) 20:21, 26 March 2010 (UTC)


 * There are chemicals used to remove rust, but they might cost as much as a new hammer, so that's why just sanding it off might be best. And be sure to keep the metal portions of this hammer oiled from now on, as obviously it has a tendency to rust. StuRat (talk) 20:23, 26 March 2010 (UTC)


 * I would second the suggestion for WD40 and steel wool. You can also paint it with a rust converter, which will turn it black, but protect it from future rust (it converts iron oxide to iron tannate). Ariel. (talk) 20:33, 26 March 2010 (UTC)

That will teach you to lend your tools to somebody else! Three rules for tools:

--Aspro (talk) 20:47, 26 March 2010 (UTC)
 * 1) Buy the best tools you can afford.
 * 2) Learn to use them safely and thoroughly.
 * 3) Never lend them out for any reason.


 * I'd have to disagree with 1 and 3. Number 1 because there are times when you only need a tool for a single use, and buying the premium model would be a waste, and number 3 because that will result in your friends not lending you any tools either.  If you and a buddy each lend the other tools and treat them with respect, you can double the number of tools each of you have at your disposal. StuRat (talk) 21:00, 26 March 2010 (UTC)
 * Rule 3 depends on the tool - you may borrow my pots and pans as much as you like but you may NOT, not ever, borrow my shiny new Santoku. Equisetum (talk) 21:11, 26 March 2010 (UTC)
 * Wow! OK, I am envious. I'm left handed and thus find their sharpened on the wrong side, can they by ground the other way?--Aspro (talk) 21:38, 26 March 2010 (UTC)
 * Do you mean THEY'RE sharpened? Cuddlyable3 (talk) 21:54, 26 March 2010 (UTC)


 * I'm left handed too, and my santoku is actually sharpened on both sides, and isn't Japanese, which I guess means it isn't a proper santoku. If you're interested the knife is and it only costs $20, I have several of that series of knives, recommended by my uncle who takes his cooking quite seriously. Neither of us has any idea how Kuhn Rikon makes such good knives so cheaply - my only concern is that at that price I don't know how long they'll last, but for $20 it's worth taking a chance. The reason I won't lend it is mainly that it's a very thin blade and if you tried to cut inappropriate things with it (like bones) it would get damaged. Equisetum (talk) 22:39, 26 March 2010 (UTC)

A dip in hydrochloric (muriatic) acid to dissolve the iron III oxide followed by a dip in phosphoric acid may remove and prevent rust. --Cheminterest (talk) 20:55, 26 March 2010 (UTC)
 * If you are exceptionally proficient with a tool, even if that proficiency is largely a self-held opinion, you would not want to loan such tools to anyone. The other person will always be using that tool in a less desirable way. And most tools are not indestructible. Bus stop (talk) 21:48, 26 March 2010 (UTC)


 * For those that now find themselves in the mood for some real hard Engineering porn, here is the Snap on online catalogue - enjoy!--Aspro (talk) 22:31, 26 March 2010 (UTC)


 * Wow, 751 different kinds of screwdrivers — this is great. Thanks. Bus stop (talk) 22:39, 26 March 2010 (UTC)


 * It's worth periodically squirting a little WD40 onto a shop cloth and wiping down all of the metal parts of your tools once in a while - especially those used to cut wood such as saws and chisels. That thin film of water-displacing oil keeps them shiney for months.  I usually use a Dremel with a wire-brush head for removing superficial rust from old car parts and such like...but once something has gotten rusty, any surface coating it may once have had is gone and it'll rust again, soon after you've cleaned it - so using some kind of water-repelling oil on the surface is a good idea.  (Bonus Fun fact: WD-40 is so called because it was Norm Larsens 40th attempt at creating a Water Displacing oil!  You've gotta admire Norm's determination - even if you're less than impressed by his product naming skills!) SteveBaker (talk) 22:53, 26 March 2010 (UTC)


 * For tools I don't like much, is WD39 an acceptable alternative?Edison (talk) 03:55, 27 March 2010 (UTC)
 * Molasses - I remember reading more than once that you can put rusty things in them and after some days (as far as I recall) they come out shiny new. 78.149.198.14 (talk) 01:09, 27 March 2010 (UTC)
 * Are you sure you weren't thinking of Coca Cola? Its phosphoric acid content makes it a good mild rust remover.  (And, in fact, a demonstration of its rust-removal properties is often used as an object lesson in how bad the stuff is for your teeth...) —Steve Summit (talk) 17:25, 27 March 2010 (UTC)
 * No. The molasses article confirms what I wrote. Although I've heard that Coca Cola is used by people to clean car chrome. 89.243.43.75 (talk) 19:06, 27 March 2010 (UTC)
 * There's the electrolytic technique (I don't remember where I found this link but I bet it was from the ref desk). The molasses fact is excellent, I wonder if there's a way to speed the reaction up though. 213.122.27.130 (talk) 19:14, 28 March 2010 (UTC)
 * Molasses may prevent corrosion by blocking off the supply of free oxygen needed to corrode the iron. Also, if you put the tool as the cathode in an electrolytic cell containing copper sulfate or silver nitrate and use a copper or silver anode, respectively, you may copper or silver-plate your tool. Copper and silver will get tarnished eventually, though; then just dip them in hydrochloric acid. --Cheminterest (talk) 20:24, 29 March 2010 (UTC)
 * The molasses article says it works by chelation. 84.13.173.45 (talk) 00:23, 30 March 2010 (UTC)

Pyrophoric qualities of Ni-MH cells
What substances would spontaneously ignite in a nickel-metal hydride cell? I took one apart, and some particles from one electrode contacted particles from another electrode. After a couple of minutes, both the electrolyte paper and the cathode material were up in flames. All of the black corrosion on the cathode was burnt away, and the paper was charred. I quenched the fire by putting a heavy piece of metal on top of the materials. It immediately extinguished it. There also seems to be a strong oxidizer in the anode, because it produced large quantities of chlorine gas when reacted with hydrochloric acid. --Cheminterest (talk) 20:53, 26 March 2010 (UTC)

Diet defined by required and forbidden foods
I have found a table of foods which distinguish carnivore from vegan diets and Kosher from Hindu diets. Is there a list of required or forbidden foods that can be added to the table to distinguish Muslim (or Islamic) diets and Christian diets from the rest? 71.100.5.192 (talk) 21:46, 26 March 2010 (UTC)
 * I think Halal refers to a diet in keeping with Islam. Bus stop (talk) 22:02, 26 March 2010 (UTC)
 * I don't think there is a "Christian diet" for mainstream Christian churches. At some time in the early first millennium what was to become the orthodox church decided to interpret Matthew 15:11 as abolishing Jewish food laws and allow Christians to eat everything, even Big Macs. But see Pentabarf. --Stephan Schulz (talk) 22:18, 26 March 2010 (UTC)
 * The LDS Church has the Word of Wisdom, though no foods are specifically forbidden in it (some other things are, though). ··· 日本穣 ? · 投稿  · Talk to Nihonjoe 22:29, 26 March 2010 (UTC)
 * What comes to mind are Friday Fast and Lent in food-related practices in Christianity, other than that there is no specific blanket forbidden food. Well except for cannibalism of course. --Kvasir (talk) 22:35, 26 March 2010 (UTC)
 * Taking that last point seriously, I don't think Christianity explicitly forbids cannibalism in all circumstances (though obviously it forbids most actions that would enable cannnibalism, such as murder). I recall reading that after the events of the Andes flight disaster, in which some survivors ate flesh from the frozen bodies of those killed in the crash in order to last out until rescue, the then Pope stated that they had acted correctly. If this was true and not misreporting, it might be added to the article. 87.81.230.195 (talk) 07:22, 27 March 2010 (UTC)
 * That's pretty funny! Matthew 15:11 says: "Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man.".  So an off-hand comment that's clearly intended to mean that you shouldn't talk nonsense is taken to overturn an entire raft of detailed rules about diet?!  It's just as well nobody actually reads the Bible isn't it?  Anyway - there is at least one dietary law for many christians - where does the Catholic "Fish on Friday" rule come from?  SteveBaker (talk) 22:42, 26 March 2010 (UTC)
 * That's a very interesting point, Steve (if I may call you by your first name). Hospital dietitians of today normally recommend a 30% fat, 60% carbohydrate and 10% protein diet with exceptions made for particular aliments on doctors orders. I found a table more or less for meals based on various combinations of foods but I do not know where in the Wikipedia to find or simulate this. 71.100.14.194 (talk) 23:16, 26 March 2010 (UTC)


 * Not all catholics follow that rule. Many do it  only  on Good Friday. Dauto (talk) 22:54, 26 March 2010 (UTC)


 * Re Matthew: Well, I suspect that the conflict between Christianity as a Jewish sect, with all the inconveniences of food restrictions and Sabbath and Circumcision, and Paul's more radical "it's a new religion. Eat pork and keep your bits" had more to do it than the actual (pre-)text. If you are looking for a justification for anything in the bible, you're likely to find a suitable passage. And Paul won...  --Stephan Schulz (talk) 23:31, 26 March 2010 (UTC)
 * I thought the no-meat-on-Friday thing was obsolete? I thought it was now acceptable for a catholic to substitute some other penance? Even a penance that was not food-related. APL (talk) 02:51, 27 March 2010 (UTC)
 * It was also circumvented by theologically defining beavers and other aquatic animals as fish, I seem to remember. I wonder if Christians thought their God would be hoodwinked or favourably impressed by such manouevring? 87.81.230.195 (talk) 07:22, 27 March 2010 (UTC)
 * Jews certainly think so. See Eruv. --Tango (talk) 10:43, 27 March 2010 (UTC)
 * In southern Germany there is a kind of ravioli called Maultaschen. The local rumor is that Catholics can eat them on Fridays, since god won't see the meat inside the pasta ;-). More seriously, this kind of dissimulation makes sense if the purpose of many religious rules is understood to not be in the commandment itself, but rather in the function of setting followers of a religion apart from others. --Stephan Schulz (talk) 14:43, 30 March 2010 (UTC)
 * Shouldn't this discussion be moved to the humanities reference desk? --The High Fin Sperm Whale 23:17, 26 March 2010 (UTC)
 * I suppose it all depends upon whether the diet plans are based on religious belief or have a health or scientific basis. For instance, not eating pork may have a religious basis but prior to that the basis appears to be health. 71.100.14.194 (talk) 23:34, 26 March 2010 (UTC)


 * That table probably shouldn't be there - it's redundant to the one directly above, with the only difference being that it is much less attractive.  Intelligent  sium  23:36, 26 March 2010 (UTC)


 * The new Wikipedia is about being attractive? What ever happened to the idea of presenting content in a usable and meaningful way. You can always add color and take care of the attractive end but I find it completely atypical of a lack of anything better to do than for administrator to remove content for such a stupid rational. 71.100.5.167 (talk) 00:52, 27 March 2010 (UTC)


 * The content was largely already there, you were simply duplicating it and in a non encyclopaedic manner to boot (wikipedia is not an instruction manual nor do we refer to readers in the first person). This is neither useful, nor meaningful to most readers who are likely to simply wonder why wikipedia has two tables that basically say the same thing except with the axis reversed perhaps wondering if wikipedia editors think they are so stupid they are incapable of using a table if the axis aren't the way they want them (fortunately most editors think more highly of our readers). And given your history, I strongly suggest you do not edit war further over this Nil Einne (talk) 10:06, 27 March 2010 (UTC)

I don't know whether any of you were raised Christian but these are some pathetic explanations of Christian doctrine related to diet. The new covenant between God and man in Christ frees people from old Jewish law, including circumcision and dietary restrictions. The Reformation was a "reboot" in a sense, shedding a thousand years of accreted non-scriptural Catholic customs and restrictions that most people could not distinguish from Christ's primary teachings. The Protestants explicitly disavowed this type of "rule-based salvation" since a person cannot "earn" salvation by his own power and actions and is wholly dependent on God's grace. In other words, there are no Christian dietary laws. The Catholic custom of avoiding meat on Fridays was a custom that arose to honor Christ's carnal sacrifice on a Friday but has never had the strength of law. I have no idea what Mormon teachings are because Mormonism appears to be about as closely related to Christianity as Christianity was to Judaism around 200 AD. Now if there is anyone left unoffended, let me know and I will try to include you too. alteripse (talk) 11:18, 27 March 2010 (UTC)
 * There's also a specific repudiation of dietary law in Acts 10. Now, it's been pointed out to me that, in this case, food is almost certainly a metaphor for humanity (i.e. Peter is being informed that Cornelius is not unclean).  But Christians are, as a whole, happy to also accept the surface meaning, i.e., they get to eat bacon now. Paul Stansifer 13:19, 27 March 2010 (UTC)
 * Unless I missed it, no one seems to have mentioned blood, and food offered to idols, which are forbidden to Christians in Acts 15, verses 19-20. The only major grouping I know of that pays attention to this is the Jehovah's Witnesses. --Trovatore (talk) 03:53, 28 March 2010 (UTC)
 * your extra comma changes your meaning. The significance was not the food, it was participating, or even appearing to condone, idol worship that was the prohibition. This is not really a dietary prohibition but a co-worshipping prohibition. And I think the blood prohibition for the Jehovah's witnesses is from the Pentateuch, not Acts, but i am not familiar enough with that sect to know the scriptural justification. alteripse (talk) 04:32, 28 March 2010 (UTC)
 * Could be. --Trovatore (talk) 06:03, 28 March 2010 (UTC)
 * Well, in the NIV, it clearly seem to be independent commandments. The same seems to be true (if in archaic grammar) for Luther's translation and in modern German translations. Even the KJV seems to list these as independent. --Stephan Schulz (talk) 11:56, 28 March 2010 (UTC)
 * Looks like you are corrrect about consuming strangled animals and blood being a separate prohibition. Never seemed to catch on, though. alteripse (talk) 14:00, 28 March 2010 (UTC)
 * Well, it's only James' opinion, after all. --Stephan Schulz (talk) 18:29, 28 March 2010 (UTC)
 * Alteripse, I'm pretty sure you're right. See 1 Corinthians 8, where Paul argues that idols being powerless, the only reason to be concerned about eating food sacrificed to them is whether people will take that as an endorsement of the idols.  Paul Stansifer 18:38, 28 March 2010 (UTC)

Chile
I heard that in plate tectonics, Chile is being slowly pulled away and separated from South America and will one day move away as an island (can't find this on wikipedia)- is this true? Thanks, --AlexSuricata (talk) 23:33, 26 March 2010 (UTC)


 * No. The Nazca Plate is being subducted underneath the South American Plate. Chile is part of the South American Plate. As the Nazca Plate is forced under the South American Plate, it causes the South American Plate to kink, forming the Andes. --The High Fin Sperm Whale 23:37, 26 March 2010 (UTC)


 * (ec)You're probably thinking of California. From what I can see on the article on the nearby Nazca Plate, the Nazca Plate is perpetually moving towards and underneath the South America Plate. That wouldn't cause Chile to split, just to become ever more mountainous. &mdash;ShadowRanger (talk 23:39, 26 March 2010 (UTC)


 * Yup. As the plate moving in from the west gets pushed underneath South America, it melts and rises upwards to form the Andes. That's what I learned in high school geography anyway. And yes of course it's not quite that simple, but I think it's a fair approximate. Vranak (talk) 16:12, 27 March 2010 (UTC)


 * You're right Vranak, it is a bit more complex than that. The subducting plate itself doesn't melt, water from the sediments carried down with it are driven off, hydrating the asthenosphere of the over-riding South American Plate, thus lowering its melting point, causing large-scale partial melting. The magma rises up causing chains of volcanoes. This doesn't explain the origin of the Andes on its own, as much of the uplift is orogenic even though there is no continent-continent collision involved. There is, as yet, no generally accepted mechanism for the shortening along the andean margin, although relatively high convergence rates or high levels of coupling across the plate interface are amongst those suggested. Mikenorton (talk) 16:45, 27 March 2010 (UTC)