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February 17

Plant from Bangladesh

Which plant is farmed here? I've never seen such fruits.--Sascha GPD (talk) 13:45, 17 February 2017 (UTC)[reply]

Hard to tell. The fruit resembles durian or maybe jackfruit or maybe breadfruit. --Jayron 32 14:22, 17 February 2017 (UTC)[reply]

Amongst other things, the leaves look wrong for all 3 of these to me. Nil Einne (talk) 15:01, 17 February 2017 (UTC)[reply]

Doing more google searches, other spiky green fruits include guyabano, or some species of cucumber, such as a luffa or Marah (plant) (aka manroot). --Jayron 32 16:37, 17 February 2017 (UTC)[reply]

I'll admit the first thing I did was take a quick look at the breadfruit article... then I realized this would be hard. I suck at botany, but my notion is that the first thing you do is fire up the glossary of leaf morphology and open the image to full resolution. At center-right far-top there's a little clearing and you can see the leaf beneath it, and various others, have branching leaf veins and jagged edges, with the veins apparently running to the narrowest parts of the edges. So I would say these are simple leaves (our redirect just takes you to leaf). The margin I would call "dentate" rather than "serrated" because the "teeth" seem symmetrical, and not "crenate" because they seem roughly zigzag. I think the shape of the leaf is "heart-shaped" = "cordate" - not to be confused with a chordate! In places the vein branching matches our figure for "dichomatous", in others "palmate" - I'll let someone else take a bite at that apple. And while the perspective confuses me a bit, I think I can see there are long stems supported on a framework that have leaves branching "alternately" in each direction, toward and away from us. So I am going to suggest that additional searches include dentate cordate alternate ... and I'll hope for a miracle. ;) Wnt (talk) 19:35, 17 February 2017 (UTC)[reply]

I should mention I did have a look at various other Artocarpus, none of them seem to have similar leaves. So perhaps either a speciesly less commonly cultivated or somethign else. Nil Einne (talk) 03:24, 18 February 2017 (UTC)[reply]

My guess is some member of the family Cucurbitaceae, superficially it resembles Echinocystis lobata but it seems that species is not cultivated. Most likely it is of the genus Cucumis (same as cucumbers) Cucumis zeyheri has similar morphology but appears to grow on the ground rather than as a climbing vine. Hope this helps. 204.28.125.102 (talk) 00:31, 18 February 2017 (UTC)[reply]

Is abstract thinking unique to Homo sapiens?

--IEditEncyclopedia (talk) 14:19, 17 February 2017 (UTC)[reply]

Wikipedia has an article on Animal cognition which would be a good starting point for your research. --Jayron 32 14:24, 17 February 2017 (UTC)[reply]

Is there non-circle Neanderthal geometric art? Like squares or triangles? If there isn't then maybe yes. Or maybe not. Even were that 100% foolproof maybe there were millions of Neanderthals in all time and only one had abstract thought and we've just never found his drawings of cubes and icosahedrons. Sagittarian Milky Way (talk) 14:31, 17 February 2017 (UTC)[reply]

And what do you call a 1/8th homo sapiens who had the smarty genes from her homo sapiens great-grandparent and the ability to bench press hundreds of pounds from her 7 Neanderthal great-grandparents? Sagittarian Milky Way (talk) 14:45, 17 February 2017 (UTC)[reply]

Apparently John Urschel ;-). --Stephan Schulz (talk) 15:56, 17 February 2017 (UTC)[reply]

It would be difficult to test for animals fully understanding abstract thought, so we might do better to test for their understanding of things like scale models first. For example, show them a scale model of a room with a treat hanging out of a box, then take them to the full-sized room and see if they check out the full-sized box first (don't actually put a treat in it or they might smell it). If they don't understand scale models, there doesn't seem to be much hope for them understanding more complex abstract concepts. StuRat (talk) 16:33, 17 February 2017 (UTC)[reply]

Yes, it is difficult, but a cursory search shows that a number of scientists have designed a range of test for assessing abstraction on non-humans, and then published the results in peer-reviewed studies. Science is often difficult, but that is no reason things can't be studied and understood. I wonder- how long did you look for references on this? SemanticMantis (talk) 18:33, 17 February 2017 (UTC)[reply]

If you can find animals that can handle scale models, then the next step is to make it a scale model, except that it's a mirror image, and see if they can handle that, then start changing details, like make it a different type of chair and box in the room. Then perhaps try a photo of the room, then a map. At this point, we are getting into fully abstract thought, or we can identify precisely where each animal falls short. StuRat (talk) 22:23, 17 February 2017 (UTC)[reply]

This being the science desk, I don't think abstract thought has a definition sufficiently precise to qualify for use in the question posed, which is Is abstract thinking unique to Homo sapiens? Bus stop (talk) 17:06, 17 February 2017 (UTC)[reply]

There are certain terms which have more precise meaning in psychology and philosophy which may be more precise, such as metacognition and theory of mind. We even have an article titled Theory of mind in animals and Animal consciousness, although both of those suffer from the same issues as human definitions as noted in hard problem of consciousness. --Jayron 32 18:24, 17 February 2017 (UTC)[reply]

No. Not according to some definitions and some research. See e.g. Visual categorization: accessing abstraction in non-human primates [1] and A non-human primate test of abstraction and set shifting: An automated adaptation of the Wisconsin Card Sorting Test [2]. Both articles are freely accessible, you can look at the prior work they cite, and you can use google scholar to look at other articles that cite these works. SemanticMantis (talk) 18:32, 17 February 2017 (UTC)[reply]

First of all, I'm not entirely sure that I use the term "abstract thought" in the same way that others do here, so forgive me if I go off on a tangent. There were some famous observations by Wolfgang Kohler which may be relevant here. Kohler had a large enclosure containing several chimps. There was a bunch of bannanas hanging very high in the enclosure, and on the ground there were various items, including several crates and sticks. The story goes that one day, a chimp piled 3 crates on top of each other (without trying to get the bannanas between stacking crates). After the third crate had been stacked, the chimp grabbed a stick,climbed the crates, and reached up with the stick to get the fruit. One account of this is here[3]. There are a couple of other terms used in this area of ethology which might be helpful for research. These include "gestalt" or "gestalt thinking", or the Eureka moment. DrChrissy ^(talk) 18:58, 17 February 2017 (UTC)[reply]

I wouldn't call that abstract thought, it's tool use. Visualizing how to stack the boxes is not abstract, but rather a concrete thought process. Similarly, crows use tools [4], and any bird building a nest or perhaps spider building a web is using similar concrete thought processes. StuRat (talk) 19:08, 17 February 2017 (UTC)[reply]

Oh yes, it could be classified as tool use - it could be placed in several other categories of behaviour - perhaps cognitive trial-and-error. What do you mean by a "concrete thought process" - this is not an ethological term I have encountered before. DrChrissy ^(talk) 19:20, 17 February 2017 (UTC)[reply]

side conversation, no references, open at your own time-wasting peril SemanticMantis (talk) 23:40, 17 February 2017 (UTC)[reply]

Perhaps tangible is a better word for it then. I mean thought processes which can be visualized physically, like the stacking of blocks, as opposed to an abstract concept like "honor", which can't be. StuRat (talk) 22:20, 17 February 2017 (UTC)[reply]

But this is now becoming circular. You are using words which can not be defined for non-human animals, such as "honour". If we can't define it, or at least develop a working definition, we can't test it. DrChrissy ^(talk) 22:34, 17 February 2017 (UTC)[reply]

This is part of the problem. It's difficult to even define what abstract thought in animals would be, much less test for it. But it's not being able to visualize how to stack blocks. From what we know about humans with no language skills (who later developed them so they could describe what it was like before, like Helen Keller), they thought in terms of pictures, making abstract thought an impossibility. If animals also think this way, then they would have similar limitations. Of course, animals do have some language skills, but they seem to be rather rudimentary. StuRat (talk) 22:57, 17 February 2017 (UTC)[reply]

I'm sorry but this is going off on tangents which have nothing to do with the OP. You are throwing in terms such as "tangible", "concrete", "visualise" with no definition and in ways that simply do not relate to my understanding of ethology. This is really not helping the reader. DrChrissy ^(talk) 23:12, 17 February 2017 (UTC)[reply]

@StuRat:. Why don't you try reading a bit about the topic? I have given two very relevant references, each of which contains working definitions of abstraction, and each of which cites many additional scholarly works. The ones I posted are freely accessible, but some of the works they cite are not. If you would like to read some of them and do not have access, just let me know, and I will be happy to provide copies if I can. This is not a desk for you to approach a field from an ignorant position, and hope to work things out from first principles. This is a reference desk, where our goal is to serve our patrons with references. Since you clearly don't know much about this topic, and cannot (or will not?) supply any suitable references, try reading some of the references provided - try to learn from the experts, rather than stumbling around the topic like a chihuahua in a sock. SemanticMantis (talk) 23:39, 17 February 2017 (UTC)[reply]

I think that referencing a "chihuahua in a sock" is borderline WP:NPA. It's uncalled for. A questioning of the term abstract thinking is appropriate to the question asked in this thread. Even the distinction between abstract thinking in humans and non-abstract thinking in humans is a worthwhile discussion and, in my opinion, not entirely irrelevant to the the question posed in this thread. Bus stop (talk) 04:18, 18 February 2017 (UTC)[reply]

Hopefully this def of abstract thought, which contrasts it with concrete thought, will help you understand the difference better and will help us define, and hence answer, the OP's Q: [5]. StuRat (talk) 23:39, 17 February 2017 (UTC)[reply]

This being the science desk, I don't think abstract thought has a definition sufficiently precise to qualify for use in the question posed, which is Is abstract thinking unique to Homo sapiens? Bus stop (talk) 17:06, 17 February 2017 (UTC)

By abstract thought, I mean the ability to hypothesize. To create ideas about different things such as God, moon, sun, rainfall, thunderstorm etc. Humans created abstractions about these things, which are gradually evolved with new knowledge. At first, humans thought sun and moon to be planets revolving around Earth. Do other animals have this ability to create ideas about things? --IEditEncyclopedia (talk) 07:58, 18 February 2017 (UTC)[reply]

According to Gorilla#Intelligence, "Some researchers believe gorillas have spiritual feelings or religious sentiments". Does religious feelings count as abstract thought? --IEditEncyclopedia (talk) 08:25, 18 February 2017 (UTC)[reply]

Elephants are known to visit the bones of their dead relatives, and this can be taken as them assigning some deeper meaning to those bones, but not definitely. StuRat (talk) 16:42, 19 February 2017 (UTC)[reply]

I , for one, am getting completely lost in the moving goal-posts of this almost totally anthropocentric thread. How can we possibly discuss whether non-human animals "think" about God when so many humans would deny his/her existence? Then on the other hand, do animals have abstract thoughts about rain. I don't know whether they have abstract thoughts about rain, but I know that many, many animals react to rain and many animals appear to be able to predict rain. Going back to anthropocentrism and God. Here comes my bit of OR. I have two cats. They have a collection of toys which I tend to keep all lumped together. One of my cats regularly, without any prompting, goes to this pile of toys and brings back the same toy each time for me to throw for him. Anthropocentrism means we are essentially locked in our human skin. How can I possibly know what my cat is thinking when he walks to the toy pile to get his favourite toy. Perhaps he believes it is a God in the same way that some humans have an abstract thought about God? DrChrissy ^(talk) 10:59, 18 February 2017 (UTC)[reply]

Perhaps some animals will weigh in on this question... Bus stop (talk) 14:48, 18 February 2017 (UTC)[reply]

Several already have - we refer to them as editors. DrChrissy ^(talk) 15:42, 18 February 2017 (UTC)[reply]

So, the question restated is "Is abstract thinking possible in humans?" Bus stop (talk) 16:15, 18 February 2017 (UTC)[reply]

Well not really, you are asking a completely different question. DrChrissy ^(talk) 16:25, 18 February 2017 (UTC)[reply]

A related question is whether animals and birds are required to obey the Ten commandments, and whether they are aware that they sin by disobeying. I regularly watch birds eating thrown-out bread, and it's not at all unusual to see one of them stealing a piece that another bird is eating, when there are plenty of unclaimed pieces on the ground. It's obvious that not all humans obey the commandments at all times, indicating free will to sin or not sin and guilt if they do. If the commandments are universal, we could conclude that animals also experience guilt when they disobey one. Akld guy (talk) 19:50, 18 February 2017 (UTC)[reply]

The survival instinct often overrides everything else, in both humans and non-humans. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:53, 18 February 2017 (UTC)[reply]

@ Akid guy. I can not agree. Even if the 10 commandments were universal, this in no way means we can conclude non-human animals experience guilt if they violate one of these. I feel guilt if I find a £10 note in a shop and decide to keep it for myself rather than find the owner. There are many persons in our prisons who feel no guilt at having committed serious crimes against others. Even within our own species we would be pushed to conclude that the feeling of guilt due to violation of the 10 commandments causes guilt throughout our species. DrChrissy ^(talk) 21:22, 18 February 2017 (UTC)[reply]

My username is AKLD guy. Akld is one of the abbreviations in NZ for Auckland. Akld guy (talk) 23:41, 18 February 2017 (UTC)[reply]

Apologies for mis-reading your username. DrChrissy ^(talk) 00:03, 19 February 2017 (UTC) [reply]

Now, if your name was aphid guy you could weigh in authoritatively on this question pertaining to animal intelligence... Bus stop (talk) 00:58, 19 February 2017 (UTC)[reply]

Don't know about survival instinct overriding all else, humans do seem to have exceptions in this regard. Suicide is an everyday concept in most human societies (some even deem it honourable in certain circumstances, others see it as a disgrace, and yet others see it to be sympathized with, but discouraged, and even forcibly prevented), but would you ever see an animal intentionally do it, on the lines of human suicide? Do they have the thought processes to allow for the kinds of suicide logic seen in humans? Eliyohub (talk) 18:19, 19 February 2017 (UTC)[reply]

We actually have an article Suicide in animals but in my opinion it is so poor I can rarely bring myself to edit it. DrChrissy ^(talk) 18:25, 19 February 2017 (UTC)[reply]

Spider and snake

About this video: http://videos.elmundo.es/v/0_ynih8y9m-esta-arana-acaba-con-una-serpiente-10-veces-mas-grande?uetv_pl=virales&count=1 What kind of spider is this and what is she planning to do with the snake, eat it somehow?? Thanks, --ZygonLieutenant (talk) 16:39, 17 February 2017 (UTC)[reply]

I tried three times on two different browsers, and got a "connection error" on the video every time. If you can find another copy of the video hosted elsewhere, or can tell us where it originally appeared, that might help.

However, there's a decent chance you saw this video [6] of an Australian redback spider attacking a snake, though the version I link ends before the snake is clearly dead. The video clip is understandably very popular, and has been shooting all around the internet the past few days, so I think that might be what you saw. SemanticMantis (talk) 19:36, 17 February 2017 (UTC)[reply]

_{Ummm yes it's the same video and it's faked. Blooteuth (talk) 19:03, 17 February 2017 (UTC)}[reply]

Is that your opinion, or do you have some reference to support the claim? Are you claiming it's not a spider? Or not a redback spider Or not a snake? Or that it is a spider and a snake but the spider is not at Can you explain what you mean by that, and give references if possible? Also, you have interjected you comment in the middle of my post, in violation of WP:THREAD. Please follow our guidelines, they help us keep things intelligible and organized here. Rather than move all the related comments around, I will simply sign again above, but please don't make extra work for us. SemanticMantis (talk) 19:08, 17 February 2017 (UTC)[reply]

I was just about to reply supporting Blooteuth. My opinion, and it is only opinion, is that the video is likely to be faked. I lived in Australia for 12 years and have plenty of experience of red-backs. The one in the video looks absolutely ENORMOUS. Our Redback spider states "Females have a body length of about 10 millimetres (0.4 in), while the male is much smaller, being only 3–4 mm (0.12–0.16 in) long." The beast in the video looks very much larger than this. DrChrissy ^(talk) 19:15, 17 February 2017 (UTC) [reply]

I have no strong opinion on this specific video, but have no problem believing such a thing could happen, given the descriptions in the ref I just posted below. I agree the spider looks a bit bigger than 10mm, but the angles are odd, and there is considerable variance in female size [7] SemanticMantis (talk) 19:18, 17 February 2017 (UTC)[reply]

Oh, I agree this behaviour could happen, I'm just not sure about this particular video. It's a shame there were not more objects in the background to help judge size and perspective. Or better still, a person in a white lab coat placing a ruler by the side of the spider, perhaps with a running commentary about how many of her mates she had eaten in the last month! ;-) DrChrissy ^(talk) 19:52, 17 February 2017 (UTC)[reply]

As for the second question: some spiders can and do eat snakes sometimes. The spider venom of some species can act to essentially liquify the interior of prey, letting the spider suck out all it wants (some additional info here [8]). See here [9] for a similar example. SemanticMantis (talk) 18:18, 17 February 2017 (UTC)[reply]

re the Daily Mail story: I'm not sure I have heard of red-backs throwing their web at potential prey. I know some spiders hunt a little like this (see bolas spider) but I always thought the red-back was a sit-and-wait character. DrChrissy ^(talk) 19:07, 17 February 2017 (UTC)[reply]

Yeah, I wouldn't vouch for anything the DM says with respect to biology. However, this review article [10] says, with additional reference "Latrodectus hasselti spiders enjoy a varied diet, trapping some 60-70% of beetles as well as other kinds of insects, spiders, small mice and occasionally lizards which blunder into their sticky trap lines." It continues to describe how the spider incapacitates prey by "squirting a swathe of viscous silk over its target." The article does not specifically describe snakes being caught in this manner, but to me, it's not hard to believe that a spider that can catch lizards can also catch a small or even (perhaps rarely) medium-sized snake. SemanticMantis (talk) 19:17, 17 February 2017 (UTC)[reply]

Great reference - thanks very much. DrChrissy ^(talk) 19:25, 17 February 2017 (UTC)[reply]

The video got an article on National Geographic's website. [11] 209.149.113.5 (talk) 19:50, 17 February 2017 (UTC)[reply]

Thanks! They don't seem very skeptical... SemanticMantis (talk) 20:17, 17 February 2017 (UTC)[reply]

Looks like there's a fishhook holding the snake in place. Justin15w (talk) 20:12, 17 February 2017 (UTC)[reply]

February 18

What is the difference between IS:733 and IS:736

Dear all, Kindly clarify what is the difference between aluminum alloy standards as mentioned in Indian standards Is:733 and Is:736. for example i am giving manufacturing drawing for a milled box sizing 60x60x40 mm. Should i mention material to be as per IS:733 or IS:736. Ex: 1.Material:Aluminium alloy To IS:(733 or 736),Grade:64430-T6 Please clarify SD — Preceding unsigned comment added by Sameerdubey.sbp (talk • contribs) 03:55, 18 February 2017 (UTC)[reply]

Please note: Someone here might be able to tell you something about the difference between the standards, but you should understand that we cannot tell you what you "should" do. We're not here to give advice, only information, and legal advice is something we have specifically decided we're not competent to give. We are very unlikely to have someone around with real competence regarding technical points of Indian law, and even if someone here says they do, we have no way to verify he is telling the truth. Wnt (talk) 10:04, 18 February 2017 (UTC)[reply]

One is for aluminium bars, rods and sections - the other is for aluminium plate. Use the one relating to the type of aluminium that will be used to manufacture whatever you are designing. If you start with aluminium sections (which would seem probable if your box is milled), it will be 733 - if you start with aluminium plate, it will be 736. Wymspen (talk) 12:29, 18 February 2017 (UTC)[reply]

Scientific coincidence

The Titius–Bode law is an example of a scientific coincidence. Are there other examples of scientific coincidence apart from it? --IEditEncyclopedia (talk) 15:09, 18 February 2017 (UTC)[reply]

I am a little confused. What is the difference between "scientific coincidence" and "coincidence"? DrChrissy ^(talk) 16:05, 18 February 2017 (UTC)[reply]

The OP may be looking for other examples of apparent scientific laws that have turned out to be rules that don't really apply. An example is Vitalism, the notion that living organisms are fundamentally different from non-living entities because they contain some non-physical element or are governed by different principles than are inanimate things. It was discredited by Friedrich Wöhler's discovery in 1828 that Urea can be produced from inorganic starting materials. See the article about Superseded scientific theories for other examples. Blooteuth (talk) 17:09, 18 February 2017 (UTC)[reply]

Dirac large numbers hypothesis may be of interest. Loraof (talk) 17:38, 18 February 2017 (UTC)[reply]

A famous example is that a total solar eclipse is just possible. Solar eclipse#Types says: "The Sun's distance from Earth is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size". It has been called a sign that God designed it. If you believe more in science and an old universe then the Moon is moving slowly away from Earth so the coincidence is the current distance. PrimeHunter (talk) 18:05, 18 February 2017 (UTC)[reply]

Did you know total solar eclipses would be impossible if the orbits were perfect? An averagely far Sun is 0.533° wide and the closest you can get to an averagely far Moon makes it 0.527° wide (both sea level and in an aircraft). The only thing making total solar eclipses possible at low Earth orbit or below is that the Moon is sometimes closer than average (less often, the Sun being further than average is sufficient) Sagittarian Milky Way (talk) 19:51, 18 February 2017 (UTC)[reply]

See also Mathematical coincidence#Fine-structure constant. The article mentions other examples from the physical world but they rely on units invented by humans. PrimeHunter (talk) 18:13, 18 February 2017 (UTC)[reply]

Can dogs and cats eat cooked foods?

What happens if they are fed cooked foods? Are they really carnivores? Why do packaged pet foods contain fruits and vegetables? Can they be fed peas and carrots? 166.216.159.13 (talk) 15:40, 18 February 2017 (UTC)[reply]

Regarding dogs. Please read our article Dog food. Dogs are usually classified as carnivores but contrary to popular use of the term, as the article Carnivore explains, this does not mean they eat only meat, rather, carnivores get their requirements from a diet consisting mainly or exclusively of animal tissue. Dog food also explains dogs can eat cooked meat - most tinned dog food is cooked. They can also be fed a vegetarian diet. DrChrissy ^(talk) 15:59, 18 February 2017 (UTC)[reply]

Regarding my Cat. 1) Eats it, asks for more and never says thank you. 2) He's a facultative carnivore not an obligate carnivore, but why bother hunting prey when master serves Cat food (see article) that may indeed contain some plant matter, just as long as no one seriously expects to convert this cat to Vegetarianism? Blooteuth (talk) 16:52, 18 February 2017 (UTC)[reply]

Why are you stating the cat is a facultative carnivore when there is a multitude of scientific papers stating they are obligate carnivores, e.g. [12]? DrChrissy ^(talk) 17:03, 18 February 2017 (UTC)[reply]

Yes, CATS ARE OBLIGATE CARNIVORES. IT IS COMPLETELY INCORRECT TO SAY THEY ARE FACULTATIVE CARNIVORES, AS SHOWN BY NUMEROUS RELIABLE SOURCES LINKED ABOVE AND BELOW. Please forgive my typographic emphasis - this is important, and an issue of animal welfare, so I wanted to make it unmistakably clear for any casual reader :) SemanticMantis (talk) 23:26, 18 February 2017 (UTC)[reply]

This vegan cat food site admits "Some cats have a more difficult time adapting to a vegan diet than others". Note that domestic cats know only what they like and not what is good for them, which is why they are liable to ingest things that do them no good, such as Melamine in wheat glutin (see 2007 pet food recalls) and lactose in cow's milk that gives pussy Diarrhea. See also. Blooteuth (talk) 17:29, 18 February 2017 (UTC

I really don't think it is appropriate on a sci-ref desk to try and counter my RS with information from web-site advertisements. Please could you provide an RS that states cats are facultative carnivores. DrChrissy ^(talk) 18:10, 18 February 2017 (UTC)[reply]

Cats are natural carnivores which occasionally eat some vegetable matter such as grass. ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:26, 18 February 2017 (UTC)[reply]

Dogs also eat plant matter but they are classified as carnivores. Cats are classified as "obligate carnivores" for a scientific reason. If we are going to bend or misuse these scientific terms on this REFERENCE desk, the least we owe our readers are RS to support the terminology we use when this clashes with other RS. RS please. DrChrissy ^(talk) 18:31, 18 February 2017 (UTC)[reply]

Both cats and dogs are members of the order carnivora, but that is an evolutionary classification that does not necessarily have anything to do with current culinary requirements or preferences. Cats are obligate carnivores because they rely on external sources of arginine and taurine. Arginine is primarily sourced from meat, and AFAIK there is no significant natural vegan source of taurine. If a cat's nutritional needs are met, they can, of, course, eat some additional plant food. Most of that is not poisonous to cats, it just does not meet their requirements. Dogs, on the other hand, can live on a mostly vegetarian diet - indeed, some of the key genetic differences between wolves and dogs relate to the efficient digestion of starchy foods in dogs. --Stephan Schulz (talk) 19:07, 18 February 2017 (UTC)[reply]

Our article on taurine says that about 3,000 tons of it are synthesized annually for addition to pet foods. I may not be a fan of veganism but I can't say no to a good chemistry experiment on animals. ;) Wnt (talk) 19:40, 18 February 2017 (UTC)[reply]

Point taken and qualifier inserted above. --Stephan Schulz (talk) 19:44, 18 February 2017 (UTC)[reply]

I feel it is required to point out that cats are obligate carnivores, as any reliable source will tell you. This means forcing them into a vegan or even vegetarian diet is highly unnatural at best, and really can only be described as animal cruelty. It will lead to deficiencies in taurine (causing retinal degeneration and cardiomyopathy), arginine (causing dangerously high blood ammonia levels), arachidonic acid and other essential fatty acids (causing problems with liver, kidney, skin and more), and other essential nutrients such as iron, calcium and phosphorus. Lack of meat also screws with cats' urine pH, possible causing kidney stones, and the high carbohydrate nature of vegetarian/vegan foods puts them at risk of diabetes. Vegan diets would need extensive supplementation to be even remotely healthy for a cat. The link provides by User:Blooteuth is incorrecnt. The company is either lying for the economic benefit of their company, or incredibly ignorant. Dogs are of course essentially omnivores, and are much more flexible when it comes to diets. Fgf10 (talk) 20:52, 18 February 2017 (UTC)[reply]

This reference is a very accesible analysis of why dogs are classified as "carnivores" and cats as "obligate carnivores"-VERONIQUE LEGRAND-DEFRETI. Proceedings of the Nutrition Society (1994), 53, 15-24. Differences between cats and dogs: a nutritional view. DrChrissy ^(talk) 20:57, 18 February 2017 (UTC)[reply]

Excellent link, should have looked for something like that, rather than type out that whole rant. Much obliged for the reference. Fgf10 (talk) 21:06, 18 February 2017 (UTC)[reply]

Absolutely no problem at all - that is what this ref-desk is for. Your post was not a rant - it was a clearly informed contribution to the discussion which is always welcome. DrChrissy ^(talk) 23:45, 18 February 2017 (UTC)[reply]

You can feed your pets some vegetables as snacks, but there are some you should never feed them. The ASPCA has a decent list here: link EvergreenFir (talk) 17:09, 18 February 2017 (UTC)[reply]

sentiment

Cats are obligate carnivores, but vegetable products are added to cat food to provide fiber and nutrients that they would get in the wild from animal sources. For example, they get fiber from hair and feathers, but that is replaced with plant fiber in cat food. They also require a lot of fat in their diets, and can be harmed by garlic, onions, and other ingredients commonly added to human food. Also, they do not require vitamin C in their food, as their body manufactures it and unlike humans, they need complete proteins in their diets as they cannot manufacture them from amino acids. That's why you should not feed cats table scraps. Dogs are much closer to humans in their diets, which is why dog food is different from cat food. TFD (talk) 20:38, 18 February 2017 (UTC)[reply]

Distraction ---Sluzzelin talk 18:54, 19 February 2017 (UTC)[reply]

(offending post was here) Asmrulz (talk) 04:15, 19 February 2017 (UTC)[reply]

This post is absolutely no help whatsoever to this thread and I ask an uninvolved editor to strike it or perhaps place it in a collapsible box. DrChrissy ^(talk) 23:57, 18 February 2017 (UTC)[reply]

You should discuss this on the user's talk page rather than screwing around with his edit here. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:12, 19 February 2017 (UTC)[reply]

Thanks. I had already removed it (for OP's sake) but the user reinstated it for some reason, with their silly formatting, too Asmrulz (talk) 04:15, 19 February 2017 (UTC)[reply]

...and I stand by the general sentiment in it Asmrulz (talk) 04:22, 19 February 2017 (UTC)[reply]

For those who might not be aware of markup for deleted text, please see [13]. By simply deleting the comment, the ensuing thread can become confused. Hardly "screwing around". DrChrissy ^(talk) 12:58, 19 February 2017 (UTC)[reply]

Personally, given that it was in small text, I'd consider the "offending post" acceptable (small text being used to imply less-than-scholarly remarks), but let's not go off in tangents, or all this argument should be hatted. Eliyohub (talk) 18:08, 19 February 2017 (UTC)[reply]

If it had been slightly related to the question, I would have let it go. However, it seemed to me to be more a statement of how the OP should run their lives. Totally unacceptable for a SCI-REFERENCE desk. DrChrissy ^(talk) 19:05, 19 February 2017 (UTC)[reply]

To address some of the other Q's:

1) There's nothing in being a carnivore which requires eating raw food.

2) As for adding fruits and vegetables, they may provide needed dietary fiber. In nature, eating a mouse would likely include it's (vegetarian) intestinal contents, so a bit won't hurt. Also, such a pet food may sell better, if people think it's better for their pet, regardless of if it really is. In the past, they've included things like sawdust for fiber, sometimes disguised as "cellulose", but that just sounds bad and turns off potential buyers. StuRat (talk) 23:55, 18 February 2017 (UTC)[reply]

Scientific American "Veggie Cat Food? Why Not All Cats Need Meat" The vegetarian pet debate is a contentious one among vegetarian pet owners and veterinarians and is one not likely to go away anytime soon.

Web MD says If you are considering a vegan or vegetarian diet for your dog or cat....Only consider or feed commercial diets that have gone through feeding trials and meets the requirements for AAFCO (Association of American Feed Control Officials) compliance.

In some medical cases (allergies, liver or bladder disease) veterinarians use specially formulated pet foods only available by prescription that are made from nonmeat protein sources (egg or soy, for example). Blooteuth (talk) 00:11, 19 February 2017 (UTC)[reply]

There could also be moral or religious reasons. After all, a Jain isn't allowed to cause the death of one animal to feed another, right? StuRat (talk) 03:48, 19 February 2017 (UTC)[reply]

Are they allowed to deliberately help the cat nab mice, or give the cat a live mouse to kill and eat? Eliyohub (talk) 18:09, 19 February 2017 (UTC)[reply]

No, not if I read our article correctly: "The first major vow taken by Jains is to love and cause no harm to other living beings. It involves minimizing intentional and unintentional harm to other living creatures by actions, speech or thoughts. The vow of ahiṃsā is considered the foremost among the 'five vows of Jainism'.".StuRat (talk) 18:59, 19 February 2017 (UTC)[reply]

I didn't see a link for that article about dog-cat differences, so here it is: [14] notably it cites

"the cat has limited ability to regulate the catabolic enzymes of amino acid metabolism, which causes the cat to require a higher level of dietary protein for maintenance than the dog
the cat has a lower capacity to synthesize the sulphonic acid taurine than the dog and is unable to conjugate bile acids to glycine. Thus the cat, unlike the dog, cannot meet its taurine requirement from dietary S-containing amino acids
the cat cannot synthesize sufficient nicotinic acid from tryptophan because of an increased activity of alpha-picolinic acid decarboxylase (EC 4.1.1.45) leading to the endproduct glutamate rather than nicotinic acid
the cat is unable to convert carotene to retinol and, therefore, cannot satisfy its vitamin A requirements with a herbivorous diet alone
the cat cannot convert sufficient linoleic acid to meet its requirement for arachidonic acid
the cat seems to be unable to cope with high levels of carbohydrate in its diet and appears to be in a constant state of gluconeogenesis."

Wnt (talk) 22:00, 19 February 2017 (UTC)[reply]

Antidepressant vs recreational drugs

In as much as I understand it, most, but not all, antidepressants focus on serotonin—I do not profess to know the mechanism. However, recreational drugs seem in most, but not all, cases to focus on dopamine. Why the discrepancy?--Leon (talk) 18:28, 18 February 2017 (UTC)[reply]

They're different neurotransmitters that do different things. See Neurotransmitter#Examples_of_important_neurotransmitter_actions for a cursory overview. Shock Brigade Harvester Boris (talk) 19:24, 18 February 2017 (UTC)[reply]

Yes, but both antidepressants and recreational drugs are used for, in very broad terms, to help people "feel better", or at least "less bad". So one might expect them to work with the same neurotransmitters in more cases than not.--Leon (talk) 19:36, 18 February 2017 (UTC)[reply]

It depends on what neurotransmitter you want to mess with. Some depressed patients in a clinical setting respond positively to Dopamine reuptake inhibitors others need Norepinephrine–dopamine reuptake inhibitors. Some street drugs mess with your serotonin levels and druggies choose, MDMA, aSerotonin releasing agent.

I believe that in many cases where your split (in antidepressant/serotonin and recreational drug/dopamine) is wrong. — Preceding unsigned comment added by Hofhof (talk • contribs) 20:03, 18 February 2017 (UTC)[reply]

So, if someone needs serotonin but not dopamine, does that suggest, albeit weakly, that they may not enjoy e.g. heroin?--Leon (talk) 20:18, 18 February 2017 (UTC)[reply]

If someone is low on serotonin to a pathological level, he will enjoy heroin and can get easily addicted to it. Heroin messes with a lot of neurotransmitters, including serotonin. Source: [15]. Also remember that depressed people can have panic attacks or not be depressed all the time. Heroin will be pretty enjoyable for them. Hofhof (talk) 20:33, 18 February 2017 (UTC)[reply]

The dirty truth that us neuroscientists don't like to say very often is that we really don't know anything about depression. The use of serotonin modulating drugs comes from observations of low levels of breakdown products of serotonin in the cerebrospinal fluid some (not all) depressive patients, and the clinical improvement some (again, not all) patients see when prescribed serotonin modulating drugs. However, we don't know why serotonin is down in some patients, we don't know how serotonin alters mood, and we don't know why some patients don't respond to serotonin modulating drugs. Of course, the pharmaceutical industry has made good money on selling their SSRIs, so will glance over these minor details. Why we don't know more is a long and ugly story, but it has a lot to do with our inability to really model depression in animals models. What we do know is that for some patients, cognitive therapy, exercise , or other drugs such as mentioned above, work a lot better than SSRIs. Hell, in some trials even placebos work as well.

As for dopamine and recreational drugs, dopamine is crucial for the reward system in the brain. It is thus involved in 'pleasure' and positive reinforcement. Fgf10 (talk) 21:04, 18 February 2017 (UTC)[reply]

Interesting on all counts...

Perhaps a slight digression: I've read conflicting accounts on the possibility of not enjoying opioids. Some people believe it is almost impossible because "everyone" likes dopamine, but some people seem to dislike opioids. How is it possible if dopamine feels good?--Leon (talk) 21:11, 18 February 2017 (UTC)[reply]

Also Fgf10, whilst you are explicit on some points, it is not at all clear on what you or the establishment has to say about the role of serotonin. Is it necessary for the feeling of pleasure, or not?--Leon (talk) 21:34, 18 February 2017 (UTC)[reply]

The first problem with answering that question is to define 'pleasure'. Human affection is a mess of complex processes, which are poorly defined, and the neural basis for even a single of those processes is generally poorly defined. We know a lot of effects of serotonin, see for instance serotonin syndrome. You'll note everything mentioned in that article is a physical property, such as body temperature and pupil diameter, which are easily measured. How do you measure pleasure? In humans, this is normally done with questionnaires, which are a poor measure of anything. To directly measure the effects of serotonin on pleasure (whatever your definition), you'd have to drastically alter the levels and measure the effects. This is essentially impossible in healthy humans (for practical and ethical reasons). Therefore we usually do these experiments in animals and try to extrapolate the results. However, if measuring 'pleasure' in humans is difficult, try doing it in animals. We're stuck with poor proxy measures such as (an)hedonia, measured by preference for sweet foods etc. Long story short, we don't really know how serotonin affects mood. That is does seems true, as raising serotonin levels in depressive patients often elevates mood. Your question perfectly illustrates how seemingly simple questions are still really difficult to asnwer. Good things they are, or I'd be out of a job! Fgf10 (talk) 23:08, 18 February 2017 (UTC)[reply]

Our article on the Nucleus accumbens - the reward and pleasure center of the human brain - may be helpful to your understanding. Opiates, drugs that regulate reuptake of serotonin and other neurotransmitters, and even sugar stimulate different parts of the nucleus accumbens in different ways. Instead of reproducing that article in large part, I'll just point out two relevant sections of the article: Nucleus_accumbens#Neurotransmitters and Nucleus_accumbens#Function and let you discover the fine points of how recreational drugs tickle the nucleus accumbens (reinforcing both recreational use and addiction to drugs) as opposed to how drugs that make more serotonin and other neurotransmitters available to circulate in the brain do that.

As Fgf10 says, we're not really sure how selective serotonin reuptake inhibitors work in treating depression, but our article on the nucleus accumbens Nucleus_accumbens#Depression points to research showing some success in treating depression by electrically stimulating the nucleus accumbens with deep-implanted electrodes. The authors of that paper point to two other research papers they say demonstrate that parts of the nucleus accumbens don't work well in depressed patients, and that some dopaminergic compounds such as dextroamphetamine (used as "dopaminergic probes") show a detectable change in the cellular metabolism of parts of the nucleus accumbens. loupgarous (talk) 02:07, 19 February 2017 (UTC)[reply]

About serotonin versus dopamine, it's not at all a case of a clear divide. Almost all antidepressant medications have at least some effect on both transmitters. The SSRIs (SS=selective serotonin) have relatively little dopaminergic effect, but it is not zero. And people who have depression vary greatly as to which antidepressant works for them. Also, one should not understand the effects of drugs that affect reuptake as simply "increasing" or "decreasing" the amount of neurotransmitter. (Inhibit reuptake, and there is more transmitter in the synapse but less available to be released from the neuron that releases it.) Perhaps it has something to do with how the timing of availability of the transmitter affects neuron firing, but neuroscientists do not have any clear understanding of that yet. And as for recreational drugs, cocaine almost entirely affects dopamine whereas LSD almost entirely affects serotonin. And LSD obviously is nothing like an SSRI antidepressant. Again, recreational drugs differ greatly as to which transmitters they affect the most. And about enjoying or not enjoying opiates, it's very interesting that during the Vietnam War, many US military people used heroin – at the end of the war, most just walked away from heroin with no addiction, but a subset of the population were addicted for life. Very likely, there are genetic differences that cause that, but their nature is presently unknown. --Tryptofish (talk) 00:50, 20 February 2017 (UTC)[reply]

Killing a tree without copping it down

Would drilling a hole into a tree and pouring weed killer into the hole kill it? — Preceding unsigned comment added by 189.201.241.54 (talk) 19:22, 18 February 2017 (UTC)[reply]

Check out girdling. EvergreenFir (talk) 19:27, 18 February 2017 (UTC)[reply]

You would probably need to drill several holes at various points around the circumference to have the same effect as girdling. Both glyphosate and hormone weedkillers such as 2,4-Dichlorophenoxyacetic acid can be used to kill trees in this way. Another method is a circle of copper nails. Dbfirs 20:54, 18 February 2017 (UTC)[reply]

Stage of development when freezing developing humans

Up to what stage (and why not further) can you freeze a developing human? I assume that's past being a zygote, but before turning into a baby. Where and how can you determine the limit?--Hofhof (talk) 20:10, 18 February 2017 (UTC)[reply]

This is just a guess but I would imagine it is the point just before when cells need chemical signals to instruct them to start specializing into liver cells, brain cells, arms and legs etc., (thalidomide interferes with the chemical instructions needed for newly forming cells).--Aspro (talk) 21:40, 18 February 2017 (UTC)[reply]

Embryo cryopreservation may be a good starting point. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:40, 18 February 2017 (UTC)[reply]

Illnesses from indirect accidental consumption of animal faeces during outdoor activities

Are there a lot of known cases of people who do outdoor activities in first world countries becoming ill from indirect consumption of animal faeces? For example they touch something with traces of animal faeces (maybe touching equipment which has touched it) and consume food with their hands. 2A02:C7D:B957:3B00:74AC:C58F:30BC:44E2 (talk) 23:52, 18 February 2017 (UTC)[reply]

Define "a lot". Foodborne illness often results from consuming something contaminated with fecal matter, though I'm not sure this has any particular correlation with "outdoor activities". There are reasons other than fecal contamination to wash your hands; your hands can carry other pathogens such as influenza and bacteria that can infect wounds (like ones you might get from outdoor activities). --47.138.163.230 (talk) 00:29, 19 February 2017 (UTC)[reply]

Some children have lost their sight through touching dung and then rubbing their eyes. 80.5.88.48 (talk) 08:37, 19 February 2017 (UTC)[reply]

Toxoplasmosis can definitely come from handling the faeces of an infected cat. I'm sure others can quote similar animal-faeces-borne infections? Cats are usually fastidiously clean animals, though, and tend to cover their faeces with either soil or kitty litter. But they do tell you to be careful. Eliyohub (talk) 17:58, 19 February 2017 (UTC)[reply]

February 19

I'd like to have my car tires vulcanized .......... by Buster Keaton's mechanic

youtu. be/UWEjxkkB8Xs?t=2m31s

In an unnamed Buster Keaton movie, bad guys are after him and he tries to hitch a ride by sitting on a car's rear spare tire. The car drives away and Keaton finds himself remain in the same place. The spare tire is actually used as a roadside sign placed behind the car with a cardboard saying "Vulcanizing" and an arrow pointing to the shop.

Did people of the 1920s really have to have their car tires vulcanized by someone? -- Toytoy (talk) 01:55, 19 February 2017 (UTC)[reply]

Our article on Vulcanization describes it as "a chemical process for converting natural rubber or related polymers into more durable materials by the addition of sulfur[1] or other equivalent curatives or accelerators".

Clearly, that was already done to the rubber in tires before it was used to make them. However, the term "vulcanization" was also widely used to refer to the process of patching inner tubes of tires with thin pieces of vulcanized rubber, which I've done myself. You clean the spot around the hole of the tire, apply a solvent to the tire and the patch, then apply the patch to the now sticky rubber inner tube. Since almost all cars of the 1920s had tires with inner tubes, yes, they did from time to time require vulcanization in the sense of "repairing the inner tube of a tire with a patch of vulcanized rubber". loupgarous (talk) 02:19, 19 February 2017 (UTC)[reply]

Vulcanisation was the older process of repairing a puncture with a patch of unvulcanised rubber, then vulcanising it in-situ with heat and pressure. It's no longer performed, as later tyres gained greater quantities of filler materials and became less like pure rubber. Andy Dingley (talk) 02:56, 19 February 2017 (UTC)[reply]

Wups. You're right. We called it "vulcanization" when I was a kid, but in the 1960s you had to really hunt to find someone who did "hot vulcanization". But your answer is correct in the OP's context. loupgarous (talk) 03:22, 19 February 2017 (UTC)[reply]

Menstruation

Can high levels of stress or anxiety stop, delay, or otherwise affect menstruation? Benjamin (talk) 01:57, 19 February 2017 (UTC)[reply]

According to our article on Amenorrhoea, specifically the section Secondary Amenorrhoea, yes. Quoting:

"Secondary amenorrhea is also caused by stress, extreme weight loss, and excessive exercise. Young athletes are particularly vulnerable, although normal menses usually return with healthy body weight. Causes of secondary amenorrhea can also result in primary amenorrhea, especially if present before onset of menarche." loupgarous (talk) 02:39, 19 February 2017 (UTC)[reply]

Can it be caused by stress alone, and if so, how much? Benjamin (talk) 03:09, 19 February 2017 (UTC)[reply]

In standard units, that would be 3.27 mother-in-law days. :-) StuRat (talk) 03:27, 19 February 2017 (UTC) [reply]

Yes. The brain actually controls the cascade of events which lead to menstrual flow through the Hypothalamic–pituitary–gonadal axis, part of the neuroendocrine system.. As to "how much stress", that really depends on the individual woman. Each of us have unique bodies, and there's no single amount of stress sufficient to cause any physiological response across the human race - it varies from person to person.

And Stu, I've found mother-in-law mediated stress to be independent of the neuroendocrine system, and in some cases to be pathognomonic of Vistaril deficiency on the part of the mother-in-law. loupgarous (talk) 03:39, 19 February 2017 (UTC)[reply]

If the Solar System were brought to rest relative to the Galaxy then allowed to follow real physics what would the new orbit be?

Would the sum pulls of dark matter and gas, dust, and star clouds etc. cause an orbit that's not "drop to the center like a stone?" Sagittarian Milky Way (talk) 02:43, 19 February 2017 (UTC)[reply]

No offense, but "new orbit around what?" If all the masses in the Solar System lost their proper motion with respect to the rest of the Milky Way (the motion causing their galaxy rotation curve, specifically), strictly speaking the Solar System as a whole wouldn't have an orbit around the center of the galaxy. You'll have to define your question better, and while you're doing so, supply a mechanism by which this might be done. You'd have to supply an arresting force to every mass in the Solar System somehow which discriminated between the orbits of the objects in the Solar System around the Sun and those planets with moons or captive asteroids and their proper motion attributable to their galaxy rotation curve in the galaxy. Then you'd have to keep applying it unless you somehow abolish all the other mass in the Milky Way. :"Dark matter and gas, dust, and star clouds etc." either part of the Milky Way or they're mass in other galaxies. Working out the resultant vector for a Solar System in which we woke up and found the rest of the Milky Way had gone away... we can't do that here in the Reference Desk.

We could, I suppose, estimate extragalactic masses from observation of their motion, but I don't think we'd get meaningful results, since those motions are likely much smaller than the limits of accuracy of how we measure them. And "dark matter" will be even harder to estimate the mass of, for obvious reasons. loupgarous (talk) 02:55, 19 February 2017 (UTC)[reply]

Around the center of mass of the Milky Way Galaxy. Why would you have to keep applying the force? Once it's stopped it has lost all it's galactic rotation curve momentum/proper motion and that is when you turn on real physics again and see what happens. It's not a plan, it's a thought experiment like Einstein's riding on a beam of light (even harder than stopping the galactic orbit as your body cannot reach the speed of light). Sagittarian Milky Way (talk) 03:47, 19 February 2017 (UTC)[reply]

Oh, I see. For your thought experiment, you postulated being able to switch the gravitational attraction between the galaxy and the solar system off for a while. If you've ever taken a pail with a rope tied to the handle, filled it half-full of water, then swung it over your head, you've got a heavenly body orbiting a massive object, with the rope representing the gravitational attraction between them. Now let go of the rope. See what happens? That's what happens to the solar system once the gravitational attraction between it and the center of the galaxy abruptly goes away - angular momentum sends the solar system away from the galaxy on a line tangential to its orbit around the center of the galaxy. Unless you are cancelling the Solar System's inertia while you're turning the gravitational attraction from the center of the galaxy off, too.

That's actually more plausible. Once you throw the switch back "on", are you restoring the gravitational pull from the galaxy, or not? loupgarous (talk) 04:31, 19 February 2017 (UTC)[reply]

You're focusing too much on how to get there from here. A thought experiment doesn't require that, you just jump to the new state. Nobody worries about how Schroedinger got the cat in the box. "Free ~~prussic acid~~ food inside !" StuRat (talk) 04:38, 19 February 2017 (UTC)[reply]

There would be some attraction to the matter in the arm, that might restore a portion of the solar system's original galactic rotation, but certainly not all, causing it to fall towards the center. As it did, it would pass other solar systems, potentially causing chaos as multiple solar systems are pulled out of position. What would happen to ours would be difficult to predict. It might even be possible for it to be ejected from the galaxy, at least temporarily. And the planets might get pulled away from the Sun in the process. StuRat (talk) 03:24, 19 February 2017 (UTC)[reply]

"Might" is a mighty weak word ;-). When two galaxies collide, actual close encounters of stars are still very very rare. Look up one clear night - how much of the sky is taken up by stars and how much by void? If the solar system magically lost its proper motion, it would - very slowly - start to fall towards the center of the Milky Way. Most likely, it would interact with enough other random stars to not pass exactly through the center, but bypass it at some distance. It would then drift out to about the current distance and there momentarily come to rest, before repeating the process. Unless it gains additional energy by some close three-body encounter, it will not be ejected from the galaxy. And the time scale for one full passage (back and forth) would be on the same order of magnitude as the current galactic orbit - hundreds of millions years. --Stephan Schulz (talk) 07:24, 19 February 2017 (UTC)[reply]

While stars are spread far enough apart that they aren't likely to collide, they are close enough so that they have gravitational effects on each other, especially over billions of years. Take a look at this page on galactic collisions, and note the animation of a simulation of such a collision, about 3/4th down, showing stars flying everywhere: [16]. StuRat (talk) 16:15, 19 February 2017 (UTC)[reply]

Yes, but that's a billion stars falling through a billion stars (give or take an order of magnitude). The vast majority of stars form the merged galaxy - the ones that are flung out are a small fraction. --Stephan Schulz (talk) 16:30, 19 February 2017 (UTC)[reply]

Correct, but that doesn't mean the stars that remain in the galaxy weren't affected by each other's gravity. Indeed, that's critical to changing the orbit of each into the new orbit in the resultant galaxy. If they didn't affect each other, the two galaxies would just pass through each other and continue on their way. StuRat (talk) 16:33, 19 February 2017 (UTC)[reply]

The gravitational pull would reduce as the planet approached the galactic center, so I think the orbit would take somewhat longer. Stars passing by at a distance (so as not to appreciably accelerate the Sun to puppy-dog along behind) would be expected to push and pull by roughly equal amounts. But there is substantial frame dragging from the galactic rotation that would pull on the Earth. Its magnitude is described in this interesting paper which has been published in Europhysics Letters. However, I don't know how to get from that to an orbital deflection. I would suppose the chance of collision should be much higher due to the greater relative velocity between the infalling star and the "usual flow of traffic". Wnt (talk) 13:01, 19 February 2017 (UTC)[reply]

Actual star/star collision chances would still be low, but the chances of passing close enough for a significant gravitational deflection of one or both stars (depending on relative masses) would be much higher. StuRat (talk) 16:48, 19 February 2017 (UTC)[reply]

Infections

Why don't all localised infections become systemic infections? Surely, if bacteria or other infection causing organism has entered the body, it will eventually spread? 2A02:C7D:B921:AD00:F95A:A035:E07C:21D6 (talk) 09:33, 19 February 2017 (UTC)[reply]

Any pathological organism entering the body will trigger a response from the immune system. Most minor infections will be suppressed but a few may become systemic. The result will vary according to such factors as the age and health of the individual, the type of infecting organism, for example. Try this site or Immune system for starters. Richard Avery (talk) 09:41, 19 February 2017 (UTC)[reply]

Then the next logical Q is how infections can overcome the immune system. Some methods are to attack the immune system itself, like AIDS does, or to just overwhelm the immune system when you are exposed to a large dose of bacteria or other microbes. StuRat (talk) 16:30, 19 February 2017 (UTC)[reply]

Search for Alien life

Have been looking for some information about the search for alien life; Yes i am aware of the usual Carbon based biological search but was looking for some good articles of people thinking out side of the norm and some fresh ideas of what could be a starting point. So the question i guess would be - What is the current thinking with regard to the search for alien life outside of the normal parameters? Also what if any ideas have people come up with to detect alien life forms that do not match the criteria layed down for life as we know it? Thanks for your help and/or thinking Adrian — Preceding unsigned comment added by 5.175.64.53 (talk) 11:27, 19 February 2017 (UTC)[reply]

Keep in mind that we are way far beyond searching for any particular type of life form. Other star systems are simply too far away to directly tell if they contain life, carbon or otherwise. Rather, searches for alien life have focused on looking for radio signals that cannot be generated naturally (thus far, no unambiguously artificial radio signals have been detected that were not created by humans, obviously). This type of search doesn't matter on the nature of the alien life. Searchers also have an eye for visual signatures of megastructures around stars, which again, doesn't matter on the nature of the alien life. See Search for extraterrestrial intelligence for more information, for starters. Someguy1221 (talk) 11:50, 19 February 2017 (UTC)[reply]

The question asker may be thinking about the chemical tests being performed by Mars Curiosity and not SETI. It's true that the search for Life on Mars has mostly been to look for organic compounds, or evidence of metabolisms like those seen on Earth life. The Life on Mars article is still worth a read. ApLundell (talk) 15:26, 20 February 2017 (UTC)[reply]

See Hypothetical types of biochemistry. --IEditEncyclopedia (talk) 12:00, 19 February 2017 (UTC)[reply]

Even biochemistry may be too limiting. Suppose, for example, that the complex magnetic patterns we see in the Sun are actually the result of some type of magnetic plasma life forms. StuRat (talk) 16:25, 19 February 2017 (UTC)[reply]

The article Search for extraterrestrial intelligence has extensive references and further reading. Blooteuth (talk) 18:55, 19 February 2017 (UTC)[reply]

Thank you Hypothetical types of biochemistry was a good article Adrian (from the article i am thinking best way to narrow down silicon based life would be to look at sulphuric acid rich environments ( just need a lot of equipment now )then look for structures) ment added by 5.175.64.53 (talk) 05:54, 20 February 2017 (UTC)[reply]

Theobromine toxicity

from the articles on theobromine and theobromine poisoning, it is clear to me that rats and humans can tolerate higher amounts of it because they have a much easier time metabolizing it than other animals, eg cats/dogs. My question is-- why? What digestive/metabolic adaptations do rats and humans have that allow them that much higher tolerance? is it a specific enzyme or something that other animals lack? i didnt see it mentioned in the articles if it was there, so apologies if this is redundant 206.47.249.251 (talk) 13:10, 19 February 2017 (UTC)[reply]

Seems like there's multiple pathways with multiple enzymes potentially involved in metabolising theobromine. Our article does mention metabolism in the liver by CYP1A2 and CYP2E1. This study shows a different metabolite pattern in different species, suggesting involvement of different enzymes. Fgf10 (talk) 15:13, 19 February 2017 (UTC)[reply]

[17] mentions several different pathways of metabolism and different profiles of products but also mentions the key difference seems to be in rates. BTW to clarify your later point, as I understand the source (sort of mentioned at the end of the abstract, but clearer if you check the full article), the same metabolites were mostly observed in all tested species. The qualitative pattern did differ, in other words the amount of each one. While it's possible different enzymes were involved in different species, this suggest to me more likely is the similar enzymes were involved in all species but different enzymes are more significant in each species. Nil Einne (talk) 15:31, 19 February 2017 (UTC)[reply]

Correct, my phrasing was inaccurate. Fgf10 (talk) 16:54, 19 February 2017 (UTC)[reply]

LDL and HDL are different from cholesterol?

I have been taught that cholesterol is divided into two: LDL and HDL so when I'm saying cholesterol it includes the two. But now I saw a short lecture made by university of Reading in the UK that states: "So how does HDL work? Well, we're not quite sure, but we think that it may work in the reverse way to LDL. LDL takes cholesterol from the blood into the arterial wall. HDL may take it the other way, from the arterial wall from atherosclerotic lesions back into the blood." it says that LDL takes cholesterol and that means that cholesterol is different from LDL. what is that? I'm a little bit confused. 93.126.88.30 (talk) 16:17, 19 February 2017 (UTC)[reply]

Let's start with your first sentence: "I have been taught that cholesterol is divided into two: LDL and HDL". You were taught wrong. Cholesterol is a

Lipid. HDL and LDL are Lipoproteins.

**Lipoprotein structure (chylomicron)**
**ApoA, ApoB, ApoC, ApoE** (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids)

Lipoproteins (LDL and HDL) transport lipids (fat) in your blood. Cholesterol is one of the lipids they transport. --Guy Macon (talk) 17:35, 19 February 2017 (UTC)[reply]

Thank you! I hope that I didn't understand my teacher properly rather than it's his mistake, because he is a scientist. Now I understand that LDL is like insulin which takes the glucose inside to the cell, but LDL takes cholesterol to the cells, and HDL take them out from there. Isn't it? 93.126.88.30 (talk) 20:18, 19 February 2017 (UTC)[reply]

That was a good try, but ... no, insulin is something else. It is a separate signal that goes to the cells and bangs on the door and says, "really, let this glucose in". The glucose just sits out in the bloodstream as a solution and is potentially available to the cells at any time. But a type I diabetic can essentially starve to death for lack of glucose even while his bloodstream contains five times more of the stuff than a normal person's. Wnt (talk) 21:42, 19 February 2017 (UTC)[reply]

Sorry, regarding to the first question now I'm reading on an article of the Open university in the UK the following things (which are similar to what my teacher said): "One of the risk factors for coronary heart diseases (CHD) is an inappropriate ratio of different types of fats in the blood, including the two sorts of cholesterol (known as HDL and LDL)." How can you explain these things, are they also incorrect or maybe I don't understand them well? 93.126.88.30 (talk) 00:15, 20 February 2017 (UTC)[reply]

This is an issue where context is important. A "serum cholesterol" lab does not pick out little bits of cholesterol in the blood and count them. It is not a count of the total cholesterol in the body. There is a hell of a lot more cholesterol in the body. The serum cholesterol lab estimates the amount of cholesterol in serum and separates it into the type of lipoproteins used: HDL, LDL, and VLDL. If you want an overly specific name, you can say "total cholesterol being transported inside a lipoprotein in the blood stream." We just say "total cholesterol." 209.149.113.5 (talk) 14:34, 20 February 2017 (UTC)[reply]

Are there any microorganisms that wouldn't taste bad if you drank or chewed many grams of them?

Without added microorganism food, waste products, extracellular water etc, just piles of nothing but cells and still alive or at least not rotting yet (some microorganisms produce very polyunsaturated fatty acids that go rancid quicker than plant/animal fats, maybe that'd be tastable). Sagittarian Milky Way (talk) 18:21, 19 February 2017 (UTC)[reply]

Well, the food manufacturer that produces Quorn thinks their micro-organisms tastes OK (no comment as to what I think of it). Yet again their is yogurt, blue cheese, lactic acid fermented vegetables, etc., etc.--Aspro (talk) 18:43, 19 February 2017 (UTC)[reply]

Many foods contain a small portion of microorganisms, but that doesn't mean those would taste good when isolated. StuRat (talk) 19:55, 19 February 2017 (UTC)[reply]

And I'd bet much of the home sapiens population would dislike the taste of blue cheese. Maybe the Quorn species wouldn't be bad for most of humanity. Or the baker's yeast species (I forgot about yeast). If it tastes like the dry yeast packets then I'd say it's not bad. Sagittarian Milky Way (talk) 20:10, 19 February 2017 (UTC)[reply]

Bet most home sapiens can't enjoy a late-night supper with some really good Stilton and a wee dram or two of a really good double distilled malt (which imparts a heavenly peaty taste). Until they have tasted ambrosia they are just treading water, on this, their short sojourn through-this-world. Make the most of of a very short life and live a little; and dare to dip into the cornucopia. Enjoy! .--Aspro (talk) 20:46, 19 February 2017 (UTC)[reply]

Pro tip: Do not eat too much yeast. If you drink 2 cups of Snapple and swallow a 21 gram packet it'll ferment in your stomach and carbon dioxide will keep burping out. I imagine that 0.2 kilos of yeast and 0.2 kilos of sugar would be inadvisable. Sagittarian Milky Way (talk) 21:22, 19 February 2017 (UTC)[reply]

I think you have just invented the next "challenge" for teenagers to torment themselves with ;) Wnt (talk) 21:40, 19 February 2017 (UTC)[reply]

This does sound like great fun although the desired (?) result may be difficult to achieve. The stomach is a highly acidic environment and IIRC from my homebrewing days fermentation stops at pH of 4-ish and below. Shock Brigade Harvester Boris (talk) 23:11, 19 February 2017 (UTC)[reply]

Well, maybe yeast and its archrival baking soda/powder can collaborate on this one. ;) Wnt (talk) 00:39, 20 February 2017 (UTC)[reply]

Nutritional yeast is added in fairly large quantities to many recipes. I think it tastes good. Some people put it on popcorn. See also Spirulina_(dietary_supplement)#Historical_use, a bacteria the Aztecs used to cultivate and eat. SemanticMantis (talk) 23:01, 19 February 2017 (UTC)[reply]

Penicillium camemberti, Penicillium roqueforti, Penicillium glaucum, etc. --Jayron 32 01:31, 20 February 2017 (UTC)[reply]

Spirulina_(dietary_supplement) can be eaten straight. Tellingly, the article doesn't mention how it tastes. ApLundell (talk) 14:35, 20 February 2017 (UTC)[reply]

Need bibliography about how, when and why to apply statistics

Need bibliography about how, when and why to apply statistics: what the median and the mean tells us, correlation not implying causation, problems that are intractable for stats, and so on.--Dikipewia (talk) 19:00, 19 February 2017 (UTC)[reply]

See arithmetic mean, median, correlation to start. As for when not to apply stats, one of the biggest problems is too small of a sample size. If you flip a coin and it comes up heads 9 out of 10 times, you can't conclude that it will continue to happen 9/10th of the time. You probably need over 1000 tosses to consider it a reliable sample size. (If it comes up heads or tails 900 of those times, it's probably not a fair coin.) Then there's the problem of introducing statistical bias, especially problematic when dealing with people, such as doing surveys. There's also the issue of cherry-picking. For example, many stocks can be said to have performed well or poorly, depending on how far back you go.

One interesting problem that can't be solved by stats is the likelihood of extraterrestrial life. Since we have only one sample case to work with (Earth), or perhaps a few more if you include our negative results (so far) looking for life elsewhere in the solar system, we really have no idea how common life is in the universe. See Drake equation. StuRat (talk) 19:11, 19 February 2017 (UTC)[reply]

That's a great post Stu, thanks! SemanticMantis (talk) 22:52, 19 February 2017 (UTC)[reply]

It would be very useful if the OP provided more details of why this bibliography is needed. Statistics is an incredibly complex area, although the OP's question seems to focus on the most basic of statistics. A couple more articles of relevance at this level are Parametric statistics, Nonparametric statistics, Statistical power, and Sample size - the last 2 are especially useful to avoid ethical concerns if the research involves animals . DrChrissy ^(talk) 20:02, 19 February 2017 (UTC)[reply]

I already included that last link. StuRat (talk) 20:12, 19 February 2017 (UTC) [reply]

I see you did - apologies for the repetition. DrChrissy ^(talk) 20:16, 19 February 2017 (UTC) [reply]

Also, Correlation does not imply causation. Loraof (talk) 22:00, 19 February 2017 (UTC)[reply]

Some additional reading: Inference, frequentist inference, statistical hypothesis testing, frequentist, bayesian, statistical regression, statistical model. We do have a whole category Category:Statistical_theory that you can browse using the little box at the bottom of an article like statistical theory. And yes, we can probably do better than a shotgun approach if you let us know what area your interest is in, or perhaps why. SemanticMantis (talk) 22:57, 19 February 2017 (UTC)[reply]

Huff's How to Lie with Statistics should be required reading for everyone, everywhere. Shock Brigade Harvester Boris (talk) 00:54, 20 February 2017 (UTC)[reply]

Apollo 8

Apollo_8#Lunar_orbit "The SPS ignited at 69 hours, 8 minutes, and 16 seconds after launch and burned for 4 minutes and 13 seconds, placing the Apollo 8 spacecraft in orbit around the Moon. The crew described the burn as being the longest four minutes of their lives. If the burn had not lasted exactly the correct amount of time, the spacecraft could have ended up in a highly elliptical lunar orbit or even flung off into space. If it lasted too long they could have struck the Moon."

How did they calculate the exact burning time of 4 minutes and 13 seconds? --IEditEncyclopedia (talk) 19:07, 19 February 2017 (UTC)[reply]

Remember following this mission as it was happening. It was calculated on Earth by computer and relayed up to them before disappearing out of contact with Earth. They then had to time the burn on the Swiss made 'mechanical' wristwatches made by Omega -as the US did not have digital wristwatches at that time. planet-omega, space. This was the technique use on all Apollo missions. Newtons laws gave them all the algorithms they needed and Turing's work told them how to build the computer. Plan B was to use some plastic bags to defecate into; in case plan A didn’t work. --Aspro (talk) 19:32, 19 February 2017 (UTC)[reply]

They had watches, but the Apollo spacecraft had a digital clock (in the computer). I'm pretty sure that the start time and length of the burn were controlled by the computer. Bubba73 ^{You talkin' to me?} 01:08, 20 February 2017 (UTC)[reply]

Also, I don't think that the article is right about it having to be that exact. For one thing, it does NOT say that in the reference. Secondly, if it is off a little one way or the other, it would just go into an orbit of a different size. Bubba73 ^{You talkin' to me?} 01:13, 20 February 2017 (UTC)[reply]

On your second point, absolutely correct. They could make as many corrections as they like later on, until the fuel is exhausted, if a particular orbit is required. The reason to get it right the first time is that it is more efficient. On the other hand, mid course may not be (almost certainly is not) the most efficient place to do it either. Greglocock (talk) 07:44, 20 February 2017 (UTC)[reply]

In fact they did make a correction to the orbit later. They wanted a circular orbit 60 or 70 miles above the surface. The initial orbit was good at the perilune but 90 or 100 miles too high at the apolune. Another short burn made it more circular. Bubba73 ^{You talkin' to me?} 16:05, 20 February 2017 (UTC)[reply]

Question about cryogenic preservation and transgender people

Out of curiosity--if a transgender person gets cryogenically preserved after they die (especially if only one's head or brain is cryogenically preserved), would it be possible to use stem cells or whatever to grow a new body for this person which matches his or her gender identity? Or would that create a risk of rejection due to the chromosomes (XY and XX) not matching?

Any thoughts on this? Futurist110 (talk) 19:11, 19 February 2017 (UTC)[reply]

So you would replace an X with a Y, or vice versa, right ? In the case of a male-to-female change, you could double up the X in their XY combo to create an XX, but you would run the risk of making X-linked recessive inheritance problems worse. An alternative would be a donor X or Y chromosome, as needed. See Chimera_(genetics)#Humans for evidence that a person can survive with two or more sets of genes (of course, this doesn't mean that all combos are viable). The bigger problem would be how to get the frozen brain into the new body, including the moral dilemma of what to do with the new brain that developed with the new body. Presumably the brain's development could be halted early on, but that would still be an ethical problem for many. StuRat (talk) 19:32, 19 February 2017 (UTC)[reply]

This is very speculative; I would be highly surprised if transplant rejection exists in a world where adult cloned bodies can be grown or tissue printer manufactured from scratch - but I cannot exclude it categorically. Technically little of the Y chromosome is actually needed for apparent maleness; the SRY gene handles most of the obvious morphological details. Functional testes would need other important genes. To make a female, the SRY could be inactivated with similarly little effort. Repairing and reviving the frozen brain is almost surely going to be the tough part. So far it looks like most tissues can be put through a tissue printing process at the cell level of resolution and the cells can figure out where they were supposed to be. But if you do that with a brain you have a blank slate, because the connections are synapses, i.e. subcellular, and long term potentiation similarly is not going to be represented with a newly printed cell. Some will say that any substitution of tissue at all makes it a "different person". (Others like me will say it's all atman so the cryonics is only potentially useful as a means of memory storage) But if you want to go through cell by cell and fix whatever freezing does to them, that could be a very finicky process... Wnt (talk) 21:36, 19 February 2017 (UTC)[reply]

American '80s car

What car is this on the right? https://scontent-lht6-1.xx.fbcdn.net/v/t31.0-8/16715950_10212273380500364_6250702806737612264_o.jpg?oh=fd4898f3e20308f8e608768000f67040&oe=592C9E04 212.30.205.63 (talk) 19:27, 19 February 2017 (UTC)[reply]

Looks like a Mercury Grand Marquis, to me. Compare: [18]. StuRat (talk) 19:36, 19 February 2017 (UTC)[reply]

Yes! you found it, thank you so much!! 212.30.205.63 (talk) 20:08, 19 February 2017 (UTC)[reply]

You're quite welcome. StuRat (talk) 20:10, 19 February 2017 (UTC)[reply]

Resolved

What is the reason that it's more healthy to eat unsaturated fats than saturated fats?

What is the reason that it's more healthy to eat unsaturated fats or trans fats than saturated fats? In the end of the day all of them fats (or lipids). They have the same atoms just with a minor different structure as it's easy to see on wikipedia articles and on google images. In addition I've read that in the room temperature (25C degrees) the saturated fats are solid (because of their straight chains) - such as butter etc. while those which are unsaturated fats are tend to be liquid in room temperature (because of their bent tails) - such as olive oil etc. Then I'm asking another question: Is there relation or correlation between the recommendation to avoid of saturated fats to their character to be solid (and maybe because of that they sink in the blood vessels and make troubles) or no relation between this character to the mentioned recommendation? 93.126.88.30 (talk) 20:34, 19 February 2017 (UTC)[reply]

Trans fats are generally considered much worse than saturated fats, not comparatively good like unsaturated fats. But "The exact biochemical methods by which trans fats produce specific health problems are a topic of continuing research" (see Trans fat § Health risks). And there are even several subclasses of unsaturated that have various patterns of effects. For example: "Polyunsaturated fats protect against cardiovascular disease by providing more membrane fluidity than monounsaturated fats, but they are more vulnerable to lipid peroxidation (rancidity). On the other hand, some monounsaturated fatty acids (in the same way as saturated fats) may promote insulin resistance, whereas polyunsaturated fatty acids may be protective against insulin resistance." (see Monounsaturated fat § Relation to health). Some of our articles only go so far as to note correlations with health effects, rather than being able to explain the actual biochemical/biophysical processes. DMacks (talk) 22:33, 19 February 2017 (UTC)[reply]

See here, 13 minutes 40 seconds into the video. Count Iblis (talk) 00:16, 20 February 2017 (UTC)[reply]

There isn't any reason, because it (unsaturated better than saturated) is almost certainly false. (Basically everyone agrees that trans fats are bad, worse than the other two.) What happened is that a few decades ago a vocal minority of scientists, mainly in the USA, jumped the gun and decided what was right based on equivocal evidence. Their (still) unproven (more like disproved) hypotheses became institutionalized dogma - for instance they came up with dietary recommendations which virtually certainly have done more harm to public health than good - e.g. leading to insouciance about carbohydrate intake for diabetics that would have horrified earlier generations. (They horrify me!) But Slllooowwwwllly minds & institutions & recommendations change - e.g. European countries and recently the USA have stopped giving dietary recommendations on cholesterol & demonizing it. Read e.g. Gary Taubes & many others on the history.

The far more important metaprinciple to absorb is - Science sometimes goes Backwards. The human race, no more than an individual is destined to always Do Things Right. The human race gets something right, a brilliant genius or a school of researchers or many competing thinkers discover something, enlighten everybody & then ...... everybody kinda forgets it, it becomes unfashionable, they stop understanding it (or more accurately, enough realize they never did understand it well enough). It is replaced by something inferior, sometimes grossly inferior & a generation can become attached to the inferior cognition, usually because they never even heard of anything else. But however long it takes, the steps forward tend to exceed the steps backward; while individuals often emotionally cannot, the human race as a whole does admit: "Mistakes were made." But again, denying that many spheres of science sometimes go full speed backwards - in many fields & not just in the Distant Past of Yore, but Right Now - is to not understand history & philosophy & the history & philosophy of science, for there really isn't any other way for things could be.John Z (talk) 05:51, 20 February 2017 (UTC)[reply]

But that's not because unsaturated fat isn't so bad, rather it's because unsaturated fat is not as good for us as we used to think, see here: "The Mediterranean Diet is healthy IN SPITE OF olive oil, not because of it." So, the best diet you can eat is a salt, sugar and fat free diet where all your essential Omega-3 and Omega-6 fats come from what is in the vegetables and grains. Count Iblis (talk) 06:43, 20 February 2017 (UTC)[reply]

See cherry picking. There's enough individual studies to back up any statement you wish to make. Understanding comes not from individual studies but rather from the preponderance of all studies. --Jayron 32 13:52, 20 February 2017 (UTC)[reply]

Temperature of boiling liquids

When we boil water in a pot, at what temperature is the surface or middle of the water in the pot when the bottom starts to bubble?

If we heat two mixed liquids (like water and alcohol, which evaporate at 100 and 79 C respectively), will the boiling point of both change? Would the whole alcohol evaporate before water starts evaporating? --Llaanngg (talk) 21:46, 19 February 2017 (UTC)[reply]

For your second question, you may want to read our Azeotrope article. CodeTalker (talk) 22:04, 19 February 2017 (UTC)[reply]

There's no easy single answer for your first question. Heat transfer mechanics is extremely messy and complex and requires some serious advanced mathematics to model, especially for fluids such as water. Convective heat transfer is where you want to start your studies. Good luck. --Jayron 32 01:27, 20 February 2017 (UTC)[reply]

Also, for the theory behind boiling points of mixtures, see Eutectic system. This is mostly refered to when melting Alloys but it is the same principle for many other nonmetal elements. --Kharon (talk) 02:29, 20 February 2017 (UTC)[reply]

February 20

Where did electronegativity come from?

Everything I've seen tells me what it is and how it affects chemical bonds, but where did the idea come from? Why did anyone think it was necessary? I read something about energy levels, which makes me think somebody must have measured something, but what did they measure and how did they measure it? Bogwon. — Preceding unsigned comment added by 50.43.36.155 (talk) 03:54, 20 February 2017 (UTC)[reply]

Our "Electronegativity" article has historical notes and cites for them if you want to learn more. DMacks (talk) 05:12, 20 February 2017 (UTC)[reply]

While no one doubts the meaning of "positive" applied to numbers (root is Latin positivus[19]), its usage for a particular Electrical polarity seems to have arisen quite arbitrarily, around 1755 according to the etymology reference. That was before the main electrical current carrier, the Electron was found and has lead to generations of students being taught that "Electric current is electrons flowing in the opposite to conventional current direction". It gets worse when we grapple with n-type and p-type doped semiconductors in explaining how Transistors work. Blooteuth (talk) 10:34, 20 February 2017 (UTC)[reply]

One of the best (and surprisingly easy to follow) books on this subject is The Nature of the Chemical Bond by Linus Pauling. Most of what is taught in a typical first year chemistry class is straight from Pauling's work. --Jayron 32 11:44, 20 February 2017 (UTC)[reply]

Biology

Hormones — Preceding unsigned comment added by 197.210.44.44 (talk) 15:40, 20 February 2017 (UTC)[reply]

Hormones. StuRat (talk) 15:44, 20 February 2017 (UTC)[reply]

What dangerous in Diesel exhaust fluid to human body?

According to the article (Diesel exhaust fluid) it contains 32.5% urea and 67.5% deionized water. Urea we have naturally in our body, then I think the thing that can damage or interrupt homeostasis is the deionized water. Isn't it? --93.126.88.30 (talk) 16:05, 20 February 2017 (UTC)[reply]

Just because something is found in the human body, in some concentration, doesn't mean it is safe at any concentration. For example, you probably have some arsenic and uranium atoms in your body. StuRat (talk) 16:10, 20 February 2017 (UTC)[reply]

To support StuRat's statement, please read The dose makes the poison. Also, understand why urea is in your body. Urea is toxic, and it's main function is to be a water-soluble way of flushing nitrogen wastes out of your body. Your body doesn't use it so much as get rid of it as best as it can. See also Urea cycle. --Jayron 32 16:16, 20 February 2017 (UTC)[reply]

"The dose makes the poison". Diesel exhaust fluid is urea, diluted with water until it is acceptably safe to handle. It is still far from safe. This 1/3rd urea solution is considerably more concentrated than even "strong" human urine (3× - 10×). I believe it's similar to that of some pigs, and pig urine will be familiar to anyone with a farming background. Urea creams are used as a topical skin treatment for some conditions such as psoriasis for their debriding effect. Regularly handling exhaust fluid (i.e. mechanics and fuelling staff, rather than domestic drivers) is known to give rise to dermatitis.

The body only contains urea because it's trying to excrete it. Andy Dingley (talk) 16:21, 20 February 2017 (UTC)[reply]

Does long-term urea touching have a dermatitic effect besides osmosis? Does the bladder, kidney, ureter, prostate and urethra have special urea-resistant cells? Sagittarian Milky Way (talk) 16:29, 20 February 2017 (UTC)[reply]

Please read the article Urinary bladder and ureter which directly address your question. Urine does not normally come into contact with the prostate gland, which is separated from the urine stream by the valves of the Seminal colliculus. --Jayron 32 16:45, 20 February 2017 (UTC)[reply]

Multiple infections simultaneously

Is it possible for a human to have multiple infections at the same time caused by different bacteria or virus? For example, maybe a cold from other infected people, a parasitic infection from ingesting contaminated food and another systemic infection (maybe tetanus) from a wound. If this is possible, how would the immune system react to it? Would it cause a major life threatening illness or would it not make much difference? 2A02:C7D:B97E:DF00:C401:C078:9E85:9104 (talk) 22:28, 20 February 2017 (UTC)[reply]

I have several ancestors who caught the flu during the post-WWI pandemic. The one that died was already suffering from tuberculosis. So, the answer is Yes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:31, 20 February 2017 (UTC)[reply]

Each infection the immune system has to fight weakens it, making the individual more susceptible to further illnesses. Remember that HIV doesn't in itself kill you. It just makes you vastly more open to all the other bugs that surround us. Rojomoke (talk) 23:48, 20 February 2017 (UTC)[reply]

I disagree with your first sentence. Many infections cause an immunity to that disease in the future, and potentially to related diseases. Famously, a mild cowpox infection provides immunity to smallpox. StuRat (talk) 01:01, 21 February 2017 (UTC)[reply]

Superinfection. Fgf10 (talk) 08:07, 21 February 2017 (UTC)[reply]

each person has thousand of micro punctures developing in the vascularisation - every day?

I saw this video (8:20) in which the lecturer say that "every day even in the perfect healthy person, thousand of micro punctures developing in the vascularisation.". Is there any source that supports that claim? 93.126.88.30 (talk) 22:29, 20 February 2017 (UTC)[reply]

February 21

Wendy's Frosty

I'd like them better without trans fats, which they say they have, at least in the large size: [20].

I've noticed if I put one in the fridge for later, it separates into a liquid with a thin skin on top. If I remove this skin, will I also remove the majority of the trans fats ? StuRat (talk) 00:31, 21 February 2017 (UTC)[reply]

Both the menu you linked to and our article Frosty (frozen dairy dessert) say it's dessert made with milk and it's frozen, strongly imply there's at least some milk fat. In fact if you check it out, the description of that page you linked to explicitly says "Nothing beats this Wendy’s original that's made from fresh Grade A milk and rich cream." In other words, you should not need to look at the nutrition info to tell you it contains transfat anymore then you need to look at the nutrition info on your 100% organic all natural ingredients ice cream or Kobe beef contains transfat.

P.S. I have zero interest in getting involved in the argument over whether or not naturally occuring transfat are as dangerous as industrially produced ones i.e. whether or not people are right to be concerned over such transfats. Simply pointing out that labelling in most places including I'm pretty sure the US [21] does not distinguish between naturally occuring and industrially produced transfats. So by definition, any product with sufficient naturally occuring transfat to exceed any nutrition labelling requirements, including many products with significant cream and some beef edit: and lamb and maybe very occasionally pork and chicken and other meat products, will have transfats so it's silly to make a big deal over the nutrition labels when simply common sense will tell you already.

Nil Einne (talk) 03:57, 21 February 2017 (UTC)[reply]

Wendy's either doesn't provide a full ingredient list of their site is broken. But if [22] is accurate, and that does list the same amount of transfats plus a similar list is elsewhere, it does seem quite likely that most or all of the transfats comes from the cream, perhaps with a small amount from processing to make the dessert. Again I'm not saying whether this means you should or shouldn't be worried, simply pointing out it's silly to be using the nutritional facts info. It's a product which contains a significant amount of cream so it also contains transfats, an educated consumer should already know this. Edit: Actually found [23] which does work properly for me and you can get stuff like [24] which seems to basically be the same ingredient list as earlier.Nil Einne (talk) 04:12, 21 February 2017 (UTC)[reply]

I've had Frostys. They're just a milkshake. You can find a million milkshake recipes online. A Frosty is perhaps a little thicker than your average milkshake, so a little experimentation with some recipes might be necessary. --47.138.163.230 (talk) 05:31, 21 February 2017 (UTC)[reply]

But that's not likely to significantly change the amount of transfat unless you use very low fat milk (which tends to significantly affect the flavour and texture). You'd need to use some sort of milk fat substitute. Nil Einne (talk) 09:05, 21 February 2017 (UTC)[reply]

Question about the Newton's Universal Law of Gravitation

Let we have

Spherical Mass M = 5.97219 x 10^24 kilograms (= mass of earth)

Spherical Mass m = 7.34767309 × 10^22 kilograms (= mass of moon)

Radius of Mass M; R = 6371 km (= radius of earth)

Radius of Mass m; r = 1737 km (= radius of moon)

Acceleration due to gravity of mass M = g1 = GM/R^2

Acceleration due to gravity of mass m = g2 = Gm/r^2

G = 6.67408 × 10-11 m3 kg-1 s-2

O/C distance between M and m = 8608 km (center to center)

This means surface-to-surface distance between M and m = 500 km. Let X be the point on the said center-to-center distance of 8608 km where both falling bodies M and m strike each other violently due to Newton’s law of gravitation (F = GMm/d^2).

Can somebody calculate the following

1- Final velocity of M at the time of hitting m

2- Final velocity of m at the time of hitting M

3- Falling time of M and m when hit each other

4- Location of point X on aforementioned o/c distance 2001:56A:7399:1200:D12B:44DC:83EE:1060 (talk) 01:34, 21 February 2017 (UTC)EEK[reply]

See the top of this page: "We don't do your homework for you." Shock Brigade Harvester Boris (talk) 02:04, 21 February 2017 (UTC)[reply]

Indeed, especially not for the MIT MOOC on Advanced Introductory Classical Mechanics. Big clue, you know something about the system you haven't considered yet. Do the lecture again. It's not exactly a trick question but it would be tricky to bumble through to the right answer. If you are on the right track it is solvable in about 4 lines. Greglocock (talk) 06:07, 21 February 2017 (UTC)[reply]

SpaceX

Why does SpaceX choose to use rocket engines to land their reuable rockets?

Wouldn't it be much more efficient if they install an air-breathing engine on (maybe) top of the rocket so they don't need to carry so much oxygen all the way up and all the way down?

The exact weight of the spent rocket is a fixed and predetermined number. They can licence a proven jet engine design and have it optimized for the home coming trip. Maybe a small engine running at the highest efficiency rpm can save much weight of oxidizer and its expensive reusable rocket engines would have more time to cool down. -- Toytoy (talk) 09:11, 21 February 2017 (UTC)[reply]