Wikipedia:Reference desk/Archives/Science/2014 February 5

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February 5

Heroin (why cook it?)

Thread retitled from "Heroin".

What's the point of cooking heroin in a spoon before injecting it? Is it basically to speed up the dissolving process for quicker injection? Is the reaction more potent when it enters the blood stream if it's warm?

Note: I'm not (I think this is obvious) a heroin addict. I don't plan to be one. I don't plan on using this information for my own use or to inject anyone else. This is not homework. Please don't hat this medeis. Not a junkie, Dismas|^(talk) 01:13, 5 February 2014 (UTC)

It's to get it to go into solution. Bad enough to be injecting it in the first place, last thing you want is particulate matter in the bloodstream. μηδείς (talk) 01:17, 5 February 2014 (UTC)

• This I think is more of a chemistry question. Good quality heroin ( the medical type) is a salt and will dissolve in cold water. Much street heroin is of the smoking type Free base. Hence the the need to add acid and heat. Citric and ascorbic are the most common but hydrochloric will yield diacetylmorphine hydrochloride (have purposely missed out how to obtain the precipitate, so don't try this at home folks). Most 'Nam' vets will tell you this because smoking heroin was all that was on offer over there. --Aspro (talk) 02:17, 5 February 2014 (UTC)

I am not quite sure how saying getting it into solution with a link is not a question of chemistry. In any case, our article doesn't give the solubility of the pure salt, but I'd be very surprised to see someone on a jones using a precious portion of a gram of heroin mixing it in a flask and hoping it all dissolves and he leaves no waste behind rather than assuring he utilises it all and gets almost all of the product by dissolving it in a very small amount of boiling water. μηδείς (talk) 04:36, 5 February 2014 (UTC)

Primitive tribes can dissolve things in boiling water but they are using a method of trial and error rather than an employing an understanding of chemical science. So, that is why I am not considering your comments as having any connection with true chemistry (no slight intended). Brown heroin (as was readily available in Vietnam) and on many street corners today, is free base. It is only good (if that is the right term) (in its bought raw form) for smoking or snorting. To inject it, it needs processing in order to provide the sort after 'hit'. Injecting dissolved brown heroin will not achieve this effect. Every Jones knows this. Boiling in a spoon with an the addition of a little acid changes the chemistry to a form that is absorbed from the blood stream rapidly – providing the sudden and sort after hit. Ascorbic appear to be the favourite as it doesn’t create a burning sensation in the vein like citric is reputed to do (COI notification: I have done some volunteer work with addicts).--Aspro (talk) 18:01, 5 February 2014 (UTC)

"sort after"? --Trovatore (talk) 04:02, 6 February 2014 (UTC)

I'm guessing that Aspro meant "sought after" and was either mis-typing it or was auto corrected by software. Dismas|^(talk) 18:21, 6 February 2014 (UTC)

Thank you for the responses. I had never seen the acid being put into the spoon. I guess filmmakers and such leave that part out in order not to be teaching people how to use drugs in their films. Films and TV being the source of my knowledge of taking heroin. Dismas|^(talk) 18:23, 6 February 2014 (UTC)

The other possibility (which I think is more likely) is , that film makers come from mainly middle class families and thus have only tried/seen pharmaceutical quality heroin being prepared. Therefore, this is what is reflect on the cinema screens. I haven't read the following link because it requires payment but it probably backs up what I am putting forward as the reality. DIFFERENT FORMS OF HEROIN AND THEIR RELATIONSHIP TO COOK-UP TECHNIQUES: DATA ON, AND EXPLANATION OF, USE OF LEMON JUICE AND OTHER ACIDS--Aspro (talk) 19:58, 6 February 2014 (UTC)

• To counter Aspro's OR, I have seen people shoot up in front of me, on at least three occasions (South Bronx, Washington Heights, Harlem), with yellow smack. They didn't add acid, but they did boil it on a spoon. Having passed Organic Chem Lab I am fairly certain they were driving it into solution regardless of the fact that they were members of the Yanomamo tribe, lol. μηδείς (talk) 21:54, 7 February 2014 (UTC)

• • Whoo, Slow down. S-l-o-w D-o-w-n. You saw members of the Yanomamo tribe in South Bronx, Washington Heights, Harlem shooting heroin? Not statistically impossible but statistically unlikely to my mind. Having seen seen (fortunately - on just one occasion) someone collapse in front of me with blue lips and in need of mouth-to-mouth resuscitation, who may not only have HIV but they also smoked like a chimney and they had not washed for several weeks (months?); it was not my OR that saved him but what I had been taught. You say (above) you saw yellow boiled. Maybe they did. Addicts like the ritual. One can cold brew coffee etc. Cold brew but the ritual amongst most civilized folk is to heat it... You say they didn't add acid – but you say it was yellow – the salt version – so it doesn't need it. You didn’t say (presuming you're middle class who wares a watch and other items) how many times did you got mugged whilst observing this?!!! So your comments suggest you were many city blocks away from the real Joneses. i.e. In civilised company (who were salary earners) that could afford weekend shoots of opiate salts and who could go back to work on Monday and did not need to resort to shooting brown heroin needing the addition of acid or robbing you. Which is what you have admitted to, because you have said it was yellow. Stop trying to prove white is really black.--Aspro (talk) 23:37, 7 February 2014 (UTC)

Thanks, User:Aspro. I had my pocket picked once (funny thing was I had $500 cash in the other pocket), had an attempted forced entry (I stabbed him with my French knife), got robbed once, and had an attempted mugging against me. In all cases I either retrieved what was taken or fought off the attacker. (On two occasions I had higher-ups from local gangs offer me (benevolent) protection, and an offer by two crack addicts once to off the guy who mugged me for a mere $50. They brought an Uzi and a .358 to show their earnest. I turned them down with a $10 tip.)

None of these was by junkies. But a pot dealer of mine did ask to shoot up, which surprised the eff out of me. I allowed him out of curiosity, and due to the fact that he was very small, and I could have drug him into the stairwell had I needed. I attended a party once in the village where people I didn't know were shooting up. And had a homeless guy who lived on the stairs between my floor and the one above who used to shoot up. I used to let him use my shower and toilet on occasion, since my bathroom was by the front door, and the rest of my apartment invisible around a hallway. He died in the hallway, apparently from a heart attack, since there was no drug paraphernalia. I also witnessed shootings and shootouts on a common basis.

You might look at the history of Mott Haven in the early 90's, described by the NY Times as the biggest open-air heroin market in the Western Hemisphere. μηδείς (talk) 21:47, 9 February 2014 (UTC)

Does the Coanda effect make pyroclastic surges hug the ground?

Since hot air normally would rise, I'd find it natural that the Coanda effect is what confines pyroclastic surges to relatively close to the ground. Is that true?--Jasper Deng (talk) 03:50, 5 February 2014 (UTC)

This source [1] makes clear that a pyroclastic surge is a mixture of hot gas and volcanic particles - the latter will add significantly to the density. AndyTheGrump (talk) 04:03, 5 February 2014 (UTC)

Long term memory

what is the real mechanism of storage of long term memory in human brain?Singh.ssm (talk) 05:23, 5 February 2014 (UTC)

Isn't it connections formed between the brain cells ? StuRat (talk) 06:52, 5 February 2014 (UTC)

Yes. Either new, or more strongly or less strongly potentiated existing synaptic connections. See long term memory. μηδείς (talk)

Spark Generator

I have completed a physics experiment. A cylinder (solid with nearly no air resistance) was dropped from the top of a free fall apparatus. I used a spark generator and a free fall apparatus to create marks on a peice of tape to measure the acceleration of gravity on earth's surface. The tape was marked every 1/60 second. The mark was made at the location of the cylinder during that time. What would be some errors in the experiment caused by the spark generator? For instance, do spark generators fire exactly every 1/60 seconds? — Preceding unsigned comment added by 99.146.126.108 (talk) 06:40, 5 February 2014 (UTC)

If it's using the A/C frequency from the wall outlet, then it should be quite accurate. However, the spark may sometimes deflect more upwards or downwards from the source. I'd expect more error from that. Then there's air resistance to consider, so the actual acceleration is less than g. StuRat (talk) 06:48, 5 February 2014 (UTC)

Also, 'g' varies considerably from place to place - depending on things like the kinds of rocks beneath your feet, your latitude and your elevation above sea level. It's possible that your answer differs from the text-book value for 'g' - yet is still an accurate measurement of your local gravitational acceleration. Gravity_of_Earth#Variation_in_gravity_and_apparent_gravity says that this variation is about 0.7% over the surface of the earth...about 0.5%.

The spark generator itself could possibly add some delay - but you'd expect the delay to be the same each time it 'fires' - so that shouldn't create an error if all you're doing is measuring the distance fallen between two sparks. SteveBaker (talk) 14:47, 5 February 2014 (UTC)

Assuming the USA electrical system is like the UK's, then the frequency of the mains will be accurately 60 Hz in the long run, but not necessarily in the short run. When demand is high, the frequency is lowered slightly, and this is caught up at times of light load.--Phil Holmes (talk) 18:01, 5 February 2014 (UTC)

The delay will vary slightly from spark to spark. This variation is called the jitter of the spark generator.--Srleffler (talk) 18:15, 5 February 2014 (UTC)

He didnt actually do the experiment. This is obviously a homework question.109.144.144.200 (talk) 00:35, 6 February 2014 (UTC)

Our OP clearly states (in the first and third sentences) that (s)he actually did do the experiment - and you are required by Wikipedia guidelines to Assume Good Faith - which means not accusing our questioners of lying to us! SteveBaker (talk) 13:32, 6 February 2014 (UTC)

How Exactly Did Gay Males Reproduce Several Centuries Ago and Beyond?

I apologize if this question is perceived as offensive, but I do think that this is a legitimate question to ask here. How exactly did gay (not bisexual) males reproduce back in the old days, centuries before modern technology such as in-vitro fertilization became developed and available? For reference, an example of a gay male who reproduced several hundred years ago was Philippe I, Duke of Orléans, so obviously this event indeed occurred sometimes even several centuries ago and perhaps even earlier than that. Futurist110 (talk) 06:46, 5 February 2014 (UTC)

I think gay men who are incapable of having sex with a woman are relatively rare. In that case, I suppose they could always have somebody else do the deed and they could take the credit. StuRat (talk) 06:51, 5 February 2014 (UTC)

How exactly would they get sufficiently aroused, though? Would they be able to successfully pretend that the woman that they are sleeping with is a man, or what? (For instance, I myself, as someone who is not attracted to males, might find it extremely hard, if not impossible, to successfully ejaculate if I ever actually have intercourse with a male.) Yeah, taking credit for another man's children is certainly possible, though. Futurist110 (talk) 07:06, 5 February 2014 (UTC)

I suppose there's always a 3-way, with another man providing the arousal for the gay man. StuRat (talk) 17:01, 5 February 2014 (UTC)

Yeah, that might work. Out of curiosity, can't a gay guy also have gay sex and/or masturbate and then rub or stick in his dick and/or his hand(s) on/into his wife's private areas right afterwards? (Sorry for being graphic here--I am simply trying to make a point.) Can this work? Granted, this solution might be a little creative, but still. Futurist110 (talk) 17:52, 5 February 2014 (UTC)

Renly Baratheon would have gotten away with it, too, if it weren't for those meddling shadows. InedibleHulk (talk) 17:13, 5 February 2014 (UTC)

The same way as straight ones, but with fewer tries.

Or their sisters did so for them. You might also read kin selection and hybrid vigor assuming you think there's a gene that causes homosexuality. μηδείς (talk) 06:52, 5 February 2014 (UTC)

Why exactly with fewer tries? Futurist110 (talk) 07:06, 5 February 2014 (UTC)

Thanks for these articles. I will make sure to read them. As for their sisters doing the deed, you mean having their sisters sleep with someone else and then falsely claiming to be these children's actual father, correct? Yeah, this might work, especially if one replaces the word "sisters" with "wives" here, considering that I don't see how a male would be able to marry his sister back then (and since at least some of the children which gay males fathered back then were indeed legitimate, as in being born within a marriage). Futurist110 (talk) 07:06, 5 February 2014 (UTC)

Your question was ambiguous. If you meant produce a live heir on their wives, the answer was with less enthousiasm than straight husbands would, but it only takes one or a few successful attempts. If the question was, how did the gayness gene (assuming you believe in that) get passed on, it would be kin selection--the children of gay aunts and uncles somehow benefitted from some other trait, like higher intelligence or higher fertility or some other reproductively beneficial effect of the gene. I.e., hybrid vigor; two copies of the gene makes uncle gay, but one copy makes dad smart, or mom fertile, etc., μηδείς (talk) 07:17, 5 February 2014 (UTC)

My dad figured getting married and acting straight would help him "kick the habit". It didn't (for long), but he managed to make me. If there's a hereditary gay gene, it didn't work, either. InedibleHulk (talk) 07:15, 5 February 2014 (UTC)

You are aware that gay people are the same species as straight people, and so we "reproduce" in the same way. Regarding the comments about enthusiasm, does this mean that straight men masturbate with "less enthusiasm" because they are with a hand? Gay men are equipped with imagination, like many homosapiens, and there are certainly 100% gay men who have been fooling their wives and female lovers for generations. Quietmarc (talk) 00:27, 6 February 2014 (UTC)

Given that hands resemble women much more than they do men, I would assume straight men are much fonder manual masturbators. μηδείς (talk) 01:18, 6 February 2014 (UTC)

Point is that lots of people, throughout history, have been "enthusiastically" having sex with lots of people, animals, and things regardless of their attraction to it. This is the science desk, so it would be nice if people used science to answer questions, even questions as ill-informed as this one.Quietmarc (talk) 02:54, 6 February 2014 (UTC)

Your point is unclear, are you asking that we do an experiment? Are you saying kin selection and hybrid vigor are not scientific answers? There's also heterozygote advantage to look at. μηδείς (talk) 03:06, 6 February 2014 (UTC)

I am proposing that people do not speculate about other people as if they were zoo animals. Your links were helpful, the other comments were not. "Supposing" what gay people do or "debunking" a "gay gene" based on one's personal family history are neither respectful nor scientific.Quietmarc (talk) 03:45, 6 February 2014 (UTC)

I am queer myself, and happy about that fact. Among other things, I have a bachelor's in biology, and I have read on this subject for decades. I don't get the impression anyone here is treating people as zoo animals. I wouldn't get too worried over people's comments, although references and links do help. My only personal problem with the idea of a gay gene, and the reason for my scare quotes, is that looking at a single locus for a very complex phenomena that probably has many, many causes like cancer or diabetes, rather than one cause, like chicken pox, is a fatal oversimplification. And, no, I am not comparing homosexuality to diseases, so don't get upset at my biological analogy. It is easy to be suspicious of people's comments on the internet, but I don't see anyone above trying to be disrespectful or abusive. μηδείς (talk) 04:04, 6 February 2014 (UTC)

Unfortunately, offence can be given without it being intended. I'm happy that you were not offended, I, however, was. Whether you are queer or not or happy about being queer or not does not strike me as relevent. Speculating what gay people may or may not do or may or may not have done, as if they are not even in the room (so to speak), can appear offensive to those who have been marginalised. It is interesting that rather than using any of the many, many human traits that are genetically complex, though, you chose to use illnesses to illustrate your point. I believe that no one here intends to harm, but intent is not magic, and as I said, offence can be given accidently. It might bear mentioning that our current ideas about sexuality are likely socially constructed: homosexuality is a new term, and many (most, probably all) cultures through out history have had a wide spectrum of sexual behaviours, it's foolish to assume that our current framework is the best, which would make the OP's original question even more meaningless.

Again Medeis, your links struck me as helpful. It's everything else in this thread that was not.Quietmarc (talk) 04:33, 6 February 2014 (UTC)

As for the use of diseases for analogy, (true or near-)exclusive homosexuality is a deviation from the norm. Most deviations from the norm are diseases. There are also things like genius or giantism that people might not consider undesirable. But if you want science you have to leave your personally being offended out of the question, and think objectively. There's no denying diabetes and homosexuality are both syndromes with multiple causes.

Your last point is one I can agree with heartily, although I would say the problematic word is "gay", not "homosexuality". (The latter is a pretty objective term biologically, while "gay" is a modern Western social construct.) You are absolutely right that views that aren't fully synchronic and diachronic, and don't look at our biological relatives, are not fully integrated scientific views. μηδείς (talk) 04:44, 6 February 2014 (UTC)

This is not a forum, so I'll wrap up my participation here now. I think the idea that "most deviations from the norm are diseases" is a potentially harmful generalisation, and while I'd agree that most diseases may be a deviation from the norm, the opposite is not necessarily true. Red hair is not a disease. Left-handedness is not a disease. Generalisations like this have been used historically to harm groups of people, especially when we are only beginning to have an idea of what "normal" is (the animal kingdom as you point out is full of surprises). Further, science is a human endeavour and is not immune to bias. If homosexuality and diabetes are both to be considered as syndromes, I'd suggest that is not cold, dispassionate science, it is human (specifically heterosexist) bias intruding into our understanding of the world. This is a giant tangent and I'd be fine with discussing this elsewhere.

I take your point regarding homosexuality vs gay, with a lot of caveats, but again, not a forum.Quietmarc (talk) 05:10, 6 February 2014 (UTC)

Yes, agreed this is not a forum, and agreed deviation from the norm is not the definition of disease, it's just I think most clear syndromic examples of that are diseases. μηδείς (talk) 05:20, 6 February 2014 (UTC)

I can only say that I've never seen a remotely persuasive answer to the evolutionary biology of homosexuality. Homosexual behavior in animals demonstrates that homosexuality does not exist solely, probably not even primarily, due to behavioral suppression under oppressive regimes. Kin selection is a very controversial concept, and I can't picture a compelling explanation why any sexual characteristic of women with a gene necessitates taking men with the gene out of the gene pool. After all, the whole point of having sexes is that they can evolve different characteristics. The review cited in Homosexuality#evolutionary perspectives isn't a bad one, and gives a number of other explanations... none of which really seem very persuasive to me. Even the most extraordinary notions that I can speculate (like endocrine disruptors being widespread in the environment) are hard to hold up: the range of sex hormones in invertebrates seems quite different from those of mammals, and you'd have to suppose that there is some undiscovered universal sex hormone target in all Metazoa bound by some contaminant in the environment. The bottom line is, it is still an absolute mystery. Go ahead - think of creative explanations, bash your brain against this obstacle, maybe it will open up for you and you can lead us to an answer, but if so, you'll be the first. Wnt (talk) 05:54, 6 February 2014 (UTC)

Wouldn't the simple answer be that, based on empirical evidence, homosexuality is influenced by several factors and maybe the least of which is genetics?165.212.189.187 (talk) 17:54, 6 February 2014 (UTC)

Well, you can say it's just random variation, but... that begs the question of why it would be so difficult. For example, we expect that very, very often, a baby bird will turn out to be able to fly, despite all the ways in which the mechanism could go wrong. Genetically speaking, the pressure for animals to reproduce is even stronger than the pressure for birds to fly, but surely getting mating behavior to be functional in reproduction is not difficult compared to flying. There are hundreds of millions of homosexuals ... how many people are there who actually can't tell a man from a woman? So I'm not any more convinced by that kind of explanation than the others. Wnt (talk) 20:35, 6 February 2014 (UTC)

Two points. First, kin selection is hardly controversial itself. It explains eusociality in insects an mole rats. The use of the concept to explain homosexuality is a supposition, and one that's likely false, unless it can be proven that grandparents with a gay child tend to have more grandchildren than grandparents who don't have a ay child. Heterozygote advantage is a much more likely mechanism, but it's also speculation.

The second point is there is no simple answer because homosexuality is not one thing. Effeminate gay men who assume a female gender role and are only passive partners in sex may simply have been feminized during early development by genes or environment. Masculine men who simply prefer the way other men smell may be targeted to male, rather than female pheromones. Both these "types" if they exist, may end up being exclusively homosexual without sharing an underlying cause for the overt behavior. Given many people know of their same sex attraction long before they even know what sex is, and given heterosexual men don't usually report that at a certain age they "chose" to be heterosexual, i does make sense to look for biological causes at whatever level, psychological, physiological, hormonal, developmental, etc. μηδείς (talk) 20:48, 6 February 2014 (UTC)

Well, eusociality occurs in insects where sterile haploids are more closely related to their diploid family members (haplodiploidy). The naked mole rats are an exception - however, all the females can potentially become queens, so this is really not much different from the harems of males of other species. The females avoid breeding because they'll get put in their place if they try. Depending on environmental conditions, there can be more outbreeding. By contrast, among homosexuals there are a lot of Rock Hudsons who don't have zero chance to reproduce unless they stay 100% gay, who aren't simply waiting for an opportunity to change role and move in on the women. It's just not the same situation. And as far as multiple causes - if that turns out to be true, it doesn't make the situation more comprehensible, but more mystifying, because then there are two ways that a genetically lethal phenotype is carried at an unrivalled high frequency in the population! Wnt (talk) 04:04, 7 February 2014 (UTC)

Let me re-emphasize that you said kin selection is controversial--it's not. And I said it's a sometimes proposed explanation that's likely false as regards homosexuality, yet you still correct. Furthermore, "gay" is not one phenotype. It's likely at least four or more mechanisms that lead to a trait, just like grey, albino, Pinto and Lippizaner horses have white coat as adults. μηδείς (talk) 01:27, 8 February 2014 (UTC)

Hmmm... it's funny. It sounds like we're arguing but we're really not; we're just speaking a bit differently. Wnt (talk) 03:03, 8 February 2014 (UTC)

Oh, no. I am always righter-than-thou. So, perhaps you are sleep-arguing, and just don't realize it...? You may want 12a, next door. μηδείς (talk) 03:43, 8 February 2014 (UTC)

Britain's sea erosion

Hello sciency people and enthusiastic amateurs.

Loads of news stories in Britain in recent weeks about sea defences being washed away, along with significant sections of cliff, beach etc.

My simplistic understanding is that material destroyed in one place comes ashore elsewhere, so that Britain is neither shrinking nor expanding.

Is that right, or is there a nett gain/loss for the British mainland?

And where are the main areas of deposition and erosion for Britain?

Cheers --86.12.139.50 (talk) 15:33, 5 February 2014 (UTC)

1) The land washed away may be deposited elsewhere, as sand bars, etc. Erosion would be expected to eventually result in the grinding down of all land into the sea. It's only the forces which cause uplift of the land, like collisions of tectonic plates or volcanoes, which fight this tendency. So, if an area ceases to be geologically active, erosion will eventually grind it down into the sea. You can see this process in action in Hawaii, where the smaller Hawaiian islands no longer have active volcanoes, so are being eroded away into the ocean.

2) Sea level rise as a result of global climate change is expected to reduce the land area along the coasts.

3) Silt is deposited at the mouth of rivers, so you could expect land area to grow there, under normal conditions. However, when they dredge the rivers to allow for more ship traffic, this allows the silt to move farther out into the sea before it deposits, replenishing the sea floor instead of extending the land. StuRat (talk) 16:15, 5 February 2014 (UTC)

Post-glacial rebound has caused raised shorelines in many parts of Britain, still recovering from the ice age. And sand dunes have buried former villages, Forvie comes to my mind, and at Culbin Sands the estate was inundated with sand and the area is now extensive coniferous forest. Thincat (talk) 20:44, 5 February 2014 (UTC)

Also, remember that what started out as nice firm chunks of stuff, held together with rocks and vegetation turns into thin sandy mud wherever it ends up. Eventually, plant life may grow into this 'new land' and start to bind it together - but in the meantime, you're definitely losing solid ground and replacing it with muddy ooze. The good side of this is that this oozy stuff makes a great place for wetland plants to grow - and those are very good at preventing future erosion. If mankind wasn't getting in the way, everything would eventually settle down to a more stable setup. But centuries of sea defenses, dredging of channels for shipping and redirecting of natural rivers to provide drinking water and such has resulted in the coastline being changed - and without more centuries of letting it sort itself out, you're not going to have a stable situation. SteveBaker (talk) 21:39, 5 February 2014 (UTC)

I hadn't thought about it much until I saw the OP's question, so I scanned a few things.

• Coastal erosion here on Wikipedia has some good info and led to Template:Coastal geography and Category:Coastal erosion to see lots more on the subject.
• Future Flooding and Coastal Erosion Risks on Google books looks promising.
• Google Scholar search for "coastal erosion management Britain" has some free articles right on top of the list.
• A report on Guidance from the UK government on the subject.

Alas, my attention span is not big enough to read all of these. Perhaps yours is. My impression in the focus is more on erosion then deposition, so figuring out the net gain/loss is hard. Richard-of-Earth (talk) 21:44, 5 February 2014 (UTC)

This site gives a lot of relevant information, but lacks a map showing those parts of the coastline subject to the most erosion and those subject to deposition. Coastal erosion maps can be accessed here and there is more relevant information here. This site gives some information on so-called "coastal erosion hotspots", but I'm unsure of its reliability. There's a more academic study here, and some more information here. Ghmyrtle (talk) 22:02, 5 February 2014 (UTC)

• I agree that in general plate tectonics is required to raise mountains. Note in that article that Britain lies near the edge of a plate that is spreading from a center in Iceland - it is not likely to become the next Himalaya any time soon. There are some events that theoretically could raise mountains in Britain again, such as a hotspot (geology) happening to form beneath the islands, or maybe delamination (geology) ... maybe if its continental plate fractures and a new spreading center is initiated?? But these are all very hypothetical - I haven't gone and searched for them, but I wouldn't really expect to find anything but an end by erosion in the long run. Wnt (talk) 06:07, 6 February 2014 (UTC)

DAR (what kind of fish is a)

I know that a dar is a type of fish, how come I can't find it in your wikipedia/ — Preceding unsigned comment added by 65.96.139.197 (talk) 19:27, 5 February 2014 (UTC)

Dar fish or Dar Fish Market?--Aspro (talk) 19:46, 5 February 2014 (UTC)

Instead of a dar fish, do you perhaps mean dartfish? Red Act (talk) 22:07, 5 February 2014 (UTC)

Well, that's the problem with common names, isn't it? We do have redirects for common names to scientific names, but articles are always named for the scientific name of the organism. We do have a List_of_common_fish_names#D, which suggests common dab or dartfish as the closest matches do "dar". The only other thing I can think of is Hawaii's Department of Aquatic Resources, which goes by DAR [2]. SemanticMantis (talk) 20:15, 5 February 2014 (UTC)

There is also a type of fish curry, with several different spellings/names known as "Masalay Dar Fish", or "Masaledar Fish". For example, see here: [3]. As I understand it, "Dar" is part of the name of the dish, not the fish. SemanticMantis (talk) 20:23, 5 February 2014 (UTC)

Another possible option would be the gar fish. Justin15w (talk) 20:42, 5 February 2014 (UTC)

LASIK. (and depth perception)

Thread retitled from "LASIK.".

In LASIK#Onset_of_presbyopia, we describe a technique to use laser vision correction to 'fix' both nearsightedness and long-sightedness by zapping one eye to the ideal distance vision prescription and the other to a reading glasses prescription. Our article says that this is well-tolerated by patients who have it done.

I wonder what happens to their depth perception though...seems like it would be hard to fuse a stereo image at a distance where one eye produces a sharp image and the other a super-blurry one.

SteveBaker (talk) 21:43, 5 February 2014 (UTC)

"Monovision" contact lenses are basically the same deal.

Here's a publication by the American Association of Optometry saying that monovision contacts reduce depth perception. [4]

And Here's the NTSB report on Delta Flight 554, blaming monovision contact lenses for a non-fatal crash. (Sounds like it wrecked the plane, though.) I think it's more about an optical illusion produced by the mismatched eyes, and not actual (stereoscopic) depth perception which would be non-existent (or nearly so) at the range they're talking about. [5]

APL (talk) 23:50, 5 February 2014 (UTC)

I get the same effect when I wear one contact lens for long-distance vision, and leave the other out for short-distance vision. Stereo-optics is just one way to determine depth. Judging distances by object's relative size is another common one. This works well for driving, but not so well for parking in tight spaces. I sometimes have to get out and look several times to properly judge parking distances. But fortunately I live in a city that's lost 2/3 of it's population (Detroit), so I can usually find a parking spot with nobody on either side. StuRat (talk) 05:27, 6 February 2014 (UTC)

Sounds like our article should mention this somewhere - although without a reference specifically talking about the LASIK version of this, maybe that's a bit "iffy". But people reading our article about it are going to be mislead into thinking that this is a good choice - and I'm not sure it is. SteveBaker (talk) 13:26, 6 February 2014 (UTC)

I wear contacts for monovision, and haven't noticed an effect on depth perception; perhaps I compensate with other cues, as Stu mentions. Once, upon putting on new spectacles, I was startled to find that everything appeared to be a couple of yards away: evidently I had come to rely on blur as a depth cue. (Conventional depth perception returned in a few hours.) — A schoolmate of mine had LASIK done for monovision, and says she can't enjoy 3D movies. Me, I got plenty of 3D effect in Avatar but little in The Hobbit. —Tamfang (talk) 08:51, 8 February 2014 (UTC)