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May 18

Incandescent light bulb color

The last paragraph of the intro of Incandescent light bulb says "their light color which is almost identical to the sun's spectrum". To me, a traditional soft-white incandescent bulb is distinctly yellow/orange. So what color is an incandescent soft white bulb, and how close to sunlight is it? Bubba73 ^{You talkin' to me?} 01:42, 18 May 2014 (UTC)

That's a misleading statement. See color temperature. The lower the wattage, the cooler the filament will be and the redder the light will be. The higher the wattage, the hotter the filament, and the whiter the light will be (if it was hot enough it would actually turn blue, but I don't think a filament that hot would last long enough to be practical). StuRat (talk) 01:55, 18 May 2014 (UTC)

There is a tendency for manufacturers to make lower wattage bulbs run at a lower temperature, but this is just manufacturing convenience, possibly avoiding very thin filaments. There is no logical connection between rated wattage and filament temperature. The filament will be hotter if it is run at greater than the rated wattage by applying a higher voltage. (Not recommended because it reduces the life of the filament.) Dbfirs 12:36, 19 May 2014 (UTC)

Yes, perhaps I should have added "given the same filament". Of course, a thicker filament would waste expensive tungsten (not sure if that's a significant part of the total incandescent bulb price, though) and a thinner filament would burn out too quickly, as you noted. StuRat (talk) 15:32, 19 May 2014 (UTC)

I think it's not so much about the cost of the tungsten as it is about the balance between bulb life and color temperature. A thinner filament gives whiter light and higher energy efficiency, but burns out quicker. A thicker one lasts a long time, but is redder and less efficient. --Srleffler (talk) 03:20, 20 May 2014 (UTC)

I agree the statement is problematic, I've tried to reword it to more closely follow the source but I think the problem is it's trying to summarise different ideas. The actual article more accurately describes the situation. Incandescents eare close to an idealised black body radiators, but their colour temperature is far lower than the sun. They also don't filter through the atmosphere. They therefore have a fairly continous spectrum and a near perfect color rendering index but their spectrum doesn't match the sensitivity characteristics of human vision and they appear far redder than daylight. Many people seem to prefer these redder than daylight colours, particularly for home lighting, and there's some suggestion of psychological reasons for such a preference for dim light sources (like most home lighting) but either way the preference doesn't seem to be universal. LEDs and fluourescents, even ones with a fairly high CRI still have a somewhat discontionous spectrum, although there's some controversy over how well the CRI matches subjective color rendering anyway. Nil Einne (talk) 08:25, 18 May 2014 (UTC)

My wife also prefers the soft white (yellow/orange) color, but not me. I think that is probably because that is what we all grew up on, for the most part. But to me it makes the colors of things unnatural and it is much harder for me to read my soft white than it is bright white or daylight colored lights. Bubba73 ^{You talkin' to me?} 18:24, 18 May 2014 (UTC)

People certainly look better in soft white. Under harsh fluorescent blues, people look pale and veins tend to stick out. StuRat (talk) 15:35, 19 May 2014 (UTC)

I removed the statement. The claim that the spectrum is "almost identical" to the sun's is simply false, and is not what the source said.--Srleffler (talk) 03:30, 20 May 2014 (UTC)

The brain automatically corrects the white balance, so we don't notice a big difference. To see the real difference between light from the Sun and light from an incandescent light bulb, you can take a picture with a digital camera of white objects in a room lit by incendescent light with the white balance set to sunlight. Count Iblis (talk) 15:10, 20 May 2014 (UTC)

The brain tries to correct, yes, but red objects appear brighter under a red light and blue objects brighter under a blue light, and the brain doesn't go so far as to lower the brightness of those objects, to bring everything back into balance. StuRat (talk) 15:13, 20 May 2014 (UTC)

How long would the TGV take to stop?

Hi, I'm asking this question because I'm curious about using it as a hypothetical to get students talking. How long would a train at top speed take to come to a stop on the Beijing–Shanghai High-Speed Railway, if the brakes failed, and it just rolled to a stop? How long for this one? P.S. I'm editing on a quick break, so if this question is actually answered in the articles, please just abuse the c**p out of me, and we'll all feel a lot better, right? P.P.S. Is it "in" a quick break or "on" a quick break? IBE (talk) 09:51, 18 May 2014 (UTC)

I don't think we can accurately answer using first-principles of physics. But we can inaccurately answer: you can estimate the coefficient of friction by observing:

• at maximum speed, all engine power is expended to overcome frictional losses
• P = F v
• The engine power, speed, and mass for each train can be read out of our article
• Assume that full engine power is used at maximum speed. Assume that frictional losses are identical at all speeds. These are flakey assumptions, but if you understand their limitations, you'll see exactly why the problem can only really be answered using empirical data.

With the above assumptions and about two lines of algebra, the braking distance can be solved using Newtonian kinematics. Nimur (talk) 13:36, 18 May 2014 (UTC)

(EC) Three points. One, I'm pretty sure most high speed, trains, heck most trains have multiple independent braking systems (which are frequently designed to be as fail safe as possible) making complete brake failure (meaning with absolutely nothing in the train trying to slow it down, even if it isn't enough to stop it completely under whatever conditions) difficult. See e.g. [1] [2] [3] SNCF TGV Duplex or even Railway brake#Accidents with brakes.

Two; the time taken will surely depend significantly on the conditions. For example if the train is going a slight incline going upwards it will obviously slow faster than if it's completely level which will likewise take longer than if it's going downhill. (If it's going downhill potentially it may never stop until it either derails or reaches the end of the incline. Of course if it's going uphill it may eventually start going in the other direction, but let's not worry about that.) Similarly a train going at 200 km/h is going to stop fasrer than one going at 300 km/h everything else being equal. I suspect at that level even things like if it's going in to a headwind or tail wind may make a noticable differences. Similarly while high speed trains have gentle curves (as with their inclines) I suspect turning a curve will slow the train more than if it's travelling completely straight.

Three; I'm fairly sure any maglev system will be even more complicated. In many systems I'm fairly sure braking will at least partially come from the propulsion system, but loss of propulsion will often likewise mean a loss of levitation. They are of course designed to fail safe (and some designs may maintain levitation under low speeds) so I guess may have wheels or whatever and so should keep going if this happens (and I guess may have some sort of emergency brakes for when this happens), but it's clearly far from a simple case of 'complete brake failure'.

Nil Einne (talk) 14:09, 18 May 2014 (UTC)

And the fourth point: At high speeds (80 mph or above), air resistance becomes a significant part of the "frictional losses", and that force varies directly with the square of the velocity -- so the assumption that frictional losses are identical at all speeds is completely inaccurate. I've taken the liberty of deleting the first two paragraphs of Nil Einne's response, because they duplicate the following two paragraphs word-for-word. 24.5.122.13 (talk) 00:05, 19 May 2014 (UTC)

(Aside: I was going to joke with Nil, yes, I thought you tended to repeat yourself a bit ;) but I was worried it might come out wrong. I was also assuming someone (probably Nil) would take care of it.) Yes, I do remember reading that about friction - at high speeds it is the dominant factor; at low speeds, rolling friction predominates. Interested people can read about it in Energy - a Guidebook by Janet Ramage [4]. I think rolling friction is proportional to the velocity. However, the square of the velocity (for the wind drag) arises because the vehicle has to get the whole column of air moving - the more streamlined the vehicle, the less the wind matters, as it can just slip through the air. Also, for a long vehicle, the head-on air column matters less proportionally. There will be wind drag along the sides of the train, but that again would only be in simple proportion to the velocity. IBE (talk) 00:40, 19 May 2014 (UTC)

Extra comment: no, I was just reading about friction, and it seems it is constant, and has nothing to do with velocity. IBE (talk) 01:00, 19 May 2014 (UTC)

Propagation of extremely high frequency sound in air

I'm involved in an off-wiki argument with a friend about the "detectability" of sound in air at 11.5GHz. I argue that the attenuation is so rapid that the sound is practically undetectable over a distance of several metres - unless the power level is ridiculously high - enough to obliterate the stones! My friend maintains that such sounds are found in "stone circles" - yes there are other pseudoscience issues that I'm dealing with but for this one I need some help with specific facts and figures. Roger (Dodger67) (talk) 12:13, 18 May 2014 (UTC)

Let me see if I understand this correctly - you're asking if acoustic pressure waves - i.e., longitudinal compression waves - in air - on Earth, with normal atmospheric conditions - carry energy in the gigahertz range?

No. Vibrations at those frequencies are uncommon in air. Even if we include vibrational modes that are uncommonly described as "acoustic waves", we still don't find energy at 11.5 GHz. For example, atmospheric oxygen has molecular vibrations - the diatomic molecule "spring" stretches and wobbles - in the infrared range. We would consider those vibrations as part of the optical spectrum - still not at 11.5 GHz. And, no microphone in the world exists that could detect such motion as a "sound." And these vibrations do not propagate energy between molecules, through the bulk of the air, in the form of a pressure-wave, so these vibrations are very much not sound-waves.

When we consider Earth atmosphere temperatures and densities, we find that the attenuation won't just take place over several meters - it'll take place within less than one wavelength. The wave will attenuate to "negligible strength" within a distance that we can measure in units of inter-molecular distance: i.e., a few microns. (Millionths of a meter!) The energy doesn't propagate.

Let me see if I can dig up a proper but simplified equation to describe attentuation of acoustic waves as a function of frequency. My first instinct is to pull out Bittencourt, Fundamentals of Plasma Physics, which generalizes the wave equation for a fluid to incorporate electromagnetic forces - because without a superheated ionized plasma - the sort of soup-y mess of dense hydrogen you'd find inside the Sun - there's essentially no way to convey acoustic energy at those frequencies. Even plasmas in laboratories or in near-Earth space resonate at much lower frequencies. Even plasmas near Jupiter resonate at lower frequencies.

At reasonable normal atmospheric temperature and pressure, and atmospheric gases, if a compression wave existed at 11.5 GHz, individual atoms would be moving so fast that the electrons would separate from the nuclei. The wave would devolve into a superposition of many oscillations - the atomic nuclei, and the electrons that cannot move coherently at this frequency. (To do so would imply that the atomic nucleus and the electrons have different temperatures). This would cause a separation of charge and would induce an electromagnetic wave. The wave will disperse. We can write an equation to give you the scale length for that dispersion relation, but it appears to require nine pages in my textbook. Bittencourt writes the spatial frequency (wave number) for a longitudinal wave in terms of electron plasma frequency, which is a long equation and would take some time to define.

Long story made short: your friend is either pursuing counterfactual science, or they've mixed up their S.I. prefixes. Acoustic waves do not propagate in the gigahertz range, not at any condition we find anywhere in our solar system outside of the interior of the sun. Nimur (talk) 12:50, 18 May 2014 (UTC)

Not disagreeing with any of that, but perhaps a simpler way of putting it is that the gigahertz range is where microwaves live, and if something did vibrate at that frequency, it would generate microwaves, which could easily be detected. Looie496 (talk) 13:55, 18 May 2014 (UTC)

Thanks Nimur & Looie496. This is exactly what I need. I'm far more familiar with calculations involving electromagnetic energy - I'll do a path loss calculation for a radar without breaking a sweat, but mechanical vibration waves are not my thing at all. I gather that for sound the attenuation v. frequency graph (in air at STP) crosses the fuhgeddaboudit! line well below 11.5GHz. As a radio frequency 11.5GHz is in a band widely used for satellite communication and radars - it's just a bit below the Ku band that most people would come across as it is commonly used for satellite tv transmission. The irony of the whole situation is that both myself and my "opponent" are radio hams! BTW the source of the argument is this video. Watch it at your own risk, I will not accept any responsibility if someone following the link does themself a serious injury due to uncontrollable laughter. Roger (Dodger67) (talk) 14:12, 18 May 2014 (UTC)

I agree with everything said above - but I would just mention that in Ultrasound#Imaging it mentions that: "The potential for ultrasonic imaging of objects, with a 3 GHZ sound wave producing resolution comparable to an optical image, was recognized by Sokolov in 1939 but techniques of the time produced relatively low-contrast images with poor sensitivity." - which suggests that GigaHertz-range audio is possible, although perhaps not through air. Our ultrasound article also says that ultrasound reaches up to "several gigahertz".

The obvious way to debunk your friends' argument is to follow the trail of knowledge back to the source. Where did he find out about this? Go there and figure out how the person who told him knew about it...and so forth. One will inevitably find that either the trail goes cold because some idiot just made this up - or a mistake was made and MHz got turned into GHz somewhere - or that you find how this "fact" was ascertained in some kind of experiment or other. My bet it that it's the first of those things. This is obviously complete B.S. pseudoscience. Very likely someone thought about the reputed "energy" found by people in and around stone circles - and when they thought about how it might be transmitted without anyone being able to measure it, they guessed "ultrasound" and made up a plausible-sounding frequency without thinking about whether it's possible or not.

here, for example is one such site - it mentions stones that it's claimed produce ultrasound - and also block ultrasound (weird!) - and it references a book "Circles of Silence" by Don Robins (Souvenir Press, London, 1985). From what little I could find about it in Google Books, it does make mention of ultrasound - but I couldn't find "GHz" or "gigahertz" in a search of the book. Don Robins also wrote "The Secret Language of Stone: A New Theory Linking Stones and Crystals With Psychic Phenomena" and has made claims that ultrasound is the cause of crop circles. (<sigh> - this isn't looking good is it?!).

Anyway, those claims for stone circles come from something called "The Dragon Project". Digging into that a bit turned up "The Dragon Project and the talking stones." an article in the "New Scientist" journal(!) - which has graphs and stuff in it! Now we might be on to something! That article says that these ultrasonic waves were detected using a bat detector...well, our bat detector article says that these work in the 15 kHz to 125 kHz range. So right there - we're not talking Gigahertz - or even Megahertz - we're in the range only just above human hearing...and far from being hard to detect, a $85 (Amazon.com) detector (or this $26 kit) is sufficient to pick them up.

Now, those graphs of the ultrasonic energy of the stone circles says that the energy is highest in March and November...and I'd bet that March is breeding season for bats. They talk about building a whole series of increasingly sophisticated ultrasound detectors - but there are no details about what frequency range they detected or what intensity levels. The article is full of self-contradictions (eg he says that February is one of the high points of ultrasound levels - when his graph says March).

So I'd have to say, that this was a fairly amateur effort and the results are not accurately reported. There is certainly no evidence that I could find for frequencies up into the Megahertz range - let alone gigahertz...and far from being hard to detect, you can pick them up with a sub-$100 piece of equipment.

SteveBaker (talk) 15:32, 18 May 2014 (UTC)

Hi SteveBaker - The "trail of knowledge" starts with this video - I also linked it in my post just above yours - see my "disclaimer" above. Roger (Dodger67) (talk) 15:43, 18 May 2014 (UTC)

Yes, the guy who posted that is Michael Tellinger - who is a politician, song writer and trained as a pharmacist. I wouldn't put much store by his science credentials, and from all I can find, he's basically just repeating the claims of Zecharia Sitchin. That guy is into the whole "aliens came to earth and played god" thing...and our article about him says "Sitchin's ideas have been rejected by scientists and academics, who dismiss his work as pseudoscience and pseudohistory. His work has been criticized for flawed methodology and mistranslations of ancient texts as well as for incorrect astronomical and scientific claims.". So that just about wraps it up for that trail of evidence! At least the Dragon Project made an effort to some up with something. SteveBaker (talk) 16:59, 18 May 2014 (UTC)

Just a quick comment: any physicist could recognize that a 3 GHz sound-wave would permit acoustic images with high resolution. In the same way, I can recognize that a glass lens whose refractive index were an imaginary number would allow me to build an infinitely-thin camera. But I still can't make one! That's the difference between theoretical physics - in which we crunch the equations just to see what should happen - and experimental physics, where we see what actually happens, then write a better equation to describe it! Nimur (talk) 18:33, 18 May 2014 (UTC)

• There are some great arguments here for why gigahertz frequency sound is impossible. The only nagging problem I have is that our article on ultrasound pointed me to acoustic microscopy, which uses gigahertz frequencies routinely. There are lots of articles that come up in a search for "acoustic microscopy" and "gigahertz"; unfortunately, sampling these, it looks like this is one of those fields you're not allowed to know much about unless you pay or your owner did. Wnt (talk) 15:51, 18 May 2014 (UTC)

There is no air involved in acoustic microscopy - it's all about solids and liquids. See Acoustic microscopy#Sample types and preparation. The highest frequency mentioned in that article is 400MHz - a very long way from 11.5GHz! Also take a look at Medical ultrasonography where "microscopy" is discussed as an experimental technique to examine structures in the eye - the highest frequency mentioned there is 100MHz. The medical article also briefly discusses attenuation in (mostly liquid) human tissues. Roger (Dodger67) (talk) 16:21, 18 May 2014 (UTC)

I invite you to run the search - many snippets mention 1 GHz or 3 GHz. I don't deny that ultrasound attenuates rapidly in air, but the argument about the frequency turning into microwaves should apply in water too, shouldn't it? Actually, this reminds me of an old question that never got an answer about whether materials where slow light travels at the speed of sound are able to convert sound to light or vice versa. It'd be interesting to hear more. Wnt (talk) 19:38, 18 May 2014 (UTC)

I think the suggestion that they would turn to microwaves is simply fishing something out of the air. Given the massively different propagation velocities, even if there was a radiative mechanism (e.g. relative displacement of nuclear orbital charge), it would not be self-reinforcing. This speculation simply does not belong here. —Quondum 20:56, 18 May 2014 (UTC)

Breast shrinkage

Why do not womens breasts shrink back after finishing baby feeding?--86.160.193.27 (talk) 12:17, 18 May 2014 (UTC)

Who says they don't? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:34, 18 May 2014 (UTC)

Breast#Hormonal_change covers this pretty well. SteveBaker (talk) 14:26, 18 May 2014 (UTC)

Also, they aren't filled with milk the way a water balloon is filled with water. It not just a bag to hold the milk, it's still fat, tissue and all the other stuff. Mingmingla (talk) 17:32, 18 May 2014 (UTC)

The question is a little unclear. In humans and a few other species, the post-pubescent females have noticable breasts. In most other species, the swollen breast only forms during lactation, and sometimes not even then. There have been a number of reasons proposed for why this arrangement is the way it is (Desmond Morris proposed that the cleavage of breasts was meant to evoke the cleft of the buttocks, but I don't know how popular that hypothesis has been). Whatever the original cause, female breasts are a classic secondary sex characteristic. When a woman is breastfeeding, the size and shape of the breasts will change depending on how much milk has been expressed and other factors. But once that's all done and the child has been weaned, women retain their breasts because they still fulfill their original role. Matt Deres (talk) 16:46, 21 May 2014 (UTC)

Sunset time and darkness

How long does it take to get completely dark in London after sunset in May? Can you provide reliable evidence for this? 82.40.46.182 (talk) 13:46, 18 May 2014 (UTC)

See Twilight#Duration - Roger (Dodger67) (talk) 14:41, 18 May 2014 (UTC)

Since it's a big city with lots of artificial lighting, it never gets "completely" dark in London. Our article Dusk discusses the various definitions of twilight and sunset. Basically, the definition depends on whether you're talking about "civil", "nautical" or "astronomical" twilight - and the definition is in terms of the angle of the sun below the horizon rather than how dark it actually is. This site (amongst many others) documents the sunset time and the time that twilight ends for each definition of twilight. So for London on 18th May 2014, the sun officially sets at 20:50:28, Civil twilight ends at 21:32:42, Nautical twilight ends at 22:31:21 and Astronomical twilight ends 00:08:09. Which of those you take to be "completely dark" is entirely a subjective matter since it's never going to be particularly dark in or near such a large city - and for any definition based on actual light levels, it's going to depend a lot on the cloud cover, moon phase and whether you are standing in a dark alleyway or on top of a tall building. I suppose the best generic answer is "about 40 minutes" - which is the duration of civil twilight - but in truth, this is one of those "How long is a piece of string" questions. SteveBaker (talk) 14:42, 18 May 2014 (UTC)

The rule of thumb that I use is about an hour. Bubba73 ^{You talkin' to me?} 18:27, 18 May 2014 (UTC)

Observant Jewish people need to know these sorts of things and have precise definitions for them, see Zmanim. The times you're talking about would correspond to Shkiyat Hachama and Tzet HaKochavim. According to chabad.org those times for today, May 19, are 20:50 and 21:42 respectively, so 52 minutes, pretty close to Bubba's hour. --Dweller (talk) 17:15, 19 May 2014 (UTC)

After reading the Zmanim article you linked to, I really wouldn't describe the Jewish reckoning of times pertaining to twilight as involving "precise definitions". The definitions aren't particularly precise given that they involve such vague quantities as the amount of time it takes to walk a mil, the amount of light needed to recognize a person four cubits away, or the amount of light needed to distinguish the blue threads of a tzitzit from the white ones. The Jewish holy books aren't even internally consistent about daylight reckoning, with the Talmud in Pesachim saying there are four mil between sunset and nightfall, and the Talmud in Tractate Shabbat saying there are just three-fourths of a mil between sunset and nightfall. With all that vagueness, it's unsurprising that when exactly nightfall is considered to be depends on which group of rabbis you choose to follow the interpretations of. And even if the Talmud and the rabbis did all agree, it would still just amount to a rather arbitrary set of definitions that only have meaningful significance to the 0.2% of the world's population that follows Judaism. Red Act (talk) 20:36, 19 May 2014 (UTC)

Believe me, by the time the Acharonim finished with the Talmudic definitions, the calculations have become very precise indeed. I appreciate very few people follow these arcane rules, but it seemed a way to answer the question using references, rather than finger-in-the-air speculation, which is, after all, what we're here for. And "52 minutes" is a nice, specific answer, from a proper reference, for the OP. Whatever religion they may or may not follow. --Dweller (talk) 06:56, 20 May 2014 (UTC)

The definitions for "civil twilight", "maritime twilight" and "astronomical twilight" are incredibly precise - we have references (indeed, entire Wikipedia articles) for them - you can calculate their times to the nearest millisecond for any day of any year on any point on the Earth if you want to. They are also employed more or less universally by people who care about such things (versus the very small percentage of people who are jewish and the yet smaller percentage of that small percentage who either know or care about these religious pronouncements). So if you need a 'hard' number (like "52 minutes") - then choose "civil twilight" or another one of those entirely arbitrary definitions. But the unassailable point here is that it's still not going to answer the OP's question and tell him/her a damned thing about when it gets dark in London in May 2014 - because that depends on things like "How dark does it have to be for our OP to call it 'dark'?" and "Is it a weekday or not and are the floodlights turned on at Wembley Stadium that night?" and "How cloudy/foggy is it?". Compared to the HUGE differences those kinds of things make to the final determination of when darkness has actually arrived (indeed, *if* it ever arrives!) - specifying a number accurate to within plus or minus an hour would be ridiculously over-precise.

So, the answer is STILL "there is no good answer" - and pulling some nonsense definition from some arcane religious sect surely isn't any better! SteveBaker (talk) 16:22, 21 May 2014 (UTC)

May 19

Games that computers can't play

Computers won't play the games in Brueghel's painting. 84.209.89.214 (talk) 15:02, 19 May 2014 (UTC)

I thought that since this isn't a troubleshooting question, this was a more appropriate forum than the Computing desk.

My question, basically, is are there any games that computers simply cannot play, for whatever reason? Given the right programming, computers can easily play (and win) a game with high complexity, multiple game pieces of varying function, and fine strategy such as chess, and a mathematical puzzle-game like sudoku would probably be orders of magnitude easier for a computer to complete in a fraction of the time. A computer could probably solve a crossword puzzle, given access to information of the sort Watson had when he took down those Jeopardy! champions, though there's obviously very little entertainment value in watching a computer solve a crossword, at least more than once or twice.

What I'm wondering, though, is if there are any games that are simply too complex for a computer to understand and/or put into practice. To come up with a workable definition of "game," I guess it helps to narrow things down. There are certain intellectual pursuits that computers are obviously not capable of (yet?); a computer couldn't compose an essay on Shakespeare, for instance (or at least not one that contains any original ideas), but we wouldn't term that a game. On the other hand, a computer is absolutely capable of analyzing data sets and finding statistical patterns, instances of correlation between different sets, etc. That isn't a game, either, but it is more pertinent to how some board games work. Literary criticism, though, is just a tad more complex, and a bit too abstract.

So I guess we'll impose the requirement of some level of strategy being involved, and a multi-player format, as in chess, checkers, or most card games. Charades has a physical component that makes it hard for a computer to put into practice—though I suppose a particularly language-savvy computer with a large library of pre-recorded gestures might be able to keep up. Drinking games and paintball are similarly outside the reach of computers for physical reasons, but are there games that are beyond computers' capacity for (for lack of a better term) intellectual reasons? Evan ^{(talk|contribs)} 04:25, 19 May 2014 (UTC)

Game complexity may be relevant. Among widely played "chess-like" games, Go has been famously difficult—see Computer Go#Obstacles to high-level performance. -- BenRG (talk) 04:38, 19 May 2014 (UTC)

Despite the plethora of soccer robots, true bipedal soccer robots are still no match for a human. Bipedal robot control usually depends on inverse kinematics, and state-of-the-art algorithms suffer from instability, slow speed (i.e. solutions cannot be computed fast enough), and poor error recovery. These are mathematical problems that present-day computer software can not easily solve, even though there has been a lot of research in this exact topic. To be clear: this isn't a mechanical problem - it's a software problem. The actual moving parts in a bipedal robot are perhaps expensive but they are not very complicated. It is the control algorithms that suffer from numerical instability and computational complexity. A robot with two legs has, in addition to the usual multidimensional kinematics matrix, a branched kinematic chain topology. That means, for example, that the robot doesn't know which foot is on the ground, and which one is in the air. As easy this identification-task is for a human brain, it is a difficult challenge even for a supercomputer. If you can write a software program to answer that question, you've got yourself a solid career as a robotics programmer! Nimur (talk) 05:11, 19 May 2014 (UTC)

There are games that are based on creativity and storytelling, such as role-playing games and perhaps the ultimate, Calvinball. 88.112.50.121 (talk) 10:34, 19 May 2014 (UTC)

Computer game designer Chris Crawford (game designer) distinguished between a competition where a player can only outperform the opponent, but not attack them to interfere with their performance, and a game where attacks are allowed. By this logic a computer can't play a game with you unless it can attack you. 84.209.89.214 (talk) 15:02, 19 May 2014 (UTC)

• Let's be clear that when you ask whether computers could play a certain game, what you are really asking is whether programmers would be able to figure out how to write a computer program that could play the game successfully. There are certain things that people find easy but are very difficult to write programs for. For example the game Who Is This?, in which you show the contestant pictures of famous people doing various things and ask for identification, would be extremely difficult to program on a computer. Another game that would be very difficult to program is Twenty Questions. Looie496 (talk) 15:20, 19 May 2014 (UTC)

This online version of Twenty Questions is actually pretty good with common objects. I got it to "hairdryer" in twenty-two questions. Evan ^{(talk|contribs)} 16:22, 19 May 2014 (UTC)

In Pictionary, I would expect a computer to be very good at drawing pics, as long as it had a pic in memory for the word in question, but very bad at recognizing pics drawn by people. More generally, any game that requires the computer to do visual processing of an image to determine what it's seeing will be problematic. Even Watson didn't do character recognition, but rather they fed it the questions as ASCII code. (I don't imagine it would have been a problem to recognize the consistent, printed text used on Jeopardy, but reading cursive handwriting, etc., would have been more of a challenge.) StuRat (talk) 15:27, 19 May 2014 (UTC)

Of possible interest: mathematical game, solved game. Up until ~2006, no computer was very good at playing angels and devils. But now that some people have done some very difficult math, computers can win easily. So in the field of complex games, it is usually operator/programmer knowledge that limits the computer, not the computer itself. (Sometimes the solution to a game is provably NP-hard, and in a sense, you could say that the restriction is more due to the computer than the operator, insofar as P_versus_NP_problem does not result in P=NP ). SemanticMantis (talk) 15:44, 19 May 2014 (UTC)

Mornington Crescent (game) would make a very good test for a computer - I'd imagine it's the game-playing equivalent of the Turing test. It'd be hard for a computer to join in convincingly, in a way that fulfilled the game's real intent, which is to entertain. --Dweller (talk) 15:50, 19 May 2014 (UTC)

I don't know how I'd judge that a computer had successfully been entertained by playing Mornington Crescent. But I rather think I could write a program to play the game. I think Inform 7 might be well-suited to it - create a map representing the network, so that convincing-sounding justifications and objections can be written on the fly. The new adaptive-text feature could make it refer back to earlier rounds fluidly, too. Allowing it to play with multiple human opponents would be a little more challenging, but not impossible. AlexTiefling (talk) 15:58, 19 May 2014 (UTC)

Sorry, I wasn't clear. The purpose isn't to entertain the computer (let's not go there) but the audience. While the computer could for sure spout random station names, I find it difficult to imagine any kind of programme that would capture the humour behind its pronouncements, including providing new and sufficiently wacky variants of rules, except by means of mixing up a database of old ones, which would fall flat in much the same way (or worse) than an unfunny fan of the game thrown into the programme would do. In short, a computer would be able to play the game alright, but very badly, because, to coin User:Dweller/Dweller's first law of computers: Computers aren't funny. Much. --Dweller (talk) 16:53, 19 May 2014 (UTC)

How German homes are built

I am building a new house and I want it to be made of cinder block, but well insulated. No builders in my area do ICF. I read somewhere that in Germany they make houses out of cinder block, then add Styrofoam insulation to the outside, then cover it with stucco. I would like specific information on how this is done and any problems with it. I am concerned about bugs and ants eating the Styrofoam and also about water or moisture getting behind the Styrofoam and caused mold. ( I am allergic to mold) Is this a problem? Also how is it done, do they put tyvek or a waterproof membrane between the Styrofoam and the cinder block? and how do they attach it to the cinder block? If they have to drill holes does that cause problems with air sealing it? And what thickness Styrofoam do they use?--Interestingusername123 (talk) 05:50, 19 May 2014 (UTC)

I don't know but bear in mind your house will have to be built according to your local building code, which might not have provision for that type of construction.--Shantavira|^{feed me} 07:40, 19 May 2014 (UTC)

Leca Isoblokk is a ready-made sandwich of cinder block and Styrofoam, shown in this video. I found nothing about it in English but you can try asking at your nearest Weber Saint-Gobain plant, found here. 84.209.89.214 (talk) 14:40, 19 May 2014 (UTC)

Note that Styrofoam is both flammable and gives off toxic fumes when it burns, so putting that much of it in a house may make it into a deathtrap. However, given the choice, it might be best on the outside of the cinder blocks, in the hopes that most of the toxic fumes would be released outside the house. A secondary concern is outgassing of toxic fumes as it sits. Since most of this happens when it's new, just letting it sit for a few months before using it in the house should help here. StuRat (talk) 16:32, 19 May 2014 (UTC)

I'd be surprised if German building code didn't ban toxic, highly flammable foam like ordinary styrofoam. After all, we're talking about Germany. ¡Aua! (_Rammstein \ ^Kraftwerk) 07:14, 20 May 2014 (UTC)

I had a house built down here in Texas using ICF (we used "Greenblock") - it comes as a bunch of foam blocks - like lego bricks. Each one has two sheets of foam - held together with two or three pieces of carbon-fibre. They pour a conventional concrete slab, then build the house up out of these bricks - threading rebar down between them. Then they pour concrete down into the gaps between the foam. So the resulting wall is about 1" of foam, 3" concrete and another 1" of foam. Then you put brick or stucco on the outside and sheet-rock and plaster on the inside. It worked amazingly well - the house is incredibly well insulated. If I ever get the chance to have another house built, that's exactly how I'd do it again.

The key here is that there is foam both outside AND inside the concrete. I don't know whether using hollow cinderblock for the core is good or bad. The walls are certainly going to be a lot less physically massive - so their thermal properties will be very different. My house stayed more or less the same temperature through day and night because of the thermal inertia of all of that concrete - plus the two layers of insulation.

Personally, in your situation, I'd use cinderblock - but have them insulate both the inside AND outside of the blocks with an inch or so of fire-resistant foam. (It's not really "stryrofoam" it's denser and not only does it not burn easily, if it does start to melt, it actively suppresses the fire somehow. It's been 15 hears now, so I forget the details.

The tricky part about using two layers of foam is having some way to tie the brickwork (or stucco or whatever) to the inner core - and the Greenblock system solves that with those carbon-fibre pieces that are embedded in the foam. They have tabs inside the foam that you can screw into - which is how the sheet-rock is held up, and how you can hang siding on the outside. There were special metal straps that they used to tie the brickwork to it...I forget how those work. There was also a way to apply stucco to it - but we didn't do that, so again, I don't know.

Definitely a great way to build a house though. It added about 5% to the cost of building it - and our heating/AC bills were about half that of our neighbors with similar sized houses. I calculate that the extra cost paid for itself in 5 years - but bear in mind that Texas summers are ferocious and they high cost of airconditioning is what kept the payback time that short. The CO2 benefits are harder to calculate because concrete manufacture is incredibly bad for generating CO2, I never did figure out what the "payback time" was in terms of carbon footprint - but since the concrete structure should still be viable in 50 to 100 years - I'm pretty sure it's a net win.

I also liked that the house was so quiet - and because the walls and slab formed a continuous piece of concrete, there were very few insects getting into the house.

SteveBaker (talk) 16:59, 19 May 2014 (UTC)

"15 hears" ? That's definitely hearsay then. :-) I'm curious if the outgassing was a problem. Did the house smell like plastic for the first year ? Also, putting holes through the wall for cable TV, etc., can be a bit more work with concrete walls. And if less air naturally flows through the walls, then you might need active ventilation with a fan running all day, and that cuts into your energy savings. StuRat (talk) 17:06, 19 May 2014 (UTC)

No, I didn't have a problem with outgassing...you can see details of their materials as [5]. Making holes in the steel-reinforced concrete walls was indeed a major problem. Our builder mistakenly put the cooker vent three feet away from where the cooker hood was, and he had to get some very exotic drilling equipment to make the new hole. When the house was built, he had a large hole in the bottom corner of the garage (made by putting a length of 4" plastic pipe into the wall before the concrete was poured) - phone and TV lines came in through there as well as power cables, A/C drain hoses, etc. The reduction in air flow was something we were very concerned with, so we had a couple of large fans built into the upstairs ceilings that would pull air out of the house and dump it into the attic. There was enough gaps around door and window frames to let air in whlie it was running. However, since (here in Texas) there is only about a week between needing to heat the house and needing to cool it(!), the airflow through the heating/cooling system was plenty to keep the air inside fresh. On those few days when we didn't need either A/C or heat, we'd have the windows open anyway - so I don't think we needed the vent fans for more than a few days each year. We had heat-pumps for the household heating - things would probably been different if we'd had a different heat source. SteveBaker (talk) 20:20, 19 May 2014 (UTC)

Haven't done this for a while, but in the UK existing brick houses have been insulated on the outside using either flame-retardant insulating foam slabs or rockwool/glass fibre insulating slabs, with fixings going through the insulation into the outer skin of brickwork. The slabs were then covered with glass fibre reinforced stucco (or rendering in UK terms) which provided a waterproof outer layer. Having the insulation on the outside meant the brick structure would warm, giving a lot of thermal inertia, and the dewpoint for condensation would be outside the brick structure. If the building was to be quickly heated intermittently you could perhaps add an internal layer of insulation, but care would be needed to include a vapour barrier and calculate that the dewpoint was somewhere that condensation wouldn't occur or matter. This is to cope with a challenging climate, very variable with a lot of condensation problems in cold weather. Other countries differ. . . dave souza, talk 17:13, 19 May 2014 (UTC)

I was always told not to insulate the inside of a cinder block building, only the outside, becasue the cinder block acts as thermal mass and will hold the heat or cooling that you are putting into the house (basically acting as insulation itself). I'm not sure why you say I should put Styrofoam on the outside and the inside.--Interestingusername123 (talk) 03:45, 20 May 2014 (UTC)

A thermal mass isn't quite the same as insulation. A large thermal mass will tend to delay when the outside temperature makes it to the inside, not stop it. In the case of most masonry, it seems to delay it about an hour per inch of thickness. So, 12 inches of masonry would delay the heat of the day from hitting the interior until about 12 hours later, so the middle of the night, when the extra heat might actually be appreciated. Unfortunately, most homes have maybe half that thickness, so it gets hottest inside some 6 hours after the hottest part of the day, putting it somewhere around 9 PM, when opening the windows to cool the house down might not work yet, since it's still warm out.

I'm also not sure why putting insulation on the outside and inside of the cinder blocks is better than putting a double thickness on the outside. Perhaps each creates a vapor barrier, and that prevents moisture from getting into the cinder blocks from the inside, condensing on the cinder blocks when they are cooler than the air in the morning, and causing mold to grow. I'd expect this to be a potential problem by the bathrooms, if you take showers or baths in the morning, or by the kitchen, if you boil food in the morning. You can create a vapor barrier without foam, however. StuRat (talk) 13:36, 20 May 2014 (UTC)

I disagree about how thermal mass works. If you take a brick, pile ice-cubes around one side of it for a few hours until it's at 0 degC, then quickly remove the ice and apply a blowtorch to the outside for 30 seconds before putting all of the ice back, it is not the case that an hour or two later, the inside of the brick suddenly gets too hot to touch for about 30 seconds and then cools off again! So your "delay" theory is busted.

What the thermal mass does is to slow down the rate of change of temperature. So as the temperature outside slowly warms up towards noon, the masonry slowly warms up too - but with a considerable delay. When the hottest part of the day passes, the masonry still won't have reached that maximum temperature - but as soon as the outside temperature starts to fall, the rate at which the masonry is getting hotter gradually decreases. As soon as the outside temperature falls below that of the masonry, it'll start to slowly cool off. This doesn't so much delay the outside temperature change (although it does do that) as smooth off the peaks and troughs. That's what you really want - a "moving average" of day and night temperatures. Removing the highest peaks and lowest troughs tends to reduce heating and cooling bills - and keeps the house more comfortable. It also allows the A/C and/or heating unit to operate with fewer on/off cycles. If the temperature isn't ideal, then the unit kicks in until the house (with all of that thermal mass) gets to the temperature you want it to be - when it turns off, that large thermal mass continues to maintain that temperature for a long time. This allows you to narrow the band of acceptable temperatures. If you had a regular thermostat with a 5 degree "hysteresis" band (so the A/C turns on at 75 degF and turns off again at 70F then it turns on and off more frequently than one with limits at 80 and 65 degrees...but it keeps the house closer to the ideal temperature. Having all that thermal mass allows you to set tighter limits on the thermostat without it turning on and off too frequently...so the house is more comfortable as a result.

Insulation is a bit different, it allows you to have a larger temperature difference between inside and outside without having to use a lot of energy to maintain it. I suppose that slowing the rate at which energy enters and leaves the thermal mass will also increase the 'averaging' effect.

Having insulation on both the inside and outside definitely complicates the description of what's going on...but having more insulation is better than less. If you're going to have 2" of insulation (which is what I had), then having half of it inside the wall and half outside is perhaps just convenient from a construction point of view (remember, the foam acts as a "form" for the concrete during construction - holding the concrete in place until it hardens).

SteveBaker (talk) 17:44, 20 May 2014 (UTC)

Certainly there is some mixture of a narrow heat band with the surrounding temperatures in the masonry, just as a 100 MPH wind gust on an otherwise still day would blend in with the surrounding still air and you'd get a longer and less strong wind gust as it moved along. This doesn't "bust" the underlying effect. I live in a brick house, and the thermal load from the bricks does indeed hit after sunset, around 9-10 PM, and temperatures inside soar. When it's hottest outside, around 3 PM, it's not bad inside. If you live in a brick house, try leaving the A/C off one day, and windows shut, and measure the inside temps, to see if you don't notice the same effect. Choose an unshaded west-facing room for the measurements, so it will have received afternoon sun.

Now, if the masonry was thick enough, you would eventually get an averaging of the daily temps, as you say, and if far thicker still, even an averaging of the yearly temps. However, both of these would require far thicker walls than are the norm. StuRat (talk) 14:04, 21 May 2014 (UTC)

ICF houses frequently have foot-thick walls. Mine was over 10 inches thick...4" brick, 1" foam, 4" concrete, 1" foam and a half inch of sheet-rock. (I was mistaken earlier when I said the concrete was 3" thick - I just checked on http://greenblock.com).

However, I'm still strongly skeptical about your "delay" theory. For what you say to be true, heat would have to flow through the material at an incredibly slow speed. The thermal conductivity simply isn't that low...even in materials like brick and concrete. The thermal conductivity of brick, cement and concrete are all around 1 W/(m.K) (see http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html). So a change in external temperature will rapidly propagate through the entire thickness of the material - it can't progress as a slow wave of heat moving through it with cooler material on either side - as you seem to imagine. So the 'lag' between the hottest outside temps and the hottest inside temps simply can't be measured in hours. If the outside temps max out at between 3pm and 4:30pm (fairly typical for most places in the world) - then what conceivable mechanism can delay that rise for the 6 or so hours that you claim?! There is simply no possible way that can be true. With that kind of thermal conductivity, the temperature throughout the wall will even out within a relatively short period of time. The 'averaging' effect comes about because the rate of change is so slow - but the moment the temperature outside starts to drop, the walls inside must also start to gradually cool...and the only delay is in the time it takes for heat to be transmitted through the material - but with a conductivity around 1.0, that's only going to be a matter of minutes - not 6 hours. It's thermal mass, not transport delay that makes this stuff work.

Put another way, lean beef has a thermal conductivity that's about half that of brick - heat takes as long to travel through 2" of beef as it does through 4" of brick. So...how long does it take to roast a 4" thick joint until the middle is cooked? Do you think that you could turn off the stove once it reached 450 degrees and have the heat continue to penetrate through it until the middle finally got hot enough 6 hours later? That's precisely what you're suggesting is happening with the bricks. It's not like a sound wave travelling through some material.

So I don't know what you are measuring or how - but there is no physical possibility that it's working as you seem to imagine.

SteveBaker (talk) 16:06, 21 May 2014 (UTC)

The flaw in your meat example is that the interior is also meat, which has a high thermal capacity, so takes a lot of energy to heat. The interior of a house, on the other hand, is mostly air, with a low thermal capacity, and heating that takes very little thermal energy. Also, the meat typically starts out as either refrigerated or frozen, while the interior of the house starts out around room temperature. Finally, assuming no significant bacterial growth or radioactivity, the meat has no internal heat source, while the house has people and pets, cooking, water heaters, lights, and electronics; all creating heat inside.

As for thermal conductivity: Perhaps it's not just the masonry then, but also the air gaps, which require radiation to jump from one surface to another. Also note that "insulating brick" is listed as "0.15", so much slower, and plaster and gypsum board have similarly low values. All I can tell you is what I've observed.

And I'm not quite sure what effect the insulating foam has on the process. I suspect that actually stops the thermal conduction (well, reduces it to a level that's insignificant compared with other sources of heat), as opposed to just slowing it down. My walls are uninsulated brick. StuRat (talk) 16:55, 21 May 2014 (UTC)

I live in a colder climate and use gas central heat so is it better to put the insulation on the inside or outside on the cinder block?--Interestingusername123 (talk) 08:41, 21 May 2014 (UTC)

I don't think the temp makes a diff on where you should put the foam, just how thick it should be. So, the answer given before, both inside and outside, still applies. As far as using gas central heat, that would only be an issue if the air ducts are on exterior walls. If so, you want them inside all the layers of insulation, so there's no insulation between them and the interior. And be sure you have the full amount of insulation between the air ducts and the exterior, too. If you need to reduce the thickness of the insulation to make room for the air ducts, then use a more effective (and more expensive) insulation in that area. StuRat (talk) 20:43, 21 May 2014 (UTC)

The material you describe at the top of the page is called exterior insulation finishing system or EIFS. Dryvit and STO are prominent trade names in North America, and are widely used there. A version of the system was used in the southeastern US over wood frame construction, but suffered from moisture penetration issues, resulting in extensive litigation. I'm not aware of problems when used as originally intended, over masonry. All the theorizing above aside, building codes and energy codes encourage the placement of insulation as far out on the building envelope as possible, keeping the greatest possible mass on the inside of the thermal envelope. That way you can use the thermal inertia of the masonry to advantage: having on the outside wastes the mass. However, while the use of concrete block or clay tile is commonplace in Euopean houses, those materials are not widely used above grade in North America and tend to cost more. Acroterion (talk) 14:14, 22 May 2014 (UTC)

How does knowing the gene for a disease help you treat the disease?

How does knowing the gene for a disease help you treat the disease? 203.45.159.248 (talk) 07:03, 19 May 2014 (UTC)

As far as I know, it doesn't. It is not the reason why one would want to know the gene for a disease. Plasmic Physics (talk) 08:42, 19 May 2014 (UTC)

It might help if you were developing a drug to target it specifically, or perhaps a corresponding bacteriophage. ←Baseball Bugs ^{What's up, Doc?} carrots→ 09:28, 19 May 2014 (UTC)

How is that supposed to work? Plasmic Physics (talk) 09:40, 19 May 2014 (UTC)

I think there's some ambiguity here between sequencing the genome of a pathogen (say a virus or a bacterium) as assumed by Bugs' reply, and knowing the relationship of individual genes in a larger genome which produces a given genetic disorder in that genome's owner. The latter was my interpretation of the question, and I think yours too, but it's definitely ambiguous. AlexTiefling (talk) 09:43, 19 May 2014 (UTC)

Yes, I agree. Although, I wouldn't normally associate a disease with a pathogen. Plasmic Physics (talk) 09:55, 19 May 2014 (UTC)

Why not? Our article disease even lists pathogenic diseases first in its typology of disease near the end of the the lead. AlexTiefling (talk) 10:00, 19 May 2014 (UTC)

Habit - I'm not saying that it's wrong, it's just not my primary go-to. Plasmic Physics (talk) 10:04, 19 May 2014 (UTC)

It can help a great deal indeed. If the exact mechanism of disease development wasn't know before, but becomes more clear after finding the genetic association, you can start far more targeted studies for therapies. Fgf10 (talk) 14:45, 19 May 2014 (UTC)

• Biologists generally dislike the term "gene for a disease", because it is an easily misunderstood way of saying "gene whose malfunction causes a disease". Knowing that a certain gene malfunctions may be a step toward understanding how to cure a disease. In most cases the result of a gene malfunction is either (a) a certain type of protein is malformed and does not work properly, or (b) a certain type of protein is made in quantities that are either excessive or deficient. For any of those mechanisms, pinning down what happens is a step toward figuring out how to deal with it. Looie496 (talk) 14:48, 19 May 2014 (UTC)

• "Gene" is commonly used, at least in everyday language, to refer to a specific allele of a gene; for example, one might speak of the "gene for type A blood". Perhaps biologists are careful not to use the word "gene" this way; but saying "the gene for a disease" or "the gene that causes a disease" (as OttawaAC does just below) is just another example of it. --50.100.193.30 (talk) 03:56, 20 May 2014 (UTC)

If the gene(s) that cause a disease are identified, that can lead to a test for diagnosing the disease. Not all diseases are easily diagnosed, for example mental illnesses like schizophrenia, bipolar disorder, and so on. They can be tricky to diagnose and sometimes it takes years, simply because there's no way to do a test to find the correct diagnosis. And the more quickly a disease is accurately diagnosed, the more quickly the correct treatment can begin. If the genetic basis of these illnesses was more fully understood, the effects on the brain would be known with more precision, and medications that target brain chemistry more effectively could be developed. Some illnesses are developmental problems, meaning the genes are "programmed" to trigger the problem at a certain point in the patient's development, like autism in toddlers. If the genes triggering those issues were known, then testing and perhaps preventative gene therapy could be introduced. OttawaAC (talk) 15:47, 19 May 2014 (UTC)

It is rare, but knowing the gene that causes a disease absolutely can lead directly to a treatment. Figuring out that chronic myelogenous leukemia is typically caused by a mutation of BCR and ABL1 led to the creation of imatinib. Figuring out that cystic fibrosis is caused by mutations to CTFR led to the creation of ivacaftor.

Those are just examples where treatments were developed that target the gene (or rather, it's protein product) directly. There are countless more examples where knowledge of the genes that cause a disease expanded our knowledge of how disease occurs, and led to treatments in more indirect manners. Someguy1221 (talk) 06:15, 20 May 2014 (UTC)

Is it true that RNA helix viruses mutate faster than DNA helix viruses?

And if so, then why does the MMR vaccine (which treats an RNA helix group of viruses) only require one vaccine while the flu vaccine only works for 1 year and even then sometimes doesn't work. Both being RNA viruses, one would assume they mutate at about the same rate. ScienceApe (talk) 15:00, 19 May 2014 (UTC)

I'm not expert in viruses, but I assume this is at least partly due to the fact that the flu is not caused by just one, but an entire family of viruses, the orthomyxoviridae, which typically generate new strains not just by mutating but by recombining with one another. Someguy1221 (talk) 06:19, 20 May 2014 (UTC)

What's relevant is that DNA helices bind more strongly and repair more deftly that RNA carriers of genetic material. For this reason DNA mutates less readily. μηδείς (talk) 04:00, 21 May 2014 (UTC)

DNA polymerase has error checking so DNA viruses are copied more carefully, RNA polymerase doesn't. This doesnt address the issue really though.Polypipe Wrangler (talk) 05:12, 22 May 2014 (UTC)

Inconspicuous transport by sea

I was watching some film and they had to smuggle millions in cash from the US to Switzerland and I wonder couldn't they transfer it via a private boat? What's the problem sending a yacht or something else? Range? Inclement weather? --78.148.110.113 (talk) 15:22, 19 May 2014 (UTC)

Perhaps they were worried about being intercepted by the Swiss Navy. Gandalf61 (talk) 15:28, 19 May 2014 (UTC)

I should point out that it could be transferred by land after reaching the European continent. 78.148.110.113 (talk) 16:05, 19 May 2014 (UTC)

The more times they transfer it and cross borders, the more chances they will be caught, by customs agents, etc. Since cash is fairly compact, a private plane would be the obvious method, needing to pass inspection only once. And weather is also a concern for a boat trying to cross an ocean, as is the time it takes. Both work together, in fact, as it takes too long to cross to get an accurate forecast for the entire trip before you leave. And taking a small boat across an ocean is sufficiently rare that it might garner extra attention, particularly looking for drug smuggling or illegal immigrants. StuRat (talk) 16:11, 19 May 2014 (UTC)

It depends on how much money one is transferring. One million dollars in hundred dollar bills is about the size of a briefcase. Thus, a hundred million dollars would require 100 briefcases to transport. This page gives an interesting perspective on the size of large sums of money, from a geometric point of view. --Jayron32 18:19, 19 May 2014 (UTC)

Don't use the train 95.112.250.227 (talk) 19:08, 19 May 2014 (UTC)

The constraint of using cash per se severely limits the options - I'm very surprised though that we haven't heard a lot about solar powered micro-boats or balloons designed to pop and send a radio location signal when they exit a certain polygonal area. Of course if you didn't have to use cash you could use Bitcoins, traditional IOUs with criminal organizations (what was that, "Premium Rush" I think - ahh, hawala, clearly a system that needs to learn how to do marketing in "news" reports to compete), gray-market art that hasn't been seen since the Holocaust, heavy gold necklaces, etc. Customs shouldn't have a chance against a good idea with a decent cover story. Wnt (talk) 21:55, 20 May 2014 (UTC)

Green Dot Corporation issues untraceable prepaid cards, which are often used by criminals. StuRat (talk) 13:23, 21 May 2014 (UTC)

Is it true that blood glucose can change your eye prescription if you wear glasses?

^Topic ScienceApe (talk) 15:28, 19 May 2014 (UTC)

[6]< reference. --Jayron32 16:02, 19 May 2014 (UTC)

Creatures with 3 pairs of limbs

There are a lot of mythical creatures that look quite like Tetrapods but with an additional pair of limbs, mostly wings or arms. (Centaurs, angels, pegasus to give just a few examples.

I always wonder how the additional pair of limbs would be attached to the skeleton in a was that is not obviously dis-functional.

So what in real nature comes closest to those creatures, or, to avoid all the answers saying "this is impossible because we have not observed such a thing": if some students would have a joke and fake such a skeleton, working real hard avoiding obvious mistakes, how would that look like?

95.112.250.227 (talk) 18:49, 19 May 2014 (UTC)

Perhaps like this Meganeura. And that has an extra pair of legs and an extra pair of wings over and above what you wanted. Dmcq (talk) 19:34, 19 May 2014 (UTC)

Also try googling "six legged cow" to get some examples. Dmcq (talk) 19:40, 19 May 2014 (UTC)

In vertebrates, limbs come from girdles formed during development. We don't have a page on general girdles, but see pelvic girdle and pectoral girdle. The pectoral girdle developed in bony fish. Here is a paper that specifically discusses evolution of girdles and mechanisms that account for the change in development [7]. In short, a putative six-limbed vertebrate would come from a whole lineage of three-girdled ancestors. This is not a sport that can spontaneously pop up and survive to reproduction, let alone have some advantage among extant tetrapods. In nature, we do have ants with three-limbed workers. They have imaginal discs that allow development of separate limb pairs, but they don't have internal skeletons. Certain Odonata are slightly closer to the pegasus, but they have three pairs of legs and two pairs of wings. I can't think of any animal that has exactly four legs and exactly two wings. SemanticMantis (talk) 19:41, 19 May 2014 (UTC)

With respect to Dmcq's cow comment, here's a science article presenting a dissection of a six-legged goat [8]. From what I can tell, it did not have an extra girdle, and the legs would have been totally useless. SemanticMantis (talk) 19:46, 19 May 2014 (UTC)

I guess the same applies to other creatures mentioned in our article on polymelia (such as Stumpy)? ---Sluzzelin talk 19:55, 19 May 2014 (UTC)

Thanks for the answers so far. I was really thinking about Tetrapods (to be distinguished from quadrupeds), not about arthropods. So the hint to girdles seems crucial. Those polymelia forms look like they are not even good for an additional Eisbein.

But I know that there are additional vertebral notches occurring in nature, either genetically or somatically. Nature does all kinds of "mistakes", so is there anything known about additional girdles? 95.112.250.227 (talk) 20:25, 19 May 2014 (UTC)

The problem with having an extra limb girdle is that it changes the entire vertebrate bauplan. The few genes (HOX being probably the best known) that account for correct rostro-caudal segmentation and development of an animal, in my understanding do not separately encode developmental "commands" like "make an extra pair of lungs" or "make a shoulder girdle here". Rather, by modifying those genes, it is possible to change the developmental "fate" of certain body segments: e. g. have a Drosophila grow legs instead of antennae, or have a duplicate thorax (example here: http://biobabel.wordpress.com/tag/abd-b/). Duplication of a limb girdle in a vertebrate animal would probably result in duplication of some of the internal organs as well. There is no funcdamental reason why this would be impossible, though. In fact, a centaur is supposed to have two hearts, two stomachs, and two pairs of lungs; and a catbus 8 or 10 pairs :) Dr Dima (talk) 21:22, 19 May 2014 (UTC)

For centaurs I was always wondering if they had duplicate precious parts.95.112.250.227 (talk) 21:49, 19 May 2014 (UTC)

I can imagine an evolutionary path (if conditions somehow favored it) where a bird develops longer and longer talons, and shorter legs, until the talons essentially are the legs. At that point it might have 6 "legs" and two wings. StuRat (talk) 22:25, 19 May 2014 (UTC)

• Obviously mythologers were both ignorant of and unconcerned with anatomy. The wings of gryphons are speculated to be the dislocated head shields of fossil ceratopsians Where are the scapulae and musculature going to go for a harpy? Not to mention how is it going to carry the extra weight of the arms? Forelimbs in tetrapods develop cranially in relation to the thorax, hindlimbs develop caudally to the abdomen. Nothing develops medially to the abdomen and thorax. The disruption to the abdominal diaphragm alone would be a lethal malformation. Even how turtles manage to develop their limbs inside their ribcages remains an evolutionary mystery. And four-legged ruminants inevitable have a doubled set of rear limbs, not three pairs of limbs equally spaced. Given the presence of two dorsal fins in the ancestors of tetrapods, there doesn't seem to be any a priori reason why we couldn't have a third arm and leg in the middle of the back, but the purpose that might serve excapes me. I'd actually be surprised if some competent physiognomist hasn't examined the conundrum. Good luck. μηδείς (talk) 02:08, 20 May 2014 (UTC)

Drug tests, "cleansing"

so i have a drug test tomorrow and i bought this strip nc extra strength body cleanser. It contains a 1 fl oz liquid and 4 pills. How long does it last and when should i take it? — Preceding unsigned comment added by 50.185.136.93 (talk) 21:24, 19 May 2014 (UTC)

I added a header so your question appears in its own section. Please use the "ask a new question" button at the top in the future. As to your question: we cannot give you medical or legal advice here, and your question could easily be seen as asking for one or both. I can point you to this site, which seems to have some good information about the various sorts of drug tests, how they work, etc. [9]. Good luck, SemanticMantis (talk) 21:37, 19 May 2014 (UTC)

If any reference is given here, it should be to the Wikipedia article Drug test rather than to a marihuana promotion site. 84.209.89.214 (talk) 23:29, 19 May 2014 (UTC)

I should have looked at our article first. Here is a link from our refs there that might be more reliable than the one I posted before [10]. SemanticMantis (talk) 13:30, 20 May 2014 (UTC)

May 20

Efficacy of vaccines

If I got three different vaccines, let me say Gardasil, One against pneumonia, one against flu, in a time span of just 3 weeks, can that negatively affect the efficacy of vaccines? 112.198.90.97 (talk) 07:00, 20 May 2014 (UTC)

Sorry, questions calling for medical advice aren't allowed to be answered here. Please ask a doctor or pharmacist. --50.100.193.30 (talk) 07:25, 20 May 2014 (UTC)

We can't give medical advice, but we can direct you to information published in reliable sources. If you are really concerned about yourself, seek a medical professional. If you are interested in the general topic, here is a recent journal article titled "Long-term health effects of repeated exposure to multiple vaccines" [11]. Here's another one titled "Simultaneous administration of childhood vaccines: an important public health policy that is safe and efficacious" [12]. SemanticMantis (talk) 13:40, 20 May 2014 (UTC)

Identifying a bird

Hello. I found a wounded bird and have called the regional bird sanctuary to take care of it. In the meantime, can you help me identify what species it is? It comes from north-eastern Spain.

Picture of the bird.

Thank you! Leptictidium (mt) 07:22, 20 May 2014 (UTC)

A juvenile common starling, I think, but given that you're in Spain, it might be a juvenile spotless starling instead. 2.220.78.158 (talk) 08:14, 20 May 2014 (UTC)

I concur. http://2.bp.blogspot.com/-slZCKJpTRz0/UNZRTfwqfeI/AAAAAAAANVA/eQKRLw5eAwk/s400/Starlings+feeding.jpg 196.214.78.114 (talk) 09:44, 20 May 2014 (UTC)

Projectile dynamics

With no air resistance and perfect elasticity, the simplest approach would say that a ball thrown ahead without rotation on level ground will perform an endless sequence of identical parabolic arcs, but I feel that the degree of friction between ball and ground would have an effect on trajectories after the first arc. Is this so, and if so what would the effect be? What would happen in the limiting cases of the coefficient of friction being 0 or 1?→86.146.61.61 (talk) 12:38, 20 May 2014 (UTC)

The friction with the ground would induce more spin with each bounce, and accelerating the ball from no rotation or less rotation at each bounce would use up some of the forward momentum, so the parabolas would get narrower with each bounce, but remain just as high, given your assumptions, until the spin was such that the ball matched the ground, so rolled perfectly on it with each hit. Of course, in addition to being impossible in the real world, one set of your perfect assumptions are also inconsistent with each other. If it was perfectly elastic, then it wouldn't deform at all when it hit, and would hit for an infinitely short period of time, and thus there would be no friction, either. StuRat (talk) 13:20, 20 May 2014 (UTC)

Perfect elasticity is the assumption, friction is a "feel" that the OP has. I'm not sure if perfect elasticity leads to zero friction, but if it does, then the solutions to the model would just be identical repeating parabolic arcs forever.

As for the claim that "perfect elastic, then it wouldn't deform" -- that depends on what OP means by perfectly elastic. E.g. if the modulus of elasticity is infinite, then no deformation occurs, and contact time (hence friction) is 0. But if the elastic limit is infinite, then even with a small elastic modulus, some sense of "perfect" elasticity is retained, even with positive contact time and friction. My impression is that "perfect elasticity" usually refers to the sense given at Elastic_collision, in which case, I agree that there is no friction, as that would fail to conserve kinetic energy. SemanticMantis (talk) 13:52, 20 May 2014 (UTC)

I actually meant by perfectly elastic that there was no loss of kinetic energy but that some compression was possible on impact - in which case, I would assume that in the case of non-unity coefficient of friction there was the possibility of momentary ground-contact sliding before the next parabola, which would certainly occur if the coefficient was zero, with the threshold value depending on the initial angle of projection.→86.146.61.61 (talk) 14:22, 20 May 2014 (UTC)

If we allow that the ball deforms, then the shape will continue to wobble back and forth into a variety of shapes until it hits the ground again - making the height of the second bounce harder to predict depending on whether or not the ball was already compressed along the vertical axis when it impacts that second time. If it's also spinning, then it's not necessarily a clean, symmetrical shape when it next impacts the ground - so the second bounce will launch it off at some angle that's crazily hard to predict. You can see this in practice if you take a "super-ball" (which is extremely bouncy) and spin it as you drop it - the resulting motion looks chaotic. The trouble is that deformation without energy absorbtion is impossible - and that makes talking about what happens rather difficult! A zero here causes an infinity there! SteveBaker (talk) 16:55, 20 May 2014 (UTC)

However, in this idealized world, we can assume the ball would continue to move in the same horizontal direction, whereas, in the real world, a pebble it hit on one bounce might change it's heading entirely. StuRat (talk) 17:20, 20 May 2014 (UTC)

Chaotic? My experience with a "super-ball" as a child was that there was a predictable trajectory, with alternation (on a smooth level surface): depending on the initial spin and velocity vector, it might retrace a parabola back and forth (ignoring decay from energy loss), bounce along a zig-zag line, or do a short hop, long hop sequence. Without the energy loss, every second bounce would be essentially identical. —Quondum 01:27, 21 May 2014 (UTC)

"the parabolas would get narrower with each bounce, but remain just as high, given your assumptions" Assuming the angle of each bounce remains the same, and given that adding spin uses up kinetic energy as well as momentum, shouldn't we expect the height of each bounce to decrease (until the spin reaches maximum)? Olaf Davis (talk) 10:33, 21 May 2014 (UTC)

No, because only the horizontal component of the motion would be converted to rotational energy. Thus the angle would not remain the same. Consider two tests, one with only vertical motion, which would never slow down, given the assumptions, and one with only horizontal motion, which would start out sliding on the ground but slow down and spin up, until it's spin made it roll on the ground. Now combine those two motions together. StuRat (talk) 13:13, 21 May 2014 (UTC)

Yes, you're right of course. Thanks. Olaf Davis (talk) 15:12, 22 May 2014 (UTC)

You're quite welcome. StuRat (talk) 15:24, 22 May 2014 (UTC)

In the ideal case of no slip, you get a pattern that repeats itself with a period of 2 bounces. The ball initially without rotation starts to rotate after the first bounce and in after the next bounce that rotation vanishes. Count Iblis (talk) 14:35, 22 May 2014 (UTC)

Why ? StuRat (talk) 14:42, 22 May 2014 (UTC)

Musical instruments

Why do people say it's harder to learn music instruments, the older you get? Isn't this true with any skill? Aren't all skills best learn when young, when the brain is at it's best? People say it applies more to musical instruments but I don't know why. Clover345 (talk) 15:05, 20 May 2014 (UTC)

The first thing that comes to my mind is time. Most people have more responsibilities when they are older, leaving less time to practice. This applies to all skills, of course, but because so much of learning an instrument is muscle memory, without regular practice for months at a time (if not years) it is very difficult to do. OldTimeNESter (talk) 15:43, 20 May 2014 (UTC)

I doubt it's true of all skills, for example, I could imagine some skills that can only be learned once some other discipline is deeply understood and mastered - which might take a long time. Other skills only become fully matured after a lot of practice - so again, being young might make that impossible. I'm sure it's true of many subjects - but I doubt that such a sweeping statement as "all skills" is justified.

I'm also skeptical of User:OldTimeNESter's claim that it's a matter of time. Older people who become unemployed and have to learn a new skill presumably have just as much time in school as a younger person...and retired people often take the opportunity to learn a new skill. Certainly there are skills that are vastly easier to learn when young. Notably, it's well known that a young child can learn new languages extremely easily - just by listening to people speak it in context...that's an almost impossible task for an adult. SteveBaker (talk) 16:38, 20 May 2014 (UTC)

I somewhat doubt the last statement. If I throw you into China, with no dictionary, no relatives, and no English anywhere, you might learn Chinese as quickly as a Chinese newborn. When most adults try to learn a foreign language, they're still mostly working with their native language, which is hardly a fair comparison. --Bowlhover (talk) 17:16, 20 May 2014 (UTC)

• I believe the ability to learn things, from a neurological point of view, falls into the study of neuroplasticity. However, our article does not mention any aging effects on neuroplasticity. However, there are lots of scholarly articles on the subject. See [13] and [14] and [15] for a start, just some random articles I found. --Jayron32 17:24, 20 May 2014 (UTC)

A decade or so ago it was quite noticeable in large public institutions that people older than 50 had trouble mastering new technology, in particular the Internet, and preferred to do things old fashioned way even if it was obviously inefficient. --AboutFace 22 (talk) 17:54, 20 May 2014 (UTC)

I think Bowhover's claim about language is clearly not correct. I immigrated from Poland to Australia with my parents when i was seven years old and picked up the language in about 12 months. 30 years later, my parents, as well as their remaining thick accent, are still not nearly as fluent in English as I am, even though they both work and have English speaking friends. There are definitely language milestones that you automatically reach at a young age which are either very difficult or impossible to achieve later in life. Actually I just found the article Second-language acquisition which discusses this, in particular the section called Comparisons with first-language acquisition. Vespine (talk) 23:36, 20 May 2014 (UTC)

To make the above not completely off topic, I believe there are parallels between learning language and music. Anyone can learn to play a few tunes on a musical instrument, but to become truly "fluent" I think you need to start early. Vespine (talk) 23:38, 20 May 2014 (UTC)

Heh. My ex-wife was born in Australia, but because her parents had arrived only 6 months earlier and spoke next to no English, they very wisely decided not to try to teach her their rotten English but let her assimilate the proper language when she started mixing with anglophone kids. So, her native language is Russian, but she started learning English from around 2-3 years, and that quickly picked up pace once she started school. The upshot is that she is totally bilingual. Her Russian is so good that she has appeared in Chekhov plays, she has coached Australian diplomats about to head off to a Moscow posting, and has been praised by Russian-born people for her eloquence (many have asked which area of Russia she was born in). Her English is so good that when she tells people she was born in Liverpool, they blithely assume she means Liverpool, UK, not Liverpool near Sydney. -- Jack of Oz ^{[pleasantries]} 23:57, 20 May 2014 (UTC)

Clover, I notice that several responders above have correctly identified neuroplasticity as the root phenomena at work in how many skills ares best assimilated at an early age, but have not addressed the finer (and very fascinating) distinction you inquire about as to why the skill in question might be of the type that is especially easier to assimilate by younger learners. The answer to that question lies with two forms of processing which the human brain excels at broadly, but which are constrained and specialized during childhood in a window known as the critical period -- auditory cognition and syntax. Some of the earlier responders also quite correctly noted the link between the exercise of music and that of language; the two share some striking similarities in how the human brain processes them a sensory (and communicative) phenomena -- so much so that evolutionary psychologists and other cognitive scientists have been engaged in strong debate in recent decades in a chicken-and-egg style debate as to which one evolved to its current form first in our evolution into anatomically modern humans, as well as to how much they incorporate the same modules of the human brand and mind. Putting aside the finer points of that debate though, it's clear that there is significant crossover in how music and language are constructed from discrete components (phenomena like notes in music and phonemes in language) which are combined to form structures which can impart complex meaning and sensation that often seem to be far more than the sum of their parts.

I know I've just thrown a lot of different terminology at you with minimal contextualization, so let me tie it all together a little better now. The reason I've addressed the issue incorporating language is that it is the much more heavily studied of the two phenomena in terms of neuroscience and cognitive science broadly (though neurological and psychological studies of music aren't exactly unheard of either), to we understand how the critical period works in language acquisition especially, and some of those lessons can be carried over. One of the great revelations with regard to language in the last century was the formation of the concept of universal grammar -- the notion that all healthy human brains come complete at birth with a language organ that allows us to process language in (mostly) the same way as every other human. However, the brain needs to be "fine-tuned" to the specific rules of the language spoken by those around the child, and this is where the critical period comes in; during this time the child begins to specifically internalize the various rules and distinctions that are the basis of their particular native language(s). This includes a vast number of phenomena, but they can somewhat be divided into two groups -- phonology, the differences between the basic units of sound, and syntax, the rules for combining units of meaning together to make statements that other parties can comprehend. So for example, as regards phonology, a child who grew up speaking only Japanese will have difficulty in making the distinction between "r" and "l" sounds in a language such as English, because their language does not have that distinction; to a certain degree, that will vary between individuals, they just simply will not be able to "hear" that difference, because the auditory-linguistic centers of their brain have already learned to filter it out while specializing on other distinctions that were more germane to their linguistic upbringing. Likewise, word-order and other principles of grammar and syntax, will vary between their native tongue and any language they might try to learn later in life, and these rules are very much ingrained by adulthood as well.

Returning to the focus of your question, music shares many of these principles in common; it has specific sounds which the person who wishes to employ it must be able to distinguish between and produce reliably, and it has combinatorial rules which -- though experts are divided on calling syntax -- govern how these sounds are put together to form their intended meaning. In the context of music of course, the "meaning" is much more diffuse than it is in language -- more likely to instill a general emotional response than a concrete concept, but nevertheless, the order in which the sounds are combined and how they are stressed in relation to one another have a profound impact on how the effect those listening, as in language. And also as in language, the earlier the exposure to these principles of the distinctions between sounds and how they are combined (including the motor control necessary for producing them), the better the chance that the learner will be able process and reproduce these distinctions with finer control. It's worth noting, of course, that there are people who can become quite fluent in a language later in life and others who can learn a musical instrument with a fair degree of skill, but by and large, polyglots and musical virtuosos tend to be exposed to the relevant skills at a very early age.

I hope that answers your question in a basic fashion. I wrote the above in a bit of a hurry, so I hope its basically intelligible. If you have more refined questions along these lines, don't hesitate to ask some follow-ups. If you are interested in reading material along these lines which incorporate the relevant sciences (biological and social) but which are written for a very broad audience with no experience in those fields, I can strongly recommend Oliver Sachs' Musicophilia and Daniel Levitin's This is Your Brain on Music. Both are quite informative without being too heavy in the technical sense and written more elegantly than any of the above. Snow talk 23:10, 21 May 2014 (UTC)

Metric prefix

In Metric prefix it says "An exception is emission rates, which are typically on the order of Tg/yr."

Emission rates of what, where? Anyone know? -- SGBailey (talk) 15:27, 20 May 2014 (UTC)

Carbon emissions (sadly just a redirect to Greenhouse gas). There isn't a really standard unit for carbon uptake or emission. Two common ones from the ecosystem ecology and biogeochemistry fields are kg C/m^2/yr and Mg C/ha/yr. I've personally not seen terragrams actually used much, perhaps because the key fluxes in the global C cycle tend to be on the order of petagrams [16]. As with all metric prefixes, scientists usually use the ones most appropriate for the scale of interest. So we might use kg C/m^2/yr for a forest or town while PgC/earth/yr for the planet. Altogether a weird mention, that doesn't add much. I might edit there a bit later. SemanticMantis (talk) 16:16, 20 May 2014 (UTC)

Gay parenting vs heterosexual parenting

I hope this is the right reference desk to ask this question.

Have there been any systematic studies that compare adults adopted as children by a same-sex couple with adults adopted as children by a heterosexual couple? By 'compare' I mean look at things like IQ, divorce rates, crime rates, rate of mental disorders, etc. I tried to find such a study with Google, but what I found instead was 1) studies which compare children adopted by homosexual parents with children raised by their biological parents, or 2) studies relying on parental self-reports of their children's well-being. 65.92.7.8 (talk) 18:10, 20 May 2014 (UTC)

Given that adoption by same-sex couples is a relatively new phenomenon in most countries (see LGBT adoption#Legal status by country/jurisdiction) I very much doubt that studies exist comparing divorce rates or crime rates for example - it is simply too soon for meaningful data to exist. AndyTheGrump (talk) 18:20, 20 May 2014 (UTC)

This study claims to have contacted and examined a significant number of "adult children of parents who have same-sex relationships". Unfortunately, the author does not compare them to adult children adopted by heterosexual parents, which is what I'm looking for. 65.92.7.8 (talk) 23:49, 20 May 2014 (UTC)

DeBoer v. Snyder has a list of the witnesses called by both sides, and a brief summary of their positions. They did cite actual research, so the article could be a good starting point towards finding those studies. Katie R (talk) 19:58, 20 May 2014 (UTC)

LGBT parenting#Children's outcomes. Short answer: the kids are okay. TenOfAllTrades(talk) 20:29, 20 May 2014 (UTC)

While there's certainly a consensus among academic psychologists that 'the kids are okay', I'm concerned about how this consensus was reached. For example, this study supports the claim that "[a]dopted children thrive in same-sex households" by using parental self-reports of whether their children conformed to "expected gender role behaviour", a method I don't consider to be rigorous or complete. If the consensus was formed from studies such as this, then I don't believe that the consensus is merited. IMO, the only legitimate way to determine whether children raised by a same-sex couple fare as well as children raised by a heterosexual couple is by directly comparing adults adopted as children by a same-sex couple with adults adopted as children by a heterosexual couple, and as far as I can tell such a comparison has not been made. 65.92.7.8 (talk) 23:49, 20 May 2014 (UTC)

See WP:NOTFORUM. This is a reference desk - we aren't going to engage in debate over the merits of adoption by same-sex couples, or over the validity of studies of adoption by same-sex couples. If you wish to engage in such debate, please do so elsewhere. AndyTheGrump (talk) 00:11, 21 May 2014 (UTC)

The OP has done nothing of the sort of "engaging in debate over the merits of adoption by same sex couples." As for questioning the validity of studies, he has only said it in reference to particular suggestions, to alert us that he is still looking for an answer to the question. I regard this as a perfectly reasonable approach, and can see no forum style debate - only an attempt to search for quality references. IBE (talk) 07:59, 21 May 2014 (UTC)

It is fortunate, then, that in the study you refer to (Farr, Forsell, and Patterson, 2010 PDF) the researchers made a point of collecting evaluations from teachers and outside caregivers, as well as from parents. The differences between evaluations by independent individuals and evaluations by parents were small, and not significant for either homosexual or heterosexual adoptive parents. I get the impression, though, that you're going to keep moving the goalposts until you get the answer you want. Per Andy, please go looking for debates elsewhere. TenOfAllTrades(talk) 00:58, 21 May 2014 (UTC)

Agreed. This is descending into a "help me selectively find proof of my preconceived notions" We don't do that here. The OP has been provided ample means to find the information they are looking for. No need to keep this farce going any longer. --Jayron32 01:40, 21 May 2014 (UTC)

I wasn't trying to enter a debate over same-sex adoption, and I'm not sure why Andy thought I was. Nor am I anti-same-sex adoption, as TenOfAllTrades suggests. My original question was, "have there been any systematic studies that compare adults adopted as children by a same-sex couple with adults adopted as children by a heterosexual couple", with the caveat that such comparisons use objective measures like IQ, divorce rates, etc. In reply, TenOfAllTrades directed me to the 'Children's Outcomes' section of the LGBT parenting article, which describes the consensus among academic psychologists that LGBT-adopted children fare no worse than hetersexual-adopted children. But this fact doesn't answer the OP, unless this consensus was formed by comparing adults adopted as children by a same-sex couple with adults adopted as children by a heterosexual couple with aforementioned objective measures (and I really hope it was). Admittedly, the study I mentioned before did better than rely exclusively on parental self-reports, but nonetheless I'm not exactly satisfied even with third-party subjective assessments.

Ultimately, I asked this question because comparing things like the IQ of same-sex adoptees with heterosexual adoptees should be both straightforward in principle and also the most objective way of assessing same-sex adoption, and I'm thus bewildered that such a study has not yet been done. 65.92.7.8 (talk) 01:55, 21 May 2014 (UTC)

Fair enough. But be aware that this is a charged topic, and people are likely to read subtext into your requests and comments, so choose your words carefully, with a mind to how they are likely to be understood. --Jayron32 02:08, 21 May 2014 (UTC)

Thank you, and I'll pay closer attention to my wording from now on. 65.92.7.8 (talk) 02:17, 21 May 2014 (UTC)

Hmmm. I presume that you are aware that you're asking the impossible, or at least the extraordinarily difficult. Same-sex marriages have only been legal – anywhere in the world – since 2001. 'Civil unions' for non-heterosexual couples haven't been around much longer. It has been extraordinarily difficult for homosexual couples to adopt children under any circumstances until relatively recently; many otherwise-civilized countries (or states, within the U.S.) still actively discriminate against non-heterosexuals for the purposes of adoption. Asking for outcomes for adult children – particularly of measures like divorce rate, which may require decades of adulthood to properly assess – isn't reasonable. TenOfAllTrades(talk) 03:14, 21 May 2014 (UTC)

In Canada at least, same-sex adoption has been legal since 1985. It unfortunately took a lot longer for same-sex marriage to be legalized, but to my knowledge gay couples in a civil union have been able to adopt since at least 1985. I also know of at least one study that looked at adult children of homosexual couples, though the study in question was flawed because it compared children adopted by same-sex couples with children of heterosexual couples, not taking into account that children put up for adoption are not representative of the general population. 65.92.7.8 (talk) 04:42, 21 May 2014 (UTC)

Speaking specifically to Canada, those dates do not appear to be correct. The summary and timeline here is linked from our article, and seems pretty thorough. The only thing that happened in 1985 was that Section 15 of the Charter of Rights came into effect, which eventually led to court decisions that expanded the rights of same-sex couples. Legislative changes and court challenges that allowed same-sex couples to adopt trickled in beginning in the mid-1990s. (Near as I can tell, British Columbia was the first province to legally recognize the right of same-sex couples to adopt, in 1996.) The landmark decision came in 1999, with the Supreme Court's finding in M. v. H. that an Ontario law precluding same-sex couples from being considered common-law partners was unconstitutional. This precipitated a massive number of legislative changes to bring an assortment of federal and provincial laws into compliance with the ruling. (Even then, official discrimination against adoption by same-sex couples persisted in some parts of the country: [17].)

Incidentally, from your comment above I'm not sure that you were aware that a civil union is a specific, formally recognized relationship conferring many (or all) of the same rights as – or sometimes legally substituting for – marriage. (In some jurisdictions, a 'civil union' option for same-sex couples has been offered as a sort of 'separate but equal' or 'separate but nearly equal' option that avoids some of the emotional and political baggage of allowing same-sex 'marriage'.) This is in contrast to a common-law partnership – which may have been what you were thinking of – which can be established without any paperwork, just by living together. In any event, most of those court cases in the 1990s dealt with establishing that same-sex couples enjoyed the same right as opposite-sex couples to have their common-law partnerships recognized for various purposes (spousal benefits, eligibility to adopt, substitute decision-making for medical care, etc.). In Canada it then required another six years – with the Civil Marriage Act in 2005 – before same-sex couples were allowed to marry. TenOfAllTrades(talk) 13:00, 21 May 2014 (UTC)

Thank you for correcting me on the timeline of Canadian same-sex adoption, and yes I confused a civil union with common law partnership. 65.92.7.8 (talk) 18:56, 21 May 2014 (UTC)

It would be difficult to prove that IQ has anything to do with it. And a factor that I don't see mentioned here is where the adoptees come from. If the natural parents are troubled, it's not unreasonable to expect the adoptees to be troubled likewise, despite the best efforts of their adoptive parents. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:36, 21 May 2014 (UTC)

I think that you're absolutely correct about how troubled natural parents can lead to troubled children. A conservative study, which I cited above, tried to 'prove' that same-sex couples raise children more poorly by comparing adults brought-up by same-sex couple to adults with heterosexual parents, despite the fact that adopted children are unlikely to be representative of the general population. So it's not surprising that the study concluded that same-sex couples made worse parents than heterosexual couples. This is actually why I asked this question in the first place: the fairest way IMO of comparing same-sex couples with heterosexual couples is by looking at children adopted by heterosexuals, not children raised by heterosexuals in general. 65.92.7.8 (talk) 04:42, 21 May 2014 (UTC)

Yes, it's an apples and pomegranates comparison. Maybe you've heard the old saying, "Figures don't lie, but liars do figure." Also, those various "rates" are subjective. Kids from theoreticaly model families can end up as serial killers. One quantifiable figure (which Canada's data might go back far enough to provide) would be what proportional percent of adult homosexuals were raised by opposite-sex parents as opposed to same-sex parents. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:51, 21 May 2014 (UTC)

Why would that be an interesting figure? I would for example expect that bisexual or homosexual children raised by same-sex couples would be "out" much earlier and without much hassle, while children raised by opposite-sex couples would encounter the "usual" anxiety. There is no objective way to seperate sexuality from upbringing in an adult, IMHO. And another point to the discussion: Why would you even require IQ score (or some of the other measures mentioned above) to be equal? Is IQ suddenly a magically marker for "good upbringing"? Are children with lower IQ somehow "bad"? Remember, IQ does not equal general intelligence, and high IQ score (or intelligence) do not mean that you will lead a happier live or be more or less productive under all circumstances. These are really murky waters. Heterosexual couples are allowed to raise their children the way they want, why should homosexual couples have to conform to some form of "predescribed" upbringing? The children should not be actively harmed, in that I do agree, but that is a very different point than requiring "equal" upbringing. To clarify that point: No one is for example requiring the (heterosexual) Hillbillies to move into the Big City because the education there would be much better for their children. --TheMaster17 (talk) 14:30, 22 May 2014 (UTC)

And another thing I just realized: Would you find it really worrisome if gay parents would raise more gay children? After all, heterosexuals are also raising more heterosexual children at the moment. Neither of those is bad, or do you disagree? --TheMaster17 (talk) 14:32, 22 May 2014 (UTC)

May 21

What type of tree is this?

The image is a partial screen shot of a scene of Foyle's War which is set in Hastings, UK. The scene takes place outside a manor. A closer shot of the trees shows that they have fairly smooth bark between those knots that you see on the trunks. The scene is set in February which I'm guessing is why there are no leaves. So, what type of trees are they and are they trimmed like that on purpose to be more ornamental? Thanks, Dismas|^(talk) 07:04, 21 May 2014 (UTC)

Those are Common lime (tilia × europaea) trees, called Linden trees in the US. They are deliberately cut that way partly so that they are size controlled and some people (me included) like the knobbly aged appearance when it has no leaves. You are right about the season, in summer the tree grows shoots of up to 3 feet long giving a slight lollipop appearance to the tree. The process of pruning the shoots back each year is called pollarding. Richard Avery (talk) 07:32, 21 May 2014 (UTC)

Thanks! Dismas|^(talk) 08:24, 21 May 2014 (UTC)

Pick proof lock

On my new house I would like to install a lock on the door that cannot be picked even be a professional locksmith. Does such a lock exist. I have heard about electronic locks that use a small keyboard built into it, then you make a password and then enter in your password to open the lock, and also another lock that uses your fingerprint. Can these be picked? And what happened when the battery runs out are you locked out forever? Also the one that uses your fingerprint is is possible for someone to extract your saved fingerprint from it?--Interestingusername123 (talk) 08:37, 21 May 2014 (UTC)

On Mythbusters, they managed to get into a couple of fingerprint locks quite easily. Electronic ones with no key backup require electricity to open. I don't think there's an "unpickable" lock. Keyboard locks are good, but they can wear in a pattern of the most used keys, which makes it easier to guess. 217.158.236.14 (talk) 09:07, 21 May 2014 (UTC)

Easier to guess...maybe...but not necessarily! If you have a single 4 digit code with no repeated digits then the wear pattern says what the four digits are...but not in what order - that would result in the bad guy having to try 4x3x2=24 patterns. That's way too easy! But with a 6 digit code (no repeats), he's got to go through 6x5x4x3x2=720 patterns. My wife and I each use a different 6 digit pattern - which (I suspect) cover all of the ten buttons on the pad...so all of the buttons wear out more or less equally fast and the bad guy is out of luck! If you really must have just one 4 digit code - then at least change it every few months to even out the wear on the buttons! SteveBaker (talk) 14:08, 21 May 2014 (UTC)

And after a change or three, they will forget the curent code and, wait for it, need a locksmith. Oh the irony. - ¡Ouch! (^{hurt me} / _{more pain}) 11:49, 22 May 2014 (UTC)

I once read about a door key lock which had only I, V and X keys in an attempt to avoid this problem. I can't find any online references though, so I guess it didn't catch on. 2A01:E34:EF5E:4640:E572:F28:C9E1:6456 (talk) 07:01, 22 May 2014 (UTC)

Clever! But you end up with much longer key sequences to remember...so I guess it's diminishing returns. Incidentally, last night I took a look at my door lock - and while there are actually three keys that are not in either my wife's or my key code - I can't see or feel any difference between those and the ones that get used half a dozen times a day. The buttons are all very smooth - I'm guessing they're made that way for precisely this reason. I think the "smooth key" exploit is a bust for decently made digital door locks. SteveBaker (talk) 16:47, 22 May 2014 (UTC)

I was also reminded of a key lock we had on a gate at work that used multiple simultaneous button presses (2 then 4 then 3 and 5 together). Using "chords" like that increases the number of combinations a LOT and also makes it vastly harder to use the "worn keys" trick to make brute-force searches work. SteveBaker (talk) 16:50, 22 May 2014 (UTC)

I'm reminded of this story: Ouch! William Avery (talk) 10:55, 21 May 2014 (UTC)

If this isn't just a case of "I want to start a forum chat about this topic because I'm bored", then you probably should talk to a professional to figure out what your security needs actually are. Note that most burglars aren't picking locks anyway—they're breaking a window or using a short prybar to separate the door and lock from the door frame. Making one small component harder to break doesn't magically secure your entire house; having a totally unpickable lock doesn't protect your valuable goods from a chainsaw through the wall attack. TenOfAllTrades(talk) 11:39, 21 May 2014 (UTC)

In a lot of places, people don't even lock their doors. If the house is far enough away from any other houses where nobody would hear a window breaking, there's not much use in locking the doors. Dismas|^(talk) 12:28, 21 May 2014 (UTC)

You should make a room of your house easy to enter, such that you can't easily enter the rest of your house from that room. You put some stuff there that looks like valuable items that are clearly visible from the outside but in reality they are worth nothing. E.g. fake jewelry, fake laptops, smartphones etc. Smartphones with GPS tracking that are configured to automatically take pictures and send them to you by email are also useful. Install motion detectors in that room such that the police is automatically called when anyone enters that room. This can only be switched off from outside the room allowing you to enter the room without problems. Count Iblis (talk) 12:42, 21 May 2014 (UTC)

Not necessarily good advice. Our police Crime Prevention unit advised that internal locks were rarely worthwhile as once someone is inside they can easily break almost anything being out of site. Evidently the repair bill often outweighs the value of items taken. -- Q Chris (talk) 12:50, 21 May 2014 (UTC)

My God—that's brilliant! I should sacrifice one whole room of my house, filling it with valuable-looking but useless crap and the security system from an action movie, forever, on the off chance of attracting a burglar who might otherwise have walked right on past. This sort of nonsense is why you should demand references at the Reference Desk. TenOfAllTrades(talk) 13:12, 21 May 2014 (UTC)

Yeah - I agree. It's like the old joke about how fast you have to run to get away from a charging grizzly bear...faster than the guy standing next to you! All you really need is better security than your neighbors - and that's usually very easy. Security cameras (even fake security cameras), digital locks and good outside lighting (front and back of the house) are enough to make the bad guy look at your house, and one further down the street - and figure that the other house is an easier target. SteveBaker (talk) 14:14, 21 May 2014 (UTC)

Is that assertion based on crime statistics, though? Or is it just a hunch based on a general opinion you've formed about criminal psychology?

To confound the statistical research, the FBI's nationwide Uniform Crime Report, which is the authoritative nationwide crime statistics database in the U.S., defines burglary as unlawful entry. Many local jurisdictions define separate crimes for breaking and entering and larceny and burglary. If a door is unlocked, the FBI considers home-invasion and theft to be be "burglary", but some states do not. If a door is locked, and an entrant picks the lock,... some places consider that burglary, and others do not. American law - and therefore, crime research in the United States - is about fifty times more confusing than it seems at first glance. Nimur (talk) 15:27, 21 May 2014 (UTC)

And if they just break down the door? 24.5.122.13 (talk) 21:27, 21 May 2014 (UTC)

In my state, it depends why they broke down the door. In other words, it is burglary if they broke the door with intent to commit additional crime, specifically intent to commit larceny. Contrast, for example, a case where some fool breaks down a door and promptly leaves: they have probably committed felony vandalism. Obviously, a criminal court needs to convict a defendant, i.e. by proving intent before we consider them guilty of this type of crime. Nimur (talk) 22:21, 21 May 2014 (UTC)

That's right, but then many burglaries are committed by people in the neighborhood who are familiar with the owners of the house, they know when they are on vacation and are then not fooled by such measures. Also you explain, physical security is problematic from a collective point of view, you depend on your neighbor's home having less security. A honeypot strategy makes more sense from a collective point of view. If burglars know that they'll get busted when they succesfully steal something (the problem being caused by what they steal), they won't attempt to break into a house in the first place. Count Iblis (talk) 16:01, 21 May 2014 (UTC)

It depends on what you mean by "pickable". That term normally means opening a lock without destroying it, which is important for say, spies, who don't want to give away the fact that they were there. Making a lock that must be destroyed to open it should be possible, although the lock could be replaced by an identical one, given enough time, so cameras that send images to a remote, secure location for storage might be a better option. StuRat (talk) 13:04, 21 May 2014 (UTC)

I think a bunker would deter most criminals but it is expensive, perhaps a safe room might do the job okay? :) Dmcq (talk) 13:28, 21 May 2014 (UTC)

If you are in the USA, you could go to the library and look at back issues of Consumer Reports at your local library. Consumer Reports rates locks (among other things). The good part is they're impartial and about as proficient as you could expect from generalists. The bad part is that since they're generalists, they don't get into subtle differences between products that would be important for a professional in a particular field. Jc3s5h (talk) 13:52, 21 May 2014 (UTC)

The digital locks that I have (which cost ~$80 in HomeDepot) are "unpickable" by mechanical means because there is no keyhole or other means of getting to the mechanical stuff. The keypad can be programmed to use any number of codes of either 4 or 6 digits - and you can do things like creating a time-limited code that only works for one day (so if you have someone calling at the house to do some work, they can let themselves in - but their code expires). It's handy to create temporary codes for visiting friends and such too.

The thing is indeed battery operated - and when the battery dies, you're certainly locked out. The machine uses a small electromagnet to engage a clutch when you enter the correct code - then you can turn the knob to open the door. So the battery only has to power the pad and the magnet...and only then while you're actually opening or locking the door. I change the battery once a year (when I change the smoke detector and thermostat batteries) - but I know I forgot one year and the battery was still just fine after 2 years of use. When the electromagnet isn't engaged, the door knob just spins uselessly because it's not physically connected to anything.

The only way to get in (short of smashing down the door) is to enter one of the right codes...which would take a LONG time to do by trial and error if you use a 6 digit code...but maybe the bad guy could guess it if you used your birthday or something stupid like that! I suppose there might be some incredibly clever thing you could do with magnets to cause the clutch to engage without the lock's own electromagnet...but the actual mechanism is buried in a lot of metal, a couple of inches behind the faceplate...that seems unlikely.

Fingerprint locks are relatively easy to fool if the bad guy can lift one of your fingerprints (eg from the door handle!)...that's been demonstrated many times and there are lots of websites showing you exactly how to do it.

Nothing is ever going to be perfect - but since it's so insanely easy to learn to pick or destroy the standard cylinder locks that 99% of people have, anything is better than nothing. IMHO, unless someone is specifically out to get **YOU**, your locks only have to be more secure than your next-door neighbor because the bad guys will always take the softer target. But unless you have bars at the windows and a sturdier-than-normal garage door, smashing a window is always going to be easier than getting past a digital lock. SteveBaker (talk) 14:02, 21 May 2014 (UTC)

I hope you've got a good one! There's quite a lot of simple hacks for digital door locks published on the web. The best ones I've seen involve inserting a wire strategically through the space beside one of the keys so it makes a contact inside which opens the lock, they have competitions with different locks to see how quickly people can crack them. It is a bit disturbing to see how easy it is to get lock picking equipment. And without even picking the lock they have things like a flexible arm with a camera and gripper st the end you shove through a letter box and control with a joystick to open doors. Dmcq (talk) 16:24, 21 May 2014 (UTC)

My door lock has a solid sheet of deformable plastic between the buttons and the switches beneath - I think it's there to stop water from getting in - but it might also be to stop the exploit you describe. Also, US houses don't have letter boxes...we have to walk two blocks to the array of mail boxes to get our post! SteveBaker (talk) 16:41, 22 May 2014 (UTC)

Being permanently locked out of your house if the battery dies is still unacceptable, IMHO. If you have multiple doors with independent battery power, it's less of a problem. But, if you have an apartment with only one entrance, I'd expect it to work on either battery or mains power, and to beep loudly when the battery runs low (using mains power to make the loud sound, so it doesn't run the battery down even quicker or use the short, high pitched sound that smoke detectors make when their batteries are low, which is notoriously difficult to track down). StuRat (talk) 16:49, 21 May 2014 (UTC)

You're only locked out from one door if the battery fails - my house has two doors and a garage door - all with digital locks. It's a stretch to imagine all three of them failing! Apartments are a different deal - I agree. But with at least a 2 year battery life, it's really not a big deal to change them once a year along with the thermostat and smoke detector batteries. SteveBaker (talk) 16:41, 22 May 2014 (UTC)

Practically speaking, I think most people want locks that can be picked so that it doesn't cost too much to lose the key or other access method. As long as the lock is harder to pick than it is to break in another way, what difference does it make? The crook will still get in. Wnt (talk) 21:28, 21 May 2014 (UTC)

The beauty of digital locks is that there are no keys to lose. You might forget the code - but it's unlikely because you use it several times every day. My door lock also has a 'master code' with a dozen or more digits which I keep carefully buried in an obscure web page somewhere online! I think I can open a regular cylinder lock using a decent set of picks a little faster than I could reliably break it open...but perhaps an expert at the "hammer a screwdriver into the keyhole" might do better. Breaking the digital lock seems like it would be insanely difficult. You could smash the outside part completely - and still be no closer to getting in. If the door itself is reasonably sturdy and you used those really long bolts to hold the striker plate to the door frame - it would be hard to break the door down by kicking it. So I think the difference between "pick-time" and "break-time" is less important than how long the "break-time" is. IMHO, digital locks are better because they are harder to break - not just because they are harder to pick. But in the end, the ultimate question is "Is it easier than smashing a window?" ...and that's where you hit the limits of what's worth doing with the door lock.

Personally, I just like not having to carry a key - and never being accidentally locked out! SteveBaker (talk) 16:41, 22 May 2014 (UTC)

LASIK surgery

Is lasik surgery done when you are consious? Is it painfu Zonex shrestha (talk) 10:08, 21 May 2014 (UTC)ljonesh

[According to lasik.com|http://www.lasik.com/articles/common-lasik-fears], the patient is awake but they're given numbing eye drops and sometimes a mild sedative. They say " some patients notice mild discomfort". Olaf Davis (talk) 10:25, 21 May 2014 (UTC)

My wife recently had it done - they used sedatives - but she was conscious though it all. She said that it was a bit scarey - but not painful - although her eyes felt 'gritty' and a bit sore afterwards..."kinda like if you'd been awake all night" was how she described it. She told me that the worst part was the smell. A representative of the company that makes the equipment happened to be there and we got chatting after I mentioned that we own a couple of laser cutters at home. So I got a ringside seat and he talked me though the whole thing on a couple of large-screen TV's they have in an adjacent room with a window overlooking the Lasik suite.

There is evidently more than one way to do this - so I can only describe the procedure they used for my wife - but maybe it'll be of some help. If you're squeamish - skip the next paragraph!

First they have to remove the outer layer of the eyeball so that they can get at the lens beneath. So the laser cuts out an 8mm diameter circle of the outer membrane leaving a gap at the top (this takes about 3 seconds) and then cuts out a thin channel, maybe a millimeter long off to the side. Then it switches focus so it's delivering energy beneath the surface of the membrane and scans back and forth over the circle in a series of close-spaced horizontal lines, making the fluid underneath vaporize (maybe 10 seconds) - the resulting gasses vent through the tiny channel they made earlier. The bubbles this produces gradually detach the circle of membrane from the underlying lens, leaving it connected at the top. The doctor then lifts the resulting 'flap' out of the way. Next, a different laser scans across the exposed lens surface shaping it into the new form (maybe 30 seconds) and then the flap is dropped back on top of it and gently smoothed out with a small plastic tool to remove air bubbles. Once all the bubbles are gone, the flap stays 'stuck down' by the surface tension of the fluids under there - so it doesn't move around or anything like that.

Then you're done...the whole thing was over in 10 minutes...it would have been faster but the fancy height-adjusting chair that she sat in had developed a problem and they had to reboot the chairs' computer to fix it(!!).

The moment the procedure was over, her vision was instantly hugely improved. They gave her a very quick eye-test to be sure everything worked out OK. She was given sedatives to take through the rest of the day - and some transparent goggles to wear that are just there to ensure that you don't accidentally forget and rub your eyes. (That's really important during the first 24 hours because they don't want you to displace that membrane flap until it starts to heal.)...for most of the rest of that day the sedatives kept her asleep...over the next few days, up to maybe a week, she had a complicated schedule of three different eyedrops to use at different times of the day. Throughout that time, her eyesight got slowly better and better (although it was vastly, amazingly better right after the treatment). After a week or two, she was down to just one over-the-counter eyedrop that just added lubrication. She was still using those a couple of times a day more than a month later. She had to go for checkups a half dozen times over the next few months - they just gave her an eye test and that was that.

SteveBaker (talk) 13:39, 21 May 2014 (UTC)

This description (in small font) appears to confuse a few terms and parts of the procedure, described at LASIK. The lens of the eye is not involved at all – it is the cornea that is reshaped, by ablative removal of tissue at a shallow depth inside the cornea. The initial lifting of a "flap" consisting of the surface of the cornea (along with epithelium) is done with a mechanical blade. At no stage do they affect anything more than about 30% into the thickness of the cornea, thus leaving the remainder of the depth of the cornea intact. —Quondum 14:23, 21 May 2014 (UTC)

The technique using a blade is very obsolete. These days, "bladeless LASIK" is the thing. And heck, please don't call me a liar - I was there and watched the whole thing - my description of how they removed the flap is what I saw, there was no blade involved and the entire procedure was explained to me by one of the guys who works with these machines every day. I saw the flap being cut, the bubbles being made and the membrane gently separated by the expansion of those bubbles (not "cut"). You're correct about the cornea rather than the lens being involved...it's actually forming the cornea into a corrective lens - so we need to be a little more careful than I was about that. The bladeless approach is better for many reasons - less risk of infection from the blade, less cornea being removed (because the laser-created flap is precisely the thickness of the membrane) - and less of the cornea has to be removed to form the lens because you don't have to fix the problems that cutting the cornea with a knife caused. Also, the laser is vastly more accurate than the blade - so the shape of the flap is more accurately formed and the resulting flap fits precisely back into the hole that the laser made - so recovery time is faster. SteveBaker (talk) 16:15, 22 May 2014 (UTC)

Personally, I would stick with spectacles rather than risk an unnecessary surgical procedure see: http://www.lasikcomplications.com/ Richerman (talk) 21:52, 21 May 2014 (UTC)

Yeah - my wife and I worried about that - but her eyesight before the procedure was truly terrible. Glasses did a poor job of correcting it because when lenses are powerful enough to correct her vision, the distance of the lens from the eye becomes super-critical and she never got good results with glasses. She was badly astigmatic too - and contact lenses that correct astigmatism tend to gradually rotate and when they do, everything goes blurry until you blink a few times and everything goes sharp again. Her contacts needed to be so asymmetrical that even blinking didn't always get them rotated back the right way. That's really a bad thing when you're driving! For her, LASIK was a truly amazing thing. Well worth the (very, very small) risk of problems with modern LASIK systems. My eyesight is reasonably well corrected with a combination of driving glasses and reading glasses - so I won't be getting LASIK anytime soon. SteveBaker (talk) 16:15, 22 May 2014 (UTC)

Synovial fluid agonist?

Can one raise it's levels of Synovial fluid by Nutrition for example? thanks Ben-Natan (talk) 16:23, 21 May 2014 (UTC)

Hyaluronan, a major component of synovial fluid, is a potential supplement. Apparently it is such a large molecule that the body has a hard time absorbing it. Injections into the joint are recommended. There is also chondroitin and glucosamine, although I don't believe these supplements directly increase synovial fluid. Justin15w (talk) 22:33, 21 May 2014 (UTC)

Identification of an Electronic Componenet

Various forms of Variable capacitor showing a compression trimmer at bottom center.

the following component was sold to me as 50 picoFarad Variable capacitor. but i am not sure about its variable & fixed legs. i also do not know how to connect it to the circuit for varying capacitance. front & back picture is attached. please help. picture link: https://drive.google.com/file/d/0B6hyDm8QXr34M2tnaS1hVDJPTkU/edit?usp=sharing https://drive.google.com/file/d/0B6hyDm8QXr34NXhTOEtmVUU4Rjg/edit?usp=sharing https://drive.google.com/file/d/0B6hyDm8QXr34dVNmMWJGcms3emc/edit?usp=sharing — Preceding unsigned comment added by 223.223.151.164 (talk) 19:07, 21 May 2014 (UTC)

Your pictures are unsharp but it looks like two compression trimmer capacitors side by side. Such components are used for one time settings in oscillator and tuning circuits. The tuning screw should be connected to rf ground; this is so the effective capacity does not change when you touch it with a screwdriver. A weakness of the compression trimmer is that there is no easy way to show the variation in capacity on a calibrated scale such as for manual tuning of radio stations. 84.209.89.214 (talk) 13:43, 22 May 2014 (UTC)

Eye scream [stolen eyes and retinal scans]

There's a news story linked above about a man who had part of his finger chopped off by criminals as a result of owning a car with a fingerprint-activated ignition.

This got me thinking about those retinal/iris scanners that seem to have gone beyond the realms of sci-fi in recent years. Has there yet been a confirmed real-world case of someone having their eye gouged out, or even being decapitated in order that criminals might gain access to <whatever> by fooling the scanner?

I suppose that there are more people in the world who'd be prepared to cut off someone's finger than would take someone's eye, with regards to the squeamishness factor of the thing... --Kurt Shaped Box (talk) 20:33, 21 May 2014 (UTC)

Violent criminals are NOT known to be squeamish about much of anything -- but the obstacle here is more practical, in that an eye is more likely to be damaged in the process of being gouged out, which would make it unusable. 24.5.122.13 (talk) 21:23, 21 May 2014 (UTC)

Plus of course the fact that it takes more effort to gouge out an eye without completely destroying it than to cut off an intact finger. 24.5.122.13 (talk) 08:46, 22 May 2014 (UTC)

Trouble is, they could have gotten much the same result by pushing the persons finger into a gummy-bear and using that to start the car...but hey, if they were smart, they'd be rocket-scientists and not criminals. Selling the car, complete with the dismembered finger needed to start it, is going to be difficult! It's really ridiculous to use fingerprint scanners - they are so easily fooled, and they cause problems like this one. Retinal scanners are a little better - but their usability is a major hassle. Biometrics in general are not a great way to do security. SteveBaker (talk) 16:02, 22 May 2014 (UTC)

Hammering a nail

Okay, a fairly simple question, yet one I still cannot understand. According to Newton's laws of physics, if I hammer a nail with a force, the nail will also produce an equal and opposite force to oppose mine. I understand that since the forces are on two separate objects the forces do not simply "cancel out;" however, if the magnitude of the force I apply is equal to the magnitude of the force applied by the nail, why then am I still able to hammer a nail into a piece of wood? I was not sure if the answer was simply "my force is greater than the force required to puncture the wood," or if it was a more scientifically-based answer. Thanks for any input. 23:29, 21 May 2014 (UTC) — Preceding unsigned comment added by 74.15.7.68 (talk)

When the hammer strikes the nail, the nail exerts a force on the hammer and the hammer exerts a force on the nail. ( Note: these two forces are indeed equal in magnitude and opposite in direction. However, they are applied to two different bodies, and can not cancel each other ). The force exerted by the hammer on the nail is not initially cancelled by anything: it simply accelerates the nail. Indeed, the nail was stationary before, and now it's moving forward, relative to the observer. The force exerted by the nail on the hammer decelerates the hammer, slowing it down a bit. After a while, the velocities of the nail and the hammer equalize, and they now move together. As the nail progresses into the wood, the nail exerts a force on the wood, and the wood exerts the force on the nail. This force is then (mostly) passed by the nail onto the hammer, decelerating both the nail and the hammer further, until they both stop. Does this help? --Dr Dima (talk) 01:02, 22 May 2014 (UTC)

Well, think of it this way: What would happen if you tried to use a wooden board to hammer the blunt end of a nail into a steel hammer? The forces are equal, but what the force does to the adjacent object can vary. Wnt (talk) 02:13, 22 May 2014 (UTC)

The forces are equal, but the same force has a greater effect on the nail than it does on you because:

1. You're much heavier than the nail, and F=ma

2. The nail is narrower, so the force per unit area (pressure) exerted on the wood is much greater than the force exerted on your hand. --Bowlhover (talk) 05:07, 22 May 2014 (UTC)

Newton's laws obviously apply here - but they don't really help very much in the explanation of what's going on.

If you hit a piece of wood directly with a hammer, it'll leave a shallow dent about the same size as the diameter of the hammer head. When you hit a nail into wood, it too makes a "dent" in the wood - this time it's only just the diameter of the nail - but much deeper. In both cases, the energy that you applied to the hammer is absorbed by the wood as it is compressed, distorted and torn...all that really changed was the shape of the hole and how the wood fibers had to be bent and broken in order to conform them to the shape of the impacting object.

A nail is a clever little "machine" that takes a force that's distributed over a broad, flat surface and concentrates it at the tip to drive a very thin object deeply into the wood. What actually makes the hole in the wood is the amount of energy applied to each little wood fibre. The hammer head by itself has to share the available energy between a heck of a lot of little fibers - but the tip of the nail only touches a very few of them - so the amount of energy applied to each fiber is HUGE. Consider the head of a typical hammer is probably 4 square centimeters - the tip of a nail might be maybe one square millimeter...so the amount of energy applied to each wood fiber is maybe 400 times more! In fact, the nail mostly pushes the wood off to the sides of the hole rather than bending them downwards as the hammer head would - and that stretches the fibers and the resulting extra tension is what allows them to grip the nail and stop it from falling out again.

SteveBaker (talk) 15:56, 22 May 2014 (UTC)

May 22

Quitting Smoking and Weight Gain

Not a medical question, just can't seem to find an accurate answer and am curious. Disclaimer out of the way - gaining weight is associated with quitting smoking. From what I've read, thus far, I've heard that this is due to three different things: smoking increases metabolism, increased eating, changes in gut flora. The common amount of weight gain is supposed to be around 10 pounds - but I've also read that that number isn't useful for individuals since some smokers gain a much larger amount that skews it. So, here's my question (I'm hoping that there is some reliable data to actually look at): what is the primary cause of this weight gain, is it harder to reverse gain after quitting, what determines who will gain a lot as opposed to a little? Essentially, how does this all work? --back to the disclaimer: when I can't sleep, I just google random things that pop into my head, this happened to be one of those things; but, since I can't find any really rock solid details, now I'm even more curious. Thank you for any help (sorry for the ridiculously long question):-) Phoenixia1177 (talk) 08:00, 22 May 2014 (UTC)

This recent review article says "The mechanism of weight gain includes increased energy intake, decreased resting metabolic rate, decreased physical activity and increased lipoprotein lipase activity." (and also lists several complicating factors, e.g. age, genetics, heavy smoking, etc.) [18]. This google scholar search has many relevant articles, some seem are more focused than the general review [19]. SemanticMantis (talk) 13:52, 22 May 2014 (UTC)

I suspect that the sense of taste plays a role, too, although that's a bit difficult to quantify, so less likely to be studied by science. I certainly know that for me, a nonsmoker, the smell of cigarettes makes me lose my appetite. Interestingly, it's not the tobacco itself, as pipe tobacco, which is relatively pure, doesn't cause this effect. Specifically, I suspect it's the ammonia they add to cigarettes, to draw out the flavor, that turns my stomach. I once bought a candy bar from a vending machine and immediately spit it out as inedible. I went back and looked at the rest of the vending machine to find they had cigarettes in there ! StuRat (talk) 14:00, 22 May 2014 (UTC)

Genetic engineering to alter genes

You can add genes to cells with a vector such as a virus. How do you remove or alter existing genes? [20] 203.45.159.248 (talk) 08:40, 22 May 2014 (UTC)

Well, when adding genes to a specific location, you would make a vector containing the gene of interest (plus a selection marker) flanked on either side by a stretch of DNA that is the same as the genomic region you're planning on inserting the gene into, this to facilitate the homologous recombination. Now imagine doing the same, but instead of the gene of interest, you put nothing in between the flanking genomic regions. You would remove from the genome any sequence that is in between the flanking regions. Also note that it's not necessary to remove the whole gene of interest from the genome to knock out the function, just the first exon or so is normally enough. Now, in practice you wouldn't have nothing in between your flanking regions, you would still introduce something to help with selection, like an antibiotic resistance gene, or a fluorescent protein. Note that this is the traditional way of doing things, these days with things like CRISPR the methods can be different, though the basic principle is the same. Fgf10 (talk) 08:52, 22 May 2014 (UTC)

I have -4 power in my left eye but almost neutral in my right eye. If i stop to use the spectacle then what problem may arise ?

I have -4 power on my left which is in X-axis in some degree rotation due to which my contact lens always move when i blink my eyes and everything go blur. What kind of contact lens is suitable for me? — Preceding unsigned comment added by Zonex shrestha (talk • contribs) 09:40, 22 May 2014 (UTC)

Wikipedia's reference desk will not answer requests for medical advice. See an eyecare professional, who can answer this question. --Jayron32 09:42, 22 May 2014 (UTC)

See here. Count Iblis (talk) 11:20, 22 May 2014 (UTC)

Persistance of Electromagnetic radiation

Do electromagnetic radiation persist even in a reduced scale and in that case can electromagnetic radiation from distant past be detected and amplified and thus people can witness events from arbritrary past without affecting the past that is travel backward in time.Why is in not research directed to develop theory and contrivance to achieve this in reality.In time travel page there is a reference to such claims.When stars stars several light years away are detected why is this not possible.I want to ask that staying in this planet can people travel back in history or visualise it in some television type of device.Do laws of physics pose a barrier to this and then why cannot these barriers circumvented when technology has advanced to a state where traces of gamma radiation from distant space detected and analysed, then why not local visible EMR.Cannot be there any EMR from past in atmosphere.Sorry for my absurd insane naive question. 117.194.253.103 (talk) 16:19, 22 May 2014 (UTC)

Certainly. We can detect electromagnetic radiation from the "Big Bang". That's because it takes time for light to get from one point to another. If we do some absurd approximations of reality, we can hypothesize of a perfectly sealed box containing perfect (non-absorbing) mirrors. If we turn on, then immediately turn off, the a light source inside such a box, I don't see why said photons shouldn't remain there in perpetuity. The problem is that no such box, and no such mirrors actually exist; even the best mirrors absorb enough light that said photons would dissipate within fractions of a second. --Jayron32 16:39, 22 May 2014 (UTC)

3D printers

It's looking like my expensive, high-tech 3D printer is actually a pile of junk that breaks every few days, falls apart for no reason, and costs a lot to keep repairing... Whilst I would love to get a proper expensive model, from what I've seen they cost at least ten times as much, money I don't have right now, so I'll have to resort to buying a nice cheap one, in fact if this experience is anything to go on, something as cheap as possible, so I don't regret having wasted even more money.

Trouble is, back when I bought this, there were basically three different models available for less than £20,000 whereas now there are about 50, and I have no idea which are any good, which are available in my country, how much they cost, and so on.

What I need is some place where I can find out which 3D printer options there are in the UK, giving the actual price, including shipping, tax and so on, and preferably with some example of what they can do. That or just someone's recommendation of a reasonably cheap but good model to look at.

213.104.128.16 (talk) 16:55, 22 May 2014 (UTC)