Wikipedia:Reference desk/Archives/Science/2015 October 17

= October 17 =

Band in my head
When I listen to my hi-fi through headphones, the band is playing inside my head. This is not desirable. Is there any signal processing trick (hardware or software) that can be used to make the band appear in front of me as it does with speakers?--213.205.252.35 (talk) 00:48, 17 October 2015 (UTC)


 * I suspect that part of the effect is because, when you turn your head, the relative volume in the two ears does not change, as it would with an actual sound in front of you. I suppose headphones could be designed that would change the relative volume in each ear depending on your head position, to make it sound like the source of the audio was at any point in the room you choose.  If nobody has yet designed such a device, it sounds like a good idea, to me, and you could use existing stereo channel signals to specify the arbitrary location of any two sound sources (or quadraphonic sound would allow you to specify 4 sound locations).


 * Since the hardware requirements are minimal, this could be a much less expensive way to get the desired effect than using multiple speakers located throughout the room. Note that the recordings would be a bit different, though, as you would want 100% of each instrument to be on one channel, rather than a mix on each channel, unless the instrument is actually supposed to move from one location to another, in which case it would move from one channel to another.   StuRat (talk) 00:53, 17 October 2015 (UTC)


 * I'm not sure if there is a signal processing trick that can be applied after the recording is made, but if you make a binaural head recording of a band in front of you and play it back using appropriate headphones it does sound as if it is front of you. The sense of location is not perfect, in particular sounds about 45 degrees above your head in front are easy to confuse with those 45 degrees up and behind you. (Or at least 15 years ago this was the case). Incidentally for many years I did not get a sound picture from headphones, I just heard left ear and right ear. Greglocock (talk) 08:30, 17 October 2015 (UTC)


 * Ah. Growing up in the age of early stereo like West Side Story (soundtrack) and finding feed it between my ears and not out there before me I know what you mean. Our article Binaural recording can help you understand the issue.--Aspro (talk) 14:24, 17 October 2015 (UTC)


 * My fossilizing brain is failing me, I was searching for Brewer rather than Bauer stereophonic-to-binaural DSP. One can download it now for free. In the good old days, one could buy custom headphone amps (deploying the crossfeed method) to achieve the same result.--Aspro (talk) 15:04, 17 October 2015 (UTC)


 * Bauer was what I immediately thought of as well. There's also the Dolby Headphone engine which uses some heavy signal processing to create a virtual surround sound environment. The functionality is contained in the dolbyhth.dll which is sometimes bundled with software DVD players. Certain software music players have a wrapper plugin in order to use the library. Asmrulz (talk) 15:41, 17 October 2015 (UTC)


 * After much net trawling found a page right here called Crossfeed --31.55.64.161 (talk) 03:40, 19 October 2015 (UTC)

Expected Lifetime of F-type Star
What is the expected lifetime of a main-sequence F-type star? The article for the purpose doesn't say. I know that it is less than the expected lifetime of a G-type star. My real question, of course, has to do with KIC 8462852. The question is whether an F-type star has a sufficiently long life in the main sequence for advanced life to evolve. We know that in our case, with a longer-lived G-type star, it took about 4.5 billion years, with about 2.5 billion years after the oxygen catastrophe. So, based on modern scientific thinking, does an F-type star last long enough for advanced intelligent life to develop to where they can build a Dyson sphere or some similar megastructure? Can someone either show me an article that shows how long an F-type star will stay in main-sequence, or otherwise answer whether there has been enough time? I had thought that K-type stars would be more likely to have advanced life, having much longer lives, and not being as small as M-type stars to involve tidal lock conditions. What is the expected lifetime of a main-sequence F-type star? If it is at least a billion years, we need to listen to them, very carefully (and maybe stop transmitting to them). Robert McClenon (talk) 02:16, 17 October 2015 (UTC)


 * Main sequence gives an equation that tells you how long a star will stay on the main sequence. But, I'm not sure about the units it's asking for. Are the masses supposed to be in kilograms, or something else? Maybe someone more versed in astronomy can answer. Anyway, F-type stars apparently are only slightly more massive than our Sun, so I assume they stay on the main sequence for slightly less time than our Sun will. Mass is what determines a star's lifetime, because it determines the pressure at the core, which in turn determines the rate of fusion, as well as whether the star can fuse heavier elements. --71.119.131.184 (talk) 08:47, 17 October 2015 (UTC)
 * It says in the caption: "The mass and luminosity are relative to the present-day Sun." and the symbol means the solar mass.  Rojomoke (talk) 12:23, 17 October 2015 (UTC)

Enchroma glasses for colorblindness
I read an entertaining and interesting article in Aftenposten's weekend magazine (unfortunately behind a paywall). It describes the experience with the EnChroma glasses of a journalist suffering from severe protanomalic trichromacy. The article ends with an anticlimax:


 * "But is [my experience with these glasses] just a result of the placebo effect? Have I so intensely wanted the glasses to work, that I have managed to convince myself that they actually do?
 * (Name redacted), professor in optometry and visual sciences at (Institution redacted), thinks so.


 * - Unfortunately, the glasses cannot give you a normal color vision. To do so, they would have had to change the sensitivity of just one of your visual pigments, and that is simply not possible to achieve by wearing glasses. The colors you already see, will appear more distict, and it is probable that you perceive more nuances, but the colors that confuse you, will continue to do so, she concludes.


 * So thus ended that dream. But damned how fun I had those hours that I thought that I saw exactly the same colors that the rest of you do."

I have read the information on EnChroma's website, and this blog post, and it appears to me that the theory behind these glasses is sound. The professor that was quoted may not have taken the time to read the product description thoroughly, and may have been unaware that the glasses work by removing spectral overlap in the incoming light, not by "changing the sensitivity of one of your visual pigments".

However, I was unable to find any pubmed links to papers evaluating the glasses. So I have two questions:


 * Are the glasses capable of considerably enhancing color recognition in a person with protanomalic or deuteranomalic trichromacy?
 * Can anybody provide links to academic papers or websites that evaluate the glasses, in the context of color blindness?

Thanks, --NorwegianBluetalk 10:21, 17 October 2015 (UTC)


 * The links in their "news" section help point out the limitations of this approach: "First, they’re sunglasses. They don’t work indoors unless the light is very bright. Second, they’re not designed for use with a computer screen. And, weirdly enough, these glasses won’t help you pass the standard Ishihara colorblindness test, the ones where you try to see a number composed of hundreds of dots in a circular test pattern. I still failed that test."


 * It is important to understand what this product is not. What you might imagine is that the eyeglasses take all the light, process the colored components into whatever frequencies happen to be best distinguished by a user's color blind eyes, then deliver that signal for maximum resolution as seen.  But they don't do this - no electronic device presently sold (that I know of) can arrest and reproduce light in mid-flight from all angles.  A device can only record it as a 2D entity, then redisplay it - which requires some kind of Google Glass like display.  The exception is that you can block out some of the light according to its frequency (filter it).  The result is that these glasses cannot deliver to the color blind person any actual signal he's not already seeing; but they can block out what you might call the "glare" of the intermediate-frequency signal that he can't do anything with.  So they can't make pixels on a screen or in a printed color blindness test look any different than they do (except, perhaps, dimmer if they are in the blocked bands).


 * An approach that I would find more interesting would be like the 3D glasses that block transmission many cycles per second. If you had one such filter that blocked red, another that blocked green, then the red and green components would alternate in brightness.  Perhaps by flashing them in a particular sequence, the user would become accustomed to distinguishing them.  Or maybe by flashing a monochromatic light at the same time as each channel, you can "blind" the receptors for the other channel.  (i.e. red-only transmission plus uniform green -> you see variations of red; then swap with the reverse)  Anyway, this isn't that. Wnt (talk) 11:52, 17 October 2015 (UTC)


 * Instead of time-multiplexing two filters, you could use different filters in each eye. -- BenRG (talk) 02:22, 18 October 2015 (UTC)


 * You could do that without electronics, just using red and green tinted lenses. I assume that would have been tried by now, and doesn't work to the extent that they can recognize red and green without closing each eye in turn and thinking about it.  I think flashing either red or green (in the case of that form of color blindness) would lead to more automatic recognition.  Of course, that might be annoying and might trigger epilepsy attacks, so, if you did have this option, you would need to be able to turn it on and off.  (Also, actual blinking lights might be harder to spot when this was turned on, so would be bad to use when driving, since some traffic lights blink.)  As for the type of blinking, having red (or green) slowly fade to black and then back to full brightness might be easiest on the eyes. StuRat (talk) 02:52, 18 October 2015 (UTC)


 * I tried that once using some colored filters I had for my camera. I have normal color vision. I did it just for fun, wanting to see if I would be able to simulate being a hexachromat. It didn't work. The colors didn't blend together, I either saw the color of the image seen by the left eye or the right eye, or both at the same time. And the parallax effect was nauseating. --NorwegianBluetalk 07:49, 18 October 2015 (UTC)


 * Tried what, blocking red in one eye and green in the other ? I think you'd get over the nausea after your brain became accustomed to it.  Somebody did a weird experiment where they used mirrors so they saw the mirror image of everything, and it took about a week for them to become accustomed to it (and about a day to go back to normal).  But I suspect that we lack the "hardware" to combine the images into one, and know where green and red are on the combined image.  That is, other than parallax to determine depth, which is determined in a "pre-processing" step, I believe the images, once combined into one, no longer store which color came from which eye, and this info would be needed to distinguish the colors. StuRat (talk) 17:51, 18 October 2015 (UTC)


 * I was able to view the article that you linked without logging in, maybe because I have Javascript turned off by default. Here it is Google-translated to English (you might still need Javascript to be off).
 * As the professor said, a filter can't turn nonstandard color vision into standard color vision. What it can do is change nonstandard color vision into different, and perhaps more useful, nonstandard color vision. Someone wearing these glasses will be able to distinguish spectra that someone with ordinary color vision can't. For example, 560nm monochromatic light will look almost identical to some mixture of 540nm and 590nm light if you have normal color vision, but if this diagram is correct, they will be easily distinguishable with these glasses on because the 560nm light will be much dimmer. The paint-color difference that the author saw and his wife didn't might have been a real spectral difference that was invisible to people with normal color vision (although in that case I would expect his wife to have seen it in other lighting conditions).
 * Whether the altered color vision is useful depends on what sorts of real-world spectra it's useful to distinguish between, which I don't know. The real-world experience of someone with normal color vision is not a reliable guide to this. The glasses might have entirely different effects on incandescent vs LED traffic lights, and whether you can pass the Ishihara test might depend on how it's shown to you (CRT vs LCD vs OLED vs inkjet-printed vs professionally printed, with possible large variation within those categories too). -- BenRG (talk) 02:22, 18 October 2015 (UTC)


 * I think I get it. The frequences that the color-blind individual is physiologically incapable of telling apart, are dimmed. In the article that Wnt linked to, the person exclaimed: "Then I put on the glasses. Unbelievable! Now I saw two entire additional color bands, above and below the yellow arc. It was suddenly a complete rainbow." Which of course it wasn't. A complete rainbow is a continuous transition between the colors of the spectrum, not three separate bands of colour. Thanks, everyone. --NorwegianBluetalk 07:37, 18 October 2015 (UTC)


 * Another idea, from the world of newspaper cartoons, would be to use cross-hatching to show one color, either red or green. This would only work on large areas of color, but would be less annoying than blinking.  I believe you could distinguish from actual cross-hatching in the real world in that the CH pattern produced by the glasses would move as you moved your head.


 * Something we hadn't yet discussed is that you could alter all colors to be in the frequency range the person can distinguish, but that would be rather annoying in that all colors would then shift, not just the problem colors, every time you put the glasses on or took them off. StuRat (talk) 17:56, 18 October 2015 (UTC)


 * NorwegianBlue, I've previously looked for sources of the sort you want, and I've failed to find any; look for my username at User talk:Doc James/Archive 82 to get further information. As far as effects: if you're interested in original research, read on.  I'm a bit colorblind, having trouble distinguishing between green/red and resulting mixes of those colors with others, such as pink/grey, blue/purple, yellow/orange, and yellowgreen/yellow, although I can still tell the difference between brighter colors; unlike my grandfather, I can distinguish the colors of stop and go at a traffic light.  If I remember rightly, it's a deuteranomaly situation.  Relatives gave me some EnChroma glasses several weeks ago, and while the experience wasn't as drastic as the ones appearing in some YouTube videos (it took a couple of minutes before I noticed differences), I've been able to see significant differences in certain situations.  For a simple example: it's currently the height of the colored leaf season here in Ohio, and I've been able to see lots of "new" colored trees; acquaintances have asked me to point out red trees in the past, and I was completely helpless, while I'm now able to do this rather easily and (for the first time) point out red and orange boughs of trees that are otherwise still green.  Lots of other differences have become visible in things like older buildings with faded bricks (these now look like those of newer buildings), flowers (after putting the glasses on for the first time, I saw an orange marigold and asked an acquaintance if this were normal; I could see that this plant was orange, but I'd always thought marigolds were always yellow), and agricultural fields (I've never before realised that cornfields had brown shades, and soybean fields have changed from a pale grey to a rich color).  Perhaps a good example is the file to the right: the soybeans in the row with the left-hand sign are a slightly darker edition of the color that I've seen in soybean fields when wearing the glasses, while the row next to the left is the color I see in the same soybean field as soon as I take off the glasses.  Alternately, consider File:Jennings Township wheat field.jpg and File:Countryside in Washington Township.jpg.  If you changed the darkness of either one so that they were at the same point on the dark/light spectrum, Jennings would still have stronger/brighter colors than Washington; this is comparable to my experience, because the red-influenced colors (and to a lesser extent, the green-influenced), including browns, are routinely coming out a lot more strongly when I'm wearing the glasses.  Final example — when I've worn the Enchroma glasses for a good while, and then I take them off, the experience is comparable to that of starting to look through a somewhat grimy piece of glass.  You can still see fine, but the colors become rather washed out, they fade, and the less-bright areas tend to merge with each other.  Nyttend (talk) 02:00, 19 October 2015 (UTC)
 * Thanks for the link and for sharing your experiences with the glasses! Following the advice on the talk page you linked to, I did a Google scholar search as well (should have thought of that). 40 hits when putting "EnChroma" in quotes. Among the hits were a couple of papers in a technology journal that I don't have access to, but which did not seem to be very relevant. Then there was the patent application, and an interesting Review of Color Blindness for Microscopists, which has a section on visual aids for persons with red-green color-weakness to make sense of multicolor microscopy images, in which the EnChroma glasses are mentioned. Multi-color fluorescence microscopy images which include read and green fluorochromes are of course difficult to interpret if you cannot tell the colors apart. Software solutions (such as color substitution in image processing software) were described. I also learned that there exist smartphone apps that can be tuned to a person's color deficiency, and present a color-shifted version of the image from the phone's camera to the viewer in real-time. Interesting stuff, but no papers about the Enchroma glasses. --NorwegianBluetalk 12:26, 19 October 2015 (UTC)


 * The thing about colorblindness is that there are something like 15 different variations of the condition - some common, others incredibly rare. The glasses can't possibly help with all of them.  My understanding is that they DO fix the most common 'weak red' and 'weak green' variations ("red/green colorblindness").  In those cases, the person has two sets of perfectly good color sensors and one set of weak sensors.


 * Suppose you have 'weak green' - you can still perceive some green light, but at much lower levels of sensitivity than red or blue. But the weakness makes it hard to distinguish things on the red/green section of the spectrum.  I believe that the glasses work by selectively dimming down light in the range covered by the two 100% functional sensors to the level of the weak sensor - while allowing light in the range covered by the weak sensor through unchanged.


 * The net result is that all three colors are now presented in equal quantities - albeit all quite a bit dimmer than before. The net result is like wearing dark, neutral colored glasses with normal vision - and in bright light, that should result in near normal vision.


 * This approach clearly can't work for variations where there is absolutely no vision in one or more of the three colors...but those variations are quite rare. The company website include a color vision test that'll let you know whether these glasses will work for you or not.
 * SteveBaker (talk) 23:18, 19 October 2015 (UTC)
 * I don't think your description of how the glasses work is correct. I'll use the RGB analogy, even though we strictly don't have red, green and blue photoreceptors. My understanding is that in the majority of cases of red-green color deficiencies, either the "red" receptor has a response spectrum that is shifted, and closer to that of the "green" receptors, or vice versa. This creates a larger spectral overlap between the signals from the "red" and "green" receptors than in a person with normal photoreceptors. The glasses work by filtering out the frequencies with spectral overlap (i.e. which create an equally strong signal from the "red" and "green" receptors). The removal of the confusing frequencies in the incoming light, increases the difference in the output from the "red" and "green" receptors. Since a colored surface usually reflects a mixture of frequencies, this will make it easier to tell a red object and a green object apart. --NorwegianBluetalk 08:04, 20 October 2015 (UTC)
 * The articles on color blindness should handle this. My recollection is that red and green receptors recently diverged in evolution from a single sequence.  In some people, their sequences get mixed together, producing something that is a part-red-part-green receptor, or even just the wrong kind.  It's more a matter of frequency than intensity (in general).  It is for this reason that the company is telling people it should test their eyes and make a customized filter set for their particular use.  Of course, a well-run company would cheaply mass produce one or two standard filters, sell them to everyone who is close to one of those models, then tell the others not helped by these most common models they can't really be helped... Wnt (talk) 15:39, 21 October 2015 (UTC)

Do electric vehicles need brakes?
Do electric vehicles need brakes, or, can they always brake using the motor itself? At least, wouldn't they need a different type of braking compared to normal (combustion motor) vehicles.--Scicurious (talk) 13:15, 17 October 2015 (UTC)
 * Typically, they cannot brake hard enough using regenerative braking from the motor, and so always have a normal braking system as well. This is also used when regenerative braking is not available: when the batteries are fully charged is a notable example of this.--Phil Holmes (talk) 14:30, 17 October 2015 (UTC)


 * Don't disagree with the above about requiring conventional brakes, but the first vehicle to use regenerative braking (trains), just switched the excess energy through a ruddy great resistor. Even if the car batteries are discharged there is a limit an how fast energy can be pumped back in.--Aspro (talk) 15:17, 17 October 2015 (UTC)
 * Terminology note: when the energy is dissipated that way, it's usually called rheostatic braking, not regenerative. --174.88.134.156 (talk) 04:40, 18 October 2015 (UTC)
 * Trains are rather larger and heavier than cars. Well-designed electric cars try to keep mass as low as possible, to achieve greater efficiency and range.  So carrying around a "ruddy great resistor" isn't a great design choice, even if the vast amount of heat could be safely dissipated within a car.  Much easier to use conventional brakes, which are required in any case as a "hand" brake.--Phil Holmes (talk) 16:00, 17 October 2015 (UTC)
 * Err - the kinetic energy of the car needs to be converted to heat in both cases - it's just a question of whether that's in the resistor or the brake discs. Tevildo (talk) 16:40, 17 October 2015 (UTC)
 * And trains still have to carry separate emergency braking systems, at least in countries with regulations. As to the original question, why would electric vehicles need a different type of brake than chemically-fueled vehicles? Friction brakes work by pushing something against the wheel. As long as you have wheels, they'll do the trick. Aircraft use them too (some large jets have thrust reversers, but they're used in conjunction with friction brakes). You don't have to use rheostatic or regenerative braking with an electric vehicle. And as mentioned, pretty much all electric vehicles also have friction brakes as a secondary. --71.119.131.184 (talk) 16:45, 17 October 2015 (UTC)
 * I hate to devolve the question into one of pure semantics, but I think the core issue is how we define "need."
 * "Do electric vehicles need brakes?" Strictly, no: I can build and operate a vehicle that has no brakes.  Perhaps my vehicle would be unsafe or illegal, but those are separate issues.
 * "Do safety regulations require electric passenger automobiles to use conventional disk brakes?" We must follow up by qualifying the question: safety regulations for which locale?  In the United States, such regulations are immensely complicated, and are codified in many different documents by Federal and State governments, not to mention other jurisdictions.  You can find a general overview at NHTSA's Laws and Regulations webpage.  The Federal Motor Vehicle Safety Standards, 49 CFR §571.105 Hydraulic and electric brake systems standardizes the majority of the Federal safety requirements for brakes; but this standard does not exist in isolation: it must be considered in the context of all other applicable laws and regulations.
 * Tearing this regulation apart: 49CFR§571.105(S5)(1) states: "Each vehicle must be equipped with a service brake system acting on all wheels." Does an engine-brake or a regenerative braking system (RBS) meet this legal requirement?  Does the requirement even apply to a specific vehicle?  These are not easy questions - exactly the type of question upon which we might call for a specialized attorney's opinion.
 * "Is there a scientific or engineering reason that favors conventional disk brakes over regenerative or electromagnetic brakes?" The answer depends on how specific you wish to be.  In general, any reactive or retarding force of the same magnitude, no matter how it is created, will slow and stop a vehicle.  As we investigate the details, we may find that the machines we know how to reliably build are better at producing large-magnitude mechanical frictional forces, as opposed to equivalently-large-magnitude electromagnetic forces.  If cost, size, and reliability are not at issue, we can produce the same net force by any mechanism we wish.  Here is a state-of-the-art training course from SAE: High-Perfomance Brake Systems.  Chances are, if you are not actively professionally employed in the design of automobiles, you won't spend thousands of dollars on this kind of seminar; but by inspecting its syllabus, you can see how real automotive engineers think about the problem: there is an element of pure physics (like energy budgets, force, momentum, acceleration, kinematics) and there is a lot more effort expended on analyzing engineering non-idealities, like material properties, reliability concerns, safety issues, vehicle dynamics, and so forth.
 * Nimur (talk) 17:51, 17 October 2015 (UTC)


 * Our article on regenerative brake says they don't work well at low speed, so they always need conventional systems even aside from the safety aspect. I'll also put out a guess - don't know that it's true - I'm thinking a regenerative brake should be limited by the overall size and conductivity of its wiring, strength of its supports, something having to do with the engineering.  Because you want to brake at many different rates, and only very rarely at the fastest rate possible, setting the whole regenerative brake up to work at the fastest speed might be a waste, compared to adding a simpler friction brake for those rare instances, which deliver insignificant amounts of power overall in the vehicle's life. Wnt (talk) 18:15, 17 October 2015 (UTC)
 * In particular, consider the very low speed of 0. With regenerative braking you won't get any braking force until the vehicle has moved some distance.  With repeated small applications of force it would creep away from its original stopping position.  With conventional braking it won't even start moving (beyond the amount of play in the suspension) until enough force is applied to overcome static friction in the brakes, so small forces won't move it at all. --174.88.134.156 (talk) 04:40, 18 October 2015 (UTC)
 * Actually, my electric car (a BMW i3) can come to a complete halt without using the disc brakes, and can also hold itself on a hill by electric means alone (BMW call it "hill hold"). I assume it does this by effectively running the power to the motor backwards.  Providing your anticipation is good enough (and other road users don't do anything unexpected) you can drive without ever touching the brake.--Phil Holmes (talk) 09:42, 18 October 2015 (UTC)
 * "Hill hold" or "Auto-hold" is not an exclusive feature of electric cars. It usually works through the mechanical ABS system (with electronic monitoring and electro-mechanical activation, of course), but you could well be correct that the BMW i3 uses a different system.  Also, you don't need regenerative braking to drive without brakes — engine braking is sufficient in most circumstances, but I agree that it might be easier in the BMW — I've never driven one!    D b f i r s   11:51, 18 October 2015 (UTC)
 * Here is a link to BMW's promotional literature on this topic: Electromechanical Parking Brake. This brake technology is related to several of the other vehicle features, including Hill Descent Control and Dynamic Stability Control, and BMW's version "offers an autostop and hillhold function."  Their literature is not perfectly clear, but it appears that the electronic control actually engages the conventional, hydraulic brakes; when hydraulic pressure is unavailable (because the engine is off), the electronic control engages the conventional brake using a cable system.  In other words, the control is electronic, but the mechanical brake force is still applied by way of a conventional, friction disc brake.  We have an article on Electric Park Brake, which talks about the feature as it was implemented by BMW and by other vendors.  BMW also has other fascinating brake technology, including Dynamic Brake Control, Adaptive Brake Assistant, and of course, ABS.
 * User:Phil Holmes, if you are very certain that your BMW i3 is able to reach a complete halt without engaging the disc brakes, I would be fascinated to read about that technology - I am not familiar with it. Do you have a link to a reference that explains that?
 * I did find, at least, this humorous video, in which the reviewers at Auto Express made a valiant effort to drive without applying the brake pedal... but they did need it to hit the pedal at least a few times. Even still, this does not make clear whether the brake-pedal actually engages the disc brake or simply alters/engages the regenerative brake system.
 * Nimur (talk) 01:19, 19 October 2015 (UTC)
 * I am completely certain that my i3 can stop without using any mechanical (disc) brake. I very rarely use the brakes at all, and if they are applied you can hear them: the lack of use means they almost always have a slight rust film.  Also I know that if I try to stop regeneratively when the battery is fully charged, I can again hear them.  So I know that if I can't hear them, then the car has stopped with purely regenerative braking.  On the i3, the "hand brake" is an electrical switch that causes some sort of motor to push the pads onto the discs of the rear wheels: you can hear a whirring sound when you pull the hand brake switch.  Finally, hill hold is purely electric: you let the car roll to a halt at a junction on a hill and it stays there with no application of the mechanical brakes.  Again: if there were any application, it could be heard and would slightly delay move off.  That what's happens if you are miserly and apply the hand brake to avoid using battery power to hold the vehicle on a hill.--Phil Holmes (talk) 13:17, 19 October 2015 (UTC)
 * Someone claimed in the Youtube comments if they'd shifted to neutral they could have avoided the creeping near traffic lights which would have reduced the cases of using the brake pedal down to one namely entering the parking lot. (And I wonder whether the movement of the passenger really made a difference in the light where it happened, it would seem probably not since he was in the car, but perhaps something to do with the situation meant it did.) I'm not so sure about the neutral suggestion though, most searches confirm that the i3 isn't supposed to creep (some other electric vehicles do, to stimulate the behaviour of a normal auto), so it seems more likely the problem was it just wasn't that good at coming to a complete stop, perhaps because it was on a mild slope . Of course some of the behaviour shown there may not have been best driving behaviour (as would shifting to neutral at what appear to be fairly short lights), and in any case you probably want to apply the brake for safety reason. Also even if the car isn't using disc brakes internally, some of the extremes like not applying the brakes at the traffic lights stop the creep is largely pointness even ignoring safety issues, from an energy saving standpoint. Nil Einne (talk) 05:53, 19 October 2015 (UTC)
 * These two responses are assuming (1) that someone is driving the vehicle and (2) that situations are predictable. Consider an unattended car in the presence of wind gusts. --174.88.134.156 (talk) 15:20, 18 October 2015 (UTC)

Jung, and is this the right reference desk for psychology?
This is my first use of the reference desk and so forgive me if it is the wrong place or the wrong sort of question. I posted a related question over at the Tea House to see if there is a policy that describes what level the lede or overview should be for articles that are not in highly specialized domains. So I am asking the question and the meta-question here at the same time.

While looking at some article related to psychology I saw and clicked on a link to Carl Jung. But reading the lede has me scratching my head. So the non-meta question here is: in a layman's nut-shell, what did Jung contribute to psychology?

For the meta-question, the first and third paragraphs of the article lede are fine. But in the second it says: ...individuation—the psychological process of integrating the opposites, including the conscious with the unconscious, while still maintaining their relative autonomy. The meta-question is: should an article lede make sense for the layman or not? Even drilling down to the pages on Individuation and on Analytical Psychology don't make sense to me. Is there a presumption that one already be familiar with the field in order to gain from a WP article? Arbalest Mike (talk) 20:32, 17 October 2015 (UTC)


 * Your Q isn't about psychology (in which case this might be the right Desk). The general Help Desk is probably the best place for questions on the audience for our articles.  However, you are right that the lede should be written for the layman, as much as is possible.  We do have a continuing problem here, though, that articles written by PhDs tend to be written for PhDs, and any attempt to make them readable to a general audience encounters fierce resistance.  The most contentious issue is typically that some degree of simplification is needed to convey concepts to a general audience, and they are absolutely opposed to that.  I think that's fine in the lede, with the detailed sections explaining all the details more precisely. StuRat (talk) 00:42, 18 October 2015 (UTC)


 * Seems like Carl's article is already oversimplified. Nary a mention of enantiodromia... :) - Nunh-huh 03:21, 18 October 2015 (UTC)


 * To clear up your question about what should be in the lead you should read Manual of Style/Lead section. It says there:

 The lead should be able to stand alone as a concise overview. It should define the topic, establish context, explain why the topic is notable, and summarize the most important points, including any prominent controversies...The lead is the first part of the article most people read, and many only read the lead. Consideration should be given to creating interest in reading more of the article, but the lead should not "tease" the reader by hinting at content that follows. Instead, the lead should be written in a clear, accessible style with a neutral point of view... 


 * I have heard it said that Wikipedia articles should aim to be understandable by a bright 16 year old. Although for some subjects that isn't always possible, it is something that we should aim for as much as we can. As has already been mentioned, however, some will resist that concept as their subject is not to be understood by anyone who is not as educated or as brilliant as they are. Good teachers are able to reduce their subject to its simplest terms and make it accessible to as many people as possible, and that is what good writing is all about. Richerman    (talk) 10:02, 18 October 2015 (UTC)

History of the wiki
Does anybody know where I can get a good, comprehensive book that talks about the wiki and the developments around it for the field of computer programming? I am writing something about it and do not have a ton of technical expertise, although I can learn. I have read a lot of the mainspace articles about it, but would like something more historical than a lot of the sources that they point to. I'm just wondering if there is a gold standard history of computer programming book that everyone uses. Kllrmvs (talk) 21:24, 17 October 2015 (UTC)
 * A wiki is a website which allows collaborative modification of its content and structure directly from the web browser. This article tells more and there are other uses. Bestfaith (talk) 13:10, 18 October 2015 (UTC)