Wikipedia:Reference desk/Archives/Science/2014 January 28

= January 28 =

Stereo sound from one ear bud
In the movie, Her, the main human character has single earpiece (a futuristic Bluetooth-type earbud) he uses to interact with his phone/computer. It's implied that he can listen to stereo audio. Obviously, we don't have this technology today (at least not at the consumer level). But how would something like this work? --Navstar (talk) 01:33, 28 January 2014 (UTC)


 * Well, if the single ear bud blocks ambient noise and delivers one channel (either left or right), and you have another speaker somewhere in the room with the other channel playing, that could work. Others in the room would hear mono, while the person with the ear bud would hear stereo.  StuRat (talk) 02:17, 28 January 2014 (UTC)


 * It does not work. It's just a prop in a movie. 202.177.218.59 (talk) 02:21, 28 January 2014 (UTC)


 * The Q wasn't whether the prop really works, it was if there is any way such a system could work. StuRat (talk) 02:39, 28 January 2014 (UTC)


 * There is a technology (see Sound from ultrasound) to direct sound to appear from a point in space that's remote from the equipment that produces it. There have been efforts to use this in advertising and as a military weapon.  Imagine you're walking with a crowd of people in a shopping mall and some facial recognition software recognizes you as a frequent shopper at one of the stores...a directed sound system could whisper into your ear: "Hi Navstar!  There's a special offer waiting just for you at our store, over to your right."...and nobody but you would hear it.  The sound system could follow you around in three dimensions, beaming sound into your ears no matter where you go.  It's a horrible idea - but advertisers love it.


 * So I suppose, with enough advanced technology, you could wirelessly beam sound into people's ears without needing ear-buds at all...and certainly it could be possible to have a device that fits in one ear transmit sound to the other ear using that kind of mechanism. Of course this is all science fiction right now - but it's definitely not impossible. SteveBaker (talk) 02:56, 28 January 2014 (UTC)

Don't know what show so not sure what the prop is. But human sound perception of sound is more complex that just L/R. If you just had a left ear, receiving the same signal delayed and modulated might mimic some aspects of reflections and source. One eyed people can drive, not because they have binocular vision, but because of cues they perceive give them a form of depth perception. --DHeyward (talk) 03:05, 28 January 2014 (UTC)
 * I agree with you...but your one-eyed driver analogy could use some explanation. Our ability to estimate distances uses at least six different mechanisms (focal distance, binocular accomodation, parallax from small head movements, relative size of object compared to those at a known distance and image size on the retina of a known-sized object, atmospheric attenuation).   A person with only one functioning eye can still use five out of those six methods.  Furthermore, the binocular accomodation method (which is the one they don't have) is only effective over a range from a couple of feet out to maybe 20 or 30 feet.  Beyond that, it has little value.
 * It's not clear to what degree effects like phase lag and relative sound amplitude have on directional hearing, and it gets more complicated still when sounds are able to reflect off of the bones of the skull and are refracted by the higher speed of sound through the brain compared to the air. HOWEVER, when sound is fed to you through two earbuds, then ALL of those tricks are wiped out - or worse, they are subverted to making it even more obvious to the listener that this isn't "real" surround sound.   So the analogy to the one-eyed driver who has lost only one of the available perceptual mechanisms - isn't really correct.  SteveBaker (talk) 20:10, 28 January 2014 (UTC)
 * You're right. Still I suspect adaptations by individuals are beyond interpretation. I suspect slight adjustments of head position would allow perception of location that is not explained by a fixed position.  A differential analysis by the brain of 0 degrees and 45 degrees of the same source tone would easily isolate location and possibly distance.  Coupled with the data of moving the head to adjust amplitude makes me think the brain is more sophisticated than a 2 input DSP.  --DHeyward (talk) 06:23, 29 January 2014 (UTC)

Finding milliamps of electric batteries (Ni-Cad) used in portable drills (such as a Black/Decker 12 volt unit from Lowes)
I have a few portable drills several years old that are missing battery charges. Buying (if available) would be costly and would make no sense. I have 12 volt DC plug in transformers with various ratings from 300 ma to 3 -4 amp. I will experiment by attaching a transformer to the internal battery posts but need some idea of amperage range. I could insert a pot and start at the low range but a bit stuck on risk of damaging motor. Can anyone advise me on getting unstuck or do I remain within my Scottish clan which include Gearloose McDuck. Thans — Preceding unsigned comment added by 108.195.4.48 (talk) 04:38, 28 January 2014 (UTC)


 * The current drawn will depend on the motor of the drill and also on the load in use. I would expect that under heavy load the drill might require five or even ten amps, so your transformers might be inadequate and might be overloaded.  Another suggestion would be to connect your drills to a car battery (or one of those handy 12v portable booster batteries), but you will need to include some protection against short circuits.  (If it is only the charger that is missing but the battery is OK then almost any 12v DC charger will work, but limit the current to one tenth of the total capacity i.e. charge at the "ten hour rate", or to the rated current of the charger if this is lower.  The battery is unlikely to hold an adequate charge if it has been unused for years.)   D b f i r s   11:19, 28 January 2014 (UTC)

F-102 safety record
Hello all, I've just watched an amateur "documentary" film that alleges that the F-102 Delta Dagger had suffered "literally HUNDREDS of... crashes" due to the bad low-speed handling characteristics of its delta wing; however, I strongly doubt this claim, because had that been the case, most if not all F-102s would have crashed at some point. I tried reading the article, but it says nothing about the type's safety record. Does anyone happen to know whether what the film says is true, or whether it's just another piece of anti-military bullshit? 67.169.83.209 (talk) 06:47, 28 January 2014 (UTC)


 * The F-102 does seem to have had a high loss rate: "Of the 875 F-102A production models that entered service, 259 were lost in accidents that killed 70 Air Force and ANG pilots." AndyTheGrump (talk) 07:07, 28 January 2014 (UTC)


 * Thanks! So, the "literally HUNDREDS" part was somewhat of an exaggeration, because that phrasing connotes at least 300-400 losses -- at least, the way I see it. 67.169.83.209 (talk) 07:17, 28 January 2014 (UTC)


 * Well, to me 'hundreds' would suggest 'at least two hundred'. Actually though, the more meaningful figure may be the hourly accidental loss rate: 13.69 per 100,000 hours flown - three or four times the figures for most current U.S. fighters (same source as above). Modern zero-zero ejection seats will probably have reduced fatality rates considerably too. AndyTheGrump (talk) 07:39, 28 January 2014 (UTC)
 * Note that 1950s high performance interceptors were all a lot more dangerous than their modern counterparts. I can't find any comparable figures, but the Lockheed F-104 Starfighter was known as "The Widowmaker" and its British contemporary, the English Electric Lightning, was given the soubriquet "The Flying Coffin" (see List of accidents and incidents involving the English Electric Lightning). The F-104 initially had an ejector seat that shot the pilot down through the floor; not only did this make ejecting at low altitude impossible, but in case of a wheels-up landing, the ejection hatch was ripped off and soil was scooped up into the cockpit, burying the pilot alive. Alansplodge (talk) 13:58, 28 January 2014 (UTC)
 * I can't put my hands on the figures but during the two years of the battle of Britain, more than twice the number of aircraft where being lost in training accidents than in combat. It was not so much that the aircraft per se were dangerous but the were being flown to their very limits. Thus, often escaped their Flight envelope. When were you last on a Boeing Jumbo, where the pilot treated you to a few low altitude  barrels rolls and a loop de loop? Simulators have done a lot for safety and pilot/crew survival.   Back in the days of the English Electric Lightning, learning by trial and error, often lead to a short career if one got it wrong -just once. It wasn't the aircraft's fault nor that of the pilot.  It was the need to be better skilled than the enemy -should that day come to prove it.
 * When I worked on flight simulators, our scenery artists were instructed to put invisible barriers under all of the bridges in order to persuade pilots (who seemed unable to resist the temptation to fly under them) from coming to believe that they could do so safely! The temptation to push that envelope is everywhere in the rather extreme "Type A personalities" of many fighter pilots. SteveBaker (talk) 21:32, 29 January 2014 (UTC)
 * Note that "literally HUNDREDS" of crashes may be referring to a different number than the "259 lost in accidents". Many crashes leave the aircraft in a repairable situation - in which case it's not considered to be a "loss" - which implies that the airplane is too severely damaged to return to service.   With the near-certainty that there were more "crashes" than "losses" - it's seems almost certain that more than 300 "crashes" have occurred - with 5 our of every 6 crashes resulting in a loss and one out of 6 resulting in a repairable plane.  However, I agree with Andy - even 200 does indeed count as "hundreds" - it's basic English language - the word "hundred" means 100, stick an 's' on the end to form a plural and all you need is more than one "hundred" - so 200 certainly counts as "hundreds".  If the phrasing had been "several hundred" - then maybe I'd agree that this expresses a number over 300.  SteveBaker (talk) 20:00, 28 January 2014 (UTC)

Wood burning stove/ Creosote build-up
Will throwing an aluminum beer/soda can in my woodstove help reduce the creosote build-up? Donna — Preceding unsigned comment added by 2001:5B0:21FF:2CF0:0:0:0:32 (talk) 16:20, 28 January 2014 (UTC)


 * Do you run your wood stove mostly at low heat with the damper in most of the time. The relative coolness of the stove under these conditions will encourage tars to condense out. Forget chemical fixes. Occasionally, run the stove at a high temperature to burn off these residues. (what type of flue do you have? You don't want to get a chimney fire in the process.)--Aspro (talk) 17:15, 28 January 2014 (UTC)


 * It looks like that would probably help creosote to flake off, but it is not usually a recommended as a safe/efficient method. More of an "old country fix." Here's some discussions I've found , , . There's a lot of people saying it works, and here's a video that claims to show evidence . I've never tried this personally; proceed at your own risk. Also note that chimney fires are very dangerous. Cleaning creosote can prevent them, but attempting to burn something much hotter than wood could also start an nasty fire, especially if you have lots of built up creosote. SemanticMantis (talk) 17:17, 28 January 2014 (UTC)


 * I have a lot of respect for folk wisdom. So I have found this:Aluminium fume The predominant risk associated with aluminium welding is exposure to ozone.. Ozone would indeed degrade tars. My folk-wisdom of a hot-burn dates back to before aluminium cans, when  pepsi and coca cola came in steel cans and had to opened with one of these things. . Still, I am open to new ideas and methods, indeed - I don't need aluminium cans anyway as I have adopted modern central heating. It seem to be only in counties like the US that have to resort to soda cans ;-)--Aspro (talk) 20:45, 28 January 2014 (UTC)


 * Cola cans without pop-tops ? I didn't know they ever made such a thing.  I though it only came in bottles before the pop-top.  StuRat (talk) 23:33, 28 January 2014 (UTC)


 * Here is a photo of the two triangular holes in the steel can that had to be made with the tool linked to above. The other end, lifted off the crowns on bottles. Oh happy days, one could fill up the Pontiac, grab a coke and still get change from a five dollar bill.--Aspro (talk) 00:08, 29 January 2014 (UTC)


 * Having just reread what I wrote, I wondered if my memory was playing tricks on me -but in my mind's eye I can still see those five dollar bills in my hand. So I looked it up. http://www.google.com/url?q=http://oregonstate.edu/cla/polisci/faculty-research/sahr/gasoline.pdf&sa=U&ei=tEfoUsmwFMbR7Ab71IGABQ&ved=0CDsQFjAF&usg=AFQjCNFcGVDyqTbHh1wdORRrFPn9le_yJQ  Yes, gas was less the 30 cents a gallon, so one could fill up the auto for the week ahead and get a coke for oneself and my seat-cover and still get change from a five dollar bill. And the coke came in a steel can that we had to open with one of those can openers--Aspro (talk) 00:47, 29 January 2014 (UTC)


 * I'm familiar with that method of opening cans, as I've used it on cans of oil (although the air hole doesn't need to be nearly as large). I've just never seen it applied to cola.  (I wonder how many absent-minded mechanics poured their Coke into the car engine instead of motor oil.)  What would be the advantage of that kind of can over a bottle ?  Easy opening pop-tops seem to be the main point of cans, to me.  StuRat (talk) 00:57, 29 January 2014 (UTC)
 * I've had one of those all my life, and have only ever used it on tomato juice cans. I have no idea why every other beverage around here has some sort of "hands-only" design. Makes even less sense considering tomato acid reacts with the metal after opening, and it's suggested to put it in a glass or plastic pitcher. InedibleHulk (talk) 01:07, 29 January 2014 (UTC)
 * Of course back when you could fill up your Pontiac for $5, the gas consumption would have been so appallingly bad that you wouldn't get much further than a modern car does on $30...but that's another story! SteveBaker (talk) 21:27, 29 January 2014 (UTC)
 * Aluminum fumes are toxic, so I don't recommend this method. StuRat (talk) 23:33, 28 January 2014 (UTC)


 * You'd probably also need a very hot fire and a bunch of cans. Having a very hot fire in a creosote-laden chimney isn't smart. Best to just buy one of these "logs". I can vouch for them. InedibleHulk (talk) 00:16, 29 January 2014 (UTC)
 * I can't find an official ingredients list of that product online, but some of my linked discussions above say that they contain aluminum in some form. It should say on the package. SemanticMantis (talk) 15:17, 29 January 2014 (UTC)
 * It might. I burned my last package before Christmas, right after the log. In any case, the recipe is certainly different from beer cans, and it burns at a much lower heat. Cans are cheaper, though. For now. InedibleHulk (talk) 23:36, 29 January 2014 (UTC)

Cold hands feeling like they're pulsating
When I was kid at school in the UK in the winter, we had to play football which I had no interest in. My hands would become exceedingly cold and eventually I would feel this very unsettling, exaggerated pulsating. It felt like I should be able to see the pulsating but thankfully did not. Is this usual? I would never allow my hands to reach anywhere near that temperature now so I don't know (or much mind) whether it still (would) happens. --78.148.110.69 (talk) 20:20, 28 January 2014 (UTC)


 * We don't give medical diagnosis here on Ref Desk and this is what your really asking. However, I can give you some pointers that you can run by your General Practitioner for reassurance. Yes, it is common if the pulsation is in the wrist and you are terribly cold. In less server weather extremes it might get diagnosed as Carpal tunnel syndrome. It is worth running by your GP because as though you don't suffer from it now, one of your children or grandchildren might suffer from it and you can inform their parents that is they are not complaining about a trifle. Good gloves, jumper etc mitigates to discomfort – but the condition first, has to be recognized as real, so that the the school allows extra clothing on the football field.--Aspro (talk) 21:16, 28 January 2014 (UTC)


 * It is not a medical question! I absolutely will not make an appointment to see my GP (free on the NHS but that doesn't make it okay to waste their time) to ask him about a sensation I experienced 14/15 years ago! If I pricked myself sewing and a drop of blood formed on my finger, would it be a medical question if I asked about its colour or why it clots? To clarify, it was the main body of my hands, not my wrists, and the grass field was frozen which is pretty extreme weather to be standing around outside in shorts and a crappy rugby jersey. 129.215.47.59 (talk) 17:15, 29 January 2014 (UTC)


 * I'm not asking for a medical diagnosis; I want to know of human physiology. If I had the mind I have now, I'd have told the teacher to speak to my lawyer (an idle thread) and have gone inside. I think the temperatures my extremities experienced were beyond normal. No-one can "force" me now to stand outside in inappropriate clothing at the age of 29. Also, it wasn't my wrists but the flesh of my hands in which I felt this. If I'm the only one to report this then fine, but I suspect others know what I've experienced and maybe understand why. Maybe the cold affects pressure sensors in this way. 78.148.110.69 (talk) 22:07, 28 January 2014 (UTC)


 * RE: 'No-one can "force" me now to stand outside in inappropriate clothing at the age of 29' ... just don't join the military. School coaches aren't the only sadistic people. StuRat (talk) 23:37, 28 January 2014 (UTC)


 * Did you try tucking your hands into your armpits? That's usually a good way to warm them up. ←Baseball Bugs What's up, Doc? carrots→ 23:44, 28 January 2014 (UTC)


 * I've just realised that by "football" the OP probably means that strange sport where you aren't allowed to do anything with your hands, except letting them just hang there to get frozen. Though Bugs's suggestion might be on the right track. HiLo48 (talk) 23:47, 28 January 2014 (UTC)
 * What? You realized that by football, they meant a sport where they use their feet? WTF is your point? I'm a fan of football, not soccer, but your response makes no sense to me. --Onorem (talk) 23:55, 28 January 2014 (UTC)
 * Well, it's obvious that not being allowed to do anything with one's hands as part of the game is going to make this problem worse. Where I come from "football" means a game with big involvement of both the feet and the hands. My statement was true. I didn't realise initially that the game in question was probably "soccer". HiLo48 (talk) 00:01, 29 January 2014 (UTC)
 * The OP geolocates to, and specified, the UK - hence, football would equate to soccer. Obviously, the hands are required in certain parts of the game: goalkeeping, throw-ins, etc. I was just wondering if the OP had tried tucking his hands, or if he found that impractical. ←Baseball Bugs What's up, Doc? carrots→ 00:22, 29 January 2014 (UTC)


 * When you're cold, blood vessels near exposed skin contract more than in warmer parts. The pulsing is your blood squeezing through tighter spaces there. At this point, you're probably close to or at frostnip, then frostbite. InedibleHulk (talk) 01:19, 29 January 2014 (UTC)
 * That sounds like what I've usually heard about exposure to cold: If your extremities are in pain, they're still in pretty good shape. Once they go numb, you're in trouble. ←Baseball Bugs What's up, Doc? carrots→ 01:41, 29 January 2014 (UTC)
 * You get some leeway time between numb and serious tissue damage. Not long in very cold weather, probably a fair window in England. But it's best not to wait, because thawing hurts a lot more than freezing. InedibleHulk (talk) 02:40, 29 January 2014 (UTC)
 * A key question would be whether it was above or below freezing. Is it possible to get frostbite if the temp and the wind-chill are both above freezing? Also, would being "interested" in the game help the OP stay warmer? ←Baseball Bugs What's up, Doc? carrots→ 02:59, 29 January 2014 (UTC)
 * Can't get frostbite above zero, but the vessels will still contract somewhat at whatever temperature a body decides is too cold. Gotta figure an interested player will play harder, and that'll warm him up. Thinking about anything intently should create some warmth in the brain, but the humanly imperceptible and virtually insignificant kind. InedibleHulk (talk) 03:38, 29 January 2014 (UTC)
 * Just passing by. Anyway, a good advice : if you smoke, quit NOW ! (are you aged 29 ? are there any such cases in your family ? did you hear of Raynaud's syndrome ? ). But I must stop, of course ...Good luck to you Arapaima (talk) 09:10, 29 January 2014 (UTC)
 * See: Raynaud's phenomenon Richerman    (talk) 10:52, 29 January 2014 (UTC)
 * Thanks guys but I don't smoke and it really isn't a medical issue. My extremities do not discolour like that and I'm not prone to it. It was just poor child care (I probably should have been sent to run laps around the field but didn't think to do this myself because I was a stupid kid) and I still think I was experiencing a normal phenomenon. I will scour the Internet for answers and will report back if I find anything. 129.215.47.59 (talk) 13:35, 29 January 2014 (UTC)
 * It's hard to answer about "unsettling, exaggerated pulsing". I mean, I always feel my pulse throughout my body, and of course it's stronger after exercise, so why would it be unsettling or tied to cold weather?  Yet I've heard people assert that they don't feel their pulse, even to the extent of saying they don't feel their own heartbeat, even to the ludicrous extreme of seeing them physically taking their own pulse with their fingers.  That I don't understand, so we should clarify whether you fall into that category and if so try to get to the bottom of the more interesting question of why you wouldn't feel your pulse at other times. Wnt (talk) 17:45, 30 January 2014 (UTC)
 * In my own case (which may be similar or not, I smoke like a chimney, but don't seem to have many Raynaud's symptoms), there's a distinct difference between the smooth and subtle "normal" pulse and the sharp, squeezing, slightly electresque feeling when I work in the cold. The harder my heart beats, the sharper the feeling, but it's only ever in the hands (probably would affect my feet, if I ignored my boots and socks like gloves). I haven't felt anything like it in warm weather (so far), so I figure my issue is cold constriction. InedibleHulk (talk) 22:59, 30 January 2014 (UTC)