Wikipedia:Reference desk/Archives/Science/2017 September 18

= September 18 =

Disability-affected life years from falls


According to this map, in 2004, Iraq had by far the world's worst statistics for disability-adjusted life years related to Falling (accident). It accurately reflects its source, according to which, 50 of the 192 countries tracked had a score of 200+, with 28 being 200-299, 13 being 300-399, 6 being 400-499, and the top three countries being Yemen at 524, Sri Lanka at 649, and Iraq at 1002. Why would Iraq have such horrid statistics? Is this merely an artifact of damage to the medical infrastructure during the ongoing war? It seems a bit extreme, especially since Afghanistan and Somalia, which both had less medical infrastructure in 2000 than Iraq, were tied for eighth at 417, and another country with a war during the data collection, Liberia, had just 133. Nyttend (talk) 01:53, 18 September 2017 (UTC)


 * ISIS has a habit of throwing people off roofs (homosexuals): . If those are included in the data, that might explain it. StuRat (talk) 02:06, 18 September 2017 (UTC)


 * I strongly doubt that ISIS is at all relevant, since this map relies on figures published in 2004. Nyttend (talk) 02:26, 18 September 2017 (UTC)


 * Good point, but such violent practices did not begin with there with ISIS. Their predecessors were also quite violent.  StuRat (talk) 02:29, 18 September 2017 (UTC)


 * And they were really good at making it look like an accident? Of 19 (talk) 22:37, 18 September 2017 (UTC)


 * Somehow I doubt if there was much of an investigation when they found a body on the street under a tall building with fall injuries there, unless the victim was a friend or relative of whoever was in charge at the time. StuRat (talk) 23:01, 18 September 2017 (UTC)


 * Those awful DALY things from the beginning included an absolutely arbitrary curve claiming that young adults are more important than anybody else; they were then immediately used to show that more funding emphasis should be put on treating diseases of young adults. Think of a slavemaster prioritizing his stock.  Scientific fraud is almost too kind a description for this.
 * That said, the article says that some sources have stopped using the arbitrary curve (though this indeed is its own kind of arbitrary decision, and another value judgment ...) The figure points straight at an Excel spreadsheet as its source ... it might be worth looking into. My thought is that if Iraq is a war zone that has chased out all the old and young people, it may have more people per capita, by DALY standards, than other countries. Wnt (talk) 02:14, 18 September 2017 (UTC)


 * According to http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131834, in Iraq the majority of falls occur in houses, and the majority of victims are women. Only a small fraction are fatal.  The causes are not clarified, but I suspect that one of them is the fact that the great majority of Iraqis sleep on their roofs during most of the year -- so they spend a lot of time going up and down stairs while sleepy. Looie496 (talk) 02:53, 18 September 2017 (UTC)


 * Holy.... what's wrong with Motherland. Do they think they're cats or something. "See, Ivan, 5 storeys isn't high. Hold my beer..." 78.53.109.203 (talk) 03:16, 18 September 2017 (UTC)

Stud finder
Yesterday I had to do some assembly work that required drilling into the wall, and my fancy-schmancy $50 stud finder indicated a wall stud just where I wanted one to be, but when I drilled into that "stud", there was only drywall with nothing behind it! What could have caused this gadget to give me the false positive, and (more importantly) how can I prevent this from happening again? 2601:646:8E01:7E0B:3DB7:8D6E:A762:14CC (talk) 07:47, 18 September 2017 (UTC)
 * 1. How some work: http://www.nytimes.com/2001/04/12/technology/how-it-works-detectors-can-find-just-the-right-spot-to-drive-that-nail.html
 * 2. How to lessen chance of false positives: http://zirconcorp.custhelp.com/app/answers/detail/a_id/28/~/is-the-stud-you-found-really-a-stud%3F-minimize-false-positives. 129.55.200.20 (talk) 13:09, 18 September 2017 (UTC)
 * Thanks! So the key is to look for regular intervals, right? 2601:646:8E01:7E0B:EDA1:6DA2:2F4C:8E0A (talk) 05:43, 19 September 2017 (UTC)


 * Most stud finders find a difference, not a stud. If there is a 4 inch air gap next to a 2 inch air gap, that is a difference. It will beep or light up when you are over the difference. When you find a stud, the indicator goes off on each side of the stud. Mark both sides. It should be about 1.5 to 2 inches wide, depending on what is used for the stud. Move to both sides. You should find another stud on each side about 14 or 15 inches away. They are normally set 16 inches to the center of each stud, leaving about a 14 to 15 inch gap between studs. If you find that, you likely have a stud. If you don't, you need to keep looking. Also, don't assume there is a stud. When people do work themselves, they do all kinds of silly things like putting up drywall without any studs behind it. 209.149.113.5 (talk) 13:02, 19 September 2017 (UTC)


 * Most studs in your house are vertical and run from floor to ceiling. Therefore, you can cross-check the stud location by looking for it at several heights on the wall. If these separate heights disagree, be suspicious of a false reading or an unusual situation. Find the same stud from both sides at each height. -Arch dude (talk) 14:48, 19 September 2017 (UTC)
 * It's worth noting that most stud finders out there are "edge" stud finders. As previously mentioned, they sense change, so it's important that when you initially start scanning you do so in place known not to have a stud, for calibration. Or, you can do as I do and use a strong magnet to find the screws that anchored the drywall to the stud. Drewmutt ( ^ᴥ^ ) talk  02:21, 20 September 2017 (UTC)

Do tree trunks really bend at 32 miles per hour?
That's what the Beaufort scale implies. How much could a deciduous trunk bend before breaking? (though in some cases it would uproot before that happens). Why is the Beaufort scale 12 description "devastation" while the Category 1 hurricane description doesn't seem as bad? (and Floridians even drive over bridges in that). Sagittarian Milky Way (talk) 09:59, 18 September 2017 (UTC)


 * The best reference I could find is Trees, regardless of size, all break at the same wind speed. Here’s why. from the American Association for the Advancement of Science.
 * Anecdotally, a youth activity centre in Essex used to have a wooden abseiling wall attached to an old sweet chestnut coppice (before the days of health & safety obsession) which had three large trunks each of more than 2 metres circumference. Even in a light breeze, the top platform which sat between the three trunks would sway rather alarmingly and had to be closed on windy days. Although the trunks weren't bending visibly, the swaying motion could only have been caused by the flexion of the trunks. Alansplodge (talk) 10:35, 18 September 2017 (UTC)


 * That article actually says the wind speed required does vary a bit, but not by much, for the factors they considered (wood elasticity and tree size). They also didn't look at the effects of leaves.  A tree with lots of leaves (that stay on during the storm) will absorb more wind than a leafless tree.  And some tree forms, like palm trees, with only a small clump of leaves at the top and a massive trunk, seem like they evolved to resist tropical storms better, too. StuRat (talk) 23:14, 18 September 2017 (UTC)


 * Tree trunks would bend at any wind speed, just not noticeable so at low speeds. For that matter, any material would bend, with crystals bending perhaps the least, but still a tiny bit.  Buildings bend and sway, too. StuRat (talk) 23:04, 18 September 2017 (UTC)


 * Presumably the person who extended the scale to land meant "visible to the naked eye" when he said whole trees in motion = 7, large branches in motion = 6. In our tropical storms I'd been so distracted by trying to get "air" from sprinting downhill with umbrellas and seeing how many degrees I could lean that I forgot to test the whole trees in motion thing. Sagittarian Milky Way (talk) 23:49, 18 September 2017 (UTC)
 * Yes, the point of those notes is that a layman can assess the wind speed without any specialist knowledge or technical equipment. Out article says it was adapted "in the 1850s". Alansplodge (talk) 10:18, 19 September 2017 (UTC)

activated charcoal effect on carbohydrates, proteins and fats
The activated charcoal article specifically states that it does not work on alcohol. What about the other macronutrients; carbohydrates, sugar/glucose, proteins and fats? Does it bind to those and prevent their absorption by the gastrointestinal tract? I've tried researching this on my own but I can't seem to find an answer one way or the other. I realize that carbohydrates, proteins and fats are not poisons but how would activated charcoal differentiate between a poison and a macronutrient? I would assume that it would bind to all of them. Thanks for your help. — Preceding unsigned comment added by 62.16.22.76 (talk) 11:32, 18 September 2017 (UTC)


 * You didn't say so, but are you asking because of one of the activated carbon diet and/or "detox" fads? If so, I'd suggest you save your time and money.  By weight, in a pure solution, you may need 10 or 100 times as much activated charcoal as the substance you want to adsorb before you can capture most of it.  For small quantities of poison, that may not be too hard to accomplish, but for bulk foods the corresponding quantities involved are likely to be impractical or even dangerous.  Dragons flight (talk) 13:48, 18 September 2017 (UTC)


 * I'm not following any kind of fad diet, I was just curious when reading the article because the article specifically mentions activated charcoal does not work on alcohol but omits to mention any of the other macronutrients. I wondered if that was because activated charcoal does indeed work on the other macronutrients, so I searched for answers but found nothing helpful. Still curious, I then came to the reference desk to ask in the hope that someone more knowledgeable and better at finding references than me could shed some light onto the question. I hope that is okay. 62.16.22.76 (talk) 14:38, 18 September 2017 (UTC)


 * The "Mechanism of action" section of that article is woefully unreferenced, if some kind editor has time to take a look at it. shoy (reactions) 15:05, 18 September 2017 (UTC)


 * I doubt if much of any of those would pass through an activated charcoal filter. They would quickly clog it.  As for consuming activated charcoal, you'd need a huge quantity to bind to all that, which would make you sick.  BTW, if you want a fat binder, try Orlistat (but be prepared for "anal leakage"). StuRat (talk) 16:29, 18 September 2017 (UTC)

Does normal charcoal have any poison absorbing properties?
I understand that activated charcoal greatly increases the surface area of charcoal to make it effective at absorbing poisons. But does normal charcoal have any poison absorbing properties? Again, I did try researching this myself but everything I found was about activated charcoal. I want to know if normal charcoal can bind to poison or not. Thanks for your help. 62.16.22.76 (talk) 11:50, 18 September 2017 (UTC)
 * Yes, but they work by adsorbing material onto their surface, rather than absorbing it into their bulk. Activated charcoal is just charcoal produced by a process (either thermal or chemical and thermal) which increases this surface area. Andy Dingley (talk) 12:32, 18 September 2017 (UTC)

How useful is the telescopic sight on a rifle
When shooting a rifle with a telescopic sight, the bullet will drift due to the wind and gravity to one side and down. Since it will never hit the crosshair, would it be any difference if the shooter had some binoculars attached to his face or helmet?--Hofhof (talk) 17:12, 18 September 2017 (UTC)
 * It will hit the crosshair. The turrets on the side of the sight allow the crosshair position to be adjusted, to compensate for bullet drop, windage etc. When the sight is 'dialed in' for the range and conditions, the bullet should go where the crosshair indicates.
 * Although simple "crosshairs" aren't the only form of reticle available. Some have a scale on them, so that the shooter chooses an aim point on that scale, rather than adjusting the turrets. Andy Dingley (talk) 17:18, 18 September 2017 (UTC)


 * Should a marksman use head-mounted binoculars he would have to sight the bead of the rife which would end up looking fuzzy at short short focal distances. The bead is also rather large and can be larger than the target at 400 yards on some rifles. Of course, he may have infinity focus binoculars – if there are such things. P.S. Why do we  call them cross hairs. All my sights up until I gave up shooting used spiders web ( with the exception of a laser sight which I borrowed).  Think  also, that AD was over simplifying things. On a 2500 range with a 303 one need little flags all down the range to show moment to moment fluctuations in crosswind. It is nearly one  and a half miles and the round takes several seconds to miss the targets I was hopefully aiming at, regardless of where the scope was pointing at. Aspro (talk) 19:07, 18 September 2017 (UTC)
 * For an example of actual-hair "hairs", see Mary Babnik Brown. DMacks (talk) 19:21, 18 September 2017 (UTC)
 * Articles: Telescopic sight, Reticle. Blooteuth (talk) 23:19, 18 September 2017 (UTC)

Can sniper rifles be automated ?
I've often thought that sniper rifles should be automated. Some reasons:

1) The shooter's movements make it difficult to maintain aim. If the operator was instead seated some distance away, or even on the other side of the world, controlling the apparatus remotely, this variable would be removed.  Also, the shooter could then be hidden from snipers in the opposing army.

2) An automatic correction method could be used, where the target is painted with a laser (possibly IR, to keep it hidden), then each shot would be tracked (perhaps tracer rounds would be needed for this) and the error corrected for each subsequent shot. I would suggest 2 or 3 rifles in an array, all precisely aimed the same, yet physically isolated so as to not be affected when another fires.  This would allow multiple shots in rapid succession, each correcting for the previous error, without allowing the target time to flee.

I would suspect that this setup could significantly extend the effective range, and require far less training and experience to use effectively. Also, fewer snipers would be needed, since the same one could operate weapons in multiple locations without needing to travel from location to location (somebody else could roughly position them). So, has anyone done this ? If not, why not ? StuRat (talk) 20:40, 18 September 2017 (UTC)


 * The US already have semi- automated sniper rifles. The operator identifies the target's thermal infra-red signature and if the target should lean against a tree, suggesting he may be there long enough for the round to reach him/her/it – gun goes off (no need to squeeze the trigger) . Should target move earlier than expected – well  EXACTO will correct the trajectory in-flight. This type of technology  is what your tax dollars are paying for. When the 3rd world war comes, just follow me into a cave and let Arnold Schwarzenegger and  Linda Hamilton sort it all out for us, so that we can look forward to a sequel, providing of course that they win, in a real war. Aspro (talk) 21:25, 18 September 2017


 * Articles: Sniper, Narcissistic personality disorder, Serial killer. Blooteuth (talk) 23:07, 18 September 2017 (UTC) (UTC)


 * I've heard that bolt-action rifles tend to be the most accurate, with the design (not sure how, but...) being more accurate overall than semiautomatic rifles; no source, but it's something to look into. Remember that with a sniper rifle the point is being supremely accurate and delivering sufficient firepower in the perfect spot, not delivering a ton of firepower to the general area; it's like using smart bombs versus carpet-bombing.  Also, "fewer snipers" — part of the point of having lots of snipers is redundancy: individual snipers are vulnerable, having lots of snipers means that you can cover the enemy from lots of angles, and eliminating one sniper doesn't do the enemy much good if he can't get rid of the rest.  Nyttend (talk) 23:21, 18 September 2017 (UTC)


 * Right, but with this system one sniper could do the job of many. That is, when motion is detected on one scope, he could connect to that rifle and take a shot.  If motion is detected on another, he can then switch over to that one. StuRat (talk) 06:36, 22 September 2017 (UTC)


 * A couple of problems with this proposal: (1) The loss of the datalink between the operator and the rifle positions (such as through enemy jamming) will make the latter useless; (2) A remotely-controlled rifle cannot change position unless mounted on a mobile platform, and even then, such a platform cannot conceal its movements as well as a human sniper (i.e. it will be easier for the enemy to see and destroy, or at least get out of its line of fire). 2601:646:8E01:7E0B:EDA1:6DA2:2F4C:8E0A (talk) 05:41, 19 September 2017 (UTC)


 * This "mobile platform" could be made rather stealthy. Place it in position when no enemy is around (or perhaps they are distracted by an attack from elsewhere), put the equivalent of a ghillie suit over it, and have it move slowly enough that nobody spots the movements.  No need for breaks for food, water, the toilet, etc., should then make it less noticeable over the following days, as should a lack of IR light leaking out.  As for the datalink, you could do a direct shielded wire to somebody in a bunker nearby, and they could take over if jamming occurs.  StuRat (talk) 17:44, 19 September 2017 (UTC)


 * While you're at it ... what has kept them from putting sniper rifles on drone aircraft? I mean, obviously the bombs are more powerful, but having some drone far away -- potentially solar powered, even -- making virtually unlimited shots would be damned demoralizing, emphasis on the damned. Wnt (talk) 08:59, 19 September 2017 (UTC)


 * That's the Autonomous Rotorcraft Sniper System. There are technical issues to be dealt with. To shoot a bullet instead of a missile implies stronger recoil. You'll need a more solid base. You'll need a bigger drone. This defies the purpose of shooting bullets for having a small drone. Since bullets are not guided, your sniper drone would also need to be more stable in flight. (also implies bigger drone, with maybe a longer wings or tail). Modern drones like the Predator drones fire AGM-114 Hellfire, which are bout 100 lb and can be used to disable armored vehicles, bridges and so on. Jihadi John was killed inside a vehicle by one of these. That would be hardly possible with a mere bullet. B8-tome (talk) 12:35, 19 September 2017 (UTC)
 * Wild speculation from my part, but it could have to do with the altitude. Killer drones fly high to avoid detection by potential targets; Unmanned_aerial_vehicle pointed me to this page saying one of the earliest killer drones flies at an altitude of 26000 ft, I am going to assume it is higher for more modern stuff. On the other hand, Sniper gives a record sniping distance of 3.5km. Supposedly deviations in the air and the like prevent accuracy at larger distances; I doubt that a flying drone could beat a grounded human for steadiness of the aim. If so, maybe sniper drones would lose much of the operational advantage because of the required approach distance. Tigraan Click here to contact me 12:49, 19 September 2017 (UTC)


 * Of course it could be automated! But if both sides of a war automated their rifles, what would be the point of shooting?

Besides which, gentlemen, the exigencies of war compel us to remember one thing. A man is much more dispensable than a computer.
 * Nimur (talk) 14:21, 19 September 2017 (UTC)


 * I can indeed imagine a time when warfare is only between drones. Once one side's drones destroy all the other side's, they would need to surrender or be wiped out. StuRat (talk) 17:34, 19 September 2017 (UTC)
 * On 2: Sniper Rifles are already on the edge of still being mobile. For example the .50 caliber M96, broadly used in US Services, has a hefty Weight of 11.35 kg. Unloaded, with no scope attached! If you would add laser targeting and automatic aiming that Weight would easily triple or go beyond. A "mobile" BGM-71 TOW-Launcher weights 92.5 kg, to give you some direction what "mobile laser targeting system" only may add. If it was practical some army would have it today. But actually most armies already have what you imagine. Infact the Germans invented this in WWII. On some of their Infantry fighting vehicles (originally called "Schützenpanzer" which could be translated to "Snipertank"). --Kharon (talk) 21:00, 19 September 2017 (UTC)
 * Btw. German Engineers perfectly implemented your imagination already in 1960. They called it Flakpanzer Gepard. In case you are interested in a promotional video impression: . On top it was capable to operate autonomously without crew (stationary), only wired by cable to a hidden command post - in principle like a drone. Tho with its 50 tons weight hardly confused with todays drone "toys" ofcourse. --Kharon (talk) 04:04, 20 September 2017 (UTC)
 * There was a demo on TV of a remote-controlled small tracked vehicle with a rifle which could shoot more accurately than a human gunman. A remote-controlled rifle on a rooftop would have an easier time staying still all day than a guy in a gilly suit. As far back as WW1 the Brits, French and Germans had excellent hiding places  such as a fake tree stump made of iron which could be erected in darkness on a hillside facing the enemy so an observer could report by phone back to a command post, without being detected by the enemy, and even with some protection against stray rounds. Some were built to look like actual tree trunks so no one would notice a "new tree" at dawn. Today they would hacve to have IR emission/reflection like the real thing.  Emitting any IR would be a bad idea and would likely be detectable and draw mortar/RPG/artillery fire. It would be easy to hide a remote-controlled sniper rifle on a rooftop or in a highrise window, or in a pile of rubble. It could similarly resemble an air conditioning unit or chimney. The Washington DC sniper was undetectable firing through a hole cut in the trunk of his car. But once the device starts firing it would likely get high-powered counterfire, since a video camera or IR detector could catch the muzzle flash. A sniper weapon could be a camo version of existing Sentry guns which could acquire and kill targets automatically, but which typically require human permission to fire. Edison (talk) 16:16, 20 September 2017 (UTC)


 * Reminds me of the "automated sentry units" from Aliens (the sequel to Alien). It was a seriously dangerous weapon, as it was just a motion detector and aiming system, and it would open fire on anything that moved, until it stopped moving or the device ran out of ammo.  Just be extremely careful which way you point it. :-)


 * I also saw one potential problem with this device besides "friendly fire". It might use up all it's ammo firing at one alien, after it's dead, as the bullets would keep it bouncing around and continue to trigger the motion sensor.  Occasional short delays would help prevent this.   StuRat (talk) 05:09, 21 September 2017 (UTC)