Wikipedia:Reference desk/Archives/Miscellaneous/2007 July 3

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[edit] July 3

[edit] Adjusting knobs on a sniper rifle

When a sniper "dials-in" a shot during windy days, he/she usually turns the horizontal and vertical knobs on his/her scope. I know this is to compensate for the wind and gravity, but what exactly does twisting the knobs do? Does it move the scope minutely, or does it move the barrel of the gun? Thanks. Acceptable 02:35, 3 July 2007 (UTC)

It just adjusts the telescopic sight adjustment controls. You adjust the sight to compensate for wind and other conditions and then aim the gun according to the adjusted sight. If I knew the bullet was going to list to the right, I would adjust the sight so that when I aimed at the target I would be aiming a bit to the left, for example. --24.147.86.187 02:42, 3 July 2007 (UTC)
But what exactly is happening to the telescopic sights when the windage and elevation knobs are turned? Does the Sights actually rotate a minute amount to the left or right when the knobs are turned? Acceptable 03:45, 3 July 2007 (UTC)
Yes, exactly - a tiny fraction of a degree left or right or up or down. SteveBaker 04:41, 3 July 2007 (UTC)
If the target is farther away, you must raise the rear sight, or equivalently raise the gun barrel, to hit the target. Obviously, if the wind is from the left, you must so adjust the sights to move the barrel to the left, to hit the target. The farther the target is away, the more important such corrections are. If the target is moving, then it will not be at the aiming point when the bullet arrives. In real life situations, it can be a second or more between trigger squeeze and impact, plenty of time for the target to see the muzzle flash and to dodge left or right. Edison 05:47, 4 July 2007 (UTC)

[edit] Live Free or Die Hard

After seeing the movie, I have several questions:

Would shooting a fire extinguisher with a gun create enough force to propel someone through a window?

In a city like Washington DC, are all of the traffic lights networked so that they could be controlled by a single source, or do they all operate individually?

thanks 68.231.151.161 03:11, 3 July 2007 (UTC)

  1. This is an over the top action movie. PLEASE do not try to inject reality into it.
  2. The fire extinguisher, maybe, maybe not. On one hand, they are under quite a bit of pressure, so a small hole in the tank could easily have quite a bit of energy. On the other hand, I think the type of foam used in those would probably plug it's own hole before much happened.
  3. Some cities do have networked roads to help them monitor and control traffic- and yes, in some cases they are used to turn lights green/red, although this would normally be for something like making travel into the city easier in the morning, and out of it easier in the afternoon.
Fire extinguisher as rocket? I don't think so. Foam is pretty light, so it would take a heck of a velocity to move a body plus the extinguisher itself. Clarityfiend 04:17, 3 July 2007 (UTC)
It also seemed to me like the bullet hole would be on the side facing the shooter, not on the side of the person being shot at, and the explosion would go towards the shooter. Corvus cornix 16:05, 3 July 2007 (UTC)
The shooter and the shootee could both be on the same side as the extinguisher but with it positioned behind the shootee. Or the shooter could shoot the side of the extinguisher to line the resulting jet / explosion / blast at the shootee. Lanfear's Bane
This article is quite interesting. The more I think about this the more interested I become therein. I have accidently dropped a fully pressurised 3litre diving cylinder onto a concrete floor and witnessed the look on the faces of the other people around me and have watched 12litre bottles scoot around the floor if you open the valve too wide. If the fire extinguisher was a CO2 cylinder I would say this is pretty plausible. You can also check out the gas cylinder article. Lanfear's Bane
In the movie, Bruce Willis throws an extinguisher at a bad guy and shoots it, exploding the extinguisher and driving the bad guy out a window. The hole in the tank is on Willis's side, not the bad guy's side. Corvus cornix 03:02, 4 July 2007 (UTC)
This is at least consistent with the laws of physics. As the CO2 shoots from the hole, it acts as a rocket exhaust and propels the cylinder into the person, ramming him out the window.The hole is much bigger than the tiny hole inside the nozzle you use when you fight a fire with the extinquisher, so the same total energy is delivered on a much shorter time, resulting in a much more powerful push during that time. I don't know what the pressure in an extinguisher is, but if is the same as a diver's air tank, we talking 4000PSI. If the bullet creates a hole with an area of one 1/4 sq. in, then the cylinder is driven with 1000 pounds of force.-Arch dude 02:11, 5 July 2007 (UTC)
I have to say I'm skeptical - but it seems from [1] that the smaller extinguishers contain a couple of kilograms of CO2 under 15 MPa of pressure. 15 Mega Pascals == 2100 psi! So, yes - in principle you'd get a brief force that would easily produce a few g's of acceleration to a typical human. However, the force would be quite brief with only a couple of kilos of gas - the final speed that the person would be travelling at would be determined by: mass-of-gas x velocity-of-gas / mass-of-human - so if we have a 75kg human and 2kg of CO2 then the person will fly backwards at about a fortieth of the speed that the gas is shooting out of the hole. I doubt that would be more than a few hundred miles per hour - so the human will be hit hard by the cylinder - but that brief force will only end up staggering them backwards at a few miles per hour - maybe just enough to push them out of a window...probably not. SteveBaker 13:12, 5 July 2007 (UTC)
Different cities have different light controllers, but if the city is using an Advanced transportation controller, it would presumably be as hackable as any other Linux box -- which is to say, either devilishly difficult or childishly simple depending on the design. I would doubt that the traffic system could be accessed from the public internet, though. I imagine they use private lines. See also the "Control and Coordination" section of the Traffic light article. --Mdwyer 04:37, 4 July 2007 (UTC)

UPDATE: I finally got to see this movie today - and the fire extinguisher thing has been completely misrepresented here. What you actually see is that the extinguisher is hurled across the floor towards the feet of the bad guy. Our hero shoots at it and it explodes - throwing up an enormous cloud of white gas - which blows the bad guy out of the window. This is vastly different from the impression I got that he was hit by a flying extinguisher which had a quarter inch hole in it. The way it's played in the movie makes no physical sense - with the gas able to expand in all directions equally (in a fairly large space) - there would be nowhere near enough pressure differential to push him anywhere. I definitely don't buy it. My previous calculations suggested that if all the force of the gas expansion was pushing in exactly the right direction, then just MAYBE it would happen that way - but with at best maybe a 20th of the energy pushing him out, and at a much lower velocity - there is just no way. SteveBaker 01:41, 8 July 2007 (UTC)

[edit] Diesel/Petrol

I have a diesel engine 4x4 and I inadvertently put about 10 litres of petrol (gasoline) in the tank. Will this do any harm to the engine? Do diesel and petrol mix?

Fill the tank full with diesel to dilute the petrol and you may get away with it. Anything more than 5l of petrol in a diesel tank is not recommended. You may want to syphon instead of risking it, may become more expensive to correct in the long run vs. cost of replacing a tank of fuel. http://www.google.co.uk/search?hl=en&q=mixing+petrol+and+diesel&meta= 194.168.231.2 12:01, 3 July 2007 (UTC)Wes.
Yeah, I too would recommend siphoning it out, - Akamad 13:46, 3 July 2007 (UTC)

[edit] Wikipedia as volunteer activity?

Suppose you are a contributor to wikipedia, and you consider your contributions to be non-destructive, helpful, and demonstrative of a certain level of maturity and responsibility. Is it acceptable to put that activity on your resume under "volunteer activity"? If yes, who would you list under "supervisor"? NoClutter 16:03, 3 July 2007 (UTC)

I wouldn't list it under supervisor, you don't supervise anybody here. I have made reference to my Wikipedia editing ability on resumes when discussing my ability to write. Corvus cornix 16:06, 3 July 2007 (UTC)
The question was who would you list under supervisor. Go look at any job application form. There is usually a slot asking who was the supervisor for employment and volunteer positions that a person claims as prior experience. This is so the HR department can contact the previous supervisor. ¿Comprende? NoClutter 17:18, 3 July 2007 (UTC)
Yeah, i would definitely include this where relevant; and I imagine there are many volunteer activities that don't have supervisors, so they wouldn't reject it if you left it blank.Gzuckier 17:15, 3 July 2007 (UTC)
I think it is entirely proper to list editing Wikipedia as a voluntary activity, as for supervisor - the Wikipedia community is the supervisor. DuncanHill 17:59, 3 July 2007 (UTC)
You don't have a formal supervisor. For the purposes of the application/resumé, it would be of little value — there is nobody for them to easily call who would have the authority to vouch for your behavior or quality. (Which doesn't mean it isn't worthwhile, obviously, just that it would have little meaning to a potential employer, unless they were a company that developed wikis or something like that.) --24.147.86.187 18:14, 3 July 2007 (UTC)
On my resume, I leave off any supervisor for volunteer stuff, but then I have enough previous job supervisors for employers to call, it's just to show that I do other stuff, too. — Laura Scudder ☎ 18:37, 3 July 2007 (UTC)
You could always go to the Wikipedia:Adopt-a-User area and have someone 'adopt' you - adopters watch the activity of the adoptees - and might reasonably be called upon to vouch for behavior and the quality of contributions. But I would expect that any reasonably intelligent employer would be at least roughly cognisant of what Wikipedia does - so I doubt they'd expect there to be a supervisor. In point of fact, the deal is that when you work here you are self-motivated and it shows off your ability to drive your own agenda. One of the big things you get with Wikipedia is that all of your work is public. You could give your potential employer your username - and mention that they can see samples of your work by clicking on the 'Contributions' button in your user page - or perhaps give them the URL of any pages you've done most of the work on and are especially proud of. I did this very thing on my last job application (not failing to mention my two featured articles and 6000+ other contributions of course!) - and I was surprised to find that one of the interviewers had actually taken the time to look at one of my FA's and was aware of just how amazingly difficult it is to get an article to that degree of polish. So I don't think it hurts. (Of course if your time here is a long series of blocks and bans and flamefests - you might want to leave it out of your resume because your future employer might find those too!) SteveBaker 19:47, 3 July 2007 (UTC)
Hmm ... that "adopt a user" thing sounds a little dodgy ... how do I know someone "adopting" me is legit? What if the adopter says bad things about me just because he later finds out I am Serbian? Nevertheless, Good answer, I like the idea of just giving links to featured content that I wrote (or at least a diff, just in case someone vandalizes it). Thanks a lot SteveBaker. NoClutter 20:04, 3 July 2007 (UTC)
Well, it is certainly up to the adoptee to pick an adopter with whom they are happy - but remember that they can walk away from the arrangement at any time and pick someone else if they don't get on with them. Can you be sure that they won't unfairly say bad things about you? No - but the exact same thing could be said about "real" job supervisors. One really good thing about Wikipedia is that before you pick your adopter (yes, it works that way around - they don't pick you) - you can take a look at their contribution history and see how they've behaved with everyone else around them - you can talk with people who have 'graduated' from the system and easily find out who the bad ones are. It's a good system. SteveBaker 20:47, 3 July 2007 (UTC)
Maybe you should get a username under your real name so they can be sure it's you if you want to show your contributions. Also, although people here all think wikipedia is great, it does have a bit of a joke reputation in some quarters, due to the mistakes, vandalism and endless trivia. However it obviously worked for SteveBaker, so don't be too put off. It depends on the job, it would certainly be relevant for something like journalism, if you write well for example. It may also not be what employers are looking for under volunteer work, so maybe if it seemed appropriate under another section, maybe 'activities' or 'relevant experience'? Anyway that's a more pessimistic view, in the name of neutrality! Cyta 07:15, 4 July 2007 (UTC)
It can certainly help to mention your work on Wikipedia. That was one of the things that drew the attention of my present employer. I don't put in my resume, though, but in the application letter, where applicable. Also, using your real name as a user name may make you look less like a 'geek' in the eyes of some and to make clear it's really you, you could put a photograph of yourself on your user page, where you could also list your most important contribution, as I did, because I also make loads of small contributions that employers won't want to have to look through. DirkvdM 12:54, 4 July 2007 (UTC)
Wikipedias' reputation for errors is not deserved - lots of studies have shown that we're more reliable than Britannica. Our reputation for accumulating trivia is very well-deserved - but that's OK - I use it to look up trivia all the time! From the point of view of a resume/application-letter, you can mention the titles of the articles you've worked on. If your contributions are the meticulous documentation of 14 rare species of outer-Mongolian butterfly - and you're applying for a job in museum of natural history - then that's great. If your contributions are creating a page for every track of every album of some obscure punk band that you happen to be a fan of...then maybe leave that out of your resume when applying for that same kind of job! Your contributions are likely to be an accurate representation of your interests. If you are trying to tell your potential employer that you have interests that have something in common with their business - then that's great - but even if they are not relevent, demonstrating that you can work with other people, that you have a command of the English language, that you have writing skills, that you are self-motivated and full of spare energy...all of those things are of value.
Think about it:
  • CANDIDATE A: "Hobbies: I love to watch horror movies and I spend my spare time chatting with friends on MySpace."
  • CANDIDATE B: "Hobbies: I maintain a series of articles on Wikipedia about Italian Architecture and my article about 18th century Venetian glassware was honored as one of the top 0.1% of articles by appearing on the Wikipedia front page in June 2007."
Even if your business is making beermats in Iowa...all else being equal...who would you invite to the job interview?
SteveBaker 15:46, 4 July 2007 (UTC)
Adding yet another answer to the original question: yes, if your contributions include creating substantial content on traditional encyclopedic topics, I most certainly would include your Wikipedia activity on your resume. Others above have already answered the question well, but here's my two cents, since I'm a hiring manager in a large company.
If you are applying for a job where writing skill, technical literacy, and initiative are valued (as is true of the jobs for which I hire), Wikipedia is a strong selling point. I'm biased in favor of the project, of course, since I write here, but I'm not alone in saying that people who hire for professional jobs like people who engage in volunteer activity -- it shows that the applicant cares about something other than himself. I'm more likely to pull someone in for an interview who organizes leukemia runs, animal shelters, or writes encyclopedia articles than someone who spends her free time promoting her garage band on MySpace. These are good people to have working for you.
Leave the "supervisor" blank, and include a single-line description of the project's overall purpose, since I still find lots of people who haven't heard of it. Antandrus (talk) 15:57, 4 July 2007 (UTC)

[edit] Military escorts

In the British army a prisoner under escort must be in the charge of a person of senior rank, and accompanied by someone of the same rank. i.e. A corporal and a private are needed to escort a private. Who would escort a WOI (Regimental Sergeant Major)?86.219.35.208 16:16, 3 July 2007 (UTC)petitmichel

Using the articles on British Army officer rank insignia, Regimental Sergeant Major and Major I assume you could work it out. There seem to be a number of variations within the Major rank and the question sounds like it is based on a guideline in the event of a military police escort rather than a fixed and fast rule. Lanfear's Bane

Difficult to work out, which is why I asked. The next rank up from RSM is 2nd Lt. But I wonder if an officer would escort in such cases...? Incidentally major is an officer's rank, the first Field rank. Sergeant major is the senior private soldiers' rank. Major General used to be Sergeant Major General. Let's not get confused over nomclature. I am not talking about the MPs. And let's not guess.86.197.43.57 14:40, 4 July 2007 (UTC)petitmichel

[edit] Minors' criminal records (USA)

They're obviously sealed, and not a matter of public record, and employers are not allowed to ask about them. But what happens when the person turns 18? (or whatever age the state mandates as "adult")? Are the records released, or are they expunged? What happens if the person is currently serving a sentence when they come of age? Are they transferred to an adult facility?

I realize that laws are drastically different between states but I'm looking for a general-knowledge sort of answer --frotht 16:36, 3 July 2007 (UTC)

IANAL, but I think it's 18 when the records are finally sealed or expunged or whatever. So if you get in trouble at 15 and then at 17, the court can look at the records from when you were 15. But if you then get in trouble after 18, it's as if the old arrests never happened. The idea is to get a chance at a clean slate when you're finally supposedly able to make adult decisions. — Laura Scudder ☎ 18:43, 3 July 2007 (UTC)
What if you get in trouble as a minor but aren't convicted until after you're 18?
The date of the crime / criminal activity should be controlling, not the date of conviction. Many crimes are committed by youths and presumably some of these take years to weave through the court system. The concept is that a minor is not fully capable of appreciating the criminal actions at the time he committed the offense ... regardless of whether or not that took "a long time" to get through the courts to result in a conviction. He may be 18 when the case is resolved, but only 16 when he committed the criminal conduct. It is the youthful age of 16, when he was (theoretically) unable to appreciate the criminal conduct, that is the basis for discriminating juvenile records from adult records. (JosephASpadaro 22:34, 3 July 2007 (UTC))
So is there any point in continuing to "work its way though the system" if the person has passed 18, since the person's record is sealed anyway? --frotht 03:34, 4 July 2007 (UTC)
I don't know if I understand your question exactly. Yes, every case needs to "work its way through the system." Just because a 16 year old gets accused of a crime, does not necessarily mean that he actually committed that crime. So, if he needs to wait 1 or 2 or 3 years for his case to come to trial -- let's say, to ultimately be acquitted -- yes, there was a very good point in letting the case continue to work through the system. In this case, the person would have no criminal record at all, as opposed to having "just" a juvenile record. Not to mention, no punishment (e.g., prison) at all ... as opposed to whatever the juvenile punishment is. (JosephASpadaro 04:02, 4 July 2007 (UTC))

[edit] Who was P. J. Gaffney?

Who was P. J. Gaffney? What did he do in the early to mid-Twentieth Century that led the American Geographical Society to invite him to sign the famous Fliers’ & Explorers’ globe? Gaffney wrote his signature on the globe on northern Canada in the vicinity of Great Slave Lake. Did he set a record in aviation in that area? Or did he set a record in exploration? --Prassea 18:40, 3 July 2007 (UTC)

It doesn't appear that the location of signing has anything to do with who he is. I've put a message in at the AGS and asked for a reply. Having lived in the Northwest Territories back for a while I can add that I don't recognize the name. --Charlene 20:58, 3 July 2007 (UTC)