Should I say "She is in the park" or "She is at the park"?

Question: I am really confused.  Which preposition is correct?

She is in/at the park.
  They are in/at the park.
  I am in/at the park.

Should I use in or at in these sentences?
Answer: In and at and on are notoriously difficult for learners to grasp and native speakers to explain.
These are called prepositions of place.
at conceives of a place or location as a point. Like an X on a map. You are at a particular place and not some other place. If there is an inside and outside to the place, at does not indicate whether you are inside or outside.
I'm at the bus stop.
I'm at the corner of 5th Avenue and Elm Street. =conceive the corner as the point of intersection.
I'm at the southeast entrance of the parking lot.
I'm at the park. (park is conceived as a point in space)
I'm at the parking lot. (conceived of as a point in space)
I'm at the shopping mall.
I'm at the south concession stand of Section 111 of the ballpark.
I'm at the swimming pool. (somewhere near the swimming pool, not in the swimming pool!)
I'm at the elevator. (as in at the elevator entrance)
Sometimes these expressions become fixed phrases, such as in
at school
at home
at work
at the office
In conceives of a place or location as containment or enclosure, often as inside or within.
I'm in the store. =inside the store.
I'm in the park. =within the park.
I'm in the parking lot. =within the parking lot.
I'm in in the garden.
I'm in the city.
I'm in the world.
I'm in the corner of my room. =confined in the corner
I'm in the swimming pool. =within the water.
I'm in the chair. =enclosed by the chair.
I'm in the car.=within
I'm in the bus/train/airplane/boat/trolley/streetcar=confined within or inside.
I'm in first class (section of the aircraft)! =confined in or within the first class section or compartment.
On conceives of a place as on a surface or in contact with a surface
I'm on the chair. =the surface of the chair, including the seat or the arm or the back.
I'm on the corner of 5th Avenue and Elm Street. =conceive the corner as a surface area.
Im on the world (and I want to get off) =conceive the world as a surface area.
I'm on the school =on top of the school roof, for example.
I'm on the automobile (car) =on top of the autombile (car), it's roof as a surface
Note well: I'm on the bus/train/airplane/boat/trolley/streetcar (conceive of being in contact with a surface; these methods of transport are large enough to have a walkway, which is the surface.)
The fly is on the wall =in contact with a surface.
Notice corner was used with all three; which preposition depends on how the speaker conceives of the corner (at the point of intersection of two lines, in a place that confines her, or on a surface area.)
Compare:
The bird is at the tree, as compared to at the bird feeder.
The bird is in the tree=within the tree branches, for example, or confined in the tree.
The bird is on the tree=on a branch, for example.
The bird is at the bird feeder, in the bird feeder (stuck inside, for example), on the bird feeder (on a surface, either on top or on a peg...
The boy is playing hockey on the street=street as a surface area.
The boy is playing hockey in the street=confined within the street.
Jill is at the stairway.  (point in space)
Jill is on the stairway. (on a surface)
Jill is in the stairway. (within or confined)
Write your name in the top left corner of the page. (confined within the corner)
Now, print today's date at the top of the page (a point).
On the bottom of the page, draw an X.(on=on the surface of the page).
Draw a C in the middle of the page (confined in the middle).
Edit to add elevator:
We are at the elevator to mean at the entrance to the elevator.
We are in the elevator. We are inside the elevator.
We are on the elevator. (You are riding on the elevator, like on the bus. Here, the elevator floor is the surface area.)
Two people trying to find each other:
A. Where are you? (in some dialects, Where are you at?)
B. I'm at the zoological park.
A. Me too! Where at the park are you?  Are you already in (inside, within the park)?
B. Not yet. I'm out on the parking lot (surface area) arguing with this other person.
A. What? What happened?
B. I was parking my car in the parking lot (within) when some clown hit my car. Where are you?
A. I was waiting at the 4th entrance like we agreed, but little Joey got bored, so we are already  in (inside) the zoo.
B. Where in the zoo are you?
A. We were at the first taco stand; then we waited at the entrance of the Panda House for 20 minutes.
B. Cool! Are you in yet? (within/inside, the Panda House)
A. No. There is a delay. There is a worker on the Panda House, (on the surface of the top/roof).
B. Okay, I am now in line (fixed phrase) trying to get in (inside) the zoo.
A. I'll come meet you. At which entrance are you?
B. I'm at the southwest entrance.
A. Don't move. We're coming.
B. Too late. We're already in. (within, inside, confined in).
A. Where (at)?
B. I'm on the zoo train. (train conceived of as a surface). But these seats are so small, I sitting on the seat, not in the seat.
A. What do you mean on the seat?
B. Well, on the back of the seat (the back as a surface).
A. Are you (located/seated) at the back of the train? (a particular point ).
B. No, I never sit in back (fixed phrase, but means confined in back).
A. Guess what? We're on the ramp (surface) of the Lion Exhibit. Now we're in the exhibit (confined/inside).
B. What do you mean in the exhibit? You're really inside (=within, in) the exhibit, among the lions?!!
A.-----
B.Hello? Hello?...Well, I hope she is not in the lion!
Comment: A great answer, but I'd like to add that these prepositions have other ancillary meanings that go beyond the basic meanings you've listed here. _On_ is probably the most vexing, as we can be _on hold_ while we're _on the phone_, until the radio host takes our call, at which point we'll be _on the air_, before the host _moves on_ and takes the next caller _on his show_. There are also phrases like: He's _in_ trouble, the show is _in_ color, she's _on_ a trip, pay me _in_ cash, and I'm _at_ a loss. Lastly, you answered this question _in_ November, _on_ the 26th, _at_ 4:30 in the afternoon.
Comment: I agree, your answer is fine (and I've upvoted it). But I thought those other uses deserved a mention in a footnote. I wouldn't want a learner reading your comprehensive answer and then walking away thinking that they now _fully_ understood these three versatile words.
Comment: Perhaps a way to indicate J.R.'s and syntaxerror's point without excessive wordiness would be to say that conceiving of a location as a point, as an enclosure, and as a surface are the _primary_ meanings of _at, in,_ and _on,_ but there are endless conventions for how to extend them, which are quite irregular and unpredictable. For example, the following sound strange: "I'm at New York", "I'm in the butcher's", "I'm on the airport." And the following are ordinary: "I'm at sea", "I'm in business", and "I'm on homework problem #6".
Comment: Yeah, @J.R. and I'm sure you know that *in*, *on*, and *at* demonstrate similar 'behavior' as *prepositions of time* as they do of *place,* but I didn't want to get into that in an already overlong answer...
Comment: This is almost an essay, and "answer" would be quite an understatement. But in all that lots of text, I missed a classic example for the sole use of *at*, and that's stores and shops derived from a __profession__: __at__ the butcher's, __at__ the hairdresser's. If I remember correctly, you're even required to use "at" for *at the butcher's house*, when the butcher has invited you privately into his home as his guest, e. g. for a dinner. *BUT*: "The butcher's wife was __in__ the butcher's house, and could not hear me" (calling her from outside; *in* is in fact short for *inside* here)
Comment: @syntaxerror That may be classic, and certainly some *at* phrases can be explained that way, but it adds nothing to the answer. *At the butcher's* says nothing about whether I am within the butcher's or not. Which is why *in* the butcher's is used the way it is. Both situations are already covered in the answer
Comment: Well, I've been through it 2 times, and I didn't come across anything too specific TBH - so I posted my comment. But I understand that my post did not encourage *you* too much to expand your answer in order to cover this case, since you insist it *is* already covered (which may be doubtful, but it won't be worth an argument). Nevertheless, I can live with that; I was just proposing - go ahead, and ... nevermind.:)
Comment: If you go with "these are the primary meanings, and then there are lots of extensions", you could shorten the answer by removing questionable examples or examples that don't clearly illustrate the primary meanings. For example, these all sound strange to me (Midwestern American accent): "playing hockey on the street", "the bird is on the tree", "Jill is in the stairway", "I'm on the world". "I'm on the chair" typically means "I'm standing on the chair", not "I'm on the surface of the chair".
Comment: I went ahead and posted another answer, saying essentially what you've said here, but focused on "at the park" and "in the park", and omitting "on". Hopefully both answers are useful to readers.
Comment: @J.R. I had the same thought in November as I do now: that your added examples are not really *prepositions of place*.
Comment: δοῦλος - I would agree. That's why I upvoted the comment left by Ben – I think @BenKovitz explained it rather well.
Comment: what I'm curious about is that why on earth we can't say "at London" as well as we say "In London" if we might say "I'm at home " or at the airport/supermarket/park" when we want to specify a location where we are? London is also a location, a point in space, one of the cities in England. Similarly, just as we say "I'm at home" by analogy with other locations in the city, couldn't we do so for rooms by analogy with other rooms at home? or countries in comparison with other contries in the world - "at Norway", implying both, "inside the country and anywhere near the country"
Comment: @CavidHummatov Kevin's answer partially explains it. London is a large place and can hardly be described as a point. I don't know...
Answer: Both are equally correct, and have nearly the same meaning. In would mean physically within the bounds of the park, while at is slightly less precise, because she might be inside the park, or perhaps just outside the gates.
Comment: It's worth adding that "in the park" would rarely be used in an urban setting, per Kevin's answer.  If I were at a park, in a city, and someone called me, I would *always* say "I'm at the park."  So while this answer is technically true, I think it's a fine point that could be misleading to a beginner.  For the majority of practical use, "at" is correct and "in" is, if not "wrong" then at least awkward.
Comment: @Jonah that may be a regionalism (sounds like USA English to me). In NZ, I would definitely say "I'm in the park", even if the park was in the city.
Comment: In would probably be used mostly, as Colin points out, to distinguish *where* at the park you are. "I'm in the park"; "I'm at the gate"; "I'm across the street parking my car".
Comment: What Blogbeard says.  In Australia I'm in the park, or at the park with equal correctness.  The only time I'd differentiate them is when you have just arrived there, eg: 'I'm at the park now', which as Colin infers is due to not necessarily being inside its borders. 'In' the park is fine.
Comment: I don't even think it's a regionalism. I'm from America and I would say "I'm in the park" if I were, as Colin says, inside the bounds of the park.
Comment: It's all about context. If I know you are going to the park and I'm trying to find you I may expect "I'm in the park" so I know if you're within the boundaries or waiting outside. If I'm just generally asking your location, you'd say "At the park". Essentially, "In" the park would only be used when the differentiation between just inside it, and just outside it, is important. "At the park" would be used in most real conversations, and is the safe default option. **If in doubt, stick with "at" unless the question is "Are you inside the park boundaries?"**
Comment: @JonStory `Are you inside the park boundaries?` is a yes/no question though...
Answer: As a native speaker of American English, I can't justify this, but to me, in subtly connotes a much larger park than at.  A person might be at the city park, but in a national park.
Comment: I could see that.  You never say someone is at the woods, they are always in the woods.  Similarly proximity has a bit I think, She is "at the store" if you're asking while we're at home.  She is "in the store" if we're in the parking lot looking for her.
Comment: My sense (also as a native AmE speaker) is that you use "at" when you're making a statement that you expect to uniquely(ish) identify the location - that is, I'd say "at the park" when I expect that the listener could go to the park and, without further clarification, probably find the person they're looking for just by looking around. I'd say "in the park" if the park is big enough that the listener would first need to narrow down their search to only part of it. But this is an _incredibly_ subtle distinction, and not one that I ever really thought about before.
Comment: This is exactly right. If folks had gone down to the little lakeside park a couple blocks from my home, I'd say they were at the park. But if instead they had chosen to drive up on into Rocky Mountain National Park, I would say there were in the park — somewhere; it's a big place, and *at* doesn't work for big places.
Comment: I think *in* has this connotation of a bigger park because the implication is that *at* the park is not specific enough to describe where you are, because there are multiple nearby areas that could be considered *at* the park.
Comment: @David Z *at* definitely refers to a *point in space or time (at 3pm)* but both parties would have to know ***where** at the park* you mean in order for *at* to identify a specific, known location
Comment: Considering that this grammatical finesse was born before GPS existed, even if a person is *in* the national park, he/she would be easily to locate via GPS nonetheless. (Because who is found these days without their personal satellite nearby, the cell phone?) So more exactly, we should put it like (as a rule of thumb): "in" means "diffcult to locate *without technological help*" :-) * smirkingly *
Answer: Both "at the park" and "in the park" are correct English, but they mean slightly different things.
At the park treats the park simply as a location without regard to being inside it or outside it.
In the park specifically means the interior of the park.
So, if you're standing just outside the gate to the park, you could say you are "at the park" but it would be wrong to say you're "in the park". If you're inside the park, then "at the park" and "in the park" would both be correct, but they have different emphasis. "At the park" emphasizes just the fact of being at the park; "in the park" emphasizes that you are at one place inside the park, as opposed to many other places inside the park.
Some examples to illustrate the difference:

I work as a groundskeeper at Golden Gate Park.

Here, "in" would be incorrect, because you don't mean a specific location within the park, you mean the park as a whole.

The Conservatory of Flowers is the oldest building in Golden Gate Park.

Here, "in" is more appropriate because you're distinguishing the Conservatory of Flowers from other locations within the park. But "at" would still be correct; it would just de-emphasize the fact that Golden Gate Park is quite large. "At" leads the listener to imagine the location as if it were a single point, no matter how big it really is.

I'll meet you at the park.

Here, "at" suggests that if you both go to the park, it will be easy for you to find each other. Maybe there is an obvious location where you'd go, like the gate. Or maybe the park is small enough that you'd see each other no matter where in the park you're standing.

I'll meet you in the park.

Here, "in" suggests that you'll need to specify where inside the park you'll meet.

Let's play softball at the park.

Here, "at" is more appropriate if you mean to use the park's facilities, like a softball field. All that matters is that the park has such facilities and you intend to use them. Once you're at the park, it will be obvious where to go: the softball field.

Let's play softball in the park.

And "in" is more appropriate if the park doesn't have a softball field. This sentence suggests that you want to go to the park and search for some unoccupied grass to play softball. But in both of the last two examples, both "at" and "in" are still correct. The difference is the emphasis: the way they direct the listener's attention and imagination.
The same kinds of distinctions attend many phrases where "at" and "in" are both correct English. For example, "I'm at the Fairmont Hotel" could mean that you've booked a room at that hotel, even though you might not be physically present inside the hotel right now; or it could mean that you're physically present inside the hotel, or maybe standing just outside it. "I'm in the Fairmont Hotel" specifically means that you are physically somewhere inside the hotel right now.
More about the differences in meaning and customary usage among at, in, and on is explained in the article on "at" in Webster's Dictionary of Synonyms.
Comment: @J.R. Here's why I think it's so hard to explain "at" vs. "in" (and most prepositions) completely: In a sentence, they get their meaning by analogy with phrases in other sentences, and these analogies often conflict. For example, in "I launched a missile at the park", an analogy with "throw at" can lead "at" to mean "aimed toward". But it can also indicate the location of the launcher, by analogy with "I'm at the park". Many analogies tug at "at" in every sentence in which it occurs, and only common sense can decide the winner. Why do _you_ think a complete, concise explanation is so hard?
Comment: "_At the park_ treats the park simply as a location without regard to being inside it or outside it. _In the park_ specifically means the interior of the park." is wrong. Look at your own examples of "at". Every one contains an active verb: *work, meet, play* and it is this that triggers the use of *at*, not whether one is inside or outside the park or the 'meaning'. This is because "at" and "in" are functional words with little or no lexical content. The 'meaning' in your examples derives from the presence of the active verb. There is a lot more to meaning looking in a dictionary.
Comment: If you want to get past the look-it-up-in-a-dictionary phase, try Frege's *On sense and Reference*; Grice's *Logic and Conversation* and/or *Meaning*; Russel's *On Denoting*, and Searle's *How to do things with words*. These will give you a broad background on how meaning is generated, and why reference to a dictionary is quite pointless.  Consider this:"Dictionary meanings are by definition out-of-context meanings. They can never be part of either sentences or utterances, since, as soon as we are to assign a word a value in any kind of context, we contextualize it." ~ Beatrice Warren
Comment: @RoaringFish Most of the examples are pairs of sentences that differ only in one word: "at" vs. "in". They illustrate how the context affects the meaning. I'm not finding your comments helpful or relevant.
Comment: Okay... then explain why we don't say "he is at his room" or "he is at Rome" if it just a matter of meaning. If your claim were true and it were only a matter of being "without regard to being inside it or outside it" they should be commonly used statements. My explanation is that they have boundaries that trigger the use of "in" but have no function in terms of activity to trigger "at". What is yours?
Comment: @RoaringFish - I have no problem with "_at the park_ treats the park simply as a location without regard to being inside it or outside it; _in the park_ specifically means the interior of the park." (At least, I wouldn't call it "wrong.") If you text: "Where are u?" and I reply, "I'm in the hotel" that pretty much means I'm inside the hotel. If I answer, "I'm _at_ the hotel," I could be in the lobby at the front desk, in my room, or in the parking lot. I do agree with the general gist of some of your comments, though: there's more to this than an inside/outside the boundaries differentiation.
Comment: @RoaringFish This answer does not propose a general theory of language or even of all the things "at" and "in" can mean. It explains the difference between "at the park" and "in the park" and then points the reader to further information. I think your comments are extremely misleading and confusing for a beginner learning English.
Comment: @Ben - There's that side of it, too. The O.P. asked: "Should I say _"She is in the park"_ or _"She is at the park"_? Which one is correct?" The short answer is, "**Either one can be correct, depending on what you are trying to say**." (And the short footnote is, "and did you ever open Pandora's Box by asking us to explain how to use _in_ vs. _at_ when dealing with a person's location.) Prepositions are the hardest simplest things in English. :^) I think Fish's comments are only meant to say, "There's more to it than what this answer says here" – which isn't bad for a beginner to know.
Comment: @J.R. Do you have a suggestion for how to do that without overcomplicating the answer? I tried to suggest near the end of the current version that the "park" example applies to _some_ other phrases but also point to further info about the vast clash of idioms and conventions that make up the full generality of "at", "in", and "on". The answer ran much longer than I'd hoped, so I'm hoping to keep that part brief as well as avoid discouraging a beginner (since prepositions are so hard to learn).
Comment: @BenKovitz... unable to speak English well does not equal 'stupid'. An educated professional or a universtity student can understand the concept, even though they have trouble putting it into English words. IMO, accepting and giving them a concept is less confusing than vacillating by saying "Aaaah weeeell... it is not really wrong... you can say either... it all depends..." and then the OP wanders off telling everybody they had a holiday at Paris last year because the 'teacher' failed to give them anything solid to work with. I have seen it 1,000 times but it still irritates me.
Comment: @J.R. ~ the simplest answer I know of is the one I already gave. "In" if it has boundaries, but if the location is primarily to perform a function they can use "at" if the function is what they are wanting convey. "Malcolm is at the pub" if you want to convey that Malcolm has gone drinking with friends, because that is what a pub is for. "Malcolm is in the pub" if you are in the beer garden and somebody asks you where Malcolm is, to convey that he is inside and not outside.
Comment: Ben - RE: _Do you have a suggestion for how to do that without overcomplicating the answer?_ No, I don't. If I did, I would have left an answer here. :^) Then again, I think that **is** the answer (or at least part of the answer): _there's no simple rule that will tell you which of these two preposition(s) are "correct" in all contexts._ @Roaring - that's not bad, but it's still not foolproof. _Where are you now?_ I'm **in** traffic; I'm **at** the accident.
Comment: @J.R. ~ I agree. It is not foolproof, but not much in language is. I am puzzled by your examples though... **in** traffic because it surrounds you, and **at** the accident because it to one side of you... and because if it does surround you so you are **in** the accident you have problems.
Comment: @Roaring - I'm not sure what's so "puzzling" about my examples. Sure, those prepositions are natural for the native speaker, but I was trying to show a quick example of something that might be hard for a learner, particularly if their only available rule of thumb is: _use "in" if it has boundaries, but use "at" if the location is primarily to perform a function_. An accident scene or a traffic jam isn't quite the same as a pool, pub, or park; that's all I was trying to say.
Comment: @J.R.~ got it! I thought you were telling me that you found them strange, which is why I was puzzled. Yes - once you move away from physical locations the game changes.
Comment: Yes, most of my comments on this question are not really remarks about things I find strange or difficult, but things I think the learner might find perplexing. The only thing I find "difficult" about this is how hard it is to explain it completely yet concisely. I think this answer does a pretty good job of it, but, as the ensuing discussion shows, English often has odd exceptions or peculiarities.
Comment: This answer's strategy is to explain clearly what's happening in the two phrases and avoid stating a general rule, since all such rules are false. Other, similar phrases will make sense because they work analogously to "at/in the park". Others will conflict. I think it's wiser to let learners meet those when they come and adjust then, than to hang them up on memorizing some confusing, doubtful attempt at a complete theory (which no one needs anyway).
Comment: @Ben - Excellent example, "launching missiles **at** the park." As for why I think explanations are so elusive, I hint at my reason in my [profile](http://ell.stackexchange.com/users/113/j-r), where I exhort the learner: _Never make the mistake of thinking that a tiny preposition has only [one](http://www.onelook.com/?w=in&ls=a) meaning._ Moreover, many prepositions have meanings that overlap.
Comment: @J.R. Actually, your profile led me to ask your own explanation of the difficulty. I've encountered precious few people who've thought seriously about the amazing complexity of prepositions. :)
Comment: @BenKovitz quite the contrary to what you suppose, I myself as a learner never get discouraged by a  comprehensive, longly explanation  unless it's just irrelevantly put-up verbosity. In contrast, a short, brief explanations could mostly bring about different questions itsel and might be quite perplexing for the O.P, moreover I personally feel a bit carelesness by that sort of short, brief answers . So I'd wanna encourage you that you're on the right way... even If you need to write a paper article to get your point across the reader just do it without any hesitation.
Comment: @CavidHummatov Thanks for the encouraging words! The above is one of the earliest answers I wrote here. Since then I've gone on and written 300+ mostly longish answers that try to explain the subtle and often messy forces at play in English—often wishing I could make them shorter. Maybe I've been on the right track after all. :)
Answer: I would use "at" when referring to a location, like "the airport", "the bus stop", or "school". In my mind, it is a specific place I can go to, although that may not apply to every context.
"I'm going to the bus stop. I'm at the bus stop. I have walked to the bus that is stopped at the bus stop, and I am at the bus waiting for the doors to open."

"Where is she?"

"She is at the park."

"I'm at the park, and I don't see her."

"It's a big park. She is probably in the park somewhere."

The park is a location that both people in the conversation above know how to get to. "In the park" is somewhere inside the boundaries of the park, but isn't a location you could give someone exact directions to like "the park on Elm street".
"Where is Dad?" "He went to go grocery shopping, so he's at the market."
"Where did you find that lamp?" "I bought it at the antiques store on main street."
I bought the lamp while I was inside the store, but what the person asking the question wants to know is the location.
I would use "in" with a place that has boundaries that I know the person or thing is inside.
"Where did you park?" "I parked at the airport in lot G."
"Where is your brother?" "He's in the arcade over there. He got bored waiting for you."
In this sentence, even though I'm not currently in the airport, I was at the time that I dropped my glove somewhere inside the airport, so I use in.
"Where did you find your missing glove?" "I had dropped it in the airport."
"Where is your glove?" "I think I lost it at the airport."
I know I had my glove before leaving the airport, and I noticed it was missing after I left the airport, so it is at that general location, but I don't know if it is inside the airport or lying on the sidewalk outside the airport.
Answer: I think I would say "at" if she is significantly farther away then we are.  I would say "in" if I you and I were closer to the perimeter of the park.
Consider you asking me where she is while we are home.  I would say she is at the park.
Consider you asking me where she is while we are on the road surrounding the park.  I would say she is in the park.
Answer: In the park is used more than at the park.
Check the Ngram here
One rule of thumb is that we use in for places that have boundaries - a city for example, or a park, which is why we say "he is in Paris" and never "he is at Paris".
But... an airport has boundaries, but we often say "she is at the airport". One explanation for this, and I have tried to find the source but no luck so far, is that we can use at for locations with boundaries if they exist to perform an activity, and the activity is more important than the location. In other words, we say "at the airport" because we go there only to catch an aeroplane or meet/see off somebody else who is, and we say "at Carrefour" because we go there to buy stuff, or "at school" because we go there to learn.
Compare with the situation if you are waiting for your luggage at the carousel, or queuing at the checkout, and somebody calls to ask where you are. Then you would say "I am still in the airport" or "I am still in Carrefour" because the location has now become more important than the activity.
Comment: It's difficult to see the usage of the phrases in that ngram. For example, "We were feeding pigeons in the park" seems like it would be used more, but that is entirely different from "She is at the park".
Comment: You might say "he is at Paris" when referring to a train journey for instance.
Comment: It's interesting that English speakers *used to say* [I was born **at** such-and-such city](http://books.google.com/ngrams/graph?content=born+at+London%2Cborn+at+Boston%2Cborn+at+New+York&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cborn%20at%20London%3B%2Cc0%3B.t1%3B%2Cborn%20at%20Boston%3B%2Cc0%3B.t1%3B%2Cborn%20at%20New%20York%3B%2Cc0)
Comment: In the examples in your last paragraph, I'm pretty sure I'd say "I'm still at the airport" and "I'm still at Carrefour."
Comment: @RoaringFish Which phrase is more appropriate depends on the intended meaning, not the frequency of occurrence of the phrase. Confusing distinctions of meaning with frequencies of usage is a serious error, hence the downvote. I don't think statistical evidence can establish that "at" and "in" emphasize different things, if that's what you're demanding. If you'll count thoughtful observation of the language as evidence, try the article on "at" [here](http://books.google.com/books?id=8N4UReTJYhUC&lpg=PP1&dq=webster%27s%20dictionary%20of%20synonyms&pg=PA70#v=onepage&q&f=false).
Comment: Hi yes @Octopus, *in the park* means *inside or within the park,* whereas *at the park* the use of *at* just means *a 'point' in space*.  It's like *at the corner of 5th and Park Avenue.* Consider I'm at the movie theatre. Where at, exactly? I'm inside *at* the concession stand.
Comment: The airport example is a nice one :) I (native BrEng speaker) largely agree with @DavidRicherby that I would use "at" in (say) the carousel case, *unless* the person calling was coming (say) coming to collect me - in which case I'd say "in" the airport to emphasise that I was still inside and hadn't managed to make my way out yet.
Comment: Don't use frequency counts, like Ngram, to determine what words mean. The count reflects how often the different meanings occur in print, not just which phrase is more conventional.
Comment: @BenKovitz ~ who is saying anything about the meaning? I am using Ngram to illustrate which *usage* is more prevalent. If you think Ngram is wrong and everybody is saying *at the park* except when they write, then do the grown up thing and bring some evidence to support your argument instead of down voting.
Answer: In practise, they are interchangeable and both correct.
However, at would be more often used in situations where you are highlighting the park from other locations where you might be.

A)where are you now?  B) I'm at the park.
Yesterday I had a picnic at the park.

In would imply enclosure so more likely to be used if you are describing location relative to the park specifically.

I'm in the park by the pond.
There's a gazebo in the park.
Answer: 'in the park' is a location
'at the park' is more of an activity (but also could be a location)
Eg.  Where is susan? She is in the park. (location)  Where is Tom?  He is at football training. (activity)
Eg. Bob is in the supermarket. (location)  Bob is at the supermarket (activity or location or both)
Eg. I am at the hockey game (implies watching) or in the hockey game (implies playing).
Comment: James, I think what you ought to do here is massage this answer a bit. As @TRomano says, there's a kernel of truth here, but you've expressed it so succintly that you've invited arguments. I recommend editing the answer and giving some specific examples.
Comment: James, your answer did not deserve to be downvoted, because it has a kernel of truth. In the park = within the bounds of the park; At the park = doing something within the bounds of the park (e.g. strolling, relaxing, etc)
Comment: How is "at the park" an activity? How is "The homeless man lives in the park", a location rather than an activity (living)?
Comment: @DavidRicherby Do you not see the difference in emphasis between "*in the* park" and "at *the park*"?  "What is she doing?",  "She is at the park or at the shop". Being at the place is the activity. vs "The homeless man living in the park" where living is the activity.
Comment: How does "I'm playing football in the park" differ from "I'm buying milk at the supermarket"? In both cases, a location and an activity are specified and the activity is the primary focus of the sentence but "in" is much more natural in the first case and "at" in the second. If there's some obvious difference between the two, it should be easy for you to explain. If you can't explain it, maybe it isn't quite as obvious as you seem to think it is.
Comment: Well maybe I can't explain it well, to me the implication is intuitive.  Even looking at @DavidRicherby 's examples there is a clear difference in meaning between "I am buying milk at the supermarket" and "I am buying milk in the supermarket" but its hard to put a finger on what exactly the rules are.
Comment: @James - I think the rules are so vague because the differences are so minor, which leaves a lot a wiggle room. The only difference between being _in_ the supermarket buying milk and being _at_ the supermarket buying milk is that one of thpse (namely, _in_) puts you squarely under the roof. You might still but under the roof with _at_, but you could also be, say, in the parking lot walking toward the front door.
Comment: @J.R. are you a native english speaker? The difference may be hard to explain but it is not minor.  Eg. I could say I am at the hockey game (implies watching) or in the hockey game (implies playing).  I could say I am in school (implies in a school) or I could say I am at school (even if I was on a field trip to a museum and nowhere near a school building).  At can be a location but often it refers more to the activity done at a location.
Comment: @James - I said "minor" in reply to the interesting example you gave earlier. I understand there are times when the differences are clear-cut, but the meanings also overlap enough that a hard-and-fast rule is elusive. As for your locaton/activity distinction, that's hardly a foolproof differentiation. For example, "at/in the swimming pool" is pretty clear-cut, but "at/in the library" could both mean studying, working as a librarian, looking for a good book, using the internet, or staring outside the front door waiting for a ride home, and either prepostion is acceptable for all of those.
Answer: According to Cambridge Advanced Learners Dictionary:
The preposition 'in' emphasizes 'inside a place'. So you might say: I don't like walking in the park.
But the preposition 'at' is used to talk about time spent at a place. So you might say:
We spent a really good time at the park yesterday.
Comment: Maybe it's because your answer limits the prepositions too much. There's nothing wrong with saying, "We spent a really good time in the park yesterday," or "I don't like walking at the park."
Comment: I'm surprised ! Why down-vote?! This explanation is based on 'Cambridge Advanced Learners Dictionary'. If this answer is not correct, explain the reason please.
Answer: I think it more depends on which type of park you are at. Like a neighborhood park (one without a restricted access) you would generally say "I am at the park". But if you are talking about a park like say a ballpark or a theme park (IE: DisneyLand, with a restricted access) you would say "I am in the park", letting them know you have entered the park. This is of course assuming a friend or parent knows what park you would be referring to.
Comment: I sort of agree with where this was going, but think you veered off course near the end. After all, people **do** say, "I am at the park," even when referring to large, restricted access parks.


Touchpad doesn't respond when power is plugged

Question: Upon upgrading Ubuntu 11.04 through 12.04 on a Dell System, the touchpad doesn't respond until the power plug is unplugged. Any idea why? To better clarify the behaviour of the touchpad: The touchpad moves in slow motion when the power is plugged otherwise, it works perfectly.
Comment: Just to clarify... So, the touchpad doesn't work when the power is plugged in, or when the power is unplugged? (I think you mean just when it's plugged in, but @Leopoldo Pla's edit entirely changed the meaning of your title...)
Comment: I thought that the title was mistaken, but maybe the body of the question is mistaken. Can you clarify and correct retnan?
Comment: Make bootable usb...use live session & check your touchpad....i would recommend to use 13.04..
Comment: sorry...my bad.. edited
Answer: My guess is that there might actually be something wrong with the power supply as suggested in this clip from Wikipedia:

If the computer is powered by an external power supply (PSU), the
  detailed construction of the PSU will influence the virtual ground
  effect; a touchpad may work properly with one PSU but be jerky or
  malfunction with another (this does not imply any electrical risk
  whatsoever, a delicate capacitative ground, not a contact ground, is
  at issue). This has been known to cause touchpad problems when a
  manufacturer's PSU, which will have been designed to work with the
  touchpad, is replaced by a different type. This effect can be checked
  by touching a metallic part of the computer with the other hand and
  seeing if operation is restored. In some cases touching the
  (insulated) power supply with some part of the body, or using the
  computer on the lap instead of on a desk, while working can restore
  correct operation.

Maybe try another charger and see if the problem resolves.
Comment: That's right! tried the same charger on another DELL system and got similar idiosyncracy. You are very right @BiggJJ, it is the power supply
Answer: As I said here and some other people say, a fast workaround is to touch notebook ground: Make a couple of loops around power plug with a clip and touch it while using the touchpad. You can also use any USB cable, just plug it and touch the other end, the metal shield (grounded). You can buy or make a DIY anti-static grounding wrist strap connected to the notebook ground (USB or clip/power plug), like  Roreru's answer.
It's a ground loop problem with Synaptics touchpad (Dell Inspiron 14 in my case), maybe related to a bad power supply. I'll edit this reply if other PSU fix the problem.
More info here and here.


Can I transfer my Thunderbird Lightning Calendar from home computer to my Android phone

Question: I use Thunderbird with the Lightning extension on my home computer for email and calendar. Is there a way of transferring just the calendar to my Android phone? It would be so useful when away from home so I can make appointments. The only way to do it now is to print the page or remember!
Answer: If you use Google calendar, you can

Export the calendar from lightning as an .ics file
Import that .ics file into Google Calendar
Comment: Missed and important step.  To avoid having to do that going forward (ie, automatic syncing), after you import the .ics file you can also add your Google calendar to Lightning, make it the default calendar, and then delete the local only calendar.  This will ensure that all future TBird calendar events go on your Google calendar, which will then be pulled down by your phone calendar app as well.
Comment: Google calendar doesn't just accept any ics from any guy. I tried one from banana soft and it stops with `Error at line 11: String index out of range: 5`. Line 11 is `11 TZOFFSETFROM:0100` (line 4 is `4 PRODID:-//Apple Computer\, Inc//iCal 3.0//EN`).
Comment: @ott: that's obviously a bug; please report it to Google.


Women giving birth daily ( Olam Ha-Ba )

Question: I have read on an article that in the world to come , every day women will bear children and I want to know if this is true and if so where it says that in the Mishnah.
Answer: The source is in a gemara in Masechta Shabbos 30b:

בְּדִבְרֵי תוֹרָה מַאי הִיא? — כִּי הָא דְּיָתֵיב רַבָּן גַּמְלִיאֵל וְקָא דָרֵישׁ: עֲתִידָה אִשָּׁה שֶׁתֵּלֵד בְּכָל יוֹם, שֶׁנֶּאֱמַר ״הָרָה וְיוֹלֶדֶת יַחְדָּיו״. לִיגְלֵג עָלָיו אוֹתוֹ תַּלְמִיד, אָמַר: ״אֵין כׇּל חָדָשׁ תַּחַת הַשָּׁמֶשׁ״! אֲמַר לֵיהּ: בֹּא וְאַרְאֶךָּ דּוּגְמָתָן בָּעוֹלָם הַזֶּה. נְפַק אַחְוִי לֵיהּ תַּרְנְגוֹלֶת.
In matters of Torah, what is the case with regard to which the verse said that one should respond to a fool's folly? As in the case where Rabban Gamliel was sitting and he interpreted a verse homiletically: In the future, in the World-to-Come, a woman will give birth every day, as it says: "The woman with child and her that gives birth together" (Jeremiah 31:7), explaining that birth will occur on the same day as conception. A certain student scoffed at him and said: That cannot be, as it has already been stated: "There is nothing new under the sun" (Ecclesiastes 1:9). Rabban Gamliel said to him: Come and I will show you an example of this in this world. He took him outside and showed him a chicken that lays eggs every day. (Sefaria translation and notation)
Answer: From Din Online:

The Talmud (Shabbos 30a) writes that there will be a time when a woman
will conceive and give birth on the same day, without having the
difficulties of pregnancy and childbirth.
This will be after the sin of Adam is rectified. This is because the
pains of pregnancy and childbirth are to atone for the sin of Eve,
however after that is rectified things will return the original way
that God wanted it to be.
Have no fear. At that point there will be no concern about having
food, or housing for all of them. Nor will there be any concern of how
the parents will put them through college.
Best wishes.

Women giving birth daily ( Olam Ha-Ba )


I want to put a 4'X8' platform in my garage to hoist stuff up

Question: I'd like to frame up a 4'X8' hole in the ceiling of my garage.  Rafters above are 2x6 on 24" centers.  So I'd have to cut through 4 of them to do it.  Obviously I would have to make a really sturdy frame.  Is this even possible or reasonable?
Comment: I get the feeling you should contact a structural engineer. This kind of work probably requires permitting, which in turn requires drawings and load analysis. Check with your jurisdiction, but I'd advise against doing it completely yourself.
Comment: it is possible. that sort of thing is done in floors to make stairwells.
Comment: do you really need a full 8 feet? You get like 7ft-10+ with only three cut..and of course if you turn it the other way maybe only cut one.
Comment: Rafters or engineered trusses? The latter would require doubled (or tripled) girder (beam) trusses at each side and beams between to carry the truncated trusses. It's not a simple thing.
Answer: If you have a hand framed roof with a non-structural ridge beam and you want to cut the rafter ties, then you will need to add collar ties. The rafter/collar ties are in tension, so you need one or the other to prevent the roof from collapsing in on itself and pushing the exterior walls out. The other option is to add a structural ridge beam for at least that 8' section, but that's not an ideal solution.
If you have a hand framed roof with a structural ridge beam, then there is a chance you don't need rafter/collar ties at all. It depends on what it looks like up there.
If you have engineered roof trusses with metal gussets, then it gets a little more tricky. An engineer would definitely need to get involved.
If you upload some pictures we might be able to help you size it, but more than likely you'll need to contact a contractor or engineer in your area.
Comment: All thanks for your help.  I'm thinking I used the wrong word and caused major confusion with "rafters".  I'm talking about ceiling joists above my garage.  I'll see if I can upload pics.

I want to put a 4’X8’ platform in my garage to hoist stuff up


Minecraft: does the server auto-updates the new features into the existing save?

Question: Does the minecraft server automatically add the new features once updated, even in the old saves, or it only does that in the new games?
Answer: It depends what you mean by new features.  I can't guarantee how things will go in the future, but here's how things generally have happened in the past.

New block types will not be added to the existing map.  They WILL, however, start appearing in new chunks.  This was part of the reason lapis lazuli seemed exceedingly rare after its update, people were looking in previously generated chunks.
New mob types will spawn in existing parts of your map.  They can appear wherever their spawning algorithms determine is "valid," and chunk age isn't factored in.

Those are the only two cases I can think of at the moment.  If you had a specific question or wanted an answer about another group I forgot about, I'd be happy to update my answer.
Answer: Mobs and craftable items and stuff appear in existing save files after updates. New blocks that randomly spawn on a game when it starts will only appear if you go to a new area far away called chunks. I don't know how many blocks make a chunk.
Comment: Thank you, but your answer does not tell anything that the accepted one already does, unless I'm mistaken.


Java-Sockets: InputStream.read() vs BufferedReader.read()

Question: I'm reading from a Socket's InputStream. Because I'm parsing the incoming data on the fly, I'm required to read character by character.
Does BufferedReader.read() the same thing as InputStream.read() does ? (assuming that BufferedReader has been constructed with the InputStream as base)
Is it more efficient to use InputStream.read() when reading each character separately? Or is there any better way?
Answer: BufferedReader will read multiple characters from an underlying Reader. An InputStream is providing bytes. So they're working on 2 distinct datatypes. How are you wrapping a Reader around a Stream ? Presumably you've go something like:
 BufferedReader in
   = new BufferedReader(new InputStreamReader(socket));

in which case I'd be careful to specify your character encoding.
From the perspective of optimisation, it would be better to use the BufferedReader, since it'll read several kilobytes at once, and you can take each character when you want (not necessarily forcing a new IO read).
Comment: Note that a Stream will give you bytes. A Reader will give you characters. So you need to be clearer in terms of what you're receiving and what you need.
Comment: thanks. then you advise me to use InputStream? I'm reading the stream until some special characters appear. Then I parse that piece and await the next "package". Is there any better way to do this?
Answer: read() method of InputStream class is an abstract method. It should be InputStreamrReader I guess. Comming back to your question, both read() method of InputStreamReader and BufferesReader class do the same thing- return the ascii value of a character, the only difference being BufferedReader uses what is called buffering that allows us to reduce the how often we read from the disk/STDIN by copying chunks to main memory where as  using InputStreamReader each invocation of read() could cause bytes to be read from disk/STDIN, converted into characters, and then returned, which can be very inefficient.


When playing piano and singing is it better to voice the chords out of the way of the vocal?

Question: When I study lead sheet on the piano. The left hand plays the chord and the right hand plays the melody in the next octave up. Should this be the case when singing and playing too? So if I have a lower bass-baritone voice should I voice the chords differently to allow the notes of the melody to have their own octave?
Comment: In my opinion, the accompaniment should not be playing parallel (regardless of whether in unison or an octave apart) to the melody.
Answer: This is something you have to experiment with and decide for yourself, on a case by case basis, and based on what sounds good to you, rather than based on some theoretical principles.
The principle of using different portions of the spectrum for different instruments tends to become more important as the number of instruments grows. In other words, if you are dealing with a lot of different instruments, like in the case of a big band or an orchestra, then placing them in different notes ranges is an important aspect of arrangement and orchestration.
Alternatively, if you have two or more identical instruments, e.g. two or three guitars, you also probably want to avoid playing in the same range.
But your case is the opposite extreme, it's only piano and voice, i.e. only two instruments, and with very different timbres too. Therefore I wouldn't worry too much about overlapping notes. I would choose whatever chord voicings sound the best, overlapping or not. I'd also record the whole thing, to listen objectively and evaluate what works well and what may need change.
Answer: "The left hand plays the chord and the right hand plays the melody in the next octave up."
That's one way to interpret a lead sheet.   Or you can play a strong bass line, cover chords and melody in the RH as best you can.   Or, if there's a singer, play bass and chords, let the singer take care of the melody.
Too little doubling of the melody can leave the singer floundering, too much can be restrictive.  If this is a jazz performance, perhaps play no melody at all, or improvise a counter-melody, or play all the melody for the singer to scat around or...
Look at the repertoire of accompanied song - Mozart, Schubert, Britten etc. etc.  for the many ways in which piano can support and complement a singer.


Trigger Process Builder when Contact added to Opportunity

Question: Is it possible to kickoff a Process Builder flow when a Contact is added as a Contact Role to an Opportunity? I don't see Opportunity Contact Role as an object that can be used to start the PB, so I'm wondering if there's another creative way to kick off the process?
Comment: Doubt it as triggers aren't support on Opportunity Contact Roles either.
Comment: @Girbot I wonder how many eager junior product managers come to SFDC to enable OCR as a trigger-able object only to discover that it will  be on the roadmap for 2050 ?  This limitation has been around for so long
Comment: One way to do it is to have a batch process evaluate new OCR records and do what you need to when you find a new one. Not ideal, or real time, but kinda what we are stuck with
Comment: @Eric how would you query just the new OCR records? Didn't see any sort of created date to base the SOQL on for batch process.
Answer: Like everyone in the comments said, creating Apex Triggers on the Opportunity Contact Role is not currently a functionality offered by Salesforce. There is currently an Idea on the community for this if you would like to go vote for it here. The other option is to run a query through Apex. Unfortunately this is not real time like Eric said.
We have been trying to get this for years and I have had to come up with numerous workarounds for different clients because of this lack of functionality. Best of luck!
Comment: You might want to just make it a wiki if you're simply summarizing comments.
Comment: Why is this an answer? It just restates what is in the comments
Comment: Wanted to summarize everything so a best answer could be selected so we can keep the community clean. Also, wanted to provide the link to the idea that OP could go and vote for so we can get this functionality changed.
Comment: I can remove it if you believe it is not necessary. You have the reputation seniority lol
Comment: Nah. Let community decide. I am just one person


Aluminum rivet used to join stainless steel and aluminum sheet

Question: I am using Aluminum pop rivets to join stainless steel and aluminum sheet together. I am aware of the galvanic corrosion risk in this situation. Are there any other risks the joint may face over time due to material mechanical properties differences ( Aluminum - soft and stainless steel - Hard )?
Comment: Galvanic corrosion requires an electrolyte, most commonly water.
Answer: It depends on the rivet's toughness and the thickness of the sheets.
Either the stainless steel will cut the rivet, or the rivet will cut a slot in the aluminium.
The use of rivet or any other fastner on  the sheet work is optimal only when the alasticity of the two sides being joined is equal at the joint. That's why the revets are lined up at equal spaces as much as possible.


Techniques to estimate constant states with particle filter?

Question: I have an application where some of my states are constant and therefore have no process noise.  Over the course of the estimation process, the uncertainty in these states drops several orders of magnitude, so it doesn't work to just use the initial scatter in these dimensions.  I've had some success with various ad-hoc techniques, but they all corrupt the uncertainty to some extent.  The underlying PDF is not Gaussian.  Can anyone suggest techniques to address this problem?
Comment: but theyre random at time 1? yeah this is a difficult problem. theres no real solution to the degeneracy/impoverishment issue here
Comment: yeah that's a better way to phrase it. and you're experiencing all of your particles have the same values for the portion of your state that's constant?
Comment: I can give some papers, but I don't think that there's any total fix that exists.
Comment: I'd state it as:  the uncertainty is very large prior to obtaining observations and then is relatively very small after all the observations are utilized.  No problem with a KF and Gaussian representations, but problematic with particles.  KF is not applicable due to extreme non-linearity of measurements (observations).
Comment: Yeah, without some sort of process noise, the resampling process will eventually collapse the constant dimensions to single values.  The simplest way around it is to add some artificial process noise, but this makes the uncertainty bigger than it should be.  If I make the (invalid) assumption that the PDF is Gaussian, I can add process noise and then collapse back to the mean in such a way that the mean/covariance is unaffected, but this can ruin the shape of the uncertainty.  I've played with other hacks along these basic lines.
Answer: I think "A self-organizing state space model" by Kitagawa was the first person to describe what you're doing. What I think you're doing is replacing your initial model's parameters (random but not dynamic) with dynamic ones. Really the new "parameters" are states of a different state space model. And this larger model's parameters you're thinking of as tuning parameters.
"Combined Parameter and State Estimation in Simulation-Based Filtering" by Liu and West suggests using more intelligent artificial dynamics for the parameters, improving the idea from above. These ways seem to work fine, but it's a totally different model, so it's really apples to oranges here. You're not really looking at $p(\theta|\text{states},\text{data})$ when you're looking at these nice looking samples.
"Following a moving target-monte carlo inference for dynamic bayesian models" by Gilks and Berzuini and "Markov chain monte carlo, sufficient statistics, and particle filters" by Fearnhead suggest the idea of using MCMC moves within a particle filter to "jitter" the sample elements that corresponded to parameters. This is like an extra final step in your particle filter. The goal is to simulate from your parameter posterior.
If you use Metropolis-Hastings with the idea from above to simulate from your parameter posterior, the likelihood that's proportional to this distribution is still hard to evaluate because it depends on your increasing dataset. The Fearnhead paper, "Particle filters in state space models with the presence of unknown static parameters" by Storvik, and "Particle learning and smoothing" by Carvalho et al. get around this algorithmic problem by using recursive formulas for sufficient statistics.
Comment: Thanks.  In my case I think the sufficient statistics assumption is not applicable.  In particular, I receive observations that are a function of both the dynamic and static states.  A joint estimate, where each particle has a full vector of all of these states, provides an estimation benefit that is lost if I look at the dynamic states in aggregate and regenerate the static states at each time step.  This isn't my exact application, but a similar one would be estimating the location of a robot and several base stations when given only range measurements between the various elements.
Comment: There are a few things I don't understand in your comment. Hopefully my first paragraph edit helps a bit more.
Comment: If I understand the last paper properly, the approach requires that the static state particle values are able to be drawn anew as a function of overall statistics of the non-static states.  Again, I may not have "got it" yet, but this would imply that relationships between static and dynamic states at the individual particle level are not retained.  Is that right?
Comment: @user2364295 that sounds right if by "static states" you mean "parameters." However, your last sentence is weird. When you say "relationships," I take that to mean all the conditional probability distributions of a specific state space model. Those never change. However,if by "relationships" you mean the exact pair values for each particle ($x^i$ and $\theta^i$), then yes, they change after the jitter. That's the whole point of the algorithm. This sounds like a separate question, though. If you post a separate question I'll probably see it and be able to answer your questions more fully.


can i replace a linear100k potentiometer with multi turn potentiometer 100k to get more resolution

Question: can i replace a linear 100k potentiometer with multi turn potentiometer 100k to get more resolution. The linear potentiometer 100k which i mentioned is used in pwm which i brought from ebay for controlling speed of a 12v 9a 500rpm dc motor but when i am using 100k linear pot i am not able to get proper resolution in speeds of dc motor eg:at 1,2,3,4....hz.so i wanted to replace linear pot with multi turn pot is it possible or not.Do i need to mention anything else
Comment: Yes, you probably can replace it that way. Whether that solves the remaining problems would be hard to say. But I don't see a reason why you can't try it out and see.
Comment: Add schematics. It really depends on other circuitry as well, not just potentiometer. It really depends on whole chain of translating analog signal to pwm. Yes, you can change the pot. But resolution depends on other things as well.
Answer: Allow me to be a dissenting voice. Maybe not. Multi-turn pots are not inherently higher resolution than single turn pots of the same element length (and type), many merely contain a mechanism that may make it easier to set the wiper to a given position. The mechanism may have effects such as backlash that are annoying.
Generally if you find yourself using only a small range of a pot, perhaps near one end, a better choice is to replace the unused part of the pot element with fixed resistors.
For example, if you had a 100K pot voltage divider with 5V applied and only used the first 1V of it you could add a series 80K resistor and shunt the element with 25K.
Some pots such as the 10-turn panel-mount Helipot wirewound style actually have a very long (helical) element and do give you greatly improved resolution, however it may still be worth considering limiting the range where appropriate.
Comment: +1 You are correct, 10-turns just make it easier to adjust the 1 turn and add other effects that are just as annoying. For a one-time trim pot they are better than the singles.
Answer: Yes, if they are both 100k and the new one is rated at, or above the old one (in power and current), you can safely make the part swap.
Whether this will yield the results you are hoping for is unknown. We would need the schematic to know for sure.
Comment: You say yes, but will the result be what the OP wants? Ie more resolution?
Comment: @SolarMike I doubt it, but I was answering to the fact that it is safe to make the swap. Your point is valid though, on a second reading of his question title. I'll update. Thanks.
Comment: I doubt it as well, at least he's prepared to find out though...
Comment: @SolarMike Agreed. And who knows? If it's a simple pwm generator, it might be exactly what he needs to do.
Comment: If he's that lucky - if it was me ... never seems to work the first time..


django tastypie support for mashery iodocs?

Question: Mashery iodocs is a tool for documenting API. It needs two configuration json objects to run. It would be nice to have this objects generated automatically by tastypie. Tastypie can generate json with schema, however it's incompatible with iodocs expectations. Any ideas of how to generate this configurtion automatically using tastypie?
Answer: Presently, I do not believe there is a way to generate that kind of documentation from TastyPie directly.  However, I have found this project useful in creating interactive API documentation.
https://github.com/Hipo/Django-API-Playground
Answer: One more project to generate documentation automatically - https://github.com/minism/django-tastypie-swagger
Though so far I haven't find anything convincing!


How will a studio camera with tilt and shift compare to stacking 35mm images?

Question: I use a  Nikon d850 with 200mm micro Nikon lens mainly for jewelry photography and stacking is my regular approach. The major problem I have with that is in the shades where definition, detail, etc. drop in quality. Has anybody tried a studio camera with a Nikon attached to it and tilt/shift the lens? What lens and what results should I expect?
Comment: What's your actual working method? What are you stacking with? I do a lot of focus stacking on a significantly less pro camera/lens with more than satisfactory results, so I doubt it's your 5 grand's-worth of gear that's lacking here.
Comment: I'm stacking with both rail and/or focus and a lot of jewelry is silver and gold crosset rings and bracelets/necklaces. In these if you go 10x print the details and shadows have a problem.
Comment: Are you using flash?  My macro improved considerably when I started using flash instead of continuous lighting. Keeping the camera still enough for macro is difficult, flash solves this.
Answer: A Nikon PB-4 bellows is a nice piece of kit for close up + macro photography. It will give you a very limited set of movements (shift + swing) and these are not geared but workable.
I haven't tried using a 35mm camera on a studio 4x5. I imagine that you want to use 35mm lenses as those made for the 4x5 camera will be low resolution for the 35mm format. However, 35mm lenses may not give you a large enough image circle to allow for the movements you want. All that being said, If you already have a studio camera and necessary adapters around you might as well give it a go.
The following general knowledge for macro/closeup may be helpful (which you may already be aware of): 1) If you're magnifying the item above 1:1 reversing the lens will generally give you better results. 2) Once you approach 1:1 diffraction becomes a much bigger issue. f8 at a magnification of 2:1 will give you diffraction effective to f24 or f stop * (magnification + 1).
I hope that something above helps, good luck!
Answer: Camera movements & focus stacking do different things: which to use depends on which of those things you want.
Camera movements allow you to take the focal plane of the lens and put it where you want to, within reason.  So in particular you can slant the focal plane with respect to the sensor plane.  This is useful, for instance, for landscapes where the focal plane you want might be essentially the surface of the land (you can't actually adjust the plane that far, but you can make things better).
What camera movements don't do is to alter the depth of field around the focal plane: if the depth of field is very thin, then camera movements will allow you to set the plane where things are in focus where you like but will not increase the thickness of the region either side of that plane where things are acceptably in focus.
Focus stacking will do that.  It allows you to take a bunch of images with different focal planes, each with a rather small depth of field, and then synthesise a single image from them which has a much larger depth of field.
So focus stacking increases depth of field, while camera movements allow you to put the focal plane where you like while leaving depth of field (around the focal plane) unaltered.
Which to use depends on what you want to achieve:

if  the thing you are trying to photograph has a natural plane which you want all to be in focus, that plane is not parallel to the sensor plane and you don't care about whether things out of that plane are in focus (or you actively want them out of focus) then movements can do that;
if the thing you are trying to photograph has multiple planes which you want in focus, and is static, then you want focus stacking.

I suspect that, for jewellery, focus stacking is the answer.
Comment: Thank u all for taking time to answer.


Linux distro for cloning Windows SSDs, to run from a pendrive

Question: I will have to back up a few SSDs to the cloud, and clone my Windows installation from one SSD to another. What's the easiest Linux distribution to do so? I could use dd on pretty much any distribution, but having access to graphical interface, and software like CloneZilla that offers progress bar, would improve my quality of life when doing it. Support for wireless networking would also help greatly, to push images to my NAS.
Answer: Clonezilla has a bootable "live" image (I've never tried it though)
GParted is another option with a live image. It's been great for partition clones for me. Web browsing isn't something I've done, but I've heard it has some sort of web browser.
I think the ubuntu live image comes with gparted and a browser, I think that might be the easiest way to do it. (You could install packages while it runs too) I might try this first.
If you're doing this multiple times it might be worth setting up some non-live distribution (ubuntu is popular) on an external hard drive with persistence. That would let you do things like save credentials and install software that will stay around after a reboot.


Why does light bend at an angle when it passes through a prism?

Question: i mean when the light go throw the prism it Deviates.  At an angle and dissolves at the same time.  Do prism atoms have anything to do with this? why it can't go directly in a straight line?
Comment: Are you familiar with [Snell's Law](https://en.wikipedia.org/wiki/Snell%27s_law)?
Comment: I guess that proper understanding of Huygens principle is the key for enlightenment here. Light ray propagates along a direct line owing to the phase of concurring rays being the same. If these side-rays are relatively retarded by glass-air interface, light refracts under angle. If they are absorbed, light passing through a narrow slit diffracts (it loses its means of keeping straight direction).
Answer: Light consists of quanta. These photons have two oszillating fields, an electric and a magnetic, both perpendicular to the direction of propagation. This is the key to the question, how light is redirected at the surface between two media as well as how the double slit experiment works.
The prisms surface contains surface electrons. These electrons interact with the field components of the photons. An evidence for this fact is the polarization of reflected photons on a mirror or another reflecting surface.
An incomming photon gets influenced by the interaction of the part of his fields near to the surface more as the photons opposite parts. The photon gets deflected towards the prism. Leaving the prism the inverse process takes place.
Last not least, infrared gets displaced in a different way as red, blue and so on. This has to do with the energy content of photons with different wavelength.
As you guess right, the displacement of light on a prisma has to do with the atomic structure of the prism.
Comment: Really nice answer. Here is an interesting one: https://physics.stackexchange.com/questions/578325/why-does-linear-motion-not-emit-gravitational-waves
Comment: Maybe you could note that it is elastic scattering (Rayleigh) because the atoms in the prism are much smaller then the wavelength of visible light, and this causes the photons to change angle (bend) more when the energy of the photons is higher (shorter wavelength).


What do you call a person who collects funds for a charity?

Question: For example, if someone walked up to my home asking for me to donate to X cause on the behalf of Y group of people, what are they called?
Answer: That's one definition of a solicitor Merriam has: 'an agent that solicits contributions (as to a charity)'
Answer: At least in American English, fundraiser would do it—one who raises funds.
https://www.merriam-webster.com/dictionary/fundraiser
Comment: Fundraiser is used in Britain; solicitor means something completely different (a kind of lawyer).
Comment: We are accustomed to fundraisers in Britain. The term solicitor, while formally correct, would not be understood here by the majority of contributors, who understand solicitor as a legal person. That said, a fundraiser solicits donations.
Comment: The main meaning in AmE is a *project* that raises fund. There would have to be contextual clues for it to be understood as being a person.
Comment: No, it's not the main meaning. It's one of two. In any case, the question clearly refers to a person.
Answer: There is also a more jocular term in use in the UK, namely 'charity mugger', sometimes shortened to 'chugger'. 'Charity mugger' would be understood by many (50%, at a guess), whereas 'chugger' is more restricted in use. 'Charity mugger' usually, but not always, goes hand in hand with the image of somebody wearing a hi-vis jacket with the name of their charity printed on the back and carrying a collection 'tin' (often made of plastic nowadays).
While the concept of mugging usually assumes that the mugged person (muggee!) is walking the streets rather than at home, you could certainly extend the use to e.g. "I just got doorstepped by a charity mugger". Along these lines, you could also say "charity doorstepper", which, though not widespread, would be well-understood and is rather accurate. This somewhat derogatory terminology is justified, I believe, given that many of these people specifically target the homes of well-off senior citizens, as I have learned from long observation in West London.


What is Considered to be a Large Portfolio to be Sent to Agents/Publishers?

Question: I am currently looking for an agent to represent a portfolio of books. But I was wondering, what is considered to be a large portfolio in that how many unpublished books ready for an agent is considered large or small? I have about five THOROUGHLY REVIEWED novels within the Christian fiction genre. They are not series, they are standalone. Is this considered a good number to send to agents? Is this too much? Am I pushing myself too hard?
Answer: The fact that you have five books completed is a plus point to literary agents and publishers, but it is not how you approach them. Offering to send an agent or publishing editor five books to read/consider would overwhelm them.
In their mind, you are initially the enemy in that you're going to have, alas, another dud that will waste their timer and energy. The reality of their daily affairs is they are overwhelmed with poorly written manuscripts and aspiring authors who haven't done their homework in how to approach them properly.
You are doing your homework, so I commend you for that!!
My suggestion is to select your best work to submit to literary agents.
You do not submit a portfolio, but rather a query letter and book proposal about a single book you want them to consider for representation. If it's a small to mid-size publisher, you can approach them directly with these items. The larger publishers will not communicate directly with first-time authors and require they have a literary agent as the liaison.
Ideally, you will approach an agent (or publisher) with your query letter. This is typically a one- or two-page professional letter inquiring whether they would be interested in your book. If they are, they will ask for the book proposal, which you need to have ready to send off immediately. Otherwise, you lose your opportunity by screaming, "I'm not a professional" or "I' slow at getting things done and would be a bad candidate for an agent."
There is an expected format for book proposals and query letters too involved for this post. But if you would like more help with this, contact my team at my company.
You're off to an amazing start with having five books already!
Answer: If you're an illustrator, you send a portfolio, because you are selling your talent, not any individual piece of work, and because you'll be using that talent to illustrate someone else's writing. But as a writer, you're selling an individual piece of writing, not your talent, so you should pick the best one, and sell that. Once you have a confirmed sale under your belt, you'll have the inside track on selling additional books.
A portfolio of writing is only for writers who have already proven successful, or who are doing writing-for-hire assignments such as ghostwriting or web content. There might be an exception to this rule if you were selling a series as a series, but no one ever buys or sells five unrelated stand-alone books as a group.
Also keep in mind that having multiple completed unsold projects is not generally considered a plus. Agents and publishers will be primarily interested in your past publications, and their reception. If the work you are submitting is very good, they will be glad to know you have follow-ups ready, but even writing quality is not a guarantee of sales, so they'll be more interested in a good sales track-record, if you have one.


How to take advantage of Mega-Blaziken's Speed Boost ability

Question: On my Omega Ruby game, I chose to get Torchic as my starter which eventually I evolved into Blaziken. Then, using my blazikenite I can mega-evolve Blaziken into Mega-Blaziken, giving him the ability Speed Boost. I know that there are moves such as Electro Ball that get stronger when the user has higher speed, but is there any moves that my Blaziken can use that would be able to take advantage of his speed stat gains?
Comment: I'm afraid not. Another similar attack to Electro Ball is Gyro Ball, but none of them can be learned by Blaziken.
Answer: Their aren't any relevant moves that Blaziken can use that specifically give bonuses based on Speed. The best move to "take advantage" of Speed Boost is actually Protect, giving Blaziken 'free' turns of Speed Boost buffs by being (almost) invulnerable to damage (the move 'Feint' hits through Protect).
Following on from that, generally the best way to take adantage of Speed Boosted Mega Blaziken is to outspeed & hit as hard as possible. With the combination of it's high attack stats, coupled with access to powerful moves like Flare Blitz, Overheat, Superpower, Knock Off and Stone Edge, Blaziken can be a real threat for your opponent to contend with.
For a more in-depth look at how Mega Blaziken works in a competitive sense (in both single and double battles), you should check out the guides on Smogon which can give you a broad idea of how to run it which you can then tailor to the needs of your team.


Why do the other kids remain friends with Cartman?

Question: Cartman generally behaves in a mean way and not solely towards Kyle. Neither of Kyle, Stan or Kenny is antisocial and thus in desperate need of friends. Why do they keep Cartman in their friend circle?
Answer: I wouldn't say that Cartman is anyone's friend, but the rest of the kids tolerate him being around. The best proof of that comes from their response, when Cartman wants to go to Somalia to join the pirates - Kyle is quite happy to even buy him a plane ticket and comments with enthusiastic "good!" when he finds that Cartman has indeed gone to Africa.
While Eric is annoying to have around as a "friend", he can be very dangerous as an enemy: he either outright killed or orchestrated the death of many people, and even tricked one kid to eat his deceased parents. It is definitely not someone that you'd like to be on the wrong side of!
Cartman can also be entertaining - either as the butt-end of the "fat jokes" or because he has enough leadership skills and imagination, to make other kids join in his schemas - be it turning ginger kids into fanatical hair-color supremacists or convince the team to "grind" levels in World of Warcraft to kill a trolling player.
All in all, he is always useful to have around, even just to make teams even
Answer: The most basic reason is simple - there wouldn't be a show if they didn't.  The format requires the usual team to investigate the weird thing of the week and have wacky adventures together. Often there is a reset button between episodes to restore the status quo.
Comment: The show can still be about cartman as the enemy of the group
Comment: Exactly - dramatic continuity


How do I get my GPS working on iPhone 3GS after upgrading to iOS 5?

Question: I've upgraded my iPhone 3GS to iOS 5 and hence changed my baseband to 5.16.05. Now it is not possible for me to unlock the phone. Is there any way I could get both GPS and phone working?. I've done jailbreak with redsnow. I don't need iOS 5 and is willing to downgrade without breaking anything. Is it possible to do it?
Comment: Why doesn't your GPS work?  I upgraded my iPhone 3GS and GPS works just fine.
Answer: No. You are out of luck.
Even if you had saved the SHSH blobs for iOS 4.X (which are what you'll require to rollback), you can't revert the baseband, which is required for the unlock. So even if you did manage to install iOS 4.X, you'd still be running baseband 5.16.05.
Comment: Is there any way to make the phone work again, without switching to ipad band?. Will there be any unlocker for this band, to be out soon?
Answer: By now it is possible to down-grade your baseband - at least for the iPhone 3G and 3GS (unfortunately not 4/S) - from the iPad's 06.15 to 05.13.04 (un-lockable) thanks to the great work of the iPhone Dev Team:

The iPhone Dev Team is happy to announce a baseband downgrade option in redsn0w for those who are using the iPad's 06.15 baseband on the iPhone3G or iPhone3GS.
Typically you'd have the 06.15 baseband if you unlock with ultrasn0w but updated your iPhone baseband past 05.13.04.  With this new capability, you can now downgrade specifically from 06.15 to 05.13.04 (even if you never had 05.13.04 on that device before).  This gives you the best of both worlds: ultrasn0w compatibility and a normal iPhone baseband with full GPS and the ability to use stock IPSWs again.

See this post on their blog.
Comment: Does this restore GPS by just doing the downgrade?
Comment: @bmike: Yes it should restore GPS and push-notifications - as it's a fully functional iPhone baseband (and unlockable)


In Romans 8:2 what is "the law of sin and death"?

Question: Interlinear:

http://biblehub.com/text/romans/8-2.htm
BSB Romans 8:2For in Christ Jesus the law [principle] of the Spirit [breath] of
life has set you free from the law of sin and death.
Comment: According to [my exegesis](https://hermeneutics.stackexchange.com/a/29475/13583), it is concupiscence of fallen man, or the life and mode that is "according to the flesh." Whereas a 'law' or mode or way of living that is according to the Spirit would be that which saves us therefrom.
Comment: There have been some very good answers here (and marked as answers). My own answer is contained in the the following answer I posted to another question:  https://hermeneutics.stackexchange.com/questions/18632/in-1-cor-1556-what-is-the-power-of-sin
Answer: The first mention of the "law of sin and death" in Rom. 8:2 is a summary of the  dynamic between LAW, SIN, and DEATH that Paul has been developing since Rom. 6. There is no reason to interpret LAW as a "principle" or anything other than Torah in light of the themes of the previous chapters.
Being free from "the law of sin and death" or its parallel passage  having "died to the law" (Rom. 7:4 ESV) is built on the theme that sin takes advantage of the law for its own ends. Notice the progression of verses along this line: "the law came in to increase the trespass," "our sinful passions, aroused by the law, were at work in our members to bear fruit for death," "sin, seizing an opportunity through the commandment, produced in me all kinds of covetousness," "The very commandment that promised life proved to be death to me," "For sin, seizing an opportunity through the commandment, deceived me and through it killed me," (Rom. 5:20; 7:5, 8, 10, 11; emphasis mine ESV).
But how could something as good and holy as the law (Rom.7:12) appear to be complicit in sin and death? The answer is in an assumption Paul makes clear in at least three verses: 1) "For while we were living in the flesh, our sinful passions, aroused by the law, were at work in our members to bear fruit for death" (Rom. 7:6 ESV emphasis mine)  2) "For we know that the law is spiritual, but I am of the flesh, sold under sin," (Rom. 7:14 ESV emphasis mine)  3)"For God has done what the law, weakened by the flesh, could not do," (Rom. 8:3 ESV emphasis mine). When the flesh, a flesh that is radically antagonistic to the law ("The fleshly(σαρκὸς) mind is hostile to God, for it does not submit to the law of God, nor is it able to do so" Rom. 8:7), is confronted with the law, then sin and death result and it may appear that the law is causing both. But this is not the case, and Paul emphatically denies that the law is culpable. "By no means," he says, is the law sin, and "by no means," did that which is good bring death (Rom. 7:7, 13 ESV). The blame must fully lie on SIN's doorstep; though the law plays a role in the dynamic between sin and death, it is innocent.
Paul anticipated that these unexpected connections between sin and law would raise eyebrows. As a result, Romans 7 stands as the strongest apologetic (Kümmel) of the law in the entire Pauline corpus.
So the "law of sin and death" is a description of God's law as it plays out in the life of one who is still in the flesh. Thankfully, as Rom. 8 expounds, being in the Spirit reorients the believer in relation to the law so that the law is now characterized as the "law of the Spirit of life" in order that "the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit (Rom 8:4 KJV).
Answer: In reality there is no place where Paul suggests that the "law" itself provides freedom for believers. To do so here would contradict his thesis in chapter 7: The inability of the law to produce righteousness. It is true that Torah can function in different ways. Here, in my opinion, which is also that of the majority of commentators, nomos--law--in v.2 is figurative/metaphorical. I believe it means the "controlling influence' of Sin and Death contrasted with the 'controlling influence' of the Spirit.  [Cf "principle" (Witherington III, Mounce, Shedd;  "controlling power" (Ekstrand), "authority producing regulated action" (Sanday & Headlam), "rule" (Morris).]
In Romans 6:1, Paul asks the church: "What shall we say, then (in response to the reign of Sin and Grace)? Should we continue in (a relationship with) the Sin (that reigns in Death) so that the Grace (of God that reigns through righteousness) may increase and abound? See Rom.5:20-21; cf. Rom.3:8. Or, literally, his question is: "Should we remain (or continue) in the sin that the grace may increase?" Shedd comments that the article denotes Sin as a state and condition, the Sin that came into the world by the one man. Grant R. Osborn notes that the singular sin in the Greek stresses that they remain under the power of Sin, which emphasizes more than multiplying the number of sins. That Sin is a power is clear from the context and the way it is described. Sin enters the world through Adam and exercises its influence over all humanity (Romans 5:12-19). Sin "reigns" in death (5:21). Those outside Christ are "slaves" to Sin (6:6), but believers have been liberated from the Sin that enslaved them and they are now enslaved to Righteousness (6:16-18, 20, 22). Sin no longer "rules" (v.14) over them. Therefore, believers must not permit Sin to "reign" over them any more (6:12), etc. Sin is being personified. So the law of Sin and Death is the controlling influence of Sin (as a tyrannical, enslaving master) and Death.
Answer: This is one of those topics where the answer was obvious - until someone or something causes you to take another look.  (As in incorrectly assuming that the 'law of sin' had to do with the 10 Commandments.)
The first find was that the "law of sin and death" is:
Gen. 2:17 - "...for in the day that thou eatest, thou shalt surely die."
Gen. 3:19 - "...till thou return to the ground; for out of it was thou taken: for dust thou [art] and unto dust shalt thou return." (Definition of 'death'?)
The best find, thus far, was a pdf by David Clemens:
The law of sin and death:
Ecclesiastes and Genesis 1-3
https://s3.amazonaws.com/tgc-documents/journal-issues/19.3_Clemens.pdf
Sin and death. Genesis clearly associates sin with death (Gn.
2:17; 3:3, 17-19; cf. Rom. 5:12-21). A similar connection emerges
in the course of E; it is stated most clearly in 9:3, where 'evil' and
'insanity' eventuate in death; similarly 7:17; 8:8; 8:11/13.

Genesis 1:27 ... Therefore, just as sin entered the world through one man, and death through sin, and in this way ... –Ecclesiastes 7:20 ... in his sight by observing the law; rather, through the law we become conscious of sin. ... –John 1:1-3,14.
((Many writers say that the 'one man' is Adam.  However, to me, plugging in Greek mythology, the 'Tree of the knowledge of Good and Evil' consists of Aphrodite/Venus and Ares/Mars - Mars being the 'evil impulse'; the 'one man/male entity' by whom sin entered, when ingested.))
Several Bible verses show 'sin' to be a living force.
One of the neat Hebrew expressions of animate sin is "yetzer hara".
Wikipedia
In Judaism, yetzer hara (Hebrew: יֵצֶר הַרַע, for the definite "the evil inclination"), or yetzer ra (Hebrew: יֵצֶר רַע, for the indefinite "an evil inclination/((impulse))") refers to the congenital inclination to do evil, by violating the will of God. The term is drawn from the phrase "the imagination of the heart of man [is] evil" (Hebrew: יֵצֶר לֵב הָאָדָם רַע, yetzer lev-ha-adam ra), which occurs twice in the Hebrew Bible, at Genesis 6:5 and 8:21.
Comment: The answer should be found in the context which is Romans.


How to get Facebook chat on Asus Transformer?

Question: So I just got my wife the Asus Transformer and for some reason there is no Facebook app available in the Market... She can use the web site, but chat is not available there as far as I can see. Any good solutions for this problem? :)
Comment: i'd check to make sure you have the latest version of the market; usually apps display according to version compatibility, so if you have an older market version, it may not think your device can run the app. Updating the market would help in this case.
Answer: The Facebook app (at least as of July) simply doesn't support the Transformer. It's pretty bad on a tablet anyway, and I don't even use it on my Xoom. However, some solutions you could try include:

Try to download Facebook from a different app store (Amazon, SlideMe, etc). You may also be able to use Market Enabler, though I'm not sure if it will bypass device restrictions. There is a question that discusses this already.
You could try the about:debug trick to switch your useragent to "Desktop". That is discussed here. This works on my Xoom and allows me to view the chat bar.
You can install Opera Mobile and then go into the Settings and select the "Desktop" user agent (Press the "O" button, then Settings->Advanced->User Agent). This also works on my Xoom. Other browsers also allow you to switch the User Agent string, so these may also work (Dolphin, for example).
You can use a third-party IM client like Trillian, which supports Facebook accounts. Facebook chat is, I believe, XMPP under the covers, so other chat clients will probably also work.

If you want a tablet-oriented Facebook app, I recommend Friend Me, though it does not currently support Facebook chat. Friendcaster also has a beta version for tablets that you can try out.
Comment: Excellent answer! I did get a hold of an older version of the Facebook app; works, but looks unholy... ;)
The browser can identify itself as Desktop/Tablet/Mobile already. By using desktop my wife gets the Chat window in Facebook... Just too bad that all other sites also get the desktop version and not their tablet version then...


Why does operating system need to know subnet mask?

Question: If I understand correctly, the operating system gets subnet mask together with IP and other stuff from the DHCP server. And this subnet mask seems to be important for router because it knows if packet goes from/to LAN or should be sent somewhere else or it's received from Internet. But why is the subnet mask needed for the operating system? What does the operating system do with the knowledge of the subnet mask?
Answer: Based on the combination of an IP and a subnet mask the OS can figure out if a destination IP that it's user space application wants to contact is in it's local network or needs to be sent via some router. If it needs to be sent via a router, it does a routing table lookup to determine which router to use.
Comment: Of course, normally the default gateway is the only route.
Comment: @Skyhawk that depends if he's talking about home networks or host centers. In host centers it's very common to have routing tables with multiple gateways.
Comment: Of course. I sincerely hope that this question was not asked by someone working in a datacenter.
Answer: There are 3 major components to the network configuration:

IP Address
Network Mask
Default Gateway

The Operating System needs to know the network mask in order to determine where the data needs to travel. Your IP address combined with the network mask tell the OS whether a target IP address exists on the local subnet, or if it exists outside of your subnet. Some computers have multiple network connections, whether physical (multi NIC) or logical (think VPN). Without a subnet mask for each network, the OS would not be able to determine which traffic should leave which interface.
If the target exists within your subnet:

Your OS determines the hardware address of the destination by referencing its ARP table. If there is no entry in the ARP table for that address, the system sends out a hardware broadcast that is flooded to all devices on the layer 2 network. The system who owns the IP address would then respond to the broadcast with its hardware address (MAC ADDR). The OS would then send the data along, with it never leaving the local network.

If the target does NOT exist within your subnet:

Your OS determines where to send the packet based on its routing table. Most often than not, the packet will be destined for the default gateway. This gateway is generally a router which will use its own routing tables to send the packet on its way to its final destination. The process of sending to the default gateway is the same as sending to another host on the subnet. If the gateways MAC address isn't in the ARP table, it will send a broadcast out to determine the gateways hardware address, and then forward the frame.

So as you can see, the subnet mask is very important as it is used to determine the location of the destination network, and route them accordingly.
Comment: To clarify: An ARP broadcast will be sent to the physical address FF:FF:FF:FF:FF:FF, not to the layer 3 broadcast address.
Comment: Thanks for catching that, I've revised the answer to reflect it.
Comment: Glad to help...
Answer: See Mauro's answer, but in addition the subnet mask allows the host to determine the IP broadcast address. I think this is less important in these days of DNS based name resolution, but in the old days before Active Directory NETBIOS name lookup could fail if the subnet mask was wrong because the broadcast address would be wrong.