Does anything exist in the intergalactic space?

Question: I am a part time physics enthusiast and I seldom wonder about the intergalactic space.  First, it is my perception that all(almost all) the objects in the universe are organized in the forms of galaxies; or in other words, the universe is a collection of billions and billions of galaxies which are spaced far apart.  Does anything actually exist in the empty space between galaxies?  If yes, how did it reach there?
Comment: according to wikipedia, it's almost empty there http://en.wikipedia.org/wiki/Intergalactic_medium#Intergalactic
Answer: As others have said, it's almost empty, but not quite, as there are gas particles and so on floating around.  As wikipedia states:

Generally free of dust and debris,
  intergalactic space is very close to a
  total vacuum. The space between galaxy
  clusters, called the voids, is
  probably nearly empty. Some theories
  put the average density of the
  Universe as the equivalent of one
  hydrogen atom per cubic meter.
  The density of the universe, however,
  is clearly not uniform; it ranges from
  relatively high density in galaxies
  (including very high density in
  structures within galaxies, such as
  planets, stars, and black holes) to
  conditions in vast voids that have
  much lower density than the universe's
  average.

And that's only if you consider empty to mean void of matter - there's also electromagnetic waves permeating most (all?) of space.  And when you get down to the subatomic level, quantum mechanics ensures that particles are constantly popping into and out of existence as well, even in 'empty' space.
As for how the matter got there, well aside from the normal ways (being shot out of exploding stars and so on), don't forget that before it all started expanding, all of the matter was in the same place anyway, so the particles in intergalactic space haven't necessarily travelled anywhere to get there.  They could have simply stayed where they were while particles around them got gravitationally drawn into nearby clumps of matter/galaxies.
Answer: I might add some further notes to the actual material things existing in intergalactic space. One might wonder but the notion that there is space is already stating that there is more than nothing.
It implies that there is at least vacuum which is a pretty interesting thing on its own.
Quantum Mechanical harmonic oscillator
Maybe you know that the harmonic oscillator has energy levels
$E_n = \hbar \omega \left( n + \frac{1}{2}\right)$
and an astonishing result is that the lowest energy state is $E_0 = \frac{1}{2}\hbar\omega > 0$.
Quantum electrodynamical oscillator
Coming back to the vacuum, the situation is somewhat comparable. Considering Heisenberg's Principle of Uncertainty in its energy-time form,
$\Delta{t}\cdot\Delta{E} \geq \hbar$
we can see already that a state of a quantum system with definite zero energy for all times cannot exist, even though the expectation value might vanish.
Going more into detail, we see that the operator of the vector potential fullfills the wave equation
$\Delta{A_l} - \frac{1}{c^2}\partial_{tt}A_l = 0$
and a Helmholtz equation if one puts $\partial_{tt}\rightarrow{-\omega^2}$. This equation is usually tackled by separation of variables and after some math we arrive at a Hamilton
$H = \frac{1}{2}\sum_{\lambda}\left({p^2_\lambda+\omega_\lambda^2\lambda{q^2_\lambda}}\right)$
where now $\lambda$ accounts for some mode index. And here comes the magic. This is a description equation for harmonic oscillators! But here we run into a conceptional difficulty. The vacuum energy
$E_{vac} = \frac{1}{2}\sum_\lambda{\hbar\omega_\lambda}$
is infinitely large since there are infinitely many modes of the vacuum. But this is not very physical, so most of the time for calculations you just "leave out" this part.
Implications of a vacuum energy
In the case of different separated domains where you are able to allow a different  different number of modes (e.g. via metal plates), this energy will be different for those domains resulting in a force which is the famous Casimir effect.
But vacuum energy has other implications. One hope it that it might some day explain the cosmological constant in terms of a unified field theory.
So, I hope, I could convince you that "empty" might be much more one would expect :)
Sincerely
Robert
Comment: +1 you could also mention the connection of $\Lambda$ to dark energy
Comment: @Robert --nice post +1. Sidney Coleman was a great guy with a wicked sense of humor. One of his famous papers is titled "Why is There Nothing Rather Than Something". Lubos posted a great lecture of his on his blog --"Quantum Mechanics in Your Face".
Comment: Why was this accepted as the correct answer?! It answers a completely different question, that of quantum mechanical void. The question was about intergalactic void - again, completely different cases.
Answer: At higher redshifts, we actually see huge clouds of neutral Hydrogen (atomic, not molecular) in the form of absorption lines from distant quasars, called the "Lyman alpha forest"
These clouds may eventually form galaxies and stars, but they are currently just gas, an not particularly low density either.
Comment: probably the only answer that is trying to go over what observations might have to say that is relevant to the question at hand, instead of just cropping sentences together from read-elsewhere speculatia; for you +1
Answer: There certainly is gas within galaxy clusters. It tends to have very high temperature, circa a hundred million K, and is detectable by diffuse x-ray emission. Of course we have the elusive dark matter, which is probably more diffusely spread out than luminous matter. So maybe your question should be modified to, "is the space between galaxy clusters a vacuum?". I suspect the answer to that is also no, although the density is clearly very low.
Answer: A simple picture is the following: stars are organized in galaxies of various types (like elliptical, spiral, ...). These galaxies are organized in groups which are local aggregates of galaxies (our galaxies is in the so-called "local group" of around 40-50 galaxies). The largest structure is a cluster of galaxies: the groups are bound by gravitational interaction in a cluster.
This classification is not really precise but still. A logical conclusion is that the "empty" space in between these cluster is quasi-completely empty, the density of particles being much much lower than in a galaxy (in average) and is uniform: if it was not uniform, the particles would start to gravitationally interact and start to form other structures.
I think that's a valid reasoning for, say, hydrogen gas (atoms). The conclusion as pointed by @Mark Eichenlaub is then that it can be considered empty and that it is often called "the void".
But of course the space cannot be considered empty: the photons (light) traveling from one place to another are as real as other particles.
The next step in the discussion would involve things like dark energy, but that's a different story.
Comment: dark energy is now discussed mentioned in [robert's answer](http://physics.stackexchange.com/questions/560/does-anything-exist-in-the-intergalactic-space/1887#1887)
Answer: In 1997 the Hubble discovered a large numbers of intergalactic stars. Others have since been discovered. It is now believed that about 1/2 of the stars in the universe may well be rogue stars that are located in intergalactic space. The AVERAGE density of intergalactic space is still very small, however, because of its immense size.
Answer: Some of the comments and answers suggesting that the space between galaxies is near-empty appear to be somewhat misleading (although, note that some of the answers - like the answers by @Grant Crofton or @Cedric H. - seem to address the space between galaxy clusters rather than between galaxies). Other answers elude to the info below, but here is some clarification about the intergalactic, intracluster space, which from a large-scale viewpoint is very far from empty.
Even without considering dark matter, the majority of matter in galaxy clusters it not in the galaxies, but rather between them in the intracluster medium (ICM), which is a plasma consisting mostly of hydrogen and helium ions (observable in the X-ray portion of the electromagnetic spectrum). In galaxy clusters, around 85% of the mass is in the ICM rather than galaxies / stars. (Then, dark matter makes up even more of the cluster's mass.)
Of course, since galaxy clusters have diameters spanning multiple megaparsecs, the density of the intracluster medium is very low compared to a planet or star. However, the main idea here is that most of the (even baryonic) matter in the universe is actually in the "empty space" between galaxies - so it doesn't make much sense to view that space as "empty" at all.
Answer: http://www.dailygalaxy.com/my_weblog/2017/10/everybody-knew-it-had-to-be-there-missing-half-of-normal-matter-in-the-universe-has-been-detected.html
The matter, baryonic not dark, has mostly been found.
Comment: Your answer would be much more appreciated if you could expand it to be self contained rather than just provide a link for people to read.
Comment: I added a more self-contained answer that addresses the intracluster medium eluded to by this answer.
Answer: Try this link for a semipopular view of the overall picture.
http://www.nasa.gov/multimedia/videogallery/index.html
Answer: Let us look at numbers.  Exponential numbers.  The "luminous" matter in the universe (what is visible) comprises a volume that can be calculated.  I've come up with a (very) rough total (choosing the cubic kilometer) of 4x10 to the 40th power.  Now calculate the volume of the observed universe - again roughly, 10 to the 70th power.  In this scenario the volume of interstellar and intergalactic space is 10 to the 30th power greater than the volume of observed luminous objects.  That is one million-million-million-million-million times larger.  If the density of that "empty" space is actually 10 to the -29th power of the luminous objects, that would still leave 10 times more matter in the void than in the galaxies, and would account for what is referred to as "dark matter" and its overall gravitational effect.  It is dark because it does not emit light, but IT IS STILL THERE!  It no doubt ranges from subatomic particles to enormous chunks of non-luminous matter.  How can a scientist assume that because we cannot "see" something we can assume it is not there?  It seems obvious to me that Dark Matter is simply the residue left after the formation of galaxies, and that it is far too sparsely scattered to emit light, and even sparse enough to allow the passage of light over vast distances with little aberrational effect. I can't believe I said all that at once.  Sheesh
Comment: Welcome to Physics SE! Please refrain from pitching personal theories in your posts: this site was never meant as a substitute for peer-review (see [the policy on non-mainstream physics](https://physics.meta.stackexchange.com/a/4539/132157)). On the particular topic at hand, there are apparently good reasons why dark matter cannot simply be ordinary matter that happens to be dark: see [this answer](https://physics.stackexchange.com/a/2955/132157). So maybe "scientists" are not that stupid after all, who would have thought?...


How to fix a bent earphone jack

Question: How can I fix this kind of bent earphone jack? It still works if I constantly push it in, but it won't work if I don't push it, because it doesn't really fit inside anymore...
Comment: Its a problem because of covid 19....
Comment: So how can i do it myself? I have tools
Answer: The best hack is a proper replacement. An electronics repair shop can do it for you in just a few minutes.
If you insist using the broken connector, you risk damaging the electronics in which you plug it, by creating some short-circuit.
Comment: You also risk the loose part of the jack breaking off completely and getting stuck in the port.
Comment: That's not how this works: https://electronics.stackexchange.com/a/65079/227085
Comment: @SurpriseDog: if the equipment is designed properly (you know, the part with "dc blocking capacitors and series resistors"), then there is no much risk. But there are devices, and branded, which skip every component which is not strictly mandatory for the basic function. I would not risk destroying any equipment just to save a few cents / dollars - the cost of replacing the connector. Not to mention, as @ Hobbes said, that part of the connector can remain stuck in the device after it breaks completely.
Answer: You get a pair of pliers and slowly and carefully bend it back straight. You then put the pliers down, grasp the plug in two hands and try to pull it apart with your fingers (try to break it using the same forces it will be subject to in-service). Pull at least twice as hard as you'd pull to get the plug out of the socket
At this point one of two things will be the case:
The internals of the plug are secure and aligned enough that they work. You aren't able to pull them apart; it'll be fine until you can get around to replacing it.
The internals of the plug are weakened or break off while you're bending it back or pull testing it  - it was a goner anyway and now you can definitely know you need to replace it (and you don't have to pick it out of the socket of the phone :) )
ps; quick note on terminology here: strictly speaking the jack is the socket into which the plug goes but people do variably use jack to mean either side of this (jack being a contraction of jack plug), so I've deliberately used plug and socket for clarity
Comment: Note that it has to be fairly accurately straight. A slight bend can already lead to intermittent or no contact, depending on the socket (leading to the 'it only works when I hold it exactly like this' problem). Also make sure the pliers don't put dents in the plug material, that will also lead to contact problems.

How to fix a bent earphone jack


Wanting More Guidance on Today's "What is a word for not seeing obvious warning signs?" Discussion

Question: There was a strange discussion today which I would like explained. I'm not emotional and I hope I don't appear emotional; I'm just mystified. I posted an answer. It appears it was first. Hank proposed edits which I could not understand, which removed most of the cited uses of the word oblivious, although I was told the edits would not do this. Another user (Hot Licks) claimed that I posted after him and copied his citations, although in fact I posted first and cited my source, Merriam-Webster, one of the most widely cited authorities on the English language. I don't even agree that the proposed edits were an improvement (although Hank has a reputation of 1976 and I have a reputation of 128). Who can explain what it going on?
Comment: I've just looked at the page. Your answer has many more upvotes, count yourself lucky. The edit was a good one because it included a link and your answer became visually more appealing (tricks of the trade). But you are under no obligation to agree, and you can rollback the edit, or edit your answer again and do what you want, it's *your* post.
Comment: Hank needs his editing authority removed.  He has edited (and then re-edited) posts many times that (in the end) change what the original poster has asked.  He adds tags that don't make sense and does small styling edits.  Perhaps he is trying to pad his numbers through so many edits,.
Comment: P.S. I also don't understand why Hank thinks that Hot Licks' answer "was delivered in a much better way" [than mine, apparently], and why Hank thinks that his discarded answer is distinguished from mine by "definitions, proper formatting, and examples." What is so great about Hot Licks' unsupported feelings about poetic resonance and conscious ignorance and whatnot, and what's wrong in my remarks?
Comment: Why? Does your down-vote reflect that my original post was worse than you thought?
Comment: Originally, I thought the post was mainly concerned with who came "first" and accusations of plagiarism, if you can call citing a dictionary that. But instead, from your comment beneath Hank's answer it seems you were mostly confused by the suggested edit, and you're still unconvinced that the edit was an improvement. Well, it was. A downvote on meta just means a disagreement, nothing more nor less.
Comment: 1976 is not very much reputation, btw.
Answer: It appears that Hank added a link to the relevant page of Merriam-Webster Online; if so, that was a significant improvement to your answer because it enables people reading your answer to jump directly to the source of the material you quote. Hank referred to it as improving the formatting, which is a reasonable way to express it. The important thing was adding the link (which as far as I can tell from looking at the edit history wasn't there before).
Hank also removed some examples from the MW entry for oblivious, which you had included in your block quote. I'm not sure why he did, but I imagine he was trying to make your answer more succinct. I would not have done that—partly because I'm long-winded myself, and partly because I think judgments about how much material to include from a quoted definition are properly the poster's to make. But of course you can still make that choice, simply by reinstating the examples that you had originally included.
When an edit makes useful improvements but exceeds what you approve of, you can put it right either by rolling it back to your original version and then reintroducing the useful points from the edit or by accepting the edit and then reediting the post to reintroduce the lost portions of your original wording that you feel were useful and worth preserving.
As for the dispute over who's on first, what's on second, and I don't know's on third, I share medica's disappointment that such a controversy blew up on one of your first efforts to contribute to the site. The problem, I believe, is largely with the popularity of single-word requests in situations like this one.
From the commentary here and the answers and comments on the page in question, it appears that four different participants suggested or were in the process of suggesting oblivious within a few minutes of each other. This happened because (not to be dismissive of anyone's efforts) it is a pretty obvious (and suitable) answer to the poster's question. The reality is that the answer doesn't belong to anyone. Four people saw the question at an opportune time to respond with oblivious as a suggested answer—one (Mark Hubbard) in a comment; two (you and Hot Licks) in formal answers, and one (Hank) in a formal answer that he declined to post because you two got there first.
To the extent that English Language & Usage is a trivia game where whoever presses the button first gets to claim a particular answer, there are liable to be occasional bad feelings when someone answers just ahead of someone else—particularly since answers are never of exactly equal quality. But if everyone takes a step back and doesn't worry about the rep points that are rightfully theirs, I think they will see that there is little reason to get excited about the fact that a fairly obvious answer occurred to multiple people at virtually the same time.
I hope that your future experiences at EL&U are more pleasant, Chaim. Welcome!
Comment: In addition, there's no rule prohibiting users from suggesting the same answer, but if there is a significant time difference (in the region of 30 minutes), and the most recent answer does not add anything "new" to the older one, then it should be deleted. In this case, the amount of detail is significantly different in both posts.
Comment: A far better answer than mine.
Answer: It's easy to find out who posted when. You answered at 20:48:54Z; Hot Licks at 20:59:12Z. You answered first, by 10 minutes and a few seconds.** However, you had no links, no MW definition until your first edit at 21:07, 8 minutes after @Hot Licks. So the accusation.
However, this is a busy site and two people are often in the process of writing an answer simultaneously. These two answers were posted closely enough that assuming the worst on the other party's part is possibly unwise. If you see a pattern of such behavior, you can comment, or flag a moderator who might look at the user's pattern of answering.
I often use Merriam Webster and so do many others; it's a popular dictionary and this was probably a coincidence.
The edit actually was an improvement to your answer (in my opinion); it linked your definition and formatted it well, in a manner that is quite common on the site. The removal of several instances of the use of the word oblivious did not detract from your answer; the definition and a good example or two is usually enough.
However, if you feel anything untoward was done to your answer, you can always roll back to the original; that is always your right as the OP. But I would not take this edit personally at all. I'm certain it was kindly meant.
Welcome to the site. This kind of activity is not par for the course as far as I'm aware, though I haven't been following much for a few months. I'm sorry for your bad experience, and hope it doesn't get repeated. The last bit isn't really common behavior.
**Unless there's something about timestamps that I don't know; in that case, I'm out of line here and owe someone an apology big time.
Edited to add: I owe an apology to @Hot Licks, big time. I'm sorry for impugning your character. I was utterly wrong, and I stand corrected. @sumelic is correct.
Comment: Come back medica, all is forgiven :). No, seriously, the ***main*** site needs your contribution.
Answer: I want to start by saying I hope none of my comments or actions offended you but I will gladly explain them all, along with all of my edits.
The reason I said Hot Lick's answer "was delivered in a much better way" is because he posted a link to the definition that he included, formatted his answer in a way that is more pleasing to the eyes, allowing for easier reading, and he added an explanation of his opinion on that word.
Your first draft, on the other hand, only included a mention of the word, used in a sentence to explain its usage very minimally, a quote of someone using the word, and two other word suggestions. It didn't provide enough structure and support for people who may be wanting to know more about the word. Some "definitions, proper formatting, and examples", once included in your post, improved the appearance and readability of the post.
As for the edit I suggested after your additional information, the information I deleted was over the top. You clearly copied and pasted the whole word entry and it had 5 different examples of usage; that many are not necessary. I also formatted it slightly, as to provide a better look to viewers.
My sole intention was to make edits to improve your answer and give you the best chance of receiving up-votes, not to cause any distress. Although this may be an opinion and not a rule of thumb, I personally prefer assisting someone who beat me to an answer over posting my own in a better way, even if it would have information the initial answer lacks. That is why I decided to discard my answer, instead of trying to outshine yours.
As everyone else suggested, regardless of my intentions or opinions, the final decision is always YOURS. Even if others agree there is nothing wrong with my edits or suggestions, YOU still have the final say. IF you want to revert back to having 5 example usages, then go for it. If you think my edits diminished the intended effect of your answer, then change it. We don't want you to get the impression that you are being bottle-necked, especially when nothing you posted was officially "wrong".
Comment: @Chaim   But... you have difficulty `picturing the improvement`? The edited version is the one on display on the main page, compare that to the [original](http://english.stackexchange.com/revisions/371202/1), or to your second [2nd edit](http://english.stackexchange.com/revisions/371202/2), and tell us that there was no improvement.  The edit was a *very significant* improvement.
Comment: The answer *oblivious* is emphasised, place in bold, and linked, that alone makes it visible. In the game of SWRs, clever formatting is an essential element when a question hits the Hot Question Network. Best study how to format your answers from now on :) The stylings and explanations (click on the tiny question mark icon) are all on the toolbox. Here's the page with instructions: http://english.stackexchange.com/editing-help
Comment: Nothing offended me. But I'm just having trouble picturing the improvement. I received an image green on the left and red on the right, with stuff crossed out and symbols that look like the old Word Star formatting codes. It took me some time to understand where you added the link; I thought you meant that I I would see the URL, but in fact you had made a link of the word "oblivious." Anyhow, it seems that numeric scores are supposed to show us what we're doing right (or wrong), but I rarely see it. After your edits my little thoughts were somehow a home run, so I'm glad you edited. But...
Comment: Well your words "compare that to the original, or to your second 2nd edit" contain links to images of the earlier post; I actually still don't know how I could have viewed those images if you had not linked me to them. Maybe I should stop commenting if my comments lead you to lower my score still further, but I meant to say that I don't know how the omission of almost all the citations made the post better. But more on that question under separate cover.
Comment: Hello @Chaim, if you want to notify a user, place @ followed by their username. So, a downvote on meta does not effect your reputation points, just check your profile page. Secondly, the images of the edits are there if you click on the edit history button: You should see this: http://english.stackexchange.com/posts/371202/revisions, click where it says *link* and you'll see the post untouched as it appeared on the site. Hope this helps.
Comment: @Chaim: Are you still struggling to view previous versions of a post?  You know how to get into the Revision History, right? (That's the presentation with the red and green in two columns, that you access through the "edited *date time*" legend.) In that page, click on the word "link" in the heading for a revision, [like this](https://i.stack.imgur.com/f0pJh.png).
Answer: Here is what I see in the edit history.

20:48 - First draft of Chaim's answer posted, with no MW link or quotation.
20:59: First draft of Hot Licks' answer posted, with a link and quotation from MW.
21:07: Second draft of Chaim's answer posted, with updated content including MW quotation.

As far as I can tell, none of the other edits that were made were relevant (edit: Sven Yargs pointed out that Hank added a MW link to Chaim's answer, which was useful).
Chaim, if I'm reading these correctly, your answer was first, but Hot Licks' answer was the first to link to and quote Merriam-Webster.
The site "be nice" policy requires users to assume good intentions.
So it would not be right to accuse Chaim of improper behaviour. However, this assumption of good intentions must also be applied to Hot Licks' comment. It seems to be factually true that Hot Licks provided the MW definition first, and while saying that Chaim copied this might be interpreted as an accusation, I don't think it needs to be. Personally, I've never considered it wrong to edit one's answer to incorporate useful information from other answers. Hot Licks may have assumed that is what Chaim did, and this assumption may have been mistaken. So I think it's quite possible that nobody did anything wrong, and it's just a misunderstanding. That is what I will assume.
Hank's edits changed an introductory sentence before the quotation, and removed some examples. The edit summary may have been misleading: "Formatting for better reading". Chaim, you should keep in mind that you can look at the actual edit as well, in addition to the summary. Hopefully that will help you avoid approving edits that you don't agree with in the future. As medica said, I don't think Hank did anything malicious, and in my opinion removing some of the examples did in fact improve the answer.
Comment: I appreciate and agree with everything said in all responses. I never resented what happened, and I am sorry if I lowered the tone. It just seemed a bit like a group of friends sitting around praising each other. Perhaps with a bit more reflection and time on the site I will see the criteria that recommend one correct response over another. My feeling is that few people, once offered the synonyms in all responses, would be so oblivious, clueless and dense as to require guidance to Webster's Dictionary. But perhaps the oblivious, clueless and dense one is me. Or I.


Mechanism of gear rotation

Question: Is the smaller gear (pinion) always mounted to the input shaft when meshed with a bigger gear that is mounted on the output shaft? Are there places where the bigger gear drives the smaller gear?
Comment: Who says it's never the other way around? I've seen lots of examples, such as the common "salad spinner".
Comment: @DaveTweed - yes, that is what he is asking.
Answer: There are many examples of low input speed to high output speed gearing:

kitchen "salad spinner"
old-fashioned hand-cranked siren
electrical generator attached to a tractor PTO (power takeoff) — also wind-powered generators
the "overdrive" gear in any vehicle transmission
the speed regulator on a steam engine, or in many kinds of clockwork mechanisms

Indeed, any sort of spring- or weight-driven clock works this way. The spring or weight is used to apply torque to the slowest-moving gear in the mechanism, and the escapement (e.g., balance wheel or pendulum) at the other end of the system of gears regulates the speed.
In some cases, it's more efficient to use a belt drive for this kind of speed change. For example, an old-fashioned "spinning wheel" for making thread.
Answer: Two meshed gears are used to transfer rotational drive between two shafts.
The relative speeds of rotation are inversely proportional to the number of teeth on each gear.  That is -
$$\text{Input}_{\text{RPM}} / \text{Output}_{\text{Rpm}} = \text{Output gear}_{\text{teeth}} / \text{Input gear}_{\text{teeth}}$$
So, if it is desired that the output shaft rotate more slowly than the input shaft then the output gear is larger. But, if it is desired that the output shaft rotate faster than the input shaft then the output gear is smaller.
The reason for the relationship above becomes obvious "by inspection".
With the arrangement shown below, for every complete (360 degree) rotation of the small gear the large gear rotates only part of a turn. The large gear has a lower RPM rate than the small gear.
IF the small gear was the DRIVING or INPUT gear then the large DRIVEN or OUTPUT gear would be turning more slowly.
But
IF the large gear was the DRIVING or INPUT gear then the small DRIVEN or OUTPUT gear would be turning more rapidly
Which arrangement is used depends on whether an increase or decrease in RPMs is required.
Torque or "twisting force" is inversely proportional to speed.
That is the slower turning shaft will have proportionately more torque.

Diagram from Wikipedia - Gear ratio

Look at the examples below and you will see how the gear size relates to relative shaft speed:
Several animated examples
3 meshed gears animated example
Animated 2 to 1 speed example

1:1 and 1:2 example from Essentially unrelated stack exchange biology question
Answer: Any mechanical clock or watch relies on the motive power applied to the large gear (the "wheel") which drives the smaller one (the "pinion").  Thus the weight in a longcase clock is suspended by a cord, rope or chain from the "great wheel" (usually making a rotation every 12 hours) and the rate of rotation is geared up to the escape wheel (which often has the seconds hand mounted on it).
Note that the tooth form is usually different when gearing up : friction is critically important in a clock, transmitting high forces is usually less so (and is usually catered for by making the great wheel thicker than the others). So the teeth are usually cycloidal in form, where the deep part of the slot in a tooth is approximately rectangular, which means the base of a pinion tooth is undercut. This is a fundamentally weaker tooth form, especially since pinions may have as few as 6 teeth, but runs freely with little friction and zero pressure angle (see below).
For example

(from this page)
An extreme case is the lantern pinion

(from this page) where the pinion tooth is completely undercut!
You never lubricate the teeth of a clock or watch wheel : that only adds viscosity (i.e. friction), wasting power, and does nothing to eliminate wear. This is because the contact surfaces of the teeth roll over each other, there is no sliding motion involved. (The pivots, unless running in ballraces, do need lubrication. John Harrison employed ballraces for a prototype marine chronometer).
In contrast, while gearing speed down also involves contact surfaces rolling over each other, the purpose is usually to amplify force, and to do that with the least material, a stronger tooth form is required. This is normally an involute tooth form, where each tooth is wider at the base, like a wedge.

This means the teeth press each other outwards as well as turning each other, at an angle known as the pressure angle (usually 20 degrees in modern gears, formerly 14.5 degrees). Thus the axles are pushed apart, increasing friction on the pivots and requiring a stronger gearbox. (The animation on the Wikipedia page exaggerates the pressure angle). Traditionally, involute pinions are only cut down to 12 teeth, with the 20 degree PA making for more friction but stronger teeth  with wider roots.
So : yes, gearing can be used to increase rotational speed, but it usually requires a different tooth form, otherwise it loses a lot of power to friction.

Mechanism of gear rotation


Unity gone after installing Nvidia Prime

Question: I wanted to replace Bumblebee with Nvidia Prime for more performance. I used these commands:
<code>sudo apt-get purge libvdpau-va-gl1 bumblebee* nvidia*
sudo apt-get install nvidia-331 nvidia-settings nvidia-prime
</code>
Then i rebooted. At first everything looked fine. Nvidia drivers was enabled with perfect graphic performance. Then I tried to use power saving mode(Intel card) from Nvidia Settings. It said i have to log out and log in. I did as it said and then, Unity was gone. No launcher, no top bar, no folders and shourtcuts nothing but my wallpaper and cursor. Right clicking or Ctrl + Alt + T didn't work either. I could get unity back when I reinstalled drivers and Prime with commands I gave above. I tried to reinstall Bumblebee, get back to Nouveau drivers, using different versions of drivers but none of them helped. I don't want to reinstall my system just because of this so can anyone help me about this? How can i use Prime properly or at least get back to Bumblebee?
Answer: After latest updates, it seems to be working now. I hope it stays like that. Cheers!


Does the type of music you listen to factor into determining which speakers to buy?

Question: When I browsing Amazon for speakers I see in the description specifications like maximum input power, Frequency response curve, Audio Sensitivity etc. Does the type of music you listen to factor into determining which ones to buy? Like personally I listen to soothing and pleasant music instead of high beats. Will this mean I should look for some specific parameters/specifications in the speakers for the best experience?
Comment: To the close voter: I would consider questions about music equipment on-topic because having the right system is all about music appreciation :-)
Comment: See my [meta question about equipment](http://meta.musicfans.stackexchange.com/questions/26/is-the-act-of-listening-to-music-on-topic).
Answer: Definitely.
Ideally, you always want a system (speakers, amps, room, etc) that can accurately reproduce the complete frequency spectrum of human hearing (around 20Hz to 20kHz), but this is not always possible, so building a system that favors your musical taste is a good idea. Knowing where to make sacrifices and where to re-enforce can make a big difference.
For example, if you are mostly into simple guitar-voice Nueva Trova (a genre that features guitar and voice prominently, often exclusively), you might want to pass on a subwoofer and focus in the other ranges. Lowest guitar note is normally around 80Hz, the human voice is normally above 100Hz, and subwoofers normally reproduce frequencies bellow 80Hz, so a subwoofer here isn't doing a lot of work, it wouldn't make a huge difference.
In contrast, if you are mostly into electronic music genres, which normally have a lot going on bellow 80Hz, a subwoofer will make a huge difference (as in night and day difference).
Every part of an audio system (not only the speakers, but the amps, the room, your complete listening environment) has a characteristic sound. Some have more bass than others, some have more treble than others, some distort less than others, etc. Try to aim for a system that suits your musical preferences.
We are talking about frequencies here just to make a point, but the best way to decide which speakers to buy is to listen to them. Grab your favorite songs and test them through different speakers (any decent store will let you do this). They will not sound exactly the same in your living room, but it will get you a good idea of their character.
Comment: The relative position of the two stereo speakers and you is also very important (as well as the shape of the room), because sound emitted from two coherent sources (two speaker playing the same) will interfere constructively or destructively, depending on where you are sitting. This results in places where you can hear some frequencies louder and some where you here those more quiet. So you have to place your boxes right to avoid sitting in a destructive interference spot. All frequencies are the loudest, if the distance from you to both speakers is equal. (Sorry for the physics ;D)
Comment: Subwoofers are useful in a lot of rock genres too, a lot of which is due to the use of drop tunings, 7 string guitars and 5 string basses etc. Try listening to Puddle of Mudd, Korn or Pitchshifter with a decent sub and you suddenly realise just how much low end audio you have been missing out on.
Answer: Every speaker or amplifier has a specific sound and therefore strengths and weaknesses regarding specific tracks or even genres. E.g. there could be speakers that play e-guitars very well or some that are good at the kick-bass of some sorts of electronic music. Especially in the lower price range it is difficult to get an "allrounder" that is decent at everything. You might even be able to break down your preferred music to some technical details. A reference curve of a speaker would be a good factor for that. This of course requires you to know which frequencies matter in your music.
So what should you look for if you want the best experience? Forget about the first paragraph of my answer! The most important factor is taste and feeling. A speaker might play your music very well in theory but still sound horrible to you. You can buy some 50,000$ sound system that is very highly rated and still end up not really liking it's sound. So stop browsing Amazon, pack some of your music, go to a store and listen :-)


Client that can run behind a firewall

Question: Is there any client that can run behind a firewall?  I tried bitcoin-qt and Electrum and neither could work because of blocked ports.  I know I could use a web-hosted solution but I'd prefer a local wallet.dat.
Answer: Electrum is perfectly happy running through either standard HTTP ports (443 and 80) or through a SOCKS proxy like Tor. Both options are viewable under the server settings in the main panel, and both will help you break through a restrictive firewall.
Answer: You'll need to open up something to let the traffic your client needs through.
For instance MultiBit needs port 80 and 8333 open to do some HTTP gets and to make the bitcoind connections, respectively.
The other clients will have similar port needs.
Alternatively you could set up a SOCKS 4/5 proxy together with an SSH port forwarding tunnel so that your local client could make connections out. Then you would have a specific connection from your machine to the SSH server but nothing else would be open. I use this setup on my Mac to encrypt my traffic and MultiBit works fine.
Answer: No.
In principle, electrum supports this. In practice however, only electrum.no-ip.org seems to accept HTTP or HTTPS on the standard ports and it can rarely be reached. Judging from the host name it is a machine connected to the internet through a residential internet connection with a dynamic IP; not exactly a heavy-duty server.
Comment: Instead of only downvoting, could somebody correct me? I'm actually trying to connect electrum via HTTP right now and it is not working. If I'm wrong and there is a way to get this working, then I'd like to know how.

Client that can run behind a firewall


Why do I have low hot water pressure in my kitchen?

Question: I have very low hot water pressure in the kitchen only.  I have disconnected the line and have great pressure from the valve.  It is a two handled faucet and the cold water pressure is very good.  There are no kinks in the line from the valve to the faucet.  No doubt there is some build up but where to look.  The aerator is clean also.
Answer: It sounds like the valve in your hot water handle has some blockage.
There are hundreds of different different designs, so it's hard to diagnose without brand/model. However, many faucets are made with valve cartridges (see link below) whose narrow channels can easily pick up bits of pipe scale. Take the handle apart and have a look.
Image http://community.homedepot.com/t5/image/serverpage/image-id/28699iE1106DE14461EE20/image-size/original?v=mpbl-1&px=-1


Are we graduating to a full site?

Question: I saw this question, just a couple days old. Does this mean we are graduating to a full site now with the design work being done?
Answer: Eventually, YES. We are officially cleared to graduate, but that is a process not an instantatnious thing.

The design work isn't done, it's only a concept and Jin is still actively working on it. Once the design is finalized it also has to be implemented.
Once the design is implemented and goes live, other things steps will be put in gear. These are in no particular order and there is no particular timeline for them to happen within.

The beta moniker will be dropped and we'll be listed along with the full fledged sites where such lists break out beta sites separately.
We'll host regular elections and the pro-tem mods (such as myself) will be replaced with the winners of those elections.
We'll likely get our name a few special announcement and we'll have some promotional materials to work with (such as a logo if nothing else) that we can use in the process of declaring ourselves official instead of on parole.
Our site database will get added to the SE Data Explorer.
Comment: I didn't mean the design work was *done*, as in final, I meant it was *being done*. My bad on that. Thanks
Comment: @SSumner Your English is slightly ambiguous on that point, and for the sake of other dropping by that aren't as up to speed on where we're at I thought clarification might be useful.
Comment: I agree it's ambigious. Clarification is no problem, I wasn't thinking carefully when I wrote it

Are we graduating to a full site?


Polynomial Identity Testing Evaluating a polynomial on a circuit

Question: Say I have a polynomial over $Q$. Let it be given in the form of arithmetic circuit family ${C_n}$. The randomised poly time algorithm evaluates the polynomial at a random point. What if the number of bits required for the intermediate calculations is too high i.e How can we guarantee that the evaluation does not require more than polynomial bits (polynomial in the size of the circuit) ?
Comment: Please define the question more precisely. What field are you working over?  $\mathbb{Z}/p\mathbb{Z}$?  $\mathbb{Q}$?  What research have you done?  This is covered in standard resources on polynomial identity testing.
Comment: I saw a few resources. In all of those, there was this assumption that the polynomial can be evaluated at any given point effeciently. But still, you are right. I should have done more research.
Answer: If you're working over $\mathbb{Z}/p\mathbb{Z}$, you don't have to do anything: the intermediate results can't get larger than $p$.
If you're working over $\mathbb{Z}$, the standard trick is to pick a random $k$-bit prime $p$ and then reduce everything modulo $p$, so you are effectively working over $\mathbb{Z}/p\mathbb{Z}$.  One can show that the probability of getting a wrong answer using this method is exponentially small in $k$ (using the prime number theorem).
If you're working over $\mathbb{Q}$, you can reduce this to working over $\mathbb{Z}$ by clearing all fractions.


Where can I leave my kids to visit Las Vegas casinos?

Question: Travelling to Las Vegas with my two kids (1.5 years and 5 years old) in September. Can we see people roaming around in Vegas roads during night times with their kids? In almost all the pictures and videos I could only see adults roaming with drinking and laughing. All adult activities. I really want to show my wife casinos in Vegas before going back to my country.
Comment: We left ours with the nanny for the first two children.  But with the last child I started to take them along and simply did stuff like David Copperfield and Go Faster Wally. If somebody didn't like it they could take a hike :)
Answer: Most of Las Vegas is very family friendly so you shouldn't have any problem taking the whole family pretty much everywhere.  You can visit all the major hotels and attractions with the kids.
However, while they are allowed in the hotels, the kids are technically not allowed in the gaming areas so unless you want to actually gamble, you don't need to leave the kids anywhere.
You can still watch a lot of table action from the pathways through the casino though.  These are usually noticeable because of different carpet or other delineaters.  So long as the kids stay inside the lines, you're ok.
Comment: We asked, minors (meaning < 21) are allowed to walk through any casino while they _pass through_. Not for stopping and looking; that is _illegal_ in Nevada (the casino wouldn't care, but they get hefty fines when they let it happen).
Comment: @CMaster Did your partner have an obviously over 18 parent in tow at the time?
Comment: It's because they don't want to take the change you wander into the gaming area.
Comment: My partner had a different experience at age 18. Hassled everywhere and anywhere by members of staff, including throughout the hotel (Lobby, corridors etc)
Comment: @PatriciaShanahan nope.
Comment: @Aganju - can confirm as I was there under 21, even with my parents, we weren't allowed to even stop and watch in the designated "pass through" walkways.
Answer: There plenty of activities for families with children as young as yours are, and lots at no cost such as Circus Circus or the Children's Park and Playground at Town Square Shopping Mall. You also want to visit a casino with your wife, and that means child care, which can be done through most hotels. Those that don't offer in-house childcare services can arrange for an independent, licensed babysitter to come to your hotel. Before you arrive, try exploring the Las Vegas Kids web site which is loaded with information and ideas.
Answer: (Really a comment to Johns-305's post, but it won't fit.)
I must disagree with Johns-305.  While there was a period where Las Vegas tried to market itself as a family destination it was a flop and they went back to the adult playground model.
The basic problem is there is very little for kids to do here.  Gambling is age-restricted and the gaming commission makes them be pretty strict about this, while it's permissible for children to pass through because the layout of the casinos generally makes it impossible to not go through gaming areas and get anywhere they're expected to keep on going, not stop and look.
There are a few shows which would be interesting to kids but most are not--nudity is common, as is some pretty raunchy humor.  Also, shows that don't fall into either of these categories often have a lot of content that's aimed at those of middle age or above--there will be too many references that will fly right past the younger crowd leaving them puzzled.
There are a few things like magic acts that don't fall into any of these traps but that doesn't add up to much for kids to do.  There are a few kid-friendly attractions but again it's limited.
That being said, showing your family Las Vegas would not be a problem.  Just expect to shell out a fair amount for child care if you plan to stay very long.
Comment: I disagree. Check the answers to http://travel.stackexchange.com/questions/18147/what-to-do-in-las-vegas-without-having-to-sin?s=1|1.0043 . While these won't appeal to the preschool set, the blanket "nothing for anyone under middle age" claim is just not supported.
Comment: @KateGregory I'm not saying there's nothing.  I'm saying there's not a lot.
Answer: From our personal experience, which I've written down the following blog posts, there are surprisingly lots of fun things to do in Las Vegas with kids.
If you are going to be there during the summer, you should choose a family-friendly hotel with a nice pool, like Mirage, MGM Grand, or Mandalay Bay. Many of the resorts along the strip also have kid-friendly Vegas shows, like Terry Fator at Mirage, Blue Man Group at Luxor, and Tournament of Kings at Excalibur.
There are even some places to grab a meal and listen to live music with kids like House of Blues at Mandalay or Nine Fine Irishmen at NYNY (kids allowed from 9-11pm while seated for dinner), which is one of our favorite family hangouts in Vegas.
There are various attractions all along the strip that kids will like, for example the shark aquarium at Mandalay Bay, Dolphin and Lion Habitat at Mirage, and Bodies/Titanic Exhibits at Luxor.
I am a family travel blogger and we cover Vegas a lot on the blog (see hyperlinks above), mostly because it is one of our favorite places to visit each year with kids!!


if the hypervisor is hacked are all guests affected as well?

Question: I'm guessing that all guests would be screwed, if the hypervisor is hacked. I found this article, but it seems to be more focused on privilege escalation of guests. I'm more interested to hear about other exploits on hypervisor managers. Many providers use VM control panels like SolusVM. Wouldn't it mean that a security vulnerability in the admin control panel would allow getting control of an array of machines?
Comment: Compromised? YES; Affected? Who knows. "Compromised" means risk, "Affected" is more vague ..
Answer: Simple answer is yes. If an attacker controls the hypervisor they can potentially get access to everything within it, including the memory space of a VM (which could include keys)
Worst case is to assume all may be lost if the hypervisor is compromised, so in order to prevent this, a well structured, layered security architecture may make it incredibly difficult for an attacker to exploit the vulnerability.
One of the reasons we always encourage defence in depth!
Comment: If hypervisor is compromised, I'd rather call it damage control..
Answer: All guest OSes can be affected.
This problem is very well explained in this presentation (from the 2008 RSA Conference).
Answer: Once a system is compromised you can not trust any of its services or processes. So with a hypervisor, you can not trust any of the VM's.
Answer: Look at it this way: a hypervisor is to its guests as hardware is to a normal operating system.
If a hacker has full access to your hardware you can no longer trust anything in your operating system. The same goes for a compromised hypervisor with respect to the guests.


The SWOT analysis is applied to the company or to every decision alternative?

Question: If a company were to pursue different project alternatives in which to invest, would I perform a SWOT analysis on each project alternative or should I do a SWOT analysis of the company and, based on that, make a decision about the different alternatives I have?
Comment: The question appears to be off-topic because it's about market analysis instead of project management. Still, i suggest you have a look at this answer: https://pm.stackexchange.com/a/11074/27189 .
Comment: This question could be revised to fit this exchange quite easily.  After all, a project is an investment alternative that would undergo a strategic analysis, such as a SWOT or benefit / cost (which is pretty much the same thing), before its charter.
Answer: SWOT Establishes a Business Case, Not Comparative Value
In general, (S)trengths and (W)eaknesses in a SWOT diagram are about the company itself, while (O)pportunities and (T)hreats are usually about the market. A project often presents an opportunity or mitigates a threat. Likewise, companies have strengths and weaknesses that can make a given project more or less of a natural fit for the organization.
I've certainly seen people use SWOT diagrams to promote a project or initiative, but in the general case it isn't really an ideal tool for portfolio management. It may help to establish a business case, but doesn't intrinsically create a metric for comparing projects against one another or quantifying value.
Portfolio management is a discipline, and as such there is no One True Way™ to manage a portfolio. However, a solid mix of qualitative and quantitative criteria, stakeholder communication and buy-in, and weighted analyses using company-specific metrics are all essential elements of successful portfolio management.
Answer: An investment alternative or project alternative itself does not have strengths and weaknesses per se.  What it produces as an outcome would have strengths and weaknesses.  From an evaluation standpoint for selection, you would perform a benefit / cost / risk analysis, which is sort of way to predict its outcome SWOT, I suppose.  I think in most cases, when selecting from alternatives, folks reference the strategic analysis as a cost / benefit exercise or a ROI v. a SWOT.


what would happen if we use needle shaped nose in blended wing?

Question: We are using blunt shaped nose in blended wing,instead of blunt,if we use needle shaped nose what would happen ,it reduce shockwave or it produce bow shock?
Comment: Sounds like you should run your experiment, then report back to us!
Comment: This question might need more information, such as a context. Are we talking about the X-48 BWB testbed, or some other test aircraft, or an experimental design of yours, or a model aircraft?
Comment: The short answer is that a needle-shaped nose would reduce the leading-edge stagnation point of the aircraft, potentially reducing drag at low angles of attack. However, if it's just the nose, there will be additional stagnation points along the leading edge of the fatter wing. You could build a BWB aircraft similar in theory to the SR-71 (in fact the SR-71 was a BWB design in many ways), but there is a tradeoff; the thin leading edge will cause the airfoil to stall at a lower critical AOA, reducing the performance envelope of the aircraft.
Comment: This is my experimental design.
Answer: I assume you talk about the airfoil's nose, not the fuselage nose.
A pointed nose will cause flow separation in subsonic flow if the angle of attack is only slightly different from the angle of the leading edge. This flow separation will mightily increase drag because now no suction peak at the nose will develop. This suction peak is causing what is sometimes called "leading edge thrust" (PDF!). Without it, the aerodynamic forces will act in a direction orthogonal to the wing's surface and not (almost) orthogonal to the flow direction.
In pure supersonic flow the pointed leading edge is superior, because it causes less wave drag. However, it is preferable to sweep the wing such that the flow around the leading edge will stay subsonic even in supersonic flight, precisely because it still allows leading edge thrust to manifest itself.


Is poison venomous and is venom poisonous?

Question: I know the difference between poison and venom AND poisonous and venomous.
But I just want to know if an ingested venom would do harm to humans and if an injected poison would do harm to humans.
I really think that poison is both poisonous and venomous AND venom is both venomous and poisonous.
Comment: This wikipedia link might help you understand the difference. https://en.wikipedia.org/wiki/Venom     Read the first two sentences in particular.
Comment: I am fully aware of that. But what I am asking is that if poison is injected/venom is ingested would do harm to a person's health.
Comment: Related : http://biology.stackexchange.com/questions/53577/are-there-any-animals-there-are-both-poisonous-and-venomous
Comment: They had a tough time with venom on SE English Language and Usage [here](https://english.stackexchange.com/questions/170388/is-a-snakes-venom-poisonous-or-venomous) and [here](https://english.stackexchange.com/questions/8686/what-is-the-difference-between-venom-and-poison).
Answer: I think you are both confused about terminology, and asking a very broad question. An organism that produces venom is venomous. Poison is not venomous, the black mamba is venomous. Venom is not venomous.
According to the Wikipedia article on venom,

Venom is a form of toxin secreted by an animal for the purpose of causing harm to another.

A toxin is a poisonous substance produced by a living organism. The article goes on:

Venom is injected into victims by means of a bite, sting or other sharp body feature, which differentiates it from poison (that is absorbed, consumed or inhaled).

However, a toxin is a poison, and poisons are defined (by wiki) as

substances which cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism. (emphasis mine)

So, the definitions are kind of circular.
From what I understand of your question, you are wondering whether a venom would still be dangerous if it were, for example, ingested rather than injected, as well as whether a poison would still be dangerous if injected rather than ingested (or inhaled, or whatever), and this is where the "Too Broad" category gets applied. There are thousands if not millions of different types of toxins in the world, ranging from full proteins to peptide-based to small organic molecules to completely different structures, such as lipopolysaccharide (LPS, the component of Gram-negative bacteria that causes septic shock). Some may not survive the digestive tract, others might. Some can act through the skin, others can't be absorbed. Inhalation is the next best thing to injection, but probably not for every single one of them, so it's impossible to make broad statements about their efficacy and median lethal dose via different routes of exposure. The exact same thing applies to the "poisons" category - while something that is damaging when absorbed cutaneously, such as methyl mercury, is probably just as damaging directly injected into the bloodstream, it's impossible to say that with certainty about all poisons.
Answer: Most venoms contain a lot of enzymes. These enzymes can be split by the proteases in your stomach. So if they don't have any effect before reaching your stomach, they will probably digested like any other protein. Ofc. there are some proteins which resist digestion.
There are poisons which affect only certain cells in the digestive system, so injecting them probably would not have any effect or it can have a completely different effect. E.g. cholera toxin (if we can call it a poison) affect the glucose transport when injected, while it causes diarrhea when it is produced by the bacteria in the infected guts.
There are toxins which have the same effect from both ways. E.g. botulinum toxin can be deadly both injected and ingested. You probably heard of botox injections...
The effect can vary by delivery method as well. Injected can mean subcutan, intravenous, etc... while ingested can mean drinking, swallowing a capsule, which protects it from the proteases in the stomach, and so on... It depends on the dose as well.
I think MattDMo is right, the question is too broad because there are many different poisons and venoms and delivery methods.
Answer: To answer this question first we need to look at what is the definition of a venom and poison. This is somewhat difficult because the definition has changed slightly over the years, but looking over them we can learn of the similarities between the two.
"A venom is typically a mixture of compounds containing one or more toxins, which is produced in venom glands and injected into animal tissues via specialized morphological structures." This meaning that a venom is made and is injected into another organism (both plants and animals can do this).
"A poison is one or more compounds that are toxic. These toxins can be inhaled, absorbed, ingested, or injected. Plants and animals can produced organic poisons; however, poisons can also come directly from the environment." Example: Chlorine or Fluorine gas.
This is where it's tricky with the definitions. A venom can only be injected to be harmful, whereas a poison can be as well; however, a poison has a broader area of effect. Some snakes have venom that can be absorbed or toxins in their flesh making them poisonous to eat. So the issues are first what happened, was it injected or not, next could it have not been injected and still caused harm.
The best logical answer is that all venoms are poisons, but not all poisons are venoms. This is because both can be injected and cause harm, but venoms have to be injected when poisons don't. Like with the above, some snakes have toxins that are commonly injected so they are still called venoms even when they can be absorbed making them poisons by definition.
To conclude, it's a complicated issue that people are still trying to figure out. In the end the main difference between the two is that a venom needs to be injected, when a poison can but doesn't have to be.
Comment: Welcome to Biology.SE! Your answer sounds reasonable (although it isn't clear to me what it adds anything to the existing answers), however, it is likely to receive a more favorable response if you include supporting references (primary literature is best, but a textbook available online would seem sufficient for this question). In particular, the quotes you make must have references to the original sources. ——— Please also take the [tour] and then consult the help pages for additional advice on [Answer] effectively on this site and then edit your answer accordingly. Thanks!
Answer: Some substances can be both venom and/or poison.  According to Wikipedia, the source of all knowledge in this internet age, Blue Ring octopi are dangerous to humans if provoked because their venom contains the powerful neurotoxin tetrodotoxin.  According to the same reliable source, Pufferfish are dangerous to humans if eaten because their flesh contains the powerful neurotoxin tetrodotoxin*.
*Summations, not quotes.
Comment: Welcome to Biology.SE. The community is looking for more developed answers like the first ones in the list (they include references and citations).


How can I see if a contact has video/voice capability in Empathy?

Question: I'm using empathy for the first few weeks now on Ubuntu 12.10.
I can't find any symbols indicating a contact has the ability to do a video chat or voice chat...
Though I can see a "Mobile" symbol which say "Online from a mobile or Phone device".
PS: I can see a video call, Audio call option enables when I right click on a particular contact.
I don't see any option to configure anything like that.
OS : Ubuntu 12.10
Gnome 3.6.1 (PPA)
Empathy : 220.127.116.11
Answer: empathy uses the farstream library to enable audio and video and as far as I can tell it's not available in the 12.10 repositories. I'm also trying to find a way to enable it.


How do you say "snap judgment" in Cantonese?

Question: There isn't a translation in the Cantonese dictionary. Is there a way to say "snap judgment" or the equivalent?
Comment: Are you referring to "the first impression" or "a quick decision"?
Comment: Both, tho particularly interested in the context when someone offers an opinion without trying something first, e.g., "that restaurant is terrible." How would you say, "It's best not to make snap judgments?"
Comment: Though I live in Hong Kong and I am a native Cantonese speaker, I seldom hear people use the term "snap judgement"  directly in conversation. For written Chinese, it should be equivalent to `莽下判斷`; if translate it into verbal Cantonese phrase, it should be `咁快下定論`.
Answer: I don't think there is a Cantonese phrase equivalent to it. Usually we just use a sentence like "唔好咁快下结论" to express the idea of "Don't make a snap judgement".
Answer: "唔好咁武斷"
It is a well-known saying for the 70s generation or earlier, but much less for the 80s generation and onwards.


Resources to start with  - ideas for blog link collections

Question: @yossarian proposed a great idea in chat: Make collections of links curated by our community members.
There was a discussion about whether we should explain some really basic stuff like "How to stir fry" on the blog. Argument against: We create no new value if we endlessly repeat what is already widely available elsewhere. Argument for: community members who just do a Google search for an area they haven't experimented with, like "tofu making", don't know which hits are good, but they would trust a post written by our members who are known for a rep in this area.
The new series has the potential to be the best of two worlds. Those of us who have become an expert in an area fondly remember the informations sources which helped them along the way, and want to pass this information on. If it is freely available, it is enough to link to it, instead of investing the effort to write it from the beginning. But when they recommend the links, then our average reader can trust the links as much as he trusts a post written by the member who proposed it.
This thread is the place for you, our readership, to tell us what areas you are interested in. Tell us what link collections you would like to see, which ones will help you in your daily cooking. Everybody who notices a topic he has good links for, can mail us the link at email@example.com, and when we have a big enough collection, we will publish it. Alternatively, some of you may already have a good collection on a single topic - then use the same address to tell us about it, and we will make a post out of it.
This kind of post will be published as an addition to our regular posts. It won't require writing a lengthy text with pictures the way the regular posts do. 7-8 links with a sentence or two for each, explaining why it is good, will suffice.
This thread will also let us judge which beginner topics also need a good post from us. For now, we know that bread hydration experiments and oven steam injectors are rare on the Internet, and assume that guides to making tofu are plentiful. But if we can't find good tofu links, and nobody supplies them, and all tofu links we find are lacking in some way, we will consider making our own post on the topic.
Comment: I think this could also be a way to try to elevate the quality of answers, depending on how it is done, and aid in the pursuit of those evasive canonical answers. If any of the other stacks are doing this, could you link to some pre-existing content in this regard?
Comment: I think this is a good idea, but something to keep in mind: will anyone be reviewing these "link collection" blog posts on a regular basis (every few months or so) to make sure that none of the links are dead? Content on the internet moves around a lot - we don't want to wind up with a collection of only semi-useful links.
Answer: Coffee sourcing, methods, preparation, brewing, and storage


How to tackle browser's back and forward buttons/arrows?

Question: What is the general UX rule followed wrt to navigation that a browser provides.
I am developing a web based tool.I would be definately be enabling navigation to different screens within the tool, I want to understand should the same be allowed through the browser or not?
Comment: Leave them alone. Trying to switch them off or mess with their behaviour just annoys people who have come to rely on them working in a specific way.
Answer: The browser has back and forward buttons whether we like it or not. I would work with that.
If the buttons are present but made non-functional by the developer, the end-user is likely to find the experience frustrating.
Comment: The application should also ideally *accept* that the buttons exist and that pressing them should behave in the normal manner. For example, SPA (single page applications) use hash-tag navigation to produce browser history entries that can then move forward and backwards between application state.


Is transgender haram in islam?

Question: I'm a female & I wanted to be a boy my whole life. As far as I can remember i used to wear my brothers pants and shirts since i was 4. I've always seen myself as a guy. I've read and heard that transgender or homosexuality is something you choose for yourself. But how can I choose that at the age of 4? Am I born to go to hell? It's really depressing me. Will I get punished for being like this?
If I become a man through the surgery will allah accept me? I've also heard that even though I become a man through that surgery I will still be a female. Is that true?  ( sorry for my english)
Comment: You've asked several questions most of them sound like advice-requests which is rather off-topic try to stick on a single topic in your question, so that it will be easier to answer or refer you to an answer (also read https://islam.meta.stackexchange.com/questions/2965/why-we-should-avoid-asking-multi-question-questions)
Answer: I surveyed fatawa on this topic in this answer (see also Can transgender people be Muslims, and how do gendered rules and rules about marriage apply?).  Basically, there's some fatawa that say it's haram to transition, and other fatawa that say it's permissible under certain strict circumstances, sometimes described as "psychological hermaphroditism".
Countries like Malaysia and the UAE are generally against transgender people.  Iran is quite accepting, as long as you're consistent.  Most countries are somewhere in between.  Individual Muslims also have varying attitudes.
Practically, you're not going to be able to just get bottom surgery and magically everything will be okay:

FtM phalloplasty is expensive, complicated, prolonged, and painful.  The surgery hasn't developed to point where the results are particularly natural.  Additional surgeries will probably be required, e.g., mastectomy.
One doesn't interact with most people using one's genitals.  Even after surgery, most people won't know you've had surgery.  However, after prolonged hormone replacement therapy, many female to male transgender people become "passable", meaning that people won't be able to tell you're transgender.
The WPATH Standards of Care (available from http://www.wpath.org) requires a 1-year long "real life test".  I.e., before surgery, you're required to live consistently as your identified gender for at least one year.
Most people will spend an extended period of time transitioning (maybe 3+ years) before their body is settled.  It's not going to happen overnight.  You'll likely need to become accustomed to an "in between" state, and somehow juggle going to mosque, etc., while being in this state.

I can't address whether or not you'll be punished for this.
Before deciding, it would be best to "do your homework" regarding the religious and medical ramifications.  Also important is to consider how your family might respond.
Answer: In the signs of the last day, one will be women dressing like men or vise versa. It is prohibited for a man to dress like a woman or act like a woman. Or for a woman to dress and/or act like a man. These thoughts come from shaytaan. It is haram to modify your body, unless it is for medical reasons. So things like plastic surgery are haraam. Therefore, being transgender is haram.

Is transgender haram in islam?


Would it be viable to install a screen in front of jet intakes to prevent them from sucking in birds?

Question: Why isn't there a protective screen with large diameter holes (approx 2') mounted in front of the jet engine intake to protect the turbine blades? This would  keep larger birds and large ground debris from getting sucked in, which can cause serious internal engine damage.
Comment: Would the filter really prevent the birds to go inside the engine, considering the energy of the impact?
Comment: @raptortech97 I think the goal is to protect the engine from the bird, not protect the bird from being hit by something at hundreds of miles per hour.
Comment: What sort of screen are you imagining? It's hard to save a bird when the relative velocity is 300 mph.
Comment: If you did have a screen, what's going to happen when the bird hits it?  The suction from the engine isn't going away, since you don't want to shut the engine down in flight.  Either the bird will get sucked through the screen in pieces and go into the engine anyway, or it will get stuck on the screen and disrupt the flow of air, which seems like it might be a problem.
Comment: One also has to wonder whether the mesh can actually save an engine. It obviously cannot keep the bird out of the engine; all it can do is slice it up a bit before it hits the blades.
Comment: @NateEldredge: A 5% drop in performance, and a cheap repair both seem like real benefits. Many safety measures (e.g. airbags) aren't so much about preventing accidents but more about damage reduction.
Comment: You really only need to protect the engine core, which is more practical than protecting the whole fan.
Comment: @DavidRicherby you're right, I misread the question
Comment: mig-29 actually has a intake screen
Answer: Modern high-bypass turbofan engines work by pulling in immense volumes of air and accelerating it.  A screen as proposed would make that task far more difficult, which would ruin the efficiency of the engine.  It's also pretty well unnecessary.
Jets worldwide take plenty of birdstrikes every day.  Unless the pilots see it (hitting the windscreen will do that) or hear it (hitting something near the cockpit) or the bird goes into the engine core (which causes the smell of burned bird in the air conditioning), the chance that the crew knows about it before the next walk-around inspection is pretty slight.  The vast majority of birdstrikes are utterly inconsequential.  (Except for the bird -- ruins his day pretty thoroughly!)
Yes, there are a small number of very highly visible events where birds do disable an aircraft -- the "miracle on the Hudson" and the loss of an AWACS in Alaska come to mind, and there are others.  And it's possible for a birdstrike on an engine to cause significant damage IF the bird is large enough AND it goes into the core, but in the big picture, that is actually pretty uncommon.
Thus, the aircraft manufacturers and operators end up accepting the risk of a catastrophic birdstrike, because the alternative of protecting the engine as suggested is too expensive when the effects on the efficiency of the engine are considered.
One other point, bird flesh is pretty easy for an engine to chop up and digest.  If a big bird hits a metal shield at high speed, there would be the risk that the shield could be damaged enough that some of the metal would break apart and go into the engine as well, and THAT would cause far more damage than just the bird.
Fun video of stuff being shot into an engine during testing
Comment: more important I think is that it wouldn't really do much good. The screen would just turn the bird into chunks of bird. While that might prevent a bent fan blade at the first low pressure fan, maybe, it wouldn't do much more.
Comment: I think it's worth mentioning that decreasing the efficiency of the engines is itself a safety risk.  Less power for hot days, short runways, collision avoidance maneuvers, etc.
Comment: well said and great videos
Comment: So we notice the bird if we see it, hear it, or smell it.  Hopefully there's not to many documented cases of a flight crew noticing the bird via taste or touch!
Answer: A few Russian/Soviet fighters had retractable FOD screens on their engine intakes (MiG-29 and Su-27 IIRC). The assumption was that they would operate from damaged runways or roads and the engines would need protection against Foreign Object Damage (FOD).

Right air intake of a MiG-29 with main doors closed and louvres on the wing root opened.
Comment: Mind that these were not intended for operation in flight. They are only operated during takeoff and landing, they restrict the airflow too much to be practical during regular operations (the performance of the aircraft suffers too much) or even when taking off at high weight.
Comment: Nor are they designed to take a bird at cruise speed.
Comment: @NobodySpecial that would depend on your routing. Flights are rerouted during bird migration season to avoid high altitude flocks for a reason. There are birds that high up, just not many.
Comment: Do you encounter many birds at cruise ? I thought they were mainly a danger during take off and landing. You don't do much bird spotting at 40,000ft
Comment: Depends on your mission profile. The MiG-29 was designed primarily as an air-superiority fighter (originally the answer to the F-15, itself developed in direct response to the MiG-25), but was adapted to multirole use especially with the M variant; air-to-ground mission profiles even for deep strikes often involve relatively low-altitude cruising.
Comment: @KeithS - I meant for commercial airliners - bird strikes are only an issue at take-off/landing. Not that FOD screens are practical - but they don't have to work at mach 0.95
Comment: Screening the primary intake like this works on a jet fighter where the engine is buried in the wing/fuselage and the wing top can be used as an alternate air intake. For a "standard" configuration airliner, @NobodySpecial, with engines hung below and forward of the wings, what would be the the possible alternate air intake path?
Answer: Screens were actually used on the first prototypes of the Me-262, but soon abandoned when they were found to be more of a burden than a help.
If you look carefully at the picture of the Me-262 V3 below, you can see the spherical screens on both engine intakes.

Today, screens are used only in ground tests. See the picture below for the Rolls-Royce version:

The big surface of the sphere reduces aerodynamic losses, which are small under static conditions anyway, but this contraption would obviously be totally impractical in flight.
Comment: It's probably also worth noting that, while the big surface of the sphere reduces aerodynamic loss in the case of a test fixture that is stationary with respect to the air around it, it would cause an incredible amount of drag were it actually moving through the air.
Comment: Doesn't that show the danger of ingesting bubble gum  while running in reverse?
Comment: The screen in the second picture isn't really to block FOD, but it does have that added benefit.
Answer: There are three problems with this idea:
(1) To make a screen strong enough to withstand the body of a 15-to-20 pound bird hitting it at 500 miles per hour, would require thick wire which would significantly block air flow.
(2) Such a screen would be very liable to collect ice, so it would have to be heated to high temperature. This would be expensive and would increase the maintenance burden for the aircraft.
(3) If part of the screen failed and broke off for any reason and went into the rotors, it would destroy the engine.
Answer: When flying any surface that is exposed to the air will generate drag. That screening, although full of holes, will create significant drag when exposed to the air that is entering in the airplane.
Also, it will distort the air entering the engine reducing the efficiency of the engine and increasing fuel comsuption.
Globally, the extra drag and the higher fuel consumption is more costly than the increase of weight needed for generating extra protection on the engine nacelle.


Child XML for joomla parameters

Question: I'm creating a template with many parameters available in its backend.
Basically I have about 8 blocks in the template structure (index.php) and each block have about 30 options (background, content type, layout, animation etc) so I have about 300 options totally in the template backend. This makes the template backend is loaded very slow when opened or saved.
Is there any native way (I didn't use any template framework) to make all of these 30 options are loaded in the separated / child xml so it will be called by demand and the template backend loaded faster?
Comment: anyone? maybe by loading the extra params inside a modal?
Comment: I found the way to include extra params inside a modal by following the backend code of a free module, but it doesn't solve my problem. The backend is still running slow :( Any idea?
Answer: Because you did not use any known template frameworks, I'd be very very surprised if anyone will be able to give you a direct answer to your question.  I googled a few, and found Using a Joomla Template Framework to Design your Site, which outlines the pros/cons of the popular frameworks that are out there.
Again, not knowing how your code works at all, there's no way we can guess at a native way to implement parameters, but if you look at these known and accepted frameworks, perhaps you'll see a way that it's done with them and you can incorporate it into your framework.
Answer: There is no native way to load separated / child XMLs for template configuration. In fact, any XML loader checks if it is parsing a valid XML. If your configuration is separated in several files, it is not a valid XML until you merge all of them.
I think your issue is not in the XML size. The size of the configuration Html form may be the cause of the slow load. Most template networks simplify the configuration with several smaller forms or wizards.
Answer: It's now possible with the
Sub Form field function introduced in Joomla 3.6

Child XML for joomla parameters


What does phasing mean?

Question: What does phasing mean in genetics/informatics? I've heard that a phased file is a file that has genes separated by chromosome, but can someone give a concrete definition of what phasing actually means?
Answer: This refers to haplotype phase (aka gametic phase). This essentially means knowing which allele belongs to which copy of the chromosome, or alternatively, which alleles appear together on the same chromosome.
In short-read sequencing, for example, it is difficult to resolve the haplotype of two heterozygous SNPs if they have not been covered by the same read. If you observe A/a and B/b, you do not know whether you have AB + ab or aB + Ab. So you would say you do not know the phasing.
See the Wikipedia links for more information.
Comment: Can you shed some light on why this process is called phasing? It reminds of phase as in waves which makes no sense.
Answer: phasing is the relationship between adjacent alleles on the same chromosome i.e. if they are in cis or trans configuration. In other words, weather two alleles are indeed on the same chromosome or on different chromosome. One of the reason alleles get shuffled is by process called recombination where chromosome exchange happens. Majority of current methods infer the phase using linkage disequilibrium principle however with advent of whole chromosome sequencing it's possible to determine empirically the phase from related samples. i.e. father, mother, son

What does phasing mean?


How would I produce (stable) foamy bechamel sauce?

Question: I recently ate a dish that was topped with a foamy bechamel sauce. It had the same creamy taste a traditional bechamel has but was much fluffier and less set, a bit like a mousse. I would like to reproduce this but I am not sure whether a foamer would be enough or I'd need some stabiliser on top. Has anyone got experience with foaming bechamel and/or does someone have a recipe for this sort of thing?
Comment: Beware of cream whippers.  If you added fresh grated nutmeg or fresh cracked pepper to the bechamel, you'll need to strain it first.  Commercially ground nutmeg is typically fine enough pass through the whipper, but most grind sizes of pepper may clog the whipper.  See http://cooking.stackexchange.com/q/34996/67
Answer: I ended up getting the recipe from the chef himself! It turns out that gelatin makes little sense at the temperatures involved unless you up the quantity in which case the texture gets altered for the worse (I experimented only twice so I can't really be sure that it wouldn't work at all).
The recipe itself calls for a bechamel with a very light roux simmered for a very long time (~3 hours) and stirred occasionally so that the milk doesn't burn. At the end of the process it becomes thick enough to foam in exactly the right texture. Strangely the guy doesn't use any seasoning aside from salt and pepper but I'd think this is so that the particular dish is in balance.
Comment: @Juliano sorry for the reaaaaly late reply - I need to visit this site more often. It worked, yes but to be entirely honest, the time you put into it has to do with how light a roux you are starting with. I tried with a semi-light roux (2:1 of butter-flour ratio) and reduced the time significantly and still achieved a nice foam.
Comment: Did you manage to test the 3-hour bechamel recipe? Did it work?
Answer: It probably depends on how sturdy you want the foam to be.  There are a number of hydrocolloids that you could use.  I would start with gelatin.  If you are using powdered, start with 1%.  Bloom and dissolve into bechamel, bring to a boil. Pour contents into whipper (such as ISI brand), charge with N2O. Dispense as you see fit.  If that produces a foam that is too soft, up the percentage of gelatin.
Comment: +1 for the gelatin. I use [Beef Gelatin Powder](http://goo.gl/5QfG3q) that doesn't require blooming and it works well for, as you said, "moussy" bechamel and when you want some lightness to a sauced topping (think Moussaka.) Or you could just use traditional gelatin and bloom it first. The powdered stuff is easier for experimenting with quantities, IMO.
Comment: Thanks for the answer (+1), I will give gelatin a go. That was the only thought I had for a stabilizer so I'll experiment with that and if I get a decent result I'll edit in the quantity that worked and accept the answer. The dish was not moussaka btw but another similar fuse of greek/turkish/italian dishes called (in Greece) pasticcio which I thought couldn't go too far(it is something like ragu bolognese topped with bechamel). I was really wrong mostly because of the incredibly light but creamy bechamel.


What does "of a kind" mean?

Question: I'm not referring to "one of a kind" or "first of a kind" but "the two were of a kind".  This turns out to be remarkably un-Googlable so I am having difficulty providing examples.  In context I have always assumed it meant that two things were in a unique category unto themselves.
Comment: maybe "they were two of a kind" => "the two were of a kind" ?
Answer: "Two of a kind" means that there are two parts that make up the total. "The two were of a kind" is a little different because it doesn't imply that there are only two in that "kind", but that those two are in that "kind", where kind generally refers to a unique personality trait, state of mind, or way of looking at the world.
Answer: It really means the same as it does in the context of the phrases "one of a kind" and "first of its kind." In this context, "kind" means (loosely) "a type or variety having specific quantifiable features." So for "the two" to be "of a kind" means that they have specific quantifiable features in common. The phrases "of a kind" and "of the same kind" are more or less semantically interchangeable.
Answer: It basically means that they share some common subset.
It can be used in a manner to exclaim that a group is special and out of the ordinary.
It is often used to express distaste at certian life choices in a manner that seems less overt or crass.  In this manner the exact definition is left indefinate so that the speaker can claim misunderstanding.

What does "of a kind" mean?


Changing Time Signature

Question: I need to change a simple piece from 4/8 to 4/4. Do I only need to double the values for each note? (Ex. quarter to half note & eighth to quarter?)
Answer: If you wanted all your notes to have the same value in the new meter, you would double them to the denominator of the time signature being cut in half. For example if you had a measure like this:

It would become this:

Notice how all the eigth notes became  quarter  notes and all the sixteenth  notes become eigth notes. Also if you want the tempo of your piece to stay the same, you also need to double it.
Comment: @NeilMeyer - the tempo MARK needs to double, as Dom shows, and jjmusicnotes says. Either same number, but crotchet instead of quaver, or the number itself needs to change.
Comment: The tempo does not have to double. There is no inherent speed difference in time signatures with quaver beats vs crotchet beats. It is a commonly held misconception.
Answer: Short answer: yes. Simple double all rhythmic values and change your unit tempo to match your current unit division.  For example, if before, the music was at 8th note = 120bpm, after the unit division change, a quarter note = 120bpm.

Changing Time Signature


Looking for Open Data Source to Correlate Address to Latitude/Longitude (geocoding)

Question: Are there any open data sources that can help correlate a given address to a latitude/longitude coordinate? aka geocoding
Comment: djc391 - please consider searching for similar questions at [GIS SE](http://gis.stackexchange.com)
Comment: The term for this is "geocoding" which may help your research efforts.
Answer: You mention you want data sources, so I'm going to focus on where you can get information that helps match street addresses to coordinates, rather than APIs. If you can, go with a web service, but there's a certain masochistic pleasure in building your own geocoder from raw data!
OpenStreetMap is the most comprehensive worldwide source, and has good downloading instructions. The biggest drawback is that OSM has been focused on rendering maps, rather than gathering data, which means less visible information like postal codes and house numbers within a street are often not available. Geonames offers bulk downloads that can make up for a lot of the post code problems.
If you only care about the US, the Census's Tiger/LINE data set is very powerful. It has address ranges for house numbers, and can be loaded into PostGIS directly to create a turnkey geocoder.
Once you get beyond those, the data starts to get less structured. I'm fond of SimpleGeo's 21m points of interest, but almost any data set that includes both street addresses and coordinates is useful. Knowing more about what your application is would help me point you in the right direction.
Answer: Openstreetmap has an API which gives coordinates for an address, see Stackoverflow for an example
Comment: I'd suggest looking directly at the OSM Nominatim documentation.  The SO example is focused on city/country lookup while the docs have examples of street address lookups.
Answer: FWIW, Karsten W.'s suggestion uses R, so I'm not sure what your tool of choice is, but here're two other options:
1.) A Python client, geopy, that hooks into the geocoders from:
<code>• GoogleV3
• Yahoo!
• geocoder.us (free for non-commercial use, accounts available for commercial uses)
• GeoNames
• MediaWiki
• Semantic MediaWiki
</code>
I've used it for years. It's solid.
2.) One in Ruby (but I've no personal experience with it) that can use the geocoding APIs from:
<code>• Google
• Yahoo!
• Bing
• Nominatim
• Yandex.ru
• Geocoder.ca
• Mapquest
• Ovi/Nokia
• FreeGeoIP
• MaxMind
• ESRI
</code>
Answer: Texas A&M Geoservices has a few Geocoding Services/Tools available, however they are for the U.S. only.
Answer: Firstly, "geocoding" is the name of the task you're trying to achieve (might help with future Googling).  The Geocommons geocoder is one example of an open-data-driven geocoder; I think they mostly use US Census data.
(As that example illustrates, a lot of this kind of data is country-specific, so a bit more detail in your question may produce better results.)
Answer: The CartoDB service offers geocoding for tables stored in their service.  While CartoDB has a subscription fee, the software is open source.  In the US, they use TIGER in a PostGIS and for the rest of the world, they use GeoNames.
Answer: List of Open/Open Source/Free-ish Geocoding Services and Tools (2017-05-10)

Twofishes
A coarse forward & reverse geocoder in scala.
Geonames Geocode Webservice
CesiumJS
A widget for finding addresses and landmarks, and flying the camera to them. Geocoding is performed using the Bing Maps Locations API.
Ruby Geocoder
Complete Ruby geocoding solution.
Geocoder Repository
Yandex Maps Geocoding Service
The Yandex.Maps service provides a geocoding service for its users. This service can get the coordinates and other information about an object using its name or address, as well as the opposite, using the coordinates of an object to get its address (reverse geocoding).
Gisgraphy
geocoding and geolocalisation webservices for Geonames, Openstreetmap, and quattroshapes data http://www.gisgraphy.com
Repository
Gisgraphoid
Gisgraphoid is a library to do geocoding on your Android mobile phone or tablet with the same Geocoder API as Google but with Gisgraphy. Runs on all Android versions, free, no Google API needed by the device, no API key, no limit. You can display the result on OpenStreetMap or Google Maps (Google API key required).
Android Geocoder Class
Geocoder PHP
The almost missing PHP library!
Drupal Geocoder Module
Mapbox Geocoding Service
Carto Geocoding
From plain text to geometries.
geocodio
geocodio makes converting US and Canadian street addresses into map coordinates and vice versa as easy as uploading a spreadsheet. The first 2,500 addresses per day are free, and aditional lookups start at a $0.50 per 1,000 addresses ($0.0005/lookup).
Mapquest Developer Open Geocoding API
Apache Camel Geocoder Component
JAVA API for Google geocoder v3
Census Geocoder
Census geocoder provides interactive & programmatic (REST) access to users interested in matching addresses to geographic locations and entities containing those addresses.
FFIEC Geocoding/Mapping System
The FFIEC Geocoding/Mapping System (System) helps financial institutions meet their legal requirement to report information on mortgage, business, and farm loan applications. Geocoding refers to the Metropolitan Statistical Area/Metropolitan Division (MSA/MD), State, County, Census Tract combination (address information) that must be provided for each reported loan application and the System allows institutions to enter a street address to determine the corresponding geocode. The System also provides Census demographic information about a particular census tract, including income, population, and housing data.
Please select the appropriate activity year for the address being geocoded. The tract definitions for 2015 and 2016 data are based on the 2010 Census, for 2017 data is based on the 2015 Census. It is critical that the correct activity year is selected when using the FFIEC Geocoding System.
batchgeo
Another upload a CSV -> Spit back geocoded dataset as a service; it appears to offer some services openly, though the details where not very obvious to me.
BING Spatial Data Services
Geocode and Data Source Limits can be found here for Bing Maps Account used with the Bing Spatial Data Services or the Bing Maps Dev Center at
https://www.bingmapsportal.com/ to geocode entities and manage data sources.
GPS Visualizer's Quick Geocoder
Just an easy, in-browser tool if you need to check an address, etc.
GPS Visualizer's Easy Batch Geocoder
GPS Visualizer's Address Locator - Convert multiple addresses to GPS coordinates

References/Resources
Geocoding Resources
Answer: If i may, can i add one more platform called CSV2GEO  that does batch geocoding , reverse geocoding and plenty other geolocation services.  It has hybrid price model of free and paid options. The system can process from single line to millions of records.
Disclaimer: I founded CSV2GEO.