I need to comprehend the definition of deliberately bringing kufr thoughts to mind. All the cases. Please may Allah reward you

Question: I have been reading an enciclopedia of things about Islam in the past ten years, so please don't treat me as a beginner.  We all agree that deliberately bringing blasphemous and kufr thoughts to mind, puts you beyond the pale of islam. But the term deliberate is wide and vague. We all agree that if I bring to mind the sentence  with the intention of believing it, that puts you beyond the pale of Islam. But I can bring that sentence to mind even without believing it,  even without approving it, even without liking it. For example: I am staying idle and for no reason I (not waswas) imagine the voice of a priest that says  or I imagine the verse of the Bible that says < The almighty has children> because I remember how that verse looked like when I read it in the Bible 5 years ago out of curiosity. I visually imagine it as a sentence word by word. My question is: Are the two cases described in the last part of the questions considered or called < Deliberately bringing blasphemous and kufr thoughts to mind>  The case of imagining the voice of a priest and the case of visually imagining a sentence from the Bible word by word. To be honest with you, in seventy per cent of cases, either I haven't received an answer at all or the answer hasn't fulfilled my needs. I invite contributers like Muslimah , Medi1 Saif and others without excluding anybody to at least give their personal opinion.
Comment: I don't get what you are talking about: I wonder what you think is  blasphemous in the given "example". Have in mind that some people want to read this so use some layout to make your text readable etc. Beside this login in with different guest accounts isn't helpful if you want a question answered as you'll need to react to the comments in order to get answers.
Answer: Relevant verse from which we can draw an analogy:

وقد نزل عليكم في الكتاب أن إذا سمعتم آيات الله يكفر بها ويستهزأ بها فلا تقعدوا معهم حتى يخوضوا في حديث غيره إنكم إذا مثلهم إن الله جامع المنافقين والكافرين في جهنم جميعا  (And it has already come down to you in the Book that when you hear the verses of Allah [recited], they are denied [by them] and ridiculed; so do not sit with them until they enter into another conversation. Indeed, you would then be like them. Indeed Allah will gather the hypocrites and disbelievers in Hell all together) - Qur'an 4:140

We see that Allah (ﷻ) condemned those who stayed in the presence of disbelievers when they were mocking Islam and said that if they were to remain in the presence of such Kufr, they are "like them" i.e., if they AGREE then they are also disbelievers and if they DISAGREE but remain there then they are getting an equivalent level of sin to them. No IFs, ANDs or BUTs about it.
This is a similar situation @:

I can bring that sentence to mind even without believing it, even without approving it, even without liking it.

It's haram for you to do so. It's not Kufr but you're still getting sin for it. And not only that but calling such thoughts to mind also risks your faith, all the more reason making it forbidden.
I hope this helps settle the matter in your mind, inshaAllah.

To be honest with you, in seventy per cent of cases, either I haven't received an answer at all or the answer hasn't fulfilled my needs

Sadly, your questions about thoughts/waswasa are repetitive and slight variations of each other. You could very well come up with millions of different scenarios/cases and ask about each of them as a "new question".. but these have in reality already been answered sufficiently.


Why is a CSR hashed?

Question: What are the use cases for defining something other than the default SHA1 hash in a CSR? Is it to protect the digital signature, public/private keys? What is it protecting exactly?
Answer: It's actually not a SHA1 hash in the CSR.  It's a signature of the message.
For simplicity, I'll assume we are talking about RSA certificates, where the public key is (N, e) (the modulus and public exponent which is typically 65537) and the private key is (N, d) (the modulus and the private exponent which can be easily calculated via Euclid's extended algorithm if you can factor the modulus into p and q).
A certificate is simply a public key, with some meta-data (e.g., who you are, what domain the certificate applies to, who signed the certificate), plus the signature of the certificate.
In RSA you sign a message by attaching a signature to the end of the message.  You obtain the signature by first hashing the message and then doing modular exponentiation on that hash with your private exponent.  That is the signature is S = H(m)^d mod N.  Note anyone with the public key can verify the signature by calculating S^e mod N and verifying that this matches the hash of the message.  Note, if you do not have the private key you cannot construct a valid signature for the message, so this prevents tampering with the certificate.
A CSR is a certificate signing request, but essentially it is just a self-signed certificate that you create on a local machine, so you can give to a CA to sign (so the CA will never learn your private key).  So you locally construct two large primes, multiply them to find the modulus, and calculate the private exponent.  You add your meta-data about yourself to your CSR.  For good measure, you immediately sign your certificate with the private key associated with the public key contained within the certificate.
This prevents someone from altering your CSR in transit to the CA (to say change your organization details, challenge password, serial number, without changing the modulus/private exponent).
This probably isn't the most devastating attack as you still have to trust the CA to act in trustworthy manner, and there's no reason to give away your CSRs to any other third parties.  However, its straightforward to sign it, takes no additional effort, so it is commonly done.
Comment: @user53029 - Originally, MD5 was used. But MD5 has vulnerabilities specifically [chosen-prefix collision attacks](http://en.wikipedia.org/wiki/Chosen-prefix_collision_attack). So an attacker first carefully constructs a collision between an unsigned certificate m for a random domain and a fake intermediate certificate authority m', such that MD5(m)=MD5(m').  Then they get a CA to sign the first certificate, and take that signature and append it to their other certificate and now they can sign anything. Hence, you don't use MD5 for signatures anymore and SHA-1/2/3 should be more secure.
Comment: Thanks Dr. Jimbob :) Very nice explanation. I was wondering though, since the options are their in Openssl to create a signature with a SHA2-256/384, etc..hash, what would be a use case for wanting to create such a hash, or strong signature? Is it just to provide more protection, from, like you say, preventing someone from altering the CSR in transit to the CA?
Comment: Plus it proves to the CA that you actually have the secret key corresponding to the public key you want to have signed. Not extremely important either, but may catch some mistakes.
Answer: The RFC for CSRs - https://www.rfc-editor.org/rfc/rfc2986 - actually gives a different reason why the CSR is signed. It doesn't say anything about preventing the CSR being modified in transit, but says that it is to prevent someone requesting a certificate for a key that is not theirs (and says this is only a minor issue):
"   Note 2 - The signature on the certification request prevents an
entity from requesting a certificate with another party's public key.
Such an attack would give the entity the minor ability to pretend to
be the originator of any message signed by the other party.  This
attack is significant only if the entity does not know the message
being signed and the signed part of the message does not identify the
signer.  The entity would still not be able to decrypt messages
intended for the other party, of course."
(on page 4).
I don't think the 'prevents the CSR being modified in transit' idea actually makes much (or any?) sense. So far as I can see, any practical MITM attack requires the attacker to be in a position to intercept the communication in both directions, whereupon they can just substitute an entirely different CSR for a key pair they actually control the private half of.
I can't see a plausible scenario where any kind of plausible 'attack' can be carried out by a party sitting between a CSR submitter and a CA who can't change the public key, unless you're positing an attacker who would somehow gain something from fiddling with the certificate metadata and a submitter who doesn't bother checking the metadata on the certificate that comes back from the request...

Why is a CSR hashed?


Formula to calculate emission rates

Question: OBD tells whether I have passed the emission test or not. I want to know the formula by which it calculates the rate of CO, NOx, HC emission from my car and compares it with some set threshold value to give a pass/fail result.
The formula will be different for Petrol (gasoline) and Diesel cars, I guess.
Comment: You might be interested in the '5 gas chart' to relate a/f ratio to the different gases http://www.fixkick.com/sensors/O2%20sensor/AFR-GAS.JPG
Comment: Is this plot valid for diesel and petrol cars? Or will it different?
Comment: I am not familiar with diesel engines so I am not sure.
Comment: were you able to find an answer to get Nox and CO value through OBD2??
Answer: I think you miss-understand how OBD tells that your car is passing emissions.
All the car does is make sure that the emissions control systems are functioning and then it hopes that what is coming out of the tail pipe is OK. The car verifies that the fuel mixture is within tolerance, that the EGR is functioning, that the evaporative emissions system has no holes and is purging, that the catalytic converter can store adequate amounts of oxygen and that all the electrical components are functional.
Beyond that there is nothing else. The car could be pouring out mad amounts of NOx but never know about it if all the systems are functional.
The EGR system is verified by checking it's flow either directly or indirectly. If there is a correct amount of flow then the system is deemed functional. Ford uses a DPFE sensor that checks the flow of the EGR directly. Other cars use the MAP sensor to indirectly check EGR flow. By activating the EGR valve there should be a notable drop in the manifold vacuum. If there is too much flow then the the valve is stuck open. If there is too little flow or no flow then something is wrong.
The EVAP system is checked for leaks and flow. There are literally hundreds of different ways to check this. The most commons is using a vent solenoid, purge solenoid and EVAP pressure sensor. The system is sealed with the vent solenoid. Then activating the purge solenoid (while the engine is running) will pull the system into a light vacuum. This vacuum is read my the pressure sensor. If the system is capable of achieving a vacuum means that purge flow is sufficient. Once a vacuum is achieved then the the purge solenoid stops. The system will then watch the rate of decay. If the rate of decay is slow then the system is good. If the decay is high then there is a hole of some sorts. If a vacuum can not be achieved at all then there is a huge hole or the purge solenoid is not working.
The fuel system is checked with the oxygen sensors. The oxygen sensors verify if too much too little or just the right amount of fuel is being added. This amount is reflected in the long term fuel trim numbers. If the numbers are around zero then everything is good. If the numbers are very negative (depends on vehicle but under -12% would do it) the system is running too rich. If the numbers are very positive (over 12%) the the system is too lean.
Similar to the EVAP system there are lots of ways to check the the catalytic converter. The catalytic converter has an oxygen sensor down stream of it. By comparing the upstream and down stream oxygen sensors the oxygen storage capability of the converter can be checked.
Comment: Thanks a lot. So, here is the thing. I want to calculate the amount of CO, NOx and HC emitted from a car. For a petrol car, I have the air fuel ratio as 14.7:1 roughly; I know MAF, hence I can get total exhaust. From [link](http://www.fixkick.com/sensors/O2%20sensor/AFR-GAS.JPG) I know the %CO, NOx, HC. Hence I can calculate the mass of CO, NOx and HC. The problem with diesel is - I don't know any such plot for CO, NOx and HC composition varying with air fuel ratio or equivalence ratio. I have no clue on how to proceed. The air-fuel ratio varies to a great extent in diesel engines.
Comment: @SoumyaSen That plot is misleading. It only applies to theoretical laboratory results. The dynamic combustion in a car is far more complex. For example; the car could be exactly at 14.7:1 and have a broken EGR valve. This will cause the amount of NOx to sky rocket compared to the plot. Also the plot does not account for the catalytic converter, which will clean up the exhaust before the tail pipe.
Comment: @SoumyaSen To truly calculate what is coming out you need a 5 gas analyser, preferably a portable one. Drive around recording the the MAF and recording the percent of gases in the exhaust. Just be aware that many 5 gas analysers can't tolerate diesel exhaust.
Comment: Thanks a lot @vini_i Can you suggest me a theoretical procedure to calculate the exhaust composition from a car using generic OBD data (not car specific data). If not exact, at least an estimated value.
Comment: I am curious to know how does the car make sure that the emission control systems are working fine? I mean, how are the sensors made to know that the emission coming out of the exhaust system is within limits? What is the formula behind them?
Comment: @SoumyaSen There is no formula. I expanded my answer to hopefully give you more incite.
Answer: If you manage to get the fuel consumption from the OBDII data, you can calculate the amount of CO2 emitted. (How to calculate petrol consumption (roghly) from OBDII data)
Since fossile fuel is a mixture of different hydrogencarbons, it is  inevitable that its combustion generates CO2. I found 2.32kg per liter petrol and 2.62kg per liter diesel, but this numbers may vary due to variations of the composition (e.g. additional ethanol) and temperature (volume expands with temperature). However, these values give a good hint.
All the other emissions inadvertent by-products. A tiny fraction of the fuel may not be burned completely, causing some CO and/or unburned carbon/fuel. Too much air causes CO, and since the oxygen starts to react with the nitrogen of the air, NOx. The amount of emissions depends on the motor design and load / environmental conditions. May be the manufacturer has a table of this, but you won't get it.
Also, the car doesn't measure them. For example, the actual VW emission scandal is about NOx and was discovered when testing a newly developed, mobile NOx measurement device. It wasn't possible to measure NOx while driving on the road before.
The lambda-sensor measures the amount of remaining oxygen in the exhaust gas, so the car can adjust the air/fuel ratio to make the combustion as perfect as possible, but it can't fully avoid nor measure this emissions.
Comment: Thanks a lot. So, here is the thing. I want to calculate the amount of CO, NOx and HC emitted from a car. For a petrol car, I have the air fuel ratio as 14.7:1 roughly; I know MAF, hence I can get total exhaust. From [link](http://www.fixkick.com/sensors/O2%20sensor/AFR-GAS.JPG) I know the %CO, NOx, HC. Hence I can calculate the mass of CO, NOx and HC. The problem with diesel is - I don't know any such plot for CO, NOx and HC composition varying with air fuel ratio or equivalence ratio. I have no clue on how to proceed. The air-fuel ratio varies to a great extent in diesel engines.
Comment: Well, you don't know for your petrol engine as well. That data of your link is valid for one car/engine. While the the effects are similar for other engines, the exact numbers are not. For example, todays engines are much cleaner that those from 50 years ago, and that's not only because of the catalytic converter. So, you can't apply this data set to any car. Of course, if you don't get enough data via OBDII, this is an extra problem. But even for a Diesel, if you don't know how much NOx a particular engine generates under a particular condition, you're lost.
Comment: Then how do one calculate CO, NOx, HC conc. from OBD data? Any method?
Comment: @sweber   Nice answer.

Formula to calculate emission rates


What species of Aloe is this?

Question: Please help me to identify this Aloe species. Unfortunately I have dropped the container and that's why the plant lost a few leaves and therefore, its symmetry.
Comment: I can't be sure from the picture, but does your plant grow its leaves in a circle/spiral or do they alternate opposite? If they alternate opposite (not in a circle or spiral), it's not Aloe vera/Aloe barbadensis.
Comment: I don't remember how the leaves were. Since then I gave it to somebody else and lost track of it. But thanks for the tip, it sure is useful for the next plants.
Answer: Possibly Aloe vera var. chinensis. There's a photo here: http://davesgarden.com/guides/pf/showimage/272091/#b
Comment: Thank you very much. I have used your answer to search more on the web and I found on wikipedia that Aloe vera var. chinensis looks somewhat similar to Aloe massawana, which is very interesting.
Answer: I think that the Aloe vera var. Chinensis is smaller leaved, and has white spots on the top of the leaves, and Aloe massawana has wider, and darker leaves, without spots.

What species of Aloe is this?


Finding all picture uploads by a certain user, to a Facebook group

Question: There's a lot of promising young artists posting in Facebook groups who don't have proper portfolios yet. And I need to hire an artist or three.
But first I need to do my homework! I have to check out enough of an artist's pictures to know that the one I loved is representative of their work, and not a fluke. Doing a basic group-search by username fails: Many of these groups get enough traffic, and more of these posters comment on other posts that searching on their name returns mostly other people's pictures.
For example: Search the group "Daily Spitpaint" for posts by "Tomislav Jagnjić" today, and it only pulls back one picture by him. I know that's wrong: I've found more posts in other groups linking back to Tomislav's pics pictures in the "Daily Spitpaint" group.
Which brings me back to the question: How do I find all picture uploads by a given user in a given group?
Answer: You can do this in Facebook Graph Search
"Posts in Daily Spitpaint by Tomislav Jagnjić"
https://www.facebook.com/search/1402563099961950/stories-in/1265362181/stories-by/intersect


Why do we have two of some organs, but not all?

Question: We have two eyes, but we don't have two hearts.
Why do humans have two of some organs, but not all?
Comment: I think the question is answerable, so long as OP doesn't want to know about EVERY organ!
Comment: Several processes come into play here, e.g. 1) functional redundancy, 2) evolutionary contingency, 3) energetic costs of redundant organs and 4) developmental constraints (related to evolutionary contingencies).
Comment: Also the fact that you can easily use some of the already developed genes .
Comment: We don't have that many double organs (https://en.wikipedia.org/wiki/List_of_organs_of_the_human_body): Most of musculoskeletal system. Digestive: salivary glands. Respiratory: bronchi/lungs. Urinary: kidneys&ureters. Reproductive: ovaries/testes + tubes. Endocrine: parathyroids (four even), adrenals. Circulatory: Mostly two for minor vessels, lymph nodes, bone marrow. Nervous system: Mostly two in PNS, two eyes & ears. Plus mammary glands. Everything else usually exists only once (though possibly symmetrical).
Comment: The body appears so symmetrical mainly due to the musculoskeletal system and a handful of large organs.
Answer: Here is my overly succinct answer.
I doubt we will ever know this for sure. But, it basically comes down to ancestral bilateral symmetry in development; this defaults to two organs and is broadly symmetrical except where the organs are central. See this article for a more thorough answer regarding bilateral symmetry.

Further exceptions to symmetry occur where evolution pressured the body into not bothering to grow the second of an organ due to a waste of resources for the body, or functional advantages emerged from asymmetrical evolution. I always like the ears of an owl for an excellent example of two asymmetrical features that provided a discrete advantage when it comes to locating the source of a sound.
Comment: @DavidBlomstrom The function reasoning doesn't explain how or why two organs are generally prevalent. Using function as an explanation for evolution is the wrong way around and arguably is retro-causation. You could say "symmetry resulted in two eyes and natural selection kept them for functional advantage" but not "We got two eyes for functional advantage and hence symmetry emerged."
Comment: The heart is centrally located in fish. And when you look at how the heart develops... it is symmetrical until it starts twisting upon itself and growing partitions in its middle.
Comment: How about octopuses? Octopuses have 3 hearts
Comment: @Pablo People dedicate their lives to studying the evolution & function of the octopus anatomy! You could ask a new question on some specific piece about that. Let's not forget that the OP is aiming to find out about why human anatomy seems to have one or two of each organ.
Comment: I didnt mean to make the question about octopuses. What I meant was, if humans have one heart because they only have duplication when the organs arent centrals, shouldnt octopuses have one heart also? The comment is meant to question if humans have only one heart because the heart is in the middle , considering that rule doesnt seem to work in other species
Comment: @Pablo The three hearts of the octopus is a bit more nuanced than you've made it out to be. It has one main heart and two auxiliary organs pumping blood to the gills. Why? I have no idea, but it doesn't seem to go against anything in the answer.
Answer: For some organs, the function is really dependent on having two: two eyes offer the possibility to appreciate distances, two ears to appreciate directionality of sound and to balance oneself.
Bilateral symmetry is both a good way to obtain these twinned organs, and may also be physically easier to obtain in the course of evolution (see the work by Vincent Fleury, University Paris Diderot, e.g. http://www.ncbi.nlm.nih.gov/pubmed/21784360). Perhaps this is mechanically quite advantageous to have symmetry for balance reasons. You'll note that the vehicles designed by the human are mostly symmetrical too.
This may explain why there are two lungs, e.g. Two brain hemispheres are justified with a symmetric body plan as many anatomical features are mapped directly in the brain geometry (see Fig 5.6 in http://www.bem.fi/book/05/05.htm, of course sensory and motor are in both hemisphere). But evolution has also been able to depart from this symmetrical plan when having twin organs would be more of a coordination nightmare: e.g., two hearts would make it difficult to have a sensible circulatory system (at least some dyssymetrisation would be needed so that they would direct the flow in the same direction! [no reference on that, you can draw a symmetric circuit with two pumps and see for yourself])
Comment: Edited. As the post covers a number of subject, it'd be good to know where the moderator feels more references are needed.
Comment: @DavidBlomstrom The function reasoning doesn't explain how or why two organs are generally prevalent. Using function as an explanation for evolution is the wrong way around and arguably is retro-causation. You could say "symmetry resulted in two eyes and natural selection kept them for functional advantage" but not "We got two eyes for functional advantage and hence symmetry emerged."


Sharepoint 2013 workflow implimentation

Question: Here i have an requirement that,
we have a different users based on the categories and for every users inquiries will be assigned. Here every day i want to send the mail to them that how many inquiries was assigned to him and how many are in pending by the end of before day. May be the user have more than 10 items. All those items should be send through an email. what was the best practice to do it
How can i implement this in the 2013 workflow.
Answer: Why not use a Task List for this; it has a built-in email that is sent to the 'Assigned To' person when the Task (or enquiry) is assigned to them.  Check this guide for assistance.
The users will have the email in their inbox as a reminder.  All tasks are visible on the Task List - if you set up a view to filter only on Tasks assigned to User A, they will see their own tasks.
Or if you want to customise a List then you might like to read this post for help on using Sharepoint designer to send emails.

Sharepoint 2013 workflow implimentation


Inequality for Character Degrees of finite groups

Question: Let $G$ be a finite group, and let $d_1,d_2,\dots,d_n$ be the dimensions of the irreducible representations. It is well-known that $\sum_{i=1}^n d_i^2=|G|$. If I am not mistaken, one has the following inequality
$$
\sum_{i=1}^n d_i^{3/2}\geq \sqrt{|G|}.
$$
Is this known or obvious (or false)? For abelian groups the inequality is far from sharp, because we can replace the right hand side with $|G|$. But for the symmetric group it seems pretty sharp. For example, for $S_6$, the left-hand side is 27.2688 and the right-hand side
is $26.8328$.
Comment: Hi Harm,
welkom bij mathoverflow :)
Did you check small examples, say, with GAP? GAP has lots of character tables stored (or it can compute them, too).
Comment: The character degrees of S_6 are {1, 5, 9, 5, 10, 16, 5, 10, 9, 5, 1}.  How do you get 27.2688?  I get 227.96.
Comment: it was a typo - see Harm's own answer below...
Answer: Never mind. The inequality that I wrote down is obvious, because
$$
(\sum_{i=1}^n d_i^{3/2})^2\geq \sum_{i=1}^n d_i^3\geq \sum_{i=1}^n d_i^2=|G|.
$$
I accidentally calculated $\sum_{i=1}^n \sqrt{d_i}$ on the left-hand side. So it might
be an interesting question whether
$$
\sum_{i=1}^n \sqrt{d}_i\geq \sqrt{|G|}.
$$
I'm pretty sure this fails for large symmetric groups, because the left-hand side
is less or equal than $p(n)|S_n|^{1/4}$ where $p(n)$ is the number of partitions.
$p(n)$ grows subexponentially, whereas $|S_n|$ grows superexponentially.
So we have $p(n)<|S_n|^{1/4}$ for large $n$. So the left-hand side will eventually be smaller than $\sqrt{|S_n|}$.
Comment: the 2nd displayed inequality already fails for $S_7$. One gets $55.1\geq 70$...
Answer: Let $G$ have $k$ conjugacy classes. Then Cauchy Schwarz seems to give
$\sum_{i=1}^{k} \sqrt{d_i} \leq \sqrt{k}\sqrt{\sum_{i=1}^{k} d_i }$
and this (using C-S) again is at most $k^{\frac{3}{4}} |G|^{\frac{1}{4}}$. So as long as $k^{3} < |G|,$ the inequality you state is violated. There are many groups $G$ for which $k^{3} < |G|.$ One example is the alternating group $A_{6}$ which has $7$ conjugacy classes and order $360 >7^{3}.$
Comment: I am not sure if the text of the question was changed, but this answer now seems tto give counterexamples to the question : "Is $\sum_{i=1}^{k} \sqrt{d_{i}} \geq \sqrt{|G|}$ " asked in the OPs own answer.


Why do similar phonological shifts occur in unrelated languages

Question: Some of the shifts are obvious such as palatalization, or any consonants with adjacent places and manners, but some other more radical changes are also observed in unrelated languages. For example, Spanish has the vowel breaking of o into ue as well as changing a typically palato-aveolar j into a velar j /x/. Compare that to the Mandarin example of 约 which is pronounced /jyɛ/ in Beijing Mandarin and /jɔ:/ in Sichuanese Mandarin, and 鞋 which is /ʃiɛ/ in Beijing Mandarin and /xai/ in Sichuanese Mandarin (which also resembles the Great Vowel Shift). Given that the chronology of Chinese pronunciation is quite a bit murkier than the Romance languages, maybe "shift" is not the right word to use, but these examples do exhibit a very similar pattern of phonological differences among related languages even with very radical changes. Is there any specific hypothesis as to how pronunciation is passed down and around that would give rise to these patterns across unrelated languages?
Comment: You may want to have a look at (1) Blevins, Juliette. 2004. Evolutionary phonology: The emergence of sound patterns. Cambridge University Press. and (2) Solé, Maria-Josep & Daniel Recasens (eds.). 2012. Initiation of sound change. Amsterdam Philadelphia: John Benjamins Publishing Company.
Comment: Just a notice, [x] is velar, not glottal.
Comment: I agree with @czypsu, although I think I've heard that the Spanish phoneme may also be a uvular fricative or a voiceless glottal fricative in some dialects.
Comment: This is a legitimate question, but your Chinese examples are not good. You need to compare the modern Chinese languages not with one another, but with reconstructed Old and Middle Chinese.
Answer: I assume you aren't just interested in the specific cases of Chinese and Mandarin. The primary reason for any sound shifts is that at some point in history, the actual pronunciation of a given sound becomes ambiguous, to the point that children learning the language can't really tell which sound was uttered. For example, in most dialects of American English, /t/ at the end of a syllable is produced "unreleased", so the only acoustic clue that "heat" ends with a /t/ is a pattern of formant transition. If you release the /t/, it is much clearer from the burst of /t/ that there is a final /t/; without the burst, it's hard to tell final /t/ apart from glottal stop. And some people actually pronounce final /t/ as a glottal stop -- they have started a historical shift in syllable-final position from t to ʔ.
Likewise, one of the most common sound shifts is from k to tʃ before from vowels. It's almost universal that the tongue has to advance a bit when making /k/ before a front vowel, and often we don't notice that little bit of fronting. But sometimes people do, and make that fronting a bit more exaggerated, which results in a palatal stop (IPA [c]). That [c] sounds a lot more like [tʃ] than it sounds like [k], even though [c] is articulatorily more like [k] than it is like [tʃ].
Mark Hale in Historical Linguistics: Theory and Method gives a good account of how sound changes originate from perceptual and analytical ambiguities in speech, which leads to sound changes. The reason why there are considerable similarities in sound changes across languages is that the articulatory and perceptual seeds of sound changes are consequences of anatomy, not grammar: grammar enters the picture when children across generations make different categorial decisions about how to interpret the facts of speech.
Comment: I remember reading a claim somewhere that most linguistic shift actually occurs in adults, not children. It's really a separate question, but do you know of any research on the matter?
Comment: @sumelic Indeed I've heard it's driven by young women, but don't know any sources for that.
Comment: @sumelic Look at Section 3.3 of Sóskuthy, Márton. 2013. Phonetic biases and systemic effects in the actuation of sound change: University of Edinburgh dissertation. and references therein.
Comment: I hear that children who make phonetic mistakes in their pronunciation of adult language forms will sometimes object when adults mimic their pronunciations.  They can tell that their own pronunciations are incorrect.  This suggests that your account of acquisition is not quite right, since children can know what adult pronunciations are like in advance of the time the children can produce them.  The difficulty is articulatory, rather than perceptual.
Answer: The shifts are due to phonological processes which are universal to humans. So the answer to your question is that these unrelated languages are all learned and spoken by humans -- that is the common denominator.
There are two phonological theories I know of that say this, more or less: David Stampe's theory of Natural Phonology (which I agree with, mostly), and the markedness theory proposed by Chomsky and Halle in chapter nine of The Sound Pattern of English (which is interesting, but wrong).  In the SPE theory, the universal part of human phonological systems is the set of markedness conventions, which interpret what happens when the pronunciations of a language lose their special traditional character, and the articulatory system is left to make the best of it, so to speak.
In Natural Phonology, one important source of historical sound change is imperfect acquisition of a language by children.  Children must learn not to apply those universal phonetic processes which are inconsistent with the traditional language they are trying to learn.  When they slip up, a process which the previous generation managed to learn not to apply, now comes to apply, and we observe a sound change.
Such sound changes are due to phonetic processes universal to human articulatory systems, so we expect the same sound changes to keep cropping up in languages, regardless of their genetic relationship.  And that's the way it happens.
Comment: Is this Stampe's theory published in his book or dissertation of some sort ? I put natural phonology in Google but could not find any specific publication, and I want to learn more about that.
Comment: @czypsu, I haven't found David's dissertation on line.  Here is a general article by him and his wife on the theory: http://www.ling.hawaii.edu/faculty/donegan/Papers/1979study.pdf.  Google gives a list of references: https://scholar.google.com/scholar?q=david+stampe+natural+phonology&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ved=0CBwQgQMwAGoVChMI5qrikZflxwIVhZWICh01-wnE
Comment: @czypsu Stampe's dissertation was published in 1979. You can easily find information about it by just googling they keywords you already know. The original dissertation had the absolutely hilarious title "How I spent my summer vacation". To me, Stampe's theory isn't all that different from SPE. I much prefer the framework that grew out of Ohala's work. See my papers on phonological unnaturalness and Old English vowel reduction as examples.


What was the formulation of the Bracha about Yerushalayim in the times of the Temple?

Question: In Shemona Esrei we pray that Hashem should return to Yerushalayim. Obviously while the Jews were in Yerushalayim during the time of the Bais Hamikdash this Bracha had to be different as it would not be sensible to pray that Yerushalyim should be built during the time of the first temple when it is in all its glory. In addition perhaps Shemona Esrei was first instituted after the end of the first Bais HaMikdash. Perhaps even during the times of the second Bais HaMikdash this Bracha was worded differently. Is there any source that describes the wording of this Bracha during the times of the Bais Hamikdash?
Comment: Possibly relevant - http://www.hakirah.org/Vol14Zelcer.pdf
Comment: Are you asking about the first or second temple? I don't think there was a shmone esrei during the first temple and it definitely wasn't in all its glory in the second temple.
Comment: @GershonGold, is there anyone who places the content of Shemona Esrei in the first temple period?
Comment: http://www.hebrewbooks.org/pagefeed/hebrewbooks_org_15022_328.pdf
Comment: I've got a better one: the third Berachah of Birkath HaMazon is about rebuilding Yerushalayim, and we say the first three are DeOraitha -- What??
Comment: @SethJ It's not about rebuilding yerushalayim. It's about yerushalayim.
Comment: @double רחם  ?ובנה?
Comment: @SethJ Well that is our current request about yerushalayim. Moshe obviously didn't write that.
Comment: @double aa, why "obviously"? Because he didn't possess רוח הקודש?
Comment: @SethJ lol!
Comment: http://www.rabbibrand.022.co.il/BRPortal/br/P102.jsp?arc=1907339
Answer: The Tur in the laws of Biract Hamazon (OC 188) writes that they would pray that Jerusalem and the Temple should remain standing. The same can probably be said about Shmona esrei.
Comment: No time to look it up right now; does he say *why* they said that? Does he address the fact that we say the first three Berachoth are DeOraitha?
Answer: Regarding the bracha of רצה, apparently they used to say somethign similar to the Nussach we say on YomTov before Duchening; ותערב
This, according to an article in one of the recent קולמוס magazines (a monthly addition to the weekly משפחה magazine.)
Comment: ותערב is the standard Eretz Yisrael nusach post Churban. I don't know why you would expect them to say it pre-churban as well.
Comment: @double aa, a friend with a mild-moderate obsession with Nusah has told me that he's seen compelling evidence that, throughout Ashkenazi Nusah, certain patterns present themselves and provide hints at what was once Nusah Eretz Yisrael, including ותערב. I am not the expert, but are you strongly convinced that some form of it couldn't have existed pre-destruction?


How do holding patterns work?

Question: How does a pilot follow a holding pattern? Do pilots have to manually change heading and altitude (through the autopilot) each time they are making a turn? Or is it something the Flight Management Computer (FMC) can handle?
Comment: You might need to improve your question. You added `air-traffic-control` tag in your question but the question body has nothing to do with ATC. Also "How do holding patterns work?" is a very broad title that will call for a variety of answers.
Answer: Generally speaking the Flight Management Computer supports holding patterns. The pilot inputs the holding fix (usually a NDB/VOR), the direction of the hold (Left/Right), the inbound course, and the time/distance that one holding leg shall take to execute. These information can be found on aeronautical charts, as IFR holding patterns are published for each airport. As far as I know pilots are also trained to fly holding patterns manually, but you can understand that flying the pattern manually is not as precise as flying the pattern via the autopilot.

How do holding patterns work?


How to turn off iedit-mode quickly after finishing an edit?

Question: I like how multiple-cursors is turned off when pressing RET, and this is not the case for iedit-mode, how can I emulate that behavior?
Answer: From future. Now it is
<code>(define-key iedit-mode-occurrence-keymap (kbd "RET") 'iedit-mode)
</code>
Answer: Define a key for the iedit-mode keyboard map, like this:
<code>(define-key iedit-mode-map (kbd "RET") 'iedit-mode)
</code>
So, when you start editing a piece of text with iedit-mode, you can turn it off by just pressing RET or any key you like.


Stop Google Talk from signing in

Question: I recently had to change the password of my primary account. Now Talk keeps trying to sign-in and fails. Having no way of changing the credentials used by talk without completely resetting my phone, I just want to completely disable it (I'm using a better messaging client). Do you thing I could fathom-out how to do this? Anyone know?
Answer: I believe you are still want to use the Google Play Store to grab some apps, are you?
If you disable Talk, the Play Store will not working properly (No auto updating, can't download any app...), so I recommend you use the method below:
Hit:
Setting > Application > Manage Application.
Navigate and click on Google Apps. Then click on "Clear Data" button. Press "OK" on the pop-up dialog. Then find Gmail and Talk under Manage Application, click "Clear Data" as well.
After you've done the above, please head to "Account & Sync Settings" and press your account, then press Menu > Sync Now
Then it should pop up for you to re-enter the password.
Comment: Hey, don't worry, that's the common difference between versions to versions. You can just try to clear data of Gmail and Gtalk. Or try if you can find GApp (or something similar to Google Apps)
Comment: Hi. Thanks. This sounds like the solution but I have no Google Apps listed when I go Settings>Applications>ManageApplications>All. Why would that be?
Comment: Cleared data for gmail and Talk; no game, Sign-on Fails with annoying regularity. I know this solution has worked for others maybe just not Android 2.3.5 on HTC Desire. Thanks for the help, going to bite the bullet and just reset the phone. I think Google should be ashamed of the poor quality of that release of Talk.

Stop Google Talk from signing in


Can I put 15 amp switches on 12 gauge wire

Question: We're finishing our basement and doing the electrical ourselves. We have a bathroom that we ran 20 amps to, 12 gauge wire, but we only have a few lights in there. The lights definitely won't be using any more than one amp, so I'm wondering, can I wire in a 15 amp switch for the lights?
Answer: Yes. As long as the switch is rated for the amperage of the load served and the voltage of the circuit. Your instance is an example of this (as long as the switches are rated for the voltage).
Here is the applicable 2011 NEC code reference:

404.14 Snap switches shall be used within their ratings and as indicated in 404.14(A) through (F).
(A) Alternating-Current General-Use Snap Switch. A form of general-use snap switch suitable only for use on ac circuits for controlling the following:
(1) Resistive and inductive loads not exceeding the ampere
rating of the switch at the voltage involved

Good luck!
Answer: Yes, you can use 15A switches on a 20A circuit provided the load being switched is 15A or less.


Gene expression: which allele is considered?

Question: For human beings, we have two copies of each gene inherited from the parents. The question is, when referring to gene expression, which copy (or allele) is considered?
Comment: Could you explain what you mean by "when referring to gene expression". Do you mean in general conversation, in anlysing the results of an RNAseq experiment, or are you asking whether expression occurs on both alleles? At the moment this is quite unclear. You need to edit your question to make it more precise what you are after.
Answer: Genome assemblies usually feature a haploid set of genes, unless particular effort is applied to assemble separately the homeologs. With that said, the gene copy you have in the assembly is usually one of the two, and usually the one you had more genomic reads for.
In terms of gene expression, if you measure it by RNASeq you will get reads from both and both of the read pools will map on the same gene. The ones that come directly from it will map with no mismatches (ideally) and the ones that come from the homeolog chromosome will map with a few mismatches (probably).
The expression of the "gene" will therefore be the expression of both genes, summed together. If we consider it as the same gene, though, it doesn't really make a difference if you sum them up or count them twice separately; unless we are talking about specific homeolog silencing like the Xist mechanism, in which it is important to remember that one copy of the two is off.


Loop doesn't work, always inputs the same condition

Question: I have a loop but always inputs the same condition, please see the picture.
Comment: What are you trying to accomplish with this program? What is the IR sensor measuring? What are you testing it with? As per @DavidLechner's answer, it will spend a lot of time inside the loop after the comparison block executing the actual turn, so any changes you are making should be long enough for the code to return back to the comparison block after completing the turn.
Comment: Likely the output of your IR sensor is always meeting the same condition (either higher than 50 or lower than 50). Try doing this again but instead display the measured value on the screen instead of doing a motor action, and see what values you are reading.
Comment: Yes always print the same values on the screen. So what is the problem?
Comment: What values does the sensor show?
Answer: You have the motor power set to 1 and you are waiting for 1 full rotation. If the motor moves at all, it will take a long time to complete one rotation. Most of the loop is spent waiting for the rotation to complete (or if the motor is not moving at all, then the loop never actually loops).
Try using a higher power - at least 10. Also, use less than one rotation, or use time (just a fraction of a second) instead for the duration of the motor block.


High quality resource for Exchanged Slav defense?

Question: I am preparing the Semi-Slav defense with David Vigorito-Play the Semi-Slav ( Quality Chess, 2008 ). The exchange line is covered well, but recently GMs try to steer clear from dull ...Bf5 lines and try ...e6 + ...Qb6 formation, leaving bishop on c8 and "suffering" for the extra pawn they get with ...Qxb2. This gives excellent chances to dodge the boring, drawish lines and to sharpen the game. Also, in the book there was an opening novelty Kramnik launched in a line I am very interested in. Since then theory must have advanced a lot in Exchange Slav, so I am asking if there is any modern high quality resource ( for players 2400+ ) that covers this line?
Comment: I'm not aware of anything for 2400's except for _Informants_.  http://www.chessinformant.rs/search.php?search_query=exchanged+slav&x=0&y=0
Answer: Let me preface this by saying that I have not kept up with new publications in about a year, but there was nothing that I knew of before that.
My educated guess is that the only real "modern high quality resource ( for players 2400+ ) that covers this line" is going to be GM games. Here are my reasons for that:
1) Vladimir Kramnik-the most influential figure in chess opening theory over the last 15 years-played a significant novelty in this line. This means that other players, from the top level down to lower GMs (which is about the lowest you can go and still have the games be considered part of Theory without further examination) have probably taken to copying him and extending the line. Even if you did find a comprehensive book published 8 months ago by some mid-level GM, there could well be some game between two 2600s from 2 months ago which changes the outcome of a variation. A prepared opponent will surely know about that and the book will not.
2) You are at a level where, since you already have a solid foundation in the line, you are probably better off looking at the games that a book would present to you and drawing your own conclusions. People like Vigorito who are about your strength and publish books are basically doing the exact same thing you could be doing-applying computer analysis to positions, recognizing the ideas, and memorizing/writing down the result. People that play for a living and create theory will be more concerned with protecting novelties and using them to win games (thereby giving them to you for free) than adding them to a book to see a tiny bump in circulation.
I am not saying that there are no groundbreaking books by top players. Avrukh's repertoire series for White was incredibly well-researched and included dozens of novelties. Victor Bologan has written 3 influential books on various lines. These books are rare, though, and a large majority of theoretically-relevant openings do not have resources of similar quality. You can construct better opening knowledge by doing your own research.
Comment: ChessBase recently came out with a really cool resource, www.chesslive.de. You can click through opening lines and search positions for games in their database. It's pretty much an online MegaBase. I use it when I'm at tournaments and I only have my small laptop so cannot access CB on my desktop.
Comment: Unfortunately I must agree with you at this moment. I do not use computers that much, so I do not know how to obtain *MegaBase* or any other similar software that could help me with this. Even if I could manage to get something like that, I would still need a tutorial on how to search for positions I need and so on... Well, I doubt there will be aby good solution popping out soon so I will accept this answer and upvote it. Thank you...
Answer: If you are into ebooks, there are a couple of books related to this on the Kindle store, one of them seems specifically dedicated to Exchange Slav:
http://www.amazon.com/s/ref=nb_sb_noss/189-5866976-1535411?url=search-alias%3Ddigital-text&field-keywords=slav+exchange
Comment: I have upvoted your answer. I need to stabilize financially in order to buy one of the ebooks ( this might take quite some time as I have problems finding a full-time job ). After I read it, I will decide whether to accept your answer officially or not. Thank you and best regards!


Should Muslim teenagers join sex education classes in public school?

Question: I'm 15 and this week my class is going to teach sex education: How to have sex and how to be safe (I guess they are going to show us how to do it too). Now I want to know: Should I join the class on that day or not?
Answer: Waalaikum asalaam.
"Say: Are they equal those who know, and those who do not know?" (39:9)
I would advise that you go to the class and seek appropriate information from your masjid/Sunday school about Islamic views of sex.
In sex education classes in secular schools, the emphasis is generally on basic anatomy (of men and women), sexually transmitted diseases/infections, and preventing pregnancy. They do not teach you "how to have sex". If you are fifteen-years-old, and you do not know the definition of sexual intercourse, how a woman becomes pregnant, or what a menstrual cycle is, I would advise you speak with your parent/s regarding this.
The information covered in the class on basic health is important information for every human being who has reached puberty in order to care for themselves and for others. When you attend the class, I advise you to have the correct intentions, namely to understand human biology for the sake of appreciating the marvels of the human body that Allah has created and to prepare you for marriage one day, inshaAllah.
In a masjid/Sunday School setting, you should have the opportunity to learn the other part of "sexual education", specifically the morality, emotional, and Islamic aspects related to marriage. If you are too embarrassed to seek knowledge about this from a person or are afraid someone might shame you, perhaps ask for a book recommendation on Islamic marriage.
I encourage you, as a fellow Muslim, to observe chastity and have sexual relations within the bounds of marriage only as commanded by Allah, and to have proper intentions when attending such classes. A side benefit of attending secular sex education classes in high school is that the knowledge you learn may very well encourage you to remain on the sirat al mustaqueem as you realize that even the "safest" sexual acts may still result in unwanted pregnancies and diseases.
Comment: I would like to add as a encouraging reference http://sunnah.com/tirmidhi/41/43
Answer: I think, you should. If teenagers don't learn basic sex education, maybe they will have problems in the future such as genital infections, unprotected sex acts. Basic sexual aspects must be learned at school only, not on Internet or with parents! Very good opinion about this problem i found there: https://ask.naij.com/education/should-sex-education-be-made-compulsory-in-schools-i23980.html - read 1st answer.
Answer: i think, go there, but: 1) do not look at images/views of naked humans, also generally do not look at women and girls at your school. 2) do not believe to information that is given in atheist lections and atheist books, if they do not have strong proofs. the information for school pupil probably does not have proofs with them. for example , they teach that sex without marriage is ok and that masturbation is ok and that using contraceptives (condoms etc) is ok. do not believe that.
(Use of physical contraception (Condoms etc) is permitted in Islam only in few cases).


What are the most common newbie recording mistakes?

Question: What are the most common mistakes that new engineers tend to make when recording and mixing down their tracks?
Comment: The [producer](http://en.wikipedia.org/wiki/Record_producer) or the [engineer](http://en.wikipedia.org/wiki/Audio_engineering)?
Comment: good point, I've clarified the question
Answer: In general, overdoing everything.
New people tend to add reverb, compression, and other effects just because they can.  Audio production is one area where quantity cannot replace quality.
Comment: I think this qoute by Antoine de Saint-Exupéry applies very well: "It seems that perfection is attained not when there is nothing more to add, but when there is nothing more to remove." (http://en.wikiquote.org/wiki/Antoine_de_Saint-Exupéry).  I find this to be true in programming, photography, audio production and just about all other creative processes I can think of.
Comment: @Rick Buchal exactly, but it's hard for a newbie to pick the few, but very effective things to do.  So maybe doing a little bit of everything is a way of trying to hedge the bet?  I've certainly been guilty of doing that in the past.  I try to A/B every adjustment and effect I add now to see if I really think it makes a difference or not, but it's hard to be objective about something that ultimately is very subjective :-)
Comment: New people are not the only ones that suffer from this.
Comment: +1 I think there's a tendency to think that if you're not doing a lot of different and/or complicated stuff, you're less of a professional somehow. In reality, the opposite is true (to a point).
Comment: The key is to find your own unique style. Kitchen sink approach is not terribly unique, and often sounds rather terrible.
Comment: I suspect trying stuff cane make learning faster even if the result is worse. Furthermore, people with less trained ears need to add more in order to realise they added something. Not sure if this makes sense
Answer: Pressing "stop" before the reverb trail has died out from the last note of the performance.  Or worse, before the actual last note of the performance that he didn't know was there.
(I've done this)
Comment: In live situations, I always leave the recording running 2 minutes of empty hall after the concert. You never know when it comes in handy.
Comment: That strikes me as a pretty good idea actually.  I'm going to try that next time.
Comment: I do it before, after the sound check, or right before the doors open. Afterwards you will have the normal standbyers and the restless roadies packing up to go home. Also, you might have the DJ act coming up (pretty common in clubs and raves, festivals etc.)
Answer: A big mistake is to stop using your ears. Always keep listening to what you create!
I've seen so many people do this, they just do things because they think they are always good things. I know somebody that always used compression because he was told to do so, even when it was completely unnecessary. When I asked him why, he just said: "I just always do this." He was clearly told by somebody else that it could (could!) be useful.
If you listen once, you decide that you need for instance a compressor and you applied it with settings that you think are appropriate, don't consider the job done. Use your ears and ask yourself if you are genuinly happy with the result.
If you record speech, don't apply an EQ to increase 3KHz and 8KHz to improve the intelligibility if you don't have a real problem with it, or if you don't hear any improvements.
Never do anything to your sound if the reason for it is not coming from your ears. Always tend to trusting your ears more than anything you learned.
Comment: Another way to put it is "Always understand exactly what you're doing and why." See also: [cargo cult](http://en.wikipedia.org/wiki/Cargo_cult#Metaphorical_uses_of_the_term).
Answer: Not taking enough time to set up & test things out.  Chances are, you won't actually be able to fix it in the mix.
Comment: I'd recommend this practice to anyone just starting, I usually use the phrase "Crap in, crap out." Meaning that if you record a bad signal, there's no way you can make it sound better by processing it.
Comment: Mic choice and placement, room treatment, mic cancellation and thinking you can fix it in the mix... But everyone seems to have to learn the hard way. Also: Don't master yourself, but let someone else (who you trust) finalize it.
Answer: Perfection is the enemy of progress.  Don't spend an eternity on your first song just to realize that you don't have the time to finish the rest.
Also, for beginners it is best to finish each song before moving onto the next. This way you don't spend days recording and have nothing to show for it.
Comment: I always give a monitor mix in the studio, regardless of the session. When I know ahead of time that instruments will be recorded separately I'll still get the whole band to play. Usually in line mixers give you a really easy, painstacking workflow that allows you to do this without even thinking. For instance, on an inline console (SSL, NEVE, Harrison, etc) I'm always in Fader swap for the monitor path unless I'm bouncing (using groups). That way i can give the band a complete rough mix on the very first day of recording, and all the following.
Answer: When recording:

Not experimenting enough (or at all) with different mics and with mic placement.  (Try the kick drum mic on the back head; try different spots on a guitar cabinet, at different distances; etc)
Having an open channel but not recording a direct in feed of the guitar.  This can really save you if it turns out the amp distortion that sounded great on its own is abrasive or doesn't work in the mix.
Bass guitar.  Good luck.  Experiment a lot on this to find out what works, direct-in is always a good idea no matter how you try to mic it.
Really novice mistake that I made for years: using a little XLR to 1/4" adapter to run mics into a four-track tape machine, with no preamps.  It worked, but everything sounded bad, buzzy, with weird high-pitched artifacts, etc etc.

When mixing:

Too much EQ addition: try subtractive EQ-ing first.
Too much volume: leave headroom so you have room to work with at the end of the mix for effects and mastering.
Not being aware of the limitations of your mixing environment.  It's really hard to mix only in headphones and get a great mix, but it's also hard to properly align studio monitors and to acoustically treat a room.  At least be aware of the limitations of your setup - "My headphones do X to the sound, but my monitor setup does Y to the sound."  In a typical basement setup, your monitors and the room probably give you tons more bass than is actually in the mix - just be aware and check on different speakers, rooms, and headphones!
Comment: "It's really hard to mix only in headphones and get a great mix, but it's also hard to properly align studio monitors and to acoustically treat a room." so VERY, VERY true!!!!
Answer: 5 ways a newbie can be more professional:
1) Don't mess with the levels while the recording is in process as this changes the signal to noise ratio enough to make the track sound wonky.
Set your levels before you punch the record button, I generally run as many takes as needed to set the peak load.
2) Don't expect everything is in tune.
Make double sure that every instrument is tuned appropriately for the piece. I say 'appropriately' as some instruments may require a slight nuance differing from standard pitch. For example piano tunings have a wide range of deviation, compare a 'honky-tonk' piano to a concert grand.
3) Don't try to cram everyone into one track (assuming you have a multi-track system).
Be careful when you are recording multiple tracks simultaneously, assign as many channels as you need to give each voice it's own track. This will make mixing a lot easier.
4) Don't assume it will all 'fall together'.
You have to have a plan. Make a list of tracks, how they will be recorded, what effects might be employed during recording or later. In short, spell everything out before you start. Consider this your script.
5) Don't think you can remember all the details.
Make good documentation from session to mixing to master. Document what voice is on each track: guitar, violin, chorus, soprano, tenor, etc. Document anything special like "Hey that sax solo on track 2 needs to be redone because the sax needs a new reed".
Answer:
Not to experiment
Thinking of the job as if there are mistakes to be made, whereas actually its an art form, and its only a matter of taste whether you like this or that (the extraordinary range of audiences and styles of recordings is the proof for this).
Not to get drunk after an impressive nights perfomance with a band, losing all the files in the morning, recovering them, and coming up with a creative solutions to fix everything.
Not to go ahead and give all those silly effects a try, then get enough of all of them and know that quality lies in the story.
Being too much insecure about yourself
Spending time reading these posts, while meanwhile you could be enjoying a smokey, jazzy environment filled with rich sounds, that you feel you want to record!
Comment: Being too inscecure about yourself is a very important thing, but I respectfully disagree with most of the rest of these items. Recording is - in my opinion - although very art-related and a very creative process - definitely a craft rather than an art, where a matter of quality is definitely present and should be taken into account. Remember we are talking professional audio. Of course you should both spend time here as well as in your musical environment, these are both places of good inspiration.
Comment: On second thought, Pelle, you are right! But i thought there is no lack of the perfectionism-driven folks over here anyway, so i wanted to make a point not to forget about the artistic side of the craft.
Answer: Not listening to the master candidate through a variety of speakers (headphones, car stereo, iPod earbuds, etc).  Simply using the studio monitors isn't enough.
Comment: I respectfully disagree (probably due to terminology here): during the mixing stage, one should only listen to his studio monitors (and incidentally a pair of good headphones to get a better idea of reverberation, acoustics and noise, but really not to get an impression of the mix); doing otherwise is something I consider a mistake myself. The task of making it sound well on other speaker systems should not be taken care of during mixing, but during mastering. (i.e. after the mixing is done.) And during mastering, the mix should not be changed to solve these issues.
Comment: @PelletenCate ahh I did not check the edits but that makes sense. I always listen to my "master candidates" after doing all mixing in my car, some ear buds, my old WESC headphones, my dads old big ass headphones from the 80s, and my Sennheiser HD 380 Pros. I also use the Sennheisers while mixing just for perspective, but I can tell a difference when listening to them through my audio interface and just into an aux jack.
Comment: @Pelle Totally agree! Great insight. Thanks for the feedback. I've clarified the terminology (from "mix" -> "master candidate").
Comment: @PelletenCate why would you not do otherwise? What if you listen to it in your car and the bass is terribly overpowering and you had no idea because you only listened to the song on the studio monitors? I almost made this mistake with one of my songs a week or two ago. Luckily I always listen to my tunes to see what I can improve upon on my way to work and noticed how terribly overpowering the bass was during a certain part. If you actually read his answer, you would see he says the **master candidate**, not during the fact, but after.
Comment: @TravisDtfsuCrum Did you read Andrew's comment and have a look at the history of this answer? You'll see that Andrew changed "mix" to 'master candidate' after I wrote my comment. Don't get me wrong, I totally agree that you should listen to your song at all available systems, but not during the mixing stage. (Which was the stretch of what the initial answer was.) My point was just that you should not do this while mixing, because in general (and there are always exceptions) the mixing desk is wrong place to fix sound/balance issues caught on your car speakers.
Answer: Being too stressed when things are getting slightly complicated or something doesn't work. Musicians are generally nice people (really, this is something many people forget as soon as they get behind a mixing desk!), and they allow you to claim all the time you need. As soon as you feel any time pressure during your recording session, your focus on the quality of the music and the way it sounds is decreasing. My advice in such a situation: ask your musicians to leave the studio for half an hour or so, so you can sort things out. Remember that recording and producing should be fun to do, as long as you love the music. :)
Secondly: don't be too hard on yourself. Mistakes happen all the time, and the best thing you can do is learn from them, by making them.
Answer: Failing to save your work frequently, or worse, failing to backup your work frequently (or at all).
Don't just rely on your recording software's Undo capabilities - always enable Auto-Save if it has that feature. Additionally, setup your digital workstation to automatically save a copy of your work every 15 or 30 minutes, and also save off a snapshot of the entire project including all audio files at the end of every day. Use an online backup service or flash drive. You never know when your recording software is going to hang or crash, or when the HD is going to die.
Losing a few hours worth of work is extremely frustrating, but losing an entire album is devastating.
Comment: When I'm recording, the autobackup is on 5 minutes, so as not to weigh on the hard drive. When Im editing, its every 2 minutes. And i do a save copy in at every milestone (finished comping - save; finished editing - save; downmixed - saved; Created a satellite session - save etc)
Comment: @AntonStrogonoff Yeah, that's one of the worst feelings. When something similar happened to me, I immediately wrote down as much as I could remember on paper. Then took a week off before attempting to redo it.
Comment: I've lost a few hours of work in Logic a few days ago… So I concur—if you're working with software, save often. It could be hard to bring yourself to continue working on the track for some time—I liked very much how it sounded before the crash, and am afraid I won't be able to do it better or even keep on the same level. That's probably irrational or indicates insufficient skill, though, but anyway.
Answer: Sometimes it helps to walk away from the studio for a while, and listen to something else. That'll keep your ears fresh. Or you can ask someone who hasn't been involved with the project to listen to the mix.
Answer: Not doing enough preproduction.
Preproduction is what you do before you sit down in a session. This includes talking with the band, making sure they know what they plan to do. Get lyrics sheets, chord charts, tempo and key of the song, etc. The more you know about the song, the better you can figure out exactly which mics and techniques you want to use. Maybe you can borrow something that you wouldn't be able to if you found out what they were playing when you got to the session.
For professional engineers, preproduction also includes finding out how the band plans to pay you for the session. For some reason, there are people out there who seem to think that you will be happy to record them for free. If you don't plan on working for free, make sure they understand that, because it's alot easier to tell someone no before you start recording than it is after you're done mixing and they want the masters.
Answer: Sticking to what you know versus experimenting in new methods in music
Often times I find myself working in the same chords and instruments because I am comfortable with them. Don't be afraid to try new things. You may be surprised at what other stuff is out there!
Answer: I think too that it is important to separate recording and mixing issues.
About recording, I have one rule I think about all the time : to avoid to postpone decision making. It was not a problem some decades ago by design, when everything is done with hardware, but it is nowadays because you can edit anything with modern DAWs, and so you can procrastinate about making good mic placements, good takes, making the band play right etc. For me, good practices in recording are about doing something right once, without even thinking about fixing it later, if possible of course. It's twice more important for someone who uses his computer to record his own music.
About mixing, I think Mike Senior from Sound on Sound has given very good advice in this article :
http://www.soundonsound.com/sos/sep11/articles/mix-mistakes.htm
Answer: Not Leaving Headroom
Unless you are pushing to analog tape, you don't need to pin the meters just below the redline. Processing through plug ins will add amplitude, so you need to leave room. The best practice of pushing levels is antiquated in this world of virtual instruments and very quiet mixers.
Answer: Not using a proper audio interface (uses build-in sound adapter)
A build-in/on-board sound adapter or sound card is not made for professional audio recording. Typically it is very noisy, does not support balanced signals,  cannot provide phantom power and records in too low quality.
Not recording in 24bit!
So you got the nice external audio interface with the right inputs and all, but you forgot to set up the recording format and start recording in 16 bit. You did however read the advice on leaving headroom so the signal comes in on the low side. "No problem" you think and turn it up afterwards - HISSSSSSSS! Ouch everything is so noisy now. Always record in 24 bit or higher. Always.
Ignoring technical issues
Be it noise, clipping, lag, out-of-sync, mechanical/electrical issues with instruments, bad monitoring/headphone mixes, bad buffer settings, clicks and pops, mobile phones, fridges, CRT screens near pickups, unbalanced cables near transformators etc.
Fix it, and like suggested elsewhere don't let the band stress you out.
Not getting a proper mastering done
No, that squashed L2 limiter on the master bus, or Ozone factory preset with 27-step-fx-chain will not do it. Don't get tricked by the immediate but not long lasting refreshing new and "improved" sound. Mastering is 99% about doing relative corrective adjustments to a mix and 1% about doing generally applicable tweaks like what you get from "presets".
Thinking that the mastering will fix a bad mix
True, the mastering is likely to improve the overall intelligibility and make the mix compatible with many different listening and/or reproduction scenarios. It is however not meant to be a creative and/or healing step that fixes that annoying resonance on the snare or adds ambience and other fluffy things to it all.
Make sure your mix exports has all the qualities you and the band wants, and let the mastering take care of the corrections needed to make the mix sound good in general, not just on your setup (with your ears listening).


Why is Internet Explorer version dependent on the OS?

Question: Why are XP users stuck with IE8? It seems like such a weird tight-coupling. Almost all other applications seem to work perfectly fine with XP, Vista, 7 and 8. I don't really see why this specifically would need such a dependency.
Answer: Because that's a choice Microsoft has made.
Really. It's as simple as that. They have coupled the web browser very tightly to the operating system, and thus replacing it means replacing large chunks of the OS. Even if the differences themselves were to be relatively small, it'd still be differences and those need to be supported (coded, debugged, documented, tested, maintained, ...).
Note that this isn't even the same problem as removing the browser entirely; it's highly likely that for the type of integration done between Windows and MSIE, the APIs are quite different between versions of MSIE.
And of course, extended support for Windows XP non-Embedded ended in April 2014. So by now they have even less of a reason to support anything Windows XP.


Why does salt and seasoning stick better to hot foods?

Question: In every recipe I see for fries, popcorn, churros, and other foods where I normally want to add the salt/sugar/seasoning at the end, everybody says to make sure to do it while the food is still hot so the seasoning sticks. Why is this? Is this just something people say, or does it really matter a lot?
Answer: It's really not about temperature at all.
"While it's still hot" is a great description of when to do it, but it's not why.
You want to salt fried food when it's straight from the oil, because the surface is still wet with oil. This ensures that the salt sticks to the surface of the food. As the food sits, the surface will dry (it cools off at the same time-- which is where the "while it's hot" advice comes from).
Even with non-fried foods, heat often comes with surface moisture, either from the cooking process or from the steam being released by the hot food.
Salt sticks to "wet" surfaces. Freshly cooked, still-hot food usually has a "wet" surface (either from water, steam, or oil).
Comment: Ah I see! Thank you very much! Foods absorb moisture and oil as they cool, right? I've heard that quite often too, but again I don't know if that's true (i.e. if the lower temperature results in some change in the chemistry to make foods more prone to absorbing or if the time is just correlated with drop in temperature and absorption). If it is, I suppose that would be an indirect reason why. Thanks for the answer!
Comment: The mechanism I've heard for this effect is that as the food cools, you get a lower partial pressure of steam from the interior, and so you get a very slight suction effect, which helps the small particles of salt and seasoning adhere to the surface.


How can I comment code with a command in Vim

Question: In various editors one can mark a block of code and with a shortcut, comment it right away. Is there a possible way to do it in Vim without an extra plugin? If not, which plugin or script would you suggest?
Answer: The best way that I found is using tpope's vim-commentary plugin. You're able to use the ctrl+v I# mentioned in the question linked to in the comment to the OP, but this will automatically work with different comment types with different languages.
Answer: From my answer over here:

I use scrooloose/nerdcommenter for this.
With this plugin you can visual select your lines and hit
leader+c to toggle comments. Depending on the
file type it will use different symbols for commenting.


Does a run count if it's made on the same play as the 3rd out?

Question: Under what conditions can a run be scored on a play that results in a 3rd out for the team?  I was under the impression that if a 3rd out happens, all runs that might have scored before time during that at-bat are invalid, but apparently there is more to it than that.
Answer: If the 3rd out is the result of a force-out (example: bases loaded, batter hits to the third baseman, third baseman steps on third base before runner reaches), then the run from third base will not count.
If the 3rd out is the result of gunning for extra bases (example: bases loaded, batter hits past third baseman, batter reaches first and goes for second, left fielder throws to second baseman who tags out the batter before he reaches 2nd base), then any run scored (given the runner has reached home before the batter was tagged out) will count as the batter reached first base.
If the 3rd out is the result of tagging up (example: runner on 1st and 3rd, batter hits sacrifice fly, outfielder catches the ball for the out, runner on 3rd reaches home, runner on 1st goes for 2nd but gets tagged out), then the run from 3rd base will count because the out at 2nd was not a force-out only if the runner from 3rd base touches home plate before the out at 2nd is made.

Rule 4.09 of MLB's Official Baseball Rules of 2012 states:

4.09 HOW A TEAM SCORES.
(a) One run shall be scored each time a runner legally advances to and touches first, second, third and home base
before three men are put out to end the inning.
EXCEPTION: A run is not scored if the runner advances to home base during a play in which the third out is made.
(1) by the batter-runner before he touches first base;
(2) by any runner being forced out; or
(3) by a preceding runner who is declared out because he failed to touch one of the bases.
Answer: Basically the run is recorded only if all the runners were "safe" initially. That is, a batter made it to first base (safe) while the runner on third came home, then the batter was tagged out trying for second base.
Or a fly ball was recorded for the second out. All baserunners (not counting the hitter) were safe initially. The third base runner tagged up and came home. A first base runner tagged up and was tagged out at second.
The last out must have been through a voluntary play of the runner, not a forced out.
Answer: A simple way to think about this is to consider a "Force out" to mean the batter did not reach first base safely (and note, a force out in your batting average counts as an out).  Then this is simple: runs may score if

The batter reaches first base safely
There are not three outs at the moment the run scores.

In order for a batter to reach first base safely, though, all other runners must advance to the next base as well.  Why?  If they don't reach the next base, they would have to retreat to the base they were on - at which point the batter would be called out (when two players occupy a base simultaneously, the trailing runner is ruled out). So a force out is really a way of extending this concept.
Comment: http://sports.stackexchange.com/questions/8497/is-a-base-runner-out-if-he-back-pedals-to-first-base-to-avoid-a-tag-in-a-double?rq=1 seems to be an exception.  Runners at first and third, one out.  Batter-runner is forced out at first, runner from third touches home, then runner from first is tagged out.  By my reading, the run counts even though the batter did not reach first.
Comment: @NateEldredge The third out was not a force, there.  The point of my first sentence is that you can translate *force outs* to batter/runner reaching first safely; once that's off the table, then it doesn't matter.


Where do I add the cartThrob License Code?

Question: I may be dense, but I do not see where to add the license number. In the installation instructions it says in the "Global section", I can't find this section. Besides that installation was very simple. a route to the global section or any other hint as to where to add the license key would be helpful. thanks!
Answer: It's possible the CartThrob developers removed the field for the license number and have not updated their docs. It is not required that you add the license number and the Module will not stop working if it's not there.
Answer: Assuming nothing has changed with recent versions of Cartthrob, and Cartthrob has been properly installed you should go to Add-Ons->Modules->Cartthrob, then you should see a place to enter the licence number. (under the Global tab).
You may also have  shortcut to go directly to the Cartthrob settings page in your Control Panel menu bar.


How long is a pony year/season?

Question: As we see in the MLP universe the ponies themselves have control over when seasons change (via Winter Wrap Up, Fall Run, etc) so there is no natural reason for seasons to change. Is there any indication that a pony year progresses in the same way that our year does? Could you artificially speed up seasons?
Comment: Maybe the seasons change at the speed of plot? IIRC Winter Wrap-up _was_ going on in the background this season, so at least it's fairly regular.
Comment: One will still want to go through the seasons in order for agriculture purposes, the way crops grow, die and drop nutrients in the soil for the next year on seasonal triggers is very important in the ecosystem.
Comment: No, at least not without several hundred years of famine 'till the crops have evolved enough to counter the environmental change.
Comment: @ewanm89 true but if the growth of crops etc is tied to the seasons, one might reason that they would grow faster if seasons were artificially accelerated.
Answer: One of two things is likely. Either seasons are made to progress at roughly the same rate as they do on Earth, or they run at a faster than usual rate. Arguably the latter is more true, given the short amount of time between Winter Wrap-Up (clearing out the snow and most clouds, waking up hibernating animals, managing bird migration, etc.) and the Running of the Leaves (marathon race with the purpose of shaking leaves off of autumn trees).
The above is a bit of conjecture though, since the topic of seasons is really not mentioned much aside from in the episodes Winter Wrap-Up and Fall Weather Friends.

How long is a pony year/season?


Nervous system: Pain and Pleasure?

Question: If you have a constant pain in your body, why does a greater pain or pleasure make you not feel the original pain?
Comment: This question is way too generic as it stands. I suggest asking about a specific situation as an example.
Answer: I'm not sure if why is referring to the biological basis or the reasoning for why it is beneficial but I've briefly summarised both. If you'd like more detail just accept and ask again clarifying your exact interest in this broad question.
Pain is taken up through the spinothalamic pathway but at may opportunities it may be blocked. It may be blocked by other ascending pathways or by descending pathways. There are a number of structures involved in this including endorphins and Interneurones which are part of the gate control theory of pain. Basically ascending sensory information is blocked when other sensory information is more acute or more pertinent. This is important for survival e.g. when feeling a lion it is important not to feel pain. That same endorphin pathway is highjacked by drugs such as morphine.

Nervous system: Pain and Pleasure?


Does drag produce heat?

Question: When a solid object moves through a fluid drag is produced. Does this drag produce heat?
I believe drag should produce heat as it is the friction between fluid and surface of object. Is this true or not?
Comment: yeah! it is true
Answer: Actually drag is NOT completely the friction between the object and fluid. Sometimes there can be almost no friction, but still highly significant drag. In a non viscous fluid, there is no friction between the object and the fluid, but there IS still drag. The phenomenon of ram pressure transfers momentum losslessly between the object and the fluid without any friction. I discuss these ideas more fully in my answer to the question "Where does the energy from a parachute go?".
In a low viscosity fluid, the energised fluid will slowly heat owing to friction with itself, not with the dragged body.
So yes, ultimately all the energy transferred to the fluid from the dragged body will wind up as heat, as it must from the first law of thermodynamics, but this is often not through direct friction.
In blunt ended spacecraft atmosphere re-entry, the effect is even more dramatic. The blunt end squashes the air, which cannot get out of the way and the air's temperature rises adiabatically just as a bike pump gets hotter if you hold your finger over the output hole and squash the plunger in suddenly. Very little friction is involved and, as long as the spacecraft can withstand the adiabatic temperature rise, it rides on a cushion of air which thrusts the atmosphere further from the aircraft out of the way. The drag is ram pressure, and the frictional heat (which would be extremely dangerous) is only generate by the fluid dragging on itself through viscous shear, at a good safe distance from the spacecraft. See the links in my other answer for my answer to the question "Where does the energy from a parachute go?".
Answer: The first law of thermodynamics states, that $E_{int}=W+Q$.
Meaning, any work done by (or on) an object results in changing its internal energy (temperature). If, of course, $Q$ doesn't balance it out (this is when $Q=-W$). You need to have a well insulated object (when $Q=0$) and you'll definitely know, that work will result in temperature change.

Does drag produce heat?


How does a molecule find the lowest energy state?

Question: I understand that in a crystal lattice the molecule will tend towards the structure that is the lowest in energy (fcc, hcp, ccp, etc.). How does the molecule find these lowest energy states? Is it possible for a molecule to be caught in a local minima?
Comment: (It is 4, not 6 nearest neighbors, but that's irrelevant.) Because the global minimum is graphite, we know that for sure.
Comment: No, it's 4, and they are not around the sides. A complete explanation would deserve a separate question on your part; then again, it has been asked and answered multiple times before. Carbon doesn't form molecules (except fullerenes), it's a covalent crystal. Yes, diamond is metastable at normal conditions and graphite is stable.
Comment: Yes, local minima are totally possible. It happens all the time. Ever seen a diamond? That's an example.
Comment: @IvanNeretin Could you explain why a diamond is an example of a local minima? Wouldn't all of the carbons want to be as far away as possible, forming a cubic lattice where each carbon has only major interations with its 6 nearest neighbors?
Comment: Isn't it 6 nearest neighbors in diamond? Because you have the four around the sides and then the two above and below? So you're saying that a pure carbon molecule is metastable at diamond and stable at graphite?
Answer: The answer is it doesn't. The molecule transfers from state to state, whenever it can get over the excitation energy barrier between them.
Once it lands in the lowest energy state (or a relatively low one), it just has a hard time getting out again. And if the lowest energy state is on the surface of a crystal, the hole gets deeper and the walls get higher the more other molecules (or atoms) arrange themselves around it.
If the arrangement (the crystal lattice) only represents a local minimum, that's likely still quite (=meta)stable. Actually those metastable states tend to be created with a high probablility, see https://en.wikipedia.org/wiki/Polymorphism_(materials_science)#Ostwald's_rule


How long does a payment take to appear in my wallet, If not how do I reacieave it?

Question: Yes how long does it take for a payment to appear in my wallet, on Bitcore, if it doesnt how do I reacieve it? Because it's been 15 hours but still havent seen it
Comment: Bitcore, or bitcoin core? Is your wallet fully synchronized? Do you have a transaction ID?
Answer: Most wallets will show you incoming/outgoing transactions as soon as they appear on the network. If you are not seeing a transaction, it is possible that your node (if you're using Bitcoin Core or a similar full client) is not fully synced yet, or that the node your light wallet connects to isn't fully synced. You can fix this by either waiting for your node to sync, or connecting to one that is synced.
During times when the mempool is full, nodes might drop transactions with low fees depending on how large their mempool is. At the time of writing, the mempool is quite empty, so this should not affect you.
If you are using a hosted wallet such as blockchain.info or an exchange, their systems may have not been able to detect your transaction, and you should reach out to their customer service.
You can also ask the sender for the tx id and use a block explorer to verify that the transaction has been confirmed successfully.
Answer: If you are using node wallet then you dont need to worry about your coins as the pvt key is with you,using which you can get your coins back. Generally it wont take more than the blockformation time  which is 10min(approx) if your node of fully synchronised with bitcoin blockchain else you might have to wait till your node is sync.
You can keep trace of your transaction here.


Not allow attachments in groups

Question: I  am the owner of a Google group. I want to not allow attachments sent when people use the reply to all option or send to the group using the email address @googlegroups.com but not working?
Answer: So you have the 'Attach Files' permission disabled for normal members in Permissions / Posting permissions?
Of course, if you only want them not to be able add attachments when posting by email, but still want them to be able to do that when posting using the group web interface - then that's just not possible.

Not allow attachments in groups


Casual chess meet up in London UK

Question: I'm a (predominantly) online chess player.  My rating is roughly FIDE 1800-1900. I'm travelling to the UK next week for work.
Is there a place or club or cafe in the inner or outer London area where I can go and find like-minded strangers for a friendly casual game?
Answer: I was in London two weeks ago, and attended a causal chess club in the central London.
http://casualchess.org/
It was a quiet pub, and the environment was good. What made it special was that it had a number of woman chess players. I tested my skills against those females.
As a FIDE 1800-1900 player, you will find yourself beating everybody there.
Answer: There are lots of clubs in London, googling "chess clubs in London" brings up Hammersmith, Battersea, Greater London, Metropolitan and Hackney for starters.
I don't play in London myself, save for tournaments, but I have heard of the last one (Hackney) and looking at their web page they do seem to have quite a lot going on:
http://hackneychess.org.uk/
Comment: Try [Battersea Chess Club London](https://www.batterseachessclub.org.uk/) too
Comment: "the oldest continually-existing chess club in London. " sounds like a good bet
Answer: 120 years ago the place to go and play chess in London was Simpsons in the Strand where you could drink, play and eat. Today that honour belongs to the Plough pub next to the British Museum which is where the Drunken Knights chess club play.
Their facebook page is here.
Their London League details are here.
Note that during the World Championships Simon Williams, the ginger GM, will be doing commentary from here. There will also be blitz and other events. More details here.
Comment: looks like an amazing club to join!  If only I lived in London still
Answer: just posted: blog article answering this very question
https://www.chessable.com/blog/2018/10/05/play-chess-in-london/

Casual chess meet up in London UK


Water and explosive volcanoes in the Pacific ring of fire

Question: Most volcanoes in the Pacific Ring of Fire have an explosive nature. This is due to high concentrations of water in their magma. Obviously, this magma comes from several kilometres below the earth's crust. How is it possible for magma to contain water at such depths?
Answer:
How is it possible for magma to contain water at such depths?

This can happen precisely because the magma is at such depths. Think of CO2 in soda or coke. When the drink is closed and pressurised, the CO2 is dissolved in the liquid. This means it's part of one physical phase. There is one "thing" that contains the liquid and the CO2 together: the CO2 is not a gas! Only when you open  the bottle, the CO2 can escape being dissolved in the liquid, and separates from the liquid as a distinct gas phase.
The same thing happens in magmas. While the magmas are pressurised at depths they have water dissolved in them. Note that this water is not separate liquid water or vapour flowing around the magma. It is inside the magma in one physical entity. Think of dissolving salt in water - you can't see salt grains but it's there. Anyway, once the magma rises it loses pressure. This causes the water to separate out from the magma into a distinct vapour phase that rises and expands rapidly, causing the explosive eruption.
Answer: Brief answer (on tablet)
When an oceanic plate is formed, the crust is hydrated by the hydrothermal vents systems at the ocean ridge where it forms (hydrated means that the minerals are altered to include water in their structure). When this crust is subducted in the ocean trenches around the Pacific, it is taken down towards the mantle; as these hydrated minerals heat up again, they release water. This water then lowers the melting point of the mantle above the descending plate, which melts to produce a basaltic/andesitic melt with a high water content - the water is dissolved in the magma. When this melt reaches the surface again, the high concentration of water leads to explosive eruptions as it comes out of solution.


Magnesium powder mixed with CuSO4 solution

Question: $\ce{Mg}$ powder is stirred into $\ce{CuSO4}$, what is the balanced molecular equation for this reaction ? I have $\ce{Mg + CuSO4 -> Mg2SO4 + Cu}$. Also, is the ionic equation the same as the net ionic equation? I believe it is not, because Copper would act as a spectator ion, however, I am not too sure.
Answer: Your equation is very close, but you it is not $\ce{Mg2SO4}$. $\ce{Mg^{2+}}$ has a charge of $2+$, and $\ce{SO4^{2-}}$ has a charge of $2-$. They combine in a ratio of 1:1, so the result is
$$\ce{Mg + CuSO4 -> MgSO4 + Cu} ~ .$$
The ionic equation does not include the $\ce{SO4^{2-}}$, and in the case of this equation the net ionic equation is the same as the ionic equation. Ionic equations look at what happens to electrons.
In this case, electrons are being transferred from the magnesium to the copper (since the copper is bonded to $\ce{SO4^{2-}}$ it is in the form $\ce{Cu^2+}$).
$$\ce{Mg + Cu^{2+} -> Mg^{2+} + Cu} ~ .$$
Since the charge on the $\ce{SO4^{2-}}$ doesn't change, it's just a spectator ion.
Comment: I also have to note that in some circumstances the reaction can be ... lively.
Comment: Ebullient, one might even say.
Answer: The answer given is what all the textbooks say, and what the examiner wants. However, magnesium will displace hydrogen from water if copper ions are present which act as a catalyst. So what really happens is bubbles of hydrogen are liberated and white magnesium hydroxide solid is produced.
Comment: Did you actually try this? With aluminum metal added to copper sulfate solution, copper is produced: https://chemistry.stackexchange.com/a/128099/79678. A piece of burning magnesium can burn in water, making magnesium fires hard to extinguish. But magnesium powder is not a piece of burning magnesium and it only slowly reacts with very hot water. This is worth a quick experiment.


Petrol smell coming from vents and smoke from bonnet

Question: I recently bought a Ford C-Max 05, and have found that when I am stopped in traffic a strong smell of petrol or oil comes through the air vents and there is white smoke coming from the bonnet. Does anyone have any suggestions on what this could be?
Comment: Petrol smells very different from motor oil. Motor oil, especially burnt one, has a thick, acrid smell. Gasoline doesn't.
Comment: Has this just started or did you buy this with the problem? If you bought it from a dealer take it back, right away!
Comment: I've had the car week and I noticed it quite early on after the sale, however it was a private sale and im getting no reply
Comment: That sucks @JessCokeley! More information needed: does the white smoke start right away, or does it only happen once the engine heats up? Do you get smoke out of the tailpipe? Look under the bonnet, and under the engine, do you have any obvious fluid leaks? When it's making smoke is there an obvious source?
Answer: Smoke under the hood can be caused by many things. It is commonly caused by oil leaking into the exhaust manifold(s) from the valve covers where the gaskets have gone bad. Another common reason is sloppy adding of oil that missed the filler. You will have to identify it to know for sure.
As far as the smell coming from the vents, on most cars the fresh air intake for the cabin is located in close proximity or the engine compartment. Therefore, when the smoke from the burning oil is present, it can be pulled into the fresh air for the cabin, thus allowing the smell to come thru the vents.
You will need to inspect the engine for leaks. Once you have found them, please update your question so we can help with more detail. Hopefully it is just valve cover gaskets, which can be a simple, inexpensive fix.