Can anyone explain Sanskara / Sankara in depth?

Question: Can someone provide a canonical explanation to  Sanskara/Sankara?
I appreciate if you can provide some sources, Suttras/Suttas so that I can expand my knowledge.
Comment: I think you meant "Sankhara" for the pali word.
Answer: There's an article in English titled Anicca Vata Sankhara in which Bhikkhu Bodhi describes the various meanings of the word. Here are very brief extracts from that article, a summary:

The word sankhara is derived from the prefix sam, meaning "together," joined to the noun kara, "doing, making."

The suttas distinguish the sankharas active in dependent origination into three types: bodily, verbal, and mental.
A second major domain where the word sankharas applies is among the five aggregates. The fourth aggregate is the sankhara-khandha, the aggregate of volitional formations. The texts define the sankhara-khandha as the six classes of volition (cha cetanakaya): volition regarding forms, sounds, smells, tastes, tactile objects, and ideas.
The third major domain in which the word sankhara occurs is as a designation for all conditioned things. In this context the word has a passive derivation, denoting whatever is formed by a combination of conditions; whatever is conditioned, constructed, or compounded.

The suttas
I don't know whether there is a good/long/detailed canonical description in the Suttas.
Suminda's answer references the Abhidhamma.
One of the places it's described is the Paticca-samuppada-vibhanga Sutta, very short:

And what are fabrications? These three are fabrications: bodily fabrications, verbal fabrications, mental fabrications. These are called fabrications.

The aggregates
This page contain three essays by Ajaan Lee. The last essay on that page titled "Part III: The Buddhist Way" describes various types of Sankhara, which is "a brief outline of the Buddha's teachings based on the synopsis of the Ovada Patimokkha". It includes (again I'm heavily summarizing the article):

"Sankharas on the level of the world": status, fortune, praise
"Sankharas on the level of the Dhamma": Dhatu, Khandha, and Ayatana

I think that all khandhas are sankharas, i.e. each khandha is some-things-put-together; for example they include:

Putting things together so that they can be sensed (or more specifically, contact between the sense and sense-object)
Putting a "feeling" with the thing (e.g. "I feel that's good" or "I think that's bad")

The sense of self (identity view) is presumably a sankhara too (see the simile of the chariot).
The same article also mentions some important attributes of sankharas, e.g. impermanence:

The Buddha taught in line with the true nature of the world. He said, "Khaya-vaya-dhamma sankhara, appamadena sampadetha," which means, "All sankharas, once they have arisen, decay by their very nature. Don't be heedless or complacent. Be thoroughly mindful and completely alert, and you will attain peace and security."
What this means is this: All things that appear in the world arising from actions (kamma) are called sankharas — formations, fashionings, compounded things. Sankharas, by their nature, or of two sorts — sankharas on the level of the world and sankharas on the level of the Dhamma.

I may be wrong but I suspect that vipassana meditation might be supposed to help you understand that, at least at the sensory level. I think vipassana is supposed to make you aware of impermanence, but because sankharas are impermanent perhaps "becoming aware of impermanence" means "becoming aware of sankharas".
I also like the explanation, "All things that appear in the world arising from actions (kamma) are called sankharas": because I think that helps to explain why sankharas are sometimes translated as not just "formations" but "volitional formations": i.e. perhaps it's because kamma (action) is also associated with will (see "This volition and the resultant actions constitute kamma" in this commentary).

One of the five aggregates
The terminology turns out to be confusing because all five khandhas are sankharas, but also one of the khandhas in particular is called sankharas.
I think that means "all khandhas are fabricated or put together, but one of the khandhas is what people do when they put things together or fabricate things in their mind."
Wikipedia summarizes this meaning of sankhara as a specific one one of the five aggregates:

"mental formations", "impulses", "volition", "fabrications" or "compositional factors" (Skt. samskāra, Pāli saṅkhāra, Tib. 'du-byed): all types of mental habits, thoughts, ideas, opinions, prejudices, compulsions, and decisions triggered by an object

This too matches (is an even better match for) the "volitional formation" translation.
The footnote to that Wikipedia paragraph begins with, "The Theravada Abhidhamma divides saṅkhāra into fifty mental factors".

All conditioned things
There's an example of this usage in the Buddha's last words (in the The Mahāparinibbāna Sutta),

And the Blessed One addressed the bhikkhus, saying: "Behold now, bhikkhus, I exhort you: All compounded things are subject to vanish. Strive with earnestness!"58

This was the last word of the Tathāgata.

The footnote gives the Pali,

Handa dāni bhikkhave āmantayāmi vo: Vayadhammā saṅkhārā appamādena sampādetha.

Jayarava explores that phrase, and how difficult it is to translate, in this article, The last words of the Buddha.
Answer: The Pali word 'sankhara' has multiple meanings dependent on the context. It can mean:
(i) a conditioned thing (formed from various causes or parts);
(ii) something that conditions another conditioned thing, i.e., a 'conditioner';
(iii) the process of conditioning;
(iv) the aggregate of mental forming, such as desiring, intention, thinking, etc and
(v) mental conditioning/concocting by greed, hatred & delusion, i.e., uncontrolled disturbing mental proliferating.
For example, shampoo is a 'conditioned thing', because it is manufactured from & comprises of many ingredients. When shampoo is applied to hair, a 'conditioning' process takes place, which makes hair soft, clean & shiny. Therefore, shampoo is also a (hair) 'conditioner'.
Examples of each context from the Pali suttas are below:

1. 'Sankhara' as 'conditioned things'.

Rūpaṃ kho āvuso channa, aniccaṃ, vedanā aniccā, saññā aniccā, saṃkhārā aniccā, viññāṇaṃ aniccaṃ, rūpaṃ anantā, vedanā anattā, saññā
anattā, saṃkhārā anattā, viññāṇaṃ anattā, sabbe saṃkhārā aniccā, sabbe
dhammā anattā
Form, friend Channa, is impermanent. Feeling is impermanent. Perception is impermanent. Mental formations (saṃkhārā) are
impermanent. Consciousness is impermanent. Form is not-self. Feeling
is not-self. Perception is not-self. Mental formations are not-self.
Consciousness is not-self. All (sabbe) conditioned things (saṃkhārā)
are impermanent (aniccā). All (sabbe) phenomena (dhammā) are not-self
(anattā).
SN 22.90

The verse above contains the word 'sankhara' twice: (i) as the aggregate of mental forming; and (ii) as all conditioned things, referring to each of the aggregates.
This stock phrase – sabbe saṃkhārā aniccā – is found in the exact same context at AN 3.134 and at Dhammapada 277.
The five aggregates are conditioned things because they arise & exist subject to & dependent upon various causes and conditions. Thus, SN 22.21 states:

Rūpaṃ kho ānanda, aniccaṃ, saṃkhataṃ paṭiccasamuppannaṃ khayadhammaṃ
Form…feeling…perception…mental formations…consciousness  are
impermanent,  conditioned (saṃkhataṃ), dependently arisen
(paṭiccasamuppannaṃ), subject to destruction (khayadhammaṃ)…

Therefore, in this context, 'sankhara' also refers to physical or material things, as found in the Pali terms 'kaya sankhara' (which is defined in MN 44 as the 'in & out breathing') & 'aayu sankhara' (defined in MN 43 as the 'vitality' or 'life force' of the physical body that remains when the mind is unconscious).

2.  'Sankhara' as 'conditioners'.
Here, 'sankhara' as 'conditioners' refers to the words 'kaya sankhara', 'vaci sankhara' & 'citta sankhara', which are found at the 2nd condition of Dependent Origination & at stages 4, 7 and 8 of the Anapanasati Sutta and which are defined in MN 44 as follows:

In-&-out breaths are the body conditioner (kāyasaṅkhāro). Initial & sustained thought are the verbal conditioner (vacīsaṅkhāro).
Perceptions & feelings are the mind conditioner (cittasaṅkhāroti).
Why are in-&-out breaths the body conditioner? Why are directed
thought & evaluation the verbal conditioner? Why are perceptions &
feelings the mind conditioner?
In-&-out breaths are a bodily thing upon which the body depends on (or is bound on). That's why in-&-out breaths are the body
conditioner. Having first applied & sustained one's thought, one then
breaks out into speech. That's why applied & sustained thought are the
verbal conditioner. Perceptions & feelings are mental; these are
things that determine mental states (i.e., upon which mental states
depend). That's why perceptions & feelings are the mind conditioner.

The above translation has been done liberally to demonstrate the meaning. However, the part of the translation about why thought is the verbal conditioner is the same as all translators. This part demonstrates clearly what the mean of 'sankhara' is in this context, namely, the 'verbal sankhara' is a preceding cause that determines the happening of speech. Thus 'thought' is not the 'verbal condition' or 'verbal fabrication' but, instead, the 'verbal conditioner' or the 'verbal fabricator'.
Thus, the 'kaya' & 'cittta sankhara' have the same meaning. The breathing conditions the state of the body. Breathing gives life to the body. If breathing is healthy, the body is healthy & energetic. If breathing is poor, the body is unhealthy & weak. This is why breathing is the body 'conditioner' (rather than the bodily condition). Similarly, pleasant feelings & perceptions condition mental formations of love, greed or lust; whilst unpleasant feelings & perceptions condition mental formations of anger or hatred. This is why perception & feeling is the mind 'conditioner' (rather than the mental condition).

3. 'Sankhara' as 'conditioning'.
Below are two straightforward examples of the word 'abhisaṃkharontīti'.

Kiñca bhikkhave, saṃkhāre vadetha: saṃkhataṃ abhisaṃkharontīti bhikkhave
And why do you call them 'fabricators'? Because they fabricate fabricated things, thus they are called 'fabricators.'
SN 22.79
Avijjāgatoyaṃ bhikkhave, purisapuggalo puññaṃ ce saṅkhāraṃ abhisaṅkharoti
Monks, if a person immersed in ignorance generates a meritorious formation…
SN 12.51

4.  'Sankhara' as the 'mental formations aggregate'.
There are five aggregates (khandha) of life (body, feeling, perception, mental formations & consciousness), of which 'sankhara khandha' (mental formations/forming) is the 4th.
The  'sankhara khandha' operates in all people, including Buddhas. For example, about the end of the life of a fully enlightened being, the scriptures state:

Then, friend Yamaka, how would you answer if you are thus asked: A monk, a worthy one, with no more mental effluents: what is he on the
break-up of the body, after death?
Thus asked, I would answer, 'Form is impermanent… Feeling… Perception… Fabrications… Consciousness is impermanent. That which is
impermanent is unsatisfactory. That which is unsatisfactory has ceased
and gone to its end.'
Very good, my friend Yamaka. Very good.
Yamaka Sutta

Therefore, for a Buddha to think or speak, the sankhara aggregate must operate in the mind/brain of a Buddha. In this context, 'sankhara' is not 'mental suffering' but referring to a neutral mental faculty.

5.  'Sankhara' as the 'mental concocting'.
There are many passages about how 'sankhara' is the greatest suffering & about how Nibbana is the stilling of 'sankhara'. Since a Buddha must think (in order to teach) & is comprised of five undefiled pure five aggregates, the term 'sankhara' is these passages does not refer to 'sankhara' as 'conditioned things' or the 'sankhara aggregate'. Sankhara, here, also probably does not refer to 'sankhara' as 'conditioners' since Buddhas still have breathing, feeling, perception & thought. Therefore, 'sankhkara' here must refer to the mind being 'conditioned', 'concocted', 'stirred up' & 'polluted' by greed, hatred & delusion, i.e., uncontrolled disturbing mental proliferating.
Some relevant well-known passages are below:

Saṅkhāra paramā dukhā…nibbāṇa paramaṃ sukhaṃ.
Mental concocting is the worst suffering….Nibbana is the highest bliss.
Dhammapada 203
Tisso imā āvuso dukkhatā, dukkhadukkhatā saṅkhāradukkhatā vipariṇāmadukkhatā.
There are these three kinds of suffering, my friend: suffering due to/about pain; suffering due to/of mental concocting; and suffering
due to/about change. These are the three kinds of suffering.
SN 38.14
Construing is a disease, construing is a cancer, construing is an arrow. By going beyond all construing, he is said to be a sage at
peace.
MN 140
Idampi kho ṭhānaṃ duddasaṃ yadidaṃ sabbasaṅkhārasamatho sabbūpadhipaṭinissaggo taṇhakkhayo virāgo nirodho nibbānaṃ.
This state, too, is hard to see: the calming (samatho) of all (sabba) mental concocting (saṅkhāra), the relinquishment of all acquisitions,
the destruction of craving; dispassion; cessation [of suffering];
Nibbana.
MN 26

Conclusion: In the Pali, the word 'sankhara' is used in many different contexts. For a clear & practical comprehension of the Pali teachings, the suitable context is best discerned.
Below is an example of an internet translation & the alternate translation of this webpage.

These three feelings have been spoken of by me: a feeling of pleasure, a feeling of pain & a feeling of neither pleasure nor pain.
These are the three feelings spoken of by me. But I have also said:
'Whatever is felt comes under stress.' That I have stated simply in
connection with the inconstancy of fabrications (sankhara). That I
have stated simply in connection with the nature of fabrications to
end… in connection with the nature of fabrications to fall away… to
fade away… to cease… in connection with the nature of fabrications to
change.
These three feelings have been spoken of by me: a feeling of pleasure, a feeling of pain & a feeling of neither pleasure nor pain.
These are the three feelings spoken of by me. But I have also said:
'Whatever is felt comes under unsatisfactoriness.' That I have stated
simply in connection with the inconstancy of conditioned things
(sankhara). That I have stated simply in connection with the nature of
conditioned things (sankhara) to end… in connection with the nature of
conditioned things to fall away… to fade away… to cease… in connection
with the nature of conditioned things to change.
SN 36.11
Comment: This is wonderful! I have a question though about the first part about the meaning of sankhara as 'conditioned things.' The question is a bit involved so I'll post it as a real question and not a comment I guess.
Comment: Question here: https://buddhism.stackexchange.com/questions/49762/what-is-the-proper-translation-of-sabbe-sa%e1%b9%85kh%c4%81r%c4%81-anicc%c4%81
Answer: Most in depth explanations happens in the Abhi Dhamma. There are 52 Cetasikas our of which 50 come under Sankara (with the exception of Feeling and Perception). Explaining the 50 would need a small size book and maybe beyond the scope of an answer in this format hence refer to: Mental Factors By Dharmacharya Ruwan Buddhika, The Abhidhamma in Practice by N.K.G. Mendis, Comprehensive Manual of Abhidhamma, Mental factors.
According to the Suttas there are 3 types of Sankaran (Cūla Vedalla Sutta, (Paṭicca,samuppada) Vibhanga Sutta):

the bodily formations - breath
the verbal formations - thinking and pondering
the mental formations - feeling and perception

2 above related to the 50 Cetasikas in the Abhi Dhamma while 3 refers to the other 2 Cetasikas. Mental formations are the last to calm. (Anupubba Nirodha Sutta)
Sankara are formed when there is either greed (lobha), hatred (dosa), delusion (moha), greedlessness (alobha), hatelessness (adosa), and undeludedness (amoha) volitional motivated thoughts (this also based on sensation as any through has sensation associated with it) or when you react with clinging or aversion to any sensation that is felt. (Pahāna Sutta, Avijja Pahana Sutta 2)
Comment: Thanks Suminda! what are the pali words for "feeling and perception"
Comment: Feeling / sensation - *vedanā*, Perception - *sañña*
Answer: I recommend the book "How to Measure and deepen your spiritual realization" for the most modern analysis and cross correlations. It has been 15 years since i read this and i have not found anything better. There is a 100+ page chapter to analyzing the skandhas (including sankhara) and how they relate to daily life, samadhi, and the various gongfus as described in the surangama sutra (which is a Mahayana sutra, by the way), various modern Buddhist books, and some Theravada references as well since the 5 aggregates is a universal dharma common to many schools.
Answer: I think this entire universe is made up of Sankara, which cannot be seen thorough our 5 senses(Vinyana-Perception).Also "San" means collection and "kara" means information. It is the collection of information. Buddha said "Pragnya" eye can see this small particles..Buddha told Rahula, "you and that tree are the same"...it has a nature of "create" and "cessation" at the same time...
Answer: Sankhara as a karmic-formation can be understood to be a schema, as defined by Immanuel Kant. From this point of view, sankhara as a cognitive process that transforms experience into belief. For example, by means of a sankhara process can take a set of sensations of a chair and "put them together" into a concept of a chair, in this way a person acquires perceptual knowledge about chairs. Kant called this a process of synthesis. Subsequent experiences with chairs can result in the growth or development of this perceptual knowledge, such as having feelings about and a desire for our favorite chair. The process of "putting together" is a form of mental action and therefore a form of kamma (karma in Sanskrit). The product of the process of "putting together" is "that which has been put together," which is also called sankhara. Defined in this way, sankhara or schemata are the cause of all intelligent behavior such as perception, feeling, believing, wishing, knowing, and having emotions. Such behavior can be wholesome, unwholesome, or functional. In advanced states of mindfulness meditation, it is possible to access the history of a karmic-formation and, if necessary, correct, revise, or unlearn it. I have written a book on how mindfulness meditation works that relates meditation to various sankhara.
Answer: As ChrisW says "The word sankhara is derived from the prefix sam, meaning "together," joined to the noun kara, "doing, making."
saṅkhāra = come together & do.
What precisely does "come together" mean?
It means "orienting oneself" in sensory experience.
It means saying "I am here". (See the 36 streams of craving).
saṅkhāra = get oriented & do.
saṅkhāra = in THIS place with THIS aim, DO this
saṅkhāra = a sensory motor prediction
The sensory motor brain predicts sensory experience.
We construct maps to guide our movements in the world.
All maps, including the dhamma, are composed of saṅkhāra.
Each saṅkhāra starts off as a hypothesis with a degree of uncertainty.
However, as it predicts sensory experience correctly, it hardens into a "habit" and we cease to be conscious of the fact that it is just a hypothesis and may be proved incorrect by future sensory experience.
What does this have to do with "suffering & the end of suffering"?
Āsava are saṅkhāra corrupted by avijjā.
Āsava are saṅkhāra which predict sensory experience badly.
The destruction of the āsava is the end of suffering.
Why?
Because dukkha is a notification of misprediction.
The biological purpose of dukkha is to alert us to an error in our predictive model of the world of sensory experience.
How we respond to this arrow in the heart is important.
If we respond by ignoring the feedback and clinging to our wrong map of the world, we create an inner civil war between (1) the part which wants to predict sensory experience accurately so that our movements will be skillful and (2) the part which wants to cling to the wrong view.
This inner civil war between these 2 parts is all suffering.
All suffering that we have ever experienced is an inner civil war between these 2 parts.
When, with viriya, this bad habit of avijjā [ignoring uncomfortable truths] (avijjāsava) is extinguished, all suffering is ended.
Comment: My dead mother said, sanjhara is hurting me before she died, that is all the problem of letting go, or perhaps she was willing to accept the abuse so not to take another rebirth
Comment: @blue_ego: Re: "saṅkhāra are hurting me."
Note the word "me".
In my experience, self-absorption in the narrative is an accurate predictor of the presence of āsava.
The āsava bring suffering, decay and death.
For the welfare of all beings, the āsava must be destroyed.
The Buddha counseled anattā: The renunciation of this self-absorption in the narrative.
When this has been done and narrative has been exposed as false, it becomes possible to destroy the āsava.
Comment: The Buddha knew that humans do not need to decay and die 2500 years ago. He told us directly that our choice to cling to āsava instead of destroying them is the reason we decay and die. Longevity science says the same. Aging, the cause of most disease, is itself caused by the sirtuins in our epigenome being overwhelmed to the point where epigenetic information is lost. Why overwhelmed? Because we choose to cling to āsava instead of destroying them. We destroy them by letting go of saṅkhāra which predict sensory experience incorrectly and replacing them with saṅkhāra which predict it correctly.
Comment: Instead, we cling to wrong views and this clinging causes the suffering which overwhelms our sirtuins causing aging and death. This is why we decay & die. If we choose, instead, to see the world the way it actually is, the stress which is the root cause of aging will cease to exist. See David Sinclair's book: Lifespan: Why we age and why we don't have to.
Comment: "Sabbe saṅkhāra aniccā" does not refer to the impermanence of the material world. It refers to the impermanence of our perception of it. The map is NOT the territory. Our maps of the the world are constructed entirely of saṅkhāra. We can choose to respond to the dukkha of misprediction by creating and destroying them to more accurately predict sensory experience. By increasing our understanding in this fashion, we can solve any problem. Including the problem of aging and death.
Comment: sounds good...can u answer my question? https://buddhism.stackexchange.com/questions/48268/is-merit-just-ok-not-great
Answer: And what are fabrications? These three are fabrications: bodily fabrications, verbal fabrications, mental fabrications. These are called fabrications.
"In-&-out breaths are bodily; these are things tied up with the body. That's why in-&-out breaths are bodily fabrications.
Having first directed one's thoughts and made an evaluation, one then breaks out into speech. That's why directed thought & evaluation are verbal fabrications.
Perceptions & feelings are mental; these are things tied up with the mind. That's why perceptions & feelings are mental fabrications."
'Whatever fabrications , bhikkhus, has passed, ceased, changed: the term, label, and description 'was' applies to it, not the term 'is' or the term 'will be.'
"And what are fabrications? These six classes of intention [pali cetana] — intention with regard to form, intention with regard to sound, intention with regard to smell, intention with regard to taste, intention with regard to tactile sensation, intention with regard to ideas: these are called fabrications. From the origination of contact comes the origination of fabrications. From the cessation of contact comes the cessation of fabrications. And just this noble eightfold path is the path of practice leading to the cessation of fabrications... The fact that pleasure & happiness arises in dependence on fabrications: that is the allure of fabrications. The fact that fabrications are inconstant, stressful, subject to change: that is the drawback of fabrications. The subduing of desire & passion for fabrications, the abandoning of desire & passion for fabrications: that is the escape from fabrications...
"Intention [cetana], I tell you, is kamma. Intending, one does kamma by way of body, speech, & intellect.
"And what is the cause by which kamma comes into play? Contact is the cause by which kamma comes into play.
"And what is the diversity in kamma? There is kamma to be experienced in hell, kamma to be experienced in the realm of common animals, kamma to be experienced in the realm of the hungry shades, kamma to be experienced in the human world, kamma to be experienced in the world of the devas. This is called the diversity in kamma.
"And what is the result of kamma? The result of kamma is of three sorts, I tell you: that which arises right here & now, that which arises later [in this lifetime], and that which arises following that. This is called the result of kamma.
"And what is the cessation of kamma? From the cessation of contact is the cessation of kamma; and just this noble eightfold path — right view, right resolve, right speech, right action, right livelihood, right effort, right mindfulness, right concentration — is the path of practice leading to the cessation of kamma.
"And what is name-&-form? Feeling, perception, intention, contact, & attention: This is called name. The four great elements, and the form dependent on the four great elements: This is called form. This name & this form are called name-&-form.
"And why, bhikkhus, do you call them fabrications? 'They fabricate the conditioned,' bhikkhus, therefore they are called fabrications. SN 22.79
And what is the conditioned that they fabrications?
They fabricate conditioned form as form;
they fabricate conditioned feeling as feeling;
they fabricate conditioned perception as perception;
they fabricate conditioned fabrications as fabrications;
they fabricate conditioned consciousness as consciousness.
'They fabricate the conditioned,' bhikkhus, therefore they are called fabrications.
(Here end sutta excerpts)


Red and blue Antimo Caputo 00 flour

Question: What's the difference between the flour in the blue bag vs the red? I'm not even sure which one I have since my local Italian shop re-bags it, but I've seen the red bags in the store, so I kind of assume that's it. I've used it with great success in making pasta, but I'm thinking of trying pizza dough. The blue bag is labeled "Pizzeria Flour", but the red bag also claims that it is good for pizza. What's the difference?
Answer: Caputo Rosso (red) might have a slightly higher gluten content (~12-13%) than Blu (blue) (~10-12%) and higher stability. But mostly the blue one is just more of a niche product meeting the highest standards for traditional Neapolitan pizza.
Here are spec sheets directly from their web site:

BLUE: http://caputoflour.com/wp-content/uploads/2013/07/00-Pizzeria-SPECS.pdf
Extracted from their page:
"for the demanding technical pizzaioli", "recognized by the leading Neapolitan pizza certification associations", "ideal for classic Neapolitan Pizza in wood fired, gas or electric ovens", "produces a very soft and flavorful crust with optimal hydration", "high-quality protein and gluten result in a consistent long-rise dough.", "milled specifically for use at temperatures above 700°F", "Growth: 1'50"-2'00"; Stability: 8'-10'; …"
RED: http://caputoflour.com/wp-content/uploads/2013/07/00-Rinforzata-Flour-SPECS.pdf
Extracted from the page:
"higher protein and gluten content and water absorption is ideal for long-rise doughs", "obtains soft texture", "ideal for pasta, pastry, specialty breads and pizza", "Growth: 2'00"-3'00"; Stability: 12'-14'; …"

And since they both say ideal for pizza - nothing can go wrong ;-)

And if you don't know what the differences in stability times mean ...
I find this page quite informative:
http://www.wheatflourbook.org/p.aspx?tabid=33
Flour science is almost like airports ... with all the arrival and departure times =D
Comment: Thanks. So since I *think* mine is red, I should probably let the dough rest a bit longer. I can do that!
Comment: If I remember correctly from that flyer I had ... it said that the red one - being more stable - can withstand longer rising times where the blue one can be used with shorter rising times (30-90 mins) ... but they don't say anything about that on the Caputo web page, so I just removed it from the answer. And I extracted some buzzwords from the page, in case the links go dead at some point =) Anyways, they both seem to be good for long-rise dough =)
Answer: There is so much confusion when people don't call the Caputo flours by their real names. There is no such things called Caputo "Rosso" or "Blue". This is what everybody wants to call them, and it leads to confusion.
Caputo has a flour called Pizzeria that comes in 55 lb (25 kilo) bags which happen to be Blue. They also have a small blue bag that is 2.2 lbs (1 kilo) packaged for store shelf retail that is called Confezione.
Then they have a flour called Rinforzato which comes in 55 lb bags, and another called Chef's, which comes in 2.2 lb bags packaged for retail. Both of these come in Red (Rosso) bags.
So when you are talking about Red vs Blue, It's hard to tell what you're talking about.
I'm not sure if the Confezione is still available in the US, but it used to be, and may still be.
As far as speculation about whether or not the Chef's is really just a smaller bag of the Pizzeria or the Rinforzato or something different than either is largely speculation.
All of the above flours are 00 flours. That means that it's ground extra fine (as most of you probably already know, but just in case there are some people new to it)
There is a new type of Caputo Flour that has been out for a shorter while. It's called Pizza a Metro. It comes in 55 lb bags. The touted benefits of this flour is that it's milled/blended for a specific type of pizza called Pizza a Metro (Pizza by the Meter), which is popular in Rome and Sorrento, and works well for temperatures around 700°F.
Wood fired pizza is usually cooked in an oven around 900°F.
I've got some information on this at http://brickovenbaker.com/caputoinfo, and there should be some links in that content to some other discussions about the differences in the flours. In one of the blog posts, a food scientist named Joe goes into differences at a technical level in the comments section, and claims that each of the flours are distinct flours, and that the smaller versions for packed in 1 kilo bags for retail are not the same as the restaurant sized bags, even though people have been claiming that the Chef's is the same as the Pizzeria, and others claiming that it's the same as the Rinforzato. What makes it even more amusing is that two people got different answers directly from Caputo in Italy when asking them if there was a relationship between the Chef's and the other flours, and food scientist Joe said they are both wrong.

Full Disclosure: The link above goes to my blog and I happen to sell Caputo flour on my site. I'm not the best resource for all of the technical details, I don't speak much Italian, and I just want people to call the stuff by their real names because the colors used on the bags does not relate to what's in the bag as far as I know.
Comment: You noted - *As far as speculation about whether or not the Chef's is really just a smaller bag of the Pizzeria or the Rinforzato or something different than either is largely speculation.*. One can simply lookup the spec sheet on the Caputo website and discover that they are in fact different products. I.e. Chef's Flour Stability is 10-14, Elasticity is 13-15 and Rinforzata Stability is 12-14, Elasticity is 16-18.
Comment: I don't recall seeing a Chef's spec sheet when I originally posted it, but maybe I missed it or it was recently added. Thanks for pointing it out either way.
Answer: For now, you'll be ok with either.  And unless you noticed a price bump, you have the Red (the STG certified Blue are at a slight premium).
In simple terms, the Red is more for making quick thin crust pizza (romano style) run at 720°F whereas the blue is better for thicker rimmed (Neapolitan style) run at 900°F. That's why they both claim 'good for pizza'.
The Red you can do what you like with and even roll with rolling pin and no eyebrows are raise.
The Blue on the other hand is typically kneaded quite well and let rest in various (trade secret) positions for about 3 days (yes, days).  It is then 'opened' by hand in a particular way and cooked to show leoparding blisters and all in a fierce oven.
You can still make Romano style with the Blue, but if you did everything right for Neapolitan style and used the Red type you'd get a harder rim.  To some people, that's like serving them a well done steak.
Comment: tell me about it.  Clean cycle locks the door, and if the oven didn't self destruct, i'd have hacked it to go higher.  just not enough insulation to protect everything else.  In the mean time, if you have access to any 1/4" steel plate or [this one](http://modernistcuisine.com/baking-steel/) it'll get you part of the way there.
Comment: This came up in chat, it irks me that I can't get my oven hotter than 500F. I know it can get hotter because it has a *clean* cycle!   Someday I might see if I can outsmart the safety features on a decrepit older oven, but in the meantime, very informative answer. Thank you.
Comment: Oooh, that's purty. I don't have $100 burning a hole in my pocket right now, but maybe someday. In the meantime, my big old (belonged to my grandmother) cast-iron skillet works pretty well as a pizza stone, up-side down.
Answer: According to this Serious Eats article, there are few differences between the flours, especially with regard to protein content:

This is the gold standard of pizza flours by which most others are judged, but there's quite a bit of confusion as to exactly what it is. You'll read in countless sources that Italian Tipo "00" flour, like the Caputo, is a "soft wheat flour," with a low protein content. This is absolutely untrue and anybody who continues to spread this rumor should be immediately chastised with great prejudice.
The fact is, the label Tipo "00" has nothing to do with protein content. Rather, it refers to the fineness of the milling. Tipo "00" is the finest grade of flour milled in Italy, and it has a consistency similar to baby powder. It's available with several different levels of protein intended for different baking projects, just like American flours (which we'll get to in a moment). The ones you'll most commonly see in pizzerias are the red Rinforzato bag, which features pictures of pizzas and bread, the blue Pizzeria bag, which pictures a single pizza, and — the most common in the U.S. — the red The Chef's Flour bags, which, in fact, contain the exact same flour as the Rinforzato. All three bags of flour have the exact same protein content: 12.5%.
Answer: The chief difference between the Capitol Pizzeria (blue) and the Chef's (the same as the rinforzato, both red) is their "W" number, which many Americans mis-translate as strength, thereby confusing it with protein content. In America, strong flours have higher protein. In Italy, the W stands for the English word "Work," which refers to the flour's ability to absorb water (its hydration potential). In other words, the higher the W number, the more water the flour can absorb.
The blue pizzeria flour has a much lower W value (180 -250), and the rinforzato or Chef's (red) has a value of 250-300, which means the red is more suited to bread and pastry, whereas the blue is more suited to pizza and most tender northern Italian pastas.
An important point left out of this discussion is the Caputo blue is intended for hot pizzeria ovens (>700°F), and does not work as well in American home ovens (<550°F). For that reason, Caputo also sells a blue bag called "Americano," which is much more suited to American home ovens.
If you can source & store them, and use them in a reasonable time period (6-9 months, if stored correctly), I recommend that you keep both the Americano and the Chef's on hand. The Americano for pizza, and the Chef's for bread and pastry (including pasta). If not, my preference is for the Chef's (red), but if using it for pizza, I would recommend mixing it with American (King Arthur) all purpose flour, in a ratio of 2:1, i.e. 67% Caputo red, and 33% King Arthur A/P.
All Caputo flours are readily available online at a cost lower than at specialty stores. I usually obtain mine from Brick Oven Bakers, but always check Amazon, etc. for occasional good deals.
Answer: I have used both and I find the red creates a better crust, in my own opinion and my friends'.  The red creates crispier crust while the blue softer chewier so it's your preference. My pizza dough rises in the frig for 2-3 days.  I use 550 oven and pizza iron to bake for 6 min.  I typically heat up the oven for an additional 15-20 min after it reaches the desired 550.  I think it allows the oven to have a more stable temperature.  The pizza iron definitely is superior than the pizza stone.
Comment: Turn your broiler on in addition to that 550 preheat and you should be able to get down to the 2min bake range. Much better results that way.

Red and blue Antimo Caputo 00 flour


Not sure what this plant is... Anyone?

Question: It has reddish green leaves.. And long stems that protrude above the leaf area with little seeds or flower buds on the end.. It pretty much looks like this year round in a northern climate (Indiana) It does get browner in the winter.. This picture was taken moments ago in August.. The entire plant is only about 18 inches high.
Answer: It looks like Palace Purple Heuchera - one that's in more shade than it likes, which is why the leaves are much greener than they should be (OTOH, when I was in the trade, we'd run across brown-leaved and mostly green-leaved "Palace Purple" cultivars. It seems the original cultivar may be lost). The purple undersides to the leaves are one ID marker, and the size and flowers are both correct; the flowers aren't as tight as they should be if this were a tiarella. Tiarellas also tend to bloom in late spring, not mid to late summer.
Answer: I think it might be Tiarella cordifolia, also known as foamflower; although the leaves on yours look a bit soft and droopy, they are the right shape for Tiarella . It's a woodland plant, preferring shady, damp conditions, and the leaves may wilt or droop in sunlight - they turn reddish tones in autumn or if the soil is dry. These days there are many varieties and hybrids - there's even a cross between Tiarella and Heuchera which is sold as Heucherella. https://www.claireaustin-hardyplants.co.uk/products/tiarella-cordifolia

Not sure what this plant is... Anyone?


Is there a name for this cadence - [Tritone Sub of V] - I

Question: Sometimes I've been going through [Tritone Sub of V] - I cadences.  Is there a specific name for this?
Answer: For example, Db7 - C?
Since you took the tritone substitute of the V (the dominant), this is still a kind of dominant cadence. Specifically, it's a tritone-substitute dominant cadence.
Comment: Is 'dominant' cadence another term for 'perfect' or 'authentic' cadence?
Comment: In the context of C major, "Db7" could also be taken as a chromatic modification of vii7. How is it decided, what chord a chord is a substitution for? For me, the use of that cadence to perform the function of V-I in C has the problem that Db sounds like VI of f minor, so the cadence sounds like an imperfect cadence, VI-V, in f minor.
Comment: @RosieF - Db in key C is bii, isn't it? A tritone substitution is the chord whose 3 and 7 notes are the 7 and 3 of the other chord. Both being dominant 7th chords.
Comment: @Tim But in the context of the key of C major, the "Cb" of the "Db7" chord is better spelt as B (natural). Hence I spell the chord's notes as B Db F Ab, and I associate it with vii7, which is B D F A. Now if the chord had been Db maj7, that would be different...
Comment: @Tim and others who have suggested changing *dominant cadence* to *authentic cadence:* One definition of an authentic cadence specifically requires a **V** chord moving to a I. Using the broader term *dominant cadence* allows for the fact that Db7 - C doesn't "look" on its face like a V moving to I. (Of course, if you tweak the definition of *authentic* and/or understand the Db7 as some kind of rootless altered V chord, you could argue that this rises to the level of an authentic cadence. But my answer, as written, avoids these semantic issues.)


Why are there so many coaxial cable impedances?

Question: Why do we have 50, 75, 62 and 92 Ω coaxial cable, to name a few? Why not just one standardised cable? Is there some technical reason or did Mr. Coax and Mr. Cable have a disagreement, like Mr. Tesla and Mr. Edison?
Answer: Glad to see this question posted! This has a really interesting answer which I'm not qualified to write a comprehensive answer to, so here's a rather unsupported answer to help you along until someone writes a better one.
There are several reasons why coaxial cable is used in several different impedances.

On basic principles: if a device on one end of the cable inherently has a specific impedance, then using a cable matched to that impedance means you don't need a matching network at least at that end.
Different choices of impedance result in different characteristics of the cable, given the available choices of material and construction techniques.
It is said (I don't have a citation) that 50 Ω was chosen as a compromise between power handling capability (lower impedance would be better) and attenuation per length (higher impedance would be better). In high-power applications, 50 Ω is used to allow use of the smallest cable possible for the power (minimizing cost and bulk).
On the other hand, if you are not intending to transfer significant power, i.e. your application is very low-power or receive-only, then you only care about attenuation and so you choose the higher 75 Ω to optimize for least attenuation.
Even if there was one best line impedance to use, you would still want to have available cables of other impedances. This is because RF circuits that use transmission lines as impedance transformers don't need any specific impedance, but they do need to have an impedance that is different than the impedance of the incoming/outgoing lines. For example, in this Wilkinson power divider implemented using coax:

(Image credit: SpinningSpark on Wikimedia Commons)
If your lines are 50 Ω then you need 71 Ω in the divider. If your lines are $x$ Ω then you need $\sqrt{2}x$ Ω in the divider. No single type of coax can do this.
Comment: I was told once by a very old man, radio operator for the Army during WWII, that 50-ohm coax cable became standardized with a lot of modern (that is, anything after WWII) transmitters because it was used for most military radio equipment and the war effort created tons of 50-ohm coax which made its way into the amateur radio arena.  However, that was a single source.  Anyone else know whether it is true?
Comment: @K7PEH I don't know about the surplus equipment aspect of that, but certainly, the fact that a lot of companies agreed on a common impedance will have a lot to do with military customers.
Comment: @MarcusMüller -- I forgot to add another part of what that old man told me.  He was a ham operator before WWII and he said that everyone he knew in the hobby used ladder line (usually home-brew) for their antennas.  Coax he said was used at all that he could remember until after WWII.   Of course, one person's opinion.  I used to chat with this guy on the 80-meter band late at night on an almost regular basis several times a week.  He passed away about 10 years ago.
Comment: @K7PEH I really agree that WWII changed the *economics* of RF. My point was just that economics alone doesn't imply that all manufacturers suddenly agree on 50Ω. I was assuming it was the fact that the military customers pressed for standardization.
Answer: RF Cafe cites quotes Harmon Banning of W.L. Gore & Associates, Inc.:

In the early days of microwaves, around World War II, impedances were
  chosen depending on the application. For maximum power handling,
  somewhere between 30 and 44 Ω was used. On the other hand, lowest
  attenuation for an air filled line was around 93 Ω. In those days,
  there were no flexible cables, at least for higher frequencies, only
  rigid tubes with air dielectric. Semi-rigid cable came about in the
  early 50s, while real microwave flex cable was approximately 10 years
  later.
Somewhere along the way it was decided to standardize on a given
  impedance so that economy and convenience could be brought into the
  equation. In the US, 50 Ω was chosen as a compromise. There was a
  group known as JAN, which stood for Joint Army and Navy who took on
  these matters. They later became DESC, for Defense Electronic Supply
  Center, where the MIL specs evolved. Europe chose 60 Ω. In reality, in
  the U.S., since most of the "tubes" were actually existing materials
  consisting of standard rods and water pipes, 51.5 Ω was quite common.
  It was amazing to see and use adapter/converters to go from 50 to 51.5
  Ω. Eventually, 50 won out, and special tubing was created (or maybe
  the plumbers allowed their pipes to change dimension slightly).
Further along, the Europeans were forced to change because of the
  influence of companies such as Hewlett-Packard which dominated the
  world scene. 75 Ω is the telecommunications standard, because in a
  dielectric filled line, somewhere around 77 Ω gives the lowest loss.
  (Cable TV) 93 Ω is still used for short runs such as the connection
  between computers and their monitors because of low capacitance per
  foot which would reduce the loading on circuits and allow longer cable
  runs.
Comment: "93 Ω is still used for short runs ... [to] allow longer cable runs." ?!
Comment: I thought it was something like that.The lower impedance was better for power transfer but a higher impedance is better at low signal levels. We learn something every day!
Answer: Nearly all coax is either 50 or 75 ohms. 50 ohms is standard for radio applications, and 75 ohms for CATV and video applications.
Everything else is a specialty item.
One use of odd impedance feedlines is to match impedances. Any two impedances can be matched by a 1/4 wavelength section of feedline having a characteristic impedance that is the geometric mean of the two to be matched. For example, to match 300 ohms to 50 ohms, a 1/4 wave selection of $\sqrt{300 \times 50} = 122$ ohms can be used.
Certain devices, like a Wilkinson power divider, require transmission lines of peculiar impedances.
Or the application may be one where there's no particular need to accomodate any existing standard, and the system impedance is already set by some other design constraint. For example, antennas don't usually have a 50 ohm impedance feedpoint, and printed feedlines are not often 50 ohms either. The coax impedance is determined by its geometry, so perhaps for mechanical reasons a particular geometry is preferred and this dictates an unusual characteristic impedance.
Answer: 92Ω coax has been used for many decades in cars and trucks between the radio and the non-resonant antenna. 75Ω or 50Ω coax would attenuate the signal more than 92Ω would.
The reason is the same: because of its lower capacitance per foot which helps minimize losses in the cable under such a mismatch.


Is there a hemisphere where there's more land than ocean?

Question: From a previous question, around 40% of the northern hemisphere is land. Would there be a plane splitting the earth into two equal parts, where in one part there are more land than ocean?
Comment: From a quick visual inspection with Google Earth I think the most likely candidate is a hemisphere including most of Africa, most of Eurasia, and either (Greenland) or (Indonesia and part of Australia). But that might struggle to reach 50%, as the Indian Ocean takes up a lot of it, so I'll be interested to see if somebody has a more authoritative answer! Another candidate might be a polar(ish) view centred over north-west Russia. It includes all of Eurasia,a bit more than half of Africa, and most of Canada/Alaska.
Comment: @SemidiurnalSimon - A point centered over northwest Russia would capture too much of the Pacific and would not capture all of Africa and North America. A point in western France does a better job, capturing almost all of Eurasia, all of Africa and North America, and a good chunk of South America.
Answer: I wrote a little Matlab script to estimate this approximatively. Here is the result: colour denotes the total land area inside the hemisphere centred on a particular surface point. The red point is the maximum.

This gives me a maximum for the hemisphere centred on 1.7582°W longitude and 40.7692°N latitude, roughly in Guadalajara, Spain. If I calculated right this is 81% of all land, with 23.37% land area on the hemisphere (and 5.83% on the other hemisphere). So the answer to the question is no, there is no hemisphere with more land than ocean. There isn't even one with more than half land.

(Updated 2019-06-23 with higher resolution estimation, which moved the point south a bit.)
Comment: +1 for the interesting process and answer, but in order to answer the question the answer should include which percent of that hemisphere is actually land (that is, the area of 81% of all land divided by the area of an hemisphere).
Comment: You 43°20′N 1°06′W point is a bit south of the point designated in the wikipedia article on the [land and water hemispheres](https://en.wikipedia.org/wiki/Land_and_water_hemispheres), 47°13′N 1°32′W. That point appears to be based on 1891 maps and was determined without the aid of computers.
Comment: Added the answer and ran my model at a higher resolution. The centre is still in Spain rather than France. I think one can quibble a fair bit about the correct way of doing this: I count large lakes as not-land, for example.
Comment: snazzy; yay for Python!
Answer: The total land area of earth is approximately 29%. So, in order to have a hemisphere with more land than water, out of 29% of total land area we need to have at least 25% of it concentrated in that hemisphere.
Now for the ease of understanding, what does 25/29 of total land area means? It approximates to 86% of the total continental surface area.
Area of percentage
Asia (including the Middle East)- 30.0%
Africa - 20.3%
North America - 16.3%
South America - 12.0%
Antarctica - 8.9%
Europe - 6.7%
Australia (plus Oceania) - 5.2%
Now on analyzing this, it's possible to conclude you won't be able to get such a hemisphere using a plane along the longitudes.
If you try to create a hemisphere using a plane that cuts through 60˚S and 60˚N latitudes, you might be able to have most the major land together areas except Antartica and Australia and some parts of Africa in it. Still, it won't be enough to have more than half of that hemisphere with land covering it.
So, my conclusion is it's not possible to come up with such a hemisphere. :)


How can you have a negative voltage?

Question: How can you have a negative voltage? I don't really understand the concept of negative voltage, how can it exist?
Comment: If I define *positive* to be in one direction, then if it is in the opposite direction, what should I call it?
Comment: Voltage is a scalar quantity (J/C))
Answer: The simplest thing to do here is remember that only diferences in potential matter, and that means that we can add or subtract a constant from every voltage in a system without changing it's behavior, so we can render any negative number positive to make you feel better or just as easily render all the positive ones negative.
In short, it's just a number and you shouldn't fret about it having a sign.
Comment: You should consider the sign. If $\Delta V = V_B - V_A > 0$, it means the electric potential in B is higher than in A. If it is negative, it is the other way around. That's an important difference, no?
Comment: The difference is the same regardless of whether you add a constant to all terms to render them negative or positive
Comment: But voltages cannot cancel out if you neglect the signs?
Answer: Voltage is a difference of potential energy for electric charges, and potentials are defined from forces, so that $F=-\nabla V$, where $V$ is the potential and $F$ is the force. When you have determined the potential $V$ you can now add any constant you want, or any function $f$ that doesn't depend on coordinates, because $-\nabla V=-\nabla (V+f)$, as $f$ doesn't depend on coordinates. This last thing is what's known as setting an origin of potential energy, something you sure have heard about. Well, in that function $f$ where you set your origin for potentials, you can have negative voltages between two points.
Another way to see the voltage is the work you must do per unit charge to move that charge from one point to another, even here, when we're dealing with differences, you can also have negative voltages.
If you're talking about circuits, all of the above applies, you can set a potential difference $V$ by, let's say, a battery, then you can use some device so that the potential energy is even lower than the one set by the - sign of the battery, as you set the potential origin 0 for that battery, then that point will have a negative voltage.
Answer: Let's say you want to know the electric potential difference r meters away from an electron sitting in a void of space. We will denote this potential difference as $V_e$.
The electric potential difference describes the difference in potential energy of a unit positive charge from one point in space to another and the work done on a unit positive charge to carry it from the same point to the other.
This gives the equation: $$V_a-V_b=k\frac{Q}{r_a}-k\frac{Q}{r_b}$$
$V_a$ is the final potential and $V_b$ is the initial. In this scenario, it is conventional to make $V_b$ the zero reference point at $r = \infty$, which makes $r_b = \infty$ and $V_b = 0$. Therefore, the equation becomes:
$$V_a=k\frac{Q}{r_a}$$
Because we are looking at the potential difference of an electron, $Q=-e$, where $e$ equals the elementary charge. So, the equation, in this case, is:
$$V_e=k\frac{-e}{r_a}$$
This equation gives a negative value no matter how far away the positive test charge is from the electron. This makes sense because a positive point charge at $r_b = \infty$ loses potential energy as it is brought toward the electron (downstream), and negative work is done.
If the electron is replaced with a proton, the potential difference, denoted by $V_p$, will become:$$V_p=k\frac{e}{r_a}$$
If you have a proton and an electron you will simply compute $V_e + V_p$, because electric potential is a scalar quantity.
Comment: Hi Bionic Person and welcome to Physics.SE! Please see [this](http://physics.stackexchange.com/help/notation) help post to learn how to write your equations in a *way* nicer way i.e. in $\LaTeX$, in order to improve legibility. Thanks!
Answer: "negative" voltage is relative!  Potential is potential.  If I have two batteries connected in series and measure volts from the point where they are connected, I will measure +V on one end and -V on the other.  This is a basic electronics question and now you have a basic answer.

How can you have a negative voltage?


What is best practice for auditioning a prospective new player?

Question: Continuing on this question how is the best way to set up an auditioning session? What gamewise should you do differently? What are the expectations on the group and the potential new person? What is the best way to handle this socially?
Comment: Related but probably not duplicate: [How can I screen new players to make sure they are a good fit for my game?](http://rpg.stackexchange.com/q/25484/4398)
Answer: Hmm. I don't think I've ever auditioned players before. This was very thought provoking — as I'd never thought of this as a formal process of any kind. Upon reflection, this is what we did…
People get invited into the games I run by myself and other players. In short, we use "social networking" to pre-qualify people to join our group. Each person that wants to bring a guest is free to, given that they understand that they are responsible for the behaviour of that person.
The unspoken rule is, "Only bring people who you would…

Want to see for 4+ hours in close quarters every single week,
Trust with your (character's) life,
Think would play nice with your group."

So my answer to the question, "How do I audition new players?" is, "I don't. We invite people we know and trust." I guess I've been very lucky to always have access to lots of great people to play with.
Comment: I'm co-founder of a board gaming group with over 500 members in the SF Bay area - http://groups.yahoo.com/sb-boardgamers. In almost 7 years, even with open membership (no qualification or recommendation required) we've only had to eject one member. Now I'm SURE I'm just lucky.
Answer: Pre-discussion of styles is fine but the real vetting is when they come and meet the entire group and interact with them.

First thing is to make sure they understand it's a tryout and the terms of it.  "Hey, we'd love to have you but want to make sure you gel with the group.  Come play with us next Tuesday as a tryout, after that if everyone's cool with it you're in."  Or "We have three people trying out for our open seat, you're first in so after your time it'll be a couple weeks; we'll let you know the week of the 5th." Or maybe you're not doing tryouts, you say "hey anyone's welcome" - but if you say that, don't call them up after and say "sorry they didn't like you."  Or "come join us for this campaign, but for later campaigns' it's up to that Gm to invite you..." Set expectations with them.
It's just like a job interview - both sides need to make a good impression. Don't just focus on "putting the new guy through his paces" - if he doesn't like your group, he'll reject you.  It's the usual "don't change who you are, but put your best foot forward" thing.  Make sure they feel welcome, brief them on what they need to know (where and when the game is, social rules of the house, etc.)  Similarly, they should be on time, show normal "guest in someone's house" graces, etc.  Beware in that some established groups can be very off-putting to new people - lots of shared context, in-jokes, etc. make it intimidating.  And whoever the new person is, it's quite likely they're less of a freak than at least one of your established group.  So pre-discuss with your group how to act and try to set some kind of mutual understanding ahead of time on what should comprise a yes or no, including decision process (any veto; majority rules; GM's prerogative, etc.)
A lot of it is more about personality/group fit than anything RPG specific, so even a board game night will show if they get along with people or not.
As for trying out in game, I think it's done better in a one shot than as a guest shot in an ongoing campaign - if the campaign is too in depth then they're lost.  In my current gaming group, my first session was the climactic session of their entire several year long previous campaign; the GM handed me a hundred page sheaf of docs on world background - quite offputting and hard to do well. Or at the start of a new campaign.  If it's in the middle it's somewhat inevitable that they play a NPC for the first time - it's understood this is a tryout, and it's disruptive to introduce a new PC that might not be there next time (unless it's a casual or high death game).
Make sure and think about saying the meta-stuff you don't always say at a game.  Expectations about attendance (e.g. it's expected you call if you can't come), kinds of preparation expected, gaming style (e.g. we adhere to the book rules without exception), and that.
Everyone should relax and have fun!
Comment: Your #6 clashes horribly with #1 and especially #2.  I can't think of anything less relaxing and fun (and more off-putting) than a job interview for a game.  Were I invited to a "gaming job interview" like this I'd politely decline.  Were it sprung on me as a surprise I'd get up and leave.  To my view if you're using the word "job" in describing *anything* in your game, you're taking things far too seriously for my tastes.
Comment: And I might point out that the question here is "how to conduct them" not "whether."
Comment: That works at times for very stable groups.  Then you move.  Or someone you don't all know very well says "Hey I hear you play D&D I want to join."  Your choices are unconditional yes, unconditional no, or tryouts.
Comment: Can't help you with #1 - gaming groups do tryouts nowadays and for good reason.  If you think you should get invited unequivocally to a recurring thing with a group of people without getting approved by all of them - heck, I would be concerned about that, since next session someone might bring an intolerable stinky freak without expecting everyone to have a say in it.  As for #2, read what I say again. It is like a job interview in that the group needs to make a good impression too, not just the potential new guy.  Sorry, I guess my example there is colored by professional tech company hiring.
Comment: I think this is a generational thing.  I game with the people I socialize with.  I don't socialize with those I game with.  (They look the same there, but there's a difference of emphasis.)  I don't do the cold-call gaming thing.  I game with friends.  The decision on whether or not someone gels was taken long before a game even entered a picture.
Comment: I think the one-shot suggestion is good, that limits the amount of investment. You could even consider a quasi-roleplaying game like Fiasco for that purpose.
Answer: I "auditioned" players by asking one universally-applicable question in any kind of social setting: "Could you please describe to me your favourite character?"  This is typically in a setting where role-playing is being discussed in a social context.  The answer invariably proves enlightening.
I call this "universally-applicable" because it works, in my experience, no matter what the relative styles of play of the two people.  If I'm a dramatist-all-for-the-story GM and the person regales me with tales of a character's grand exploits, personality and thoughts and reactions to events, there's a good chance this player is a fit for my game.  If the player instead talks up the levels and stats and magic items, etc. there's a very good chance this player is not a good fit for my game.
The reverse, however, is also true.  If a GM asks me this question and I answer with the name, family, great deeds, weaknesses, personality traits, etc. of my character, there's a very good chance I won't fit into a game dominated by people who treat the game as a series of tactical puzzles.
I adopted this approach to sounding out prospective players about five years before circumstances forced me to stop gaming entirely.  In those five years I had one single bad fit.  Before that I was averaging more than that per quarter.  I've also used this on the player's side with a slight change to the question ("Could you please describe the greatest event in your last year's gaming?") to see if I'd be a good fit for a group.
Answer: We've never auditioned anyone really for our group.  On the rare occasion that someone has left our group, adding anyone else has always been an invite someone you already know kind of thing.  We've been lucky with adding some great players over the years.
Even then, though, you play a few sessions and see if things are going well.  I wouldn't change anything from what a normal session would be.  You just try playing for a bit and see how it goes.  If things mesh, you'll know it.  And if things aren't working, you'll know it.
Answer: In my Ars Magica game, I always audition new players through a series of games. The first few games the player is encouraged to first play, and then create grogs that fit with the Covenant theme and that amuse them.
After they understand the mechanics of the system, the flavour of the world, and the relative powers of magi, I allow them to play an NPC magi at the covenant for a game or two, to allow them to understand how spell-casting and spontaneous spells work.
At that point, I poll all of my current players: any player may veto the newcomer for any reason, privately. During this period I will have discussed the general play style of my game and the expectations of the group privately with the newcomer as well.
This mechanic has the least disruption to games, while proving a multiple game venue to insure that both the new player and the old players are comfortable with each other.
Comment: @JUST MY correct OPINION: I think Brian works under the assumption that the new player doesn't know the (details of) the game system. In that case allowing him to play a fully fledged mage with decades of lab experience would simply overwhelm him and probably drive him off anyway. The same thing in DnD 3E would be handing a level 13 wizard to a newbie player who doesn't even know what a "saving throw" is. Perhaps it can work but it is much more likely to overwhelm - and thus bore - the player and bring the game to a full stop every combat round the wizard is supposed to do anything.
Comment: I'm not sure that I like the approach of "you get to play the menials while we do the cool stuff" myself.  I'd probably not be back for a second session if this were done to me.
Comment: Well it helps that the grogs are the ones with the skills and who actually get things done. Magi are so focused in magic that they lack many skills that any grog would have. The other part of the system is that players play grogs fairly often, when their magi are in the lab and the story is being inflicted on someone else.
Comment: I know the system.  I still would not be back for a second session if treated this way.
Answer: I meet the person somewhere public to get a sense of them.  I try to do several things.

I outline what my game is, how I run it, and what my expectations are.
I ask whether any thing in what I've told them so far causes them any concerns.
I ask what their expectations are
I ask what kind of character they think they might want to play based on what they've heard so far.
I give them a one page summary of the campaign world and tell them I'll let them know.

If the person seems like they'll fit into my group I ask them to come and play a session.  After the session has had a few days to sink in, I ask my players what they thought and I ask the new person what they thought.  If everyone is happy then we ask them to be a permanent member and go from there.
Answer: I've never actually tried this because I've never had a shortage for players, but here's an idea I've really wanted to use.  Instead of auditioning players, audition characters.  Have the potential new players send you summaries of their characters and backgrounds.  Choose the character that will have the most interesting affect on the story.
Comment: This sounded as a great idea at first, but I suddenly realized what a bummer it would be for the potential player to spend time working out a character with an interesting background and then not get invited to the campaign.
Comment: Ravn, I don't disagree but just because the character doesn't get cast doesn't mean that character can't get used in another game.
Answer: The first 3 weeks are a trial-period for everyone. If they can't handle the bad jokes, the game in progress, etc, then they don't get to stay. I've only punted 5 people in 30 years.

1 for cheating
2 for not being able to make it to game reliably; they're welcome back when life quits kicking them in the....
1 for drawing a weapon on me
1 for failure to pick up his bloody snotrags after his frequent nosebleeds.

I've had several who decided my group wasn't for them; that's more like a dozen in the same time frame. There are a few unwelcome individuals; then again, most everyone in my circle either considers them the same, or knows that the two of us in the same room equals no game.
Comment: Is it odd that I almost want to know the story behind the cheating and "drawing a weapon" bootings? It sounds like you've had some interesting game sessions!
Comment: *Cheating:* System was GURPS; I had approved character, including required disads (there was a choice of how severe and which of two, and it didn't count against the 4/40 limit). Player, in session 3, had rewritten character without either. *Drawn weapon:* player dozed off, I shook him to tell him game was over, and he pulled a 9mm. Rest of the room then pointed an assortment of firearms at him, including a shotgun and a 45-70 rifle. Gotta love open holster and license-free concealed carry laws...
Answer: I'd never really engaged in 'interview's' as a matter of course, but have been on both sides as interviewer and interviewee in very recent months.
I guess the best advice is what 'feels' right to you, the GM and other players and it depends if the person is a perfect stranger or not - best not to meet complete strangers on your own and all that as others have said.
Check with your group beforehand to see if they have any 'deal breakers' ("no rules lawyers please!" or whatever) and so on, just so you have your expectations set in advance.
I personally couldn't have cared less about rules knowledge, previous characters (do NOT tell me about your character) and their understanding of various game mechanics or roleplaying style.  Everything is possible if you all get along, which was the most important part I found.  I tend to look for indications that the person is enthusiastic, happy to learn new tricks and appears to be reliable.  Everything else is less important to me.
When interviewing for a player I exchanged a few emails, spoke briefly on the phone and then met up with a guy at his house (met his wife and child too), along with my gamer wife.  This gave us the time to get to know each other and get a feel for things before getting the whole group together.  We talked systems, what we play, what the group was like and other stuff but the point was to get a 'gut feel'.
I let the rest of the group know my impressions and then we all got together - as it happens everyone got on great and built up a rapport that had nothing to do with game (which I think is useful but not necessary).  I checked with everyone after the first session but as we were a pretty laid back bunch we we're all cool.
I've very recently been on the other side of this having moved from the UK to USA and tracked down a gaming group.  A few email exchanges with one of the gang and then a meetup with the larger group for an afternoon of shooting the breeze and gaming started a week or two later.  Things appear to be going well so far.
Hope that helps?


Is hijrah from daar al-kufr ( the land of disbelief ) obligatory?

Question: I live and was born in a non-muslim country, i was also born in a religious family, however, my parents and grandparent came here in order to flee and escape war and the dreadful situations of their homecountry, and i later on found out that hijrah is fardh (obligatory) and my family doesn't know and i also saw a hadith of the prophet where he said something like, whoever settles with kuffaar,i have nothing to do with him. Please clarify, is it obligatory upon me to do hijrah? And if so am i sinning if my family don't support me and don't want to leave and i cannot leave alone.
Comment: This question has several issues one of them is that it includes many questions (see [on Meta](https://islam.meta.stackexchange.com/questions/2965/why-we-should-avoid-asking-multi-question-questions?s=1|27.5177)) and the other is that the last question in your question title is opinion-based.
Answer: In the name of God, The Beneficent, The Merciful

You're allowed to stay in a non Muslim country, but this only if you're able to practice the Islamic stuff such as praying, if you're not able, then move to another Muslim country.
According to al-Islam.org you can migrate or visit any non Muslim land you wish. But when you visit, you have to spread Islam so that others too will convert to Islam. But it is dangerous to travel there, why? Because it leads to many evil things and you'll probably do evil like them.

Imam ar-Rida (a.s.) explained the prohibition of at-ta'arrub ba'd al-hijra as follows: "Since there is the danger that because of at-ta'arrub, he [the immigrant] might abandon [Islamic] knowledge, get involved with the ignorant people, and drift away"

The basic principle is that, is not permissible to settle in a non Muslim land because God Says( interpretation of the meaning):

"Indeed, those whom the angels take [in death] while wronging themselves - [the angels] will say, "In what [condition] were you?" They will say, "We were oppressed in the land." The angels will say, "Was not the earth of God spacious [enough] for you to emigrate therein?" For those, their refuge is Hell - and evil it is as a destination." [The women, 4:97]

That is in case, you're not able to practice openly Islam in a non Muslim country. If you're able to practice openly Islam, then there's no sin upon you.


How do you earn bonus Merit Stamps?

Question: Occasionally when turning in an errand, you'll earn a bonus Merit Stamp ("You earned X stamps... and 1 bonus!"). What prompts the bonus stamp?
Comment: Great question.
Answer: I have tested this personally, it is for every 10 errands and bounty hunts you complete.
Do note that the count for errands and bounties are maintained seperately and the bonus merit point is awarded for completing 10 errands or 10 bounty hunts.

How do you earn bonus Merit Stamps?


Tomcat configure maxThreads per webapp

Question: is it possible to configure tomcat to use a predefined number of threads per webapplication?
The idear behind this is, if i deploy several applications on tomcat and let's assume one of those has a bug which results into a deadlock.
What happens is that this application will cause tomcat to create new threads until it reaches the maxThreads setting. After that no more Threads can be created which affects the other applications as well. It would be nice to tell tomcat something like "hey you can only serve 50 threads per application". If then the application with the deadlock reaches it's 50 Threads it will just be blocked, but the other applications will stay save.
thx,
kuku
Answer: Maybe StuckThreadDetectionValve https://stackoverflow.com/a/7484800/1349691 helps in your case.

Tomcat configure maxThreads per webapp


Visualization of de Sitter spaces

Question: When I was reading about de Sitter it said that the we looked in 5-dimensional Minkowski metric and that we had immersed in it a hyperboloid, and with some coordinate transformation we get some metric that we see resembles a known metric.
But how to visualize this? And why did we took the hyperboloid in the first place? None of the books I read on the subject really gave some simple explanation to that :\
I'm kinda puzzled about this :\ How do I 'see' things with given metric?
For instance, I have, for de Sitter:
$$ds^2~=~-dt^2+l^2 \cosh^2(t/l) d\Omega_3^2$$
And this describes a space tri-sphere that shrinks to a minimum at t=0, and then expands.
Now, this means that the $d\Omega_3^2$ is a three-sphere, contracts because of the hyperbolic cosine, and time is just normal like in Minkowski. Am I right in interpreting this?
Answer: The motivation for this construction is explained here:
He first gives the example of a space of constant positive curvature - the 3-sphere, given by taking a flat Euclidean space of one higher dimension (4) and restricting to the subspace $(x_1, x_2, x_3, x_4)$  s.t. $$x_1^2+x_2^2+x_3^2+x_4^2=a^2$$ for some $a$.  The metric on the sphere is just the induced metric from the embedding.
If, instead, we start in Minkowski space, and look at the subspace $(x_0, x_1, x_2, x_3)$ s.t. $$x_0^2-x_1^2-x_2^2-x_3^2=a^2$$  then we end up with a space of constant negative curvature, which we can draw as one sheet of a hyperboloid.  Again the metric is just the induced metric.
De Sitter space is just exactly the same thing but starting in 5 dimensional flat Minkowski space instead of 4.
Your interpretation is right, but it's important to notice that time as defined here (the one in which the spatial 3-sphere contracts and expands) isn't a Killing vector of the spacetime, i.e. isn't a symmetry like in Minkowski space.
Comment: Thank you for the explanation, I had some troubles with this. I am going to look at the pdf you provided :)
Answer: I find it helpful to visualize de Sitter space-time using Felix Klein's approach to geometry; begin with projective space and pick a polarity that transforms trivially under the congruence group of the geometry. To get 3+1 de Sitter space-time one starts with a 4-d projective space that is modelled as the rays of a 5-d vector space $V_{5}$; a point in de Sitter space is a ray vector $\lambda x^{i}\in V_{5}$ where $\lambda$ is a weight with no physical significance. In Kleinian language, a polarity is a symmetric tensor $I_{ij}$ that maps points $x^{i}$ into hyperplanes $x_{i}=I_{ij}x^{j}$. The congruence group of de Sitter space is SO(4,1) and so the polarity $I_{ij}$ has to transform trivially (be invariant) under SO(4,1). In Kleinian language $I_{ij}$ is called the absolute polarity. A natural hypersurface is  $x^{i}I_{ij}x^{j}=0$. The physical points of space are rays in projective space so that $\lambda x^{i}I_{ij}\lambda x^{j}=0$ must be the same hypersurface; that is why the RHS must be zero in order to define a hypersurface. If one transforms everything with a SO(4,1) matrix $[D(g)]^{i}_{  j}$, the points go $x'^{i}=[D(g)]^{i}_{  j}x^{j}$ and the absolute polarity remains unchanged so that,
$$
                  x'^{i}I_{ij}x'^{j}=x^{i}I_{ij}x^{j}=0
$$
which shows that all "inertial" observers agree on the natural hypersurface. In this context inertial means observers connected by SO(4,1) transformations. In Kleinian language, the hypersurface is called the absolute quadric. The polarity is a symmetric tensor so it can be diagonalized; with a natural choice of the unit of length it is diag(I)=[1,1,1,1,-1]. In projective space the absolute quadric hypersurface is ,
$$
(x^{1})^{2}+(x^{2})^{2}+(x^{3})^{2}+(x^{4})^{2}-(x^{5})^{2}=0.
$$
In the 5-d projective space the quadric hypersurface looks like a cone symmetrical about the $x^{5}$ axis. (Think of 1+1 de Sitter space-time in which the projective space is 3-d and the quadric hypersurface is the cone $x^2+y^2-z^2=0$.) However, instead of visualizing points as rays in the projective space, it is better to set up an arbitrary hyperplane and take the representation of the point as the point at which the ray intersects the hyperplane. In this way the geometry becomes a sketch  on this hyperplane used as an aid to visualization. In particular, the absolute quadric becomes a conic section. The graphic shows the absolute quadric  as an ellipse for 1+1 de Sitter space-time. The absolute quadric  divides the space  into two parts . The  points inside the quadric  are called ordinary points and the points  outside the quadric are called ultra-infinite points.  The ordinary points make  up hyperbolic geometry.  The  ultra-infinite points make up de Sitter space-time. In the graphic the observer is shown at point p  along with the observer's future and past infinity and the light cone. I got a lot of this from reading Coxeter's book "Non-Euclidean Geometry". The picture of de Sitter space here is what Schrodinger calls the elliptic view  in his book "Expanding Universes"; the compact space-like slices are elliptic spaces and not spheres.

Visualization of de Sitter spaces


How do I remove Cement Board that has been screwed in and is bonded to wood subfloor with thinset?

Question: I am in the process of purchasing a townhome and I am looking to tear up the existing 12" ceramic tile that covers the entire main level... an area close to 600 sq. ft. to make way for laminate flooring. Thinset has been used to bond the tile to the cement backer board, and the backer board has been screwed to the wooden subfloor. There is also some sort of adhesive/mortar bonding the cement board to the wooden subfloor.
What tools will I need. Are there any techniques that would make it easier? Would trying to remove the cement board damage the subfloor? If so, would it be acceptable to repair damage with some sort of floor leveling compound?
Comment: Well, it was installed right, I guess. Grab a sledgehammer...
Answer: Here is an idea to consider. If the tile comes off the cement board fairly easy, you could leave the cement board, scrape off the thinset and lay your foam and laminate over the cement board.  Just a thought depending on the overall thickness you need to achieve.
Answer: If it was installed correctly, the cement between cementboard and wood will be thinset and it will break off the wood fairly easily - it's put there to fill the space well, not to actually bond it particularly. If it was glued down with construction adhesive you might be in for a more miserable time. Safety glasses, gloves, and a sledgehammer to get started. You'll probably have to break the board around the screws and remove them with locking pliers - the screwheads will be full of thinset and it would be tedious to get them to the point you can use a screwdriver on them again. Beware of screws that break off - they can be sharp if you don't immediately remove the stub from the floor.
You can try driving a wide (4" or so) flat chisel under the edge to pop sections off, but straight sledgehammering will probably be faster.
Comment: Thanks, I'm pretty sure that it is just the thinset in between the cement board and subfloor. It is good to know that it should come off with not too much trouble. Your saying its best to approach it by breaking the board with the sledge? Would it be possible to use a prybar to take it up faster?
Comment: You could certainly try a heavy crowbar/ripping bar on it, and see which is more effective. A thin prybar (wonderbar) will probably get bent. Depending how the tile comes off, @shirlock homes has a good point - cement board, if you can get the thinset off (a silicon carbide rubbing block may be handy for the last bits) is a perfectly good base for laminate. That might make the wide chisel for popping tile off make more sense.
Comment: Thanks for the input, definitely something to think about - leaving the cement board and putting the laminate on the cement board. How hard do you guys think it would be to remove the thinset from the cement board?
Answer: I have the same problem and need to remove the tile, durock / cement board as well as the subfloor due to water leaks and mold.  Nothing is easy about this job, but scoring the floor with a skill saw cement blade has certainly helped by making the job a little more manageable.  Open windows, block all vents and mask required!  Back to work. . .
Comment: Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably [take our tour](//diy.stackexchange.com/tour) so you'll know how best to contribute here.
Answer: It's best as a 2 person job with one person busting and one removing ideally.  Just did one today.
How to to do it?  An electric chipping hammer to take off the tile first.  Then a 2 lb hammer to knock some holes, then just pull off the durock in fairly big pieces, like 3 x 3.  Don't kill yourself,.....have 2 people carry it out.
Comment: I thought this was a shower demo,....sorry.  On a floor I'd try to leave the durock if possible.  Wide blade chipping hammer and / or maybe rent a machine.  That's a lot of tile to use a chipping hammer on.
Comment: I'd also consider going with a wood look tile.   It would be easier since laminate snap together flooring requires a very flat surface or it will not work.  With tile you have the thinset as a buffer.  I personally would not do laminate in that situation due to the tile unless I could go on top of the tile.


Why evacuate upwind?

Question: Evacuation procedures after a forced landing recommend directing passengers upwind of the aircraft.
What is the reason why evacuating upwind is better than other directions?
Comment: Which way will the smoke and fire blow?
Answer: There are two problems linked to the wind after accidents:

Inflating the slides.
Running away from the aircraft when on the ground

@DavidRicherby listed the reasons related to running away upwind to try to avoid the effects of flames and fumes (visibility, heat, toxicity). This is part of the IATA guidelines for post-evacuation:

Post-evacuation. Once outside the aircraft, the cabin crew is
  responsible for the passengers until relieved by the authorities or
  emergency services. Until this help arrives, the cabin crew should:
  - Direct passengers upwind and away from the aircraft;
  - Assemble passengers;
  - Direct passengers away from fuel, fire and vehicles;

Source
While it appears running upwind is a good choice, deploying slides upwind has not always been a good idea.
A study was conducted by the National Aerospace Laboratory (NLR) in Netherlands, about slides issues during evacuation. It was published by the Flight Safety Foundation in 2005:

Analysis of Evacuation-slide Problems
Calls Attention to Recurrent Issues

The scope of the search was the period 1970–2003 and covered aircraft operations worldwide. NLR researchers identified 150 accidents in which slides were used. A total of 89 slide problems were identified:

One problem was slides not inflating due to the wind:

Wind had an adverse effect on the use of slides in 11 slide problems
  (12.4 percent) analyzed by NLR researchers. Typically, wind blew the
  slide against the side of the aircraft, preventing its use.

To allow using the upwind side of the cabin for slide deployment, today, aircraft certification include this requirement for slides:

4.20 Wind. The device must be shown, in 25-knot winds directed from the most critical angle, to deploy and, with the assistance of only
  one person who has evacuated down the device, to remain usable after
  full deployment to evacuate occupants safely to the ground.

Source
See also:

IATA - Cabin Operations Safety - Best Practices Guide
EASA ETSO-C69, Emergency evacuation slides, ramps, ramp/slides, and slide/rafts
Answer: If there is a fire, any smoke and flames will blow downwind. If there is a fuel leak, the fuel vapours will be blown downwind, risking a fire or explosion there and potentially making it hard to breathe.
Answer: The evacuation at least 500 meters upwind is to prevent from being intoxicated with toxic fumes, gases from burning materials and alike
Comment: This answer adds nothing significant to the existing answers.

Why evacuate upwind?


How to search entire hard drive for a file?

Question: Trying to locate a file, how can I search the entire hard drive for a file?
Comment: http://askubuntu.com/questions/714091/my-quest-to-find-the-fastest-search-app-for-linux
Answer: A simple find / -type f -name "" would do the trick if you know exact filename.
find / -type f -iname "filename*" if you want to match more files (ignore case).
Make sure to properly delimit \ shell metacharacters in the filename like *?[] or replace them with a non-delimited *.
Avoid -type option if you want to search for directories etc. See manual of find for more information. To see the manual, issue the command:
man find
Comment: note that one might wish to add `sudo` ahead of the mentioned command
Comment: This will also search all mounted devices as well, might want to just search `/mount/hddyouwanttosearch`
Comment: Worth noting that find is really slow, compared to an indexed search system, such as locate (but also more powerful)
Answer: You could also use locate to look for commands. Why do people use locate if find does the job? Because locate is much faster than find since it just searches through database(s) of indexed locations to find your file/regex.
Examples:
locate some-file.avi searches through database(s) of almost every file on the disk for a file called "some-file.avi".
locate -i "some-file.avi" will ignore the case of the file you are searching for.
locate -i "*.txt" will display a list of locations of all the files with **.txt* extension on your system.
man locate for more info on the file.
You might need to run updatedb first to ensure the index database is up to date, otherwise, 'locate' might not return what you are looking for.
Comment: this is WAY faster than find \ holy cow... thanks!
Comment: Note that `updatedb` must be run as root.
Comment: If `updatedb` adds `/` to the index by default, how can it still be faster than `find /`?
Answer: Start by clicking the "Home Folder" icon in the launcher.

In the window that opens, click "Search".

Type what you want to search for in the box, then press enter.

Under the dropdown for location, choose your hard drive, then click reload.

The results will then be displayed. Hope that helps!
Comment: The man who asked it states he uses a server, so there is no GUI. But that's a great answer anyway!
Answer: If you're looking for a string inside a file, you can use grep. Here's a sample command:
grep -r -i "some string" /home/yourusername

This will find "some string" in /home/yourusername directory. The search will ignore case (-i) and recurse directories (-r). You can use / as the directory to search in the whole directory but that might not be very efficient.
Answer: On Ubuntu, i know that everyone wants to be dogmatic about using command line all the time, and I have in the past been that way, but I love the Gnome "Search for files..." tool.  I think its awesome.
Comment: well i'm on a server
Comment: You should try then the KDE search. It is far better than the gnome one. I am still waiting for Nautilus to catch up with the versatility that the KDE search system has. Dolphin/Konqueror are far better because of it.
Comment: Yeah, I was thinking about switching to Kubuntu actually.  I'll take a look at it.
Answer: For a Desktop setup, Install "gnome-search-tool"
sudo apt-get install gnome-search-tool
Don't install this in a server, it will also install the ubuntu desktop package.
Thanks to @Rinzwind for pointing that out.
Filters inlude:

Choose the folder you want to search. In this case \
Contains the text - this is the file name.
Date Modified - less or more than in number of days.
File size - at least or at most a specified size. You can also search empty files.
File owner - user, group or unrecognized owner.
Regular expressions - matches regular expressions.
You can choose to show hidden files, follow symbolic links or exclude other filesystems.
Comment: @Rinzwind The question was `Trying to locate a file, how can I search the entire hard drive for a file?` There is no 'server-install' anywhere...
Comment: @Rinzwind Hahah. Nice one. Let me edit my answer and say this is for a desktop setup alone.
Comment: 3

For a Desktop setup, Install "gnome-search-tool"
sudo apt-get install gnome-search-tool
sudo apt install gnome-search-tool
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
E: Unable to locate package gnome-search-tool
  ((((( it's now 2022 ))))))
Answer: If you don't want to remember find (which is a very powerful) parameters you could install from official repos:

kfind - file search utility
gnome-search-tool - GNOME tool to search files
catfish - File searching tool which is configurable via the command line

The three of them are great, but I found kfind the best.
From Ubuntu Community help wiki you might find useful:

dpkg -L|--listfiles  ...     List files `owned' by package(s).
dpkg -S|--search  ...        Find package(s) owning file(s).
Answer: If need to find nested in some dirs:
find / -type f -wholename "*foo/bar/filename"

Answer: If you want to find a file or its contents, and you don't want the search to stop if your ssh session gets disconnected for some reason, and you want to store the results in a file that you can reference later:
$ sudo nohup find / -type f -exec grep -H -i -n mysearchstring '{}' \; -print 2>/dev/null | tee /home/rmoore/find_output.txt &


How "macro" in computer programming came about

Question: The prefix macro- is normally used for large things like macroeconomics and macroscopic. How did it come to be used to describe text macros in the programming world?
Comment: Note that *makros* normally means "long" in Greek.
Comment: I have just experienced a revelation. I thought `macro == micro`. Doh.
Answer: In computing, "macro" was first used with assemblers, which are utilities that perform simple translation of readable mnemonics into machine instructions.  Normally a single line in an input to a basic assembler produces a single machine instruction output; the line is commonly referred to as an instruction.  Productivity was increased when the use of what were termed macro-instructions were invented.  Macro- is of course a standard prefix from the Greek meaning large, and a macroinstruction was a new kind of input line which would generate several machine instructions.
The OED shows a revealing quote from 1959:

The built-in system macro instructions in SCAT presently consist of (1) two macros for generating the‥standard entry and exit from subroutines, (2) a set of debugging macros.

This shows use of both the full form, macro instruction,  and the abbreviated form, macro. (Quote is from Greenwald & Kane, "The Share 709 System: Programming and Modification", Journal of the ACM 6:133.  SCAT ("Symbolic Coder And Translator") was an early macro-assembler.)
Comment: +1. This SCAT is "SHARE Compiler, Assembler, Translator", not "Symbolic Coder And Translator". And I've found some [1958](http://english.stackexchange.com/questions/35984/how-did-the-word-macro-as-used-in-computer-programming-come-about/47059#47059) references.
Comment: So basically it came from Greek meaning "big" or "a lot" and in reference to computers refers to a programming instruction which results in more than one line of machine code which is "a lot" for a computer to do: handle more than one line of machine code? Or put another way a line of programming code which results in more than one machine instruction is a macroinstruction because it it bigger in that it results in more machine instructions? This idea then evolved into any single instruction which performs multiple actions such as a keyboard macro or excel macro?
Answer: From the Computing Dictionary:

The term "macro" originated in early assemblers, which encouraged the use of macros as a structuring and information-hiding device. During the early 1970s, macro assemblers became ubiquitous, and sometimes quite as powerful and expensive as HLLs, only to fall from favour as improving compiler technology marginalised assembly language programming (see languages of choice). Nowadays the term is most often used in connection with the C preprocessor, Lisp, or one of several special-purpose languages built around a macro-expansion facility (such as TeX or Unix's troff suite).
  Indeed, the meaning has drifted enough that the collective "macros" is now sometimes used for code in any special-purpose application control language (whether or not the language is actually translated by text expansion), and for macro-like entities such as the "keyboard macros" supported in some text editors (and PC TSRs or Macintosh INIT/CDEV keyboard enhancers).

Another explanation is that it is a shortening of "macroinstruction" which means:

a single computer instruction that initiates a set of instructions to perform a specific task
Answer: To follow on from mgkrebbs' fine answer, the SCAT in question is a SHARE 709 assembly program: "SHARE Compiler, Assembler, Translator". Both SCAT and macro are mentioned in papers presented to the Association for Computing Machinery and IIT Research Institute in 1958.
The earliest, ACM's Preprints of summaries of papers presented at the national meeting, tells us "The compiler expands each macro into one or more words of machine code ..." (1958 confirmation):

The next, IITRI's Computer Applications: Proceedings, shows we might have called them pseudos:

Finally, macroinstruction is found in 1956's Proceedings of the Western Joint Computer Conference: