If you place a pencil in an opaque box and close the box, does the pencil exist?

Question: I'm trying to explain to my friends about things existing. I gave them this question: if you place a pencil in an opaque box and close the box, does the pencil exist? They say yes and I ask how do they know and why. All they come up with is "because I put the pencil in there". I'm having a tough time explaining why the pencil ceases to exist once you close the box.
Comment: Maybe that's because the pencil **doesn't** cease to exist?   This is hardly philosophy.
Comment: Can you explain what led you to believe the pencil ceases to exist in the first place? Perhaps a misunderstanding of [Schrödinger's cat](https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat)?
Comment: When you get frustrated with your friends and take the box home, do your friends also cease to exist?
Comment: Have you considered asking friends who have not yet developed [object permanence](https://en.wikipedia.org/wiki/Object_permanence)?
Comment: I am having difficulty understanding the question. Suppose instead I said "I am trying to explain to my friends about sisters. I ask them, do you have a sister, and if they say yes, I ask them if she is female, and they say yes. I ask them how they know. Now I am having a tough time explaining to them why their sister is not female."  My scenario appears to me to be the same as your scenario. Can you explain your question to show how your scenario and my scenario are not the same? Or, if they are the same, can you explain why you find it odd that explaining counterfactuals is hard?
Comment: That's the the problem with wrong facts. They're usually harder to explain.
Comment: Even without object permanence, there's a big difference between "I cease to know if the pencil exists" and "the pencil ceases to exist"
Comment: So you don't bring money to the bank, because it 'ceases to exist'?
Comment: Correct me if I'm wrong, but this seems kind of a troll question because the title poses as a question, but the description rattles on about how convinced the OP is about his or her answer to the question and just needs to know how to explain it to his or her friends.
Comment: If I don't leave a comment here, I might not exist.
Comment: Most people learn Object Permanence before age 2, but I guess OP is an exception...
Comment: Are you trying to explain the Schrodinger's Cat thought experiment? Because that's in the realm of quantum mechanics, not philosophy. https://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat
Comment: Don't forget: Schrodinger doesn't put just a cat in the box; he also puts something which could result in one of two outcomes. In other words, when he closes the box he also destroys information. If your assumption were true, he could have just put the cat in there.
Comment: IF we all exist in a Star Trek holodeck, then yes, the computer may optimize the pencil out of existance, and simulate weight and rattling sound made by the pencil.
Comment: @JohnDoe  in theory (hah), there's a finite probability that the pencil winked out of existence after you closed the box (or Schrodinger's cat ate it, which is the same thing), and you don't know for certain until you reopen the box.  But as you hinted, we don't know the pencil doesn't exist.  We just don't know its current state.
Comment: @Nacht I think DarthFennec's point is, trying to convince someone of the pencil ceases to exist, might be easier, if he talks to someone who isn't aware that it doesn't ^^
Comment: @ Xavier-Moody-Wusik I'd love to explain it to you, but as your question (and my answer) ceases to exist when I close my browser, there is no point doing so. Actually, you ceased to exist (if you even existed at all) since I am unable to perceive you. TL;TR: Your assumption that the pencil ceases to exist is flawed, thus the explanation you seek is impossible.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/89673/discussion-on-question-by-xavier-moody-wusik-if-you-place-a-pencil-in-an-opaque).
Comment: @DarthFennec after trying to explain that a pencil in a box doesn't exist, maybe ....
Comment: What if you put the box into another opaque box? Does the first box cease to exist? What if you close or eyes? Do you cease to exist?
Comment: No, obviously the pencil ceases to exist and is immediately replaced with a different pencil with the same weight, appearance, and any other property which has been measured before closing the box; so that the new pencil is indistinguishable from the one which has disappeared.
Comment: This is the sort of thing that someone believes until you take their wallet, pop it in your coat pocket, and say "what wallet?' Neither of us sees a wallet. No such wallet exists."
Comment: The pencil doesn't cease to exist. God simply teleports it to that point in the future where the box is opened. Seriously now, your question is premised on the notion that nature can operate in a discontinuous fashion, ie., that nature obeys no laws whatsoever, and that the regularities we have observed are due to sheerest luck. The untenability of this position should be obvious with a bit of thought.
Comment: Are you going to open the box and observe the pencil?  The pencil might not be in the box, and it might be destroyed while inside the box.
Comment: I think a better question would be to ask: "If we aren't able to observe something, does it exist?" This may be the more interesting question. And the answer is yes. There are several things we couldn't observe for a long time and I'm sure there are many more.
Comment: You and your friends don't disagree about whether the pencil exists. You disagree about what standard of evidence should be required to answer the question.
Comment: if it's "real" then yes!
Comment: @MarkTO tell it to the judge!
Comment: "I'm having a tough time explaining why the pencil ceases to exist once you close the box": this is because you forgot to mention to your friends that the box is an incinerator.
Answer: If you shake the box, it rattles. If you measure its weight before you put in the pencil and after, it will have increased by exactly the weight of the pencil. That's how you know the pencil still exists in there.
And if you really want to explore the basic meaning of "existence": how and why do you know the pencil exists before you put it into the box? How and why is this different from the rattling and weight increase?
Comment: Even if you don't measure the box at all - something does exist in the box, which will cause you to see the pencil, when you open the box. So there is something in the box, which is different from an empty box - and we simply call this "being there when I look" = "existing", without any need to define the exact state in which the pen exists if I don't look
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/89796/discussion-on-answer-by-michael-borgwardt-if-you-place-a-pencil-in-an-opaque-box). Comments should only be used to suggest improvements of the post.
Answer:
I'm having a tough time explaining why the pencil ceases to exist once you close the box.

Because you're trying to explain something which is wrong physically and wrong philosophically.  Your friends are correct.
The issue is that you have no proof of its presence or absence once you close the box.  That does not mean it ceases to exist.  It just means that you cannot prove whether it still exists, or whether it ceases to exist at some point whilst the box is closed, or even whether it ceases to exist at the moment the box is closed and reappears at the moment the box is opened, or flickers in and out of existence, or becomes an alien spaceship when you're not looking.
Absence of evidence does not mean evidence of absence - that's a basic logical fallacy.  It simply means we don't know.
Comment: Also, even "absence of evidence" doesn't really apply to this case. The fact that you put the pencil into the box and haven't opened it to remove it is actually quite strong evidence that the pencil remains in the box and continues to exist. It's not proof, but it's definitely evidence.
Comment: @reirab Strong evidence isn't conclusive proof though, which I think is where the OP is coming from.  Sure, Occam's Razor strongly suggests the pencil is still there.  However Teller, of Penn and Teller, has a wonderful "smoking a cigarette" sleight of hand routine involving a pencil, which shows just how wrong Occam can be!  I personally think the line of philosophy the OP seems to be falling into is just irrelevant bullshit sophistry, but I'm happy to concede "absence of evidence" for something which is irrelevant bullshit. :)
Comment: @Graham I'm confused on how one can 'violate' Occam's Razor? As far as I know, Occam's Razor is a heuristic used to pick out the best hypothesis in the absence of complete information. Of course it's not going to always result in picking the same hypothesis as the one you'd have picked if you had more information. In the case of being mislead (by a magician, statistics or otherwise), forming a hypothesis based on what you knew at the time and it later being revealed to be 'wrong' in the presence of more information doesn't 'violate' Occam's Razor.
Comment: @Graham but "just smoking a cigarette" doesn't match the facts that the pencil has vanished (or whatever, not actually seen the trick) so it doesn't satisfy Occam's Razor.
Comment: @Graham Occam's razor says that the simplest explanation *that fits the facts* is the best. If a magician stops in the middle of an act to smoke a cigarette, "they really want a smoke" doesn't fit the facts.
Comment: @Accumulation I suggest you look it up on YouTube. Basically it looks like Teller simply lights a cigarette and smokes it. That's the Occam's Razor explanation, and it fits all the facts we can see. The subsequently-explained reality is a complex exercise in sleight of hand and misdirection, for no reason than because he can. The OP's pencil may have gone a similar way; but unless the OP is a similarly talented magician, the odds are probably less likely. :)
Comment: @Baldrickk Watch the trick then.  There's about 20s of Teller lighting a cigarette and smoking it.  Then they break it down slowly to show how he's actually substituting a pencil for a cigarette which goes in various directions thereafter, and various fakery to make you think the pencil is a cigarette, and even that the pencil/cigarette is still there when it's actually been palmed elsewhere.  The whole sequence was deliberately constructed as a violation of Occam's Razor, because everything you think you see turns out to be something else, and for no other reason than because Teller can.
Comment: Yes, however I'd say that the "we don't know" here is in a very strict sense, and in this sense we can also say "we don't know" to a lot of other things. There are many, many very good reasons to assign at least a _quite high probability_ to the statement that it still exists. That that probability cannot be 100% - which is what it means to say that 'we don't know' in a _strict_ sense - doesn't discount the fact that it's so high that it would be quite unwise to stake anything of even small value on its not being so.
Comment: @TheSympathizer Exactly. That's why I'm happy to concede absence of 100% evidence, because in every practical sense we *do* know, so arguing over the virtually-zero probability of anything else is a pointless exercise.
Comment: @Graham I don't _need_ to see the trick.  The simplest explanation that fits the facts is that it's a trick, not that the pencil suddenly metamorphoses into a cigarette or whatever 'other' object is used.  It doesn't 'violate' Occam's Razor.
Comment: @Baldrickk Then you're talking from a position of ignorance - which is fine, until you start passing judgement on things you've chosen to not know.  It's on stage and you know the guys are magicians so naturally your first thought is "there must a trick somewhere", but there's no payoff or big reveal, and all the way along he could just have smoked a cigarette for the same effect.  Just watch it and you'll see what I mean. https://www.youtube.com/watch?v=y4U-kHdXgz0
Comment: @Graham _"Then you're talking from a position of ignorance"_ yes, that is exactly the point.  _IF_ I didn't know what was happening, then that would be the conclusion that Occam's Razor would support.
Answer: The assumption that the pencil continues to exist - even when the box is closed - is the most simple hypothesis which explains all relevant observations. E.g., the observation that the pencil exists when opening the box, as @Mauro ALLEGRANZA explains.
Comment: Most simple hypothesis is usually referred to as Occam's razor
Comment: @Cell I mean "simple" not "intuitive". Intuition can be a deceptive adviser. The hypothesis of continuous existence is simpler than the opposite hypothesis. Because the opposite hypothesis has to explain how opening and closing the box destroys and recreates the pencil.
Comment: @Anush Of course, this belief is simple. But necessary and difficult is the additional explanation how things vanish and reappear; see my previous comment.
Comment: I think the word intuitive is a better description than simple. I don't see why ceasing to exist must be more complex than continuing to exist.
Comment: @Cell The OP speaks about "explaining why the pencil ceases to exist once you close the box".
Comment: @Anush but that's not what is happening. Simply believing things you can't see don't exist WOULD be simple. But you DID see it originally, so it's that the pencil DISAPPEARED somehow, and that is NOT simple.
Comment: @Jo Wehler who said that opening and closing box caused the destruction of the pencil or that it was even "destroyed"?
Comment: Actually I am not sure. Believing things don't exist when you can't see them is simple too. Just wrong :)
Comment: @Cell You would have to explain why the closing of the box affects the existence of the pencil.  And because you have a reasonable expectation that when you open the box you would again see a pencil you would need to explain why the opening of the box causes the pencil to once again exist.  You would also need to explain why the box behaves as a box that contains a pencil (eg. it rattles and weighs more than an empty box).  An existing box with an existing pencil seems like a less complex explanation to me.
Comment: @Taemyr I don't have to explain why closing the box has an effect. All I need to explain is that if "I don't see any sign of the pencils existance therefore it doesn't exist" is not more complex than "I used to see signs of the pencil so it still exists".
Answer: You are assuming that existence is a phenomenon that can undergo sudden state changes. Or in simpler words: That things can cease to exist and came (back) into existence instantly and without observable side effects.
As Carl Sagan said: "extraordinary claims require extraordinary evidence"
Your claim has no supporting evidence. No such sudden stage changes have ever been observed or measured, not directly nor indirectly. No other evidence of such stage changes exists, to the best of my knowledge. All our experience, all our physical and other natural laws indicate that objects persist even when not observed.
There is a philosophical argument that Nietzsche made (can't remember which book, sorry) in that an object is defined by its interactions with other objects. If you were to somehow remove all interactions with other objects, the object is indistinguishable from not existing at all.
However, you only remove simple visual observation. There are many, many other interactions, including gravity and electromagnetic forces both with the outside and the box itself. Eliminating all interactions with all other objects is impractical. It also suffers from the sudden state change problem: How are these interactions restored by the act of opening the lid of the box, at which time the pencil will certainly be observed to be in the exact same place again?
Also, if we complete the thought experiment, and even postulate your non-existence theorem, our experience shows that if we resume observation, i.e. open the lid, the pencil will exist again in the same place and position as it was before. Where is the information about its position, rotation, relative movement (or lack thereof), and all other conditions of that object stored? Whatever that storage of information is, is it not indistinguishable from continued existence of the object?
Comment: I think your Nietzsche book is *The Will to Power*: "The properties of a thing are effects on other 'things': if one removes other "things,' then a thing has no properties, i.e., there is no thing without other things, i.e., there is no 'thing-in-itself.'"
Answer:
If you place a pencil in an opaque box and close the box, does the
  pencil exist?

This is a Metaphysical question to which we do not know the correct answer. But here are some philosophical views
Idealism : The pencil does not exist when no one is watching
The mind is what creates matter, if something is not created by any mind (i.e : inside an opaque box), then it does not exist.
But different idealist philosophers have different stories to say, for example : George Berkeley would argue that even if the pencil is an illusion created by our minds, it still exists inside the box because it is always in the Mind of God : When we are not watching, God is watching.
https://plato.stanford.edu/entries/berkeley/
According to Leibniz's Theory of Monads on the other hand, the pencil would vanish from existence and reappear when we bring it back to our consciousness. But Leibniz does not think that the pencil is a mere illusion created by our minds, but rather that real nature of matter (that is : its substance) is mind itself.
https://plato.stanford.edu/entries/leibniz/#MetLeiIde
Dualism and Materialism : The pencil exists inside the box
Different flavors of dualism hold that both matter and mind do exist separately, While Materialism holds that only matter exists : But according to both Materialistic and Dualistic philosophies : The pencil is in the box.
In my opinion, I would argue that probably (like 99.99%) the pencil is in the opaque box. And here is my argument :
I rely on abduction, Ockham's razor, Uniformitarianism and pragmatism, to come to the conclusion that the pencil probably exists in the box.
Different modes of reasoning make it possible for me to conclude that there is no reason to believe that things disappear, when you think about it :

The idea violates Uniformitarianism (that the Universe works the same way even when we were not there to see it)
The idea is more complex, since it requires things to disappear and reappear, and your mind has to do all that work. (applying Ockham's Razor and abductive reasoning). https://plato.stanford.edu/entries/simplicity/#Int
The idea is meaningless according to pragmatism (only what can be practically applicable is meaningful)

Additionally, if the pencil is just a mind illusion, then what it is that makes it permanent, and therefore sets it apart from all the pencils that I have seen in my dreams, that are not permanent?
I know that pencil I put in the box in my dream is an illusion, which makes me sure that I probably would not find it there while awake or in another dream.
Therefore, the 'real' pencil has to be something more than what we call illusion, an illusion that persists, an illusion that the Universe does not seem to forget about...?
Comment: *it is always in the Mind of God* Or from Spinoza's point of view, God is inside the box with the pencil, and inside the pencil itself.
Comment: You probably should add "experience/knowledge" to your set of reasoning modes. If it was not a pen but an ice cube, the ice cube will cease to exist at some point, but this is within experience, as opposed to the situation of disappearing pens. (my pens always seem to disappear, but I guess this is another problem)
Comment: "According to Leibniz's Theory of Monads on the other hand, the pencil would vanish from existence and reappear when we bring it back to our consciousness."  So then what would be his answer to the question of why we can trip over objects that neither we nor anyone else around us is aware of?
Comment: @MasonWheeler, if you trip over something you cannot see, it is still brought back to your consciousness, but not in a visual form. As for Leibniz I do not know what would be his answer here.
Comment: Yes, but not until after you've already physically made contact with it.
Comment: @Stefan , I wanted to add inductive reasoning (that things tend to work the way they did in the past), but the problem is, an idealist would argue that somehow the mind keeps track of the things that are happening out of view, even if the mind is not watching : if a rock fell from a mountain,my mind will keep track of what's supposed to happen after minutes even if I am not watching, then when I look at it again it seems as though it continues what it was doing, it will reach the ground. But Uniformitarianism seems to be more relevent here : when you are not watching, the universe is working.
Answer: Simplicity is a criterion for theory or explanation selection. It can clash with other criteria such as explanatory reach. Also there is no agreement on the nature of simplicity. Intuitively, I suppose, it denotes ontological parsimony or theoretical elegance - notions which themselves stand in need of clarification.
The question asks 'how they know'. There is no necessary connection between simplicity and knowledge. Simplicity is a sound methodological rule - but why ?- but a theory or explanation can be simple but false.
I am inclined to say that we do not know that the pencil exists in the duration. (1) The belief that it does is not immune from error; (2) in the circumstances described we cannot confirm or verify the pencil's existence; (3) there is no causal connection between the pencil and our mental state of believing in its existence (invoking a causal theory of knowledge here); and (4) no epistemological intuition of continued existence is available and reliable.
At best, that the pencil exists merely fits - is most consistent with - our 'web of belief' (Quine). Given our overall view of the world, in general the continued existence of unobserved objects best fits our theoretical and explanatory assumptions. I don't deny this but I also don't see how, granting it, we know that the pencil exists in the situation described.
The crucial point is, however, that these sceptical considerations against the assumption of the pencil's existence equally apply to your own assumption of its non-existence.
Comment: @TG2. Fine, thanks, I appreciate the clarification. As a Moderator I have to keep an eye on language that might cause offence - not to me, I don't mind but there are community rules. Anyhow, it's behind us now and  I'll look forward to your further contributions. Best - Geoffrey
Answer:
I'm having a tough time explaining why the pencil ceases to exist once
  you close the box.

You're having trouble because your claim that the pencil ceases to exist relies directly on a philosophical proposition that your friend does not accept.  That would be something along the lines of "only those things that I directly detect with my senses exist."  If you accept that as true then you're taking it, or something substantially equivalent, as an axiom.
Your friend takes a different view.  He claims that "because [he] put the pencil in there," it still exists.  That seems to belie a philosophical position directly in opposition to yours: that objects' existence is independent of whether anyone observes them.  A number of additional assumptions presumably accompany that, such as that it requires the operation of some force or agent to cause an existing object to cease to exist, and your friend is probably interpreting your claim to include that no additional action or forces in play.  By that reasoning, his rejection of your proposition is entirely logical.
Overall, when you say

I'm trying to explain to my friends about things existing.

, I get the impression that you think you're trying to convey facts.  You are not.  Rather, you are advancing philosophical position that is neither provable nor disprovable -- in effect, a definition for what it means to "exist".  However, inasmuch as that definition is inconsistent, in my experience, with common usage of the term, it should not be a surprise that your friend resists the idea.
Comment: +1 for addressing the difference in viewpoint and not just trying to prove the OP wrong.
Answer: There are two hypothesis, assuming there is no gimmick in the box (i.e. a magician's box with a false bottom):

The pencil ceases to exist while the box is closed, but returns to existence when it is opened.
The pencil remains in existence while inside the box.

If you measure the weight of the box before and after you put the pencil inside, the weight is different, and that difference is equal to the pencil's own weight. As someone else mentioned, the box may rattle if you shake it inside, and its center of mass will shift when tilted.
With hypothesis one you need to explain why the phenomena of the previous paragraph happen if the pencil does not exist while the box is closed. Hypothesis two renders those observations' explanation moot (it happens because there is an unseen pencil inside the box).
Applying Occam's razor, we can discard #1. Therefore the pencil does not cease to exist once the opaque box is closed.
Answer: What you call a "pencil" - a pattern in the way certain subatomic particles are arranged, exhibiting certain properties in interactions with other things - continues to exist even inside the box.  The conditions for observing some of those interactions continues to exist (e.g. you can measure mass, mass distribution, changes in mass distribution following certain changes in orientation with respect to a gravitational field, production of certain sounds given certain applied forces, and interaction with other electromagnetic frequencies to which the box is not as opaque) even if you have temporarily removed your capability for observing other of those interactions.  At any time, whether in the box or not, you can only observe some of the interactions associated with the pattern-label "pencil," due to our limitations as observers.  By putting the pencil in the box, you are slightly modifying the set of interactions you can easily observe.
Also keep in mind that interactions with visual wavelengths are not the only interactions we use to define "pencil;" for example there are some objects which look and/or feel like pencils but don't write like pencils (e.g. they might write like pens or not write), which many ontologists would likely say is a defining characteristic, though it depends on the purpose for which the label is being applied.  You're probably not easily able to observe those properties at all times even when the pencil is not in the box.

By contrast, let us consider what happens when I put a small piece of dry ice in the same box, and let that box sit for some time at "normal" room temperature and pressure.  In that case, the dry ice does actually cease to exist.  This is because what we call "dry ice" definitionally refers to the solid form of carbon dioxide, an arrangement of particles that has certain properties in interactions with other things.  When the carbon dioxide has all sublimated to the gaseous form, it no longer exhibits those properties.
If the dry ice box were airtight, one could still observe (with a very sensitive scale) that the mass of the box + dry ice was equal to the mass of the "empty" box plus the mass of the dry ice, and if the right equipment were available one could theoretically recapture all the carbon dioxide, and re-form the dry ice.  If the box were not airtight and left alone long enough, even the mass difference would no longer be observed because the extra carbon dioxide would escape, and relative fractions of different gases would equalize with the surrounding atmosphere.
However, if the dry ice box (airtight or not) also contained a plant, even [at least some of] the carbon dioxide molecules would no longer "exist" but would have been disassembled and reassembled into patterns that we might call "gaseous oxygen" and "cell wall" based on their properties in interactions with other things.
Answer: Existence of something like the topic's pencil is unrelated to you observing it or not. Assuming we don't take into account hundreds of years intervals (one way for the pencil to disintegrate due to the passage of time) in the case the box is not perfectly sealed from the external environment (or any other such variables) and assuming nothing else is inside that may affect it, the pencil does exist.
This is related to matter and energy conversion. If the pencil wouldn't be there, it would mean it was converted to something else (due to variables like above).
Comment: But in the same sense, your lifetime experience with natural phenomena is based on observation. Obviously we don't see things disappearing in front of our eyes for no apparant reason thus you know the pencil is still there. But why should we trust your past observations instead of the present one?
Comment: Because in the instance we talk about you actually cannot do the observation. Therefore you cannot make a determination of something's state.
Answer: Since you and your friends are doubting about existence, I'll tell you this: It depends on the box...
There are a lot of magicians that would love to contradict you by bringing their own box. They will let you put a pencil inside, say abracadabra and open the box again. For your surprise and your friends', the pencil will be gone. Vanished out of existence. Don't panic, after another magic conjure it will probably reappear!
Answer: First of all, you need to understand that exist means to be present. If you are asking whether the pencil object ceases to exist when in the box, definitely it is existing although you are not able to see it with your unaided eyes because it is in the opaque box. If you used a scanner then it could be seen.
In other words, you are asking if somebody covers my eyes with a piece of cloth, does the entire world cease to exist? Definitely it is still present.
Answer: I'm not smart in this field and almost no other topic, so first I want to try and understand why we need this constant to be an opaque box. Is it because we can't allow light through to possibly consider it not existing? For example, say I put my left over pizza in my fridge to prevent it from spoiling. I can't ask that my pizza may or may not exist because I can't see it, unless I open the fridge again for the reason I stated before? How about if you paint over an item with Vantablack? One last thing I want to add, can we just use common sense like his friends are and say for example, "It still exists because no item as common as a pencil can just disappear in thin air?"
Comment: Welcome to PSE. I didn't downvote, someone else did. They did so because your answer needs refinement to count as philosophical. I suggest you read the other answers to get a clearer idea of how philosophical answers go. Everything comes with practice. It might be a good idea, just for a while, to offer comments rather than answers - just until you get the swing of things. Only a suggestion. I look forward to your future contributions. Best - GLT.
Comment: I agree. Pencils can't just sprout wings and fly away :D
Comment: The word opaque was used to imply that it cannot be perceived i.e "does something exist if it is not perceived" Of course most answers are taking the question too literally and writing about weighing the box and how physics works. Pretty unexpected for philosophy stackexchange.
Answer: This is at the root of a key confusion people often have between the endurable model of the world and the perdurable.
In an endurable model of the world, the world is viewed as snapshots, thin slices of time.  While the pencil is in your hand, it's easy to point and say "in this time slice, there is a pencil right here."  Once you put it in the box, it's harder to do this.  Unless you have X-ray vision that permits you to directly observe the pencil, it's hard to say "in this time slice, it's right here."  We have to fall back on the less strong "we don't know."  Note that this is less strong than saying "there is no pencil in this time slice."
In a perdurable way of thinking, we connect the existence of this object through time.  In most cases, this is obvious.  If we are holding onto the pencil, it's typically easy to argue that the pencil continues to exist in my hand.  Once it is put in the box and the lid is closed, most people find it reasonable to assume that the pencil continues to exist inside the box.  They find it reasonable because they have done this countless times in their life and every time they've found the pencil is there when they open the box (or it's a magic trick).  However, a 1 year old does not demonstrate this way of thinking.  For them, put an object in a box and it ceases to exist until you open it again!
Why these disagreements?  Well perdurable models are tricky.  The most famous issue of this kind is the Ship of Theseus, which is similar to your box but doesn't have an "unknown" element because you can "watch" the ship through the entire process.
From there, one can dive into the question of whether the pencil exists in an ontological sense, or if all you can state is whether an image of it exists in your mind.  That's a fun rabbit hole to explore.
But in the end, the purpose of the whole exercise is not to demonstrate that the pencil does not exist while it is in the box.  It's to demonstrate something else, something that only makes sense if you draw the conclusion that the pencil did not exist while it is in the box.  For example, one line of reasoning that can be drawn from The Ship Of Theseus is that the ship is actually only a concept that exists in your mind.  Some thing does exist as part of reality, but it is only a "ship" as part of your mental image of what this thing is and does.  This line of reasoning is consistent, though typically unpopular.
You might also make a statement about our ability to know things about reality.  If you bet your life that the pencil exists while the box is closed, you might be in trouble when you failed to observe my assistant opening a false bottom in the box, taking the pencil, and throwing it in a woodchipper, ending its pencil-ness.  A worldview which encourages one not to take such a bet might explore the question of whether the pencil existed at all.
Answer: You haven't given specific objections they had, but I think there's two points that would be helpful to make.

As others users commented, the pen's existence can be verified by shaking the box. By "opaque" you probably meant opaque to all senses, not just vision - ie. the question is not a puzzle. You can enforce this by slightly modifying the question: You watch a man on live video put the pen in the box. The feed is one way.
One common method of proof is counterexample.

What if the pen teleported away?
What if the box has a hidden grinder?
What if the man used sleight of hand to whisk the pencil away?

These do also run into the issue of using an unconventional meaning of "exists" - specifically, we mean "exists inside the box", not anywhere. The hidden grinder is an exception, and should give you an idea of how to modify further if this semantic hurdle is a problem.
Comment: I am somewhat confused with what you are trying to say. If you have a reference this may help make your answer clearer and give the reader a place to go for more information.
Answer: If you are placed in an opaque box, and the box is closed, do you cease to exist?

Let's suppose that you and a friend are in a closed suite, with no windows.  The suite contains two rooms, with a door between them.  There are no windows in either the divider wall or the door.  The door is open.  May I assume that both you and your friend exist?
Suppose you are both in the same room, and you close the door.  May I assume that both you and your friend still exist, since you can both verify each other's presence in the room?
Suppose your friend opens the door, and goes into the other room.  May I assume that both you and your friend still exist?
Now your friend closes the door, so that you and your friend are now in separate rooms.  In other words, your friend has placed you in an opaque box, and closed the lid.  Do you still exist?

Note that it can equally well be said that you have placed your friend in an opaque box, and closed the lid.  If you still exist, then it can equally well be said that your friend still exists.
Suppose your friend is dressed up like a pencil, complete with an eraser and a writing tip.  You have placed a pencil in an opaque box, and closed the lid.  If you still exist, then so does the pencil.
Answer: Well, as always, when judging the plausibility of an idea, we must bring to bear all relevant prior information that we have.
So, when I see someone place a pencil in a box, and I ask myself, 'does the pencil still exist now that it's been placed in a box?' I must consider what I know about that person, the pencil and the box.
If I know that the box or pencil are somehow special, e.g., special 'trick' ones with elaborate mechanisms for making something disappear, I might guess that the pencil no longer exists inside the box. If I know the person is a magician, I might again think they are up to something and that the pencil may have disappeared from the box. If the person approached me unprompted in this scenario, I might assume they are playing a trick on me, and that it would disappear. And so on and so forth.
But generally, based on my prior experience with putting things in boxes, they tend to still be there when I open it the next time. So I would probably consider that to be the overwhelmingly most likely outcome. This is not, however, a deductive proof that the pencil continues to exist.
In summary, I think the closest correst statement to the one you are making to your friends is, 'our uncertainty about the existence of the pencil should increase once it is placed inside the opaque box'.


using torrent encryption

Question: everyone, I have some problem with my torrent, I encrypted my torrent but still can't download files from the net, what may be the problem?
Answer: First, some clarification on terms.
You are using a BitTorrent client and you have a problem with your BitTorrent setup. A torrent is a file describing a particular set of files that you download from a site and/or the small network of peers/servers that transfer that file. Usually, people say it's that site's torrent, not "my torrent". People who say "my torrent" are usually the uploader of that torrent.
Anyway, you should check your firewall settings and see if uTorrent is allowed through. Also, give more info on what uTorrent is yelling about in the info tab of the torrent.
Answer: You probably need to forward your ports. Look at this, it may help: http://portforward.com/

using torrent encryption


Can males pluck their eyebrows?

Question: The Hadith which refers to the one plucking eyebrows being cursed is to females so can males pluck them? (Mine have a few long hairs and it would be nicer to remove these longer ones to look tidy. Some are thicker hairs which stand out on close inspection).
Answer: It is Haraam for men to pluck their eyebrows.
From fatwa of Shaykh Abdul Azeez ibn Baaz rahamatullah alaihi we can say, plucking of eyebrows is not allowed, whether for men or women.
Check fatwa of Sheikh Muhammed Salih Al-Munajjid for more details: https://islamqa.info/en/3928
Answer: Summary: Fatawa mostly describe men plucking eyebrows as forbidden, derived primarily from the hadith for women and arguing that it's "changing the creation of Allah".

Scholars (see below) tend to apply the ruling for women also to men:

... Allah has cursed those women who ... remove their face hairs ...
Sahih al-Bukhari 5931; see also Sahih al-Bukhari 5939, Sahih al-Bukhari 5943 and Sahih al-Bukhari 5948

Variations of this hadith are reported in Sahih Muslim 2125 a, Jami` at-Tirmidhi, Riyad as-Salihin, Sunan Ibn Majah, and Sunan Abi Dawud 4169.  These are generally interpreted as applying only to eyebrow hair (see e.g. Islam Q&A).
Precisely why eyebrow plucking is forbidden for women is not clear, and there's a range of opinions as to when it applies (see my answer to Why is plucking the eyebrow haram?).  Thus, it's also not obvious as whether the same reasoning can be applied to men.  In fact, the reasoning is additionally unclear for men, since other reliable ahadith encourage men to shave their moustache and pluck their armpit hair, e.g.:

Five are the acts of fitra: circumcision, removing the pubes, clipping the moustache, cutting the nails, plucking the hair under the armpits.
Sahih Muslim 257b

Several fatawa declare men plucking eyebrows is haram:

It is not permissible for men, just as it is not permissible for women, to trim their eyebrows. Islam forbids plucking even one hair, and trimming could affect every hair, which is worse.
Islam Q&A, fatwa 3928: Men trimming their eyebrows
Namas is haraam for both men and women, because it is changing the creation of Allaah, and there is no difference between men and women in this case.
Islam Q&A, fatwa 98477: Ruling on a man plucking hair from his forehead and between the eyebrows

Other similar fatawa are by AskImam (In principle, it is impermissible for both men and women to trim or shape their eyebrows) and MutfiSays (No, men are not allowed to pluck, trim or shave their eyebrows).  So it seems the normal scholarly stance is that men plucking eyebrows is forbidden.
However, one fatwa expresses skepticism about this kind of ruling:

Yes, one could possibly argue that the hadith mentions "changing the creation of Allah" and thus the 'illah should be tagyīr khalqIllah or changing the creation of Allah, as was the opinion of Hafiz ibn Hajar and others. To this end our response would be that the statement "changing the creation of Allah" refers specifically to "those who split their front teeth seeking thereby adornment" as hinted to by Imam Nawawi in his Sharh Sahih Muslim. In addition, if we were to assume that removal of facial hair is haram since it is tantamount to "changing the creation of Allah", then we'll have to consider the shaving of the moustache for the male also as haram for the very same reason, an opinion that probably no scholar ever held.
Shafi'i Fiqh, sourced from IslamQA.org

It also seems to conflict with another Islam Q&A fatwa:

Whatever has not been mentioned in the teachings is pardoned. That includes hair of the nose, chest, back, legs and forearms.
Islam Q&A, fatwa 221496: Is it permissible for him to remove his body hair with a laser? Will that affect his fast?

Nevertheless, a cautious approach would be for men to not pluck their eyebrows.
Answer: no, as it is an organ given by Allah subhanahu ta'ala. it is the amanat for him.
and he must asked for this
Comment: Welcome to Islam.SE! Answers here should be elaborate, and focused on addressing the question. Claims should be supported by evidence. Please visit our [tour](https://islam.stackexchange.com/tour) in the [help center](https://islam.stackexchange.com/help), and refer to [how to answer questions](https://islam.stackexchange.com/help/how-to-answer).
Comment: Hairs and eyebrows are not Organ. Yes it is a part of body like your nails. As cutting nails are allowed. There is several ruling for hair of different parts of our body, shaving some are allowed, some are forbidden and cutting to a certain length is ordered for some hair. Even there is different ruling for men and women and shaving hair of private parts are obligatory after certain time.

Can males pluck their eyebrows?


Cucumber : Is it necessary to create multiple step defination class for single feature with multiple scenarios?

Question: I have created one feature file which has 4 scenarios. Do I need to create 4 step definitions or only 1?
If 1 then is it ok to have multiple @Given, @When and @Then in one step definition?
Answer: You not only can place all the steps in one class, you probably should.
I generally create one major steps class for a project, correspondingly, an epic (suite of related stories/features)
I might conceivably have a separate class for steps that are common across projects (which is rare) but I generally keep all my steps in one class.
When I first started out in automation, I kept one class for each story. I use that terminology because I mostly use JBehave and it's the corresponding term for feature in Cucumber.
This tended to make us have to re-word a lot of similar steps (like log-in) to avoid potential duplicate step definitions, which is easier to avoid and easier to maintain when all the steps are combined into one class.
Comment: i always packaged my project as below
Answer: Preface
What I usually do, is separate these into areas of functionality.
For instance, I have step definitions relating to login functionality separated from the step definitions relating to registrations, search functionality separated from the ordering of our products functionality, and navigation separated from other various common interactions.
This essentially means that when you're searching for a step to use, you go to the file/class that best suits what you are hoping to achieve, which lessens duplicate step definitions.
Answer
If you're asking whether you need multiple step definitions, yes you do, however, if you're asking how you should group these step definitions, then it is up to you, but I would definitely recommend grouping them by functionality over something like the ticket number that it was worked on (that usually is a tag in the feature file itself).
Answer: No, it's not necessary to create multiple-step definition classes for single feature file with multiple scenarios; one step definition file can manage multiple scenarios and multiple feature files.
Even though we can create multiple-step definition classes for different scenarios based on the functionality but it's not necessary.
Answer: A step, as a "normal" function, should follow the Single-responsibility Principle. I.e., it should do one and only one job, perform a single step.
The @given, @when and @then tags serve to increase the meaning of the phrases, but in 99% of the cases, one phrase only make sense in the context of one tag.
If your phrase contain connector, as and, or, but, probably it is doing to many things.
Gherkin has the tags @and and @but which are used to connect simple phrases. See it here.
Answer: At the current stage you can keep all your step definitions in single step definition file, but as your project will grow, it will be difficult to maintain one huge step definition file/ class serving a lot of scenarios.
In that state, you 'll have to break it up in multiple step definition classes, basically one for each page class and share the common state so that you don't initialize the same web driver, page objects again and again in step defs and simply use shared instances ( Singletons) across step defs.
This way your step defs will be simple and short(although multiple) and will be sharing common objects state globally.
Answer: I always package my project as below

You can have one step definition class, so if an already-defined step definition can be used in another feature file.
it is not required to write a similar step definition in another step definition class.


Why not use scarce California water for almond milk?

Question: Many argue that we should not drink almond milk as it uses scarce water. (e.g. https://www.ethicalconsumer.org/food-drink/shopping-guide/soya-non-dairy-milk). However given that consuming almond milk helps finance removing carbon from the atmosphere, would it not be defensible to consume it? For example in California, the water shortage does not drive species into extinction not does it deprive people of necessary access to clean water. But it could mean less industrial animal husbandry and less area of green lawns. I think less water to such purposes is no problem and means we probably should step up consumption of almond milk, especially in areas where water shortage is more of a nuisance and not an ecological or social issue.
Comment: *For example...clean water*. I did some quick googling and that statement seems untrue.
Comment: Hi Jan, this is exactly what I learnt in the very helpful answer below! I will stick to locally, EU-produced organic oats for dairy alternatives.
Answer: The issue is really with sustainability rather than scarcity, and it is also linked to ecological issues. An article in the Berkley University web site gives some background information. In order to maintain their farms through long droughts the farmers want more rivers dammed. Damming a river means flooding an ecologically rich valley. There might be potential for a beneficial impact on the carbon budget, but the creation of a new artificial reservoir also has the potential for a very damaging impact on global methane emissions (a side effect of drowning the valuable biosphere in the river valley).
A report from the Pacific Institute describes the ecological damage associated with reduced flows of fresh water into the Sacramento Bay caused by unsustainable extraction of water for agriculture (as an example .. this is not an exhaustive study of damage caused). The water shortage is threatening a rich ecosystem in the delta, which also has potential economic impact because it is a an important home for wild salmon.
The Pacific Institute report also suggests that current agricultural output could be produced with less water (or more efficient use of existing water through better management), so it may be possible to get the almond milk in a sustainable way, but there does appear to be a need (or at least a valid case) to exert some consumer pressure to reduce the level ecological damage caused by existing levels of water use.
Answer: Quick answer, from best to worst, in terms of water only:

Good:  Oat milk, soy milk
Okay:  Almond milk
Worst: Dairy milk

There are a lot of "news" articles about the water and carbon impacts of milk. I cannot find the one I just read, but I've included a few below as a reference. Some of it depends on where things are grown, and how a rise in one type displaces another. Water and carbon evaluations need to be measured from the food sources and land displacement, so it is a little tricky. That being said, there are some rough generalisations that seem to simplify this decision for most of us in our daily lives.
This finding surprised me a little but dairy milk is the worst for water. It's also the worst for GHGs, which is less surprising.
Almond milk was reported as being better than dairy milk for both, but it is still worse for water than all of the other milk sources. Plus almonds are displacing other crops in California, which is bad. Apparently there's a good return on almond crops, but only because they're not paying for the water, the cost of which is kept relatively low so that it doesn't stunt all farming in general. It's like fuel costs, it needs to go up in price to change use, but has huge impacts everywhere if it does.
Soy and oat milk are both good for water and GHGs (relative to the other options) and, depending on where you live, have a good chance of being grown locally (vs. say coconut milk). That helps on GHGs, but obviously cannot be applied equally to everyone. If you are in the US or Canada, there's a good chance it's being sourced locally.
Note that if you're switching from dairy milk you will need to up your protein from other sources. Soy has about 2/3rds the protein of dairy, and oat about 1/2 the protein of dairy. You also have to watch for sweetened alternative milks, as if we're not getting enough sugar as it is.
My favourite for cereals is soy milk as it has a wheatier taste, which goes great with grains. I've generally found all of the other alternatives (other than soy) a little thin and watery. They're not unbearably so and you get used to it, but it's an adjustment. They're more like (dairy) skim milk.
A bonus for these milk alternatives is that they don't curdle. I often cut up fruit in my cereal, and if left too long it would curdle the dairy milk, especially if it was acidic. I've heard all of these milk alternatives can be used for DIY yoghurt, which surprised me too.
Sadly soy milk is a high-FODMAP food in the US/Canada. Apparently the New Zealand/Australian production uses the whole bean and works out to be low-FODMAP. (Not than anyone asked. :)
Note that diary milk is rated worst when it's from big, industrial farms. Since they're the major source of milk (and beef, etc.), it is these sources that are usually evaluated and reported. When it is from small farm holdings the GHGs are apparently negligible. I presume it is because the waste is in proportion to what can re-used locally (e.g. tilled back into the soil) and there aren't giant piles of manure degrading anaerobically, producing lots of methane. I guess on small holdings, methane burps are relatively negligible. :) They still have sizable use requirements, however.
Also, if these cattle are used for meat (which, I know, has the same water and GHG issues), the water and GHG side effects of this dairy milk are similarly negligible.
References:

BBC.com: Feb 2020: Which milk alternative should we be drinking?
BBC.com: Feb 2019: Climate change: Which vegan milk is best?
MedicalNewsToday.com: (Nutrition) Almond, hemp, oat, soy, and cow's milk: Which is best
Comment: UK Dairy Milk - 8L of blue water per L of milk. Californian Almond Milk - 158L/L - https://www.nfuonline.com/nfu-online/sectors/dairy/mythbuster-final/


Vertical antenna on HF?

Question: What are some of the advantages and disadvantages of using a vertical antenna on high frequency? Are there any better antenna types that I should use?
Comment: Amateurs: Please do not vote for closing a question just because it feels too basic. The question is relevant and there is a good answer below.
Comment: possible duplicate of [Should I chose a vertical or a horizontal antenna?](http://ham.stackexchange.com/questions/146/should-i-chose-a-vertical-or-a-horizontal-antenna)
Answer: The primary advantages of vertical antennas are that they are omnidirectional, and with an appropriate ground plane (radials) yield a low radiation angle; this reduces the number of "hops" that HF signals must make to reach their destination. Ignoring the ground plane, which might be radial wires or metallic screening buried just under the surface, vertical antennas don't take up much space.
The primary disadvantages of vertical antennas are that they are vertically polarized, which makes them more sensitive to man-made noise when used for reception as compared to horizontally-polarized antennas like a dipole, and that they require a good ground plane to be effective when transmitting.
Vertical antennas for the lower bands require a significant mechanical support; for 80m, for example, a quarter-wavelength vertical antenna would be 66' tall. Verticals can be made shorter with top-loading or various tuning schemes, but at the cost of lowered efficiency -- meaning less of the transmitted signal is effectively radiated.
Comment: Low-band (160m-80m-40m) vertical antennas are often shortened using coils or top-loading, which also brings the disadvantage of making them quite sharply tuned and narrowband. For example, my Bencher HF6V 6-band vertical is only good for some 60 KHz on 3.5 MHz, so I get to choose if I want to work CW, digital, or some subset of the SSB band. Retuning requires a trip to the roof. Shortened horizontal antennas have the same property, but it's easier to hang a 40-meter wire horizontally than to make it stand upright.
Answer: Verticals work very well near the sea or salt water lake, your ground radials can be minimal and there is a good 6-10dB uplift in your sent and received signal. This is mainly due to much better ground conductivity and lack of obstructions. The much improved ground conductivity lowers the angle of radiation even more and lowers ground losses considerably.
This is backed up by practice and documented in plenty of articles, books and journals. (Look up Naval shore electronics criteria, it's been digitised by Googl)
To get close to this on dry land, you'll need plenty of ground radials. Rudy Severns, N6LF has done some very good empirical research on this. He suggests using around 32 radials and they don't have to be 1/4 wavelength.
Source : https://www.antennasbyn6lf.com/design_of_radial_ground_systems/
Comment: Welcome to ham.stackexchange.com!  Being a former Navy man myself, I looked up Naval Shore Electronics Criteria, but I couldn't find anything about antenna radials with a quick glance through the document.  There was lots about grounding.
Answer: One advantage of a vertical antenna (not yet mentioned) is that you can hang a vertical wire over a single tree, while a horizontal antenna needs at least two trees.  I use my 50 foot high tree for my vertical 80 meter.  Yes, it needs 66 feet of wire to tune properly, but I simply bend the wire over the top and then down.  Most of the signal radiates from the lower parts of the vertical antenna, where the most current is.
My method of building the antenna was to throw a string over the tree, and tie the wire to the string and pull up the wire, up and over.
Comment: Seems to me that "bending the wire over the top then down would result in considerable cancellation of your radiated signal, resulting in a very odd radiation pattern.

Vertical antenna on HF?


Code to sample from & integrate light of a cluster?

Question: Are there any publicly available codes to sample from an initial mass function (common ones... Kroupa, Chabrier, Salpeter) to construct a cluster, then use stellar models to generate an integrated spectrum?  I imagine such codes must be quite common, as they're relatively easy to write, but require access to stellar model databases or very simple stellar models.
Comment: SLUG (https://sites.google.com/site/runslug) does a lot of what I want, but only incorporated into full-scale Galaxy simulation.  It's probably possibly to make it generate just one cluster.
Comment: The astrophysics source code library (http://asterisk.apod.com/viewforum.php?f=35) is another place to look. I did a quick search for "initial mass function", and SLUG came up, but nothing that seemed much more specifically suited to your purpose.
Answer: The one population synthesis code I've used is GALAXEV, which can be found here. It allows you to choose either the Chabrier or Salpeter IMF, as well as select a star formation history from a few simple models, and it outputs the integrated spectrum. The stellar models and evolutionary tracks are all included in the code and supporting files.
I will caution, however, that this code, despite its popularity, is written in near-defunct Fortran. It took me several days to get it working, between figuring out its ancient I/O format, running preliminary scripts to convert between ASCII and binary files (yes the authors believe reading in a few kilobytes of ASCII data somehow takes a significant amount of time), and finding a compiler from the post-vacuum tube era that actually accepted the source. Yet one more example of astronomy being several decades behind when it comes to computers...
Comment: Well, sounds like a great candidate to get wrapped in python... astronomy's not ALL behind, but there are plenty of astronomers who are.


What is the meaning of Meethaaq taken from the prophets (Anbiaa)?

Question: A Solemn pledge was taken from the prophets (Anbiaa) to believe in any Messenger (Rasool) coming after them (Verse 3:81). This pledge seems to be mentioned again in verse 33:7. What is the exact significance of that pledge?
That Rasool (messenger) will recite the same verses which were given to the Nabi (a.s.) that every one will believe in that Rasool and will offer help to him. These are the words. Seems to be difficult to understand that a Rasool comes after a Nabi (prophet).
Answer: In verse 3:81 we learn that this pledge has been taken from the Prophets (Anbiya'), where they promise to believe and follow (and support) a (any) Messenger (Russul) that might come later (while they are alive) and in verse 33:7 it was taken from Prophets and Messengers too (including Muhammad). So at first sight there seem to be a difference.
About the meaning in 3:81

Allah states that He took a pledge from every Prophet whom He sent from Adam until `Isa, that when Allah gives them the Book and the Hikmah, thus acquiring whatever high grades they deserve, then a Messenger came afterwards, they would believe in and support him. Even though Allah has given the Prophets the knowledge and the prophethood, this fact should not make them refrain from following and supporting the Prophet who comes after them.  (Tafsir ibn Kathir)

About 3:81 Imam al-Qurtoby said that most scholars say that this means that any Prophet (Naby) has confirmed and promised to support a Messenger (Rassul) if he'd be alive to do so. The Kufi's added that not only a Prophet but all his followers would follow and support a Messenger. He also quoted that ibn 'Abbas and 'Ali that "the Messenger" in this verse refers to Muhammad.
Sheikh Taher Benachour in his at-tahrir wa tanwir said this pledge was taken from all Prophets and it consists in ordering their followers to follow, believe and support a Messenger if they came confirming their message! The goal of this is informing their nation so that this pledge would be transmitted by generations. He also gave quotes from the Book of Deuteronomy (Musa asking Allah to send a Messenger out of the descendants of 'isma'ail)  and Gospel of John ('Isa asking Allah to send somebody to confirm his message).
Note that this solemn pledge taken from all the Prophets emphasizes the importance of the message of Muhammad and pays a special tribute to it.
About the meaning in 33:7

Allah tells us about the five Mighty Messengers with strong resolve and the other Prophets, how He took a covenant from them to establish the religion of Allah and convey His Message, and to cooperate and support one another, ...
  (And when Allah took the covenant of the Prophets, saying: "Take whatever I gave you from the Book and Hikmah, and afterwards there will come to you a Messenger confirming what is with you; you must, then, believe in him and help him.'' Allah said: "Do you agree, and will you take up My covenant'' They said: "We agree.'' He said: "Then bear witness; and I am with you among the witnesses.'') (3:81) This covenant was taken from them after their missions started. Elsewhere in the Qur'an, Allah mentions five by name, and these are the Mighty Messengers with strong resolve. They are also mentioned by name in this Ayah and in the Ayah (42:13)...
  (And when We took from the Prophets their covenant, and from you, and from Nuh, Ibrahim, Musa, and 'Isa son of Maryam.) This Ayah begins with the last Prophet, as a token of respect, may the blessings of Allah be upon him, then the names of the other Prophets are given in order, may the blessings of Allah be upon them. Ibn 'Abbas said: "The strong covenant is Al-`Ahd (the covenant). (tafsir ibn Kathir)

Al-Qurtoby didn't add much to that expect that he quoted that the named Messengers were the five Mighty Messengers أولو العزم من الرسل (the Imams/leaders of the nations) and he added a hadith which is quoted in tafsir ibn Kathir (The translation above is summarized and maybe "cleaned") which has a weak narrator in the chain, to explain why Muhammad was named first :

وقدم محمدا في الذكر لما روى قتادة عن الحسن عن أبي هريرة أن رسول الله صلى الله عليه وسلم سئل عن قوله تعالى وإذ أخذنا من النبيين ميثاقهم ومنك ومن نوح قال : كنت أولهم في الخلق وآخرهم في البعث .
(My own translation of the quote take it with care) - - -
He began with Muhammad because of what is narrated by Qatadah from al-Hassan (al Basry) on the authority of abu Hurrairah: that the Messenger of Allah peace be upon him was asked about "And [mention, O Muhammad], when We took from the prophets their covenant and from you and from Noah ..." he said: I was the first being created and the last being sent.

He also added that part of this pledge was "to establish the religion and not be divided therein." as avoiding division is equal to avoiding following disbelievers.
Taher Benachour added that this verse is the beginning of the story of al-Ahzab, so the emphasis is on the pledge of supporting the religion or word of Allah which they have been sent with (in general and Islam in special) this means:

saying and spreading the truth,
spread what they have been ordered to without any fear nor (false) politeness towards disbelievers and munafiqeen,
not to follow their desires and nafs,
and not to leave aberrant and corrupt people doing their bad deedswithout interfering or guiding them,
...

if they did so Allah promised them success.
Conclusion
As you see on the whole both verses are equal to some extent, but maybe the emphasis and context play a role on making a slight difference on what exactly is meant in each of them.


How do you improve Chinese writing beyond HSK4 or HSK5?

Question: I am learning Chinese (not student, just private interest) and my Chinese is somewhere between HSK4 and HSK5 (half part of HSK5 finished). I am not focussing to improve my vocabulary as when I speak, I am only using very simple sentences. I thought now to improve by writing small texts now. What do you recommend how to improve writing? Any book recommendations?
Also wondering if you know a list with common Chinese expressions for me to check (e.g. 在我看来 ... , 从的来说...)?
Comment: Can you give an example of a "simple sentence"?
Comment: "simple sentences" are like this:
我很喜欢和我的朋友出去吃饭。
我家有一只小狗叫往往。
我很喜欢读书,但是我平常没有很多时间读书。下班回家以后,我常常太累了,就在沙发上躺着休息。 The problem is that I know quite a lot of vaculary, but I need to learn how to use them, how to create more "complicated" sentences.
Comment: Could start with writing diaries for any new language.
Comment: If you are not in China, you could find a tandem partner, you meet online, help each other. Bist du Deutscher? I'm sure you could find someone who wants to learn your language, whichever language that may be. Romance may follow!!
Answer: Read, read, read. It might seem strange to focus on reading when what you want to do is improve your writing. Reading more ofter will allow you to become more familiar with Chinese writing style and sentence structure. At some point you will be able to start emulating the style and structure you have encountered in your reading. You will still need to practice writing though.
Something you might want to give a try is to read books, articles, blogs, news etc. Then write something about what you read. Maybe write a summary or give a point of view on the content or its philosophy. Doing this will give you a chance to practice writing and will also let you reference whatever it is you have read, making it more likely that you will pick up on its style/structure.
Answer: I would say, however simple sentences are constructed from basic grammar... The difference between simple/complicated, in my opinion, is mostly in the vocabulary used in and the length of the sentences. So the best way you can take, is learning Chinese grammar, and then make your own sentences, communicate with others or post in this forum to get them reviewed. But if you just want filling-blank style handbooks, there are plenty of them on the Internet. (●°u°●) 」.
Answer: To improve writing without a teacher, then there really is only one feasible option: read Chinese books, etc., and adopt their writing into your skill set.  (See: Is it true that improving the reading skill also enhances the writing skill and improving the listening skill strengthens the speaking skill? at LanguageLearning.SE.)
Without a teacher, progress is surely going to be significantly slower.  (Part of my motivation to get a teacher was the realization that native Chinese speakers have spent considerable hours with Chinese teachers (many more hours than me).  The other part was Nankai students going from nothing up to my level very quickly.)
Study methods vary with one's goals.  E.g. wanting to pass a HSK test vs. wanting to use Chinese for conversations.  With respect to writing...
To improve writing, we need a way to get feedback; a book cannot do this.  Simple sentences are feasible to get right most of the time, but more sophisticated sentences is challenging:

How do you know if a metaphor works in Chinese?  (My experience is that if I take an instantly recognizable metaphor in English, and translate it into Chinese, nobody "gets it".)
How do you know if there's a better choice of words or sentence structure?
How do you know if an idiom is recognizable?  (E.g. I recall using 有嘴没舌 and 一字不改, and my teacher couldn't figure them out.)

I sometimes ask questions here using the writing-critique tag, but I can't just flood the site asking about every single sentence in Chinese I write.
In any case, many Chinese textbooks are listed at Chinese textbook grammar index at the Chinese Grammar Wiki (but they're much cheaper on e.g. Jingdong).

The HSK Standard Course books are incredibly boring, but are good for passing HSK tests.
I'm currently going through 发展汉语-高级口语 with my teacher; it's challenging, but more interesting.

Actually there is one technique that might help, which I asked about on LanguageLearning.SE: Translating paragraphs then comparing with an existing translation: is this technique used to improve writing skills?.  The idea is to

Obtain a copy of a Chinese book and a translation your native language.
Proceed paragraph by paragraph, and translate it into Chinese.
Compare the paragraph with the Chinese version.

It's not going to point out errors, but it might help indicate smoother ways of writing (e.g. better word choice and sentence structure).
(See also How to improve writing fluency at LanguageLearning.SE.)
Answer: My advice is to read and memorize as many 成语, (idioms) as possible.
The reason being that the Chinese language, (beyond the beginners' level), is highly idiomatic because the Chinese language, or rather its stylistic beauty, thrives on an economy of words, and idioms, especially Chinese ones need only 4 simple words to summarize and convey a whole market place of ideas. Perhaps the language's scarcity of prepositions has something to do with it.
Coming back to idioms, when you hear educated native speakers speak among themselves, they either quote some well worn idioms a lot of the time or actually make up idioms on the fly. I mean why spout a whole ten worded sentence when 4 tiny words would do and do it with style, especially one concocted on the spot?
You will find that as you use idioms often, (when the idioms could just roll off the tongue effortlessly), your mind begins to think in a certain way; (like mathematicians always think in terms of equations), and always constantly trying to express even complex ideas with as few words as possible.
Good Luck on your journey which, hopefully, begins with 4 little words.


What is the blue glow around trunks SSJ2?

Question: Is it some sort of pre-God Ki that is going to eventually transcend him to the level of a God? And how was he able to even remotely fight black after Goku and his dad were already defeated?
Comment: I am 99.99% confident that no official explanation of the blue glow currently exists, so your speculation is as good as anyone else's.
Comment: There is no official explanation, but thinking it's god ki it's a decent speculation. Perhaps Trunks learnt something about god ki when he was training with Vegeta and faced Vegeta in Super Saiyan Blue
Answer: There is no official explanation, but manga #24 has given a very important hint that can possibly be the answer (spoiler)

 Trunks is officially a kaioshin apprentice, he can use kibito technique to heal other people, and since kaioshins have god ki, as kaioshin apprentice he probably has some grade of knowledge on god ki.
Answer: There is no official explanation. Even in the show none of the characters seem to care enough to question it. I like to call it SS demigod blue because that sounds cool. I'd say he just started to adapt blue god ki after feeling it from his dad and Goku. As for why this lets him fight evenly it's probably just cause there isn't going to be another arc involving him. He deserved to have this moment and the author just gave it to him.
Answer: When goku fought Beerus, Beerus said goku's body learned from the experience the power was now his and later goku revealed that vegeta learned to harness god ki without the ritual I believe with the saiyans ability to grow stronger after each battle that's how this was possible but with trunks being half human he won't be able to fully harness saiyans god ki fully but he learned from the experience of fighting a diety and was able to somewhat harness it or if he can fully use saiyan god ki this is the form in between regular super saiyan and the god forms because he is still learning to use god ki that's what I believe
Comment: Please include relevant sources/references. Specify specific anime episodes and manga chapters, if needed.


Why most of the supersonic or fighter aircraft use all-moving control surfaces?

Question: What are the advantages of using all-moving control surfaces? can someone give explanations based on aerodynamics?
Comment: Well treated here: http://aviation.stackexchange.com/questions/5003/what-control-issues-did-the-x-1-have-to-overcome-to-achieve-supersonic-flight and some info here: https://en.wikipedia.org/wiki/Stabilator
Answer: The biggest two reasons to have a stabilator (the most common all-moving control surface) are stability at supersonic speeds and increased maneuverability.
As an airfoil approaches its critical Mach number, the diverted flow moving past the wing's leading edge, because it has to move faster than the wing itself to follow the contour, starts to exceed Mach 1 and then decelerates below it, causing a transsonic shockwave to form behind the wing's leading edge. This shockwave causes boundary separation of the airflow at the trailing edge of the wing, where traditional elevator surfaces are placed. This reduces the wing's lift and also the effectiveness of elevator surfaces, a phenomenon known as "Mach tuck". By instead moving the entire control surface, this problem is avoided as the entire airfoil, regardless of the quality of the flow of air over any point of it, is used to direct airflow and thus rate the aircraft's nose.
Second, and more intuitively, the larger the elevator surface, the more air it redirects and thus the more force it places on the tail section, in turn allowing the pilot to pitch the aircraft at higher rates. The ideal endpoint of this line of thought is that the entire stabilizer also becomes the elevator surface; a "stabilator".
Both of these considerations are critical to the design of fighter jets, which as of the fourth generation were almost all capable of Mach 1 (and a few could exceed Mach 2), and which also have to be highly maneuverable even as the moment of inertia of the airframe in the pitch plane increases (an unavoidable side effect of wrapping an airframe around two high-performance jet engines traversing the length of the fuselage).
Comment: I always thought it was the kink in the airfoil contour (in case of a elevator deflected upwards) that caused a lot of problems in terms of shock waves and that this was a reason to install all movable airfoils. Am I completely mistaken, or is this another reason for all-movable elevators?
Comment: In fully supersonic flight that may well be the case; however, transsonic airflow causes the problems I mentioned long before the aircraft itself gets to Mach 1, and these problems are often encountered on aircraft with sufficient power to approach Mach 1 but which aren't designed for transsonic flight.
Comment: But I guess a kink can also give problems before mach 1, as the increased local curvature will greatly increase the pressure, I don't think you need supersonic flow for this
Comment: Many thanks for your great explanations KeithS! Apart from the reasons given by you (shockwaves, Mach tuck and more force), I have always wondered is there any aerodynamic theories or calculations than can be proved or related to those considerations? Does larger surface area on all moving control surfaces really provide more moment as compared to conventional tailplane (fixed+elevator)? Why most of commercial aircraft not using all moving control surfaces?
Comment: @syahmiamirhamzah - All-moving control surfaces increase the maximum theoretical force the tailplane can provide because the force on the surface is a function of the relative angle of the airflow and the area that airflow impacts. The bigger the surface, the more force the tailplane can produce. In practice, you may not see a difference because there are other loading limits inherent in the airframe design. This is why commercial airliners don't use them; the forces produced exceed what the aircraft is required to do (and thus is built to withstand). A 747 doesn't need to execute a 9G turn.


Where did the idea of the inerrancy of the King James Bible come from?

Question: Many Christians believe that the King James Bible is the only correct translation of the word of God. And they say that all other versions of the Bible are not inerrant.
What is the historical origin of this way of thinking?
Answer: Today's "King James-only" movement, and its argument that the KJV is itself inspired, does indeed have historical precedence, though it's debatable if the 20th-century movement can claim a strong link to similar thinkers in previous centuries.
There are two major precedents to today's movement, so we'll look at those first:

Pre-KJV elevations of particular translations (Septuagint, Vulgate, and Luther's Bible)
Nineteenth century elevation of the KJV
Late 20th-century KJV-only movement

Pre-KJV
Before the KJV was completed in 1611, several other translations of the Bible enjoyed particularly high status, with some groups going so far as to identify them as inspired in and of themselves.  Three frequently cited examples are the Septuagint, the Vulgate, and Luther's Bible.
The elevation of the first, the Septuagint, dates back as far as 100 BC, in the Letter of Aristeas.  Much of the letter is rejected as fictitious, but it does describe supernatural guidance in the writing of the Septuagint, and a curse laid on any who dared edit it.  In the early first century, Philo describes how all the translators of the Septuagint independently came to have the exact same text:

They, like men inspired, prophesied, not one saying one thing and another another, but every one of them employed the self-same nouns and verbs, as if some unseen prompter had suggested all their language to them. (Works of Philo Judaeus, III, 82)

Philo's account influenced early church fathers like Justin Martyr and Irenaeus, and they defended the accuracy and even inspiration of the translation.
Much later, in 1546, the Vulgate was similarly recognized by the Council of Trent, which said that "no one is to dare, or presume to reject it under any pretext whatever."  When Erasmus published his own critical Latin text, he was opposed by Martin Dorp and Petrus Sutor (a.k.a. Pierre Cousturier), the latter of which said:

If in one point the Vulgate were in error the entire authority of Holy Scripture would collapse. (Quoted in Preston and Jenkins, Biblical Scholarship and the Church, 27)

And similarly, some advocates of Luther's German translation of the Bible, completed in 1534, considered it inspired:

Some indiscreet friends of the reformer, impressed by the beauty of the translation, imagined they could recognize in it a second inspiration. (History of the Reformation, III, 337)

So we see then a very early tendency to elevate particular translations, and thus it shouldn't surprise us that something similar happens in English.
KJV onlyism in the 19th century
The KJV enjoyed dominance in the English-speaking world for many years after its publication, and was not seriously challenged until the 19th century, when the Revised Version was prepared.  This new translation was not undertaken without major debate, during which the "inspiration" argument was adopted by many opponents of a new translation.  Many authors briefly note the existence of such arguments, such as:

Henry Alford, 1866: "Yet this is the version which some would have us regard as infallible, and receive as the written word of God!" (Commentary on Hebrews)
Around 1840: "Some had gone so far as to pronounce the Bible as translated by the distinguished forty-nine, a perfect work!" (Life of Spencer Houghton Cone, page 355)
Armitage, 1850: Some "hinted" that the KJV "had come down from heaven in about its present shape, printed and bound" (History of the Baptists, I, 901)

Thus the idea of perfection of the KJV itself has existed for a long time, at least as early as the mid-19th century.
KJV onlyism in the 20th century
Roy Beacham and Kevin Bauder, opponents of KJV onlyism, provide more historical details than I have, and conclude that "no traceable connection exists between those of the nineteenth century who held such a view with those of the later part of the twentieth century" (One Bible Only?, 44)  They find the modern movement's origin to a book published in 1930:

That book, Our Authorized Bible Vindicated, was written by Seventh-Day Adventist missionary, educator, and theologian Benjamin G. Wilkinson (1872–1968).

Wilkinson opposed the English Revised Version, Beacham and Bauder say, because "it robbed him of several favorite Adventist proof texts," but his book was uninfluential until it was discovered by James Jasper Ray, who published a derivative work, God Wrote Only One Bible, in 1955.  And this work, in turn, inspired David Otis Fuller and Peter Ruckman, two highly influential KJV-only proponents.  Ruckman's The Bible Babel (1964) and Fuller's Which Bible? (1970) both rely on Ray, and in 1978 Fuller founded the Dean Burgon Society to promote KJV onlyism.  Both argue that the KJV is an inspired translation and absolutely authoritative, and Ruckman has bombastically claimed that the KJV has new revelation, above and beyond the original scripture.
According to Beacham and Bauder, all notable KJV-only proponents, like Jack Chick, D. A. Waite, Jack Hyles and Gail Riplinger can be linked "back to Fuller or Ruckman or both," though they admit the existence of at least one scholar loosely associated with the movement, Textus Receptus proponent Edward F. Hills, who was uninfluenced by them.
Conclusion
The history of the modern KJV-only movement can be traced primarily to Benjamin Wilkinson and his 1930 book.  But to do so would ignore a long history of claims of inspiration for the KJV and other translations, stretching back as far as the time of Christ.  As the Oxford Handbook of the Bible in America says:

As an identifiable entity, the King James Only movement is rather young, overwhelmingly Baptist, and thoroughly American.  While its ideological roots stretch back to nineteenth-century Britain and the first calls to revise the KJV, the movement is properly a product of the second half of the twentieth century. (source)
Comment: It's worth noting that Ms Riplinger was taken to task by the Trinitarian Bible Society (who only use and promote the KJV). Despite her advocacy of "the KJ only" they showed up various scholarly flaws in her arguments. The TBS is also clear that although they think the KJV is the best translation we've got today, it is not infallible, or perfect.
Answer: The question is less the "inerrancy of the King James Bible" than it is the
reliability of the Word of God. One either believes that God is God, that He,
in effect, "manufactured" us and that the Bible is the "owner's manual" for
how to properly maintain the life He gave us, or one does not.
Assuming we do so believe, we are faced with the problem that there is no
"original Bible." What we have is a pile of fragments, written in some fifteen ancient languages: hand-copied renderings of the Epistles and Gospels, passed around from place to place throughout the entire Roman Empire, painstakingly
preserved, collected and copied in the underground scriptoria of a Church which was still largely in hiding.
The Council of Nicaea, in 325 AD, was the first time all the bishops of Christendom were able to meet openly, and bring their scrolls of Scripture
(at that time a "Bible" was a collection of parchment scrolls carried about in several segmented baskets) with them for comparison. Miraculously (literally),
the consistency between these was remarkable, and from them the Canon of
Scripture was determined and later confirmed at the Councils of Hippo (393) and Carthage (397 and 419) that the 46 Books of the Old Testament and the 27 Books of the New Testament were finally declared the Canon by the whole Church.
This is not to say, as the secularist Modernists do, that the Bible was "still being written" all this time. What it was, was a matter of collecting, translating, sorting and ordering what had been written some four hundred years past, copied and re=copied and transported all over the Roman Empire by foot, camel, ship and donkey cart, painstakingly preserved by a Church that had been under persecution for much of that time.
We call these early autographs the "fragments:" some whole books, some partial,
lovingly and painstakingly copied letter-by-letter to ensure accuracy (it's
where our expression, "letter perfect" comes from). This became the standard for
the great monastic scriptoria that emerged in the Fifth Century.
Up until the Fifteenth Century the Bible was only available in the universal languages of the Roman Empire: Greek and Latin. As the Empire faded, these languages were only known by the few who studied them and the vast majority of the people didn't. One of the objectives of the Reformation period was to make
the Scriptures universally available, and this involved translating them into the vernacular.
In the matter of English, the KJV was preceded by the Geneva Bible and the Bishop's Bible. Both of these relied mainly on the Latin Vulgate (both were
preceded by the translations of Tyndale and Hus, directly translated from
the Vulgate, but which were underground affairs that got them burned at the stake).
In 1604 the English Bishops approached King James and asked him to subsidize
a version of the Bible that would be researched from the ancient autographs
of the New Testament. The result was the Authorized King James Version of 1616.
Twelve years in the making, it was the result of one of the most monumental scholarly efforts ever launched on behalf of anything. It has stood the test of
time, and has become recognized universally as the "gold standard" of Bible
translations.
Its high, poetic English comes closest to capturing the highly-nuanced Hebrew,
Aramaic and Greek in which the earliest fragments were written, and so enables
the reader to fulfill God's purpose in delivering the Scriptures to us in the first place: to enter into a relationship with them, rather than "just reading" them.
Variants of he KJV have included the Revised Standard Version, which has been
interfered with in the publication of the NRSV, which many believe to accommodate Modernist political tendencies, and the New King James Version,
an excellent and faithful rendering of the KJV in modern, but a very high modern, English that retains the poetic flavor.
I'm an Orthodox priest, and the Orthodox Study Bible New Testament uses the
NJKV. I went to Roman Catholic undergraduate seminary and grad school, and
in both the KJV was spoken highly of. In fact, at grad school at the University of Steubenville we had Fr. Francis Martin, a universally-recognized Bible
scholar, as our Scripture prof. We used the Oxford Study Bible, which uses the KJV.
Bottom line: it is the Word of God in Scripture which is considered infallible.
The KJV is recognized by most as the most accurate English-language rendering of the ancient autographs.
Comment: Forgive me, Father, but the question is exactly about the inerrancy of the King James translation, which a few Anglophone Protestants hold onto (see, for instance, [this](http://christianity.stackexchange.com/questions/284/what-is-the-king-james-only-movement?noredirect=1&lq=1) question — which is linked to the question we are answering now). It is a pity, because this is a very thoroughly researched answer for a slightly different question.
Comment: @wtrmute, I'd say it's good enough as a basis of an answer for why people like the KJV so much - ignorance of what I believe is a belief shared by a fairly small minority doesn't necessarily disqualify someone from answering the question.   This is just another angle, but I agree, a stellar answer would have something to do with them.
Comment: //Up until the Fifteenth Century the Bible was only available in the universal languages of the Roman Empire: Greek and Latin. //

I think there were Bibles in languages as per the order of all the local Church though the world, e.g. Ge'ez, Coptic, Old Slavonic, &c.
Comment: Hi, Thomas--I meant in the West. Sorry for the confusion.
Answer: Where did the idea of the inerrancy of the King James Bible come from?
2 Timothy 3:16-17
2 Peter 1:20-21
John 17:17
Isaiah 40:8
Matthew 4:4
Matthew 5:18
1 Thessalonians 2:13
Matthew 24:35
Revelation 22:18-19
Hebrews 6:18
2 Thessalonians 2:14-15
Isaiah 8:20
Comment: Welcome to the site, Mack. Just to point out that the KJV wasn't in existence until some 1,500 years after those Bible texts you list were penned. Different Bibles had been translated prior to 1611, when the KJV first appeared. So, if you could address reasons why those earlier translations were not considered inerrant by those in favour of the KJV, that would be interesting. Then you could progress to why they thought the KJV was superior. Fulsome answers are appreciated on here!
Comment: As it's currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer).


Is it worth roasting my own red peppers?

Question: I recently realized roasted red peppers make so many of my dishes pop, but it's a pretty pricey ingredient. A small jar costs three bucks and a big jar is seven. At my local grocer I can get red peppers for two dollars a pound. Does anyone have experience roasting their own and, if so, do you save cost and how do I store them?
Answer: I roast them "fresh" as I need them, but my method scales up easily.
I use a gas grill and turn it to high.   Set the whole peppers on the grill, and turn them when the skin is black on the hot side.   When they're black all over (after maybe 2-3 minutes per side for all 4 sides of the typical ones in my local supermarket), I put them into a large disposable plastic container with a tight fitting lid and let them cool in it.   The skin peels off quite easily, and they can be seeded and de-stemmed quite easily.
If I were going to preserve them, I'd probably chuck them into a plastic container or zip-top bag and freeze them.
Comment: I also recommend your method, as my family uses it for many years. Besides using a grill, you can put directly the peppers on the stove (works for gas stoves) or on a piece of metal sheet (for cooking purposes).
Answer: In my culture we make so called ajvar (and it is usable for the whole winter). It is usually made in late summer when red peppers come to season (and are cheapest too). We prefer it home made rather than buying it ready. It is not all about the money :) And we do it big scale operation (whole day or weekend event). This is the recipe with notes:

buy "thick" pointed red peppers (they have more "meat") - not "bell" ones
make small cut on tips (on pointed side - for later processing)
preferably do grilling, peeling and cooking outdoors - the process is messy and stinky
I advise to grill them on high until skin is black (makes them easier to peel)
prepare enough dishes - do not use plastic dishes as they tend to leave red stains
when grilled leave them to cool down a bit, then peel while warm (you may like to use gloves because your fingers will also catch hard to wash stains)
place then in dish, point down, to drain from inside and cool down (that's why cut on the point tip) - there will be a lot of water coming out from the inside
remove stems and seeds, wash them with cold water, drain them
cut into convenient pieces (of your preference) some folks here also mince them, I prefer "strips"
when done with all grilling, peeling, draining, cleaning and cutting, place them in large pot, then cook them with a little oil until there is no "water" at the bottom of the pot (will dry them and pasteurize them a bit further)
when almost done, mix in salt and essence (concentrated vinegar) - these are preservatives (essence very stinky - do outdoors)(salt to taste)
you may add garlic (for taste) - I don't (you can always add garlic later if needed).
pour in jars while still hot (important!)
top it with oil (olive or vegetable oil) - this is another preservative
put a lid or cover with double plastic wrap while everything is still warm.
when cooled down, jars will "vacuumize" (a plastic wrap can be better as to see which jars are not as air-tight later
store in a cool place, e.g. the basement (does not need to be fridge or freezer) - e.g. next to wine :)
important - once you open one jar, use it fairly quickly (2-3 days) and keep opened jars in the fridge (always top with oil) - tip - use smaller jars rather than large, also use jars that are not as air-tight first!

In Bulgaria, they make "ljutenica" which is similar to this, but they also add grilled eggplant and in some cases tomato paste (makes amazing taste).
Some folks here like "ajvar" to be hot, so they add hot chili peppers to mix, or buy hot red peppers.
Amounts: 10kg of peppers will make 1-3 1kg jars, but, it is worth the works, the most important thing is that you exactly know what is in that jar! Calculate the number of jars you will consume during winter, and you may actually save money on the amount. And do an experiment - compare what you have made, and what you can buy, as this makes the point where money is not everything :)
Ajvar can be used as is, also it can be roasted, toasted or cooked additionally - examples:
 - as "winter salad" (on its own) e.g. accompanied by pickles (decorative too: red ajvar and green or white pickles),
 - can be used as spread on bread, with some good cheese, or prosciutto, also try all of this toasted!
 - can be added to pastas or mixed/cooked in pasta sauce with tomatoes or other ingredients
 - also it makes even better and tastier pizza spread than tomatoes
 - can be added to soups and stews
Kick your imagination off - it is a versatile ingredient! Enjoy!
Answer: I halve them, smear with oil and roast them cut side down for about 30 - 40 mins at 200 deg, then cover with foil (or put in a plastic bag) to cool. Peel off skin, usually easy, then use straight away or freeze
Answer: Once you roast your own you will never go back!
Mine keep for around 1 month in the fridge.  That is not conclusive however!  Cost depends on season (when peppers are cheap, it is worth it.  When they are out of season, maybe not), and the quality of the olive oil you use.
Method - slice them into large, fairly flat pieces - about 4 per pepper.  Lay them flat on an oven-proof tray, skin side up.  Grill them for about 10 minutes on fairly high heat, or until the skins are blistered and dark.  This will depend on your oven.  Put the pieces (while hot) into a plastic or paper bag and let them sit in there for about 10 minutes until they are cool enough to handle.  This allows them to sweat a little to make it easier to remove the skin.
Remove the skin with your fingers.  It should lift off easily.  The bits around the cut edges will be more difficult. This is why I try to minimise the number of pieces from each pepper.
Slice the pieces and pack into a jar.  Cover with olive oil.  Personally, I like to add garlic slivers, 1 clove per small jar, but that is up to you.
The peppers should be covered with oil at all times, otherwise the bits sticking out may go mouldy.
Answer: FWIW,
I generally buy/cook organic, and my local co-op sells roasted red peppers in the bulk section.  Per pound, the roasted peppers are half the price of the fresh red peppers.
Yes, by the jar they're crazy expensive, but if you can get it in the bulk section you'll save money.
And, of course, freshly roasted is very yummy, so if that's what you want, there's no comparison.
Comment: @Jefromi You are correct that water cooks out, and BECAUSE of that the roasted peppers are even more of a deal (if the price/pound were the same, after roasting the fresh you'd end up with less product).
Comment: Comparing prices by weight before and after cooking doesn't seem useful - water cooks out.