What was David's motivation in Prometheus?

Question: For me, perhaps the most interesting person aboard the Prometheus was the android, David. I'm still confused by his seeming fascination with the movie, Lawrence of Arabia. Although I couldn't make notes during the film, I believe that he quoted Peter O'toole's character, Lawrence, on more than one occasion. Was he attempting to attain a similar achievement with the Engineers as Lawrence did with the Arabs? Why did he infect the Crew leader? What was his motivation?
Comment: +1 For me *David* was the most fascinating aspect of the movie, too (which is also in part to blame on *Michael Fassbender*, I guess). He and his character gave me more questions and things to think about than the "obvious" questions about the *Engineers"*.
Answer: There are 3 possible motives for David.

He wanted to test the black-goo to "try harder".

David was receiving orders from Weyland as he told "Try Harder!".The scene where David spikes Charlie's drink happens after the 'try harder' scene (with Vickers). David goes to Holloway, asks him how far he is willing to go to find his answers, and Holloway replies he would do whatever it takes. David takes this as an invitation to experiment with the goo on Holloway, ultimately at Weyland's request. David is simply following orders.
So my guess is that, he probably wanted to test it, just in case it turned out to be what Weyland was looking for, an immortality potion or something

He wanted to kill the crew to gain his freedom .

David starts to hate the humans. Note how antagonistic Holloway had a jerk towards David.When Holloway asking David why he's wearing a suit as much to say 'you're not one of us, why are you bothering to try?'

He wanted to kill Dr. Holloway to remove him as competition for Dr.
Shaw

He seemed to pay more attention to her from the start by looking in
on her dreams and taking special care of her when she awoke from cryo. I think when he tried to put her back into cryo he was trying to do what was best for her. I also thought that, at the end, when
he    said he was afraid she had been killed that he was being
genuine.

David: I was scared you were dead.
Shaw: you know nothing about being scared, david.
Comment: #1 is backed up by the movie's writer [here](http://io9.com/5917448/all-of-your-lingering-prometheus-questions-answered).
Comment: I don't remember any evidence of David hating humans. And as android, he doesn't seem capable of hate. I thought he took holloway's abuse in stride. And if he hated humans, why would he help like he did at the end?
Comment: I'm not sure if David was trying to do what was best for Dr. Shaw. At one point he antagonizes her about the death of her father, and dryly comments about her great survival instincts.
Comment: David certainly is brutally honest at times. The actions he takes that could be considered harmful (contaminating Holloway and advocating Shaw enter cryo-freeze) are consistent with his mission to help Weyland contact the engineers. To me, there is no malice behind these actions -- he is just a computer obeying his programmer.
Comment: In fact *David*'s urge to put *Shaw* back into cryo-sleep seemed to me as if he was actually trying to ship the creature inside of her back to earth. But while I could not come up with any motivation for him (or even *Weyland*) do this (even more so, when trying to get into contact with it, why deep-freeze it?), your 1st possibility seems the most reasonable.
Comment: There is no evidence for points 2 and 3. It is pure speculation.
Answer: David has multiple motivations:

to help Weyland achieve Weyland's goal, which is to contact engineers so engineers can help Weyland cheat death. After all David is a computer with a programmed purpose: serving Weyland.
("Try harder" is Weyland telling David to keep looking for a living engineer, which David then does successfully.)
to reveal how humans were not special but instead -- like David -- were created by other intelligent beings. This is the irony underlying Holloway's insulting David.
Answer: In the very beginning of the film David's hair style is different, then we see him watching the film while he is coloring the roots of his hair to match Peter's, and then he combs it so that he has the same hair style. He later repeats the phrase "The trick, William Potter, is not minding that it hurts". I think David repeats that line two or three times. I took this to imply that David's natural appearance is different including his hair color.
Is this sequence connected to David's fascination with the Engineers. Absolutely, because this scene defines a repeating theme that David tents to overly obsess over things related to the human condition. I think you have to watch Lawrence of Arabia to understand what was being implied by that scene.
Why did David infect the Doctor?
David is seen reporting to Peter Weyland that the Engineers are all dead, and he then explains that Peter Weyland ordered him to "try harder" to discover what happen to them.
Did Peter tell David to infect a crew member, or did David conceive this idea on his own? That isn't made clear in the film. Later in the film, Peter Weyland is told to take off his helmet and Elizabeth protests saying that the infection that killed the Doctor could be air born. Peter Weyland appears to not know that the Doctor is dead, and David just gives Elizabeth a look.
What was his motivation?
David says "big things have small beginnings" and then later while talking to the Doctor. He says "if you could meet your creator, what would you say?". I really feel that David understood that the dark fluid was a virus, and that it created life. In that scene David expresses a fascination with meeting ones creator, and also his disapproval of humans. I think he gave it to the Doctor, so he could destroy his creator and turn himself into a creator at the same time. While answering the question, what does this black stuff really do?
Comment: *"it mutated life as a means to destroy"* - Really? It is not clear this *"destruction"* was its actual intent. It just evolves life into something new, no matter if *we* like this new version or not.
Comment: Down-vote because virus did not create life, it mutated life as a means to destroy. Also, David does not just give Elizabeth a look -- he says something like "the virus is not airborne" which apparently causes Elizabeth to realize that David contaminated Holloway.
Answer: Here's my biggest problem with it: David knows absolutely nothing about the black goo. What would make him think that it could create, change, preserve, whatever, human life? I mean, if you happened to come across a bunch of black goo would your first thought be to feed it to some animals. Even if it contains a bunch of nutrients, eating an egg doesn't cause a chicken to start growing in my body. So he just comes up with this alien virus/embryo idea out of nowhere.
Not only that, but they have an awesome lab there, why doesn't he just use that to run some experiments on it? Why doesn't he work with the other scientists to find out more about it? Surely that would aid the old man just as much if not more than david working alone.
Even if you make the argument that he is just following orders, that just shifts the blame from him to the old man. It doesn't really change the fact that his motives make no sense whatsoever.
Comment: This is my pet peeve too. All other posts about motives are great and all, but the vehicle of discovery used by the director just doesn't make sense at all. "Hey, some black goo! Let's randomly grab it and put it in my crew!" "Hey, I only care about rocks, too bad there's nothing for me to do here other than to cry about ancient dead aliens!" Oh wait, that's another pet peeve. Oh gosh, so many pet peeves here... Who run a science unit like that. That too probably the most expensive one ever produced. grrrr
Comment: Indeed. This is a big gaping plot hole that makes this and the following movies very hard to believe. It is astonishing why sir Ridley Scott made and left  such a blaring mistake
Answer: My 2 Strongest theories about this are:

He turned out to hate the humans due to the actions of Dr.Holloway. To me, since the first time David and Holloway met... I always had the gut feeling that David was going to do something to Holloway sooner or later. I mean, Holloway was being such an ass towards David! Plus, not only that.. but.. to me, it seemed as if he knew that the black goo was dangerous. One reason why I believe he knew is that he didn't inform the crew about taking that black goo back with him.
He has a thing for Shaw. If you think about it, what Vijin said is true. And, I do not want to type all about it when the informations already up here, lol.
Comment: Again, as android, isn't David incapable of hate, and incapable of having a thing for a human? David is a computer programmed to serve Weyland.
Comment: @ShaneFinneran While I agree that *David* probably didn't do fall in love with *Shaw*, isn't the ambiguity of *David*'s intentions and his maybe own developing motivations what makes this character so fascinating? This extremely obvious *"Good morning David"* at the beginning cannot have been mere coincidence.
Comment: Come on guys. Why say David cant Hate. What Has movies(I robot,Eagle Eye etc..) about robots taught us..?? "ROBOTS EVOLVE" :p lol


How can people pray in space?

Question: I have been wondering about the interpretation of scholars regarding praying in an environment rather then earth. For example today there already astronauts living on the space station for months. Or in the not far future it seems that people would be able to travel or maybe establish colonies in mars. How would they pray under these conditions? I want focus on issues like direction, how to perform praying rituals under lack or low gravity force, the time of pray etc.
Answer: Well I have found this Hadith related to your question. It may be answer you want.

حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا شَيْبَانُ، عَنْ يَحْيَى، عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ، أَنَّ جَابِرَ بْنَ عَبْدِ اللَّهِ، أَخْبَرَهُ أَنَّ النَّبِيَّ صلى الله عليه وسلم كَانَ يُصَلِّي التَّطَوُّعَ وَهْوَ رَاكِبٌ فِي غَيْرِ الْقِبْلَةِ.
Meaning : The Prophet (ﷺ) used to offer the Nawafil, while riding, facing a direction other than that of the Qibla.
Source

An astronauts can't really know time while in space and direction too so if you don't know the direction, you can offer pray in any direction by using local time.
Comment: What were the conditions that led The Prophet (ﷺ) to offer namaz in a direction other than that of Qibla?
If he was on land, then he could have stopped and faced the direction of Qibla and offered Namaz, then why he chose to do otherwise?
Answer: We don't have to wonder about this, because there have been many muslims in space, and the first Sultan bin Salman Al Saud (who incidentally is also the first royal, arab and the youngest person ever in space), gave an interview to NPR in 2011 on his experience:

MARTIN: One of the aspects of space travel that I think people find
  fascinating is how astronauts cope with the routines of daily life, be
  it eating or brushing their teeth. And traditionally, Muslims are
  required to pray five times a day. How did you address this
  responsibility while in space?
SAUD: Very easily. Because we have been acclimated, whether from a
  religious point of view or whether from just a personal point of view,
  I myself have grown up in the central part of Arabia, and we're
  surrounded by great deserts. And, of course, I'm a diver also at the
  same time. And I'm a flyer and I'm a glider pilot. And in doing all
  these things at the same time, they become natural when you work on
  them and practice them.
We never really saw Islam or religious duties as being something out
  of the ordinary. I remember, you know, whether we're flying or in
  different places - as a Muslim, you can pray anytime. You can face any
  direction. Like, in the space shuttle, you know, we can't really face
  to Mecca, although we're flying east, because we're flying at such a
  great speed. Like I said, those days, by the time you face Mecca, you
  probably already passed it.
(SOUNDBITE OF LAUGHTER)
SAUD: So, you know, in fact, also...
MARTIN: So what did you do? Just stop or - how did you manage it? You
  couldn't have a rug, I presume. You couldn't have a prayer rug.
SAUD: No rug. No magic flying rugs.
MARTIN: No.
SAUD: But, you know, I had to strap my feet so I can kneel. You know,
  you can't kneel fully because lack of lack of gravity, actually. But,
  you know, I prayed like a traveler. As travelers, we pray three times
  a day, not five times a day. And I prayed according to Florida time,
  when we launched. And, in fact, it was the end of the fasting month,
  which is approaching now, as you know, in about three weeks.
And we did fast the whole month of Ramadan in Houston, on Clear Lake.
  And we - in fact, the NASA people were very kind enough to say if we
  wanted to adjust our program to start a bit later, and wee said we'll
  start exactly the same time we started every day, which is about 6:30,
  7:00 in the morning. It was hot in the summer those days, like these
  days, and we went on through the day. And I'd need no more than five
  or six hours of sleep, and we were never the healthiest. So the last
  day of the mission was actually the last day of Ramadan, or so. So I
  also was the first person to fast a day of the month of Ramadan in
  space.
Comment: This is an interesting input but lacks any evidences or explanation on how they derive the ruling on how/when to pray and fast! It also rather seems to display a personal opinion not an overall ruling.
Answer: In my opinion, if you know the direction of earth, then that is where you should face, because, we pray in the direction of the Kaaba, and the Kaaba is the centre of earth. So, as long as you are facing earth from outer space, then you are facing the Kaaba. But that is just my own personal opinion. Allahu Aalam.
Comment: Salam and welcome to IslamSE the Q&A site about Islam. Unlike the usual internet forum we want answers which are well elaborated focused on answering the question and any claim to be supported by evidences (see [answer]) and for further information on our model take the [tour] and check our [help].

How can people pray in space?


Coupling two 15 Amp circuit breaker for 20 Amp

Question: My Bosch micro/oven need 120 volt 20 Amp receptacle. I do not have a 20 Amp circuit breaker for this purpose. Can I couple two separate 15 Amp breakers as a dedicated source to provide higher Amperage limit (20 Amp)? Theoretically this will increase wire cross-section area for a higher Amp. limit. Is it permissible by code?
Comment: Possible duplicate of [How can I get 30 Amps @120V using several 12AWG and/or 14AWG cables?](https://diy.stackexchange.com/questions/108788/how-can-i-get-30-amps-120v-using-several-12awg-and-or-14awg-cables)
Comment: You're talking about using two separate circuits, joined at the oven, right? Not putting two breakers on the same circuit.
Answer: Paralleling is NOT Allowed
You can't do this (except under very limited circumstances that don't apply to your situation). The problem (ignoring the code violation) is that if one of those wires breaks (disconnected at any point between device and breaker) then all of the current will flow on one wire, which is not safe as it would put all 20A on one wire. If the wire that breaks is a neutral wire then things are even worse because then the breaker will never trip because it is protecting the hot wire with the assumption that the neutral will carry the same current as the hot wires. (In a 240V-only circuit, the neutral carries the difference between the hot wires - as little as "0", but in a 120V circuit it carries the same as the hot.)
You also must NOT simply replace the 15A breaker with a 20A breaker. Almost definitely the existing wire is 14 AWG, rated for 15A, and not 12 AWG (or larger) rated for 20A. So upsizing the breaker without upsizing the wire will also be a real fire hazard (and code violation).
The only real solution is to replace the wire and the breaker (i.e., a new circuit) or to find an oven that is rated to run on a 15A circuit.
Comment: But if more than 15A shifts to the one wire, its 15A breaker should blow. I'm not saying it is safe (it sounds a horrible idea), but the explanation of _why_ it is unsafe needs expansion.
(One possibility is that the 15A breaker _should_ blow, but might not. That problem also exists if a 15A appliance develops a fault. But in this case you know for sure you will be drawing 20A, whereas the chance of a 15A appliance developing a fault that draws enough to overload the cable but not enough to trip the breaker is smaller.)
Comment: I have encountered electrician that would do this, thinking "15A + 15A = 30A".  Failure scenario is that you set your house on fire.  You don't even need a full break.  Corrosion will cause the current to shift to the other wire.
Comment: Makes perfect sense as a physicist, actually. If you have a 20A rated wire, and it gets damaged (e.g. bent) to the point of only carrying 15A safely, the situation is comparable to the 15A+15A parallel wires example where you lose one wire. Except, the parallel situation is safe because one of the 15A fuses trips over a 20A current, whereas the damaged 20A wire will overheat as its 20A fuse does not trip. In fact, parallel wires are so safe that there's even intentionally manufactured. We call those _braided wires_.
Comment: As for the "if a neutral wire breaks", that should trigger _two_ ground faults. And that leads me to the issue that I **do** foresee. With parallel wiring, how are you going to prevent ground faults in the normal situation? There's just no practical way to guarantee that the return currents exactly match the "respective" live currents. And yet the GFCI's are essential, precisely because a neutral wire might break.
Answer: Absolutely not!
Circuit breakers don't work like that.
Did your microwave come with a plug that has 1 straight blade  and 1 blade at 90 degrees? If so you will probably need a dedicated 20 amp circuit with #12 wire.
2 breakers depending on how located in the panel could provide 240v and if connected together "boom"
If they could be paralleled they would not work correctly as breakers are inverse time devices.
And as mentioned above if you have 15 amp breakers your wiring is probably only 14 gauge and 15 amp is the max breaker size. Large micro waves are one of the few devices that I have seen that require a 20 amp circuit so if the blades are not parallel 15 amp you will need a new circuit.
 To parallel wires they have to be 1/0 or larger, we do not parallel breakers.
Comment: Yes I have seen that and even a 240v model those are about the only normal appliances I can think of I have a deep fryer that is also 240 but it is a commercial model you don't see those in homes very often.
Answer: The short answer is NO.  Of course it might help to explain why.
"In theory" this would work as you expect (the part about increasing the wire cross section), but it's forbidden by code because there are a lot of dangerous issues related to this as well as practical ones.
You can't use two 15 amp breakers because that would still trip at 15 amps.  You might be tempted to take two existing 15A circuits and connect them both to a 20A breaker, and that would "double" your wire size and work, but it's not safe.  If there is just one bad connection somewhere (or a connection goes bad over time), the circuit would appear to work fine, but you would be pulling all that current over one wire instead of two which would overheat and potentially cause a fire.  Even with all of that there's still the problem of trying to connect those two wires to devices that only expect one larger wire.
Answer: No, for reasons the other answers already address well. Moreover, rather than adding a circuit, it would be a lot less expensive and more useful just to replace the microwave with a normal 15A one. There's no need for high-wattage microwaves; to do anything other than heating water (cooking/reheating/thawing/etc.) you have to run them at lower power levels, which are usually just short duty cycle. A 50% duty cycle at 1000W is going to heat your food more evenly than a 25% duty cycle at 2000W.
Answer: Nope. You are not allowed to parallel conductors like that.
Comment: The op is asking about breakers, again absolutely not. Wires can be parallel if 1/0 or larger.
Comment: It takes more than that Ed, it also requires special equipment at the source rated for paralleling.  You can't just run six 1/0 conductors 190' out to your shed and punch four of them down on any old 100A breakers and call it a 200A feeder.  Becuase stock panels are not rated for paralleling.
Comment: But you can pigtail as long as the conductor length and terminations are the same on both or all 3 it is that easy I do it all the time  double triple and quad lug breakers are quite common with larger sizes in fact it is more common to parallel than run huge wires.
Answer: Sounds workable in theory, but...
As already stated in other answers, it would be a code violation because it would be unsafe; electrical codes exist for good reason.
Going beyond safety issues, there are all sorts of reasons why this just isn't a workable idea.
Most kitchen outlet boxes are wired with two "hot" lines so that top and bottom outlets can each serve up to a 15A load, for 30A total at 120V right? WRONG! The two hot lines are on opposite phases; between them you actually have 15A capacity at 240V. Yes you normally use them as if it was 30A worth of 120V, but that's not what is actually going on, so you can't simply join them in the outlet box. If you attempted to join them in the breaker panel (VERY BAD IDEA) you'd theoretically have 30A capacity on the hot lines, but only 15A capacity on the one neutral feeding the box (all sorts of unsafe/bad/fire hazard). If you tried to gang up power from other outlets, you might as well just run a new 20A circuit.
As already stated, your only two options are:

Exchange the appliance for one which can operate on a 15A circuit, or
Run a proper 20A circuit to feed your microwave.


Fixing a dry cake batter

Question: I made a chocolate cake batter last night to test for my sons birthday cake. I made a batch of cupcakes with it to test it and it came out dry. Now I'm not sure if it's from over baking or something in the batter. Can I add anything to the left over batter at this point to save it?
Comment: Hello Mari and welcome! This isn't an answer, rather a suggestion. If you want to test a cake batter, make a cake layer rather than cupcakes. Some batters that work well for layers don't fare well when used for cupcakes.
Comment: Thank you! It was the cake boss chocolate decadence cake. It has melted unsweetened chocolate and buttermilk and hot water in it. Along with all the other usual chocolate cake ingredients. I figured it came out dry due to over baking a cake recipe in a cupcake. So I made another batch, and shortened the baking time, 15-20 mins opposed to 25-30 mins for the first batch and they came out better. It has a great taste so I don't think I want to adjust the recipe.
Comment: Welcome! What was the recipe, or was it from a boxed mix? If we don't know what's in it, we can't know how to adjust it :)
Comment: Hey Mari, nice to see you found the likely problem. On our site, it is perfectly legit for users to answer their own questions, because this helps the next person with the same problem who stumbles upon it. You will even probably get upvotes and reputation for it, if you do it down in the large "Your answer" box and not just as a comment under the question itself.
Answer: Most commercial bakeries pour simple syrup into their cakes and cupcakes after baking. To make a simple syrup mix water and sugar in equal parts by volume and heat on the stove, stirring until dissolved. The simple syrup should keep for about a month if you have any left over.
Answer: To save your cake batter, add milk to the batter. Also to save tour dry cake/cupcake, drizzle some sugar syrup to your cake. It will moisten it.

Fixing a dry cake batter


Using QR codes for bitcoin giveaway

Question: Suppose I wanted to have a bitcoin treasure hunt, where QR codes were used. The first person who scanned a given QR code should receive some preset amount of bitcoins. Is this possible? (Preferably with as little need for knowledge on the part of the recipient as possible.) As a bonus, is it possible to have a single QR code to have a "pool" of 5 bitcoins it is attached to, give 1 bitcoin away per scan, but only allow scanning by unique devices. (ie; so 1 QR code could be used to claim 1 bitcoin for 5 unique devices) or easiest just to create 5 QR codes? Essentially the same functionality as the "send to QR code" in the Android client, only in reverse - (Scan QR code, and receive coins)
Answer: The easiest way to do this is to have the QR code be a URL. For example, http://www.example.com/bitcoingiveaway/E34IKJ. Just assign a unique code to each location, the E34IKJ in my example.
What that web page does is up to you. It has to track how many times it has been accessed, of course. The first time, it can send a form that allows a person to fill in some kind of identifier, which can be a Bitcoin address. You then send them the coins (or if using some kind of account, credit their account).
Making this work without the scanners having Internet access is much trickier. It can be done, but it would require your to control the scanning devices such that they included a time stamp, and there would be no way to reliably inform people whether they were first right at the point of scan.
Another possibility for the "first come, get coins" model is to have the QR code be the actual private key used to claim the Bitcoins.
Comment: I would prefer the latter (have QR code somehow be actual private key used to claim the bitcoins). However, ideally it would not require any manual steps of behalf of participants other than scanning the code with their client on either iOS or Android. Maybe we aren't there yet with the clients...but would be nice to be able to use QR codes for a one step receipt of bitcoins rather than just a one step send.
Comment: Then probably the best solution is to have the QR code be the private key, but also offer a web page where people can enter a private key and their Bitcoin address to have the balance transferred.
Comment: Depending on your knowledge level / abilities it may also be possible to grab one of the open-source Android clients and modify it to allow private key import via QR code scan.
Answer: QR codes are completely passive. They do not collect any information about the devices used to scan it.
If you want to set this up using only the Bitcoin network, you can create QR codes with private keys of Bitcoin addresses. The device used to scan the code should be able to import the private key and send its bitcoins to another address chosen by the user. The user should destroy the QR code afterwards to avoid stealing attempts by other users.
Having a "pool" of bitcoins in a QR code is not possible in this scenario.

Since mobile clients currently can not import private keys, another easy way to do this would be with Instawallet. People would scan an Instawallet QR code, open the url, type in their address and cash out the bitcoins.
But again, this solution does not allow for a bitcoin "pool". If you really want that feature you should design a dedicated website, like David Schwartz suggested in his answer.
Comment: I suppose I should have been more clear and asked, is there any mobile client that would support the following scenario using QR codes. Not the codes themselves.
Comment: @lemonginger It shouldn't be hard to implement, but I don't know of any mobile client that currently supports this.
Comment: @lemonginger As an alternative, you could encode an Instawallet URL.

Using QR codes for bitcoin giveaway


Find all values that make the expression a perfect cube

Question: Find all the positive integers $n$ such that $n^3-n$ is a perfect cube.
Answer: If $n > 1$, then $3n^2-4n+1 = (3n-1)(n-1) > 0$.
Hence, $(n-1)^3 = n^3-3n^2+3n-1 < n^3-n < n^3$.
Since $n^3-n$ is strictly between two consecutive perfect cubes, $n^3-n$ is not a perfect cube.
The only remaining positive integer is $n = 1$, which yields $n^3-n = 0 = 0^3$.
Therefore, the only positive integer $n$ such that $n^3-n$ is a perfect cube is $n = 1$.
Answer: Here's another way to do it. Let $n^3-n=k^3$. Then we have
$$n=n^3-k^3=(n-k)(n^2+nk+k^2).$$
However, $n-k\ge1$ and $n^2>n$ whenever $n>1$. Hence $(n-k)(n^2+nk+k^2)>n$ for $n>1$, which contradicts the above equality. Finally, checking that $n=1$ works gives us our only solution.
Answer: Or think of the fact that $$n^3-n=n(n^2-1)=(n-1)n(n+1)$$, is the product of three consecutive numbers. But any two consecutive numbers are relatively-prime, so the center number must be a perfect cube itself, say $n=m^3$. Substituting back in the top expression, we have a product $$(m^3-1)m^3(m^3+1)=m^3(m^6-1)=m^3((m^2)^3-1) $$ .
But $m^3((m^2)^3-1)$ cannot be a perfect cube, because $m^3$ is a perfect cube, but $(m^2)^3-1$ is not.


Flow for alternate (to SMS) security verification

Question: For our 2FA (2nd Factor Authentication) process, we default to having an SMS sent to the user's phone.
This is causing issues for users who can't receive SMS messages; eg, they're overseas.
The safety-net we have to allow an alternate method of verification is a 'verify another way' button on the SMS code entry screen, where the user will be directed to answer security questions they have set up.
However, we are receiving feedback from users, and the business, that there are problems actioning the alternate method, with suggestions being everything from 'make the button bigger' to an interstitial screen to select between SMS or Security Questions.
Any thoughts? I was hoping a technical solution could change the default, from SMS to security questions, if we could find out the user's phone was not able to receive SMS messages - but that's not possible atm.
Comment: security wise: Security questions suck! you can make users set a 2FA app like Google auth, even better than SMS.
Answer:
Slight rant here, skip to Adjust your call to action for the
  actual answer.

IMHO, security questions are super gross in terms of UX. It causes a harsh break in the normal flow of authentication and not many designers use them anymore because of the aforementioned UX problems and the user stigma that has built up around them. Security questions make people want to use a different app.
Use Email instead of security questions
You mentioned that your users are interacting with a mobile app, which means email could be an alternate option over the internet connection you're already using to verify the user's answers. This is mostly a preference tidbit, and you should still consider the section below if you go this route.
Adjust your call to action
Without seeing the UI, it's hard to gauge whether that's part of the issue (as mentioned with the button size suggestion). I would imagine that making the SMS vs. Security Questions an explicit step would be better than your authentication just not working, but that would really suck if the secondary method is used for every authentication.
A potential way to make this more manageable while being more clear is to instead present two buttons, one for entering an SMS code, and one for using "verify another way".
I get the impression that the actual user experience is something like this:

As a user, when I'm presented with an input field, I start looking for the SMS message because that's what I'm used to.
When I don't find it, I then see the button for "verify another way" (which is probably below the input field without enough contrast), which is undesirable.
If I don't see the "verify another way" button, I circle back and try to figure out how I messed up, or retry the operation.

Having two buttons and presenting the user with a speed bump could make them think about whether or not they can even receive SMS before switching over to their messenger app of choice. I would still put the "Additional method" button on the SMS entry screen as a way to bridge over in case of a different problem preventing SMS, but I think this will help your users more.
Edit: There's a demonstration of the idea here.


How can I attach a security gate where there are no studs?

Question: I installed a Munchkin MK004 security gate in drywall (no studs were available at the location) using the supplied screws and plastic anchors.  The gate hinges on one side of the opening and opens at the other.  Within a day, the hardware at the bottom where the gate hinges was pulling out of the wall (probably not helped by kids opening it every 2 minutes).  I replaced those anchors with molly bolts.  The same thing happened.  Should I call it a day, remove the gate and patch up the holes or is there another solution - such as using a snaptoggle or screwing a wood board across two studs and screwing the hinge into the board?  (Where there are studs on that side of the opening, it is also where there are bull nose corners and I think they are covered with metal and there is no wall on the other side of the opening).
Comment: Can you post a pic?
Answer: You need to mount it in studs, concrete or something else that can handle the load; drywall by itself will not.
If there are no studs available where you want to mount it, you can open up the wall and either install a stud at that location, or depending on how the gate mounts, you might be able to add bracing between two existing studs and then mount to that.
I wouldn't be too concerned with the metal corner bead, you can screw through it pretty easily.
You might also be able to put up a seperate structure (ie: mounting a metal pole in concrete, etc.) to support the gate.
Answer: ... screwing a wood board across two studs and screwing the hinge into the board?  That's the direction I'd recommend.  But not just slats/boards, but rather a single panel, wide enough to cover both studs and the same height at the gate itself.  Ideally something like sanded plywood, about 5/8" or thicker, but something like 3/4 mdf would probably be fine, and has a cleaner finished appearance.


Why doesn't the ISS use ion engines to maintain altitude?

Question: So the ISS uses small thrusters on the Soyuz (usually) to perform occasional reboost burns to raise its orbit. This goes through, from what I can tell, around 3,500 kilos of fuel per year. Would it not be far more efficient to use ion drives to counter the drag instead? It would require far less fuel and I don't understand what the reason is for not doing it. The thrust can easily be higher than the force of atmospheric drag on the station, from what I've read.
It could simply fire on and off periodically, and of course other stronger thrusters would be kept for evasive maneuvers and whatnot.
Is there some obvious problem I'm missing?
Comment: @OrganicMarble I don't think this is a duplicate of [Will the ISS have electric propulsion to maintain altitude? Is there enough power for it?](https://space.stackexchange.com/q/19816/12102) but not sure.
Comment: How much electrical power would this ion drive need?
Comment: Question seem to ask, if its efficient why it is not being done. Well, probably it is low priority for NASA. Though they have considered it and work was also started but was terminated for unknown reason.
Answer: @Hobbes' great answer and the question there as well show that both NASA and Ad Astra felt since 2008 that high power ion propulsion was both technically and practically worthy of consideration and testing for at least some of the routine orbit-raising maneuvers required for regular compensation of the constant drag at about 400 km altitude.
See VASIMR Testing On ISS.
However the plan was ultimately cancelled in 2015.
The conventional propulsion situation in 2014 is outlined by several answers to the question What propulsion methods does the ISS use for station-keeping? but the situation has possibly evolved since then.
It is not clear to me if ion propulsion could potentially handle regular orbit-raising. However, should they need MORE thrust than that for changing orbits to move out to the way of space junk, or possibly for some situations requiring quick phasing related to meeting spacecraft from Earth or sending them back there, they would likely still have to rely on chemical engines to do it quickly enough.
So while the use of ion engines could reduce the weight of conventional propellant regularly shipped from Earth, it would not completely replace conventional engines on the ISS.
Answer: To add to the other answers - low thrust means long "burn" time, ion engines are used for continuous thrust for days. And that might be a problem for ISS which is used as a zero-G (well, micro-G) experiments laboratory, because even the ion engine-induced acceleration might mess with these.
Comment: A continuous ion engine thrust which could be somehow adjusted to be equal and opposite the variable atmospheric drag force would actually leave the ISS in a more perfect free-fall condition. But yes, a 3 to 5 day "burn" every 15 days would for example would not be so helpful.
Comment: Is the drag changing slowly and "continuously" or in rapid steps? You would have to measure it to counter it and if there are too many quick changes it would lead to some "shaking".
Comment: That's a fascinating question! I've just asked [How steady is the atmospheric drag force experienced by the ISS?](https://space.stackexchange.com/q/26580/12102)
Answer: Ion propulsion uses accelerated ions to produce thrust, AKA Coulomb's Law of electrostatic attraction/repulsion. A neutral substance is ionised to produce the ions.
Due to this, only a neutral gas (usually Xenon), and a power source for the charged electrodes (and neutraliser) are needed. Depending on size, the power consumption of current ion thrusters use 2-3kW. The Deep Space 1 used a 2.3kW NSTAR thruster.
However, thrust forces are very low compared to any liquid fuel or solid fuel rocket engine, being anywhere between 30 and 300 millinewtons for ion thrusters, up to 92mN for the NSTAR. Due to the low mass of fuel required, independantly the engines have a reasonable thrust to weight ratio, so for small probes this is an ideal solution, resulting in incredible amounts of Delta V due to the Ion Thrusters high efficiency and specific impulse rating.
For your original question, Ion engines would simply not be practical currently for an effective propulsion method for the ISS. Primarily due to the huge mass of the ISS, many, many Ion thrusters would be needed, being extremely costly and even then the thrust to weight ratio would be extremely low. Furthermore, the power consumption would also be far too high, for the quantity of thrusters needed, and their increased burn time due to the low thrust to weight ratio.
In short: Ion thrusters are ideal for low mass satellites or probes, but until technology advances are made they are too small and power demanding for high mass applications.
I will run some numbers later for thrust to power input ratios.
EDIT:
I believe, at least one incarnation of NASA's LOPG or previously Deep Space Gateway plans use electric propulsion to adjust orbits, however I believe this may well be plasma rather than Ion.
Comment: Yes, I don't recommend removing chemical engines, hence "and of course other stronger thrusters would be kept for evasive maneuvers and whatnot."
Comment: DSG Propulsion module is officially called Power and Propulsion Element (PPE), PPE's baseline capabilities include the generation of 50 kilowatts of electrical power as well as hosting a 40-kilowatt electric propulsion system, with storage of up to two tons of xenon propellant and the ability to be refueled. It's supposed to provide around 50mN/kW of thrust, or around 2 Newtons


Can I leave my car sitting outside for about 5 years?

Question: I need to park my car for about 5 years. I have a 2006 Civic with 244k miles.. I'm going to cover it and start it every 2 weeks.. someone told me that after that many years it's going to fall apart and is better to just sell it, not really sure what to do at this point.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/102047/discussion-on-question-by-eugene-g-can-i-leave-my-car-sitting-outside-for-about).
Comment: @Zibbobz - Two things: 1) KBB over prices vehicles. 2) It may say it's worth that, but if you ever tried to sell a used Civic with 244k miles on it, you'll discover you wouldn't get anywhere close to the numbers you're quoting. Not trying to discourage the OP, just being realistic here.
Comment: plus, assuming you own the parking spot, you might be able to rent it out. even at $10 a week that's $2600.
Comment: Even a single dollar a month will be about what the car is worth today ;-).
Comment: @Peter-ReinstateMonica Not true - a quick check at Kelly Bluebook shows a Honda Civic from around that time can go anywhere from $4000 to $6000. https://www.kbb.com/cars-for-sale/cars/used-cars/honda/civic/?searchtype=used&atcmake=honda&atcmodel=civic&vehicleid=743&year=2004-2008&distance=500#survey
Comment: Maybe it provides a better suggestion than providing the only possible and logical answer. but ok if you insist- Yes you can park it outside for 5 years.
Answer: Can you? Yes. Should you? Not in my opinion. 2006 Civics with 244k miles are a dime a dozen. Sell it and put the money in something like a savings or 5 year CD, then instead of losing money you will earn money.  Cars sitting that long take a lot of care to prep properly and even then a lot of things that are usually lubed or turned tend to dry out and will need to be replaced.
Comment: The US rate of inflation for this year is 1.8% as of October. https://www.usinflationcalculator.com/inflation/current-inflation-rates/
Comment: I don't know where in the world you are, but here [the best 5-year rates are 3.5% over 5 years](https://www.tagesgeldvergleich.net/tagesgeldvergleich/sparbriefe.html), less than inflation, so you will lose money still.  The time that banks gave people money for saving appears to be permanently history in much of the world.
Comment: I have a friend who recommissions cars for a living. He's told me it can cost $30,000.
Comment: Why a CD instead of a index fund?
Answer: I've done it.   I don't recommend it, unless the car has exceptional sentimental value or is especially equipped for an unusual job.
Sell it on Craigslist or better method, and then, buy another one in 5 years.  You can buy the exact same year make model and color  if you really want to, but I rather doubt you will.
OK, so the logic is, "but wait. This car is a known quantity.  I know what's been fixed recently, I know how the engine performs, etc.  If I buy another car, shrug, who knows what kind of problems I'll inherit?" This argument ignores the fact that your car is going to deteriorate where it sits. Age can be just as hard on a car as miles. I have had a car's 2-year-old brake job freeze solid after sitting for 6 months.  (Granted, it was a nasty winter). If you're in territory where cars rust, parking it off-street does not stop the rust. So the fact is, this car won't be a known quantity.  You may end up having to put a lot of work into it to unwind 5 years of decay.
Answer: Having stored many cars - both successfully and unsuccessfully - I can pass on the following advice, should you try to do this:

Pick the location carefully. All "outside" locations are not equivalent. You want a solid, dry, non-living substrate to park over. Parking on grass is about the worst. A paved driveway is the best. The earth is a wet planet, the ground breathes and exchanges moisture with the atmosphere. Parking over grass, dirt, or gravel will mean that your vehicle is exposed to that moisture. Parking over a hard substrate significantly reduces that moisture exposure. A vehicle parked on grass may have corrosion problems after just a month or two, while a vehicle parked in the middle of a large paved parking area may be okay for years.
Pick the cover carefully. You don't want a cover that can move against the vehicle at all - a loose cover will chafe and quickly wear through the paint after being blown around in the wind for a few years. Tight fitting but poor quality covers can trap moisture against the vehicle and/or encourage mold, moss, and other biologicals. If you don't want to spend on a high quality cover, it may be better to leave it uncovered.
Prepare the vehicle. Make sure all fluids are fresh and topped off. You don't want to leave old contaminated oil, coolant, brake fluid, etc. in the vehicle. Change them all now and consider the fluids you put in as sacrificial - in 5 years, you'll need to change them all again before putting the vehicle in service. Store it with the gas tank full of fresh non-ethanol gas with stabilizer added. You don't want an empty gas tank, as the airspace will contain moisture which will attack the gasoline and the fuel system. Changing fluids also gives you the chance to make sure all the drain plugs, nipples, caps, and other fittings related to fluids are in good shape. It's really frustrating to store a vehicle, only to set out to replace the brake fluid before putting it back in service and discovering that the nipples for bleeding the calipers are all totally frozen with corrosion. So, as you change fluids now, consider putting anti-seize or oil on the various threads and fittings as you go.
Protect the vehicle from uninvited guests. Mice love to make nests in air filters, blower motors, seat cushions, and exhausts. Plug any openings with rags wrapped up with mothballs. Important: make a list of where you put these plugs so you can remove them later.
Wash the car and clean the inside. Go through every cupholder, storage bin, door pocket, and so on. You want to make sure you're not leaving anything important inside the vehicle, or anything that may invite pests (so - obviously, you don't want to leave food or food residue in the vehicle. But you also don't want to leave paper, clothing, or anything else that a rodent could rip up and use for bedding).
Protect bare metal surfaces as much as possible. Many parts can just be wiped with a rag with some oil on it or given a shot of penetrating oil. Things like brake disks need to be treated with a purpose-designed rust preventative coating (do some googling, you can find products in liquid or aerosol that are designed for this). If you skip this step, you can pretty much bet on needing a brake job at least, and potentially other costly work, as bare parts will corrode if not in regular use.
Disconnect the battery. Remove it and store it elsewhere if possible. There's no reason to leave the vehicle energized while in storage. Keeping the battery in a climate controlled environment may preserve it well enough to still be useful after 5 years, but you should probably just plan on buying a new one then.
Check your tire pressures. Plan on replacing the tires if you're unable to drive the vehicle at all during storage - they'll get permanent flat spots after sitting this long. UV will slowly break down the rubber anyways, so they're almost certainly a write-off.

Once stored, you should not start the vehicle every two weeks. Damage to engines comes from the few fractions of a second after startup, before oil pressure has stabilized. Two weeks is a pretty short interval, you'll be hitting the engine with wear every time you start it and not really gaining any advantage - plus, if you've prepared the vehicle correctly, starting it every two weeks will be a pretty big chore. However, leaving the vehicle totally cold for the entire 5 years is also probably not a good idea. A good compromise is to start the vehicle once a quarter - and once it is started, let it run long enough to get to operating temperature (at least 15 minutes). This will help burn off any moisture that has collected inside the engine. Once a quarter is a good interval to give the vehicle a once-over and check for any issues, so you can remedy them before they get worse. It'll also give you a good margin for error for detecting deterioration in the gasoline. You will likely find that you need to drain and refill the gas tank about once a year.
This list will probably sound like a lot of effort. That's because it is a lot of effort to store a car successfully. And even after the best preparation, you can still bet on having some unexpected deterioration that needs to be addressed before the vehicle can be placed in service. The last vehicle I stored for multiple years needed about $1200 in work (that was parts, I did my own labor) before it could be driven.
If anything, letting this all sink in for a few minutes should help deliver the message that is expressed in many of the other answers - it's probably not worth storing an older, common, easily replaceable vehicle.
Comment: @CPHPython That car had been stored for 2 years. There was corrosion damage to some suspension components and the lines to the oil cooler had corroded and started leaking. Plus it needed new rotors and pads all around. I also replaced the fuel injectors although afterwards it hadn't been clear if they were really at fault or not. It was a 10 year old Saab 9-3 with about 120,000 miles on it at the time.
Comment: Incredible answer. Taught me a lot.
Comment: I appreciate the detailed explanations you have provided from your own experience. Though I am still curious, for how long that car ($1.2k repair) was stored and what parts did you need to replace?
Answer: Apart from the value loss (if it even has any value today), you are taking a couple of risks. Assuming you're not moving it just starting it every other week these are some of the risks I see:

Vandalism (I have seen this many many times, cars just standing, gets it's screens smashed, or some idiot trying to steel a screwdriver left on the back floor or something other stupid)
Tires might deflate, and get flat spots
Rust, depends on where you park it and how you cover it. Do not park in grass, and make sure it's as dry as possible. I'm not sure covering is a super idea, if it gets damp inside the cover and never dries, that's no good. On the other hand, no cover will mean very dirty, stuff might start growing on it (this will probably increase risk of vandalism)
You shouldn't really just start the car once every second week, preferably you should run it so the oil get's up to working temp, to burn any water (condense) out if the engine
Stuff just degrading, like rubber parts doesn't react to good on just sitting still, it gets hard and seals might start leaking (eg. A/C), hoses might get perished (coolant etc), bushes might get harder, timing belt will age just as much (if not more) as when running
Mice, rats etc might start nesting
Mold
Comment: Tires getting dry rot is more of a consideration over 5 years rather than just flat spots. I let a car sit for 3 years outside, and the tires were shot, not that they were great before it sat.
Comment: Tyres are dead after 5 years not moving. Brakes will be dead, including likely calipers especially on civics. Oil needs to be changed. Fuel tank could get problems with water/rust. Battery will be dead. + all that you said. Repairs are more expensive then throw away now and buy a good one then ...
Comment: + car left for a while on public road attracts attention from the police and/or local authorities. Depending on where you live, it may get towed for whatever reason (road cleaning/repair) and quickly accumulate unpleasant bills. 5 years from now, the road status may change (parking may get forbidden).
Answer: At best, starting it every two weeks will benefit the engine and anything the engine oil touches. Keep in mind that you should change your oil every X number of miles OR yearly; whichever comes first.
Tell me, do you plan to:

Clean the car interior so that mold does not grow
Turn on the wipers to make sure they haven't seized
Use some washer fluid to make sure your pump hasn't seized
Run the A/C to lubricate those components
Run the fuel tank empty at least yearly or drain+refill so that your gas doesn't go bad
Let the alternator charge the battery enough so that your car can actually start up next time
Check the battery health occasionally or remove it and put it on a charger/tender in between start ups
Move the car a bit so that it doesn't develop a noticeable flat spot on the tires
Check the tire pressure regularly so that you don't end up with a complete flat
Check the tires for tire rot
Run the car long enough so that the radiator kicks on and circulates the fluid
Test your brakes to make sure the piston hasn't seized
And a host of other things which are just average maintenance procedures which you should still do but receive no immediate benefits because the car is not in use

If you plan to drive it 50 miles every 2 weeks then you're going to maintain car insurance and an inspection?
At the end of the day just be honest with yourself. Do you really plan to dedicate enough time to the tasks mentioned above every two weeks? Within no time at all you'll barely turn your head in the car's direction every 6 months.
You should check out questions such as:

How long does it take for gas to go bad?
Why is it suggested to change oil prior to storage?
https://www.edmunds.com/car-maintenance/how-to-prep-your-car-for-long-term-storage.html
https://www.quora.com/Whats-the-best-way-to-store-a-car-for-1-5-years

I'm not suggesting that you sell this vehicle but putting it into dis-use for such an extended period is certainly a bad idea.
5 years is a very long time and I am 95% certain that you would end up thinking to yourself "Dang, I should have sold it or let someone use it for the past 5 years. To get this thing running it's gonna cost me more than the car is worth."
Do you have a family member that you trust who would benefit from using the vehicle?
Comment: The last sentence is a great idea.
Answer: This doesn't make any economic sense. If you include the cost of your time, looking after the car properly for 5 years will probably cost more than it is worth. And at the end of the layup you are going to discover what unexpected problems need fixing when you start using it again.
Also people's life situations change over 5 years, so there is no guarantee it will still be the car that you actually want or need at the end of it.
Answer: The answer depends a lot on where you are, because of the climate. In Seattle I would do it only if you have a customer for a ton of iron oxide in 2024.
In El Paso you don't even need to cover the car (actually, a cover may increase or prolong condensation after a cold night) unless you want to keep the varnish's shine during the sand storms — but that seems unlikely if you live there in the first place.
Answer: 5 years outside? if you were talking about a storage facility then possibly especially if it was a rare car...
But you should consider selling it then getting another in 5 years time.
Answer: Of course you can! It may need insurance and tax if it's left on a public highway, and without insurance, you may come back to no car, a vandalised car, and no recompense.
That's before the depreciation of the car itself, as already mentioned. Then there's the tyres - left in the sun will mean some are scrap, and will have flat spots. The brakes may well seize, and the clutch could do the same. If it's petrol, that will be no use after a year, so will have to be kept topped up if you waste time running the car every couple of weeks.
Were it a classic car or collectors item, you wouldn't be leaving it outside for that time. Even in a garage, it's a bad idea. On grass, even worse. In public gaze - someone's going to target it in the five years.
In five years time, you will come back to a car that's worth little, to huge amounts of work (and/or bills) and maybe things will have changed for you and you don't even like it. Better to sell on, give away, lend it to a family member, and start again later.
Answer: Let's take a look at how cars depreciate in value.
I bought a car 3 years ago. It has fallen in value over 30%. So, 10% per year is a reasonable depreciation for a car.
Stocks, on the other hand, appreciate 8% per year, or 47% per 5 years (taking into account interest accruing even more interest). Of course investing to stocks has risks but putting your money to a car has even higher risks!
So, I would generally recommend you to put the money to stock market where it appreciates 47% in 5 years instead of depreciating about 50% in 5 years.
Now, your car is an old car with many miles on the clock. If you don't know of any particular large problem in the car, and it's a car you can trust, I can see why you want to keep the car instead of selling it, investing to stocks and buying another car later.
In general, the transaction costs of buying/selling a car are about 3000 USD. If you do all yourself, then you could reduce the transaction costs, but only if your time has no value.
I would assume your car is worth perhaps 4000 USD. If half of the transaction costs are paid by the buyer and half by the seller, you can expect to get 2500 USD, which grows to 3670 USD in the stock market, and then after 1500 USD other half of the transaction costs, you can get a car worth 2170 USD. (And I didn't take into account capital gains taxes; at the tax rate where I live, it woud be only 1820 USD).
By keeping the car, its value drops to perhaps half of its current value, or to 2000 USD. So, there's not much gain in buying/investing/selling; you are almost as well off by keeping the car. Especially, if you know the full history of the car (example: you have owned it since it was new), the only way to get a replacement car with full known history may be buying a new car, which costs a lot.

someone told me that after that many years its going to fall apart and is better to just sell it, not really sure what to do at this point

In your particular situation (old car with lot of miles on the clock), I would decide in the following way:

Known history and no major problems: keep it
Unknown history or major problems: sell it, invest the money to stock market, buy a replacement car later when you need it
Comment: I'm glad I don't live in the US - $3k to buy a car? I'd be annoyed if the transaction costs buying a car of that age came to more than £50 (most of which would be the insurance company's admin fees, and the fact that our system means that you usually lose a month's vehicle tax each time). Selling cost is zero here...
Comment: "In general, the transaction costs of buying/selling a car are about 3000 USD." - You really ought to clarify what you mean here or how you got that number. I bought a car in the US at a price of $1,500; the transaction costs were $90.
Comment: This $3k includes the value of your time, including the time spent for searching for a good deal...
Comment: @narkeleptk Sure you can. List it for $4,000 and have the person haggle you down to $3,000. There's only one "right" buyer, the one willing to pay the price; ignore all wrong buyers.
Comment: @narkeleptk It took me a whole 2 minutes to find https://www.carfax.com/vehicle/19XFA16529E048541 so pick your favorite car shopping site and I'm sure you will find the same thing.
Comment: No way you could get $4000 for a 06 civic w/ 244k miles. More like $1000~1200


Should we turn our oil hot water heater off every night?

Question: My husband and I are considering shutting off our hot water heater from 8pm to 8am every night to save on energy.  Is such a time frame long enough to create a noticeable difference in our oil bill?  We already know it is effective to shut it off if going on vacation but are more interested in shorter periods of time. Could turning it on and off like this cause any other problems?
Comment: I would think it takes a lot more energy to heat the cold tank every day than it does to maintain the temperature after it's heated.  Plus you would wake up every day with no hot water.
Comment: I know this is an old question, but @Jason your hypothesis is not entirely correct.  There are a lot of factors that influence whether to turn down or turn off the water heater or A/C or whatever, but leaving it on full temperature when you're not using it is not a valid option for energy reduction.  Things affecting `off` versus `down`: difference between interior and exterior temperatures, oversizedness of unit for need, programmability for slow build up to temperature, i.e. doesn't over stress the unit by ramping up to temperature too quickly, etc.
Answer: Electric water heaters lose very little heat.  Putting a blanket on them or putting them on a timer won't save much money.
NG/propane/oil water heaters, on the other hand, lose significantly more heat, as they not only lose heat through their outside surfaces, but also even more heat via the flue.  Putting a blanket around the outside will prevent perhaps 10% of the standby losses -- worth it if you're using propane but not NG.
Turning the water heater off will lower the temperature difference between the water inside the tank and the air outside the tank, so it can save you a significant amount of money ($3-4 for propane; I'm not sure how oil compares to propane) if you go out of town for a week and turn the water heater off (because after a few days, the temperature difference for the disabled water heater will be nearly zero and standby losses, being proportional to the temperature difference, will also be nearly zero.)  Turning the water heater off for only 12 hours a day will probably only save you ~40 cents a week if you have propane.  Perhaps worth it if you can find a cheap device to do it for you, but not worth the trouble of doing it manually.
NOTE: By mentioning that lowering the temperature difference between water inside the tank vs. air outside the tank, one might be inclined to lower the setting on water heater to ~115 degrees Fahrenheit.  While this will indeed decrease your standby losses, this is not safe.  At lower temperatures, bacteria commonly known as "legionella" will grow, which is particularly dangerous to elderly and children, and sometimes causes death.  If you would like to lower the setting on your water heater, you must raise the temperature on the water heater to 135-140F for at least one day each month.
Answer: I've heard of people claiming savings when installing a "warming jacket" over the tank, to insulate it and keep the water at least a little warmer, which results in a saving over time due to less energy required to maintain the same level of heat.
Does your tank have a cover? Also remember to check requirements for safety - your type of tank may not be a suitable type for a cover. The covers are sometimes called blankets.
Answer: I have mine off in the day during the summer. It's only powered from midnight to 6 a.m.
However, I live in FL and I live alone. Also, during the winter I will reverse the hours so it comes on in the morn and runs till evening.
Comment: Could you explain **why** you do this?  As it stands, you're not answering the question about whether it saves money, or if it's harmful to the heater.


Does Morrowind have levels or just level the individual skills?

Question: Does Morrowind have levels in the traditional RPG sense?
Or do you just level each individual skill?
Answer: In order to gain a level in Morrowind, you must improve your Major and Minor skills by a combined 10 levels.  You can gain 1 level in each skill, or 10 levels in one skill, or any combination thereof.
Afterwards, you need to sleep (not just rest/wait, but sleep, either in a bed or in the wilderness), and you will be able to gain a level.
When gaining a level, bonuses will appear, up to +5, for your different attributes, depending on the skills you leveled up since your last level.  This includes skills that are neither major nor minor skills.  Therefore, increasing these other skills can be a good way to ensure you get a +5 in the stats most important to you.  The bonus is defined by the attribute associated with the skill, so therefore, Luck will never get a modifier.
You pick 3 attributes to increase at levelup, so if you have bonuses on 4 or more attributes, extra bonuses will be lost.
It's also important to note that, if you gain more than 10 major/minor skills before you get a chance to sleep, the extras will carry over towards counting for your next level.  You will only gain one level for each time you sleep, so if you've gained 20 or more skills, you'll need to sleep at least twice to gain all your levels.
Any attribute bonuses you've accrued go away as soon as you've gained a level, so it's generally preferable to level as soon as you get the 10th skill, or else you're liable to waste attribute bonuses you could have used otherwise.
Answer: Morrowind does in fact have levels, which is obtained when you gain enough skill levels in your primary and secondary skill categories.
Each time you level, you get to choose 3 attributes to improve (with multipliers depending on which skills you advanced during that level)
Gaining levels will affect how much health you gain (based on your endurance), and improve enemy quality as well as loot.
Answer: As a related answer: it quickly becomes clear that if you train related skills at a good rate, and then level up, that you get MUCH higher stat bonuses (for example, if you level maces up +10, then you'll be able to increase strength +5, if you level maces +10 and restoration +10, strength +5 & will +5, etc). It's also true that if you put one of the skills you use most as one of your "level" related skills, you're going to level very inefficiently (for example, if your level skills are swords and heavy armor, and you level after +5 swords and +5 heavy armor, you're going to get +2 str, +2 stam, and +1 something else...The same point total you'd get for one stat, if you'd worked your skills more efficiently).
The best thing to do is to base your class around skills that you don't use heavily, that build different stats, and that you can still easily level. Then you can choose when to level, and have time to build up the related skills, so you can get better stat levels.


How to sort views table columns alphabetically with exposed filters?

Question: I'm working on a table view that will be populated with five columns and many rows of data. I would like to be able to sort the table by selecting a column and then sorting it alphabetically. Ideally, I should be able to sort the table based on any of the columns. Is this possible with views exposed filters? If so, how would I approach this?
Answer: Install and configure DataTable module.
Please follow the steps given below:

Create a new view at admin/build/views/add
Add fields to show in the table.
Select DataTables as the view style.

The DataTables module integrates the jQuery plugin DataTables into
  Drupal as a views style and a callable theme function.
Comment: Hey Nikhil, not to hijack your answer for posting new questions, but ... After the DataTable***s*** (with "s") module is installed, HOW should it be configured to answer this question here? And how should the view (as in the question) be configured? I suggest you expand your answer to avoid it is perceived as a link-only answer (at risk to be deleted via moderation).
Comment: @Pierre.Vriens Thanks for suggestion. Modified the answer.
Comment: Merci for considering my prior comment. A bit better already, but (1) the module name is ***with*** "s" (2) if you only complete the steps you mentioned, I doubt a user will be able to "*to sort the table by selecting a column*" (as in the question), since for that you need to perform additional configuration. You know how to complete that part of it, or should I rather post an extra answer to complete yours? PS: I'm a fan of DataTables (with "s"), can you tell?
Comment: You please go ahead to complete my answer :)
Answer: After the DataTables module (with "s" ...) is installed, enabled and configured as described in the previous answer, make sure to also review the settings of the DataTables format (in the Views UI).
By using that settings-link, you should at least review these settings specific to sorting of the columns of your view:

Sortable (check to enable, uncheck to disable).
Default order (Ascending or Descending).
Default sort (to select the column to be used for sorting when the Views results are first displayed, select "none" if you don't want any sorting to start with).

Refer to the (short) video about Create Powerful Tables with the DataTables jQuery Plugin and Views for an intro about it, and how to use it as a views style plugin. Using the "settings" link for this views style, you can specify all sorts of dataTables options/features. In the above video starting from around 3:00 you see many of them.
Example
Below is a screenprint of such display using DataTables. It's a display I created using Views (of course) with a table with:

8 fields in (defined in my view).
5 table columns for the 5 fields I have decided to always show.
3 table columns which I defined as "hidden and expandable" (within the DataTables settings after you select DataTables as the Views style).

Here is how the DataTables display looks like:

Hiding selected columns
If you only have 5 columns, they should easily fit within the width of a screen. But if you have many more (eg 10 or even more), you may want to use hide selected columns (which is different from "exclude from display" in standard Views!).
This technique is also used in the example above. For each row there is a link 'Show Details' (in its 1st column). If you click on one (or more) of them, the hidden fields of such row are shown below that row (with grey background here) and the link you clicked changes to 'Hide Details'. Obviously, I've not done any styling for such expanded row (hence the grey background, etc). But you can see the 3 fields that were initially hidden.
Bonus
Assume none of the rows are shown expanded, and you type "Basic" in the DataTables search box. It will then dynamically (in the browser, no server calls) reduce the table display to only those rows with Basic Page as value for "Type". But wait, there is even more: if you'd type a string like part of "21:15" instead (hidden in some of the rows), it will also dynamically reduce the table display to only those rows, like the expanded row shown in the screenprint. But wait, there is even (quite) a bit more: a search string like  "basic 21:15" will filter the rows to a combination of both search strings. For only this one feature I often recommend the amazing DataTables module, one of Drupal's hidden gems I think. And then there are the other features like pager, sortable columns, etc.
Remarks

Make sure to use the 1.9.x version of the DataTables library (not 1.10.x or above), as mentioned also on the project page, which states:

While there is work in the 7.x-2.x branch to upgrade to the latest DataTables version (1.10.x), the 7.x-1.x branch only works with DataTables <= 1.9.x. Since it's not listed in the projects download page, you will have to download it directly.

When creating a view, disable the pager of your view, since DataTables provides its own paging features (the video talks about that starting from 2:05).


How can I insert a space between several clips in Premiere?

Question: In Adobe Premiere Pro CC 2015 I want to select 20 or more clips to drop on the timeline at once (in this case they are audio clips).  However I would like to have a configurable space or gap between each clip on the timeline (say a 5 second space between each clip) rather than having them be one right after the other.  How can I do this?
Answer: The best way I've found is based off of "User" above but much simpler, no need to copy and paste:

Drag and drop all 20+ clips on to the timeline to add them.
Press 'a' and hold Shift, then click on the leftmost clip on the sequence to select all video clips to the right of the first clip on a single track.
Right click and choose Speed/Duration. Choose a setting like 95% (relatively small gap, enough to be able to set Default Transitions on multiple clips all at once using a single sequence) and check Ripple Edit, Shifting Trailing Clips. This is the important part.
Right click the selected clips again and choose Speed/Duration. Set the Speed back to 100% and uncheck Ripple Edit, Shifting Trailing Clips.
Answer: I believe I figured out a workaround to do this (based on the idea of using the speed duration from putting a gap between each clip)

Drag and drop all 20+ clips on to the timeline to add them.
Select on the clips and copy them onto a new audio track
Select all the new clips you just copied and right click and choose Speed/Duration.  Choose a setting like 50% and check Ripple Edit, Shifting Trailing Clips
Delete the clips on the new track you just copied and time stretched, leaving you with just the original clips.

The original clips should now be spaced out.  Obviously could be problematic if you have lots of other stuff on your timeline but you could lock those tracks.
Answer: You could generate 5 seconds of silence and do an insert edit between each one. It's pretty easy with the keyboard shortcuts - in the timeline window ↓,, ↓,, ↓, and so on
Comment: Also it looks like the cleaner way to do this is to have the source patcher in the black/silent state by Alt clicking in the "source indicator column" in the track headers and then doing the insert edit as you suggested.  This way instead of having silent audio you actually have a true empty gap between the clips.
Comment: Sound promising can you flesh this out a little more? As it is now I don't know how to do it:  1. How to generate 5 seconds of silence? And how to insert edit? When I press the comma key nothing happens.  I'm on Windows if that makes any difference
Comment: You could generate 5 seconds of silence with Audition, if you have it. Make a new waveform file and go to edit>insert>silence and save the file out. Otherwise you could do the same with Audacity (free), or you could probably download silence from the internet (make sure you get silence that's licensed under a creative commons license though ;). As for the insert edits, comma is the default key for insert edit on Windows and Mac, at least on US English keyboards. Check your keyboard shortcuts ( Ctrl-Alt-K ).
Comment: My comma key is set for `Application->Clip->Insert`. When you press the comma key, how does premiere know what you want to insert?  I'm thinking there must be a step before this
Comment: oh, sorry, yes you need the clip in your source window. Without in and out points set it should insert the whole clip, otherwise in the source window hit `x` to select the whole clip.
Comment: Ok it still wasn't working but after some searching I found I needed to select a track for source patching (see https://forums.adobe.com/thread/1420758).  I had selected tracks in the "track target column" but not in the "source indicator column" (as described here: https://helpx.adobe.com/premiere-pro/using/source-patching-track-targetting.html)
Answer: I know the easiest way: first select all the clips you want to move to the right to create space, right click on them and tap 'group' now they are all considered as one clip. Now all you have to is drag it to the right and later if you want to select only one file just right click on the whole group and then press 'ungroup'. That's it, you're done.


K2:How to run a certain task every time an item is saved

Question: I am using k2 to buildg my Joomla 3.5 site. My k2 items are basically youtube videos, every youtube video has a URL pattern for its preview image and I want it to be the item's image. But I don't want to bother with the repetitive job (copying the video ID, fitting it into the URL, and saving it as the item's image) every time I create an item. So I am thinking maybe I can write some script to automatically get the images(it is easy to do once the video's id is provided). The problem is, this script has to be exectued every time I create an item.
I just start to learn some basic things about Joomla extension developing, my question is, which category does the thing I want to fall into? Shall it be a plugin? Or a k2 plugin? Or there is totally no interface for this kind of thing and I will have to hack some PHP file?
Furthermore, I also have some node.js script to scrape the description of the Youtube videos(Yes I am being lazy again, I don't want to copy and paste those descriptions every time I create an item). How do I get Joomla to run these node.js scripts?
Answer: You need a K2 plugin if you are not yet using K2 V3, otherwise a regular Joomla plugin, if I remember correctly.
Basic sceleton for what you need would be something like
<code><?php
defined('_JEXEC') or die ('Restricted access');

JLoader::register('K2Plugin', JPATH_ADMINISTRATOR . '/components/com_k2/lib/k2plugin.php');
JLoader::register('K2HelperUtilities', JPATH_COMPONENT . '/helpers/utilities.php');
JLoader::register('K2ModelItemlist', JPATH_COMPONENT . '/models/itemlist.php');
JTable::addIncludePath(JPATH_COMPONENT_ADMINISTRATOR . '/tables');

class plgK2Myplugin extends K2Plugin {

   //params needed for K2
   public $pluginName = 'myplugin';
   public $pluginNameHumanReadable = 'My plugin';

   public function __construct(&$subject, $params) {
      parent::__construct($subject, $params);
   }

   public function onAfterK2Save(&$item, $isNew)
   {
       // this is where your logic goes
   }
}
</code>
Then you can edit the $item variable and change the image variable to what you want


What is on or off topic?

Question: When defining the scope of a site like this one, we need to decide what is on topic and what is off topic.
How can I discuss such things in Latin?
It can be a pair of adjectives or some other construction to make the distinction.
The best option that comes to mind is situi aptus/ineptus, but I wouldn't be surprised if there is something better.
Comment: Why not use the feminine, as in _rogatio_ apta?
Comment: I decided to collect the suggestions from the comments into a CW answer. Feel free to edit it if something new comes to your mind.
Comment: @Rafael The adjective *aptus/ineptus* with a [question word](https://latin.stackexchange.com/q/1320/79) sounds like a good idea. Can you give that suggestion as an answer?
Comment: I'm still hesitant about _aptus_. It is good, but I wonder if there is something better. Would a Roman understand what we mean by _ad hoc_?
Comment: @Rafael I think using *ad hoc* in this meaning would be a little... *ad hoc*. I don't think a Roman would understand it in its modern (English) meaning. It could work with some other words to support it. I'm hesitant about *aptus* too, and that's why I asked. Perhaps *gratus* would work?
Answer: Here are some ideas (mainly adjectives to go with rogatum or some such word) that have been proposed so far in comments and the question itself.
Feel free to add any new ideas here.

situi aptus/ineptus
ad hoc
gratus
pertinens
decens
decet
adhibere/prohibere and adhibitus/prohibitus

This list contains no explanation or justification, just possibly useful ideas. If you want to elaborate on one or more idea, please write it up in a separate answer!
This answer is community wiki so that anyone can edit to add a suggestion but no one gets reputation for the votes.
Answer: One of the pleasures of this site is the civility shown to those who enquire and to those who reply. In keeping with this nonjudgmental ethos I would therefore suggest:
nitēns, (present participle of niteō) brilliant, shining --to show approbation, on-topic
nītēns (present participle of deponent nītor) on one's knees, striving, making an effort --for off-topic.
Provided that it was not said out loud, or marked with a macron, the only giveaway, I suppose, would be the Accusative/Ablative situm/sitū.
Comment: I was going to post a finger-wagging about how far-fetched the "off-topic" meaning was, but then I saw [meaning I.B.3 of *nitor*](http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dnitor1) and lost all composure :)
Comment: This is the best thing
Comment: I added macrons to show that the two are indeed marginally distinct; feel free to roll back if you don't like them.
Comment: @brianpck To help (?) you get your composure back together, I decided to ask [a question about the meaning I.B.3 of *niiti*](https://latin.stackexchange.com/q/4931/79).
Comment: This is a fun one! It's a little difficult to make the distinction between *nĭtens* and *nītens* in writing, but not impossible.
Answer: My submission is [situi] consentaneus:

agreeing or according with something, suited to, becoming, meet, fit, proper

The formulaic phrase consentaneum est, in this context, would mean "That is on-topic," based on its L&S meanings:

it agrees with something, it is according to reason, fitting, consistent, proper

Off-topic could be non/haud consentaneus or even, as attested in later Latin, [situi] inconsentaneus.

What is on or off topic?


What lenses other than MD can I use with a Minolta XG-7 camera with an adapter?

Question: I recently bought a Minolta xg-7 camera at a thrift store. The store only had the body available but it was so cheap that I thought I could by a lens separately. I have found a few MD mount lenses that would work but I am wondering if other lenses would work. Is there a converter I can purchase to use modern lenses?
Comment: Possible duplicate of [Can I use lens brand X on interchangeable lens camera brand Y?](https://photo.stackexchange.com/questions/62000/can-i-use-lens-brand-x-on-interchangeable-lens-camera-brand-y)
Comment: Please read the linked question above. To sum it up, while adapters to various lenses do exist, there are significant drawbacks in using them and for *most* people, not worth it. Personally, I'd stick to eBay/craigslist/local photo store for lenses designed to be used with that camera.
Answer: I've encountered adapters that allow lenses with M42, T2, TX, and Adaptall mounts to be used on Minolta cameras with SR/MC/MD mounts. You can adapt some other mounts, such as DKL, via M42.
The reason for so few adapters isn't technical, but limited market potential. No new cameras with SR-based mounts are being produced. Also, it usually makes more sense to adapt MD lenses to other systems than to adapt other lenses to MD.

Most third-party lenses of the time are available for MD mount.
Minolta lenses are very good. There aren't significantly better system lenses that would be worth adapting for much better prices.
Consider this YouTube video: Cheap vs Steep Lens Comparison: $50 Minolta or $950 Zeiss Loxia – The difference is marginal.


Magento 2.1.1 How to load Order with Increment ID using OrderRepository object

Question: What would be the latest best practice to load Order using increment ID (instead of Order ID) using OrderRepository
Comment: **Not a duplicate** - the linked answer is about retrieving the order by order id, not by increment id
Comment: Too late, now that it is already closed. But I nominated the question to be reopened.
Comment: ekk! Is there a way to undo the mark as duplicate? I meant to mark the answer below as the answer to the solution.
Answer: Magento 2 uses Service Contracts for retrieving and saving objects. In Magento this layer is formed by Repositories, which are managers with get() and save() methods. This keeps user code away from Model calls. Don't call model methods (like load() or save() or loadByIncrementId()) directly, they are being deprecated as custom code should use the Service Contracts. Also, don't use the API from within Magento like Khoa is suggesting, it does not make sense. The API is for connecting Magento with other systems.
Inject OrderRepository and SearchCriteriaBuilder in your constructor:
private $orderRepository;
private $searchCriteriaBuilder;

public function __construct(
        \Magento\Framework\App\Helper\Context $context,
        \Magento\Sales\Model\OrderRepository $orderRepository,
        \Magento\Framework\Api\SearchCriteriaBuilder $searchCriteriaBuilder
){
$this->orderRepository = $orderRepository;
$this->searchCriteriaBuilder = $searchCriteriaBuilder;
parent::__construct($context);
}

And in your function:
$searchCriteria = $this->searchCriteriaBuilder
    ->addFilter('increment_id', '000000001', 'eq')->create();
$orderList = $this->orderRepository->getList($searchCriteria)->getItems();

// $orderList is now an array of Orders with this incrementId, which is just one order obviously

/** @var \Magento\Sales\Model\Order $order */
$order = reset($orderList);
// Your logic here
$order = $this->orderRepository->save($order);

Official Magento PHP Developer guide on magento.com
Code by Mulderea on github
Comment: I had a bug with the accepted answer. This solved it. Thanks for the good solution
Comment: @ph.dev `$order = end($orderList)` would be better since `'000000001'` here is order ID which you probably don't know.
Comment: I am getting error like : Cannot use object of type Magento\Sales\Model\ResourceModel\Order\Collection as array at $order = $orderList[0];
Comment: That's odd, I got an array. Which version are you on? But with a collection you can just replace `$order = $orderList[0]` with `$order = $orderList->getFirstItem()` to get the first (and only) item from the collection.
Comment: I am in version 2.1.3. and I need to load order object for load payment object .. I have done `$order = $orderList->getFirstItem();
$payment = $order->getPayment();`
But getting nothing in `$payment`

Please check my problem here
http://magento.stackexchange.com/questions/158935/magento-2-unable-to-set-payment-transaction-id-after-successful-payment-process
Comment: In Magento 2.3.x I need to get the order this way: `$order = $orderList['000000001'];`
Comment: @KrzysztofWołowski Upvote and you are right. `$order = reset($orderList)` could be used too, and maybe more semantic.
Answer: As far as I know, we should use \Magento\Sales\Api\Data\OrderInterface.
/** @var \Magento\Sales\Api\Data\OrderInterfaceFactory $order **/

protected $orderFactory;

public function __construct(
    \Magento\Sales\Api\Data\OrderInterfaceFactory $orderFactory,
    ......
) {
    $this->orderFactory = $orderFactory;

}

Load order object by increment id:
$this->orderFactory->create()->loadByIncrementId('00001952-42');

[EDIT] should try with service contracts. Try Jacco's answer.
Comment: Please don't use underscores in your variable names. PHP has had access modifiers since PHP 5, which is now 12 years old. You should use modern programming practices, especially in answers here.
Comment: version 2.2.2, use `\Magento\Sales\Api\OrderRepositoryInterface` and its `get()` method
Comment: service contracts must be taken in consideration.
Comment: This method should not be used even if it "works".  One: the di injection is a shared object unless it is specified to not be; anytime you insert OrderInterface in you'll be using the exact same object.  If you really want to go this route use OrderInterfaceFactory and then call create(). Second, you should be using the service contracts as in Jacco's answer.
Comment: @ThiagoLima yes, I agreed with you! I also voted the service contracts answer.
Comment: @JaccoAmersfoort Thanks your input. However, I also took a look your answer below. I need to check and confirm.
Comment: this is not working in my controller... please suggest why?
Comment: @AshishRaj you can show me your controller? You should open new question. I will take a look.
Comment: yes but its little big in lines... so will not come inside the comment box... but i m doing the same thing .. loading as above in constructor and using as like `$order = $this->order->loadByIncrementId('00001952-42');` and then doing `$payment = $order->getPayment();` But getting nothing in `$payment` Please check my problem here http://magento.stackexchange.com/questions/158935/magento-2-unable-to-set-payment-transaction-id-after-successful-payment-process
Comment: @AshishRaj Okay! I'm checking your question.
Comment: @Ian I agreed with you that we should use service contracts. I also voted up Jacco's answer.


Choice of basis in FEM

Question: Briefly, what are the different types of basis used in FEM and why is the nodal basis so popular and advantageous in the finite element context?
Answer: People use all sorts of bases in practice. For example, people use orthonormal bases in DG methods to ensure that the mass matrix in time stepping schemes is diagonal. People also use hierarchical bases when doing $p$ adaptivity because it makes the construction of constraints at faces where different polynomial degrees come together trivial. For higher order methods, people also use other constructions to minimize the condition number of the matrix.
In other words, there is a wide variety of bases that are in actual use. We just happen to start teaching the FEM with nodal bases because it's so easy to understand and because they're sufficient for most cases.
Answer: The nodal Lagrange bases are nice because they interpolate the functions at the knots: $$\phi_i(x_j) = \delta_{ij}$$ This means that you can read and plot solutions by looking only at the coefficients $u_j$ in the representation:$$u_h(x) = \sum_j u_j\phi_j(x)$$ That's much nicer than having to evaluate the sum at every point you care about knowing $u_h$.
Answer: There are a variety of different bases in FEM, but most involve basis functions which are associated with topological entities, like vertices, edges, faces, and element interiors.  This makes it possible to enforce various types of continuity by ensuring that degrees of freedom for such functions match at shared vertices/edges/faces.
These basis functions can also be defined in a hierarchal fashion (define 1D functions, blend those into 2D functions, blend 2D functions into 3D, etc). Bases defined this way can be used to expose sparsity or guarantee other mathematical properties, though their construction is more involved.
Nodal bases are simpler way to define such functions, so long as an appropriate number of nodes are placed on the vertices, edges, faces, and interior of an element. Continuity can be enforced by ensuring that two nodal values are identical at shared vertices/edges/faces.  Additionally, if such nodes are co-located at quadrature points, this can be exploited for efficient time-stepping and mass-matrix assembly on quadrilateral and hexahedral elements (this is at the root of the Spectral Element Method).
Answer: In Engineering nodal bases are a good starting point for solid mechanics problems because the principle of virtual work for the discretised system $\mathbf{K} \mathbf{u} = \mathbf{f}$ reads
$$
\delta \mathbf{u}^T \mathbf{K} \mathbf{u} = \delta \mathbf{u}^T \mathbf{f}
$$
showing that $\mathbf{K} \mathbf{u}$ are indeed (equivalent) nodal internal forces, and $\mathbf{f}$ are (equivalent) nodal external forces. For other bases, although the principle of virtual work is still valid, $\mathbf{u}$ are not nodal displacements, and therefore the meaning of $\mathbf{f}$ is much more abstract.
Early FEM developments were mostly driven by engineering applications, and the intuition of point forces applied at nodes was very important for the method diffusion.
Answer: Ideally, one would like to have an orthonormal basis with respect to the $L_2$ or energy inner product, or both (e.g., the eigenmodes of the operator at hand), because many matrices would be diagonal and thus very easy to invert.  But that's hard to get (solving eigenproblems is a nonlinear procedure).  Lagrange bases is provides sparse matrices, which in some sense is the next best choice to diagonal, and it very easy to build; so they provide the best of both worlds.  But some more sophisticated choices, such as hierarchical, wavelet bases, Bernstein polynomials, are indeed possible and work better in special applications.

Choice of basis in FEM


Identify partially built LEGO set

Question: Can anyone help me identify what LEGO set this is from?  My son has it half built and we cannot find the instructions and the bricks have been mixed with his other LEGO.
Comment: Are you sure this is all from one set? I cannot seem to find a set that contains both [Wedge 6x2 Inverted Left](http://www.bricklink.com/catalogItemIn.asp?P=41765∈=S) in Light (Bluish) Gray, [Wedge 4x2 Sloped Left](http://www.bricklink.com/catalogItemIn.asp?P=43721∈=S) in White as well as [Technic, Brick Modified 2 x 2 with Pin Hole, Rotation Joint Ball Half (Horizontal Top), Rotation Joint Socket](http://www.bricklink.com/catalogItemIn.asp?P=47452∈=S) in Dark (Bluish) Gray.
Comment: Oh and one more observation corroborating my previous statement - even though the picture is of very bad quality, it seems to me that the front part and the two 1x6 bricks in the back are of a different color gray than the rest - which leads me to think that you have a mix of Dark Gray and Dark Bluish Gray in this build, which would not have happened in the same LEGO set.
Answer: Based on the different shades of gray and the odd placement of the ball joint, I believe this is not a Lego set. Its more likely that it is something your son made out of his imagination and other Lego pieces.
Answer: I personally don't think this is lego. I've seen some of the elements in the pictures in Kre-o battleships sets. Perhaps you can evaluate on that?
Comment: These all exist as Lego parts. I see no reason to assume they are not Lego. :/

Identify partially built LEGO set


Whats an easy way of installing a VPN client on my webhost?

Question: I have a webhosting account in the UK (Linux)
Is it possible to install some sort of a web app that will allow me to use Windows VPN client to connect and use my server's IP address as a VPN server?
Thanks,
Comment: Not programming related...
Comment: semi-related...
Comment: Looks like ServerFault would be a better place for this question...
Comment: What is the goal? To proxy your http traffic? To access files? Do you have shell access?
Answer: pptp for client, pptpd server. There's plenty of tutorials on installing and configuring if you google those.