Why is there a reputation system on this site?

Question: I want to make this clear, the idea of a reputation system on a Q/A website is foolish. Why would you create a system that prevents people from posting their ideas, comments, etc. isn't that the point of the site? To ask and answer questions freely? What made you think restricting peoples access to express them and their opinions was a good idea?
For the sake of this website I would recommend removing this system, because it may make people feel like their opinions do not matter, so please remove it before it becomes a problem.  If you choose not to then that's how you choose to handle it, I'm just suggesting an alternative that allows people to ask/answer questions without having to earn a right we already have, that being "freedom of speech" which the reputation system stands in the way of.
Comment: 'Freedom of Speech' doesn't apply here. It means the government can't arrest you for what you say, it doesn't mean anyone else has to listen to it, nor is a site compelled to host it. As for the rest: our model is 'Ask questions, get answers,  no distractions',  as described on our [tour] page. Even with the base 1 reputation point, you can still do the most fundamental part of our site which is ask and answer questions. Commenting unlocks at 50 rep, which is not much: 5 upvotes across questions or answers. Everything else you can unlock is just housework: voting, editing, reviewing etc.
Comment: welcome to the site. The SE network is more than just gaming.se, and the system has been in place for many years now. Yes, there are negatives to the system, but looking at it objectively can show you that it does help people find the answers they are looking for. In regards to "opinions", that is one thing we certainly avoid here, specificity for that reason. An opinion is not right or wrong, and therefore cannot be judged properly. That's why we push people to back up said theories and opinions with facts, so that can be judged as useful, or helpful, or not.
Comment: I'm the resident malcontent here and even I disagee with this post.
Comment: "Freedom of Speech" is about a citizen's relationship with the government.  It isn't a law that **forces** private entities to do whatever you want.
Comment: Cross Sans, I didn't understand the purpose of it at first when I joined a little over a year ago,  but it is a great way to filter out trolls and other people who would come in and ruin the site with awful posts. Also a great way for making sure new users who haven't been around here long are i  charge of the site. It would be mayhem.
Comment: Plus, you can already ask questions and post answers - what you *can't* do without a very easily gained  50 rep is offer random comments (such as this one).
Answer: Arqade, and StackExchange in general, is a site that squarely focuses on quality questions and answers. It is by definition a Q&A site.
There are two main purposes for the reputation system here.

Discerning quality: Good questions that show research effort get upvoted. Good answers that actually answer the question and are of good quality are also upvoted. Questions that show no research or are unclear are downvoted; same with answers. This allows visitors to the site to easily distinguish the quality from the crap. It is designed in such a way that the askers and visitors find exactly what they're looking for - good quality answers to a question they have.
Permissions and moderation: This site is moderated by the community, as in fellow users to the site. If the site was structured to allow anyone to moderate content, a lot of griefing could easily take place, which would overall reduce the quality of answers. This is why you unlock privileges as you gain reputation: ask good questions and author good answers, you gain a better understanding of how the site works, and thus are entrusted to do more. This also helps filter out garbage content, such as spam or intentionally damaging edits.
For more information on these, see why voting is important.

Another thing to note is that Arqade is not a traditional forum. The purpose of this site is not for opinions and discussions - again, it is for questions and answers. On this site, your opinion does not matter - it is your knowledge, expertise, and experience that does.
You are welcome to say whatever you'd like on this site, but you are still subject to following the rules of asking. This is very similar to almost any website - no matter what site you're on, if you continually post garbage you'll get banned. The only difference is that on StackExchange sites, the rules of what garbage is are quite a bit different than traditional forums. Most forums don't count open-ended discussions as off-topic, but it is here. It takes some getting used to, but overall it provides a focus that other sites can't provide.


Can other players kill me and loot my items?

Question: I played softcore and was invited into a public game to do Baal speed runs, but worried that someone might try to kill me and loot my items. Is it possible?
Answer: No, when you die you'll drop a corpse, and you're the only one who can grab it. You can either get back to the location where you died, or you can quit and join a new game, which will cause the corpse to move to your spawn point in town.
No one else will be able to get your items from your corpse.
In earlier (like super early) patches of the game there was a mechanism where you could drop items upon death, but that was fixed.
Comment: You'll also know when someone wants to duel ahead of time. Their name will go red and they will be read in the party member area. Everyone in your party will be allied against this person. They can only do this from the town, so no one in the map will have this option available. They will also be unable to take any of your member's portals, so they will have to run all the way to where you currently are. No one in multiplayer games bothers with doing this, as there is no benefit except your gold that drops and gold is worthless.
Comment: If memory serves, rejoining had 2 disadvantages - all the enemies respawn and there's a loss of some gold,
Comment: @JourneymanGeek I'm pretty sure you lose the gold anyway.
Comment: Also: "In Diablo II, the player is revived without any equipped items or minions, in the act's town. To regain their lost items, the character has to return to the place they died, and pick up their 'corpse' - often a dangerous proposition, as any monsters in the area remain. Further deaths (even of an itemless character) result in more corpses. A corpse will appear in town only if the player restarts their game, but only the most recent corpse would appear - thus, if a character died multiple times, they might lose all items they had equipped." per https://diablo.fandom.com/wiki/Death
Answer: They can only kill you permanently if you play on 'hardcore'. In this game mode every death (no matter who or what killed you) will delete your char and all your items. In this mode you can allow players to get your inventory (if you are playing with friends for example).
Most players play softcore (the default setting) and there it is impossible to lose anything from your inventory.
To kill you a player must declare you the enemy. You will see a big red skull icon on your screen. After he declared you his enemy, he is not allowed to enter any teleport portals or way points. So let's say that you are in baals chamber and a player declares you his enemy. He then needs to start from the town and move through the whole act 5 to get to baals chamber. This gives you enough time to react and go back to safety in town or leave the game. You can even go to a random location via WP and your enemy wouldn't know where you are, since this information is exclusively shared in parties.


Matching new oak floor planks to old planks

Question: For reasons not worth explaining I had to replace some oak floor planks.  The new planks aren't quiet flat and are obviously the wrong color.  I don't plan on refinishing the entire floor right now, any suggestions of easier things I can do for the time being.
[EDIT] Added picture, better late than never:
Comment: Yeah Ed, you're correct, it was the sanding and finishing. I ended up sanding it with hand sanders, I made a custom mix of stains to match the color, and I sanded back a couple planks that I faded clear urethane over to make it blend and it came out great.  By far the bigger issue than color ended up being the style grain, which made a much much bigger difference.
Comment: Have you looked in a closet floor for something that matches?
Comment: We dont have enough closets to cover the area, roughly 30 sq ft.
Comment: You say it doesn't match but other than being unfinished what is the problem? If the new section is left unfinished and dirt gets ground into the flooring it may be hard to fix FYI. Nothing easy about flooring time to start sanding.
Answer: A picture of the area would have been good to see how the ends tie into the existing but here goes. 30 sq. ft. of floor is a lot to do. You may want to rent a random orbit floor sander to do the bulk of it, then detail the edges where it meets the existing.  When you write that the "planks aren't quite flat meaning they are higher than the rest of the existing floor, you can carefully mask off the existing floor around the new wood with 2" wide blue painters tape and sand the floor down to where the hand sander touches the tape, but not cutting through it. Of course if you do you will damage the finish of the existing floor. Start with 60 or 80 grit first and when the sander first touches the tape, change to the next finer grit. If it was 60 grit, change to 80, if it was 80 change to 100. Then take a regular #2 pencil and mark across the freshly sanded planks so  there are lines all over the place. Sand with that next grit until the pencil marks are gone. This will help you keep track of where and how well you have an area sanded. You may have touched the painters tape again, but as long as it hasn't torn through, that is ok. Mark the wood again with the pencil, and sand again with 120 grit, that is the last cut.
You will need a piece or pieces of the floor to test the stain on to get a good match. then stain the bare wood carefully and wipe it down with a rag to get the excess off the surface. Actually wipe the surface anytime you stain, even if there is no excess, there is always a residue that is naturally left in the process that needs to be removed before sealing. Read the directions on the stain for the time between stain and finish coats. Sand lightly (220G) after the first clear coat, then remove the tape, vacuum and dust thoroughly then apply the second coat of finish. cut it in carefully. Make sure to match the sheen of the existing floor.
Comment: I agree with @Jack since I don't know any other way that you can get them flat and match the color. It's a lot of work though. Best to take your time. Also, pay particular attention to Jacks statement about testing for a color match. That's the deal breaker. Don't do it and you won't get the results you want.
Comment: It might be a bit late now, but sanding and staining to match is a lot easier to do before installing the replacement boards. You most likely will have to use a couple of stains and maybe some natural to mix a color that matches well. Experiment on some scraps or the new flooring to get color right before applying it to the repaired area.
Comment: If the new work is an unfinished floor, there is most likely a bit more going on than just the difference in the new to old. When a prefinished floor is made I believe the tolerance for thickness are much closer. If there is a difference, the microbevel in the edges hides that small difference. The sanding is a much higher quality too. With the unfinished since it is made to be sanded after install, the surface has many more imperfections with the sanding to rid the surface on the unevenness between planks and the "washboard" of the planer marks from the manufacturer.
Comment: I know this thread is a year old, but I added a picture to the original question for posterity.


how to show list of properties and methods of a class reference in xcode4?

Question: In xcode3, list of properties and methods of a reference where displayed in a frame.
Can we do the same thing in xcode4?
Answer: Try esc on the code editor, the avable methods appearing.
If you want to see the documentation: press alt + click on the object


I need to download some data from html embedded code

Question: I have a website with an embedded code with some weather data (and I'm interested in temperature and other things to turn them into data that I'd like to put in a graph and so on...)
But if I use the CURL command with the page I need to get (for example curl -L www.website.com), I just get the full HTML code, but there is no data inside
So, if there is this embedded code in that site...

...I just get this code.
However, using a browser you can see some data in the iframe (temperature, wind, weather...). I need these datas.
Answer: It sounds like you are downloading an outer HTML container for the web page and the rest is loaded in the iframe.
If you change your URL to the contents of the iframe:
curl -L "http://www.ilmeteo.it/box/previsioni.php?citta=5913&type=real1&width=200&ico=1&lang=ita&days=6&font=Arial&fontsize=12&bg=FFFFFF&fg=000000&bgtitle=0099FF&fgtitle=FFFFFF&bgtab=F0F0F0&fglink=1773C2"

you should get the contents you are looking for. If the website has a API for downloading the data you should probably use that, but for a small amount of data like this it doesn't seem to be a big deal.
Answer: I have to try again in my Linux, because now it's working on my mac. I think I forgot to use the " chars before and after the link. I almost sure of this...
doh..!


openID component for cakePHP (and an easy way to Google)?

Question: I have integrated the openID component for cakePHP from http://code.42dh.com/openid/ into my application. When I put in my openID URL (http://openid-provider.appspot.com/XXXXXXXXX ) I am prompted to log into Google from the openID page which and I get properly redirected back to my page with a whole lot of stuff in the GET string and a "successfully authenticated" message so I know that is all OK.
However this requires one to know the URL at lead of time. How can I go directly to a screen to enter one's username and password?
[Sorry if this sounds like a beginner's question, I am still trying to figure this out]
Answer: Unfortunately you can't: the username and password are for the OpenID system that the user is logging into, and you need the URL to specify which system.
You could hard-code this to use the Google OpenID provider but your best bet would be to copy the StackOverflow login page and have 'click here to login with Google', 'click here to login with Yahoo' links that use the default Google OpenID URLs, etc.
Comment: Doc here: http://code.google.com/apis/accounts/docs/OpenID.html#endpoint It looks like you use https://www.google.com/accounts/o8/id as your OpenID URL
Comment: How do you use the Google OpenID?
Comment: Wow, those docs are pretty complicated, I'm not really sure I understand what to do here.


Can V resolve to iii?

Question: Would the iii be a substitute for I under such circumstances or does iii make another deceptive resolution kind of like when V progresses to vi? iii also has ^3 and ^5 which belong to tonic harmony but since it doesnt have ^1 I cant say it sounds the same as when V goes to vi.
Comment: You couldn't be more wrong.  Using your ears you hear all the rules and broken rules in composition.  You go ahead and rely on the textbook as final verdict and make boring predictable music.
Comment: actually a music theory textbook is the final verdict, then by all means use your ears, but only after you have done it the way the text says.. first we must learn the rules before we break free with our own ideas
Comment: The textbooks were written by people who have dedicated their lives to music theory, I think Ill take their word for it... at least as an introduction
Comment: You could try to listen and use your ears to hear if it resolves.  If it doesn't sound right, would you let theory dictate that it should resolve although it doesn't to our ears?  How it sounds is the final verdict not a music theory textbook.
Answer: There are rules. Some people even follow them.
In C, a G7 resolving to e would likely have an F resolving to E, but the B doesn't resolve to C, so the tritone resolution feels merely half-satisfying. If you instead have a three-note G chord resolving to e, the only note that needs to change is that D moves to E. This would feel much less like a resolution.
Entire eras are defined by how they fail to resolve the V chord. V -> iii would not be an earth-shattering addition to the canon.
Comment: *'Entire eras are defined by how they fail to resolve the V chord'* - can you give some examples please?
Comment: @Nigel Forgive the hyperbole. The [Tristan Chord](https://en.wikipedia.org/wiki/Tristan_chord) comes to mind but only as metonymy.
Answer: In a ii-V7-I-vi or  I-vi-ii-V turnaround iii often substitutes the tonic:
example:
the answer my friend is blowing in the wind
I used to accompany: IV-V-iii-vi
Comment: But is iii really substituting for I, or is it extending V? I think I read a source once on Music Stack Exchange that referred to I and vi as well as V and iii being able to be substituted for each other.
Comment: @Dekkadeci I agree that it extending V. In this case it is emphasizing the deceptive resolution into the vi, acting as v/vi
Answer: iii Could never (or rarely) be a substitute for I, because iii loses the tonic and changes it for the leading tone, which makes the chord minor and less stable, while I is major and stable. (Talking about major tonality)
In the other hand, iii could be a substitute for vi, because they both are minor and share one important tonal degree (iii's third (dominant) and vi's third (tonic) which makes them sound similar. They give the same feeling of 'unfinished' that is used in interrupted cadences.
(Remember that even though iii and vi sound similar, interrupted cadences finish in vi (V-vi) This happens because the leading tone of V  leads to the vi's third (tonic).This also happens in V-I resolution. This way, vi sounds more like 'I' that iii does.
Comment: The fact that iii is minor has no bearing. vi is also minor but substitutes for I just fine.
Comment: iii would not be a good substitute for vi because they are a 5th apart and so there is a natural sense of motion from iii to vi. Substitution chords are generally a 3rd from the chord they're replacing. The only exception I can think of off the top of my head is a tritone substitution.
Comment: The fact that iii has the leading tone instead of the tonic is a very good point and, at least in theory, implies iii cannot effectively substitute for I. Not like vi can, anyway.
Comment: but what if iii is in first inversion? Would iii be a reasonable option?
Comment: As a sub for I? I don't think that makes it better. iii shares as many notes with V as it does with I. Putting it in 1st inversion means putting ^5 in the bass which will emphasize its dominant qualities. And the only time you'd see a I64 (that is I with ^5 in the bass) is when it decorates a dominant chord and does not act like a tonic chord.
Comment: I64 is very useful in passing between IV and IV6 and also between ii65 and IV6
Answer: V to iii (if not V7 to iii) is quite parallel to I-to-vi, after all.
No, it's not that I "resolves" to vi, nor does V to iii. But that motion-by-thirds (with motion by fifths following) "sounds pretty good". :)
Comment: yes but I to vi is also functional and progresses in a good functional way, does V to iii?
Comment: @armani, well, it is literally the same thing, in the dominant key, anyway, ... I think "good" depends on context. There are several jazz classics/standards where the movement is by thirds. I do not know of "classical" music that does this.
Answer: For a "resolution" you need to have a semitone between one note in one chord and another note in the other chord. Between V and iii there is not a semitone.
Answer: V can lead to iii in a continuing sequence  (@Albrecht Hügli's example of 'Blowing in the Wind' is a good one). I wouldn't say it 'resolves', as in making any kind of a cadence.
V goes nicely to III though, in an 'inside-out' sort of way.

Can V resolve to iii?


Why is config files in Windows not in .config

Question: I actually have been wondering for a while why does neovim not use the .config directory that windows has instead of appdata/local
Comment: I don't know but if it starts with a dot, it doesn't sound like a Windows thing.
Answer: On Windows the usage is to push the programs to store their user configuration in:

~/Local/ (%LocalAppData%) or in
~/Roaming/ (%AppData%)

A fair fraction of the program are doing so.
You can see %LocalAppData% as a Windows equivalent of ~/.config in Linux.
Remark: There were a time where the Windows Explorer was refusing to create a file or folder that starts with ..


Inkscape; how do I add end markers for two lines that are combined?

Question: I've been creating a diagram on folic acid metabolic pathways in mammals and I have two lines I've grouped together, that I'd like to give end markers to but for some reason only one of these two lines has an end marker. I've tried adding a start marker (as I was wondering if Inkscape was counting the other line as the start of the overall path) and a centre marker (out of desperation), neither worked.
Comment: How have you grouped the lines? With a group or with a combine or with an union? Are the paths connected? Can you provide the source?
Answer: You might not need steps 1 to 3:

Chose the Edit Paths by Nodes tool.
Select the top node.
Break Path at selected nodes.
Path → Break Apart.
Select the right path.
Path → Reverse.


Difference in HR diagram clusters

Question: I was wondering what the difference in an HR-diagram would be between an open and globular cluster.
I've trying to compare both by looking up diagrams online, but can't find diagrams with same axes. I appreciate the help!
Answer: The main difference is due to the age of the cluster. In our Galaxy the globular clusters are old ($>10^{10}$ years) and as a result the main sequence turn-off is down at something like $0.9 M_{\odot}$. In contrast, the open cluster population is younger (in fact old open clusters are rather rare), this means that their main sequence turn-off is at higher masses, commensurate with their younger ages.
The older ages of globular clusters also means that a bigger fraction of their populations have lived their lives and become white dwarfs, sitting well-below the main sequence in the HR-diagram. For open clusters, the fraction of stars that have become white dwarfs will be age dependent, with almost no white dwarfs if the cluster is younger than about 50-100 million years.
Another difference would just be the number of stars. A typical globular cluster might have $>10^5$ stars, whereas a typical open cluster might have more like $\sim 10^3$. This means the various features in the HR diagram are much better delineated in a globular cluster - the turn-off, a red giant branch and a horizontal branch. The latter may be absent from an open cluster if it not old enough for its $<2 M_\odot$ stars to have evolved to core helium burning.
There are secondary, smaller differences associated with differing compositions. Galactic globular clusters tend to be metal-poor, though there is a dispersion. This means that a main sequence star of a given mass is bluer and more luminous. The net result is that the main sequence sits slightly lower in the H-R diagram. Further differences arise in galactic globular clusters with multiple populations. These produce multiple sequences in the HR-diagram (that are only seen in high quality data), that are associated with differences in the composition of the multiple populations within the globular cluster. Open clusters appear not to have these multiple populations, at least in our own Galaxy.
Answer: So, @ProfRob's answer is absolutely amazing and covers the bulk of star-cluster properties that I could think of.
Nevertheless, since the question specifically asked for HR diagrams of open vs. globular clusters, I am sharing some plots that I made myself using Gaia data exactly because, a couple of years ago, I stumbled upon the fact that I couldn't find nice didactic figures for a class I was a teaching assistant for. Here it goes!
Few caveats:
(1) the axis are the same, but on slightly different scales.
(2) I do not know where are my codes to reproduce all these figures. Sorry.
(3) Titles on top of panels and legends are in Portuguese, because, well, I am Brazilian. In any case, you can use Google Translate.
Open clusters:
Pleiades

Jewel Box

Globular clusters:
NGC 3201

Omega Centauri / NGC 5139

About these plots.
Left panels: all stars in the field of the clusters. Do not remember exactly what I adopted at the time, but probably just took from catalogs linked below. Middle: same thing, but color-coded according to the probability of each actually belonging to given cluster based on proper motions and positions (evidently from Gaia). Right: clean HR diagrams with prob. > 99%.
Globular cluster catalog:
Vasiliev & Baumgardt 2021
Open cluster catalog:
Poggio+2021
Ah, another thing to keep in mind is that Omega Centauri is not a regular globular cluster, but rather the stripped nuclear star cluster of a dwarf galaxy accreted by the Milky Way in the past (see Limberg+2022).
Well, developing on the secondary properties @ProfRob started to list, I would like to add that, because open clusters are young, hence born within the Galactic disk, and globular clusters are old, and belong to the Galactic halo/bulge, their spatial distributions in the Galaxy are dramatically different! Open clusters are mostly contained within few 100 parsec from the Galactic plane even in the outermost regions of the disk. On the other hand, globular clusters can be found at 100s of kpc out in the halo. The refs. linked above account for these assertions. See this figure I prepared with the same data:

The instructions (and data) to reproduce this one are in this repository: https://github.com/guilhermelimberg/Star_cluster_distribution.
Finally, another consequence of this dichotomy in the properties of open and globular clusters is that their motions, i.e., orbits around the Galaxy, are completely different! Open clusters are (almost) always on quasi-circular orbits (low eccentricity). On the contrary, globular clusters can have all kinds of crazy orbits! See figure below that I made myself.
.
(To calculate these orbits, I used the gravitational potential of McMillan+2017 and line-of-sight velocities from APOGEE survey)
Ah, of course, open clusters dissolve quite quickly as was already mentioned, because they are not so massive and weakly bound gravitationally, so they actually do not complete these many full orbits around the Galactic center. Keep that in mind.
Hope this is useful to someone (:
Comment: Thanks a lot for the HR diagrams and additional information!

Difference in HR diagram clusters


I am looking for alternatives to the phrase "way too" or "far too" as in "Way too often..."

Question: I am editing a work written for professions and have come across a sentence beginning "Way too often I encounter ..." First, this seems very colloquial. In doing some research on google ([alternative to "way too"], [alternatives to saying "way too", grammar girl and grammarist, which did not not pull anything, I came here. Urban Dictionary states: A phrase originating from Welland, Ontario, Canada. The phrase means to do/be something to a great extent. The alternatives are professional than what I am starting with: [urban dictionary.com]. Any help appreciated. This is the first question I've posted; Apologize for posting errors.
Comment: Take the the advice of one of my favorite editors, and eliminate superfluous words at every turn.  "Way" and "far" may be safely consigned to the scrap basket.
Comment: Do you and your editor also consider "very" to be superfluous?
Comment: I agree with your comment, Rob_Ster, about being superfluous. Thank you.
Comment: @scott, I was taught to avoid the use of the word "very" because its usually superfluous.
Comment: Urban Dictionary is good for motivation but is not a particularly good source for reliable definitions or provenance.
Answer: "Much too" is a more "professional" way of saying "way too."
Answer: Since you are a little vague on the  contents are usage and did not give example as to when and what manner it is being used, it leads me to think you are reffering to time in a sense.
Like: She uses the words "way too" way too much and "far too" often.
If I am wrong please let me know and I will do my best to help you with how it is being used. I have done a lot of editing.
Check: http://www.thesaurus.com/browse/often
One Word:
Considerably, Consistently, Customarily, Decidedly, Eminently, Exceedingly, Exceptionally, Extremely, Frequently, Generally, Habitually, Intermittently, Notably, Oft, Often, Oftentimes, Recurrently, Regularly, Repeatedly, Routinely, Surpassingly, Usually, Very
More than One Word:
A great deal, As a rule, At regular intervals, At times, Every now and then, Fairly often, In many instances, Many a time, Time after time, Time and again, Time and time again, Very often
Hope these help. If you need more help, please feel free to ask.


Allshare Cast on Samsung Galaxy S III

Question: How can I use Allshare Cast feature on my Samsung Galaxy S III? I have a samsung LCD with internet, Do I still need allshare dongle to use this feature?
Answer: If your Samsung LCD TV doesn't have DLNA certified software or its not a DLNA certified device, you'll need AllShare Dongle. Check your TV's manual.
If your TV is DLNA certified, look its menu to use it. DLNA was designed for simplicity. Its truly plug-n-play. To use it, first connect both devices with same Wi-Fi network. Make one device server and other one client. Done!
Comment: Sachin. My TV is DLNA certified but how can I use Allshare Cast feature on my Samsung Galaxy S III?
Comment: @Shahid Updated the answer..
Comment: Well it's not working. There is an option of Allshare Play which can be used for multimedia files to be played on my TV. But Allshare Cast is for mirroring my device on my TV. It's a new feature of Samsung Galaxy S3. How can it be used? Please help.

Allshare Cast on Samsung Galaxy S III


Who is in the Crypt?

Question: When Obi-wan goes to save Leia from the Third Sister, he discovers the Crypt - full of bodies encased in amber (or some such)
Who are these people?
Answer: The Wikipedia page reads:

Having escaped Vader on Mapuzo, Kenobi and Tala arrive at a Path facility on Jabiim. Meanwhile, Leia, being held in Fortress Inquisitorius, the stronghold headquarters of the Inquisitors located on Nur, is now being interrogated for details on the Path by Reva. Kenobi and Tala plan to infiltrate the fortress to rescue Leia. Once inside, Kenobi discovers a trophy vault filled with the preserved corpses of Jedi who had been captured and killed, including a Youngling.

Further proving the fact is the presence of Tera Sinube, who is elderly jedi who most prominently appeared in the clone wars
So though certainly not sure, but we can say that it was either a tomb of the jedi killed in order 66 by the inquisitors and the inquisitors kept their bodies as trophies or the tomb of the enemies of the empire overall and they were just there as trophies for the inquisitor's.
Another theory quoted by Screenrant -

The purpose of the Inquisitors preserving Jedi corpses is unclear in the episode, but other Star Wars properties imply their potential uses. In Star Wars Rebels season 1, the Grand Inquisitor uses the corpse of Luminara Unduli to lure Jedi (or potential Jedi) into a deadly trap. The Mandalorian strongly suggests that the blood of powerful Force-sensitives is being harvested for experiments, potentially the creation of Force-sensitive strand-casts (such as Snoke) or the eventual resurrection of Emperor Palpatine.

.
Comment: Is there any reason to trust Wikipedia, a fan written third party source? Also in the future when quoting from other web pages you should provide a link to said web page.

Who is in the Crypt?


Clustered Google Map

Question: I'm new in drupal(2 days), never used it before. I have taken over this site knowing nothing about it and right away got new assigment to create clustered looking map and markers should be put from already data in drupal site. So there is a page on the site https://esc.gsfc.nasa.gov/view-all-saves that shows all information needed to place markers on the map. How do I connect to that table, loop through records to call google API to place markers. Do I have to create my own php file and put inside the root? I looked in database and couldn't find any tables that stores that data.
Answer: The best way (the Drupal way) is to build on top of available Drupal features, rather than creating a custom solution that may do the narrow task at hand, but bypasses a lot of the built-in structure that carries a lot of value when using Drupal.
Views module is used to build the page you linked to, and Views is also the best module to use to list the geo-data to be displayed on a map.
Each node from that table has Longitude and Latitude coordinates (visible when you visit a node page, not directly in the table). These coordinates fields can be used to feed a Views map display.
You'll need to install a module that provides a special Views Format that renders a map. Then add that Display type to the same Views where the page you linked is built. Adjust the fields (override) to provide for the map display.
Are your Longitude/Latitude fields from Geolocation Field? Check under Structure > Content types > SAR Saves > Manage fields. Also check under Extend which geo-modules you have available.
With Geolocation Field you already have everything you need, you just need to configure a new map display in Views configuration, no coding required ;)

Clustered Google Map


GFCI outlet indicator light is green but no power in the circuit

Question: My wife overloaded a circuit when plugging in a hair dryer.  I attempted to reset the GFCI outlet but the reset button would not engage.  I purchased a new GFCI outlet and after installing, still no power at any of the outlets in the circuit, even thought the green light is lit on the new GFCI outlet.  Just like the old outlet, the test and reset buttons would not engage.  Do I need to change the outlet where the hair dry was plugged into?
Comment: Can you post photos of the inside of the box please?  Is there power at the circuit to begin with? (Check for a tripped circuit breaker or a blown fuse at the panel)
Comment: @ThreePhaseEel There shouldn't be a green light on the GFCI if the circuit was unpowered... GFCI's don't have batteries in them.
Comment: How are you testing the outlets for power?
Comment: plugging in an electrical device such as a paper shredder
Comment: Push the reset button harder.
Comment: I did, I actually used a flat head screw driver on the button
Comment: Welcome to Stack Exchange. You should [take our tour](https://diy.stackexchange.com/tour) so you'll know how to participate here with upvotes on answers that are helpful.
Comment: Make sure the wires from box mark line is going to the line side of the Gfci.
Answer: If you don't have a non-contact voltage tester you should buy one to help solve this problem.
Start at the breaker and make sure it is on for the problem circuit. Remove the faceplate of the GFCI and carefully check for voltage on the "Line" side of the GFCI. Assuming there is voltage on that side now check the "Load" side of the outlet. If the green light is on you should have voltage there as well. If you do, continue downstream carefully checking each outlet as you go. Remember the circuit is live.
The problem will probably be in the first outlet with no power or possibly in the cable between the last outlet with power and the one with no power. Once you find it, shut down the power back at the breaker. Check the GFCI to make sure you have turned off the correct breaker and there is no power in the circuit. Then  check the connections to the outlet particularly the pigtail. A loose pigtail at that point would be the prime suspect. In these cases the problem is typically something basic like a loose connection. If this is the outlet where the hair dryer was plugged in and the connections on the outlet and the pigtail are all tight, I would replace the outlet. They are inexpensive and not worth fooling with.
Turn on the breaker and test for power again. My guess is you will have power at this point. If not, the problem, unfortunately, is going to be in the cable between the GFCI and the first non-working outlet. In which case it might be time for an electrician.
Edit
Forgot to mention backstabs. Check for them. They are notorious for arcing and failing. Alaways better to attach wires securely with the contact screws.
Comment: Phantom voltage is not low voltage it has to be high enough to trip a no contact tester most are triggered above the low voltage contact limit. I am talking about true line voltage without a significant load, maybe even a few watts but a large load like a hair dryer 1200-1500 the back stab or damaged contact point usually opens From arcing when it heats up. this happens in less than a second and is very common in backstab failures. I have seen boom boxes run fine then plug in a real load  and This takes the voltage down close to zero unplug and when things cool off the radio may work again.
Comment: I am not sure if a non contact tester will help in this case because the GFCI receptacle is lighting up. It could be a bad back stab at a previous device and the non contact will show voltage even at a fails hot, and won't tell if a neutral is the problem if the failure is on that side.
Comment: Got it. Thanks. I would have suggested a multimeter but not knowing experience level I was concerned with OP handling two leads on a live circuit.
Comment: Even a standard multi meter will show voltage without a load unless it is a low Z meter , fairly uncommon for homeowners.
Comment: You referring to phantom voltage. Right? - which would be very low voltage.
Answer: Since you have a green light that tells me there is voltage ,some gfci's require the test then reset reset to be pushed to activate them I would try that first.
One of the things that goes wrong quite often with a overloaded circuit is a connection point fails some place in the circuit it could be on the hot or neutral.
A common source of the failure is a back stab. These push in connectors get hot and may loose contact or direct contact with the wire in some cases leaving only a carbon path or a very light contact that may power a radio but not a light bulb. You just replaced the GFCI so it is time to work back towards the breaker panel.
I would use the hair dryer and start plugging in at the other receptacles on this circuit. You may find several that won't power the hair dryer in older homes.
Once you find a working receptacle on that circuit it will be that receptacle or the first non working receptacle that has the bad connection.
It may also be a broken wire or a wire that came out of a wire nut and last it could be a bad connection in the breaker panel. We normally work back towards the breaker as this is how homes (under the NEC) are wired. If a room has a common wall the receptacles in that room are on the same circuit most of the times in older homes.
I find the backstabs ~96+% are the culprit. I mention this because you have a green light on the GFCI and on all the ones I can remember are green when properly connected.


How does bash print to the screen if not with a framebuffer?

Question: I noticed that a framebuffer doesn't always exist on some systems. In these cases, how does bash print to the screen (assuming it ever uses fb devices at all)? Since there's no framebuffer device, does this mean that bash knows how every graphics card out there works and can directly write to their registers, or does it use some other API?
Answer: Shells are command-line utilities - they read input and write output. Typically interactive shells are open on terminal devices - which are generally kernel-buffered serial-mode character devices - something like | pipes but with extra stuff like modem control and i/o interpretation modes. Some other program reads and interprets data written to terminal devices for display and writes its its standard input into the end of the terminal device which the shell reads.
This is a terminal emulator. At least - that is the typical configuration. A terminal might be an actual terminal - like a big, humming, glowing piece of hardware replete with vacuum tubes the size of your head, or perhaps it is a room-sized printer around which you should take special care of where you rest your hands lest you lose them.
But typically a terminal emulator is a program that understands a more or less standard protocol for text configuration and can translate the shell's i/o into something which might be drawn to a screen. The linux kernel comes with the kernel virtual consoles - which are built-in display ports and to which it connects its built-in terminal emulator. xterm is another kind of terminal emulator - one which draws to a framebuffer by way of the X11 protocol.
However it is done, though, the shell is quite a ways removed from the process.
Comment: @cat - those are the virtual console mentioned.
Answer: First, the bash does not print to a screen nor framebuffer device directly. It just writes its output to a simple file descriptor.
Second, linux supports both graphics mode consoles and text mode consoles. So, when your configuration does not use framebuffer driver then the text mode console is activated. There is a good article at wikipedia on the topic.


Is it OK to plant flowering plants near my herb garden?

Question: I have mint, tarragon, sweet basil etc. Beside is another plot for different kinds of roses and daises. Then the roses started to lose leaves or have bites on the leaves. Do the herbs attract insects that cause this?
Comment: No. Insects don't distinguish between herbs, veggies and ornamental plants. They choose between "tasty" and "bleech".
Answer: If anything, I have heard arguments (likely anecdotal) that plants like Tarragon and Basil actually repel some insects, possibly at a range of a few feet. Roses on the other hand, tend to be victimized by a wide range of insects and diseases regardless of what they are planted near. They are not exactly a low maintenance plant.  I would suggest searching through our questions on roses. If nothing there looks like what you're seeing on your roses post a question about it with a picture.
Answer: It's been years since I posted this broad question, but over the years of experience in gardening and finding helpful resources online, I was able to discover companion planting for cut flowers [1]  and for vegetables [2].
All plants, including ornamentals and cut flowers, attract and/or repel different sets of pests. It is best to find reputable resources about which plants go together. Also, the climate, zone, season, and environment are also some major factors to consider as it can affect which pests and diseases normally exist.
For medium to large-scale vegetable or cut-flower production, synthetic pesticides seem to be practical to maintain a good profit. But for home gardening, small-scale farming, and hobby farming, avoiding pesticides will benefit the surrounding community in the long term. Some saying goes that "if nothing eats your plants, then it is not part of the ecosystem."
For organic gardening, insects in general are not necessarily enemies, but companion planting is one option, aside from bio-pesticides, that may aid in minimizing the effects of pest damage.
For roses, geranium may repel pests, but other factors apply, including soil quality as plant health is integral to overall plant survival from pests. As for most vegetables, French marigolds and chrysanthemums has pesticidal and deterrent properties. It can be planted near the vegetables or used as a bio-pesticide spray.
When using both synthetic and bio-pesticides, skip broad-spectrum products and just focus on the specific pests attacking the plants, if possible implement manual 'squishing' of pests.


Duplicating a rig doesn't work

Question: When I create the left side of the body with ik bones and then I duplicate them for the right part to be symmetrical and then I try to armature deforme with automatic weights only the left side is attached to the body and the left side also controls the right side. Why is that?
Answer: There can be different situations, but the concept is that the stack order of operations is important:
When you duplicate (or mirror, or copy and paste inverted, etc ....) something, the copies will retain all the issues of the source: this is the reason why your right side of the character is piloted by the left bones (probably you copied or applied the mirror AFTER assigning wheights).
One of the  correct sequences could be:
Finish half a mesh, set a mirror modifier and apply it (so you have a complete mesh).
Finish half a rig (Left side); rename all bones with a name which ends with .L (or .l); select all .L bones and copy and mirror them; while all new copied bones are selected, choose "Armature - Flip names";
So, when you have  a complete mesh and a complete rig, you can go with automatic weighting and everything will work as expected.
Remember that - before parenting - you could need to ALT P clear parent and delete all vertex groups of the mesh, to "clear" any previous unwanted setting.

Duplicating a rig doesn't work


Will my phone (carrier unlocked but initially locked to verizon) get locked after Kitkat update?

Question: I've bought Motorola Droid Razr M from eBay. It is locked with Verizon by default, so seller unlocked device for me and it is working fine. It comes with Jelly bean 4.1.2 and I found that Kitkat update for this device. Now the question is Will my device get locked again after update from 4.1.2 to 4.4.2???
Answer: There's a 50-50 possibility of getting the phone locked because if the seller has unlocked through the proper way(legally) then you can go ahead and update your O.S else if your seller has unlocked by other means then definitely the phone will get locked to the Carrier with which it has the contract with(here Verizon).
I suggest you to get in contact with your device supplier and ask him his mode of unlock. An unlock never comes free of cost although some sites offer a legal unlock .The Same thing is what observed in other mobile OS(like ios) if you have unlocked it by other means and have updated your device then the phone gets locked to the carrier with which it was sold and you need to unlock it again.
Answer: I unlocked my HTC One by "other means" and had no problem with updating/rooting/ROMing, so I would expect the same for you.


Hanging on metal studs

Question: I want to add shelves and storage to my closet. The idea was to install battens along the wall and then lay the shelves on top. I only have thin metal studs to work with. On the left wall I only have two studs and they are in the corner. Should I use some kind of toggle screw into the metal studs or is that not a good idea? If not what is a good screw to use with the stud? What screw should I use between the studs? Shelves would be 1 73x23 (more like a desk) and probably 2 73x14 shelves.
Answer: Metal studs, like wood studs, should be spaced at a consistent distance, except for extra studs in corners, around windows, etc. That distance will typically be 16" or 24", so for a 73" wide desk/shelf/cabinet/etc. you should have no problem mounting to 3 or 4 studs.
As for how to mount things, toggle bolts make sense to me - I have used them myself, but it has been a while as I don't often deal with metal studs.
I would not recommend:

Screws into metal studs - they only get a very thin layer to grip. Fine for lightweight stuff, but not for desk/shelf/cabinets.
Toggles or other anchors only through drywall - you really need to get into the studs. Drywall by itself is simply not strong enough.
Answer: You don't need screws between the studs.  Screwing the batten properly to a stud at each end (depth-wise) and at least 3 along the back edge (width-wise) will be plenty.
As for screwing to metal studs, this answer about using sheet metal screws is excellent, and there's more useful information in that Question including an answer from me about using toggle bolts, if you want ... but I'm recommending the sheet metal screws.
Your 24-inch shelf might be a little bouncy along the front edge.  Depending on what you use for the shelf and what you're putting on it.  You might want to add something to stiffen it.

Hanging on metal studs


Energy harvesting circuit output inquiry

Question: I am doing an energy harvesting circuit experiment (LTC3108 IC chip).
There was an example in the LTspice program.
I observed the current of Vout and it was 99nA as follows. The voltage was found to be about 5V.
Is this circuit a voltage-boosting circuit? Should the current increase in other ways?
Comment: 50 ohm is a lot when you're using expressions like "energy harvesting"
Comment: That measurement probably represents leakage current through C5. You don't have a load on the output, so there's no real current flow. Put a resistor from Vout to ground and measure the current through it. It should be much higher.
Comment: @JRE I added a 50 ohm resistor to Vout and simulated it. But there is no current. Is this the right thing to add?
Comment: How are you measuring the current? I am not familiar with using this software (although I probably should start using it... alot of people do!). Have you put a measurement device in *series* with your output? Rather than in parallel?
Answer: Yes it is - the idea of voltage boost that most people don't understand is how much power (watt) the source can generate. For example you have energy harvested power source is 0.5 watt (5 volt x 0.1 amp) and you want to boost the voltage to 8 volt or 10 volt for example then the amp will go down to 0.0625 amp or 0.05 amp respectively but still generate 0.5 of power.
Which means if you boost voltage the current (amp) will decrease likewise if you boost the current(amp) the voltage will decrease. And the power it is generated still equal to the same. However this does not apply to the household electricity because the amp it can generate is huge and you can go up to 1000 volt and produce 12 amp, 24 amp etc depending on your circuit
Actually i did experiment on the LTC3108 before but not very efficient circuit due to the breadboard platform. If it is direct on the circuit board it would be much efficient. Energy Harvesting LTC3108
Answer: Use transformer impedance ratios to match load to source. Your X1 is 1:10k might be too high or f too low.
Define Zs(f) source then choose Z(f)load wiser.


APNS Push Server with multiple Apps

Question: I'm currently in the planning phase to implement push notification functionality in my PHP-based web service, which will support multiple applications. My current service structure includes non-persistent auto-scaling servers used to hand large traffic/request loads.
For using APNS, I am having troubling coming up with an architecture.
I've read through APNS Getting Started.
Apple, states that connections need to be maintained for push with APNS, to avoid being seen as a DDOS attack:

Keep your connections with APNs open across multiple notifications; don't repeatedly open and close connections. APNs treats rapid connection and disconnection as a denial-of-service attack. You should leave a connection open unless you know it will be idle for an extended period of time—for example, if you only send notifications to your users once a day it is ok to use a new connection each day.

For large number of pushes, Apple states:

"You may establish multiple connections to the same gateway or to multiple gateway instances. If you need to send a large number of remote notifications, spread them out over connections to several different gateways. This improves performance compared to using a single connection: it lets you send the remote notifications faster, and it lets APNs deliver them faster."

I've found this post about Persistent APNS connections on the site, which states "...appears a rule of thumb is 15 connections max"
My questions are:
1.How should I handle these pushes to multiple apps, without risking being seen as DDOS?. I don't think I can use my non-persistent auto-scaling servers, because they would be connection/disconnection on boot/shutdown. Do I need to spread my connections out over multiple static servers?
2.If I spread my connection out over multiple servers, will that allow me to get around this pseudo-restriction of 15 connections? If I need multiple connections for each app to send large amounts of push notifications, I feel like I would go beyond 15 as my client base grows.
Answer: Have looked at a similar use case and TBH it seems easier to just use Amazon SNS Mobile Push. You can maintain multiple platformApplications using their service and just ping an endpoint when you want to send a notification. It also comes with out of the box support for

Sending to Additional platforms (GCM/Android/Baidu Push, WNS/MPNS/Windows phone, ADM/Kindle, SMS, AWS Lambda Functions, SQS queue producers, HTTP/HTTPS endpoints, SMS, Email, MacOSX etc.)
Handling of the APNS Feedback service to prevent APNS sanctions for spamming de-registered devices - you would have to implement this yourself if you were to use APNS
Topics (A single endpoint for all of your users or subsets of your users allowing you to send thousands of notifications with a single call)
Instrumentation with CloudWatch and logging with CloudTrail to track your delivery rates, failures etc. and provide alerts based on metric levels you can define
A Service Mock for integration tests
SDKs, documentation and examples for most major languages

Between keeping connections open indefinitely (for each app, on multiple gateways), resending failed notifications in a stream, and managing the feedback service APNS is just a massive PITA. Plus if you trigger any of their service limits they will revoke your cert or worse and you won't be sending any notifications until you update your system with a new one.
May as well let someone else handle all those headaches for you :D
Comment: You are 100% correct with suggesting Amazon SNS Mobile Push. It has plenty of options and supports on multiple platforms.

I was unable to use this service due to company restrictions, and therefore had to implement everything myself. The "headaches" you mentioned are all too real. Error handling and recovery can be a real pain, especially with socket-based transmissions like APNS requires.
Answer: My own solutions to the problem was:
-A series of dedicated servers with their own IP address
-Monitoring and adjusting the speed of outgoing request during times of high volume transmissions to avoid DDOS cut-off.
A secondary problem I found was that specific phone carriers limit the number of pushes you can send them, before they cut you off. So even if the APNS restriction was 15 connections or so, I couldn't even have that many running at full speed without hitting the limit for specific carriers and having their servers shut me out. This may be a problem specific to Japanese carriers though (docomo in particular was strict, I ended up with a dedicated server just for them with heavy transmission load adjustments).

APNS Push Server with multiple Apps


How can I use 2.80 mode!s in 2.79?

Question: I can't use models that were made or edited using 2.80 in 2.79 without the UI acting weird.
Comment: That is normal and expected. simply append the 2.8x objects into your 2.7x project.
Comment: @David. Your comment should be an answer. I made it and it worked almost fine. I had to decrease the lights strength a lot and all was good. Note: I cannot use the 2.8 version because I don't have a graphics card.
Comment: @LeoNas done. added an answer.
Answer: 2.8 was a compatibly braking release, meaning files edited in 2.8x will not work in older versions, even 2.79b.
That interface acting weird is normal and expected when opening a 2.8x file in 2.7x (or any pre 2.8 version). I've had blender flat out crash when trying to open a 2.8 file.
Fear not, you are not locked to 2.8.
Create a new file in blender 2.7x  and append whatever you need from the 2.8 file. I have had appending the whole scene fail, but appending objects always worked for me. Simply
From the Info window File > Append or ShiftF1 then find the 2.8 file. Go to the objects category, and if needed simply select everything.
Proof this really works
I just tested this with this Tesla Model S made for eevee. It is setup for eevee so obviously it's 2.8, even the description says "Blender 2.80 required"
Yet I simply selected all the objects when appending and as you can see it works perfectly (even the materials!)
Answer: Export the object in .fbx format. Only catch is that you have to apply all modifyers. Upgrading to 2.8 is worth it, don't believe the talk about it being difficult to transition to. It's very easy.

How can I use 2.80 mode!s in 2.79?


How do i hang shelving on drywall over concrete

Question: i do know that there is concrete behind the drywall because it is a fire wall. I cannot drill into it for obvious reasons not to mention, the owner wont allow it. Any ides? thanks. Lewis
Answer: I would get some prefinished 1 x 4's and glue them with construction adhesive (liquid nails) to the drywall vertically to provide a solid surface to fasten the shelving to. Place one every 16 to 24 inches and you will be fine.


Which test to use to compare means/medians when one variable has normal distribution and the other does not?

Question: Which 2-tailed test is best to use to compare means/medians when one variable has a normal distribution and the other does not?
Comment: How do you know one is normal and one is not?  How big are your samples?  What kind of data are they?  What have you looking into?  Is this homework?  If it is, tag it as such.
Comment: Can you confirm you mean the mean/median of a variable from two groups which are independent?
Answer: There are whole books - or at least chapters and sections of books - dedicated to just this question, and there is no simple answer.  Hence you will get comments asking for more information on what you need and the overall research question and characteristics of the data.
Unfortunately the "mean/median" distinction is non-trivial.  Partly because they have a breakdown point of zero (a single extreme outlier makes them completely unrepresentative), means are particularly susceptible to outliers and in general dangerous to estimate from unknown distributions, but most of the traditional techniques are explicitly aimed at means (those are minuses and pluses for using mean as your target parameter).
Sometimes you really need to know the mean - for example, because an official statistics agency need to know the total (mean x population) expenditure from some subgroup, and cannot deal with a general measure of the "average" expenditure such as trimmed mean or median (which is really just a trimmed mean with 50% trimming). In other cases the median or trimmed mean is more useful because you are after a general sense of if a particular group has a higher score "on average" than the others.
Here is an extended quote from the section "Making decisions about which method to use" from Rand Wilcox's Modern Statistics for the Social and Behavioral Sciences, CRC Press.  I thoroughly recommend the full book.

Numerous methods have been described for comparing two independent
groups.  How does one choose which method to use?  There is no agreed
upon strategy for addressing this issue, but a few comments might
help.
First, and perhaps most obvious, consider what you want to know... Despite the many problems with methods for comparing means, it
might be that there is explicit interest in the means, as opposed to
other measures of location... in this case, the R function yuenbt() (a bootstrap-t method of comparing timmed means provided by Wilcox and available from R-Forge)
seems to be a relatively good choice for general use (setting the
argument tr=0), with the understanding that all methods for means can
result in relatively low power, inaccurate confidence intervals, and
unsatisfactory control over the probability of a Type I error....
... If, for example, boxplots indicate that the groups have no outliers and a similar amount of skewness, a reasonable specualtion
is that using other measures of location (not the mean) will make
little or no difference.  But the only way to be sure is to actually
compare groups with another measure of location.
If the goal is to maximize power... comparing groups with a 20% trimmed mean is likely to be best, the but the only certainty is that
exceptions occur....
... If the goal is to make inferences about a measure of location, without being sensitive to heteroscedasticity and skewness,
methods based on a 20% trimmed mean seem best for general use.  The
bootstrap method for medians also performs well based on this
criterion.  Generally it is better to use a method that allows
heteroscedasticity rather than a method that assumes homoscedasticity.
Bootstrap methods appear to have an advantage over non-bootstrap
methods when sample sizes are small.  Just how loarge the sample sizes
must be.... is unknown....
...A final suggestion is to take advantage of the various plots that were described (earlier in the chapter).  They can be
invaluable for understanding how groups differ.


How do I configure a linux machine to ignore wifi when connected via LAN?

Question: My laptop is set to automatically connect to my campus wifi network, which is desirable under most circumstances. However, in my office, the signal is quite poor, so I rely on a wired connection. Unfortunately, my machine tries to make both connections. There are two problems:

This wifi connection is terrible, and traffic seems to go through that even when I have an ethernet cable.
Connecting to wifi in general requires password entry to unlock my keyring.

I think I can take care of problem 1 using this question, but problem 2 would best be solved by not trying to make the connection in the first place. Any recommendations for that?
Answer: You need to configure the metric of the interface, which defines the "delay" or "slowness".
First, install the ifmetric program for your distribution, which allows you to easily change the metric for an interface.
Next, you want to edit your /etc/network/interfaces to call ifmetric when the networking interfaces are connected:
iface eth0 inet dhcp
    up ifmetric eth0 10

iface wlan0 inet dhcp
    up ifmetric wlan0 20

(I'm assuming that eth0 is the wired interface here, and wlan0 is the wireless interface. You might have other lines around the iface line, the key part that you want to add is the
    up ifmetric wlan0 20

part. This tells the system that it should assume that the wlan0 interface is twice as slow as the eth0 interface. This will cause your system to use the wired interface if it is connected, but automatically fall back to the wireless interface.
Depending upon your distribution, there might be a GUI tool to configure this much more easily (such as NetworkManager in the Ubuntu distribution)
Answer: If your computer has hardware switch to disable/enable WiFi card you can shut it down while you are in the office.
If your computer does not have a switch, you can shut wireless interface down. By doing:
ifconfig wlan0 down

Where wlan0 is name of the wireless interface.
Once you are out of the office you will turn it back on:
ifconfig wlan0 up

You can obtain list of network interfaces by issuing following command:
ifconfig -a

That should solve your problem.


Multisig with oracle

Question: I am trying to develop an use case in which a user has its funds on a multisig 3-2 (one key staying with him, another with my app and another one with a type of oracle that can attest if some conditions are met). These conditions would be retrieved with some type of script that can consult API's with BTC price, etc. Would that be possible to do in the base layer of bitcoin? Can anybody point to me some articles that explore this question?
Comment: You should try discreet log contracts using bitcoin-s: https://bitcoin-s.org/docs/wallet/dlc
Answer: 2-of-3 multisignatures are indeed possible with Bitcoin's base layer scripting language. In fact, there is an opcode decidated to it - OP_CHECKMULTISIG.
Note that all the Bitcoin base layer sees is three keys, and two signatures from those keys. It doesn't understand price, APIs, or any other oracle logic. The oracle would have to be independently developed and operated to check if whatever conditions you want are satisfied, and if so, to sign a message of your choice (a transaction). That would be the real challenge, and would have to be trusted and secure.
Answer: DLCs, or 'Discreet Log Contracts' could be interesting for you to explore given the use-case that you appear to have in mind.
DLCs allow for the creation of onchain Bitcoin contracts using an external oracle to determine the contract outcome. The DLC spec has built in refund logic to prevent locked funds for if for some reason the oracle is unable to attest, following a timelock. Given your stated goals, I would suggest that you explore the DLC specs and specific implementations linked above as DLCs already achieve your stated goal using 2/2 multisig and adaptor signatures.

Multisig with oracle


What should I do if I have inadvertently busted class b airspace?

Question: I was giving an introductory flight to a friend who I am trying to get interested in obtaining his pilots license. While he had the controls, I was so focused on watching and helping him that I think I busted the bravo. It may have only been for a cpl seconds, as I realized it immediately. But, nonetheless, I still did. What steps should I take with the authorities to acknowledge this mistake?
Answer: File an ASRS report with NASA saying what you did wrong and what you should have done differently. If the FAA decides to take certificate action against you, this will be taken as evidence of a constructive mindset, and it provides immunity to certificate action, so long as this was a first offense and was inadvertent. Make sure you keep the submission confirmation number and the identity strip they send you. NASA keeps no record of who submits these reports so you will need to keep this for evidence that you submitted the report if the FAA comes knocking.
Just as importantly, learn from the experience. If you are PIC, anything your passengers do is your fault. You should be at least as vigilant when a passenger has the controls as when you do, and be certain that your proficiency is up to the task of monitoring them without losing situational awareness. It's probably prudent to only give the controls to a passenger when well-removed from busy airspace.
Answer: The recommended course of action is to submit a NASA ASRS report  (full form here) admitting your mistake and explain the situation. These are non-punitive reports and are a good sign you understand what you did, acknowledge it, accept the responsibility and are working to remediate should the FAA launch an investigation.
Depending on when this happened if you and/or the flight school has not received a phone call about it you may be in the clear but keep in mind they can be slow. Assuming your aircraft had ADSB out they would have known who you were.


Is there a rigorous exploration of the relationship between core strength and kick power?

Question: I've read numerous sources indicating that improving core strength can improve your kicking power, especially for kicks that involve twisting. Has there been a rigorous exploration of the exact relationship between them? In particular, has anyone developed an exact mathematical model (presumably based on biophysics) of the relationship between muscle strength and kicking power?
Comment: @Sardathrion I remember that episode! Like you said, it was not rigorous at all. They used one subject per martial art they were testing, so the data they gathered is for pure entertainment only.
Comment: Please do not accept an answer before at least 24 hours have passed. It encourages others to write their own (potentially better) ones.
Comment: I remember a sport science episode on just that… However, cannot fathom which one it was and is certainly not rigorous.
Answer: Ok, so the concept to keep in mind is the bigger the muscle the more potential for power.  Think of a horse and how those incredible strong legs can move so much more than that of a human.  Then think of an elephant and how the power is enormous that they push down full grown big trees for fun thus maintaining the environmental atmosphere of the plains instead of letting them turn into forests.
Ok, with that in mind the largest muscles on the human body are the Rectus Abdominis muscle, External Abdominal Oblique muscle, Latissimus Dorsi muscle, and Gluteus Maximus core muscles.  The issue is that these muscles are not direct striking muscles, but more protective and pivoting muscles which protect the torso structure and the organs underneath and the one that is the butt which allows us to sit.  Where I'm sure we are all very thankful for this protection, the techniques and forms of martial arts are designed with body mechanics to harness these larger muscles and use them to channel additional strength and energy to kicks and punches.
Now all the abbendage muscles (i.e. arms/legs) are groups of corded muscles.  if you watch body building this creates the ripples of muscles as you can see the individual muscles working together.  That being said, no one muscle duplicates the function of another muscle.  It's important to strengthen all related muscles to a specific movement as they each support their function.  When looking at kicks specifically you can track the exact muscle usage and focus attention to those muscles specifically.  Careful not to detract from other muscle sets those as when you change body position it changes muscles.
So, back to the biggest muscles and how to incorporate those.  The position and muscle usage is key.  If the position is off the muscles utilized are different.  So the twisting of the hips and the movements are critical as those are the things that select the combination of muscles utilized for the body movement.  That being said, all speed/strength comes from the muscles, so you are really just trying to select the right muscles.  Thankfully systems of martial arts are developed that already do this positioning and you don't have to learn from scratch like the original practitioners did.
The "core" is focused on because that constitutes the main external muscles mentioned as well as the many supporting muscles that allow for muscle body and joint movement.  The goal is a whip motion in that the force starts at the center or "core" and moves out through the supporting muscles to the point of impact.  The more core power the more the final impact.
There is no "math" formula as there are so many varying factors depending on all the muscle conditions and usage it would be thousands of variations.  The important thing is what is "your" formula.  That is a body mechanics and personal training thing though and an instructor would need to help you work that out.
Fun thing to try is the belly thwomp or push.  Naturally the more you have the easier it is, but this exercise uses those core muscles directly.  Thus being able to push things with your belly is surprisingly strong even with the little movement that you do.  Get a friend and try to push them with your belly, if you do it correctly with just the belly and not body checking them you will see that regardless of the person you are able to move them and displace their weight with your belly.  That is the "core" power that is being harnessed in the kicks.  It doesn't feel like alot, but the fact you can move them with such a small motion is powerful.  The same power requires a full shove from an arm vs. a little nudge from the belly.
P.S. Please also note that injuries to muscles are often compensated for by varying the body movement again so other muscles more healthy can take over while the injured one heals. This compensating is sub-conscious and happens without you thinking about it, thus changing your formula to match.
P.P.S. Due to the amount of combination/variations if you want a specific set each kick needs to be done separately as there are way to many muscles and muscle combinations to indicate generically for "kicks".
NOTE: This is not about physical fitness.  Strength and overall fitness of muscles should be addressed in the fitness SO as they are key points.  Mass vs. Density and tone fits into the fitness category.  This is merely talking about a muscle that is larger has more potential than a smaller muscle and the body mechanics to help incorporate larger human muscles into movements to generate more power.  For a complete solution please consult muscle building and strength/endurance training for muscle development.
Comment: The statement that "[…] the bigger the muscle the more power." is either inaccurate or unclear: free climbers do not have massive muscles like body builders yet the formers are very powerful indeed. Muscle mass vs density is also not addressed. Finally, [Chimpanzees vs. Humans: Sizing Up Their Strength](http://abcnews.go.com/Health/Wellness/chimpanzees-humans-sizing-strength/story?id=16696826) addresses some animal vs human strength.
Comment: it's a granular level.  you never use a single muscle by itself, and neither does any other animal.  So your are right in that the motion + combination of muscles determines it.  Like a chimp constantly uses the same muscles their whole lives, thus it's stronger, but on the chimp the larger muscles on it's body have more strength capability than the smaller muscles on it's body.
Comment: Just think of bruce lee, his tone of every muscle is incredible thus resulting in crazy strength overall...but his bigger muscles are capably of delivering more power so his kicks with poor technique will be less powerful due to less core muscle usage.  I hope that makes sense, it's hard to fully articulate in a short post.
Comment: and to be clear you can't compare two different people as one's condition is different than the other one, so it would be comparing one person with different motions and where they have the most power.
Answer: Kicking power is a dubious term.  Some people who ask about power do not know what they mean when they use the phrase, and others do and want answers involving physics.  Is force a result of multiplying mass times acceleration?  Or is it a result of multiplying mass times velocity?  Be careful here, you get two very different answers because of two very different applications.
I'll give a parallel example, in golf.  The same applies to kicking, but it's easier to understand without the bias of subjective understanding of body mechanics and forces in martial arts.
Suppose Tiger Woods was at the tee, and the hole is 300 yards away.  Does he use a putter or a driver?  Both clubs have a vertical face, so what is the difference?  When he swings a putter when on the green, his body moves with the putter as if the whole body assembly were sort of like a pendulum (that is, his center moves with the club head, and not ahead of it nor behind it).  Would he swing the driver like a pendulum?
No, on both counts.  Here's why:
The driver and putter do have vertical faces.  But the driver is longer than the putter.  That means, if his hands move at the same rate, the club head moves faster, because geometry tells us that two points about a radius, the one further from the center of the circle moves at a faster distance over time than the closer point as long as both points remain on the same radius.  A golfer will tend to choose a lower numbered club head (longer shaft) than a shorter one and use the same swing when he needs a little more distance.  He could swing faster with a shorter club and impart the same force, and not considering club face angles, the ball will land in the same spot - but that requires much more experience to pull off.  It's easier to make the same swing and have a longer or shorter club (again, not considering club face angles).
Another thing about Tiger Woods: he would never drive a ball by swinging a driver like a pendulum as he would a putter.  Why not?  Isn't the longer driver going to drive the ball farther than the putter?  Doesn't his core impart the same twisting force on the driver and putter?  The answer is yes, the driver is longer and thus will have its head moving faster than the putter's head; and yes, the same twisting force (torque) is applied to both clubs when swinging as hard as he can.  But that difference in head speed is negligible when the goal is to move the ball 300 yards.  He needs more... power/speed/strength/force.
So how does Woods move the club head to get the ball to move 300 yards?
The answer is he needs more speed.  He could go to Gold's Gym and work on those abs, but even the best body builders in the world don't have enough core strength to move a golf ball 300 yards by moving their body like a pendulum, no matter the size of a typical driver.
So, we can't increase the torque (or else body builders would be the best golfers, baseball hitters, and kickers in the world, agreed?)
But we can increase the speed of the club/leg by making use of potential energy.  By twisting the body and pulling the club/leg, we are in essence whipping the thing around the radius at a much faster rate of speed then if we moved like a pendulum.  Ever hear a golf or batting coach tell his protege to move the hips through the swing?  He wants the hips to pass the ball before the arms do.  This is just another way of saying twist the body: you can't twist the body without getting the hips to move through first.
And therein lies your answer: the core moves the body through the kick to help it gain speed (technically, it's velocity, not speed).
But we're not really done yet, because we don't know whether we are dealing with momentum or force.  Or both.
Momentum is a result of multiplying the mass (the weight of the leg, although strictly speaking, it's not really the weight)... times the velocity (speed) of the moving leg: that's momentum.
Force is... well, that's complicated.  Yes, it's mass times acceleration, I'm sure you hear that a million times.  But does anyone really understand what that means?  Momentum itself is all about the thing moving, but force is about the thing being moved.  In other words, momentum is all about the club, and force is all about the ball.
To explain a little more, think of two kids playing a game of "toss the egg".  One tosses an egg to the other, who must catch the egg without breaking it.  If the catcher keeps his hand stiff and unmoving, and the thrower manages to get the egg into his hand, guess what's gonna happen to the egg?  Yep: it'll crack.  That's because the amount of time that egg hits the hand is a very short period of time.  100N has been applied to the egg if you catch it in 1/20 of a second to stop the egg's motion, and that'll crack it.  But if you carried your hand in the direction of the egg's movement, and it takes a half second to catch it and stop it (instead of 1/20 of a second), only 10N has been applied, and might not crack the egg.
The catching hand, therefore, makes the difference in the amount of force needed to break the egg - not the tossed egg.
The more a kicker moves his kicking leg like a pendulum (not necessarily vertically where gravity plays a role - it doesn't - but where the body and the kicking leg are moving with the radius of the kick), the more core strength has relevance.  The more a kicker relies on twisting force, the more core conditioning has relevance.
Bigger muscles don't necessarily translate to a faster kick - it can contribute to a slower kick.  Developing fast-twitch muscles in the abdomen (conditioning), and making use of the joints like the knee (technique), and pulling the leg around to the target (technique) creates much more impulse force because it reduces the time of impact.  This is like the egg-catcher who does not move the catch with the egg's motion.
A kick which moves slower imparts less impulse because of its increased contact time with the target.  This is like the egg-catcher who moves with the egg's motion.
To directly answer your question ("is there an exploration of the relationship..."), yes, this is all embodied in Newton's laws of motion.
The method of improving core strength is the key: building muscle mass is less important than building the fast twitch reflexes to help change your technique, so that a whipping motion can be used.  Building "core strength" necessarily requires defining the method of building "core strength".
Comment: This answer is a good explanation of golf physics, but the extension to kicking is not clear at all. Who kicks using gravity to move the leg as a pendulum? Also, the final conclusion seems to be that core strength/conditioning always has relevance.
Comment: Ok, made clarifications, HTH


I often use "is being" and "are being" in my sentences. Is it correct grammatically?

Question: For example "lasers are being used to treat different skin conditions". It is a passive form without a subject. Please guide.
Comment: As long as you are not saying "I am being happy this morning" when you mean "I am happy this morning"...
Answer: Short answer: Yes, it's fine. Totally fine.
If you're interested:
It's the progressive passive; a combination of the progressive aspect and the passive voice. It does have a subject, which is lasers. But being passive the subject is the patient rather than the agent of the verb.
There're two passive forms in English.

Lasers are used.
Lasers are being used.

This latter uses the progressive aspect in a passive construction.
The progressive passive (and later the related progressive-of-be, which is another form of "are being") was one of the bêtes noires of some 19th Century grammarians, but is now completely accepted. (Bar some general dislike of the passive in some quarters, though even they tend to dislike it rather than claim it is ungrammatical).
(The other passive construction is much older, and raised no such objections).
There's a degree of irony, in that while some complaints from that time that persist to this day are about forms that were in the language for many centuries before some people decided they were incorrect, this form actually was quite new, and nobody complains about it.
A big part of the reason is that we don't have as much use of the passival any more. Once upon a time we could say something like "lasers are using to treat different skin conditions" to mean the same thing. Only we couldn't really because Einstein didn't develop the theory behind lasers until 1917, and that form was pretty dead then. It would be considered ungrammatical today, though the remnant persists in some middle voice constructions ("the dinner was cooking", "the document was printing").
Answer: It is grammatically correct but it has not quite the same meaning as

Lasers are used to treat different skin conditions

which may just explain the function of lasers.

Lasers are being used to treat different skin conditions

indicates they are actually in operation.
Comment: this is the answer I am looking for. Thank you for spelling it out clearly.
Answer: Yes, it's grammatical. It's a passive construction in which the subject is lasers. You perhaps meant that there is no agent (we don't know who the lasers are being used by), but that is not unusual in a passive construction.
Answer: Yes, it's correct. As Barri mentioned it's a passive construction. We use the passive construction when when are more interested in the action. For example:

He killed them. Active.
They were killed [by him]. Passive.

In the second example, you are merely interested in saying that they were killed. You either don't know who killed them or are merely interested in the action itself.
Comment: Your passive construction isn't progressive passive, so it doesn't match the question. That would require "They were **being** killed".


Periodic waking up from deep sleep

Question: what are the main used ways of how to handle deep sleep of some microcontroller (atmega or a cortex m0/m0+) with waking up periodically?
Right now, I'm building a Sigfox GPS tracker that should send GPS position every ~10 minutes and this interval should be configurable.
I solved this problem in previous projects either by using external RTC IC (temperature compensated for great precision) or counting of 8sec intervals (let's see https://github.com/rocketscream/Low-Power). What are the other ways and their advantages?
My plan is to either stick to the Arduino ecosystem or switch to the STM32 world (maybe with a bit of help of mbed platform).
I really appreciate all your feedback.
Comment: How much power will the GPS receiver use in relation to the uC?
Comment: Counting 8 sec. intervals should be almost perfectly efficient. This way you'll probably be deep sleeping 99.9999% of the time. Not much more to be gained here.
Comment: Thanks for the feedback.
GPS chip (Ublox NEO-M8N or Quectel L86) shall be turned off or in sleep mode while uC is sleeping. I suppose it should be OK to start with the counting of intervals (because it's simple) and after a few tests decide what to do next.
Comment: Notice that many AVRs have one timer that supports an  "asynchronous mode" where the timer is clocked by an independent external watch crystal (32kHz). This timer runs in deeper sleep modes and can wake up the CPU in flexible intervals defined by the prescaler and TOP value of the timer.
Comment: I ask about the GPS chip because I assume that it will take several seconds of relatively high power consumption to (re-)acquire the position after 10 minutes, which may make any power saving in the uC futile.
Comment: I definitely agree. I just wondered what are the other ways to solve this problem (in general).
Answer: Generally an RTC interrupt is the best way to go for a long period in deep sleep. If you can use the RTC built into the micro this will generally give you a simpler implementation but may not be the absolute lowest power possible or most accurate.
If you do go the mbed route then this library will probably be of use. However take care, some of the boards are not really well designed for lower power, while the processor will go into deep sleep on just about all of them some of the boards can't shut the rest of the circuits into low power modes and so the total system deep sleep power draw can be far higher that you'd hope for. Other boards are better able to cope with this and can get down to tiny power consumptions.
Comment: Thanks for the link. I'm going to explore the 32kHz crystal way more closely in the future.
I used external RTC for outdoor weather sensor (temperature range from -25°C to 40°C). Reporting was performed once every hour. So I suppose that was perfect use case for such external IC.
Comment: +1 for mentioning the significant amount of power wasted by the support boards (looking at you, Arduino). A single "power on" LED can take more current than the uC running full throttle.
Comment: I had fun once with an mbed board where the deep sleep power consumption was 60 times higher than it was supposed to be. It ended up being the internal pull up on an unused input pin fighting the external pull down on that pin to set the boot mode. Configuring that pin to disable the default pullup cleared the issue. It's the sort of detail that is so easy to overlook and when running it's a drop in the ocean. But when you are aiming for 2uA current draws it doesn't take much to ruin things.
Answer: Your problem here is your 10 minutes mark, because (as you already know) the maximum interval of the watchdog timer of ATmega MCU is just 8 seconds.
One option would be to use a low-power, programmable, external timer like TPL5110. You can set an interval of up to 120 minutes by selecting the appropriate value of the programming resistor.
This kind of timers can be used to drive the gate of a logic-level P-channel MOSFET that acts as a switch for the power line of the Arduino (and for other parts of the circuit, if you want to cut down power consumption), like this:

Then, you simply you do all your stuff on the setup() function and leave loop() empty. You can switch off the Arduino by sending back a DONE signal to the TPL5110 at the end for your setup().
Comment: Thanks a lot for the feedback.
"You can set an interval of up to 120 minutes by selecting the appropriate value of the programming resistor.".
So I would need a digital potentiometer for the DELAY pin to be able to change the interval.

Periodic waking up from deep sleep


How is repentance understood in Lutheranism?

Question: Christ talks a lot about repentance, and how we must repent and believe to be saved, he asks the woman caught in adultery to sin no more (John 8:11). But if we are unable to do any good as Paul says in Romans (Romans 7:18), how can we repent of anything? And also, can we truly say we live a life of "repentance" if we will sin for the rest of our lives, sort of "the old Adam still haunting us", when in contrast we should be as "dead to sin" (i.e. sin no more)?
Answer: Lutherans would say that we are by nature sinful and unclean, and are only able to repent because we are enabled by the call of God the Holy Spirit to respond to the Grace of God.
Comment: but when I sin, am I not out of God's grace?  Therefor how can I further repent? Could you simply elaborate a little more?
Comment: A Lutheran's thoughts on this would be highly informed by Matthew 18:10-14, where Jesus leaves the 99 righteous to go in search for the 1 sinner. A Lutheran would argue that one cannot be out of God's Grace; one can only think one is.
Answer: I hope you please allow me a little patience and latitude to answer your question, since, in fact it's a number of questions wrapped up into one post.

the Teachings of the Lutheran Church are found in the book of concord. Specifically, the Augsburg Confession has a useful article on Repentance (https://bookofconcord.org/augsburg-confession/of-repentance/)

To flesh out the historical context, For Lutherans, one quickly notices that repentance is used in a narrow and a broad way/sense:  Narrow: "terrors, smiting the conscience because of sin."  Broad: Both terrors smiting the conscience and faith/trust in God's promises.

It is vitally important to understand, that, from a Lutheran context, there is much overlap between repentance and faith.  Just as one is unable to choose his/her way into heaven due to the lack of a free will (Ephesians. 2; 5:8; Romans 8:7; 1 Cor. 2:14, et al), so also a person is not able to make themselves repent. Repentance is not a good work we perform for God. It's a gracious gift given to us and worked in us through God's word (cf. —Acts 3:26
—Acts 5:31
—Acts 11:18
—Rom. 2:4
—2 Tim. 2:25)

"How can we repent" then?  Really good question. Repentance is caused by God, not found in us. But, through water and word, Christians are 'born again'. Alongside our old, sinful self, there is a new nature. This contrast is shown in the long, beautiful section of scripture in Romans 7.  For example, look at "For in my inner being I delight in God's law" (Rom. 7:22 NIV11-GKE). The inner person "ⲉⲥⲱ ⲁⲛⲑⲣⲱⲡⲟⲛ" repents of sin and clings to God's promises. This inner/new self "lives a life of repentance" every day.

Will we "sin for the rest of our lives" then?  Since we have an old, sinful nature to the moment of our death, then the answer is, "yes." But that's not the only answer. We also have a new self for whom the answer is also "no."  As Paul speaks elsewhere:  "For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever you want." (Gal. 5:17 NIV11-GKE). Notice the present tense ("ἀντίκειται" (Γαλάτας 5·17 THGNT-T)).  This continues, again and again, until you die.

With this continual struggle in mind, we can answer the last question.  Do we, as Christians, "put sin to death?"  Luther, in the small catechism writes:

What then is the significance of such a baptism with water? Answer:
    It signifies that the old creature in us with all sins and evil desires is to be drowned and die through daily contrition and repentance, and on the other hand that daily a new person is to come forth and rise up to live before God in righteousness and purity forever.
Where is this written? Answer:
St. Paul says in Romans 6[:4], "We were buried with Christ through baptism into death, so that, just as Christ was raised from the dead through the glory of the Father, we, too, are to walk in a new life."
Robert Kolb and Timothy J. Wengert, eds. The Book of Concord: The Confessions of the Evangelical Lutheran Church. Accordance electronic ed. (Minneapolis: Fortress Press, 2000), 360.
Notice the paradox: We die and are raised to spiritual life—yet this happens repeatedly.  That is what our life as Christians looks like. We repent of our sin and grieve over it. We rejoice that Jesus paid for the sins of the entire world (John 1:29).  We rejoice that through all the power and promises in his word he delivers this salvation to me in those waters of baptism.
Let me close where I began.  Your post was a network of a number of questions.  I hope you will have patience with my answer, since I sought to give you a Lutheran answer to a series of questions about the Bible from official, substantive Lutheran sources.


Most efficient way to purify household vinegar: distillation or freezing?

Question: I am aware that there are better ways to purify acetic acid out of a water-acid mixture than these, but which one out of distillation (using heat) and fractional freezing (using cold) would gain a higher concentration of acetic acid?
Comment: That's just an approximation intended to explain how eutectics work. But anyway, typical household vinegar is of course less concentrated than needed for fractional freezing.
Comment: I think that would be an awfully overcomplicated and expensive method (and dangerous too, in case of beryllium). Also, it probably wouldn't work anyway.
Comment: With the correct equipment and technique distillation of the vinegar will produce glacial acetic acid however things can seem easier in theory than in practice. Freeze precipitation and centrifuge may also produce glacial acetic acid from vinegar but again this might not be so easy without access to the right equipment.
Comment: Related: http://chemistry.stackexchange.com/questions/2506/acetic-acid-freezing-distilation
Comment: @Ivan Neretin , the link suggest the acid be approximately 72% for fractional crystallisation . The household vinegar wouldnt be anywhere near this concentration?
Comment: So distillation would be the most practical method? I've thought of converting the acetic acid to an insoluble acetate salt , filter off the water then react the dry acetate salt with an acid to form acetic acid at a high concentration which could then be purified easier.
Comment: @Ivan Neretin , what do think of the suggestion I posted above if a silver or basic beryllium acetate were formed by adding there carbonates to the household vinegar at the correct temp then cooled to precipitate?
Comment: @ Ivan Neretin I agree it was just a theory. (:
Comment: In another Q&A we see " If you want to isolate acetic acid from a solution that is mostly water, I would distil the solution until the composition is mostly acetic acid, and then fractionally freeze it."  -  https://chemistry.stackexchange.com/questions/2506/acetic-acid-freezing-distilation
Comment: The internet sells 1 L of pure acetic acid in food quality for less than ten euros. ;)
Answer: There is no acetic acid/water azeotrope, so distillation can produce glacial (pure) acetic acid.
Comment: Freezing can do the same, once you've got a mixture more enriched with acid than eutectics.
Answer: Some experimental data after a 4 liter jug of 5% distilled white vinegar accidentally froze at -25°C:

The first 0.5 liter to melt out had an acetic acid concentration of about 13%, substantially above the starting concentration, and a pungent vinegar smell.
The next 1 liter to melt out had an acetic acid concentration of about 7%. The remaining ice was very porous and slushy, slow to drain and probably trapping lots of liquid, and helping explain the non-sharp separation between acetic acid and water.
The next 1 liter to melt was about 3% concentration, below the original.
The last-to-melt liquid measured at approximately 1% concentration, pH still measures about 3, but has almost no smell.

These concentrations, reported as mass percent, were estimated by measuring the solution density, which for acetic acid changes only slightly (e.g., 20% acetic acid is only 2.5% denser than water). Assuming a 0.1% absolute density measurement error (e.g., thermal compensation difference since the liquids were measured at near 0°C), there aren't a lot of significant figures in the percentages above.
The data above was batch gravity melting, followed by pouring off the liquid fraction. Particularly for the first pours, the melting is mostly on the exterior of the jug. The exact yield curves likely depend on the thermal profiles during both freezing and melting, the vessel shapes, and details like how the liquid is removed from the ice.
Unlike when freezing pure water, the bottom of the frozen vinegar jug wasn't visibly distended or ruptured, and actually showed no signs of significant volume change. At 20C, a 4 liter jug takes over 1 day to fully melt.
Overall, freeze distillation does appear straightforward to concentrate vinegar somewhat over normal household levels. Repeated freezing may improve the concentration further, although there's a freeze eutectic at 30% acetic acid / water (mol/mol), so reaching 100% glacial acetic acid would likely require a different approach.