iOS 3.x support in Xcode 4

Question: Is it possible to write apps that support iOS 3.x versions using Xcode 4? If so, how? And does Apple have any official recommendations on app backwards-compatibility?
Answer: To get your app successfully run in iOS 3.x device, follow these steps (Xcode 4.2):

Click on your project name, select your Target and under "Build Settings"
a) Set "iOS development target" (under "Deployment") to 3.0
b). Add "armv6" to list of "Architectures" (under "Architectures").
c) Set "Other Linker Flags" (under "Linking") to "-weak-lSystem".
In your Info.plist file remove value of "armv7" from "Required device capabilities" (UIRequiredDeviceCapabilities).
In your code:
a). Do not use userInterfaceIdiom. If you need to know, what device is it (iPhone or iPad), see How does one get UI_USER_INTERFACE_IDIOM() to work with iPhone OS SDK < 3.2.
b) Do not use window.rootViewController. Instead use [window addSubview: self.mainViewController.view]; to add your main controller's view to window.
Click on your project name, select your Target and under "Build Phases" / "Link Binary With Libraries" set "UIKit.framework" to "Optional". Also set to optional any extra framework, which is not available in iOS 3. For example, if you're using iAd or Twitter frameworks they should be set to optional. Check availability of extra framework in your code before use.
When run on real device, compile app against last version of SDK. To do so, select second item from "Scheme" drop down (otherwise you'll get compile error related to your optional SDKs):
Comment: @MikeKeskinov I followed the steps above in Xcode 4.2.1 for Lion and it works. If I open the same project in Xcode 4.3, I encounter the same error that I was having before: an exception is thrown when the app tries to load the MainWindow nib saying:

 "-[NSKeyedUnarchiver initForReadingWithData:]: incomprehensible archive (0x4e, 0x49, 0x42, 0x41, 0x72, 0x63, 0x68, 0x69)'".

Any suggestions? I'm stuck right now, so all ideas are appreciated.
Comment: Thank you! I'm using XCode 4.2 with iOS SDK5, and for step 3B, I got my app working by replacing `self.window.rootViewController = self.viewController;` with `[self.window addSubview: self.viewController.view];` in AppDelegate.m
Comment: Use:
    [self.viewController.view setFrame: [[UIScreen mainScreen] applicationFrame]]; in AppDelegate.m, to work around the black gap in bottom
Answer: Yes, you can develop apps that support previous iOS versions with the current iOS SDK.
For official recommendations, see Apple's SDK Compatibility Guide.
Answer: The version of Xcode that you use isn't related to the version of iOS that your app can support. To choose the version of iOS that your app supports, simply change the iOS deployment target in your project settings. Then just be sure not to use any APIs from versions later than that.
Comment: Also: anecdotally, Apple are no longer accepting apps with deployment targets earlier than 3.1; it's likely they'd have been requiring 4.0 by now but for the desire to allow developers to support the iPad's iOS 3.2 in universal apps, given that the iPad wasn't upgraded to iOS 4 for quite a while. If that helps at all with the "... does Apple have any official recommendations" part of the question.
Comment: Apple support apps with development target 3.0 and above (see [here](http://stackoverflow.com/questions/5842178/minimum-ios-target-version-that-apple-accepts-in-appstore)).
Answer: to be sure, you can use Xcode 4 for targeting iOS 3.x as a deployment target, but you will not be able to simulate your program on a iOS 3.x SDK simulator. So you are pretty on your own (i.e., if you use any iOS 4.x-only feature, you will not find out it until you test on a physical device).
You need an older version of Xcode to debug against an older simulated SDK.

iOS 3.x support in Xcode 4


Why did Arthur Pendragon turn evil?

Question: In the original Nanatsu no Taizai anime series, Arthur Pendragon was a good guy. But in Mokushiroku no Yonkishi, he's the main antagonist. What happened in the middle? Why did Arthur Pendragon turn evil?
Answer: In chapter 77 (Four Knights of the Apocalypse) Arthur states that he has come to the conclusion that historically humans have been puppets or collateral damage in wars between other races, and that, in light of this fact, true, lasting peace for humanity can only be achieved through an ethnic cleansing of all other races.
Another matter of conflict is that, in order to build his Eternal Kingdom, he is literally stealing portions of land from the existing nations and moving them to Camelot.
Arthur is shown to alternate semi-voluntarily between two personalities: one being serene and jolly, and the other being disturbing, ominous and ruthless. A visual queue for the switch are his sclerae being white or black respectively (as well as his demeanour and magic changing accordingly). It's clear that this is bound to the dual, highly polarized nature of chaos as was briefly described at the end of The Seven Deadly Sins. It's implied that this might be influencing Arthur's judgment, but the extent and nature of this influence has not been described fully as of chapter 127. It's worth noting that, despite visible changes in behaviour, Arthur appears to be of one mind in either state and, if indeed some  magically induced personality disorder is at work, he has not shown signs of distress towards his psychological situation yet.

Why did Arthur Pendragon turn evil?


Don't want to leave freelancing

Question: I am not getting customers who pay well for Mobile App Development.  All the customers I meet either don't have money or they do not like to spend much money.  I am a freelancer in India, and Indian customers do not want to spend anything; still they want best service.  What can I do in this situation?  I don't want to leave freelancing but I am finding it difficult to survive.
Comment: Look outside of India.
Comment: Are you really so good or you think you are good? I have seen many good guys who prove to be just juniors when I started checking their projects. This means improve your skills. Other point is set your price and stick to it. Bid to 1 project in a day or more days, but analyze it in details. If a client see your expertise in the bid, he will pay you more than he would pay another person. You will not get $100/h, but you will get enough to make a good living in India.
Comment: Here in this question I am focusing on the customers who are looser, don't have money to spend but still think they can make good app or website. Hope you understand my point.
Answer: Assuming that you have the technical skills that are in demand, have you asked yourself why you might not be getting the work?
Are you chasing mom/pop type business who don't have the skill/knowledge to communicate effectively with what they want? Perhaps your ability to understand or even ask the customer is not strong (don't be offended - we all have our strengths, and often, we fail to acknowledge or weaknesses).
Consulting/freelancing/contracting... whatever you want to call it is not easy - its can be profitable, highly profitable, but its not easy. You have to have technical skill, marketing ability, accountability (both from a financial management sense, project management and communication sense). Few manage to perfect all of these.
I'm not trying to scare you away but by posing these thoughts and giving honest consideration it might help you find what part of your strategy is letting you down.
The customers you approach might be less familiar with getting others in another timezone, or even another continent to deliver a project. It depends heavily on communication - I've been contracting/consulting since 1994 and most of the rich work is available when the customer can see you if not daily, at least at some frequency. Projects change, costs change, timelines change - having to communicate this puts up front risk on the customer.
Then there are liability risks - despite your best and most honest efforts, if your code results in the customer being held liable, the customer will have to pursue you thru expensive international courts if they are to hold you liable.
Some customers might think the risk/reward is just too much. Lean towards thinking of benefits the customer will win, then figure out how you can profit from making your customer win.
Example... A friend of mine was one of three founders at a Brazilian viral-ad making company. Their initial attempts to win customers proved unworkable so their alternative approach was to create products and sell the ideas to marketing companies who in turn would sell the ideas on to their customers. It made them a small fortune which included a couple of awards at Cannes film festival (which I believe, includes awards for adverts).
Thus - perhaps you might want to consider creating products that are easily customizable with templates that target a specific market like real estate, car buying or health/sports/wellness. Select ten clients from somewhere in the world, copy/paste their branding from their website into your solution and contact them to try your product out. Cost accordingly - don't be shy - if you are too cheap, they won't look and if they are too expensive, they won't search either (do your own research for the market and region you are targeting). Don't sell the code, but sell the solution (thus allowing you to re-use the code with someone else's branding).
You might get one in ten who say yes - and failing that, you'll have learned other skills in the process.
Best of luck!
Answer: Spend a bit of time and work on your onboarding process.
When a client comes to you for a mobile app, they are already in a state of mind that they will be spending money. They just need to know how much money.
With your onboarding, make the client feel comfortable that you are able to bring their ideas to life. Explain in detail how you will approach the project and how you will add value to their idea.
Clients are more likely to say yes if they understand exactly what value they will be getting for their money.
Sure, in the end, they will get a mobile app, but it will be an app that brings value to their company, personal life, or other people.

Don't want to leave freelancing


What will happen if a client of mine sends the IRS an incorrect form?

Question: A client is asking me to fill a W9 with my name and the LLC EIN instead of a W8 which seems to be wrong. What's the worst that can happen if he sends the incorrect form to then IRS and who has to amend the potential issue? Can I be held liable in any way or is my client responsible for asking me and submitting the wrong form?
Comment: A W9 is an extremely common form for record keeping, what do you think the problem is?  Your LLC is being contracted not you, so you use that EIN and name.
Comment: This article says the exact opposite of what you are saying: one should not use the LLC EIN in a W9 https://www.w9manager.com/how-should-an-llc-fill-out-a-w-9-form-correctly-ssn-vs-ein/
Comment: https://www.irs.gov/pub/irs-pdf/fw9.pdf  Part 1 is a section for Taxpayer Identification Number, which accepts either SSN or EIN... Based on the instructions attached to the form, if your LLC is nothing more than a pass-through, use your SSN; or ITIN.  It's my understanding that W9 is for internal accounting of their expenses in case THEY get audited; they don't get filed with the IRS.
Comment: @quid: and the instructions for line 1 case e say "... If the owner of the disregarded entity is a foreign person, the
owner must complete an appropriate Form W-8 instead of a Form W-9. This is the case even if the foreign person has a U.S. TIN." (which OP does not, per previous Q) also the last item in the instructions for Part I is "Caution: A disregarded U.S. entity that has a foreign owner must use
the appropriate Form W-8."
Comment: @dave_thompson_085 Ah, I didn't see that this person is a foreign person.
Answer: Neither W-9 or W-8 is filed with IRS; quid's comment is correct on that point.
However, since you are a non-US person (aka NRA, nonresident alien) and the payments to your disregarded (single-member) LLC are treated as payments to you -- see pub 515 -- depending on the type of income the payer may be required to withhold using the information that they should get on W-8, and liable if they fail to do so. If they instead treat you as a US payee, which is what W-9 implies, they aren't required to withhold but may be required to file reports on the payments using the W-9 info, and e.g. if this payment is for work, IRS will detect that their 1099-NEC does not match to a resident return on 1040 (or 1040SR!) with schedule C from you. Whether IRS will do anything about it, especially if you file 1040NR and pay as required, is a different question; I'd expect this is low on their priority list. And they'd probably go after the payer first, both because the payer is in US jurisdiction whereas you are not, and because if a business is paying you wrong there's a good chance they're doing so for other people too, whereas there is no indication you are being improperly paid by other US payers.
See the (extensive) links at https://www.irs.gov/individuals/international-taxpayers/nra-withholding
Comment: Thank you for the concise answer! Afair there are no withholding because my services are performed outside the US https://www.irs.gov/individuals/international-taxpayers/nonresident-aliens-source-of-income says the factor determining source of income for salaries, wages and other compensation is where services are performed.


Database Design for for Drug store

Question: I have designed a db for Drug store which will sell medicine both wholesale and retail. I store each strip, capsule and vial of medicine in a separate fields for retail selling. Is there any better approach for this? As a programmer, I can't think of whether it is necessary to store amount paid by each customer in the order table. And is it necessary to have in and out inventory in separate table? Here is my DB:

Could there be any issue with this db design? Please suggest a better approach.
Comment: `(20,2)`?  I knew drugs were expensive, but that allows more than a trillion dollars/Euros/dinars/etc.
Comment: "Could there be any issue"?  Of course.  You will find out after you start populating _and_ querying the db.  (Nothing is obvious to me at the moment.)
Answer: You might want to consider abstracting product into a SKU for the order detail.  Instead of having order details show which specific pills were sold, show more generically which medicine was sold.  The reason for this is that you may sell, for example, 100 pills of a certain type.  Perhaps you only have 40 left of one batch and so you fill the order with those plus 60 from another batch.  That would show as two order details on a sales receipt, which would be less than ideal, since the customer doesn't want or need to know this detail.
Another advantage of abstracting the product list from the actual product batches is that you can get a simple list of products without repetition.  This is just good database normalization.  The name of the product and the batch number of the product have different functional dependencies, so they don't belong in the same table under Third Normal Form (3NF).
You can and should have inventory movement records that record the specific stock used to fill each order.
You should store the amount actually paid with the order details.  This is because the MSRP price can change over time so failing to store the price actually paid could lose information.  Similarly, you may decide to sell for a promotional price, which would be lost information if you only store the regular price (or MSRP).
I recommend against having inventory ins and outs in separate tables.  All inventory movements should be in one table with either two quantity columns (in/out) as per old-style accounting methods or preferably, a single quantity column with positive and negative numbers for receipts and sales, as per newer computerized accounting methods.  Keeping inventory in a single table reduces your code complexity considerably.
Comment: thanks for your insight. What I do not understand from your answer (probably communication gap) is 'All inventory movement should be in one table'. Please can you show me the sample. I would post my latest design.
Comment: @MawiaHL - What I mean is that you should have a table called `inventory_movement` or something similar.  In this table you will have both shipping/sales and receiving transactions.  The quantity in this table will be positive or negative depending on the direction of the inventory movement.  Pick a convention that makes sense to you.  Often receipts are positive and sales are negative.  This way when you sum over transactions grouped by SKU (product) you get the stock on hand as a positive number.

Database Design for for Drug store


Can you paraphrase "How long do we give it" in the excerpt below?

Question: I'm still developing my English so it's great if you answer my question in a very short and direct way; the shorter it is, the better.
I don't get the meaning of "HOW LONG DO WE GIVE IT" in the excerpt below. (Edit: thank you. ..I can't search where to reply..)

Does any man strive to gain wealth or influence for any reason other than to reach a point where they can abuse with impunity those under their control? How long do we give it before we start treating anyone who wants to become rich, famous or powerful in any way as automatically suspect?
Answer: "How long do we give it" means "how long do we wait". We can have a long time as well as a long distance.


Have an unused receptacle in the ceiling that used to have a fan. What is safe way to cap it?

Question: I have an unused receptacle in the ceiling that used to have a fan attached. Now the wires are dangling out of the box (all are wire nutted to keep separate except the ground). If I go to  and get a cap, how do I ensure the wires are safe to stuff in there?
I don't see any exposed wire except the ground which is all exposed. Do/should I tape that?
Answer: You can leave the ground wire bare, it's fine. As long as the other wires are capped off so that no bare metal is exposed, then those are fine, too. You can bend the wires and stuff them all into the box, then put a blank faceplate on the box. You cannot cover the box with sheetrock or anything. You have to leave it accessible.
Comment: +1 Some people like to wrap electrical tape over the capped wires for extra protection.
Comment: @bib That's good, too! In fact, that may protect against the (slim) chance of inadvertently poking the end of the bare ground wire into the wire nut with one of the conductors when you stuff the wires into the box.  ;-)
Comment: If you removed the power to it (permanently) you could bury it.
Answer: Cap the wires (done) and simply fold them into the box. Obtain the cover plate of your choice at the nearest home center.
Electrical codes to not permit permanent covering of junction boxes, but there's a qualifier: if the circuit is disconnected at the panel (wires detached from breaker) then it doesn't count as a circuit anymore. But it is unlikely that a ceiling light has a dedicated circuit.
You can cover the nasty-looking blank plate with a ceiling vent to make it disappear. By "disappear" I don't mean you can't see it, but it looks "normal". We expect vents in ceilings, we don't expect electrical cover plates. Same with switches - a blank plate in the wall says "something is out of place", a switch that doesn't do anything appears normal.


How can I detect accessibility gestures from within a custom view?

Question: I need to make a custom view detect and react to Jellybean's accessibility gestures (eg: scroll a page, swipe focus). An example would be appreciated. I can't seem to find anything definitive in the docs.
Answer: I was able to intercept some AccessibilityEvents by writing a custom AccessibilityDelegate (call View.setAccessibilityDelegate()): http://developer.android.com/reference/android/view/View.AccessibilityDelegate.html
Unfortunately I have not been able to find a way to intercept the swipe focus event that tabs between view elements. I think you may be able to do so by writing an AccessibilityService and then having it pass information back to your app, but it seems like Accessibility Services are designed to be used with multiple apps, and they have to be manually enabled in accessibility options by the user, AND the order in which they receive events depends on the order in which they were enabled.


Did Illyrio Mopatis know what he was doing when he offered dragon eggs to Daenerys as a wedding gift?

Question: At her wedding, Daenerys received a chest containing three dragon eggs. These were given to her by Magister Illyrio Mopatis, the man who helped arrange the marriage.
Was it part of a plan?  As...

 ...she managed to hatch the dragons.
Answer: We do as of yet not know. In his conversations with Tyrion, he does not seem to have placed much faith in Dany, but it is impossible to say with any certainty, due to the secretive nature of Illyrio and Varys.
I would assume he did not know, just as he did not forsee that Dany would hijack his ships and start a crusade in Slaver's Bay.
Answer: Not sure if Illyrio did know, but Dany and Ser Jorah seem to think he didn't; at least not in A Clash of Kings:

"Illyrio believes in no cause but Illyrio. Gluttons are greedy men as a rule, and magisters are devious. Illyrio Mopatis is both. What do you truly know of him?"
"I know that he gave me my dragon eggs."
He snorted. "If he'd known they were like to hatch, he'd would have sat on them himself."
That made her smile despite herself. "Oh, I have no doubt of that, ser. I know Illyrio better than you think. I was a child when I left his manse in Pentos to wed my sun-and-stars, but I was neither deaf nor blind. And I am no child now."
  -A Song of Ice and Fire: A Clash of Kings (pg 365), Daenerys.
Answer: I think a plot relating to his gift would be beyond the reach of his knowing. There were no portends pointing to that outcome, nor had previous attempts in the later years of the Targs showed any successes in doing the same.
Other potential evidence:

In A Clash of Kings Illyrio confides in Tyrion that he didn't expect Daenerys to have survived the Dothraki sea (or something to that effect).
When asked by Daenerys to see if he felt the same within these gifts as she did, he did not and I believe he declared them lifeless.
Had he been aware of what would happen, he likely would have passed them on to another pony he was plotting on in an attempt to produce the same outcome.

[citations probably needed]
I think he did not know what would happen. He passed them on to Daenerys as a rich, but useless (to him), gift to the beggar Queen of a bloodline renown for dragons. It would carry deep sentimental purpose to her, gaining favor for him, and help re-inforce her legitimacy, if even symbolically.
Answer: No, he did not know
In the fifth book, when young Griff were planning the invasion of Westeros, they claimed they were told to wait by Illyrio Mopatis that Daenerys would be joining their cause with a Dothraki horde. No mention of dragons at that time.

 "Which plan?" said Tristan Rivers. "The fat man's plan? The one that changes every time the moon turns? First Viserys Targaryen was to join us with fifty thousand Dothraki screamers at his back. Then the Beggar King was dead, and it was to be the sister, a pliable young child queen who was on her way to Pentos with three newhatched dragons. Instead the girl turns up on Slaver's Bay and leaves a string of burning cities in her wake, and the fat man decides we should meet her by Volantis. Now that plan is in ruins as well.

So, no mention of Dragons in the first plan. And, if someone like Illyrio Mopatis wanted them, he could have gotten them before they reach Astapor. He sent the ships to Astapor to find her. The mention of dragons in the second plan proves that he had no idea Daenerys could make them hatch. Otherwise, it would be the part of the first plan.
Answer: I don't think that Illyrio would have known. But, Varys seems to be pulling Illyrio's strings. I think that Varys might have suspected that the Dany might be able to hatch them.


Sharepoint 2010: Assign a user permissions to edit other users items without adding "Manage List" permissions

Question: In our Sharepoint we have the need to assign permissions to a user so he can edit the entries created by other users, while the remaining users maintain their current permission to add/modify/delete only their own created entries. We don't want to give this user "Manage List" permissions, only the permission to modify entries from other users. Is this possible? Thanks!
Answer: You can run an Impersonation Step and do the highlighted line below in a SharePoint Designer (SPD) 2010 workflow.
I created a custom permission that gave the users only create rights. Then assigned permissions based on some conditions.
Answer: You cannot override the "add/modify/delete only their own created entries"
Answer: Create a new permission level as a copy of Contribute and add the "Manage Permissions" permission only. I call this "Contribute and Permissions Mod". Then assign your user this new permission level on the list.


What will be the output of a single supply voltage follower circuit if negative voltage applied to the non-inverting input?

Question: I am providing 1.8 V as supply in a single supply voltage follower circuit. Now my concern is if I put negative voltage (Range -1.3 V to -500 mV) in the non-inverting pin, what will the output from the voltage follower circuit?
Comment: Check the datasheet of the OP amp you intend to use. Usually, input voltage below the negative supply violates the maximum rating of the op amp. So you should avoid it all together.
Comment: It's unlikely to be specified, as the input voltage you want to use is outside the permitted input range. It will depend on the particular opamp. The two most likely values are hard against one or the other rail. But it could be something else. The opamp may survive if you limit the input current with a series resistor.
Answer: Typically for 0~-300mV nothing much will happen except the op-amp will be railed near ground at the output.
Below -300mV, especially -500~-600mV or more (at room temperature), significant current will start to flow in the internal isolation and protection junctions. The output may shoot up to the positive rail (called "phase reversal") or do nothing much, but at some point, with many op-amps, the current may get to the point where permanent damage takes place.
Adding series current-limiting resistance may prevent that, but it's a not typically a good thing to do. Other op-amps on the same chip may be affected, for example, or  supply current and heating may increase.


How do I get my dog back on The Sims FreePlay app?

Question: I lost my dog after trying to relocate it. I don't know what happened. Is there a way to get it back or get another one?
Answer: You either did one of three things:

Accidentally click the "Put up for Adoption" which basically deletes the pet.
Solution: If its deleted, you will have to buy another one. Check each household to make sure.
Relocate the dog to a different house than you intended to.
Solution: Again, check each household.
Relocate the dog to a house, and the dog is just hiding somewhere. Especially, in the larger lots and in more complex houses, the dog is usually hidden from view.
Solution: Navigate the camera in the household. If you want an easy check, buy a dog bowl(Food at 10,000 Simoleans or Water at 8,000 Simoleans), have a sim fill it if not already filled, and do the action "Call Over". If the dog is there, he/she should come.
Answer: If you are relocating a dog to the teen idol mansion, the dog, for some reason, shows up in the island created in the center of the swimming pool. You can rescue the dog from this trap by removing one of the pools so there is a way to walk out from the island.
Answer: Maybe,you put him a other household (if you unlocked the front beach homes you will MAY find him/her) it may been a glich you know sims freeplay have SO many GLICHES so I suggest to turn off your game then click back on the app see if it worked.Or get some that has the dog do an action like call over to eat!
Hope this helped!And I hope you find your dog!
Answer: After a certain rank, and after buying the Pet Shop, you get a Pets tab in the shop. There, you can buy more dogs or even other pets like bunnies, but they cost those green things (sorry, I forget what they're called.)
Actually, I have no idea what could have happened to your dog, probably a glitch, but if you want, you can just buy more. Hope this helps.


Double planet climate

Question: How far would 2 tidally-locked (to eachother) planets need to be from their blue star host to be habitable, but have a cold-weather climate similar to our Ice Age?
Comment: To which is the planet tidally locked, its sister planet, or the star?  Because it can't be both.
Comment: You're asking a lot of different questions in this post. Worldbuilding has a strict 1 question per post requirement. Can you [edit] it so you're asking 1 specific answerable question.
Comment: Please give a good read at our [help], in particular to the section about how to ask a good question. You are now asking many different questions, without showing any of the research you have made.
Comment: Thank you for the edit, I've retracted my close vote.
Comment: DItto, the questions clear and answerable now.
Comment: That is going to depend on the *exact* class of the star saying it's blue doesn't tell us how big it is so working out the radiation budget is problematic, otherwise good question.
Answer: TL;DR: binary planets probably handwaveable to be OK, iceage climate can also be arranged. Making a habitable world around a blue star is basically a non-starter, though. Too hot, too bright, far, far too much UV. You should probably change that.

It is difficult to say exactly how the climate of a binary planet will differ from the situation on Earth... the day length will be longer, and so the days will likely be warmer and the nights colder. It is possible that some atmospheric super-rotation will help even things out... strong prevailing winds will help warm the night side and cool the day side to some extent.
Having an ice-age like cold weather climate is easy though... just slap em in the habitable zone and call it a day. After all, Earth has been both ice free and entirely frozen over in its time, without having any kind of dramatic orbital change. Just handwave in your desired conditions, and you'll be basically good to go.
The habitable zone of a blue star is a bit more awkward, though. There are multiple problems with having such a hot star as the primary, but I won't cover them all here. Lets consider a a star like 18 Tauri. It is a main sequence B8V star, so it is quite small and cold by the standards of the some hot blue stars. As you can see from the Wikipedia page, it is larger than the sun... nearly triple its radius. Its luminosity though is more like 160 times that of the Sun. Its surface temperature is over 13000K. That's pretty hot and bright.
In order to receive about the same amount of solar irradiance, your worlds might need to be a factor of $\sqrt{160}$ or more than 12 times further away from the star than Earth is from the Sun (this is a very lazy approximation for a habitable zone, but it'll do as a starting point). That gives your star, as seen from your worlds, and angular diameter of about 0.12 degrees. Compare this with the Sun's apparent angular diameter of more like 0.52 degrees... your star has a quarter of the diameter and so a 16th of the apparent area. It'll look like a tiny, blindingly bright light in the sky, producing hard-edged shadows. It won't look like a cool blue version of the sun. The very blue-white light will make everything look quite washed out and sterile.
That's just aesthetic though. More concerning is the nature of its radiation. . The sun, with a surface temperature of ~5778K, has the peak of its radiation spectrum at 510nm, a faintly bluish green, and only about 3% of the total output is of UV wavelength or shorter. 18 Tauri has a peak at 210, which is hazardous and destructive UV-C.  More than 20% of the total radiated output is vacuum UV, and nearly 50% of the output is any kind of UV (or worse). (Worked out using another handy calculator on hyperphysics)
This will be exceedingly destructive to pretty much anything made of chemical bonds. The oxygen in your atmosphere is particularly good at absorbing UV (that's what the ozone layer does on Earth). The increased rate of oxygen-bond splitting increases the amount of high-altitude monatomic oxygen and ultimately atmospheric escape. Your atmosphere will be rendered unbreathable much more quickly than it will on Earth.
Even if you handwave that away things will still look very weird and alien... plants won't be green. I'm not sure quite what colour they will be, but I could imagine a white or black might work. It will look very alien indeed.
Comment: On last paragraph: White or black to an Earthling, but whatever lives there (if anything lives there) will likely have their visible spectrum sitting around the UV region, so will perceive colour completely differently to Earthlings.
Comment: Upvoted.. completely overlooked the aspect.. a *blue* star.. can it have an habitable zone at all.. maybe only a goldilock zone (water + ice)
Comment: Can you perhaps tune wavelengths somewhat by using a dust cloud (maybe ex-moon) between the planets and the sun? Even if expected particles are too big for Rayleigh scattering you could have reflectance wavelength-dependent. Say silver, gold and copper all reflect visible much better than UV so you could solve problem somewhat. Besides, we have N=1 sample of habitable planets and even here some bacteria are annoyingly UV resistant, so I believe life would find a way.
Comment: Green plants will be Okay-ish. The plant usable spectrum is generally limited by the chemical bond stability and not the available light spectrum. So is human vision. On the other hand, blue stars tend to evolve quickly and may not allow for a complex life evolution.
Comment: @ZizyArcher life could be fine... chasmoendolithic and deep ocean biomes under an ice cap could both theoretically work here, assuming they had time to evolve before the parent star went foom (the light that burns twice as bright, etc etc). I get the impression that the OP isn't quite so interested in that particular kind of setting, though.
Comment: @ starfish prime, it sounds like the simplest solution is to not use a blue star.  As it is a fantasy world and the star is supposed to tongue-in-cheek represent "God" I didn't want to go with a red dwarf or Sol-like star.  Blue seemed the most God-like.  Thanks for the info.
Answer: One very well studied planet, the planet Earth, has a distance from its star, the Sun, which is exactly 1 Astronomical Unit (AU) by definition.
You ask for climate like Earth had during the Ice Age, which was really a bunch of separate ice ages, separate glaciations.  In those glaciations Earth's average temperature was a little lower than now, and glaciers covered a much larger percentage of the surface than now, and the lands at the edges of the ice sheets were (obiously) not warm enough to melt the ice very vast when the edge of the ice was advancing or when the edge was standing still.
Those events happened when Earth was at a distance of one AU from the Sun.  And as I rememeber, during the last one or two million years the glaciations have been much longer than the interglacial periods like the one we are now in, though the maximum extent and peak of the ice lasted for a much shorter period than the total period of each glaciation.
So Earth's ice ages happened when Earth received about as much energy from the Sun as Earth receives now.
And before the last million or two years ago there was a period of tens or hundreds of millions of years with no glaciations on Earth, even though Earth received about the same amount of radiation from the Sun then as it did during glaciations and as it does now.
You should study the various theories about the causes of Earth's glaciations and see how well you can give your planet similar contributing factors.
https://en.wikipedia.org/wiki/Ice_age
Since Earth is now in a state of recurring glaciations, you should calculate what I call the Earth Equivalent Distance (EED) of the star, the distance at which the planet receives as much energy from its star as Earth receives from the Sun, and put your planet at that distance from its star.  That should be enough to explain the glaciation the planet is currently experiencing, if you can also give the planet the factors which contribute to the onset of glaciations on Earth.
I note that during the glaciations on Earth, the lands adjacent to the ice fields and at high altitudes were quite cold, but there were vast regions near the equator which were quite warm and lush.
I don't know if that is acceptable to you. Maybe you want most of the planet to be covered with ice caps, and the small regions of bare land and sea to be cold and occpupied by cold wether plants and animals.
In that case you might need something more like the periods of snowball Earth than like ice ages.
Periods of snowball Earth supposedly lasted for millions or tens of millions of years  and happened several times in Earth's history.
I note that astrophysical calculations suggest that the Sun slowly and steadily gets more luminous, and so it seems an obvious guess that the end of a period of snowball Earth might result from come the amount of radiation Earth gets from the Sun increasing past a critical tripping point.  But that could not explain several different periods of snowball Earth separated by warmer periods.
Thee sems to be considerable uncertainty about the causes of those snowball Earth episodes.
https://en.wikipedia.org/wiki/Snowball_Earth
Both the current period of alternating glaciations and interglacial periods, and the periods of snowball Earth, are examples of Earth during icehouse periods.  The climate of Earth seems to have alternated between greenhouse and icehouse periods over geologic time.
So possibly some of the icehouse periods in Earth's past may have been better for your purposes than either the more recent glaciations or the more distant snowball Earths.
https://en.wikipedia.org/wiki/Greenhouse_and_icehouse_Earth
Answer: Goldilock- or habitable zone
For each type of star, there exists a certain minimum and maximum distance  for planets, that could support fluid water. When your Ice Age would be anywhere earth's, you'd still have fluid water.. so when these planets are both Earth-like, you could put it at a position comparable to Earth, but not closer.. Earth is actually quite hot.. on the inner edge of Sun's habitable zone, which is 0.95 AU[*] wide. You could put your planet e.g. where Mars is, in the middle.. 1.524 AU from the Sun.
https://physicsworld.com/a/earth-is-closer-to-the-edge-of-suns-habitable-zone/
Atmosphere
If Mars would have an Earth-like atmosphere, you'd get a lot of snow and ice. With a denser atmosphere, planet Mars could become Earth-like, or an ocean planet.
Double planets
This planetary system of yours better be stable ! For climate, I see only one effect between the planets affecting temperature. Size matters.. if your 2 planets are close and differ considerably in size, the smaller planet gets periods of solar eclipse, which can cool things down. But apart from that, atmosphere and sun-planets orbit distance is the key to get an icy, inhabitable planet.. they could have 2 different atmospheres, one -70 degrees Celcius and Mars like, the other Earth like.
[*] AU = Sun-Earth distance
NOTE: this explanation ignores the fact that we have a blue star. As Starfish Prime has pointed out, these are quite hot and emit deadly radiation. There could be a goldilock zone (supporting water) however it may be doubtful there is a habitable place on these planets, unless its inhabitants are very resistent to radiation.

Double planet climate


Authenticate an email

Question: I have received an email from Mr. A. In court Mr. A denies sending this email saying that I am making up with everything. How can I prove that this email was sent from Mr. A?
Comment: In the future it may be useful to request your correspondents to digitally sign their emails, for example like https://support.office.com/en-us/article/secure-messages-by-using-a-digital-signature-549ca2f1-a68f-4366-85fa-b3f4b5856fc6
Answer: You can print a copy of the email, ideally with metadata showing, and testify that you received it and did not modify the email.
The lawyer in the case against Mr. A can ask Mr. A if that is his email address, and can ask other people who have received email from him if that is his email address.
Mr. A's computer and/or email provider can be subpoenaed. The computer can be forensically examined for evidence that the email was sent or deleted, and the email provider can be asked to provide evidence that the email was sent.
Your email provider can be subpoenaed and asked to provide evidence that the email was received.
In general, people who deny sending emails in court who are confronted with copies of those emails authenticated by the testimony of the person who allegedly received the email lose their cases and are not believed by the judge or the jury. This doesn't always happen, but it is by far the more common outcome.
Comment: @ManRow "Can phone service providers be subpoenaed to verify text messages too?" Yes. "What if these providers delete such content from their servers as soon as the destination party receives it?" Then the response to the subpoena will be that there are no such records in its possession.
Comment: @ManRow "Since emails can be spoofed, and screenshots of text messages can be forged/edited, I'm wondering how this would not open up a can of worms in terms of cases with potentially spoofed emails and forged screenshots of text messages" Anything can be forged. If you have information from the source, you can disprove the existence of a spoofed electronic communication. You can also get discovery (pre-trial exchanges of information) that include metadata and third-party inspection of hardware upon which data is stored.
Comment: Can phone service providers be subpoenaed to verify text messages too? What if these providers delete such content from their servers as soon as the destination party receives it? (In other words, such that's it is only stored on the recipient's device, who is also free to delete it anytime?)
Comment: I see, good point! But, does the last paragraph in your answer also apply to text messages too, and even if providers do not have records of such content in their possession? Since emails can be spoofed, and screenshots of text messages can be forged/edited, I'm wondering how this would not open up a can of worms in terms of cases with potentially spoofed emails and forged screenshots of text messages. (note: emails that are digitally signed cannot be easily spoofed, but by far [not everyone digitally signs their email!](https://bit.ly/33VgFeH))
Comment: Interesting! From further research, it seems many (but possibly not all) "major" email services have [at least some countermeasures](https://bit.ly/2WZVgjh) against such spoofing attempts. Furthermore, users can also inspect their email metadata to determine if there may or may not be some form of spoofing going on too. While I'm not certain how many email users are aware of those technical details, it does seem that, as long as relatively well-known or "major" email services are used, uncertainties of authenticity could (or would!) be quite rare indeed!

Authenticate an email


How is it possible that we can't really trace C&C(or other hidden) server?

Question: With the recent breakout of WanaCry, how is it possible that we know on which hidden service it connects, we still don't know where the physical device is located and thus we cannot take it down.
Answer: This is because an infected device "talks" to hidden service through 6 different Tor nodes. All those machines do not track any routed traffic - and they cannot be configured to "track Wannacry traffic" because none of them know what exact traffic they route (it is encrypted end to end, so only the sender machine and Wannacry server can see the content). Also only the first machine in this chain knows which is the real IP of the sender, but it does not know that the sender is a hidden service.
So to trace a connection, theoretically you'd need to:

Build a circuit (establish a connection through rendezvous server) to a hidden service. This is easy.
Find out who is the first Tor node in your circuit, and talk to them to trace the next node in the chain. This is way more difficult - not only the node operator may be unreachable or skeptical (how could they know you're really tracing WannaCry, and not some underground resource), but will also require modifying the Tor client and inspect traffic - latter might also be illegal in some countries.
Repeat the same with the next five circuits. Which will likely be in different countries - different timezones, different languages and different ideas of what is acceptable and what is not.

Add to that that you need to do this within the circuit lifetime - which, as far as I remember is rather short, less than 30 minutes - and you see the problem.
Comment: But we know the IP of the hidden service, right ? Because the infected machine must know where it wants to connect. And when we have the IP, how it comes we don't have the location ?
Comment: No, we do not know the IP of the hidden service. We know some hash, which can be used to find Rendezvous Points for a specific hidden node (of which you don't know the IP either). The hidden server communicates with the same node (but again not directly, so neither party knows each other IP).
Answer: Simple. If you control an infected machine (via honeypot or other means) you can observe the traffic coming and going. This will tell you what protocols are in use and which IPs are using them.
However, you do not normally have the same visibility to the traffic that those other IPs are sending and receiving. Therefore, you can't really definitively say if those machines are the source of the attack or simply being used as a relay.
Now add in all the issues of finding the actual physical location of an IP, coordinating with local resources, gaining legal access, etc. and you should quickly recognize how big the problem really is. Also with a worm the number of sources grow with every new infection. At some point, the "bad" IP list is expanding so fast a human probably could not keep up with identifying, checking, validating, and blocking the IPs.


Running 10.7.5 server but would like to remotely manage it with a 10.8 macbook pro

Question: I have downloaded the server app for 10.7.5 but I can not install it on my 10.8 MacBook Pro.  Can this be done?
Answer: According to the Apple Web site:

Lion Server
To administer Lion Server, use Server app and the Server Admin Tools 10.7 on OS X Lion. The Server Admin Tools 10.7 are are available from Apple Support Downloads.
To administer Lion Server from a client with a different version of OS X, connect to the server using Screen Sharing or Apple Remote Desktop. You can also use Workgroup Manager 10.8 on Mountain Lion to connect to Lion Server.

One alternative to what Apple suggests is to run a VM of whatever OS you need to use to do remote management. This is what I do on my laptop with Lion. I don't have the same luxury with Snow Leopard, although I guess I could virtualize an instance of it, and run it on the desktop side as well.
Answer: You cannot install 10.7 server on a 10.8 client.
You will need to purchase 10.8 server to install it on your 10.8 client.
Answer: You might try redownloading it from the Mac App store - Server
Since the version of Server changed between 10.7 & 10.8 you won't be able to install it using the same package as you did for the server but if you can redownload it from the Mac App store I believe you should be able to connect it to your 10.7 server.  I'm currently running 10.8 server on our Mac Pro server and using Server beta on my 10.9 MacBook Air to administer it.  It seems like I was in a setup similar to yours this time last year.
Once you launch the Server app you can connect to the 10.7 server by choosing "Other Mac" from the main window (see attached image), enter the server address/name along with your server admin credentials.

Hopefully this works for you!
Comment: Server changed substantially between lion and mountain lion and you can't run backwards like we presumably will be able to do come fall when Mavericks is out. Clearly some people have access to pre-release software, but if you could test 10.9 server app connecting remotely to 10.7 that might help some people decide to delay or not their upgrades.


A single word for expressing 'Feeling like I am no one'

Question: What single word can be used for expressing 'I feel like I am no one'? Something which fits in the context of 'I feel so small in this vast universe'.
Comment: Hi Vpd, welcome to EL&U StackExchange! With single-word requests, it is essential that you provide at least one **sample sentence** where you might use the requested word. It would also be helpful to explain whether you've come across this word in the past, but have forgotten it (in which case, the more you can tell about the circumstances in which you've seen it, the better), or if you have no particular reason to think such a word exists, and are just hoping for the best.
Answer:
'I feel like a feckless midget in this vast universe'.

or

'I feel feckless in this vast universe'.

feckless  TFD

feeble and/or ineffective


How many max healers on queen will be enough?

Question: I am doing queen walk these days. I have level 15 queen. I put three healers on her and they are enough if not faced by xbows. Whenever both xbows or even one of them beasts starts shooting the queen she dies easily. My question is if I use 7 or 8 healers, will that provide enough heal to her if faced by both xbows?
Answer: using more than 4 Healers will decrease the amount heal given to the heroes...So you should not use more than 4 or 5 healers.
When targeted by XBows, use rage spell on the healers to increase the healing..The point defences like cannon,archer tower and xbows are the main enemies of the Queen Walk..So you have to take them out quickly.
Good luck


Considering our methods of exploration, how likely is it that there are unfound planets (not dwarf planets) in our solar system?

Question: I think it's probably unlikely that there are more planets between Mercury and Mars, but out from Jupiter, there's lots of empty space between the planets. Could there be some small planet hidden out there?
Comment: FYI when the first speculation about a large planet hiding in the Oort cloud came out, I took the worst case numbers given then to do some estimating about how hard it would be to find.  The potential orbit's been refined since then, but the baseline conclusion of "too faint to be found in an prior all sky survey, but detectable via a targeted search if where expected" is still valid; and such a search is ongoing now.  https://astronomy.stackexchange.com/questions/13270/9th-planet-location/13279#13279
Comment: Consider https://astronomy.stackexchange.com/questions/50444/how-many-undiscovered-planets-might-be-in-our-solar-system
Answer: There are no undiscovered planets between the sun and Neptune.
Objects closer (to Sun) than Neptune that are large enough to be considered planets (and not dwarf planets) can't remain 'hidden'. If it's there, the light from the sun will bounce off it and we will see it. As it moves in its orbit, we will notice the position in the sky change, so we will know it isn't a star.
I would like to give a more broad answer to this question though:
What is the maximum size of an undiscovered solar system object and how does it change as you get further from the sun?
The further out a solar system object is, the harder it is to detect. The rate at which it gets harder is severe; the light we receive from an object scales roughly as $1/r^4 $.
($1/r^2$ for the light travelling from the Sun to the object, and again, $1/r^2$ for the light travelling from the object to us on earth).
We are able to detect some very small earth-crossing asteroids. Some as small as ~50 metres across. At a guess (and this is just based on my intuition, not any calculations), there are probably no undiscovered objects larger than 1 km close to earth.
As you travel to the outer solar system (Jupiter to Neptune), the number of bodies increases dramatically. There are currently ~700,000 known solar system bodies and most of them occur in this area. It is believed that all asteroids larger than 10 km have been found.
In the area immediately beyond Neptune (30 AU to 100 AU), we have been finding many pluto-like objects in the past two decades, objects with diameters of 500 km or more. For reference, Pluto is about 2200 km across. It is entirely plausible that there are some, if not many, similar objects at this distance range that have not yet been found. Some of these would classify as dwarf planets, in that they are round, orbit the sun, but have not cleared 95% of their orbit of other matter.
And finally - and this is where it gets exciting - where it gets really far out, there may be an undiscovered large planet, out at ~700 AU. Referred to as Planet Nine, this is a hypothetical object that some (noteworthy) astronomers believe exist because of patterns they see in the orbits of other distant dwarf planets. From calculations, they estimate that it would be as heavy as 10 earths and travel between 200 and 1200 AU. However, these distances are so large and the sunlight out there is so dim, that even with the best telescopes and two years of looking, they haven't found it.
Finally, I'd like to share two graphs. The first one is of distance (of closest approach, or perihelion) vs diameter of various outer solar system bodies. In the bottom right corner there is a noticeable lack of dots, indicating roughly where we don't yet have the capability of seeing objects that small and distant.
The second is an expanded but slightly less accurate diagram of the same.

Image 1 from Johnston's trans-Neptunian objects page. Image 2 from xkcd.
Comment: And even if the planet was somehow invisible, we would still detect its impact on the orbits of other planets as long as it's close enough - after all, that's how we found e.g. Neptune.
Comment: +1 for a detailed but simply-explained answer that adds value to not just the question but our site as a whole!
Comment: @Mast by definition, as long it is orbiting the sun, it's part of the solar system...
Comment: @Flater - There is really no possibility of there being such a "counter-Earth". Unless it is in a *perfectly* matched orbit, it will slowly overtake Earth, or Earth will overtake it. And it cannot be in a perfectly matched orbit because the other planets will perturb its orbit and Earth's orbit differently, since Earth and counter-Earth would be in different places. There really is no place for a planet inside the orbit of Neptune to hide. Careful surveys have been made of the entire sky, and space is so empty that there is nothing to get in the way.
Comment: @Mazura WISE rules out large planets. Look at the XKCD cartoon.
Comment: `If it's there, the light from the sun will bounce off it and we will see it.` Just as an extreme example, if there were a "second Earth", exactly 50% further along Earth's orbit; would we have observed it? (I know that Earth's orbit isn't perfectly circular and the other planet would occasionally peek out, but would we really see it if it was only visible when looking into direct sunlight?) Have we ever looked at the solar system from a vantage point not near Earth?
Comment: Quoting intriguing question from @Flater "Have we ever looked at the solar system from a vantage point not near Earth?"
Comment: @Edoardo There's the [Family Portrait](https://en.wikipedia.org/wiki/Family_Portrait_(Voyager)) from Voyager 1 that was taken a small distance from Earth (about 40.11 AU and about 32° above the ecliptic), though it's not quite a complete survey of the solar system.
Comment: @Edoardo If memory serves there is or was a Solar observatory probe stationed near either Lagrange 4 or Lagrange 5. That might still be counted as near-Earth. The Voyager probes and probably some of the stuff send to Jupiter and Saturn (Cassinni ?) also took images looking back towards Earth/Sun.
Comment: I'm not convinced by the 1/r^4 figure - would you really multiply? Surely it would scale with 1/(2r)^2, or 1/4r^2, which is still O(r^-2)
Comment: About that possible 9th planet, would that still be considered inside of the bounds of our solar system? I mean, 700 AU is what, over 15x the distance between Pluto and the sun?
Comment: And to the best of my ability to track it down, the source for the first image is [Johnston's trans-Neptunian objects page](http://www.johnstonsarchive.net/astro/tnos.html).
Comment: No mention of WISE?  That's how we know there isn't.
Comment: You seem to know your stuff - so is there any chance that a  rocky planet 9 could have a very low albedo?
Comment: @RobJeffries it would have to have a very low albedo to not be readily visible. The main method now of finding new planet(oid)s is to calculate their estimated position and size based on perturbations in the orbits of other objects caused by their mass (gravity...) and then look with the best instruments we have in the predicted area of the sky.
Comment: @jwenting  There are perturbations of KBOs. Planet 9 has not been found. Planet 9 is not readily visible. Hence my question. What is the distribution of albedos of KBOs? And I guess we may never know about the really dark ones.
Comment: xkcd also has an "explain" page that unpacks the information in each comic. The [xkcd explanation for this comic](http://www.explainxkcd.com/wiki/index.php/1633:_Possible_Undiscovered_Planets) is well worth reading, as it provides an excellent *scientific* background.
Comment: @Tonny this should be made a question on its own, if there isn't already: it appears is not of any general interest though if the only attempt with the family picture was made in 1990
Comment: The "planet" in the chart appears to be Neptune at 30 AU and 4000 dia.  What is the cubewano to the right at 39 AU and bigger?  (Pluto/Charon orbit)?
Comment: @chux Hadn't noticed that. I think it's supposed to be Pluto. It looks about ~2000 km on the graph and pluto is about 2200 km. The dot to the right must then be Eris, whose perihelion is 37 AU.
Comment: 1/r^4 is because both at the source and the reflecting planet, light is scattered in all directions. 1/(2r)^2 would apply to the sun reflecting off a perfect mirror.


Can rsync ignore a directory's atime entry when creating it's file list?

Question: I am using rsync to copy data from a local LVM drive to a locally-mounted glusterfs mount.  I'm trying to bring them in to sync and eventually cut over to just using the glusterfs mount.  Here is the command that I am using:
<code>rsync -av --inplace --no-whole-file /mnt/lvm-ext4/ /mnt/gluster
</code>
I currently have the initial data push done and am now trying to catch up with the new files that have been added.  The LVM volume currently has around 14TB of data with around 25 million small files, but I think rsync is suffering with this many files.
While watching the output of this second run I see that most of the entries that rsync is outputting are directory entries, with a small set of actual files being moved.  I believe this is because the directories have been touched and their atime has been updated thus requiring rsync to update them on the remote side.  I've recently learned about the nodiratime mount option and have applied that today so hopefully that will help with future syncs.
Is there a way to have rsync ignore including these directory updates and only transfer the new/changed files or new directories?  I've seen the options for --ignore-times and --checksum but they seem to be all inclusive.
Comment: Answer in: https://stackoverflow.com/questions/35829263/ignore-subdirectories-timestamps-when-syncing-from-shell
Answer: I don't think that your problem is really related to directory timestamp.
With so much data, rsync will simply need some time to discover changed files and to begin to transfer them. If the meantime it discover a directory a/m/ctime change it will replicate that change on the receiver side, but this should be almost instantaneous.


Who were the Jedi attending the report on the Outer Rim sieges?

Question: In Revenge of the Sith, Anakin arrived late for the report on the Outer Rim sieges. While hurrying in, he passed by five fellow Jedi coming out of the door, and yet a couple on the stairs of the briefing room. Do we know the identities of these Jedi?
Comment: The script isn't much help; Scene 79 -
*ANAKIN rushes into the Briefing Room. By the time he reaches the Chamber, **the last of the Jedi are leaving.** Only OBI-WAN remains at the front of the lecture hall. He is shutting off some holograms and electronic charts and maps.*
Comment: The scene doesn't appear in the official novelisation, it just cuts straight to Anakin's conversation with Obi-Wan; "*But now here was Obi-Wan-Obi-Wan would help him, Anakin knew he would-if only Anakin could figure out the right

way to ask …

While he was still hunting for words, Obi-Wan reached him. "You missed the report on the Outer Rim sieges."*"
Comment: The junior novel doesn't name them *"and even as he pointed out the latest battle zones for the crowd of Jedi and answered their questions in the briefing room."*
Answer: Just ran into the Wookieepedia page of Melik Galerha, which states:

In 19 BBY, the final year of the crisis, Galerha, alongside fellow
  Jedi Koffi Arana, Olana Chion, Jurokk, Ma'kis'shaalas, J'oopi Shé and
  Shadday Potkin, attended a meeting in the Jedi briefing room regarding
  the Republic's siege of the Outer Rim. The meeting was presented by
  Jedi Master Obi-Wan Kenobi shortly before the Supreme Chancellor
  Palpatine initiated Order 66, which caused most clone troopers to
  eliminate their Jedi Generals.

Even the count matches; seven Jedi! So, it looks like the solution to the mystery was at plain sight - as usual in the Star Wars universe. :-P
Comment: For the record, the article in Star Wars Insider (#137) that the wookieepedia author is referencing doesn't *actually* say that these are the Jedi at the meeting. The writer of the article on wookieepedia appears to have decided that anyone not seen elsewhere in the film must have been one of the Jedi at that meeting. Obviously you can match some of them up visually...


Eddy currents oppose motion . Why?

Question: A copper plate is allowed to swing like a simple pendulum between the pole pieces of a strong magnet . Eddy currents are induced due to constant change in magnetic flux . This damps the motion of the plate . But why ?
Comment: [Lenz law](https://en.wikipedia.org/wiki/Lenz%27s_law).
Comment: That doesn't tell why the velocity decreases
Comment: I am sorry . But can u elaborate, please
Comment: Lenz law: "*The direction of current induced in a conductor by a changing magnetic field due to Faraday's law of induction will be such that it will create a magnetic field that opposes the change that produced it.*" The appearing eddy currents will counteract whatever caused them. In this case it is the changing magnetic field that causes them, in turn causes by the swinging. Counteracting the magnetic field changes means counteracting the swinging. I am aware that this is not a full answer to your question, so I'll only leave this as a comment.
Answer: In terms of energy transformation the energy of the swinging pendulum is converted into heat in the copper plate.
Consider what would happen if there was no opposition to the motion of the pendulum ie the induced current would be in such a direction as not to oppose the motion producing it.
In this case every time the copper plate was swinging down between the magnetic poles the induced current would be such as to produce a force of attraction.
This would me that the copper plate would have an extra accelerating force on top of that due to gravity.
Thus the speed and hence the kinetic energy of the copper plate would be larger.
So you still have a heating effect in the copper plate but on top of that you would also have an increase in the mechanical energy of the pendulum.
Overall the system would gain energy which is contrary to the law of conservation of energy.
So that induced current cannot help the motion producing it, rather it must oppose the motion producing it.

Eddy currents oppose motion . Why?


Over-extrusion on curved surfaces?

Question: I am having issues with my Creality CR-10 S5 running Cura 4.6.1. If I use the Ender-3 G-code, it prints perfect. If I do the exact same print with S5 printer selected, I get garbage prints with lots of burps.
Comment: If both files are printed on the same machine, then incorrect E steps would affect both prints (unless there is `M92` call in one of the files, fixing or spoiling the print, e.g. in the start G-code). The one at right looks like it has fuzzy skin enabled. I added an answer with troubleshooting hints, maybe someone can make use of them.
Comment: Have you calibrated your E steps?
Comment: could be diffeerend print speed settings...
Answer: Comparing printing results of some G-code with results of samples generated by a slicer with many unknown settings is too superficial. You need to do more insight.
You can learn by comparing G-code files, but I suppose it would not be sufficient to have successful prints. You can also learn from tutorials on how to properly configure slicer. Understanding slicer setting, common printing issues, physics of plascic and printing is very helpful for troubleshooting.
Between files there are number of parameters which could be different, including:

slicer software, its approach (algorithms) and settings - most probably it was Cura in both cases, but many settings could be different - if you have both profiles, then you may comare them setting by setting (thoguh it is not easy in Cura, but see next)
notes in comments (in opening and ending sections of file) - Cura is printing lot of profile settings at the end of the file
G-code initialization commands in opening section of file - *there may be key changes to printer configuration, and also information about following *
temperature settings - you can read it from G-code or from LCD, when print is started
retraction and speed settings - you can read it from E move commands
layer height - you can read it from Z move commands
total use of filament per print - use analyzer, see below
printhead movements (including experimental Fuzzy Skin) - check settings, and use visualisation in Cura just after slicing

Machine profile ("S5 printer selected") in Cura intoduces subset of default settings. In CR-10 S5 profile created by Creality many settings may be very different than in profile for Ender 3. And still author of original G-code file could update many of these settings before slicing.
You can compare two G-code files for the same shape in GCode Analyzer. For easier work you may open two or more analysers in separate browser tabs. There are many useful information calculated from G-code - about Model (like "Total filament used") and and Layer (like "Retract speeds"). Layers may be changed in 2D view with right scroolbar (clik the square scroll indicator and use Up and Down arrows on keyboard).

Over-extrusion on curved surfaces?


How can i add some custom text to Cart Page?

Question: Right when we click the cart icon we are taken to cart page where all product or products added to cart are shown.
On this page I want to add some custom text and icons below the cart summary by removing Estimated Shipping Tax and placing my text instead of Estimated Shipping Tax.
Please just tell where I can add these changes ?
Comment: Maybe this helps you: http://magento.stackexchange.com/a/72903/243
Answer: Magento has something called template path hints. Template path hints are little tags which would lie on top of your shop frontend. These little tags enable you to view where exactly the code of a specific element is stored within your file structure.
To activate template path hints:

Log into the magento back-end admin
Go to System -> Configuration in the main menu
Go to Developer on the bottom left under ADVANCED
Switch to the store view on the top left to your current website or
store view.
Under the Debug tab of the same Developer config page you will see a
new option appear that will allow you to turn on/off template path
hints.

Source
Comment: I find it bit sarcastic :) but let me check
Answer: To remove Estimated Shipping
In File
app/design/frontend/[YOUR THEME]/[YOUR PACKAGE]/template/checkout/cart.phtml

Comment out below code
<?php //if (!$this->getIsVirtual()): echo $this->getChildHtml('shipping');
        endif;
        ?>

or
In file
app/design/frontend/[YOUR THEME]/[YOUR PACKAGE]/layout/local.xml

add below code
<checkout_cart_index>
        <reference name="content">
            <remove name="checkout.cart.shipping" />
        </reference>
    </checkout_cart_index>

To Add custom cms static block at the same location as of shipping block
Create a CMS Static block and add below code in file app/design/frontend/[YOUR THEME]/[YOUR PACKAGE]/template/checkout/cart.phtml just before closing div class="cart-forms"
<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('your_static_block_id')->toHtml(); ?>

Answer: In Magento CE 220.127.116.11 the Estimated Shipping Tax is loaded in the following template file.
[your magento install dir]/app/design/frontend/YOURPACKAGE/YOURTHEME/template/checkout/cart.phtml

If your theme does not contain this file then you can copy it from the
  /base/default/ theme and add it to your own theme.

Open this file and look for the following line of code
<?php if (!$this->getIsVirtual()): echo $this->getChildHtml('shipping'); endif; ?>

replace this line with the following lines of code

<?php echo $this->getLayout()->createBlock('cms/block')->setBlockId('block_identifier')->toHtml(); ?>

The first line comments the Estimated Shipping Tax preventing it from rendering. So it will no longer be displayed. The second line will insert a CMS Static block to the cart page with identifier block_identifier, but only if this static block is active.
In your Magento Admin Panel go to CMS > Static Block and click on the Add New Block button.

Fill in your new block title
Fill in your new block identifier (this is important and should match the identifier that you have used in the cart.phtml file)
Choose the proper store view(s)
Enable the block
Add the code for the custom text and icons that you want to display
Save the block

Now refresh all cache and go to your cart page. The Estimated Shipping Tax block should be replaced by your new text and icons.
Comment: That's great.You Rock. :)


Is it worth using "pretty URLs" if you don't care about SEO/SEM

Question: I'm designing a hosted software-as-a-service application that's like a highly specialized version of 37Signal's Highrise product.  In that context, where SEO is a non-issue, is it worth implementing "pretty URLs" instead of going with numeric IDs (e.g. customers/john-smith instead of customers/1234)?  I notice that a lot of web applications don't bother with them unless they provide a real value (e.g. e-commerce apps, blogs - things that need SEO to be found via search engines)
Answer: Depends on how often URLs are transmitted verbally by its users. People tend to find it relatively difficult to pronounce something like
http://www.domain.com/?id=4535&f=234&r=s%39fu__

and like
http://www.domain.com/john-doe

much better ;)
Answer: In addition to readability, another thing to keep in mind is that by exposing an auto-incrementing numeric key you also allow someone to guess the URLs for other resources and could give away certain details about your data. For instance, if someone signs up for your app and sees that their account is at /customer/12, it may effect their confidence in your application knowing that you only have 11 other customers. This wouldn't be an issue if they had a url of /customer/some-company.
Comment: Non-pretty URLs aren't really any less obvious.
Comment: d03boy - Could you rephrase that without the triple-negative? Pretty URL's are the same or more obvious? I think you broke my English parser, because it sounds like you're saying it's just as easy to guess a valid company name as it is to add one to the number twelve.
Comment: If you are going to use IDs, GUIDs are a bit harder to guess, if that is an issue.

Even so, that isn't necessarily more secure.
Answer: It's always worth it if you just have the time to do it right.

Friendly-urls look a lot nicer and they give a better idea where the link will lead. This is useful if the link is shared eg. via instant message.
If you're searching for a specific page from browser history, human readable url helps.
Friendly url is a lot easier to remember (useful in some cases).
Like said earlier, it is also a lot easier to communicate verbally (needed more often than you'd think).
It hides unnecessary technical details from the user. In one case where user id was visible in the url, several users asked why their user id is higher than total amount of users. No damage done, but why have a confused user if you can avoid it.
Comment: I'll add to this : easy to guess and easy to type
Answer: I sure am a lot more likely to click on a link when I mouseover it, and it has http://www.example.com/something-i-am-interested-in.html.
Rather than seeing http://www.example.com/23847ozjo8uflidsa.asp.
It's quite annoying clicking links on MSDN because I never know what to expect I will get.
Answer: When I create applications I try my best to hide its structure from prying eyes - while it's subjective on how much "SEO" you get out of it - Pretty URLs tend to help people navigate and understand where they are while protecting your code from possible injections.
I notice you're using Rails app - so you probably wouldn't have a huge query string like in ASP, PHP, or those other languages - but in my opinion the added cleanliness and overall appearance is a plus for customer interaction. When sharing links it's nicer for customers to be able to copy the url: customer/john_doe than have to hunt for a "link me" or a random /customer/
Marco
Answer: I typically go with a combination -- keeping the ease of using Rails RESTful routing while still providing some extended information in URLs.
My app URLs look something like this:
http://example.com/discussions/123-is-it-worth-using-pretty-urls/
http://example.com/discussions/123-is-it-worth-using-pretty-urls/comments
http://example.com/discussions/123-is-it-worth-using-pretty-urls/comments/34567
You don't have to add ANY custom routes to pull this off, you just need to add the following method to your model:
def to_param
  [ id, permalink ].join("-")
end

And ensure any find calling params[:id] in your controller is converted to an integer by setting params[:id].to_i.
Just a note, you'll need to set a permalink attribute when your record is saved...
Answer: If your application is restful, the URLs that rails gives you are SEO-friendly by default.
In your example, customers/1234 will probably return something like

Customer

Name: John Smith

etc etc

Any current SEO spider will be smart enough to parse the destination page and extract that "John Smith" from there anyway.
So, in that sense, customers/1234 is already a "nice" URL (as opposed to other systems, in which you would have something like resource/123123/1234 for customer 1234 resource/23232/321 for client 321).
Now, if you want your users to be regularly using urls (like in delicious, etc) you might want to start using logins and readable fields instead of ids.
But for SEO, ids are just fine.


Variability of Regression Coefficients

Question: What does it mean when your coefficients in linear regression change, after you removed some variables?
I already checked the assumptions of linear regression. They seem to hold.
Comment: They are expected to change when you add/remove variables.  If they change a lot, that means there might be confounding between the variable you removed and another variable.
Answer: Regression coefficients are a collection of weights that SIMULTANEOUSLY relate the target series to a linear combination of the specified input series. If the input series are merely observed rather than fixed via a designed experiment little can be said about the effect of any one input series (selected) on the target unless you assert and "prove" that there is no evidence of cross-correlation between the other input series and the selected input.
This is why when you add or remove an input series the coefficients will settle on another set of coefficients as @Demetri Panonos commented.
Answer: In some fields, it is common to discuss "shared" and "unique" covariance between an outcome (dependent) variable and the group of independent variables on which it is regressed.
If you some dependent variable y being regressed on independent variables x1, x2 and x3 it is the usual case that some of the ability of each x-variable to predict y overlaps with the predictive ability of the other x-variables. In fact, sometimes that tendency is so pronounced with say that x1, x2, and x3 are "collinear" to the extent that a multiple regression model can't easily estimate the precise effects of each x-variable on y.
An exception to this is a designed study which collects the data in such a way as to guarantee that x1, x2 and x3 are "orthogonal" which simply means the predictor variables are not correlated at all with each other. In most fields, you just don't see that sort of dataset.
So when x1, x2 and x3 are to some extent "sharing" their predictive ability for y then taking one of those x-variables out of the model causes the parameter estimates for the others to be readjusted. If both the parameter estimates and the standard errors of the parameter estimates of the remaining independent variables change a great deal when one independent variable is removed, that's a sign of the "collinearity" effect that I mentioned, above.
There are regression diagnostics such as "variance inflation factor" or "tolerance" which can be computed if you think there may be a collinearity problem. But if the estimates for the remaining parameters are only changing slightly with the removal of one variable (as usually happens) then that's just the way multiple regression models tend to work.
One bonus "food for thought" is this. If you compute the R-squared statistics for each of your independent variable predicting your dependent variable in individual simple linear regression models, then compute R-squared for the model with all the x-variables predicting y in a multiple regression model, that combined R-squared is almost always less than the sum of the individual R-squared. And in most cases it will be a lot smaller.
P.S. The answers before mine were correct and succinct. I just elaborated on the topic in case you wanted a bit more background.

Variability of Regression Coefficients


Broken geodesics in the hyperbolic plane and bending angles

Question: Let $\gamma$ be an infinite broken geodesic in the hyperbolic plane, that is a curve formed by consecutive geodesic segments. Assume also that each of these segments is longer than a certain positive constant $C$. For any two consecutive geodesic segments $[p,q]$ and $[q,r]$, we can consider the angle $\theta_q$ between the two segments. I would like to say that if these angles are always close enough to $\pi$ (i.e. the line does not bend too much) than the whole broken geodesic does not go back to itself, as opposite to what would happen in Euclidean geometry. I think this could be proved by some explicit hyperbolic geometry computation, but maybe it's a well known fact and somebody could point me to a good reference. Thank you.
Answer: I think that your conjecture is correct. I'll use the Poincaré half-plane model to describe my attempt at a proof.
Take the line $L$ parallel to the real axis a certain height above, I'll take it one unit up. In hyperbolic geometry, this is a horocycle, a circle tangent to the horizon; in this case the point of tangency is $i\infty$. Now draw a hyperbolic geodesic tangent to $L$ at the point $i$, and on this "straight line" go a distance $C/2$ in either direction. So you have a segment of length $C$, symmetrically placed. Let its endpoints be at $\pm a+bi$, with $0<b<1$ of course. Now shift the segment over by the transformation $z\mapsto z+2a$, a hyperbolic rigid transformation. You get, on the right, another segment of length $C$, also tangent to $L$, and it makes an angle $\theta_C$ with the original segment. (You see that as $C$ is taken smaller, $\theta_C$ will be closer to $\pi$.) Now I say that if you restrict your angles to be at least as close to $\pi$ as $\theta_C$, your broken geodesic will not come back to itself. That should do it.


Posting info to Twitter with a known username / pass and the Oauth token without having to grant access

Question: I'm using C# to build some functionality for a website. They want to twitter a message to their account at the point when a new vacancy gets added to their website. I face the issue that when i try to do this using the OAuth token approach i have to grant access to the application everytime. I want this all to work automatically without the need for permission. Can i login the user and then just post a message or how do I approach this?
Answer: With OAuth you only need to get their permission once, and you can save the Access Token that Twitter returns to you and use it to act on behalf of the user as long as the user does not deny you permission to act on their behalf or the token hasn't expire.  Twitter does not currently ever expire tokens see Twitter OAuth FAQ.
Just save the token along side the username in the database and use it to send post requests whenever you need to post to twitter.
Twitter puts it this way in this Transitioning from Basic Auth to OAuth Guide:
Prepare long-term storage for access tokens and secrets
Whatever your storage system may be, you'll need to begin storing an oauth_token and oauth_token_secret (collectively, an "access token") for each user of your application. The oauth_token_secret should be stored securely. Remember, you'll be accessing these values for every authenticated request your application makes to the Twitter API, so store them in a way that will scale to your user base. When you're using OAuth, you should no longer be storing passwords for any of your users.


Safari context menu search extension

Question: Does safari has an extension like this Chrome extension called Context Menu Search? It enables user to search highlighted text from the context menu.
It should be something like this:
Answer: I needed something similar too!
So look up: CustomSearch. It's highly adaptable by using the integrated CustomSearch Entry Editor.
"CustomSearch allows you to easily send the selected text to one of up to eight search engines — right from the toolbar or a contextual menu. CustomSearch includes search entries for Wikipedia, Google, Bing, and Amazon."
Comment: It is no longer available.
Answer: Mac Services
Not at the Safari-level, but on MacOS one can add custom context menu Services that are context sensitive. I do this to add arbitrary search engines for any selected text (from any application).
Steps

Open Automator.
Choose File > New.
Select Quick Action, then click Choose button.
Create the following workflow, replacing the search URL (currently shows DuckDuckGo search):

Save the Action with the name you wish to appear in Context Menu (e.g., "Search DuckDuckGo").

Try it out. Select some text in Safari or elsewhere, right-click, go to Services, and select your custom search.
Answer: It has built-in Dictionary & Search with... on the right-click menu

I think the Search with… defaults to whatever your chosen search engine is.
The dictionary can also be triggered using  Cmd ⌘   Opt ⌥   D  in many other apps/text areas.
Comment: I've added an screenshot of what I am looking for. I hope i can choose from search engines from the menu.

Safari context menu search extension


How can I teach High School kids that rest is important in progression and resistance training (supercompensation)?

Question: How do you explain to your athletes/players that rest is important in simpler English? Some of my guys go 7 days/week playing basketball and I need a compelling argument to tell them to take a day off once in a while.
Comment: Consider sports.stackexchange too.
Comment: It depends on the type of training - there's no reason why you can't do skills training 7 days a week. But fot strength/aerobic training consider this argument - it's not the training that makes you improve, it's your body's _recovery_ and supercompensation that makes you improve
Answer: Maybe not?
I'm not sure that high school athletes need to take a day off of playing basketball. Their recovery is probably amazing, and a game of ball isn't necessarily very taxing.
A day off is definitely necessary if they're getting sluggish or feeling beat up, or if they're actually training — meaning sprints, distance running, lifting weights, or drilling hard. But if they're only doing light drills and scrimmaging, I don't see a reason to mandate a day off unless they specifically need it. Young athletes are very durable.
Deontological policy
Then again, maybe they really should rest. I wouldn't try arguing the point. Just make a soft rule for them. Tell them that even the very best usually reserve Sunday as a day of rest. They can go for a walk and shoot hoops, but no organized games. If they break the rule, they experience the consequences, and will learn from it.


Is the prime P is fixed for an elliptic curve defined over a particular prime field F_p?

Question: I have seen the NIST, SEC and Brainpool standards. They have used same prime for a particular bit curve (128,192,256,521). Is the prime value fixed for a particular security (field size)?
Comment: The question in the title isn't repeated in the body of your post. Actually, it seems to me that you ask two (strongly related) questions. Could you adjust and make sure that the body and the title match?
Comment: (i) Of these three standards, only SEC publishes a 128-bit curve. (ii) All the Brainpool primes are different from all the NIST primes. (SEC and NIST use the same curve parameters, not just the same primes.)
Answer: In general you start by fixing the field, which translates into fixing the prime, and then you start to look to a suitable (i.e. secure/safe) elliptic curve defined over that field.
Note that, once you've fixed $p$, there are $\sim2p$ isomorphism class of elliptic curves defined over $\mathbb{F}_p$, which grants you a big set where you are supposed to find a curve with all the desired security properties, unless you are looking for very specific properties such as low CM discriminant.
There are two good reasons for it.
First: the field is linked to the curve's cardinality by Hasse's Theorem. which means that by choosing the size of the prime you also strictly bound the size of the cardinality (within a bit).
And second, and most important, a particular choice of the prime provides faster-than-generic modular reductions, which provides performance benefits of elliptic curve computations.
For example, all NIST P curves are defined over Solinas primes (also called generalized Mersenne), except P-521 which is over a Mersenne prime.
The idea is that using Solinas reduction is faster than a generic modular reduction and can be used to speed up the computation.
Similar arguments are used in more modern elliptic curves such as curve25519 which uses a pseudo Mersenne prime ($2^{255}-19$) or FourQ which uses is defined over a field $\mathbb{F_{p^2}}$ with $p=2^{127}-1$.
Note that the Brainpool standard uses random primes, however its deterministic algorithm for curve generation selects first a random prime, and then look for a suitable curve. See appendix A of RFC 5639.
Comment: @Venkatesh you in fact have multiple (~p) elliptic curves, defined over the same field, with the same j-invariant and same number of points. Those are in fact isomorphic to each other. These belong to the same isomorphic class.
Comment: What do you mean by isomorphism class ?
Answer: The NIST curves as published in FIPS-PUB 186-3 and SEC curves are identical. The P-xxx curves are the same as the secpxxxr1 curves (where xxx is the bit size). NIST just standardized most of the curves and gave them separate names from the SEC curves by the Certicom corporation.
I'll show you the Bouncy Castle code for the NIST curves:
defineCurve("B-571", SECObjectIdentifiers.sect571r1);
defineCurve("B-409", SECObjectIdentifiers.sect409r1);
defineCurve("B-283", SECObjectIdentifiers.sect283r1);
defineCurve("B-233", SECObjectIdentifiers.sect233r1);
defineCurve("B-163", SECObjectIdentifiers.sect163r2);
defineCurve("K-571", SECObjectIdentifiers.sect571k1);
defineCurve("K-409", SECObjectIdentifiers.sect409k1);
defineCurve("K-283", SECObjectIdentifiers.sect283k1);
defineCurve("K-233", SECObjectIdentifiers.sect233k1);
defineCurve("K-163", SECObjectIdentifiers.sect163k1);
defineCurve("P-521", SECObjectIdentifiers.secp521r1);
defineCurve("P-384", SECObjectIdentifiers.secp384r1);
defineCurve("P-256", SECObjectIdentifiers.secp256r1);
defineCurve("P-224", SECObjectIdentifiers.secp224r1);
defineCurve("P-192", SECObjectIdentifiers.secp192r1);

The prime fields of the Brainpool curves and SEC curves certainly differ, for instance the prime field over 256 bit curve is:
FFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF

for the SEC curve and
A9FB57DBA1EEA9BC3E660A909D838D726E3BF623D52620282013481D1F6E5377

for Brainpool.
Here the SEC / NIST specified curve uses a specific prime while the Brainpool curve was (semi-) randomly generated. More information in the answer of Ruggero

So no, the prime value isn't fixed for a particular field size. There is no specific way to calculate the prime for a particular field, but you may at least want to make the generation of curve parameters opaque. Most cryptographers will probably agree with D.J. Bernstein that the domain parameter generation must be verifiable. I'll gladly point out the SaveCurves website for more information.
Brainpool scores better in this regard although the choice of prime is probably not the biggest issue here; the SEC primes are well known primes and it seems unlikely that they are part of some specific plot. You may want to make sure that you choose the right prime for speedy calculations (lots of 0 bits or 1 bits set generally helps, to simplify the requirements to the extreme).


Arduino and hard drive

Question: So in a laptop you have a CPU and a hard drive. The hard drive feeds data to the CPU and the CPU executes it. In Arduino you flash the CPU and the "hard drive" is built into it. Is it possible to have a hard drive or SD card feed data into the Arduino to be executed and then feed more data in and so on? If it is possible how is it done?
Answer:
Is it possible to have a harddrive or sd card feed data into the Arduino to be executed and then feed more data in and so on. If it is possible how is it done?

A harddrive would be difficult to connect, but an SD card will work just fine.
You can write a sketch that reads data from an SD card. There is library support for both SD and FAT16/32 file systems.
Another interpretation of your question is; is it possible to load a sketch from an SD card. The answer is yes; there are a number of projects that have done that.
Cheers!
Comment: will loading sketches take long and will it reduce the lifespan of the chip?
Comment: Depends on how often you want to update the sketch? It is not a very good idea to load the sketch from SD every time. There should be some logic to when the sketch is updated and should be loaded.

Arduino and hard drive


Clarification on UID creation

Question: I have a series of matrix blocks that use a ton of the same fields and was hoping I could simply duplicate them in the database and update the context and id of the fields. It'd be a LOT faster this way however i'm unsure of the UID column, how/when that is created and if i should leave it blank, or if that column existing means i'm going to have to it all manually
Comment: I needed a different number, But I saw another tool that helped me so much that the tool is also very nice, I hope that's tool will be more useful too. https://codebeautify.org/guid-generator
Answer: As aberkie pointed out, Craft does use them internally, but they should not be left blank or you'll potentially run into some issues now and you'll miss out on some upcoming features.
You can programmatically create one with StringHelper::UUID or use a site like guidgen.com to get a valid one.
Comment: @Sandwich Within the database itself, UIDs are never used as references in foreign keys; only ID columns. However Craft does use them in a couple places as as an alternative to IDs when selecting rows, and there will be much more liberal use of selecting rows by UID in an upcoming release.
Comment: Thanks Brad, so is there little to no concern about there being duplicate UIDs if using something like guidgen? I've already got all my fields created now (did it manually) but this will be very helpful for future reference.
Comment: Nope... the chances of a proper GUID/UUID conflicting are so astronomical it's not worth worrying about.
Comment: If I'm understanding this correctly, does this mean that the `uid` column for any given table row is not used anywhere else to _reference_ that row (unlike columns like `fieldId`, `layoutId`, etc.)?
Answer: Don't worry about the UID column. Check out this comment from Brad Bell. Craft uses the UID internally, and will add them when needed. You should be fine by leaving them blank.

Clarification on UID creation


Bitcoin sent to Bitcoin Cash address in blockchain

Question: I sent bitcoin to a bitcoin cash address in my blockchain account. Are the coins going to the account and if not what if anything can I do to recover my bitcoins?
Answer: If you have the private key of the bitcoin cash address, you can import it into your bitcoin wallet and send it somewhere else.
If not, you have to ask the one, who has its private key, for example an exchange.


PGP Encryption Marketing Cloud File Transfer

Question: I'm attempting to setup a file transfer activity from the Marketing Cloud Safehouse to our FTP Export Folder, encrypted. However, to do this, I have to enable a 'Customer Public Key'. On the activity it shows 'No Items' in the drop down. Is this something I need to setup or have Salesforce enable?
Answer: You need to upload your PGP key under Key Management in Setup.
Select Asymmetric, fill out Name and External Key fields, and upload the file containing your public PGP key:

 Find more information on how to do this, on these pages.

When creating an upload file transfer activity that moves a file from
  your Marketing Cloud account to an external location, you can encrypt
  the file using PGP or GPG encryption. Upon execution of the activity,
  Marketing Cloud encrypts the specified file and moves it to the
  specified location.

Once created, the key will appear in the drop down of your file transfer activity
Comment: Thank you Lukas! When I attempted to configure/create the SSH key for the encryption, I got a saving error message stating "Object Reference not set to an instance of an object". Do you have any idea what that means?
Comment: @chorlesbarkley7 - you should not be adding an asymmetric key, not ssh key. See my updated answer above
Comment: @chorlesbarkley7 - please remember to mark answers as accepted. I can see some of your questions have really good answers - without being marked as accepted. It is beneficial for the community to be able to identify the good answers.
Comment: Good Call Lukas. Sorry new to the community. I'll go through and ensure answers are accepted. Thank you!
Comment: @chorlesbarkley7 - no worries, we all have been new here at some point
Answer: In the screenshot above, the only thing that you missed is to select the Radio Button "PGP", following which your Automation/Activity would have encrypted the File in PGP format.
Comment: I did select that but even when I did it still didn't work.


Force.com - custom report type

Question: I made a custom report type . I included a few objects and related them using object relationships which was correctly displayed in the set (Venn) diagram . However , the fields of these objects are not available for editing in the edit layout detail of 'Fields available for reports " section. The fields are visible but am unable to make changes to them . Please help.
Comment: Could you share a screenshot of the issue you are facing, as it is unclear to me where it's going wrong?
Comment: Thank u very much for your help . Actually the fields were not visible at all but i tried it again today and they are visible now must have been some error in the page .
Answer: This is somewhat tricky and is explained well here.

Go to Setup -> Create: Report Types -> Click on the Report Type's Label -> Click
  "Edit Layout" within the "Fields Available for Reports" box on the
  right, you'll see the "Field Layout Properties" section. You can drag
  and drop desired fields to this layout. If a field you wish to include
  is not visible under one of the selected objects, you may be able to
  add it via lookup.
  To do this Select the respective object from the
  "View" drop down field on the right side of the page.  Click on the
  "Add fields related via lookup »" link directly below the "View" drop
  down field.  Select the appropriate link and subsequent fields. Repeat
  this process as needed per object.

Force.com - custom report type