Check if user has access to a certain page

Question: How can I determine whether a user has permission to access to a certain page?
Comment: You didn't specify which version of Drupal you use.  More details about your goal would also be useful; in the most common cases Drupal will handle menu access automatically.
Answer: If you want to verify if the currently logged-in user has access to a page, you can use the following code:
if ($router_item = menu_get_item($path)) {
  if ($router_item['access']) {
    // The user has access to the page in $path.
  }
}

$path is the path of the page you want to check (e.g. node/1, admin/user/user).
The code works in Drupal 6 and higher versions, and it is the one used from menu_execute_active_handler().
The reason I am not suggesting to directly call the access callback is because the arguments that need to be passed to that function.
The code used by _menu_check_access() is the following one (Drupal 7):
$arguments = menu_unserialize($item['access_arguments'], $map);
// As call_user_func_array is quite slow and user_access is a very common
// callback, it is worth making a special case for it.
if ($callback == 'user_access') {
  $item['access'] = (count($arguments) == 1) ? user_access($arguments[0]) : user_access($arguments[0], $arguments[1]);
}
elseif (function_exists($callback)) {
  $item['access'] = call_user_func_array($callback, $arguments);
}

The code, which needs to be as much generic as possible, doesn't directly handle a user object. This means that is not possible to replace the user object for the currently logged-in user with another user object.
The code must be generic enough to handle menu definitions such as the following ones:
$items['node/add/' . $type_url_str] = array(
  'title' => $type->name,
  'title callback' => 'check_plain',
  'page callback' => 'node_add',
  'page arguments' => array($type->type),
  'access callback' => 'node_access',
  'access arguments' => array('create', $type->type),
  'description' => $type->description,
  'file' => 'node.pages.inc',
);

$items['node/%node'] = array(
  'title callback' => 'node_page_title',
  'title arguments' => array(1),
  // The page callback also invokes drupal_set_title() in case
  // the menu router's title is overridden by a menu link.
  'page callback' => 'node_page_view',
  'page arguments' => array(1),
  'access callback' => 'node_access',
  'access arguments' => array('view', 1),
);

In both the definitions, the access arguments don't include a user object, and node_access() in this case uses the user object for the currently logged in user. In the second case one of the argument is the node object that is obtained from the URL; for example, if the URL is example.com/node/1, then the second argument passed to the access callback is the node object for the node with node ID equal to 1.
Writing code that handles these cases too would mean to duplicate code already existing in Drupal. Even if you duplicated that code, there would be still the problem of the access callbacks that are checking the access against the currently logged-in user.
If you want to check if a user that is not the currently logged-in user can access a menu is to first change the value of the global variable $user, use the code I reported at the beginning of my answer, and then restore the value of $user. For how to change the value of the global $user, you can see Programmatically impersonating another user without causing the currently logged-in user to log out. The difference is that, instead of using the value returned from drupal_anonymous_user(), you use the value returned from user_load().
Comment: May I know in which hook this code should be written.
Answer: Try drupal_valid_path().
The function returns TRUE is the path passed as argument exists and the current user has access to it. So, if you are working on Drupal 7 and you need to check the access on the currently logged in user, it's the easiest way to go:
if (drupal_valid_path('my/path')) {
  // Your code here...
}

Comment: In D7, `drupal_valid_path` does the job perfectly and is made to fulfill this exact need. It uses menu_get_item and checks access as well.
Comment: That's true, but it only works for the currently logged-in user.  If you want to know if some other user can access the path, `drupal_valid_path` won't help you.
Comment: @AndrewSchulman I don't think there is an API for that, but you can temporarily switch users.
Comment: In Drupal 8, this has moved to `\Drupal::service('path.validator')->isValid($path);` -
 see the [API documentation](https://api.drupal.org/api/drupal/core%21lib%21Drupal%21Core%21Path%21PathValidator.php/function/PathValidator%3A%3AisValid/8.4.x)
Answer: Call the access callback that is specified in the menu entry that is responsible for the page. That menu entry is usually created by Drupal calling the implementation of hook_menu and is stored somewhere in the database. Beware that the data returned by hook_menu might be changed by a module implementing hook_menu_alter.
Beware that some modules might not pass the user as a separate argument (as specified by the access arguments key of the menu entry), but might instead use the global $user object instead. You will have to check this for each module that you use.
Comment: Calling the access callback is not as easy as calling any other function, as the access callback needs specific arguments; see [_menu_check_access()](http://api.drupal.org/api/drupal/includes--menu.inc/function/_menu_check_access/7), which is the function that check if the currently logged in user has access to a menu.
Comment: This method can be used to find out whether the some other user than the acting user is allowed to access the page.
Answer: Check out the user_access() function.  See the link for the specified parameters for each version of Drupal.  From the documentation page for Drupal 7-8:

Parameters
$string The permission, such as "administer nodes", being checked for.
$account (optional) The account to check, if not given use currently logged in user.
Return value
Boolean TRUE if the current user has
  the requested permission.
All permission checks in Drupal should
  go through this function. This way, we
  guarantee consistent behavior, and
  ensure that the superuser can perform
  all actions.
Comment: user_access() is for checking if user has a certain "type" of permissions. What is need is if user can access to a certain "path"; for example, if user can access 'node/12'?
Comment: Well how are you determining when a user has permission or not then?  I would assume there is an option on the permissions page that you either have checked or not to give certain roles the permission
Comment: `user_access()` is not always the access callback used by a menu; even it would be, you should know the access arguments that you need to pass to `user_access()`.
Comment: I know it's not always `user_access()`, just figured the OP had a permission in mind to check to see if user should have access.  Not a very descriptive question
Comment: Even though user_access can't check access to a specific path, I think using user_access whenever possible is the best way to check access. Good answer @Laxman13 +1.
Answer: If you need to know if a user can access a particular node, and are using a node access module, you can use node_access().  (without a node access module they just need the 'access content' permission.)
If you want to figure out if a user can access an arbitrary path that is defined by a hook_menu() implementation, you may have to retrieve the menu entry from the database and evaluate its 'access callback' parameter.
Answer:     $node = node_load(123);

    $account = user_load(456);

    if (node_access("update", $node, $account) === TRUE)
   {

         print "access";
    }


How do you deal with conflicting schedules?

Question: I'm trying to get a group together for a campaign. They've all already created character concepts, and all seem excited to join. The problem is, it seems like every day of the week, someone is taken, and I know that if we don't keep a consistent schedule, the group will eventually cease meeting. Does anyone know how to get everyone together, or how to break the idea that someone may have to drop out?
Comment: Does your game require every player to always be present? For example in my game there is a faily large group of seven players (plus me as GM) - obviously there are nearly always 1 or 2 missing when we meet at different times, but we decided that that's okay for us and the game itself does not require everyone to always be present. What did your group say about this issue? Did you talk about this with them? Do they already know that they like the game or is it a first game - meaning that some may drop out simply because it's not like they imagined it would be?
Comment: What system are you using? Or what is it based on if you're homebrewing. And how many people are you talking about having in the group? Different systems have different tolerances for group sizes and missed sessions. You may need to drop players regardless of scheduling anyway and the game may or may not handle missing characters.
Comment: Are you playing in person, or is playing using online tools an option?
Comment: See also this question: [How to fairly schedule sessions when not everyone can make it anymore](https://rpg.stackexchange.com/q/106773/2451)
Comment: @Secespitus No, it would not, and I'm happy to find a way around absent players. But we're all young and I think only one of us can drive, so if we don't keep to a consistent schedule it'll fall apart. It's a first game but they are already familiar with the world (I'm an extensively homebrew DM) and seem to like it. I haven't yet talked to them yet, but I know I'll need to.
Answer: First determine if the game required the whole group to be present
I've heard that some games require that the group is consistent more than others (somewhere I've read that you should be careful in The Dark Eye for example because you need certain characters to progress past certain story points, but I've never played it), while others are more forgiving (DnD 5e for example). If your game doesn't require the whole group you can try to find ways around this issue, otherwise splitting your group might be better - run two games with smaller groups whose schedule alines nicely.
Handle absent group members out-of-character
This is something you need to discuss with your players, but often you can find ways to work around a few players that are absent. To give a personal example: I am the playing DnD 5e with a few friends. We are seven players plus me as the DM. This is a big group. We managed to get two introduction sessions where everyone was present so that I could teach them the basic rules they need to know to play the game.
Afterwards we changed the schedule a bit and stopped requiring everyone to be present. It just doesn't work, especially with so many people. During the week is difficult and everyone puts a lot of the personal stuff in the weekends, so we decided to play once or twice a month on the weekend as long as we get at least four players plus DM.
It's quite some work on the part of the DM to accomodate varying group sizes,  but as long as everyone is on-board with the idea of changing the group size because "characters x and y are staying in the town to gather information while you are exploring the goblin cave" and "characters y and z came to the goblin cave last night and found you after they gathered information in the town" everything is fine. It's not a style that works for every group but for our group it does work and you might want to talk with your players about this.
Another idea we explored was to use Side-quests of one or two sessions length whenever there was only half the group and progress with the main story when everyone is present. It's important to decide on one or two sessions to have the time for a dungeon or little adventure arc, but then it's easily possible. For the side-quests you could just make a "quest-board" in the main town. Maybe you know that half the group will make it to the next two sessions and then the other half will be available, so sending them on "Orc extermination"-style quests might, depending on your group, be an option.
Try to find regular times to meet
Every other week on a Saturday for example. Or your alternate weekly between Tuesday and Friday. Try to come up with something so that everyone can be present every other session for example.
Work with milestones
You used "DM" in your comments, so I assume you are playing DnD. In DnD 5e you can also use the milestone rules for advancing. That way your players might feel better about being available only every other week, because the level-ups are given out after every big main-adventure story arc. Or maybe your group would like to progress as a group and it doesn't really matter to them whether the characters are present or not.
In my group this wouldn't work. I give out experience whenever they overcome some kind of challenge and they like it that way. It feels better to be rewarded instantly, but using milestones is nevertheless an option and might work for your group. Talk to them to find out how to do it.
Be prepared for drop-outs
If this is a first game as you mentioned in the comments then there is a possibility that some may drop out after a couple sessions, for example because they realized that there are more rules and difficulties than they imagined. Every new RPG is a completely new experience and every group has their own style. Devoting so much precious time to a game that is not quite what you were hoping for may have the effect that some people are dropping out. Of course you should talk to them and try to make the game something everyone on the table enjoys, but nevertheless someone may drop out. Which would make scheduling easier. So maybe you only need to find a schedule that fits for two or three sessions and then you can see how you want to progress.
Answer: Needs of the many outweighs the needs of the few
Your problem is one of the most common people out-of-school have: conflicting schedules. Find a day when you can get most people and go with that. Make a decision and roll with it, the alternative to one person being out is to not have a game at all, which is worse.
If you really want everyone to play, have you considered running two different campaigns (with player overlap)?
TLDR There is no one simple, unified answer (the others did post good advice...)
Answer: Split into two games.
Just separate the group into two that play at different times, like that everyone can play and you have twice less schedules to match. You can either run twice the same game or two different ones.
Comment: Just be careful not to get into a "[Head of Vecna](https://1d4chan.org/wiki/Head_of_Vecna)" crossover situation, that's messy.
Comment: That would work, but the problem is that I don't have enough players to split into two groups large enough. Also, I'm a beginner DM and I don't think I'd be able to run two campaigns without burning out. Thanks for the suggestion tho!
Comment: @FaerieDragon You might have enough players if group one and group two share a couple of players. You don't have to _run_ both games if you're worried about the workload you can run one, play one instead.
Comment: how many players do you have? If there are 3 of them and their schedule is already exclusive to each other it sounds like an unsolvable issue.
Answer: You could change the frequency and length of the game. Instead of a once a week on a specific day, have the game run at different intervals so that all players have to cancel the same number of extra activities. If it comes to that, you can run the game monthly on first weekend: both days, from 10:00 till midnight. Note that if your game is not regular, a good calender application is  essential so players do not forget when the game is running.
It requires some planning and flexibility from your players, but worked really well.
Personally, all the games I run have a schedule posted in advance. If you cannot make that, you cannot be in the game. Tough.


High Octane petrol's effect on turbos

Question: I have a 2001 SAAB 9-3.  I was told that I should use a high octane fuel...that it would extend the life of the turbo.  Is this true?
Answer: I would suggest checking the owners manual to see what Sabb requires for a minimum octane fuel.It should be 93 octane for your motor.That being said higher octane fuel will not help the turbo last longer.Octane ratings are a measure of the fuels ability to resist engine knock.Engine knock is caused by fuel ignition with the piston in the incorrect position.Engine knock will cause engine damage and shorten it's life but won't effect the turbo.What you can do to increase the turbo's life is change the oil regularly and allow the engine to idle for a minute or two after highway speed driving.This allows the turbo to slow down while engine oil is still being circulated through the turbo's bearings.
Comment: @qes What octane ratings are available is totally dependent on country, as different countries vary in how they rate octane. In the US, (R+M)/2 is used. In New Zealand, the research method is used. This means most pumps in NZ are rated 91, 95, or 98(relatively rarely).
Comment: His Saab does not require a minimum of 93 octane.  That is not even widely available; there are many areas where 91 is the highest commonly available octane.  The owner's manual, as you suggest, will list the recommended octane for optimum performance (and mileage), and the minimum - which for Saab 9-3's is likely to be either 87 or 89 (and many Saab owners find the increased mileage from using 90+ makes it more economical than using a lower octane fuel).
Answer: mikes is right: the octane is required for the engine, not the turbocharger on it's own.  Said another way, the requirement for higher octane is a consequence of having a turbocharged motor vs. a normally aspirated one.
We've discussed some of the associated issues before.  Here is some relevant discussion on the subject:
What are the benefits of premium (high octane) petrol?
Difference between high octane and low octane?
Static vs. Effective compression: Why does higher effective compression not require higher octane gas?
Answer: Well, if you run fuel that's too low an octane and the ECU is forced to retard the timing to compensate, then exhaust gas temperatures would go up...  Turbos run pretty hot to begin with.  Making it even hotter will in theory decrease it's lifespan some.  Measurable though?  I don't know...

High Octane petrol's effect on turbos


What do Muslims teach about the schism of faiths after Jesus Christ?

Question: After Christ's ministry, Islam and Christianity went two separate directions. I'm Christian, from Christian teachings, Mohammed founded Islam around 600AD, but it is my understanding that Muslims believe the same as Christians, the they are the same Church of the ancient prophets. How do Muslims view their relationship to Christians? How are the faiths related and when or how did they go their separate ways?
Answer: Muslims believe that Christianity today is a corrupted form of the original religion of One God. Because of this, Quran was revealed to Muhammad(puh), just like Bible was revealed to Jesus(puh) to correct the corruption of his time. But Muslims also believe that today's Bible is not the same Bible revealed to Prophet Jesus(puh). Today's Bible is a corrupted form by mankind. Muslims also believe that Jesus(puh) was a man, a prophet only, not the son of God. Because in Islam, there is no relative of God. Here is the claim of chronology of Islam:

The first man and prophet Adam(puh) was created.
Mankind reproduced.
Mankind corrupted the belief.
A prophet among them was sent.
Mankind corrupted again after some time.
This process repeated through numerous prophets.
Jesus(puh) was sent as a prophet, but with a miracle. He was born without a father.
Mankind corrupted the religion again.
Muhammad(puh) was sent as a final messenger with Quran.

As you see, the separation begins at the very beginning. Muslims believe that there maybe (possibly) remain some real verses in today's Bible. But, we can't differentiate them from manmade ones. Thus, we shouldn't make comments about them much and follow the final revelation, which is Quran.
There are some prophets who has successful (at least for a time) like Moses(puh) or Muhammad(puh); and there are some prophets who hasn't much successful like Lut(puh) or Noah(puh). Successful here means convincing their people. It seems like Jesus(puh) was one of the unsuccessful ones. Because he couldn't convince lots of people during his life and his followers corrupted the religion in the very early times like allowing to eat pork etc.
Muslims view Christians and Jews a little closer to them rather than atheists, other religions or idol worshipping. Muslims think at least they have a part of the truth. For example, a Muslim man can marry a Christian or Jewish woman if the woman doesn't believe trinity. But a Muslim can't marry with someone who is atheist or believing any other religion.
By the way, these are the thoughts which should be. Today some Muslims think bad about Christians and Jews because of politics.
Comment: What does the (puh) mean?
Comment: The view that a Muslim can marry a Christian or Jewish woman only "if the woman doesn't believe trinity" (or as we say in correct English: "...believe in the trinity") is a view held by some, but by no means all Muslims. This restriction is not spelt out explicitly in any verse of the Qur'an.
Comment: Peace be upon him. Short version of Peace of Allah be upon him. In plural version, peace be upon them. We say this after the ones we highly respect, especially prophets.
Comment: /@aasheq, You are right at some point, but from [At-Tawbah 9/30](http://quran.com/9/30) this kind of action can be considered as Shirk. And marrying with mushriks are prohibited.
Answer: Well, if you say eating food, drinking water, breathing air like other Christians and Jews did of the past as 'Copying', then yes, Islam derived most of the roots from Christianity and Judaism. This way...

Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. Mat 22.

And there is nothing astonishment in it, because Jesus (pbuh) already said the same thing pretty clearly...

On these two commandments hang all the law and the prophets.

analogues to saying, "this is the way man lives by eating food, drinking water and breathing air and this is common sense".

How did they depart?
Well the basic understanding of Islam and with intellect given to the Muslims, we believe, there is something wrong with Gospel of John especially John 3:16-18, but Christians say 'no, we believe this to be perfectly authentic and on this we rely'.
This is how Islam and Christianity departed, else and otherwise, they're pretty similar.
May the creator guide us all.


How do people sing the high notes using their head voice without making it sound like they are using their head voice?

Question: I heard rock singers etc., who sing really high notes, and I think that they use their head voices. But when I use my head voice, it doesn't sound melodious. What can I do to improve on this?
Comment: For the same reason that you can probably sing low notes that they can't; it's part of their (your) range.
Comment: You're probably using falsetto, not head voice. They are two different things. https://music.stackexchange.com/questions/14834/what-is-the-difference-between-male-head-voice-and-falsetto
Answer: You need to exercise your voice. Taking voice lessons from a professional teacher is the best, quickest way to achieve what you want.
That said, if you're determined to start on your own, I'd begin with singing scales (notes next to each other, usually over the range of a 5th (5 notes) or an octave (8 notes), starting in a comfortable range, and moving your starting note one half step higher each time. (Half steps are notes directly next to each other on a keyboard, including the black notes.)
Most people are most comfortable with an 'ah' vowel sound OR an 'ee' vowel sound. Spend 10-15 minutes twice daily doing this. You can also find lots of how-to voice videos online. You have to take good, low, breaths with a relaxed but tall posture, and be sure the air-flow is adequate to keep your vocal folds moving easily, without tension. If you're feeling a lot of tension, you should stop.
Comment: Is this specific to head voice or just general advice?
Comment: Both specific to head voice and general advice. That's why taking lessons from a pro teacher is the best advice. It's really difficult to teach voice via text descriptions.
Answer: There are a whole lot of rock singers, some of which do use head voice. I think your definition of head voice means falsetto, and some rock singers absolutely do this; some, however, use "head voice" to mean other things. Some rock singers do sing in falsetto (AC/DC's lead singer does a lot of this), but that hair-metal high voice is usually a regular voice singing up into the high tenor range (which takes a whole lot of practice), and I'm not sure everyone can. Of course, most rock singers are male, and if you are female, you probably won't sound very idiomatic for rock music in any type of head voice (meaning a separate vocal register). Either way, I must recommend a vocal instructor (and yes, that's a real thing for rock singers). The last thing you want is to permanently injure your vocal cords trying to sound like that guy from Guns & Roses.


Question about tide

Question: Let's say a canal is built in the middle of Kansas in the shape of a ring that stretches 100 miles in diameter. The band of water is 100 feet wide and 10 feet deep throughout the entire canal, and the land where the canal is built is flat in every way aside from conforming to the curvature of the earth.
Would a current develop from tidal forces? If so, in what direction would it flow? How rapid would it be?
Answer: Most likely, tides would not cause a current.  To create a current, the tidal forces need to be asymmetric enough to produce a preferred direction of flow.  In this example, unless the canal were at one Earth's poles, the geometry is such that tidal forces are acting orthogonal to the plane of the canal---effectively canceling itself out once you average over a day.
Additionally, the size scale of the canal is fairly small, decreasing the strength of the tides, compared to (for example) winds, which would dominate on such scales.
Comment: Thanks- I can't upvote your answer due to my low rating, but that was very informative

Question about tide


What is "Dragging the Shutter"?

Question: I've heard this term of "dragging the shutter". What does this mean and why would I use it?
Comment: possible duplicate of [How does dragging the shutter work?](http://photo.stackexchange.com/questions/33896/how-does-dragging-the-shutter-work)
Comment: The other question is more about the *how* than the *what*.
Comment: Possible duplicate of [How does dragging the shutter work?](https://photo.stackexchange.com/questions/33896/how-does-dragging-the-shutter-work)
Comment: Possible duplicate of [Orange "aura" around people/objects in photo, usually present with older cameras?](https://photo.stackexchange.com/questions/103085/orange-aura-around-people-objects-in-photo-usually-present-with-older-cameras)
Comment: There's some better answers in this question - can a moderator merge them instead of closing?
Comment: @mattdm seems to me the proposed dupe is specific to dragging the shutter while using flash (i.e., front/rear curtain sync), whereas this question is more generic than that. Perhaps title of other question should be modified to include "... when used with flash", or something like that. That would provide a bit more separation between the two of them... ?
Comment: I have never heard the term "dragging the shutter" to simply mean a long exposure. I'd love to see either an authoritative resource for that or a demonstration of it in common use. I can see the argument about how vs. what, though.
Comment: @mattdm Hmm. Good point. I guess I've always assumed "dragging the shutter" is just long exposure (but I've never referred to it that way).
Comment: May be a duplicate of: https://photo.stackexchange.com/questions/103085/orange-aura-around-people-objects-in-photo-usually-present-with-older-cameras. I find the question and the answer much more well written in it.
Answer: It just means using a long exposure, usually in the context of mixing flash with ambient light, in order to let in more ambient light to better expose the background. See this related question:
How does dragging the shutter work?
Answer:
What they said.
You need to be aware that in some situations this effectively occurs unintentionally as a consequence of the way most modern shutters work - and the effect on images can be other than intended.

The following applies mainly to "aperture priority" mode of operation - but similar effects can occur if care is not taken in other modes.
When flash is used, maximum available shutter speed is limited by the nature of the commonly used "two curtain" / focal plane / roller blind shutter.  For practical purposes these typically have a maximum speed in the 1/100th - 1/200th second range when using flash. (Multi-flash flash is a seperate situation and much less common).
Excellent super slow motion video of a 2 curtain shutter in action

I'll just use the term "shutter" here to mean a two curtain shutter of some form.
A  shutter fully uncovers the sensor (or film) only up to a preset maximum shutter speed - typically in the 1/150th to  1/200 second range but sometimes faster. For faster shutter speeds (or shorter exposure times) an effective faster shutter speed is achieved by "sliding a partially opened window" across the sensor. If the "window uncovers only say 1/4 of the sensor at any given moment then the effective shutter speed is increased by a factor of 4.
For ambient light the window can be as small a fraction of the sensor width as desired.
But, for a single-flash flash the shutter must be wide open when the flash occurs so that the whole sensor sees the light from the single flash event. This means that the maximum shutter speed when using flash may in some situations be slower than the camera in aperture priority mode would use if ambient light only was being used.

If the shutter speed with flash is say 1/200th second max ( = 5 milliseconds) and conditions are very dark then without a flash in the same conditions you might require a shutter speed of say 1/10th second. In that case, as the actual shutter speed  is 1/200th second with flash = 20 times faster, the ambient light will contribute minimally to the overall exposure.
However, if you are photographing a  stage show with eg brightly spotlit dancers, or are using the flash as fill flash to reduce facial shadowing on a bright day, them if using the ambient light only, your shutter speed might be 1/100 th second, or 1/250th or even 1/500th. Actual value will depend on aperture, ISO and light level. If you now enable the flash the shutter speed will be forced down to the maximum value that thecamera supports in flash mode. As you have set the aperture manually and as the shutter speed is now similar tp or even slower than the value that you would use with ambient light only, the ambient light will contribute substantially to the end result.
On  sunlit day with fill flash the result can be massive overexposure as the camera is not able to increase the shutter speed adequately.
With a stage show with fast motion the effect can be more subtle but just as undesirable. The flash will now expose the scene about correctly but the overall slow shutter speed and high ambient light levels will allow extended images of moving dancers to be recorded. You may get a sharp image from the flash with the dancers surrounded by a movement "halo" from the lower speed ambient exposure. Wit care this can be used tp produce very "arty" and desirable effects. Without care this can produce a blurred and fuzzy mess. Actual result depends on actual shutter speed, aperture and ISO and amount of movement.
If yu wish to avoid or at least minimise this sort of effect set aperture and ISO such that the requried shutter speed with ambient light is far lower than the max flash-sync shutter speed. eg if ambient light requires 1/200th second at ISO 400, f/2.8, then using ISO 100 and f5.6 would push the required shutter speed down to about 1/15th second. If the camera is now arranged to expose correctly with flash at 1/200th second the ambient light will provide only about 5% of the light. Smaller apertures will further reduce ambient contributions.
Even if the scene is relatively static, varying  desired results may be achieved by adjusting flash and ambient balance. A photo of a speaker at a podium lit with a halogen spot and with other dignatories seated close behind may benefit with more flash and less ambient to achieve better overall colour balance and colouring. A DJ at a party with several coloured spots washing his equipment may require some flash to allow equipment details to be seen but benefit from substantial mounts of ambient light so that the spot colours are not totally washed out by the flash. Dancers will generally look better if at least some of the lighting comes from coloured spots -  while limiting the blurring which will occur if too much ambient effect is allowed.
By careful juggling of aperture & ISO and possibly also adjusting the flash power level you can produce any mix of flash and ambient in the image that you desire, with appropriate effects accordingly.
Comment: 'With care this can be used tp produce very "arty" and desirable effects'.
One of the reasons to buy higher end cameras is that they have the 'rear curtain sync' feature that lets you do this
Comment: @ClaraOnager - Yes - raer curtain shutter lets you do more - eg very notably it lets "light trails" from lanterns etc appear BEHIND the subject and not in front. BUT you can get many arty effects with front curtain shutter in the above situations. FWIW you can get light trails BEHIND a subject with a front curtain shutter by having the subject walk backwards ! :-) - may not be perfect but better than what you get otherwise.
Comment: I think it might be safer to buy a better camera than try to get models to walk backwards after a flash has gone off in their face...
Comment: @ClaraOnager re " ... get a better camera ..." -> :-) . You'll always find something more you want your camera to do, no matter how many times you upgrade to a "better" one. After rear curtain you want high speed sync. After HSS you want ... ? [Power limitations imposed by HSS are a pain] . After ...  :-)
Comment: You can also get trails using 1st curtain sync that look like 2nd curtain sync by panning past the subject faster than the subject is moving.
Answer: Dragging the shutter refers to allowing the shutter to stay open a longer time in flash photography to allow more of the ambient light to be captured.  By only partially exposing the shot with a brief burst of intense light, the shutter can be left open longer than the flash burst to allow more influence from the ambient light and potentially give a more natural feel while still limiting the duration the shutter has to be open for a standard exposure.
There is still a slight trade off in the time stoping properties of a fast shutter, but since a lot of the light is captured in a fraction of the shutter time (from the flash) there is less impact than would occur in an exposure without a flash at all.
Answer: Dragging the shutter (also known as slow-sync) is a term used in the context of flash photography. It refers to the practice of leaving the shutter open longer than required by the camera's sync speed. The sync speed is the shutter speed needed to allow the relatively short duration flash to fire while the sensor is completely exposed between the time the first curtain has completely opened and the second has not yet begun to close.
Many times dragging the shutter is combined with second curtain sync.
This video explains in simple terms how a focal plane shutter works and why sync speed is important when a focal plane shutter is used in concert with a portable flash unit.
The purpose of dragging the shutter is to allow more of the ambient light in the scene to strike the sensor. Areas of the scene that would be too dark because they are too far away from the flash unit that is adjusted to properly expose the main subject can then be seen in the photo.
Another use of dragging the shutter is to allow light trails. Imagine a car driving from left to right at night. By dragging the shutter the lights on the car will create a trail of light across the frame. The short duration flash will illuminate the car and freeze it for the instant the flash is lit. If first curtain sync is used, the flash fires as soon as the first shutter curtain is open. The result of this looks unnatural to our eyes because that leaves the light trail leading in front of the car as the lights continue from left to right after the flash has fired. By using second curtain sync, the flash will fire just before the second curtain begins to close. Thus the light trails are exposed before the flash fires, and they appear to be trailing the car.

What is "Dragging the Shutter"?


Where does the Departure End of Runway (DER) exactly begin?

Question: I am having trouble understanding the concept of Departure End of Runway. Most sources state that DER is at the end of the portion of the runway that can be used for takeoff (which, as far as I can tell, excludes the threshold at the end of the runway). But from the official FAA's Aeronautical Information Manual one can clearly see that DER starts at the "utmost" end of the runway (including threshold). Many other sources seem to support this, like this picture. Could someone point me to the right direction?
Comment: I always understood it to be the "opposite end" of where you start the takeoff run, i.e. the very first point of the opposite runway... standing by to learn something here!
Comment: I'm not sure what context it's being used in, but would expect it does not include the RESA. For more info refer to [this question](https://aviation.stackexchange.com/q/31397/8730)
Answer: The picture you linked is from an FAA publication. As pictured the threshold is the end of the runway pavement, it is a thin line that separates usable runway from either taxiway, blast pad, grass, or an emergency overrun area. It is marked at night with a single row of green or red lights (depending on your direction). It can be displaced or reloacated from the original pavment but in this case it will have noticeable markings that include a well defined line marking the exact end. Some ends are usable for takeoff but not landing or vice versa but that is down to individual runways.
The paint bars near the threshold of an instrument runway are simply for visual reference to help indicate the width and length of landing zone during approach, they have nothing to do with takeoff or departure. VFR runways only have a number and dashed center line, no white bars at all.
To summarize: the threshold is a line not an area, it separates usable runway from non-runway, it may be marked with paint or lights but it can also simply be a change in surface such as tall grass to short grass. Standard departure obstacle clearance climb gradients are calculated with the plane at 35feet above the ground, directly over the threshold at the departure end of the runway.
Comment: The problem with that picture is that it does not show a displaced threshold. When the white 'piano keys' (or the numbers on VFR runways without them) are at the end of the pavement, there is of course no ambiguity. That only occurs when there is a displaced threshold (white arrows).
Comment: For departure end, it is the red lights. The green lights visible from the other direction may be at different place in case there is a displaced threshold, no?
Answer: According to the FAA's Terminal Instrument Procedures (TERPS), the definition is:

Departure end of runway (DER). The end of the runway opposite the landing threshold (see figure B-1).
Answer: Just guessing out loud here, but if you go to airnav.com and look up any airfield, two points are given for opposite ends of the runway. For MOR or Morristown, TN,

Runway 5 = Latitude:  36-10.456562N,  Longitude:  083-22.968408W, Elevation:  1312.9 ft. and the other end,
Runway 23 = Latitude: 36-11.069353N, Longitude: 083-22.085700W, Elevation:    1274.4 ft.

As an Engineering Consultant, everything that is done on this runway is done considering these two points - measurements for placing markings, setting up the RSA and all Part 77 surfaces and safety lines, etc. Approach surfaces, departure surfaces, everything is established off these two points, including length of runway, TODA, TORA ASDA, LDA, etc. are all configured off these FAA established runway endpoints, whether there is any extra pavement beyond or not. In my estimation, the DER is going to be the opposite end runway coordinate of the end you are rolling out on.
Answer:
ICAO Doc 8168 defines the Departure End of the Runway as "the end of the area declared suitable for take-off (i.e. the end of the runway or clearway as appropriate.)"
Comment: Welcome to aviation.SE! Please don't post images of text; it isn't possible to search the text, which makes it more difficult to find answers like this. The [tour] may be helpful if you're new to the site.
Comment: Ooops, sorry about that. I thought the screengrab from the official source itself would be good to justify the basis for the answer, especially since ICAO's definition differs from FAA's. In future would it be better to crop the screengrab to just the relevant portion?
Answer:
Most sources state that DER is at the end of the portion of the runway that can be used for takeoff (which, as far as I can tell, excludes the threshold at the end of the runway).

The displaced threshold, marked with white arrows, can be used for take-off (and roll-out), so the departure end of runway is at the end of that if present.
Blast pad/overrun area, marked with yellow chevrons, and taxiway, marked with yellow edge and possibly centre line, cannot be used for take-off, so the DER is before they begin.

But from the official FAA's Aeronautical Information Manual one can clearly see that DER starts at the "utmost" end of the runway (including threshold). Many other sources seem to support this, like this picture.

The pictures don't show any displaced threshold nor overrun areas, so they are not really indicative of anything.


Learning suggestions for AI and neural networks for a mathematician

Question: I am a mathematician who has done programming in Python, Java, and R. I would like to learn to make neural networks and artificial intelligence. Are there any good books for self learning AI for a person like me who loves learning theory behind neural networks, and who can learn by proving theorems and thinking the theory behind AI? When I just read Tensorflow's or Keras's documentation, I found that I couldn't understand how the networks work.
Comment: Thank you both - I've converted it to an answer.
Answer: Higham and Higham's Deep Learning: An Introduction for Applied
Mathematicians is a fairly short introduction to neural networks that is written with mathematicians in mind.
Another reference I would recommend is Shalev-Shwartz and Ben-David's Understanding Machine Learning: From Theory to Algorithms, particularly chapter 20.
Both of the above approach neural network theory in the more traditional Definition–Theorem–Proof structure.
I think it is worthwhile to build a simple network yourself in order to learn the principles before diving into a framework such as TensorFlow, if you're hoping to gain understanding of the principles rather than treating a neural network as a black box which might work, or not. The recommendation of Neural Networks and Deep Learning in kaya3's answer is useful for this, as Nielsen does write neural networks from scratch to demonstrate.
For some theoretical background you may also find interest in Hornik et al. (1989) and Rumelhart et al. (1986) if you have access.
Answer: @kaya3's comment links an excellent e-book, which describes the math in fair detail.
I'll never get tired of recommending 3blue1brown's amazing video series that both motivates the problem and gives basic intuition but doesn't shortchange the math: https://www.3blue1brown.com/neural-networks
Answer: The online textbook Neural Networks and Deep Learning by Michael Nielsen is quite good for mathematical content. It assumes the reader understands calculus, but requires no prior knowledge of machine learning. The book's own introduction explains fairly well what the book is about:

The purpose of this book is to help you master the core concepts of neural networks, including modern techniques for deep learning. ... One conviction underlying the book is that it's better to obtain a solid understanding of the core principles of neural networks and deep learning, rather than a hazy understanding of a long laundry list of ideas. If you've understood the core ideas well, you can rapidly understand other new material.


Multiple Tor Browser instances without using VM/Sandboxies

Question: On Windows is it possible to have multiple instances? I tried to copy paste Tor browser folder and running Tor Browser from it but did not worked.
Comment: Why would you want to run multiple instances?
Comment: multiple anonymous ip
Comment: That does not seem currently possible, because each instance of TorBrowser will try to run Tor, and if the latter is already running, you'll get an error message and the browser won't start.
Comment: What benefit do you think you'll get from running multiple instances of Tor that you wouldn't get by simply running one Tor instance (and letting Tor handle streams for you)? Tor is designed to be anonymous when used in the normal way. Multiple instances is probably not going to actually help you at all, and might even hurt your anonymity.
Answer: I answered this here.

This method launches multiple Tor instances, each with its own SocksPort and ControlPort. This ensures that the Tor Browsers are fully functional, portable, and self-contained. However, someone should confirm that I haven't missed anything that could compromise TBs security.

Optional: Download, verify, and install Tor Browser.
Make copies of the Tor Browser folder with different names (eg. Number them)
Launch Tor Browser
Edit about:config

Modify extensions.torlauncher.control_port to a new ControlPort (eg. 9052 for Tor Browser 2)

Edit Torbutton Preferences

Use custom proxy settings, and change the Port to SocksPort (eg. 9152 for Tor Browser 2)

Close Tor Browser
Edit torrc-defaults in \TorBrowser\Data\Tor

Change SocksPort to what you set in step 5
Change ControlPort to what you set in step 4

Launch Tor Browser, and check that everything was configured correctly

Homepage (about:tor) should say "Congratulations!"
Click "Test Tor Network Settings". check.torproject.org should say "Congratulations."
Go to ip-check.info. Test should be all green and orange except Tab name. Authentication should be "protected". Note: It may not say that you are using Tor, but this is incorrect.
Optional: Go to ipleak.net for IP, DNS, Geolocation, Browser and other info
Optional: Test your browser fingerprint at panopticlick.eff.org

Optional: Edit about:config

Type "banned" and modify the ports of the two entries. Add all the new SocksPort and ControlPort to the list (Copy the ports from other Tor Browsers)

Optional: Turn on "Forbid Scripts Globally" in NoScript for further security and privacy (also reduces browser fingerprint)
Repeat 3-10 for each Tor Browser folder

Alternatively, this might be possible with a single Tor instance as the SocksPort and ControlPort. This would require the use of the control_auth_cookie (CookieAuthentication) or HashedControlPassword, and about:config extensions.torlauncher.start_tor=false. However, the browsers would not be self-contained and portable, as they would require a process that isn't in their own directory.
Inspired by mirimir's answer which seemed to compromise TB's security.
Answer: Enable the proxy port by downloading privoxy: http://www.privoxy.org/
Set the browser proxy as following:

ip address : 127.0.0.1
port : 8118

Verify that proxy port is running. If so, you may request multiple Tor browsers.
http://www.privoxy.org/config/


Extending the User Registration Form

Question: To add fields to the User Registration one can directly use the admin/config/people/accounts page. However, I am required to some other fields to the User Registration like food choice which is to be selected from drop-down list of foods, Email and Confirm Email fields (which should check whether both are same and whether the email was used in db), country (If UK/US is selected, text field for state, postal code should appear). Now, I could add the fields to the user registration page, but how can I handle the validations for the fields and how do I show such dropdown list. Am I required to create my module that extends the User Registration form. If so, how do I do this? Thanks.
Answer: If your only need is to add new required fields to the user registration form, you do not need modify the form through a module; by marking any user entity field as a Required field in the field UI, it will be presented in the registration form as a required field for registration.
If you require custom validation that goes beyond "it must be non-empty" you might need to employ a custom validation handler in a custom module, another helper module (e.g. Field validation), or a custom field module that matches your use case (e.g. Address field module).
Comment: So, if I were not to use any external module like Field Validation, should I create a separate module for user registration making own forms with validation.
Comment: Generally, if core/contrib modules don't cover your use case, yes. A custom module would be the route to go to add your own functionality as its needed.

Extending the User Registration Form


Coriolis effect discrepancy. How to deduce the direction of the effect?

Question: From what I understand (please correct me if I'm wrong), the Earth rotates counterclockwise as viewed from the north pole. That means from the perspective of the equator to the north pole, it is rotating clockwise. Hence, if I shoot a projectile towards the north pole from the equator, it should move leftwards likewise if I throw a ball towards the person in front of me in a clockwise-rotating turntable. But, in my textbook and Wikipedia it says that it would go rightwards. Where did I get it wrong?
Comment: Cross-posted at physics.SE: https://physics.stackexchange.com/questions/385877/coriolis-effect-discrepancy
Comment: Just to verify... you mean **counterclockwise** rotating turntable, yes?
Comment: @user12202 I hope you don't mind I added a second part to the title, as the original one was to broad and didn't tell much about the real question you were presenting.
Comment: Whoops, user12202, looking back at how the question started, maybe you were more caught up in the idea that looking from the equator, the Earth would seem to be rotating clockwise. I do suppose that's true (though you'd be looking up from the center of the Earth rather than down onto it! But yes, from that (odd) perspective Coriolis would cause apparent left deflection. But the thing is, since you're looking "upside down", that "opposite spin" is still causing the same true direction deflections. Your north is down and south is up...
Comment: Someone could just as easily say gravity makes things rise (because they turn head upside down, and see "up" as what most of us call down). But we have a standard reference frame we're taught and all questions assume that viewing direction. Likewise, when we talk weather and physical processes, we usually speak of "map-wise"... from above, so as to be speaking the same perspective.
Comment: Inverting viewing direction flips rotation, but also inverts the direction relationship, so it's still the same actual movement. Indeed, even a normal Northern Hemisphere tornado, (or even the eye of the hurricane), looking straight up from the ground... [would actually appear to be rotating clockwise](https://www.youtube.com/watch?v=LVSad0CQDAE)!
Comment: I seemed to make this more complicated sounding than needed in some points, getting focused on rotation direction and relative motion and perhaps being confusing.  The concise answer is... it actually moves (apparently) right, because it has more angular velocity (i.e. west-east component of motion) at the spot you release it (the Equator in your example) than where it goes (higher latitudes).  Likewise on the turntable, it'll miss the person to your right (their left) because you're moving right compared to them, and thus so is the ball you threw.
Answer:
That means from the perspective of the equator to the north pole, it is rotating clockwise

That's the part you got wrong.
As seen from the Equator (as any other point on the Earth), the North pole is not rotating. The rotation only shows up in an external frame of reference. And is actually using an internal frame of reference (like an observer on the equator) what gives rise to the Coriolis force, that is not a real force but just the inertia seen from a rotating frame of reference.
From the Equator, the North pole is in a fix position, as well as the celestial north pole, that is fix to the Equatorial horizon due north. But the starts and the Sun moves around it from East to West, which is COUNTERCLOCKWISE. That's is because the observer is moving Eastwards.
Coriolis is easier to understood if you imagine that any point on the Earth's surface (or the atmosphere) north of the Equator, have to complete a smaller circle around the Earth axis every 24 hours. Therefore, those points are moving Eastwards at a slower speed than the ones at the equator. Hence, if you shoot a projectile to the North, it will have an excess Eastwards velocity relative to the ground under it, so it will tend to go Eastwards. Which will apear like it is turning rightwards.
If the projectile is flying south from the Equator, Eastwards will mean leftwards.
This schematics from Facts About All will help in an example:

Let's imagine you are at at the monument "La Mitad del Mundo" right on the Equatorial line on Ecuador. And you shoot a projectile straight North to Raleigh, North Carolina, 3,960 km North of "La Mitad  del Mundo".
Let's say your canon shoots a frictionless projectile at speed of 1,000 km/h. Then the projectile had a Northwards speed of 1,000 km/h, and an Eastward speed of 1,666 km/h which is the speed the canon at Ecuador have in order to go around the earth center every 24 hours.
Now, in 3.96 hours, the projectile would have reached the latitude of Raleigh, but in the same amount of time the eastward component of its speed took it 6,600 km to the East. However, the eastward velocity of Raleigh is only 1356 km/h
That is because at latitude 35.7° the distance to the Earth rotation axis is only 5,179 km (in contrast with 6,378 km at the equator), therefore, the distance it have to travel around it every 24 hours is only 32,540 km (in contrast to 40,000) requiring a speed of just 1356 km/h.
That means that, while the projectile wast traveling, Raleigh only moved 5,369 km eastwards, 1,231 km less than the projectile, with the consequence that the projectile ended up, 1,231 km to the East of Raleigh (The right as seen from "La Mitad del Mundo"), catastrophically missing the target, and falling in the Atlantic ocean somewhere north of Bermuda.
This excess eastward velocity visualization of Coriolis, seemingly falls apart when considering a projectile shoot due East or West. But it would still be deflected to the right (in the northern hemisphere). An explanation in such case can be found in this answer, however that answer is not as clear as I would like, as it just ignores the vertical effect, also known as Eötvös effect, which is important to make sense of the deflection of a projectile traveling East/West. In short, the increased/decreased velocity of a projectile moving East/West, increase/decrease the centrifugal force, so it moves away/towards from Earth's axis of rotation. This means "moves up" at the equator, and move south/north and up (in different proportions) north of the equator. The rightwards deflection is considered part of the Coriolis effect, while the upwards deflection is the Eötvös effect.
Answer: It's been a while since I've thought about this... and every time it still does take some careful thinking through it all.  But hopefully this can really help you get it put together!
First: Yes the Earth rotates counterclockwise around the Pole...

The thing is, when you shoot an object "due north" towards the North Pole...   you really aren't shooting it with a due northward velocity!
Why?
The initial motion of the rocket isn't just it's fired trajectory... but also includes the motion the location it's launching from has.  This is much like if you were in your car driving forward down the interstate, and chose to toss something out the window "directly sideways"... you'd find the can actually continued to move forward as it bounced along the road.
And the thing is, the further poleward a place is, the less eastward velocity those places are rotating with.  Yet your projectile has brought its higher eastward velocity it started with.  So it winds up ahead of where you think it should if going true north, because it rotates eastward faster than that location.  [For the car-can analogy, if someone was driving slower in the lane beside you... the thrown can would actually seem to travel forward away from him, until air resistance worked enough to slow it down......]
(Likewise, hopefully you can also see that "eastward" itself is actually changing the direction it points on the overhead view [originally east of Algeria is straight to the right, but by the time it has moved to the end of the green arrow, it becomes up and right].  However the projectile keeps its exact same direction arrow.  If you follow along the path of that arrow, in terms of cardinal directions... its "northward" progression slows, and it actually eventually starts moving what is then south .  So the rotation of the Earth not only alters what we perceive to be east-west movement [turning it to the right in the NH], but also likewise alters the north-south movement [the same turning to the right in the NH occurs, regardless of whether].  We see the rocket as behaving oddly, but the issue isn't with the rocket, but due to the fact that we're actually continually moving AND changing direction to rotate around the Earth.)

(Note the Earth rotates too of course, so Algeria will truly have moved around near the area where the yellow arrow ends by the time it gets up there.)
And it may well help a lot to note: it actually does the exact same (turn right) when operating from a counter-clockwise rotating turntable too!
Comment: If the earth wasn't rotating, then the projectile would go over the north pole and head southward along the anti-meridian through the Aleutians and cross into the SH by Tuvalu on its way to the south pole.   With rotation, I think the path would be some great circle around a static globe, tangent at the point of launch, but then the path is warped on the ground by the turning of the earth beneath the static great circle.
Comment: A few notes: air resistance won't help nearly as much on launched projectiles... because the air nearer the ground is moving the same speed the Earth is (apart from the difference... which is what we perceive as wind).  [In Florida I'm moving 1000ish mph continually... but so is the air above me.  You won't notice the air moves... anymore than you realize the air inside your car is moving 70 mph if you're going 70 mph down the highway.  Motion is **relative**.  If you threw that can out the car... and the wind was blowing the same direction at 70 mph... the can wouldn't slow down!
Comment: Also, will say, the one thing proving a little stickier, at least sitting here after a very long day, is the diagram seems to suggest the projectile will cross the edge of the map (and thus move out of the NH into the SH) by the time Algeria has completed 180°... *regardless of how fast northerly you fire the projectile!!!*. That's obviously not the case!!! Think it may be in the failings of a flat diagram... something in the vertical from the direction of gravity/centrifugal force changing, or maybe likewise truly seen in vertical component of Coriolis on a sphere. Will try to update later.
Comment: I'm still not feeling confident in this answer I have given, as I think most of it may indeed be the artifact of compressing three dimensions into two.  Camilo's answer is great, except I think it gets a bit muddled in its first few sentences about rotation from different perspectives [see also my comment to the initial question].  But the diagram he gives and the points he links to to help explain Coriolis deflection for zonal motions... are very good and helpful improvements on my graphic.


Stardust or the elements in our bodies

Question: How do we know we are made of stardust? As our cells divide, are our atoms repurposed from existing materials or spontaneously generated? Do we consume materials after we are born that contain elements that were in stars? This I would understand. Or, as our cells are initially dividing after conception, but before birth, are we already repurposing existing materials to grow?
Answer: The saying that you are referring to is from Carl Sagan, when he stated that:

"We are a way for the universe to know itself. Some part of our being knows this is where we came from. We long to return. And we can, because the cosmos is also within us. We're made of star stuff,"

Quote source
In answer to your question, yes, we are 'repurposing' the elements that make us up, as are all living and non-living matter.
Chris Impey, professor of astronomy at the University of Arizona is quoted in the article Are We Really All Made of Stars? (Melina, 2010) as stating:

the fact that the carbon, nitrogen and oxygen atoms in our bodies, as well as atoms of all other heavy elements, were created in previous generations of stars over 4.5 billion years ago. Because humans and every other animal as well as most of the matter on Earth contain these elements, we are literally made of star stuff

The elements that make up the cells etc in humans and any life forms, as with the materials that make up the Earth itself were ultimately formed by nucleosynthesis processes (mostly fusion and neutron capture) in stars, explained in the webpage Origin of the Chemical Elements as being:

the early Universe consisted almost entirely of the element hydrogen, with a small amount of helium present too. Hydrogen, therefore, is thought to be the starting material from which all other elements have been built. This is consistent with the very high abundance of hydrogen in the solar abundance profile. The process may be thought of as a series of fusion reactions which weld together simple atomic nuclei to build increasing complex atomic nuclei.
Answer: Unless you are inside a star or a fusion reactor- Matter is neither created nor destroyed. However, fission of unstable isotopes is fairly common on earth's surface.
You may accumulate one of such isotopes but usually the ones that are generally absorbed in our bodies such as C-14 have very long decay times (more than your lifetime). So for all practical purposes you are created from the atoms of existing matter and these keep getting recycled from the environment.
Now the composition of different stars is different and statement like "Do we consume materials after we are born that contain elements that were in stars", is too farfetched. Many millions of years have passed since earth came out of a star and lot of nuclear reactions have happened in this time. So the composition is of course different.
Answer: It might be helpful to think about where elements in general come from. Here is a plot of relative elemental abundance.
Note that the Y axis is logarithmic, so H and He are much much much more common than anything else. You'll notice that Li, Be, and B are rare, and C, N, and O are fairly common, and are the main components in biological chemistry. Fe is relatively abundant, and after Fe elemental abundance falls off. The explanation for the abundances comes from the processes involved in nucleosynthesis.
Big bang nucleosynthesis was the generation of hydrogen and helium within the first 3 minutes of the universe as the quark-gluon plasma cooled and formed the protons and neutrons. As the universe expanded and cooled, it lost the energy needed to keep making atoms within 20 minutes, so only very small amounts of Li, Be, and B could be made.
Stellar nucleosynthesis is the creation of "heavy" elements by nuclear fusion in stars. This is how we get C through Fe. As the stars age and use up their fuel, they generate elements up to Fe because energy can be released from fusion of atoms up to iron, past iron fusion takes more energy than can be released.
Elements heavier than Fe must be created through supernova explosions. This is the only natural way to get enough energy to jam the nuclei together. This only works well for elements up to uranium, where nuclei become unstable and decay at relatively fast rates. These unstable elements are produced in nuclear reactors and particle accelerators. Note that supernova explosions don't just make heavier elements, they are also responsible for blasting the elements made in stars into space where they can form new stars and planets. This is where the matter that makes us comes from, hence the stardust.
Another method for generating light atoms is cosmic spallation, where a cosmic ray hits an atom and blows some protons and neutrons out of the nucleus. This material becomes light atoms, such as Li, Be, and B.
Here is a periodic table that shows where each element comes from.
Comment: @AMR I believe I found it on wikipedia, probably in one of the links I posted in the answer. Pink elements are produced by supernova, it may be that Np and Pu were detected in small amounts from other supernova, making them "natural", but I'm not a physicist.
Comment: What was what source of this periodic table? As far as I am aware, at least in our solar system Uranium is the last naturally formed element. Edwin McMillan and Glenn Seaborg were credited with the synthesis of Neptunium and Plutonium respectively.

Stardust or the elements in our bodies


YouTube URLs yield 404 error, only in Chrome

Question: I have Google Chrome 6.0.447.0 (dev). Since a few days ago, YouTube basically doesn't work for me anymore. When I try to access anything but the home page, I get a YouTube-specific page saying that "we're sorry, couldn't find the requested page".
Also, when I land directly on an internal page (like when I click on a link to a video), I get a security warning from Chrome saying that "youtube.com" is trying to redirect to a server at "google.com" and that I should not proceed. Then I (obviously) tell Chrome to "proceed anyway" and it gets me the situation described above.
I searched Chrome's support area and found a similar problem with respect to the Kaspersky antivirus. I don't use it (but do use NOD32), and the problem exists in both computers I have (one with Windows Vista and one with Windows 7). Also, the problem is strictly browser-specific, since in Firefox YouTube works just fine.
What should I do?
Comment: reinstall!!!!!!
Answer: Try to clear the browsing data of Chrome.
( Option -> Under the Hood -> Clear browsing data )
Comment: Just tried that now too, still no success.
Answer: Maybe the issue is related to your YouTube/Google account? Try to open Chrome in Incognito mode.
Comment: Tried that now, doesn't work either.
Answer: Amazingly enough, the problem went away without any distinguishable action.


Changing Gmail account belonging to my Google+ account

Question: I've had the same Gmail account now for 5+ years. I have a Google+ account associated with that Gmail account. I want to change my email address, so I created a new Gmail account.  How do I associate it with my Google+ profile?
Answer: It is not possible. Here is the error that I received.

And the full page in the settings menu.
Answer: As you're creating a new GMail account anyway you can do this, but you have to do it from the Google+ end.
Click on the "Mail" link:

and you'll be redirected to this page where you can create a new GMail account which will be associated with your Google+ account:

It means you'll create another new GMail account, but as you're doing that anyway you can just abandon the first "new" account you created.


Data Source for Speed Limits

Question: I am not even quite sure how this data would be organized. But I am looking for a data source for different speed limits in the US correlated to street name.
Answer: The best source at a broad level is from the Federal Highway Administration.
There is a also variety of open data on traffic safety. Some of this has embedded speed limit information as well as other information, such as fatalities and accidents. There are also some state speed zone data zones, such as those for Virginia.
There was a question on another Stack Exchange about this as well: "you can derive an approximate max speed limit by looking at the national speed limit for the type of road in the country of interest" derived from OpenStreetMap.
The DOT National Transportation Library has FAQs about the National speed limit and speed limit laws. Speed limits are governed by state and local jurisdictions. Some roadway data from a subset of states is made available through the Turner-Fairbank Highway Research Center (TFHRC) (or pull a data request). Reference librarians are available to help with specific data requests.
(Disclaimer: I am the Evangelist for Data.gov. A contractor with Dept. of Transportation also provided information for this answer.)
Answer: Considering that Google and others estimate travel time, it seems likely that this data may have been compiled (unless they are just guessing by road type). I know of no way to get to this directly but it might be worth pursuing/requesting. I could imagine that they might want to protect it, assuming they actually have compiled it.
Another source of data is http://www.wikispeedia.org. They seem rather interested in speed limit signs but they do have an API.
Otherwise, you may be able to get some government data but smaller roads are generally regulated by local authorities.

Data Source for Speed Limits


What resources would you use to determine if something's real or woo?

Question: If you've been told about something for the first time (for example ice circles from William Shatner's "Weird or What?"), what resources (eg specific websites) would you use to determine if it's real or not?
Answer: Well, if it's something like a treatment or a phenomenon that there is a well defined term for, and you just want to read up on whether or not there's scientific support for it, I'd say Skepdic is a handy resource.
If it's something completely novel; apply skepticism. That's not the same as dismissing something. If you can't determine if something's real or woo, then you can't, and you should approach it accordingly. It's less credible than something that's been proven real, and it's more credible than something that's proved to be woo. This is where you can unleash your own common sense, and just ponder how plausible it sounds.
Sometimes you'll be wrong. Lucky for you, skepticism is not about 'being right all the time'. Looking back at this image of the Guatemala sink hole, I remember thinking it looked pretty damn photoshopped. I still reckon it does!

Back then, this was pretty much the only image you could find, wherever you looked, and everybody was citing the same loose news story. All warning flags up - be skeptic about this one!
The reason I picked that example is that I no longer doubt that it exists. My skepticism led me to the wrong conclusion, but that doesn't mean I was wrong to apply it. So what's with the rant? Well, what I'm trying to say is simply that as long as your default mode is skepticism, you can be reservedly optimistic about a news item or cautiously dubious. Be aware that you don't know, and you'll be fine.
The cases where you can actually go to a source and read up on something are the boring cases. For those, Skepdic or Wikipedia will do.
Reliable go-to sources are not an excuse not to be skeptic, anyway. The Oxford English Dictionary had the wrong definition for how a siphon works for a hundred years, remember.
Comment: If it's any consolation, that looks photoshopped to me too.  I've been doubtful of quite a few things that turned out to be true.
Comment: +1 for "skepticism isn't about being right all the time". Exactly! It is better to be wrong for good reasons than to be right for the wrong reasons, in average and in the long run. A psychic can have a lucky guess, and a skeptic can have been too skeptical, but in the long rung the skeptic gets fooled less.
Answer: Your question seems to be more on seeking then on skepticism. The general approach would be: Find something on the internet (using search-engines, but also to batlle 'the hidden web', special database-drive sites), check your source, repeat.
But to give some more substance to this answer:
Meta / General advice
this site
Start out by searching the site your are looking at If you cannot find the answer, but you do find questions, come back and add your findings as an answer after you've searched
Wikipedia
Looked down upon as it may be, wikipedia is a great resource. Or better, Meta-resource. If you can find a good article, the references are the stuff you are looking for. The general information on the page should be referenced (if you are lucky), and you should use these references as a starting point. As it is wikipedia, check these references for validity.
Google
Even more meta is ofcourse google: look up your subject, and then do the meta-check: find out something about the formerly-unknown-to-you sources. You can try to pinpoint known sources using the site: tag.
General skepticism
The various skeptic societies have a lot of articles online. But most of the time they are easily found using google, or even better: the specific pages within their sites (about your subject) can be found like that.
Specific sites
Urban legends: Snopes
Another good startingpoint might be Snopes, for those hard-to-kill urban legends.
Medical
The go-to site for medical articles is PubMed
More could be added later, I must be off to work now
Comment: @Andrew Grimm:  One thing you can do with a Wikipedia article is look at its edit history.  If there's lots of sizable edits, and when I look at one version it's much different from what's out there now, I wouldn't trust it much.
Comment: Wikipedia's not bad (I contribute to it myself), but so many woo believers try to hijack it with varying levels of success.
Comment: I would add that this site should be added to the list now.
Comment: How could I forget that! Fixed :)
Answer: For scientific questions, a better resource than Google is Google Scholar. This searches for scientific articles. Caveat: It looks for documents that are formatted like scientific articles. This does not automatically mean that the article has any scientific merit. Look what Journal the article appears in. Is it Nature, or is it the Journal of Homeopathy and Woo?
If you are affiliated with a University, chances are you have access to the ISI Web of Knowledge, which is a powerful database for scientific publications.
Comment: Is the ISI likely to include the ''Journal of Homeopathy and Woo''?


Can I buy Xbox Live games via PC and transfer them on a flash drive to a Xbox 360 internal HDD?

Question: Due to the region restriction I cannot access Xbox Live on my Xbox, even if I purchased a Gold membership. However it seems that I can purchase games from Xbox Live Marketplace on a PC. I assume this means I can then download them on the PC, and I would like to know if I can transfer them through a flash drive to the 250GB internal HDD of my Xbox 360 console, and then run them from the HDD.
Comment: I can't speak to other regions, but I don't believe downloading them to a PC is ever an option. Also, the portion of a USB drive formatted for the Xbox isn't accessible to browse or copy data to on a PC without likely something that isn't quite legal.
Comment: I never tried, but it seems that as long as I was asked for the credit card details, I may be able to buy a game or download a free demo on the PC HDD or on a flash drive connected to it. Then I will try to play the game from the flash drive or transfer it from the stick to the HDD of the 360 console. The region I am in is Romania. It's at least strange, as long as the XBOX consoles are officially sold in this market.
Comment: How are you downloading the games to your PC? Where are you based?
Comment: Ah, I understand what you were thinking. I've edited that guess into the question to make it clearer what your situation is.
Answer: You have the option of purchasing games for download to an xbox with your profile on it, however, you can NOT download xbox games to the PC and then transfer to your xbox.
Quite the opening for piracy if you could.
I speak from experience in purchasing games online. After buying ANY non-avatar item in the Marketplace you will be presented with a notification stating that your item will be downloaded to your 360 and will appear in your My Games list after it has been downloaded.
It is also entirely possible that the full Xbox Live (Marketplace et al.) is not available in Romania. While it may be a market for Xboxes to exist, governmental issues may be blocking access. If you wish to attempt to play on Xbox Live, Try finding a proxy to run through, I can't go further into detail as I've never had to look that information up. I also don't know international law or the conflicts invited therein.
Source:
Comment: Not bad, not bad. Not actual freehand, but good line weight, colour saturation, and an pleasing amount of aliasing. ;)
Comment: @SevenSidedDie ALL THE MSPAINTS!
Comment: +1! Would be improved 1000% with a freehand circle though.[/deadpan]
Comment: @SevenSidedDie You mean a circle on the image?
Comment: Around the "Your items will appear in…" part, yes. Arqade has many freehand circle connoisseurs among its users who would approve. (It's a bit of a meme / in-joke.) Also, it would just nicely highlight the relevant part of the image.
Comment: @SevenSidedDie Done.


Are there any businesses that will do all of the marketing of photography for you?

Question: There have been some recent discussions about a very similar subject in the chat room, but I thought I'd ask here. Are there any businesses that as a photographer you sign on with them, they do the marketing entirely for you, they find clients for you, they take a cut of your profit, and let you be on your way? Just curious if such a group exists.
Answer: There sure are. There are literally hundreds of companies which perform these sorts of services, they're called 'Photographer's Agents' or 'Photo Reps' and they're analogous to agents and agencies that actors, directors, models, etc. would hire to manage their business for them.... In fact, a great many agencies 'overlap' between photography and filmmaking, so it's not unusual to see talent rosters that include both photographers and directors (and this is often how photographers such as Michael Bay and David LaChapelle make the transition from photography into the world of filmmaking)...
The one thing that these agencies won't do is your last point: 'and let you be on your way'... I've never heard of a situation (and doubt such a situation exists) where a photographer isn't exclusively tied to an agent or agency via a multi-year contract.
It's not necessarily a 'comprehensive' list (it's quite a dynamic industry and agents/agencies are always going under, merging, etc.), but this list will give you a jumping-off point on the range of agents and agencies that are out there, as well as the level and quantity of talent that they represent.
Comment: What types of photography do these agents represent? Is it commercial work, fashion, social, nature, or some combination of the above, plus others?
Comment: I would suspect that the list I cited will skew towards commercial, editorial, and fashion, although I'm aware of several agencies that represent wedding photographers exclusively, and a couple that specialize in 'cause' photography. I would venture to guess (though I don't know for sure) that the representation options would be low, or non-existent for nature and landscape photography, simply because the money to be made in those two fields is miniscule compared to the rest of the genres I mentioned...
Comment: BTW, the list I cited is from a website called 'APhotoEditor' (http://www.aphotoeditor.com/) and it is one of the very best resources on the business side of photography around, in my opinion...


Does a person who curses others lose his right to intercession?

Question: I once read in an Islamqa fatawa that cursing others will revoke your right to intercession if you are among the believers who were appointed to heaven. Is it true? If it is, then what are the hadiths that say so?
Comment: Can you please explain what you mean with "revoke your right to intercession" Thanks.
Answer: It seems Islam Q&A fatwa 21672 is the one being referred to here.  They write:

It was narrated from the Prophet (peace and blessings of Allaah be upon him) that the intercession of some people will not be accepted on the Day of Resurrection, including those who cursed a great deal. Muslim narrated that Abu'l-Darda' said: "I heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say, 'Those who curse will not be witnesses or intercessors on the Day of Resurrection."

It seems to be referring to this hadith:

Zaid b. Aslam reported that 'Abd al-Malik b. Marwan sent some domestic goods for decoration to Umm Darda' on his own behalf, and when it was night 'Abd al-Malik got up and called for the servant. It seemed as if he (the servant) was late (in responding to his call), so he ('Abd al-Malik) invoked curse upon him, and when it was morning Umm Darda' said to him:  I heard you cursing your servant during the night when you called him, and she said: I heard Abu Darda' as saying that Allah's Messenger (ﷺ) said: The invoker of curse would neither be intercessor nor witness on the Day of Resurrection. -- Sahih Muslim 2598 a (sunnah.com)

Searching sunnah.com yielded other sources repeating this hadith: (a) Riyad as-Salihin (sunnah.com), (b) Bulugh al-Maram (sunnah.com), and (c) Sunan Abi Dawud 4907 [grade: sahih] (sunnah.com).


Why is there so many identical Android folders?

Question: I was using the ES File Explorer app, when I noticed there's many different folders with all the same content. Like, there's a "legacy" folder, a "0" folder, and an "sdcard" folder, and it all goes to the same place where my DCIM is and such. I'm wondering if whatever I have takes up three times the space, or its all shortcuts to the same place. I'm confused with all this folder nonsense.
Comment: [What is /storage/emulated/0/?](https://android.stackexchange.com/a/205494/218526)
Answer: Because of how Android has evolved over the years many newer devices have the same files mounted (usually with a bind mount) in multiple places. Others are symbolic links. It's really too bad that the file manager app isn't showing you these details :-/
Comment: I think Ghost Commander app does
Answer: Prior to ICS, Android used /system/mnt/sdcard as the point for mount.
Some versions by manufacturers used /system/sdcard instead.
ICS, thereafter, changed it, but kept existing mount point  for backwards compatibility with legacy apps.
Now,  /system/storage/sdcard0 or /system/storage/sdcard1, particularly, JB on tablets, is used to accomodate multiple user accounts.
Crucial point is the name or alias for external storage is sdcard for legacy reasons and will stay that way. Or in technical parlance, symbolic link in filesystem terms points to sdcard.
Usually, 0 represented internal storage, 1 represented external storage.
The increased trend in dropping SDCard at expense of cheaper to manufacture rewriteable flash drives, bigger capacities, is prevalent.
Answer: I don't know about "legacy" or "0", but /sdcard is a symbolic link to the sdcard device folder.
At the terminal, run "ls -l". Add the end of some lines, you will see:
sdcard -> /mnt/sdcard
etc -> /system/etc

and maybe others depending on your setup. This is standard Linux setup, and makes both places link the same place - so there is no duplication.
Answer: It is not exactly true that they go to the same place. The "0" folder as you call is is what is actually stored on the phone. So if you have your camera taking pictures and storing them on the device as opposed to the SD card, you will see those pictures (DCIM folder) under /storage/emulated/0/DCIM. Under EXTSDCard you will see things stored on your removable card.
Comment: This is not universally true. For example Sony devices sometimes have the external SD in /storage/emulated/1


Does it make sense to watch Better Call Saul before Breaking Bad?

Question: For someone who hasn't seen either of the two shows, in order to get the most clear and continuous plot experience, does it make sense to watch Better Call Saul before Breaking Bad?
Comment: Related: [Does Better Call Saul contain Breaking Bad spoilers?](http://movies.stackexchange.com/q/37076/49).
Comment: It would be more fun that way (if you haven't seen either of them). However the weird thing would be seeing the quality drop once you start season 1 in Breaking Bad, which wasn't very good right from the start and had pretty low-quality cinematic whereas Better Call Saul is a top-quality production from the first second...
Comment: While I think it's better to first watch BB and then BCS (I advocate the same for Star Wars: real world chronology over in-universe chronology); I am **definitely** rewatching BB when BCS ends. I think the shows are cleverly written, enough that I want to rewatch BB and understand Saul better than I did the first time (when I considered him an auxiliary character).
Comment: I'm interested in the slightly different question - which I'm not sure has been asked - whether for _rewatching_ there is a way for serious fans to interleave episodes at all.
Answer: It doesn't matter.
Surprisingly, despite being set before Breaking Bad your enjoyment of Better Call Saul does not depend on whether you have seen Breaking Bad or not. Although characters from Breaking Bad make an appearance in Better Call Saul, as of the end of the first season you do not need to know anything about Breaking Bad to enjoy Better Call Saul, and you do not need to know anything about Better Call Saul to enjoy Breaking Bad.
However, there is no saying that this won't change in the future, and as such I recommend that you watch them in the order they were released — so, all seasons of Breaking Bad first, followed by Better Call Saul.
Edit: As of the end of the second season of Better Call Saul, I stand by this answer for the most part. The second season has reintroduced more characters from Breaking Bad, and although knowledge of them isn't required to understand what is happening in Better Call Saul, some of their appearances have more impact if you know who they are from Breaking Bad.
Edit 2: As of the end of the third  season of Better Call Saul, I now think that the best way to enjoy Better Call Saul is by having first seen all of Breaking Bad. As the show has progressed, it has slowly reintroduced more and more characters from Breaking Bad and shown us events and interactions only hinted at in Breaking Bad - these are far more enjoyable with the context provided by Breaking Bad rather than relying solely on the information given to us by Better Call Saul. While Better Call Saul can still be watched and fully understand on its own, I now believe that those who have first seen Breaking Bad will enjoy the show significantly more.
Comment: While I agree that it doesn't matter from a plot standpoint, I personally *enjoyed* Better Call Saul more after watching Breaking Bad than I think I could have watching it before Breaking Bad.
Comment: I think a lot of the Cinnabon mono-chromatic sequences definitely bear weight to watching BCS after BB too. It helps explain to the viewer WHY he's working there and in obvious disguise (mustache, etc.) from who he originally was in New Mexico. Viewing BCS before, BB might confuse a viewer about what the heck that all means.
Comment: I appreciate very much how you came back to your answer for 7 years to give updates. Well done (and +1 of course)
Comment: I would say that until all the seasons of Better Call Saul are available, it is better to watch Breaking Bad first.  However once the series timeline catches up to when BB takes place, it probably would be a choice of personal preference at that point.
Answer: Prequels are just sequels that happen to take place in-universe at a time prior to the original. In that it's a sequel at heart, there will be arguments to watch it after the original.
There's no hard-and-fast rules but typically a prequel will subtly reference the original. While it's not a requirement to see the original to understand the prequel, it's often a bit more enjoyable as you'll be able to spot those references.
I think the best analogy I can think of is Pulp Fiction. Could pulp fiction be re-edited so the entire film takes place in chronological order? Of course. Would it be as enjoyable of an experience? Probably not.
Comment: Dang, now I've been spoiled that Pulp Fiction does not take place in chronological order.
Answer: At this point it is hard to know, because Better Call Saul is mostly a prequel, but each season also opens with a scene (shot in black and white) close to the end of Breaking Bad. It's unclear if Better Call Saul will eventually recover parts of Breaking Bad and/or if later seasons will jump ahead and tell a full fledged story in the post Breaking Bad world.

"We couldn't really give you an exact amount of episodes," Gilligan
told us. "The reason being—and I'm not being coy here—it's just hard
to know exactly. But you did put your finger on something important.
Just from watching this show you can tell that it's a finite story.
And we know that even further from the fact that this show has to butt
up against the beginning of Breaking Bad. So there is a finite nature
here."
But there's one difference in Better Call Saul's finite nature that
wasn't there with Breaking Bad, which is that there is yet again the
possibility of a whole other story to be told through the
black-and-white beginnings of a post-Breaking Bad world that we've put
at the top of each season," Gilligan says. "So while I think that
there is a definite end in sight for the pre-Breaking Bad story, there
still seems like there could be a lot in the post-Breaking Bad world.
I'm kind of fascinated by that, simply as one of the first fans of the
series. What could come out of that? No promises, but it seems to me
that there's a little more opportunity for scope there than there even
was in Breaking Bad."
http://www.denofgeek.com/us/tv/better-call-saul/264179/better-call-saul-could-become-breaking-bad-epilogue-vince-gilligan-reveals

Season 4 However, has been teased to go right up against Breaking Bad, including introducing more characters that were mentioned in Breaking Bad, but never before seen.

"This is the best season yet," Vince Gilligan told Comic-Con today of
Better Call Saul's fourth season that starts next month. "The overlap
between Better Call Saul and Breaking Bad gets closer and closer,"
added the creator of the Bryan Cranston-Aaron Paul Emmy winner and
co-creator of its prequel of sorts, driving the cavernous Hall H crazy
with anticipation.
"You are going to see some stuff," Gould cryptically declared before
showing a clip of the Bob Odenkirk-portrayed slimy lawyer who first
appeared on Breaking Bad in its second season in 2009. "You want the
last hill on the rollercoaster to be the scariest of all," Gilligan
added.
https://deadline.com/2018/07/better-call-saul-breaking-bad-crossover-tease-season-comic-con-panel-trailer-video-1202429718/

UPDATE - Future Scenes:
Upon the new "future scene" in episode 4.01's opening sequence, it has been suggested by Vince Gilligan, Peter Gould, and Bob Odenkirk that these future scenes may take place right before the end of Breaking Bad in between episodes 5.15 & 5.16. Also Episode 4.01 features an uncredited cameo from a well-known Breaking Bad character. Tonelly there is also a shift in mood, which is most likely closer to how Breaking Bad feels in comparison.
From Screen Rant discussing a recent Podcast:
SPOILER Warning!!! The full article contains Breaking Bad spoilers AND discusses Better Call Saul 4.01 opening scene.

 On this week's edition of the Better Call Saul Insider podcast (via
 The Wrap), a brand new, quite intriguing curveball has been thrown
 into the mix when it comes to those aforementioned flashfowards. While
 speaking on the program, Gilligan, Gould, and Odenkirk suggested that
 these sequences might be set prior to the events of Breaking Bad's
 series finale, and that the person "Gene" most fears the wrath of is
 possibly ...

UPDATE #2 - New Movie:
As it turns out there will be a feature film that takes place post Breaking Bad, featuring the character Jesse Pinkerman.
Not much is know about this yet, including if 'Breaking Bad' will be included in it's title or if it will get it's own name, but more over it doesn't also explain what this would mean for Better Call Saul's future either, if that character will end up in this film or if Jimmy McGill will still also go on past Breaking Bad on the TV series or if it will stay more strictly a prequel?

I'm someone who has not seen more than the Pilot of Breaking Bad, but I do know some spoilers/character arcs. I know that most likley Breaking Bad viewers are getting a lot more out of Better Call Saul then I am, because there are a lot of easter eggs and such, but I have decided to wait until Better Call Saul is over and have the opposite experience, as I enjoy the show greatly without knowing every little detail of Breaking Bad.
Answer: No.
You should watch the shows in the order they were released, not in chronological order of the scenes.
On a practical level, if you watched BCS first and became familiar with the characters, you would experience a jarring jolt to your suspension of disbelief when they noticeably lost a decade in age. Mike Ermentraut would blow your mind.
More importantly, it's a common trick in BCS for a character, familiar from BB, to appear in an apparently innocuous scene. However, we, having seen BB, recognise him immediately as a key character from that show (and therefore from the future of BCS). This gives us insider knowledge about his motivations and likely behaviour that is unknown to the other characters in the scene. Tuco Salamanca popping his head out the door is a good example of this. You would lose this effect if you watched BCS first.
Answer: If Better Call Saul was never made (shudder the thought), then Breaking Bad could be enjoyed on it's own. I watched Breaking Bad first, and now am watching Better Call Saul. I think it's kind of cool to go back in time as "Saul's" character is built for the audience. Both shows can stand on their own, though having Both of them makes for a synchronicity that is of the highest level in my opinion.