Can pentatonic scales define a tonal center?

Question: I have a simple progression F#m > E with two bars to each in 4/4. If I play F#m pentatonic it sounds bluesy and with a bit of attitude, if I play the E major pentatonic scale it seems more "classical". The two scales sound different. Looking at the notes, neither  of these scales have enough notes to say whether the tonal centre of the progression is F#m or E major but even without having all the notes does using E major pentatonic somehow imply E major more than F#m since it has the key notes from the E major chord? And conversely, does the F#m pentatonic scale imply F#m since it has the main notes of the F#m chord.
Comment: Even a single note can define a tonal center. Play C for a few seconds. Now that's your tonal center. Whatever note comes next, will get interpreted relative to C. The F# minor pentatonic scale has the same notes as the A major pentatonic scale. Which notes of the scales do you play, in which order, when, how strongly, in relation to a rhythmic pulse?
Comment: Does this answer your question? [How to find a root note of an unknown scale?](https://music.stackexchange.com/questions/87298/how-to-find-a-root-note-of-an-unknown-scale)
Comment: @piiperiReinstateMonica - yes, and no. I've been 'training' my absolute pitch over several years, and use a single note to check, each time I pass a piano. That note *is* C. However, I hear it as the M3 of key Ab. For what it's worth, it's the 1st note of a t.v. theme - 'Coronation Street' - (which I *don't* watch!).
Comment: Then it seems that you have a chronic Ab syndrome? :) It is subjective, and I can force my mind to deliberately move the tonic somewhere else by simply imagining sounds and feelings. But generally speaking, I'd say that even a single note paints a picture, and you don't need to explicate an entire scale to have a tonal center. And it's subjective - you cannot objectively "calculate" the tonal center from given notes, there's always a listener who forms the perspective. The harmonic context is some kind of a probability field. You might calculate probabilities.
Answer: Let's check which notes they are.
E maj. pent. comprises E F♯ G♯ B C♯.
F♯ min. pent. comprises F♯ A B C♯ E.
Common notes are the same, except for G♯ (in E) and A (in F♯m).
It just happens that those two notes are definitive!
The 3rds in each case!
In key E, there's G♯, in key F♯m, there's A. So that's where the difference comes. The third of any key is maybe the most important, apart from the root, of course! That 3rd is the defining note - is it major or is it minor?
EDIT: there are always two keys which will contain exactly the same notes, especially in their pents. Take E pent. major, and C♯ pent. minor. Exactly the same set of notes, but usually, there are clues as to which key they belong to. Various clues such as 'resting place', 'feels like home', cadences, et al.
Comment: The 3rds are important in determining if the scale is minor or major arent they? In this case I am asking about whether the choice of pentatonic can influence the perception of tonality. If the F#m pentatonic is missing the 3rd (G#) of E major then using it to play a melody over the progression doesn't make the E major chord any less "major". We know the chord is not E minor so the 3rd is irrelevant in the melody isnt it? In this progression the note that is the important one is the D or D# and that is missing. THat is the defining note, not the 3rd of the scales in question.
Comment: @armani - I think I know what you're asking. There are defining notes. Root is an obvious. 3rd is another, and leading note comes into it. Passing notes play their part too. And which note is used on beat 1 in a bar. It makes sense that in an E bar, all I quoted will work anywhere, and the sam e for the F# bar. The awkward (maybe) is fitting A into an E bar, and G# into an F# bar. Not impossible, by any means. If that's what you're getting at.
Answer: A short motif of only 2 chords  often can't define the tonic.
But if you have an entire song you can ask yourself:

what is the final chord of your song?
with which  chord does it start?
is there a dominant tone in the melody?
where do you have a "home feeling" in the tune or in the chord progression?

There are surely many examples that are oscillating between 2 modes or keys (pentatonic or not). Just to name a few spontaneously:

Lady in black
a hundred miles
don't let me down
black is black

But the key of all these songs can be identified - some only by the continuation.
Probably we need more information about your song to tell you on what key it is based.
E major has 4 sharps, F#m has 3 sharps, and both pentatonic don't have a D#.
But what does it matter?
Comment: Then we get songs in nebulous keys - Sweet Home Alabama comes to mind.
Comment: By 'dominant tone', do you mean a note that may be root, or the leading note/tone, or the actual dominant note?
Comment: no, I mean the repercussion tone which is usually the 5th (in modes) e.g.: B in E, C# in F#m
Answer: In general, a collection of notes cannot define a tonal centre.
If we take just "the notes in the C major scale" as a collection of notes (and remove any indication that C is the tonal centre), then depending on the phrasing and cadences you create, that collection can be used as C major (with C as the centre); D  dorian (with D as the centre), E phrygian, and so on. And the same logic will be true of pentatonic scales, or any other scale - what's percieved as the tonal centre is going to depend on the phrasings you use.
The only time a collection of notes can define a tonal centre is when there's only one note in your collection. If your scale is just { A }, with no other notes in, you're going to have a hard job creating the impression that any other note is the tonal centre. (Even then, if you were synthesizing the note, you could do it by emphasizing certain harmonics...)
Comment: Let's take C D E G A (or A C D E G) - Cmaj. pent. or Am pent.. I guess those are the only two options for that set of 5 notes? Or are there modes of pents? Asking, 'cos it's not something I've met yet. Modes of major work fine (except Locrian!), but pent. modes? Maybe not - no leading note/tone.
Comment: @Tim I don't know if anyone actually calls them modes, but I'm pretty sure you can play the group of notes {C D E G A} such that any of them sounds like the tonic.
Comment: so if it is about the phrasing then lets say the melody starts on F#m and ends on E then according to you, the chord progression must be some kind of E. If I had all the 7 notes of the scale I would know but I don't as I only have 6 notes (2 pentatonics) and no D or no D sharp to know if it is E mixolydian or E ionian. My ear tells me that when I play the E major scale over this progression it sounds more like E major is the mother key, when I play the F#m pentatonic scale I hear E mixolydian as the key. Is this how it should be?
Comment: @armani "lets say the melody starts on F#m and ends on E then the chord progression must be some kind of E" - well, maybe, though the way phrasing relates to perceived tonic is more complex than just how the phrase ends. "when I play the F#m pentatonic scale I hear E mixolydian as the key" - I don't see why that would be, as there's no D in that pentatonic scale that would be characteristic of the mixolydian - but if that's what you hear, it's no-one's business to tell you you're wrong!
Comment: You are right, I shouldn't have said Mixolydian. forget that please. My reasoning is that when I play the F# pentatonic it has the notes F# A C# which belong to F#minor whereas if I play E major pentatonic, the E major chord tones are present and that tells your ear something doesn't it? My question here is basically, can the progression sound like F#m even though there is no D or D# in the melody and EVEN if the phrase ends on E? T
Comment: This is the song that I am learningthat has this progression and if you look at the songs melody you will understand why I am asking. Is the opening verse in F#m or in E? Then when the B minor chord comes in it gets even more confusing https://www.youtube.com/watch?v=uZSobH1wiiM


Who pays title fees when selling a car that is titled out of state?

Question: I live in California (where my car is registered) and my car is titled in Virginia (where I bought it). Who would pay the title transfer fees if I sold my car to someone in California? Is the title fee just the published $15 for California and $10 for Virginia, or are there hidden fees? (Could the title transfer trigger some random document request 10 years later that costs $500, as is common with DMV)
Answer: The law will say who does and pays what
The law in Virginia will impose obligations on sellers and buyers to do things and pay fees on the transfer of a vehicle. Similarly, the law in California will do the same.
I'm not going to look up those laws for you but they will be pretty clear and straightforward - vehicle transfers happen hundreds if not thousands of times a day in each jurisdiction.
The contract can, of course, require the seller or the buyer to pay all transfer fees irrespective of who is legally obligated to do so. Failing to do that and causing damage to the other person would be a breach of contract. Most vehicle sale contracts don't do that, they just let the fees fall where they fall.
Answer: You can't register a car in California with an out-of-state title. You have to surrender the out-of-state title and retitle it in California. If it's titled in California, you'll have to pay the California fee. If it's titled in Virginia, then I don't understand how you managed to register it in California.


as of 4/2015 OS X Kindle App: Where are the books located?

Question: After I updated my Kindle for Mac app 2 mos. ago I can no longer find the azw book files on my Mac to convert them so I can read them on my KOBO ereader. I use to find them in a My Kindle Content file but that has disappeared. I have Ult. DRM & Calibre but they won't work without the azw files, and I can't find them on my mac anymore. Can anyone help me?
The answers on this site about this are years old & do not apply to my problem.
Comment: With the latest Kindle version, it's here: `~/Library/Application\ Support/Kindle/My\ Kindle\ Content`
Answer: Kindle.app now uses the Apple Sandbox functionality.
This means that it can only affect and see files in a subdirectory under ~/Library/Containers. The .azw files are in ~/Library/Containers/com.amazon.Kindle/Data/Library/Application Support/Kindle/My Kindle Content
This directory is shown in the Kindle app in Preferences->General as the value of Content Folder and it appears that this can be changed there.
Comment: +1 for the **Preferences -> General** info, which seems to apply to all versions.
Answer: The answer to OS X Kindle App: Where are the books located? indicates that Kindle books get stored in ~/Documents/My\ Kindle\ Content. If this folder doesn't exist or is empty, you can open Terminal and run
find ~ -name '*.azw' -print

to search for them within your user folder.
Comment: As noted in the question the latest Kindle release on 20.4.15 has changed that
Comment: That `find` command works well to find the files quickly, regardless. +1
Comment: Mine are still located in the location specified in this answer. +1 for the search command.
Answer: In order to access the Kindle Content folder, the actual folders you need to navigate through will be visible. In Finder, click on either the Boot Drive on your desktop, usually your only drive, or on the Boot drive, or the item in your left hand panel that corresponds to your User name, and then navigate to the correct path is as follows:
~/Library/Containers/com.amazon.Kindle/Data/Library/Application Support/Kindle/My Kindle Content/

Once you have access to your Kindle content, you can then copy the files to another folder to be processed for conversion, or whatever you plan to do with them. Once you've found your content folder, you can then go into Preferences in the Kindle App and change your destination folder.


Fermenting 1/2bbl and 1bbl batches

Question: As I start planning my pico brewery, I've been thinking about fermenters. I'd love some thoughts on ways to ferment 1/2 and 1bbl (15.5 - 31 gallon) batches. Options for when price is and is not a concern would be great.
Comment: The thought for this question came from a probrewer.com thread -- http://www.probrewer.com/vbulletin/showthread.php?p=52206#post52206
Comment: I would think half barrels would be best as the vessel (sanke keg) is readily available, and still manageable as far as manually moving it around.  A full barrel is pretty darn large, awkward to handle and too heavy to move manually.
Comment: @brewchez the benefit of a 1bbl would be double brewing, saving on yeast and space. But ya, getting a sanke is way easier than a 1bbl conical.
Comment: I would think a one barrel conical would be a waste of money when compared to the cost of a 3bbl conical.  I don't know the actual costs but it seems that a 1bbl would be very pricey over getting a 3bbl.
Comment: From what I've been reading so far, 1 bbl conicals exist for retail purchase, whereas anything 3 and over requires fabricating. But, if someone has a resource, I'd love to see it here :)
Answer: I ferment 10gal batches in a 14gal conical but have been looking at this kit from Brewers Hardware recently to add some capacity at a better price.
The single 1bbl vessel .v. two 1/2bbl vessels is not going to affect yeast pitching quantities, you are just going to take the same original starter and split it between the vessels. The space saving and cleaning labor savings would be quite significant over the long run though.
When you start modeling your production expenses, you will quickly see that at pico brewery scale, labor costs are the most significant component of your costs. This shifts quickly to ingredients and then to energy and space as you move up in scale. Forecast and estimate your production volumes carefully and realistically. You could find that investing in bigger equipment will pay for itself quickly if your brews are in demand quickly. If, that takes longer, then making smaller investments in pilot-scale equipment and brewing more frequently (2-3 batches a day) might make more sense at the beginning.
Comment: Awesome, thanks for the info Jim. Do you work in or around a brewery? Are you on the twitter?
Comment: Nice comments about scale and economies.
Comment: PJ, I think I have been following you for a while - you are @hookedonwinter right? I'm @jmdenmark and like yourself, I only contemplate brewing for a living.
Answer: I use a Sanke keg for fermenting my 10-15gal batches, works great. You can also look into using plastic conical fermentors. You can get them in 15-500+gal sizes.
http://www.usplastic.com/catalog/item.aspx?itemid=25197
http://www.tank-depot.com/product.aspx?id=854
I'm looking at getting a 15gal and a 65gal.
Comment: How do you convert your Sankey's? and where do you get them from?
Comment: You ferment 15 gallons in a sankey?

Fermenting 1/2bbl and 1bbl batches


Could unwanted magnetism be part of my soldering problem?

Question: First off, I'm already resigned to the fact that I am a failure at soldering. (hours of research into dozens of website/youtube how-tos, 4 different soldering irons (albeit inexpensive), 9 or 10 different tips, fluctuating flux amounts, 3 different brands of solder, innumerable attempted techniques, 2 or 3 permanent tiny scars from sub-dermal blistering, and a small pile of charred electronics had, some months ago, broken my will and led to my surrender). But I'm still left with an unproven theory that others here might help confirm or reject. Being that, when faced with being placed onto a targeted location, the solder--after assuming a spherical shape--would, at times, refuse to separate from the iron's tip or, more often, flee the area, rolling the length of the workspace, around obstacles, up walls, or--I imagine--down entire city blocks until I would decide to break off the chase and simply create a whole new obstinate silvery blob, could it be that I had inadvertently magnetized the soldering tip by storing it next to a battery or some other atmospheric anomaly and thereby causing it to disrupt the normal soldering process and ultimately revealing it to be the cause of my circuitrous disability? While I eagerly await your replies I will click on the "unwanted magnetic induction" question to the right that I just now discovered. My gratitude to the team, --smf
Comment: (a) solder is non-magnetic, (b) the classic temperature-controlled soldering iron uses magnetic bits to disconnect the heat when they reach Curie temperature. So ... no. Clean the metal surfaces, and add flux...
Comment: apply heat to the pad for a second and then apply solder. If the iron is hot but the pad is still cold, the solder will just blob up on the iron. My advice would be to look at youtube videos of how to solder, because you're doing something wrong.
Answer: Adding to all previous comments, my experience is to avoid cheap (hobbyist) irons altogether as they do not reach a high enough temperature and cannot maintain that temperature when the tip is presented to the job very well. A tip that is clean and tinned (but not running with solder) should be presented to heat the joint slightly prior to the solder being applied and if the iron is hot enough and the component and board are clean, the solder will flow and it should be possible to do it in around a second. There should be no balling at all. My advice is to invest in a Weller or similar make iron if you are doing a lot of soldering and avoid the cheap ones altogether.
Answer: If you have a clean iron tip but (very) dirty target surface, the solder will "stick" to the iron... well within reason. If you add a lot solder you'll get a large blob rolling. It seems this is the scenario you're describing, although sans a short clip (which you could upload to youtube), it's hard to tell exactly what's going on there. But if you follow the advice below and clean both the iron and target surface (or buy those that don't need extraordinary cleaning measures), you should be fine.
A cheap (not temperature controlled) tip is usually covered in copper. Solder creates an alloy at the surface when you "tin you tip", this is why it sticks to it. If you add a large amount of solder to the tip (not a recommended technique by the way), the blob that forms is kept in place by surface tension because the molten solder acts as a liquid; there aren't any significant magnetic forces involved. If your iron tip gets too hot (or even if it's not too hot but let it on for a long time) you get an oxide layer over it; this oxide becomes visibly black after it gets thick enough. The oxide layer prevents (additional) solder from adhering to the iron, so you get those spherical blobs because of surface tension. You need to clean an re-tin the tip periodically.
The same issue, oxidation, can affect the targets surface, so when that happens you get to chase blobs there too. You're not saying exactly what you're soldering on. Assuming it's a cheap copper protoboard that was not covered in anything protective, you need to clean it thoroughly with (separate) flux solution and possibly even scraping it, although the latter can result in uneven copper. There are some reviews of ad-hoc board rubbers... and the damage they cause... and the residues they leave behind. For single-pad protoboards, it might be ok, but when using a protoboard with any kind of pre-made strips, I stay away from rubbing/scraping. Furthermore you cannot rely on abrasion alone (i.e. just scrubbing/rubbing) to clean copper well enough for soldering; you still need flux (preferably in your solder wire) to deoxidize at microscopic level and keep the copper oxide-free right until the alloy forms.
The best solution (in terms of time wasted) is not to buy the really cheap protoboards. The semi-decent ones are covered in organic solderability preservative (OSP) which prevents the copper from oxidizing (majorly) until you get to work (example). I can solder directly to FR2 OSP'd boards (sans any cleaning) even after a couple of years in storage. The (2% or so) flux contained in the typical hobbyist flux-core solder wire is enough cleaning for those.
The more deluxe version of protoboards (typically those made of FR4) have all the pads pre-tinned (usually through hot-air leveling) and have solder mask between pads; (example). These boards are basically instant success at soldering and have long storage life (they're like post-production PCBs). As this comparative presentation of OSP and HASL says (regarding the advantages of HASL/pre-tinned boards): "Nothing Solders Like Solder", which reflects my own experiences. However, I personally find the added cost of FR4 HASL'd protoboards is generally only worthwhile if you have at least some surface-mount components involved, and then I prefer to buy combo THT/SMD boards (example) [for hand soldering] because cause I'm rather fat-fingered when it comes to tiny surface-mount passives (resistors etc.).
Proper soldering technique matters too, of course; see https://youtu.be/AY5M-lGxvzo?t=102 for instance. But you've probably seen something like that already. The magic that you see in that clip involves a pre-tinned board. A typical example of amateur soldering on (non-tinned) copper board is https://www.youtube.com/watch?v=jr2Z_fztpxg&t=300 You can see it takes longer to make each joint and sometimes the solder doesn't cover the whole pad immediately. The essence of the technique [if you still need a repetition of that] is to have both things you want to solder (e.g. pad and lead) heated up (with the iron's tip) and then touch the joint with the solder wire. Better/faster heat transfer is enabled by a small amount of liquid solder on the iron tip (increasing the contact surface), but this shouldn't be your main source of solder for making the joint.
Let me say finally say that an expensive iron alone (even temp-controlled) will not be a substitute for a clean target surface. It would be a foolish way to allocate your budget if you keep using cheap/oxidized boards. Furthermore, even on a clean surface, temp-control of the tip is nowhere near the ultimate factor in success/failure of the joint; you need consider the thermal mass the whole assembly. Then again, you haven't told us what you're soldering.
And yeah, you can get good results with a totally cheap iron, prolly under $4 by the looks of it... on pre-tinned boards and with a modicum of technique. That guy reminds me how built by first radio kit as a teenager.
Comment: For some experimental data of copper solderability with/without OSP after accelerated/simulated 8-month atmospheric corrosion see http://www.osti.gov/scitech/servlets/purl/10103434/ TLDR version: the effect of OSP is substantial.
Answer: No, magnetism very unlikely has anything to do with your soldering problems.  Solder is not magnetic, and storing a soldering iron near a battery is meaningless, as batteries aren't magnetic either.
You can run into magnetism issues with soldering guns, which are quite different from soldering irons.  With a gun, the "tip" is heated by directly running current thru it.  The current has to make a about-face at or near the tip, which causes a meaningful magnetic field since the current is so high, even though it's just a 1 turn.  Even then, it has little effect on solder or copper.  The only issue I've had with a gun related to magnetism is that some transistor leads are steel inside, and they would be attracted to the bend of the current.
That all said, it seems your real problem is lack of practice.  Nobody is born being able to solder well.  No matter how much you read or watch videos, there is no substitute for doing it, and doing a lot of it so that you develop your own intuition and "feel" for how solder behaves and flows.
You talk about large balls of solder stuck to the iron.  That implies you are feeding the solder on the iron instead of the heated part.  That also means the part itself was too cool, not clean enough, or no flux got onto the part.
It's tempting to feed solder onto the iron because it melts nicely, but that won't necessarily make it flow onto the part.  The right technique is to hold the iron firmly against the part, then feed just a little solder as best you can between the iron and the part.  That solder isn't meant to do any soldering, but to reduce the thermal resistance between the iron and the part.  This also applies a little flux in there, which should allow the solder to flow between the iron and the part.  Once that happens, the part will get heated by the iron.  Wait a second or so, then feed solder into the joint that you are trying to connect.  A little of the first solder should already have wicked there, so the additional solder should now flow nicely around everything and "fill" the joint.  Remove the iron while keeping everything still and blow on the joint gently until it hardens.  You can see that happening by the solder turning from a nice and shiny silver look to a dull silver look.  This shouldn't take more than a couple of seconds.
A temperature controlled iron is a really useful tool for soldering.  A fixed wattage or even "adjustable" iron may seem like a good entry level tool, but these are much more difficult to use well.  Last time I looked around, the Weller WES51 was the cheapest temperature controlled soldering iron out there.  It can usually be found at about $100 street price new.  This is worth it even for medium level hobby soldering.
Comment: "blow on the joint gently until it hardens". LOL.
Answer: It is clearly better to use the best tools available.
I have had success using a sub 5 GBP soldering iron, but I knew how to solder already. Very good soldering irons are the best way to go, however, IMHO it is a bit like bicycle stabilisers, they give extra confidence and mitigate against some types of accident, but once the technique is good, it is less important (unless you plan on doing a lot of soldering).
If you can track down access to a good soldering iron (maybe you are at college), then practice using that. You won't necessarily need anything as expensive once you've 'cracked it.
Better yet, try to practice with someone who knows how to solder. They will likely see some of the errors and quickly help you to fix them.
As everyone has explained, you problems sound like 'dirt', and not magnetism. Cleanliness is key.
I strongly recommend you start with a flux-core tin/lead solder. Tin/Lead solder is much easier to use than lead-free solder. I've taught many people, including children (under 11) to solder, and the difference between 60/40 tin/lead and lead-free solder is extremely noticeable; beginners find tin/lead solder is much easier. Always wash your hands after you handle lead, and don't use lead solder paste.
Clean the thing you are soldering. Don't use water. Use an 'abrasive rubber block', fine emery paper, or clean wire wool (not the type with soap in).
A flux pen can help too, though my experience is cleaning immediately before soldering works well.
I'd recommend a modest-price temperature controlled iron, for example, lots of suppliers, even shops, seem to have this soldering station under their own brand. They are so generic, they often pop up in shop's sales for under 40GBP.
Once you get the technique then you can move on to lead-free solder with silver (which is a bit harder for beginners to use than leaded solder), then once you have that, move onto lead-free. I spend, maybe an hour with people, and the vast majority have the technique within the hour. Some people are a bit diffident, and spend too much time heating the joint, or not enough. It takes some practice to get the 'rhythm', iron-in heat, solder-in melt, solder-out, iron-out.
The most common errors are:
Trying to carry solder to the joint on the soldering iron tip, so the joint isn't heated, and the solder flux has boiled off, producing balls of solder which won't coat the joint surfaces.
Heating the wire, but not the copper track, so the solder 'globs' around the wire only.
Dirty surfaces, so the solder 'globs' and doesn't 'wet' the surfaces.
Heat applied to the track for too long, so that the track peels off.
People have given good advice on successful soldering.
Prepare to do lots of practice. I use stripboard (cheap knock-off veroboard) and ordinary through-hole resistors. Both are relatively cheap, so many hundreds of joints are only a couple of GBP.
Get a magnifying glass, or 'watch makers eye glass' (a few GBP) and inspect each joint every couple of joints. Look to see if the solder has melted and coated the two surfaces. With tin/lead solder it should look shinny, unleaded solder has a duller, less obviously good, finish.
Best of luck.


File transfer 8 GB to 32GB SD card

Question: Can I transfer osmc/kodi files from 8GB SD card to a new 32GB card with up to 80 MB speed?
Answer:
up to 80 MB speed?

There is no possibility of this.  The SD card reader on the pi has a theoretical maximum of 25 MB/s and I have never seen a report of anything much over 20.
Answer: Depends on your hardware and SD card.
If you're using your Pi, the maximum real-world limit would be around 20MBps to 22MBps assuming your SD card can handle it.
If you copy your data using your computer with appropriate hardware (UHS2 microSD and readers, USB 3.0), it would be happy to perform at 80 MBps. But, once you're back on your Pi, it's back at 20MBps.
So basically, you can speed up SD card preparation by using your PC, but you can't go around the Pi's limits once you're using the SD on the Pi.

File transfer 8 GB to 32GB SD card


Where does the phrase "That's a wrap" come from?

Question: Where does the phrase "That's a wrap", meaning "we are finished" come from? I suspect it is from the movie making process, but I couldn't find much information on its origins.
Answer:
...
The O.E.D.'s first citation is from a 1974 cinematographic novel by
Michael Ayrton: "Other cars are heard starting up out of shot and the
lights on the pergola go off so I assume it's a wrap and the crew is
listening to the director saying something consequential and busy
about tomorrow's call."
However, assiduous research turns up this 1957 entry in Charlton
Heston's journal, quoted in the 1998 edition of "This Is Orson
Welles," by Welles and Peter Bogdanovich: "We rehearsed all day . . .
the studio brass gathering in the shadows in anxious little knots. By
the time we began filming at 5:45, I knew they'd written off the whole
day. At 7:40, Orson said: 'O.K., print. That's a wrap on this set.' "
Thus, it appears that the switch from wrap it up to that's a wrap took
place in the 50's. That seems to make its use in "The Aviator" about a
party in 1930 an anachronism (from the Greek ana, "back," and chronos,
"time")."
...
William Safire; "It's a Wrap," The New York Times, Feb. 27, 2005

The 1974 citation quoted is still the earliest in the OED.

A quick look in Google Books turned up:

Where you have five or six union guys sitting around who do nothing
but jack up the cost. There's always one guy who invariably falls
sound asleep before the second take and doesn't wake up until it's a
wrap. Marketing/Communications. Snippet view 1971(?)

as well as this similar, earlier version:

"...I think it's a wrap-up. Now everybody take a breather, will you? Four-thirty run-through, please. Will you all kindly get back here
promptly?" People drifted off the set, the musicians following with
slothlike languor. Monte Sohn; The Flesh and Mary Duncan (1948) Snippet view

It could be that "It's a wrap-up" (perhaps from "Let's wrap it up!") was the first version. And it may have first been used in the theater.
Answer: The noun comes from the verb "to wrap"
OED

2.a. To cover or envelop (an object) by winding or folding something round or about it; to surround with or enwrap in a covering, wrapper, or the like, esp. so as to protect from injury, damage, loss, etc.

In the transferred sense, to wrap something is the final action in dealing with it.
This gave rise to:

7. to wrap up (figurative).
a. transitive. To put an end to, bring to completion; also, to defeat; to wrap it up, to stop doing something. slang.
1922   T. E. Lawrence Seven Pillars (Oxford text) xxxviii. 90   The British were wrapping up the Arabs on all sides—at Aden, at Gaza, at Bagdad.
1937   Amer. Legion Monthly May 9/1   Only one shot to finish before midnight and we'd wrap it up in thirteen days.

Hence "That is a wrap" - "That is finished".
Answer: From Google,

Peter Hider. I believe that WRAP is wrap and it stands for 'Wind Roll And Print'. It comes from the early days of filming in the States when the roll of film having gone through the camera had to be rewound through the camera onto the original spool before being sent for processing and printing.
Comment: The source: http://tech-ops.co.uk/next/retake-thats-a-wrap/ suggests it may be a back-formation.


Best Way To Implement Site Analytics in WordPress

Question: I ran an SEO audit on my WP site and one of the recommendations was to "Implement an analytics tracking tool" so I figure instead of just adding any old plugin or adding the code to the page I would ask in terms of SEO and optimization, what is the best way to add google analytics to my WP site? If there is something better than Google Analytics I am open to ideas. I use WPRocket and I was thinking of going that route. Thanks in advance!
Answer: Try reading https://www.wpbeginner.com/beginners-guide/how-to-install-google-analytics-in-wordpress/#installga-wptheme for steps on how to install in WP without using a plugin.  If you have a child theme, it is much better than using a plugin. Note the link is assuming you don't have a child theme, hence their recommendation to not use the method.
Also, since you're using WP Rocket, WPR don't expect WPR's local caching of the GA tags to work using the code that Google currently generates.  Not a big deal, but you don't want to waste your energy trying to make something work, that must be coded differently.
Keep in mind that the more GA triggers you add, the slower your pages will load.  So, if you're trying to keep your page speed super fast, make sure you limit GA triggers to only one's you are sure you need.
Comment: I get it, i like the functions.php option as I already added some custom code to it, but before I chose this option, is there any downside to letting it get added to all pages? I have not used GA in a while so if I do add it to functions and its on each page, does GA show the hit came from this part of the side?
Comment: @SimpliFixed, I think you're asking if GA shows the hit comes from specific pages??? If so, then the answer is yes.  You can go to Behavior>Events to see what pages had what events triggered.


Locating server for too long

Question: So, I have met a fellow player on Survival Games, we have had so much fun together. I told the person I would be on, but the server won't locate. How can this be if I was playing on the same server just the day before?
Answer: This might be a server side problem, you may be able to try again later the connection might be successful. It could also be a client side problem, and rebooting your device may resolve the problem.

Locating server for too long


Why are all Craft files executable?

Question: I just downloaded the latest version of Craft (2.3.2617) and extracted the zip to check it out. Every file has execute permissions turned on for all users. Is there any reason for this?
Answer: Folders need to be executable for Apache/PHP to be able to open them and read their contents.
I'm guessing it's more of a a case of our build script being overly aggressive and setting the execute bit on files.
From what I can tell, though, setting the execute bit on a PHP script is effectively pointless.
Comment: I believe setting as executable applies to more of a command line functionality. To execute a PHP script in terminal, you set it as executable before you can run the script.
Answer: (I'm fairly new to the Craft CMS Stack Exchange - so I lack the minimum 50 reputation to reply to the comment by @jason-mccallister; apologies in advance for the etiquette faux-pas)
If you're using a Shebang at the top your PHP file (#!/usr/bin/php or similar), then your script will need the relevant execute bit set (for the user, the file's group, or world).
However - if you're calling your PHP script by passing it as an argument to your PHP binary as follows:
<code>/usr/bin/php foo.php
</code>
then you do not need an execute bit set (or the Sheband at the top of the PHP file, for that matter) - only an appropriate read bit.
Comment: So it sounds like it'd be pretty harmless for us to stop setting them to be executable.

Why are all Craft files executable?


Let n belongs to +ve integer and $(1+x+x^2)^n=\sum_{r=0}^{2n} {a_rx^r}$ prove that: $a_r=a_{0<r<2n}$

Question: Let n belongs to +ve integer and $$(1+x+x^2)^n=\sum_{r=0}^{2n} {a_rx^r}$$ prove that: $$a_r=a_{2n-1},{0<r<2n}$$ as well as prove that $$\sum_{r=0}^{ n-1} a_r=\frac{1}{2}(3^n-a_n)$$. I tried to solve this problem by using multinomial theorem and comparing the coefficients but was confused how should I proceed please help me out.
Comment: Not every $a_r$ between $r=1$ and $r=2n-1$ (inclusive) are equal.
Comment: Should be $a_r = a_{2n-r}$.
Answer: The first property $a_r=a_{2n-r}$ comes from the symmetry of the original expression. More formally:
$(1+x+x^2)^n=x^{2n}(1+x^{-1}+x^{-2})^n = x^{2n}\sum_{r=0}^{2n} {a_rx^{-r}} = \sum_{r=0}^{2n} {a_rx^{2n-r}}=\sum_{r=0}^{2n} {a_{2n-r}x^r}$
$\Rightarrow \sum_{r=0}^{2n} {a_rx^r}=\sum_{r=0}^{2n} {a_{2n-r}x^r}$
Equating the coefficients of each power of $x$ gives the required result.
Now that we know the coeffciients $a_r$ are symmetric we can rewrite the original expression as:
$(1+x+x^2)^n=\sum_{r=0}^{n-1} {a_r(x^r+x^{2n-r}})+a_nx^n$
Note that we split out the middle term $a_nx^n$ because it is not paired with another symmetric term. Now substitute $x=1$ and re-arrange.


How do I re-enable the Tags part of Tags and Notes in SharePoint 2013?

Question: We have enabled Tags on the server and we see the option for Note Board but we do not have the option for Tags. Our production server should be set up the same as our development server yet on the production server we have the Tags tab listed in Tags and Notes. We are using SharePoint 2013 (not online) on Server 2012 R2.
All the links I have come across are to enable BOTH the Tags and Notes section. We already have that section enabled but for some reason we cannot see the Tags part and only see the Note Board.
Answer: Couple of things to check for tags part.

Make sure you have Managed Metadata service provisioned in your farm
Make sure Managed Metadata service is connected with the web applicaton. Central admin > application management > manage web application > highlight the web application then click on Service Connection in Ribbon. in pop up make sure MMS connected.
Also from UPA make sure user has permission for tags and notes.Go to Central Administration -> Application Management -> Manage service applications -> User Profile Service Application -> Manage User Permissions -> make sure you have enabled "Use Tags and Notes" for All Authenticated Users.
If above are in place, lastly check if you can browse Managed Metadata service in Central admin. may be recycle the app pool for the MMS service application.
Comment: Yep that was it, our Managed Metadata Service is only running on Prod not Dev. I don't know if this will resolve the whole issue but I have a feeling it will. There are a list of other services that are running in Prod and not Dev as well so we will be sure to fix that. Thank you for your help.
Comment: I also used these links to enable the Managed Metadata Service.
Comment: https://absolute-sharepoint.com/2013/02/step-by-step-guide-to-configure-the-managed-metadata-service-application-for-sharepoint-2013.html
Comment: https://social.technet.microsoft.com/wiki/contents/articles/12713.sharepoint-2013-how-to-configure-managed-metadata-service.aspx


Why was this question about whether airlines check the weight of the passengers' clothes closed as off-topic?

Question: The question Do airlines sometimes check the weight of the passengers' clothes? was  closed as off-topic, whereas there exist many questions pertaining to item weight when checking-in or boarding that are open and upvoted. Why was it closed as off-topic?
Answer: It would be nice if people who have voted to close would take a voice. Because closing on-topic question as off-topic because there's something wrong but other close reasons are hard to match is simply lazy.
I feel your question is much to broad. With over 5000 airlines worldwide, and you asking for anecdotal evidence instead of regular policy, it's impossible that anyone can give a reasonable answer. It's impossible anyone knows enough people to cover all those 5000 airlines with enough statistical data to know for sure that none of them is doing so.
On the other hand, even one single case would be 'yes' to your question. If only 1% of airlines are doing that, you'll have at least 50 answers, each of them correct, only one can be accepted.
AFAIR there was a close reason for list questions, but then it was replaced with too broad, and finally, with need more focus.
Comment: Thanks, the spirit of the question is whether any airline checks for it, not listing all companies who check. If I'm aware that some companies do check, then I'll check the policy of the specific airlines I'm flying with (if I happen to have voluminous clothes).


Sample code for validating custom metabox?

Question: I've found very little on this site or in Google searches for examples of validating metabox custom fields.
If anyone wants to give examples, here are some cases that would be useful
1) Date entered as  05/02/2011 is valid date format
2) Number entered in text box is numeric and between 100 and 500
3) Text in text box is > 25 chars long
My question is not so much the code to validate the fields but where to put the validation code? Use Javascript or PHP?  If it hooks on save-post, techniques for dealing with failed validation -  Update the post?  Don't update the post? - how do you stop it from updating?  Best way to notify the user of the problems.
All suggestions are appreciated.  Sample code is more helpful than just a description of a technique.  ( This would be a very good topic for someone to write an article on. )
Thank you
Comment: Similar question: [Add validation and error handling when saving custom fields?](http://wordpress.stackexchange.com/questions/5102/add-validation-and-error-handling-when-saving-custom-fields)
Comment: Also see: [Use WordPress (built in) Error handling](http://wordpress.stackexchange.com/questions/715/objective-best-practices-for-plugin-development/16246#16246)
Comment: The point of my question was more how to display the error messages to the user than how to validate the individual fields using PHP or Javascript.
   After researching several approaches I finally found one I was able to get working
http://wordpress.stackexchange.com/questions/15354/passing-error-warning-messages-from-a-meta-box-to-admin-notices/15355#15355
  Thanks to those who did answer.
Answer: Straight from the WP Codex @ http://codex.wordpress.org/Function_Reference/add_meta_box, you call the save_post hook and specify the function that will be run to validate/save your data:
/* Do something with the data entered */
add_action('save_post', 'myplugin_save_postdata');

Then you define that function, which will automatically be passed the post id. Additionally, you can access the $_POST array to get the values in your metaboxes:
/* When the post is saved, saves our custom data */
function myplugin_save_postdata( $post_id ) {
  // verify if this is an auto save routine.
  // If it is our form has not been submitted, so we dont want to do anything
  if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE )
      return $post_id;

  // verify this came from the our screen and with proper authorization,
  // because save_post can be triggered at other times

  if ( !wp_verify_nonce( $_POST['myplugin_noncename'], plugin_basename(__FILE__) ) )
      return $post_id;

  // Check permissions
  if ( 'page' == $_POST['post_type'] )
  {
    if ( !current_user_can( 'edit_page', $post_id ) )
        return $post_id;
  }
  else
  {
    if ( !current_user_can( 'edit_post', $post_id ) )
        return $post_id;
  }

  // OK, we're authenticated: we need to find and save the data

  $mydata = $_POST['myplugin_new_field'];

  // Do something with $mydata
  // probably using add_post_meta(), update_post_meta(), or
  // a custom table (see Further Reading section below)

   return $mydata;
}

All of your routines to valid data will be done within this function. In the end, you will likely save the data using something like:
update_post_meta('meta_key', 'meta_value');
EDIT: I realize I did not address the breadth of your question, but since I put the time into this I leave it here to get you a quarter of the way there.
Answer: There's really no suitable way to validate a date field, all you can do is split it up and check it in parts..
There's checkdate(), but as mentioned in the comments on the docs page it cannot be used as an effective means to sanitizing date input..
First thing i usually check is the type of data, if expecting a string then cast to a string and likewise for integer and array values.
// Casting example
$string = (string) $string;
$num = (int) $num;
$array = (array) $array;

For date fields you typically have a seperator between each part of the date, split based on that and cast the parts(however many you're expecting) as integers.
$date = explode( '/', (string) $string );
$date = array_map( 'intval', $date );
// Now count the parts and validate them further - eg. you don't want negative values

Of course this really depends how you store the date and what you're expecting in that field, it's something you'll just have to sanitize appropriately according to your specific needs.
Numeric values are quite easy, first cast to int..
$num = (int) $var_with_num;
// Or
$num = absint( $var_with_expected_non_negative_num ); // absint is a WordPress function

Then check it's within your given range(per your question).
// If it's not in range
if( $num < 100 || $num > 500 ) {
    // Number is not in range
}

or..
// If it is in range - including 100 & 500 as possible values
if( $num >= 100 && $num <= 500 ) {
    // Number is in range
}

Checking if a string is a particular length is easy, so easy in fact i'm just going to link you to the PHP documention for strlen.
http://php.net/manual/en/function.strlen.php
The date values are the most tricky in my opinion, but really it's a case of writing your code to suit what you expect from that field. If you have a field with a date format of D/M/Y for example you know that the / (forward slash) will(should) be present and that splitting on that delimeter should give you an array of 3 numeric values... (if the split doesn't give you 3 values, or any aren't valid numeric values, then the data was invalid)..
Hope that helps.. (and i'm open to critique if anyone has a better method for any of the above).
Answer: To properly validate input, you will need to use a combination of Javascript and PHP.
I highly recommend using the jQuery Validation plugin: http://docs.jquery.com/Plugins/Validation. It will let you validate the inputs immediately and provide feedback to the user that something is wrong.
The second step is to validate the data using PHP.  WordPress has a bunch of built-in validation functions, so I'd start there and if you can't find what you need simply build in the logic that you need.


What was the purpose of the lightning tree?

Question: I don't feel like The Hunger Games: Catching Fire fully explained this. It seems awfully convenient to have a tree where lightning strikes 12 times every hour. What would possibly be the point of this in the "game"? It would only kill someone if they were on it.
Comment: One note: The lightning does not strike the tree 12 times an hour. It strikes once at noon and once again at midnight.
Answer: This is explained a little more in the Novel, and is easier to understand with the hindsight of knowing Plutarch Heavensbee was subversively finding ways to assist the tributes who were complicit in the revolution...
It doesn't explicitly state 'Plutarch did this because of this and this...' because that would be terrible clunky writing, and Collins is a much better writer than most people will give her credit for... it just takes a little logic and deduction.
The 'Lightning Tree' is in the section of the Arena which endures a lightning storm within its hour. The lightning tree introduces (naturally, without raising the suspicions of anyone else) the element of controlled, predictable burst of electricity in a pre-designated location, which obviously is of benefit to Beetee.
Furthermore, it is a clear and concise way for the tributes to keep track of what time it is, even if they aren't anywhere near the section that is enduring it's 'hour'. It's the equivalent of Big Ben striking 12.
It's never pro-filmically shown that Beetee had discussed a plan with Heavensbee beforehand, but it's interesting that Beetee is insistent on carrying around that spool of electrical wire throughout most of the film. It's quite an encumbrance to keep hold of, 'just in-case', so it could be inferred that Beetee had the plan all along.
Answer: Note that Heavensbee, the current gamemaker, is in fact working for the insurgents. He would have absolute power to decide to create something like a lightning tree, for Beetee to use. And since its hazardous nonetheless, it doesn't raise any other official's eyebrows.
Comment: Does the book or movie state that Heavensbee intentionally wanted the tributes to short out/explode the dome, using the lightning? I guess I'm just struggling with that plot point.
Comment: Sorry, I haven't read the book. I'll consult my sister, who have, though it was a while back...
Comment: @NicholasHead in as so much that Beetee and the others were in on the plan. Only Katniss and Peeta were not. As Haymitch says to Katniss in the jet after the rescue, "that was always the plan" to get her out. So yes, the plan was always to have Beetee electrocute the force field to blow it up.


what does it mean to "measure a qubit" if measurement is defined on operators

Question: As far as I know "measurement" depends on the two variables : state and operator.
So what exactly does measuring a qubit mean? is it implied that the operator is
the $Z$ operator on that qubit? In that case does the "deferred measurement principle"
apply to all operators or just the single $Z$?
Comment: Without any other context I would interpret an algorithm with instructions to "measure the qubits" to mean to measure in the computational $\{|0\rangle,|1\rangle\}$basis. But if there were instructions to "measure the qubits in the Hadamard basis" then that means either do a Hadamard first and then measure in the computational basis, or equivalently measure in the $\{|+\rangle,|-\rangle\}$ basis. The principle of deferred measurement applies regardless.
Answer: I'm not sure if your question is about "what is a measurement", or what does "measuring a qubit" mean if we don't specify the operator or basis.
For the first answer, a generic measurement (called POVM: positive operator-valued measure) is defined by a set of positive semi-definite Hermitian matrices $\{\Pi_i\}_{i \in M}$ such that $\sum_i \Pi_i = I$. For instance, if you measure a qubit in the computational basis, then the operators are $\Pi_0 = |0\rangle \langle 0|$ and $\Pi_1 = |1\rangle \langle 1|$ (and you can trivially extend it to multi-qubit). Then, when you measure a quantum state $\rho$ (where $\rho$ is the density matrix of the state, that can be obtained for any pure state as $\rho = |\psi\rangle\langle\psi|$) using a POVM, you get two objects: a classical string $i \in M$ (the outcome of your measurement) and a post-measured state $\sigma$. More precisely, the probability of getting outcome $i$ is $Tr(\Pi_i\rho)$ and the post-measured state is $\sigma = \frac{\Pi_i \rho \Pi_i^\dagger}{Tr(\Pi_i\rho)}$ (the denominator is just used to renormalize the state). That's all.
For the second answer, typically, if you read "measuring a qubit" or "measuring a quantum state", you need more details to know exactly which measurement you need to apply on the qubit. Depending on the context, either you can guess the basis/POVM that is used, or it can also mean "for any POVM". Typically, however, when we say "measuring a qubit", it often meanss "measuring a qubit in the computational basis" (see above for the corresponding POVM).
Concerning the "deferred measurement principle", it applies for any measurement: you can always choose the postpone the measurement to the very end of your computation (unless, of course, if your operations depends on the result of the measurement… and still you can purify the state if you really want to postpone everything). This comes from the fact that $U \otimes V = (U \otimes I) (I \otimes V) = (I \otimes V) (U \otimes I)$, or, pictured:
 =  =
(I used random gates as I was lazy to draw it for arbitrary gates, but this is true for any quantum process) This is directly linked to non-signaling (if the order of the measurement were important, then you could use it to transmit information, for instance by measuring later or sooner a quantum state).
Comment: I was quoting what I see in many papers, presentations...no additional context is provided. Your answer seems to be providing the implied context. You use a set of projections instead of a single operator. To me a single operator seems more natural...you can build up the projections from it, for example $\Pi_0=(1+Z)/2, \Pi_1=(1-Z)/2$,...
Answer: Measurement is defined with respect to a measurement basis. Given a state $\rho$, and a measurement basis $\{|u_k\rangle\}_k$, the measurement results in the outcome probabilities $p_k = \langle u_k|\rho |u_k\rangle$. More generally, measurement can be defined as a POVM $\{\mu_k\}_k$, in which case the outcome probabilities are given by $p_k=\operatorname{Tr}(\mu_k \rho)$.
This is always the case. When people say that they are "measuring an operator/observable", call it $A$, what they usually mean is that (1) the state is being measured in the eigenbasis of $A$, and (2) that the measurement probabilities are being (classically) post-processed to compute the expectation value $\langle A\rangle_\rho\equiv\operatorname{Tr}(A\rho)$.
In many-qubit circuits, unless otherwise specified, when just talking about "measuring the qubit" most sources will probably implicitly talk about measuring it in the computational basis (or if you prefer, the eigenbasis of the Pauli $Z$ operator).
Comment: an operator carries more information that its eigenbasis. For example, its eigenvalues are redundant information if all you're interested in are outcome probabilities. Operators are often used in the context of computing expectation values, in which case they describe computing specific linear functionals of the outcome probabilities in a given basis, in which case the eigenvalues are the associated weights. Note also that *any* (orthonormal) basis is a "measurement basis", and any orthonormal basis is the eigenbasis of some Hermitian operator.
Comment: Is there a case when the measurement basis is *not* the eigenbasis of an operator $A$?...what's the advantage of using basis instead of operator? is it ordering of the basis?
Comment: To me measuring an operator seems more "natural" than measuring in a basis or measuring a qubit...I'm sure that depends on what you learn first. At any rate I see the translation between the different variations now; thanks.


ASP.NET Get Web Response when HTTP Status is NOT 200 OK

Question: I need to read the response from an HTTP GET in situations where the Response Status code is not 200 OK. Sometimes it is 401, other 403, however there will be a Response content. If I try to use the HttpWebResponse and HttpWebRequest classes, it throws an exception when the response status is not 200 OK. Any suggestions?
Answer: <code>var request = (HttpWebRequest)WebRequest.Create("http://stackoverflow.com/1");
try
{
    using (WebResponse response = request.GetResponse())
    {
        // Success
    }
}
catch (WebException e)
{
    using (WebResponse response = e.Response)
    {
        HttpWebResponse httpResponse = (HttpWebResponse)response;
        Console.WriteLine("Error code: {0}", httpResponse.StatusCode);
        using (var streamReader = new StreamReader(response.GetResponseStream()))
            Console.WriteLine(streamReader.ReadToEnd());
    }
}
</code>
Comment: Except if `response` in the catch is null, like it was for me, then it throws another exception and is utterly useless...  I was testing with a deliberately disconnected server, though.  My exception "Unable to connect to the remote server" was good enough for me for that.  But yeah, normally exceptions are light on the Status Codes and details for other issues.  My advice with this code - just handle for null `response` - probably  `return e.ToString();` would be good enough for that case.
Comment: AND NEXT TIME -- add a `request.Credentials = CredentialCache.DefaultCredentials;` as the 2nd line to this code!!  I kept getting `(401) Unauthorized` errors and couldn't figure it out, because I was calling a web service where I had added that line, and then I was trying this code!  Gotta do it to this one, too!
Comment: And this code doesn't deliver the `401`, it will say `Unauthorized` for the StatusCode.


Any exercise to extend my finger flexibility?

Question: When playing guitar, the fingers need to be extended flexibly in order to hit the right part of a string. Is there any exercise to make them more flexible when I am not playing guitar?
Comment: I don't have any particular answer but I know this: Better be careful when trying to come up with alternative offline exercises. It often does harm than good due to the mismatch between the real playing and the emulated one.
Comment: Your question doesn't appear to match the title. You really don't want to be trying to extend your tendon unless you already have a problem with your fingers. I'll leave an answer, but can you confirm what you actually mean?
Answer: The single best thing you can do to improve flexibility, speed or strength for playing guitar is to play the guitar. A lot.
Try different styles as this will provide bbth a benefit from speed and strength, but also open you up to different types of music, eg fingerpicking, classical, flamenco, rock, metal etc


Getting Chatter to include Opportunity name on mentions

Question: Here's a fun one.  We are using Chatter in order to notify team members as to new opportunities.  The problem comes when a member gets mentioned and the email sent out includes the subject line of "Joan Salesforce mentioned you in a post"...how can I get this notification to send with the subject line similar to when someone comments on the opportunity (e.g. "Joan Salesforce also commented on a post on Opportunity: VisualSalesForceApex - 2013)?
Answer: I was discussing this very topic with a colleague earlier today. As far as I know Salesforce generated chatter emails are not configurable.
Your only option will be to roll your own... The 2 biggest problems I can think of would be:

you could exhaust your daily email limit if you are a big organisation
Users will receive 2 emails about the same thing, or you will have to disable chatter email altogether. Disabling chatter emails could be a very big problem all on its own.
Comment: my org is not very large, so we're a respectable distance away from the email limits.  Would you know how to go about programming it, or possibly point me to a resource that would guide me?


When do I use two-way mixed, two way random and one way random for the Intraclass correlation coefficient?

Question: I have a question about the intraclass correlation coefficient. I have 62 patients for whom I calculated the breast tumor volume. The surgeon who resected the tumors did the same thing, but without seeing my calculations. Now I want to know something about the inter-observer agreement for this group by using the ICC. Can someone help me: should I use the two-way mixed, two-way random or one-way random method?
Answer: Your question has been downvoted with no explanation as to why, which is not very helpful in my opinion, as you don't get any hints on how to improve your question to get an appropriate answer.
Anyway, the question as to which ICC to use depends on 3 things (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4913118/):

The "Model" (e.g., 1-way random effects, 2-way random effects, or 2-way mixed  effects);
The "Type" (e.g., for decision-making, will you use the average of the measurements produced by the surgeon and yourself or just the measurement produced by the surgeon);
The "Definition" of relationship considered to be important (i.e., consistency in measurements between the surgeon and yourself OR absolute agreement between the surgeon and yourself in terms of measurements).

Please read the article and see if you can figure out what the answer is - then you can come back with a more pointed question here.
Answer: The two-way mixed and two-way random methods will yield identical ICC values, so this choice will likely be inconsequential. The only difference is in interpretation: The two-way mixed model treats rater as a fixed effect, the two-way random model treats it as a random effect. The estimated ICCs will however be the same, see e.g., Table 4 in McGraw & Wong (1996).
The one-way random approach assumes that there is only a random effect of patient. As your question indicates that there are two raters, most likely you will want to model this rater effect, so a two-way (mixed or random) method seems most appropriate.
McGraw, K. O., & Wong, S. P. (1996). Forming inferences about some intraclass correlation coefficients. Psychological methods, 1(1), 30. https://doi.org/10.1037/1082-989X.1.1.30


What Happens to OTM Puts Following a Cash Aquisition?

Question: Say I purchase OTM puts with a $5 strike and the underlying company is acquired through a tender offer that pays $19.00 cash per share. My contracts are accelerated and adjusted to reflect the new terms. The contracts become worthless, but do I receive the premium, and which premium, if any, do I receive? The premium that the acquiring company is paying per share or the premium of the $5 strike?
Comment: Buying an option is a debit transaction.  You paid that premium.  The only way to get some of it back (or profit) is to sell it.  In your scenario, as Joe pointed out, with the accelerated expiration, your  put has no value and is  worthless. Buh-bye premium :->(
Comment: The option is only a right to sell the stock at the strike price.  If someone acquires the company (buys all of the stock) at a certain price, then the price of the stock is effectively fixed from that point on until the stock is de-listed.   As a result, any right to sell the stock at a lower price becomes worthless (unless of course, the deal falls through).
Answer: You purchased a $5 strike put. Basically betting the stock would drop to lower than $5. The stock ends its life at a value of $19/sh. Your put expires early, worthless.


Does lens age affect color produced?

Question: I came into some discussion with my friend, and my friend said that age may affect the color produced by the lens, i.e., a newer lens produce better color than an old lens (of the same model). Is this true? And why is it so? What component in the lens that is subject to wear and tear in a way that affects color?
Answer: In general, lenses do not degrade in this way. However, some old lenses made up until the 1970s contain elements made of thorium oxide — a radioactive element which yellows as it ages. These were used because they have a different refractive index, with low dispersion — so, generally, better-quality lenses, just as fluorite crystal or other exotic elements are used today. It's also possible that adhesives (used to bond lens elements to each other) or coatings used in older lenses may yellow as they age. In both of these cases, if there's enough effect to make a difference, you should see it when just looking through the lens.
The other difference may be in newer lens designs vs. older ones. This shouldn't affect the case your friend is talking about (same model over time), but may be the source of the confusion. Design of coatings changes, as does the types of glass used. And this can be very strong between manufacturers — for example, while I haven't found this anywhere official, many people believe Sigma intentionally introduces a slight color warming effect in their lenses.
Comment: With thorium lenses, [dosing with UV](http://www.rangefinderforum.com/forums/showthread.php?t=101883) can reverse the yellowing.
Answer: Nonsense.  Lens glass does not generally discolor over time, and the coating is very thin.  Even if some discoloration occurred, you could easily see this simply by looking thru the lens.  I have some old lenses, some made before WWII, and none of them are tinted to the point where I can notice this by looking thru them.
Even if some discoloration occurred for some reason, it would be slight enough to be correctable.  The difference between lenses would be significantly less than the difference in the color of ambient light.  Your existing methods of dealing with ambient light color variations will cover any additional slight shift due to lens discoloration.  Take a white or gray reference shot as usual, and all should be well.
Comment: My "negativity" (read: downvote) was because you used the word "nonsense" about a real phenomenon. Even if you consider it rare, it's certainly not nonsense. Here's a Super Takumar 35/2 that I briefly owned... the discoloration was apparent by looking through the lens, or in shooting with different lenses. https://dl.dropboxusercontent.com/u/20239870/20140202-K5ii-04903.jpg
Comment: Some older lenses containing trace amounts of rare earth elements do yellow with age. It can be ameliorated by prolonged exposure to UV light (without a UV filter blocking the UV rays, LOL). See http://camerapedia.wikia.com/wiki/Radioactive_lenses
Comment: Also, http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm
Comment: As I said, lens glass does not *generally* discolor over time.  Some types discolor a little, but the other point is that this is small compared to the variation in ambient light color you have to be set up to deal with anyway.  I don't understand all the negativity here.  Think of all the lenses you've seen, and then how many of them were visibly discolored.  Betcha most people here haven't seen a single discolored one.

Does lens age affect color produced?


Converting jiffies to milli seconds

Question: How do I manually convert jiffies to milliseconds and vice versa in Linux? I know kernel 2.6 has a function for this, but I'm working on 2.4 (homework) and though I looked at the code it uses lots of macro constants which I have no idea if they're defined in 2.4.
Comment: What is the function used in kernel 2.6?
Comment: @kaciula See jiffies_to_msecs() in include/linux/jiffies.h
Answer: As a previous answer said, the rate at which jiffies increments is fixed.
The standard way of specifying time for a function that accepts jiffies is using the constant HZ.
That's the abbreviation for Hertz, or the number of ticks per second.  On a system with a timer tick set to 1ms, HZ=1000.  Some distributions or architectures may use another number (100 used to be common).
The standard way of specifying a jiffies count for a function is using HZ, like this:
schedule_timeout(HZ / 10);  /* Timeout after 1/10 second */

In most simple cases, this works fine.
2*HZ     /* 2 seconds in jiffies */
HZ       /* 1 second in jiffies */
foo * HZ /* foo seconds in jiffies */
HZ/10    /* 100 milliseconds in jiffies */
HZ/100   /* 10 milliseconds in jiffies */
bar*HZ/1000 /* bar milliseconds in jiffies */

Those last two have a bit of a problem, however, as on a system with a 10 ms timer tick, HZ/100 is 1, and the precision starts to suffer.  You may get a delay anywhere between 0.0001 and 1.999 timer ticks (0-2 ms, essentially).  If you tried to use HZ/200 on a 10ms tick system, the integer division gives you 0 jiffies!
So the rule of thumb is, be very careful using HZ for tiny values (those approaching 1 jiffie).
To convert the other way, you would use:
jiffies / HZ          /* jiffies to seconds */
jiffies * 1000 / HZ   /* jiffies to milliseconds */

You shouldn't expect anything better than millisecond precision.
Comment: If you're interacting with HZ from userspace, use USER_HZ instead.  'man 7 time' says to use sysconf(_SC_CLK_TCK) to fetch this value.
Comment: I don't see an obvious way of doing this from a shell script, but it's generally a constant unless you've been doing unnatural things to your kernel.  On x86 USER_HZ is 100.
Comment: Is it possible to obtain the HZ value using CLI?  E.g. after reading utime from /proc/[pid]/stat on 2.6 kernel, can I easily convert it to seconds without need to compile it from C code?
Answer: Jiffies are hard-coded in Linux 2.4.  Check the definition of HZ, which is defined in the architecture-specific param.h.  It's often 100 Hz, which is one tick every (1 sec/100 ticks × 1000 ms/sec) 10 ms.
This holds true for i386, and HZ is defined in include/asm-i386/param.h.
There are functions in include/linux/time.h called timespec_to_jiffies and jiffies_to_timespec where you can convert back and forth between a struct timespec and jiffies:
#define MAX_JIFFY_OFFSET ((~0UL >> 1)-1)

static __inline__ unsigned long
timespec_to_jiffies(struct timespec *value)
{
    unsigned long sec = value->tv_sec;
    long nsec = value->tv_nsec;

    if (sec >= (MAX_JIFFY_OFFSET / HZ))
        return MAX_JIFFY_OFFSET;
    nsec += 1000000000L / HZ - 1;
    nsec /= 1000000000L / HZ;
    return HZ * sec + nsec;
}

static __inline__ void
jiffies_to_timespec(unsigned long jiffies, struct timespec *value)
{
    value->tv_nsec = (jiffies % HZ) * (1000000000L / HZ);
    value->tv_sec = jiffies / HZ;
}

Note: I checked this info in version 2.4.22.
Answer: I found this sample code on kernelnewbies.  Make sure you link with -lrt
#include <unistd.h>
#include <time.h>
#include <stdio.h>

int main()
{
    struct timespec res;
    double resolution;

    printf("UserHZ   %ld\n", sysconf(_SC_CLK_TCK));

    clock_getres(CLOCK_REALTIME, &res);
    resolution = res.tv_sec + (((double)res.tv_nsec)/1.0e9);

    printf("SystemHZ %ld\n", (unsigned long)(1/resolution + 0.5));
    return 0;
 }

Answer: To obtain the USER_HZ value (see the comments under the accepted answer) using CLI:
getconf CLK_TCK

Converting jiffies to milli seconds


How do I find the source of my virus that creates popups when new programs start up

Question: I have a virus on my windows computer. It seems to create new chrome tabs when I start using a new application. For example, if I go to Youtube and I start up flash, it may create a new tab.
When I navigated to the superuser question entry field it created a new tab and that tab was an advertisement for a survey to win 50 bucks.
A friend of mine commented:

Hmmmm. You might be able to delete it manually if you find where it is
  on your computer. If you go in the Task Manager, there's an option to
  show the command line argument that was used to run a program so you
  might find its filepath that way. You could also just try and stop it
  from launching by deleting the launch operation from the Windows
  Registry. Just google Regedit and find the section for .exe files and
  check if there are any fishy things in it.

Any help is appreciated! :3
Windows 8
EDIT:
I've run
avast antivirus
ad-aware antivirus
ad-aware quaranteened some files, but the problem persists.
Comment: I typically am reluctant to point out the obvious, but couldn't you just run an antivirus program? I assume one is installed, right?
Comment: Matt sorry i should have added that. I'll edit the original with an update mentioning those things.
Comment: I wonder if its a browser 'addon' - does this happen with all browsers?
Comment: "just google regedit and find the section for .exe files" hehehe good advice. ;)
Comment: JourneyMan -> It appears to be happening on firefox and chrome
Comment: http://www.wikihow.com/Use-Regedit
Answer: I assume this issue also occurs across different browsers not just Chrome?  Do a test...can you download a new browser ie Firefox , fresh install and see if the ads still pop up right away.
It is very likely and simply a resident program and can be killed from within Task Manager -- Just post here a list of your running tasks and we can tell you which one is the evil doer.  Sadly i dont have Windows 8 (only using W7) so i may not be entirely familiar with all the new System processes.  I suggest you open Task Manager, right-click for Properties for each running process and identify and close each app (via "End Process") that is not an executable file located within the C:\Windows folder.  And then see if the pop ups still persist.  Also run Microsoft's monthly updated "Malicious Removal Tool" (type "mrt.exe" from the Run dialog -- assuming the tool is updated for July 2013) to make sure none of your System files have been tampered with.  Yes the obvious thing a spam tool writer would do is copy their file into the system folder and rename itself as a benign filename but just want to narrow the field.  After you do all that and the problem persists then jump into the Services (via "services.msc" from the Run dialog) and turn off Services that are not system specific.  You should be able to identify which ones via "msconfig" (via Run dialog) and clicking the "Services" tab and selecting "Show only non-Microsoft Services" -- the ones that remain try turning them all off (or rather: Stopping the service) and then checking your browser.
Another possiblity is that they replaced your winsock stack with their own infected one which monitors your in/outs.
If they are really creative they could simply inject their dll into a running browser like Chrome which then it could do all sorts of things.
But in most cases you have a evil running process (or service) which can be spotted and killed via he Task Manager.
Anti-Virus/Anti-Malware tools aren't very reliable since its way too easy to make apps to get around them.  Experience to know what is happening and why is the best defense.
Comment: http://imgur.com/EZCjglc

Here is another symptom. underlined links with advertisements associated.

They appear in firefox and in chrome.
Comment: http://pastebin.com/689EyS6P

heres a list of my processes using get-process in powershell
Comment: windows maliciious software removal tool finds nothing.


How are LEDs timed? (How is the pulse latency measured?)

Question: Please excuse the awkward phrasing of the question; it seems that LEDs have pulse latencies of nanosecond and sub-nanosecond durations. The question is, how was it possible to measure such precise increments of time? Is there ultra-high frame rate footage of this?
Comment: Not really hypothetical: It's commonly required to determine maximum usable signal frequency of an LED or laser diode, to allow binning for different applications. Manufacturing variations are high enough that a general datasheet or manufacturer's info is not good enough for determining actual maximum data-rate.
Comment: What are you really trying to do, and how well do you need to know the latency? Generally if you're designing something with pulse widths or delays below 5 ns or so, you try to design it so the exact value of the delay doesn't matter.
Comment: This question came up in a comment to http://electronics.stackexchange.com/questions/86717/what-is-the-latency-of-an-led. It is a theoretical question.
Comment: Yes, this is more of a hypothetical question regarding how manufacturers actually determine such latencies.
Answer: An inexpensive method of measuring rise and fall time limitations of an arbitrary waveform, is to start with a square wave of a moderate frequency, and then systematically increase the frequency while keeping duty cycle constant at 50%.
The average intensity of emitted light is easily measured, even by using something as basic as a CdS light-dependent resistor (LDR) cell.
As the switching frequency increases, rise and fall slopes become dominant factors in intensity of resultant signal, as illustrated in the graph below:

Note that the rising slope, and separately the falling slope, are nearly identical for signals of 50 through 200 MHz. What changes is the amount of time per cycle the signal stays high, or low. At 200 MHz, the LED intensity never reaches the plateau at all.

For very low frequencies, the average intensity is reasonably close to 50%, dominated by the "on" plateau and the "off" plateau.
As frequency rises, the sloped edges take up a significant part of each time cycle, so average sensed intensity begins to drop.
Once the frequency hits a level where the LED cannot fully turn on at all, the sensed average intensity drops much faster.

In the experiment from which the graph was taken (the paper is not publicly accessible), the average measured intensities were reported as:

49.125% at 50 MHz
43%  at 100 MHz
31.6% at 200 MHz (note the drastic intensity drop)

Thus, with fairly low tech, non-exotic means, the sum of LED rise and fall times can be determined.
To distinguish between the rise and the fall time values, the same exercise is repeated with different duty cycles, alternately minimizing the "on" plateau, and the "off" plateau to insignificance. Thus, the contribution and thereby the duration of each of the edges can be determined. I don't really understand the math of this last bit, so I'd leave it to someone else to explain it.
Comment: Wow, that's ingenious. For the math part, perhaps it's the oscillating integer function or some similar transforms. Has this ever been captured on camera though? using some thing [like in this video](http://www.youtube.com/watch?v=snSIRJ2brEk)?
Comment: Thanks, @abckookooman. Ingenious, inexpensive solutions are crucial in a country like mine, where throwing thousands of dollars at a problem simply is not an option. :-) Best of all, the end result is often easier to obtain and more reliable, as one avoids the problems of keeping a more delicate, fancy piece of equipment in perfect calibration.
Answer: It is possible to measure optical pulses of LEDs and Lasers to picosecond resolution, and it is something I do regularly as an electronics/photonics person. The trick is to work in the time domain.
To give an example of this, I have seen photodiodes exhibiting bandwidths of GHz, 40 GHz is quoted by a previous answer. However, I would imagine such a detector being quite expensive, and secondly you would need an oscilloscope of a matching bandwidth to record the resultant waveform for analysis (which would be horrendously expensive, I have only ever seen such scopes loaned on a day by day basis!).
Time to Digital Converters (TDC) have resolutions of 100ps or less, with modern low cost devices typically having ~30ps resolution. Single photon detectors often have electrical resolutions of a similar order, hence time measurements are feasible (without silly budgets!) to ~30ps. A technique known as Time Correlated Single Photon Counting (TCSPC) can then be utilised to measure the optical pulse of the LED to a resolution determined by the experimental setup. TCSPC is essentially just the histogramming of time differences between two TDC channels. I.e. measure the time difference between two signals a million or so times, and form a histogram of time differences.
The process is as follows:

Drive the LED from a pulsed source. Utilise the trigger for the pulse source as the START input of your TCSPC device (i.e. Start measuring time!)
The LED should be "seen" by the single photon detector << 0.1 of the time. This is essential. Single photon detectors have dead times (i.e. when you see a photon, you are blind for 50ns or so). If you always detect the first photon emitted by the LED, you will not be measuring the actual optical pulse of the LED (assuming the optical pulse is shorter than the dead time). Seeing 0.1 or less of the photons allows for the detector to randomly "see" photons anywhere within the optical pulse. This 0.1 requirement is achieved by optically attenuating the light via neutral density filters.
The electrical output of the detector will now be utilised as the STOP input of your TCSPC device. (I.e. stop measuring time. Add the time difference, STOP-START to the histogram).
This process is repeated a million or so times, until a statistically valid histogram is obtained. The histogram of time differences represents the optical pulse of the light source with high temporal resolution.

There are some very good documents and books by Wolfgang Becker of Becker and Hickl (freely available) which describe this process and others in far more detail.
Hope that helps!
Rich
Comment: @Anindo Ghosh: The average intensity method makes many assumptions, and gives the user no ability to determine the actual rise and fall time independently. There is an exponential decay in the optical output after the current pulse whilst the minority carriers recombine. Hence the optical rise and fall times are far from symmetrical. In addition to this, the technique offers no method to determine the latency, or relative latency between various LEDs or the optical pulses shape. High speed pulse generators are also going to be considerably expensive and modern day TDCs self calibrate.
Answer: Photodiodes are pretty fast. They are used in optical cable communications exceeding several giga bits per second. I've only ever used them at sub giga bits per second but I believe they should be able to measure a period of light that is below 0.1 nano seconds (which is certainly acceptable for most standard LEDs and quite a few laser diodes).
Frame rate footage of an LED being lit and extinguished isn't really required to determine it's ability to pulse light I would have thought.
Measuring time down to periods of pico seconds is something that is beyond my knowledge so maybe someone else will cover this.
Comment: The main problem with trying to measure "latency" of an LED turning on (or whatever) to better than 1 ns accuracy is that every 2 cm of trace or coaxial cable adds *about* 0.1 ns of delay. And if too many of those "about"s add up, you've got a substantial measurement error.
Comment: @ThePhoton Actually, the transfer function would be a constant time period added per unit length, while not significantly shaping the pulse **profile**. Regardless of the delay from emitter to sensor, the shape of the pulse will remain essentially the same. Thus rise time, fall time, and slopes can still be measured accurately regardless of transmission distance, until inverse square fall-off or light contamination kills the light or makes the SNR too poor to sense.
Comment: @AnindoGhosh, 1. The question asked about latency, not rise or fall time. (Of course its possible the OP is confusing these concepts). 2. Once you get below 1 ns you'd better be careful about your assumption that a transmission line is just a delay element with no effect on the pulse profile.
Answer: They use photodiodes and other high speed optical detectors.  You can get photodiodes with very wide bandwidths.  This one has a 40 GHz bandwidth, so it should have a rise time of around 9 picoseconds or so (BW is approx. 0.35 / rise time).
http://www.enablence.com/components/solutions/transmission/photodiodes/product/40-gbs-ingaas-photodiode


Is my mortgage more likely to be sold if I pre-pay principal?

Question: I've had a mortgage since 2011, and it's already been sold twice. I pay about 10% additional principal each month. Is this a practice that mortgage holders might find undesirable and make it more likely that they sell my note to someone else? I'm going to pre-pay either way, I'm curious to see if someone has insight on the matter.
Comment: Why do you care?  I don't mean to be flippant - I'm just curious, what effect does the collateralization of your mortgage have on you?
Comment: Collateralization might not have a big effect, but servicing changes do have a big effect.
Comment: I'm just wondering if it's a fact of life that I'll need to fill out a bunch of paperwork every year on a mortgage I already have. But like I said, it's not really going to affect my behavior.
Answer: There are two ways that mortgages are sold:
The loan is collateralized and sold to investors. This allows the bank to free up money for more loans. Of course sometime the loan may be treated like in the game of hot potato nobody want s to be holding a shaky loan when it goes into default.
The second way that a loan is sold is through the servicing of the loan. This is the company or bank that collects your monthly payments, and handles the disbursement of escrow funds. Some banks lenders never sell servicing, others never do the servicing themselves. Once the servicing is sold the first time there is no telling how many times it will be sold.
The servicing of the loan is separate from the collateralization of the loan.
When you applied for the loan you should have been given a Servicing Disclosure Statement

Servicing Disclosure Statement. RESPA requires the lender or mortgage
  broker to tell you in writing, when you apply for a loan or within the
  next three business days, whether it expects that someone else will be
  servicing your loan (collecting your payments).

The language is set by the US government:

[We may assign, sell, or transfer the servicing of your loan while the
  loan is outstanding.] [or] [We do not service mortgage loans of the
  type for which you applied. We intend to assign, sell, or transfer the
  servicing of your mortgage loan before the first payment is due.] [or]
  [The loan for which you have applied will be serviced at this
  financial institution and we do not intend to sell, transfer, or
  assign the servicing of the loan.] [INSTRUCTIONS TO PREPARER: Insert
  the date and select the appropriate language under "Servicing Transfer
  Information." The model format may be annotated with further
  information that clarifies or enhances the model language.]
Answer: It's not unusual/undesirable.
If everyone prepaid their mortgage, banks would not like this, but we're in no danger of that :). Also, the amount you are pre-paying is not so significant as to make them pay special attention. In many cases when a borrower pre-pays, they will not continue to do so over the life of the loan since it's so easy to stop at any time, and the extra payments are voluntary.
Depending on who originated the mortgate, it might be sold even more often than in your case. It's no longer commonplace for a bank to hold a mortgage to maturity, now that banks and other institutions have separated the origination of the loan from its servicing.
It's likely that your mortgage was bundled with others through a process called securitization, and will be bought/sold based on the bank's need for liquitity or to balance out the maturity of its assets and liabilities (whether they need more cash now versus later), or based on the types of ways your bank has decided that it wants to make money versus farming out other types of business to others.
What would substantially change the value of your mortgage to a bank is if it were performing (ie you are paying on time) but then became non-performing (ie you fall behind in your payments). It's also possible that if you have a very small mortgage or principal balance, that there is very little risk to the bank, and little difference between the present and future values of your loan, but banks don't typically make these types of transactions based on the characteristics of an individual loan.
Answer: In a process called collateralization, your mortgage is combined with others to form a security that other can invest in. When done right, this process provides liquidity, more money to be lent for more loans. When done wrong, bad things happen.
My mortgage happens to be held by the issuing bank. Yours was sold into such a pool of mortgages. One effect of this is the reselling of the servicing of the loan. I've had other mortgages that were sold every year, but I never paid ahead. With this bank, I'm on my fifth refinance, but the bank keeps the loan in house no matter what. I don't know if there's any correlation, it depends on the originating bank, in my opinion.


Resize widget in Experience Builder

Question: I'm developing a custom widget in experience builder. I need to increase the height of the widget. I tried to adjust the deafaultSize in  Manifest.json, but it is not reflecting the widget size.
Answer: The defaultSize in Manifext.json will only set the initial size the widget will be when added into an app. That is, when you first add the widget in Experience Builder. Once it is added, any changes to that value in the manifest will not override the layout within the Experience.
More information on the properties in Manifest.json can be found here

Resize widget in Experience Builder


Are spacecraft visits to Uranus and Neptune hard to plan?

Question: Until today, Voyager 2 remains the only spacecraft to visit these planets. Are spacecraft visits to these planets hard to plan or develop?
Comment: Define "hard".  You have to squeeze $4 billion plus out of governments, and that's before you get off paper, but after you have at least a partial design and detailed plan.  Then you have to build stuff.  And it has to work, because you don't get second chances.
Comment: Voyager 2 was able to use multiple [gravity assists](https://en.wikipedia.org/wiki/Gravity_assist).
Comment: https://space.stackexchange.com/a/45634/37747
Comment: Setting a goal and planning is difficult, but it is possible. But what is the purpose of such a journey?
Comment: Further to StephenG-HelpUkraine's excellent comment, can you  also define 'plan'?

Is that simply to plot the course, or does it include all the administration and logistics, as for instance what cargo is carried and even, how the cargo is distributed in the holds?
Answer: Uranus and Neptune are far - in orders of light-hours away. It took Voyager 2 nearly a decade to reach Uranus since its launch, costing almost $1B to build it in the first place.
It's not that we can't launch another mission, we're more than capable of doing it again, especially with the evolution of technology - but rather that it is ludicrously expensive and time-consuming, so NASA chose to allocate capital to other projects.
Even if we chose to launch another mission to the ice giants, expect up to a decade for development (depending on how fancy they make the probe(s)), then another decade for arrival. Not very timely.
Comment: In addition, if we were going to send a mission to one of the ice giants, we'd probably want to drop into orbit out there and get an extended data collection period, which is really difficult. You can either get there in a relatively reasonable time and be going so fast that you can't stop, or you can get there at a reasonable speed and take so long that the probe might fail from general wear and tear before it arrives.
Comment: I would expect the delta V requirement for either kind of mission could be greatly affected by the relative positions of Earth, Jupiter, and Saturn in their orbits.  The Voyager probes were launched when they were to exploit the particular alignment of the planets at that time; if you can readily find information about whether any future launch windows would be particularly advantageous, it might be useful to include it.
Comment: @supercat, most of the Voyager boost came from Jupiter.  An ideal Earth-Jupiter-Neptune or Earth-Jupiter-Uranus alignment happens about every twelve years; sub-ideal alignments happen almost every year.  (The Voyager Grand Tour alignment happens every 175 years, but you don't need that if you're just going to a single destination.)
Comment: @user253751 I'm not so sure about that. In a quick search it looks like the federal budget as a % of GDP has been relatively static, though overall trending slightly higher, for the last 50+ years. The definition of "public interest" has changed - NASA budget as % of federal budget peaked with Apollo and has been trending downward ever since (except for a slight bump early 1990s).
Answer: They're expensive for sure, and you will be giving something up if you plan and build for such a mission.  Since Voyager, the priorities haven't aligned for any such mission to be chosen over other alternatives.
However, the most recent Decadal Survey (which gives an idea to priorities that folks would like to see) has selected a Uranus orbiter and probe mission as the highest priority for flagship (big/expensive) missions.
So there is a reasonable chance of such a mission being funded this decade.
Answer: No, it's not. You shoot a probe past Jupiter for a slingshot assist, and you reach Uranus in six, and Neptune in eight years or so. You can build that probe from old blueprints of Galileo and Cassini, and more recent Juno etc.
The problem is to plan and design a probe and mission that will show something we haven't seen and don't already know or can guess very well. If Cassini hadn't been more than a somewhat improved version of Galileo, it would have sent back nice pictures of Saturn with little scientific value. That would've been, paraphrasing Ernest Rutherford, "stamp collecting".