Villages on "Old" Worlds?

Question: I have the iPod 4th generation so I can't use "infinite" worlds. Are you still able to get villages on the "old" world? If you can, do you know any seeds that have villages on the "old" world?
Answer: Yes, you can find villages on old worlds, and any 'new' randomly generated terrain features as well.  This happens with any 'old' world that is updated to use the newest/a new Minecraft build that includes new features.
What will happen is, your old chunks that have already been loaded will remain as they are, but any new chunks, such as ones you find while exploring beyond the limits of your old world, have a chance of spawning any number of new things from the latest update.
Note that you won't find any of these things in the old chunks you've already explored - you need to explore new regions in order to find new features.  This doesn't affect mob spawning - new mobs can spawn anywhere in an old world.
Comment: Note, old worlds generated pre-0.9.0 will not expand to be infinite, and will **not** contain villages. What the OP means by "old" is the finite world size.
Answer: Yes, as a matter of fact I have an iPod 4th generation as well and I have came across many seeds for the old world type. Here are a couple
~ 1405715475 ~
~ 999 ~
~ Minecraft ~
~ wand ~
I hope I helped.
Answer: A seed for a village is:   village is village
No caps just go straight then make a left turn
It has a blacksmith that has 2 iron and gold ingots and 2 ink sacks note: you will have to break into the blacksmith

Villages on "Old" Worlds?


Adding a search bar for page numbers

Question: Sorry if this is a duplicate, but could we have a search bar next to the page numbers so that we can easily find the nth page? For example, there are 740 pages in Meta SE unanswered, so it would be difficult to find the 100th page without changing the URL manually. It would be great to have this additional feature, perhaps next to the 'next' button?
Comment: @ChristianRau Yes thanks for pointing that out.
Comment: As well as: https://meta.stackexchange.com/q/12330/162011.
Answer: As a workaround, just modify the URL manually. When you click on page 5, the URL shows e.g.
https://meta.stackexchange.com/questions?page=5&sort=newest
or
https://stackexchange.com/leagues/3/week/superuser/2018-08-26?sort=reputationchange&page=5
and you can easily change the 5 into another number.
TBH, I just don't see any situations where you would use this. If you know a certain post is on page 39 of the list, you can navigate to it directly; if you are viewing a list of questions in chronological order and want to jump quickly to the questions from 2015, just use the Advanced Search options.
Comment: I mentioned URL already in my post. To give a more interesting example, searching user leagues.
Comment: Right. I'm just leaving it in case other users don't know what we mean. Note that the user leagues have a similar paging structure.
Answer: But what would be the point of going to page X specifically?
There's no inherently significant information derived from a question being on page 57 of the question list. The actually important information is what the order derives from, like its age, its score, whatever else you can sort by. And for that you have better search options already. But going to a specific page doesn't seem to be a meaningful action.
Instead of trying to guess the mysteries of what questions land on what page and maneuvre to that, just improve your search and look for what you really want to know.

Adding a search bar for page numbers


What is the difference between the MBA and EMBA?

Question: Somewhere I found Executive MBA degree program. How this program is different from regular Master of business administration, and which one is better program?
Comment: Which one is better is an ill-defined question, because it depends a lot on personal factors. For the differences, Investopedia has a [nice comparison](https://www.investopedia.com/articles/personal-finance/022415/mba-vs-executive-mba-which-better.asp) of the two types of programs.
Comment: @Anyon, I'm not sure why you deleted your answer. The question doesn't seem to me to be a shopping question.
Comment: @Buffy I agree it seems more like a contrasting question than a shopping one. As for why I deleted it, well I can't decide if a link + short quote makes for a good enough answer. I don't really have any input of my own to add.
Answer: Both MBA and EMBA are Master's of Business Administration programs whose learning objectives are identical.
MBA usually means full-time MBA, and EMBA is normally taught part-time (could be modular, evenings, weekends, etc).
However, there is a twist! There are two kinds of EMBA programs - just part-time versions of full-time MBA programs, which are geared for working professionals, and truly "executive" MBA programs, which seek to recruit senior executives and deliver their teaching globally, often in partnership with other leading business schools.
What's "better" depends on where you are in your career, what reasons you have for doing an MBA, and what mode of delivery works best for you in your current circumstances.


Is there a general formula for image size vs. print size?

Question: What size images do I need for common print sizes, such as wallet size, 8x10, and 16x20?  Is there a general formula?
How could that size change if, for example, a 16x20 was printed on canvas rather than photopaper?
Comment: See also @jrista's answer to a related question here: http://photo.stackexchange.com/questions/1715/how-do-i-generate-high-quality-prints-with-an-ink-jet-printer/1716#1716
Comment: For any of the answers given, canvas prints need less resolution due tot he texture of the canvas itself being a limiting factor to some extent. You simply cannot get a really sharp image on canvas, but the size usually makes up for that.
Answer: There are some general rules you can use to determine the "maximum" (I use that term loosely) print size. Keep in mind that the quality of a print is often more dependent on what is being printed than its size in megapixels, and even if your image size is not dense enough to mathematically fit onto a certain page size, you can still blow most images up pretty large without significant or noticable loss in quality.
Anyway, as a general formula:
$$
\begin{align}
\frac{\text{width}\,[pixels]}{\text{print resolution}\,[px\ per\ inch]} &= \text{print width}\,[inches] \\
\frac{\text{height}\,[pixels]}{\text{print resolution}\,[px\ per\ inch]} &= \text{print height}\,[inches] \\
\end{align}
$$
Screen/camera pixels do not directly translate to print pixels (PPI, pixels per inch), so you need to translate your image pixel size into a print size by dividing your screen pixel sizes by the PPI of your print. Assuming you have an 8mp camera, your image sizes are likely to be around 3200 x 2400 or so. If you print at the native "photo quality" PPI of an Epson printer of 300ppi, you would end up with the following:
$$
\begin{align}
3200\text{ px}\,/\,300\text{ ppi} &= 10.7'' \\
2400\text{ px}\,/\,300\text{ ppi} &= 8''
\end{align}
$$
That boils down to an 8.5" × 11" print at full resolution without any loss of quality or resolution in the translation between screen and print. However, this is not a general rule for print quality... it is simply a rule for ascertaining the lossless print size for a given image size. You could still blow up your 8 MP photo and print it at 11×16, or 13×19, and still have a good print.
You can use this formula in reverse as well, to determine the screen pixel size your image would need to be to be for a particular paper size:
$$
\begin{align}
\text{print width}\,[inches] \times \text{print resolution}\,[px\ per\ inch] &= \text{width}\,[pixels] \\
\text{print height}\,[inches] \times \text{print resolution}\,[px\ per\ inch] &= \text{height}\,[pixels]
\end{align}
$$
Using this, you could determine what size image you would need for a 2×3 inch print:
$$
\begin{align}
2'' \times 300\text{ ppi} &= 600\text{ pixels} \\
3'' \times 300\text{ ppi} &= 900\text{ pixels}
\end{align}
$$
There are other things you can do with your image to improve its quality when printed. Sharpening an image before printing, assuming you do so with the proper care, can improve the quality of your printed copies. It is also possible to use image editing software, such as Photoshop or QImage, to digitally blow up your image to a higher resolution, perform some post process sharpening, and print at even larger sizes.
Beyond this relatively simple explanation, the discussion of how to translate a photo image to its printed paper size is a relatively complex topic. It is possible to print at a variety of PPI, from as low as 100 to as high as 480 or higher. The PPI you choose to print at, the size of your image, and the quality of the algorithms you may have used to scale your image up or down, the texture, brightness, thickness, and color of your paper, and the kind of printer all determine how good a photo looks when printed.
Comment: Fpr photographic prints (Not offset comercial print) a good resolution is 200 ppi or 150. 200 ppi on a photo print has more final resolution than one in a normal magazine.
Comment: Magazines have very low resolution in the grand scheme of things, and personally, most magazine images look very grainy to me. I would call 200ppi too low for a decent photographic print unless your printing quite large. For smaller prints, stuff that might be held and viewed closer, you want much higher resolution than 200ppi. See: http://photo.stackexchange.com/questions/1715/how-do-i-generate-high-quality-prints-with-an-ink-jet-printer/1716#1716
Answer: I'm going to sort of disagree with all the other answers that talk about DPI or PPI rules of thumb, and suggest two different 'rules' (based on PPD, from another answer of mine)
Rule 1 — The 'Retina' rule
(aka the Pixels-Per-Degree (PPD) / 'better than your eye can see' rule)
This comes pretty much straight from Apple's Retina display designs, the idea being that our eye can resolve some number of pixels per degree, so the resolution of the image/print must be taken in consideration with the intended viewing distance.
In short, Apple suggest a minimum 53 PPD, others suggest up to 100 (especially if your vision is better than 20/20).
You can easily calculate one of PPD, PPI and viewing distance (d) based on the other two:
$$
\begin{align}
PPD &= d \cdot PPI \cdot 2\tan(\pi/360) &&\approx d \cdot PPI \cdot 0.01745 \\
PPI &= \frac{PPD}{d \cdot 2\tan(\pi/360)} &&\approx \frac{PPD}{d \cdot 0.01745} \\
d &= \frac{PPD}{PPI \cdot 2\tan(\pi/360)} &&\approx \frac{PPD}{PPI \cdot 0.01754}
\end{align}
$$
You may have a constrained PPI (if already printed), a constrained viewing distance (based on the intended usage or space limitations) and/or a PPD you're trying to achieve (e.g. 75 to pick an arbitrary value between 53 and 100). Note that larger viewing distances than the \$d\$ calculated are OK, it's just going closer that will allow viewers to 'see the pixels'.
If you're asking this question well ahead of time, you can choose your PPD (and I suggest you pick at least 53, and anything beyond about 100 is wasted effort), and based on your viewing distance determine the required PPI. This either tells you the maximum print size (if your camera resolution is the limiting factor) and/or the required image resolution from your camera/photographer.
Examples
Anything hand-held may be viewed as close as about 15cm (~6"), though more likely about 25cm (10"), so for 75 PPD you'd want 430 PPI (10"), but even at 300 PPI you're getting ~52 PPD at 25cm (10"). If it's really for close-up viewing (or magnified viewing) you're going to want to go well beyond 300 PPI (and you'll have to work out the effects of any magnification to achieve a suitable PPD).
Anything framed or wall-mounted is more likely to be viewed at 50cm (20") to 2m (80"), so for 75 PPD you'd want about 215 PPI to 55 PPI respectively.
A billboard could be designed for viewing from 10m (33') away, so 75 PPD would require a mere 11 PPI for the print (go and look at a billboard or really large poster advertisement close up some time, the photo's 'pixels' are often clearly visible and several mm wide).
Rule 2 — The '45' rule
(aka the 'Comfortable viewing distance' / 'yes, your camera is good enough' rule)
This is a simplification of the first rule, which applies to any image that you will only view in its entirety. That is, you're not getting in closer to see detail (like you might in a big group photo, a huge panorama, a magazine product photo, etc). This can be anything from a framed photo up to an enormous billboard, and wall/gallery-hung prints in between. For most people, I think this would apply to most of their images.
The basic idea is that you are going to view the image as a whole, so the bigger it gets the longer the viewing distance. I'm going to define the 'Comfortable Viewing Distance' as "the distance at which the image fits within a 45º field-of-view", which happens to be about the same as the field of view of a 45mm lens on a 35mm/full-frame camera (and is vaguely similar in some ways to the FoV of your eye).
It's an arbitrary number, and you can adjust accordingly, though if you have a specific context or space in mind, you're probably using the first rule anyway (after all this is just a simplified version for a specific use case).
Since the required PPI is linearly dependent on the viewing distance, and the viewing distance is linearly dependent on the size of the image, and the size of the image is dependent on the resolution and PPI... the PPI ends up cancelling out and you can just work out a required resolution given your desired PPD and FoV angle (I've picked 45).
For an angle of \$\theta\$ (degrees), this ends up being simply:
$$
\text{Pixel dimensions} = \text{desired PPD} \times \theta
$$
Again, useful PPD ranges are 53–100, and useful viewing angles might be 20º–60º (even 60º you're not really seeing the whole image anymore, so go back to rule 1).
So for the our arbitrary 75 PPD requirement and 45º viewing angle, we'd want an image that's about 3400 pixels wide (2250x3375 ~ 8 megapixels)—always.
The image resolution required is static, if the viewing angle is fixed.
For Apple's lowest Retina PPD of 53, this could be as low as ~1600x2400 (~4MP) and for the higher 100 PPD requirement, you'd need ~3000x4500 (~14MP). Even that isn't a very high resolution in today's cameras (my old 450D does 12MP).
And that's why some argue that some specific (and often quite low) resolution is plenty for just about any purpose (meaning purposes where the image is viewed as a whole, from whatever distance makes sense to do so for the size of the print).
I have a poster-sized print made from a 6MP photo (from my old 450D, which for some reason I was shooting at half-resolution JPEGs) but you'd never notice is printed at "only" ~75 DPI, because its mounted on the wall and there's no reason to get up close and personal with it (other than to pixel peep). It's mostly viewed at 1–2 metres (3–7') so works out to about 53–107 PPD.
In defense of minimum DPI/PPI rules
Ok so as much as I dislike hard DPI/PPI rules, the other side of the coin which is certainly still valid is that especially high print resolutions (e.g. in glossy magazines/brochures) add a sense of quality/precision that goes beyond simply not seeing pixels at the expected viewing distance. The viewer may not be looking closer at individual photos to see their detail, but instead may be looking closer at the magazine/brochure itself (not necessarily intentionally) and become aware of the print quality (or lack thereof).
Also if your viewers are pixel peepers.
Comment: After writing all that, I saw [this from @jrista](http://photo.stackexchange.com/a/1716/889), which covers plenty of the same material (he is effectively using the same concepts with 60 or 87 PPD for 20/10 or 20/20 vision respectively).
Comment: The interesting result here is that in many cases the "best" resolution for printing doesn't depend on the *size* of the final print, since bigger prints are seen at proportionally bigger distances. Most of the time you choose a PPD value that is good for your needs, and then calculate the actual resolution to use for your image to print, regardless of the size of the print.
Answer: The information above is quite good, so I won't try to compete, but here is a nice infographic:

The boxes are the number of megapixels for a print of the size in inches according to the scales on the axes. This is at 300ppi, which is a standard for the print resolution of many images.
This great graphic comes from an article at D215.
Comment: What are the units on the axes?
Comment: It is said that we tend to adjust the viewing distance until the image subtends a viewing angle about 60 deg. (very useful graphic btw)
Comment: @drfrogsplat Inches apparently.
Comment: The same. You can use 200 ppi on a photo print.
Comment: Those are not standard print sizes in inches.
Answer: jrista has the start of the formula, and it covers images viewed at arm's length quite well. But that 'conventional wisdom' devolves into unreasonable numbers as soon as you get to anything "big", say even a 16x20... requiring 5-6000 px. And if you hit poster size, say 30x40... 9000x12000... 108 MPix?!
When you're talking about really big prints, it's important to realize that the vast majority of folks want to view the entire image, they're going to stand back far enough that they can see the whole thing comfortably. At that distance, the human eye can't resolve 300ppi density. So you can easily decrease the density when you start getting bigger and bigger. You can find lots of discusion about the fidelity of the human eye and it's relation to viewing distance and quality of images if you google for "apple retina display arc second", in particular, this article is a great intro to the concept.
Many print vendors use this same reasoning to set their minimum print resolutions for larger print sizes, at SmugMug our minimum values take this into account. (disclaimer in case it wasn't obvious, I work for SmugMug.) That's not saying you should print at those sizes, just saying that we won't let you print anything smaller.
As an example, I have a 30" wide shot that's printed at a mere 100 ppi density. (roughly, the file is like 3123px wide or so.) Being 30" wide, folks don't hold it at arms distance to view it... they tend to stand 3 or 4 feet away and look at it on the wall. No one comments on the resolution. The exception is a couple of photographers that have seen it... and then it's only after they've stepped back to enjoy the scene that they step up close, like a couple inches away, and look at the image in a few key places to spot check the focus. On the bell curve of viewers, those folks are way way way outside the norm.
Answer: The big problem you have here is that your aspect ratio is wrong. A0 (or any other A size paper) has an aspect ratio of 1:sqrt(2) or 1:1.414 or so. Your image has an aspect ratio of 2048/1152 = 1.777. You're going to have to decide whether to crop your image, or print it "letterboxed".
Other than that, see the question linked by mattdm.
Answer: 300 pixels per inch (118 pixels per cm) is safe for standard photos, assuming you are not going to look at them with a magnifying glass. If you are very picky, go for twice larger 600 ppi.
The formula (for 300 ppi): size in pixels = size in centimeters * 118.
Example: 8x10 centimeters format. 8 * 118 = 944 pixels. 10 * 118  = 1180 pixels. So you need 944x1180 pixels photo to get it looking good. This number of pixels has a typical HD TV or better smartphone. Think it will be squeezed into 8x10 size.
1200 pixels per inch look great in professional print, as you can see every tiny detail. File sizes are huge for larger paper formats.
Very large prints, such as art or street advertisement meant to be viewed from far away, do not benefit from such high resolutions above. They can literally have pixels visible when looked close, but look great 10 meters away.
Comment: The Library of Congress claims 400 dpi is as high as you need to go: https://blogs.loc.gov/thesignal/2013/07/you-say-you-want-a-resolution-how-many-dpippi-is-too-much/. I'd need a citation to believe that magazines are printed at 1200 ppi.
Comment: Sure you are right. This is my experience. 1200 is great if there are high contrast fine lines in the print, or printing passport photos. 300 ppi -> 1200 ppi is only 4x pixel density increase, but it really makes a difference visually.
Answer: Most printers print in 300 dpi.
If you use Photoshop you can go to Image --> "Image Size" --> uncheck "Resample Image" and then change the Resolution to 300 dpi (pixels/inch).
Then the you will see maximum Width and Height in cm (or inches) that you can print this image without resizing it.
If you want to print on canvas then you will probably use the same size as for photopaper (if the canvas printer will print in 300 dpi) but for canvas print you probably will need to sharpen the image more than for ordinary photopaper.
If you want to print 8x10 at 300 dpi then you will probably need an image that is 2400 pixels (width) x 3000 pixels (height).
For 16x20 at 300 you will need image that is 4800 pixels (width) x 6000 pixels (height).
Comment: Printers print at PPI, not DPI. DPI is the number of single ink dots that can be laid down in an inch. In some printers (i.e. dye sub) this may be the same, however in many they are different. For example, in with ink jet printing, many colored dots are required to print a single pixel. Most ink jet printers print at a baseline 2400x1200 dpi (although this may vary between brands), with a native resolution at around 600ppi or 720ppi. When you print, you are generally choosing the PPI, which should evenly divide into the native PPI (i.e. 300ppi divides evenly into 600ppi.)
Comment: Your numbers aren't even close to the results I'm seeing.  Will a 28.8MP(!) image really be required for a 16x20?  I've printed them from as low as 5MP.
Comment: 150PPI is fine for a big print to hang on the wall (I've made a 100x70 cm print like this). That's a 7Mp image for 16x20 image which means that Roger's 5Mp image got marginally resized in the process, rendering an acceptable result.
Comment: What numbers are you seeing?

It didn't say required but if you are printing from 5MP camera 16x20 inch print then you are resizing the file and that will always affect the quality  but sometimes that doesn't matter at all.

If the original image file is good (in focus, low noise, etc.) then you should still be able to get a good 16x20 print.

The numbers I am referring to are so you don't need to resize the image file.


How i can create new wallet

Question: I want to create new own wallet without using ready wallet. But there are random generator that create random number and then private key builds from it. How I can realize that there is no two equal private key in the world?
Answer: If I was writing wallet software I would use BIP 39 for generating private keys from seed phrases.
Generally I would use standard algorithms (as defined in the BIPs) and standard libraries rather than invent my own.
You avoid generating duplicate keys by using sufficient numbers of words from carefully prepared lists of words and using publicly vetted algorithms carefully designed for the purpose. For example hashing algorithms are designed to minimise the chance of "collisions" (two different sources producing same result).
Choosing a large number of seed words using a properly initialized random number generator should minimise the chances of two users generating the same seed phrase.
Comment: thanks, but it may that two standard bip generate same private key, true?

How i can create new wallet


Would it be impolite to ask the time of selection decision, although the information is available online?

Question: I applied for summer internship(BSc level) in applied math in one of the North European countries a month ago. I would consider myself as a good applicant but I suspect that they accept very few international candidates, and range of countries of applicants is pretty wide. It is stated that the time of selection decision is march-april. I'm very curious and impatient about knowing the answers to "am I accepted or not?", "when will I get the answer?". In addition to curiosity, the reason of sending such email is to show that I'm ambitious(?) and serious and didn't applied just for fun. I believe that this might increase a little bit my chances. But I'm afraid that this email might turn against me, because I disturb the committee for almost(?) no reason, and it might give them an image of impatient student.
Comment: Now that we're here...did you get in the program?
Comment: I decided to edit a little my 3 year old question and it got on the top again. I'm sorry for that. That wasn't my goal.
Comment: @Emilie I did not :)
Answer: I would not suggest to write an email that does only ask for the status of the application before the announced time of selection is over—even when the email is totally calm and polite. The program has a schedule, the applicants are supposed to know the schedule.
However, you may have some other good reason to write an email. As Thomas commented to another answer: A good reason to ask for the status would be an offer for another opportunity. You could also try to find another good question to ask (but be sure that it is not already answered in the FAQ or wherever). Also, you could provide some new relevant information, if there is any (e.g. some new grades, completed projects,…).
Answer: Sending a simple email politely asking about the status of the applications should neither hurt nor hamper your chances of acceptance. Anything more and you risk annoying the committee and hurting your chances.
Comment: It might also help to explain why you are asking. e.g. "I need to decide whether to accept a different internship."


Audio mixers versus computer software

Question: I am an absolute beginner at creating music, mainly interested in hip hop. I have been reading up on how to create music and websites suggest audio mixers, and others suggest using computer software such as FL studio. My questions are: are audio mixers still used, or are they being left in the past? Do they do the same thing that computer software can do? And can both audio mixers and software be used simultaneously? Thanks in advance!
Comment: If you're going to be working almost entirely in a DAW instead of doing a lot of recording, I personally would just rely on the DAW's mixing tools. But I don't have much experience with recording...
Answer: The main point of using an audio mixer over software is having good manual controls to work with.
To get the same with a Digital Audio Workstation, you need a digital control surface.  To be useful for fine-tuning a mixed version, it needs motor faders as well (meaning that the software can also move the controls).  Digital controllers with rotary knobs can just make the knobs "endless", so that the software working on the knobs can just do it in its imagination.  However, that's quite less hands-on than motor faders.
An excellent used analog audio mixer will set you back a lot less money than they equivalent digital solution.  It also cannot hang or show time lag.  Since its settings are not readily available, it is not useful for incrementally working on some take: you do your work once.
In live performances, that may be all that actually counts (and good mixers have recording outputs after the preamps so that you can use the digital workflows offline on the live recordings).
Even when doing studio recordings, what you play into the monitor speakers and/or headphones does not necessarily need reproduction: you can work analog here as well.
For every setting that you'd rather want reproducible, digital controllers are advisable.  If the money is there...
Answer: Audio mixers in the most literal sense are a device for mixing sounds relative to each other to gain a good balance.
In days of old, these were physical devices with knobs and sliders to turn. However software audio mixers have software versions of the same thing - you would generally see a layout of a mixer on the screen, but to turn the knobs/sliders you use the mouse.
However an important part here is that the interface on a physical mixer (the part where you plug instruments/micropones in) which still has to be physical somehow for  a software mixer:  you have to be able to plug your stuff in!
So some software DAW packages come with an interface of varying complexity, allowing you to plug thiongs in.
These vary from just one input for say a guitar or mic, up to a bank of inputs which can all be recorded at once- thus simulating just the input part of a physical mixer.
The other part is what comes out :  Physical mixers generally output as a stereo pair to some recording device (varies depending on era).
Software mixers can do this but also mix to a final output file on the PC.
Some packages include a physical mixer which is software controlled - motorised faders, etc, meaning that you use it much like you would a physical mixer but the software can also control what happens when. These tend to be expensive because the cost of producing the physical device is higher than writing to software once and then copying it.
Sitting in the middle are Digital Audio Workstation type devices which are a mixer with recorder built-in. These are excellent for getting started but can be limited on facilities, as the manufactureres generally skimp a bit on physical connections.
So far I've made it seem like there's not much difference between a physical mixer and a software one, but there are. Because sfotware costs virtually nothing to duplicate, some 'extras' become very easy to get hold of.

Effects
Physical mixer: If you need say a chorus effect and three different types of reverb, and some compression then you'd gegerally ahve to go a nd buy those devices as separates and plug them in.

Software mixer : Often you can just download aplug-ins for all these effects and run them. If you wasn three differnet reverbs, you may be able to just use the same one with different settings.

Extra tracks
Physical mixer: No option for extra tracks unless you buy another mixer and link them up (whcih isn't that hard)

Software mixer: You can normally extend the tracks as many times as the PC can handle

Copy/Paste:
Physical mixer : Well really this is more about the recording device so the mixer itself doens't help.

Software mixer : Almost always, one of the major advantages is abiity to tweak sounds after they've been recorded - be that copy/paste parts of a song or amend nuances in the recording or autotune etc.

Repeating a mix ('trying again'):
Physical mixer : May not be controlled by anything other than human touch so if you amend a setting, it's amended, and that's that.

Software mixer : Ability to save mixe & settings, abaility to amend a setting while the tracks are playing, and record that the setting was changed so it happens again next time.
In this area, software mixers (which I'm assuming here will include the recorder as the same bit of software) win out - you can do a lot much more easily using software.
Big advantage of physical mixers:
Immediate ability to tweak things wihtout having to wonder through menus to find the right thing. If it can be changed,there's a knob for it.
Some argue this simplicity helps loads with being creative- you don't have any technical challenge to wade through.
Big advantage of software mixers:
Ability to save mixes
Ability to save dynamic changes while mixing (eg dip the volume ointhe guitar for 3rd verse)
Easy to move/amend/copy sound
Disadvantage of physical mixers:
No ability to save mixes (unless you photograph the settings- which I have done, and it works well)
Effects normally have to be separate devices
Disadvantage of software mixers:
Complexity. This is a biggie - don't underestimate how art-destroying it can be to be wondering through menus trying to find some setting or other. When you finally find it, you've probably forgotten what you wanted to try. I have heard this said by several colleagues.
Lag/latency:  Software takes a time to run, even if it's only nanoseconds. Sometimes this is appreciable and the stuff you've recorded may appear out of time. This goes for effects too- processing to compress a signal takes time.
Computers, generall : How annoying would it be to be getting a great mix together only to have your PC blue-screen at you ? horrible. If you go the software route, make sure your PC can do all you ask of it, nd either get a dedivcated one or switch off things like virus scanning and wi-fi-scanning whcih may pop up just to annoy you.
One final part is that some software mixers don't have to deal exclusively with sound - you can record MIDI and play that back too. this opens up huge possibilitiesd of being able to program drum machines or any midi device, or record what you've played and then tweak it seamlessly afterwards if you fluffed a note. That's only available with software mixers (or a sequencer as a separate thing).
I'd invite people to comment on other advantages/disadvantages of physical mixers vs. software mixers

Audio mixers versus computer software


What numbers (on my tuner) to tune my guitar to

Question: Like on my electronic tuner I Have C3 C4 C5 E3 E4 etc so what numbers on notes am I supposed to tune my guitar too, I keep breaking,and loosening my strings ._.
Comment: My advice would be to use an [online guitar tuner](http://www.fender.com/community/guitar-tuner/) to generate the pitches you need to aim for -- then you can match the sound before fine-tuning with your electronic tuner.
Comment: When I tuned my guitar I got a online guitar tuner then pulled out my electric tuner to see what number that was and tuned that way.
Answer: E2 is the bottom (fattest) string, followed by A2, D3, G3, B3 and the thin E is E4.              However, on a guitar tuner, there usually is a 'guitar setting' which recognises the actual open string notes.
The thing to be very careful of, as a beginner, is that an E note in one octave can sound like a different E. Indeed, to a tuner, play an E and it'll recognise E. Play a different E and it'll still tell you it's E. Obvious, maybe, but by then, you could have a string an octave too high. It happens !
Comment: For guitar specifically, the E2 at the fifth fret is the same note and octave as on the open A2. This pattern repeats, except on the B where the 4th fret is the same note and octave as open E4. This at least gives one a check against octave doubling or can get one into the ballpark and then fine-tune with the tuner.


Why does an image get blurry beyond a limit of zooming?

Question: As we have came cross a phenomenon where a picture get blurry and more blurry as we zoom in a image beyond a limit.
Why does it happen?
Answer: Digital zooming is commonly done by using some form of interpolation, which commonly represents making up some form of smooth change between actual data samples.  Assuming the data was low pass filtered (or roughly near bandlimited) before sampling, the information about where any sharp (non-smooth) changes were located between samples has been lost.  Adding back any non-smoothly-changing details would be arbitrary (guessing from context, etc.), and thus possibly incorrect (non-corresponding to the optical field before sampling).
Smooth changes or interpolations across a large area of pixels looks blurry to humans, since this effect does not occur in real life vision often unless one's eye or optical instrument is out-of-focus or not focused on the feature of interest.
Answer: If it wouldn't get blurry, then where would the information in the image come from?
Since you can only store images of finite size, it's impossible to contain infinite detail in a picture (totally ignoring the physical impossibility of that).
The fact that images typically are displayed "blurry" when you enlarge them (and not mosaic-y) is really just due to the fact that the viewer software has been designed to make the picture look blurry when interpolating the pixels that are actually in the picture to the larger number of pixels that you're trying to show.
Answer: Lens structure can no longer focus the image to the image sensor. Every lens system has a depth of field and focus distance. Once you are outside the focus distance and depth of field, photons from the target area are no longer hitting the same pixels and start to hit adjacent pixels which you perceive as blurry. As you come closer impact will be more severe.
That's the optical explanation. If you enlarge an image more than its resolution the application you use will have to interpolate the missing information. It creates new pixels using some interpolation such as bicubic. If it doesn't interpolate, you will see pixelation. Either way the info is estimated therefore contrast is lost.
Comment: I don't think OP is asking about the optical zoom – this is DSP.SE...


Cards granting emblems

Question: Are there any spells (sorceries, instants) that grant emblems? The only way to get an emblem that I've seen so far is for a planeswalker's ability to grant an emblem. I wonder if there is any other spell that can be cast to receive an emblem.
Answer: No, not at this time.

o:emblem means the Oracle text (rules text) of the card must include the word "Emblem".
-t:planeswalker means the card must not have the type "Planeswalker".

The 18 cards that do mention "Emblem" are all Planeswalkers.
Comment: Did you follow the link?
Comment: In addition to that, the new keyword action "the Ring tempts you" creates an emblem called The Ring. As a result, a number of non-planeswalker cards now create that emblem.
Comment: I'll take that answer, but how do you know?
Comment: This answer is technically still accurate, but could probably use an update to account for new cards (found at the links you already provide). The second link lists several non-planeswalker cards now, but they're all DFCs with planeswalkers on their back that actually create the emblems. The first link now goes to Teferi's Talent, which is an enchantment that *defines* an emblem but only lets a planeswalker create it; a near miss in my opinion.
Answer: While not strictly speaking emblems, there are non-Planeswalker cards which create effects with durations of "for the rest of the game," which is the original wording for Elspeth, Knight Errant (before she was errataed to have an emblem).
Cyclopean Tomb removes mire counters that it put onto a land each turn for the rest of the game after it leaves the battlefield.
Praetor's Counsel gives you no maximum hand size for the rest of the game.
Stigma Lasher prevents a player from gaining life for the rest of the game.
The Epic ability from Saviors of Kamigawa prevents you from casting additional spells for the rest of the game. (Enduring Ideal, Eternal Dominion, Neverending Torment, Undying Flames, Endless Swarm)
Answer: Planeswalkers are the only sources of emblems
Mark Rosewater, the Head Designer for Magic, has said on his Tumblr blog that

We have chosen to make emblems a planeswalker-only thing.

That is one of many answers Mark has given regarding emblems, stretching at least as far back as 2011, and continuing to the present day, where Ascend (which is a "for the rest of the game" mechanic which could have been designed using emblems) has prompted questions about the issue again.  All of them say basically the same thing.
WotC could, of course, change this decision and decide to let non-Planeswalker cards create emblems.  But they have so far shown no signs of being interested in doing so.
That said, until any cards are printed which interact with emblems in any way, effects which last "for the rest of the game" are functionally equivalent to emblems, and those do exist on a number of different card types.  The distinction that makes one of these effects an emblem has far more flavor significance than it does mechanical significance.
Special mention goes to Obsidian Fireheart, the card that held the title for "Greatest Reminder Text" ("The land continues to burn after Obsidian Fireheart has left the battlefield") until the Unstable card Gimme Five stole that title with "Offer high fives.  Don't hit people."
Comment: No longer accurate - "The Ring" is an emblem and is granted by the "The Ring Tempts You" mechanic that appears on non-planeswalker cards
Answer: As of today (Dec 24, 2014) there are 18 cards with Oracle wording that gives an emblem. As you can see, they are all Planeswalkers.
(source: this search here - I've cleaned up some un-necessary details for readability)

Name
Type

Ajani Steadfast
Planeswalker — Ajani

Dack Fayden
Planeswalker — Dack

Daretti, Scrap Savant
Planeswalker — Daretti

Domri Rade
Planeswalker — Domri

Elspeth, Knight-Errant
Planeswalker — Elspeth

Elspeth, Sun's Champion
Planeswalker — Elspeth

Garruk, Apex Predator
Planeswalker — Garruk

Garruk, Caller of Beasts
Planeswalker — Garruk

Kiora, the Crashing Wave
Planeswalker — Kiora

Koth of the Hammer
Planeswalker — Koth

Liliana of the Dark Realms
Planeswalker — Liliana

Ob Nixilis of the Black Oath
Planeswalker — Nixilis

Sarkhan, the Dragonspeaker
Planeswalker — Sarkhan

Sorin, Lord of Innistrad
Planeswalker — Sorin

Sorin, Solemn Visitor
Planeswalker — Sorin

Tamiyo, the Moon Sage
Planeswalker — Tamiyo

Teferi, Temporal Archmage
Planeswalker — Teferi

Venser, the Sojourner
Planeswalker — Venser

Cards granting emblems


Use of negative frequency for the sake of simplifying mathematics?

Question: How can we use the idea of negative frequency for the sake of simplifying mathematics if negative frequency does not exist (to my knowledge) in nature ? For example, when plotting the spectra of a Fourier series.
Comment: Duplicate: https://dsp.stackexchange.com/q/431/
Answer:
negative frequency does not exist

Depends on how you define frequency. If defining such a thing as negative frequency makes the math easier (it does), why not do it? It's probably less objectionable than defining an imaginary anything, and we do that all the time.
Answer: As other answers, if it makes the mathematics smoother or more tractable than equivalent mathematics without the use of negative frequency, why wouldn't you embrace the technique?
However, this is a physics site, so a more satisfying answer is going to give a meaning for negative frequency. Already you have the beginnings of a good answer in user safesphere's comment:

Oscillation is equivalent to rotation where frequency is equivalent to rpm (revolutions per minute). A negative frequency is simply equivalent to rotation in tbe opposite direction.

and his/ her linked DSP SE answer here that fleshes this comment out.
An application of this idea in physics is the diagonalization of the Maxwell curl equations through the use of Riemann-Silberstein vector $\vec{F} = \vec{E} + i\,c\,\vec{B}$, which I discuss in more detail in my answer here. Both Maxwell curl equations are replaced by one:
$$i\, \partial_t \vec{F} = c\,\nabla \times \vec{F}$$
and recover electric and magnetic fields through the real and imaginary parts. The positive frequency parts of this solution represent the left-handed circularly polarized field, the negative frequency parts are the right-handed circularly polarized field.
In the equivalent notation of the exterior calculus, one can build self and anti-self dual parts of the electromagnetic field $\tilde{F} = F + i\,\star F$, but you may not have come across this yet. Its positive and negative frequency parts have the same interpretation in terms of oppositely handed circularly polarized parts of the field.

However, note that, as discussed in the other answer, the modern use of the Riemann-Silberstein / Self+Anti-Self Dual notation is to use two separate Riemann Silberstein vectors $\vec{F}_\pm = \vec{E} \pm i\,c\,\vec{B}$ fulfilling the separate equations $$i\, \partial_t \vec{F} = \pm c\,\nabla \times \vec{F}_\pm$$ and then to keep only the positive frequency parts. In this usage, the left and right hand circularly polarized field components are separated and given by $\vec{F}_\pm$, respectively.
Answer: The only time I've seen negative frequency used is in Quantum field theory where it is proportional to the energy of a particle (i.e. $E=\hbar\omega$) In QFT, Feynman interpreted the negative frequency/energy results of the Klein-Gordon equation (used to find the field for a relativistic particle) as corresponding to an antiparticle with positive energy and frequency moving backwards in time rather than a normal particle with negative energy and frequency moving forward in time. This makes computation easier as it allows for the particle and antiparticle parts of the field to be incorporated into one field. I have never seen it used elsewhere, although it may have. I hope this answers your question
Comment: Negative frequency comes up all the time in signal processing and various areas of physics that are *way* simpler than QFT. It's really funny how people who know QFT think so many simple mathematical issues are only relevant in QFT. Another example is moving poles of a Green's function off of the real line. See [here](https://physics.stackexchange.com/questions/138217/complex-integration-by-shifting-the-contour).


How much memory is a block on the Wii?

Question: I have an older Nintendo Wii that I would like to sell.  Before I can list it, I'd like to include how much memory the console has.  I searched Nintendo support and they said I could see this under Data Management.  However, when I go into that area, where the installed games are shown, I see "693 Blocks".  What does that mean?  Is there a different way I should use to determine how much memory the console has?
Answer: Your unit doesn't have 1GB of RAM (as you assumed in your comment).
Every Wii has 512 MB of storage on a flash chip (some of which will be in use by the system itself) and 88 MB of RAM (24 MB fast 1T-SRAM and 64 MB slower GDDR3 SDRAM).
These 512 MB would equal to 4096 blocks. Your 693 blocks would then be equal to 86MB (1 block = 0.125 MB).
Comment: Got it.  So is the model I have one of the first ever released?
Answer: Blocks was how Nintendo measured data for a while. There are calculators online like this one: https://nblocksconverter.herokuapp.com/mobile that show you that 1 block equals 0.125 MB.
Comment: How do you get to this conclusion? 693 free blocks would equal to 86 MB.
Comment: Dang, so my unit has 1 GB of RAM?  I wonder if anyone would ever want to buy it...

How much memory is a block on the Wii?


How to use Azure Sql Always Encrypted with Dapper ORM?

Question: Is there any possibility to use DapperORM with (Azure) SQL 2016 Always Encrypted? Is there any documentation how to use and best practises?
especially how to deal with the new parameter property input direction and input length?
Answer: The following links will help you get started on Always Encrypted.

Getting started with Always Encrypted
Parameterization For
Always Encrypted

I have not used Dapper ORM, but, as long as you have the ability to enable Always Encrypted using the connection string  and to parameterize your literals you should be fine.
Here is a quick sample that I tried. Note Column Encryption Setting=Enabled in the connection string which enables Always Encrypted for the given connection.
private static readonly string connectionString = @"Data Source=.;Initial Catalog=dbName;Integrated Security=true;Connection Timeout=60;Column Encryption Setting=Enabled";

static void Main(string[] args)
{
    using (SqlConnection conn = new SqlConnection(connectionString))
    {
        conn.Open();

        int id = 1;
        var dog = conn.Query<Dog>("select age, name, weight, idcol from  DogTable where idcol = @Id", new { Id = id });
    }
}

public class Dog
{
    public int? age { get; set; }
    public int idcol { get; set; }
    public string name { get; set; }
    public float? weight { get; set; }

    public int IgnoredProperty { get { return 1; } }
}

Answer: To add to Nikhil's answer, it is possible and the resources he cites are helpful, however the parameterization article might be a little misleading, I'll include a snippet that I just got working in case it helps. You do not have to use a DECLARE @SSN... in your sql like you would in SSMS, the blow works just fine for me once I fixed my type issues (see paragraph after the code block).
string sql = "SELECT * from dob.ExampleTable WHERE IsActive = 1 SSN = @SSN";

var results = await this.DbConnection.QueryAsync(sql, new
{
    SSN = 999999999
});

Also, keep an eye out for mismatched data types. I was not able to make char or varchar work as the target type for my SSN column using Dapper (I was able to use straight ADO.NET configuring the column explicitly as CHAR or VARCHAR but Dapper seems to assume NVARCHAR(4000) for all string fields, which resulted in an error using Dapper). NVARCHAR and NCHAR worked fine. I think it has something to do with the fact that when you encrypt the column, it changes the "real" datatype to NCHAR(50) and something about the conversion of dapper from nvarchar(4000)=>CHAR(9)=>NCHAR(50) wasn't working, but only in Dapper.
Comment: Yes, implicit data type conversions are very limited with Always Encrypted. Always ensure your parameter type (and length) matches your column type.


Explain how (or if) a box full of photons would weigh more due to massless photons

Question: I understand that mass-energy equivalence is often misinterpreted as saying that mass can be converted into energy and vice versa.  The reality is that energy is always manifested as mass in some form, but I struggle with some cases:
Understood Nuclear Decay Example
In the case of a simple nuclear reaction, for instance, the total system mass remains the same since the mass deficit (in rest masses) is accounted for in the greater relativistic masses of the products per $E=\Delta m c^2$.  When a neutron decays and you are left with a fast proton and a relativistic electron.  If you could weigh those two without slowing them down, you would find it weighed as much as the original neutron.
Light in a Box
This becomes more difficult for me when moving to massless particles like photons.  Photons can transmit energy from one heavy particle to another.  When a photon is absorbed the relativistic mass (not the rest mass) of the (previously stationary) particle that absorbs it increases.  But if my understanding is correct, the energy must still be manifested as mass somehow while the photon is in-flight, in spite of the fact that the photon does not have mass.
So let's consider a box with the interior entirely lined with perfect mirrors.  I have the tare weight of the box with no photons in it.  When photons are present the box has an additional quantifiable amount of energy (quantified below) due to the in-flight photons.  Say there are $N$ photons... obviously assume $N$ is large.
$$\Delta m = \frac{ E }{ c^2 } = \frac{ N h }{ \lambda c}$$
Interactions are limited to reflections with the wall, which manifest as a constant pressure on the walls.  If I hold this box in a constant gravitational field (like the surface of Earth) then there will be a gradient in the pressure that pushes down slightly.  Is this correct?  Wouldn't there still technically be mass as the photons are in-flight, which would cause its own gravitational field just as all matter does?  How is this all consistent with the assertion that photons are massless?  Is it really correct to say that photons don't have mass?  It seems to be a big stretch.
Please offer a more complete and physically accurate account of this mirror-box.
Answer: The statement that photons are massless means that photons do not have rest mass.  In particular, this means that, in units where $c=1$, the magnitude of the photon 3-momentum must be equal to the total energy of the photons, rather than the standard relationship where $m^{2} = E^{2}-p^{2}$.
But, you can create multi-photon systems where the net momentum is zero, since momentum adds as a vector.  When you do this, however, since the energy of a non-bound state is always non-negative, the energies just add.  So, this system looks just like the rest frame of a massive particle, which has energy associated with its mass and nothing else.
The statement about gravity is a little bit more subtle, but all photon states will interact with the gravitational field, thanks to the positive results of the light-bending observations that have been made over the past century.  So you don't even need a construction like this to get photons "falling" in a gravitational field.
Comment: @Zassoundtsukushi: YOu can do that, but it's somewhat conceptually complicated to use the term "relativistic mass" eventually--the "relativistic mass" is really just the energy, and has properites closer to an allergy.
Comment: Would it then be correct to say that the relativistic mass, not the rest mass, of a photon is $m=\frac{h}{\lambda c}$?  Then all statements I would make about the mirror box could be done using this.  I think that $(m_0 c^2)^2 = E^2 - (p c)^2$ (this might be what you had in mind) still holds, however, since $m_0=0$.
Comment: Yes, to the extent that your unit system allows it (like $\frac{MeV}{c^2}$ for mass) I agree that the energy of the photons can be looked at as "just the energy".  My question is sufficiently answered by nothing that this photon relativistic mass or energy (which one you use is semantics) exhibits all of the properties expected of that quantity of mass.  This means that it is affected by gravitational fields and warps space-time itself.  This is more than I previously felt comfortable claiming, but the conceptual picture here seems to be consistent.
Comment: @Zassoundsukushi: the reason why it won't work out is technical--radiation gravitates, but not in the same way as matter, and rest mass and relativistic energies don't add together in the same way when you're creating systems out of many particles.  At a first glance, you're ok using them semi-interchangeably, but realize that it's complication-prone if you plan on going deeper into this stuff.
Comment: @Jerry "not in the same way as matter" -> how so? Gravitation couples to stress energy tensor which doesn't really differ all that much between massless and massive systems...
Comment: @Marek: the equation of state is different.
Comment: For all we know, can't electrons and quarks be made up of smaller orbiting low-mass or zero-mass particles?  I'm not proposing a real theory of the universe right here, just making the theoretical point.  That's why I'm getting frustrated with this word "massless", since rest mass itself comes from motion of something (provably to some limited extent by nucleus physics, and unproven to unknown degree).
Comment: @Zassounotsukshi: Sure, there are theories involving substructure to existing elementary particles.  In particular, people are interested in theories where the Higgs is a composite particle.
Comment: Yeah ,but this answer says,$E^2-p^2=m^2$ ,only applicable for single particle?
http://physics.stackexchange.com/questions/175444/is-mass-conserved-in-special-relativity/175451#175451
Answer: There are no confusions in your understanding, everything you said is correct, and it is the nontrivial content of Einstein's E=mc^2 paper. These systems are the reason that "relativistic mass", as introduced by Tolman is pedagogically useful. The concept that we call "mass" in our day-to-day life is the energy of a system (in mass units), and when you only use the word mass to mean "rest-mass", the intuitive concept is changed somewhat.
For the atomic fission, the fast moving fragments have energy which is equal to the initial bomb energy. If you weigh them without slowing them down (for example, if they are charged and you capture them by making them do circles in a magnetic field), the weight you would field on a scale once they are captured would increase by the relativistic mass (the energy over c^2).
The photons in a spherical mirror box weigh the box down exactly as the relativistic mass of the photons inside. The pull of the Earth on these photons is on the relativistic mass. If you replaced the photons with a particle gas at the same pressure, and removed a little mass from the walls to make the total mass be positive, the gravitatonal field outside will be the same, this isn't true replacing the photons with a pressureless block with a weight equal to their relativistic mass, only because the pressure contributes to the gravitational field too.
Answer: I think that there is some confusion in your understanding of relativistic physics in the statement here:
In the case of a simple nuclear reaction, for instance, the total system mass remains the same since the mass deficit (in rest masses) is accounted for in the greater relativistic masses of the products per E=Δmc2. When a neutron decays and you are left with a fast proton and a relativistic electron. If you could weigh those two without slowing them down, you would find it weighed as much as the original neutron.
The correct statement is that the summed four vector of all the decay products would have the effective mass of a neutron.
Masses are not conserved in relativistic physics, in an analogous way that lengths are not conserved when adding vectors in three dimensions. What is conserved is energy and momentum, a four vector whose measure is m*c, where m is the effective mass of the system, similar to the length of a three-vector after the addition of three-vectors .
When a pi0 goes into two photons, it is true that the available energy for each gamma in the centre of mass system   of the pio is half the mass of the pio, and the measure of the invariant mass of those two gammas will be the mass of the pio. When more particles are involved , lets say two pio's then the invariant mass of the four gammas four momenta is not additive to two pio masses. It is better to forget about convoluted arguments with masses and think of four momenta when in the relativistic regime.
Now a box of photons will have a four momentum sum in measure equal to E*2/c*2 - |p|*2=m*2*c**2. (please see the wiki link for clear terminology)
If the three vector momentum sums up to zero, the effective mass of the photons in the box will be E/c**2. Small but there to be weighed.
Comment: There is no confusion, these statements are unambiguously 100% correct, and are the reason physicists used relativistic mass as a concept.


Covariate balance diagnostics using TMLE function in R

Question: I am currently using the tmle function in R to perform targeted maximum likelihood estimation as a doubly-robust alternative to propensity score methods in identifying an average treatment effect. This is an ideal method, as I have a large number of covariates, and I'm not worried in estimating the effect of specific covariates on the outcome. However, with propensity score methods, I generally report on covariate balance. I've been trying to find some similar diagnostic to show that the estimation of the probability of treatment resulted in a sufficiently low level of bias. Anyways, just wondering if anyone knew of a way to pull such diagnostic info?
Answer: See my answer here for a related question. TMLE does not balance the covariates or adjust the sample in anyway; it estimates potential outcomes for each individual using an outcome model and adjusts the difference in the estimated potential outcome means using a function of the propensity score (called the "clever covariate"). You cannot report balance after TMLE, which is why it is unclear how well it is doing at removing systematic bias in your sample. This is the basis of my critique of it here. You basically have to just trust that it is doing its job based on its asymptotic properties. You can evaluate the quality of some of its predictions using cross-validation statistics, but those do not correspond exactly to how well bias is being removed.
Comment: Thanks, Noah! This is really helpful.


What to place underneath a convection microwave oven?

Question: I bought a Sharp convection microwave oven months ago but to date, I have only used its microwave functions. The reason is because I am worried about the heat generated by the oven in the convection mode and what it might do to the wood-based countertop. What can I place on the countertop to protect it from the heat of the oven?
Answer: I'd get a small granite or marble "cutting" board just the size of the oven.
It will help diffuse the heat.
Answer: If your oven is not broken, you probably shouldn't need to place anything underneath it. I just reviewed few instruction manuals of Sharp convection microwave ovens and found no word about it. There was a warning about putting things on top of their ovens, but nothing about things under them in "safety" section.
That said:

Read your instruction manual, especially "SAFETY INSTRUCTIONS" section.
If you still don't trust it, you can try using a wooden cutting board. If nothing happens with it, probably nothing will happen to your countertop, either.
Stone or metal pad might help to diffuse heat, but also may get slippery easier than wood can. You don't want your oven to fall on the floor, so please be careful not to turn it into "medicine worse than the disease" situation.
Answer: I have two, both Panasonic. One is on solid oak, the other on solid beech (the latter in my camper van). There's never been a smell of hot wood (or hot worktop oil) and no scorch marks, including after long use in oven mode. They are designed to be safe on typical work surfaces and have some space underneath and insulating feet.
Comment: I have the means to measure the temperature of the underside and the worktop after use, but may not have the time any time soon


Weak convergence in measure for negligible sets.

Question: Let $X$ be a Polish space and $(P_n)$ a sequence of Borel probabilities which converges weakly in measure to a Borel probability $P$. By this i mean that for any $f\in C_b(X)$ which is continuous and bounded $$\lim \int_X f(x) P_n(dx)= \int_X f(x) P(dx)$$ I further assume that there is a $A$ such that for any $n$ A is $P_n-$negligible i.e. for any $n\in \mathbb{N}$ there is a Borel set $B_n$ with $$P_n(B_n) =0$$ and $$A\subset B_n$$ My question is the following : does it imply that $A$ is $P-$negligible i.e. that i can find a Borel set $B$ with $A\subset B$ and $$P(B)=0$$ ???
Comment: For more information about the relation between weak and a kind of "set-wise" convergence look at the so-called *Portmanteau theorem*.
Answer: The answer is obviously "no" (take for $P_n$ the sequence of $\delta$-measures at the points $1/n$ on the real line). However, it is "yes" if the set $A$ is open.
PS I think giving the right answer should be a reasonable prerequisite for declaring a question to be too easy for "research level".
Comment: I stand corrected.


macbook pro question mark on start up -no harddrive?

Question: Am having an 13" macbook pro from 2011, recently during dj-ing my software just stop working.
After the restart I've only got the question mark sign .I've try to fix it via internet recovery  but my hard drive could not be found in disk utility at all. I've tested my hard drive on another mac book pro same as mine and it's working perfect. So does that mean is the hard drive cable, or could be even something else, and if it's so what are my options
Thanks!
Answer: It looks like it's the SATA Flex cable used in the MacBook Pro that has died.  I have the same laptop and it's died as well.  You can either go to the Apple Store to have it replaced for a nominal fee, or do it yourself by ordering this part.
Comment: hmm i think it's the SATA cable as well but am wondering is there a chance to be something else ? motherboard or else????
Comment: If you've verified that the drive works in other laptops, then yes it's likely the cable.  Like I said in my post, I had the same exact problem with mine where the laptop does not recognize the drive at all.


how to run background thread after application termination in iphone?

Question: is it possible to run a background thread after the application termination specifically, say after the method applicationWillTerminate call from appdelegate?
is it possible to reflect the thread timer value in application preference after application termination?
Answer: No. When the process terminates, all threads terminate. However, there is a way to have the process stay in the background. Read up on iOS 4+ multitasking.
Answer: More specifically, see the Completing a Finite-Length Task in the Background section of the iOS Application Programming Guide. Wish I could help more, but having issues myself.


Money Plant Leaves

Question: What can I do to make my money plant healthy? It's leaves are like burnt and also has holes in it. If I place it indoor, the leaves become yellow and fall off. Posting pics too.
Comment: Money plant is a common name usually used for Crassula ovata, sometimes  for Pachira aquatica, but your plant is neither of  those. It looks vaguely like Devil's Ivy (Epripremnum aureum) but can we have another photo from further away, showing the whole plant to try to ID what it actually is please
Comment: Hi Bamboo, I have added another pic of the plant , perhaps it can be identified now. Thanks
Comment: How long have you had this plant  and where are you in the world?
Comment: I have had it for around 20 years . I am in India.
Answer: I think this plant is Epipremnum aureum, but its hard to be sure because its in such poor condition. There's a similar plant known as Heartleaf Philodendron, but fortunately, the care for both is similar.
If you've had your plant for 20 years, and its been in the same pot for some years, its time  to repot it, preferably cutting the rootball in half and potting up the two sections separately. Remove all badly damaged leaves at the same time, as well as inspecting closely for insect infestation. If you can, use new, sterile potting soil, but I am not sure you can get that where you live. Water thoroughly after this procedure, and allow the pots to drain freely prior to replacing into any outer tray. Ongoing, water when the surface of the soil in the pot feels just about dry to the touch, then water thoroughly, emptying out the tray or pot beneath after 30 minutes so its not left standing in water.
These plants do not like direct sunlight, preferring bright daylight instead. That obvious damage on the plant might be from sunlight,  or a combination of that and insufficient watering, possibly caused by the fact its likely rootbound. Usually grown indoors in bright light as houseplants, they can be placed outdoors, out of sunlight, in countries  where the temperatures are high enough. More info here https://www.proflowers.com/blog/pothos-plant-care
Comment: Thanks a ton. Will follow your advice. And yes we do get sterile potting soil here.

Money Plant Leaves


Additional drop down box to Cognito Form entries listing

Question: On the entries page, there is a drop down for status. Am I able to add another three drop down boxes so I can say when the job was started and finished, and add any comments?
Answer: In Cognito Forms, you can mark any field as Show This Field - Internally, which will make the field or section only appear when you are managing entries through administration.  These fields are sent for email notifications (sent to you) but not sent for email confirmations (sent to your customers).  You can also trigger automatic email notifications and confirmations when you update entries, such as sending a followup email when the job is marked as finished.


If a user is creating a collection with the same name as another collection, should we allow it?

Question: I work on a system where people can create their own content and share it internally with their colleagues. I am creating a method of organizing favorite or most recently used items into collections as a way to personally organize the items that you create and consume. I was wondering if we should prevent users from giving multiple collections the same name.
Answer: I think it largely depends on how you intend to use the collections and more importantly display the list to users.
If collections have the same name, you need another value to distinguish them. I would suggest perhaps "created by" will suffice for this.
With that in mind, I strongly suggest you ensure that collection names are at least unique to each user (that created them).
The decision of making them unique system-wide though is going to have to be one you make yourself based on your evaluation of how the system will be used. Perhaps a starting point for your decision is as follows:
If collections are mostly private, and rarely shared - then make them unique to the user creating them.
If collections are rarely private, and mostly shared -then make them unique on a system-wide level.

I important consideration though. If you don't make them unique system-wide from the start, then it will be more complex to change that later.
Where as, if you start with them unique system-wide and later find the requirements need to change (because users are getting annoyed that it's too restrictive) then it's easy to switch over.
So perhaps follow this logic if you really can't make your mind up which is better.
Comment: Thank you so much! That was very useful


How to highlight data points in a scatter chart in excel?

Question: I have a scatter chart with a series of numbers in Excel. Most of the time, those numbers are high (>1000). I would like to display the scatter chart with those numbers in the default color, but if the number is < 1000 then display those in red. So essentially I want to highlight just those.
Answer: There's at least three ways to accomplish what you've asked about:

Adding a helper series for your highlighted points (as pnuts),
Manually formatting (as Rhys Gibson added),
Adding a formatting "band" to highlight the values.

The method you choose will depend greatly upon your chart layout (scatter charts can be laid out in at least two different ways), how many points you need to highlight and how often they'll change.  I've included samples of 2 different ways to highlight your points: adding a helper series and adding a highlight band (personally, I'll almost never manually highlight a few points).

If your scatter chart is laid out in a traditional XY configuration (like the top right chart), you'll need to consider which axis' values you're evaluating to be less than 1000 (vertical or horizontal or both)?  I've highlighted both for the sample.  The general steps for this are:

Organize your base data (two columns X2 and Y1, in this sample).
Create your base chart, using your base data (blue values are the original series).
Create a helper column for your highlighted values (in this case less than 1000, X3 and Y1 for the vertical, and X2 & Y2 for the horizontal).  If you're highlighting both axis, you'll need two helper columns); or
Create a helper column for your highlight bands (in this case Y4).

Once you've added the helper column, you'll need to change that series chart type to Column.
Then change your formatting to your preferred color, change the gap to 0, and you'll probably need to tweak the axis' labels.

If your scatter chart is laid out more like a line chart like the bottom chart (which is much more flexible than a typical line chart), then you'll need to do things a little different:

Organize your base data (two columns X1 and Y1, in this sample).
Create your base chart, using your base data (blue values in are the original series).
Create a helper column for your highlighted values (in this case less than 1000, X1 and Y2 in this sample); or
Create a helper column for your highlighted bands (in this case Y3), and follow the formatting columns from above.

EDIT:  It's worth noting that in the highlighted values, I've returned NA() if the value didn't match the target requirement.  This keeps the point from being plotted at all, instead of having to deal with points plotted as 0 (or some other value).
Answer: Plot the high and low values from separate columns (or rows):

The data point shapes and their colours will probably need to be changed if you want red + another colour and a particular shape but now each 'series' can be selected separately (by clicking on one of the data points from each 'series', in turn) and formatting to suit. I take it that how to format (described all over the place) is not a required part of an answer to your question.
Comment: Could you maybe add a few steps on how to do this or provide a screenshot? I guess that would be very helpful!
Answer: Excel doesn't support 'conditional formatting in charts'.
If you can't plot these numbers in separate series (as per pnuts solution) then another option is to manually colour each data point (right click|Format Data Point) as long as you don't have too many. This is a hassle though if your data changes.
Answer: For people with the same problems, there is a usefull tool named FunFun, which allows people to use web languages like Html, Css and JavaScript in Excel.
Javascript has a lot of powerful libraries for data visualization, like Charts.js and D3, that you can use with this Excel add-in to create any chart you want.
If you want to test out different libraries, Funfun hosts an online editor with an embedded spreadsheet, where you can see the output of your code instantly.
I made this chart with Chart.js on the FunFun website that I directly loaded in Excel by pasting the link of the funfun online editor below:
https://www.funfun.io/1/edit/5a32ad9f61242f75d940543f
Here are some screenshots(Website to Excel Add-in):

You then load the project in excel with funfun:


Why did my established pond suddenly have a mass death event?

Question: For over 8 years I have had a pond in the corner of my home. It is of a triangular shape, about 10' x12' x15' (3 x 3.6 x 4.5 m) by two feet (60 cm) deep. For years I have had two koi, random other pond fish and some carnival won goldfish. The last three years or so, frogs have found a home there, too. I have a waterfall and a couple plants.
I've never had any problems and I do very minimal maintenance with no issues.
About a week ago, a fish or two died. For the next couple days, I lost two to three a day. On the third day, I had water tested and it was fine. Next day, more dead fish. I drained 2/3 of the water and refilled, also added stress coat/chlorine reducer from pet store. Next day, more dead. One koi was about seven inches (18 cm) and he held out long, but finally died, leaving just the one koi left. Two days later, that 12 inch (30 cm) koi died.
When no fish were left, suddenly the water got extremely clear. I saw nothing wrong with the fish, except they showed signs of a lack of oxygen. They would float like dead till you attempt to net them, then they would swim. No spots or visible redness was to be seen around gills. Water has been pumped into a fountain the same all year, so why would O2 levels suddenly drop within a week enough to kill all the fish? Water was not warm.
Comment: Does your city spray for mosquitoes or other pests?
Comment: Did you have the water tested for chemicals, or for micro-organisms? If O2-levels drop without excessive heat, with the waterfall running and the plants all happy, all that is left is, really, micro-organisms "stealing" the oxygen....
Comment: Ohh, another question: is this an indoor-pond? and if yes, did you have any excessive scum on the ground? (I have not yet found an outdoor-pond without it...)
Comment: We experienced a similar issue... Is there any acidic leaf litter that may have effected the pond? How is other life like frogs/newts? Are the plants in your pond also uneffected? Our fish looked completely healthy when they all died also, but plants and newts survived.
Comment: I had the water tested and it was fine. Plants are all fine and sitting here now the frogs are croaking away fine. The pond is outdoors and I have not done a thing to the pond or surrounding areas. No chemicals or granular lawn treatments. Water and fish were fine a week ago. Water has its usual green tint nothing out of the ordinary, no excessive algae. Then fish die and water is now crystal clear. Like so clear I can see every little root to the plants at the bottom. It's like the first day I put water in it. That's what gets me, why did it get so crystal clear now.
Comment: Does clear water == low oxygen? That might explain things.
Comment: ??? Not sure ??? But I have changed nothing and the weather has not been extreme, so why after all these years did this happen?  Almost feels like I lost my favorite toys. So now the question is, how long do I wait before trying to introduce new fish. I'm in no hurry, would like to let the pond go through whatever cycle it us going through for a while. Since all fish are dead I did place a small piece of chlorine from my pool in the pond right next to the pump. Let that cycle through a bit and hopefully kill any parasites or diseases that may be in there.  That's all I got for an idea.
Comment: Try a bio bomb, sounds similar to our issue.
Comment: Adding onto @Spyral's answer, where I live you need to only call a hotline and they will come and put chemicals (or mosquito fish) in any standing body of water that is reported to breed mosquitos, no questions asked.
Comment: I would recommend doing rlb.usa's suggestion and also to call in a vet or professional to examine the fish and the tank.
Comment: I have a few different things that could have happened in mind, so here I go :) -Do you think a poisonous frog or other animal could have contaminated the water?
-Perhaps acidic soil/leaf litter/plant life could have gotten in in semi-large amounts?
-Was there an excessive amount of algae or other aquatic plant?
-Could a wild animal have killed the fish?
-Did you spill anything into the water?
-Could a weed killer have gotten in?
Answer: Based on the info in your question and comments: water tested "fine", plants are still alive, and death over time (not all in one day) suggests fish illness. Since you didn't mention any signs of sores, gasping for air, or swollen eyes or abdomen, I would assume you got a parasite. Your water will test fine and your plants will live. Doing a water change would've only helped if a treatment had begun. Parasitic infections (unless it's ich) can be a little harder to spot, since SYMPTOMS are less noticeable than bacterial infections, swim bladder, dropsy or pop-eye. ALOT of fish In pods hide in live plants, you may have never noticed if a few of your fish were hanging out at the bottom, rubbing up against plants or rocks, have swollen gills, or behave erratically at random (aka flashing-quick spurts of jumping or quick swimming or circular swimming).... These are all signs of a parasitic infection, that ESPECIALLY in ponds with or without live plants, is difficult to spot. Parasites are very common in outdoor ponds, and simply a windy day, where debris is blown from further away can cause an infestation.


What would a picture of Galactus show?

Question: As seen in Has Galactus ever been depicted as anything other than a humanoid? , Galactus looks different to every race, because the mind cannot comprehend what it is seeing. If one would take a picture though would his true visible form show up in the picture, being that a camera just records what is on the visible spectrum, rather than interpreting what it sees?
Comment: This brings to mind the seen in Terry Pratchett's The Light Fantastic, where Rincewind looks at the pictogram of Death's house : Rincewind: That's not what it looked like! It was a house. Imp: I paint what I see and I see whats really there.
Comment: Would there be anyway of knowing considering each person would still have to interpret the picture?
Comment: you wouldnt need to interpret the picture because if you couldnt comprehend what  was shown, your mind would treat it like modern art (shudder)
Comment: Picture of Galactus is also Galactus.. Umm.. sorry.. wrong canon.
Comment: Wouldn't the viewer of the image / video interpret what they were seeing?
Answer: According to Marvels, Galactus captured on camera looks like Galactus as humans see him:

We don't see a non-human watching this transmission, so we don't know if another species watching this would also see Galactus as humans do, or would see him as their race does. As Kevin Workman points out in the comments, it could be that the picture does capture the true image of Galactus, and the viewer would continue to see said image as what they'd see in person.
In practice, however, a picture of Galactus won't reveal that true form (as asked in the question). Whether what's captured is somehow the cultural image of the picture taker, or the "true form" in some way, someone looking at the picture will not see the true form.
(Note that this story was written after Byrne established that Galactus doesn't look like we think he does - however, this story wouldn't be advanced by an image that didn't match what the people saw. And, on top of that, Alex Ross tends to be a traditionalist, and might ignore Byrne's call on general principles.)
Comment: This could also be interpreted the other way: the camera sees his "true" form, and that's what's displayed on pictures / tv, but the viewer does the "translation" into whatever they see.
Comment: @KevinWorkman - I see your point. Edited.
Comment: I think the theory of the camera capturing what the camera operator sees leaves a lot of other questions: what if there are two beings from different species operating the camera? What if the camera was not operated by anybody at all? ...what if Galactus took a selfie?
Comment: I'm allowing for weirdness due to "cosmic power". Whether the image captures a true form that somehow still gets seen as the form the viewer's race would see if they saw Galactus in person, or the perspective of the person taking the picture (or even who created the camera) impacts the image captured, some sort of high weirdness is involved.

What would a picture of Galactus show?


Where does the "o" sound fit into Chinese phonology? Is it a mid vowel?

Question: So I've been looking at San Duanmu's The Phonology of Standard Chinese, and in the vowel section, the pinyin /o/ from 中 is not mentioned. An allophone of the middle vowel is described as [o], which is said to appear "in open syllables after labials". The examples given are 我 and 波, so fine we could understand the liprounding in 卓 as being a "bilabial" and so it's realized as [zhwo]. That however doesn't explain 中 which is clearly not an open syllable. What gives?
Answer: According to the two-vowel analysis of Standard Mandarin phonology, the statement that:

An allophone of the middle vowel /ə/ is described as [o]

... still 'holds' for closed syllables ending in /-ŋ/, not just for open syllables. The medial can be either /w/ or /ɥ/.
For closed syllables ending in /-n/, the same /ə/ nucleus corresponds to wen / -un (as in 文、敦) and yun / -un (允、群) in Pinyin.
This is actually the 'literal' interpretation of the 注音符號 (aka bopomofo) renditions for Standard Mandarin phonology. See how 征 is ㄓㄥ (zhēng = zh + eng), whereas 中 is ㄓㄨㄥ (zhōng, literally zh + wu + eng) with a kind of 'compound final'. This also applies to the endings in -n (ㄨㄣ for wen = wu + en and ㄩㄣ for yun = yü + en).
Comment: wonder why this source would omit such a common detail, given the depth it goes into about all the other allophones...
Answer: start quote << The precise realization of each vowel depends on its phonetic environment. In particular, the vowel /ə/ has two broad allophones [e] and [o] (corresponding respectively to pinyin e and o in most cases). These sounds can be treated as a single underlying phoneme because they are in complementary distribution. The mid vowel phoneme may also be treated as an underspecified vowel, attracting features either from the adjacent sounds or from default rules resulting in /ə/. (Apparent counterexamples are provided by certain interjections, such as [ɔ], [ɛ], [jɔ], and [lɔ], but these are normally treated as special cases operating outside the normal phonemic system.[b]  >> end quote
So yes, it is considered a midvowel, but is also underspecified with multiple features/ forms apparent.  This is why not everything matches a single format/ IPA value/ whatever you want to call it.

Direct quote from the wikipedia of standard chinese phonology.  See the chart of the sounds including o on the original page as well as more info:
https://en.m.wikipedia.org/wiki/Standard_Chinese_phonology


Selenium for MacOS Setup

Question: I wanted to know if there is a good source for setting up Selenium in Eclipse on MacOS. I have MacOS 10.9.4.
Comment: @BobDalgleish I'm not sure how to use Selenium on my Mac, is there a guide out there to follow? I don't know where to start.
Comment: What exactly are your questions? Does following the installation instructions for Unix not work?
Answer: You can download the Java jar from http://docs.seleniumhq.org/download/. Unzip the file and move the (non-source) jar to where you keep your libraries for your Eclipse project.
In Eclipse, you will need to add the jar to the list of libraries for your project build.
You should now be able to create a test class and run some Selenium tests. There is a good starter test class in the Selenium documentation at http:seleniumhq.org.
Assumptions
All of the above assumes:

You are using Java in Eclipse and you know how to set up Eclipse projects.
You can unzip and move files to where you need them and know how to a jar to your list of libraries.
You have a unit/function testing framework such as JUnit or TestNG.
You know how to write Java programs.

Selenium for MacOS Setup


Set off Vs Set out

Question: He set out southwestward,made his way after great hardships to Palestine,found one friend there and set off again toward the west.
                                                (By Philip Khuri Hitti)
I couldn't understand why didn't the writer use set out and set off alternatively?
Comment: Sorry? I'm not understanding your question. The writer *had* used "set out" and "set off" alternatively, no? For [variation](http://www.dailywritingtips.com/elegant-variatio/), most likely? If you mean why the author hadn't used "set off" first and "set out" second, he could've, but he had probably just liked it better this way.
Answer: According to the Cambridge Dictionary: there is no difference between these two phrasal verbs:
set off - to start on a trip
set out -to start a journey
I can think of no particular reason why he should use one form in preference to the other. As TeacherKSHuang suggested, he might have alternated their use for variety, but changing just the adverb half of a phrasal verb does not give a lot of variety.
Note that Philip Khuri Hitti was born and raised in Lebanon, although he moved to America in his twenties, where he taught Arabic. It may be that he was trying to express some distinction that is better defined in his mother tongue.
Answer: The above is right but let's remember "set off" also has a different definition and is wayyyy more versatile.
Set off fireworks, set off the smoke alarm.. You obviously can't say "set out the smoke alarm". You can say that but it would mean you just took it out of your drawer or whatever and placed it in plain sight.
Comment: While this is true, the question is specifically about journeys.

Set off Vs Set out


inductance of multi-stranded wire

Question: The inductance of a single loop of wire will increase in inverse proportion to its diameter. Are there exceptions to this rule when applied to multi stranded wire (not litz wire). I should make it clear that the diameter refers to the wire used to form the loop.
Comment: huh? are you saying that smaller loops have higher inductance?
Answer: For a notionally thin wire, you can say that the magnetic flux produced by any part of the flow of current couples to flux produced by all other parts of the flow of current. This maximizes the wire's inductance.
When the effective cross sectional area of a wire gets larger, current flowing on one edge of the wire can produce a small amount of magnetic flux that does not couple entirely with current flow on the opposite edge. This begins to degrade the overall inductance of the wire.
In an extreme scenario, you could imagine a wire being cut down the centre so that the current splits into two distinct and separate paths. If these two half-wires are at some distance to each other, very little magnetic flux will couple from one half-wire to the other and the net inductance will tend to become 50% of when those two half-wires were united as a whole.
Comment: In the experiment in which 17 ft. of 44/030 was used as a transmitting loop at 7 mhz the r.f resistance(0.900 ohms)  and the inductance(9 uh) were much greater than predicted by formula which does indicate that the effective diameter is much less than stated .
Comment: Well, that's nice to know but I neither know what formulas you used nor have I any idea how you physically constucted the loop. Neither do I know if there were any ferrous objects in the vicinity of the loop and neither have you said how much bigger the inductance actually measured was. I don't understand your measurement method either. A lot of uncertainties here dude.
Comment: I will also add this. 7MHz has a quarter wavelength of about 11 metres. 17 foot is 5.2 metres. Because of the relative closeness of these two numbers you will be beginning to see a good few percent error due to standing waves i.e. the electric field and magnetic field will be starting to form a true electromagnetic wave (radio transmission) and this will certainly affect your resistance and inductance more than you might expect or have considered. Add to the is the feed wire length that you may have used (and the mismatch to a quarter wave) and strange things can start to happen.
Answer: the answer is that when calculating the inductance of a multi stranded wire it is the effective diameter that is relevant to formula.

inductance of multi-stranded wire


Usage of pushar and empujar

Question: I would like to know if pushar is also used in Spain and is it only used by teenagers ?
Comment: I've never heard or seen "pushar" in Spain. It sounds like made-up Spanglish.
Comment: "Pushar" it's totally an Spanglish term made up and used by Mexicans in the USA. It straight comes from the Enlgish verb 'to push(empujar)'.
Answer: I think you are trying to say "PUJAR". Pujar, from the verb "Empuja" meaning push in english, is used in Spanish when we are related to an expulsion of something out of a body, mostly our bodies. Therefore is commonly used for women giving birth and people who are expulsing a kidney stone for example. "Empujar" is used as to push something outside of our bodies.
Comment: Not to be confused with the verb "pujar" which means "to bid" (offering money at an auction).

Usage of pushar and empujar


Book with protagonists jumping between parallel Earths of various time periods (but not time travelling)

Question: I just remember this one bit of this book: the idea that the protagonists jumped from world to world in a set of parallel universes but, because of the world's differences, it looked like time travel: one might go from an Earth post-WWII to an Earth pre-WWII... but it wasn't time travel.
Comment: That kind of fake time travel by parallel worlds has been used more than once, for instance, in Crawford Kilian's *Chronoplane Wars* series, see [this old Q&A](https://scifi.stackexchange.com/questions/161494/time-travelling-parallel-universe-subway-protagonist-a-james-bond-like-agent) or [this one](https://scifi.stackexchange.com/questions/38349/id-a-novel-in-which-the-protagonist-was-sent-back-in-time-to-pull-forward-indivi). It might help if you could tells us more about the book: how long ago you read it, anything about characters, settings, or plot.
Comment: H. Beam Piper did this well in his Paratime series: https://en.wikipedia.org/wiki/Paratime_series
Comment: I agree; this is pretty common.  I just ran across it yesterday in a short story called "Recreation" by Kenneth Bulmer (*Authentic Science Fiction*, 1956).
Comment: This also features in Charles Stross' "Merchant Princes" series.
Comment: It drives me crazy when people post an answer as a comment :)
I think it might well have been the paratime series... which would be why I don't remember that much... cause of all the different plots. I definitely remember the 'walked around a horse' story. So, Dosco...
Answer: This was the idea behind Andre Norton's The Crossroads of Time (1956). It's about a man in our Earth - Blake Walker - who gets mixed up in a hunt for a criminal from a different Earth and travels through several different Earths throughout the book.
Answer: That's one of the conceits of Michael Crichton's Timeline (1999); they aren't actually traveling in time, but rather jumping sideways into parallel Earths that are very similar to our world, but slightly ahead or behind in the timeline.
I'm not sure why parallel world hopping is supposed to be less ridiculous than time travel, though, to be honest.
Comment: Except for someone in the "other timeline" being able to bury a message in the 14th century and have it found in the 21st, "back home"...  Still, this is the most likely answer (I think).
Comment: Right?  I have no idea why he decided to go down the "not really time travel" path and then go right ahead and leave traditional time travel clues!  Still, this is not about whether the author's choices were good ones or not, just what I think is the most likely book the OP read that used this particular idea.
Comment: I suspect his idea was that the different timelines were so similar that the professor in our own 14th century from another timeline sent almost exactly the same message as the one from our timeline in the other 14th century.  But time travel (even if its crosswise) tends to make your head hurt if you think about it too hard.
Comment: Oh, I know how he explained away that discrepancy. I just don't know why that's supposed to be better than just saying "It's time travel, yo" and moving on. From a hard-science perspective they're both equally absurd propositions, and from a narrative perspective, it's actually *less* convincing than just saying "It's time travel!" and moving on.
Comment: At the time it came out, many-worlds was relatively new in the public consciousness (never mind us SF fans who've known about it since the 1970s or longer), and there were "too many" competing novels with "actual" time travel at the time (I think).  That might make a good question, though it might get closed as "opinion based".
Answer: Per the suggestion by user Dosco Jones and the confirmation comment by the OP, this was most likely a story from H. Beam Piper's Paratime series. The 1951 story "Genesis" (part of the series) has previously been asked about and answered (with confirmation by comment) here.


Is the Current Location/Compass heading button available in the iOS sdk?

Question: I am working on a sample map kit app for iOS. I have everything working and a toolbar button to toggle the MKUserTrackingMode. This may seem like a silly question but I have searched all the options in the IB and looked in the documentation, and I can't find any button options like the one for the current location/compass heading used in the iOS Maps app. Is that particular button available to developers?
Answer: You need to create a MKUserTrackingBarButtonItem and pass it the MKMapview in the constructor, then add that button item to the navigation menu (or where ever it is your button should be).
- (void)viewDidLoad
{
    [super viewDidLoad];
    MKUserTrackingBarButtonItem *buttonItem = [[MKUserTrackingBarButtonItem alloc] initWithMapView:self.map];
    self.navigationItem.rightBarButtonItem = buttonItem;
}

Comment: Thank you very much! Exactly what I was looking for. I didn't expect it to be it's own class, thought it would just be a button style. I even wasted time making my toggle function. It comes built into the class!!!
Answer: Maybe I am misunderstanding your question but it sounds like you want to be setting the userTrackingMode property of your MKMapView to theMKUserTrackingMode.MKUserTrackingModeFollowWithHeading.
Comment: Thanks for your reply, but I have that part working. I am using a toolbar button with text label. I would like to replicate the button used in the Maps app to toggle the tracking mode states. I've looked all of interface builder and the docs and can't find that button.


Why there is 96 dots per inch in description but when i opened image it is 300

Question: Can some explain me please? Why  if i right clicked the information about the file there is 96 dots per inch . But when i opened image in GIMP it says it's 300? Images were saved/downloaded from the web.
Comment: What are you actually trying to do? The dpi setting stored in an image only really has any significance for printing (and sometimes not even then) - it doesn't have any significance when it comes to displaying the image on your screen, and has no significance as an indicator of quality or size. You can mostly just forget about this value.
Comment: https://www.gimp-forum.net/Thread-Image-size-in-Gimp
Comment: @osullic, why isn't that the/an answer?
Comment: Related: [Is there any practical difference between saving at 300ppi or 72ppi?](https://photo.stackexchange.com/q/46671/15871)
Answer: 2 things.
I.
The PPI information on a digital image is just a small piece of text embedded in the metadata in some file formats. Some file formats have it, some do not.
II.
Some programs use this information, some do not care at all about it.
When you say "I right click" you do not say where you are right-clicking. On the browser? Is it Firefox, Edge, Chrome, Brave, etc?... there are a lot of them. On the operating system, on the file manager? Which operating system?
Some programs, if the PPI information is missing, can assume a default resolution, some can say 96, some choose 72, and some 300. In reality that is irrelevant.

So the answer is: some programs and file formats handle the PPI metadata or the lack of it, in different ways.

(A side note. The correct unit is PPI; Pixels per inch. Dots is a unit to define the physical density of a printer)
Answer: The DPI can give an indication of the size, if the image was obtained from a scanner (with auto-cropping). You can calculate the actual size of the original image from its pixel dimensions, and the DPI or PPI.
96 PPI is unlikely to be a scanner resolution though. It is usually 300 by default, and on some scanners can be set to lower or higher values.
Comment: This answer is probably true if you're looking at a faithful copy of an image file that was produced by some scanner. But like Rafael's answer implies, any software that is used to open and then "save" or "export" an image potentially could change or discard the resolution metadata.