What will happen to compass with north all around it?

Question: If I keep a compass with bar magnets all around it, all of equal strength and a compass in a center then what will happen? Will the compass start rotating?
Answer:
What will happen to compass with north all around it?

This happens at the North pole:
Here is an image of the magnetic lines at the poles.  The simple compass follows the imaginary lines of the magnetic field and this is what it will do, follow the field line.

On the magnetic pole itself it will try to stand up if held horizontally, pointing towards the ground, making the needle unstable turning around since the south of the needle will be repelled and the north attracted by the field crossing the needle. If held vertically it will steadily point to the ground.
If left on the ground, it will be in an unstable position. It will stabilize in an arbitrary direction when the kinetic energy is dissipated, and will move if some is supplied ( vibrations) arbitrarily.

If I keep a compass with bar magnets all around it, all of equal strength and a compass in a center then what will happen? Will the compass start rotating?

The situation is similar, there will be field lines which from a distance will simulate one north pole. If the compass is held it will be rotating randomly, if left undisturbed the kinetic energy will dissipate and it will be in an unstable state pointing randomly.
Answer: Viewing the compass as a dipole (it is not infinitesimal in size) if there is no field at the center the compass direction is not defined.  It won't rotate-what will drive it?  It will point in an arbitrary direction.  In practice the field won't be zero-the magnets will not all be exactly the same (and if they were, the usual earth field would be sensed) so the direction will be well defined by the errors of the magnets.
Answer: No force applied: no acceleration. It'll simply maintain whatever speed you spun it with (gradually slowing due to friction), or if its speed is 0, it'll point arbitrarily at whatever direction you set it to.


Can there be an equilibrium between humanity's increase of carbon dioxide output with plants since plants harness CO2?

Question: Is it possible that, prior to hitting a thermal equilibrium in the atmosphere, the increase in CO2 that humanity puts out every year will come to an equilibrium due to the consumption by the world's plants, which may respond by growing, reproducing and feeding more off of the additional CO2 in the atmosphere at a faster rate?
Comment: Wow this is one single long sentence! Do you mind splitting up your question is several sentences in the hope of clarifying it? Note that a forest at its climax does not intake more carbon than it outtakes. Plants intake carbon from the atmosphere as they grow but this carbon is being released when they die. Definitely, not all forests are carbon sinks.
Comment: Also consider that even if plants could lock the CO2 produced by mankind's use (which doesn't necessarily work that way as Remi.b notes), there's more deforestation and more urban development worldwide. We have less plants and trees so where will they come from? Plant growth is set at a certain rate by its genetic code even at optimum conditions. More CO2 doesn't speed up growth.
Comment: Well, what you should also consider isn't just the static environment that exists today, but rather how plants evolve, which maybe  to intake more CO2.
Comment: Oceans, rather than forests, are actually the largest carbon sink
Answer: Yes, with 2 caveats.
More CO2 encourages plant growth up to the local plants' limit. After that limit, the plants are saturated and extra CO2 backlogs into the air. If you intend to prevent atmospheric CO2 buildup, you're better off gradually supplying CO2 rather than deploying it in large surges.
The other caveat is dead trees and other plants that should be harvested or logged to make way for new growth (while providing lumber, fuel, and employment).


How to secure my job position, considering outsource jobs?

Question: I'm in the IT industry, and many companies are outsourcing it jobs to India, China etc.
What can I do to secure my positions within the industry?
Comment: Really this is more of a rant than a question.
Comment: It is still not a good question for SE.  We just removed the parts that did not belong here at all.  That improved the question but did not fix it completely.
Comment: The core question is good. But that part ends after the second sentence. ollon, if you would edit out the rant parts, might produce better feedback.
Comment: It's a questions. The question is how I can secure my job and salaries fighting these hard competitor with nothing to lose.
Comment: Yes, that would be a better question text for example.
Comment: please feel free to edit and I'll approve the edit if it still focus on the main question.
Comment: @ollon there you go
Comment: if not outsourced, the indians will come here and compete with us on the spot.
Comment: I would look at who you are supporting politically, typically more liberal parties are more worker-friendly than right-wing parties.
Comment: Thanks, Still, @JoeStrazzere What can we do and young people do to secure a job?
Comment: I am wondering why the now heavily edited question is receiving close votes?
Comment: Yes i am also wondering why it receives negative votes after all the heavy edits?
Comment: [This question](http://workplace.stackexchange.com/q/11816/2322) has a lot of perspective which is the majority of the answer here.
Answer: Be better.
All of the things you say are true. There are billions of people in the world, and in a job market where location is decreasingly important, you are competing with more and more people for jobs. In the end, you're going to have to be better than those you're competing against.
So what can you do to differentiate yourself?
Don't believe the hype, the traditional differentiator - location still matters, even if it's lessened. Even in IT, people work in teams. Working in teams requires communication. Communication is always easier in person. "So put all of the Indians together!"; sorry, they have to get their requirements from somewhere, which requires communication. For you the OP, knowing the Swedish language, customs, and laws provide you with a distinct advantage over foreigners in this regard.
Beyond that, you can differentiate yourself by skill. The US went through an outsourcing binge around the turn of the century, and quickly found that not all programmers are made equal. Projects would go overseas and then fall apart. Work would be catastrophically broken or ill documented. Cheaper is worthless if people can't do the work.
Yes, you might have to take less money to compete. Yes, you might have to live somewhere with a lower standard of living to accomodate that less income. But remember that it works both ways: if you are truly exceptional, you have a whole world of companies fighting to hire you, not just the limited subset within commuting distance. Likewise, more and more people means more and more jobs.
Answer: In addition to what @Telastyn said, domain knowledge is extremely important.
Anyone can learn IT, but can they learn YOUR company's business, too?
More and more companies will need people who can walk "both sides of the line" where business meets IT.  Become an expert in your company's financials, manufacturing process, or inside sales work.
Learning IT is a great skill, but it's a fairly easily-learned skill, based on a lot of memorization.  The VALUE of IT is its ability to support business, either by reducing expenses, generating revenue, or improving capacity / efficiency with existing resources.  Become an expert at that.  It's easy to write a program to do a task.  The value is realizing, "Hey, if we wrote a program to do X, it would cost us $5,000 to develop and let us ship 75 more units per week, increasing revenue by $750,000 per year and earnings by $300,000 per year.  I can make that happen."
Think of it like learning to drive:  Billions of people know how to drive a car.  But 25 or so people are good enough drive a Formula 1 race car through a chicane at 200+ MPH less than a foot away from another car doing the same thing.
Almost anyone can learn to put up a server, connect it to a network, and set up user accounts.  Can you see where one needs to be?  Do you know which one to use?  Do you know how much will be saved or accomplished if you do?  Can you present that to the people who control the money?
THERE'S your long-term job opportunity.
Comment: @Telastyn - respectfully, I have made a great deal of money throughout my career cleaning up after that particular mindset.
Comment: @Telastyn So if you got a job in an investment bank tomorrow, you'd be able to write risk management software that will pass audits just by changing variable names? Let me tell you from experience: it's much easier to teach someone to code than it is to teach them finance.
Comment: @Telastyn if almost all of the code you are writing is business logic code, then your grasp of business logic is at least as important as your coding ability. Relying on the "experts" doesn't work, as these experts can just as well code it themselves in less time than it would take to explain the whole business to you. But worse, you'd make logical bugs, not because you're a bad coder but because you have gaps or misunderstandings in the bus. knowledge - these are the **worst** problems to have, and that's why I'd rather have a passable coder with solid bus.knowledge than star dev with none.
Comment: `Learning IT is a great skill, but it's a fairly easily-learned skill, based on a lot of memorization` <-- I've had a lot of people attempting to convince me otherwise over my career so far. If it's so easy, you would think more of IT would be qualified and competent...
Comment: @Telastyn, domain knowledge is critical and you probaby create would creat significantly better software if you paid attentiono it.
Comment: While I agree with the jist, the rest is garbage. I am a software engineer by trade, and frankly, I can make a great program to generate value for a company while knowing next to jack squat about the domain I'm working in. It doesn't matter if I'm working with widgets, genomes, t-shirts or marketing data the code and the engineering principles don't change... just the variable names.
Comment: Heh, everyone loved that... @MrFox - No, but I can ask people who _are_ experts at finance what that risk management software needs to do. In my experience, people who think they're experts at finance **and** software engineering are _neither_.
Comment: @MrFox - *shrug* I respectfully disagree, but I've also spent the past 8 years going from company to company fixing untestable, unmaintainable, inscrutable catastrophies. It's just as likely that logic bugs are caused by domain knowledge deficiency as programming domain deficiency - except with good programming skills you can at least effectively test, maintain and extend the code when these issues are found. And best of luck to any financier who thinks they can hack together some code better than a skilled professional.
Comment: @WesleyLong - Same here, but I would give my left arm to never have to do it again because it was all made better.
Answer: I read the original post, since it was obvious it had been 'cleaned up' in various respects. A lot of people go off like that, and I heard a lot of it in the early 2000s in the US when legions of older engineers and developers were losing their jobs.
Given the planet's population of 7.1 billion, and roughly 65% are of working age and work, we're talking about 4.5 billion people in the global workforce.  Of these, around 20 million are software developers.  This is roughly one programmer for every 250 people in the workforce.  There are probably 3 billion 'programmable devices' from smartphones to servers, which would suggest there are 150 boxes for every programmer on the planet. Fundamentally, there is more work than there are programmers.  Computer hardware prices are declining at a good clip, even the cheapest software developers aren't getting any cheaper.
If one is seated in a cubie and finds more and more foreigners and fewer and fewer of their fellow countrymen in their team over the space of a few years, it looks scary.  The litany I used to hear was 'why isn't our employer retraining us for current skills?'. Thus the old mainframe and Unix programmers were being dumped instead of retrained in C++ or Visual Basic or the web scripting languages, etc.  One has to ask the people getting laid off what they were doing when they went home. I programmed on minicomputers in the 1970s and 1980s, learned dBase and FoxPro in the late 1980s, learned Visual Basic and relational databases in the mid-1990s, and learned web scripting languages in the late 1990s and early 2000s. I've been out of work, in some cases, for a few weeks in all that time.
To answer the question: first, know your market. There is a certain amount of demand for Perl or JavaScript or COBOL, and a certain number of people that know it. You should first rank the demand for your skills in comparison to skills you could acquire quickly.  If demand for the skills you have is soft, learn ones where employers are struggling to find anyone, anywhere.
Second, people from other countries don't know your banking laws, privacy rules, regulatory reporting, etc. Thus anyone trying to explain to them what you have to watch out for when writing a financial program won't be understood for awhile. In some cases the cultural barrier is a bit more stark - one company in the US makes 'comfortable work shoes for women'. While lots of companies make shoes for women, in some countries no one cares whether women are comfortable, therefore why would anyone make nice shoes for working women?
Third, ultimately your work is to solve problems. I run into a lot of people who think work is something you show up for, follow instructions, and go home at 5:00 PM. They pay no attention to their 'value proposition' - why does someone prefer me over any other employee? I would run into prospective clients that clearly needed some software work but couldn't tell me the brand of their server, the language their application was written in, or what kind of database it ran on.  I've had meetings in which the people asking for software work could not articulate even the simplest requirement. In such circumstances it is good to know how to read minds, however these days that involves expensive equipment and a bunch of egghead academics. Failing that, one has to be a 'spy' - gathering clues from document flow, interviews, looking over people's shoulders, etc. Look at the questions posted by some of the 'foreigners' on this board, and tell me how close any of them are to doing this.
Answer: You secure what value you bring to the company and recognize that there may well be new positions over time. For the past 16 years, I've worked in North America as a web developer where while I've heard this line repeatedly and wonder how well do people really understand how the world works? There will be some positions outsourced and other jobs created instead. Some grunt work may be migrated and other work may be opened up. "The World is Flat" by Thomas Friedman has some good points on how some people may have new jobs that didn't exist years ago and I believe this trend will continue. 23 years ago, there wasn't the world wide web and 13 years ago there wasn't Facebook so new things will come along and the question is how well do you know which roles suit you.
I like solving problems and helping people. Thus, I enjoy working as a developer that fixes and builds systems for companies. While some work did get off-shored to 3rd world countries for a time, some of it came back as they realized the model of being partly on-shore and partly off-shore works better. Thus, there is still a rather good demand for various IT workers in parts of North America.
For all I know, I may end up becoming more of a mobile application developer someday that I'm pretty sure 20 years when people had big bricks for cell phones would have seemed ridiculous yet look where we are. You don't know the future but you should know what roles suit you and thus which kind of work you do well.


How to find a lost vertex?

Question: I have what I thought was a clean model of a shot glass made from seven circles of 32 vertices each. The inside and outside 'bottoms' converge to a single vertex. That should make it 226 vertices in total however it reports there to be 227 vertices. I have 'removed doubles' but cannot find the extra one. What am I missing?
Comment: You are missing a vertex. ;) But how can we help without the file?
Comment: @m.ardito good suggestions ( I didn't know removing doubles had a 'range' so will have to read more). Am I missing a vertex? Seven circles x 32 = 224 + 2 x convergence at bottom and top inside and out = 226? Thanks so far.
Comment: What is a good place to use to upload a file? I don't generally do that as I don't trust them.
Comment: http://blend-exchange.giantcowfilms.com/ it's a resource specific for this site, and permanent. After uploading, post the provided link in the question or comments. I said you're missing a vertex, because it seems there is one missing somewhere... whaen you use L or CTRL-L how many selected vertices are diplayed in the top bar, 226/227?
Comment: This is the file. Still not completely sure what's wrong. [](https://blend-exchange.giantcowfilms.com/b/4033/)
Answer: Select a good vertex, Ctrl+L to select
 all good 226 vertices, then Ctrl+I invert selection, then delete the extra vertex.
Comment: this works if the missing vertex is not connected, but it could also be connected but either close to another, but outside of the remove doubles range or could be that he by mistake subdivided an edge. In other words, if ctrl-l selects 226 vertices, it should work.
Comment: thanks @josh alas did not work. I must still be misunderstanding something...
Answer: For some tedious tasks, Blender has nice tools built-in. One of them is hidden in the Select menu, and is called select by trait. It offers selecting mesh items based on certain criteria. In your case, the additional vertex might be a stray one floating around in space.
To locate that vertex: Make sure you're in Vertex selection mode, then run the command from the menu: Select > Select All By Trait >
 Non-Manifold or Loose Geometry. Potentially that vertex is off-screen, so hit . on the Numpad to view it.
Comment: thanks for your great response however I still have (what I think is) the wrong number of vertices??
Comment: @MarkMars When you execute the Select all by Trait -> Loose Geometry, or Non-Manifold, does something get selected? If so, how many verts? If it's only one, all you need to do is delete it. Otherwise, it might be a good idea now to upload the blend file to http://blend-exchange.giantcowfilms.com/
Answer: With your file provided, it was easy: here it is the "lost" vertex:

:) and it is connected, that's why none of the method suggested until now worked...
and here is how a "remove doubles" with a "merge distance" slightly incremented removes exactly one of those two vertex
Comment: Oh my. That was so easy to miss! Thank you @m.ardito It may not seem so but that's a BIG help. I need to pay more attention to detail. I now know how to look closer.

How to find a lost vertex?


SWR reading problems

Question: Hey I'm new to using CBs I have a classic Cobra 29 I had it peaked and tuned supposed to be pushing about 60 watts also supposed to have everything set as far as my SWR however I am still only getting out about as far as I did with the stock radio at 15 watts I was told I needed to run in s/RF mode when I do and I key up I transmit at about 1.5 but sometimes while receiving the meter goes up past two and three while people are talking is that normal?
Comment: Not sure I can help much, but you might want to check the manual. Often the meter has dual functions: when sending, it shows your SWR, during receive is shows your received signal strength. Does the meter have a seconds scale besides SWR?
Comment: Highly unlikely your Cobra 29 can output 60 watts without serious modification to the final section. According to what I find, the final transistor is an ERF-2030 which in the updated version can output ~25 watts https://datasheetspdf.com/pdf/713512/EKLComponents/ERF-2030/1 Also, even if you can output 60 watts from the 15 you had earlier, that is only 1 S-unit difference to the folks who can hear you anyway. The question is, what are the signal reports now compared to before, from the people you contacted before the modification?
Comment: 60 watts is [illegal](https://www.wearecb.com/cb-radio-range.html#:~:text=End%3A%20Increasing%20Range-,CB%20Radio%20Power%20Output,TV%20and%20emergency%20communication%20radios) on CB.
Comment: Please [edit your question](https://ham.stackexchange.com/posts/21923/edit) so that it is not a run-on sentence.
Answer: The process is a bit more complex - first you need to calibrate the internal SWR meter, then you need to read it on the antenna.
the manual says:

Calibrate for SWR (Standing Wave Ratio) SWR calibration is done to
properly adjust the length of the antenna and to monitor the quality
of the coaxial cable and all RF connections. This calibration is
critical to achieve optimum performance.

Select Channel 20.
Switch to the CAL position. NOTE: Antenna Indicator LED will illuminate when transmitting if the SWR is high.
Push and hold the mic button.
While holding the mic button adjust the SWR CAL knob so the meter swings to the CAL mark on the right side of the meter. NOTE:
Calibration must be made in an open area (never in a garage). The
vehicle's doors must be closed. No one should be standing near the
antenna. (See your antenna directions for more complete information.)
While still holding down the mic button, set the S/RF SWR CAL SWR position, to read the SWR reading.
Repeat the same steps two through five on Channel 1 and 40. This will check SWR for all channels.

NOTE: When switched to SWR position
the meter needle should ideally be as far to the left as possible.
Anything over 3 is not acceptable. The antenna indicator will light. A
slight antenna height adjustment (higher or lower) may be required.
Repeat recalibration steps

It also says:

S-Meter
The S-Meter swings proportionately to the strength of the incoming signal when receiving. The S/RF-SWR-CAL switch must be in the S/RF position to read the meter

so this makes sense when you are receiving.
I think it's very unlikely that the radio can produce 60 watts without an external amplifier. It's specified for 4 W and some tweaking might double that, though it would overheat more quickly. And if you have an external amplifier, the SWR meter won't show you whether the antenna is working or not.
There is a fair amount you can do to improve the antenna performance on a vehicle, with the antenna position, improved grounding, panel bonding, etc. Search the internet for "HF Moble Antenna Installation" for a lot more suggestions.
Answer: Joe Lee, it's nice to see your first question on this web site !
Someone may have told you that your Classic Cobra 29 pushes out 60 W, but i believe some wishful thinking or just plain exaggeration was involved there, this radio is only capable of 5 - 10 W max.
Then, despite what may seem, in reality the difference in getting out between 10 W and 15 W will be hardly noticeable. If you increase the power of a CB from 10 to 15 W, at the other end the person listening to you will only notice a tiny amount of improvement.
To answer your question, the S/RF meter in your CB radio has two functions, it shows the received signal strength of stations or people you can hear when you are listening, and then it shows the output power of the CB when you are talking or transmitting.
When you are listening or receiving, the meter reads the signal strength of the people you can hear, this is the "S" part of the S/RF meter.
Then, when you are talking or transmitting, the S/RF meter will read the output power of your CB, this is the "RF" part of the S/RF meter. It should normally go up to about 2/3 of the way when you are talking.
You just have to make sure that the left most 3 position switch on the front of the radio is set to S/RF. The other settings for that switch are for checking if the antenna is tuned correctly, i would just leave that for now. This switch has no effect on how you get out, regardless of what it's set to, it only affects what the meter is showing.
When listening or receiving, it is normal for the meter to go from zero all the way to the end, or anywhere in between, depending on how strong the people or signals are that you are listening to.
Hope that all makes some sense !

SWR reading problems


Low fat muffins won't rise

Question: I'm really trying to make a great low fat muffin. No matter how hard I have tried with this one (I am not over stirring), I can't get these to rise past a mini muffin height, and this batter is so sticky, it's all I can do to get it off the spoon. Any insight/suggestions?
https://www.averiecooks.com/skinny-blueberry-muffins/
Comment: Is your baking powder relatively fresh?
Answer: Muffin mix should be a pourable batter, not a thick dough, your mix is too dry. If it's too dry and claggy it won't be free to expand, and you don't get a rise from water vapor. Try adding more cashew milk until you get a pourable batter, and try it again. You want it to be ribbony, not so loose it evens out right away.
Comment: I'm not sure about pourability being needed for rise. I don't make many muffins, but I have a cake recipe which has to be dug out of the mixer bowl with a spoon, and it rises very high, more than a typical pound cake, for example.
Comment: upvote for "claggy".
Answer: Try a different sour milk product.
I am suspicious of the pectin and guar gum and other stuff that turns up in Greek yogurt.  Suspicious for baking and cooking purposes; I think that stuff is fine to eat as yogurt.  Different "greek yogurts" vary a lot as regards what thickeners are in them besides milk.  Maybe the author used something different than what you have.
I never bake or cook with nonfat yogurt but if that is an important part of this, you could try a brand with minimal additives.  Or if your goal is to make good muffins you could use plain full fat yogurt.  Or substitute sour cream thinned to the correct consistency with some extra cashew milk.  Sour cream makes good muffins.
Comment: A proper Greek yogurt shouldn't have **any** thickeners added to it. Yes, many brands do use them, but your answer asserts that they all do, which is false.

Low fat muffins won't rise


Does cut and paste work in terminal?

Question: Does cut & paste work in terminal? As in ctrl+c and ctrl+v?
Answer: For pasting in the terminal you have to use Ctrl+Shift+V, and for copying, Ctrl+Shift+C.
Answer: In Ubuntu and Linux in general you have several ways of copying and pasting.
For apps not related to a terminal environment you can simply do the following:
CTRL+C - Copy
CTRL+V - Paste
CTRL+X - Cut (Not available in Terminal by default)
On the terminal you simply add SHIFT to this shortcuts, like this:
RIGHT SHIFT+RIGHT CTRL+C - Copy
RIGHT SHIFT+RIGHT CTRL+V - Paste
The difference is that you need to use the Right keys.
Additional to this, if you have mouse support, this includes a quicker way to copy and paste information. by simply highlighting a text you are actually copying to a special clipboard that holds the last highlighted text you have selected. To paste this text, either on a non-terminal app or even inside the terminal you can simply click on the middle mouse button. This will paste the last text you have highlighted with your mouse.
Comment: The `RIGHT` isn't necessary, just Ctrl+Shift+C and Ctrl+Shift+V will work.
Comment: If you use other languages the default shortcuts change to the right only. In English it works on both sides.
Answer: Ctr + c is used to terminated a program (sending kill signal to current process). I think that there's a way to change that. Google is your friend to find how.
Answer: You can also use Ctrl+Ins for copy and Shift+Ins for paste

Does cut and paste work in terminal?


What is the largest possible rocky body?

Question: Suppose you start with a rocky sphere about 12,742 kilometers in diameter and continuously add more rocky material such that you don't smash this sphere to bits.  What is the upper limit for this?  What happens as you approach that limit?  What happens once this limit is exceeded?
Comment: You may get better answers for this particular question by asking it on the  [physics](https://physics.stackexchange.com/) or [astronomy](https://astronomy.stackexchange.com/) stack exchanges
Comment: If you are careful to keep it from getting too hot you could do it for a while (by which I mean many earth masses).  There'd be a phase change when pressure in the core turned it into degenerate matter; don't know if that would heat it up suddenly enough to get an explosion or silicon fusion started.  You'd probably end up with something resembling a black dwarf.
Comment: [This answer](https://astronomy.stackexchange.com/questions/12558/is-there-an-upper-limit-to-the-mass-of-terrestrial-planets) looks relevant!
Comment: It could depend on how much angular momentum you add.
Comment: What are your conditions for the limit?
Comment: Very interesting question. I think you are more likely to have it answered on astronomy or physics sites.
Comment: A related question on Physics.SE: [What if Jupiter or the Sun was made of rock, like Earth and Mars, rather than gas?](https://physics.stackexchange.com/q/583331/123208)
Answer: An article from 2016, yes old, stated that it was once thought any planet with a radius about 1.6 that of the Earth would become a gas giant, based the 2015 paper, Leslie A. Rogers, MOST 1.6 EARTH-RADIUS PLANETS ARE NOT ROCKY, The Astrophysical Journal, Volume 801, Number 1.
Since then, a rocky exoplanet, TOI 849 b, was discovered in 2020 which supposedly is the largest rocky exoplanet yet discovered. It has a mass 39 times that of Earth and its radius is 0.307 that of Jupiter (3.369 times the radius of Earth). It's calculated average density is 5.638 g/cm3 (1.023 times that of Earth). Its gravity would be 33.826 m/s2 (3.44 times that of Earth) and its escape velocity would be 38.1 km/s (3.41 times that of Earth). The surface temperature is either 1093 °C or 836 °C.

TOI-849b's odd properties suggest that it could probably be the core of a gas giant planet that should have grown more massive than Jupiter.
One possibility why TOI-849b has cleared a gap around its star is because it ran out of material to collect, and stalled. Or this massive planet could have been a huge planet that somehow lost its atmosphere because it was too close to its star.
The third possible explanation is that cataclysms during the planet's early years both bulked up TOI-849b's core and stripped away its atmosphere.
Comment: Nice information, but doesn't quite address the question. OP doesn't ask what is the largest discovered rocky planet, but what is the largest possible rocky planet. OP doesn't put limits on the atmosphere, so presumably the "rocky planet" could be the core of something which looked like a gas giant.
Answer: In theory (and from a God like perspective putting practical considerations to one side) it should be possible to build a rocky planet of any size you want. The only limiting factor would be when the mass of the planet was so great that the escape velocity exceeded the speed of light and a black hole formed.
Comment: Are you sure it would not become something different than a planet when it got really massive? A star, supernova, black hole, neutron star, etc... Where's the supporting source for "...it should be possible to build a rocky planet of any size you want."
Comment: Well it does depend on the composition. Provided the core was made of iron it wouldn't be susceptible to nuclear fission or fusion. But radioactive impurities could  melt the surface. If it got hot enough and big enough it might take on some of the characteristics of a brown dwarf, but with less energy.  If there was a thick mantle layer with a lot of oxygen, silicon and aluminium they might eventually be forced into some form of nuclear reaction but I doubt there would be enough pressure or a high enough temperature. More likely a lot would boil off into a superheated atmosphere of sorts.


What is the origin of the four cardinal directions (North, East, South, and West)?

Question:
Why are there four? I would guess it was fixed after the egocentric/"relative" directions (left, right, front, back). Or was it because human used to consider the ground as flat and 2-dimensional?
How are they defined? Wikipedia says their English names have origins in Proto-Germanic words related to sunrise, so probably East is defined as the direction where sun rises. But how exact is such directions? As we know, in the northern hemisphere the sun rises precisely due east only on the equinox. Why was East not picked as a direction somewhat eastnorth or eastsouth? Or did cardinal directions origined in a civilization living near the equator? Did the Inuit have a more southern East?
Are they "natural concepts"? I remember I was taught the directions at school when I was a little kid. Could a person develop the concept of cardinal directions without influence from teacher/parents? How important are the directions for hunting/gathering/agriculture in a prehistoric environment? Do animals have concepts of directions?
Did the early civilizations have different definitions for the directions? How do they influence each other? If civ A traded with civ B and noticed they used a "somewhat rotated map", would any of the civs change their direction system?
Comment: There are too many questions for one post, could you focus on something in particular? Most of these questions are answered by [Wikipedia](https://en.wikipedia.org/wiki/Cardinal_direction): cardinal directions were traditionally associated with prevailing winds, some cultures had five, people did not care about exactness for everyday purposes, navigators used astronomical markers or magnetic north. Part 3 is not really a history question, maybe Psychology SE is a better place to ask.
Comment: Also note that North = negative(south) and East = negative(West) .    Your questions 2,3,4 are anthropology, not math/ science.
Comment: ref *Do animals have concepts of directions?*, think of birds migrating northwards or southwards in spring or automn. They must understand something about general directions.
Answer: The origin is astronomical. North is the direction to the North Pole of the celestial sphere. (To the point about which the sky performs its daily rotation as seen from the Northern hemisphere).
The opposite direction to this is called South. South is also the direction to
the Sun in the middle of its daily way over the sky. These directions are of fundamental importance.
East-West are perpendicular directions (in the horizontal plane). East to the side where the Sun rises, and West where it sets. But the Sun rarely rises or sets exactly in the East/West.
Why 4? Because the horizontal plane is 2-dimensional. So you need two axes to describe the points and directions in this plane. But it is convenient to have
different names for the "positive" and "negative" directions of these axes, therefore we have 4. (We are talking of the times very long before negative numbers were introduced, possibly before ANY numbers were introduced. So the subject does not belong to history in the technical sense, but rather to pre-history).
There are natural concepts, even long before civilizations. The period in time when they were really needed was the introduction of agriculture. (Long before "civilization" which is usually associated with writing, states, etc.)
To do agriculture you need the notions of the year and seasons of the year, when they start and end etc. All these notions are of astronomical nature, and you can
clearly establish them (and most importantly PREDICT them)
ONLY by observing the sky.
When you just begin observing the sky, the first thing that you notice is that the sky as a whole rotates about certain point with period of revolution which we call day-and-night (or simply "day" in English, which is highly confusing, see the below).
This point in the sky is seen in the North direction.
The South direction is even easier to observe: it is where the Sun is
in the middle of the day.
These directions never change.
The directions to the points where the Sun raises and sets do change during the year, but to describe them one needs some fixed points of reference, and these are East and West, so that EW-axis is perpendicular to the NS axis.
Reference. The oldest surviving treatise on agriculture,
Hesiodes, Days and Works. (Translated from the ancient Greek to all modern languages, I suppose, and free of copyright:-)
Remark. Some languages have a single word for the day-and-night period.
The technical name in English is nychthemeron (how many English-speaking people have ever heard this?) If your native language does not have this word, see Wikipedia about it. This word is clearly Greek,
not native to English or German languages.
Wikipedia gives a very interesting list of languages which have such a word as a native word. I always wondered what this list says about history or prehistory of various languages and peoples and astronomy etc.:-)
Comment: @Peter M. The easiest thing to notice is the Sun:-) It raises and then sets. At the moment when it stops raising and reaches its maximal height, it is due South. All other conspicuous points (when it appears or where it sets on the horizon) vary. But this point of maximal height is always due South.
Comment: +1 Also, I read somewhere that 20-30KY ago the North Star was Vega. Much easier to notice.


Job for apache2.service failed because the control process exited with error code.

Question: I tried to restart my Apache after updating my config
sudo service apache2 restart
I kept getting this

Job for apache2.service failed because the control process exited with error code. See "systemctl status apache2.service" and "journalctl -xe" for details.

How do I prevent that ?
Answer: Here is the answer: https://askubuntu.com/a/1022319/850782
cd /etc/apache2
apache2ctl configtest

probably has some typo in some config file that you have created:
vi /etc/apache2/sites-enabled/yoursite.conf

Answer: You may mixed up something in apache2 configuration better to remove and reinstall a fresh apache2 , Hope this will help you .
First uninstall apache2
sudo apt-get purge apache2
sudo apt-get purge apache2-common
sudo apt-get purge apache* # this will remove completely

sudo apt-get update

Next install fresh apache2
sudo apt-get install apache2

Next Check for the apache2 status
systemctl status apache2

Answer: In my case i was already running nginx server on the same PORT.
So i used sudo service nginx stop then sudo service apache2 restart and it worked.
netstat -plant | grep 80 use this command to see if port is already in use.
Answer: Re-install apache2
sudo apt-get install apache2

And start your server
sudo service apache2 start


In the Alan Wake video game, is Bright Falls based on anywhere real?

Question: I just played the Alan Wake game (more correctly, for the fourth time) and begin to question whether the town of Bright Falls, around which most of the game is set, and all its mystery is based on anything real? Any good information?
Comment: Is Bright Fall the video game's name ? Can you give some details about the game's world ?
Comment: No, the game's name is Alan Wake, the overall detail is rather complicated, it'a town with many mystery which I find more amusing than other mysterious world (ex: Silent Hill)
Answer: I know this post is old, but I'd figure I'd add to it. I've heard some people say it looked  a lot like some of the nothern parts of Washington, specifically the areas heading toward the North Cascades National Park. There's a small town/village/living area called Newhalem, Wa, which is only used by people who work for Seattle Light, but this is one of the pictures of the town I found:

(source: panoramio.com)
and the Bright Falls Light & Power Company:
Answer: Wiki says:

The story follows bestselling thriller novelist Alan Wake, as he tries to uncover the mystery behind his wife's disappearance during a vacation in the small fictional town of Bright Falls, Washington

and more specifically about what it's based on:

The game's setting, Bright Falls, draws inspiration from the early 1990s TV show Twin Peaks, which was set in the titular town; both fictional small towns in the state of Washington. Alfred Hitchcock is also cited as an inspiration, with the flocks of birds that often attack the protagonist being influenced by his classic horror film The Birds.

So, the mysteries etc... are NOT based on anything real but have some inspirations in existing popular culture properties.
Answer: The accepted answer seems authoritative to me. The only thing I'd add is that one of the other locales in the game, Cauldron Lake, certainly seems inspired by the real Crater Lake in Oregon:
Cauldron Lake:

Crater Lake:
Answer: the game was actually built around a town that does exist in Detroit Oregon.  to be specific, the game was based directly on Detroit lake.  If you research it further or read interviews with the developers of the game you will find them refrencing this town multiple times along with pictures of existing places like the diner, power dam, gas station that end up appearing in the game looking almost exactly as they look in the actual pictures from the destination.  Best bet for you is to use google maps on this location, look around for a good 20 minutes and you will see multiple reference points that they put into the game.  really cool stuff if you ask me.
how do i know this?!? I'm a huge alan wake fan, travelled to Detroit 2 times just to explore based on the game.  good luck!
cheers
Comment: wow! really? can you point out some of the details, maybe the similarity of the game and the real place? i would love to research it further
Comment: 2020 Update: Detroit, OR was destroyed by fire in real life in the western states 2020 wildfires, circa September 2020. It was widely reported the town of Detroit and surrounding area was "burned to the ground," and all but unrecognizable.

One resident's account unfortunately looks like it could be a scene of horror from a horror video game: https://youtu.be/on9D5r719gM

Detroit Lake State Recreation Area only reopened to full services earlier this year in 2021.
Answer: Though not directly affecting the game, there are also a lot of towns in Maine (Stephen King's backyard, and the location for most of his works) that, though not what Bright Falls is modeled after, definitely have the same atmosphere, with the bars, diner, trailer parks, and logging mills.
King's work is a major influence in the game's lore.
Wake says as much at the start.
As previously stated by other users, Oregon (where Life is Strange is based) is full of similar town types, as well as Washington state.
Inland California also have some towns with the Bright Falls/Twin Peaks/Haven/Secret Circle/Ozark/Silent Hill/Hawkins vibe.
Their pretty much littered all across the US, and Canada (specifically Ontario), as a lot of Supernatural episodes are also filmed in the Land of the Mounties.
Comment: Hi, welcome to SF&F.  This would be a better answer if you could point to specific elements or individual places in the story and their real-world counterparts.  As it is, this is too general actually answer the question.
Answer: So based off the game map compared to a map of WA it looks to me to be a sort of rearranged version of the islands near Seattle and Olympia.. But it's the closest similarity I can find..
Comment: Hi, welcome to SF&F.  You could improve your answer by showing both maps and how they compare.  And is there a town in that area that might correspond to Bright Falls?


Do single items on the Windows Start Menu need a folder?

Question: My team is creating an application that has a single entry point. There will be a single entry point, meaning only one item on the Windows 7 start menu/Windows 8 start screen. Other than "that's how it is done", can anyone explain why users would benefit from placing this one item a folder?  I say that going directly under "All programs" makes it faster to access for users who don't search or use the desktop to start applications.
Comment: maybe there was benefit in Windows <= XP when single items would sort after the list of folders, but in 7, single items are at the top, and in 8, I think all items in a folder are displayed (grouped) anyways
Answer: As far as I'm concerned, putting single entry points into folders is just annoying. However, if I have multiple program entry points and they can be categorised, I'd put them in folders. But that's just my preference.
To be frank: users will put things wherever the f*** they want. I know people who OCD-style categorise everything and would put your entry point in two hunderd layers of folders. I also know people who don't give two s**ts where their programs are.
The point being, as a developer it is irrelevant to you where users put their icons, as long as they can get at them. However, you might want to know what your users find most useful so you can install it there to start with. I can only say 'do some research' to that: every group of users is different, so talk to yours and find our what they like.
Comment: This has been an OCD of mine. I definitely prefer single entries to not have a directory. There also should not be an uninstaller in the start menu, there's a dedicated UI for uninstallers. The readme does not belong in there, either, nor do product links, etc. A good example of using a folder is Microsoft Office, a bad example is anything by Adobe.
Comment: +1 for being driven to the point of obsenity, but pulling back and going with asterisks. I feel your pain, truly.


How to upgrade MongoDB on Windows Server

Question: How do you upgrade MongoDB on Windows server? Running the Windows installer for the new version only installs a new copy of MongoDB and ignores the existing copy.
Answer: Edit:
First start the cmd.exe in admin mode and cd to the location of the old installation, for standard installations:
cd C:\Program Files\MongoDB\Server\3.2\bin

Stop all applications, which are accessing mongodb, then enter
mongod --remove

Then install the new mongo db, copy the mongod.cfg file from 3.2 to 3.4 directory. When you had one, otherwise follow the installation instructions for setting up the new service. This update worked fine for me, all data available, I didn't need to use this features switched off.
Comment: I have read that document and it's target audience is Linux, not Windows.
Comment: I'm doing the update right now on a separate machine, because I'm curious, I will update the answer soon.
Comment: Updatet, the old code is inactive afterwards, I didn't removed it.
Comment: I guess the issue is how we define "upgrade". We are effectively installing a new version and pointing it to our existing data, which I guess you can call an upgrade. If you are dealing with an msi usually the package upgrades existing files. This is just install new application, point at old data. /end rant. Thanks for your help though, it's appreciated.
Answer: I upgraded from version 3.6.0 to 3.6.2 just today and below are the steps involved:

Download the latest version from the [mongodb wesbite][1].
When downloading is complete, stop any running instance of mongodb by typing 'Ctrl+C' on the command console.
Run the installation file and it automatically installs the new version at the same path as the previous version (at C:\Program
Files\MongoDB\Server\3.6).
Start the database server by typing 'mongod'.
All previous databases will be accessible to you.
Comment: This worked for me and all my collections where intact
Answer: Windows MongoDB major version upgrade can be performed easily in-place , here i am describing the steps to upgrade MongoDB 4.2 to 4.4 with existing data directory. You can follow the same for any version upgrade.
We will use the Windows command prompt to perform all steps below:

For safety take a backup of existing DB, provide a path to backup them

cd C:\Program Files\MongoDB\Server\4.2\bin

mongodump -o D:\DB_backup

Stop all the application writes and shutdown the MongoDB service

type "services. msc" and hit Enter or press OK

Services -> MongoDB Server -> Right click & stop

Install the new MongoDB mongodb-windows-x86_64-enterprise-4.4.8-signed.msi file msi package by using GUI provide the old exixting directories. Meanwhile rename directory from 4.2 to 4.4

Data dir - D:\MongoDB\Server\4.4\data

Log dir  - D:\MongoDB\Server\4.4\log\

This will replace all the bin files with older version ones and MongoDB will be started automatically.

Finally , move to the bin directory, run mongo.exe client and check the DB availablity

cd C:\Program Files\MongoDB\Server\4.4\bin
Answer: On windows pro.
It worked for me like below:

Install new version without uninstalling existing.
Stop the mongodb service.
Copy data folder from previous mongo to new mongo folder.
Repair new mongo installation.
Uninstall previous mongodb.


Remote control of older Yongnuo flashes

Question: I have been searching everywhere but I can't find a clear answer. I have a few older Yongnuo flashes, specifically the 560, 560ii, and 565ex. I am trying to find a transceiver trigger that will allow me to remote control flash power from on top my camera. Is this even possible with the older flashes? Or is it just time to upgrade and get some new flash units?
Answer: There is no transceiver/trigger that will have remote power control over the YN-560 or YN-560II. They don't have built-in RF with power control, and the single pin on the foot means the only signal that can be communicated over external radio triggers is sync.
You can remotely control the power on the YN-565EX if you use TTL-capable triggers, such as the YN-622s.
You basically have two choices, if you want to stay with Yongnuo:

Dump all your units, and go with the YN-560-TX triggering system.  This is manual-only triggering (no TTL or HSS), but you will have remote power control if you use a YN-560-TX or a YN-560IV or YN-660 on the camera hotshoe. As slaves, you can use the YN-560III, YN-560IV, or YN-660. You cannot add Yongnuo TTL gear into this setup without losing TTL capabilities to make it compatible with the triggering system. Any non-Yongnuo speedlights cannot be power-controlled through RF-603II or RF-605 transceivers. Yongnuo's YN-622 and RF-60x systems are incompatible.
Dump the -560 units, and get TTL-capable speedlights and add YN-622 transceivers, or get the YN-685EX (which has a built in 622 receiver). You can use a 622 or 622-TX unit as your on-camera transmitter. But any flashes you want to add into this setup must be TTL-capable (and if you're a Canon shooter, menu-commandable) if you want to set manual power levels (vs. TTL ratios).

There's also a third option that may make more sense for future growth (well at least this month; low-end Chinese flash gear churns at an alarming rate. The FlashHavoc blog is a good way to keep up with what's current):

Dump all your units and go with the Godox X system. The UI/UX isn't quite as nice for Canon (especially if you're shooting with a pre-2012 body), but you can easily mix TTL and manual-only speedlights, and, unlike the RF-60x/YN-560 system, you will have HSS with either (assuming you're shooting with a body that can do FP/HSS--Nikon 3x00 and 5x00 bodies can't).  The TT600--the Godox equivalent of the YN-560III/IV/-660 plays nicely in the same system with the TT685 (the Godox equivalent of the YN-685--only it has a transceiver built in, not just a receiver).  And the same radio system is built into Godox's other lights: the Li-Ion powered speedlights (V850II/V860II), the bare bulb flashes (AD200, AD360II), and the monolights (SKII series, QSII series, QT600II, and AD600). If you ever want to go bigger than speedlights, Godox gives you a lot of choices; Yongnuo not so much.

See also: What are the Yongnuo flash naming conventions?
Comment: It would be much more accurate to say, *Yongnuo's YN-622 and YN560/RF60x systems are only partially compatible in only one direction* than to say they are totally incompatible. **All YN622 capable receivers made since late 2014 can be controlled by YN560/RF60x transmitters with the full capability of whatever YN560/RF60x transmitter is being used.**
Answer:
Or is it just time to upgrade and get some new flash units?

Yes, it is time.
The manual power only YN560 and YN560 II have no provision for power control beyond the controls on the flash units themselves. With no connectors for any external unit to communicate with the flash's internal controls, there is no way for any current or future triggering system to set power externally.
Your YN565 EX is externally controllable by radio in either manual or TTL modes via a YN622 set of triggers. You need a YN622 transmitter attached to both the camera's hot shoe and on the foot of the off camera flash. The YN622-TX is a transmitter only unit that includes an LCD screen showing various menus and settings. The YN-622 is a transceiver that can be used as either a transmitter on the camera or as a receiver attached to the flash. It has no LCD screen and displays selected settings via an LED light next to each switch or via the switch position itself. It is a bit more difficult to use as the on camera unit unless your camera has menu based external flash control (pretty much a post 2008 Canon EOS model). Both the YN622-TX and YN-622 come in Canon and Nikon flavors. The YN-622 transceivers were updated in 2015 to the YN-622 II.
If you decide to stay in the Yongnuo system you can use a YN622-TX controller/transmitter on your camera and a YN-622 II set to receive mode attached to your YN-565EX. For the other two flashes (to replace your YN-560 and YN560 III) you can either use a YN685 that has a built in YN-622 radio receiver, a YN568 EX II combined with a YN-622 II attached, or a YN-565EX II with a YN-622 II attached.

Remote control of older Yongnuo flashes


Changing Python version in Xubuntu

Question: I am in the processing learning python. I was previously learning in Python. I used version 3. Today, I installed Xubuntu 13.04. I am a very new Xubuntu user. The os had two versions pre installed. 2.7.4 and 3.3. When I type python in the console, v2.7.4 opens up. How do I change that to v3.3?
Answer: To run Python 3, use the python3 command. To set Python 3 as default, add a symlink to /usr/local/bin as root:
sudo ln -s /usr/bin/python3 /usr/local/bin/python

After doing that, you can still execute Python 2 with python2 or python2.7.
Answer: Type python3 instead of simply python. Python runs 2.x, whereas python3 runs 3.x
Answer: The Debian way typically involves using update-alternatives
So for Python:
sudo update-alternatives --config python

Changing Python version in Xubuntu


Database vs File system storage

Question: Database ultimately stores the data in files, whereas File system also stores the data in files. In this case what is the difference between DB and File System. Is it in the way it is retrieved or anything else?
Comment: related: https://dba.stackexchange.com/q/2445, https://stackoverflow.com/q/662488, https://stackoverflow.com/q/815626
Answer:
A database is generally used for storing related, structured data, with well defined data formats, in an efficient manner for insert, update and/or retrieval (depending on application).
On the other hand, a file system is a more unstructured data store for storing arbitrary, probably unrelated data. The file system is more general, and databases are built on top of the general data storage services provided by file systems. [Quora]

The file system is useful if you are looking for a particular file, as operating systems maintain a sort of index. However, the contents of a txt file won't be indexed, which is one of the main advantages of a database.
For very complex operations, the filesystem is likely to be very slow.
Main RDBMS advantages:

Tables are related to each other

SQL query/data processing language

Transaction processing addition to SQL (Transact-SQL)

Server-client implementation with server-side objects like stored procedures, functions, triggers, views, etc.

Advantage of the File System over Data base Management System is:
When handling small data sets with arbitrary, probably unrelated data, file is more efficient than database.
For simple operations, read, write, file operations are faster and simple.
You can find n number of difference over internet.
Comment: first half of this answer is copied from https://www.quora.com/What-is-the-difference-between-a-file-system-and-a-database/answer/Christian-Smith-2
Comment: The only difference between database and file system is that the way and structure in which the data is stored. But both the system stores. right?
Comment: yes,but structured or unstructured data is the question
Answer: "They're the same"
Yes, storing data is just storing data. At the end of the day, you have files. You can store lots of stuff in lots of files & folders, there are situations where this will be the way. There is a well-known versioning solution (svn) that finally ended up using a filesystem-based model to store data, ditching their BerkeleyDB. Rare but happens. More info.
"They're quite different"
In a database, you have options you don't have with files. Imagine a textfile (something like tsv/csv) with 99999 rows. Now try to:

Insert a column. It's painful, you have to alter each row and read+write the whole file.
Find a row. You either scan the whole file or build an index yourself.
Delete a row. Find row, then read+write everything after it.
Reorder columns. Again, full read+write.
Sort rows. Full read, some kind of sort - then do it next time all over.

There are lots of other good points but these are the first mountains you're trying to climb when you think of a file based db alternative. Those guys programmed all this for you, it's yours to use; think of the likely (most frequent) scenarios, enumerate all possible actions you want to perform on your data, and decide which one works better for you. Think in benefits, not fashion.
Again, if you're storing JPG pictures and only ever look for them by one key (their id maybe?), a well-thought filesystem storage is better. Filesystems, btw, are close to databases today, as many of them use a balanced tree approach, so on a BTRFS you can just put all your pictures in one folder - and the OS will silently implement something like an early SQL query each time you access your files.
So, database or files?...
Let's see a few typical examples when one is better than the other. (These are no complete lists, surely you can stuff in a lot more on both sides.)
DB tables are much better when:

You want to store many rows with the exact same structure (no block waste)
You need lightning-fast lookup / sorting by more than one value (indexed tables)
You need atomic transactions (data safety)
Your users will read/write the same data all the time (better locking)

Filesystem is way better if:

You like to use version control on your data (a nightmare with dbs)
You have big chunks of data that grow frequently (typically, logfiles)
You want other apps to access your data without API (like text editors)
You want to store lots of binary content (pictures or mp3s)

TL;DR
Programming rarely says "never" or "always". Those who say "database always wins" or "files always win" probably just don't know enough. Think of the possible actions (now + future), consider both ways, and choose the fastest / most efficient for the case. That's it.
Comment: This answer seems to best address the practical use of both. Maybe add a section to cover the way a DB stores information on disk vs the way a file may store data. I mean to clarify that a DB is not just a bunch of lines in a big file, which seems to be part of what the question implied.
Comment: @MaxPower you're absolutely right, but that could fill a few books. I'm sure even here on stacko there's more than one article explaining balanced trees and indexing algorithms. What we conveniently use through simplified interfaces is, in fact, the heavy science of IT. I only know a handful of guys who could implement a db-like storage from scratch and most of them are 50+, which is also true for SQL itself. (Systems like Elastic are very different, I'm not brave enough to make such statements about them but again: science. It's there behind.)
Answer: Something one should be aware of is that Unix has what is called an inode limit. If you are storing millions of records then this can be a serious problem. You should run df -i to view the % used as effectively this is a filesystem file limit - EVEN IF you have plenty of disk space.
Comment: But you can storage many "records" in JSON format in 1 file. You don't need to treat 1 file as 1 record. The 1 file could be a DB "table". Don't you?
Comment: Issue there is that the single file is going to get mighty big and need to be read in memory. I don't know how the database systems handle that but I think file size would then become your issue.
Answer: Context: I've written a filesystem that has been running in production for 7 years now. [1]
The key difference between a filesystem and a database is that the filesystem API is part of the OS, thus filesystem implementations have to implement that API and thus follow certain rules, whereas databases are built by 3rd parties having complete freedom.
Historically, databases where created when the filesystem provided by the OS were not good enough for the problem at hand. Just think about it: if you had special requirements, you couldn't just call Microsoft or Apple to redesign their filesystem API. You would either go ahead and write your own storage software or you would look around for existing alternatives. So the need created a market for 3rd party data storage software which ended up being called databases. That's about it.
While it may seem that filesystems have certain rules like having files and directories, this is not true. The biggest operating systems work like that but there are many mall small OSs that work differently. It's certainly not a hard requirement. (Just remember, to build a new filesystem, you also need to write a new OS, which will make adoption quite a bit harder. Why not focus on just the storage engine and call it a database instead?)
In the end, both databases and filesystems come in all shapes and sizes. Transactional, relational, hierarchical, graph, tabled; whatever you can think of.
[1] I've worked on the Boomla Filesystem which is the storage system behind the Boomla OS & Web Application Platform.
Comment: @ns94 Usually once a partition is mounted or the like raw I/O with that part of the disk becomes the purview of the OS alone and everything else is meant to use the filesystem there as the OS presents it (otherwise filesystem corruption would be the likely result). That said, a database can represent its data on the filesystem however it likes in however many files it sees fit to use. The syscalls are generally on the level of open/read from/write to/close/memory-map/etc. a given file; the database program can do whatever it likes with that set of operations.
Comment: The third party database (eg: postgres which stores data in files) will still have to interact with the filesystem using sys calls, correct? or do these databases  access the disk directly bypassing the filesystem?
Answer: The difference between file processing system and database management system is as follow:

A file processing system is a collection of programs that store and manage files in computer hard-disk. On the other hand, A database management system is collection of programs that enables to create and maintain a database.
File processing system has more data redundancy, less data redundancy in dbms.
File processing system provides less flexibility in accessing data, whereas dbms has more flexibility in accessing data.
File processing system does not provide data consistency, whereas dbms provides data consistency through normalization.
File processing system is less complex, whereas dbms is more complex.
Comment: I think the question was about databases and not the database management system.
Answer: The main differences between the Database and File System storage is:

The database is a software application used to insert, update and delete
data while the file system is a software used to add, update and delete
files.
Saving the files and retrieving is simpler in file system
while SQL needs to be learn to perform any query on the database to
get (SELECT), add (INSERT) and update the data.
Database provides a proper data recovery process while file system did not.
In terms of security the database is more secure then the file system (usually).
The migration process is very easy in File system just copy and paste into the target
while for database this task is not as simple.

Database vs File system storage


Changing time signatures

Question: As a songwriter im wanting to understand how to change the time signature/ meter of my lyrics to give them a more interesting affect? I've read many articles indicating that changing the rhythm/ meter of your lyrics can give a different affect? Can someone explain this concept from a songwriter perspective, please? Thank you!
Comment: You'll need to expand a lot on what it actually is you want to do here. It sounds like you want to do something odd. Explain please.
Comment: Do you really want to change the meter, or do you just want syncopation?
Comment: Why on Earth would you want to do that?
Comment: I suppose you mean to change the time of your lyrics and create a new melody.
Comment: I elaborated more on my question. Thank you for the help!
Answer: I can't help specifically with song writing, but I stumbled onto this old video the other day, where Mack the Knife is played with several different time signatures -- 4/4, 3/4, 2/4, etc. If this sort of thing were done in way that was coordinated with lyrics, to be part of a single song, it could certainly have interesting effect. Perhaps listening to this -- while maybe trying to ignore the stylistic changes that are also made -- might give you some ideas. I hope it is helpful.

ADDENDUM: I also ran into the following link, which looked useful. Since you've probably read a lot more on the topic than I have, the content may already be familiar to you. If so, please ignore. https://www.izotope.com/en/learn/time-signatures-explained-creating-interesting-motion-with-meter-changes.html

Changing time signatures


2 WordPress install with same database

Question: I am tring to make 2 sites (1 domain and 1 subdomain) in WordPress. Subdomain should have different logo,menu,ads..etc but both of them,same database with same article.I know it is risky for Google, but I have other plans with this. I upload wp to principal domain and subdomain. In wp-config I put same database, but the links displayed on subdomain are exactly like the ones from principal.
Here is a domain example: http://wow7.ro and a subdomain one: http://lol.wow7.ro . I try to duplicate wp prefix _options table in phpmyadmin to have different siteurl, but I can not find the php file in wp structure where is the code which selects this from duplicate table.
Answer: Do not alter any table names. In both sites (just to be sure) in wp-config.php set the WP_SITEURL and WP_HOMEURL to the related domain so these constants should be http://wow7.ro on the main domain install and http://lol.wow7.ro on the subdomain install.
See Codex.
Note that it doesn't work for links insrted inside post or page content, because they are saved statically in  post content, so in the database, and once the database is the same...
Also note that if you install some caching plugins it can brings problems...
After that inside the template you can use that constants also to conditional show content in the site:
if ( ! defined('WP_SITEURL') || WP_SITEURL = 'http://wow7.ro' ) {
  // do something for main domain
} else {
   // do something for subdomain
}

PS: in WordPress multisite means a WordPress installed with network of sites enabled, and this not seems your case.
Comment: I've done exactly that. But for some reason. Theme loads but all linked css/js/media goes to server not found or 404 (not handled by theme).

2 WordPress install with same database


how to easily make complex Euler/Venn diagrams in R?

Question: From my microarray data I have selected three subsets of probes. I would like to display these subsets as a Euler diagram to visualize the overlaps, but am struggling with inputting the combinations into Eulerr. All three subsets need to be nested within the full set of probes; one subset is fully contained within another, and the third overlaps with the other two. Is there a package into which I could feed the vectors of probe names and let it determine the overlaps for me? Many thanks in advance!
Answer: Since you are in R, consider using the UpsetR library.  It doesn't make Venn diagrams but it helps to visualize overlaps between any number of groups.
http://gehlenborglab.org/research/projects/upsetr/#:~:text=UpSetR%20is%20an%20R%20package,based%20on%20groupings%20and%20queries.
Answer: You might consider different ways of using the venneuler package. I'm not super thrilled with its usability (or with the accuracy of the overlaps), but you can get it to make custom Venn diagrams.
Here is a thread with some suggestions along these lines.
Below is some sample R code that I slightly modified from an old project that I used to make a 3-category Venn diagram.
I didn't run this to make sure that it works because of an irritating Java dependency issue on my OSX laptop that I don't feel like fixing right now, but as long as you have a JDK on your machine and can install the packages it should work.
# note irritating rJava dependency of venneuler
library(plotrix)
library(venneuler)

#A-B sharing: 200414
#B-C sharing: 17561
#A-C sharing: 16764
#All share 14201

# get coordinates for circles- replace as needed
# this function is supposed to plot stuff, but doesn't actually
ven = venneuler(c(C=48147-17561-16764+14201,
                  B=347181-17561-200414+14201,
                  A=325971-200414-16764+14201,
                  "C&B"=17561, "B&A"=200414, "C&A"=16764, "A&B&C"=14201))

cats = c('A','B','C')

# note- this following only shows up in the .pdf printer, not in the X11 utility plotter
pdf('venn.pdf')
plot(c(-.5,1.5), c(-.5,1.5), type='n', xaxt='n', yaxt='n', bty='n', xlab='', ylab='')
draw.circle(ven$center[1,1], ven$center[1,2], ven$diameters[1],
        col = hsv(1,1,1,.5))
draw.circle(ven$center[2,1], ven$center[2,2], ven$diameters[2],
            col = hsv(.5,1,1,.5))
draw.circle(ven$center[3,1], ven$center[3,2], ven$diameters[3],
            col = hsv(.1,1,1,.5))

text(ven$center[1,1]+.065, ven$center[1,2], labels=cats[3], cex=1.3)
text(ven$center[2,1], ven$center[2,2]-.2, labels=cats[2], cex=1.3)
text(ven$center[3,1], ven$center[3,2]+.2, labels=cats[1], cex=1.3)

dev.off()


Is it a best practice to exclude retweets from the data set?

Question: I am going to build machine learning algorithm to identify fake tweets. The data set has huge retweets which I think might be an issue. Do you think given that the focus is the original tweet, it is better to remove all the retweets?
Thank you,
Comment: It depends: what do you call a fake tweet? Is it a tweet not originally written by the user?
Answer: No. I do not believe so and I can explain a few reasons why.

If an entity wants to create waves in twitter with false tweets retweets are probably apart of the plan.
If you want to detect tweets generated by bots looking at the statistical data on said tweets and retweets like time stamps could be relevant to detecting if the tweet is generated by a bot.
If You have a way of checking retweets by bots then removing all retweets would also remove that data.

You should remove retweets if.

The project is focused on analysis of text to determine if a tweet is bot or not.
There is no labeled human or bot retweet data.
Answer: There might be a chance that the retweet has an entirely different context compared to the original tweet.
It is also possible that some retweets with different opinion/comment gain more popularity than the original one.
In these cases I don't think you can classify them as fake tweets.
You can classify tweets as fake when they are widely retweeted but with no context,
One such example is retweets due to a giveaway or charity.
If you can figure out how to separate the spam retweets and original tweets it would help for better analysis and accurate results.
Answer: Removing retweets would make sense to me, if you want a model where each single original post has the same weight.
However, it doesn't make sense to me if you want to measure each original tweets impact, except if you add one of the below features:

amount_of_total_people_reached (measured in e.g. total impressions from the original tweet and all retweets)
amount_of_people_reached_via_retweets (measured in e.g. total impressions from retweets)
amount_of_retweets

The exact purpose of the model and how you want it to fit to the real wolrd matters here I suppose.
Answer: To me it depends on what you want to focus on : do you want to create a model dealing with original posts that are fake news, and then make an algorithm finding the original from a retweet then applying your model ? Or do you just want a model that takes one tweet, not looking if it's a retweet or not, and trying to guess if it's fake or not.
In the first case, you should remove them, because you'll have many information about the people retweeting fake news, while you only want to find info about origin posters, which will make your model biaised.
In the second case, of course, since that's exactly what your model aims to do, you should keep them.
Answer: Removing retweets from your data set could potentially help improve the model's performance by reducing noise and focusing on the original tweets, but it could also result in the loss of valuable information that could be useful for identifying fake tweets.
One approach you could consider is to keep the retweets in your data set, but to also include additional features in your model that capture information about the retweet, such as the number of times the tweet has been retweeted, the user who initially tweeted the message, and any other relevant metadata. This could allow your model to use the information from the retweets in a more structured and controlled manner, potentially improving its overall performance.
Experiment with different approaches and compare their performance to determine the best approach for your specific use case.


Conducting research at my alma mater

Question: I'm thinking about conducting a research at a specific division of the university from which I received my PhD. I had a negative experience while I was there. And I keep hearing that many other students there are going through horrific experiences of abuse. I'd like to conduct a study case and perhaps better understand what's going on there. I know many other institutions have similar problems, but, as I said, I'd like to do a case study and then perhaps go from there to researching other institutions.The problem is that I don't work there, I'm just part of their alumni. I work at a different university. So, basically, this would be an independent study. My question is, given that this is not a dissertation proposal, can I simply complete the IRB form as an independent researcher? Or do I have to write a whole proposal? I know each university is different, but can someone give me an idea of how this works? I'm new to this idea. Thank you.
Comment: You should probably integrate quite a lot of what you say in comments here into the question itself. That information is quite essential to any answer.
Comment: Why would you want to do that if you're already at another university? And why would your old university want to make its facilities available to someone unrelated at no cost?
Comment: Because I had a negative experience while I was pursuing my PhD. And I keep hearing that many other students there are going through horrific experiences of abuse. I'd like to conduct a study case and perhaps better understand what's going on there. I know many other institutions have similar problems, but, as I said, I'd like to do a case study and then perhaps go from there to researching other institutions.
Comment: Thank you for your suggestion, Buffy. Makes sense.
Answer: Since the other university is actually the subject of your study, then I think that the IRB of your current university is the better place to judge it. It avoids a conflict of interest within the other university.
Your former colleague at the other university probably shouldn't be a co-researcher, but could be integrated into the study in another way; say as a source of information. This lets them, also, avoid a conflict.
Proposing it to the Dean at that university may also be problematic. Your "want to help them fix the problem" will very possibly not be well received. You might get quite a lot of blowback.
If they recognize the problem on their own and come to you as a consultant, then it is a different story. Otherwise you will come across as an unwelcome outsider and a disgruntled alum.
I won't recommend against your study, but I think that you should keep it as independent of the other university's administration as possible.
Comment: Yes, I've done a lot of thinking and I do agree that the dean might not be very pleased to hear what I'd like to say. Thank you so much!
Answer: Some universities offer their alumni access to resources (and perhaps their old affiliated email address). If your university offers this to you, you can certainly take them up on it.
You are asking for more than just access to resources, you are asking for IRB approval (presumably) to conduct a study involving people/animals. This would involve the university's legal department, and some other researchers reading through your plan. Even if you agree to pay for the experiments out of pocket (I'm going ahead and assuming you're not asking IRB approval to dissect rats, because if that's what you're planning I hope you understand that the university won't endorse it), you are asking for the university's legal endorsement of your research activity, which is not be something they'd be willing to extend to someone not officially affiliated with them.
So the short answer is - the university is not likely at all to endorse your IRB (unless it operates in a vastly different way from most places I know).
If you have a good idea which you want to push forward, why not seek employment/studies in a university? Seems like you're ready to conduct research, seems like it might be easier, no?
Comment: Yes, I still have an email address that links me to it as a member of their alumni. One current professor working there has talked to me about feeling that "enough is enough", given that apparently what I experienced there was not unique. They keep seeing other students going through similarly negative situations. I would be requiring no funding. In fact, I'd like to propose this study to the dean, but I wonder if they'd take my request as something really odd. I want to help them fix the problem.
Comment: But that's something different: You state that you want to do research there. That is, as stated, not in their interest, and they're going to say no. Wanting to help them change (assuming they want to change) is not a research project, but a concrete work item for which they might want to hire someone -- but it's not research.
Comment: I still think it is research if I am able to conduct a case study and then provide them (and the academy) with the findings -- particularly if my co-researcher is the professor who has contacted me about the issue. I'm thinking about proposing this partnership to them. Thoughts?
Comment: You might want to update this answer in light of all the other info that emerged in comments here. There are important points made that weren't in the original question.

Conducting research at my alma mater


How to disable x-ray for annotations (grease pencil) in 2.8?

Question: Is it even possible in 2.8? In 2.7 we had such ability, but now, when grease pencil and annotations are separate things, xray possible disable only for grease pencil, but not for annotations
Answer: This can be done with annotations programmatically. To my knowledge there's nowhere currently in the front end UI to do this for annotations though. Copy this line, go to the Scripting workspace, paste this in the console (place where you see >>) and press Enter.
bpy.data.grease_pencils['Annotations'].layers[0].show_in_front = False

Or this to change all existing annotation layers.
for layer in bpy.data.grease_pencils['Annotations'].layers: layer.show_in_front=False

I'm not sure why this was not kept accessible in the default UI for annotations. If it is somewhere (as of Blender 2.82), please someone let me know where. A fix for right now would be to paste in and run the code (after opening a new blank file) then go to File > Defaults > Save Startup File. You would have to run the code though for every new annotation layer you create, so maybe make a few dedicated layers and name them "non see-through" or something for when you want to use annotations that aren't see through.
Even if this option never returns to the default UI, would be pretty easy to create an addon that handles this. This will definitely be an option in the next version of Sensei Format.
Comment: I tried doing this code, but it didn't work.  It gave me an error:  Traceback (most recent call last):
  File "", line 1, in
KeyError: 'bpy_prop_collection[key]: key "Annotations" not found'
Answer: @RBlongus2us
You must use single or double quotation marks: "Annotations" or 'Annotations'.
"Annotations" as well as "True" and "False" have to be written with a capital first letter (but not the entire word!) so that Blender and Python can recognize it:

The annotation layers are numbered beginning with "0" at the bottom of the layer list. This index is used in the square brackets, so that you for example switch off the x-ray visibility of the first and the fourth grease pencil layer (indices "0" and "3") in the last two images above with the commands:
bpy.data.grease_pencils['Annotations'].layers[0].show_in_front = False

bpy.data.grease_pencils['Annotations'].layers[3].show_in_front = False

'Annotations' is the name of your annotation data block. As long as you don't manually edit the name, the next annotation data block created would have the name 'Annotation.001' and the corresponding python command for switching it's first layer's x-ray display off would be:
bpy.data.grease_pencils['Annotations.001'].layers[0].show_in_front = False


Can async/await be used in constructors?

Question: As the question stated. Will I be allowed to do this:
class MyClass {
    async constructor(){
        return new Promise()
    }
}

Comment: async/await is not part of ES7.
Comment: A possible solution would be to add a `static async` function that does the asynchronous initialization prior to actually constructing the instance of `MyClass`.
Comment: Does this answer your question? [Async/Await Class Constructor](https://stackoverflow.com/questions/43431550/async-await-class-constructor)
Comment: Even if it would be possible (hint: it's not), [it would be a horrible practice](http://stackoverflow.com/q/24398699/1048572)
Comment: @Bergi - luckily [real world code](https://github.com/mozilla/source-map/blob/282ab0ced853c80056d425de68af2989d794a6f4/lib/source-map-consumer.js#L17-L27) makes these questions relevant anyway
Answer: To expand upon what Patrick Roberts said, you cannot do what you are asking, but you can do something like this instead:
class MyClass {
  constructor() {
     //static initialization
  }

  async initialize() {
     await WhatEverYouWant();
  }

  static async create() {
     const o = new MyClass();
     await o.initialize();
     return o;
  }
}

Then in your code create your object like this:
const obj = await MyClass.create();

Comment: Thanks for answering the spirit of the question instead of just saying, "No, it's not allowed."
Answer: Without trying to fortune-tell about future decisions, let's concentrate on practicality and what is already known.
ES7, like ES6 before it will try to be a backwards compatible expansion to the language. With that in mind, a backwards compatible constructor function is essentially a regular function (with some runtime restrictions) that's meant to be invoked with the new keyword. When that happens, the function's return value gets special treatment, specifically, non-object return values are ignored and the newly allocated object is returned while object return values are returned as is (and the newly allocated object is thrown away). With that, your code would result in a promise being returned and no "object construction" would take place. I don't see the practicality of this and I suppose if anybody takes the time to find what to do with such code it will be rejected.
Comment: Makes sense. It isn't clear in the proposal. I was wondering it because you can still use a return value in the constructor so you won't receive your instance.
Comment: I didn't really get the chance to go through the proposal hence my hypothetical answer, but I'm fairly confident this will be defined as static code error.
Comment: If they were to add it, I think they would also have to add some way of defining an async class so that you would know to await the constructor function (which sounds tacky) in order to get around the issue that Amit presents.
Comment: I don't get the **(and the newly allocated object is thrown away)** part. Any article ref or spec ref?
Comment: @AnubhavSaini - I meant the object is not referenced by any variable, is inaccessible, and is later garbage collected. The language spec is publicly available.
Answer: In a nutshell:

Constructor is a function that needs to provide a concrete object.
Async returns a promise; exactly opposite of concreteness.
async constructor is conceptually conflicting.
Answer: You can get a promise from the return value, and await on that:

class User {
  constructor() {
    this.promise = this._init()
  }

  async _init() {
    const response = await fetch('https://jsonplaceholder.typicode.com/users')
    const users = await response.json()
    this.user = users[Math.floor(Math.random() * users.length)]
  }
}

(async () {
  const user = new User()
  await user.promise
  return user
})().then(u => {
  $('#result').text(JSON.stringify(u.user, null, 2))
}).catch(err => {
  console.error(err)
})


Which artificial neural network model can I use when trying to predict gene expression?

Question: I need help choosing a model for my data. I have 50 genes that I need to test for their expression levels. I was thinking of implementing either an SVM or a multilayer perceptron model where the output can be on a scale of 0-1 to show the expression level of each gene. The input data is from single-cell transcriptomic datasets. Can I use either of these models? Which model is better and how? If not, can you please suggest some other models that better fit the data?
Answer: You can use any model you want.  The answer in machine learning is normally that you have to try each of them out and see how they work; it's usually hard to know in advance what is going to work and what won't.  That is the only way to know which will work best.
If you can find published papers in the literature that have tried to solve this problem or a similar problem, you can look at what they did and get some ideas, but if you can't, then you just need to try different approaches and see how well each works.
If you want to predict whether the gene is expressed or not, you are looking for binary classification, and either a SVM or a neural network with a binary softmax output layer.
If you want to predict the degree of expression (from 0-1), then you have a regression problem, and you may need a slightly different technique.  You haven't given enough details about the meaning of the output or about the training data you have available, so it's hard to make a recommendation, but one possible option is a neural network with a sigmoid function at the output.
Comment: I want to predict the gene expression from RNA-seq data, but there are no datasets available for this type. I want to somehow find the gene expression by combining two datasets. For example, if there is a dataset for gene expression for breast cancer, and one for lung cancer, I want to predict which genes are being expressed by both these cancers from the influence of each other. (this is not a biologically feasible idea, I just wanted to present an example). Are unsupervised learning algorithms a better idea? But I know what I want to predict: Expressed or not expressed- either 0-1 or 0/1