Android 7.0 call block feature

Question: I have honor 8 lite with android 7.0
I block a number from default dialer app, It should be blocked now but instead when someone calls me from that number he hears 1 or 2 seconds of my phone ringing, then the call hangs. So that the other party can easily understand that his/her call has been blocked.
I want that the call must be blocked silently, without the calling party knowing anything about it.
The caller must get message such as -- Not reachable or phone is switched off.
I know that this feature may be network dependent but my old feature phone was doing it very smartly but my smart phone fails to do so.
Any suggestions on how to block calls with android 7.0 stealthily.
Thank you.
Answer: I do something very similar on my device running Marshmallow to prevent tele callers and quite successfully so :)
automation is the preferred option. Many apps are available. I prefer using MacroDroid , since it is free (upto 5 macros) and easy to learn.
Since I don't have Nougat can't test, but should run fine
In the first macro, it is configured here for non contacts. You can select individually the numbers in your case

The SMS portion of first macro is expanded below - you can configure it to your liking

Note: Two macros are strictly not required. You can add action of second macro in first itself - I needed two macros for customisation which is not shown here

Android 7.0 call block feature


Neck hunchbacked: How do I straighten it?

Question: Today, I noticed that my my neck appears to have a small hunchback.  Do you know workouts that could improve my neck posture in order to straighten it?  Additionally, my bed is orthopedic and I have a soft pillow.  I think the way I sleep and my soft pillow may be a cause.
Answer: Thoracic Kyphosis and Forward Head ("Computer Guy" Hunchback): Upper cross syndrome is another posture issue caused by sitting while hunching forward (at a computer, over books, etc).
Pectorals and the upper back/next tend to be tight as a result and the scapular muscles (shoulder blades) and neck flexors tend to be weak. This post has excellent information on why you're doing different exercises, but many of the links have degraded.
This pdf demonstrates how to do the specific exercises mentioned (skip to page 4 for the specifics for this section, although all of the stretches are good).

Source: reddit.com/r/fitness
Answer: The spine is nothing to take lightly. If it's a question about the spinal column I always say get a professional to look at it in person.
Answer: This is a common problem for most of the IT guys as well as heavy social media users on mobile. I got this problem a month back I tried some good Yoga Pose suggested by Baba Ramdev( India). It helped me a lot. You can search for his reference in Google.


Why is the Patellar reflex not triggered when the tendon is extended slowly?

Question: I have been previously told that the Patellar reflex (knee-jerk-reaction) exists to prevent the hyper-extension of the patellar tendon.  Yet if the impact to the tendon is delivered slowly - i.e. by pressing down on it rather than striking it - there is no reflex response.  Why is this, as surely the tendon is being extended by the same amount?
Answer: This effect you are observing has to do with the nature of the afferent neurons (Ia fibers), which carry a signal into the spinal cord and synapse onto motor neurons directly.  See this text (scroll down to section 1.10) for a diagram.  At their other end, these Ia fibers penetrate into the muscle and wrap themselves around the body of the muscle spindles, <code>"[which] are specialized receptors that signal (a) the length and (b) the rate of change of length (velocity) of the muscle."</code>
Because the main role of these spindles is to monitor the muscles for very rapid changes in length, the neurons have a static range which is optimized for these quick jerks (rather than firing over a wide range of velocities).  When you are stretching the muscle slowly, the Ia fiber is not building up a sufficient depolarization to fire off an action potential.
Comment: Presumably because (a) is handled by higher, slower, functions. If nothing is happening particularly quickly the spinal cord can 'wait for instructions' from the brain. Reflexes exist because when things are happening very quickly it's too slow to contact the brain and wait for a reply. If they're happening slowly, that's not an issue.
Comment: +1 this explains the mechanism nicely, but it makes me wonder: if the neurons are capable of measuring the length, then why isn't there a need for a reflex based on length? To bring in some teleology: why would the system be optimized only to automatically respond to (b) and not also to (a)?


Trying to find Latin resource I used to have years ago

Question: Once I found online an old (I believe 16th century, but not sure) list of simple sentences, Latin and their English translation side by side. I've tried with no avail to find them again through google, and I looked through my old Latin folders because I knew I had a few pages printed out at one point. But I guess threw them out. Any help with this is greatly appreciated.
Comment: Unfortunately, we're going to need more detail to help you with this kind of request. Do you remember anything else about it?
Comment: Unfortunately not.. I've been trying to rack my brain to remember the author or the title. I've gone through my old folders and flashdrives. Nothing yet. But I'm not expecting a miracle, this was just my last resort
Comment: This might have to be closed then. Although you would obviously recognize the resource, the description you provide probably fits a huge number of different sources, and it's anyone's guess which is appropriate. You could rephrase it as a resource request ("What are some examples of 16th century Latin instructional textbooks").
Answer: Mathurin Cordier was a theologian and teacher of the 16th century, and his work, known as the Corderii Colloquiorum, sounds a lot like what you're describing. Here's a screenshot:
Answer: It's quite possible that you remember the Eton Latin Grammar of (Arthur?) Hay, in widespread use in English public schools a couple of hundred years ago. It was adapted from the sixteenth century Eton instruction manual, but was much revised over the years and published in two parts. I remember from years ago an edition published in the 1880s by John Murray (London), which was partly constructed in the way you describe. You could begin your search by looking at https://www.forgottenbooks.com/en/books/TheEtonLatinGrammar_10853396
[Added later] This is a sample from the source I suggested, returned to the two-column form used by Hay, as nearly as I can manage it:
(246) Qui significans causam éxigit ut es stultus qui crédas huic (homini). //
Who, signifying the cause, requires a subjunctivum (modum) subjunctive mood as, you are a fool who can beliéve, that is, for beliéving  this fellow.
Ut pro postquam sicut quomodo jungitur indicativo (modo) autém cum dénotat quamquam utpoté finitem causam jungitur subjunctivo (modo) ut, ut sumus in Ponto, Ister constitit frigoro tér. // That or after that, or, since that, as, at and how, is joined to an indicative mood, but when it implies or signifies although, for as much as,or the final cause, it is joined to a subjunctive    mood: as, since that we are in Pontus, the  Danube has stood with cold, that is, has been frozen three times.
I hope that this is helpful to you.


Premature blueberries dropping buds

Question: Blueberry flowers are dropping off. I raise mason bees so, I know pollination is not the cause, and Lane County Oregon has had an over abundance of rain.
I am baffled. Last year I had a bumper crop. What gives?
Answer: Do you know if there were any freezes at night?  Doesn't take much dipping n the temperatures to cause plants to do wig out. My blueberries last year got a few sudden freezes, they were acclimated but all the buds fell off. Please send pictures and more information.  Lane county, huh!  I am in Deschutes county south of Bend.  I had bumper crops for the first 3 years and this last year zilch...all the flower buds dropped off.  The temperature change between day and night time is humongous.  Just one freeze at night that you might not even notice will kill the flower buds. Hopefully they'll recoup and get a second chance.
Answer: Are you sure they are not too wet? I have some in a container and have poor drainage after lots of heavy rain which made them look sick, so I pulled all the compost out, put in fresh and drilled extra drainage holes.

Premature blueberries dropping buds


Is there a mathematical symbol for a reversed, palindromic number?

Question: If there is X, can it be reversed (made palindromic) by simply adding a character, a mathematical symbol?
Answer: No, not a standard one. And I doubt there is even a non-standard one. It's not a common or important operation at all.
Answer: The closest concept that is commonplace is bit-reversal, an effect which actually occurs in in-place FFT algorithms. The Wikipedia page lists no standard notation for it.
The reason this operation is not so interesting is that it depends on the base in which the number is represented.
Answer: You can 'palindromize' any string of symbols, if you want--but it will take more than just one symbol addition or deletion in general.
Here is one way to palindromize a sequence. Simply take your sequence X, write it in reverse order, then concaconate X with the reversial. I.E
Your sequence: Math
Your sequence palindromized: MathhtaM. I don't know if this was what you were thinking of.


Finder: Spotlight shortcut and command+tab switching apps stopped working

Question: Both these functions stopped around the same time.
El Capitan, but I think these worked after the upgrade and now don't.
Both functions work in other apps. Just not in Finder.
Repaired permissions on MacHD, checked and unchecked the command for spotlight in System Preferences>Keyboard>Shortcuts>Spotlight.
Using command+space in Finder gives the error chime.
Answer: Solved by resetting NVRAM.
Power down.
Restarted holding down command+option+P+R until I heard the second chime. Released all the keys.
Now both functions work in Finder. Command+Space brings up Spotlight search box. Command+Tab brings up the list of apps to toggle through.
Comment: Great! Please mark this as solved.


Turn-off WiFi / WLAN & Bluetooth completely (electrically off), how?

Question: In windows, most laptops these days have a hot-key to turn off wireless modules completely (i.e. airline mode), including WLAN and Bluetooth. I am currently on Ubuntu 11.10, and wondering as to what is the way to have the same effect, i.e. make sure that those modules are electrically off - not consuming any power, and the radio beacon is off.
Comment: I believe hardware buttons work the same way in Ubuntu. Something like Fn-F5 or special "wifi" button etc.
Comment: The problem in my case is that the hardware buttons never worked. I am using a Compaq Presario CQ42 laptop, and never managed to find the scripts that'd get the hardware hot-keys to work. This means, I do not have screen backlight control, touchpad control, wireless control, volume control etc., any of it working ! :-(
Comment: Well, from my experience the buttons usually do work out of the box - it must be something with Ubuntu on your particular laptop model. I'm just trying to clarify - your question sounds a bit too general.
Answer:
Press F10 right after turning the laptop on to enter BIOS settings.
Go to the "System Configuration" tab.
Disable Action Keys.
Save and Exit.

This should solve the problem. Now, when you press F1-12, It will activate the function (wireless, etc.). To access the F-keys normal functions ans function keys, press and hold Fn and then press the key. Hope that helps!
Comment: Thanks. Part success, but I had to 'Enable Action Keys' in BIOS, not the other way around. Not sure if it was a typo, or I misunderstood. Now, I can at least see that the on-key LED change from White to Red and back. After enabling 'Action Keys' in BIOS, LCD backlight works, but screen-blanking, volume-control, and other music-control (which I actually have no use of), still don't work. Does it require some extra configuration or additional software to be installed ?
Comment: Yep, typo. Sorry about that. As far as the volume and music controls. etc. Unfortunately, the volume and music controls are Windows functions that require Windows drivers. You can try looking at the configuration in System Settings -> Keyboard Shortcuts and seeing if it is possible to assign the keys. But, if it doesn't work there, your'e out of luck.
Answer: I use rfkill for this.  Here's the online man page that gives you the package name and other miscellaneous data.
Comment: It's weirdness with the hp wireless driver.  My laptop does the same thing.   I'm speculating, but hp-wireless could be the controls for the buttons that control wireless.  phy0 is the raw card.
Comment: Thanks. A "rfkill list" shows 3 interfaces -- hp-wifi (Wireless LAN), hp-bluetooth (Bluetooth), phy0 (Wireless LAN), and each one of them seems to be Soft-blocked:NO and Hard-blocked:YES. Wondering why it shows 2 Wireless LAN interfaces. I do not have any USB WiFi (additional WLAN) interfaces.


Syncing photos to iCloud and deleting them

Question: I want to save all my photos to iCloud and then delete them from my iPhone.  How do I delete them from the iPhone while still keeping a copy on iCloud?
Answer: iCloud is a syncing system and not a just a backup.
If you delete the pictures on your iPhone (assuming you're logged into the same iCloud account) you're also deleting the pictures in iCloud. This is not what you want to do.
Find a backup solution to keep your photos like Dropbox or Amazon Photos. Those will allow you upload your images without keeping them on your other devices.


Strategies on steepen yield curve

Question: Believe that the yield curve is going to steepen very soon. It may be fall in short-term rates, a rise in long-term rates, or some combination of these. What strategy should we pursue in the bond market to position ourselves to profit from our beliefs?
Answer: Translate your forecast of yields into a forecast of bond prices: you believe long term bonds will fall in price rel. to short term bonds. So, what to do? Shorten the duration of your portfolio, i.e. sell long term bonds and/or buy short term bonds.
Since you don't like long term bonds (and the fixed payments they make to you), you may also enter into (long tenor) swaps where you receive floating and pay fixed. A situation known as "being short the swap" (you can think of it as another way of getting rid of the risk from your long term bonds).

Strategies on steepen yield curve


Automated forecasting of 1000 weekly time series (food product retail)

Question: I have a set of 1000 time series with weekly data.
These time series data are concerning the sales of food product retail.
Can anyone suggest me the best/correct way to make good forecasts of this set of time series with R?
Obviously I can't analyze them one at a time because there are too many of them!
Anybody have a few pieces of advice for me, please?
Answer:
Learn R, at least well enough to program for loops to loop over your time series. Plus, learn enough R to read and write your data (e.g., using the read.table() and write.table() commands). There are tons of introductions to R around, pick almost any one.
Read Hyndman & Athanasopoulos "Forecasting: principles and practice", which contains many worked examples in R.

This will get you a long way. Retail time series will likely exhibit some yearly seasonality, so concentrate on seasonal methods (e.g., seasonal exponential smoothing, but don't necessarily include trends).
Skip ARIMA models - ARIMA doesn't like "long" seasonal cycles, and 52 weeks qualify as "long", plus, you may need to take seasonal differences, and most retail time series don't cover many years, so each differencing loses a lot of data.
Consider some kind of regression-based forecast to capture the effect of promotions, if there are any in your data.
Potentially:

Attend this year's International Symposium on Forecasting in Cairns, in particular one of the pre-conference workshops, like the one on forecasting with R or the one on forecasting to meet demand, which is given by an experienced retail forecaster.

(Disclaimer: the guy giving the second workshop is a colleague of mine. If you come to Cairns, say hello to me and feel free to ask me all about retail forecasting.)
Comment: Which function you suggest? the `ets` function? How can I add the regressors with that function? I'm just using the `auto.arima` function of the `forecast` Hyndman's package with the `xreg` parameter and it seems to works weel enough...
Comment: `ets` cannot handle external regressors, only level, trend and seasonality. If `auto.arima()` with `xreg` works for you, all the better! I'd recommend you read ["The ARIMAX model muddle" by Hyndman](http://robjhyndman.com/hyndsight/arimax/) if you plan on using ARIMAX or regression with ARIMA errors, because there are subtle differences between the two that may trip you up if you don't know them, especially if you work off multiple sources.
Answer: AUTOBOX ( a piece of software that I had helped develop)  has an R version that you can try out . It will detect not only the ARIMA structure but the week of the year structure  and changes in the week-of-the-year structure along with level shifts and local time trends while incorporating the lead and lag effects of user-specified causals.


Ableton impulse drum rack switch

Question: I like to use the preset racks in Ableton Impulse. The problem is I for the life of me cannot figure out how to switch the positions of the drum samples. Say I wanted to have the kick drum in 3rd position rather than 1st position? Dragging won't work... anyone know a simple way to say, switch the kick with the hat or whatever?
Comment: Have you tried dragging the samples from the browser on the left to the positions you want? Also, if you have Live Intro I'm pretty sure you *can't* change the samples or positions of the samples.
Comment: sure, that works, but I'm trying to stick with the samples currently in the preset. I just want to change their positions.... Why go look for it in the browser when it's right there in the preset?
Answer: Well. I have Ableton Live 9 Suite and I just dragged one drum rack position to another one and it swapped the samples between those two positions.
From the Ableton Live 9 PDF manual (page 275):

Dragging a pad to another pad swaps the note mapping between the pads. This means that any MIDI clips triggering the affected notes will now play the "wrong" sounds — although this might be exactly what you want. ALT / CMD-dragging one pad to another will layer any chains from both pads in a nested Instrument Rack.

Ableton impulse drum rack switch


No power to Mindstorm EV3 Brain

Question: My 11 year old just spent her entire Christmas Day assembling the Mindstorm EV3 Reptar, but when we put batteries in the brain nothing happened.  It didn't turn on, no lights, no sign of power at all.  We made sure the batteries were in correctly but still no luck.  Does it need to be replaced or are we doing something wrong?  Help!
Answer: If you are 100% sure that the batteries are in the correct direction and the batteries are brand-new, unplug all of the cables from the EV3 brick and try again to make sure they could not be causing a short circuit. If it still doesn't now power up, contact LEGO customer support.
In the US, you will be directed as follows...

We have a dedicated Tech Support team for MINDSTORMS products. They can troubleshoot the problem and either resolve the issue or help you to get a replacement part. Tech Support can be reached at 1-877-680-2800 from Monday through Friday, 7:30am - 5:30pm CST.
Comment: Thank you!  Yes, we unplugged all the cables and still no power.  Lego store has reluctantly agreed to trade out the brain for us so we don't have to wait for support or shipping of a new brain.  That goes a long way when you're dealing with the disappointment of an 11 year old ;-) Happy holidays.

No power to Mindstorm EV3 Brain


How can I determine Max CPU speed at runtime?

Question: I'd like to know the max cpu speed for the processor on an Android system at runtime. I've seen at least a couple different techniques that result in the current cpu clockrate, but not the max.
Root privileges should not be required.
Answer: After digging through the source that roxan mentioned a bit, it looks like the following in /proc can tell you what cpu speeds are available and how much time has been spent in each:
/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state
However, it does give some other states that aren't appropriate. For example, on my Samsung Vibrant, I get:
1400000 0
1300000 0
1200000 0
1000000 214141
800000 40092
400000 25273
200000 6159308
100000 389

But the chip's standard clock is 1 GHz. So it looks like it should be fairly trivial to find the highest listed speed that has a non-zero time to it.
For my purposes, this should be very adequate.
Edit: I've observed that sometimes the order in which the frequencies is listed can vary, so you'll want to iterate through the whole list and find the fastest (as opposed to stopping at the first non-zero).
More Edit: Here's a function that works for me:
/**
 * Get max cpu rate.
 *
 * This works by examining the list of CPU frequencies in the pseudo file
 * "/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state" and how much time has been spent
 * in each. It finds the highest non-zero time and assumes that is the maximum frequency (note
 * that sometimes frequencies higher than that which was designed can be reported.) So it is not
 * impossible that this method will return an incorrect CPU frequency.
 *
 * Also note that (obviously) this will not reflect different CPU cores with different
 * maximum speeds.
 *
 * @return cpu frequency in MHz
 */
public static int getMaxCPUFreqMHz() {

    int maxFreq = -1;
    try {

        RandomAccessFile reader = new RandomAccessFile( "/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state", "r" );

        boolean done = false;
        while ( ! done ) {
            String line = reader.readLine();
            if ( null == line ) {
                done = true;
                break;
            }
            String[] splits = line.split( "\\s+" );
            assert ( splits.length == 2 );
            int timeInState = Integer.parseInt( splits[1] );
            if ( timeInState > 0 ) {
                int freq = Integer.parseInt( splits[0] ) / 1000;
                if ( freq > maxFreq ) {
                    maxFreq = freq;
                }
            }
        }

    } catch ( IOException ex ) {
        ex.printStackTrace();
    }

    return maxFreq;
}

Comment: Thank you but development questions are off topic here :D
Comment: Yeah, I realized this was not placed appropriately. I can't move it though :)
Answer: To contradict the above
/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state

Does not return the correct values. For example on my own device
cat /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state
1000000 192
800000 3
600000 12915
300000 20519

# cat /proc/cpuinfo
cat /proc/cpuinfo
Processor       : ARMv7 Processor rev 2 (v7l)
BogoMIPS        : 1197.81
Features        : swp half thumb fastmult vfp edsp thumbee neon vfpv3
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x3
CPU part        : 0xc08
CPU revision    : 2

Hardware        : mapphone_UMTS
Revision        : 0000
Serial          : 0000000000000000
CPU Tier        : 10

The frequencies are not correctly reported. As you can see, the clock speed on my device is 1200MHz - but only 1000MHz max shows in time_in_state.
However, the following is correct
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
1200000

Answer: Read this file to get the Max frequency:
/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max


Similarities between Hindu and Greek Mythology

Question: Why there are similarities between Greek and Hindu mythology?
Comment: No need to add a bold sentence to say offending is not your intention. It attracts the users than your main question. If you want to keep it, you may add it as a note in superscript
Comment: @Hindu Flag it with reason for deletion.
Answer: The proof is in the pudding, as the expression goes. However, your question is on Vedic & Greek mythology (about gods) whereas in your description you ask about Aryan migration (about people). These are two different questions.
From reading the Adi Parva of Vyasa Mahabharata (or from Bala Kanda or Aranya Kanda of Valmiki Ramayana), we come to know that the Creator created Prajapatis first and asked them to procreate and fill the planet with life. Sanskrit 'Prajaapati' means 'Lord of people' in English. Then, Vedic theology is all about the descendants of 'Kashyapa' Prajapati, son of Maareechi Prajapati, who is son of Creator. Kashyapa prajapati had 28 wives that we know of. Most important of his children were called 'Aadityaas' (12 in number), 'Rudraas' (11 in number), Vasus (8 in number) and Ashwins (2 in number). These 33 gods and all their descendants are collectively referred to as the '330,000' gods or '33,000,000' gods or '3,3000,000' gods in Hinduism.  These great grandsons (sons of Creator's grandson, Kashyapa) and their step brothers (brother from another mother) and their cousins are all collectively called in puranas as 33 crore devas. 33 crore and not 31 crore or 45 crore because these 33 were the most important ones among all of them, most important to vedic peoples actually. And crore because no one could count all of them (as you can imagine they wouldn't be in living in 1 spot and were dispersed making humans counting them impossible).
The most important of the 'Adityaas' was Indra, and he was crowned as King of gods some where in modern Armenia region and his kingdom existed somewhere in modern Siberia and Northern America (per Kishkanda Kaanda - SUgreeva's instructions to his commanders in Vaalmiki Ramayana). The other most important 'Adityas' were Vayu (wind god), Varuna (god of justice and waters and oceans), Agni (god of fire and volcanos and heat and the primordial Sun).
Per Homer's Illiad and Hesoid's poems we learn that their gods descended from Uranus and Gaea (pronounced Geya). The pantheon of ancient Greek gods starts with their children. Uranus or Ouranos is believed to be the 'Varuna' of the Adityas by mythologists and historians, i.e. Varuna was called as 'Uraanus' and 'Ouraanus' in the west, and per vedas Varuna is the lord of the western direction. The ancient Greek pantheon begins with Uranus/Varuna and his wife Gaea, and their children (called Titans) who were later supplanted by Titans' children, called Olympians.
So imho, our 33 vedic gods were great-uncles of Greek Olympians, i.e. their were the grandchildren of one of the 33 primary vedic gods Varuna. Naturally, they ruled and lived in those western lands, whereas the 33 vedic gods ruled other lands, Indra ruled east, Agni ruled south east, Vayu ruled north west, etc.
This is also the reason why all Vedic concepts are found in the greek mythology (cremations & not burials, animal sacrifices, linga worship as 'Omphallus' stones, etc.), but all greek concepts are not found in Vedic mythology (ex: ancient greeks' obsession with anal sex, sons killing fathers is not a sin, ancient greeks' obsession with maternal incest, no importance given to businessmen and vocational folk, etc.). Obviously, if vedic gods are plagiarized from Greek ones, we would have imported all these missing greek concepts also. But they are missing in our ancient religion. That is because there was no plagiarizing between ancient vedic and ancient greek religions. The author of your article is incorrect.
However, subsequent to Alexander's loss to Porus and his vengeful return back to Persia, several historians hypothesize that several vedic concepts such as vedic astronomy, concepts of vegetarianism (look up Pythagoros), etc. were imported by the greeks.
Comment: Welcome. We appreciate your inputs. It is called 33 crores but they are only 33 in number. Koti refers to group. 330 million is a  is a wrong number. Can you modify some words in your answer? Presence of some words makes the post detected by radar.
Comment: In the west, 330 million is commonly used, so I used it. But it doesn't change the point being made. No, they are not just 33. They had sons and descendants. Koti meaning crore is a collective term referring to countless items. So my answer is appropriate and no change is needed.
Comment: Okay. It's your wish whether to change or not. Their sons and descendants don't count as devatas. They are just sons of devatas. Infact, they have stopped reproducing after the curse of parvati. All the sons they have are before that curse. See this question. [Which shloka or scripture states that there are 33 crores of Hindu gods?](https://hinduism.stackexchange.com/questions/16693/which-shloka-or-scripture-states-that-there-are-33-crores-of-hindu-gods)
Comment: @sreecharan, Parvati's curse didn't kill those who were already alive and born. Koti means a large number, usually referred to countless in number. In couple language scriptures in India (south), they are not even referred to as 33 crores, but just 3 crore. That doesn't make sense unless you consider their descendants. And don't quote upanishads. If you go there, then you will end up with only one god at the end of the day.
Comment: Koti means group /set. @sreecharan is right. And just because they say something in the west does not make it correct.
Comment: The answer above and your comment are in the language of the west (english), naturally western terms were used. Your comment thus is irrelevant @user1195


Answering my own question

Question: Is it correct to answer my own question to share the information I knew about a place. Though Stack Overflow states this as correct, my questions have been blocked since I asked and answered them immediately. Why is it so?
Answer: answering your own question is perfectly valid, that's what the

is for. This has always been allowed on all SE sites, and was reinforced in 2012

Since Stack Overflow began, spontaneously sharing what you've learned
by posting a question and immediately answering it has been allowed
and even encouraged:

if you have a question that you already know the answer to
if you'd like to document it in public so others (including yourself) can find it later
it is OK to ask, and answer, your own question on a relevant Stack    Exchange site.

Providing the question and answer is on topic there is nothing to stop you doing this.
Answer: Asking a question, then going off to investigate, and finding a solution later which you then share is fine
Asking a made up question just to give a specific answer isn't generally approved of, but can be OK in certain situations
Asking a made up question to give a promotional answer is never allowed
(Thinking of a question when you're off-line, finding the answer later, then asking + answering here is normally fine, but make sure you really are sharing something useful from it, not just showing off or promoting something)
Remember - the site is about solving problems. Answers that don't solve real problems aren't right here. If you just want to share some general information about travel, try Wiki Voyage or your own blog!
Comment: Asking a question when you already know the answer is fine too. If you did the research before you got around to asking here, that's no objection against asking and self-answering. There's even a user interface feature to post a question and answer at the same time.
Comment: Why is Travel an exception to the [general SE rules on this](http://meta.stackexchange.com/questions/132886/what-is-this-answer-your-own-question-jazz/132887#132887)? Providing the question is [on topic](http://travel.stackexchange.com/help/on-topic) why can't a user simply make up a question they think might be useful and post an answer?
Comment: @Liam We follow the same rules laid out in that post. It all needs to start with a problem, which you either need solving, or you've already solved. If you just want to share some general info without there ever being a problem, SE isn't the right locate for that
Comment: Based on the other answers kols has given, it's safe to assume he isn't a spammer.
Comment: It's great now I got all my questions removed.(even the previous ones). Why?
Comment: There is mostly a doubt on the made up question. I would say it depends whether someone would ask the question. And obviously it should meet all the requirements of a question.
Comment: I got it. I'll post questions regarding problems and solutions only. Thakyou for the information.
Comment: @Gilles It still needs to start with a question though! Starting with the answer is the problematic thing

Answering my own question


How does the stock market affect the average person who has no money in it?

Question: I  frequently hear that the DJIA is up and down, often 100's of points.  For people who do not own stocks or 401K plans, does this  affect them financially?
Comment: This question is asking about stock indexes (on-topic) and asking about the importance of the index to him personally (personal finance). I believe this question should be reopened.
Comment: https://budgeting.thenest.com/mean-dow-falls-24770.html
Comment: I agree with other-Joe; the question is specifically asking about the economic consequence.
Comment: Hitler's rise to power was facilitated by the crash of 1929.
Answer: The Dow Jones Industrial Average (DJIA) is a stock index made up of 30 large American companies.  The number is simply the price of each of the 30 component stocks added together.  When you hear on the news that "The Dow is up 200 points," it means that today the price of the 30 stocks in the DJIA added together is $200 higher than it was yesterday when the market closed.
The idea behind it is that these 30 stocks are representative of the entire market as a whole.  However, as you can imagine, it is hard for 30 stocks, no matter how big the companies are, to accurately depict the health of the entire stock market.  There have been other attempts to improve on the DJIA, most notably the Standard & Poor's 500 (S&P 500), which is made up of 500 stocks averaged together and is also often reported daily.
When it is reported that the Dow is up 200, if you know nothing else about the price, you have learned nothing.  If the price of the Dow was $100 yesterday and went up 200 today, that is obviously a lot.  But if the price of the Dow was $24,000 yesterday, then 200 is much less significant.  The quick reporting that you hear assumes that you know the context behind the numbers.  It means absolutely nothing otherwise.

What does that entail in a larger scope for people who has not invested in 401K or any stocks?  How does that affect the public in a economic scale?

The value of the stock market affects the public in a few ways.  First, most people have a stake in the stock market in one form or another, whether they own individual shares in a particular company or have retirement savings in a mutual fund.  Even if you don't have anything invested in stocks, your employer and your employer's customers certainly do, and their welfare affects your welfare.  The stock market is often seen as a barometer for the economy as a whole.

Why is it very important to keep track of this? OR is it if I have no stake in stocks?

It is not important for you to keep track of it, whether or not you have anything invested in the stock market.  I am invested in the stock market; in fact, I have the majority of my money there.  I don't follow the daily movement of the Dow or the S&P 500, I don't watch CNBC, and when they start listing stock prices on the radio I change the station.  But I am employing a buy and hold strategy in mutual funds, and I am banking on the fact that over time the stock market as a whole tends to increase in value.  Therefore, when the stock market goes down I don't get nervous, because I believe it will rise again.  For people using other investment strategies, the daily movement of the stock market might be more significant.
Answer: Frankly, if you have not invested in stocks, you should not be concerned about short-term DOW JONES trends. By short term, I mean daily or weekly gains or losses.
However, you may find long-term trends useful for financial "real-life" decisions. You will know why:
Stock markets in the long term tend to reflect the broader economy. For example, assume DOW JONES is falling for several months. That may indicate some economic distress like rising interest rates, lowering GDP, some industries not performing well, etc. These are factors which affect everyone. For example, rising interest rates will be a factor to consider if you plan to buy a new home or car. And, lowering GDP and below-par performance of companies may force you to prepare for pay cuts or even potential job loss.
P.S: Why ignore short-term trends? Investor emotions weigh a lot in short-term price movements. Hence daily trends, daily point gains/losses are not a good indicator of the broad economy.
Answer: It's a gauge on how the market performed in a certain period...day, week, month, etc. It tracks the stock prices of 30 companies that make up the Dow.  So if the Dow was up 200 points today, that means the combined prices of those 30 companies were up 200 points (or dollars $).  The DOW is not a good gauge of the market though, a better average to look at would be the S&P 500.
It doesn't really mean anything to you if your not invested. If you have no money in the stock market, you probably won't pay any attention to it's use as a gauge...however you could still look at it and get a quick idea on what happened (or is happening as a trend) in the stock market.
It's not really that important to keep track of, it's just a tool to give you a sense on what the market is doing (or has done). If you are not invested, than you don't have to really worry.  There are many indexes (or gauges so to speak) to look at to get a better view of the market...hope this helps!
Comment: Welcome to PF&M. While there's nothing wrong with the information you provide, it does not answer the OP's question. Please edit your answer to explain what this means for someone who owns no stocks.
Answer: If you don't have any money invested in the stock market, then rising stock prices, in themselves, have little impact on you. However, there are two caveats to that. First, just because you don't have stocks, that doesn't mean that you aren't invested in the stock market. For instance, many pension plans are backed by stock market investments, so if the market underperforms, pensioners can lose out.
Second, while rising stock prices may not themselves affect you, the stock prices reflect developments that affect you. Rising stock prices often mean a booming economy, which means more employment. The DJIA is a quantifiable, objective (albeit somewhat blunt) economic metric. In a sense, the stock market acts as a daily (or business day-ly) poll on general sentiment about the state of the economy. It's like Gallup, except it's free. In fact, people pay to tell everyone else their opinion.


How to think of a set?

Question: I am doing self study for the last two months on functional analysis. As I get a bit used to the terms like space, topology, manifold, etc, etc, I realized that everything is defined in terms of set. If I look at the wikipedia page on set or set theory we can get quite a bit of explanation, but it did not clear me how to think of a 'set'. May be I am trying to think 'set' as some geometric object from which everything an be derived. May be I am wondering how a physicist would think of 'set'. I am worried that this question will be closed with lot of down vote but I still decided to try my luck. May be I asking few remarks from community how they think of 'set'. That might help me to develop some missing link, which I cannot explain properly.
Comment: What are your thoughts after [reading the Wikipedia article about sets](http://en.wikipedia.org/wiki/Set_%28mathematics%29)?
Comment: "Set" is a fundamental notion and has no formal definition...
Comment: Formally, the real numbers are defined as certain sets of rationals (Dedekind cuts), and rationals are equivalence classes of ordered pairs of integers, and  integers are defined in terms of natural numbers, which are certain peculiar sets built up out of the empty set. But one should think of the reals visually, as a number line.
Comment: I have read extremely good answers; however I want to add mine too. In a formal axiomatic setting a **set** is anything that satisfies the axioms. In *naive set theory* a **set** is a concept that is taken for grant: it is a notion that is inborn in any individual and cannot be explained (as for the notions of **element** and **property**) - the words to explain it would be *collection of objects*.
Comment: It is a collection: but how can everything be defined in terms of collection.
Comment: Yes, @DVD is correct but if you want to think of a set as a geometric object you probably need to define a relation on the elements in your set if its not clear from context for example; $$\{(1,0),(-1,0),(0,1),(0,-1),...\}$$ here I am trying to geometrically describe the circle group, but from context and only four elements this set could be anything. Basically a set is nothing until you impose properties on the elements (again unless it is clearly understoof what that property is).
Comment: A set is just a thing. It can be compared to other sets (things) via the relations $\in$ and $=$. For any two sets $x, y$ we have either that $x\in y$ or that $x \notin y$, and we have either $x = y$ or $x \neq y$. These relations, together with the entire collection of things we call sets, are usually assumed to satisfy certain axioms, most commonly the Zermelo-Fraenkel ones.
Comment: @Arthur: That assumes that all things are sets.
Comment: @creator: Well, it's not just the informal notion of a collection that allows us to implement mathematical objects, but the properties we suppose the universe of sets to have in the formal theory of sets. It's an important distinction to make, lest your thinking get hung up on what you can do with some single collection (which isn't much).
Comment: @user21820 No, it assumes that all things that satisfies the axioms are sets.
Comment: @Arthur: That is correct if you are outside the formal system. But then what formal system are you working in?
Comment: "In other words, general set theory is pretty trivial stuff really, but, if you want to be a mathematician, you need some and here it is; read it, absorb it, and forget it." ― Paul Halmos  *"Naïve Set Theory"*
Answer: The bad news
You're not alone in being confused about how to think of a set. Working out a sensible language for talking about sets cost mathematicians a great deal of sweat and tears. It's now considered one of the major achievements of 20th-century mathematics, and it's still being built upon today.
If you set out to explore our universe of sets, or the universes just beyond it, you'll quickly encounter sets that are dizzyingly, terrifyingly, hilariously counterintuitive. If you want my opinion, the best way to think of sets like these is don't.
The good news
On the other hand, if all you want to do is geometry, all the sets you meet will be tame enough that you can learn how to handle them just by looking at examples. In that spirit, let me give you some examples of sets that show up in geometry. It's often useful to have lots of examples, so this answer will be rather unfortunately long. Sorry!

Any finite collection of things. The three musketeers are a finite collection of people, so intuitively they should form a set, which I'll call $\mathbf{M}$. In formal notation, we might define this set by writing
$$\mathbf{M} = \{\text{Athos}, \text{Porthos}, \text{Aramis}\}.$$
The individual musketeers are called the elements of this set. Where a normal person would say "Porthos is one of the three musketeers," a mathematician might say, "Porthos is an element of $\mathbf{M}$," or write $\text{Porthos} \in \mathbf{M}$.

The natural numbers. The numbers 1, 2, 3, 4, and so on are a collection of things, so intuitively they should form a set, which is usually called $\mathbb{N}$. Logicians, who need to use very formal language, talk about this set by giving a precise logical description of it. Fortunately, as a geometer, you can get away with an informal description like this:
$$\mathbb{N} = \{1, 2, 3, 4, \ldots\}.$$
The dots are just another way of saying "and so on," in the hope that your reader will know what you mean.

The natural numbers whose squares are less than 100. These numbers are a collection of things, so they form a set, which I'll call $\mathbf{S}$. We can produce this set by rummaging through the set $\mathbb{N}$ and grabbing all the elements whose squares are less than 100. This way of building sets is so useful that people made up a special way of writing it:
$$\mathbf{S} = \{n \in \mathbb{N} \mid n^2 < 100\}.$$
This could be read out loud as, "$\mathbf{S}$ is the set of natural numbers $n$ with the property that $n^2 < 100$."
Because every element of $\mathbf{S}$ is also an element of $\mathbb{N}$, we say $\mathbf{S}$ is a subset of $\mathbb{N}$. In writing, $\mathbf{S} \subset \mathbb{N}$.
If you do some thinking, you can find a more concrete expression for the set $\mathbf{S}$:
$$\mathbf{S} = \{1, 2, 3, 4, 5, 6, 7, 8, 9\}.$$

The Euclidean plane. Imagine an infinite sheet of paper, perfectly flat and unmarked. Although it seems like a funny way of thinking at first, you can think of this sheet of paper as an infinite collection of locations, called points. This allows you to talk about the sheet of paper as a set, which I'll call $\mathbf{E}$.
One of the most interesting things you can do in the set $\mathbf{E}$ is measure distances. Given any two elements $p$ and $q$ of $\mathbf{E}$, I'll write the distance between them as $d(p, q)$.

A circle in the plane. A circle can be described as a set of points in the plane that are all the same distance from a certain point $a$. The point $a$ is called the center of the circle, and the common distance is called the radius. The circle with center $a \in \mathbf{E}$ and radius $1$, which I'll call $C_1(a)$, can be described formally by writing
$$C_1(a) = \{p \in \mathbf{E} \mid d(p, a) = 1\}.$$
Every circle is a subset of $\mathbf{E}$.

A line in the plane. Pick two different points in the plane—that is, let's pick $a, b \in \mathbf{E}$ with $a \neq b$. Let's say $V(a, b)$ is the set of points which are equal distaces from $a$ and $b$. That is,
$$V(a, b) = \{p \in \mathbf{E} \mid d(p, a) = d(p, b)\}.$$
If you think about it, you should be able to convince yourself that $L$ is a straight line!
Notice that many different choices of points $a$ and $b$ give the same line $V(a, b)$.

A set of circles in the plane. Sets are things, so a collection of sets should form a set! Logicians have to be very careful about constructing sets of sets, but as a geometer, you shouldn't run into any problems.
Here's a description of the set of all circles with radius one:
$$\{C_1(a) \mid a \in \mathbf{E}\}.$$
If we unpack the meaning of $C_a(1)$, our description of this set of circles expands to
$$\{\{p \in \mathbf{E} \mid d(p, a) = 1\} \mid a \in \mathbf{E}\}.$$
This expanded description makes it clear that we're dealing with a set of sets.

Another set of circles in the plane. Here's a description of the set of all circles whose radii are natural numbers:
$$\{C_n(a) \mid a \in \mathbf{E}, n \in \mathbb{N}\}.$$
Every circle with radius one is a circle whose radius is a natural number, so
$$\{C_1(a) \mid a \in \mathbf{E}\} \subset \{C_n(a) \mid a \in \mathbf{E}, n \in \mathbb{N}\}.$$

The set of all lines in the plane. Let's say $\mathcal{L}_{\mathbf{E}}$ is the set of all lines in the plane. This set can be described by writing
$$\mathcal{L}_{\mathbf{E}} = \{V(a, b) \mid a, b \in \mathbf{E}\}.$$
If we actually went through all pairs of points $a, b \in \mathbf{E}$ and drew the line $V(a, b)$ for each pair, we would draw each line many times over. That's okay: when you're describing a set using this notation, it's okay if you describe some elements more than once.
The set $\mathcal{L}_{\mathbf{E}}$ is useful because it tells you a lot about the geometry of the plane. In fact, even if you forget how to measure distances, you can do a lot of geometry just by playing with the sets $\mathbf{E}$ and $\mathcal{L}_{\mathbf{E}}$. For example, here's an expression for the set of lines that pass through a pair of points $a$ and $b$:
$$\{L \in \mathcal{L}_{\mathbf{E}} \mid a \in L \text{ and } b \in L\}.$$
It's a very important fact about geometry that when $a \neq b$, this set always has exactly one element!

The Fano plane. Once mathematicians got the hang of doing geometry by thinking of the plane as a set of points and then thinking of lines as a set of subsets of the plane, they realized that they might be able to create new kinds of geometry by starting with a set other than $\mathbf{E}$.
A cool example is the Fano plane, a set of seven "points" organized into "lines" of three points each. The relationship between the set of points $\mathbf{F}$ and the set of lines $\mathcal{L}_{\mathbf{F}}$ is very similar to the relationship between $\mathbf{E}$ and $\mathcal{L}_{\mathbf{E}}$. For instance, if you pick two points $a, b \in \mathbf{F}$ with $a \neq b$, you'll find that the set
$$\{L \in \mathcal{L}_{\mathbf{F}} \mid a \in L \text{ and } b \in L\}$$
always has exactly one element. In the Fano plane, just like in the Euclidean plane, there's exactly one straight line through every two different points.
Comment: May be I am asking if I can have a subset of a subset? I think I got the answer from your example as yes. Because, I am asking if we can keep on taking a part of a subset till it gets empty. Thank you.
Comment: @Creator: For a more complicated example, let $N_2$ be the subset of $\mathbb{N}$ you get by removing all the multiples of $2$ except $2$. Then, let $N_3$ be the subset of $N_2$ you get by removing all the multiples of $3$ except $3$. Then, let $N_4$ be the subset of $N_3$ you get by removing all the multiples of $4$ except $4$, and so on. As you construct this chain of subsets, you're running the sieve of Eratosthenes one step at a time. If you keep on forever (there's a way to make sense of that), you'll end up with the set consisting of all the prime numbers and $1$.
Comment: Thank you for your answer. May I ask can we have more than one subsets in a set? As an example let me consider your example  of "A set of circles in the plane" , now can we add another another subset to it is such that only certain points of the circles are on it not all the points of the circle?
Comment: @Creator, I can't quite tell what you're asking. Can you rephrase your question? In case it helps: a set can definitely have more than one subset. The example set $\mathbf{M}$, for instance, has eight subsets. If you go out to capture the three musketeers, you can think of each subset of $\mathbf{M}$ as one of the possible things you might haul back.
Comment: If you're lucky, you'll capture a pair of musketeers, like $\{\text{Athos}, \text{Porthos}\}$ or $\{\text{Aramis}, \text{Porthos}\}$. If you're really lucky, you'll get all the musketeers: the subset $\{\text{Athos}, \text{Porthos}, \text{Aramis}\}$, which is actually all of $\mathbf{M}$. If you're unlucky, you'll get a single musketeer, for example $\{\text{Aramis}\}$. If you're really unlucky, you'll bring home nothing: the *empty set* $\{\;\}$.
Comment: @Creator: Oh, yes! For example, as you probably noticed, $\{\text{Aramis}\}$ is a subset of $\{\text{Porthos}, \text{Aramis}\}$, which is a subset of $\{\text{Athos}, \text{Porthos}, \text{Aramis}\}$.
Answer: The easy answer, which probably isn't useful to you who do quite advanced courses, is that a set is a collection of objects.
However the interesting part of sets are really the strength which this implies if we do interpretations of different sets.
Sets can not contain the same element twice, but we may identify $\{1,\{1\}\}$ with the ordered 2-tuple (1,1).
Functions may be simulated using sets by creating the graph, for instance $\{\{x,\{x+1\}\} : x \in Z\}$ could be identified with the function $f(x)=x+1$.
In the same sense we may define almost all mathematics by using such a simple humble concept. So to answer your question; I think about sets as the small very simple buildingblocks which we build mathematics from, and it all starts by just having a collection of things.
Answer: Unfortunately, "set" is as nebulous a concept as sets themselves. It is not a geometric object, and certainly not a physical object. It is instead an abstract concept that arose from the desire to specify what kind of collections can be described. Clearly the specification would be essentially specifying some kind of property that the elements in a collection must satisfy and that everything else does not satisfy. At the same time, certain mathematicians wanted the elements of a set themselves to be sets for whatever reasons that are clearly not related to the physical world. And so naive set theory was constructed, where it is allowed to create any set (of sets) that satisfy a property. Unfortunately, this is just an identification of sets with functions from sets to boolean (true or false), and anything of this sort is doomed to a contradiction in any reasonable formal system. Therefore Zermelo and Fraenkel came up with a set of axioms where the kind of set you are allowed to construct is severely restricted but there are other axioms make up for that. In this way the naive idea of having sets identified with their indicator functions is preserved, but at the cost of having some collections being proper classes instead of sets. There are other alternatives such as various type theories some of which more closely reflect the actual way we do mathematics than ZFC. But that is another topic.
And if you study first-order logic, you will realize that ZFC is a first-order theory where the domain is intended to consist only of sets, but that is when viewing it from the outside! Within the theory you cannot define the domain at all, and all you 'know' are the axioms of ZFC. Similarly, the basic 2-input predicate "$\in$" cannot be defined within ZFC, because you cannot express "$t \in u$" if you are not allowed to use any predicates at all! Thus if you do mathematics completely within ZFC both sets and "$\in$" will be undefinable. How then do we talk about ZFC itself? We would have to go outside it. If you notice, when studying logic itself we are using some kind of mathematics to state and prove theorems about logic, and that mathematics is usually ZFC!
This phenomenon is intrinsic to all languages, including formal languages like ZFC and natural languages like English, where some notions are not definable in the language. For example, one cannot understand the meaning of "if" without already understanding something equivalent to it. This is in fact related to why we need at least one inference rule in logic, usually modus ponens, because without rules we cannot do anything. But rules cannot be defined! Moreover, to use modus ponens we already need to understand "if", because the rule says "If you have derived formulas $α,α \rightarrow β$, then you can derive $β$.".
Comment: Thanks to all. I will think more in coming days and hopefully it will clarify a lot.
Answer: A set can be thought of as an inclusion rule, or "All the objects which satisfy a given inclusion rule."
"All odd numbers".  If you're an odd number, you're in the set.  If you're not, you're not in the set.  Or, "All the states in the US whose names start with 'A'".
The set might be empty: "All odd multiples of 2".  The empty set is actually important, but you'll learn that as you go.  Just like zero is an extremely important and useful number but they don't teach you that at first.
You can even have a set defined like this: "The numbers 1, 2, and 5".  Anything that is not one of those numbers is not in that set.
Answer: What really matters about a set, $S, $ is that for any element, $ x, $ in the 'universe' exactly one of $x \in S, $ $ x \notin S$ is true. You can put stuff inside of a set, thus distinghishing it from everything that isn't inside if the set. It's a symbolic way of talking about "this stuff here."
Don't confuse how to think about a set with how to define a set. What you think about a set controls how you use a set and how well you understand theorems that use sets. How you define a set is how you prove those theorems.
The important thing is, if a theorem conflicts with what you think about a set, then you have to change the way you think about a set. The definitions that describe how a set is used are what a set really is. those definitions should correspond to your intuitive idea of what a set is. But once you state a definition, then the set becomes the thing you defined; which may no longer be the thing you imagined.
Answer: Let me begin by saying that this is I think of sets. Hopefully it is helpful.
My intuition of what a set is, as vague as it is, is that it is a thing with stuff in it (or in the special case of an empty set, with no stuff) (more exactly, a set theory is a theory that has an epsilon relation). However, that is not quite enough to work with, so one naively begins to ask that we have various ways of building sets that reflect our activities. So one may want to be able to take the union of two sets, or more importantly, specify a set whose elements are all things that satisfy some property. More precisely, one may want to form the set, $$evenInt=\{x:x\mbox{ is an integer, and } x \mbox{ is even}\},$$ or other such things.
So one posits a universe (never mind where it or it's inhabitants came from), and we can form all sets that satisfy some property, or even perhaps form "random subsets". However, all is not well in this paradise since using this formulation, one may form the set, $$Russ = \{S: S\mbox{ is a set, and }S\notin S \}.$$ This looks like a perfectly good thing to do, until you ask the question "Does $Russ$ contain itself as an element"? Well if it does then it doesn't and if it doesn't then it does. This is called Russell's paradox. See http://en.wikipedia.org/wiki/Russell's_paradox .
So then people asked "How do we fix this"? An answer that was come up with is the ZFC axioms. These axioms appear to be consistent. Moreover, they seem to capture the types of constructions that people want to make on sets, without running afoul of Russell's paradox and other paradoxes.
This theory also has the effect that large chunks of mathematics is formalizable in this theory, which is another goal of set theory. One problem or feature with ZFC is that it treats everything as the same kind of thing, namely a set whose elements themselves sets, all the way down to the empty set (one might argue that certain type theories are set theories that do not have this property). See https://golem.ph.utexas.edu/category/2013/01/from_set_theory_to_type_theory.html form more on that.
Comment: Sometimes those things that aren't sets are called urelements. In some alternative set theories the universe strictly contains in its own power set because urelements are not in the power set.

How to think of a set?


IIS7 Directory Browsing reseting

Question: I have a IIS 7 running where one of the sites is just a bunch of files exposed through Directory Browsing. I can enable it without any problems, but within a few hours the setting resets itself. Any idea what this could be caused by?
Answer: The configuration being rolled back somehow, or not rolled back but simply changed in that regard, for some reason. Directory browsing doesn't just turn itself on or off; someone or something has to be taking action.
Edits to either system32\inetsrv\config\applicationhost.config or a web.config file in the content directory (or at a level above it) are the most likely source of a configuration change.
Any changes to apphost.config will be backed up to \Inetpub\History , so can be reviewed in reverse there.
File auditing might be your best bet for working out what's doing it.
Incidentally, if IIS 6 Metabase Compatibility is installed, an older script or re-installer might be doing it.
Comment: Great answer, I'll be sure to check out the apphost.config History. I'm a developer and this is the customers machine, so I have limited rights.
Answer: A possible issue is that Directory Browsing can be set in ApplicationHost.Config and also the local web.config.  If your development Web.Config doesn't have the Directory browsing setting and you publish your web site, you'll overwrite the setting.

IIS7 Directory Browsing reseting


How should "the human genome" be interpreted?

Question: What does sequencing "the human genome" mean? Don't individuals have unique genomes?
Answer: Certainly individuals have unique genomes. The human genome sequencing project used DNA from a handful of volunteers, and the reference human genome that resulted from this project can be thought of as an "average" genome for those individuals. Where sequences differed between the individuals, a representative consensus sequence was chosen. Hence, the sequence of a gene from a given individual may not perfectly match the reference genome, although mostly the differences are small: genetic difference between humans is estimated to be around 0.1 --- 0.4%, which means a few million base pairs in total.
As DNA sequencing is nowadays orders of magnitude cheaper, genomes for larger number of individuals are being sequenced; see for example the 1000 genomes project.
Comment: A good start to an answer - might you want to talk about SNPs and gene variants (various blood groups, for instance) to get into a little more detail?
Comment: What percent of genome same for each individuals and What is the maximum number of genetically unique individuals that human genome allows?
Comment: @Abusayed  added a point about % differences. Theoretically I guess there are 4^(3*10^9) possible genomes with 3 billion base pairs, but of course it doesn't work like that  :)  But still there is enough variation that there is virtually no chance of encountering two completely identical genomes by chance.
Comment: @MattDMo, feel free to edit if you want.  It was a short, focused question though and I didn't want to respond with a population genetics lecture ;)
Comment: @Abu sayed: You might also be interested in these two facts: 1. The human reference genome's current release is version 20 (hg38). 2. Every newborn carries about 60-100 (which is not much at all) new private SNV due to mutations in the parents germline.
Answer: I think there are two concepts that you need to understand to understand what "sequence the human genome" mean; within vs between species variation and genome consensus
Within vs between species variation
There is indeed variation in the human population. We are not clones of each other. One can for example consider the average number of pairwise differences as a statistics of variation. Consider the two following sequences

ATCAATTCAGAA
AGCAATTAAGAA

Here, there are 2 pairwise differences. One can average the number of pairwise differences among any pair of individuals to get the average number of pairwise differences. The average number of pairwise differences within species is much lower than the average number of pairwise differences among species. It therefore makes sense to consider a standard genome of a species as variation within the species is negligible compared to variation among species.
Genome consensus
In order to obtain the "human genome", we samples DNA from a number of people, sequence them and then try to form a consensus among al these slightly different genomes. You can think of this consensus as some kind of average genome. Consider for example the following sequences:

AATGCA
AATGCA
AATGTA
AATGCA
AATGCG
AATGCA
AATGCA
ATTGCA
AATGCA

Sure, there is some variation but a priori AATGCA seems to be a good consensus.
Interestingly, it is very likely nobody on earth has the exact same genome as the consensus genome just. One simple reason is that there are sequencing errors occuring at a known rate but the other reason is that as sequences becomes long enough (the whole genome), every single individual carries at least one rare mutation that will not end up in the consensus.


Tracking vehicle 6 states extended kalman filter required?

Question: I'm trying to track an accelerating vehicle using a camera, an IMU, and a GPS.
I use for the state space equation a constant acceleration model:

The states are the position, the velocity, and the acceleration of the vehicle in the x- and y-direction. No input is used.
All the measurement equations are linear.
I'm wondering if I should use a discrete normal Kalman filter, or a discrete extended Kalman filter. (i.e. is my process non linear?)
Comment: @jsotola Thx for the heads-up! I improved the picture!
Answer: If you can write the dynamics with a matrix, which you have, then a normal kalman filter will be best.
However, your measurements will probably be nonlinear. You will find that you won't be able to write your measurements equations using matrices. You will almost certainly need an extended kalman filter because your measurements will be nonlinear.
Answer: there is some error in your matrix I think. P(k+1)=V(k) And
V(k+1)=A(k) so I don't kwon what is the A(k+1) maybe the jerk(jolt) of the vehicle.
Comment: On *Robotics* we are fortunate enough to have MathJax support enabled, allowing you to easily create subscripts, superscripts, fractions, square roots, greek letters and more. This allows you to add both inline and block element mathematical expressions in *robotics* questions and answers. For a quick tutorial, take a look at [How can I format mathematical expressions here, using MathJax?](https://robotics.meta.stackexchange.com/q/130/37)


I have bought bitcoin in the past but forgot which wallet it was. Anyway to find it with wallet address?

Question: Is there any possible way? I bought it back in March, 2017 and forgot about it and now I remember I bought it in the past with coinmama but forgot which wallet it was sent to.
Answer: No.  Bitcoin addresses conform to a standard, and that standard purposely does not include any indicator of the wallet that generated it.  As such, any bitcoin address could be generated from any wallet.
Answer: unless you used an exchange/pool/service such as bittrex / poloniex, the answer is no.
You could always try to fill it in here -> http://walletexplorer.com and see if it returns any service, or just a generic wallet.


How can I find out which devices allow installations of up to date custom ROMs easily?

Question: When I purchase an Android phone, I prefer to install a custom ROM on it, instead of using the manufacturer's version of Android. Is there a way for me to quickly figure out if a given phone supports custom ROMs or not? Ideally I want a way to list down every phone that supports custom ROMs by date and price, so that I could quickly figure out which are the latest/cheapest phones that fulfill my requirements.
Comment: Unfortunately, pretty much no. XDA-Developers is a good starting point, but there are still many phones that are region-specific and/or too unpopular to have a place there, and as such you can't have an exhaustive list of phones, let alone one with price (which varies greatly) and release date (which means that such list has to be human-maintained all the time).
Answer: As Irfan and Andy have already said. A custom ROM is just a ROM that is from a third party and has now been developed to boot on your device.
A quick look is every android can boot a custom ROM but getting a ROM that is bug free, that is, if it can at all boot on your device.
Booting a ROM on a phone requires an appropriate boot image containing a kernel that can work on your phone and correspond to hardware files and software apps in the system.
A few years ago before the dawn of android 8, porting a ROM used to need one to port a boot image of the custom ROM by the kernel of the stock boot image, considering the system space and partitions to write boot and system images to respectively, and also maintaining vendor data so as to support the hardware devices like cameras and speakers a phone has.
This made Google to think about a way to make any theoretical system to be compatible with the residing hardware. This made google to isolate vendor data to an independent partition as from Android 8 Go and above.
This made the deletion of or replacement of system files not to render phone's hardware unusable. They introduced Project Treble - a project aimed at developing universal ROMs for Project Treble supported devices.
This only requires flashing of the system partition without touching any other partition. This means a kind of universal boot image is already existing in Project Treble devices and all Treble ROMs have a universal  Build Properties file.
One has to unlock the bootloader of the device and then flash a sparse system image from fastboot and the phone seamlessly works
So my recommendation is any device running Android 8 Go and above. All devices succeeding Android 8 have native support for Project Treble ROMs - the easiest way to run custom ROMs on phone
Don't even think about manual porting it can be mostly disappointing. Read about Project Treble and you'll be amazed
Comment: Sure, but not every phone supports unlocking the bootloader as far as I understand?
Comment: @JonathanReezSupportsMonica many have the settings hidden. In developer options that requires to activate the setting first. But bootloader unlock in most devices like the MTK based is a basic element. Maybe you should say not all phones have fastboot mode, but bootloader unlock is found in most devices. Like Samsung. Bootloader unlock works primarily for ODIN to side load third party system images unlike the official locked one that only flashes in factory signed images


Controlling Raspberry pi from website

Question: I need to create asp.net website (on windows), the website should be installed on a windows computer.
The website (installed on windows OS) should be able to control the raspberry pi pins(with raspbian OS installed).
I don't know how and where could I start! any hint would be so appreciated.
Comment: Have you thought about the types of communication needed? And if their is a need for real time data? And what types of information your going to need to transfer to the Pi? And if you need 2 way communication? If you are going for simplicity maybe just setting up a web server will work for you? Maybe even just having it long poll forever?
Comment: Welcome -- but this is not a discussion forum -- please take [the tour](http://raspberrypi.stackexchange.com/tour) again and pay attention to the *"Get answers to practical, detailed questions"* part.  You need to break this project down into smaller tasks and ask more specific questions about  the ones you need information on.  For example, there is no point making a web site for remote control of the pins until you can control the pins locally, so you might want to start there.
Comment: Sorry if my question wasn't clear enough, but I know how to control the pins locally. I'm not asking to get full procedure, I just asked about the starting point (I don't know how and where could I start) and I'll proceed on after that... The starting point means the required tools and skills to make the web interface, not the full web interface itself.
Comment: http://raspberrypi.stackexchange.com/users/43607/mohammad-ali all I need is to send commands and control rpi pins. suppose a simple project just lighting a led on or off from internet web based application.
Comment: I don't think it's clear enough in the question that the ASP.NET website will be running on a Windows machine.
Comment: I mention that to clearify that I don't want using asp.net on the raspberry pi with windows 10 iot! I'm using it on another windows pc to control a raspberry pi with raspbian os.. may be my lack english language make my explanation unclear.
Comment: I've re-opened this but I will warn you that this is likely to be ignored by the people most able to help you because 1) Your title is very ambiguous, 2) You have filled in details using comments instead of editing information into the original question.
Answer: As indicated by @goldilocks this is a very wide open question, to answer properly much more details are needed.
Like on every small or large project, divide it into development units, each one with it's own testing methods then, connect the pieces together. Think LEGO: you will write some pieces, others you will integrate.
You want to control GPIO pins from another system (ASP.NET IIS web site): Why not locally on the RPi Apache using PHP/Python? There are some examples elsewhere. Will assume the IIS have public access and RPi is on you intranet.
You then need to define a protocol to connect both devices: this can be your own creation or a complex REST/SOAP standard.
Do you need to obtain status from the RPi to show on you ASP.NET page? If yes, the you need to have a method to remote query the RPi from Windows.
The following draft is a very simple protocol, that allows you to send and receive low data volume, allowing the RPi to be local or on the other side of the world, making it a truly IOT.
In a loop, as fast as your requirement, from a few second to hours, the RPi send status to your IIS, posting a web query (using wget) and receiving back data from your server:
wget http://<YourIISServer>/xxx.aspx?status="<RpiStatus>" -o /dev/null -O /tmp/xxx

You then read and parse the /tmp/xxx data received: if you are brave enough, your data can be a bash script to be executed on your RPi.
Will leave the ASP xxx.aspx details for you, just process the form query "status" (data from RPi to Server) and send a reply with your RPi instructions:
To send your data from IIS, on the ASP.NET page Init event add the following (assuming VB.Net):
    Response.Clear()
    Response.Write("<your instruction message to RPi>")
    Response.End()

On your ASP.NET app, you store the RPi instructions elsewhere and you send them back when the RPi poll the server. You can use a simple SQL table to keep track of it.
This is not real time, a very asynchronous process but effective a easy to implement.
Answer: I do not know what a asp.net website is that you mention in your question's original post, but in the comments section, you describe

"...a simple project just lighting a led on or off from internet..."

I've just spent the day installing a RPi project which is based on just that.  After considering many approaches, I finally settled on using Python to write an extremely simple server-client relation (between a desktop PC at home and a RPi at work) using "sockets". I did a good deal of reading, like articles, tutorials, forums, documentation, knowledge bases, retail site's "learn" pages etc. and found PySocks to be the best all-around.
If you just want the essentials (in Python 2.7) for a jumping off point:
(THIS IS THE BARE MINIMUM FOR YOUR SOCKET SERVER - I chose to use UDP instead of TCP because it used less code! This is an echo server - anything it receives from the CLIENT is promptly echoed back)
(set up)
import socket

dgramSock = socket.socket( socket.AF_INET, socket.SOCK_DGRAM )

dgramSock.bind( ('', port number) )      <--- please note: two single quotes, NOT one double quote

(body)

incomingMessage, (addr, port) = dgramSock.recvfrom(bufferSIZE)

dgramSock.sendto(incomingMESSAGE, (addr, port))

(NOW FOR THE SOCKET CLIENT)

(set up)

import socket

dgramSock = socket.socket( socket.AF_INET, socket.SOCK_DGRAM )

(body)

dgramSock.sendto( message2send, (addr, port number) )

But really, check out the link I gave, it's really very good.
I have tested all my code on my LAN here at home and it all works properly.  Haven't tested yet over the WAN that separates my home and work, but I'm assured that SOCKETS are real working things actually used on THE internet.  Yes, I'm really quite the NOOB, but I can really relate to the way your post went, and how perplexing starting from a dead stop with nothing to push off against can be (or, in my case, ALWAYS IS). And you gotta love those members who have to chime in with their sarcastic comments; they're SOOO helpful.
Answer: i dont know windows iot how can help you for this!
but if you wann use python and raspbian(or another linux distro) you can create rest api and call this api from your asp.net website to control your rapberry pi by parsing rest api in .net
for creating this api you can use flask or another python framework
you have a wide choice for your programming language in linux such as python, go, nodejs ,even php ,... and any of them can help you to build your own Rest-api
:)
Comment: Oh how I missed that! Thanks for your valuable answer. I'll try it.

Controlling Raspberry pi from website


Why hasn't this question been reopened yet?

Question: I asked this question, and it was closed because I did not clarify what I meant by the word "randomly". Now I've clarified it but it is not reopened. What is wrong with it now?
Comment: @S.S. Anne PostRockGarfHunter added about some duplicates in the arrays.
Comment: You clarified it, huh? Are you sure it wasn't a volunteer?
Comment: @S.S Anne I clarified the question. PostRockGarfHunter helped me do this.
Comment: I was the one who added the note about "random". You even approved the edit.
Answer: Reopening takes time
An unfortunate fact is that this site is not as active as it once was.  That means accumulating the required reopen votes can take a while.
What you can do
The things I would recommend to do about this are

Sandbox your challenge first.  It is too late for this challenge but when a challenge is sandboxed issues can be addressed quickly without needing to attract voters.  You can fix a problem and move on to other improvements very quickly.
Do reviews.  If you are upset that reviews are not being done quickly by enough people, it is a good idea to take up the initiative yourself.  Of course this won't help your specific challenge, but I'm sure other people have been in your location and if you all start doing reviews you can help
Ping the users that closed it.  People don't always go back and check on things they have voted to close on their own.  If you ping them and explain how you have addressed their concerns they will likely respond with other concerns or vote to reopen.  If no one voiced concerns in the comments then it is a good idea to ask them why they voted to close.  Since you are asking for help please try and provide as much relevant information as possible in the comment.  "I fixed this" will likely appear in their inbox with little or no context requiring some work on their part before they can vote.
Post in chat. Posting in places where people go brings the idea to their attention.  Of course the effectiveness of this depends on the activity of these places.
Post on meta.  You have already done this, but if the two above options are failing you this can be a place to ask.


Is there a word or an idiom for barging in a room with anger?

Question: Opening a door frustrated and rushing in like you are about to scold someone inside... Barging in a room with anger. Is there a word or idiom for that, other than storm in?
Comment: Related: http://english.stackexchange.com/questions/19138/whats-a-word-for-saying-entering-a-room-suddenly-and-fast
Comment: I think that "raging into" would work in place of "barging into." I've always loved the comparison of a person's intrusion into a peaceful setting to the behavior of a barge, though: The momentum of a fully laden barge seems almost irresistible—and certainly impossible to ignore.
Answer: Storming in and barging in are great, but for some added oomph, how about erupting into the room?
Comment: To me "erupting into the room" comes across a little strange, as "erupting" has an association of "bursting *out*". But that may just be me :)
Comment: +1, 'Barging' implies rudeness a bit more than anger, but still works well. 'Storming' seems best, as that implies both rushing and anger. I get more enthusiasm than anger from 'erupting', but anger is usually pretty enthusiastic.
Answer: "Burst into the room" sounds good.
Comment: This was my first thought, too. It doesn't necessarily imply frustration or anger though, just entering a room energetically (e.g. you could burst into a room joyfully). Context is necessary for the emotion(s) associated with the action.
Answer: 1) Barged in
2) Stormed in
3) Broke in
4) he/she pushed forward into the room with anger.
5) thrust ahead.
Comment: *Barge* and *storm* are perfect fits in my mind. The others are stretches. *Break in* doesn't suggest any particular attitude or even energy, as you can silently and carefully *break into* a room with no anger or frustration on your mind at all.
Comment: after a thought, I agree.
Answer: Charged into the room

charge
intransitive verb
:  to rush forward in or as if in assault :  attack; also :  to charge
  an opponent in sports
Merriam Webster

A couple of examples

UNCONTROLLABLE anger surged through Wilson as he charged into the
  room. Google Books: Crimson Moon by Rebecca York

and

'Wayward and contrary!' Gwenhwyvar cried. 'Easily given to despair!'
  She charged into the room and planted herself before us, fists on
  hips. 'Gwenhwyvar,' Arthur said, somewhat startled. 'I thought you
  were asleep.' 'Listen to the both of you,' she scolded. 'I will tell
  you what troubles me, shall I? You haughty Britons think you are the
  only men alive who know how to throw a spear.'
Google Books: Pendragon By Sahın Akbulut
Answer: Loaded for bear
To be prepared, mentally and/or physically, for extreme opposition; typically used in reference to an aggressive or potentially violent situation.
For example:
He showed up loaded for bear and wouldn't leave until he gave everyone a piece of his mind.
Comment: Worth noting that this idiom is based on arming oneself. It is sometimes used in military contexts. A helicopter that hasn't fired any of its missiles is l[oaded for bear](http://en.wiktionary.org/wiki/loaded_for_bear).
Answer: You can consider flounce into.

Go or move in an exaggeratedly impatient or angry manner
OD / flounce

But the strongest sense of anger can be conveyed with explode into.

Again the door burst open and again it slammed against the wall. A genuinely angry President exploded into the room...
Madame President by Wee Dilts
Answer: You could say the person went ballistic.

to be extremely and uncontrollable [sic] furious
Fred went ballistic, and managed to punch 5 holes in the wall, in addition to throwing a microwave halfway across his house.
Urban Dictionary
Answer: He came barreling into the room. Describes intensity and single-mindedness but not necessarily anger.
Answer: I'd say the idiom muscle in.

Forcibly intrude on or interfere with something, as in The children
  were determined not to allow the school bully to muscle in. [Colloquial; 1920s]  (Free Dictionary)
Answer: Perhaps the informal idiom: "Bust the door down" or "Bust the door open." In this context, "bust" is used informally for the word "break". Depending on the context, this idiom can suggest a violent disposition towards whomever is "behind the door", either actually or metaphorically. "I will bust the door down to get answers."


Would a Response.Redirect() loop cause IIS service to die?

Question: If classic asp got into a redirect loop, would it be enough to kill the IIS service.
Or does the act of redirecting not consume that many resources?
Answer: I believe there is a setting in most browsers that restricts the number of redirects. I believe IE is 7, FireFox is something silly like 20.
I don't entirely agree with Joe.  Whilst the act of an unending loop is generally bad, and will eat up resources, your redirect loop involves a connection to a web server, which will clear up once the redirect message is sent to the client.  The IIS instance isn't really looping, it's telling your browser to go do something, and it will (should) cleanup after itself.
That being said, if your page does something server intensive, queries databases, holds open other connections, does a bunch of other stuff, then it will cause some issues, but IIS is pretty resilient, and will usually start rejecting connections before crashing. Throw a whole bunch of requests at that page that loops, and you may be looking at memory issues, but entirely depends on what is going on in the script.
Answer: It would seem to me that if it is in fact a loop that eventually it would cause IIS to crash. A loop has no end, therefore regardless of how little resources each iteration of the loop consumes, eventually all of the resources would be exhausted and IIS would crash.
Comment: Thanks joeqwerty - A very good point, would IIS try to restart itself by default? Or would it stay in the stopped state? Would you get a warning in IIS manager?


Open source Tool for creating reports of DB structure for SQL Server 2008

Question: Any recommendation for open source tool (or evaluation functional software) witch I could generate a report (Excel or Word) of all my tables and fields of a SQL server 2008 Database ?
Answer: You can use SQL Alchemy from Python/Jupyter and Pandas.
Pandas can use SQL Alchemy to perform just about any SQL Query into a data table and these can then be written out to excel.
All of the above software is:

Free, Gratis & Open Source
Licenced to include commercial use PSF or MIT licence
Widely Used
Actively maintained and developed
Cross Platform
Answer: TOAD Free for Sql Server (formerly from Quest software, now owned by DELL) has schema reports as well as data reports.
They have products for the most common databases with their respective free version , limited but completely usable for the purpose you need it.


Where is gravity "potential energy" gone when object has escape velocity?

Question: If an object leaves Earth with the escape velocity, meaning it'll never fall back on Earth, where does the energy go? You can't say it's converted to "potential energy" anymore because the object will never fall back. Yes, the escaping object velocity will decrease therefore energy will go somewhere else.
Answer: The energy is indeed still converted to potential energy. The object doesn't go back on its own, but it still has a potential energy associated with its distance from the other mass.
Similarly, an object perfectly on the top of a hill won't roll down on its own, but it still has a potential energy associated with its being on top of the hill.
Answer: But it is converted into potential energy. In non-general relativity terms, it is stored in the gravitational field surrounding and between the two objects (in general relativity terms, the energy is stored in how the curvature of space-time is altered).
In Newtonian gravity, you find the gravitational field of two point-like objects by adding the individual fields of the objects:
$$\mathbf{g}_{\mathrm{tot}}(\mathbf{r}) = \mathbf{g}_{1}(\mathbf{r}) + \mathbf{g}_{2}(\mathbf{r}).$$
The energy density, $u_g(\mathbf{r})$ (energy per unit volume of space), stored in the gravitational field is given by $[G / 8\pi] \mathbf{g}_{\mathrm{tot}} \cdot \mathbf{g}_{\mathrm{tot}}$, giving:
$$\begin{align}
 u_g(\mathbf{r}) &= \frac{G}{8\pi} [\mathbf{g}_{1}(\mathbf{r}) + \mathbf{g}_{2}(\mathbf{r})]\cdot [\mathbf{g}_{1}(\mathbf{r}) + \mathbf{g}_{2}(\mathbf{r})] \\
& = \frac{G}{8\pi}\left[\mathbf{g}_{1}^2 + \mathbf{g}_{2}^2 + 2 \mathbf{g}_{1} \cdot \mathbf{g}_{2} \right]
\end{align}$$
The $\mathbf{g}_{1}^2$ and $\mathbf{g}_{2}^2$ terms are the density of energy needed to create objects 1 and 2, and add up to an energy that is infinite. The energy density of the interaction between 1 and 2 is given by the cross term:
$$u_{g\, 1,2} = \frac{G}{4\pi} \mathbf{g}_{1} \cdot \mathbf{g}_{2}.$$
Since only differences in energy are relevant in classical Newtonian physics, the self energies don't contribute to the dynamics. If you integrate $u_{g\, 1,2}$ correctly over all space, you'll find that
$$\Delta U = \frac{G m_1 m_2}{|\mathbf{r}_1 - \mathbf{r}_2|},$$ exactly as expected.
Answer: There are three important things to note.
One is that you have simplified things by treating the Earth and point mass system as though there is nothing else in the Universe.
"Escape" means that of its own accord the point mass will never return back to the Earth but that does not mean that it ceases to exist.
Lastly you have implied that you can actually travel an infinite distance.
If the system is the  mass under consideration and the Earth and there are no external force acting on the system (ie nothing else in the Universe) then as the separation between the mass and the Earth increases the kinetic energy of the system decreases at an every decreasing rate whilst at the same time the gravitational potential energy of the system increases at an ever decreasing rate.
If used in such a context, "infinity" is a word which means "the distance between the mass and the Earth is such that, on the scale set by the example, if there is a change in the distance between the mass and the Earth then the kinetic energy of the system can be sensibly taken to be zero and the gravitational potential energy can be sensibly taken to be constant.
So "mass at/reaches infinity" is a shorthand way of writing "the separation between the mass and the Earth tends to infinity" and this is a very useful idea when one starts to model a system mathematically as the limiting process is implied to have been performed - eg making one of the limits of an integration infinity.
Answer: the energy after the object gone out of gravitational field of earth remain constant as it remains in equilibrium in space and does not fall to the earth afterward

PE=mgh   remain constant if h<=value of g at 'h' height)
Comment: this isnt correct, your formula is an approximation for trajectories small enough for G to be constant. But G isnt constant . Plus my question mentionned escape velocity, meaning the object must moving away and not be "in equilibrium"


disabled field with help icon

Question: If a field is disabled, should the accompanying help icon also be disabled?  The content within the help does not discuss why the field is disabled btw. The user needs to fill out a field previous to this field to "unlock" it.
Answer: Logically speaking, as the help-text for that field offers no value to the user when the field is disabled, you should be OK disabling the icon along with the field.
If, on the other hand, the help-text contained information that helped the user to understand why the field was disabled or helped them re-enable it then, logically, you would need to leave the icon enabled.
I understand that your particular situation falls into the first scenario rather than the second but I wanted to be clear for anyone else reading who may have a different situation.
Comment: Thanks Andrew.  I agree with you too.  This is so helpful and thanks for taking the time.
Answer: You could keep it enabled so that users can get a bit more of an idea of what it is and hence how to enable it. It would also satisfy those who are just curious what it is.

disabled field with help icon


Should I block a user from using banking app if they fake the location?

Question: I was wondering if this could be a security issue for banking application and if so, why? What are the risks if I allow it?
Comment: What to you mean by *faking the location*? I know what Tor and other proxies are, but I do not know how you intend to control user's location. Use the IP address? Some large organizations may have a unique outgoing proxy so a user in LA could present an IP address from NY.
Comment: I mean using some GPS mobile application that helps the user to fake their location or any other means.
Answer: Are you talking about faking location services in a browser or on a mobile device, or connecting through a VPN to appear to spoof IP-based geolocation?
Personally... if my bank asked for access to geolocation data from my phone for anything other than finding a branch or ATM, I probably wouldn't be using that bank. As for IP geolocation checks... I'd use that data to add weight to fraud detection.
If there are enough factors to suggest the request is not by the customer, then block as potential fraud. But current location alone probably shouldn't be enough, because people travel. Did they suddenly move from one country to another faster than one could travel by plane? Are they connected from two countries at once? Is the user-agent of the connection different than what the normally use?
Add up all these little things and set a threshold at which a block action will take place. If you want an example of how this would be structured, email anti-spam systems are a great example to look at. There's not one single factor to decide if email is spam... it's a system of different checks that work in concert with one-another.
If VPN services are a concern... add them as a factor in the system. But many people will be connecting to a VPN for banking if they are on public WiFi. I don't think that alone would be a legitimate reason to block a request. I'd probably set the system to adjust the weight of the factor based on whether the user normally uses a VPN or not.
Comment: I was talking about when a user using the fake location mobile applications.
Comment: Ya... I don't think that's reasonable. You shouldn't be using that data for anything critical (it should be treated with as much skepticism as any other user input).  On most devices, you can't even be sure they'll give you permission to access location services. It seems unreasonable to deny access unless you can be sure the data was falsified in bad faith, which the multi-factor method would help with.
Answer: You should only control what can matter. The localisation is always off on my smartphone, unless I am actually using it. Not really that I want to hide it, but I can hardly understand why a banking service could be interested in it. And I know that a legal enquiry would immediately get it from my operator. The same if I use a (public or not) Wifi access. I assume that my bank also knows it, so they do not know it but know that they could get it if an attack came from there.
Things are different when you use Tor or some other well known(*) proxies that are used for privacy, because now even legal enquiries cannot easily find where the connection came from, it they even can. So IMHO I would neither be disappointed nor even surprized if my bank rejected all Tor accesses or required at least a strong second authentication factor (nor a secret question...) for security reason. After all I have never entered a bank office wearing a mask, and I would expect that they do not let me in.
So reject Tor accesses if you want, but please do not concentrate too much on geolocalisation for a banking service. What matters here is to authenticate the clients not where they are. Anything that can prevent access point identification is suspect, but simply not giving localisation is not.

(*) Not all proxies are the same. Do not reject corporate proxies for example...
Answer: Malicious individuals attempting to break your application will probably fake their location and hide their public IP through VPNs, Tor and/or proxies. Not blocking users faking their location could expose you to their attempts
On the other hand, faking location is usually something a user worried about his privacy would do.
Also note, that this kind of controls are made client side of the application, so a malicious individual with enough knowledge in reverse engeneering may bypass that kind of filters, while a legitimate user probably won't do it
You should balance what do you prefer, block possible attackers and possibly legitimate users faking their location or expose your application to those attackers
Comment: What are some of the functions in bank app you see could be at risk here? There should valid and detailed justifications for adding such functionality.


Is there any way I can tighten my crankshaft pulley without a torquemeter?

Question: My crankshaft pulley requires 130 nm (95 lb-ft) of tightening torque. I have a torque meter but it only supports up to 80 nm. I can't afford to buy a separate torque meter just for crankshaft pulley because it is extremely expensive in my area. Is there any way I can apply the same amount of torque and prevent over-tightening? I was thinking about using a 2 meter metal rod and applying 65 nm of torque to it. 65 x 2 = 130 nm.
However, I don't know how to exert such a force on a metal rod.
Answer: Got a set of hanging scales and a longer bar? 10 foot bar and 9.5lb on the scale... etc
A basic application of force * distance.
Comment: Just pull on the scale to get the reading...
Comment: Obviously yes... but oem may have had a sealer...
Comment: So, using a 3-meter-long rod: 130 / 3 = 43.33 nm (43/33 / 9.8066 = 4.418 kg/m). Therefore, I need a hanging scale, a long rod (3 meters) and 4.4 kg of weight. Am I right?
Comment: Can I use the same technique to measure how much torque had been applied previously for tightening the pulley?