How many bitcoins are there currently in circulation?

Question: Where do I find the total number of bitcoins currently out there?
Answer: If you are running Bitcoin Core, you can see the total amount in circulation using the RPC call gettxoutsetinfo (in the Bitcoin-Qt debug console, or using bitcoin-cli if you run bitcoind).
At the time of writing, the output is:
{
  "height": 517245,
  ...
  "total_amount": 16965398.58586455
}

which means there are currently ~17 million BTC in circulation. This number takes into account certain types of destroyed coins.
See also this answer of mine about how many there will eventually be.
Answer: The number of bitcoins currently in circulation can be found at BlockChain.info or BitcoinCharts.com
Background
The rate at which new bitcoins are mined follows a predefined schedule, with a new block appearing roughly every 10 minutes. The amount of bitcoins in a newly mined block started as 50 and gets halved every 210,000 blocks.
There can be at most 20999999.9769 BTC, so nearly 21 million bitcoins.
Answer:
Fun Fact:

In fact, there are only 21 million Bitcoins that can be mined in total. Once miners have unlocked this many Bitcoins, the planet's supply will essentially be tapped out, unless Bitcoin's protocol is changed to allow for a larger supply.

Where do I find the total number of bitcoins currently out there?

https://bitcoincharts.com is a good place where you can find it.
The number in circulation at the moment is 16.523M
Comment: I've downvoted this answer because it almost exclusively repeats information from other answers and gives an outdated answer to the asker's main question: More than 16.96M Bitcoins are already in circulation.


Asymmetric routing with two ForeFront TMG 2010 firewalls

Question: I have a bizzarre networking problem.
There is a network, a single IP subnet: 192.168.60.0/24.
The network has two Internet-connected firewalls (running ForeFront TMG 2010), 192.168.60.253 (production) and 192.168.60.240 (development); this is a necessity because there are two environment and each of them needs its own Internet-publishing rules; however, for historical reasons, they share the same IP subnet, and this can't be easily changed. Thus, production computers use 192.168.60.253 as their default gateway, while development computers use 192.168.60.240. Everything works, as long as no other networks are involved.
But, of course, there is another network (actually more than one, but let's simplify things)connected to a third NIC on the production firewall, namely 192.168.100.0/24. Computers in this network use that firewall as their default gateway. They can talk with production computers in the main network, and vice-versa.
When computers in the 192.168.100.0/24 network try to talk with development computers in the main network, this doesn't work, because their default gateway (the develompent firewall) doesn't know how to send packets back. This is expected. So I added a permanent static route to the development firewall to tell it "when you need to send a packet to 192.168.100.0/24, send it to 192.168.60.253"; I also defined the network in the networking configuration of TMG end enabled all traffic between the two networks.
Now, the really strange part: pinging between the two networks works, but any other protocol doesn't. HTTP, RDP, SMB... nothing goes through, although routing seems to be working and firewall policies are open for everything.
What's happening, why, and how can I fix it (besides manually adding static routes to each development server, which I'd like to avoid)?

Update:
I examined the traffic logs in the development firewall, and it looks like TCP packets are being dropped because, from that firewall's point of view, they are not related to any open connection. This actually makes sense, because when a connection is started, the initial packet of the TCP handshake goes through the production firewall, while the answer tries to come back through the development firewall... and TMG drops it because it never saw the first packet at all. This also explains why TCP doesn't work while ICMP (and presumably UDP) does.
But still: how can I fix this and make this asymmetric routing work, if it can at all be done?
Answer: As I understand...
A packet from 192.168.100.x to a DEV box is routed:

into TMG-PROD
then to the DEV box

However, packets going from a DEV Box to 192.168.100.x go

INTO TMG-DEV
then to TMG-PROD
then to the 192.168.100.x

Therefore you need to make these routes the same so one suggestions is to add a static route to the DEV box so 192.168.100.x traffic is directed to the TMG-PROD gateway (192.168.60.253)
Comment: You understand correctly, but this is exactly the kind of solution I'd like to avoid, because it requires manually adding a static route (more than one, actually) to *EACH* development server. Can this be made to work in any way while preserving the asymmetric routing, or is it never going to work at all this way?
Comment: I dont think it is going to work.  We had similar issues when we had two routes to the internet and inbound packets only worked if they went back the "right" way they came in. You could add the routes using group policy if that helps?
Comment: Yep, pretty sure this won't work - each TMG box needs to have seen the connection setup in order to allow a packet to traverse it.


What do scriptures say regarding Immigration & Emigration?

Question: For example, one popular rule that is believed to be scripturally imposed is that brahmanas can't participate in sea voyages. Where is it mentioned that such journey is prohibited?
Comment: Related [Why are Tirupati temple priests restricted from traveling overseas?](http://hinduism.stackexchange.com/q/14987/3500)
Comment: @LakshmiNarayanan Everything need not be mentioned in the vedas. It is incorrect to discard ancient wisdom because one is unable to find a vedic reference. 1. Vedas are infinite. The portion of the veda available to us is infinitesimal 2. Hindu dharma is encapsulated in sruti (veda), smriti, purana, samhita, as well as janachara (the path trod my knowledgeable elders).
Comment: @TheDestroyer In the Tirupati example, are these references directly from the Vedas?
Comment: Not Sure, i think Dharma Sutras. But Mylavarapu Srinivasa Rao, a scholar from Andhra, says as it wasn't possible to do Sandhya vandanam and other Brahmin rites on Ships, they included this rule. He says this rule doesn't fit for today's world.
Comment: @TheDestroyer Travel by ship was also forbidden because human refuse was emptied into the sea which is a gross sin. Polluting waters is fordbidden in Hinduism. Other reasons are having to eat forbidden foodstuffs. It is not just the difficulty in observing sandhya.
Answer: Where is it mentioned that such journey is prohibited?
Chapter 22, "Varnasramavidhi" (Rules to be followed by four Varnas) of Brihan Naradiya Purana states "Samudrayatra" (voyage over sea) is prohibited for Dvijas (twice borns) in Kali Yuga.
This chapter mentions various deeds which are prohibited in Kali Yuga.

समुद्रयात्रास्वीकारः कमण्डलुविधारणम् । द्वीजानामसवर्णसुवा
  कन्यास्पयमस्तथा ॥ १३
samudrayātrāsvīkāraḥ kamaṇḍaluvidhāraṇam । dvījānāmasavarṇasuvā
  kanyāspayamastathā ॥ 13
Undertaking sea voyages, the carrying of  kamandalu (waterpot) ,  the
  marriage  of dvija (twice-born) men with damsels unequal in Varna...

After mentioning all examples, verse 23 (b) says all these practices must be shunned in age of Kali.
Comment: Did you also find anything regarding Immigration? for example, if a Dvija is born abroad are they allowed to undertake sea voyage for coming back to India?
Comment: @LakshmiNarayanan Above verse says Samudrayatra Swikaraha.. (Accepting sea voyage is prohibited). I think it is true for both journeys. Since it is only available in Sanskrit, i read only some verses in that chapter. But i will try to update the answer with other details.
Comment: Then how Hinduism went to Indonesia, Malaysia Singapore, etc?
Comment: @NarayanaSharma It could be possible this smriti was of later day. Ancient kingdoms had trade relations with even Arabia and beyond. It's not possible to travel on *Uttarapatha* (Grand Trunk Road) and Silk Road all the way to Arabia.


Can the attack titan and the founding titan be splitted?

Question: Currently Eren Jaeger has the power of the attack titan and the power of the founding titan. Can these titans be splitted again or are those 2 powers supposed to remain like this forever?
Answer: There are currently two possible ways to inherit a titan's power:

Injecting someone with Titan fluid and have him eat a Titan shifter
Wait for the Titan shifter to die to have a random person inherit it

Going by the first scenario, the person with Titan fluid has to eat the person. It has never been proven or shown that eating just a portion would also grant a portion of the power so there is no way to know. As far as I know, there is no precedent to someone holding more than one Titan power like Eren, aside from Ymir (the first one), so there's also no information as to how to split power from an Eldian holding two Titan shifter abilities. Remember, too, that Eren inherited two Titan shifter abilities from his father (the power was never split).
For the second scenario, as mentioned here, a baby will inherit a power of a previous Titan shifter who died due to the curse. It was never mentioned at all that a baby can inherit two Titan shifter abilities from someone wielding both, only that one of the Titan's power would go to a baby born after the previous wielder's death. (Notice that it's singular, not plural) This is seen in Chapter 88.
Answer: Yes it can be splitted as you when a titan holder dies their powers goes to a newly born child , so in this case when Eren dies then his each power will go to different children


How to store pizza dough in the fridge?

Question: I'm making about 12 pizza doughs. Typically when I make a few, I store each one in a ziplock and try to reduce air. But in this case I was wondering if I can just get away with a full size baking sheet and store as many dough with enough space between. Then wrap in cling wrap to secure it from drying.
Answer: From this site

Make Ahead Tips
The dough will keep in the refrigerator for up to 2 weeks. After 2
  days, tightly cover the dough in its bowl with plastic wrap to keep
  the surface of the dough from drying out. You can also freeze the
  dough in well-wrapped 1/2-lb. balls for up to 3 weeks. Thaw overnight
  in the refrigerator before using.
Comment: I always freeze mine in a ziplock bag, works like a charm
Answer: When I make a batch of pizza dough, I ball the dough (typically 12-18 oz for the size pizza I make), and put on an oiled half sheet pan (or a 2 inch hotel pan). I am generous with the oil in the bottom of the pan and cover all sides of the dough ball when I put it into the pan. I usually have 6 balls in the pan.
Even if the dough touches, the oil should prevent the balls from turning into one huge slab of dough. I cover the dough with plastic wrap, but in the pizzeria I worked at, we just covered with oil.
I never take dough out of the refrigerator and stretch immediately. I take however many I need out, and let them warm slightly before I stretch out the pizza.

How to store pizza dough in the fridge?


Differences between "fortfahren", "fortsetzen", "weitermachen", "weitergehen "and "fortführen"

Question: There may be other verbs that might also mean to continue. Whenever I practice my writing, I find these very confusing.
What are the difference between these verbs? I initially thought that they are rather interchangeable but it seems not be the case.
Comment: It's not like the English word _continue_ is out there all alone. You can _carry on, move on, proceed, keep to, pursue, …_ Having multiple words meaning very similar things is a feature in probably every language.
Answer: Those verbs differ in use and connotation, and some in meaning, too.
To begin with, fortfahren , weitermachen, and weitergehen are intransitive verbs. Fortsetzen and fortführen are transitive.
All those expressions can have both the meaning of a task, process etc. resuming after a break or going on without interruption, depending on the context.
Fortfahren and weitermachen indicate that a person or group is keeping up something, carrying on with a task, etc., and you have to add mit ... to include the task itself.
Use Fortfahren (to proceed) in a more elevated context, weitermachen (to carry on), on the other hand, on a more casual or colloquial level or as part of a journalistic jargon. Furthermore, to my experience, weitermachen is more often used for resuming a task after an interruption:

Fahren Sie bitte mit Ihren Ausführungen fort.
Sie fuhr fort, mir mit gerichtlichen Verfügungen das Leben schwer zu machen.
Mach weiter mit der Reparatur, wo ich gestern aufgehört habe.
Die Regierung macht einfach weiter, ohne an Reformen auch nur zu denken.
Weitermachen! (used to be, at least in the Austrian military, the German expression for the English "as you were!")

Weitergehen indicates the process itself going on, often after an interruption or some kind of break:

Nach dem Stromausfall ging das Fest ungestört weiter.

Fortsetzen and fortführen mean "a person/ a group etc. continue doing sth.", but again, "fortführen" is on a higher level and/or usually indicates a larger scale than fortsetzen:

Sie setzten ihre Angriffe bis zum Morgengrauen fort.
Er setzte seine Reise am nächsten Tag fort.

but:

Das Unternehmen wurde auch nach dem Ausscheiden des Gründers mit Erfolg fortgeführt.
Die Familie führte diese Tradition noch lange fort.

(Fortfahren of course has also the meaning to go/drive away, weitergehen also means to move on, with fortführen you can also say "to lead away".)
Comment: hmm... I get weitergehen but still quite unsure about the distinction between fortsetzen / fortführen group and fortfahren / weitermachen group.
Comment: I think it would be good if you have said that fortfahren is transitive while fortsetzen is intransitive.
Comment: Anyway all answers were excellent but I think this encompasses everything that I want to know about these verbs.
Comment: @Josh As to the distinction between transitive and intransitive, I actually mentioned that in the second line of my answer. I have tried to find rough guidelines how to make the best choice among fortsetzen / fortführen and fortfahren / weitermachen in the given context, but of course there always are situations where you would balance between both. Best thing to do in my view is to monitor as many examples as possible.
Comment: oh sorry I did not notice that :) thank you you did a great job on this
Answer: They're confusing because they encode differences that you, as an English speaker who uses the verb "continue", doesn't make.
In your experience, a performance may continue, or the audience may continue clapping, but those are really two different syntactic constructions. "weitergehen" corresponds to the first construction, the other to the second one. There's your first source of trouble.
Among the others, "fortsetzen" takes a noun complement. This corresponds to "I continued my career at BogusCorp". "fortfahren" usually takes "mit":

Wir fahren mit Tagesordnungspunkt 2 fort.

which corresponds to "We'll continue with agenda item no. 2."
"weitermachen" does the same, but can also be used without any complement, corresponding to "Let's continue".
"fortführen", again, takes a noun complement, usually one denoting an activity or occupation:

Nachdem der Weltuntergang abgewendet ist, können wir nun unsere Geschäfte fortführen.

Comparing this, you begin to see how versatile "continue" really is.
(However, note that all of these German verbs also have additional, non-metaphorical senses that have little or nothing to do with continuing anything. Closely related languages usually have similar complexity in such things, it just manifests in different specific places.)
Answer: They are all very close in meaning and the most appropriate use is usually driven by context rather than meaning.
Fortfahren (literally forth-driving) is usually in reference to a process or procedure such as a speech or work process: "Kann ich jetzt bitte mit meiner Rede fortfahren?";
Fortsetzen (literally forth-setting or set forth) can refer to a process but more commonly is used in reference to a movement or journey: "Wollen wir die Reise jetzt endlich fortsetzen?";
Weitermachen (literally further-making) is best used when prompting or referring to someone else to continue a process they previously interrupted: "Mach deine Hausaufgaben weiter!"
Weitergehen (literally further-walking) indicates that an interruption has taken place or may be about to take place but the previous activity should be resumed: "Bitte weitergehen, hier gibt es nichts zu sehen!"
Fortführen (literally forth-leading or lead forth) can mean to continue but also to lead someone or something away: "Sie führt die Kinder fort von hier"
Answer: There's indeed no difference between those words. The all mean to continue something you've already started.
The only 'difference' is simply a matter of being idiomatic in a certain context. And perhaps a question of register. I suspect that weitermachen is used most often in colloquial.
A few notes on some words:
Note that weitergehen is usually used like this:

(Und) weiter geht's.

Other than that, it's not used (much) in this sense I guess. It is used, however, for continue walking:

Komm! Lasst uns weitergehen.

And it is used if a road or street continues:

Die Straße geht noch 15 km weiter.

Or if a story is not finished yet:

Die Geschichte geht noch weiter.

And so on and so forth.
Fortfahren can also refer to drive away or to transport someone somewhere else. But you won't confuse it:

Wir fuhren mit dem Auto fort. (->to drive away)
  Wir fuhren die Gefangenen fort. (->to transport someone)
  Wir fuhren mit dem Projekt fort. (->to continue)

Fortführen does also cover the second use case of fortfahren, but while fortfahren connotes that you drive, fortführen doesn't add any hints in that respect.

Wir führten die Gefangenen fort. (->to lead away)
  Wir führten das Projekt fort. (->to continue)

Weitermachen and fortsetzen do not have any further meanings.


What are equivalent swimming and running speeds?

Question: How do you compare swimming and running speeds? For example, is swimming 100m in 60s comparable to running 1 km in four minutes in terms of effort or in terms the times in races (e.g. map percentiles of finish times).
Comment: This is related to [this](http://fitness.stackexchange.com/questions/5260/power-while-swimming) question.
Comment: This is like comparing apples and oranges for me; the only thing you can compare is calories burned.
Comment: If you're talking about comparing times, I've found that running is roughly 4x faster than swimming. That is, a top runner runs 400m in ~50s while a top swimmer swims 100m in ~50s. In the same amount of time, the runner covers 4x the distance. This is useful for comparing running times if you're a swimmer or swimming times if you're a runner.
Comment: Or slightly easier to measure, try to swim at the same heart rate you run at.
Comment: I don't understand the difficulty in comparing speeds? Is it difficult to measure swimming speed? Are you trying to account for swimming upstream vs downstream? In a still body of water, you should be able to simply use the distance travelled / time to calculate the speed just like you would for a runner.
Answer: A similar question was asked here.
That question included data from the 2009 Ironman Triathlon Championship in Kona, Hawaii. As you may know, the race consists of a 2.4-mile open water swim, a 112-mile bicycle ride, and a 26.2-mile marathon. A version of the scatterplot matrix from that question is shown here.

The scatterplot matrix above plots the swim, bike, run, and overall times (in hours) for each finisher. Although not shown on the plot, the correlation between swim and run times is .588, which indicates that there is a moderately strong positive relationship between swim and run performance across individuals (though not as strong as the correlation between bike and run times). The plot shows that "good" runners can be mediocre swimmers, and vice versa.
However, if one is interested in the question "what are equivalent run and swim paces for those who both swim and run?" one way to examine the data is to ask "how does the median run pace compare to the median swim pace?" Similarly, you could ask "how does the 90th percentile run pace compare to the 90th percentile swim pace?", how does the 75th percentile run pace compare to the 75th percentile swim pace?" and so on, comparing each percentile to each percentile. This is what the plot below does. It shows a quantile-quantile comparison of run and swim paces, normalized to minutes per mile for running and minutes per 100 yards for swimming. The dotted red lines show the 2nd, 10th, 25th, median, 75th, 90th, and 98th percentile times for run and swim pace.

Note the linearity of the relationship between run and swim pacing. In fact, between about the 2nd percentile and the 98th percentile, the correlation coefficient between the two is above .99. The solid red line shows the regression of swim pace on run pace, and the equation for the regression line is given. As a reminder, this shows the quantile-quantile pacing for multisport athletes who are trying to complete an Ironman, so the pacing will be slower than for single-sport athletes in standalone events.
Comment: 1) Well, if you were interested in, say 10k pace, you could convert from min/10k to min/mile, then use the regression line to get the swim pace, then convert that to, say, pace per 100 meters. 2) This is for multisport athletes and covers a wider range of abilities, so you might think of it as the "equivalent running and swimming pace for someone who does both sports." Ryan was looking at comparing record times for single-sport athletes. And 3) you'll find a slightly different relationship if you had used 2010 data, or a shorter race. I was just showing how one might address the problem.
Comment: great, two questions 1) what is the metric formula? 2) how does the Ironman race compare to the results from Ryan?
Comment: This is the best conversion I have seen, but many triathletes are swimmers as an afterthought so comparing a dedicated swimmer with a dedicated runner might bring a different result.  Also, a 100m comparison, with water resistance at speed, won't compare closely to distance.
Comment: @PeterDeWeese Agreed, and even doing this for a sprint triathlon might give different results than for an Ironman. Note also that if we looked at the run-swim times rather than the quantiles, the correlation is .588, which indicates that swim time explains about 35% of the variance in run time. But this analysis still gives a way to think about how to answer a question like this.
Comment: @R.Chung  Great answer and approach! Did you do a weighted regression or a simple linear regression (SLR).  For run vs swim it looks like the homoscedastic assumption of an SLR was violated, this will give too much statistical weight to slower individuals.  The individuals who were espeically slow swimmers likely have too much leverage on the regression line.
Comment: @Rider_X I don't remember exactly but I suspect that I did OLS regression. As for heteroscedasticity, recall that OLS produces unbiased though inefficient estimates so the coefficients will be right on average but statistical inference may be off. In any event, I was just doing this to show how one might approach the problem -- you might want to also look at [this](http://bicycles.stackexchange.com/questions/9764/how-many-miles-of-riding-require-the-same-effort-as-one-mile-of-running/9876#9876) related answer.
Answer: If you start with the world records in a 1500m swim and 10km run you get these times for 100m and 1km
approx 26min 10km --> 2:36min/km
approx 14:30 1500m --> :58s/100m
:58 vs 2:36 World record level
1:04 vs 2:51* % increase in the swim time based on the European Masters Record 1500m 35-39.
1:10 vs 3:00* based on a recent swedish swimmer 35-39 time for the 1500m, and that I know several 40+ runners that run under 35.  Also a % increase.
**Masters ER 1500m men's 35-39 is 16:00 (1:04).  This weekend one of Swedens swimmers swam 1500m in 17:54 (1:11.6).  I think these two levels are possible.  Not everyone can swim at those speeds, so its not expected that everyone could run at that speed.  Maybe we can call this group the amatuerelite.  People who train and race for fun, but are not professional athletes.
1:33 vs 4:00 might be a big jump, but this is based on a year OW river race 3km, and a series of 10km races in Sweden. Roughly 7% of those who swim the river race manage a time under 46:30 in 2012. The 10km races had less than 2% under 40min.  But this difference could be explained that swimming in 16C water is not for everyone, and in the higher number of participants in a 10km might walk parts, effecting the faster times percentages poorly.
1:55 vs 5:00 (approx 28% of race finishers in the 3km river race "Vansbro" vs 20% 10km)
2:20 vs 6:00 (approx 63% Vansbro vs approx 60% 10km)
so sure one can say it's like comparing apples to oranges, but if you scale the results from enough swimming events and running events, I am sure you will find these values to be relative close.
Open water races in warmer water will produce a higher precentage of breaststrokers that float through the race, were as warm flat races will also attrack more and more "run/walkers".  so maybe one could start by removing the last 5-10% of the finishers time?!?
Comment: The formating of this post confuses me, I tried editing, but I failed.


Is there a way to sync iPhones without iTunes?

Question: I really dislike iTunes and would like to use something else to sync.  I spent some time looking a couple years ago (for my iPod) and couldn't find anything.
Does anyone know of anything?
Answer: I think you need this article :)
Answer: I use the iFunbox its really awesome, you can just copy stuff to the
iphone just like iTunes. its basicaly more for storage videos, system files, music
and not for installing apps I believe, but tis really awesome that you don't have to
have everything double on your comp and on the iphone!!! (like in itunes)


Do the Magic tournament rules allow Rock-Paper-Scissors to see who goes first?

Question: The Magic Tournament Rules specifically state 'For the first game of a match, the winner of a random method (such as a die roll or coin toss) chooses either to play first or play second'.  My method of choice has often been Rock-Paper-Scissors, but it never occurred to me until recently that this might not be considered a valid method under the rules.  Obviously this question is more hypothetical than not; if my opponent disagrees with my method of randomization then a different option, or a judge, would be called for.  But at least in theory, spectators or judges watching our match could complain, so the question holds: is RPS (likely to be) considered a 'random method' for determining play/draw under the tournament rules?
Answer: My understanding is that it's really up to the judge.
The tournament rules just say this:

For the first game of a match, the winner of a random method (such as
  a die roll or coin toss) chooses either to play first or to play
  second.

They don't really specify a more detailed criterion for "random." (For example,  cutting to a random card of each other's decks and then comparing their mana costs is a method players use some times. It's random, but it's not actually fair: the CMC of various cards in your deck skews the results.)
My first assumption was no rock-paper-scissors, since RPS is a game that permits some level of psychological skill. However, here's a quote from an old tournament report:

The both of them shuffled up and scanned about for a way to figure out
  who went first; turns out neither of them had dice. "That's the
  problem with being up here," deadpanned Jensen. "You play against a
  random? They always have a die."
It was suggested that perhaps the two of them play rock, paper,
  scissors to decide who would go first, but Jensen said that it wasn't
  random enough. "Rock, paper, scissors is strategy," he said earnestly.
  "I think I could psych someone out at rock, paper, scissors."
  Eventually, someone donated not only a twenty, but a twelve-sider and
  a ten-sider, and they rolled all three and added them up to see who
  went first. Jensen snagged it with a 22.

Note that it was the opponent who decided RPS was insufficient, not a judge. This implies that RPS might've been acceptable if both players were fine with it.
In practice, I would expect low-level events not to care about the exact quality of the method you use as long as it's mutually agreeable to both parties (which is all the comp rules really call for), unless they've had to set up a specific system due to previous issues with cheating.
Comment: If you cut to highest CMC of the same deck, I think it would be fair. But then you'd gain some knowledge of that person's deck. I think the odds of not having a coin or die available are fairly slim… :)
Comment: @ghoppe Cutting even like that isn't really fair either. If I cut to some card I only have one of, then I now know its position in my deck and that could affect my mulligan decision. Or, if we cut before we shuffle, the cut may not be truly random if I have my deck stacked. We could shuffle, then cut, then shuffle again, but that's a lot of work. A better method: Get a random card (could be from one of the decks, I suppose), and then ask your opponent if the Collector Number printed at the bottom of the card is odd or even. If they get it right, they can go first.
Comment: @Pwngulator An interesting idea, but are the collector numbers randomly distributed? That is, are there the same number of odd collector number common cards as even? What pool is the card being drawn from? Popular sideboard cards may have 60% odd collector numbers, for examle… I realize of course, this is pedantic to the extreme and the person choosing odd or even is unlikely to make such considerations.
Comment: @ghoppe Don't underestimate how far people will go for a small edge. A tournament regular was recently banned (in part) for drawing 8 cards in his initial hand when he was on the draw and then skipping his first-turn draw to conceal it. All this cheat affords you is one card of additional information for making mulligan decisions, yet he still felt it was worth the risk.
Comment: Oh, I definitely don't expect low-level events to _care_ about the method used - I was more curious about the theoretical implications here. :-)  Still, this earns the check mark...
Answer: A method isn't random if it is asymmetrical in any way or its outcome comes from a mixture of random and non-random factors.
Examples:

Cutting decks for highest mana cost is asymmetrical if you are not cutting from the same deck.
Cutting decks for highest mana cost is still inadvisable if you are cutting the same decks you are playing with, as it could be a breach of other rules.  It might be acceptable if you use an unrelated third deck, provided that it is in a randomized state and its cards are not marked.
Cutting for even/odd collector's number is not random, since the distribution of evens and odds may be known to one of the players, or the distribution may not be symmetrical.  Odd numbers also occur slightly more often than even numbers (sets with an odd number of cards contain 1 more odd card than even).  There is a somewhat fair way to approach it (i.e. use your own deck and ask the opponent to pick odd or even), but since you might have the opportunity to rig the deck to contain only odd or even collector numbers, this could become a psychological guessing game similar to rock-paper-scissors.  I.e. most novice RPS players lead off with rock, so you might have an asymmetrical skill advantage if you throw paper.  Most analytical even-odd number guessers should guess odd, since it occurs slightly more frequently than even, so you could rig a deck to have all even collector numbers and essentially guarantee that you win the option.
You roll a d12 and the opponent rolls a d10.  This is obviously asymmetrical, but it helps highlight less obvious examples that give either player a statistical edge by a similar amount.
Each player rolls a different d20.  Your d20 might be fair, but how do you know that your opponent's d20 isn't imbalanced?
Rolling a spindown d20.  It may be outside the realm of real human control, but you could attempt to roll it similar to spinning a top so that it settles on a high number in the 14-20 ballpark.
Playing any game of skill.  Playing a game of skill is not a random method.  For similar reasons, since RPS has some skill, it is not a random method.  RPS strategy integrates elements of psychologically reading your opponent to deduce which symbols they favor, using predefined strategies so that you aren't shooting reactively (and predictably), and sometimes reacting to predictable novice behavioral patterns.
Playing high number on a random number generator app could be adequate, provided that it isn't rigged.  You could neutralize the chance of rigging it by letting the opponent decide whether the first number is yours or theirs.  In theory, this choice could be very difficult to psychologically game, but possible.

The seriousness of randomness enforcement will be greater at higher REL events.  However, even at REL casual, most opponents would require you to abide by common sense randomness practices (i.e. no spindown dice, no cutting decks).
Comment: This is incorrect, random doesn't have to be fair and in truth random is rarely fair. For your dice examples even if two people roll the exact same die/dice how they perform the roll can have a massive impact on the results and reduce the randomness of the outcome.
Comment: Another way to think of it is we could use a random method to determine who starts 100 matches and I could win the right to start all (or most) of them which wouldn't be fair. Fair would be me starting 50 and you starting 50 but that wouldn't be random.


Is killing a bee haram?

Question: A huge bee came to my bathroom while I was brushing my teeth and was buzzing around, and in panic/due to my fear of such insects I killed it. Would this be considered haram in this scenario? I feel extremely guilty.
Answer:
إِنَّا للهِ وَإِنَّـا إِلَيْهِ رَاجِعونَ
Surely we belong to Allah and to Him shall we return
  - (Quran, 2:156)

The Bee is a important creation of Allah (سبحانه و تعالى) and even has it's own chapter in the Quran, Surat 16 An-Naĥl (The Bee), in which Allah (سبحانه و تعالى) mentions that honey has healing properties - (Quran, 16:69).
We know today that the Bee pollinates various plant life, and without it's work, an estimated 30% of North American consumed food would not have grown.
- (https://beespotter.org/topics/economics/)
Everything belongs to Allah (سبحانه و تعالى) so we should not kill things that He has given life without a shariah valid reason.

Guilt is a gift from Allah warning you that what you are doing is violating your soul-Nouman Ali Khan

But do not lose hope...

"Say: 'O My slaves who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allah, verily Allah forgives all sins. Truly, He is Oft-Forgiving, Most Merciful."- (Quran, 39: 53)

Is killing a bee haram?


Python libraries for bloomberg?

Question: I am very new with python, and I am used to work with bloomberg formulas for excel. I am starting to use a lot more python in my analysis, is there any library that performs same functions as bdp, bdh or bcurve?
Thanks!
Juan
Comment: You can't use BCurve or any other DLIB functions in python. Not even in Bloomberg BQNT environment. A good alternative would be to use QuantLib. You can build curves and value instruments just like DLIB.
Comment: Bcurve is actually part of the curves toolkit (CTK) which is not related to DLIB. That said, the above comment is still correct. CTK, the swaps toolkit (STK) and the derivatives toolkit (DTK), cannot be used with blpapi (only premium data offerings would allow you to do this).
Answer: I have experimented with various choices quite a bit.
My advice is to use vanilla blpapi . There are many good examples in the git repository. Some helpful installation notes are also here .
There are packages built on top, such as pdblp that, in my opinion, are very good but not required by most people.
Answer: blpapi as mentioned it worth learning for sure. In addition to it, if you are looking to work with Pandas I would suggest using TIA: https://github.com/bpsmith/tia
At the moment, TIA is only compatible with Python 2, but here https://github.com/bpsmith/tia/issues/11 has a Python 3 conversion. I've been using this recently and it's pretty good. An example:
from tia.bbg import LocalTerminal
import tia.bbg.datamgr as dm
import datetime

sid = 'IBM US EQUITY'
event = 'TRADE'
dt = pd.datetools.BDay(-1).apply(pd.datetime.now())
start = pd.datetime.combine(dt, datetime.time(13, 30))
end = pd.datetime.combine(dt, datetime.time(21, 30))
f = LocalTerminal.get_intraday_bar(sid, event, start, end,
interval=60).as_frame()
f.head(1)

      close     high    low   numEvents   open      time                value   volume
0   162.2500    162.70  161.51  4005    162.4900    2015-02-24 14:30:00  110345672  680888

The github link above has loads of examples, too.
Answer: I normally use pybbg which is also a wrapper for blpapi.
With a logged in Bloomberg session, just import it and start a connection
import pybbg as pybbg
bbg = pybbg.Pybbg()

Then you can use bdp, bdh, bds and bdih.
bdp
bbg.bdp('PGB 1.95 06/15/2029 Govt', ['MATURITY', 'COUPON', 'ISSUE_DT', 'YLD_YTM_MID'])

You can even query deals from SWPM...
pd.options.display.float_format = '{:,.2f}'.format
flds = ['SW_CURVE_DT', 'SW_MARKET_VAL', 'SW_CNV_BPV', 'VALUE_1_BP_CHANGE_IN_FIXED_CPN']
bbg.bdp('SLPA2EZJ Corp', flds)

...and provide overrides
flds = ['SW_CURVE_DT', 'SW_MARKET_VAL', 'SW_CNV_BPV', 'VALUE_1_BP_CHANGE_IN_FIXED_CPN']
overrides = {'SW_CURVE_DT': '20190507'}
bbg.bdp('SLPA2EZJ Corp', flds, overrides)

bdh
bbg.bdh('EUR Curncy', 'PX_LAST', '20200525')

bds
bbg.bds('YCSW0045 Index', 'CURVE_TENOR_RATES')

bdib
from datetime import  datetime
flds = ['close', 'high', 'low', 'open']
ticker = 'PGB 1.95 06/15/2029 Govt'
bbg.bdib(ticker, flds, datetime(2020,6,1,15,0), datetime(2020,6,1,15,30), eventType='ASK', interval = 5)

Answer: Ask your Bloomberg rep to enable you for BQNT access. They will push a Python instance to your machine and you can go to the terminal and run BQNT
You will get a Jupyter environment that can use Bloomberg data

Python libraries for bloomberg?


Model in Blender GLSL to XNA HLSL

Question: Is it possible to make model in Blender, with enabled GLSL, add multiple textures, etc, and then just load it in XNA, where's own HLSL? Will it work?
Answer: In a word, No.
But to get you started, you will need to use custom export scripts in Blender (I export to FBX format), and a custom content pipeline processor if you want to import the GLSL/materials/effects. This sounds like a lot of work; but at least now you know what you're googling for.

Model in Blender GLSL to XNA HLSL


-skipErrors in Transactional Replication not happening

Question: I have set up a transactional replication initialized using backup for a big database(1.6TB).Due to some error(space issue in the subscriber) the replication was not happening and there were replication error for the past 5 days.
So i added space and now i am getting the 20598 and 547 error in Distribution to Subscriber.
I changed the Agent profile and created a custom profile with the -skipError values as 20598:547.
I restarted the Distribution agent by stopping and starting the distribution job in the subscriber(PULL subscriber).
After restarting i see that, Distributor to Subscriber is initialized in replication monitor,but i don't see that the skipping is happening.
How can i solve this issue.?
I prefer not to drop Publisher/Subscriber as i am initializing using backup and it is a big database.
Comment: I have similar problem. -SkipError doesn't have any impact. Did you find a solution?
Answer: You don't see the "skipped # rows" in the message window?
Can you maybe post the window screenshot?
Like this blog here (it did what you did, skipped 20598:547), restarted agent
https://www.percyreyes.com/2016/07/the-skiperrors-parameter-for.html


Deleted by moderator for looking like an advertisement

Question: My post to this question was deleted 'because this resembles an advertisement'. I assure you this is not the case. Previous to some edits I would of understood it being done for the reasons of missing the point or off topic. Having already edited it to make it look less so, and an attempt to more closely answer the question, what recourse can I take to get a deleted-by-moderator post undeleted? Now that it is, comments are closed so there is no option for discussion (to reach the moderator) other than meta questions similar to this one that I've seen.
Answer: You should edit it so it doesn't look like an advertisement. Sorry if that sounds flippant but that's basically all you can do. The moderator would only have deleted it because it was flagged as spam by another user. In fact it was flagged by two users as spam - so that's at least three people who saw the post and thought it was spam.
Once you've edited it, flag it with the "other" option and we'll take another look and hopefully we'll be able to undelete it.
On the plus side I saw the original spam flag and declined it - but only after reading and re-reading it a few times, so I'm not surprised that other people also thought it was spam. It took me that long to realise that it wasn't an advert.
Comment: wow, maybe I should be doing advertizing.
Comment: @Mazura You can link to specific products. However, if most of the post is about said product, you'll likely get hit with a spam flag.  As your reputation within the system increases, so does the trust of other users. Once you gain a certain amount of trust, you're less likely to get the spam flags.  Though a lot of users put a little blurb at the end of their posts, specifically stating that they're not affiliated with a mentioned product.
Comment: @Mazura I nearly deleted the post as well. The only thing that saved it in my mind was that you've had other non-spam posts, and you had more than 1 rep.  Quoting from forums is bad form. If you need sources, use credible ones, not some other guy on the internet. Linking to specific products or services is also dangerous, and could easily end you up with spam flags.
Comment: @tester101, forums bad, noted, but I'd of stolen his quote without a cite. I figured at Home Improvement people would want to know what name brands to use. I sure would of liked it when I was nub. I hear you guys, thanks, onward and upwards.
Answer: Deleting the post was my acknowledgement that this post was very gray, with multiple community members thinking it was spam, but myself and others not believing you were a spammer. There's a -100 reputation hit if your post was actually verified as a spam message, so I tend to use the delete button as a middle ground when things are gray.
Things to do to avoid looking like spam, don't link to or mention specific products. Rather, try to focus on types of products. Links to other other forums also get a little more scrutiny because the spam could be posted in another forum. A post saying "No, don't use what you were thinking of using. Here's product X 5001 with a lifetime warranty, user testimonials, and if you act now there's a special 2 for 1 offer!" come across as a resurrected Billy Mays. As ChrisF suggests, edit the question to remove the links and product recommendation, and instead focus on the type of product you should use instead along with your own reasons for the recommendation, and then flag us to have a look.
Comment: The other answers better anyway. Thanks for the advice and getting back to me.


Are women's voices one octave higher than men's voices?

Question: I heard this somewhere and was wondering if it's true that women's voices are one octave higher than men's?
Comment: How could this be? There are basically two male voices - bass and tenor, and two female - alto and soprano.  Given that most voices can range a couple of octaves or more - some three or even four - where would we start?
Comment: @Tim: The number range 25-35 is 5 higher than the number range 20-30. Where you start doesn't really matter; the relationship between the two ranges is clear. Also the notion that there are two male and two female voices is not correct - see below.
Comment: Does this answer your question? [What are the typical ranges of voice types?](https://music.stackexchange.com/questions/65999/what-are-the-typical-ranges-of-voice-types)
Comment: Highly related: https://music.stackexchange.com/questions/65999/what-are-the-typical-ranges-of-voice-types
Comment: @LightnessRacesinOrbit - my beef is the vague question. So a soprano ( female) is one octave above a bass (male). Sorry, the question is vague.
Comment: @Tim: Well, the answerers don't seem to have had a problem with it ;)
Comment: Yes. Pretty much.
Answer: Yes, roughly. The standard ranges are often listed as:

Bass: E2-E4
Baritone: A2-A4
Tenor: C3-C5
Contralto: F3-F5
Mezzo-soprano: A3-A5
Soprano: C4-C6

You can see that the three women's ranges are one octave above the corresponding men's, with one slight exception.
Of course, everyone's voice is unique and few people fit cleanly into these categories. Trained men frequently have a little more than the two octaves listed, and women frequently have at least half an octave more. But in general, you can fairly safely categorize voices as high, middle, or low, and think of women as being one octave above men. A great deal of vocal music is written  gender-agnostic, assuming that men and women will simply pick the appropriate octave.
Comment: @OldBunny2800 Those are the classical/operatic ranges, and in that context, [contralto](https://en.wikipedia.org/wiki/Contralto) refers to a human voice type while [alto](https://en.wikipedia.org/wiki/Alto) refers to a particular musical line in SATB counterpoint.
Comment: @NotTelling: These aren't necessarily meant to be "the range of the typical bass", but rather "the range traditionally considered safe for bass parts", so effectively more like "the range that you can typically expect all basses to be capable of".
Comment: @foreyez It's not so complicated. The three lowest ones are men (bass, baritone, tenor) and the three highest ones are women (contralto, mezzo-soprano, soprano).
Comment: I think your ranges might be a bit wide. (can't imagine a bass singing an E4 or a baritone an A4, a tenor would have to be very talented to sing a C5 without falsetto.) Also, you have Contralto but not Alto.
Comment: @NotTelling Not sure if it's the source he's using, but these ranges are as listed (with sources) in [Wikipedia](https://en.wikipedia.org/wiki/Voice_type).
Comment: Typical basses go deeper than E2. What is your source?
Comment: it's hard to tell from this answer which above are the women's and which are the men's and which ones correspond to which
Comment: Some Contraltos are able to go down to that E3 so Obviously the Women's Voice is an Octave above the Men's Voice.
Answer: Well, if you compare the ranges of male and female voice types you will see that the female types are one octave higher than the male types. This means that the highest female voice is in general one octave higher than the highest male voice, and the same for the lowest. In classical music this might be a good generalization, because composers often try to explore the singer's range. So the soprano voice can be really one octave higher than the tenor voice, for example.
In popular music I don't believe it's true. You hardly see women singing above F5 or G5, while tenors, like Bruno Mars for example, easily reach A4 or C5. At the same time, you can find women (not only contraltos) singing around F3 and G3, but I can't think of any popular song these days where a male singer reaches one octave lower than this.
In terms of speech I don't believe it is true either. I don't have references for this, but try to talk one octave higher than you do and think of a woman who talks at this pitch (or do the opposite if you are a woman). I bet it will sound too high (or too low). It could only sound OK if you have a very low (or very high) voice, but these are extreme cases, not the average.
So, in terms of voice types it's indeed true, but I don't think that's the case most of the times.
Comment: http://beyondthefourthfloorblog.com/2015/08/23/makes-men-women-sound-different-part-one-pitch/ suggests that just under an octave is about right for speech too, though interestingly that this might be partly cultural.
Comment: Looking at the graph, I would say the average of male pitch is around 120Hz, and the female one is just below 200Hz, not so close to an octave. Looking at each separate culture, the relations seem to be much closer to an octave though. We can't conclude anything for sure, but I liked the reference.
Comment: You'd be hard put to find a culture anywhere in the world where women and men don't sing together in octaves, without undue straining for anyone.  It does seem to be a happy accident of physiology that puts our voices at least very roughly an octave (maybe a seventh) apart, so that we can celebrate the second harmonic together.
Comment: In popular music, even men you wouldn't think of as particularly deep voiced (Billy Joel, George Michael...) often sing down to E2 or C#2 where it is quite rare to find women hitting even A2 or G2 (Think Annie Lennox, Tracy Chapman, Alison Moyet...).
Comment: @J... I still haven't had time to look this up, but as MattPutnam answered, E2 is the lowest theoretical range. I bet Billy Joel and George Michael don't reach C#2, only bass singers. Maybe you are thinking of Do#2, witch is C#3, no?
Comment: @coconochao E2 is common.  Plenty of Basso Profundo can reach lower - Russian bass singers will go as low as A1, some even lower than that (Vladimir Miller, for example).  Keep in mind that pop singers won't voice a note with the power, clarity, or projection that an operatic singer will - singing E2 to an operatic standard is difficult but simply sounding the note, like a pop singer would, is perfectly within range of plenty of untrained people.
Answer: Yes, that's broadly true.  A soprano can squeeze out a top C, above the treble clef, a tenor can just about manage the C an octave lower.  Basses can approach C below the bass stave (Mahler asks for a Bb!), the deeper female voices have a similar lower limit an octave higher.
This all gets a bit complicated in popular music where some women don't use their head register at all, and men often use their falsetto rather than a full-bodied tenor sound.  So if you're publishing song copies for generic male and female voices, it might be sensible to print the female version a 5th or 6th higher than the male.
This is all very general rule-of-thumb stuff though. Choose the right key for the individual singer, not their gender.
Answer: A males C3 is equivalent to a females A3 and that is close to the difference between the two voices. I would say children(boys and girls) are closer to an octave higher than male voices as they talk around a C4 while men talk at C3. Women talk around A3 in general.
Answer: The answer is definitely yes.  Not because of the relative ranges.  It's simply an innate characteristic and very easily demonstrated.
Play C3 and ask a male to sing it.  Then ask a female to audio match his pitch.
Her response will be middle C, C4.  Q.E.D.!
Comment: You're presenting a false dichotomy that men's and women's voices are either in unison or octaves apart. While it does illustrate that, men and women do indeed have different comfortable vocal ranges (contrary to your answer), what note they choose is based on octave equivalence -- of course she wouldn't sing any interval other than an octave, so it doesn't really demonstrate anything about the specific range of the intervals. Also, wouldn't their ranges be an innate characteristic?


Examples of famous problems resolved easily

Question: Have there been examples of seemingly long standing hard problems, answered quite easily possibly with tools existing at the time the problems were made? More modern examples would be nice. An example could be Hilbert's basis theorem. Another could be Dwork's p-adic technique for rationality of zeta functions from algebraic varieties.
Comment: Dear JAS, I'm not sure what you mean by "resolved easily".  As an example,  Dwork's proof is a masterpiece of brilliant argument (in my view), combining a bunch of unlikely ideas, including compact operator techniques in a $p$-adic context, and Borel's criterion for a power series to be a rational function.  If you mean "without constructing an enormous new machine", then this applies to many, indeed most, problems, I would say.  Regards,
Comment: Just a hunch, but the first place I'd check for modern examples would be [Erdos](http://en.wikipedia.org/wiki/Paul_Erd%C5%91s).
Comment: @DavidH He is famous but have you got any examples of his work?
Comment: Are you looking for "easy" proof, or "elementary" proof? For example, would Erdos-Selberg's elementary proof of prime number theorem count?
Comment: @Sanchez Yes that would count.
Comment: @MattE Yes the 'easily' is not clearcut. However it seems that there is a difference between 'new' ideas and 'new' tools. A 'new' idea could mean a new 'philosophical' path for the problem that is important enough in itself to show more/different scenic spots in its route and a 'new' tool could mean may be a new spaceship to travel the existing path which will only show the scenic spots that one knows that exist. A 'new' idea can utilize existing 'tools' that exists for the older path by modification. In this view, the 'new' idea could be elementary simply because others overlooked.
Comment: @JAS: Dear JAS, So I'm still unsure how you apply your analysis to Dwork's result.   It uses new ideas and new tools (again, in my view), with perhaps the ideas being newer than the tools.  Is is just that the argument is not super-difficult that makes it an example of what you have in mind?  Regards,
Comment: One reference where an elementary proof is provided is here where in the last page of the lecture the word 'elementary' is used http://www.math.lsa.umich.edu/~mmustata/lecture9.pdf
Answer: I'm sure there are loads. One that comes to mind is the Seven Bridges of Konisberg problem.
http://en.wikipedia.org/wiki/Seven_Bridges_of_K%C3%B6nigsberg

Basically, the problem asked: is there a path which you can walk such that you cross every bridge once and only once. (you can't do things like walk halfway onto a bridge and walk back).
It was kinda known, well... conjectured, that there was no solution to this problem. Basically because no one found a solution to this problem and no one could prove why or why not.
Until Euler of course. As usual, it is always Euler who saves the day. He showed that there was no answer to this problem, as in, it was impossible to construct a path such that you cross every bridge  just once.
The justification ended up being really simple: First, you have to put the problem in terms of the areas in town as opposed to the bridges. From the illustration, you can see that you can split the town into 4; the top, the bottom, the right and the center. Also, you have to realize that in order not to reuse a bridge, every region in town must have an even number of bridges (an entry bridge and an exit bridge). If you don't have an even number of bridges, you get stuck in one of the regions (As in, if there's just 1 bridge, you use that bridge and then get stuck. If there are 3 bridges, you go in through one, go out from the second, and then get stuck upon using the third). So, if you look closely, the regions have all odd numbers of bridges connecting them. (3 connecting to the top region, 5 connecting to the center, 3 connecting to the right and 3 connecting to the bottom)
Therefore, from this you get the idea of eulerian cycles and from there loads of properties of graphs and then graph theory was born. And if it were not for graph theory we'd be lost when it comes to the telephone network and the internet. So, yeah, long-standing problem with a simple solution and with even more long-standing benefits.
Acknowledgment: About the problem, another possibility would be if you had only 2 regions with an odd number of bridges connecting them, and all the rest must have an even number of bridges. The logic behind this would be that one of those two regions would be your "starting" point and the other would be you "ending" point or finish line. In this case, you would get an Eulerian path instead of a cycle
Comment: How famous was the Koenigsberg bridges problem before Euler solved it? Is there any reason to believe that any mathematician had considered it?
Comment: On the topic of Euler, I've always been fond of his approach to solving the [Basel Problem].
Comment: Yup, who would've thought that the answer would have $\pi$ in it? That man was a genius
Comment: Interestingly, it seems to be the same if you are paddling a boat too :) Is it the same problem that way?
Comment: A typo that goes through the post: Euler did not show that "there is no answer to the question", he proved that the answer was "No".
Comment: @DavidH Euler learned of this problem through the mayor of Danzig, Carl Ehler, who thought it had some connection to Liebniz's then-unrealized "calculus of position," which we now interpret as topology.  Euler replied that he did not think the question was a mathematical one.   It's likely that Euler was the first mathematician to consider the problem, if only because other mathematicians may have overlooked the mathematical content of the Bridges problem.
Comment: OMG! That's so true. I never realized it. Yeah. Instead of regions of town, you consider intersections of water sections and instead of bridges you consider sections of water. Since there are intersections with odd number of connections it doesn't work.
Comment: Please edit your answer to incorporate your first comment, since in its current form the answer isn't quite correct.
Comment: @bof I'm pretty sure Euler was one of the first mathematicians to consider the problem. Bear in mind it that it wasn't even considered a mathematical problem, even. That is, until Euler stumbled upon a way to prove it with math. The nature of the problem before Euler was probably more that of an amusing question the good people of Koenigsberg could debate at the pub.
Answer: I don't know how old or how famous Tarski's Unique Square Root Problem was when the young László Lovász solved it. Certainly Tarski was very famous, and I'm sure he thought the problem was quite hard. Lovász's solution, while brilliant, was surely much shorter and simpler than Tarski or anyone had expected.
Tarski's Problem. If two finite structures (groups, rings, lattices, graphs, whatever) have isomorphic squares, must they be isomorphic? (The square of a structure $A$ is the direct product $A\times A$.)
Lovász solved Tarski's problem in the affirmative with a clever counting argument, which I will try to reproduce since I'm having trouble finding a good reference. I assume that all structures are finite structures of a fixed type, e.g., finite groups. Let $A,B$ be two structures such that $A\times A\cong B\times B$.
For any structures $X$ and $Y$, let $h(X,Y)$ be the number of homomorphisms, and $i(X,Y)$ the number of injective homomorphisms, from $X$ to $Y$.
Claim 1. For any structure $X$, we have $h(X,A)=h(X,B)$.
Proof. $h(X,A)^2=h(X,A^2)=h(X,B^2)=h(X,B)^2$, so $h(X,A)=h(X,B)$.
Claim 2. For any structure $X$, we have $i(X,A)=i(X,B)$.
Waving of Hands. We can use the inclusion-inclusion principle to express $i(X,A)$ in terms of values of $h(Y,A)$ where $Y$ ranges over quotients of $X$. (I think I could write a correct proof of this, but it would take some laborious typing. Anyway, it's obvious, isn't it?) Since $h(Y,A)=h(Y,B)$ by Claim 1, it follows that $i(X,A)=i(X,B)$.
Now we have $i(A,B)=i(B,B)\ge1$ and $i(B,A)=i(A,A)\ge1$, i.e., we have injective homomorphisms from $A$ to $B$ and from $B$ to $A$. Since the structures are finite, it follows from this that they are isomorphic.
I learned this argument by word of mouth, attributed to Lovász, several decades ago. This paper (which I haven't read) seems to be the source: L. Lovász, Operations with structures, Acta Math. Acad. Sci. Hungar. 18 (1967) 321-328; see Theorem 4.1 on p. 327, which appears to be a generalized version of the Unique Square Root Theorem.
Comment: @J.A. The paper http://www.cs.elte.hu/~lovasz/scans/LocFinCategories.pdf from the list seems to be the right one.
Comment: Do you have a reference for this?
Comment: This is the list. http://www.cs.elte.hu/~lovasz/publications.html I am unable to locate the paper in your mind. Could you point me from the list?
Comment: I do not know. However looking at it, I am thinking why has not such generality been used in Graph Theory? After all graphs are finite structures and hence any result here should carry over to graphs.... right?
Comment: Do you know what an infinite vector of type $\omega$ mean in 3.6? Could you explain where should I look for an introduction to the paper?
Comment: This looks like an application of Yoneda's lemma to reduce the problem to the category of sets.
Comment: Not really since the Yoneda Lemma assumes the existence of a natural map. Here we only have "random" equalities of cardinalities.
Answer: I like the establishment of the independence of Euclid's 5th postulate from the others for winner in this category. It's arguably the first long-standing problem of pure mathematics, and maybe the oldest example we have of a mathematical community posing a problem to itself and investigating it collaboratively. Perhaps some leniency is required here as to how accessible the "methods" by which it was eventually resolved really would have been to the Greeks, but in the spirit of positive historico-imaginationism I'm going to say they could have done it. I have no doubt Archimedes could have accomplished much of the necessary editing and improvements in rigor to Euclid's Elements, had been of a mindset and motivation to do so. The harder ingredient is a brilliant mathematician with enough childish instinct to go the distance and say "I don't care if Euclid's axioms are self-evident truths of your world. This is MY world where dragons are real, my sword is magic, and parallel lines can intersect each other." Who knows. Had the Fates granted Plato a star-student interested in mathematics (instead of the metaphysician he got in Aristotle)....
Comment: Ehhhhh, Euclid was the gold standard of mathematical rigor (no, scratch that, of all intellectual rigor in any field) for centuries, so I doubt that Archimedes or any other Greek-era mathematicians were at all likely to even realize that such editing/improvements were necessary. Rigor as we currently understand it is such a recently-developed concept that even Euler's original works look almost laughably imprecise by our standards. That said, *maaaaaaybe* the Greeks could have realized that Euclid's first four postulates apply equally well to poles and great circles on spherical surfaces...
Comment: @KyleStrand Absolutely, Euclid was the gold standard of rigor, which is why it received so much attention. Virtually every ancient copy we have of *Elements* originally belonged to various later mathematicians for their personal study, as we can tell from annotations and commentaries recorded in the margins. It's a myth that Euclid laid a rigorously golden egg and that was that for 2000 years.
Answer: Steiner-Lehmus theorem is a good one: Any triangle that has two equal angle bisectors (each measured from a vertex to the opposite side) is isosceles.
To quote from "Geometry Revisited", by Coxeter and Greitzer: This theorem was sent to the great Swiss geometer Jacob Steiner in 1840 by C.L. Lehmus (whose name would otherwise have been forgotten long ago) with a request for a pure geometrical proof. Steiner gave a fairly complicated proof which inspired many other people to look for simpler methods. Papers on the Steiner-Lehmus theorem appeared in various journals in 1842, 1844, 1848, almost every year from 1854 till 1864, and with a good deal of regularity during the next hundred years.
It turns out to be a straightforward proof when converted to the contrapositive form, devised by two English engineers, Gilbert and Macdonnell, in 1963, showing that (see first diagram below) if in $\Delta ABC,\ B \neq C,$ then $BM \neq CN.$ The proof is given in Geometry Revisited, this is just an outline, but it rests on an easy lemma that if a triangle has two different angles, the smaller angle has the longer internal bisector.
![steiner-lehmus.ggb][1]
One direct proof involves solving a complicated algebraic equation based on the formula for the length of a triangle's angular bisector. See below.
$$\text{The equation BM}=\text{CN implies}\\ca\left[1-\left(\frac b{c+a}\right)^2\right]=ab\left[1-\left(\frac c{a+b}\right)^2\right]$$
To summarize, the theorem had a simple proof available using methods of the time (19th century), but was seen as difficult all the way up to well into the 20th century!
Comment: @par It's [GeoGebra](http://www.geogebra.org).
Comment: What application are you using? It looks great.
Comment: @par Yes - GeoGebra. Free, easy to use, great annotation capability.
Comment: @GregHill Why did you capture the entire screen rather than the illustration only?
Comment: @Adobe You're right, I should clip it (my only excuse is laziness I guess).
Comment: I have clipped it
Answer: From least likely to fit your criteria to most, in my opinion:
Halting problem
Special Cases of Fermats last theorem (n = 3, n = 4...)
These problems weren't around for very long, but their solutions are fairly easy to understand after you've seen them.
Polynomial time primality
This problem has been around forever, but the solution is only "relatively" easy; as in, it's simple for those who study number theory algorithms.  It's not introductory material though.  It is fairly modern though.
Sum of inverse squares
$\sum_{k = 0}^{\infty} {\frac 1 {k^2}} = \text{???}$
Definitely a winner here.  It had been known for a long time that the sum converged to something finite, but no one had any clue what.  The solution evaded the best mathematicians for generations until Euler came down from heaven and told us.
Edit:  From "A History of PI" by Petr Beckmann
$\begin{align} \sin(x) &= x - \frac {x^3} {3!} + \frac {x^5} {5!} - \frac {x^7} {7!} \cdots \\
&= x \cdot (1 - \frac {x^2} {3!} + \frac {x^4} {5!} - \frac {x^6} {7!} \cdots)\end{align}$
Let $y^2 = x$, consider $\sin(x) = 0$ for $x \ne 0$:
$0 = 1 - \frac y {3!} + \frac {y^2} {5!} - \frac {y^3} {7!} \cdots \tag{P}$
We know roots of $\sin(x)$ are $0, \pm \pi, \pm 2 \pi, \cdots$, so the roots of $(P)$ are $(\pi)^2, (2 \pi)^2, (3 \pi)^2 \cdots$.
By theory of equations, the sum of the inverse of the roots of $(P)$ is the negative of the linear coefficient.  So
$$\frac 1 {\pi^2} + \frac 1 {(2 \pi)^2} + \frac 1 {(3 \pi)^2} + \cdots = \frac 1 {3!}$$
$$\frac 1 {1^2} + \frac 1 {2^2} + \frac 1 {3^2} + \cdots = \frac {\pi ^2} 6$$

There is a property of finite polynomials, that if:
$$ 0 = a_0 + a_1x + a_2x^2 + \cdots a_nx^n = a_n(x - r_0)(x - r_1)(x - r_2)\cdots(x - r_n)$$
then
$$\frac {a_1} {a_0} = \frac 1 {r_0} +  \frac 1 {r_1} +  \frac 1 {r_2} + \cdots \frac 1 {r_n}$$
It is a major skip in reasoning to assume that this is true for infinite polynomials, but I think this is what the author was getting at.
Comment: I can't say I know what the "theory of equations is", and this argument is far from easy when all the details are added.  You completely skipped the assertion that `\sin x` is an infinite product of quadratic terms $(x^2 - \pi^2/n^2)$ (and *not* of the separate linear factors) and therefore haven't had to deal at all with the convergence issues of this product, let alone the issue of to *what* it converges.  The argument may be easy but the proof is not so simple.
Comment: Dear Daniel, Is it really the case that Euler's argument resolved the sum of inverse squares "easily"?  What is your standard for something being easy?  Factoring $sin z$ as an infinite degree polynomial (which is my understanding of how he argued, at least at first) seems like a fairly insightful step to me.  I guess I'm just unsure what the parameters of the question (and your answer) are.  Cheers,
Comment: I added how I first saw the result.  I think it's a lot easier than whats on wikipedia.  It does require knowledge of theory of equations though, so I guess it depends on your point of view.  That's why it's a soft question I guess.
Comment: @Matt I took "easily" in the question to mean something like, "the solution can be explained to someone with a high-school proficiency in math in a few minutes," which inverse-sum-of-squares fits *(compare this to, say, Fermat's Last Problem)*.  It doesn't necessarily mean the solution was easy to find.
Comment: @DanielV: Dear Daniel, Thanks for the explanation.  Regards,
Comment: I think Ryan Reich is right, there are serious questions of convergence with the argument given.  Not to mention, applying known properties of finite polynomials to infinite polynomials is a jump in reasoning, it's not a good rigorous argument by modern standards.  However, I think the argument is historically interesting and I think it's more "incomplete" than "wrong".  I haven't studied this enough so I'm not sure.
Answer: Zhang's recent result on the boundedness of prime gaps uses surprisingly simple ideas that were available for a long time before.
Comment: Although this is true, there are lots of clever ideas in the paper and one cannot call this proof easy, whatever the definition of "easy" you take.
Comment: @Proba Oh, of course, you are perfectly right. I was mostly giving an example to the "with tools existing at the time the problems were made" part.
Answer: The Sylvester-Gallai theorem was posed by Sylvester in 1893 and first proved by Melchior in 1941 (who was apparently even unaware of Sylvester's problem).  Several more proofs followed and all (including Melchior's) are fairly elementary.
Answer: $\zeta(3)$
I do not know how long it took for Apéry to prove that $\zeta(3)$ is irrational. However, as Alf van der Poorten recounted in his Mathematical Intelligencer article,

Anyhow, I considered 'A Proof that Euler Missed' a racy title. It arose after
  Cohen's report at Helsinki, with someone (specifically, an old friend I was sitting next to) sourly commenting 'A victory for the French peasant . . . '. To this Nick Katz retorted: 'No __ ! No! This is marvellous! It is something Euler could have done.'

Peaucellier's Linkage
A charming example of an elegant solution to an engineering problem is Peaucellier's Linkage to convert circular motion to linear motion, using circular inversion. James Watt had created a linkage to convert circular motion to nearly linear motion, but it wasn't perfect.  Peaucellier, a French army officer found a method that was perfect.  Körner, in his book Fourier Analysis,  recounts that Sylvester showed Lord Kelvin a model of it, and:

[H]e 'nursed it as if it had been his own child, and when a motion was made to relieve him of it, replied "No! I have not had nearly enough of it—it is the most beautiful thing I have ever seen in my life"'.
Answer: The primality of Fermat numbers. That conjecture was a great fail albeit the numbers were pretty big to calculate by hand.
Answer: Van der Waerden's conjecture on the permanent of a doubly stochastic matrix, proved independently by Falikmann & Egorychev. It turned out to be an easy consequence of an inequality which had been known for a long time.
Answer: The Dinitz conjecture maybe doesn't belong here because it wasn't all that famous, but it was an open problem for over ten years and the proof was really, really trivial.
Answer: Finite field Kakeya "conjecture"
Let $\mathbb{F}_q$ be the finite field with $q$ elements and $A\subset \mathbb{F}_q^n$ be a set which contains a line in every possible direction.  Then there exists constant $c>0$ (depending only on $n$) such that
$$|A|\geq cq^n.$$
Dvir's proof of this is extremely elementary and easy, but nevertheless ingenious.  The whole paper is 6 pages long, but one could easily fit the whole argument in less than a page. See here.
Answer: Modern example:
Polynomial time constructive proof for Lovasz Local Lemma (LLL) was proved by Moser and Tardos in 2010.
Problem's History: Lovasz along with Erdos introduced LLL in their 1975 seminal paper "Problems and results on 3-chromatic hypergraphs and some related questions". This paper only gave existential results. In 1991, Beck gave a an algorithmic approach of LLL but the algorithmic results where a constant away from LLL's existential results.
In 2010, Moser and Tardos proposed an algorithm whose results was equal to LLL's existential results.
Comment: The approach taken by Moser and Tardos is the simplest approach one can think. Thats the reason I thought this could qualify as one of the answers.
Comment: Even the tools here remain addition and multiplication, at a slightly higher level the tools are new. So this wont qualify.
Answer: A good example is the proof of the Corona theorem by Thomas Wolff in 1979 as a graduate student at Berkeley. It states that the algebra $H^{\infty}(\mathbb{D})$ has no Corona iff if $f_1,...,f_N\in H^{\infty}(\mathbb{D})$ and if $\max_{1\leq j\leq N}|f_j(z)|\geq \delta >0~\forall z\in\mathbb{D}$ then $\exists g_1,...,g_N\in H^{\infty}(\mathbb{D})$ such that
\begin{equation*}
1=\sum^{N}_{j=1}f_j(z)g_j(z).
\end{equation*}
This problem had remained open and despite links with BMO, it remained open. Then Wolff provided a proof that is remarkably simple. He summarised his result in a lemma that is based on bounded solutions of the equation $\overline{\partial}u=f$, and followed Hörmander's suggestion that one should solve the equations in a nonanalytic way and then make them analytic.
For more reading, see the references:
Bounded Analytic Functions by John Garnett
Geometric Function Theory: Explorations in Complex Analysis by Steven Krantz
Another one by I like is the algebraic Kakeya conjecture again by Thomas Wolff. In an attempt to solve the full Kakeya conjecture, Wolff suggested an algebraic variant (I think the hope was that it could be used to further the full conjecture). It states that for a finite field $\mathbb{F}$ with $E\subset \mathbb{F}^n$ containing a line in every direction, then $E$ has cardinality at least $c_n|\mathbb{F}|^n,~c_n>0$. Zeev Dvir (a computer scientist at Princeton) gave a remarkably simple proof of it.


Does reducing Lightroom export file size reduce image quality?

Question: Sometimes I reduced the file sizes of my jpeg images for faster uploading to the web.
Does this reduce the image quality?
Answer: Aside from what @Itai said: Take a look at this blog post, where the author dives into jpg quality analysis, determining empirically that there are actually 13 quality output levels spread out across the 0-100 Lightroom scale. While this was done on an earlier version of Lightroom, I'm fairly sure it still applies to LR4.
Answer: Yes it does. When JPEG compresses, it removes details by slightly altering pixels so that the image can be represented with fewer bytes.
One has to be careful how much compression to apply on a JPEG because each step down lowers image quality as well as size. JPEG quality is measured typically on a 0-100 scale (Photoshop has a 1 to 12 scale IIRC) where higher numbers represent higher quality.
When choosing to reduce image quality for the sake of size or bandwidth, you have to compromise somewhere. Going from 100 to 98 for example reduces file size but has an almost insignificant impact on image quality, so it going to 95. For web use, I typically go down to 85 which shows some obvious artifacts but still produces a recognizable image with a moderate amount of details.
Answer: For JPEG, the format you asked about, yes, reducing file size does reduce quality, as JPEG compression is always* lossy.
(*The JPEG standard actually does support lossless compression, but this is rarely implemented and is not well supported.  Your tools are almost certainly using only lossy JPEG compression.)
For other formats, though, the answer may differ.  TIFF, for example, supports lossless compression, and in this case, exporting from Lightroom to a losslessly compressed TIFF reduces file size, but does not reduce image quality.
Support for newer file formats is slowly emerging.  Unlike JPEG, JPEG-XR's maximum quality setting is lossless, so should such support appear in LR (it is already present in Photoshop), a smaller export size, in that case, would also not reduce image quality.
The answer boils down to whether the method being used to reduce the file's size is lossy  (in which case, your answer is 'yes, image quality is being lost') or lossless ('no, no image quality is being lost').


Axis and Allies 1940, why are the axis always losing

Question: I've been playing A&A 1940 Europe (without Japan) and everytime the Axis Powers losses. I've tried Sealion and stuff but its still everytime the same. At the beginning Germany is beating up france and some small parts of Russia but them the americans lands in europe and Germany cant hold it. What can i try to win with the Axis power?
Answer: One strategy to deal with one side always losing is to have an auction to decide who gets which side: each person bids a certain amount of IPC. Whoever gives the highest bid takes the Allies, and the other person gets to place units equal to that bid at the start.
Comment: This also has the beauty of being self-adjusting amongst any (relatively) small group of regular players, as new strategies for each side are developed.


How to Handle checkboxes in Selenium with Python?

Question: There are 7  unselected check-boxes available in application. How to select first and last checkboxes and how to select all checkboxes from reverse order using python selenium webdriver?
Comment: What did you tried so far? show us source and errors. See [help/on-topic]
Answer: I can give you the logic in java, you can try and convert it into python.
<code>//for clicking 1st checkbox
driver.findElement(By.xpath("XPATH_OF_FIRST_CHECKBOX")).click();
//for selecting 2nd checkbox
driver.findElement(By.xpath("XPATH_OF_LAST_CHECKBOX")).click();
</code>
You can also use other attributes like ID, class if they are available. You can use similar logic for selecting all the other checkboxes with whatever order you want to click them.
Answer: You can find multiple elements with driver.findElements (or whatever it is in python). Once you have the list with the checkbox elements in it, it's rather trivial to check (select) them anyway you want. Just make sure that the elements are in order.


What is the probability of getting 2 people out of 10 with the same birthday?

Question: If you have 10 people, what is the probability of 2 (or more) people having the same birthday?
Comment: Hint: How many days have a year?
Answer: HINT
Well, it's very easy to see the probability that no pair shares the same birthday.
Say there are 2 people. Then one has a birthday, and the probability that the other person doesn't have that birthday is $364/365$, representing every day of the year besides the first (assuming all days are equally likely and that there is no such thing as a leap year birthday). If there is a third person, then the probability that he doesn't share a birthday with the other two is...
Continuing to 10 people, you get that...
Answer: I think of it this way. You have to pick a number between 1 and 365 (365 days in a year). The number you pick corresponds to a day (birth day).
Based on the above consideration,this how we tackle your problem
1>What is the probability that none of them have the same birthday?
2>The opposite of what you get above is the probability of 2 people or more having the same birthday.
If you have to pick a number between 1-365 ten times, the chance that none of them are same is calculated as
number of ways to pick ten different numbers divided by
total number of ways to pick ten numbers
(desirable outcomes/ possible outcomes)
which is
(365x364x363x...x356)/(365 raised to 10) lets call this y
y gives you the probability of all of them having different birthdays. The opposite of y is, two or more people have the same birthday.
SO 1-y is your answer
I calculated this as 0.1169 aka 11.69%
Answer: I think this is worth reading: http://en.wikipedia.org/wiki/Birthday_problem


Where can I find some publicly available dataset for retail/grocery store companies?

Question: I am looking for some publicly available dataset for retail/grocery store companies which (preferably) includes data about there stores, number of employees and operations. I tried to look around but couldn't find any dataset related to retail/grocery store companies. Does anyone know about such datasets that I can view and download(free or paid-any option)?
Answer: The good folks at Code4Huntsville* shared a dataset containing useful info about retails and grocery stores in their city, including geolocation, which makes it really interesting. It is available here.

Code for Huntsville's twitter handle 404s (as of 2019-08-23), there is a facebook link (but I can't see it without an account, not sure if its active), and they also have an open data soft profile.
Comment: Thanks for the link but I am looking for a dataset which has information such as store size,number of employees and other operational details. The one you pointed has only location info. Also I am looking it for a retail store chain like walmart etc and not for separate individual stores like the one in the above dataset
Answer: The quarterly and annual reports from these kinds of companies are publicly available. Here is Walmart's 2018 (2019 fiscal year) filing.
In it, you can find store count, geographic location. Their information on employees is a little sparse because of things like turnover, but other employee programs might be mentioned in similar 10k or annual financial reports.
Answer: Kroger makes a lot of data available via their API:
https://developer.kroger.com/reference
This includes products, cart, customer identity, locations, chains, etc. for all stores associated with Kroger.
https://www.kroger.com/i/kroger-family-of-companies


Shelf made of 1x2 pine boards. Stable?

Question: This is just a basic project for fun and experience.
The shelf will measure about 48,24,12 (H,W,D).
Do you think this would hold an even load of 50 lbs per shelf with 5 shelves?
Comment: It is a plain lap joint, but not a half lap, which I assume is what you are thinking of. The horizontal members of the sides of the shelf lap the verticals, making it a lap joint. If they were half lap joints, it would be much stronger, but still lacking in my opinion.
Comment: I would be most concerned about racking with such small lap joints.
Comment: Seriously consider diagonal bracing to strengthen it against racking. Putting plywood or pegboard on the back and sides can serve that purpose and offer additional storage options.
Comment: Those are not lap joints, as I understand them.
Comment: Would this cover the "diagonal brace"?  [see image](http://imgur.com/XzyN8e3)
Comment: @jacob  google has failed me, sorry.
Answer: The weakest part of the design is how your substantial load is being carried to the uprights. There's not that much you can do for those joints as drawn...
I'd suggest you add actual 1x2 members beside your existing uprights that will carry the weight of the frame (perimeter) of each shelf. It's easy to build this way, and will look a little less spindly. (Comment back if you need a drawing.)
Comments above about cross-bracing to prevent racking should be taken seriously, unless you're attaching securely to a wall.
edit to add a terrible picture. (Hope you get the idea, though.)

The red parts (done all the way down, of course) will transfer load from the shelves to the floor.
One more edit:

glue and mechanically fasten (screw or nail) the additional uprights for strength.
if you start from the ground and work your way up, all you have to do is cut the additional uprights exactly the same length and the unit almost builds itself. (Exact length is easy on a chopsaw where you can gang cut everything; a bit harder with a handsaw.)
a cheap and cheerful crossbrace can be found at your local Ikea: http://www.ikea.com/us/en/catalog/products/87749600/ ("OBSERVATÖR
Cross-brace, galvanized", $5). This would keep the back of the unit from racking, and the sides would take care of themselves.
Comment: I'm not clear on where the additional 1x2 members would go.
Answer: Each shelf is capable of holding the load that you are intending with shearing or sagging. Where this design fails is in racking, both front to back and side to side.
Traditional shelves are built with solid sides and a back. This serves to hold books, or items onto the shelves, but this really is only a secondary function.
Primarily, the solid sides and back resist racking forces.
In you design, you have replaced the solid sides with a narrow stile at the front and back, and only the horizontal rails at each shelve. What this does is reduces your resistance to racking down to only the 2x2 area of your lap joints on the sides, and on the back it is even worse, being reduced to the butt joints of your shelves rails where they meet the verticals.
I would first recomend increasing the width of your vertical stiles to at least a 1x3 or 1x4. This will increase the area of your lap joints, thus increasing the resistance to racking front to back.
Next I would consider adding a full back. If you don't want a full back, then I would add a vertical 1x4 on the left and right side of the back, just like you have on the sides.
Last I would bring your shelf horizontals inside of the sides for a cleaner look.
Answer: The sagulator calculates a sag of 0.03 in over 24" for a 50 lb uniform load on a single 1x2 of (Ponderosa) pine laying on its face. So your 4-board shelf should be stable given that weight load. A 12" 1x2 on its side can support in excess of 1000 lb, so no worries about the shelf supports breaking, either.
Note that, although each shelf could hold the same amount of weight, unless the unit is secured to the wall, loading it down that way could lead to it tipping over. Even if you do load the higher shelves lighter than the lower shelves, I would still secure it to the wall, especially if there are small children around.
Comment: calculating sag for dead loads is a small part of what contributes to overall stability. It doesn't take into account the joinery or possibility of live loads.

Shelf made of 1x2 pine boards. Stable?


Could I ask a recommendation letter from a professor who left the university?

Question: One of my friends had a pretty good relationship with their undergraduate professor; however, the professor decided to retire and no longer teaches at that university. In a few months, my friend is deciding to apply to graduate school, and he is wondering if it would still be appropriate to ask his retired professor to write him a letter of recommendation?
Answer: If the faculty is retiring to emeritus status then they can still write on letterhead. Many emeritus still maintain an active research profile or use the time to write, but in any case they might be willing to write for you. Many enjoy keeping one foot in the teaching/advising world.
There's nothing to be lost by asking.
And from the perspective of people on admissions committees, a strong letter from an emeritus faculty who compares this student against their thirty or forty years of other students can be very persuasive.
Answer: I'm a retired math/cs professor and love getting reference requests from former students. I'll always tell the asker what kind of letter I would be able to write (depending on how good the student was and how much I remember). Then s/he can decide whether to include me.
I've no problem writing on university letterhead.
Comment: For what it's worth, I wrote a couple (maybe three) letters in the first few years after leaving academics in 2005, and I had no problem with it --- I was honored to do so, in fact. Of course, it helped that for these particular students it was easy to write reasonably strong letters.
Answer: Yes, I think asking them is ok, with a few caveats.
I think it's ok provided the professor has only recently retired (within the last year, say). Any longer ago than that leaves a chance that the professor has forgotten who your friend is and means that the quality of the letter may be diminished.
Another thing to consider is if the professor is still affiliated with a university or institution. When I was applying for PhDs, some universities required the reference letter to be submitted on official letter-headed university paper (or the electronic equivalent). This may not be possible if the professor is no longer affiliated with any institution.
As to whether or not it's actually appropriate to ask, your friend should consider how much the professor is enjoying their retirement and whether they would welcome a request for a reference and all the associated admin or not. This is something only your friend can judge, based on his previous relationship with the professor.
Comment: I don't see how recently the professor has retired has anything to do with their likeliness to forget, at least when separated from the context of how long ago the professor has taught the student. (That is, a professor who taught someone 5 years ago and retired last year isn't necessarily any more or less likely to remember them than a professor who taught someone 5 years ago and retired 4 years ago.)
Comment: @R.M. true, but in either case asking for a reference letter from someone who last taught you five years ago is probably not the best choice (unless you have no more recent options).


Vote locking on questions: why?

Question: I understand (without agreeing with) the vote-locking for answers.  But is tactical downvoting a problem for questions?  Or is that just a technical accident: all voting uses the same system, so vote locking goes for all votes, answers or questions?
Comment: The OP is asking why we can't change votes on questions without editing, since tactical voting can't happen on questions.
Comment: What are you even asking ?
Answer: Tactical down-voting has never been a problem with questions, as far as I know. The front page doesn't sort the questions by the vote, and the page at /questions by default doesn't do that either.

If the tactical down-voting would have the purpose of getting more up-votes for your own questions, it would not have any effect, as down-voting other questions doesn't hide them (except when the questions reach a specific negative score; in that case, they would not shown on the front page). If the purpose of the tactical down-voting is to get more up-votes for the answers given to the down-voted question, that is not necessary the effect the down-vote would get, but that could be said also about down-voting competing answers. If this would be a repeated pattern, then it would be a reason for blocking the votes on questions after X minutes, even if down-voters now don't get any penalization for down-voting a question.
The code that checks if you are allowed to change your vote for a question is probably the same that checks if you are allowed to change your vote for an answer. I don't think there is a reason to change the code for votes given to questions, also because tactical down-voting is not the only reason for blocking votes after 5 minutes, IMO.
Votes on questions and answers are blocked after 5 minutes they have been casted; that gives you enough time to change your mind, if you notice that you voted a question/answer that didn't deserve any vote. After that, you should have a good reason to change your vote. If the question/answer has been edited, and you don't think the question/answer is not good anymore, that would be a reason to decline the vote.
In which cases would you need to remove the vote given to a question after 5 minutes you casted the vote? For an answer, it could happen that a new more complete answer is given, and you want to remove the vote you gave to the other answer to make the new one more prominent. That would be not true for a question, as the pages listing questions don't sort them by their score, by default.
Comment: "only reason"... so, what is the reason for locking votes on questions, **specifically**?  "You should have"... is the system trying to nanny us, to "build character" (to quote Calvin's Dad)?  I just don't see an *acceptable* reason.
Comment: This doesn't answer the question at all.
Comment: @jae There isn't a difference between voting questions, and voting answers. I don't think it's a good idea to allow a vote change without the question/answer being edited. If somebody needs to change the vote after 2 hours, then maybe the vote was casted without to effectively consider if the question was worth being voted. You cannot vote two comments in raw in a 5 seconds time frame, and you cannot remove a vote you casted on a comment. The reason of that is not tactical down-voting; maybe the same reason applies to blocking a question vote after 5 minutes.
Comment: @endolith The question is _But is tactical downvoting a problem for questions?_ I answered that.

Vote locking on questions: why?


Religious wedding after civil wedding

Question: I am currently applying for a marriage visitor visa for UK and am wondering if we could have our religious wedding (Church Blessing with a certified Minister who has already accepted to give us the blessing) in England more than 6 months after our civil wedding. I would be entering the country as a tourist (Brazilian national)for the religious blessing+celebration with family and friends then, since the marriage visa would have expired by then (post our civil wedding). Is this illegal, which I am trying to understand in order to avoid any breach of immigration law?
Many thanks for your assistance,
Answer: A Marriage Visa is only required if you are getting married in a legal sense. If you are having a ceremony of blessing, which does not confer any legal status, then you do not need the visa. UK does not recognize a "service of blessing" as having any legal status, especially if you are already legally married in a civil ceremony. Hence you do not need a special visa for it.
To avoid confusion I would take extra care to always refer to the ceremony as something other than a wedding when dealing with UK immigration, or anyone they might be in contact with. This is especially true when arriving in the UK. Do not say you are here to be married, even if you privately consider the religious wedding to be the real one, and the legal wedding just a formality. I would also make sure you have a document with you that proves you are already legally married that you can show to immigration. Make sure when you apply for visa that you refer to each other as 'spouse'.
I am assuming that the civil ceremony has happened before the religious one, and that it is legally binding and recognized in UK law.
Comment: Thank you DJClayworth, this is very clear and something I suspected. I am being extra careful with our application and don't want to say things that could give room to doubt. My british fiance reckons we should include the paid invoice with the booking of the venue in the UK where we will have the ceremony at the end of the year after our civil wedding in June (also in UK) in my marriage visitor visa application to help prove ours is a legitimate relationship/marriage, but I am afraid like you said yourself that this will create confusion with the Immigration officials. What do you think?
Comment: This is just my opinion, but in your application for a marriage visa I would not muddy the waters by talking about plans to return to the UK after the wedding. From UK immigration's point of view the main point of a marriage visa is to be certain that you will leave the UK after the marriage. You don't want to give any hint that you might not do that.
Comment: Thank you, this is right. Better to concentrate on the relevant points for the purpose of this visa.
Answer: I'd like to post the outcome of my visa application on this thread in case it helps someone in the same circumstances - we received our Entry Clearance (Marriage Visitor Visa for 6 months - Brazilian citizen) 10 working days from my application date. I added plenty of evidence that our relationship is genuine, ie Engagement and Christmas cards, a letter from someone who's known us as a couple for a long time, my engagement ring invoice and certificate. Also letters/emails from the Registrar where we are planning to get married.
Make sure you make it clear on a cover letter to the Immigration officer that you are not planning to settle in the UK after you get married and that you have enough ties to your country of residence - work, studies etc to go back to (letters of employment from your employer and your spouse's etc).
Our Bank statements showed movement all year round and enough money to cover travel expenses stated in the application - be careful to not contradict yourself here, the bank statements must show you are able to fund your trip. We also added Savings account statements so worth adding if you have spare money somewhere other than your main income bank account.
The most important is to cover all relevant areas for them to make a decision and leave no room for doubt regarding your statements to the UK Border on your cover letter. Make a summary of the documents you are submitting on an Excel spreadsheet and cross-check against the document list they send you once you finalize your application. Show it to someone who can find gaps you might have missed, that helped as well.
Good Luck! We are on our way to giving notice of marriage very soon, wish anyone who's applying for this visa the same outcome, getting married is stressful in itself already :)

Religious wedding after civil wedding