Am I allowed to interrupt someone in the middle of Shmoneh Esreh if my question is related to davening?

Question: My friend and I are in the middle of davening Shmoneh Esreh. Rather than talk, I text him, "I don't remember if today is Rosh Hodesh. Do we say 'Ya'aleh V'yavo?'" Can I interrupt my friend for this purpose so I know what to do, and can he text me the response (interrupt his own davening)?
Comment: "Can I text him and can my friend text me back, or is texting considered like talking?" Why are those mutually exclusive?
Comment: Related: Second half of [this answer](http://judaism.stackexchange.com/a/35685).
Comment: You would be disturbing his shmonah esrai and stopping him from davening.
Comment: For those getting hung up ;-) on the phone, can I tap the shoulder of the person next to me, point at Yaale v'Yavo, and make a questioning expression?  That gets at the interrupting davening for the sake of davening, but avoids the cell phone component.
Answer: In general, most explanations deal with one interrupting ones own shmoneh esrai and explain that it is such a serious matter that one cannot interrupt unless it is a pikuach nefesh matter. For example Interrupting the Amidah for Important Matters dicusses when one is allowed to interrupt the Shmoneh esrai. In this case, you are interrupting not only your own shmoneh esrai but that of your friend.

In fact, the Mishna, Berachot 30b, states that one may not interrupt
  one's Amidah even if the king asks one about one's welfare or if a
  snake is climbing up one's leg.

This means that your friend would not be allowed to interrupt his shmoneh esrai in order to respond to you no matter what you were asking. Thus, since he is not allowed to respond, you would not be allowed to interrupt him.
The links that I show do deal with the situation in which you must interrupt your shmoneh esrai in order to be able to daven further. It seems to say that you are allowed to interrupt your shmoneh esrai in order to check the date so that the halachic question can be answered.
Rav Moshe Feinstein deals with the case in which a person notices his neighbor making a mistake and discusses when he can interrupt his own davening to point it out. He does not deal with the case of a person interrupting someone else to ask for help. One can attempt to claim that he would not allow that, but I do not have the Igros Moshe to be able to get the full details and see what he might say.
However, given the various types of interruptions that are dealt with in the various citations, it would appear (to me at least) that the preference is to first check yourself (such as by going to the calendar on the wall) and if that is not available, ask someone who may be interrupted (ssuch as having finishe shmoneh esraifor an answer.
From the way I read the various sources, it would appear that this means one should not interrupt someone else who is in the middle of Shmoneh Esrai. As I said above, the person that one would be interrupted would appear to not be allowed to respond.
There is a machlokes between the Rama and the Shulchan Aruch (see below) as to whether you would have to start from the beginning or not if it takes too much time to get the answer.
Interrupting the Amidah for Important Matters

Interrupting the Amidah for Purposes Relevant to Prayer
There are a number of scenarios that arise where it would be
  beneficial to interrupt one's Amidah for a matter relevant to the
  prayer service itself.  R. Avraham Danzig (1748-1820), Chayei Adam
  25:9, discusses a case of someone who realizes that he has a halachic
  question regarding a mistake he made in his recitation of the Amidah.
  He rules that one may certainly walk to another place in the middle of
  his Amidah in order to find the answer to his question in a book.  He
  suggests that one may also ask a rabbi a question in the middle of his
  Amidah.  Mishna Berurah 104:2, codifies the opinion of Chayei Adam.
R. Moshe Feinstein (1896-1985), Igrot Moshe, Orach Chaim 4:16,
  discusses the case of someone who hears his neighbor make a mistake in
  the Amidah.  He writes that if one is between berachot, one may tell
  the neighbor that he erred in his prayer, even if the mistake would
  not invalidate the Amidah.  However, one should not speak in the
  middle of an individual beracha.

Siman 104 . Concerning the prohibition against interrupting the Amidah [Silent Prayer]
When Is It Permissible to Interrupt the Amidah?

[10]. This is what is written in Tefillah Kehilchatah 12:86, in the
  name of Rav Elyashiv. He adds that even if there is a knock at the
  door which is distracting him so much that he cannot continue praying
  with kavanah, he is permitted to open the door and hint to the person
  that he cannot talk right now. As for the matter of perusing through a
  book to determine the halachah, Yalkut Yosef 104:5 writes that
  although there are poskim who forbid walking to look something up, he
  himself agrees that it is permissible, but that asking a rabbi is
  forbidden. Nevertheless, it seems that if this law will determine
  whether or not he fulfills his obligation, it is best that he ask, as
  the Mishnah Berurah states. If possible, it is best that he writes his
  question down on a piece of paper, instead of interrupting with words.
  If, in the meantime, enough time passed in which he could have recited
  the entire Amidah, according to the Shulchan Aruch 104:5, he must
  start it from the beginning. However, the Rama maintains that he only
  goes back to the beginning when the interruption is due to
  circumstances beyond his control.
If one arrives at Al HaNisim during Chanukah or Purim and he does not
  remember the words, he is permitted to walk to get a siddur in order
  to recite it, despite the fact that failing to recite it does not
  prevent him from fulfilling his obligation of reciting the Amidah. If
  possible, it is better that he hints to someone to bring him a siddur.
  It seems that it is forbidden to walk in order to verify a law that
  for certain does not prevent someone from fulfilling his obligation,
  since the study of the halachah distracts one's thoughts from his
  prayer, and that constitutes more of an interruption. Therefore, as
  long as it is clear that it is not a matter that prevents him from
  fulfilling his obligation, he may not look it up. So writes the Beit
  Baruch 25:22.
Comment: "In this case, you are interrupting not only your own shmoneh esrai but that of your friend." Why should that be any worse? "**If** your friend notices **on his own**... the implication of..." (emphasis original) Where do you see such an implication? You seem to be making this distinction up. If he can interrupt to help then he can interrupt to help.
Comment: @DoubleAA *R. Moshe Feinstein (1896-1985), Igrot Moshe, Orach Chaim 4:16, discusses the case of someone who hears his neighbor make a mistake in the Amidah* If a person notices his neighbor making a mistake, he can correct him. However, I would read it as the person not being able to interrupt his neighbor to ask a question.
Comment: Are you making Diyukim in R Josh Flug's summary?? Seems almost a waste of time reading this, let alone debating this. R Moshe discussed one case and there's no need to go making up what he would have said elsewhere without reading his responsum inside.
Comment: @DoubleAA I will try to rewrite it to be clear how I see it


How to destroy old credit card?

Question: What is the best (in terms of security) way to destroy old (but still working) credit card?
Comment: oh sure, I can take care of that. Send it to my address :) :)
Comment: great! What is your address and full name?
Comment: Propane torch. It will degauss the magentic strip, melt the card so the numbers are unreadable and destroy the chip/nfc components.
Comment: drop it in a blender
Comment: Cut it and/or Shred it.
Answer: Call the bank and cancel the card. It's the only way to prevent it from being used, since any merchant with whom you've previously used the card, or anyone who otherwise already has the card data (including simply a photograph of the card) could theoretically run it in a card-not-present transaction.
Once you cancel the card, the physical plastic card is relatively useless.
But if you want the most certain way to destroy a card, then the only way that is 100% effective and guaranteed to be absolutely irreversible is burning/melting it.
Comment: *(Late comment but was the first result on my google search)*: Cancelling the card may not be sufficient/possible. In my case my card expired and bank sent me a new card, but it's exactly the same number, just the expiration date and cryptogram differs. I can't cancel the new card but have to destroy the old one.
Answer: Best way? I'd say, melt it into a ball.  However, I generally just aggressively attack them with scissors and throw various parts in various trash containers.
Comment: @Thomas - Burning it would decrease security - of your house...
Comment: @martinstoeckli Well, aggressively attacking the card with scissors decreases security of your fingers :)
Comment: Why don't you just burn it? Put it in an ashtray with some flammable material, set it on fire and come back a few minutes later, there will be nothing left of the card. Plus, it's more exciting than cutting it with scissors... :p
Comment: @Thomas - Ah yes, it's a really hard decision then :-)
Comment: I also do this, cut it in infinite (yes, infinite) small pieces, and throw them in various trash.
Comment: RTFM of the CC!
Answer: It depends on how far your want to go, but my choice is:

Scrape a sharp pair of scissors across the magnetic strip on the back (thanks to the Mythbusters, it seems that running a regular magnet across the strip does not destroy the data).
For the smart chip, make multiple cuts straight thorough the centre of the chip.
Lastly, drop the remains into a cross cut shredder.
Comment: @PaulPodlipensky: Ask your favorite bank. They should accept cards and have some a card destruction policy. Likely a specialized shredder standing around somewhere.
Comment: Hmmm, my shredder can't process the card...
Comment: @PaulPodlipensky - Purchase a shredder that can.  If it can process a media disk then it should be able to process a credit card.
Answer: Nail the card to a small piece of 2X4 scrap wood that you can throw away later with the magnetic side up. Use a piece of sand paper on a block to sand down the magnetic strip and the signature box on the back of the card. Then use a drill to drill holes in each number on the card and through the microchip embedded in the card. Most of these things you will see from the back side, that's why I suggest nailing it with the magnetic strip facing up. However, some cards also have numbers inked on the front so you may have to first use sand paper on those spots on the front of the card first. Once you've destroyed the magnetic strip, the microchip, the numbers that are impressed into the card and any inked on identification information, you can throw the wood away nobody can get the info off of it after you've done all that. But anyway, I think the question was already answered, I just thought I'd put my 2 cents in too.
Answer: Shredder AND cancel it with the bank!

How to destroy old credit card?


Battlestar Galactica: what is the most critical resource?

Question: In the Battlestar Galactica basic game, what is the most critical resource between Fuel, Food, Morale and Population?
Does it change with the 6-player FFG optional rule where humans start with 8 Fuel, 7 Food, 9 Morale and 10 Population?
Comment: In our gaming group, we have a saying: " humans never lose on food." It's not quite literally true, but it's very rare.
Answer: As with most games, it depends. It would most likely shift some using the variant rule as well, but it isn't clear to me exactly which way. You lose the game if any resource hits 0, but depending upon different game states, different resources may be more important than others. For example, if you are already at 8 distance, you can probably safely allow Fuel to be reduced to 1 rather than Morale which comes up more often on the Crisis cards. If your President is a cylon on the other hand, they most likely won't be giving Inspirational Speeches to improve your morale (even worse, if your Admiral is a cylon too). Which characters are being played in the game, and which (if any) are cylons probably has the biggest effect on the importance of individual resources.
Here is an analysis that someone wrote up on BGG.  The major points are:

Fuel: You start with 8, and you need to travel 8. There are 21 destination cards, and most Destination cards allow you to move one, at the cost of one fuel. You need to save/gain fuel at some point. One third of the cards allow you to move 2, but only cost 1 fuel. Of the 70 Crisis cards, 10 can cost you fuel, but in half of those the Admiral is given a choice of losing other resources instead. If the Admiral isn't a cylon, it is unlikely you will run out of fuel.
Food: You start with 8. Food is a volatile resource. Food Shortage shows up 9 times in the crisis deck, and the President has the option of throwing away cards or losing food. On 6 other skill check cards, if you fail to pass you lose food, these vary in color. Food is one of the few resources where it is possible to lose two steps in a single turn. If the President isn't a cylon, it is unlikely you will run out of food.
Morale: You start with 10. Morale is very skill check dependent, and in 19 of the 70 cards it is possible to lose morale. Most checks are Green and Yellow. Most of the skill check are pretty easy to pass. In 9 of the cards, the Admiral has a choice of losing Morale or other resources. The president can give Inspirational Speeches to raise morale (4 of 17 Quorum cards). Horde Yellow and Green cards to avoid losing Morale, and pray your Admiral isn't a cylon.
Population You start with 12. Most civilian ships have 1 population. 12 Skill checks have the potential of losing population, but 4 of those give you a choice, leaving only 8 must pass skill checks. The checks are usually very hard to pass, and usually require tactics. If you defend your civilian ships, you can use the FTL early, and lose 5 skill checks, and still not lose due to 0 population. If you don't lose civilian ships to cylon attacks, you can jump early and avoid more Crisis cards.

You also might want to check out a rather detailed distribution of the cards in Battlestar Galactica.
Answer: It really varies based on how things turn out.
Fuel: this you know you will be using it as you travel. If you're low, you can always scout ahead to get the good destinations, but it's hard to regain and you have to burn fuel.
Food: with all of the food and water shortages in the deck, some games can drain this quickly. If you're getting these, it becomes quite vital. Galactica and civilians have some to lose also.
Morale: many cards have morale losses. It's easy to lose and is on cards with options of losing it. Keep in mind the president can make a speech to improve morale. Other than that, it's hard to regain.
Population: cards don't kill as many people. Some do, but be careful. If you draw lots of blue cards, or can't scramble pilots quickly, you could be in trouble. The civilian ships have a lot of population. Lose the double population ships, and you'll go down fast. Late fame, if you haven't had civilian ship loss, this can still be very high. It starts higher than the others, so it makes a great spot to dump losses.
Answer: It's different with each game.  That's why you can't just give the humans an advantage and arbitrarily picking one resource to start at one more.  You'd have to make it dynamic where the first one to go to 0 gets bumped back up, then whichever resource is at 0 at the end of any player's turn will result in human loss and game over.
Fuel -- mostly lost through Destination card.  The admiral has solid control over this, although other characters who draw purple can use Launch scout to make this more favorable or less.  Oh, the Destination cards (Tylium Refinery) that let you risk a raptor to get +2 Fuel is a lifesaver if you're low on Fuel, but at only 1 distance, you're subjecting yourself to more crisis cards, and can lose via Morale more easily now.  If you have a cylon admiral, you definitely need to brig him to strip him of that title.  Losses also include 1 civvy ship, 1 Galactica damage token, and few crisis cards, especially Admiral Chooses ones.
Food -- mostly lost through crisis cards, like President Chooses.  1 Gally damage token for food.  However, Food tends to be a dump resource.  A sort of gag is if you lost by Food, than that's a bit shameful.  However, I've played over 80 games, and we have lost to Food b/c we couldn't afford the other resources, and in the end, something had to give.
Morale -- Even though you start off with 10 Morale and only 8 Food, Morale losses are more common since the crisis deck disproportionately targets Morale.  1 civvy ship that results in loss of this.  While there are 4 Inspirational Speeches in the Qcard deck, the Quorum cards still need to be gone through, and a 6+ still needs to get rolled, so don't count on this!
Pop -- mostly through civvy ships, although some games, more of these are lost in using FTL Control at -3 or -1.  Some crisis cards also cause loss of this.
For all of them, Destination deck also contains a few scant losses and getting them back


How to repent from apostasy?

Question: What is the process of repentance? I know about the feeling of regret and the resolve to never repeat the sin again that form the basis of repentance but is there a prayer that has to be said by a muslim who has blashphemed or is it just enough to say astaghfirullah?
Answer: Quran says that only good deeds can compensate the evil deeds so try to compensate like that.
Comment: Salam and welcome to Islam SE. Although your statement is correct we expect answers here to be **well elaborated**, focused on answering the initial question and the claims **supported by evidences**. So please consider elaborating your answer!

How to repent from apostasy?


On modern fighter aircraft, why do most carry a rotary cannon when they tend to have little use against aircraft?

Question: I understand that in multirole or strike aircraft the cannon has a CAS use, but on a purely fighter aircraft, does the benefit of a fallback weapon outweigh the handicap of added weight?
Answer: I think this question is highly opinion-based and should be closed.
But here are my $0.02
Historically there were attempts to remove cannons but turns out too early: Missiles are not that good. The benefit of fallback weapon indeed outweight the weight.

MIG21 VS RF-4C
One instance of combat during Project Dark Gene was an engagement on
  November 28, 1973 between an RF-4C aircraft piloted by IIAF Major
  Shokouhnia and backseater USAF Colonel John Saunders and a Soviet
  MiG-21 flown by Captain Gennadii N. Eliseev. The Soviet pilot fired
  two Vympel K-13 missiles at the Iranian aircraft, failing to destroy
  it. He was ordered from ground control to press his attack at any
  cost, and with his cannon jammed after the first shot,[8] he continued
  by ramming into the Iranian aircraft and losing his life in the
  process. He struck the RF-4C's tail assembly with his wing and then
  flew into high ground. It was the first deliberate jet-to-jet ramming
  by a Soviet aircraft during an interception, a practice common in the
  propeller age of World War II. Eliseev was posthumously awarded as a
  Hero of the Soviet Union.[3][9] The crew of the RF-4C aircraft were
  captured by Soviet ground forces and released after 16 days.2[10]

US military reached the same conclusion around the same time as well, to add cannons to F-4 Phantom II.
Maybe now is the time to rethink this question again after 40+ years advancement of AA missiles. But if you ask the pilot, for the same weight, do they want fuel, gun+ammo, or nothing? A significant portion, if not the majority, would pick the gun I guess.
A lot of fighter pilots, or even astronauts, carry pistols. How useful is that?
Comment: It's not just the reliability of missiles that's a reason for guns, it's also their limited number. Once your precious 2-4 missiles (the normal warload of most aircraft) is exhausted, you're now useless except as a pair of eyes. The gun extends that to several more engagements. And do remember that it's normal practice to fire missiles in pairs to make avoiding the attack harder.
Comment: If you seriously think it should be closed, you're saying it shouldn't be answered, and you say because POB which tends for VLQ answers from low-rep users . So why did you answer it at all?
Comment: @Nij For fun, obviously.


What's the origin of the term "gold piece"?

Question: What is the literary or historical origin of the term "gold piece" to mean a gold coin? Was it used before D&D, or did D&D coin the term?
Comment: :| I think this particular question would be better off on English.StackExchange. They specialize in this kind of thing. Particularly since this question focuses on the term's origin, which is [way, way, way before it's involvement in D&D](http://books.google.com/ngrams/graph?content=gold+piece&year_start=1800&year_end=2000&corpus=5&smoothing=3).
Comment: Proving it clearly in use prior to D&D is pretty easily done - and beyond the scope of English.StackExchange. Since the term is now predominantly a gaming term, and there are some geeks here who do language, this feels more right, especially since this is not the first time I've seen the question on gamer sites.
Comment: Also, the question seems relevant to setting and worldbuilding, both of which are on-topic.
Answer: The term definitely predates D&D - the term "twenty dollar gold piece" has been in use for the $20 Double Eagle and $10 Eagle coins of the late 19th century, and also the $5 gold coin, as well.
"Gold Piece" In Print
The term is used in the Lebanon Daily News, 1 Nov 1965, of Lebanon, Pennsylvania, bottom, in an advert for old coins under the left column of text (to the right of the comics)

Four gold pieces: One (1) $20.00 gold piece, two (2) $10.00 gold pieces and one (1) $2.50 gold piece.

This alone establishes the phrase "gold piece" for gold coins in routine use prior to D&D. But let us press a little further back... say, 1913? Here's a quote from the 5 August 1913 Cedar Rapids Evening Gazette, from Cedar Rapids, Iowa, page 4, top of the third column:

The five cent piece ls the day laborer of our coinage. It la the hardest working and most successful bit at money In use In these United States. The twenty dollar gold piece Is very popular and is madly sought after In the best society; the five dollar bill has millions of friends and the hard silver dollar can be found nestling In the pocket of almost every man. But none of these like the five cent piece.

We thus have established a pattern of use for gold coins of being called "gold pieces" in the press, spanning over 5 decades; clearly not a D&D origin; not even viably a wargaming origin, for 1913 is the year of the first printing of H. G. Wells' Little Wars, the first commercially released set of wargaming rules in book form.
Searching Project Gutenberg, several ebooks have it in use...
These without clear denomination prefixed:

Pinocchio (1883, Tr. ??? ) Author: Carlo Collodi, 1826-1890Translator: Carol Della Chiesa, 1887-
The Younger Set (1907)Author: Robert W. Chambers
A Drama on the SeashoreAuthor: Honore de Balzac (1799-1850)Translator: Katharine Prescott Wormeley (1830-1908)
Tiger Cat (1938)Author: David H. Keller
Pâkia (1901)Author: Louis Becke

And several with clear denomination in dollars:

The Corner House Girls in a Play –
How they rehearsed, how they acted, and what the play brought inAuthors: Grace Brooks Hill, R. Emmett Owen
The Young Bank Messenger (1898)Author: Horatio Alger, Jr

Piece
Piece is, according to several dictionaries, a common term for coins in general, of whatever denomination is specified. The quote below is excerpted from the etymology online page:

piece
early 13c., "fixed amount, measure, portion," from O.Fr. piece (11c.), from V.L. *pettia, probably from Gaulish (cf. Welsh peth "thing," Breton pez "piece"), from O.Celt. base *pett-.
[...] Piece of Eight is the old name for the Spanish dollar (c.1600) of the value of 8 reals.

Commentary
It's pretty clear that it's a generic term for a gold coin, and for several US gold coins as well. In the US, it seems to be predominantly the popular $5 coin of the late 19th and early 20th centuries, but can be used collectively for the $2.50, $5.00, $10.00 and $20.00 gold coins; The silver coins of similar values were $0.10, $0.25, $0.50, and $1.00. Note that, still to date, "2 bits" is $0.25... a reference to the not uncommon practice of breaking Pieces of Eight (Dollares, or Reals) into 8 "bits" of an eighth-dollare each... I suspect that this is the origin of the 20:1 Silver:Gold ratio in AD&D...
Comment: @Yakk, from the Online Etymology Dictionary quoted on dictionary.com, the French word "piece" meant coin around the 12th century, and the term was used that way in English by 1570, and the Piece of Eight was made around the year 1600.

c.1200, "fixed amount, measure, portion," from Old French piece "piece, bit portion; item; coin" (12c.)
...
Piece as "a coin" is attested in English from 1570s, hence Piece of eight, old name for the Spanish dollar (c.1600) of the value of 8 reals.
Comment: @Yakk, here's an example from the 1300s: the Wycliffe Bible translation  mentions "thirty pieces of silver". https://www.biblestudytools.com/wyc/matthew/26-15.html. According to Wikipedia, the original Greek was didn't specify which silver coin was meant.
Comment: So the wargames will celebrate their 100 year anniversary, curious. Brilliant answer!
Comment: I see my last quote wasn't from the original Wycliffe Bible and used more modern language. But another part of the Wycliffe Bible has "sixe hundrid `floreyns, ether peesis of gold" https://en.wikisource.org/wiki/Bible_(Wycliffe)/2_Paralipomenon

I think the original Hebrew just says "600 gold" and Wycliffe decided to specifically refer to the piece of gold or  https://en.wikipedia.org/wiki/Florin.
Answer: Let's ask the Wiktionary.

Noun
A coin, especially one valued at less than the principal unit of currency.

It seems to be quite an old term:

Etymology
Middle English pece, from Anglo-Norman peece, peice et al. and Old French pece, piece et al., apparently from Late Latin *pettia, *pettium. Ultimate origin uncertain; perhaps from Transalpine Gaulish (compare Welsh peth, Breton pez ("thing"), Irish cuid ("part")).
Comment: That Etymology makes no claim that the ancestral forms meant "coins".
Answer: The most important historical precedent for parceling gold into "pieces" is Robert Louis Stevenson's Treasure Island (1881), an enormously popular work of fiction that was plundered and imitated by many authors in the following decades. While that work is more famous for the construction "pieces of eight," Treasure Island exemplifies usages like "pieces of gold" throughout to refer to pirate treasure. These precedents informed countless subsequent authors, especially authors of fantasy fiction, including Howard and Leiber. Conan, for example, knows of "men willing to sell their souls for a few gold pieces" in the 1930s. It is surely these usages that ended up informing the vocabulary of Dungeons & Dragons, as the authors of D&D cited these works specifically as influences.
Comment: Wait, are you claiming that Treasure Island invented "pieces of eight"?
Answer: I would say it is of historic origin.
Here in Sweden we had gold (and other valuable metal; copper was the most common) pieces that was simply weighed and that could be cut up if needed before we had coins.
At first it was simply a big hunk of metal later on it became "standard" sizes with stamps that guaranteed the weight and then after that came the coins (as we know them).


Luggage limit in trains in West Europe?

Question: Is there any strict luggage limit while travelling by train in West Europe? In Poland, for example, one can take as much luggage as one can carry, so 2 big suitcases and a rucksack and the backpack are allowed. Does the same rule apply for trains in Germany, France, Belgium etc.?
Answer: Limits as to the amount of luggage you can take is usually governed by two principles:

You must be able to carry your luggage by yourself.
Your luggage must not hinder other passengers or safe exits from the train.

Special rules exist for large luggage, such as bicycles. Those can normally only be taken if explicitly allowed. But simple suitcases and backpacks are only limited by the principles I listed above.
The rules in theory probably differ per country and even per train company, but in practice the above is true in all countries where I have travelled by train (Norway, Sweden, Denmark, Germany, Netherlands, Belgium, France, Spain, Switzerland, Italy, Austria). The only problematic situation I have encountered is when everybody in a small night-train compartment had a lot of luggage and people were forced to take luggage on their bed (but normally one can get away with simply storing luggage on the floor once everybody has gone to bed).
Comment: you can add Czech Republic to the above list. You can travel with quite a lot of luggage. Some trains have bike+luggage service that costs aroun 2 EUR and your luggage will be placed in a special wagon by the train attendent. Similar rules apply to Slovakia AFAIK as well.
Answer: in France, there is no limit either (the only rule is you should tag them all) on regular luggage according to the French company{fr}. It is really not enforced (I have never seen some train agent telling someone he had too much stuff). However, you might not be able to keep an eye on your luggage (luggage space is sometimes between the coaches) so you'd better not carry too valuable stuff. Bikes and animals can also be carried (for some fee).
For Germany, I didn't find a lot of information, I suppose it is quite the same (no actual limit and it is not enforced anyway) I know it's possible to travel with a bike for a fee too.
For Belgium, the limit is officially 3 pieces of luggage, and skis, kids' car :) ... are free to carry. But I have no idea whether it is strongly enforced.
Comment: Never seen anything about a luggage limit on German trains.
Comment: In Germany you are allowed to take as much luggage as you can carry by yourself but I've seen quite a lot of employees helping people with even more.
Answer: The tightest official restrictions in Western Europe are probably Eurostar, which does not officially permit luggage larger than 85cm in the longest dimension, except that skis and snowboards longer than that are permitted.
Larger suitcases are officially banned, as is having more than two, but Eurostar will usually allow items slightly over the limit.
Note that carrying a couple of suitcases on a local commuter train in the rush hour might be officially permitted, but will certainly be unpopular with other passengers.  If you're planning to cross London on the Underground or Paris on the Metro, try to avoid the commuter rush-hour with luggage.  For most other long-distance journeys, you should not have to do cross-city transfers.
Answer: In the Netherlands, rules state it should fit in the luggage racks or storage space between the seats. That's all that's stated, and is ambiguous as those aren't uniform in size between trains.
Just don't be an asshole and take so much you block seats and space to other passengers. One or two bags or suitcases is no problem, take several shipping trunks and you will likely get comments and be charged extra if there's a ticket check.

Luggage limit in trains in West Europe?


Willing to divorce my husband

Question: My husband married me in the year 2015 2nd feb and the next year he married another woman on 21stjan 2016 without my knowledge. We are medical students i am a bhms and he is mbbs and also my cousin. So we were not staying then as we were students. I found out now that he is living with the other girl and when i said to leave me he is not Willing to divorce me. Now what i should do please help.
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Answer: Due to the lack of information. In your case there are two possibilities as far as I understood -assuming that your marriage was legal and valid according Islam-:

Either you have made it a condition for marriage that your husband leaves you as his lonely wife (and it is written down on 'aqd an-Nikah or witnessed by the witnesses of your nikah): In this case he must abide to it

"The stipulations most entitled to be abided by are those with which you are given the right to enjoy the (women's) private parts (i.e. the stipulations of the marriage contract). (See for example in Sahih al-Bukhari and Sahih Muslim)

In case your husband nevertheless married another woman you have two options taking your 'aqd an-Nikah (or the witnesses which heard the conditions and your husbands agreement) to an islamic court and declare your marriage void as your husband didn't abide to one condition in your 'aqd an-Nikah. This is called faskh الفسخ. Or be patient and stay with this husband and forget about this condition. As Allah says:

...  But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not. (2:216)

or you didn't make it a condition to marry him and now got jealous. In this case you have two or three options: Being patient and try to get ride of the feeling of jealousy or asking your husband to divorce you if he accepted and gave you all your rights (mahr etc.) everything is fine else you'd have the option to buy yourself free. This is called khul'a الخلع and works as follows you seek a court and tell them or your husband that you can't stay with him any more as you can't stand the fact that he has another woman. In this case you may need to give some or all your mahr back and maybe even buy yourself free and you'd be divorced by court.

Note that a woman can't divorce her husband by talaq الطلاق as talaq is in the hand of the husband based on (first direct sources):
In my opinion the Qur'an addresses the men saying -I found this also as the interpretation of ibn al-'Arabi in tafssir al-Qurtobi-:

O Prophet, when you [Muslims] divorce women, divorce them for [the commencement of] their waiting period and keep count of the waiting period, and fear Allah , your Lord. ... (65:1)

There's a rather da'if hadith saying so:

"... Divorce belongs to the one who takes hold of the calf (i.e., her husband)."
  (Sunan ibn Majah -Al-Albani has qualified it as Hassan in irwaa' al-'Alyl (2041) إرواء العليل according to islamqa #26247-)

On the other hand there are many indirect ahadith prohibiting women to ask for divorce which I've already quoted in my answer on How do I ask my husband for khula, when the problem is with me? (for details on the sources refer to that post):

"Women who seek divorce and Khul' are like the female hypocrites." (See for example in Jami' at-Thirmidhi)

"Any woman who asks her husband for a divorce when it is not absolutely necessary, the fragrance of Paradise will be forbidden to her" (See for example in Jami' at-Thirmidhi)

For further information read also the following fatwas on islamqa #186325, #452 and #286920 (this only available in Arabic)
Comment: The hadith you quote in the end is graded Daif. Perhaps there is a stronger hadith that can show the same point?

Willing to divorce my husband


How does a pilot receive weather information when overflying the oceans?

Question: As the aircraft is too far from antennas and units, how do they be aware of weather changes or weather information along their route, or on the destination and alternate airports?
Comment: Aircraft might be out of contact with ATC but will remain tuned to the service they are working.  If there is a significant weather change that might affect safety, they will transmit a report on that frequency.  ATC will not hear it, but anybody else working the same frequency, i.e. in the same part of the world, might hear it.  This is very common for turbulence reports on oceanic crossings.
Comment: And before there were satellites & SATCOM, there was HF radio.  "Out of contact with ATC" -- not necessarily. Not usually, in fact.
Comment: For local weather, they get part of the information from on-board weather radar. For both local and destination weather, they can also get information through satellite links.
Comment: There are satellite based services as well, such as [XM Weather](http://www.xmwxweather.com/aviation/) that provide accurate weather reports.
Answer: It depends on what info you're after: During cruise I'm mainly interested in threats to the aircraft which normally manifest as echo on the weather radar (clear air turbulence being one famous exception) or by looking out of the window.

Do you want info on your destination and alternate airport you listen to a HF VOLMET station or ask ATC via HF (cumbersome and annoying due to often poor reception).
In our shiny new world we could also ask ATC via an CPDLC free text message. The controller simply uplinks you a message with the requested information.
Depending on your operator there might be a plethora of other information available via ACARS which - when equipped - can communicate via satellite. At my company we can get:

Updates on the winds aloft (important for fuel calculation)
Airport weather information (ATIS, METAR, TAF)
Sigmets

In general, the weather you really need is readily available. An ocean crossing is only a couple of hours. This timeframe is covered by the TAFs. So you shouldn't be too surprised when you don't have all that fancy stuff mentioned above and ask ATC once VHF COM is reestablished or you can receive a VHF VOLMET station.
Answer: Also other aircraft flying in the same area or route can give an update to the aircraft following


Why is the close queue so much more full than other queues?

Question: I realize that there have already been a number of similar questions about this, but it seems like most of the review queues (very low quality, triage, first post, etc.) are pretty short and are sometimes even empty (or close to empty). However, the Close queue has around 8,000 items in it or so. Does anyone have a definitive answer on why this is and if there are any immediate plans to address this?
Comment: @Undo If you consider the situation where most close votes age out because the queue is overfull "stable", then yeah... I guess it's stable... That doesn't mean we don't need to address it though.
Comment: *"any immediate plans to address this"* Why does it need to be addressed immediately? It's stable.
Comment: @Undo I'm not implying that it needs to be addressed immediately - it just seems like there have been a lot of proposals and I was just curious to see if any of them were going to be adapted.
Comment: I've personally found the Close Queue to be more "dangerous" to work in because of (what _I_ perceive to be) a much higher incidence of bad audits than in other queues.  I gave up looking at the close queue a long time ago and prefer to concentrate on Triage instead.
Comment: I didn't even realise there was a close queue :\ I knew I could close questions at 3k, but didn't realise there was a queue (despite it making obvious sense now)
Comment: It's even fuller because there are plenty of questions with 1-3 close votes not even shown or ageing away. Not enough motivated reviewers and too many bad questions I guess.
Answer: The close vote review queue is really big because users are inherently good at asking bad questions.
There are currently—and have been—many plans on how to deal with this, with varying levels of immediacy, popularity, and efficiency. There is even at least one chat room centered around reviewing in the close vote queue.
One example of a plan: Let's burn down the close queue!
Comment: @CodyGray the last time I checked there were plenty of users with privileges but for some reasons only a very small subset of those users really leverage their moderation privileges. Anything that helps to turn in-active > 3K-ers into active close voters will resolve the *issue*, if we assume it is an issue that needs solving.
Comment: @Cody That depends on whether you perceive the large number to a be a problem. The large number itself isn't the problem. The only problem is questions not getting closed in a timely manner if at all, which is caused by  a combination of many factors. There is no concrete evidence to say that any one factor has any more impact than any other factor, and I would say it is beyond the scope of this question to elaborate the intricacies of the close vote system
Comment: On the gripping hand: the average time to close on question is 7 minutes.
Comment: People keep asking bad questions, and other people keep flagging them and voting to close them, it's a vicious cycle. It had more than 10k, the other day, and I've seen it around 6k in recent history.
Comment: People being good at asking bad questions doesn't explain why the close-vote queue is larger than the other queues that address bad questions. Perhaps the difference is more that there are fewer users with privileges to deal with these, and it takes 5 of them.
Comment: The large number is a symptom of the exact thing we agree is a problem: "questions not getting closed in a timely manner if at all". I don't think that discussing the intricacies of the system is "beyond the scope of this question" at all. In fact, it is exactly what the question is asking!
Comment: Right, but the linked post is from 2014 and the review queue still has around 8,000 posts in it.
Comment: @Cody the number could just as easily be smaller if people *stopped* flagging and voting to close questions. The number is the size that it is because the system is working. Some things don't get closed in a timely manner if at all, and many other things do get closed in a timely manner. The system isn't perfect, but it does work. The question here asks for a definitive answer of why the number is big, and if there are any plans to do something about the size of the number. I believe my answer reasonably answers the question.
Answer: tl;dr:
Moar reviewers!
First, lets do some math. There are 40,769 users with close vote privileges, which have a potential capacity of doing reviews 1 630 760. This would allow to, assuming everything controversial (has 2 leave open and 4 close plus tie breaker), 232 965 potential questions to be dealt with. In other words, if everyone that reviews do so, all the current outstanding questions with pending reviews would have been decided (right now there are 8.8k), and we would have enough votes to deal with the 7.7k questions that are asked every day in average.
So, if there are enough users to make sure that the close queue is no more, why then the queue seems to never go down? Several potential explanations:

Reviewer weariness: reviewers get tired of the constant stream of sub par questions. It gets so bad, that some can't keep their hope for humanity. A sane approach would be to keep reviewers in rotation, to make sure they don't lose motivation.
Lack of knowledge: through the review queues have filters that allow you to review the topics you can do a sensible review about, this feature is (or I believe) underutilized. Actual numbers are waiting for some virgins blood. I suggested a way to fix this, pending of realization.
Number aversion: is not the same that you ask 100k individual to clean 100km of beaches, than to ask 100 individuals to clean 1km. There are some that has aversions to big numbers that seems to not go down, and a lack of positive feedback seems to demotivate people with time. I proposed a way to present this feedback back to reviewers, it seems to be something of sorts in the works.
The above leads to technical community moderation debt, which reinforces part of the cycle.
Overgamification: reviewers tend to stop reviewing once they acquire certain extrinsic motivators (aka badges).
Lack of desire that others moderate: there is a group of user that believes that any act of moderation is a waste of time, which by itself it's fine, but there has been cases where this group boycotts the other users moderating task, which contributes with the weariness of the users doing the actual moderation.

This is mostly a very biased interpretation of the current affairs. I think I haven't missed important variables at play, but if you feel I did, feel free to add it with the references.
Comment: @DanielStorm actually, that's the kind of solution we don't want. Instead of reviewing because you care about the quality of the questions on SO, you care about obtaining a reward.
Comment: Note that no one is obligated to use their close votes, and its OK to not want to. The fact of the matter is that there is always going to be a large portion of the user base that doesn't want to use their moderation privileges for various reasons. It doesn't have to be about thinking it is a waste of time.
Comment: Speaking for myself, I find working through the queue a pretty time consuming experience. For about 75% of the review items I need way more context so I have to go look at the question, its answers and its comments. On top of that I find being able to see other close review choices misleading as I'm not going to blindly follow them and have to reason if I agree with them or not. More often than not, I just don't have the time.
Comment: @Gimby you might find more reasonable to use the filters. For example: I filter by [debian] and off topic, which is easily to determine, since Debian is an OS, and people tend to ask general computing questions with that tag, so I can just rush through the queue. Try that. Find a tag you are familiar with and filter by the most easily identifiable problem, you will find the experience more rewarding.
Comment: In addition to all of this, the fact that you can review a max number per day means that on a day when you'd be willing to set aside some time to do it, you still have minimal impact.
Comment: @Mooz If you read the list of points, it perfectly describes why others queues doesn't suffer the same fate as the close queue. Basically, other than gamification, the other queues doesn't require of the reviewer with the same intensity as the close queue does.
Comment: This one is kinda obvious omission but since I don't have a good way to measure it, I presumed that everyone that is capable of reviewing is active and engaged with the site, but this isn't true.
Comment: Also, I'm assuming that questions enter the queue using flags and no close vote are done outside of the queue, but since you always are left with 10 extra close votes, such effect can be ignored.
Comment: @TinyGiant considering that since we only need ~3% of users to leverage their privileges, we could strike some sort of deal, don't you agree? It could be just 1 review every odd day.
Comment: @Braiam good advice, I will do that eventually when I'm good at the game, right now I'm a close-voter-in-training :)
Comment: I'm active-**ish**... but the review queues are not for me.
Comment: Incentivize users to clear the CV queue with SO swag. I know I'd definitely participate in the CV queue more if this was the case.
Comment: Excellent break-down of why the close queue is so high, but not for why it's so high *in comparison to the other queues*.
Answer: The number of open questions with at least one close vote is even higher than the displayed size of the close vote queue. The system prunes the queue and refills it automatically. So even if you could drain it, it would take some time before you'd see an effect.
However, it's probably not drained but rather filled so that many close-worthy questions stay open because the close voting process cannot be finished. The system discards some (many?) of the total casted close votes with time.
Being voluntary, the reviewers who can and want to vote probably cannot do all the reviewing work that needs to be done in order to process the large amount of closeable questions we get every day. Effectively some close-worthy questions remain open and some close votes have no effect.
We experimented with increasing the number of close votes. Quoting from the results:

We need to do something about the close votes... we'll start looking at increasing the number of close votes based on rep.

We gave gold badge owners an immediate right to close duplicates in their corresponding tag (the duplicate hammer).
We also proposed to improve question quality before they are asked by smart (rep thresholded) info/warning messages.
However, being a voluntary service, I see the fundamental issue that reviewing capacity might just not be sufficient.
Reviewing bad questions is less fun than answering good questions. This seems to be especially true for close vote reviewing.
Now if every asker would pay only a single dollar per question which is then paid out to the reviewers according to their reviewing time...
Comment: *"We gave gold badge owners an immediate closing right in their corresponding tag"* Only for duplicates. :'(
Comment: @CodyGray Thanks for pointing it out. I wasn't sure about that.
Comment: prune-and-refill reference is here: [Enough fuzzying: let's let everything into the close queue and age out questions that don't reach a threshold](http://meta.stackoverflow.com/q/252584/839601)


Is there a particular reason that EasyJet uses U2 as their code?

Question: Does anyone know why EasyJet uses U2 as the prefix for flight numbers? Other airlines have more logical prefixes. Eg. KL -> KLM, AZ -> Alitalia, BA-> British Airways, etc. Even though they do not always match the airline name exactly, they do mimic the name.
Answer: Easyjet got their IATA code fairly late on, and as such could not use EZ (which was in use by Sun Air), so they were randomly issued their IATA code of U2.
They do have the three letter code of EZY, just as British Airways has BAW as well as BA.
Comment: The three letter code is the ICAO designation, and airlines are free to use either their two letter code or three letter code for call signs.  British Airways uses "Speed Bird 123" as their call sign for most flights, and BA123 for the flight number.
Comment: I think you are wrong.  Can you give any example of the the IATA code being using in a call sign?
Comment: @Moo, the call sign is _written_ using the ICAO code on the flight plan, because flight plans are governed by ICAO. The spoken form uses a radiotelephony designator instead, which may not be related to either the code nor the airline name, as evidenced by BA's "Speedbird" and former PanAm's "Clipper". Note, that the call sign _usually_ is the flight number, but not always. You can have flight BA123 with call sign BAW55B, which would then be spoken as "speedbird five five bravo". Also don't forget that these days most flights have more then one flight number due to code-sharing.
Comment: The 2 letter IATA code is the airline code.  The flight callsign is the 3 letter code so Easyjet callsigns are "EZY321", pronounced "Easy 3-2-1".
Answer: EZY (EasyJet UK) code and EZS (EasyJet Switzerland)are the ICAO codes, whereas U2 is the code generated by IATA for them when they applied for an IATA code.
http://www.easyjet.com/ejcms/cache/medialibrary/files/travel%20agent%20online%20guides/en/amadeus
EasyJet Airline Company Limited (UK Based) - (IATA code: U2; ICAO code: EZY; Callsign: Easy)
EasyJet Switzerland SA (IATA code: DS; ICAO code: EZS; Callsign: TOPSWISS)
ICAO codes are used for operational purposes like flight planning, ATC, etc. IATA codes like U2 are generally used in timetables, reservation systems, departure/arrival information, etc. - in other words information that is meant for the general public.


Can a bitcoin transaction be reversed?

Question: If I sent bitcoins to someone, but then want to cancel this transaction after it was already made (like a chargeback on a credit card), is this possible with Bitcoin?
Comment: I think it's worth having these separated out, because users will search for them with different phrases.  That question is about typos in addresses, whereas this question is about reversability of transactions.  They're both well worth answering, but I don't think they need to be in the same question.  Let's take it up on meta and see what people think.
Comment: There is the answer at http://bitcoin.stackexchange.com/questions/157/what-are-the-perceived-advantages-that-bitcoin-has-over-other-currencies-or-other.
Comment: Related/dup - http://bitcoin.stackexchange.com/questions/194/i-think-i-made-a-typo-what-do-i-do-now

Instead of creating a new question, let's edit that one to clarify/generify it if necessary.
Comment: meta topic at http://meta.bitcoin.stackexchange.com/questions/11/should-these-two-questions-be-combined
Answer: No, a bitcoin transaction which has already been included in a block on the longest chain cannot be reversed.  This is by design as Bitcoin is intended to behave much like cash, with recipients being assured that the money is now permanently in their possession after a transaction has been included in a block.
Answer: Bitcoin transactions cannot be reversed. However, there are escrow services that make sure that transactions are safe for both parties. For example, if you want to buy an item from someone, using an escrow service, you would first send the Bitcoins to the escrow service. The seller then knows their money is secured and sends you the item. Once you've received it, you give your "ok" to the escrow service and the seller receives the money. If there's trouble with the item (or you never receive it), the issue can be settled through the escrow service.
Aside from that, fraudulent transactions can also be settled through legal means (that might be more difficult, though).
One service (that's currently not available, unfortunately) is ClearCoin: https://clearcoin.appspot.com/
If you search for Bitcoin Escrow, you will find a couple of solutions (I'm not posting them here because I can't recommend any; maybe "What are reliable Bitcoin Escrow services?" would be a good question ;-) ).
Comment: Should we add a note here about reorgs?  Maybe "Bitcoin transactions that have been confirmed in the blockchain cannot be reversed".  Something about 1 hour, 6 blocks, etc.
Comment: It is indeed a good question, and it has been asked here: http://bitcoin.stackexchange.com/questions/241/which-bitcoin-escrow-services-are-available-and-reliable
Answer: Bitcoin transactions are not reversible. This is by design.
Whether it is a feature or a flaw depends on your point of view.
Many merchants consider it a feature as it eliminates counterparty risk.
However, some people, notably Wikileaks, have called for a cryptocurrency with time limited reversibility.
Comment: You might have posted this simultaneously, but in general try and avoid [adding an answer that says pretty much the same thing](http://meta.bitcoin.stackexchange.com/questions/58/how-do-we-improve-question-and-answer-quality).
Answer: It is not possible to reverse a transaction that has already been transmitted on the bitcoin network.  However if you can keep a transaction from being transmitted then you can close the client restore the wallet file from a backup.  When the client is restored with the -rescan flag the transaction will no longer be pending.
Answer: The only way to "reverse" the transaction is to immediately double-spend from the same set of UXTOs to a different address that you control (within a few seconds after your original transmission) and pray that the doublespend reaches enough nodes and wins.
But if your tx is already confirmed in a block, then no way.
Comment: You have on average, about five minutes to figure out you made a mistake and submit a double-spend (which should have a higher tip than the original transaction, to give the miner incentive to include it an not the original)
Answer: There is a new cryptocurrency on the block (Reversecoin), that offers functionality to reverse ones transactions. Say a hacker gets your coins, you can cancel the transactions and get your coins another safe address of yours. Reversecoin does this in a completely distributed fashion, with out needing for any kind of central or third party. Check out our website Reversecoin for more details.
Disclosure: I am the lead dev for Reversecoin.
Comment: While creating the Reverse account (the account for which transactions can be reversed), user can choose the timeout, master key (used for reverting the transactions). When a hacker initiates transactions from Reverse accounts, the transactions stay in the blockchain in a pending state for the timeout period, instead of getting confirmed. User can reverse the transactions, using the master key. If user does not do anything, the transactions get confirmed, after the timeout period.
Comment: Hi Obulpathi! This looks like an interesting basis for a cryptocurrency. `For a configurable period of time, your transactions can be reversed` Could you elaborate on this? Who configures the amount of time that reversing a transaction takes?
Answer: To be honest all has been already said about this topic and all the competent previous posters are right in that Bitcoin is by design not reversible.
But to have all the facts at hand, one needs to mention also the event of March 2013 where Bitcoin underwent a 24 block reorganisation. Before people start screaming this was a network issue/program issue and no one did intentionally try to reverse a transaction - I know, it is just so no one can say afterwords, no one told me that was possible, even if it is a remote possibility.
I think people need to know that it is in fact possible, but very very unlikely. As I do not want to scare people away (and hopefully comply with other opinions on this matter and prevent any outrage) the probability is low and there is no incentive from miners to try something.

Can a bitcoin transaction be reversed?


Fixing a not working Power Functions L motor

Question: Four of my PF L motors don't work. How could I make them work again? I didn't find any information about L motors, only M and XL.
Comment: Welcome to Bricks.SE.  Are they making any noise at all?  Have you tried replacing batteries?
Comment: @chicks They dont make any noise or movement ay all... and im pretty sure its not the battery box fault, as 1 L motor that works works fine on it, and stuff like IR reciever and pole switch also works fine on same battery box.
Answer: Since the basic architecture of the motors in a line (in this case PF M-L-XL) are the same, the tips you have found for the other models would most likely apply for your case as well.
Otherwise I'd recommend some basic troubleshooting steps:

Ensure you have a working battery box and cable by setting up your functioning motor. Once you have confirmed that it runs OK, you can be sure that if after swapping the motor for a broken one, the problem must be in that motor.
Check if you can turn the motor's axle manually by inserting a Technic axle and turning it by hand. It may be more comfortable if you add a gear or a wheel to get a better grip. If you can't turn it at all or only considerably harder than the working one, you should suspect some mechanical failure (e.g. broken gears inside).
If you have a multimeter, you could check if the electrical characteristics of the broken motors match those of the working one. A significantly lower resistance between the contacts is a sign of a short circuit, while a significantly higher one indicates a broken wire. With a bit of jerry-rigging you could also measure the current flowing through a motor that should be running from a battery box and comparing it to a normal motor's to see if there is too little or too much current.
You could also try opening up the motor and checking for broken or burned parts, foreign objects or debris, etc. Note, the above guide is for the M motor, but the same principles would apply for the L motor as well.

If none of the above helps, try contacting LEGO, as they would be able to provide replacement parts or further advice.
Comment: i did mention in reply that the battery box, i tried other stuff such as working ir reciever, other type pf motors like m motor, pole switch thing, they all work perfectly fine on same battery box, but broken ones don't, it is possible to turn broken ones by placing axle in it then turn. i dont know what a multimeter is. i dont know what jerry rigging is either, also one of the broken ones, when i pull a little bit on the plug end it starts working but when i release it stops agian.
Comment: A [multimeter](https://en.wikipedia.org/wiki/Multimeter) is a device for measuring (among others) electrical resistance and current. The term ["jerry rigging"](https://www.merriam-webster.com/dictionary/jerry-rigged) refers to something constructed quickly and without regard for aesthetics or future maintainability. Here I meant "Just use some wires and clips to hold everything in place to build a circuit to measure the current across the poles of the motor". If that still sounds alien to you, I'd recommend consulting an electronics tutorial or skipping this test altogether.
Comment: Based on the observations with pulling the plug end, it looks like as if it were an issue with the electrical contacts. In this case, either measuring the resistance in both relaxed and pulled states or disassembling would be helpful to diagnose the actual problem.
Comment: I didn't notice your link to the "opening up" video before.  This was one of the videos I came across in my search and looks to contain everything one would need to fix the wire problem.  Nice find :)
Comment: i did contact customer support, if im correct they said they did send a order new motors request for me and free of charge too. But i still want to have these motors working too..
Comment: That's great news! So if all works well, you'll be having brand new working motors, as well as repairing your old ones. Make sure to update us on your progress or ask if you have tried something and got stuck! Meanwhile, take the [tour](https://bricks.stackexchange.com/tour) and visit the [help center](https://bricks.stackexchange.com/help) to learn more about Bricks.SE :)
Comment: Ok. repairing them i dont really know how, lego didnt ask for me to send the broken ones back.
Comment: Just try some of the steps described either here or in the other sites you have found for the M and XL motors.
Answer: Based on the information given in the question and comments, it sounds like an all too typical pinch-point wire failure.  On large electronics this is fairly easy to fix, but smaller things like PF motors are tedious and require some experience and skill.  Because of the design, the wire will be constantly bending against the motor case, or connector plug, in the exact same place over and over again.  Because the wire insulation is more flexible then the metal wire, it will stay intact while the wire inside of it has broken.  When you wiggle or push the wire to get it working again, you are smashing the broken wires back together again inside the insulation.  You might be able to determine whether this breakage is on the motor side or plug side of the wire by isolating one end while pushing/bending the other end, while plugged into battery box.
Since you have new ones coming, and they're already broken, this is a great learning opportunity if you really want to attempt a fix.  You are going to need a soldering gun/iron and some solder at the very least.
The basic wiring setup for all the PF motors is very similar.  Here are two examples of PF motors with the pinch-point area circled:

Because this is more or a raw electronics question (vs. Lego) and requires a lengthy description, I have placed a link to YouTube listing several videos on how to do this.  Any of these videos should help you because all of the insides and disassembling techniques are very similar to your L-motor.
https://www.youtube.com/results?search_query=Fixing+Lego+PF+motors
Here are some pictures of the tools recommended by Zovits and myself:
Comment: +1, that wire connection does really seem like a weak point and based on the comments, it is probably the culprit in at least that one motor.
Comment: @zovits - I hope he can figure it out.  Since they're already broken I figure, "What has he got to lose?".  Thank you for the +1, I will be returning the gesture as it's well deserved for all of the information and assistance you provided in your answer.


File Backup keep latest only

Question: I am looking some software for backup to an external HDD that will essentially mirror my computers documents in their current state, i.e. if I delete or modify a file that modification is applied to the backup and the previous version is removed. It needs to do this live and automatically. Any suggestions?
Answer: I've been really happy with Allway Sync.  It can do a unidirectional or bidirectional sync.  It can be initiated on a timer, on an event (like plugging in the external drive), or simply always-on.  It can keep records of your old files, or you can turn off that option.
It's free for personal use.  Very nice program.
Comment: You should be aware that in the free version of Allway Sync, there is a file operation limit of 40,000 files in any 30 day period
Answer: As per my answer here   ...
You don't mention that it must be free. I would highly recommend paying US $19.99 for a personal version of Bvckup 2. I did, and I have never regretted it.
I did a lot of research before choosing it, and what convinced me was partly that it supports VSS, so that it can synch files which are in use, and, especially, the speed, it wins every test because it uses delta copying:

Reduce the amount of data being moved around by copying modified parts
  of files only. This speeds things up, in many cases dramatically.

.
There is a 5 start review of it at PC World.
If you don't want to spend, or just want to try it out, the last beta, which is quite recent, is available here.
If you still don't like Bvckup2, then I can highly recommend FreeFileSynch, which I previously used. See my long answers to this SR question, and this one and this one too.
To save you the trouble of clicking those links, here is the feature list:

<code>Key Features

Detect moved and renamed files and folders
Copy locked files (Volume Shadow Copy Service)
Detect conflicts and propagate deletions
Binary file comparison
Configure handling of Symbolic Links
Automate sync as a batch job
Process multiple folder pairs
Comprehensive and detailed error reporting
Copy NTFS extended attributes (compressed, encrypted, sparse)
Copy NTFS security permissions
Support long file paths with more than 260 characters
Fail-safe file copy
Cross-platform: Windows, Linux, Mac OS X
Expand environment variables like %USERPROFILE%
Access variable drive letters by volume name (USB sticks)
Native 64-bit support
Keep versions of deleted/updated files
Prevent disc space bottlenecks via optimal sync sequence
Full Unicode support
Highly optimized runtime performance
Include/exclude files via filter
FreeFileSync portable and local installation available
Handle daylight saving time changes on FAT/FAT32
Use macros %time%, %date%, et al. for recurring backups
Case-sensitive synchronization
Built-in locking: serialize multiple jobs running against the same network share

Supported Operating Systems

Microsoft Windows Microsoft Windows FreeFileSync runs natively on all 32 and 64-bit Windows versions:

Windows 10
Windows 8.1
Windows 8
Windows 7
Windows Vista
Windows XP
Windows 2000
</code>
Answer: You might want to try autover, which is described by the author as,

real time backup and personal versioning system.

It let's you configure exactly this behavior, but if your requirements should change at some time, you'll be able to adapt quickly and easily.

File Backup keep latest only


If the EPU (Emergency Power Unit) on a modern fighter jet fails, will the aircraft drop out of the sky?

Question: If the EPU (Emergency Power Unit) and batteries plus engines fail on a modern fighter aircraft, basically they will fall out of the sky, there is no dead stick landing - is this correct?
Comment: Are you asking if there are other power sources that could help with a dead-stick landing, or whether an aircraft is controllable without any electrical/hydraulic power?
Comment: There may also be a [RAT](http://en.wikipedia.org/wiki/Ram_air_turbine) on board
Comment: @JanHudec tell that to the high altitude interceptor pilots... Not everyone is down in the dirt playing the penetration bomber game.
Comment: I don't think anyone really expects fighter to do a dead-stick landing under any conditions. In many mission profiles the aircraft is too low to glide anywhere useful anyway.
Comment: @jwenting: They are ever since high-altitude SAMs rendered flying above the enemy's air defences obsolete as a strategy for avoiding getting shot down, way back in the sixties.
Comment: @Sean tell that to the mid level and high level  bomber pilots over Afghanistan and Syria.
Answer: How Are Modern Fighter Aircraft Controlled?
The F16 was the first US military aircraft to be designed around the revolutionary fly-by-wire concept.  This meant there were no direct mechanical linkages between the cockpit and major control surfaces, and that all pilot input was electronically carried to the hydraulic system via wire.  However, since the F16 burst into the scene, there have been further major advancements in aircraft systems design.  Late Gen 4 aircraft, such as the F/A 18 Super Hornet, are designed around a concept now called control-by-wire.  Control-by-wire aircraft not only have removed mechanical linkages to the hydraulic system, but now the pilot is only a voting member.  This means that all input is received by a computer bank that then computes what it thinks the pilot is intending to do, and then autonomously operates the control surfaces to achieve the effect.  This means that Gen 4 aircraft rely heavily on both computer integrity (and there are plenty of self-healing backups), and the power required to run those systems.
Power Failure
If there was a catastrophic total electrical failure and the only remaining power supply was the battery, the only option is for the pilot to restart a generator.  In the event that the engines were operating and all power generation was destroyed, the aircraft would only be flyable for the duration which the battery could provide power to the aircraft--that's a very limited duration.
Possible other scenarios could include a dual-engine failure. In this instance, the aircraft may be able to fly fast enough to generate enough airflow down the turbine to turn the generator and perform an airstart, but this would only be useful in a dual engine failure, and only if there was enough altitude and airspeed to trade to make it a realistic option.  Otherwise, the battery would probably be used to power the APU, and attempt a relight.  Again, if both engines relit and the generators (including the APU) failed to produce power, then the aircraft would not be flyable.
But what about the RAT?
Although currently in limited use on some trainer aircraft like the T-45, modern fighter aircraft do not use a RAT.
So what usually happens in a total electrical failure?
If the aircrew cannot get a generator back online then they eject.
Comment: @DavidRicherby I fly the Rhino.
Comment: @raptortech97 Once the computers turn off its a crap shoot. Best case, you become a glider in the direction you were flying. Worst case, the computers died when the controls surfaces were weird and you instantly depart.  In the rhino, the batteries only give 5-10min of flight time (dependent on aircraft configuration and systems powered that drain the battery) if everything else is dead.
Comment: Wikipedia is often wrong, and this is one of those instances.  Modern US fighter aircraft do not use RATs.  Even older aircraft like the F-16 elected to use an EPU vice RAT.  Neither the Super Hornet, nor other late Gen 4/Gen 5 aircraft use them.
Comment: Its also worth noting that modern electrical systems are so reliable you're probably more likely to inadvertently kill both engines and eject than you are to totally lose all power because of a system failure.
Comment: @ChrisW The Growler has RATs to power its pods, but the Super itself, E/F/G models, relies on windmilling the engine to provide backup HYD when the engine dies.  I'm not sure about the legacy models.
Comment: [Wikipedia](http://en.wikipedia.org/wiki/Ram_air_turbine) (in a nearly-unreferenced article) says that RATs can generate electrical power i.e. "RAT will power vital systems (flight controls, linked hydraulics and also flight-critical instrumentation)", and that, "RATs are common in military aircraft which must be capable of surviving sudden and complete loss of power".
Comment: @SHAF "Wikipedia is often wrong". True but you're asking us to take your unsourced word against the unsourced word of a whole community. There's at least some chance that the unsourced Wikipedia article has been checked by people who've deleted stuff they know to be wrong. Your unsourced post certainly hasn't had that and, given that choice, I'll take Wikipedia any day of the week.
Comment: Using Google I found http://www.f-16.net/forum/viewtopic.php?t=1056 which suggests that the F16 doesn't have a RAT, but also http://www.airframer.com/direct_detail.html?company=121760 which suggests the F18 does have a RAT (but, who knows, maybe that's to power radar or something, not for emergency power).
Comment: It'd be helpful if you could address the idea of the aircraft "falling out of the sky." It obviously won't stop dead in the air and stop plummeting - I assume after some time (seconds? minutes?) without control it would stall, and then start plummeting
Comment: In the Viper it's about 10 minutes that the EPU supplies power under a normal load.
Answer: Define "modern". The A-10 is only 38 years old, is still in service and is expected to remain so until at least 2020 (its planned replacement, along with many other current service aircraft including the F-15E, F-16 and F/A-18, is the much-maligned F-35 program). It has redundant hydraulic systems for all major control surfaces, plus a set of drect cable linkages, so even in a fully unpowered glide a true "dead stick" landing is possible. However, this is probably an unfair example as the A-10 was designed in part for extreme survivability in low-altitude combat conditions where the aircraft could encounter practically everything that airplanes and their pilots don't like, from small-arms fire and flak to short-range ground or air missiles and even a well-aimed tank or artillery round.
"Modern" fly-by-wire jets typically have similar redundancy, but with no direct mechanical link from stick to control surfaces, they are at least partially dependent on electrical power for the flight control computer (in addition to the power required for the hydraulic motors). In the case of a total loss of electrical power, you're right, the aircraft would be uncontrollable until one of two things happened; the pilot got one of the electrical sources back online (typically an engine-powered generator), or he gave up and punched out.
One might wonder how much has to go wrong for the generator coupled to each engine turbine and the APU to fail, leaving the pilot with only battery power for the displays (and to attempt maybe one engine restart). The answer is "a lot"; the most likely scenario causing a simultaneous failure of all generation systems is a missile impact, and in that scenario most fighters wouldn't make it back anyway. However, a failure in the power distribution system of the aircraft might be more likely; this system is redundant as well, but there are some necessary bottlenecks, and one or two relatively minor failures in series could conceivably disable a plane mid-flight.
Comment: When being attacked by an A-10 a tanker can greatly improve his chances of survival by standing up in the open turret hatch and flipping the bird at the incoming A-10. This may cause the pilot to laugh so hard he'll twitch the stick a bit and miss the target... Oh, BTW, and in case you've forgotten - the F-35 is The Answer. The only question is, to which question..?
Comment: Only 25 years old? According to [Wikipedia](http://en.wikipedia.org/wiki/Fairchild_Republic_A-10_Thunderbolt_II), it was introduced in 1977. That makes it 38 years old!
Comment: Damn my mental arithmetic. Editing...
Comment: To be perfectly fair, depending on your point of view, the A-10s flying now are only 10 years old at the oldest; the A-10C was first flown in 2005, and is arrived at via a combination of the A-10 SLEP replacing the wings and other fatigued airframe members of older A-10As, plus the PEUP program to upgrade the avionics to a glass cockpit with the capability to fire the latest GPS-guided munitions. Despite the cockpit upgrade, the A-10s retain their triple-redundant flight linkages.
Comment: Running out of fuel would seem to do the trick, as well.  Can't run the engines or the APU without it...


How can I perform lossless compression of images so that they can be stored to train a CNN?

Question: I have a set of images, which are quite large in size (1000x1000), and as such do not easily fit into memory. I'd like to compress these images, such that little information is missing. I am looking to use a CNN for a reinforcement learning task which involves a lot of very small objects which may disappear when downsampling. What is the best approach to handle this without downscaling/downsampling the image and losing information for CNNs?
Answer: Your input image size and memory are not directly related. While using CNN's, there are multiple hyperparameters that effect the video memory(if you are using GPU) or physical memory(if you are using CPU). All the frameworks these days uses a simplified data-loaders, for instance in Tensorflow or PyTorch, you are required to write a data-loader that takes in multiple hyper-parameters that are mentioned below and fit the data into VRAM/RAM, and this is strictly dependent upon you batch size - memory occupied on VRAM has direct relation to the batch size.
Whatever may be your image size, while you are writing the data-loader you have to mention the transformation parameters to your data-loader, during the training phase the data-loader will automatically load required images into your memory according to the batch size you have mentioned. As you have mentioned about image compression, this is an irrelevant parameter at-least for most of the generic use-cases, the most relevant hyperparameters are

Scaling
Cropping
Random flip
Normalization of the RGB values
ColorJitter
Padding
RandomAffine

And many more.
PyTorch provides really good transformers in data-loader, please do check https://pytorch.org/docs/stable/torchvision/transforms.html.
For Tensorflow, have a look at https://keras.io/preprocessing/image/.
Comment: Although data loaders or generators may partially solve the problem and the information in your answer seems valid, I think the OP is specifically looking for a way of compressing single images. Maybe you could mention something about it. Also, the OP is using TensorFlow, so you may reformulate your answer so that is targets more TF rather than PyTorch.
Comment: @nbro, yes, I am looking for ways to compress single images for usage in a reinforcement learning task.
Answer: Tensorflow-Keras provides an effective data transformer and loader. Documentation is at
https://keras.io/preprocessing/image/. The ImageDataGenerator provides  for many types of possible transforms and also enables use of a user defined pre-process function. Use of the
ImageDataGenerator.flow_from_directory provides a means of retrieving images in batches from a directory containing sub directories (classes) of images. and resizing the images.
Image size can impact the results. Generally the larger the image the better the result but this is subject to the law of diminishing returns (at some point the impact on accuracy becomes minuscule) while the training time can become absorbent.
When you have large images like 1000 X 1000 where the subject of interest in the image is small say 50 X 50 the best but most painful approach is the crop the image to the subject of interest. Unfortunately this is usually a time consuming drudgery unless you can find some program that can crop the image automatically. For example there are good programs that can crop  images of people automatically where the resultant cropped image is primarily the persons face. Alternatively modules like cv2 can be adapted to provide this capability for certain images.
The batch_size you select along with the image size directly effect memory usage. If your images are large and your batch_size is too large you will encounter a "resource exhaust" error. You can reduce the batch size but this will extend training time.
Other techniques for dealing with large images include methods like sliding windows etc. Again these will increase training time because you are taking a large image and breaking it into a series of smaller images that you feed into the network.
A general though probably risky rule I follow is that if I can visibly see the subject of interest in a resized image then I assume the network will be able to detect it as well.
Will probably be less accurate than using the full image but should be as we engineers say "good enough"


Why is Tajū Kage Bushin no Jutsu a secret?

Question: In the first episode/chapter of Naruto, Naruto steals the scroll containing secret jutsus and, from it, learns Tajū Kage Bushin no Jutsu, the multiple version of the corporeal alternative to Bushin no Jutsu (which they learn in school). While Kage Bushin no Jutsu seems to take way more chakra and is a lot harder on the user than Bushin no Jutsu, it doesn't seem particularly egregious. Additionally, a decent number of characters seem to use it, if the Wikia article is to be believed. While most characters who use Kage Bushin no Jutsu don't make multiple clones, it doesn't seem like a massive leap from one to the other. So why is it kept secret and sealed away in the Scroll of Seals when other jutsus that are incredibly hard on a person or even potentially fatal (like opening the Eight Gates) aren't?
Comment: i was about to suggest that it's forbidden to Naruto out of fear that the 9-tails's seal could weaken because of it, but then that wouldn't explain why it's restricted to all other ninja which would be the point of having it sealed away and guarded effectively by the Hokage
Comment: While https://anime.stackexchange.com/q/2145/93 answers broadly why it's forbidden, I'm specifically wondering why it BUT NOT comparably or more harsh jutsus aren't.
Answer: It's a forbidden jutsu because of the amount of chakra it requires. Along with that with certain users of the jutsu it could increase their numbers from 1 to 1000 creating a small army.
Answer: The eight gate that you gave in the example is a forbidden jutsu and not just everyone can learn it (i.e. sealed). The only known users (manga canon) of this jutsu are Might Guy and Rock Lee, both are Taijutsu masters with the first was even commended as the greatest Taijutsu user ever by none other than Uchiha Madara. Even Lee are not able to open all 8 gates, only Might Guy can. Other than ability, it was also suggested that Might Guy has yet to teach Lee how to open all 8 gates. Lee was limited to the 6th gate. This means that the jutsu is somewhat "sealed" by Guy.
Another forbidden jutsu that was not sealed is the Rasen Shuriken. But that is because Naruto created it himself.
The rest of the kinjutsu are used only by powerful ninjas, sometimes by stealing the scroll (like Deidara did), or the kinjutsu requires Kekkei Genkai (like Izanami and Izanagi).
Thus the conclusion is that other kinjutsu are sealed, just like Kage Bunshin no Jutsu was.
Answer: The shadow clone jutsu was invented by Tobirama senju. The reason it is a forbidden jutsu is because it drains the user's chakra. When kakashi was fighting PAIN he lost a decent amount of chakra to the clone.
Why is the multi shadow clone jutsu a forbidden jutsu
Answer: I think it works like, the shadow clone jutsu isn't forbidden (just 1 clone) but the multi shadow clone jutsu is forbidden because anything more that 1 clone drains too much chakra ( anything over 2 clone )


Grant from private company - conflict of interest

Question: If a private company provides a grant for some research to be carried out but is hoping for a particular outcome from the research in order to take certain business decisions, should this be described as a conflict of interest?
Comment: _Hoping_ for a particular outcome is not a conflict of interest.  _Paying_ for a particular outcome is.
Comment: A conflict of interest in what context? But, yeah, by and large it sounds like a conflict of interest (but not an uncommon one).
Comment: And it's not just private companies, it's ANY source of funding. If greenpeace funds your study into the effects of tuna fishing on the tuna population you can assume they want you to conclude that tuna fishing is bad for example, because it's a well known campaign platform for them to want to get it banned.
Comment: You definitely need to mention it in the paper.
Comment: In the context that it should be described as such when publishing the results of the research i.e. should the paper describe who the grant was given by and why they gave it within a conflicts of interest sub-section?
Answer: I don't see this as a conflict of interest, but the issue itself is deserving of careful attention from both a contracts perspective and a scientific perspective. I would advise against any such funding source that puts restrictions on the publication of findings.  In particular, you state that the business is "hoping for a particular outcome."  Are you still allowed to publish results that are contrary to their expectations -- or, does the contract specifically state they have authority over what can and cannot be published. You will want your grants management officers to carefully scrutinize the contract.
Science is really about answering questions through an open, replicable and systematic process.  It is not about providing evidence for an expected outcome.  I think this type of funding will be more problematic than helpful for a scientific career.
Comment: I don't think it has to be bad. They may be hoping for it, but not coerce you to get that result.
Comment: @Davidmh It's not just about whether they can force a particular result; it's also about whether they can censor the result. If the contract says that the company has final say on whether to publish, they they can just say no if the results don't support the result they wanted. Keep doing that for long enough, and the only published papers will be the ones that support their preferred result, which makes it *seem* like that result is correct because there are no *published* papers refuting it.
Answer: A company exists to make money. They fund a research in the hope that the outcome will be beneficial for them (as a student works on a project in the hope that there will be good results out of it). There is nothing intrinsically bad there.
The problem may be with the rest of the conditions. But it will be perfectly fine if: (a) They guarantee you are free to publish whatever you consider and (b) they don't force you to get "good results".
Comment: heck, I've seen papers that could not be published not because of a conflict of interest with the funder of the study, but with one between the conclusions of the paper and a major advertiser of the publishing company it was submitted to...
Answer: Yes, it is a clear conflict of interests:

a situation occurring when an individual or organization is involved in multiple interests, one of which could possibly corrupt the motivation.

It does not disqualify your research (as long you make it with full scrutiny, etc; see other answers), but for the sake of scientific honesty you need to mention it (as it can possibly alter your motivation, e.g. to get further grants from the same company or to condition probability of publishing on the outcome).
I saw such notes, e.g. that a given scientist works for a particular drug company.
Answer: The company should not impact your choice of research methodology, interpretation of results and the dissemination avenues. If the funding agreement is clear on that, then the "hopes" of a company are isolated from the research stream, and I do not see any evident conflict of interest.
Answer: Yours and their interests do conflict but this is not how we usually use the work "conflict of interest." Say if your company actually makes cat food, and then you later got recruited as a consultant on setting up a safe cat food policy, your decisions made in the policy task force can be potentially affected by your financial involvement with the company. In that case, you will need to declare to the policy task force that you have a conflict of interest. In most cases, conflict of interest requires more than two parties, or one of the parties having two or more roles.
In your case it sounds more like a threatening to academic freedom and scientific integrity. Some preventive measures should be done now before things turn ugly. Here are some things that I have been doing in various projects, you may consider following any of them.

Set up a "statement of understanding." It's a binding contract describing who should have the interpretive rights to the data, and how to safeguard everyone's interest. There isn't a template for that, you'll need to lay out items you cannot risk to lose (e.g. your reputation, your institute's reputation, etc.) and contrast with the company's intentions. Talk to your institute's PR or legal representatives for a consultation.
Highlight your value as the neutral middle man. In that sense, express to them firmly that you would like to explore the quality of the product without any prejudice. And explain to them that if their product is substandard, it's better to know now than later when found out by consumer interest group.
Agree upon ALL the protocols, big or small, prior to any analysis. The turmoil I got into mostly about reanalyzing data. Some people just don't give up... and if you look at the same thing for enough iterations, good findings can come out just due to chance. Follow the protocols strictly, and meet to agree again on any modification.
Keep all documents, e-mails, lab books, etc. and keep copies of them.


Tasks and events custom related list

Question: Is it possible to create a custom related list for the mentioned objects? From what I've read you have to create a custom object with a master-detail or lookup relationship, I've been able to accomplish this for other objects like accounts, contacts and opportunities but tasks and events are not available on the picklist. Is there any other way?
Answer: You need to enable the "Allow Activities" (Track Activities) checkbox in the Custom Object Definition to view tasks and events in a custom related list. To do this:

Click Your Name | Setup | Create | Objects.
Click Edit to modify an existing custom object.
Check the "Allow Activities" checkbox under Optional Features.
Answer: If someone is interested in pursuing this further, I put in a request in the idea exchange (https://success.salesforce.com/ideaView?id=08730000000DqTVAA0).
Answer: That's not quite what I want to achieve. I wish to create a custom related list that would be visible in tasks and activities. When I try to create a lookup relationship in my created object (Allow activities is checked) I can't see either tasks nor events on the list.
Comment: Please edit your question instead of adding another answer
Answer: You can also create a custom VF Page for the object you are interested in, insert a <apex:detail> tag to display standard page for the object, and create your custom related list on your own, with <apex:pageBlockTable>. This is the way to create a fully customized lists, e.g. with some custom sorting.
Answer: Activities (Tasks and Events) cannot be the type of a lookup field for any object.
Out of the box an activity can only link to a single 'What' object, and can be linked to a maximum of 50 'Who' (Contact) objects if it's non-recurring and the feature has been enabled.
You would need to create a custom Visualforce page extending the relevant standard controller and build your related list completely using custom code to achieve what I think you want.

Tasks and events custom related list