Wikipedia:Reference desk/Archives/Miscellaneous/2012 February 27

= February 27 =

Free wi-fi on board?
Is the wi-fi network on planes free of charge and free of limitations? XPPaul (talk) 00:17, 27 February 2012 (UTC)
 * It's going to vary by airline. American Airlines charges for it, and it looks like Delta does, too.  RudolfRed (talk) 00:52, 27 February 2012 (UTC)


 * I'm a bit confused by the whole premise myself. During takeoff and landing, they want you to turn your phone, laptop, tablet, etc, off. As in all the way off, not just sleep mode or airplane mode. Supposedly this is because these devices will somehow interfere with the plane's avionics and cause a crash, even with all wireless features turned off. But when you are up 30,000 ft it is somehow ok to have a wireless router and dozens of devices going at once. How does that work? How do they get wifi up there at all, and could you hypothetically do it yourself with the Android phone with the built in wireless hotspot? Beeblebrox (talk) 04:04, 27 February 2012 (UTC)
 * I have long since concluded that this was a myth; otherwise Al Qaida would be looking to bring down planes by shipping a few dozen iPods. I have decided that if they allowed phone calls on planes (other than the very expensive air to ground), people would kill each other long before ocean was crossed.--Wehwalt (talk) 09:32, 27 February 2012 (UTC)
 * Airlines normally don't give you an explicit reason to turn everything off, but I could imagine several for not using your laptop, cell-phone or what-you-got during takeoff and landing: by a harsh maneuver the device could fly off your hand, you won't pay much attention to security instructions, and a laptop on your lap would delay a possible evacuation (what would you do in case of an accident, throw the laptop on the floor, where someone could stumble, or carry it and have your hands occupied?). XPPaul (talk) 12:37, 27 February 2012 (UTC)
 * No. As Beeblebrox said above, they do indeed give an explicit reason to turn such devices off, namely that they interfere with aircraft equipment.  The question is how to reconcile this with the availability of wi-fi onboard. --Viennese Waltz 12:44, 27 February 2012 (UTC)
 * I'm not sure they do say that any more because by now everyone knows that is isn't true. How could a plane that could crash because someone had a mobile phone switched on in their pocket ever pass the stringent safetly requirements for passenger planes? It's a ridiculous claim. They might interfere with the entertainment system, or something, but they won't interfere with critical systems - they are all shielded from stray EM. I think XPPaul is right - they don't want you being too distracted during takeoff and landing, they also probably don't want the stray illumination from screens (you may have noticed their turn off the cabin lights for takeoff and landing at night so as not to have a difference in lighting between the inside and outside of the plane - I expect the reading lights are designed to turn off automatically in an emergency, but your laptop screen won't). There are also issues with mobile phones connecting to too many cell towers because so many are visible from the sky. And, finally, they want to be able to charge you ridiculous amounts to use their onboard phones. --Tango (talk) 13:15, 27 February 2012 (UTC)
 * This sort of thing has been discussed many times on the RD including Reference desk/Archives/Science/2011 September 23. Some of the points discussed have already been mentioned here but I'd raise a few other key points. Airliners and regulators are generally very risk adverse and many authorities don't consider it conclusively proven that there's no way phones could interfere with the important airline systems, particularly since there have been some cases of coincidences of problems that went away when devices were turned off. And in case it isn't obviouy, landing and takeoff are considered crucial times with little room for error. Also, even if there really is some small risk, that doesn't mean it would make sense for al-Qaeda or whoever to send them to down planes. In fact iPods have lithium ion batteries, some airlines and regulators do have regulations on the size, number and packaging of lithium ion batteries because they consider them a risk. In a similar vein, the fact that some devices are occasionally left on doesn't prove there is no problem or suggest it doesn't make sense to require such devices be turned off. If there is a risk and it depends at least partially on the number of devices, then the more you turn off, the lower the risk. Finally if someone is using electronic device it's easier to tell them to turn it off then tell them to make sure it's in flight mode. (While I don't think flight attendants will generally check you actually turn it off they probably will hassle you if they see you using it again before you're supposed to. And I suspect people are more likely to comply if they know they can't use the device. Whereas if you can use the device, some may just claim it's in flight mode even if the device doesn't have such a setting or they have no idea how to set it.) BTW, remember that some planes have pico or microcells, so they do allow people to call with their phones during the flight, although generally with a high cost and not during takeoff or landing. Nil Einne (talk) 15:59, 27 February 2012 (UTC)
 * I had thought that this warning was only put for takeoffs and landings since even a small navigation error during takeoff and landing could crash the whole plane. But if a small blip occurs at 30,000 feet, it won't noticeably affect the overall flight. 67.185.1.213 (talk) 16:57, 27 February 2012 (UTC)
 * The OP asked if the wi-fi network on planes is free of charge and free of limitations. The answer to the first question (free of charge) is yes at least for some airlines. I used it last week-end on my android phone, and it worked flawlessly. The "free of limitations" question I cannot answer. What kind of limitations would that refer to? Bandwidth/Gb downloaded? Pr0n sites? Other kinds of censorship? Dunno, I just read and wrote some emails. As to the "during landing and take-off" bit, I once overheard a crew member talking to a passenger friend, saying that the real reason for the restriction, is that take off and landing are hugely more dangerous than the rest of the flight, and that they don't want the passengers to be distracted by their electronic playthings. --NorwegianBluetalk 21:50, 27 February 2012 (UTC)

Related question
Could a terrorist crash a plane by carrying a device designed to interfer with the plane's critical systems? Could (s)he fit a strong enough radar jammer or similar into his carry-on luggage and activate it in flight (given the restrictions on what can be taken on board)? What sort of interference affects the systems required for take off and landing? 203.27.72.5 (talk) 21:38, 2 March 2012 (UTC)

Watches and Water Resistance
Per Water Resistant mark, a watch that is rated as being 200m Water Resistant (not Diver's 200m) is not suitable for diving and should be used for no deeper than a recreational pool. It states that the apparent depth misconception is due to the fact that the 200m WR rating was measured under a pool of static water and does not take into consideration the extra pressure that will be applied to the watch when the wearer moves through the water.

But suppose I am wearing a watch that is 200m WR, and I am diving recreationally to say, 50m, is the additional pressure from the movement of my hand while I am swimming able to apply the equivalent of 150m of water pressure and hence, render the watch unsuitable for diving?

Edit: I am aware of the other ISO requirements necessary, such as a uni-directional bezel, for a watch to be given a "Diver" designation, but purely in terms of the watch's ability to prevent water leakage, will a 200m WR watch be suitable for diving to 200m?

Acceptable (talk) 05:15, 27 February 2012 (UTC)


 * I agree that the movement of the watch through the water is rather insignificant. If that was all that was going on here, then a watch rated for 200 m should be able to handle 190 m or more.  I suspect that they simply lied when they gave it that rating, and this is an attempt to cover up the lie. StuRat (talk) 07:26, 27 February 2012 (UTC)
 * "Water resistant to 200m" is ridiculous. If you are going deeper than about 4m then you must be diving, in which case you should get a divers watch. "Water resistant" is useful for doing the washing up and for swimming pools, that's about it. I don't understand why they give depths for water resistance. --Tango (talk) 13:18, 27 February 2012 (UTC)
 * I'd think the main difference between non-diving and diving watches is that the latter are designed for prolonged exposure. Hence non-diving watches are immersed (when tested) only 10 minutes at the rated pressure, and 1 hour at 10 cm depth, while diving watches are immersed 2 hours at 125% of rated pressure and 50 hours at 30 cm depth. In addition, diving watches are tested for immersion in salt water (24 hours) and for external forces. I've had a 50m W.R. rated watch, and eventually water came into the casing (though I never swim deeper than 2m). -- Lindert (talk) 16:13, 27 February 2012 (UTC)


 * Also, a diver's watch is likely made so that you can press its buttons while underwater without risking that the water gets in around the buttons. &#x2013; b_jonas 11:04, 28 February 2012 (UTC)

Style, academic publishing
I'm submitting a paper soon that uses Author (year) style citations. I'll be saying plenty of things like "Jones et al. (2010) showed that ...". I'm confused as to how to indicate possession, e.g. to refer to a system used by Jones et. al (2010). So, which of these is least jarring? These all look horrible and clunky to me, but I would prefer to not re-write the whole sentence to use something like "the system used by Jones et al. (2010)" I have also looked at the style guide for authors from the publishers. It does not begin to address this issue. Thanks in advance! SemanticMantis (talk) 18:41, 27 February 2012 (UTC)
 * 1) "Jones et al.'s (2010) system is..."
 * 2) "Jones et al. (2010)'s system is..."
 * 3) "Jones' et al. (2010) system is..."
 * 4) other options?


 * The option you've explicitly ruled out — "the system used by Jones et al. (2010)" — squares most completely with how I've seen it done in formal periodicals. #3 is 100% wrong. #2 and #1 both look bad. I would go with the simple re-write. --Mr.98 (talk) 19:21, 27 February 2012 (UTC)


 * Agree with Mr. 98. Generally, you can avoid the problem by putting the citation at the end of the sentence. Unless there is a good reason too, don't mention author's names in the body of the sentence. Include them in parentheses at the end. This generally avoids the use of indirect discourse.


 * Examples:


 * Members of the alliance Crothinion prefer wet, acidic subtrates in full sunshine (Korski et al., 2007).
 * One study on calciphilic lichens revealed that species growing on concrete were resistant to dessication (Pinkleton and Rabycz, 2012).


 * Using the author's name in the body of the sentence indicates that the author is significant, and not only the information they provide. This is more common in reviews or in the discussion section of a primary article, and maybe sometimes in the introduction:


 * Finley et al. (1998) concluded that the species was xerothermic, whereas Rachelson (2002) and Connors (2003) found that it grew best in moist habitats.


 * The only exception I make to this rule is with methods or formulas:


 * The study area was surveyed in accordance with the methods described by Rudolphe and Hu (2001).


 * All data were transformed using the formula proposed by Surontong and Mbembe (2005).


 * Even then, I try to make sure that the sentence ends there.


 * Avoid using indirect discourse as much as you can. Too much is irritating.


 * Last of all, don't interupt a sentence with parentheses unless it's absolutely necessary:


 * Clumsy: Vitamin C is found in cherries (Budzinski and Wallis, 2007), greengages (Porter, 2002; My et al., 2003), apples (Kurtz et al., 1999; Szojner and Myśliński, 2007) and dingleberries (Santorum, 2012).


 * Better: Vitamin C is found in cherries, greengages, apples and dingleberries (Budzinski and Wallis, 2007; Porter, 2002; My et al., 2003; Kurtz et al., 1999; Szojner and Myśliński, 2007; Santorum, 2012).


 * The first version is almost unreadable. Actually, I once translated a sentence like this with about a dozen different fruits. In the end, it worked better as a bulleted list. Dominus Vobisdu (talk) 19:52, 27 February 2012 (UTC)


 * Thanks for the responses. Dominus: my usage is much more like your 'review' example. The author is important, in that it is the only name I have to identify their method. I ended up re-writing to avoid a possessive citation, but it seems like there should be some way to do it :) SemanticMantis (talk) 14:38, 28 February 2012 (UTC)